HYSYS manual - Academics

Transcription

This electronic HYSYS v8.3 manual is a condensed
version of your purchased HYSYS v8.3 manual. It
contains mostly those pages that have web links. Use
the bookmarks to the left to go to a specific page.
Minor changes to the HYSYS v8.3 manual are required to make it usable with later
versions of the HYSYS software (v8.4, v8.5, etc.). Click here to view those changes.
Since the "E-Z Solve" software referenced in Appendix A is no longer supported,
click here to learn how to replace it with an Excel macro called "EZ Setup".
Chemical Process Simulation and
the Aspen HYSYS v8.3 Software
Michael E. Hanyak, Jr.
Department of Chemical Engineering
Bucknell University
Lewisburg, PA 17837
This electronic HYSYS v8.3 manual is a condensed
version of your purchased HYSYS v8.3 manual. It
contains mostly those pages that have web links. Use
the bookmarks to the left to go to a specific page.
Copyright © 2013 by Michael E. Hanyak, Jr.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval
system or transmitted in any form or by any means—electronic, mechanical, photocopying, recording, scanning or otherwise—without the prior written permission of the
Publisher, except as permitted under Section 107 or 108 of the 1976 United States
Copyright Act. Request to the Publisher for permission should be sent to the address
below.
Dr. Michael E. Hanyak, Jr., Publisher
Chemical Engineering Department
Bucknell University
Lewisburg, PA 17837
Email:
hanyak@bucknell.edu
I dedicated this book to my wife—Martha Jane—for her love,
understanding, and English prowess.
About the Author
Michael E. Hanyak, Jr. is Professor Emeritus of Chemical Engineering at Bucknell
University in Lewisburg, PA. He received his B.S. from The Pennsylvania State University in
1966, M.S. from Carnegie Mellon in 1968, and his Ph.D. in Chemical Engineering from the
University of Pennsylvania in 1976. From 1967-1970, he worked as a senior chemical engineer
at Air Products, Inc. in Allentown, PA, where he developed process simulation software for
cryogenic systems. He served as Professor of Chemical Engineering at Bucknell University from
1974 to 2010.
His teaching and research interests included computer-aided engineering and design,
instructional design, pedagogical software tools, and the electronic classroom. With
undergraduate and M.S. graduate students, he has developed a thermodynamic software system
(BUTS), a linear equation system solver (BLESS), a formative assessment system for teamwork
(TEAM 360), and an electronic learning system for engineering problem solving (eLEAPS), of
which the last three are an integral part of the freshman introductory course and senior design
course in Bucknell’s curriculum for chemical engineering majors. His two manuscripts—
Companion in Chemical Engineering (CinChE): An Instructional Supplement and Chemical
Process Simulation and the Aspen HYSYS Software— support a team-oriented and problembased-learning environment for the introductory course in chemical engineering. The CinChE
manual presents a novel application of a problem solving strategy that enhances students’ higherorder thinking skills of analysis, synthesis, and evaluation. The HYSYS manual is a self-paced
instructional document that teaches students how to use effectively a process simulator.
With grants from the Air Products Foundation, the General Electric Fund, and the
National Science Foundation, Professor Hanyak provided leadership with groups of engineering
faculty in pioneering the electronic classroom and active learning in the chemical engineering
department and the engineering college at Bucknell University. As an outreach since 2003, he
and his colleagues have annually presented summer workshops at Bucknell Univeristy on active
learning, cooperative learning, and problem-based learning to nearly 300 engineering faculty
from the U.S. and abroad.
In 1983, Professor Hanyak served on the original committee that formulated the Writing
Program at Bucknell University. He has integrated teamwork, writing, oral communication, and
professionalism in the freshman course on stoichiometry, the junior unit operations laboratory,
and the two senior design courses, using a fictitious consultant company, the Bison Engineering
and Evaluation Firm (BEEF, Inc.). He has authored two BEEF company handbooks to support
this integration.
As department chairman from 1998-2002, Professor Hanyak supervised the migration to
the first outcome-based format for the successful ABET accreditation in 2002, automated the
course scheduling process, and spearheaded the electronic assessment of courses in the Chemical
Engineering Department. For his love of teaching and non-traditional research in support of that
teaching, he received the Lindback Award for Distinguished Teaching from Bucknell University
in 2002. He has been a member of the American Institute of Chemical Engineers and the
American Society for Engineering Education (ASEE). He is the recipient of the 2011 CACHE
Award given by the Chemical Engineering Division of ASEE for significant contributions in the
development of computer aids for chemical engineering education.
iv
Preface
This document entitled Chemical Process Simulation and the Aspen HYSYS v8.3 Software, is a
self-paced instructional manual that aids students in learning how to use a chemical process simulator and
how a process simulator models material balances, phase equilibria, and energy balances for chemical
process units. A student’s learning is driven by the development of the material and energy requirements
for a specific chemical process flowsheet; that is, the toluene alkylation with methanol to produce styrene
monomer. This semester-long, problem-based learning activity is intended to be a student-based
independent study, with about two-hour support provided once a week by a student teaching assistant to
answer any questions. Your feedback is welcomed in order to improve the next version of this instructional
manual. Please direct your feedback to the email address hanyak@bucknell.edu.
This HYSYS manual can be used with most textbooks for the introductory course on chemical
engineering, like Elementary Principles of Chemical Processes [Felder and Rousseau, 2005], Basic
Principles and Calculations in Chemical Engineering [Himmelblau and Riggs, 2004], or Introduction to
Chemical Processes: Principles, Analysis, Synthesis [Murphy, 2007]. It can also be used as a refresher for
chemical engineering seniors in their process engineering design course.
Because the HYSYS manuscript was compiled using the Adobe Acrobat® system for document
processing, it contains many web links. In the Acrobat Reader® version of this instructional manual (the
.pdf file), you can access the web links that appear in many of the tutorials and simulation problems of the
paper copy. You are encouraged to view electronically the “.pdf” version while you read the paper copy of
this instructional manual. Type the following web link to access it:
http://www.departments.bucknell.edu/chem_eng/cheg200/HYSYS-v8.3_Manual/a_blueHYSYS.pdf
The web links access HYSYS “.hsc” files, “.pdf” documents, “.docx” files, and “.xlsx” files that appear in
many of the chapters. You can view but not copy or print content within the “.pdf” version of this HYSYS
manual. Errata for this version of the HYSYS manual are available at the following web link:
http://www.departments.bucknell.edu/chem_eng/cheg200/HYSYS-v8.3_Manual/a_errataHYSYS.pdf
Downloading the “.hsc”, “.pdf”, “.docx”, and “.xlsx” files from within the electronic version of the HYSYS
manual using Internet Explorer®, Firefox®, or Safari® should work smoothly.
The HYSYS manual contains four chapters. Chapter 1 provides an overview of the problem
assignment to make styrene monomer from methanol and toluene. Chapter 2 presents ten tutorials to
introduce the student to the HYSYS simulation software—tutorial conventions, HYSYS interface,
simulation file creation, heater operation, conversion reactor, process flow diagram (PDF) manipulation
tools, Gibbs equilibrium reactor, plug flow reactor, printing capabilities, and spreadsheet programming.
The first six of these tutorials can be completed in a two-week period for the introductory chemical
engineering course. The other four are intended for the senior-level design course. Chapter 3 provides five
single-unit assignments—process stream, pump, cooler, mixer/tee, and reactor—to develop the student’s
abilities and confidence to simulate individual process units using HYSYS. These five assignments can be
completed over a three-week period. Chapter 4 contains seven assignments—reactor section,
cooling/decanting section, methanol recycle purification section, toluene recycle purification section, feed
preparation section, recycle mixing/preheating section, and product purification section—to develop the
process material and energy requirements for the styrene monomer flowsheet. These seven assignments
can be completed over a seven-week period.
The HYSYS manual also contains fourteen appendices in support of the four chapters for the steadystate simulation of a continuous process represented by a process flow diagram (PFD). Appendix A
describes how to solve a batch example process within the Aspen HYSYS software using a spreadsheet
v
operator. Appendix B provides an overview of the steady-state simulation modules for the material and
energy balances of some standard unit operations that are detailed in the next ten appendices. Appendix B
also provides the conceptual and mathematical models for a process stream divider, often called a TEE.
Appendices C to L present the mathematical models and some of their mathematical algorithms for ten
standard steady-state process units—process stream, stream mixer, pump, valve, heater/cooler, chemical
reactor, two-phase separator, three-phase separator, component splitter, and simple distillation. Appendix
M contains the economic model and its HYSYS spreadsheet to determine the net profit for the styrene
monomer flowsheet. Finally, Appendix N contains the bibliography for the preface, four chapters, and
thirteen appendices. Some of the important web links that appeared in the chapters are also provided in the
bibliography.
During the 1980’s, a paradigm shift started to take place from the traditional lecture-based
deductive approach in the classroom (i.e., sage on the stage) to the student-centered inductive approach
(i.e., coach on the side) that incorporates one or more of the following learning techniques—active
learning, collaborative learning, cooperative learning, and problem-based learning [Prince, 2004 and Prince
and Felder, 2006]. Although the HYSYS manual has been designed for a problem-based learning
environment, it can easily be used in other active learning scenarios. Hanyak and Raymond [2009] present
the design and application of a team-based cooperative learning environment for the introductory course in
chemical engineering, where student learning is driven by solving process unit problems and is supported
by the CinChE manual [Hanyak, 2011].
As a self-study activity, how would students determine the material and energy requirements to
make styrene monomer from toluene and methanol using Aspen HYSYS? Students work individually to
complete the tutorials and exercises in this HYSYS manual according to the schedule given next:
Topics
½-Week Project P0
{ done independently }
1-Week Project Ex1
{ done as a team }
2-Week Project P1
{ done as a team }
1-Week Project Ex2
{ done as a team }
2-Week Project P2
{ done as a team }
2-Week Project P3
{ done as a team }
1-Week Project Ex3
{ done as a team }
2-Week Project P4
{ done as a team }
2-Week Project P5
{ done as a team }
Problem-Solving Methodology
HYSYS Simulation and Process Streams
Process Variables; Exp. Data Curve Fitting
Project Problems; Thermophysical Properties
Material Balances (with and without rxn’s)
Equations of State, Exam I on Friday
Source
HYSYS Section
CinChE: Ch. 1
HYSYS: Ap. C
2.1, 2.2,
2.3
F&R: Chs. 2, 3
CinChE: Ch. 3
2.4, 2.5,
2.6
F&R: Ch. 4
F&R: Chs. 5, 4
Material Balances, Recycle Processes
Chemical Phase Equilibrium
Exam II Review, Exam II on Friday
Energy and Energy Balances (no reactions)
Material/Energy Balances (with reactions)
Final Exam, Week of Finals
HY.1, HY.2
HY.3
F&R: Ch. 4
HY.4, HY.5
F&R: Ch. 6
SM.1, SM.2
F&R: Chs. 4, 6
SM.3
F&R: Chs. 7-8
SM.4, SM.5
F&R: Ch. 9
SM.6, SM.7
F&R - the Felder and Rousseau textbook; CinChE – Companion in Chem. Eng. by Hanyak
vi
where in the “Source” column, “CinChE” is Companion in Chemical Engineering: A Instructional
Supplement [Hanyak, 2011], “HYSYS” is this Aspen HYSYS manual, and “F&R” is the Felder and
Rousseau textbook [2005]. The “HYSYS Section” column identifies the tutorials and exercises in this
HYSYS manual.
Obviously, the above schedule table is for the introductory chemical engineering course on
material balances, phase equilibria, and energy balances. In this course, students must develop their lowerorder thinking skills—knowledge, comprehension, and application—and their higher-order thinking
skills—analysis, synthesis, and evaluation—in Bloom’s cognitive taxonomy [1956], in order to become
effective problem solvers and to guard against blindly using the Aspen HYSYS software as a black box.
The traditional lecture-based format tends to focus on the lower-order thinking skills and usually does not
provide a formal emphasis on the higher-order thinking skills. In a problem-based learning environment,
student teams that are required to follow the tenets of cooperative learning [Johnson, et al., 1998] can
develop both their lower-order and higher-order thinking skills, as demonstrated by Hanyak and Raymond
[2009] using team-based projects.
In a team-based learning environment, the creative problem-solving methodology emphasized in
CinChE [Hanyak, 2011] provides a general framework in which to solve any type of well-defined
engineering problem involving material balances, phase equilibria, and energy balances. It is a systems
strategy that heavily uses the mental processes of decomposition, chunking, and pattern matching, and it is
specifically designed to enhance students’ higher-order thinking skills of analysis, synthesis, and
evaluation. In applying this methodology, team members learn how to develop a conceptual model (a
diagram), formulate a mathematical model with its assumptions, create a mathematical algorithm, do the
numerical solution, conduct heuristic observations, and develop the formal documentation for a problem.
In conjunction with the CinChE problem-solving methodology, Projects P0 and Ex1 in the above
table are designed as one-week projects that essentially introduce the students to the Aspen HYSYS
interface using tutorials from Chapter 2 of this instructional manual. Projects Ex2 and Ex3 occur during an
exam week and provide the students with further challenges on using the HYSYS simulator. Projects P1 to
P5 are each two weeks in duration.
A two-week project of assigned analysis problems on material balances, phase equilibria, or energy
balances can drive the learning on how individual process units are modeled and solved. The number of
manually-solved analysis problems in a project is equal to the number of members in a team (e.g., four
problems for a four-member team). The CinChE problem-solving methodology not only guides the
students in solving the analysis problems, it also serves as the critical framework in which to foster
communication and teamwork skills using the five tenets of cooperative learning [Johnson, et al., 1998].
As team members are working to solve the analysis problems, they are also independently completing the
assigned HYSYS problems (identified in the “HYSYS Section” column of the above table) and documenting
their solutions in their technical journals. Once all team members have completed the HYSYS tutorials or
problems, they gather as a team to answer the questions posed at the end of each HYSYS problem. While
the self-study HYSYS problems serve to help students learn how to use a process simulator, the manuallysolved analysis problems provide the knowledge base of what happens within the black box.
In Chapter 4 of this HYSYS manual, Problems SM.1 to SM.7 require the students to develop the
process flow diagram to make styrene monomer from toluene and methanol. Each member of a team
begins with the process reactor unit for a specifically-assigned temperature, molar conversion, and yield.
Subsequent assignments increase the complexity of the flowsheet by adding process units, one by one, until
the complete flowsheet is simulated in Aspen HYSYS. The team’s objective is to determine the operating
temperature for the reactor, so that the net profit is maximized without considering federal taxes.
vii
I would like to thank the General Electric Fund for sponsoring during the summers of 1998 and
1999, under its Faculty for the Future program in the area of undergraduate research, the development of
this problem-based learning material on computer-aided chemical process simulation. Jessica Keith (Class
of 1998) and Cynthia Caputo (Class of 1999), undergraduate research students in chemical engineering at
Bucknell University, deserve special thanks for their contributions to this courseware development project
during the summers of 1998 and 1999. Jessica provided initial drafts of Chapters 2, 3, and 4. She also
wrote the first draft of the appendices on process simulation modules. Cynthia worked on enhancing the
process simulation modules using the MathType software, a mathematical equation editor. Dr. William J.
Snyder’s encouragement throughout this project and his idea for the batch problem in Appendix A are very
much appreciated. Finally, I thank the Bucknell chemical engineer majors (nearly 400 of them) for their
patience, understanding, and feedback while developing this manuscript. Their feedback has been
invaluable and has helped to enhance the final document.
Michael E. Hanyak, Jr.
viii
Table of Contents
About the Author ........................................................................................................................... iv
Preface ............................................................................................................................................. v
1. Styrene Monomer Production ................................................................................................ 1-1
Introduction ...................................................................................................................... 1-1
Chemical Flowsheet Description ........................................................................................ 1-2
Flowsheet General Assumptions ........................................................................................ 1-4
Flowsheet Thermodynamic Data ....................................................................................... 1-4
Flowsheet Design Variables ............................................................................................... 1-5
Flowsheet Design Specifications ......................................................................................... 1-6
Flowsheet Economic Analysis ............................................................................................ 1-6
Flowsheet Development Strategy ....................................................................................... 1-7
Your Professional Challenge.............................................................................................. 1-8
2. HYSYS Simulation Tutorials
2.1
Process Flowsheet Overview.......................................................................................... 2-1
Tutorial Conventions ...................................................................................................... 2-2
A. Keywords for Mouse Actions........................................................................................................... 2-2
B. Text Formatting ................................................................................................................................ 2-2
C. Interactive Process Modeling .......................................................................................................... 2-4
D. HYSYS at Your University .............................................................................................................. 2-4
E. Your Default HYSYS Preferences .................................................................................................. 2-9
2.2
2.3
Introduction to the HYSYS Interface ..........................................................................2-10
A. Retrieve a pre-defined simulation file .............................................................................2-10
B. Open a pre-defined simulation file in HYSYS ..................................................................2-11
C. Investigate the Navigation Pane .....................................................................................2-12
D. Manipulate stream specifications ...................................................................................2-13
E. Change global preferences ............................................................................................2-18
F. Add variables to the workbook ......................................................................................2-19
G. Add a second the fluid package......................................................................................2-22
H. Program a spreadsheet operation ..................................................................................2-25
I. Document your simulation session .................................................................................2-28
J. Close the simulation case ..............................................................................................2-29
Simulation File Creation................................................................................................2-30
A. Start the HYSYS program ............................................................................................................. 2-30
B. Create a simulation basis ............................................................................................................... 2-31
C. Find component physical properties ............................................................................................. 2-35
D. Create a process stream ................................................................................................................. 2-36
ix
E. Copy and delete a process stream ................................................................................................. 2-38
F. Specify alternative stream conditions ........................................................................................... 2-40
G. Document your simulation session ................................................................................................ 2-44
H. Close the simulation case ............................................................................................................... 2-45
2.4
Heater and Case Study ..................................................................................................2-47
A. Retrieve a pre-defined simulation file ........................................................................................... 2-47
B. Open a pre-defined simulation file in HYSYS ............................................................................. 2-48
C. Add a heater operation .................................................................................................................. 2-49
D. Specify the heater outlet condition ................................................................................................ 2-51
E. Perform a case study ...................................................................................................................... 2-53
F. Document your simulation session ................................................................................................ 2-57
G. Close the simulation case ............................................................................................................... 2-58
2.5
Conversion Reactor and Reactions ...............................................................................2-60
C. Add a reaction to the fluid package .............................................................................................. 2-62
D. Add a reactor to the flowsheet ....................................................................................................... 2-65
E. Specify the reactor outlet conditions ............................................................................................. 2-68
F. Document your simulation session ................................................................................................ 2-70
G. Close the simulation case ............................................................................................................... 2-71
2.6
PFD Manipulation Tools ...............................................................................................2-73
C. Zoom flowsheet in and out ............................................................................................................. 2-75
D. Orient some PFD icons ................................................................................................................... 2-76
E. Move some icon labels .................................................................................................................... 2-77
F. View some operating conditions .................................................................................................... 2-78
G. Add some documentation text ....................................................................................................... 2-79
H. Generate some property diagrams ................................................................................................ 2-81
I. Connect and disconnect PFD objects ............................................................................................ 2-83
J. Copy a PFD to a Word document ................................................................................................. 2-88
K. Document your simulation session ................................................................................................ 2-90
L. Close the simulation case ............................................................................................................... 2-91
2.7
Gibbs Equilibrium Reactor ...........................................................................................2-92
C. Copy a reactor feed stream ............................................................................................................ 2-94
D. Add a Gibbs reactor to the flowsheet............................................................................................ 2-96
E. Specify the reactor outlet conditions ............................................................................................. 2-98
F. Analyze results for the Gibbs equilibrium reactor .....................................................................2-100
G. Document your simulation session ...............................................................................................2-103
x
H. Close the simulation case ..............................................................................................................2-105
2.8
Kinetic Model and a Plug Flow Reactor .................................................................... 2-106
A. Retrieve a pre-defined simulation file ..........................................................................................2-106
B. Open a pre-defined simulation file in HYSYS ............................................................................2-107
C. Copy a reactor feed stream ...........................................................................................................2-108
D. Add a plug flow reactor to the flowsheet .....................................................................................2-110
E. Add a kinetic reaction set to the fluid package ...........................................................................2-112
F. Specify reactor parameters and outlet conditions ......................................................................2-116
G. Analyze results for the plug flow reactor ....................................................................................2-118
H. Document your simulation session ...............................................................................................2-120
I. Close the simulation case ..............................................................................................................2-121
2.9
HYSYS Printing Capabilities ...................................................................................... 2-123
C. Print the PFD and a process unit window ...................................................................................2-125
D. Print the reactor datasheets ..........................................................................................................2-126
E. Print the case study plot ................................................................................................................2-127
F. Create a customized report ...........................................................................................................2-128
G. Document your simulation session ...............................................................................................2-130
H. Close the simulation case ..............................................................................................................2-131
2.10 HYSYS Spreadsheet Programming ............................................................................ 2-132
C. Examine the process flow diagram ..............................................................................................2-138
D. Complete the spreadsheet operator .............................................................................................2-139
E. Compare the simulation results....................................................................................................2-142
F. Document your simulation session ...............................................................................................2-143
G. Close the simulation case ..............................................................................................................2-143
3. Process Unit Exercises
HY.1
HY.2
HY.3
HY.4
HY.5
Overview ....................................................................................................................... 3-1
Process Stream Simulation .......................................................................................... 3-2
Pump Simulation .......................................................................................................... 3-4
Heater/Cooler Simulation ............................................................................................ 3-6
Mixer/Tee Simulation .................................................................................................. 3-9
Reactor Simulation......................................................................................................3-12
4. Flowsheet Development Exercises
Overview ....................................................................................................................... 4-1
xi
SM.1
SM.2
SM.3
SM.4
SM.5
SM.6
SM.7
Styrene Monomer Reaction Section ........................................................................... 4-3
Reactor Effluent Cooling/Decanting Section ............................................................. 4-5
Methanol Recycle Purification Section ...................................................................... 4-8
Toluene Recycle Purification Section ........................................................................4-13
Toluene/Methanol Feed Preparation Section ...........................................................4-17
Recycle Mixing and Preheating Section ....................................................................4-19
Styrene Monomer Purification Section .....................................................................4-23
Appendix A. Example Batch Simulation in HYSYS .............................................................. A-1
Appendix B. HYSYS Steady-State Simulation Modules ......................................................... B-1
Process Module Format ............................................................................................... B-1
Stream Tee Module ......................................................................................................B-3
Appendix C. Process Stream Module ....................................................................................... C-1
Single-Phase Multicomponent System ....................................................................... C-1
Vapor-Liquid Equilibrium System .............................................................................C-6
Appendix D. Stream Mixer Module ......................................................................................... D-1
Appendix E. Pump Module........................................................................................................ E-1
Appendix F. Valve Module ........................................................................................................ F-1
Appendix G. Heater/Cooler Module ........................................................................................ G-1
Appendix H. Chemical Reactor Module .................................................................................. H-1
Appendix I. Two-Phase Separator Module .............................................................................. I-1
Appendix J. Three-Phase Separator Module ...........................................................................J-1
Appendix K. Component Splitter Module ............................................................................... K-1
Appendix L. Simple Distillation Module .................................................................................. L-1
Appendix M. Styrene Net Profit Analysis ................................................................................ M-1
Appendix N. Bibliography ........................................................................................................ N-1
xii
Chapter 1
Styrene Monomer Production
Chapter 1
Chapter 1
Page 1-1
Introduction
Welcome to the Internship Program in the Process Engineering Department of BEEF, Inc., the
Bison Engineering and Evaluation Firm. As a new provisional engineer in this program, you will learn
how to develop a chemical process and determine its process requirements for material and energy using
the process simulator called Aspen HYSYS®.
BEEF is a consultant company that solves chemical processing problems for governmental
institutions and industrial companies. Since our clients lack the technical expertise, they hire us to
recommend and implement solutions to their chemical processing problems. Solving a client’s problem is
a complex activity involving many departments in our company. Our department’s focus is to develop, on
paper, a large-scale solution, called a process design, for a chemical processing problem. We accomplish
this design by synthesizing a process flowsheet, solving its material and energy balances, sizing and costing
its equipment, and determining its profitability. Basically, we determine the feasibility of the process
design, that is, is it feasible to build and run this process design. Finally, BEEF communicates a process
design to our client in the form of a technical report.
Hawbawg Chemical Company has hired us to investigate the feasibility of manufacturing styrene
monomer from the raw materials of toluene and methanol. They have completed a royalty deal with
Exelus, Inc. to use their proprietary one-step process with a newly-developed catalyst. Styrene monomer is
an intermediate material used to make such consumer plastic products as polystyrene packaging and film,
cushioning materials, radio and television sets, and toys. About 90% of the styrene monomer marketed in
the United States currently uses a two-step process beginning with benzene and ethylene. First, benzene is
alkylated with ethylene to form ethylbenzene. After purification, the ethylbenzene is catalytically
dehydrogenated to produce styrene. The dehydrogenation step is endothermic and requires a large quantity
of steam mixed with the ethylbenzene to maintain the desired reaction temperature, to depress coking of the
catalyst, and to dilute the reaction concentration to enhance the reaction equilibrium. However, the Exelus
process will produce styrene monomer from toluene and methanol in one step, and steam addition is not
required. Some byproduct ethylbenzene is also produced which can be sold to conventional styrene
producers. The new catalyst discovered by Exelus might give Hawbawg the opportunity to develop a new,
low-cost route to styrene monomer. As a first step in our feasibility study for Hawbawg, your team is
assigned the tasks to develop the flowsheet and determine its process requirements for material and
energy that maximizes the net profit.
The chemical process for converting toluene and methanol to styrene monomer is globally depicted
in the diagram below.
byproduct
toluene
flowsheet
methanol
?
styrene monomer
wastes
You must synthesize the process flowsheet, where the chemical reactor is the heart of that flowsheet. This
flowsheet will be composed of process units (such as reactors, heaters, coolers, pumps, and distillation columns) that
are connected by process streams, and it will conceptually shows the flow of material and energy from the
raw materials to the products. Before you look at this flowsheet in detail, you should click here to complete
Chapter 1
Page 1-2
an interactive demonstration on the construction of a simple flowsheet to produce styrene monomer from
toluene and methanol. This interactive demo takes about two and half hours to complete. You can stop the
demo at any time. When you restart it, you can begin where you had left off. The interactive demo
illustrates the basic concepts that you will be learning about in this HYSYS manual on chemical process
simulation.
Chemical Flowsheet Description
The senior chemical engineers in our Process Engineering Department have formulated several
possible process flowsheet designs that could produce styrene monomer. They applied design rules of
thumb (a.k.a. heuristic rules) to determine those formulations. In Chapter 4 of this HYSYS manual, you
will be introduced to some of those heuristic rules as you build the process flow diagram (PFD) one process
unit at a time starting with the chemical reactor and using the Aspen HYSYS® software. Our senior
chemical engineers have recommended an initial chemical process design without energy integration to
convert toluene and methanol to styrene monomer, as depicted in the following block flowsheet:
Q
WS
heater
toluene
toluene recycle
H2 fuel
pump
Q
Q
decanter
column
organic
furnace
reactor
Q
WS
cooler
methanol
aqueous
column
methanol recycle
heater
ethylbenzene
column
pump
styrene monomer
waste water
This flowsheet is an adaption of the one presented in the 1985 American Institute of Chemical Engineers
Student Contest Problem [AIChE, 1984]. A flowsheet is a collection of blocks, circles, and arrowed lines.
The blocks and circles represent process units, such as reactors, heaters, coolers, pumps, and distillation
columns. The solid arrowed lines are process streams (i.e., chemical material flowing in pipes) that are
assumed to have uniform temperature, pressure, flow rate, and composition (as a first approximation, these four
variables do not vary along the length of a pipe). These four quantities are referred to as the process state of a
stream. The dashed arrowed lines represent energy streams of heat ( Q ) and work ( WS ). Usually, they are
draw as solid lines but were drawn as dashed ones above, in order to distinguish them from material
streams. Basically, the block flowsheet conceptually shows the flow of material and energy from the raw
materials (toluene and methanol) to the product (styrene monomer), by-product (ethylbenzene), and wastes
(H2 and water).
Chapter 1
Page 1-3
Although it is not shown in the above flowsheet, toluene and methanol at 25°C and 1 atm are first
compressed and heated to saturated vapors at 460 kPa. The toluene and methanol recycles are also
compressed and heated to saturated vapors at 460 kPa. Then, the two vapor feeds of pure toluene and
methanol entering the above flowsheet are mixed with the toluene and methanol recycles to form the
process stream to the furnace. The process stream leaving the mixer operation is superheated in a fired
furnace to around 465 to 540°C and then fed to the catalytic reactor where the following vapor-phase
reactions take place:
C7H8
+
toluene
C7H8
toluene
CH3OH
→
methanol
+
CH3OH
methanol
C8H8
+
styrene
→
C8H10
ethylbenzene
H2O
water
+
+
H2
hydrogen
H2O
water
As a first approximation, you can assume that other byproduct formation and polymerization of styrene
monomer are negligible and that the catalyst does not coke or deactivate with time. The reactor is assumed
to operate adiabatically; that is, it is well insulated and no heat is transferred to the surroundings.
In the above block flowsheet, the process stream leaving the reactor is condensed with cooling
tower water and cooled to 38°C, forming three phases—vapor, organic, and aqueous—in a decanter. The
vapor stream from the decanter contains mostly hydrogen, and it could be used as a fuel. The aqueous
stream contains primarily methanol and water, and it is sent to a methanol distillation column. This
column’s product stream is the recycled methanol, while its bottoms stream is wastewater, which is
eventually discharged at 25°C and 1 atm. The organic stream from the decanter contains mostly toluene,
ethylbenzene, and styrene monomer. It is sent to a toluene distillation column. This column’s product
stream is the recycled toluene stream containing some methanol, while its bottoms stream contains mostly
ethylbenzene and styrene monomer, which are sent to the styrene distillation column. In the styrene
column, the product stream is mostly ethylbenzene, and the bottoms stream is mostly crude styrene
monomer. Although not shown in the above flowsheet, both of these streams must be cooled to 25°C and 1
atm before each enters a separate storage tank.
In the above styrene monomer flowsheet, the process operates on a continuous basis; that is,
material is continually flowing into and out of each process unit. The Aspen HYSYS® simulator is
designed specifically for a continuous process of multiple process units. It is not designed to handle batch,
semi-batch, or semi-continuous process units. In a batch operation, no material is flowing into or out of the
process unit like a batch chemical reactor. The batch reactor is charged with materials, the reaction takes
place in the reactor container, and at the end of the reaction the material is removed. In a semi-batch
process, at least one chemical compound either enters or leaves the process unit, while all other chemical
compounds remain within the process unit. In a semi-continuous process, at least one chemical compound
enters and leaves the process unit, while all other chemical compounds are processed as batch or semibatch operations. Using the spreadsheet module in Aspen HYSYS®, you can program the solution to the
material and energy balances for a batch, semi-batch, or semi-continuous process unit. Appendix A
presents an example batch problem for expanding a gas mixture in a cylindrical tank system, a typical
problem that you will encounter in the junior-level chemical engineering thermodynamics course. It also
describes how to use the HYSYS spreadsheet module to complete the numerical solution to this batch
example problem. Before examining Appendix A, you should complete Tutorials 2.1, 2.2, and 2.3 in
Chapter 2 of this HYSYS manual.
Chapter 1
Page 1-4
Flowsheet General Assumptions
Our client, Hawbawg Chemical Company, expects the plant capacity to be 250,000 metric tons per
year of crude styrene monomer with an onstream time of 8,320 hours per year. For a preliminary design
study, our senior chemical engineers have provided a list of process simulation assumptions to determine
the material and energy requirements for the above process flowsheet as follows:
•
•
•
•
Impurities in purchased methanol and toluene are negligible.
Yield losses in the chemical reactor due to trace byproducts can be ignored.
The catalyst in the chemical reactor does not coke or deactivate with time
The chemical reactor is well insulated, and thus no heat is transferred to the surroundings.
•
•
•
•
Mostly methanol partitions into both the organic and aqueous phases of the decanter.
Except for methanol, negligible organics will partition into the decanter aqueous phase.
Negligible water will partition into the decanter organic phase.
The off-gas from the decanter will be given a credit as fuel at its lower heating value.
•
•
•
The methanol is to be recycled as a saturated vapor at 460 kPa.
The toluene/methanol mixture is to be recycled as a saturated vapor at 460 kPa.
Water, ethylbenzene and styrene monomer recycled to the reactor feed are at small enough
concentrations to pass through as inert compounds.
Flowsheet Thermodynamic Data
In your process simulations of the above flowsheet, all necessary thermodynamic calculations for
thermophysical properties (such as density and molar enthalpy) and for phase equilibria (such as vapor-liquid or vapor®
liquid-liquid) can be done using an equation of state. In the Aspen HYSYS simulator, the Peng-Robinson
Stryjek-Vera (PRSV) equation of state is recommended by our senior chemical engineers for the analysis of
the manufacture of styrene monomer from toluene and methanol. The PRSV equation is an improvement
on the Peng-Robinson (PR) equation of state, and it extends the application of the PR method to moderately
non-ideal systems.
The physical properties of the six chemical compounds associated with the above flowsheet are
summarized below. Their values were extracted from the Aspen HYSYS® databank.
Property
CAS Registry Number
Molecular Weight
Normal Boiling Point at 1 atm, °C
Critical Temperature, °C
Critical Absolute Pressure, kPa
Critical Volume, m3/kgmol
Acentric Factor
ΔHf at 25°C and 1 atm, kJ/kgmol
Hydrogen
Methanol
Water
Toluene
Ethylbenzene
Styrene
Monomer
1333-74-0
2.0160
-252.60
-230.86
1925.55
0.0515
-0.1201
0
67-56-1
32.0419
64.65
239.45
7376.45
0.1270
0.5570
-201,290
7732-18-5
18.0151
100.00
374.15
22,120.00
0.0571
0.3440
-241,000
108-88-3
92.1408
110.65
318.65
4100.04
0.3160
0.2596
50,029
100-41-4
106.17
136.20
343.95
3607.12
0.3740
0.3010
29,809
100-42-5
104.152
145.16
362.85
3840.00
0.3520
0.2971
147,400
These thermodynamic data are used in the PRSV equation of state to calculate such thermophysical
properties as mass density and molar enthalpy of a mixture of chemical compounds.
Chapter 1
Page 1-5
Flowsheet Design Variables
In a chemical process simulation, design variables are those variables that you have the freedom to
set their values. Our Research and Development Department has conducted some pilot-plant studies on the
adiabatic reactor performance of making styrene monomer from methanol and toluene using the newlydeveloped catalyst from Exelus, Inc. In this study, stoichiometric feed (i.e., equal moles of toluene and
methanol) to the reactor resulted in the following performance data for the formation of styrene monomer
(the product) and ethylbenzene (the byproduct) at a reactor inlet pressure of 400 kPa:
X - molar
conversion
Y - molar
yield
X*Y
X*(1 – Y)
Member
Symbol
Inlet
T, °C
TL reacted
TL fed
SM formed
TL reacted
SM formed
TL fed
EB formed
TL fed
α
♠
♥
♣
♦
ω
465
480
495
510
525
540
0.649
0.679
0.709
0.759
0.819
0.879
0.909
0.869
0.829
0.779
0.719
0.659
0.5899
0.5901
0.5878
0.5913
0.5889
0.5793
0.0591
0.0889
0.1212
0.1677
0.2301
0.2997
TL is toluene, SM is styrene monomer, and EB is ethylbenzene
An Excel version of this table is available by clicking here. In Chapter 4 of this HYSYS manual, you will
complete the process simulation of the above flowsheet for an assigned inlet temperature to the chemical
reactor. The first column in the above table identifies a team member symbol that will be assigned to you
by your project supervisor. That assigned symbol indicates the inlet temperature that you will use in your
HYSYS process simulations of Chapter 4.
For a HYSYS distillation column simulation, the feed, distillate, and bottoms streams are to be
saturated liquids. Nominal atmospheric distillations will operate at 135 kPa top tray pressure and 125 kPa
condenser outlet pressure. Avoid column operating pressures above nominal atmospheric. Allow 5 kPa
pressure drop between the top of the column and the condenser outlet for a vacuum distillation column.
Based on some heuristic rules in engineering practice [Woods, 2007, Ch. 2], the following pressure
drops thru process units caused by frictional losses may be assumed:
Fired heater
Reactor
Heat exchangers* (shell and tube sides)
Condensers under vacuum
Other major equipment
Distillation Trays:
1.0 kPa per theoretical stage for pressure columns
0.5 kPa per theoretical stage for vacuum columns
60 kPa
70 kPa
10 kPa
5 kPa
10 kPa
*Includes condensers, vaporizers, interchangers and all other
exchangers except condensers operated under vacuum.
For pumps and compressors, the adiabatic efficiency can be assumed to be 75%. The combined
mechanical and electrical efficiency for this type of equipment is approximately 90%.
Chapter 1
Page 1-6
Flowsheet Design Specifications
Design specifications set limits on the values of important calculated variables in a chemical
process flowsheet simulation for the stated simulation assumptions and design variables. As recommended
by Hawbawg, some design specifications for toluene, methanol, ethylbenzene (EB), styrene monomer (SM),
and water in the aromatic and wastewater streams are as follows:
Recycle Methanol
Recycle Toluene
EB Byproduct
Crude SM Product
Wastewater
No specified limit on toluene.
No specified limit on methanol.
4 wt % ethylbenzene maximum.
5 wt % maximum for sum of EB and SM.
0.8 wt % toluene maximum.
3 wt % SM maximum.
300 ppm EB maximum.
(ppm is parts per million by weight)
Governmental standards on all pollutants
The Environmental Protection Agency (EPA) standards for water pollution are given as the maximum parts
per million (ppm on mass basis). These standards are: 80 ppm for toluene, 60 ppm for methanol, 108 ppm for
ethylbenzene, and 108 ppm for styrene monomer.
With respect to any distillation column that contains styrene monomer, do not exceed 145°C in that column
with more than 50 mass% styrene monomer in the bottoms stream, in order to minimize polymerization of
the styrene monomer (i.e., solid formation of a polymer).
Flowsheet Economic Analysis
For a preliminary design study, the economic viability of manufacturing styrene monomer from
toluene and methanol can be determined by maximizing the net profit. The net yearly profit for the styrene
flowsheet can be approximated as follows:
net
profit
=
product
sales
+
byproduct
sales
+
fuel
credit
−
cost of
raw materials
−
annualized
capital cost
−
utility
costs
where each term is $ per year. The annualized capital cost for purchasing the equipment is estimated to be
(product sales + byproduct sales)/6 in $/yr. The other terms in this net profit equation can be determined
once the material and energy requirements for the above flowsheet are calculated for a specific reactor inlet
temperature using Aspen HYSYS®. Appendix M provides details on how to determine these other terms.
In Chapter 4 of this HYSYS manual, your team members will determine their net profit for their
assigned reactor inlet temperature. Your team will then plot sales (which include the fuel credit), costs, and
net profit versus the reactor inlet temperatures to determine that operating temperature that maximizes the
net profit. In this plot, you can expect to see the net profit curve exhibit a maximum value either within
the range of reactor temperatures or at an end point of the range. That point at which the maximum profit
occurs is the “best” temperature at which to operate the adiabatic reactor. Although economics are
important in determining the viability of a process flowsheet, other factors such as efficiency, health,
safety, reliability, aesthetics, ethics, and social impact are also important. You will study these other
factors in the senior-level process engineering course of the chemical engineering curriculum. For this
introductory course on chemical engineering, our focus for flowsheet viability will just be the net profit.
For the economic analysis of other engineering problems, minimizing the costs can be the objective.
Click here to review a simple tank problem that is based on minimizing costs.
Chapter 1
Page 1-7
For the preliminary economic analysis of the above process flowsheet to make styrene monomer
from toluene and methanol, the economic data in the table below are to be used to determine the net profit.
These economic data are tentative and appropriate only for a preliminary economic evaluation.
Raw Materials:
Methanol
$ 350/metric ton =
Toluene
$ 650/metric ton =
Product Values:
Crude Styrene Product
$1,540/metric ton =
Ethylbenzene Byproduct
$ 970/metric ton =
Credits:
Off-gas from three-phase separator
$ 8.53/M kilojoules
Utilities:
Natural Gas*
$12.10/M kilojoules
Steam from HP Steam:
6 bar, 158.8°C, saturated vapor
$30.29/K kilograms
$30.59/K kilograms
$30.97/K kilograms
Cooling Water
$ 0.03/K liters
Average inlet temperature
31°C
Average outlet temperature
41°C maximum
Electricity
$0.06/kW·h
*Assume 90% efficiency for the fired heater fuel usage.
The symbols K and M mean a thousand and million, respectively.
$0.35/kg
$0.65/kg
$1.54/kg
$0.97/kg
All of these data are for 2009 and apply to the Houston Gulf Coast area, where the plant will be located.
Flowsheet Development Strategy
Using the above assumptions and data, you and your teammates will be analyzing the above
styrene monomer flowsheet extensively in this introductory course as a semester-long project using the
Aspen HYSYS® process simulator. The goal of the project is for your team to determine the “best” process
requirements for material, equilibrium, and energy based on economics. This project is designed as an
independent study to sharpen your life-long learning skills. The chapters in this HYSYS manual will guide
you as you do this independent study.
The development of any process flowsheet is a very complex activity. Engineers handle
complexity by a divide and conquer strategy. In this HYSYS manual, Chapters 2, 3, and 4 are the sub-parts
of a strategy to develop the flowsheet for the production of styrene monomer from toluene and methanol.
These chapters accomplish the following:
•
Chapter 2 introduces you to the Aspen HYSYS® process simulation software, Version
8.3. Tutorials 2.1 to 2.6 in this chapter provide you with detailed instructions on how
to use HYSYS in the Windows environment, in order to do some standard process
simulation calculations in the introductory chemical engineering course. Tutorials 2.7
to 2.10 are intended for the senior-level design course in the chemical engineering
curriculum.
•
Chapter 3 provides five assignments in which you can develop your abilities and
confidence to simulate individual process units using Aspen HYSYS®. These
Chapter 1
Page 1-8
assignments focus on a process stream, pump, heater, mixer/tee, and reactor. Once
you’ve completed the assignments, you will have a mathematical understanding of
how HYSYS does its calculations for each process unit.
•
Chapter 4 contains seven assignments to develop the styrene monomer flowsheet.
Each member of your team will begin with the reactor section at an assigned operating
temperature and increase the complexity of the flowsheet by adding sections, one by
one, until the complete flowsheet is simulated in Aspen HYSYS®. While doing these
assignments, you will learn about some heuristic rules that provide guidance on
selecting process unit operations in the flowsheet and determining their operating
conditions.
You will complete the tutorials of Chapter 2 and the assignments of Chapters 3 and 4 over a 14-week
period. Once these tasks are completed, you will have finished the first step in a feasibility study on the
production of styrene monomer from toluene and methanol; that is, the development of its flowsheet and
processing requirements for material and energy.
While completing the tasks of Chapters 2, 3, and 4, you will need to access additional information,
which you can find in the appendices. Appendices B to L contain simulation modules for various
continuous process unit operations. Each appendix or module provides a mathematical explanation of how
Aspen HYSYS does its calculations for that continuous process unit. A module includes a module
description, a conceptual model, model assumptions, a mathematical model, example mathematical
algorithms, and several HYSYS simulation algorithms. You will need to consult these appendices while
doing your assigned tasks in Chapters 3 and 4.
Your Professional Challenge
As a new provisional engineer in BEEF, Inc., your professional challenge of developing the styrene
monomer flowsheet using Aspen HYSYS® is formable. To complete this challenge, you must develop
your critical thinking skills as a problem solver and document your progress in your technical journal. As
reported by Halpern [1989, pp. 29-30], critical thinking has two essential components—the mental skills as
well as a healthy attitude. As a provisional engineer, you must develop your critical thinking skills by
learning the strategies to apply the CinChE problem-solving methodology [Hanyak, 2011] and to simulate
the process requirements for a chemical process flowsheet using Aspen HYSYS®. Also, you must develop
a critical thinking attitude; that is, you must be willing to plan, be flexible in your thinking, be persistent
and not lazy, and be willing to self-correct. You cannot become a critical problem solver without this sort
of attitude.
As reported further by Halpern [1989, p. xvii], developing your critical thinking skills requires you
to be an active learner that completes reading assignments on time, drafts segments of a problem solution in
a timely manner, raises questions when needed, documents the solution in a professional manner, and
enjoys what you are doing. You begin your journey in applying the self-paced materials in this HYSYS
manual. So, please get comfortable, prepare for some hard work, and enjoy this instructional manual on the
Aspen HYSYS® simulator. It should be a cinch!
BEEF, Inc. hired you as a new employee, because you possess the talent to become a critical
problem solver and professional documenter. Welcome to our company, and good luck in your team's
development of the styrene monomer flowsheet. Remember our company’s two mottos, “Engineering is
10% Inspiration and 90% Perspiration” and “Results not Excuses.”
Chapter 2
HYSYS Simulation Tutorials
Chapter 2
HYSYS Simulation Tutorials
HYSYS Simulation Tutorial 2.1
Chapter 2
Page 2-1
Process Flowsheet Overview
As stated in Chapter 1, a fundamental aspect of chemical engineering is the design of chemical
processes. A chemical process transforms raw materials into products through a series of process units
connected by process streams. A process unit or unit operation is equipment that physically and/or
chemically changes the chemical compounds passing through it. Increasing temperature, decreasing
pressure, and mixing are some examples of physical changes, while chemical reactions cause changes in
chemical compounds. Process units are connected by material process streams that carry the chemical
compounds at a certain process state—temperature, pressure, flow rate, and composition. Energy streams
connected to process units supply the needed energy for an operation or remove energy released in an
operation. A schematic diagram called a process flow diagram (PFD) and often referred to as a flowsheet
represents a chemical process. A flowsheet shows all process units and streams and how they are
connected, as illustrated in Figure 2.1 below.
25°C
3095 kPa
330 kgmol/h
64.8 mol% benzene
33.5 mol% propylene
1.7 mol% propane
0.0 mol% cumene
Q=?
S1
E1
heater
Q=?
S2
350°C
3075 kPa
R1
reactor
S3
350°C
3025 kPa
Figure 2.1. A Simple Process Flowsheet
The arrow lines labeled S1, S2, and S3 are material streams, while the other two arrow lines are energy
streams. The two circles labeled E1 and R1 are process units. For the flowsheet in Figure 2.1, the
simulation problem is “what heat duty in kJ/h is required to raise the temperature of Stream S1 from 25 to
350°C” and “how much energy in kJ/h is required to operate the reactor at an isothermal condition (i.e., at
constant temperature)”?
A simulation of a chemical process does the material and energy balances on all of the process
units. This information can then be used to see how to manipulate the process to maximize net profit,
maximize product rate, minimize energy use, etc. Aspen HYSYS® is a computer program that simulates
chemical processes. Using a computer for a process simulation takes a fraction of the time it takes to do it
by hand. The speed of a computer simulation allows the user to observe quickly the effect of changes in a
simulation. For example, using HYSYS, you can easily compare the amount of product produced using
different ratios of starting materials. Doing this comparison with hand calculations would be a long and
tedious task and subject to human calculation errors.
In this chapter, you will learn how to use HYSYS within the Windows 7 operating system to do
some process simulation calculations. You will also gain a better understanding of some chemical process
units and how their material and energy balances are solved. This chapter presents ten tutorials to
introduce you to steady-state process simulation. They are: (1) tutorial conventions, (2) introduction to the
HYSYS interface, (3) simulation file creation, (4) heater and case study, (5) conversion reactor and
reactions, (6) process flow diagram (PFD) fundamentals, (7) Gibbs equilibrium reactor, (8) kinetic model in
a plug flow reactor, (9) HYSYS printing capabilities, and (10) HYSYS spreadsheet programming.
Tutorials 1 to 6 are designed to be used in the introductory course on chemical engineering, often called the
stoichiometry or material and energy balance course. Tutorials 7 to 10 are intended for the senior-level
process engineering or design course.
Chapter 2
Page 2-2
Tutorial Conventions
Since HYSYS is totally interactive, it provides virtually unlimited flexibility in solving any
simulation problem. Please keep in mind that the approaches used in solving each example problem
presented in this tutorial chapter may only be one of many approaches. You should feel free to explore
other alternatives by consulting the “Help” facility in the Aspen HYSYS® software.
This tutorial presents general convention adopted for this chapter. It focuses on terminology used
to describe mouse actions and on formatting conventions for text in this chapter. The tutorial also presents
general comments on interactive process modeling the HYSYS way. Finally, you will initialize HYSYS
for your use at your university.
A. Keywords for Mouse Actions
As you read through various procedures in this HYSYS manual, you will be given instructions on
performing specific functions or commands. Instead of repeating certain phrases for mouse instructions,
we will use a keyword to imply a longer instructional phrase:
•
The keywords select, choose, pick, press, or click mean to position the cursor on the object
of interest, and press the primary mouse button once.
•
The keyword double-click means to position the cursor on the object of interest, and press
the primary mouse button twice quickly in succession.
•
The phrase click and drag means to position the cursor on the object of interest, press and
hold the primary mouse button, move the cursor to a new location, and release the primary
mouse button.
•
The keyword inspect means to position the cursor on the object of interest, press the
secondary mouse button once, and then select an option in the popup menu.
•
The keyword enter means to position the cursor in an input cell, press the primary mouse
button once, type the required information, and then press the <Enter> key on the
keyboard.
For a standard two-button mouse, the primary mouse button is on the left, while the secondary one is on the
right, provided you have not changed the mouse settings within the Windows 7 operating system.
B. Text Formatting
A number of text formatting conventions are also used throughout this chapter. They help to
quickly identify menu commands, buttons, keys on the keyboard, windows, pages, areas within windows,
radio buttons and check boxes, material and energy stream names, unit operation names, and HYSYS unit
operation types. These conventions are as follows:
Chapter 2
•
When you are asked to invoke a HYSYS menu command, which is found in the ribbon
panel at the top of the HYSYS desktop interface, the command is identified in this manual
by bold lettering. For example, File indicates the File menu tab, while Home/Units Set
means the Units Sets option within the Home menu ribbon.
•
When you are asked to press a HYSYS button, the button is identified by bold, italicized
lettering. For example, OK identifies the OK button within a particular window (i.e., a
viewing area on the screen) or Simulation identifies the Simulation button at the bottom
portion of the navigation pane.
•
When you are asked to press a key or keys to perform a certain function, keyboard
commands are identified by bold lettering, enclosed by angle brackets. For example, <F1>
identifies the F1 key on the keyboard. A combination of keys is to be pressed
simultaneously, like <CTRL><Alt><Delete>.
•
The name of a HYSYS window is indicated by bold lettering; e.g., Simulation Options or
Workbook. Two types of windows exist—floating and tabbed.
Page 2-3
A floating window appears on top of the HYSYS desktop, and it has the traditional buttons of
minimize, maximize, and close (━, □, and ×) at the top right corner of the window. A tabbed
window appears in the workspace panel of the HYSYS desktop, and its tabbed name has a
close button (×) to the right of that name.
•
Most of the HYSYS windows (whether floating or tabbed) will contain tabbed views of
information called pages. For example, the notation of Workbook/Material Streams
means the Material Streams tab in the Workbook window for viewing an informational
page about the process conditions of a set of material streams. The notation of
Design/Parameters means the Parameters option within the Design tab in the currentlyvisible window for viewing an informational page about the design parameters of a unit
operation.
•
The name of an area or section within a window is identified with bold text or quoted
regular text; e.g., the Tool Tips area or the “Unit Set Name” cell.
•
The name of Radio Buttons and Check Boxes are identified by bold lettering; e.g. User
Supplied or Show Tool tips.
•
Material and energy stream names are identified by bold lettering; e.g., S1, Column Feed,
and Condenser Duty.
•
Unit operation names are identified by bold lettering; e.g., Flash Separator or
Atmospheric Tower.
Note that blank spaces are acceptable in the names of streams and unit operations.
•
HYSYS unit operation types are identified by bold, uppercase lettering; e.g., HEAT
EXCHANGER, SEPARATOR, and DISTILLATION COLUMN.
Chapter 2
•
Page 2-4
When you are asked to provide keyboard input, it will be indicated by bold lettering; e.g.,
“Enter 100 for the stream temperature”; that is, click in the temperature cell, type 100 in it
and hit the <Enter> key.
C. Interactive Process Modeling
The role of process simulation in this instructional manual is to improve your chemical process
understanding so that you can make the best process decision. A flowsheet solution in the Aspen HYSYS
system is an interactive simulation, unlike the Aspen PLUS system which is a batch simulation. The
HYSYS solution not only makes the most efficient use of your simulation time, but by building the process
model interactively—with immediate access to results—you gain the most complete understanding of your
process simulation.
The HYSYS software uses the power of Object-Oriented Design, together with an Event-Driven
Graphical Environment, to deliver a completely interactive simulation environment where:
•
calculations begin automatically whenever you supply new information, and
•
access to the information you need is in no way restricted.
At any time, even as calculations are proceeding, you can access information from any location in HYSYS.
Each location is always instantly updated with the most current information, whether specified by you or
calculated by HYSYS. This interactive calculation environment is similar to what occurs in a spreadsheet
program like Microsoft Excel. In an Aspen PLUS batch simulation, the process information is placed in an
input file, that file is then submitted for processing to the process simulator, the results from the simulation
are sent to a file, and then the results file is viewed to observe any errors or the calculated results. If errors
have occurred or the calculated results are not reasonable, then the batch simulation must be restarted by
updating the input file. Aspen Plus® is recommended for chemicals, polymer, and applications involving
solids, while Aspen HYSYS® is recommended for refining, oil, and liquid/gas/fluid applications.
Given the power and flexibility designed into HYSYS, many ways exist to accomplish the same
task. The tutorials of this chapter have been designed to show you one way to do each HYSYS task,
primarily for simplicity and speed. Other ways do exist, and you can consult the Help facility in the Aspen
HYSYS® software to investigate those ways.
D. HYSYS at Your University
Before you proceed to learn how to do process simulations, you need to configure some HYSYS
preferences and save them as a file for later use. To configure the HYSYS software, proceed as follows:
1. Press keys <CTRL><Alt><Delete> and then
login using your account name and password.
To access the Windows 7 desktop on a computer
that is connected to the network at your university.
Click the yellow Windows Explorer icon in
the bottom taskbar of the Windows 7 desktop.
To display the Favorites, Libraries, and Computer
resources available on your logged-into computer.
Under Computer resources, double-click your
account name and then double-click on your
To open your private folder on the network file
server at your university. At Bucknell University,
Chapter 2
Page 2-5
private area.
your private area is in partition (\\netspace)(U:).
Inspect your private folder [i.e., position the cursor
To create a new folder in your private area on the
network file server at your university. You will
use your private aspen_hysys folder to store your
copy of the condensed HYSYS manual and your
HYSYS preferences for later use in this manual.
in the folder and press the secondary (usually right) mouse
button once]. Select the New/Folder option and
name your new folder aspen_hysys.
Click the × on the Windows Explorer window
(i.e., the close button in the upper-right corner).
2. Open a web browser like Internet Explorer,
Firefox, or Safari and access the electronic
condensed version of this HYSYS manual.
Note that 
Select the Save a copy button appearing near
the bottom of the browser window, navigate to
your private aspen_hysys folder, and click the
Save button in the Save As window.
Note that 
To close it and view the Windows 7 desktop, often
called the computer desktop.
See the Preface section in this HYSYS manual to
obtain the web address for the electronic version,
which you must type into the web browser. You
may want to bookmark this web address.
This web address opens the electronic HYSYS
manual in the browser window. This electronic
manual is a condensed version, because it contains
mostly those pages with web links that appear in
your purchased HYSYS manual.
To store the file a_blueHYSYS.pdf for later use.
If the Adobe Reader button bar does not appear,
move the cursor near the bottom of the window.
In your purchased HYSYS manual, the phrase
“electronic HSYSY manual” will always mean the
file a_blueHYSYS.pdf. This file is a secured
Adobe Reader document that you cannot print,
copy its content, or extract pages; however, you
can access its web links.
Access the Tutorial 2.2 bookmark through the
Adobe Reader button bar and then scroll.
To find the content of this page in the electronic
HYSYS manual.
Click here to download the image file
beef_logo_256.bmp.
To fetch the logo for the Bison Engineering and
Evaluation Firm; that is, BEEF, Inc.
Select the Save button in the File Download
window. Then, navigate to your private
aspen_hysys folder and click the Save button
in the Save As window. Click the Close button
to exit the Download Complete window.
To store a copy of our company’s logo image
(which has been pre-made for you) into your private
aspen_hysys folder on the network file server at
your university.
Note that 
Click the × on the Web Browser window
If the Paint program opens instead of the File
Download window, select the File/Save As...
option, navigate to your private aspen_hysys
folder and click the Save button in the Save As
window. Then, select the File/Exit option to close
the Paint program.
To close it and view the Windows 7 desktop, often
called the computer desktop.
Chapter 2
Page 2-10
Introduction to the HYSYS Interface
You will download the existing file t2.02_intro.hsc and then conduct a process simulation in
HYSYS using that file. This HYSYS file simulates a material stream containing benzene, propylene,
propane, and cumene. It also uses the Peng-Robinson-Stryjeck-Vera (PRSV) fluid package to calculate the
thermophysical properties of the stream, such as mass density, molar volume, molar enthalpy, thermal
conductivity, viscosity, and surface tension. The conceptual diagram for this stream is:
TS1 = 25 C
PS1 = 175 kPa
nS1 = 200 kgmol / h
zS1, BZ = 0.500
S1
zS1, PY = 0.015
zS1, PR = 0.015
zS1,CU = 0.470
The process state of Stream S1 is its temperature, pressure, flow rate, and composition (in this case mole
fractions). The material state of Stream S1 is just its temperature, pressure, and composition. Knowing
the material state, many intensive properties of the stream can be determined by HYSYS, such as mass
density, molar volume, molar enthalpy, surface tension, and viscosity. Process stream states are used to
determine the material and energy requirements for process unit operations found in a process flow diagram
(or flowsheet). Note that the process state is the material state plus the flow rate.
You will practice HYSYS navigation fundamentals and some basic HYSYS capabilities in nine sections—
retrieve a pre-defined simulation file, open a pre-defined simulation file in HYSYS, investigate the
navigation pane, manipulate stream specifications, change global preferences, add variables to the
workbook, add a second fluid package, program a spreadsheet operation, document your simulation
session, and close the simulation case. To proceed, you must have completed the tasks in Tutorial 2.1.
A. Retrieve a pre-defined simulation file.
A HYSYS file has been created for you to start the simulation. It is called t2.02_intro.hsc.
This section explains how to download this pre-defined simulation file, and then save it to
either the Windows desktop on your logged-in computer or your private area on the
network file server at your university. Proceed as follows:
1. Select the yellow Windows Explorer button,
navigate to your private aspen_hysys folder,
and double-click on the electronic HYSYS
manual; that is, the file a_blueHYSYS.pdf.
Click here to download the simulation file
t2.02_intro.hsc and then select the Save button
in the File Download window.
2. Navigate to a folder in your private area on the
network file server at your university.
or
To open this file with the Adobe Reader program.
Access the Tutorial 2.2 bookmark in this electronic
manual and scroll to find the content of this page.
To begin the process of retrieving the pre-defined
HYSYS file for this tutorial simulation.
To store the simulation in one of your private
folders as a file on the network file server.
or
Chapter 2
Page 2-30
Simulation File Creation
In Tutorial 2.2 for the “Introduction to the HYSYS Interface,” you practiced basic HYSYS skills
using an existing simulation file t2.02_intro.hsc. Now you will learn how to create and save a simulation
file similar to t2.02_intro.hsc. The creation of this file is divided into eight sectionsstart the HYSYS
program, create a simulation basis, find component physical properties for cumene, create a process stream,
copy and delete a process stream, specify alternative stream conditions, document your simulation session,
and close the simulation case. To proceed, you must be familiar with the material in Tutorial 2.2.
A. Start the HYSYS program.
After you start the HYSYS program, you need to complete a task before you begin your
simulation work. That is, you must load your default HYSYS preferences to override the
global preference settings last stored in the computer user area for your login account.
Proceed as follows:
1. Choose Aspen HYSYS thru the Start menu on
the Windows desktop.
To access the Aspen HYSYS process simulation
program.
Click the × button in the tab name area of the
aspenONE Exchange window.
To close it and view the Start Page window. This
closed window will not be used in any tutorials.
Click the middle Maximize Window icon 
in the upper-right part of the HYSYS desktop.
If necessary, to expand the HYSYS desktop
window to fit the full area of the monitor screen.
Click the Message Panel button in the Quick
Access Tool Bar panel.
To close the Message panel near the bottom of the
HYSYS desktop for now.
2. Choose the File menu in the ribbon panel and
click the Options button at the lower right.
To open the Options window with its preference
categories listed vertically in the left column.
Click the Load Preference Set … button in the
lower left of the Options window.
To begin the process of loading your default
preferences to override the global preferences in
the HYSYS program.
Navigate to your private aspen_hysys folder
on the network file server at your university.
To locate the folder containing your default
preferences stored in file Aspen HYSYS V8 3.prf,
Double-click on the file Aspen HYSYS V8 3,
or
Select this file and click the Open button.
To load your default preferences into the HYSYS
program on the computer you are using.
3. Select the Units of Measure category in the
left column of the Options window.
Note that 
To view that my-fps is the “Unit Set Name” in the
Available Unit Sets area. If it is not, then select it.
The my-fps units set was cloned from the Field
units set in Tutorial 2.2.
Click Delete in the Available Units Sets area.
To delete the my-fps set of units, if it is available.
Select SI in the Available Unit Sets area.
To make it the chosen unit set for this session.
Chapter 2
Page 2-41
where temperature is calculated knowing either molar enthalpy or molar entropy plus
pressure and composition. How does HYSYS solve for temperature in the tmixH equation?
The mathematical algorithm to solve for the temperature of the mixture is as follows:
TS 1 = tmixH  Hˆ S 1 , PS 1 , Z S 1 
1. ITERATE TS 1 in
Hˆ S′1 = hmix [TS 1 , PS 1 , Z S 1 ]
UNTIL
calculated Hˆ S′ 1 = specified Hˆ S 1
Thus, HYSYS iterates on the temperature (i.e., guesses values for it) until the calculated
molar enthalpy is close in value to the specified molar enthalpy. A similar mathematical
algorithm in HYSYS exists for the tmixS equation, as follows:
TS 1 = tmixS  SˆS 1 , PS 1 , Z S 1 
1. ITERATE TS 1 in
SˆS′1 = hmix [TS 1 , PS 1 , Z S 1 ]
UNTIL
calculated SˆS′ 1 = specified SˆS 1
This section simulates the tmixH and tmixS functions in HYSYS by replicating an existing
process stream using the pre-defined file t2.03_replica.hsc. Proceed as follows:
1. Choose File/Close Case/Close Case in the
menu ribbon, and then click the No button.
or
Type <CTRL-J> and then click the No button.
To close the current simulation case without
saving it as a HYSYS “.hsc” file.
t2.03_replica.hsc and then select the Save
button in the File Download window.
HYSYS file for simulating the tmixH and tmixS
functions.
Navigate to a folder in your private area on the
or
Select the computer’s Desktop.
or
To save the file on the Windows computer.
Note that 
Click the Save button, and then click the Close
If you used the Windows desktop, you can drag
the HYSYS file from there to your private folder
on the network file server for permanent storage,
after you have finished your simulation work.
To save your t2.03_replica.hsc simulation file and
Chapter 2
Page 2-47
Heater and Case Study
In Tutorials 2.2 and 2.3, you conducted a HYSYS simulation on a single process stream that
contained benzene, propylene, propane, and cumene. In this tutorial, you will add a heater unit operation to
the simulation and then conduct a case study analysis on that heater. You will begin with the existing file
named t2.04_heat.hsc. The pre-defined simulation in this file is set for the Peng-Robinson-Stryjeck-Vera
(PRSV) fluid package with four chemical components and a liquid process stream, named S1.
The process state of Stream S1 is given below in the conceptual diagram for the heater. Using HYSYS, you
will determine what heat duty ( Q E1 in kJ/h) is required to heat Stream S1 to a saturated vapor at 162 kPa.
V f , S1 = ?
Vf ,S 2 = 1.0
TS1 = 25 C

PS1 = 175 kPa
nS1 = 200 kgmol / h
TS 2 = ?
Q E1 = ?
S1
zS1, BZ = 0.500
E1
heater
S2
PS 2 = 162 kPa
nS 2 = ?
zS 2, BZ = ?
zS1, PY = 0.015
zS 2, PY = ?
zS1, PR = 0.015
zS 2, PR = ?
zS1,CU = 0.470
zS 2,CU = ?
Then you will perform a case study to observe the heat duty-temperature profile for this heater operation.
This tutorial is divided into seven sections—retrieve a pre-defined simulation file, open a pre-defined
simulation file in HYSYS, add a heater unit operation, specify the heater outlet condition, perform a case
study, document your simulation session, and close the simulation case. To proceed, you must be familiar
with the material in Tutorials 2.2 and 2.3.
A HYSYS file has been created for you to start the simulation. It is called t2.04_heat.hsc.
t2.04_heat.hsc and then select the Save button
or
or
Chapter 2
Page 2-60
Conversion Reactor and Reactions
In Tutorial 2.4, you conducted a HYSYS simulation on heating a process stream that contained
benzene, propylene (i.e., propene), propane, and cumene. In this tutorial, you will add a reactor unit
operation to the simulation. You will begin with the existing file named t2.05_conv.hsc. The pre-defined
simulation in this file is set for the Peng-Robinson-Stryjeck-Vera (PRSV) fluid package with four chemical
components and a heater process unit, named E1.
Reaction information (i.e., stoichiometric equations with their models) can be attached to certain HYSYS
process unit operations to simulate the reaction of chemical compounds. Reactions can be specified in
HYSYS by various models—such as conversion, equilibrium, or kinetic models. This tutorial shows you
how to add a conversion reactor and the needed reaction information for the isothermal, vapor-phase
reaction of propene and benzene to form cumene, as expressed by the following stoichiometric equation:
C3H6
propene
+
C6H6
→
benzene
C9H12
cumene
Propane is an inert component, since it does not participate in the chemical reaction. In the conceptual
model below, you will determine what heat duty ( Q R1 in kJ/h) is required to operate the isothermal reactor
R1; that is, how much heat is withdrawn from the exothermic reaction, so that the inlet (S2) and outlet (S3)
streams are at the same temperature.
TS1 =
25  C
PS1 = 3095 kPa
n S1 = 329.6 kgmol / h
z S1, BZ = 0.648
z S1, PY = 0.335
Q E1 = ?
S1
TS 3 = 350  C
Q R1 = ?
E1
heater
z S1, PR = 0.017
z S1,CU = 0.0
S2
TS 2 = 350  C
PS 2 = 3075 kPa
R1
reactor
S3
PS 3 = 3025 kPa
n S 3 = ?
z S 3, BZ = ?
z S 3, PY = ?
z S 3, PR = ?
z S 3,CU = ?
The molar conversion of propene for reactor R1 (i.e., amount reacted divided by the amount fed) is eighty-three
percent for a specific catalyst. This tutorial is divided into seven sections—retrieve a pre-defined
simulation file, open a pre-defined simulation file in HYSYS, add a reaction to the fluid package, add a
reactor to the flowsheet, specify the reactor outlet conditions, document your simulation session, and close
the simulation case. To proceed, you must be familiar with the material in Tutorial 2.4.
A HYSYS file has been created for you to start the simulation. It is called t2.05_conv.hsc.
Chapter 2
t2.05_conv.hsc and then select the Save button
or
Note that 
Page 2-61
or
button, if necessary.
To save your t2.05_conv.hsc simulation file and
exit the Download complete window.
Click the × on the Adobe Reader window
To close it and view the Windows Explorer
window.
Click the × on the Windows Explorer window
To close it and view the computer desktop.
B. Open a pre-defined simulation file in HYSYS.
After you start the HYSYS program, you need to complete two tasks before you begin your
simulation work. First, you must load your default HYSYS preferences to override the
global preference settings last stored in the computer user area for your login account.
Second, you must open the pre-defined simulation file. Proceed as follows:
1. Choose Aspen HYSYS thru the Start menu on
the Windows desktop.
To access the Aspen HYSYS process simulation
program.
Click the × button in the tab name area of the
aspenONE Exchange window.
To close it and view the Start Page window. This
closed window will not be used in any tutorials.
Click the middle Maximize Window icon 
in the upper-right part of the HYSYS desktop.
If necessary, to expand the HYSYS desktop
window to fit the full area of the monitor screen.
Click the Message Panel button in the Quick
Access Tool Bar panel.
To close the Messages panel near the bottom of
the HYSYS desktop for now.
2. Choose the File menu in the ribbon panel and
click the Options button at the lower right.
To open the Options window with its preference
categories listed vertically in the left column.
Click the Load Preference Set button in the
lower left of the Options window.
To begin the process of loading your default
preferences to override the global preferences in
the HYSYS program.
Navigate to your private aspen_hysys folder
To locate the folder containing your default
Chapter 2
PFD Manipulation Tools
Page 2-73
Please consult the errata file for an update to Pages 2-88 to 2-89. To access
this file, change "a_blue" to "a_errata" in the HYSYS v8.3 manual web link.
The focus of this tutorial is the HYSYS Process Flow Diagram (PFD). You can use the PFD to
satisfy a number of functions while doing a process simulation. In addition to a graphical representation,
you can build a flowsheet within the PFD using the mouse to install and connect objects. A full set of
manipulation tools is associated with the PFD to allow you to reposition process streams and operations,
resize icons, reroute streams, and create documentation text. All of these tools are designed to simplify
your development of a clear and concise graphical process representation. You can use these tools to
prepare your documentation for your solutions to the assignments in Chapters 3 and 4.
In this tutorial, you will learn how to use effectively some of the PFD manipulation tools. You will
begin with the existing file named t2.06_pfdtools.hsc. The pre-defined simulation in this file is set for the
Peng-Robinson-Stryjeck-Vera (PRSV) fluid package with four chemical components (benzene, propylene,
propane, and cumene), a heater process unit, named E1, and a conversion reactor unit, named R1. The reactor
converts propylene and benzene to cumene with propane acting as an inert compound.
This tutorial is divided into twelve sections—retrieve a pre-defined simulation file, open a predefined simulation file in HYSYS, zoom flowsheet in and out, orient some PFD icons, move some icon
labels, view some operating conditions, add some documentation text, generate some property diagrams,
connect and disconnect PFD objects, copy a PFD to a Word document, document your simulation session,
and close the simulation case. To proceed, you must be familiar with the material in Tutorials 2.4 and 2.5.
A HYSYS file has been created for you to start the simulation. It is called
t2.06_pfdtools.hsc. This section explains how to download this pre-defined simulation
file, and then save it to either the Windows desktop on your logged-in computer or your
private area on the network file server at your university. Proceed as follows:
t2.06_pfdtools.hsc and then select the Save
or
Note that 
or
To save your t2.06_pfdtools.hsc simulation file
and exit the Download complete window.
Chapter 2
Page 2-92
Gibbs Equilibrium Reactor
In Tutorial 2.6, you conducted a HYSYS simulation on a flowsheet that contained a heater and an
isothermal reactor that had benzene, propylene, propane, and cumene flowing through them. In Tutorial
2.5, you learned how to define a conversion reaction set for the following stoichiometric equation:
C3H6
+
propene
C6H6
benzene
→
C9H12
cumene
You also associated this reaction set with a fluid package and attached it to a conversion reactor unit. Your
HYSYS simulation of this reactor determined the heat removal needed to maintain the exothermic reaction
at isothermal conditions. In this tutorial, you will add a Gibbs reactor unit to this flowsheet and compare its
simulation results to those from the conversion reactor. You will begin with the existing file named
t2.07_gibbs.hsc. The pre-defined simulation in this file is set for the Peng-Robinson-Stryjeck-Vera (PRSV)
fluid package with four chemical components and a heater process unit, named E1, and a conversion
reactor unit, named R1.
In most reactor units, catalysts are used to increase the rate of reaction; that is, the speed of
converting the reactants into products. Different catalysts when placed in a fixed reactor volume will
produce a range of conversions for the reactants; that is, some catalysts will do better than others with
respect to conversion. In Tutorials 2.5 and 2.6, you used an experimentally-determined molar conversion
for a specific catalyst at a given temperature and pressure of operation.
Thermodynamic equilibrium sets a theoretical limit on the extent to which reactants can be
converted into products, and this limit cannot be changed by catalysts. This limit is the best you could
expect, provided you could find the right catalyst to achieve it. The HYSYS Gibbs reaction model predicts
thermodynamic reaction equilibrium by minimizing the total Gibbs free energy of the reacting system, and
it does so without having to know the reaction stoichiometry, because it uses atom balances instead of mole
balances. When you add a Gibbs reactor to a HYSYS simulation, you can determine the theoretical
conversion limit for any reaction. This tutorial is divided into eight sections—retrieve a pre-defined
simulation file, open a pre-defined simulation file in HYSYS, copy a reactor feed stream, add a Gibbs
reactor to the flowsheet, specify the reactor outlet conditions, analyze results for the Gibbs equilibrium
reactor, document your simulation session, and close the simulation case. To proceed, you must be familiar
with the material in Tutorial 2.5.
A HYSYS file has been created for you to start the simulation. It is called t2.07_gibbs.hsc.
t2.07_gibbs.hsc and then select the Save button
Chapter 2
Page 2-106
Kinetic Model and a Plug Flow Reactor
In Tutorial 2.5, you conducted a HYSYS simulation on an isothermal reactor using a conversion
reaction model for the following stoichiometric equation:
C3H6
+
propene
C6H6
benzene
→
C9H12
cumene
You specified a molar propene conversion of 83%, and propane was present in the reactor feed as an inert
compound. In Tutorial 2.7, you did another simulation on the same isothermal reactor, but you used the
Gibbs reaction model to predict an equilibrium propene conversion of 99.1% for the above reaction. This
conversion represents the best you could expect with the right catalyst; it is the theoretical limit on the
propene conversion.
In this tutorial, you will again study the isothermal reaction, but you will simulate it using a plug
flow reactor with a kinetic model and then compare your results to those from Tutorials 2.5 and 2.7. An
experimentally-determined kinetic model for a particular catalyst is used to predict the behavior of a
specific reaction to changes in temperature, pressure, and concentration. You will begin with the existing
file named t2.08_kinetic.hsc. The pre-defined simulation in this file is set for the Peng-Robinson-StryjeckVera (PRSV) fluid package with four chemical components and a heater process unit, named E1, and a
conversion reactor unit, named R1.
This tutorial is divided into nine sections—retrieve a pre-defined simulation file, open a predefined simulation file in HYSYS, copy a reactor feed stream, add a plug flow reactor to the flowsheet, add
a kinetic reaction set to the fluid package, specify the reactor parameters and outlet conditions, analyze
results for the kinetic reactor, document your simulation session, and close the simulation case. To
proceed, you must be familiar with the material in Tutorials 2.5 and 2.7.
t2.08_kinetic.hsc. This section explains how to download this pre-defined simulation file,
and then save it to either the Windows desktop on your logged-in computer or your private
area on the network file server at your university. Proceed as follows:
t2.08_kinetic.hsc and then select the Save
or
Note that 
or
Chapter 2
Page 2-123
HYSYS Printing Capabilities
This tutorial shows you how to document HYSYS results by printing the process flow diagram
(PFD), informational datasheets, and customized reports. A report puts multiple datasheets into one
package, and that package can then be printed. Case study tables and plots and flowsheet imbalances on
material and energy can also be printed by HYSYS.
In this tutorial, you will document the HYSYS simulation from the “PFD Manipulation Tools” of
Tutorial 2.6. You will begin with the existing file named t2.09_reports.hsc. The pre-defined simulation in
this file is set for the Peng-Robinson-Stryjeck-Vera (PRSV) fluid package with four chemical components
(benzene, propylene, propane, and cumene) and a heater process unit, named E1, and a conversion reactor unit,
named R1. The reactor converts propylene and benzene to cumene with propane acting as an inert
compound.
This tutorial is divided into eight sections—retrieve a pre-defined simulation file, open a predefined simulation file in HYSYS, print the PFD and a process unit window, print the reactor datasheets,
print the case study plot, create a customized report, document your simulation session, and close the
simulation case. To proceed, you should be familiar with the material in Tutorial 2.6.
t2.09_report.hsc. This section explains how to download this pre-defined simulation file,
and then save it to either the Windows desktop on your logged-in computer or your private
area on the network file server at your university. Proceed as follows:
t2.09_report.hsc and then select the Save
or
Note that 
or
To save your t2.09_report.hsc simulation file and
exit the Download complete window.
Click the × on the Adobe Reader window
To close it and view the Windows Explorer
window.
Chapter 2
Page 2-132
HYSYS Spreadsheet Programming
With almost complete access to all process variables in the process flow diagram (PFD), the
spreadsheet operator is extremely powerful and has three major applications in HYSYS, as follows:
1. You can program the application of a single equation like the continuity equation, as was the
case in Tutorial 2.2, to calculate the pipe diameter for a process stream.
2. You can consolidate process information from various parts of the process flow diagram into a
spreadsheet operator. This consolidation conveniently allows you to monitor and change
process variables, as will be the case in the problems of Chapter 4 of this HYSYS manual.
3. You can provide your own mathematical model for the material and energy balances of a
process unit, because no current HYSYS process unit operator meets your modeling needs.
The third application is the focus of this tutorial. You will learn how to program the material and energy
balances to replace the HYSYS conversion reactor operator, because its current provision for temperature
dependency on molar conversions cannot represent the chemical reaction for styrene monomer from
methanol and toluene with a side reaction that forms ethylbenzene. Before we look at the HYSYS
spreadsheet implementation for this example, we need to examine its experimental reaction data and its
modeling equations for material and energy.
Based on the information in Chapter 1 of this HYSYS manual, the vapor-phase reactions to form
styrene monomer and ethylbenzene in a catalytic reactor are as follows:
Rxn 1:
C7H8
+
toluene
Rxn 2:
C7H8
toluene
CH3OH
C8H8
→
methanol
+
CH3OH
methanol
+
styrene
+
water
C8H10
→
H2O
+
ethylbenzene
H2
hydrogen
H2O
water
As a first approximation, other byproduct formation and polymerization of styrene monomer are negligible
and the catalyst does not coke or deactivate with time. The reactor is also assumed to operate adiabatically.
In a pilot-plant study, stoichiometric feed of toluene and methanol to an adiabatic reactor unit
resulted in the following experimental data for the formation of styrene monomer (the product) and
ethylbenzene (the byproduct) at a reactor inlet pressure of 400 kPa:
X - molar
conversion
Y - molar
yield
X*Y
X - X*Y
Inlet
T, °C
TL reacted
TL fed
SM formed
TL reacted
SM formed
TL fed
EB formed
TL fed
465
480
495
510
525
540
0.649
0.679
0.709
0.759
0.819
0.879
0.909
0.869
0.829
0.779
0.719
0.659
0.5899
0.5901
0.5878
0.5913
0.5889
0.5793
0.0591
0.0889
0.1212
0.1677
0.2301
0.2997
TL is toluene, SM is styrene monomer, and EB is ethylbenzene
Chapter 2
Page 2-133
An Excel version of this table is available by clicking here. Curve fitting the experimental data for the
molar conversion of toluene (X) and the molar yield of styrene monomer (Y) produces the following:
X = 0.000021429*T2 - 0.018450*T + 4.5952
(1)
Y = -0.000014286*T2 + 0.011024*T - 1.1289
(2)
where T is the reactor inlet temperature in °C. These two equations will be programmed into a spreadsheet
operator to solve the material and energy balances for the adiabatic reactor, because they cannot be
implemented in the current HYSYS unit operator for a conversion reactor. Why? The HYSYS conversion
reactor only accepts quadratic equations based on the last two columns in the above table, and these last
two columns when curve fitted against inlet temperature produce a fourth-order and second-order
polynomial, respectively. The mathematical model, variable descriptions, and mathematical algorithm that
incorporate Equations 1 and 2 are presented next, where a feed stream (F) enters the adiabatic reactor, and
an effluent stream (E) leaves that reactor.
Mathematical Model for an Adiabatic Reactor
(1)
0
n F − n E + 1R1 =
total matrial balance
(2)
0
n F ,TL − n E ,TL − 1R1 − 1R 2 =
nc -component matrial balances:
(3)
n F , ME − n E , ME
− 1R1 − 1R 2 =
0
(4)
n F , SM − n E , SM + 1R1
(5)
n F , EB − n E , EB +
(6)
n F ,WA − n E ,WA + 1R1 + 1R 2 = 0
(7)
n F , H 2 − n E , H 2 + 1R1
Eqs. ( 2 ) to ( 7 )
=
0
1R 2 =
0
0
=
(8)
n F =
n F ⋅ z F , j
,j
for j = 1, 2,  , nc
(9)
n E =
n E ⋅ z E , j
,j
for j = 1, 2,  , nc
(
X TL = n F ,TL − n E ,TL
( 10 )
( 11 )
YSM =
)
( nE ,SM − nF ,SM ) ( n
n F ,TL
F ,TL
toluene conversion
− n E ,TL )
styrene yield
2
( 12 )
X TL =0.000021429 ⋅ TF − 0.018450 ⋅ TF + 4.5952
( 13 )
YSM =
− 0.000014286 ⋅ TF + 0.011024 ⋅ TF − 1.1289
2
( 14 )
n F ⋅ Hˆ F − n E ⋅ Hˆ E =
0
( 15 )
Hˆ F = hmix [TF , PF , Z F ]
( 16 )
Hˆ E = hmix [TE , PE , Z E ]
( 17 )
∆P = PF − PE
energy balance
# vars
=
4 ⋅ nc
+
13
# eqns
=
3 ⋅ nc
+
9
DOF
=
1 ⋅ nc
+
4
Chapter 2
Page 2-134
Variable Descriptions for the Mathematical Model
Ti
is
the temperature of process Stream i, K.
Pi
is
the pressure of process Stream i, kPa.
ni
is
the bulk (or total) molar flow rate of process Stream i, kgmol/h.
ni , j
is
the bulk molar flow rate of component j in process Stream i, kgmol/h.
nc
is
the number of chemical components or compounds in the mixture.
Zi
is
the bulk mole fractions of all nc-components in Stream i.
zi , j
is
the bulk mole fraction of component j in process Stream i;
vector Z i means all elements zi ,1 , zi ,2 ,  , zi , nc .
R1
is
the rate (or extent) of the styrene monomer reaction (i.e., first reaction), kg-rxn/h.
R 2
is
the rate (or extent) of the ethylbenzene reaction (i.e., second reaction), kg-rxn/h.
X TL
is
the molar conversion of toluene (moles of toluene reacted per moles of toluene fed).
YSM
is
the molar yield of styrene (moles of styrene formed per moles of toluene reacted).
Hˆ i
∆P
is
the bulk molar enthalpy of process Stream i, kJ/kgmol.
is
the pressure drop between the inlet and exit streams, kPa.
Ψi
is
a short notation for Ti , Pi , ni , and Z i ; that is, the process state of Stream i.
Mathematical Algorithm for an Adiabatic Reactor
reactor  Ψ F , ∆P 
 Ψ
=
E

(8)
1.
nF , j ⇐
nF ⋅ z F , j
(12 )
(13 )
(10 )
2.
X TL ⇐
0.000021429 ⋅ TF2 − 0.018450 ⋅ TF + 4.5952
3.
− 0.000014286 ⋅ TF2 + 0.011024 ⋅ TF − 1.1289
4.
YSM ⇐
nE ,TL ⇐
(11)
5.
nE , SM ⇐
nF , SM + YSM ( nF ,TL − nE ,TL )
(4)
6.
⇐
nE , SM − nF , SM
(2)
7.
R1
R
2
⇐
nF ,TL − nE ,TL − R1
(1)
( 3)
8.
nE
⇐
nF + R1
9.
nE , ME ⇐
(5)
10.
nE , EB ⇐
(6)
11.
nE ,WA ⇐
( 7 ) 12. nE , H 2 ⇐
( 9 ) 13. zE , j ⇐
(17 ) 14. PE ⇐
for j = 1, 2,  , nc
nF ,TL − X TL nF ,TL
nF , ME − R1 − R 2
+ R
n
F , EB
2
nF ,WA + R1 + R 2
+ R
n
F ,H 2
1
nE , j / nE
PF − ∆P
(15 ) 15.
Hˆ F
⇐
hmix TF , PF , Z F 
(14 ) 16.
Hˆ E
⇐
nF ⋅ Hˆ F / nE
⇐
tmix  PE , Hˆ E , Z E 
(16 ) 17. TE
for j = 1, 2,  , nc
Chapter 2
Page 2-135
In the above mathematical model, the degrees of freedom are (1·nc+4), based on (4·nc+13) variables and
(3·nc+9) equations, where nc equals six for the number of chemical components in the system. The 4·nc
variables are the twelve component flow rates ( n F , j and n E , j ) and the twelve component mole fractions ( z F , j
and
z E , j ) for the feed and effluent streams. The 3·nc equations are Eqs. (2) to (7), (8), and (9) in the above
mathematical model. In the above the mathematical algorithm, the (nc+4) degrees of freedom are satisfied
by the temperature, pressure, flow rate, and nc-composition for the feed stream and the pressure drop across
the adiabatic reactor. In Step 17 of the mathematical algorithm, the tmix equation is a concise notation that
represents the following iteration on the effluent or exit temperature:
17.
ITERATE TE in
f ( TE )
(16 )
UNTIL
⇐
Hˆ E − hmix [TE , PE , Z E ]
f ( TE ) = 0
The mathematical algorithm for the adiabatic reactor described above is programmed into a
HYSYS spreadsheet operator named “CRs” with inlet Stream 10s and outlet Stream 11s, as outlined below.
HYSYS Spreadsheet for the Mathematical Algorithm of an Adiabatic Reactor
A
1
2
3
4
5
6
7
8
9
10
11
12
13
B
STREAM 10s
Vapor Fraction:
1
Temperature:
540.00 C
Pressure:
400 kPA
TL Flow Rate:
ME Flow Rate:
SM Flow Rate:
500 kgmol/h
500 kgmol/h
0 kgmol/h
EB Flow Rate:
WA Flow Rate:
H2 Flow Rate:
0 kgmol/h
0 kgmol/h
0 kgmol/h
C
D
E
CURVE-FITTED REACTOR
Pressure Drop:
70
Conversion of TL:
0.8809
mol TL reacted per mol TL feed
Yield of SM:
0.6583
mol SM per mol TL reacted
F
G
Vapor Fraction:
Temperature:
Pressure:
STREAM 11s
1
409.32 C
330 kPA
TL Flow Rate:
ME Flow Rate:
SM Flow Rate:
59.6 kgmol/h
59.6 kgmol/h
289.9 kgmol/h
0.0462
0.0462
0.2248
EB Flow Rate:
WA Flow Rate:
H2 Flow Rate:
150.5 kgmol/h
440.4 kgmol/h
289.9 kgmol/h
0. 1167
0.3415
0.2248
Total Flow Rate:
Specific Enthalpy:
1000 kgmol/h
-1.343e4 kJ/kgmol
mol TL reacted =
kg-rxn/h for SM =
440.4 kgmol/h
289.9
Total Flow Rate:
Specific Enthalpy:
1290.0 kgmol/h
-10,410 kJ/kgmol
Total Energy Flow:
-1.343e7 kJ/h
kg-rxn/h for EB =
150.5
Total Energy Flow:
-1.343e7 kJ/h
Mole Fractions:
adiabatic process
Cells B2 to B13 are imported from the process flow diagram (PFD), with Cells B3-B11 being specified and Cells B2 and B12-B13 being calculated in the PFD.
Cell D3 is the pressure drop across the adiabatic reactor. It is specified by the user in this spreadsheet named CRs.
Cell D5 = 0.000021429*b3^2 - 0.018450*b3 + 4.5952, a curve fit of the toluene fractional conversion (D5) versus inlet temperature (B3).
Cell D8 = -0.000014286*b3^2 + 0.011024*b3 - 1.1289, a curve fit of the styrene fractional yield (D8) versus inlet temperature (B3).
Cell D11 = d5*b5, is the amount of total toluene that reacts in kg-mol/h.
Cell D12 = f7-b7, is the rate (or extent) of reaction for the styrene monomer reaction in kg-rxn/h.
Cell D13 = d11-d12, is the rate (or extent) of reaction for the ethylbenzene reaction in kg-rxn/h.
Cells F2 to F3 are imported from the PFD. HYSYS calculates them once the pressure, molar enthalpy, total flow, and mole fractions of Stream 11s are set.
Cell F4 = b4-d3, is the calculated pressure for outlet Stream 11s, based on the specified pressure drop through the adiabatic reactor unit.
Cell F5
Cell F6
Cell F7
Cell F8
Cell F9
Cell F10
Cell F11
=
=
=
=
=
=
=
b5-d5*b5, is the amount of toluene entering minus the amount consumed by the styrene and ethylbenzene chemical reactions in kg-mol/h.
b6-d12-d13, is the amount of methanol entering minus the amount consumed by the styrene and ethylbenzene chemical reactions in kg-mol/h.
b7+d8*d11, is the amount of styrene entering plus the amount produced by the styrene chemical reaction in kg-mol/h.
b8+d13, is the amount of ethylbenzene entering plus the amount produced by the ethylbenzene chemical reaction in kg-mol/h.
b9+d12+d13, is the amount of water entering plus the amount produced by the styrene and ethylbenzene chemical reactions in kg-mol/h.
b10+d12, is the amount of hydrogen entering plus the amount produced by the styrene chemical reaction in kg-mol/h.
b11+d12, is the total flow rate of Stream 11s in kg-mol/h.
Cell F12 = f13/f11, is the specific enthalpy for Stream 11s in kJ/kg-mol.
Cell F13 = b13, is the energy balance for an adiabatic reactor.
Cells G5 to G10 are the calculated mole fractions for Stream 11s. For example, TL mole fraction = f5/f11, and styrene mole fraction = f7/f11.
Once Cells F4, F11, F12, and G5 to G10 are calculated in this spreadsheet named CRs, then HYSYS exports them to the PFD and then automatically calculates
the vapor fraction and temperature of Stream 11s. These two are displayed for convenience as the imported values in Cells F2 and F3 of this spreadsheet.
Chapter 2
Page 2-136
This spreadsheet implements the inlet temperature dependence on the toluene molar conversion and styrene
molar yield in Cells D5 and D8, respectively. Columns A, C, and E contain textual information solely for
documentation purposes. Column B and Cells F2 and F3 contain imported variables from the HYSYS
process flow diagram. The red values represent formula expressions from the right side of the various steps
in the mathematical algorithm. Calculated Cells F4, F11, F12, and G5 to G10 define the process state of
Stream 11s and are exported to the HYSYS process flow diagram. In summary, this HYSYS spreadsheet
completes the material and energy balances for the adiabatic reactor unit.
In the remainder of this tutorial, you will load an existing file named t2.10_spreadsheet.hsc,
examine its process flow diagram, and complete its spreadsheet operator. The pre-defined simulation in
this file is set for the Peng-Robinson-Stryjeck-Vera (PRSV) fluid package with six chemical components
(toluene, methanol, styrene monomer, ethylbenzene, water, and hydrogen), a partially-completed spreadsheet operator,
named CRs, and a conversion reactor unit, named CRc. Two chemical reactions occur simultaneously—
one converting toluene and methanol to styrene monomer and another converting toluene and methanol to
ethylbenzene. You will compare the simulation results from the spreadsheet operator to those from the
conversion reactor operator, in order to validate the material and energy balance calculations within the
spreadsheet operator.
The remainder of this tutorial is divided into seven sections—retrieve a pre-defined simulation file,
open a pre-defined simulation file in HYSYS, examine the process flow diagram, complete the spreadsheet
operator, compare the simulation results, document your simulation session, and close the simulation case.
To proceed, you must be familiar with the material in Tutorials 2.2, 2.3, and 2.5.
t2.10_spreadsheet.hsc. This section explains how to download this pre-defined simulation
file, and then save it to either the Windows desktop on your logged-in computer or your
private area on the network file server at your university. Proceed as follows:
t2.10_spreadsheet.hsc and then select the Save
or
Note that 
Access the Tutorial 2.10 bookmark in this
electronic manual and scroll to find the content of
this page.
or
To save your t2.10_spreadsheet.hsc simulation
Chapter 3
Process Unit Exercises
Chapter 3
Process Unit Exercises
Process Unit Exercises – Overview
Chapter 3
Page 3-1
This chapter provides five problem assignments to help you develop your abilities and confidence
to simulate individual process units using the Aspen HYSYS® process simulation software. Over a fiveweek period, you will have assignments that focus on finding the material and energy balance requirements
for the following individual process units:
Problem
HY.1
HY.2
HY.3
HY.4
HY.5
Description
Process Stream Simulation
Pump Simulation
Cooler Simulation
Mixer/Tee Simulation
Reactor Simulation
Each of these problems will be assigned to you by your instructor in a memorandum. A “HY” problem
contains two parts:
A. a guided HYSYS session that helps build your confidence in using the HYSYS software and
B. a simulation exercise that tests your knowledge and understanding of a HYSYS simulation.
Once you’ve completed these five assignments, you will have a mathematical understanding of how
HYSYS does its calculations for each process unit.
This chapter assumes you have completed certain tutorials found in Chapter 2. They are Tutorials
2.1 to 2.6. Each assignment in this chapter identifies those tutorials that you should complete before you
try to solve the problem.
While solving a problem, you will need to consult Appendices B, C, D, etc. in this instructional
manual for information on certain HYSYS simulation modules. Each appendix or module provides a
mathematical explanation of how HYSYS does its calculations for that process unit. A module includes the
following:
1.
2.
3.
4.
5.
6.
7.
a module description,
a conceptual model,
model assumptions,
a mathematical model,
process variable descriptions,
example mathematical algorithms, and
several HYSYS simulation algorithms.
Each assignment identifies which appendix you must consult.
In each of the five HY unit exercises, three phrases will appear: “load your preferences”, “enter
the Basis Environment”, and “return to the Simulation Environment”. The first phrase means that you use
the File/Options command to load your preferences file (Aspen HYSYS V8 3.prf) stored in your private
aspen_hysys folder on the network file server at your university. The second phrase means that you select
the Properties button in the navigation pane area to enter the basis environment. The third phrase means
that you select the Simulation button in the navigation pane area to return to the simulation environment
without being in the HOLDING mode. For the phrase “Change the … units set” in the first exercise
(HY.1), you access the File/Options command, click the “Units of Measure” category, and select Field for
the “Unit Set Name”.
Process Unit Exercises – Problem HY.1
Chapter 3
Page 3-2
HY.1 - Process Stream Simulation
The HYSYS simulation module for a process stream is fully defined in Appendix C of this
instructional manual. This process stream module contains a module description, a conceptual model,
model assumptions, a mathematical model, variable descriptions, mathematical algorithms, and some
HYSYS simulation algorithms in functional form. After you read this information about a process stream,
you are to practice the HYSYS session below and then complete the simulation exercise. You are to
provide for the simulation exercise only a printed copy of the Workbook datasheet in your technical
journal. Separately, your team is to document the answers to all questions in the simulation exercise.
A. HYSYS Session
This session will show you, in general terms, how to do a HYSYS simulation for a process stream.
It assumes you are familiar with the material in Tutorials 2.2 to 2.3 of this instructional manual. You are to
find the vapor fraction and heat flow in BTU/hr of a binary mixture of toluene and hexane at 1 atm and
100°C. This mixture is flowing at 100 kgmol/h. The stream is labeled feed and its conceptual diagram is:
TF = 100 ° C
TF = 100 ° C
1 atm
PF =
n F = 100 kgmol / h
1 atm
PF =
feed
z F ,TL = 0.7
z F ,TL = 0.7
z F , HX = 0.3
z F , HX = 0.3
Using the information above, you are to practice a HYSYS simulation by doing the following:
•
•
•
•
•
•
•
•
•
•
Click here to download file HY1.A and save it as HY1.A_xxx, where xxx are your initials.
Start the HYSYS software, load your preferences, and open your HY1.A_xxx file.
Enter the Basis Environment, complete the component list, and note the fluid package.
Return to the Simulation Environment, open the process stream, and rename it feed.
Specify its process state; that is, its temperature, pressure, flow rate, and composition.
Change the HYSYS preferences to display the “Field” units set.
Open the Workbook window using its folder icon in the Simulation navigation pane.
View the values in the Material Streams page of the Workbook window.
Note that specified values appear in blue, while calculated values appear in black.
View the Compositions and Component Flows pages in the Workbook window.
After you specify the state of the process stream, HYSYS immediately calculates all of the other properties
of that streams (such as mass flow rate, volumetric flow rate, vapor fraction, etc.) using the Soave-Redlich-Kwong
(SRK) equation of state. The answers for two of the stream properties are:
Vapor Fraction = 0.7807
Heat Flow
= -1.237e+6 BTU/h
A value for the molar vapor fraction between zero and one indicates that the process stream exists as a twophase system (vapor and liquid in equilibrium) at the specified temperature, pressure, and composition.
Chapter 3
Page 3-3
B. Simulation Exercise
What are the temperature in °F and the heat flow in BTU/hr of a process stream containing a
tertiary mixture of benzene, hexane, and toluene? The stream is at 2 atm and has a vapor fraction equal to
zero. The chemical component flows are as shown below.
Vf = 0.0
Vf = 0.0
TF =
?
TF =
?
PF =
n F =
2 atm
PF =
n F =
2 atm
?
feed
?
n F , BZ = 40 kgmol / h
n F , BZ = 40 kgmol / h
n F , HX = 70 kgmol / h
n F , HX = 70 kgmol / h
n F ,TL = 120 kgmol / h
n F ,TL = 120 kgmol / h
Using the information above, you are to complete a HYSYS simulation by doing the following:
•
•
•
•
•
Click here to download file HY1.B and save it as HY1.B_xxx, where xxx are your initials.
Start the HYSYS software, load your preferences, and open your HY1.B_xxx file.
Return to the Simulation Environment and finish the simulation for the process stream.
Print the Workbook datasheet in “Field” units for the Material Streams, Compositions,
and Component Flows pages, and then place it into your technical journal.
After all team members have independently documented this simulation exercise in their technical journal,
your team is to meet and answer all of the questions in this exercise. Click here to download a Word file,
add your team name (e.g., T2 – IGAS), and complete those questions contained within.
1. Which HYSYS simulation algorithm in Appendix C (p. C-5 or C-7) would you use to solve
the above problem? What temperature does this algorithm calculate?
2. Which assumption(s) listed in Appendix C support the fact that a process stream has
uniform properties throughout its length?
3. What steps in Mathematical Algorithm A would you use to calculate the mass fractions
from the mole fractions? Verify that HYSYS has done this calculation correctly.
4. What is the specific enthalpy of the stream in BTU/lb based on the heat flow in BTU/h and
the molar flow rate in kgmol/h?
5. What are the definitions of the dew-point temperature and bubble-point temperature?
6. How might you find the dew-point temperature of this stream? What is its value?
7. How does HYSYS calculate the bulk molar enthalpy for Vf =0.40 (see p. C-8)? Verify it.
For the team solution to the simulation exercise, your team is to document the answers to all of the
questions in the Word file that your team downloaded.
Chapter 3
Page 3-4
HY.2 - Pump Simulation
The HYSYS simulation module for a pump operation is fully defined in Appendix E of this
instructional manual. This pump module contains a module description, a conceptual model, model
assumptions, a mathematical model, variable descriptions, mathematical algorithms, and some HYSYS
simulation algorithms in functional form. After you read this information about a pump operation, you are
to practice the HYSYS session below and then complete the simulation exercise. You are to provide for
the simulation exercise only a printed copy of the HYSYS flowsheet (with a problem number, your name, and
date) and the Workbook datasheet in your technical journal. Separately, your team is to document the
answers to all questions in the simulation exercise.
A. HYSYS Session
This session will show you, in general terms, how to do a HYSYS simulation for the pump
operation. It assumes you are familiar with the material in Tutorials 2.3 to 2.4 of this instructional manual.
You are to find the power in watts to compress an equimolar mixture of n-hexane and n-octane at 25°C
from 1 atm to 4 atm. This liquid mixture is flowing at 100 lb-moles per hour. The pump is labeled P2, and
its adiabatic efficiency is 70 percent. The conceptual diagram is:
TE = ?
TI = 25 ° C
PI = 1 atm
n I = 100 lbmol / h
z I , HX = 0.5
z I ,OC = 0.5
Wa = ?
Inlet
Exit
P2
ε = 70%
PE = 4 atm
n E = ?
z E , HX = ?
z E ,OC = ?
•
•
•
•
•
Return to the Simulation Environment, open the process stream, and rename it Inlet.
•
•
•
Add a pump to the process flow diagram (PFD) and name it P2.
Connect its Inlet stream, name its Exit material stream, and name its Wa energy stream.
Specify its adiabatic efficiency to be 70% and its exit pressure to be 4 atm.
•
•
•
•
View the Compositions, Component Flows, and Energy Streams pages in the Workbook.
After you specify the state of the inlet stream, the pump efficiency, and the exit pressure, HYSYS
immediately calculates all of the other properties of the material streams (such as mass flow rate, volumetric flow
rate, vapor fraction, heat flow, etc.) using the Peng-Robinson Stryjek-Vera (PRSV) equation of state. Also,
HYSYS calculates the pump power to be:
Power = 804.4 watts = 0.8044 kW
Chapter 3
Page 3-5
Place the cursor over the Wa in the PFD to view the pump power. A positive value for the pump power
indicates that energy must be added to the process stream to increase its pressure.
What adiabatic efficiency and power in kilowatts are required to compress an equimolar mixture of
n-hexane and n-octane from 25°C and 1 atm to 40°C and 400 atm? This liquid mixture is flowing at 100
lb-moles per hour.
TE = 40 ° C
TI = 25 ° C
PI = 1 atm
n I = 100 lbmol / h
z I , HX = 0.5
z I ,OC = 0.5
Wa = ?
Inlet
Exit
P3
ε=?
PE = 400 atm
n E = ?
z E , HX =
?
z E ,OC =
?
•
•
•
•
•
Return to the Simulation Environment and finish the simulation for the pump operation.
Print the process flow diagram (PFD with a problem number, your name, and date) and the
datasheet for all pages in the Workbook, and then place them into your technical journal.
If a consistency error occurs, you forgot to delete the efficiency value. After all team members have
independently documented this simulation exercise in their technical journal, your team is to meet and
answer all of the questions in this exercise. Click here to download a Word file, add your team name (e.g.,
T1 – RGAS), and complete those questions contained within.
1. Which HYSYS pump simulation algorithm (pumpa, pumpb, etc. in Appendix E) would you use to
solve this problem? What are the given variables and their values? What are the calculated
variables and their values?
2. After you examine the process states (i.e., the temperature, pressure, flow rate, and composition) of the
inlet and exit streams, please answer the following questions. Why does the exit temperature
increase slightly? What is unique about the total molar flow rate and composition? What
equations in the math model and steps in the algorithm reflect it? What assumptions support
this uniqueness? What are the operating conditions that would invalidate each assumption?
3. What is the ideal work expressed in units of horsepower?
4. In the math algorithm, what variables are only functions of the material state (i.e., the temperature,
pressure, and composition) of the liquid?
5. What does the assumption of “adiabatic process” imply? Is this a valid assumption?
6. What is the energy relative imbalance (%RIB)? Show your calculations. The energy %RIB
equals 100*(energy flow in - energy flow out) / (energy flow in).
Chapter 3
Page 3-6
HY.3 - Heater/Cooler Simulation
The HYSYS simulation module for a heater/cooler operation is fully defined in Appendix G of this
instructional manual. This heater/cooler module contains a module description, a conceptual model, model
assumptions, a mathematical model, variable descriptions, mathematical algorithms, and HYSYS
simulation algorithms in functional form. After you read this information about a heater or cooler
operation, you are to practice the HYSYS session below for a heater and then complete the simulation
exercise for a cooler. You are to provide for the simulation exercise only a printed copy of the performance
plot for heat flow versus temperature (with a problem number, your name, and date as its title) and the
Workbook datasheet in your technical journal. Separately, your team is to document the answers to all
questions in the simulation exercise.
A. HYSYS Session
This session will show you, in general terms, how to do a HYSYS simulation for a heater and
generate a performance plot for that heater. This session assumes you are familiar with the material in
Tutorial 2.4 of this instructional manual. You are to find the duty in BTU/h needed to heat an equimolar
mixture of n-hexane and n-octane from 20°C to 200°C at a constant 2 bar. This stream is flowing at 100 lbmoles per hour. The heater is labeled H2. The conceptual diagram is:
=
TI
20 °C
PI = 2 bar
nI = 100 lbmol/h
z I , HX = 0.5
z I ,OC = 0.5
 =?
Q
Inlet
=
TE 200 °C
H2
Exit
PE =
nE =
2 bar
?
z E , HX =
?
z E ,OC =
?
•
•
•
•
•
Return to the Simulation Environment, open the process stream, and rename it as Inlet.
•
•
•
Add a heater to the process flow diagram (PFD) and name it H2.
Connect its inlet Stream Inlet, name its energy stream as Q, and name its exit stream as Exit.
Specify its pressure drop to be 0.0 bar and its exit temperature to be 200°C.
•
•
•
•
View the Compositions, Component Flows, and Energy Streams pages in the Workbook.
After you specify the state of the inlet stream, the pressure drop, and the exit temperature, HYSYS
immediately calculates all of the other properties of the two streams (such as mass flow rate, volumetric flow rate,
vapor fraction, heat flow, etc.) using the Peng-Robinson Stryjek-Vera (PRSV) equation of state. Also, HYSYS
calculates the heater duty to be:
Chapter 3
 = 3.167×106 BTU/h or 3.341×106 kJ/h
Q
Page 3-7
(place cursor over a value displayed for the Q-stream)
Since the Q-term in the energy balance for the heater operation has a positive sign in front of it, HYSYS
will always display the heat duty of a heater unit as a positive quantity.
In this session, you are to generate a plot of heat duty over the temperature range of 20°C to 200°C at
intervals of 5°C. Complete the following general tasks to generate a performance plot:
•
•
•
•
•
Open the property window of Heater H2 and select its Performance page.
Select the Setup option, set Intervals to 36, and check the Dew/Bubble Pts option.
Set Temperature, Pressure, Heat Flow, and Vapor Frac. as the only Selected Viewing Variables.
Select the Performance/Plots option and set the Y Variable to be the Heat Flow option.
Maximize the window and observe the plot of heat flow versus temperature.
You can select the Performance/Tables option to observe the bubble point of 112.8717°C (Vf =0) and the
dew point of 132.2303°C (Vf =1) for an equimolar mixture of n-hexane and n-octane at 2 bars.
Simulation Exercise
What heat duty in kJ/h is removed from an equimolar mixture of n-hexane and n-octane to cool it
at a constant 2 bars from 200°C to a saturated vapor? a saturated liquid? a sub-cooled liquid at 20°C?
What are the temperatures of the exit stream in the first two cases? This liquid mixture is flowing at 100
lb-moles per hour.
Also, generate a performance plot of the cooler duty over the temperature range of 200°C to 20°C
at intervals of 5°C. You are to observe how the cooler duty versus temperature changes within the singlephase regions (vapor and liquid) and the two-phase region (vapor-liquid equilibrium).
=
TI 200 °C
PI = 2 bar
nI = 100 lbmol/h
z I , HX = 0.5
z I ,OC = 0.5
 =?
Q
Inlet
=
TE
C2
Exit
PE =
nE =
20 °C
2 bar
?
z E , HX =
?
z E ,OC =
?
•
•
•
•
•
Return to the Simulation Environment and finish the simulation for the cooler operation.
Print the performance plot (with a problem number, your name, and date as its title) and the
datasheet for all pages in the Workbook, and then place them in your technical journal.
Since the Q-term in the energy balance for the cooler operation has a negative sign in front of it, HYSYS
will always display the heat duty of a cooler unit as a positive quantity.
Chapter 3
Page 3-8
add your team name (e.g., T4 – NoGAS), and complete those questions contained within.
1. What is the heat of condensation in kJ/kgmol to cool the equimolar mixture of n-hexane and noctane at 2 bars from the sat’d vapor to the sat’d liquid state? What is the heat of vaporization
in kJ/kgmol to heat the same mixture from the sat’d liquid to the sat’d vapor state? What can
you conclude about these two latent heat changes?
2. Which HYSYS cooler simulation algorithms in Appendix G would you use to solve for the exit
dew-point and bubble-point temperatures? To solve for the exit sub-cooled temperature of
20°C? Which HYSYS cooler simulation algorithm would you use to solve for each point in
the performance plot?
3. How do the mathematical models for the cooler and heater units in this problem differ? How
are they the same? For the two conceptual diagrams above, what are their heat duties in kJ/h?
4. The total specific energy of a process stream is composed of its internal energy, flow energy,
kinetic energy, and potential energy. Note that enthalpy is defined to be internal energy plus
flow energy ( Hˆ= Uˆ + PVˆ ). For the sub-cooled exit stream at 20°C, what additional
information would you need to know in order to calculate its kinetic energy and potential
energy? For a velocity of 1.6 m/s and a height of 10 m, what percentage of the total specific
energy of the exit stream is internal energy, flow ( PVˆ ) energy, kinetic energy, and potential
energy? What would be the pipe diameter of the exit stream for a velocity of 1.6 m/s?
5. Which equations in the mathematical model would you use to calculate the molar enthalpy of
the exit stream given the conditions of the inlet stream and the duty of the cooler? What is the
exit stream molar enthalpy for a cooling operation using the inlet stream in this problem and a
duty of 1000 kilo-watts? Check that HYSYS calculates the same result.
6. In your printed performance plot, label the dew-point temperature and bubble-point
temperature on the temperature axis. After doing this task, you should notice three distinct
areas on the plotted curve. Place a label on the liquid portion, vapor-liquid portion, and vapor
portion of this plot.
This plot of heat flow versus temperature is for a multicomponent mixture. What would the
vapor-liquid portion of this plot look like, if the mixture contained only one chemical
component (e.g., pure n-hexane)? What does the Gibbs Phase Rule state for the vapor-liquid
portion?
7. What is the energy relative imbalance (%RIB) for an exit temperature of 20°C? Show your
calculations. The energy %RIB equals 100*(energy flow in – energy flow out) / (energy flow
in).
Chapter 3
Page 3-9
HY.4 - Mixer/Tee Simulation
The HYSYS process simulator can solve the material and energy balances of many unit operations
that are interconnected by process streams. For example, two or more process streams can be fed to the
HYSYS mixer operation to form one exit stream. This exit stream can then be fed to a HYSYS tee
operation to divide it into several streams. Problem HY.4 uses this example to illustrate how to complete a
process simulation that has several unit operations in a process flow diagram (PFD).
The HYSYS simulation modules for the stream mixer and tee divider operations are fully defined
in Appendices D and B of this instructional manual. These two modules contain a module description, a
conceptual model, model assumptions, a mathematical model, variable descriptions, mathematical
algorithm, and HYSYS simulation algorithms in functional form. After you read the information about the
stream mixer and tee divider, you are to practice the HYSYS session below and then complete the
simulation exercise. You are to provide for the simulation exercise only a printed copy of the HYSYS
flowsheet (with a problem number, your name, and date) and the Workbook datasheets for the mixer and tee
operations in your technical journal. Separately, your team is to document the answers to all questions in
the simulation exercise.
A. HYSYS Session
This session will show you how to do a HYSYS simulation for a stream mixer and a tee, and how
to connect two process units. It assumes you are familiar with the material in Tutorials 2.2, 2.3, and 2.6 of
this instructional manual. First, a pure heptane stream is mixed with a pure octane stream. The resulting
binary mixture is then divided into two streams with different flow rates. You are to find the molar flow
rate in kgmol/h and the mole fractions of the tee’s two exit streams. The pure heptane stream is flowing at
100 kg-moles per hour, and the pure octane stream is flowing at 200 kg-moles per hour. Both pure streams
are at ambient conditions (25°C and 1 atm). The tee exit streams are also at ambient conditions. Thus, no
pressure drop exists across the mixer or the tee. Exit Stream E1 is to contain 40% of the molar flow rate
of the inlet Stream Mix to the tee operation. The conceptual diagram is:
TE1 = ?
PE1 = ?
n E1 = ?
TH = 25 ° C
PH = 1 atm
n H = 100 kgmol / h
z H , HP = 1.0
TO = 25 ° C
PO = 1 atm
nO = 200 kgmol / h
zO,OC = 1.0
E1
Heptane
M-100
mixer
Mix
Octane
T-100
tee
E2
n E1 = 0.4 n M
z E1, HP = ?
z E1,OC = ?
TE 2 = ?
PE 2 = ?
n E 2 = ?
z E 2, HP = ?
z E 2,OC = ?
•
•
Chapter 3
Page 3-10
•
•
•
Return to the Simulation Environment and open process Streams Heptane and Octane.
Specify their process states; that is, their temperature, pressure, flow rate, and composition.
•
•
•
Add a mixer to the process flow diagram (PFD) and name it M-100.
Connect its inlet Streams Heptane and Octane, and then name its exit stream as Mix.
Specify the exit pressure using Set Outlet to Lowest Inlet on the Design/Parameters page.
•
•
•
Add a tee to PFD, name it T-100, and then name its exit streams as E1 and E2.
Specify flow ratio E1under the Splits section on the Design/Parameters page of T-100.
Check that all flow ratios (0.4 for Stream E1 and 0.6 for Stream E2) sum to one.
•
•
•
•
View the Compositions and Component Flows pages in the Workbook.
In a tee divider, a flow ratio for an exit stream is what fraction of the total flow rate of the inlet stream is to
appear in the exit stream. Since the total molecular weight of each exit stream is the same as that of the
inlet stream, a flow ratio has the same value whether it is expressed on a mole or mass basis. After you
specify the inlet streams to the mixer and the tee flow ratios, HYSYS immediately calculates all of the
other properties of the streams using the Peng-Robinson Stryjek-Vera (PRSV) equation of state. For the
above simulation, HYSYS calculates the tee exit flow rates and compositions to be:
Property
E1
E2
Molar flow rate:
Mole fraction heptane:
Mole fraction octane:
120 kgmol/h
0.3333
0.6667
180 kgmol/h
0.3333
0.6667
What are the molar flow rates (lbmol/h) and mass fractions of the exit streams leaving the tee
divider in the below chemical process? A binary mixture of methanol and ethanol at 45°C and 300 kPa is
mixed with a pure water stream at ambient conditions. The methanol and ethanol component flow rates are
50 kgmol/h and 75 kgmol/h, respectively. The water flow rate is 100 kgmol/h. The resulting 3-component
stream is then split into two exit streams. The total molar flow rates for these two exit streams are in a 3:1
ratio, as shown in the diagram below. For the mixer, the exit pressure is equal to the lowest inlet pressure.
Using the information in the below diagram, you are to complete a HYSYS simulation by doing the
following:
•
•
•
•
•
Return to the Simulation Environment and finish the simulation for the mixer/tee process.
datasheet for all pages in the Workbook, and then place them into your technical journal.
Chapter 3
Page 3-11
TE1 = ?
PE1 = ?
n E1 = ?
TA = 45 ° C
z E1, ME = ?
PA = 300 kPa
n A, ME = 50 kgmol / h
E1
n A, ET = 75 kgmol / h Alcohol
M-200
TW = 25 ° C
PW = 1 atm
nW = 100 kgmol / h
zW ,WA = 1.0
Mix
Water
z E1,WA = ?
T-200
E2
n E1 3
=
n E 2 1
z E1, ET = ?
TE 2 = ?
PE 2 = ?
n E 2 = ?
z E 2, ME = ?
z E 2, ET = ?
z E 2,WA = ?
add your team name (e.g., T3 – MBal), and complete those questions contained within.
1. Which HYSYS stream mixer simulation algorithm in Appendix D would you use to solve the
mixer section of this problem? What other unit parameter, which is not referred to in the
algorithm, must you specify in HYSYS?
2. Which HYSYS stream tee simulation algorithm in Appendix B would you use to solve the tee
section of this problem? Note that the tee divider operation is analogous to a batch process of
taking a liquid mixture in a large beaker and pouring it into two smaller beakers. What is true
about the state of the material in all three beakers? About the amounts?
3. What are the temperature in °F, molar enthalpy in kcal/kgmole, mass density in kg/m3, molar
volume in m3/kgmole, and mole fractions of the tee’s inlet and exit streams? What is unique
about these values? What are the temperature, molar enthalpy, mass density, molar volume
and mole fractions, in the same units, of the mixer’s inlet and exit streams? How do these
values for the mixer streams differ from those for the tee? Why?
4. What is the material relative imbalance (%RIB) for the process flowsheet? Show your
calculations. The material %RIB equals 100*(mass flow in – mass flow out) / (mass flow in).
You are to draw an overall system boundary around the flowsheet, which contains the mixer
and tee operations. The only material and energy streams you are to consider in your
imbalance calculation are those that cut your overall system boundary. Therefore, you would
not consider Stream Mix in your calculations.
5. What is the energy relative imbalance (%RIB) for the process flowsheet? Show your
calculations. The energy %RIB equals 100*(energy flow in – energy flow out) / (energy flow
in).
Chapter 3
Page 3-12
HY.5 - Reactor Simulation
The HYSYS simulation module for a chemical reactor operation is fully defined in Appendix H of
this instructional manual. The chemical reactor module contains a module description, a conceptual model,
model assumptions, a mathematical model, variable descriptions, mathematical algorithm, and HYSYS
simulation algorithms in functional form. After you read this information about the reactor, you are to
practice the HYSYS session below and then complete the simulation exercise. You are to provide for the
simulation exercise only a printed copy of the HYSYS flowsheet (with a problem number, your name, and date
on it) and the Workbook datasheet for the chemical reactor in your technical journal. Separately, your
team is to document the answers to all questions in the simulation exercise.
A. HYSYS Session
This session will show you, in general terms, how to do a HYSYS simulation for a chemical
reactor. It assumes you are familiar with the material in Tutorial 2.5 of this instructional manual.
Acrylonitrile is produced by the reaction of propylene, ammonia, and oxygen:
2 C3 H6
+
2NH3
+ 3O2
→
2 C3 H3 N
+ 6 H2 O
where 30 molar percent of the propylene is converted.
A 45 mole % propylene and 55 mole % ammonia stream at 25 °C and 1 atm is fed to the reactor.
The oxygen is fed to the reactor through an air stream also at 25°C and 1 atm. The feed stream is flowing
at 22 kgmol/h, and the air stream is flowing at 78 kgmol/h. Assume an adiabatic reactor with no pressure
drop. You are to find the temperature of the reactor product stream in °C. Also, you are to find the dewpoint temperature (Vf = 1) of the reactor product stream. The conceptual diagram is:
TF = 25 ° C
PF = 1 atm
TP = ?
PP = 1 atm
n P = ?
z F , PY = 0.45
z F , AM = 0.55
Feed
R-200
R-100
TA = 25 ° C
PA = 1 atm
n A = 78 kgmol / h
z A,O 2 = 0.21
z A, N 2 = 0.79
Product
z P, PY = ?
z P, AM = ?
z P ,O 2 = ?
Air
ε = 30% of PY
z P, N 2 = ?
z P, AN = ?
z P,WA = ?
•
•
•
Click here to download file HY5.A and save it as HY4.5_xxx, where xxx are your initials.
•
•
Select the Reactions folder in the navigation pane and double-click the Global Rxn Set.
Click the Add Reaction/New Reaction button to open the Reactions window.
Chapter 3
Page 3-13
•
•
•
Select the Conversion model, click the Add Reaction button, and close the window.
Double-click the Rxn-1, specify its stoichiometry, and set a propene conversion of 30%.
Close the window, click the Add to FP button, and associate PRSV with Global Rxn Set.
•
•
Return to the Simulation Environment and open process Streams Feed and Air.
Specify their process states; that is, their temperature, pressure, flow rate, and composition.
•
•
•
Add a conversion reactor to the process flow diagram (PFD) and name it R-100.
Connect its inlet Streams Feed and Air, and then name its exit streams as Vapor and noLiq.
Select the Global Rxn Set as the reaction set on the Reactions/Details page.
•
•
•
•
View the Compositions and Component Flows pages in the Workbook.
After you specify the feed and air streams and the chemical reaction, HYSYS immediately calculates all of
the other properties of the two exit streams (such as mass flow rate, volumetric flow rate, vapor fraction, heat flow, etc.)
using the Peng-Robinson Stryjek-Vera (PRSV) equation of state. For the vapor stream, its temperature is:
T = 424.2°C
Note that the flow rate of Stream noLiq is zero, because the reaction takes place solely in the vapor phase.
Once the property variables of the vapor stream are calculated by HYSYS, they cannot be changed
by you, because they appear as black values. To find the dew-point temperature of the vapor stream, you
must place a new stream on the process flow diagram (PFD), name it Dew, set its process state by copying
information from Stream Vapor using the Define from Other Stream… button, delete the temperature of
Dew, and set its vapor fraction to 1.0. HYSYS calculates a dew-point temperature of 43.73°C.
For the simulation exercise, consider the same reaction and reactor inlet streams that were used in
the HYSYS session. Now the reactor is no longer adiabatic. Instead, it is an isothermal process, meaning
the product stream is at the same temperature as the two inlet streams, 25°C. What is the reactor duty in
kJ/h for this isothermal process? Is the chemical reaction endothermic or exothermic? Must heat be added
to or removed from the reactor?
TF = 25 ° C
PF = 1 atm
TP = 25 ° C
 =?
Q
PP = 1 atm
n P = ?
z F , PY = 0.45
z F , AM = 0.55
Feed
R-200
R-200
TA = 25 ° C
PA = 1 atm
n A = 78 kgmol / h
z A,O 2 = 0.21
z A, N 2 = 0.79
Product
z P, PY = ?
z P, AM = ?
z P ,O 2 = ?
Air
ε = 30% of PY
z P, N 2 = ?
z P, AN = ?
z P,WA = ?
Chapter 3
Page 3-14
•
•
•
•
•
Name the two exit streams as Vapor and Liquid and name the energy stream as Q.
Set the exit temperature of the vapor (or liquid) stream to complete the simulation.
datasheet for the Workbook minus the Unit Ops datablock, and then place them into your
technical journal.
At an exit temperature of 25°C, the product stream will contain two phases—vapor and liquid. In the
HYSYS conversion reactor, Streams Vapor and Liquid account for these two exiting phases.
add your team name (e.g., T6 – EBal), and complete those questions contained within.
1. For the adiabatic reactor in the HYSYS session, only a vapor product stream was needed since
the flow rate of the liquid was zero. For the isothermal case, both a vapor and a liquid product
stream are required. Why? Above what reactor exit temperature will only a vapor product
stream be required?
2. What is the acrylonitrile composition in the liquid product stream in mole fraction? In mass
fraction? In parts per million (ppm)? In kg/m3? In kgmol/m3? In molarity (M)?
3. What assumptions were used to solve the isothermal reactor simulation problem? Compare
these assumptions to those of the chemical reactor module in Appendix H of this instructional
manual. Are the assumptions the same? If not, how do they differ?
4. Write the total mole balance equation for the isothermal reactor problem. What are the value
and units for the extent of reaction? What does the extent-of-reaction or R term in the total
mole balance signify?
5. What is the energy relative imbalance (%RIB)? Show your calculations. The energy %RIB
equals 100*(energy flow in – energy flow out) / (energy flow in).
6. What is the material relative imbalance (%RIB) on a total molar basis? Show your calculations.
The total molar %RIB equals 100*(total molar flow in – total molar flow out) / (total molar
flow in).
7. What is the material relative imbalance (%RIB) on a total mass basis? Show your calculations.
The material %RIB equals 100*(mass flow in – mass flow out) / (mass flow in). How does
this value compare with the %RIB on a molar basis? Explain.
Chapter 4
Flowsheet Development Exercises
Chapter 4
Flowsheet Development Exercises
Flowsheet Development Exercises – Overview
Chapter 4
Page 4-1
This chapter provides seven problem assignments to help you develop a process flowsheet to make
styrene monomer from toluene and methanol by analyzing individual process units and then connecting
these individual units to form the complete flowsheet. Before you proceed with these assignments, you
must be familiar with the material in Chapter 1 and Tutorials 2.1 to 2.6 of Chapter 2. Also, the problem
assignments in Chapter 3 on process units should be completed before you begin your flowsheet analysis in
this chapter.
Over a seven-week period, you will have assignments that focus on particular sections of the
flowsheet, beginning with the reaction section. In these assignments, you will conduct a process simulation
on each of the following flowsheet sections using the Aspen HYSYS® process simulation software:
Problem
SM.1
SM.2
SM.3
SM.4
SM.5
SM.6
SM.7
Description
Styrene Monomer Reaction Section
Reactor Effluent Cooling/Decanting Section
Methanol Recycle Purification Section
Toluene Recycle Purification Section
Toluene/Methanol Feed Preparation Section
Recycle Mixing and Preheating Section
Styrene Monomer Purification Section
These seven sections are identified in the following block flowsheet from Chapter 1:
Q
WS
heater
toluene
SM.6
Q
SM.5
toluene recycle
H2 fuel
pump
SM.2
SM.1
Q
decanter
SM.4
column
organic
furnace
reactor
cooler
methanol
Q
aqueous
WS
methanol recycle
heater
ethylbenzene
SM.7
column
SM.3
column
pump
styrene monomer
waste water
Each sectional problem will be assigned under a separate memorandum. Once you’ve completed these
assignments, you will have synthesized the process flowsheet for continuous operation and determined its
processing requirements for material and energy for a specific reactor inlet temperature. Why a continuous
and not a batch operation? Based on a heuristic rule reported by Woods [2007. p. 11], a continuous
operation is more economical for product rates greater than 0.1 kg/s. The styrene monomer production rate
is 8.35 kg/s (250,000 metric ton per year) for the above process flowsheet.
Flowsheet Development Exercises – Overview
Chapter 4
Page 4-2
Information and data needed to solve the sectional flowsheet problems in this chapter are contained
in Chapter 1 and Appendices B to M of this HYSYS manual. Chapter 1 provides detailed technical and
economic data for the production of styrene monomer from toluene and methanol. Appendices B to L
contain simulation modules for various process unit operations. Each appendix or module provides a
mathematical explanation of how HYSYS does its calculations for that process unit. A module includes its
description, a conceptual model, model assumptions, a mathematical model, variable descriptions, example
mathematical algorithms, and several HYSYS simulation algorithms. Appendix M provides details on how
to calculate the net profit of the above process flowsheet for a specific reactor inlet temperature using a
HYSYS spreadsheet operator. Please consult the first chapter and the appropriate appendices to complete
each sectional problem in this chapter.
As indicated in Chapter 1, you are part of a team in the Process Engineering Department of BEEF,
Inc. Our client, Hawbawg Chemical Company, needs to know the process flowsheet requirements that
maximize the net profit to manufacture styrene monomer from toluene and methanol. The net yearly profit
for the styrene flowsheet can be approximated as follows:
net
profit
=
product
sales
+
byproduct
sales
+
fuel
credit
−
cost of
raw materials
−
annualized
capital cost
−
utility
costs
where each term is $ per year. The annualized capital cost for purchasing the equipment is estimated to be
(product sales + byproduct sales)/6 in $/yr. The other terms in this net profit equation can be determined
once the material and energy requirements of the above flowsheet are calculated for a specific reactor inlet
temperature using the Aspen HYSYS® software.
Under the directions of your project supervisor, your team members will determine their net profit
for their assigned reactor inlet temperature. The table below identifies a team member symbol that has
been assigned to you by your instructor.
α - 465ºC
♠ - 480ºC
♥ - 495ºC
♣ - 510ºC
♦ - 525ºC
ω - 540ºC
That assigned symbol indicates the reactor inlet temperature that you will use in your HYSYS process
simulations of this chapter. If your instructor has not assigned you a symbol, then you are to pick one of
the six reactor inlet temperatures to complete the problem assignments in this chapter.
After completing all seven problem assignments in this chapter, your team will then plot sales
(which include the fuel credit), costs, and net profit versus the reactor inlet temperatures to determine the
operating temperature that maximizes the net profit. In this plot, you can expect to see the net profit curve
exhibit a maximum value either within the range of reactor temperatures or at an end point of the range.
The point at which the maximum profit occurs is the “best” temperature at which to operate the adiabatic
reactor, based solely on economics.
Beginning with the second problem in this chapter, you will have access to the HYSYS solution for
the previous problem thru a web link provided in each problem of this chapter. You are to begin the next
problem by starting with the provided solution to the previous problem. Obviously, you are expected to
practice professional ethics; that is, not solving your currently-assigned problem by starting with the
available solution to the next problem. Failing to practice ethics here will results in plagiarism, which are
grounds for termination of your employment at BEEF, Inc.
Chapter 4
Flowsheet Development Exercises – Problem SM.1
Page 4-3
SM.1 - Styrene Monomer Reaction Section
The heart of a chemical process flowsheet is the reactor. The first step in synthesizing a flowsheet
is to define the reactor operating conditions. These conditions are usually determined experimentally by
the Research and Development (R&D) Department in a company, and these experimental data are used to
simulate the performance of the reactor. Once the reactor has been simulated, other parts of the flowsheet
can be developed.
In the “Flowsheet Design Variables” section of Chapter 1, an experimentally-determined
performance table is provided for an adiabatic reactor operating at 400 kPa with an equimolar feed of
toluene and methanol. For your assigned reactor inlet temperature (as presented in the Overview section of
this chapter), you are to use the molar conversion and yield from the performance table to complete a
HYSYS reactor simulation that forms styrene monomer and ethylbenzene from toluene and methanol.
As stated in Chapter 1, the proposed production rate is 250,000 metric tons per year of styrene
monomer. What is the production rate in kgmol/h for a 95% onstream time (8,320 hours per year)? Based
on the mathematical algorithm and HYSYS simulation algorithm for a reactor in Appendix H, what
variables must be specified in order to simulate your reactor? Your examination of the algorithms in
Appendix H should reveal that the feed flow rate and composition to the reactor must be specified instead
of the total and component flow rates leaving the reactor. What estimated value do you get for the feed
flow rate in kgmol/hr based on 100 percent conversion, no side reaction for ethylbenzene, and the proposed
styrene production rate? Please document your calculations. Click here to download a Word file, add your
initials to its name, and complete all of the questions contained within.
Using your estimated feed flow rate, you are to simulate in HYSYS the conversion reactor for the
production of styrene monomer and ethylbenzene from toluene and methanol. What chemical components
are in the reactor effluent stream and why? The conceptual model for this adiabatic reactor is as follows:
TS 11
TS 10
PS 10
nS 10
Z S 10
S10
feed
R1
reactor
S11
effluent
PS 11
nS 11
Z S 11
Using the above stream and equipment labels, you are to complete your HYSYS simulation as follows:
•
Click one of the following web links to download the starter HYSYS file for your assigned
reactor inlet temperature and then save it with your initials in its name to a team folder:
SM1_465, SM1_480, SM1_495, SM1_510, SM1_525, or SM1_540.
•
•
•
•
Start the HYSYS software, load your preferences, and open your retrieved starter file.
Enter the Basis Environment, complete the component list, and define the chemical reactions.
Return to the Simulation Environment and add a conversion reactor to the process flowsheet.
Finish the simulation for this flowsheet section as directed in the remaining paragraphs.
For the conversion reactor, two chemical reactions will occur—one producing styrene monomer and the
other ethylbenzene, as shown in Chapter 1. The HYSYS percent molar conversion of toluene to form
styrene monomer is equal to [overall conversion*yield*100] and that to form ethylbenzene is equal to
Chapter 4
Page 4-4
[overall conversion*(1.00-yield)*100]. Use these percent molar conversions for your assigned reactor inlet
temperature to define the two chemical reactions.
Since the chemical reactions take place in the gas phase, label the reactor’s liquid stream as noLiq. Label
the reactor and the feed and vapor effluent streams as indicated in the above diagram. Specify the
temperature, pressure, mole fractions and total molar flow rate of the feed stream. Use your estimated feed
flow rate for the total molar flow rate of Stream S10. Do not forget to connect the Global Rxn Set to the
conversion reactor.
After completing this simulation with your estimated feed flow rate, use the HYSYS Adjust
operation to iterate on the total molar flow of the reactor feed in order to obtain the desired production rate
of styrene monomer in kgmol/hr. Select the <F4> key and look for the Adjust operator in the object
palette. To learn how to apply the Adjust operation, follow the directions on its Connections page or
possibly access the Help facility in the Aspen HYSYS software. Mathematically, the Adjust operator
simulates the following iteration construct:
ITERATE nS 10 in
[T
S 11
UNTIL
where
, PS 11 , nS 11 , Z S 11 ] ⇐
reactorA [TS 10 , PS 10 , nS 10 , Z S 10 , CTSM , CTEB , ∆P ]
calculated (nS 11 × zS 11, SM ) = desired nS 11, SM
Z i means mole fractions zi ,1 , zi , 2 ,  zi , nc for nc components in mixture i.
Note that SM is styrene monomer, EB is ethylbenzene, CTj is the percent molar conversion of toluene to
form Compound j, and ∆P is the pressure drop across the reactor. These data are provided in Chapter 1.
The product (nS 11 × zS 11, SM ) represents the calculated molar flow rate of the styrene monomer in the reactor
effluent Stream S11.
After you have solved the above problem for your assigned reactor inlet temperature, you must
provide documentation in your technical journal for the PFD (with a problem number, reactor inlet temperature,
your name, and date), the Workbook datasheet minus the Unit Ops datablock, and the answers to all of the
above questions.
After all team members have independently answered all questions in their technical journal, your
team is to meet and compare the HYSYS simulation results for the different reactor inlet temperatures.
Click here to complete an Excel template file that contains a table and graph for this team portion of the
assignment. Your team is to plot the inlet toluene, outlet styrene monomer, and outlet ethylbenzene flow
rates versus the reactor inlet temperatures. What inlet temperature should the adiabatic reactor operate at,
so that the production rate of styrene monomer is maximized and that of ethylbenzene is minimized?
Chapter 4
Page 4-5
SM.2 - Reactor Effluent Cooling/Decanting Section
In Problem SM.1, you simulated the reactor in the styrene monomer project using chemical
reaction data provided by the Research and Development Department of BEEF, Inc. The Reactor R1 has
only one effluent stream, the vapor Stream S11, because the flow rate of Stream noLiq equals zero. Based
on physical properties such as critical temperature, critical pressure, and normal boiling temperature for
each reaction component, why should the effluent leaving the reactor be only in the vapor or gas phase? To
verify the stream phase, it may help to think of a phase (PT) diagram for each pure component. Physical
properties of various chemical components are given in Chapter 1. Click here to download a Word file,
add your initials to its name, and complete all of the questions contained within.
A global flowsheet for a chemical process depicts basically the raw materials entering the
flowsheet and the product, byproducts and wastes leaving the flowsheet. Chapter 1 gives a block flowsheet
for the chemical process of converting toluene and methanol to styrene monomer. A global flowsheet for
the styrene monomer chemical process is shown below.
Recycle Reactants
Off Gas
Byproduct
Raw Materials
Reactor
Effluent
Separation
Sequence
Pure Product
Wastewater
This global flowsheet shows the reactor producing an effluent stream (containing toluene, methanol, styrene
monomer, ethylbenzene, water, and hydrogen), which must be separated to purify the product. The reactor
effluent goes through a separation sequence in which the off gas (hydrogen), byproduct (ethylbenzene), pure
product (styrene monomer) and waste water are isolated. Unreacted raw materials are also separated in the
sequence. The reactants are then recycled back to the reactor. The number of process exit streams—off
gas, byproduct, etc.—determines the number of separation units required in the sequence. As a rule of
thumb (i.e., a heuristic rule), the number of required separation units is one less than the number of chemical
components in the effluent stream, if each chemical component in that stream is to be separated into a pure
stream for that component..
The first step in the design of a separation sequence is to decide what the first separation unit is.
Some different types of separation are phase splitting, distillation, and extraction. Phase splits are usually
the cheapest method of separation, because they only involve the cooling of the material process stream.
Think of your separator funnel in organic chemistry labs to visualize a phase split. Therefore, if possible, a
phase splitter is the first separation unit in the separation sequence.
If the reactor effluent is in the vapor state, it must be cooled to allow a phase separation to take
place. In the styrene monomer project, the reactor effluent is cooled to allow the formation of three distinct
phases, the vapor phase and two immiscible liquid phases. The two liquids are an organic phase and an
aqueous phase. To predict which components each phase contains, remember that “like dissolves like.”
The organic phase contains the organics of toluene, ethylbenzene, and styrene monomer. The methanol
partitions between both the organic phase and the aqueous phase. A three-phase separator is also known as
Chapter 4
Page 4-6
a decanter. Appendix J provides a mathematical description of how a decanter is modeled. Also,
Appendix G describes how a cooling operation functions.
You now know that the reactor effluent must be cooled from a vapor phase to a temperature at
which three phases exist. You must determine to what temperature the stream is cooled to produce the
phase separation. The cooling is typically carried out by a heat exchanger in which the effluent is cooled
by a water stream. The cooling water is not directly mixed with the effluent. Rather, the two streams
exchange heat thru a metal barrier so that the hot effluent is cooled while the cold water is heated. To
design a heat exchanger that cools the hot stream the entire way to the temperature of the cold stream is
unfeasible, because such a heat exchanger would be infinitely large in area. Applying a heuristic rule, the
hot stream is cooled to within 5 to 10°C of the initial cold stream temperature. As given in the “Flowsheet
Economic Analysis” section of Chapter 1, the cooling water is supplied at 31°C. Thus, the reactor effluent
is cooled to about 38°C. At 38°C three phases may exist, and they could be separated in a decanter.
The next step in the styrene monomer project is to simulate the first separation unit. Within Aspen
HYSYS, you are to simulate the effluent cooling and three-phase separator. The conceptual model for the
reactor, cooler, and decanter is as follows:
S13
QE3
S10
R1
S11
S12
E3
F3
S14
S15
•
SM2_465, SM2_480, SM2_495, SM2_510, SM2_525, or SM2_540.
•
•
Account for the pressure drops through the cooler (E3) and decanter (F3) using the data in the “Flowsheet
Design Variables” section of Chapter 1. The decanter is to operate adiabatically. After simulating Process
Unit E3, create a Performance Table and Plot, where the independent variable is temperature and the
dependent variables are pressure, heat flow, vapor fraction, vapor mass flow, light-liquid mass flow, and
heavy-liquid mass flow. Include the dew-point and bubble-point temperatures in the table and plot. Under
the HYSYS Home/Flowsheet Summary menu, use the Mass/Energy Balance page to view the relative
imbalances for material and energy.
After completing this simulation with the initial feed flow rate, use the HYSYS Adjust operation to iterate
on the total molar flow of the reactor feed in order to obtain the desired production rate of styrene monomer
in Stream S14 at 288.5022 kgmol/hr. To learn how to apply the Adjust operation, follow the directions on
its Connections page. Mathematically, the Adjust operator simulates the iteration construct shown below.
In this iteration construct, SM means styrene monomer, EB means ethylbenzene, CTj is the percent molar
Chapter 4
Page 4-7
conversion of toluene to form Compound j, and ∆Pm is the pressure drop across process unit m. These data
are provided in Chapter 1.
ITERATE nS 10 in
TS 11 , PS 11 , nS 11 , Z S 11  ⇐ reactorA TS 10 , PS 10 , nS 10 , Z S 10 , CTSM , CTEB , ∆PR1 
 PS 12 , nS 12 , Z S 12 , Q E 3  ⇐ coolerC TS 11 , PS 11 , nS 11 , Z S 11 , ∆PE 3 , TS 12 
 Ψ S 13 , Ψ S 14 , Ψ S 15 
0 
⇐ decanterC TS 12 , PS 12 , nS 12 , Z S 12 , ∆PF 3 , Q F 3 =
UNTIL
calculated (nS 14 × zS 14, SM ) = desired nS 14, SM
where Z i means mole fractions zi,1, zi,1, …, zi,nc for nc chemical components in mixture i.
The symbol Ψ i means the process state—temperature, pressure, molar flow rate, and mole
fractions—of Stream i. The product (nS 11 × zS 11, SM ) represents the calculated molar flow rate
of the styrene monomer in the reactor effluent Stream S14.
At what temperature in °C do two phases (vapor-liquid) start to occur on cooling? Do three phases
(vapor-liquid-liquid) start to occur on cooling? On a molar basis, what fraction of Stream S12 after cooling
to 38°C goes to the vapor phase of the decanter? To the organic phase? To the aqueous phase? On a mass
basis, what fraction of Stream S12 after cooling to 38°C goes to the vapor phase of the decanter? To the
organic phase? To the aqueous phase?
above questions. The Workbook is to contain only Streams S10, S12, S13, S14, and S15. Thus, Streams
S11 and noLiq are to be hidden.
assignment. Your team is to plot the inlet toluene (S10), outlet styrene monomer (S14), and outlet
ethlybenzene (S14) flow rates versus the reactor inlet temperatures. What inlet temperature should the
adiabatic reactor operate at, so that the production rate of styrene monomer is maximized and that of
ethylbenzene is minimized?
The reactor effluent contains the unreacted raw materials of toluene and methanol, the product of
styrene monomer, and the byproduct of ethylbenzene. Since perfect separation into a pure chemical
component is not possible (i.e., trace amounts of the other chemical components will always exist), you want to
minimize the flow rates of these four chemical components in the off-gas stream (S13) and the wastewater
stream (S15), because you must pay for the raw materials and you want to sell as much product as possible.
Based on the various reactor inlet temperatures, what are the mean averages for the molar percent losses of
toluene, methanol, styrene monomer, and ethylbenzene? The molar loss of a specific component equals the
sum of the molar flow rates of that component in the off-gas and wastewater streams divided by the molar
flow rate of that component in the reactor effluent (either Stream S11 or S12). What conclusions can your
team draw about the molar losses for these four chemical components?
Chapter 4
Page 4-8
SM.3 - Methanol Recycle Purification Section
In Problem SM.2, you simulated the first separation operation, a cooler with a three-phase
decanter, in the separation sequence of the styrene monomer project. In Problem SM.3, you will simulate
the next operation in the separation sequence, a distillation column. A distillation column uses the
difference in boiling-point temperatures to separate the chemical components of a stream. Think of a liquid
mixture of two components with each component having different boiling points. If the mixture is heated
to a temperature between the boiling points of the two components, the more volatile component (lower
boiling-point temperature) vaporizes while the less volatile component (higher boiling-point temperature)
remains in the liquid phase. By collecting the vapor, you have effectively separated the binary mixture into
two single phases, the vapor phase containing the more volatile component and the liquid phase containing
the less volatile. The same principle can be used to separate material process streams with more than two
components into two mixtures with fewer components. All of the more volatile components will vaporize,
and all of the less volatile components will remain in the liquid. Exactly where the separation occurs, i.e.
which components vaporize and which do not, depends on the temperature that the original mixture is
heated to.
A distillation column is a series of equilibrium stages or trays where each act as a separator
according to the boiling points as described above. A column separates a liquid feed stream into two liquid
streams—the distillate and bottoms. The temperature of each tray gradually decreases moving from the
bottom to top of the column. A reboiler at the bottom of the column heats the liquid in the column to a
saturated vapor. This vapor then rises through the trays of the column. As the temperature decreases going
up the column, the less volatile components begin to condense and fall back down through the column. By
the time the vapor reaches the top of the column at the lowest temperature, only the most volatile
components are vapors and exit the column. This vapor stream is condensed to usually a saturated liquid
and then split into a reflux stream and distillate stream. The liquid reflux stream is sent back to the column.
The more volatile components exit as a saturated liquid in the product stream. The less volatile
components exit as a saturated liquid from the reboiler in the bottoms stream.
To consider distillation as a possible separation operation, you must compare the normal boiling
points and composition of all chemical components leaving the decanter in the aqueous stream. What are
the normal boiling points (nbp) for all of those chemical components? What are their mole fractions? List
the components and their nbp in order of increasing boiling point in the first two columns of the table
below, using the data found in the “Flowsheet Thermodynamic Data” section of Chapter 1 in this HYSYS
manual. Then, list the mole fractions of the same chemical components in the third column of the table.
Click here to download a Word file, add your initials to its name, and complete all of the questions
contained within.
Chemical
Component
Normal Boiling
Point, °C at 1 atm
Mole Fraction in
Stream S15
Feed Type
Distribution
Chapter 4
Page 4-9
To design a distillation column, you pick two components with adjacent boiling points and largest
mole fractions from the above table. The more volatile component is called the light key (LK) and the less
volatile component is called the heavy key (HK). The split in the column is between these two key
components. A perfect separation means that all of the LK would be in the distillate, and all of the HK
would be in the bottoms. However, like in the case of the three-phase separator, a perfect separation is
unfeasible. An infinite number of trays in the distillation column would be required to perform a perfect
separation. Therefore, a separation level is chosen for the column. Most of the LK exits the column
through the distillate, with a little in the bottoms, and most of the HK exits the column through the bottoms,
with a little in the distillate. The distillate contains all components more volatile than the LK (non-LK's),
and the bottoms contains all components less volatile than the HK (non-HK's). A simple diagram to show
the component flows is given next.
non-LK' s
mos t LK
little HK
non-LK' s
LK
HK
non-HK' s
Column
little LK
mos t HK
non-HK' s
In the table above, where you entered in the first three columns the chemical components, their
normal boiling points, and their mole fractions leaving in the decanter aqueous stream, you are to complete
the fourth and fifth columns. What is the feed type of each chemical component, i.e. state whether each
component is a LK, HK, non-LK, or non-HK? What is the qualitative distribution of each component by
stating which stream(s) (i.e., distillate and/or bottoms) the chemical component appears in, and in what
relative amount, such as all, most or little? Remember that the column is being designed to separate
methanol from water.
A detailed description of a simple distillation column is given in Appendix L of this HYSYS
manual. What are the three main parts of a distillation column? The overall mathematical model for a
column consists of a series of smaller math models, one for each of these column parts. In what order are
the overall mathematical model equations solved in the column algorithm? How does the column
mathematical algorithm in Appendix L differ from the HYSYS simulation algorithm? Why?
A generic diagram for the distillation column to separate methanol from water is given below. It
contains a partial condenser and several stages above and below the feed stage. However, the simple
distillation column in Appendix L has a total condenser, meaning the entire vapor coming off the top of the
column is converted to a saturated liquid. To achieve this liquid state, all of the components are assumed to
be condensable. However, the aqueous stream from the decanter contains hydrogen, which is noncondensable. Note hydrogen's extremely low boiling point in your table above. Because the column will
contain hydrogen, a partial condenser is used in order to allow the hydrogen to be vented out of the column
as a vapor in Stream V.
The use of a partial condenser instead of a total condenser means that one more variable must be
specified for HYSYS to simulate the column. The functional equation for the HYSYS simulation
algorithm of this column is as follows:
Chapter 4
 ΨV , Ψ D , Ψ B ,=
Q C , Q R 
Page 4-10
rcolumnLK  Ψ F , PC , ∆PC , PR , ∆PR , N S , N FS , R, z B , LK , VRC 
where Q C is the condenser energy rate or heat duty, Q R is the reboiler energy rate or heat duty, Pu is
the pressure of the partial condenser or reboiler unit, ∆Pu is the pressure drop across the partial condenser
or reboiler unit, N S is the number of column stages, N FS is the feed stage number, R is the reflux ratio,
z B , LK is the total mole fraction of the light key (LK) in the bottoms, and VRC is the vent ratio for the partial
condenser. The reflux ratio of R is the reflux total molar flow rate in Stream RF over the distillate total
molar flow rate in Stream D. The vent ratio of VR is the distillate vent molar flow rate in Stream V over
the feed molar flow rate in Stream F. The vector Ψi is a short notation to represent the temperature,
pressure, flow rate, and molar composition (i.e., total mole fractions) of Stream i.
Q C
Partial Condenser
Stages
F
Feed
RF
Reflux
V
Vent
D
Distillate
Feed
Stage
Stages
B
Q R
Bottoms
Reboiler
Shortcut methods—Fenske-Underwood-Gilliland-Kirkbride—exist to estimate the distillation
column design variables for the number of trays (NS), the tray at which the feed enters (NFS), and the molar
reflux ratio (R). A shortcut analysis has already been performed for the methanol/water separation to
determine these three design variables. To solve the rigorous HYSYS distillation column, more design
variables must be specified in addition to NS, NFS, and R. For this problem, all of the design variables are:
Number of Stages
Feed Stage (from
the top of column)
Molar Reflux Ratio
=
=
=
35
10
15
5
permanent number of trays
for 465, 480, 495°C reactor inlet
for 510, 525, 540°C reactor inlet
start with and change to meet desired specs
LK in Bottoms
HK in Distillate
Molar Vent Ratio
=
=
=
60 ppm
0.001
1.0e-6
EPA mass fraction limit on methanol in wastewater
desired mole fraction of water in recycled methanol
vapor vent total flow rate over feed total flow rate
Condenser Pressure
Condenser ∆P
Tray Column ∆P
Reboiler ∆P
Reboiler Pressure
=
=
=
=
=
125 kPa
10 kPa
35 kPa
10 kPa
180 kPa
distillate pressure leaving the condenser
pressure drop across the condenser
pressure drop of 1 kPa per tray
pressure drop across the reboiler
bottoms pressure leaving the reboiler
Chapter 4
Page 4-11
The first three items in the above list were determine using the shortcut methods, based on the desired mass
fraction for the light key in the bottoms stream, and a reasonable value for the mole fraction of the heavy
key in the distillate stream. The remaining items are specifications from Chapter 1 of this HYSYS manual,
except for the molar vent ratio. A stricter vent ratio like 1×10-7 will lead to an iteration error of “two liquid
phases were found on the condenser stage.” Using 1×10-6 eliminates this error.
Using these design specifications, the next step in the styrene monomer project is to simulate the
methanol-water separation in HYSYS with the rigorous distillation column operator. The conceptual
model for this distillation column is as follows:
S17v
QcC3
S17
S16
C3
S18
QrC3
•
SM3_465, SM3_480, SM3_495, SM3_510, SM3_525, or SM3_540.
•
•
Each starter file includes a valve and heater to prepare the aqueous stream from the decanter, so that it is
fed to the distillation column as a saturated liquid at the appropriate pressure (i.e., 135 kPa plus 10, or 15 times
1 kPa per tray for the feed location). This starter file also has an attached rigorous distillation column (C3) in
the process flow diagram (PFD).
Double click the rigorous distillation column in the PFD, to open its property window. On the
Design/Connections page, check the column name, the material and energy stream names, and the entered
values for the number of stages and feed stage, which were approximated using the shortcut methods.
Make sure the partial condenser is chosen so that the vent Stream S17v does exist. Check that the pressures
were entered correctly for the condenser and reboiler, and that their pressure drops are also correct. The
pressures of every stage between the condenser and reboiler will be calculated by HYSYS. Go to the
Parameters/Profiles page, type 72°C as an estimate for the temperature of the chemical mixture in the
condenser at 125 kPa, and type 117°C as an estimate for the temperature of the chemical mixture in the
reboiler at 180 kPa. These two estimates were predicated by the shortcut methods.
Go to the Design/Monitor page and enter the four values in the “Specified Values” column for the
reflux ratio, mass fraction of the LK in the bottoms, mole fraction of the HK in the distillate, and the vent
Chapter 4
Page 4-12
ratio. On the Design/Monitor page, the degrees of freedom box in the lower right corner currently show
three. It must be zero in order for the column operator to begin the iterative process to converge the
material and energy balances for the distillation column. To make this zero, you must tell HYSYS which
specifications to use. Click the boxes to the right of the values you specified to make the reflux ratio, mass
fraction of the LK in the bottoms, and the vent ratio active specifications. Note that the third specification
for the mole fraction of the heavy key in the distillate must be inactive.
Once enough variables are specified to satisfy the degrees of freedom, the column operator will try
to find a solution using an iteration process, which will be visible in the page. If the iteration process does
not automatically start, you can reset the iterative calculations and then start them by using the Reset and
Run buttons, respectively. The green converged message will show up in the C3 column window to
indicate the rigorous distillation simulation is solved.
In the Design/Monitor page, the “Specified Value” and “Current Value” columns display the
supplied and calculated values for the four specifications, respectively. When the green converged
message appears, the current values for the three checked specifications have converged to within set
tolerances for the iterative calculations. Note that the current value for the unchecked heavy-key
specification may be far from its specified value (too high or too low). By changing the specified value for
the reflux ratio, you can manually iterate (i.e., do trial and error) on the reflux ratio until the desired value for
the unchecked specification is matched by rounding its “Current Value” expressed in scientific notation to a
value of 10.00e-4. For example, a value of 9.83e-4 rounds to 10.0e-4 or 1.00e-3, and it would be an
acceptable match to a “Specified Value” of 1.00e-3.
When you supply a change in value for the reflux ratio, sometimes the iteration appears not to
converge after 10 to 20 iterations. When this situation occurs, you should click the Stop button, select the
Reset button to re-initialize the iteration process, and then click the Run button to restart the iteration. If
convergence still does not occur after 10 to 20 iterations, you should stop the iteration process, increase or
decrease the value for the reflux ratio, reset the iteration process, and then run the iteration process again.
How might the value for the vent ratio be estimated? What are the feed, vent, distillate, and
bottoms flow rates in kg/h? What are the mole fractions of the LK in the distillate and the HK in the
bottoms? What are the composition profiles of just the LK and HK in the distillation column? Use the
Performance/Plots page to print these profiles. Note that methanol is the light key and water is the heavy
key in this problem.
your name, and date), the Performance Plot for the composition profile (with your initials in its title, square
symbols for methanol, and triangle symbols for water), the Workbook datasheet minus the Unit Ops datablock,
and the answers to all of the above questions. The Workbook is to contain only Streams S10, S16, S17v,
S17, and S18. Thus, all other streams are to be hidden.
Click here to complete an Excel template file that contains a table and graphs for this team portion of the
assignment. How does the reflux ratio vary with the reactor inlet temperature, and the condenser and
reboiler heat duties vary with the reflux ratio? As a team, present a table with two plots. What inlet
temperature should the adiabatic reactor operate at, so that the reflux ratio, condenser heat duty, and
reboiler heat duty are minimized? What conclusion can you draw about the reflux ratio and the two heat
duties? The condenser duty versus the reboiler duty?
Chapter 4
Page 4-13
SM.4 - Toluene Recycle Purification Section
In Problem SM.3, you simulated the distillation column that recovered methanol in the aqueous
stream from the three-phase decanter. This recovered methanol will eventually be recycled in a later
problem. The next operation in the separation sequence of the styrene monomer project is another
distillation column. In Problem SM.4, you will simulate a distillation column to separate reactants from
products in the organic stream leaving the three-phase decanter. The organic stream contains both
methanol and toluene that are to be recycled back to the reactor. It also contains the styrene monomer
product and the byproduct ethylbenzene.
As with column C3 in Problem SM.3, you must first compare the normal boiling points and
composition of all chemical components leaving the decanter in the organic stream. What are the normal
boiling points (nbp) for all of those chemical components? What are their mole fractions? List the
components and their nbp in order of increasing boiling point in the first two columns of the table below,
using the data found in the “Flowsheet Thermodynamic Data” section of Chapter 1 in this HYSYS manual.
Then, list the mole fractions of the same chemical components in the third column of the table. Click here
to download a Word file, add your initials to its name, and complete all of the questions contained within.
Chemical
Component
Normal Boiling
Point, °C at 1 atm
Mole Fraction in
Stream S14
Feed Type
Distribution
Furthermore, you are to complete the fourth and fifth columns in the above table. What is the feed
type of each chemical component, i.e. state whether each component is a LK, HK, non-LK, or non-HK?
What is the qualitative distribution of each component? State which stream or streams (i.e., distillate and/or
bottoms) the chemical component appears in, and in what relative amount, such as all, most or little. If
necessary, refer to the Problem SM.3 handout to refresh your memory about the concept of key and nonkey components. Remember that the column is being designed to separate the reactants from the products.
As in the case of methanol column C3, the feed to this distillation column, called C1, contains the
non-condensable hydrogen, which means a partial condenser must be used. Column C1 is depicted on the
next page. What is the functional form for the HYSYS simulation algorithm for this column, based on
knowing the mole fraction of the heavy-key component in the distillate stream? Define each of the
variables in this functional form (HINT: Refer to the Problem SM.3 assignment).
reflux ratio (R). A shortcut analysis has already been performed for the toluene/ethylbenzene separation to
Chapter 4
Number of Stages
Feed Stage Location
Molar Reflux Ratio
=
=
=
30
5th
4
LK in Bottoms
HK in Distillate
non-HK in Distillate
Molar Vent Ratio
Reboiler Temperature
=
=
=
≤
0.0001
3.5 wt%
empty
1.0e-2
145°C
desired mole fraction of toluene in bottoms stream
start with and change to meet ≤ 4 wt% ethylbenzene
combined ethylbenzene-styrene to meet ≤ 5 wt%
vapor vent total flow rate over feed total flow rate
maximum temperature of the bottoms stream
Condenser Pressure
Condenser ∆P
Tray Column ∆P
Reboiler ∆P
Reboiler Pressure
=
=
=
=
=
70 kPa
5 kPa
15 kPa
10 kPa
100 kPa
pressure drop of 0.5 kPa per tray
Page 4-14
from the top of the column
start with and change to meet desired specs
The first three items in the above list were determined using the shortcut methods, based on the desired
mass fraction for the heavy key in the distillate stream and a reasonable value for the mole fraction of the
light key in the bottoms stream. The remaining items are specifications from Chapter 1 of this HYSYS
manual, except for the molar vent ratio. A stricter vent ratio like 1×10-3 will lead to an iteration error of
“two liquid phases were found on the condenser stage.” Using 1×10-2 eliminates this error.
toluene-ethylbenzene separation in HYSYS with the rigorous distillation column operator. The conceptual
model for this distillation column is as follows:
S23v
QcC1
S23
S22
C1
S24
QrC1
•
SM4_465, SM4_480, SM4_495, SM4_510, SM4_525, or SM4_540.
•
Chapter 4
•
Page 4-15
Each starter file includes a valve and heater to prepare the organic stream from the decanter, so that it is fed
to the distillation column as a partially-vaporized liquid at the appropriate pressure (i.e., 75 kPa plus 2.5, or 80
kPa when rounded up). This starter file also has an attached rigorous distillation column (C1) in the process
flow diagram (PFD).
Double click the rigorous distillation column in the PFD, to open its property window. On the
Design/Connections page, check the column name, the material and energy stream names, and the entered
values for the number of stages and feed stage, which were approximated using the shortcut methods.
Make sure the partial condenser is chosen so that the vent Stream S23v exists. Check that the pressures
were entered correctly for the condenser and reboiler, and that their pressure drops are also correct. The
pressures of every stage between the condenser and reboiler will be calculated by HYSYS. Go to the
Parameters/Profiles page, type 74°C as an estimate for the temperature of the chemical mixture in the
condenser at 70 kPa, and type 143°C as an estimate for the temperature of the chemical mixture in the
reboiler at 100 kPa. These two estimates were predicated by the shortcut methods.
Go to the Design/Monitor page and enter the four values in the “Specified Values” column for the
reflux ratio, mole fraction of the LK in the bottoms, mass fraction of the HK in the distillate, and the vent
ratio. On the Design/Monitor page, the degrees of freedom (DOF) box in the lower right corner currently
shows zero, because the cells in the “Active” column have been checked for the reflux ratio, the HK in the
distillate, and the vent ratio. When the DOF box is zero, the column operator will begin the iterative
process to converge the material and energy balances for the distillation column. Note that the second
specification for the mole fraction of the light key in the bottoms must be inactive. The fourth and sixth
specifications for the styrene mass fraction and reboiler temperature are also inactive. Note that the
combined composition of ethylbenzene and styrene monomer in the distillate stream must be ≤ 5 wt%.
Also, when the bottoms stream contains more than 50 mass% styrene monomer, its temperature must not
exceed 145°C because the styrene monomer polymerizes and forms a solid above that temperature.
Once three variables are specified to satisfy the degrees of freedom, the column operator will try to
find a solution using an iteration process, which will be visible in the page. If the iteration process does not
automatically start, you can reset the iterative calculations and then start them by using the Reset and Run
buttons, respectively. The green converged message will show up in the C1 column window to indicate
that the rigorous distillation simulation is solved.
In the Design/Monitor page, the “Specified Value” and “Current Value” columns display the
supplied and calculated values for the desired specifications, respectively. When the green converged
message appears, the current values for the three checked specifications have converged to within set
tolerances for the iterative calculations. If the combined composition of ethylbenzene and styrene
monomer in the distillate stream is not ≤ 5 wt%, then lower the mass fraction specification for the
ethylbenzene in increments of 0.005 until the combined specification of ≤ 5 wt% is met. After convergence
has occurred, the current value for the unchecked light-key specification may be far from its specified value
(too high or too low). By changing the specified value for the reflux ratio, you can manually iterate (i.e., trial
and error) on the reflux ratio until the desired value for the unchecked light-key specification is matched by
rounding its “Current Value” expressed in scientific notation to a value of 10.00e-5. For example, a value
of 9.83e-5 rounds to 10.0e-5 or 1.00e-4, and it would be an acceptable match to a “Specified Value” of
1.00e-4.
When you supply a change in value for the reflux ratio, sometimes the iteration appears not to
converge after 10 to 20 iterations. When this situation occurs, you should click the Stop button, select the
Chapter 4
Page 4-16
Reset button to re-initialize the iteration process, and then click the Run button to restart the iteration. If
convergence still does not occur after 10 to 20 iterations, you should stop the iteration process, increase or
decrease the value for the reflux ratio, reset the iteration process, and then run the iteration process again.
Finally, redo the HYSYS Adjust operation to iterate on the total molar flow of the reactor feed
(S10), in order to obtain the desired production rate of styrene monomer in Stream S24 at 288.5022
kgmol/hr. How might the value for the vent ratio be estimated? What are the composition profiles of just
the LK and HK in the distillation column? Use the Performance/Plots page to print these profiles. Note
that toluene is the light key and ethylbenzene is the heavy key in this problem.
Column C1 is designed to separate the reactants from the products in order to recycle the reactants.
The C1 distillate stream (S23) contains the recycled reactants. The recycle stream must be prepared, in
order to be mixed with fresh raw materials before entering the reactor. The fresh and recycled reactant
streams are mixed as saturated vapors at 460 kPa. Add a pump and heater to distillate Stream S23 to reach
the saturated-vapor point at 460 kPa in Stream S26, as show below. You must decide whether to heat the
stream first, or to pump it first. Compressing a gas takes much more energy than pumping a liquid.
Therefore, if you heat the stream to a saturated vapor first, extra energy will be needed to compress the
vapor to the desired pressure. As a heuristic rule, pump the liquid first and then heat it to a saturated vapor.
Don't forget to account for the pressure drop across the heater using the data in the “Flowsheet Design
Variables” section of Chapter 1. Use the following labels in your simulation:
QE5
WP4
S25
S23
P4
S26
E5
C1
your name, and date), the Performance Plot for the composition profile in Column C1 (with your initials in its
title, square symbols for toluene, and triangle symbols for ethylbenzene), the Workbook datasheet minus the
Unit Ops datablock, and the answers to all of the above questions. The Workbook is to contain only
Streams S10, S22, S23v, S23, and S24. Thus, all other streams are to be hidden.
Click here to complete an Excel template file that contains a table and graphs for this team portion of the
assignment. How does the reflux ratio vary with the reactor inlet temperature, and the condenser and
reboiler heat duties vary with the reflux ratio? As a team, present a table with two plots. What inlet
temperature should the adiabatic reactor operate at, so that the reflux ratio, condenser heat duty, and
reboiler heat duty are minimized? What conclusion can you draw about the reflux ratio and the two heat
duties? The condenser duty versus the reboiler duty?
Chapter 4
Page 4-17
SM.5 - Toluene/Methanol Feed Preparation Section
In Problem SM.1, you simulated the reactor to produce styrene monomer from toluene and
methanol. You assumed a single reactor feed stream in SM.1 that contained the two reactants in equimolar
amounts at 400 kPa. Most likely, the raw materials (i.e., the two reactants) will actually be available
individually at some other conditions. In this case, pure toluene and pure methanol are both available at
ambient conditions, 25°C and 1 atm. In Problem SM.5, you are to simulate the preparation of toluene and
methanol.
The pure toluene and pure methanol streams are to be mixed as saturated vapors at 460 kPa. This
means that each raw material must be compressed and heated separately before being mixed. Compression
of a gas requires considerably more energy than compression of a liquid. As a general heuristic rule, you
should first pump the liquid to the desired pressure and then heat the high-pressure liquid to a saturated
vapor. You are to simulate the preparation of the two pure raw material streams, one for toluene and one
for methanol, from ambient conditions to saturated vapors at 460 kPa. The conceptual model to pump,
heat, and then mix the two raw materials is as follows:
QE1
WP1
S3
S2
S1
toluene
P1
E1
M1
QE2
WP2
S6
S5
S4
methanol
P2
S7
E2
•
SM5_465, SM5_480, SM5_495, SM5_510, SM5_525, or SM5_540.
•
•
The molar flow rates of the two raw materials have been pre-set for you in each starter file; however, you
need to supply their ambient condition at 25°C and 1 atm. The phase state of the exit stream from each
heater is to be a saturated vapor (Vf = 1.0). The adiabatic efficiency for each pump and the pressure drop
across each heater are provided in the “Flowsheet Design Variables” section of this HYSYS manual. After
Chapter 4
Page 4-18
completing your simulation, check the relative imbalances for mass and energy using the Mass/Energy
Balance page under the HYSYS Home/Flowsheet Summary menu.
What are the dew-point and bubble-point temperatures of Stream S3 and also Stream S6? What is
unique about the dew point and bubble point for each pure chemical compound? Explain this uniqueness
using the Gibbs phase rule. Click here to download a Word file, add your initials to its name, and complete
all of the questions contained within.
What are the heating curves for Heaters E1 and E2; that is, a graph of temperature versus heat duty
for each heat exchanger? Click here to view these two heating curves from 25 to 325°C at 460 kPa. On
each heating curve in your downloaded Word file, label the two sensible heat regions and the latent heat
region. What is the slope of the heating curve in the transition region from the saturated-liquid state to the
saturated-vapor state?
above questions. The Workbook is to contain only Streams S1, S3, S4, S6, and S7. Thus, all other
streams are to be hidden.
Click here to complete an Excel template file that contains a table for this team portion of the assignment.
The ratio of the toluene molar flow to the methanol molar flow is one for each reactor inlet temperature.
On average, what are the ratios of the toluene mass flow to the methanol mass flow, the P1 pump work to
the P2 pump work, and the E1 heat duty to the E2 heat duty? What conclusion can be drawn about the
mass ratio and the pump ratio and why? What conclusion can be drawn about the molar ratio and the heat
duty ratio and why?
Chapter 4
Page 4-19
SM.6 - Recycle Mixing and Preheating Section
In Problem SM.5, you simulated the compression and vaporization of the two fresh reactant
streams (pure toluene S1 and pure methanol S4) from ambient conditions of 25°C and 1 atm to a saturatedvapor state at 460 kPa. The feed to the reactor also contains recycled material from the toluene column C1
and the methanol column C3, as depicted in the following block flowsheet:
Q
heater
S26
toluene
SM.6
toluene recycle
H2 fuel
pump
SM.2
SM.1
Q
SM.5
S7
WS
Q
organic
S9 S10
S8
furnace
reactor
Q
WS
SM.4
decanter
column
C1
cooler
methanol
S21
aqueous
methanol recycle
ethylbenzene
SM.7
column
SM.3
heater
column
pump
C3
styrene monomer
waste water
where the red-dashed ovals SM.1, SM.2, etc. in the above flowsheet represent the focus of each styrene
monomer problem in this chapter.
The two recycle streams (S26 and S21) must be mixed with the fresh reactant stream (S7) and then
heated before entering the reactor, creating a recycle loop in the process. In Problem SM.6 you are to
simulate the recycle loop. Click here to view a mathematical model and mathematical algorithm for this
flowsheet simulation. The conceptual model for mixing and heating the reactor feed is as follows:
QFH1
S26
S7
S21
M2
S8
S9
FH1
•
SM6_465, SM6_480, SM6_495, SM6_510, SM6_525, or SM6_540.
Chapter 4
•
•
Page 4-20
Your HSYSY process flow diagram (PFD) contains the compression, vaporization, and mixing of the two
fresh reactants, as well as the rest of the process unit operations from Reactor R1 to distillation Columns
C1 and C3. A set operator labeled MeOH has been added to the PFD to set automatically the total molar
flow of the pure methanol stream (S4) using the specified total molar flow of the pure toluene stream (S1).
The liquid distillate streams (S17 and S23) from the two distillation columns have been compressed and
heated to saturated vapors at 460 kPa, in preparation for their recycle back to the reactor. The hydrogen
fuel stream (S13), the two vent streams (S17v and S23v), and the wastewater stream (S18) have been further
processed to exit the flowsheet at 1 atm.
The recycle loop is currently missing in your HYSYS PFD; that is, mixing the fresh reactants (S7)
with the recycled reactants (S21 and S26) to produce the mixed reactants (S8) and then heating those mixed
reactants to form the reactor feed (S9). The process state of Stream S9 is calculated based on assuming the
process state of Stream S10, which you did in Problem SM.1 for the reactor inlet stream. For valid closure
of the material and energy balances, the process state of Stream S9 exiting the fired heater FH1 must be
identical to that of Stream S10 entering the adiabatic reactor R1; that is, their pressure, molar flow rate,
molar enthalpy, and component mole fractions must agree within set tolerances. To close the recycle loop,
you will manually execute the iterative method of successive substitutions for two iterations and then use
the HYSYS Recycle operator to finish the iteration process. Proceed as follows to close the recycle loop:
1. Use the HYSYS drag Zoom button to expand the PFD view from Mixer M2 to Reactor R1 and
from recycle Streams S26 and S21.
2. Add a mixer operator labeled M2 into the flowsheet to combine the fresh reactant stream with
the two recycle streams. The inlet streams to the mixer are S26, S7, and S21, in that order. The
outlet stream is labeled S8.
3. Add a heater operator labeled FH1 to increase the temperature of Stream S8 to the reactor inlet
temperature that was assigned to you. The heater used to reach such a high temperature in
Stream S9 is called a fired heater, basically a furnace that burns natural gas. Use the HYSYS
heater with a pressure drop as indicated in the “Flowsheet Design Variables” section of
Chapter 1. The resulting outlet pressure must be 400 kPa. You must specify the temperature of
Stream S9 using the reactor inlet temperature that was assigned to you.
4. Open the Workbook window and view Streams S1 and S4. Hide Stream S8 and place Stream
S9 before S10 in the Material Streams, Compositions, and Component Flows pages.
5. Compare the temperature, pressure, molar flow rate, and molar enthalpy of Streams S9 and S10
using the Material Streams page in the Workbook window. Compare the component mole
fractions of these two streams using the Compositions page.
The temperature and pressure of these two streams are exactly the same, because you specified
them to be those values. However, the molar flow rate, molar enthalpy, and component mole
fractions of these two streams do not match.
6. Assume a new process state for Stream S10 by copying the conditions of S9 into S10 using the
Define from Other Stream… button in the property window of Stream S10.
Resetting the process state of Stream S10 causes HYSYS to recalculate all of the process units
and produce a different calculated S9. The process states of S9 and S10 should now be closer.
Chapter 4
Page 4-21
This iterative technique of successive substitutions is used to find that process state of the
reactor feed stream that closes the material and energy balances for the flowsheet recycle.
7. Copy the conditions of S9 into S10 again to assume a new process state for the reactor feed
stream. The molar flow rate, molar enthalpy, and component mole fractions should be even
closer for these two material streams.
You could continue this process, manually performing the iterations of successive substitutions
until the process state of S9 is identical to that of S10. However, HYSYS provides the Recycle
operator to automate the iteration process.
8. Open the pre-placed recycle operator RCY and connect Stream S9 as the input and Stream S10
as the output to this operator, in order to automate the iteration process.
The HYSYS recycle operator continually iterates on the process state of these two streams to
close the recycle loop within set tolerances for the pressure, molar flow rate, molar enthalpy,
and component mole fractions. It uses an enhanced version of successive substitutions called
the Wegstein method. When the recycle operator has converged, you will get a green
converged message at the bottom of the recycle property window.
9. Compare the temperature, pressure, molar flow rate, and molar enthalpy of Streams S9 and S10
using the Worksheet/Condition page in the Recycle: RCY window. Compare the component
mole fractions of these two streams using the Worksheet/Composition page. The process
states of Streams S9 and S10 should now be within set tolerances. Thus, the material and
energy balances for the recycle portion of the chemical process flowsheet have been closed.
10. Select the Parameters/Numerical page in the Recycle: RCY window and examine the
iteration count; that is, the number of iterations that were required to close the material and
energy balances for the flowsheet. Since you did two iterations manually, note that you need to
add two to the RCY iteration count.
What is the number of total iterations required to close the material and energy balances for the recycle
loop in the styrene monomer flowsheet? Click here to download a Word file, add your initials to its name,
and complete all of the questions contained within.
The Parameters/Variables page within a Recycle operator (like RCY) controls the tolerance tightness of
certain process variables for a material stream involved in the iteration process to close the material and
energy balances of a recycle loop. Based on information provided through the HYSYS Help menu, the
following table presents some of those variables and their tolerances used in Recycle Operator RCY:
Stream
Variable
P - pressure
n - molar flow rate
Ĥ - molar enthalpy
x j - each mole fraction
Recycle RCY
Sensitivity
10
1×10-4
Internal
Tolerance
0.01 kPa
0.001 kgmol/s
Tolerance
Type
absolute
relative
Actual
Tolerance
0.1 kPa
1×10-7
1
1.00 kJ/s
absolute
1.00 kJ/s
1
0.0001
absolute
0.0001
Subscript “j” is for each chemical component in a mixture of nc chemical compounds.
The actual tolerance equals the recycle sensitivity times the internal tolerance.
When a recycle operator is iterating on a material stream, the process variables that uniquely defined the
state of that material stream are the pressure, molar flow rate, molar enthalpy, and nc-component mole
Chapter 4
Page 4-22
fractions, whether that stream is a mixture of two or more chemical components or just a mixture of one
component (a.k.a. pure compound). The tolerance checks for these variables are given as follows:
Stream Variable
P - pressure
Tolerance Check
abs ( Pin − Pout )
≤
0.1 kPa
must match to within 0.1 kPa
≤
1×10-7
must match to within 7 digits
)
≤
1.00 kJ/s
must match to within 1 kJ/s
)
≤
0.0001
n - molar flow rate
abs 
Ĥ - molar enthalpy
 nin − nout 

 nin 
abs Hˆ − Hˆ
(
x j - each mole fraction
abs x j , in − x j , out
(
in
out
Explanation
must match to within
1
10, 000
for
each j-th component in mixture
Subscript “in” means Stream S9 and subscript “out” means Stream S10 for recycle operator RCY.
When these (3+nc) process variables have converged, all other variables associated with the material
stream will have converged too, like vapor fraction, temperature, and molar entropy. Click here to learn
more about the general iteration process on a recycle loop in a chemical process flowsheet (i.e., a PFD).
Once HYSYS has closed the material and energy balances, the styrene monomer production rate in
Stream S24 must be checked to see if it meets the desired rate given in the “Flowsheet General
Assumptions” section of Chapter 1 (i.e., 288.5022 kgmol/h or 250,000 mt/yr). Open the Workbook window,
select the Component Flows page, and check the styrene monomer flow rate in Stream S24. Since it is not
met, you are to conduct a manual trial-and-error iteration. Type a new value for the pure toluene flow rate
in Stream S1, hit the <Enter> key then hit the <Enter> key again, allow HYSYS to complete the recalculations, observe the styrene monomer flow rate in Stream S24, and stop your manual iteration when
the desired styrene flow is met. After completing the iteration on the toluene flow rate in Stream S1, you
must check the design constraints given in the “Flowsheet Design Specifications” section of Chapter 1 to
see if they have been satisfied. Open the property windows of Columns C1 and C3 and inspect the
“Specifications” area in the Design/Monitor page. All design specifications should have been nearly met.
What is the equimolar flow rate of pure toluene (S1) and pure methanol (S4) into the flowsheet for
a production rate of 250,000 mt/yr of styrene monomer? What are the molar flow rates for toluene and
methanol in S10, the stream entering Reactor R1? What are the reflux ratios for Columns C3 and C1?
above questions. The Workbook is to contain only Streams S1, S4, S9, S10, and S24. Thus, all other
streams are to be hidden.
assignment. Your team is to plot the pure toluene (S1), reactor inlet (S10), styrene monomer (S24), and
ethylbenzene (S24) flow rates versus the reactor inlet temperatures. What inlet temperature should the
adiabatic reactor operate at, so that the production rate of styrene monomer is maximized and that of
ethylbenzene is minimized? Although equimolar flow rates of pure toluene and pure methanol enter the
flowsheet, the molar ratio of toluene to methanol in Stream S10 that enters Reactor R1 is not equimolar.
What material stream quantity that enters the flowsheet would you vary to get the toluene-to-methanol ratio
in Stream S10 to be equimolar?
Chapter 4
Page 4-23
SM.7 - Styrene Monomer Purification Section
In Problems SM.1 through SM.6, you simulated the production of styrene monomer from toluene
and methanol, including the separation and recycle of unused reactants. In the resulting flowsheet
produced by solving these problems, the bottoms stream (S24) from distillation Column C1 contains both
the product styrene monomer and the by-product ethylbenzene. A final distillation column (C2) is needed
to purify the two product streams that meet the desired design specifications. In Problem SM.7, you are to
simulate the purification of the styrene monomer and ethylbenzene, where ethylbenzene is the light key and
styrene monomer is the heavy key.
The feed to the ethylbenzene/styrene column (C2) contains non-condensable hydrogen, but since
its composition is less than 1 ppm, a total condenser can be used in Column C2, as shown below.
QcC2
S28
S24
QE6
WP5
S30
S31
E6
P5
QEC2
V2
S24B
EC2
S27
C2
QE7
WP6
S29
S32
P6
S33
E7
QrC2
What is the functional form of the HYSYS simulation algorithm for Column C2, based on knowing the
mole fraction of the light-key component in the bottoms stream? Click here to download a Word file, add
your initials to its name, and complete all of the questions contained within.
reflux ratio (R). A shortcut analysis has already been performed for the ethylbenzene/styrene separation to
Number of Stages
Feed Stage Location
Molar Reflux Ratio
=
=
=
100
20th
value
from the top of the column
a pre-determined number for each reactor inlet temperature
LK in Bottoms
HK in Distillate
non-LK in Distillate
Reboiler Temperature
=
=
≤
≤
300 ppm
3.0 wt%
0.8 wt%
145°C
desired mass fraction of ethylbenzene in the bottoms stream
desired mass fraction of styrene in the distillate stream
desired mass fraction of toluene in the distillate stream
maximum degradation temperature of the bottoms stream
Condenser Pressure
Condenser ∆P
Tray Column ∆P
Reboiler ∆P
Reboiler Pressure
=
=
=
=
=
30 kPa
5 kPa
50 kPa
10 kPa
95 kPa
pressure drop of 0.5 kPa per tray
Chapter 4
Page 4-24
The first three items in the above list were determined using the shortcut methods and then later refined in a
rigorous distillation column, based on the desired mass fraction for the light key in the bottoms stream and
the desired mass fraction for the heavy key in the distillate stream. The remaining items are specifications
from Chapter 1 of this HYSYS manual. The distillation operation occurs in a vacuum column, because the
temperature of the bottoms stream must be less than or equal to 145°C when that stream contains more than
50 mass% styrene monomer. Above 145°C, polymerization of the styrene monomer would occur (i.e., solid
formation of a polymer).
ethylbenzene/styrene separation in HYSYS with the rigorous distillation column operator. You are to
complete your HYSYS simulation as follows:
•
SM7_465, SM7_480, SM7_495, SM7_510, SM7_525, or SM7_540.
•
•
Beginning with Stream S24, the HYSYS flowsheet in each starter file contains a valve and heater to
prepare this stream, so that it is fed to the distillation column (C2) as a partially-vaporized liquid (Vf = 0) at
the appropriate pressure (i.e., 45 kPa). Distillation Column C2 produces the distillate and bottoms streams
at pressures below ambient. These two streams are compressed and cooled to produce the by-product (S31)
and product (S33), which must be stored at ambient conditions until they are sold. The flowsheet also
contains two adjust operators—ADJ-TL and ADJ-ME—to meet the two design specifications of 250,000
metric tons per year of product and equimolar toluene and methanol fed to Reactor R1. Operator ADJ-TL
iterates on the toluene flow to the flowsheet (S1) until the flow rate of Stream S33 equals 288.5022
kgmol/h, while Operator ADJ-ME iterates on the methanol flow to the flowsheet (S4) until the ratio of the
molar flow of toluene to the molar flow of methanol in Stream S10 is 0.9999. The iteration procedures in
these two operators are conducted simultaneously.
In the HYSYS process flow diagram (PFD), the specifications for all process units between Stream
24 and Streams S31 and S33 have been pre-set for you, except for the light-key mass fraction in Column
C2. Double click on the rigorous distillation operator for Column C2 in the PFD, to open its property
window. On the Design/Monitor page, enter “3e-4” for the mass fraction of the ethylbenzene in the
bottoms stream (i.e., 300 ppm in S33). HYSYS will now continue the iteration process to close the material
and energy balances for the recycle loop in the flowsheet. While the iteration process is occurring, close
the C2 property window and double click on the ADJ-TL operator to open its property window. In the
Adjust/Monitor page, observe the “total iterations” count, which should stop somewhere within the range
of 40 to 140 iterations. After the iteration process converges (i.e., when the yellow status bar turns to green and
reads OK), close the ADJ-TL property window.
Since all HYSYS iteration processes on the flowsheet have been completed successfully, what are
the percent relative imbalances on its mass and energy balances? Select the Home/Flowsheet Summary
option and choose the Mass/Energy Balances page, to observe the percent relative imbalances. Right
click within the Flowsheet Summary window, select the Print Datasheet … option, deselect all data
blocks except for the Mass and Energy Balance datablock, preview the datasheet, select your printer, and
then print the datasheet. Close the Print Preview window, the Select Datablock(s) window, and the
Flowsheet Summary window, in order to return to the process flow diagram (i.e., the flowsheet).
Chapter 4
Page 4-25
With the HYSYS simulation calculations completed, does the flowsheet meet all of the design
specifications that are outlined in Chapter 1 of this HYSYS manual? Select the design spec (Spreadsheet)
window in the workspace panel to observe if certain calculated values are within their specification ranges.
For example, the product stream (S33) is to contain a maximum of 300 ppm by weight of ethylbenzene.
Thus, the range on this specification is 0 to 300 ppm. In the design spec spreadsheet, the mass fractions of
the organic compounds in the wastewater stream (S18) are not clear. Copy those cells from the spreadsheet
and paste them into a newly-opened Notepad document (use Start/All Programs/Accessories/Notepad), in order
to clearly observe their values. Right click within the tab area on the Spreadsheet page that appears in the
design spec window, select the Print Datasheet … option, deselect all data blocks except for the
Spreadsheet datablock, preview the datasheet, and then print it. Close the Print Preview, Select
Datablock(s), and design spec windows, in order to return to the process flow diagram (i.e., the flowsheet).
Finally, what are the flowsheet material requirements, sales, costs, net profit, and percent annual
return to manufacture styrene monomer from toluene and methanol for your assigned reactor inlet
temperature? The material requirements are the total molar flow rates for Stream S1, S4, S10, S31, and
S34. The net profit for the styrene monomer flowsheet can be approximated as follows:
net
profit
=
product
byproduct
fuel
+
+
sales
sales
credit
╚════════════╤═══════════╝
sales
−
cost of
annualized
utility
−
−
raw materials
capital cost
costs
╚══════════════╤═════════════╝
costs
where each term is $ per year. The annual return is the ratio of the sales over the total capital cost to
initially build the chemical plant, which is approximated to be equivalent to the annual product plus
byproduct sales. Appendix M provides the economic model for determining the net profit. Furthermore,
this appendix describes the HYSYS spreadsheet operator that implements this net profit model. Select the
net profit (Spreadsheet) window in the workspace panel and follow the instructions presented in Appendix
M to finish importing six quantities from the flowsheet into the spreadsheet. Once you have completed the
importing process, you can observe the sales, costs, net profit, and percent annual return at the bottom right
of the HYSYS net profit spreadsheet.
After solving the above problem for your assigned reactor inlet temperature, you must provide
documentation in your technical journal for the PFD (with a problem number, reactor inlet temperature, your
name, and date), the Workbook datasheet minus the Unit Ops datablock, the Mass and Energy Balance
datasheet, the design specs spreadsheet datasheet, and the answers to all of the above questions. The
Workbook is to contain only Streams S1, S4, S10, S31, and S33. All other streams are to be hidden.
Click here to complete an Excel template file that contains tables and graphs for this team portion of the
assignment. First, your team is to plot the pure toluene (S1), pure methanol (S4), reactor inlet (S10),
ethylbenzene (S31), and styrene monomer (S33) flow rates versus the reactor inlet temperatures. What inlet
temperature should the adiabatic reactor operate at, so that the production rate of styrene monomer is
maximized and that of ethylbenzene is minimized? Second, your team is to plot the sales, costs, and net
profits versus the reactor inlet temperatures. At what reactor inlet temperature do you make the most net
profit? What is its percent annual return? Third, when examining the economic feasibility of a chemical
flowsheet, the annual return on investment for building the chemical plant is the simplest measure used to
screen alternative flowsheet simulation solutions. Based on an economic heuristic, a percent annual return
greater than or equal to 30% (before considering federal taxes) classifies a flowsheet simulation as being
economically feasible. Using the percent annual return, what is the best reactor inlet temperature to make
styrene monomer from toluene and methanol? What is its percent annual return?
Appendices
Appendices
Example Batch Simulation in HYSYS
Appendix A
Page A-1
Batch Module Description
The Aspen HYSYS® simulator is not designed to handle batch process units, where no material is
flowing into or out of the system boundary. Using the spreadsheet module in Aspen HYSYS® and the
relationship between specific enthalpy, specific internal energy, and specific volume ( Hˆ= Uˆ + PVˆ ), you can
program the solution to the material and energy balances for a batch process. This appendix presents an
example problem for expanding steam in a cylindrical tank system, a typical problem that you will
encounter in the junior-level chemical engineering thermodynamics course. It also describes how to use
the HYSYS spreadsheet module to complete the numerical solution to this batch example for a gas mixture.
As shown below, the problem solution consists of a problem statement, a conceptual model, model
assumptions, a mathematical model, a mathematical algorithm, the numerical solution, and the heuristic
observations. Within the dashed boundary, the system is examined at its initial and final states, ti and tf.
Problem Statement
A tank contains 1.00 lbm of steam at 700ºF and 300 psia. It is connected through a valve to a vertical cylinder
which contains a frictionless piston. The piston is loaded with a weight so that a pressure of 100 psia is
necessary to support it. Initially, the piston is at the bottom of the cylinder. The valve is opened slightly so
that steam flows into the cylinder until the pressure is uniform throughout the tank and cylinder. The final
temperature of the steam in the tank is found to be 440ºF. Calculate the temperature in ºF of the steam in the
cylinder, if no heat is transferred from the steam to the surroundings. Assume three-digits of precision.
After solving this problem, what percentage error in the cylinder temperature would you get assuming the
ideal gas law? How would you solve this problem if the tank initially did not contain steam but a gas mixture
of 50% methane, 30% ethane, and 20% propane on a mass basis?
Conceptual Model
initial time, ti
final time, ti
Model Assumptions
1. batch process
2. no chemical reactions
3. neglect KE and PE
changes
4. no shaft work
5. adiabatic
6. water in the form of
steam is the only
compound in the gas
mixture
7. if the gas mixture in the
tank or cylinder contains
two or more compounds,
then it is well mixed.
Appendix A
Page A-2
Mathematical Model
(1)
( 2)
m C f + mT f − mTi =
0
total mass balance
m C f Uˆ C f + mT f Uˆ T f − mTi Uˆ Ti =
0
energy balance
( 3)
Uˆ C f = umix TC f , PC f , WC f 
specific internal energy
( 4)
Uˆ T f = umix TT f , PT f , WT f 
(5)
Uˆ Ti = umix TTi , PTi , WTi 
(6)
VˆT f = VT f / mT f
a definition
(7)
VˆT f = vmix TT f , PT f , WT f 
specific volume
(8)
VˆTi = VTi / mTi
a definition
(9)
VˆTi = vmix TTi , PTi , WTi 
specific volume
(10 )
VT f = VTi
tank volume
(11)
wC=
w=
wTi , j
f,j
Tf,j
for each j
# vars
=
3 ⋅ nc
+
16
# eqns
= 2 ⋅ nc
+
10
1 ⋅ nc
+
6
DOF
=
Variable Descriptions
Tkl
Pkl
mkl
is
the temperature of gas mixture kl in the tank or cylinder, °F.
is
the pressure of gas mixture kl in the tank or cylinder, psia.
Wkl
is
is
is
the total mass amount of gas mixture kl in the tank or cylinder, lbm.
the number of chemical components or compounds in the gas mixture.
the mass fractions of all nc-components in gas mixture kl.
wkl , j
is
the mass fraction of component kl in the gas mixture; vector Wkl
nc
means all elements wkl ,1 , wkl ,2 ,  , wkl ,nc in gas mixture kl.
Vkl
Vˆ
is
the volume of gas mixture kl in the tank or cylinder, ft3.
is
the specific volume of gas mixture kl in the tank or cylinder, ft3/lbm.
Uˆ kl
is
the specific internal energy of gas mixture kl in the tank or cylinder, Btu/lbm.
kl
Appendix A
Page A-3
Mathematical Algorithm
TC f  = batch TTi , PTi , WTi , mTi , TT f , PT f , PC f 
(5)
1.
Uˆ Ti
⇐
umix TTi , PTi , WTi 
(9)
2.
VˆTi
⇐
vmix TTi , PTi , WTi 
(8)
(10 )
3.
VTi
⇐
mTi ⋅ VˆTi
4.
VT f
⇐
VTi
(11)
5.
wC f , j ⇐
wT f , j ⇐ wTi , j
( 4)
6.
Uˆ T f
⇐
umix TT f , PT f , WT f 
(7)
7.
VˆT f
⇐
vmix TT f , PT f , WT f 
(6)
(1)
8.
mT f ⇐
VT f / VˆT f
9.
mC f ⇐
mTi − mT f
(2)
10.
Uˆ C f
(mTi Uˆ Ti − mT f Uˆ T f ) / m C f
11.
ITERATE on TC f in
( 3)
⇐
f (TC f
)
for j = 1, 2,  , nc
⇐ Uˆ C f − umix TC f , PC f , WC f 
UNTIL f (TC f
)
= 0
As shown in the mathematical model above, the number of degrees of freedom (DOF) is nc+6. For
a gas mixture that contains only one pure component like steam, the DOF equals seven. The first line in the
mathematical algorithm, called the functional form for batch, identifies seven variables that are to be
known in the mathematical model; that is, the initial temperature, pressure, and amount in the tank, the final
temperature and pressure in the tank, the final pressure in the cylinder, and the mass fraction of one for pure
steam. The primary purpose of Algorithm batch is to solve for the final temperature in the cylinder, as
indicated by the quantity on the left-hand side of its equals sign in the functional form.
The steps in the mathematical algorithm indicate the order in which the equations of the
mathematical model are to be solved for those known variables indicated on the right-hand side of the
equals sign in the functional form for Algorithm batch. Steps 1 to 8 in the mathematical algorithm directly
determine the indicated quantities on the left-hand side of each arrow ( ⇐ ). Step 9 is the application of the
total mass balance. Step 10 calculates the final specific internal energy of the cylinder using the energy
balance. Step 11 indicates that the final temperature (TCf) in the cylinder is determined by a trial-and-error
or iterative procedure. After assuming a value for TCf, the specific internal energy of the cylinder is
determine thru function umix using the assumed temperature, known pressure, and known composition of
the final state of the gas mixture in the cylinder. This calculated specific internal energy from function
umix is then compared to that value of specific internal energy determined from the energy balance in Step
10. When their difference is close to zero, the correct TCf has been found. When this difference is not
close to zero, a new value is assumed for the final temperature in the cylinder, and the iterative procedure is
repeated.
Appendix A
“EZ Setup” Numerical Solution
//
//
//
//
{ based on steam tables }
Batch Example, Applied Thermodynamics Problem
Index T is the tank, while C is the cylinder
Index f is final state, while i is initial state
Specific Internal Energies and Volumes from the Steam Tables
// Total Mass Balance, kg of steam:
m_Cf + m_Tf - m_Ti = 0
// Energy Balance, kJ:
m_Cf * u_Cf + m_Tf * u_Tf - m_Ti * u_Ti = 0
// Bernhard Spang's Steam Table for the Water Component, Excel Add-In:
u_Cf = energyW(T_Cf+273.15, P_Cf/100) // T in °C, P in kPa, u -> kJ/kg
u_Tf = energyW(T_Tf+273.15, P_Tf/100) // T in °C, P in kPa, u -> kJ/kg
u_Ti = energyW(T_Ti+273.15, P_Ti/100) // T in °C, P in kPa, u -> kJ/kg
// Specific Volumes, m^3/kg:
sv_Tf = 1/densW(T_Tf+273.15, P_Tf/100) // T in °C, P in kPa, v -> m^3/kg
sv_Ti = 1/densW(T_Ti+273.15, P_Ti/100) // T in °C, P in kPa, v -> m^3/kg
// Tank Volume Constraint:
v_Tf = v_Ti
sv_Tf = v_Tf / m_Tf
sv_Ti = v_Ti / m_T
// Specified Variables:
T_Ti = ( 700 - 32 ) / 1.8
P_Ti = 300 * 101.325 / 14.696
// volume -> m^3
// specific volume -> m^3/kg
// °F -> °C
// psia -> kPa
T_Tf = ( 440 - 32 ) / 1.8
P_Tf = 100 * 101.325 / 14.696
// °F -> °C
// psia -> kPa
T_Cf = ( T_CF - 32 ) / 1.8
P_Cf = 100 * 101.325 / 14.696
// °C -> °F
// psia -> kPa
m_Ti = 1.0 * 0.453592
m_Tf = m_Tlb * 0.453592
m_Cf = m_Clb * 0.453592
// lbm -> kg
// kg -> lbm
// kg -> lbm
Page A-4
Given:
T_Ti
=
371.111
ºC
P_Ti
=
2068.42
kPa
m_Ti
=
0.453592
kg
T_Tf
=
226.667
ºC
P_Tf
=
689.473
kPa
P_Cf
=
689.473
kPa
Calculated:
u_Tf
=
2680.64
kJ / kg
u_Ti
=
2895.64
kJ / kg
sv_Tf
=
0.324662
m3 / kg
sv_Ti
=
0.139041
m3 / kg
v_Ti
=
0.063068
m3
v_Tf
=
0.063068
m3
m_Tf
=
0.194258
kg
m_Cf
=
0.259334
kg
m_Tlb
=
0.428265
lbm
m_Clb
=
0.571735
lbm
u_Cf
=
3056.67
kJ / kg
T_Cf
=
457.783
ºC
T_CF
=
856.009
ºF
The above numerical solution was obtained by using the “EZ Setup” macro to generate an Excel
Solver formulation that minimizes the sum of squares. Click here to learn how to install and use the Excel
macro called “EZ Setup”. After transforming the mathematical model into a mathematical algorithm and
processing it with the “EZ Setup” macro, the Excel Solver utility produces the results show in the second
column. Click here to download the mathematical model and algorithm, save them as an “.xls” file, open
that file in Excel, and examine Worksheets “steam” and “steam alg”. In the above “EZ Setup” model, the
Appendix A
Page A-5
functions “energyW” and “densW” were used to determine the specific internal energy and mass density for
pure steam, respectively. Click here to download and install them as a free Excel Add-In for steam.
Heuristic Observations
A. Numerical Solution
The final temperature of the steam in the cylinder is determined to be 856°F, after accounting
for precision. Note that it is greater than 700°F, the initial temperature in the tank.
Since the internal energy initially and finally must be equal as indicated by the energy balance,
the final temperature of the steam in the cylinder must increase to maintain this equality,
because the final temperature of the steam in the tank is 440°F.
B. Mathematical Algorithm
For the above steam problem, the mathematical algorithm is as follows:
éëTC f ùû = batch éëTTi , PTi , WTi , mTi , TT f , PT f , PC f ùû
How would you solve this steam problem if you knew that TCf = 845°F, and you were asked to
solve for TTi instead? The mathematical algorithm would change, since the know variables
would be different compared to those in Algorithm batch. By slightly modifying the “EZ
Setup” model as shown in Excel Worksheet “845°F”, the Excel Solver calculates a TTi =
695°F.
C. Mathematical Model
Assuming that the pure steam within the system boundary behaves like an ideal gas, the final
temperature of the steam in the cylinder is 887°F. See the “EZ Setup” solution on Page A-6.
% error =
856 o F - 887 o F
× 100 = - 3.50%
856 o F
This solution was obtained using the mathematical algorithm in Excel Worksheet “idgas alg”.
D. Conceptual Model
If the tank initially contained a gas mixture of 50% methane, 30% ethane, and 20% propane on
a mass basis, the mathematical model would be the same, but the specific internal energy and
specific volume could be determined using an equation of state in the Aspen HYSYS program.
Since Aspen HYSYS is not designed for a batch operation, a HYSYS spreadsheet operator
would be used to implement the mathematical algorithm batch. See the HYSYS solution on
Page A-7. The final temperature of the gas mixture in the cylinder is 463°C or 865°F.
Appendix A
“EZ Setup” Numerical Solution
//
//
//
//
Page A-6
{ based on ideal gas law }
Batch Example, Applied Thermodynamics Problem
Index T is the tank, while C is the cylinder
Index f is final state, while i is initial state
Specific Internal Energies and Volumes based on ideal Gas
Given:
T_Ti
=
371.111
ºC
P_Ti
=
2068.42
kPa
// Total Mass Balance, kg of steam:
m_Cf + m_Tf - m_Ti = 0
m_Ti
=
0.453592
kg
// Energy Balance, kJ:
m_Cf * u_Cf + m_Tf * u_Tf - m_Ti * u_Ti = 0
T_Tf
=
226.667
ºC
P_Tf
=
689.473
kPa
// Specific Internal Energies for Ideal Gas, kJ/kg:
//
dH in kJ/mol; dU = dH - d(PV) = dH - R(dT); all T in °C
P_Cf
=
689.473
kPa
Tref
=
200
Rkg
=
0.461505
kPa m3
K kg
u_Cf = dH_Cf * 1000 / 18.016 - Rkg * (T_Cf - Tref)
u_Tf = dH_Tf * 1000 / 18.016 - Rkg * (T_Tf – Tref)
u_Ti = dH_Ti * 1000 / 18.016 - Rkg * (T_Ti - Tref)
// u -> kJ/kg
// u -> kJ/kg
// u -> kJ/kg
// Specific Enthalpy Changes for Water as a Gas, kJ/kg:
dH_Cf = a*(T_Cf - Tref)
+ b*(T_Cf^2 - Tref^2)/2 + _
c*(T_Cf^3 - Tref^3)/3 + d*(T_Cf^4 - Tref^4)/4
// dH -> kJ/kg
+ b*(T_Tf^2 - Tref^2)/2 + _
dH_Tf = a*(T_Tf - Tref)
c*(T_Tf^3 - Tref^3)/3 + d*(T_Tf^4 - Tref^4)/4
// dH -> kJ/kg
+ b*(T_Ti^2 - Tref^2)/2 + _
dH_Ti = a*(T_Ti - Tref)
c*(T_Ti^3 - Tref^3)/3 + d*(T_Ti^4 - Tref^4)/4
// dH -> kJ/kg
// Specific Volumes, m^3/kg:
using the Ideal Gas Law
sv_Tf = Rkg * (T_Tf + 273.15) / P_Tf // T in °C, P in kPa, v -> m^3/kg
sv_Ti = Rkg * (T_Ti + 273.15) / P_Ti // T in °C, P in kPa, v -> m^3/kg
// Tank Volume Constraint:
v_Tf = v_Ti
sv_Tf = v_Tf / m_Tf
sv_Ti = v_Ti / m_Ti
// volume -> m^3
ºC
Calculated:
u_Tf
=
39.8531
kJ / kg
u_Ti
=
262.684
kJ / kg
sv_Tf
=
0.334557
m3 / kg
sv_Ti
=
0.143747
m3 / kg
v_Ti
=
0.0652026
m3
v_Tf
=
0.0652026
m3
m_Tf
=
0.194893
kg
m_Cf
=
0.258699
kg
m_Tlb
=
0.429665
lbm
lbm
// Specified Variables:
T_Ti = ( 700 - 32 ) / 1.8
P_Ti = 300 * 101.325 / 14.696
// °F -> °C
// psia -> kPa
T_Tf = ( 440 - 32 ) / 1.8
P_Tf = 100 * 101.325 / 14.696
// °F -> °C
// psia -> kPa
m_Clb
=
0.570335
T_Cf = ( T_CF - 32 ) / 1.8
P_Cf = 100 * 101.325 / 14.696
// °C -> °F
// psia -> kPa
u_Cf
=
430.555
kJ / kg
m_Ti = 1.0 * 0.453592
m_Tf = m_Tlb * 0.453592
m_Cf = m_Clb * 0.453592
// lbm -> kg
// kg -> lbm
// kg -> lbm
T_Cf
=
474.873
ºC
T_CF
=
886.772
ºF
Tref = 200
Rkg = 8.314472 / 18.016
// Heat Capacity Coefficients for Water:
a = 33.460e-3
b = 0.6880e-5
c = 0.7604e-8
d = -3.5930e-12
// reference temperature -> °C
// kPa m^3/K kg -> kJ/K kg
Table B.2, F&R Textbook, 3rd
// coefficient range: 0 to 1500°C
Appendix A
HYSYS Numerical Solution
Page A-7
{ for three-component mixture }
Process Flow Diagram (PFD)
The process flow diagram (PFD) contains
three streams and a spreadsheet operator. The
total mass of Stream “Tk i” is set to 1.00 lbm/h,
since HYSYS uses flow rates. The fluid
package is the Peng-Robinson-Stryjeck-Vera
(PRSV) equation of state.
Click here to download this HYSYS solution,
save it as a “.hsc” file, and open it from within
the Aspen HYSYS program.
Workbook Table
Spreadsheet Operator
Columns A, C, and E contain only textual documentation.
Cells B2, D2, F2 - blue specified temperatures imported from the process streams in the PFD.
Cells B3, D3, F3 - blue specified pressures imported from the process streams in the PFD.
Cells B4, D4, F4 - black calculated molar volumes imported from the process streams in the PFD.
Cells B5, D5, F5 - black calculated molecular weights imported from the process streams in the PFD.
Cells B6, D6, F6 - red formula (e.g., =b4/b5) for the specific volumes of the three process streams.
Cells B7, D7, F7 - black calculated specific enthalpies imported from the process streams in the PFD.
Cells B9, D9, F9 - red formula (e.g., =b7-b3*b6) for the specific internal from the specific enthalpy definition.
Cell B12
- blue specified total mass flow imported from the process stream in the PFD.
Cell B13 - red formula (=b12*b6) for tank volume; Cell D12 - red formula (=b13/d6) for final tank amount.
Cell F12 - red formula (=b12-d12) for final cylinder amount, Step 9 in mathematical Algorithm batch.
Cell F13 - red formula (=(b12*b9-d12*d9)/f12) for final cylinder specific internal energy, Step 10 in Alg. batch.
Iterate on temperature in Cell F2 until Cell F9 is close in value to Cell F13, Step 11 in math Algorithm batch.
HYSYS Steady-State Simulation Modules
Appendix B
Page B-1
The Aspen HYSYS® software system is an integrated engineering environment for the development
and analysis of chemical process flowsheets. It provides you with:
• steady-state modeling and optimization for process design, and
• dynamic modeling for process controllability and control strategy development.
Aspen HYSYS® is licensed for educational use only at your university by Aspen Technology, Inc. of
Cambridge, MA. As an academic user, you have agreed to use HYSYS only for educational and not
commercial purposes. The focus of this Aspen HYSYS handbook is on steady-state modeling, often called
chemical process simulation. Appendix B begins with a description of the general format for the process
simulation modules presented in various appendices. It concludes with the process simulation module for
the stream tee, in order to illustrate that general format.
Process Module Format
A chemical process flowsheet is a conceptual representation of the transformation of raw materials
into products through a series of process unit operations connected by process streams. Appendices B, C,
D, etc. present simulation modules for the material and energy balances of some standard process unit
operations. In general, a process unit transforms the material passing through it, and this transformation is
represented by a set of algebraic equations, called a mathematical model. This model presents the material
balances, energy balance, and thermodynamic relationships for the process unit. Since the mathematical
model has more variables than equations, its degrees-of-freedom (DOF) tells you the number of variables
that must be specified to solve the equations. The order in which the model equations are solved depends
on which variables are specified. This ordering is called a mathematical algorithm.
In HYSYS more than one combination of specifications can be used to solve the mathematical
model of a process unit. For example, in a pump simulation you can specify the inlet stream and the
pressure drop in order to calculate the outlet stream conditions. This type of specification is known in
HYSYS as forward propagation; that is, knowing the inlet conditions you can find the outlet conditions.
You could also specify outlet information instead of inlet. This type of specification is known in HYSYS
as backward propagation. HYSYS can back-calculate for the inlet conditions of a process unit given the
outlet conditions and appropriate information to fulfill the degrees of freedom. This flexibility comes from
the underlying mathematical equations that exist for each process unit and the different ways these
equations can be solved.
HYSYS incorporates the mathematical models for many process unit operations and knows which
mathematical algorithm of a process unit to use according to which variables you have specified. Some of
the process unit operations supported by HYSYS are as follows:
•
•
•
•
•
•
•
•
•
material stream
energy stream
component splitter
compressor / expander
cooler / heater
heat exchanger
LNG exchanger
mixer
plug flow reactor
•
•
•
•
•
•
•
•
•
pipe segment
pump
reactor operations
separator / 3-phase separator / tank
separation column
shortcut column
solid separator operations
tee
valve
Appendix B
Page B-2
You can consult the Visual Encyclopedia of Chemical Engineering Equipment [Montgomery, 2001] for
general information on various process units and analytical instruments. If you are logged into Bucknell’s
computer network, click here to access this electronic encyclopedia; otherwise, consult with your instructor
about its availability at your university. Also, the Help menu command in the HYSYS software describes
its supported process units in detail, but it does not provide an analysis of their mathematical models.
Appendices B, C, D, etc. of this handbook present the mathematical models and some of their
mathematical algorithms for eleven standard process units, in order to help you understand how HYSYS (or
any simulation package, as well as hand calculations) solves the material and energy balances of these process
units. The process unit modules in these appendices are for the following flowsheet operations:
Appendix
C
D
B
E
F
G
H
I
J
K
L
Module
Process Stream
Stream Mixer
Stream Tee
Pump
Valve
Heater/Cooler
Chemical Reactor
Two-Phase Separator
Three-Phase Separator
Component Splitter
Distillation Column
Description
Contains chemical components flowing at a certain state.
Mixes two or more process streams to make one stream.
Divides one process stream into two or more process streams.
Increases the pressure of a liquid process stream.
Decreases the pressure of a process stream.
Heats or cools a process stream.
Reacts the chemical compounds to form desired products.
Separates a process stream into vapor and liquid streams.
Separates a process stream into vapor, organic, and aqueous streams.
Splits a process stream into two streams at different temperatures.
Separate a process stream through a series of equilibrium stages.
The format for each module has been standardized, in order to aid your learning process. This format is as
follows:
1. Module Description
2. Conceptual Model
3. Model Assumptions
4. Mathematical Model
5. Variable Descriptions
6. Mathematical Algorithms
7. HYSYS Simulation Algorithms
The module description explains the purpose of the process unit operation. The conceptual model depicts
the flow of material and energy. The assumptions list the conditions under which the mathematical model
is applicable. The mathematical model presents the material balances, energy balance, and thermodynamic
relationships for a process unit; that is, the algebraic equations that model a process unit simulation. The
mathematical algorithms are representative examples of how the mathematical model could be solved for a
specified set of variables that satisfies the degrees of freedom. The HYSYS simulation algorithms are
representative examples of what you can specify to do a process unit simulation. These examples include
calculations for both forward and backward propagation of information flow.
You may want to consult the Help menu command in the Aspen HYSYS software to discover all
of the simulation algorithms supported by HYSYS for any process unit operation. This information is also
available in the Adobe Reader “.pdf” version of the Aspen HYSYS Unit Operations guide. If you are
logged into Bucknell’s computer network, click here to access that guide; otherwise, consult with your
instructor about its availability at your university.
Process Stream Module
Appendix C
Page C-1
Process Stream Description
This simulation module models a process stream containing material that is composed of multiple
chemical compounds called components. This material is often referred to as a mixture of chemical
components. The chemical mixture in a process stream flows from one process unit operation to another in
a process flowsheet, where that process stream connects the two. In a process simulation, the material in a
process stream is assumed to have uniform temperature, pressure, flow rate, and composition. These four
quantities are referred to as the process state of a material stream. The flow rate and composition can be
expressed in terms of molar, mass, or volumetric quantities.
The conceptual and mathematical models for a multicomponent process stream are given below. In
the mathematical model, the isothermal, single-phase stream has uniform and ideal mixing, no pressure
drop, and no chemical reaction. The independent set of equations contains the relationships between molar,
mass, and volumetric quantities, and the functions for pure component densities and molecular weights. To
solve the equations in this model, (nc+3) process variables must be specified, as indicated by the degreesof-freedom (DOF) analysis in the math model. In the variable descriptions for the mathematical model, the
term bulk means the total amount of a chemical mixture quantity, like flow rate (mass, mole, or volumetric),
molecular weight, mass density, composition (mole fractions, mass fractions, volume fractions, or
concentrations), enthalpy, and energy (heat flow). The term overall is sometimes used to refer to the bulk or
total mixture quantity.
Many mathematical algorithms can be derived from this model to do the material stream
calculations. These algorithms differ in their given variables and their solution procedures. Two such
algorithms are shown below. The first math algorithm is based on knowing the total molar flow rate and
composition, while the second is based on knowing the component molar flow rates only. As indicated
below, the second algorithm is just an extension of the first algorithm. Other possible mathematical
algorithms for a single-phase stream supported by the HYSYS simulation system are summarized below.
This module closes with a brief overview of how HYSYS simulates a process material stream that
is multi-phase; that is, vapor and liquid coexisting in equilibrium within the stream. The thermo-physical
properties associated with a process stream (like mass density, molar volume, molar enthalpy, dew-point
temperature, and bubble-point temperature) are calculated in HYSYS using a fluid package model like the
Soave-Redlich-Kwong or Peng-Robinson equation of state. Since these fluid package models are based on
differing assumptions and experimental data, you should expect to see slight differences in the values of the
thermo-physical properties for a process stream.
Conceptual Model
Ti
Pi
ni
Zi
Model Assumptions
Ti
stream i
Pi
ni
Zi
1.
2.
3.
4.
5.
single phase
isothermal
no pressure drop
uniform and ideal mixing
no chemical reaction
Appendix C
Page C-6
Vapor-Liquid Equilibrium
The above mathematical model for a process stream assumes its material is single phase—either all
liquid or all vapor. At certain temperatures and pressures, the material in a process stream can be multiphase—either vapor-liquid or vapor-liquid-liquid; that is, two or more distinct phases can coexist in
equilibrium. Our discussion here focuses on vapor-liquid equilibrium (vle) only.
HYSYS indicates multi-phases through the vapor fraction of a process stream. Vapor fraction ( Vf )
is the ratio of moles in the vapor phase over the total (bulk or overall) moles of the process stream; that is, it
is what fraction of the total exists in the vapor state. For example, a Vf = 0.4 implies that 40% of the total
moles is vapor, while 60% is liquid. The numerical range of the vapor fraction is:
0 ≤ Vf ≤ 1.
In HYSYS, a calculated vapor fraction of zero indicates that the bulk or overall material is all liquid. A
calculated vapor fraction of one implies that the bulk or overall material is all vapor. A calculated value
between zero and one means a vapor and liquid are coexisting in equilibrium for the bulk material.
The vapor-liquid equilibrium for a multicomponent mixture is best illustrated by a temperatureversus-composition (TXY) diagram for a binary or 2-component system that does not form an azeotrope.
A general representation of a TXY diagram for a binary system is as follows:
Pressure =
130
a
Saturated
Vapor
Curve
120
Vapor
Region
Vf = 1
Tdp
b
L
Ti
Pi
V
T
°C
Tbp
Vf = 0
c
Vapor-Liquid
Region
80
70
60
d
Liquid
Region
0
0.1
0.2
0.3
xi,j
0.4
0.5
zi,j
Saturated
0.6
yi,j
0.7
Liquid
0.8
Curve
0.9
1
Mole Fraction of Component j
Click here to view a document that describes how to use Aspen HYSYS to generate a TXY diagram.
Appendix C
Page C-7
For process stream i at a specified pressure of Pi and bulk or overall composition of Zi , a typical condition
of vapor-liquid equilibrium at temperature Ti is represented by line segment LTV in the TXY diagram.
The end points of this line are called the saturated-liquid (SL) and saturated-vapor (SV) points, and they
represent the compositions of the two phases in equilibrium: xi , j for the liquid phase, yi , j for the vapor
phase, and component j is the more volatile component in the binary system. The molar vapor fraction for
this equilibrium is given by line segment LT over LV , or in mathematical terms, it is:
total balance :
=
ni
component j balance :
nSV + nSL
n
n
1.0 = SV + SL ⇒ 1.0 =V f + L f
ni
ni
=
ni zi , j nSV yi , j + nSL xi , j
for each j
zi , j = V f ⋅ yi , j + (1 − V f ) ⋅ xi , j
vapor fraction ratio :
Vf =
for each j
zi , j − xi , j
yi , j − xi , j
The ratio for Vf in terms of mole fractions is called the reverse-lever rule, because the contribution of the
vapor phase at Point V is given by the line segment on the opposite side of Point T. The Vf equation is
gotten by algebraically combining the total balance and one of the j-th component balances.
In the TXY diagram, the vertical Path a → b → c → d depicts what would happen to process
stream i if it were cooled at the specified pressure Pi and bulk composition zi , j . Point a indicates that
stream i would be in the vapor region, while Point d indicates the liquid region. Point b corresponds to a
vapor fraction of one, and it is called the dew-point temperature Tdp . This point is when the first drop of
liquid would form while the vapor was cooled from the vapor region like Point a. Point c corresponds to a
vapor fraction of zero, and it is called the bubble-point temperature Tbp . This point is when the first bubble
of vapor would form while the liquid was heated from the liquid region like Point d. If process stream i is
not an azeotropic mixture and its temperature satisfies the following relationship:
Tbp ≤ Ti ≤ Tdp ,
then you definitely know that vapor-liquid equilibrium exists in process stream i.
In HYSYS, you can specify the vapor fraction instead of the temperature or pressure of a process
stream. Three examples of vapor-liquid equilibrium (vle) calculations supported by HYSYS are:
Tdp , X=
 vle
V f 1.0, Pi , Z i 
=
i , Yi 
Tbp , X=
 vle
V f 0.0, Pi , Z i 
=
i , Yi 
Teq , X=
 vle
V f 0.6, Pi , Z i 
=
i , Yi 
where Teq is the equilibrium temperature of process stream i for the given vapor fraction. If you were to
specify Ti instead of Pi in the above three functional forms, you would be calculating the dew-point
pressure, bubble-point pressure, and equilibrium pressure, respectively, for process stream i.
Appendix C
Page C-8
When the material in process stream i exists as two phases in equilibrium, its bulk or overall
properties are related to the saturated liquid (SL) and saturated vapor (SV) properties through the reverselever rule, as was the case for the overall or total composition Zi above. Some common bulk molar
properties for a vapor-liquid equilibrium (vle) system are given below.
Vˆi = V f ⋅ VˆSV + (1 − V f ) ⋅ VˆSL
Hˆ i = V f ⋅ Hˆ SV + (1 − V f ) ⋅ Hˆ SL
Ti , Pi , Yi 
=
=
Hˆ SV hmixSV Ti , Pi , Yi 
VˆSV vmixSV
=
=
VˆSL vmixSL
Hˆ SL hmixSL Ti , Pi , X i 
Ti , Pi , X i 
where
Ti
Pi
is
is
the temperature of process stream i, °C.
the pressure of process stream i, kPa.
Vf
Lf
is
the molar vapor fraction of process stream i, n SV / ni .
is
the molar liquid fraction of process stream i, n SL / ni .
n i
nSV
nSL
is
is
is
the bulk molar flow rate of process stream i, kgmol/h.
the molar flow rate of the saturated vapor in stream i, kgmol/h.
the molar flow rate of the saturated liquid in stream i, kgmol/h.
nc
is
the number of chemical components or compounds in the mixture.
Zi
zi , j
is
the bulk mole fractions of all nc-components in stream i.
is
the bulk mole fraction of component j in process stream i;
vector Z i means all elements zi ,1 , zi , 2 , , zi ,nc .
Yi
yi, j
is
the sat’d vapor mole fractions of all nc-components in stream i.
is
the sat’d vapor mole fraction of component j in process stream i;
vector Yi means all elements yi ,1 , yi , 2 , , yi ,nc .
Xi
xi , j
is
the sat’d liquid mole fractions of all nc-components in stream i.
is
the sat’d liquid mole fraction of component j in process stream i;
vector Xi means all elements xi ,1 , xi , 2 , , xi ,nc .
Vˆi
Vˆ
is
the bulk molar volume of process stream i, m3/kgmol.
VˆSV
is
the molar volume of the saturated vapor in stream i, m3/kgmol.
is
the molar volume of the saturated liquid in stream i, m3/kgmol.
H i
H
is
the bulk molar enthalpy of process stream i, kJ/kgmol.
SV
is
the molar enthalpy of the saturated vapor in stream i, kJ/kgmol.
H SL
is
the molar enthalpy of the saturated liquid in stream i, kJ/kgmol.
SL
The value of any bulk or overall vle property must fall between the values for the saturated liquid and vapor
properties. If you expand the property view of a process stream, HYSYS will display its overall, saturated
vapor, and saturated liquid properties for the vapor-liquid equilibrium that exist in that process stream.
Styrene Net Profit Analysis
Appendix M
Page M-1
Net Profit
For a preliminary design study, the economic viability of manufacturing styrene monomer from toluene
and methanol can be studied by examining the net profit of the chemical process flowsheet. This net
profit can be approximated as follows:
net
profit
=
product
sales
byproduct
sales
+
fuel
credit
+
−
cost of
raw materials
−
annualized
capital cost
−
utility
costs
where each term is $ per year, and federal income taxes are not considered. In the net profit analysis, the
onstream time is 8320 hours per year, which allows for a 2.5-week shutdown of the chemical plant for
annual maintenance.
Once the material and energy requirements for a chemical process flowsheet have been calculated using
Aspen HYSYS®, the six terms on the right-hand side of the above net profit equation can be modeled
by the algebraic equations presented below. All economic data used in these equations can be found in
the “Flowsheet Economic Analysis” section of Chapter 1 of this HYSYS manual. This appendix ends
with the description of a HYSYS spreadsheet operator that simulates the economic model to determine
the net profit for the styrene monomer flowsheet.
Product Styrene Monomer Sales
product
sales
=
$
Stream S33
flow rate
kg
=
yr
*
*
h
sales
price
*
$1.54
*
kg
onstream
time
8320 h
yr
Byproduct Ethylbenzene Sales
byproduct
sales
$
=
Stream S31
flow rate
kg
=
yr
*
*
h
sales
price
*
$0.97
kg
*
onstream
time
8320 h
yr
Hydrogen Fuel-Value Credit
fuel
credit
$
yr
=
=
Stream S13
flow rate
kgmol
h
*
*
Stream S13
LHV
kJ
kgmol
*
*
fuel-value
credit
M kJ
M kJ 106 kJ
$8.53
*
*
onstream
time
8320 h
yr
Appendix M
Page M-2
where the lower heating value (LHV) is the energy realized by combusting the fuel minus the latent heat
of vaporization for water, since water appears as a vapor in the combustion process. The lower-heating
value is automatically calculated by Aspen HYSYS® as one of many properties for a process stream.
Streams S13, S17g, and S23g contain off-gases that can potentially be used as fuel. Streams S17g and
S23g are ignored in the fuel-value credit, since they only represent 2% of the total molar flow of off-gas
in the flowsheet. Stream S13 contains mostly hydrogen and accounts for the other 98% of the off-gas.
Raw Material Methanol Cost
methanol
cost
$
yr
=
=
Stream S4
flow rate
kg
*
*
h
cost
price
$0.35
kg
*
*
onstream
time
8320 h
yr
Raw Material Toluene Cost
toluene
cost
$
yr
=
=
Stream S1
flow rate
kg
h
*
*
cost
price
$0.65
kg
*
*
onstream
time
8320 h
yr
Annualized Capital Cost
Capital cost is the amount of money that you must spend to build the physical plant for a chemical
process flowsheet. That money usually must be borrowed from a bank, in order to complete the
construction of the physical plant, which can take two to three years to finish. Considering the time value
of money, how is the capital cost in dollars accounted for as an annual cost in $/yr over the lifetime of the
physical plant, assuming no salvage value for that plant at the end of its lifetime.
Money has a time value, known as annual interest. At 6% annual interest, $1000 today is not $1000 in
one year, but it is worth $1060 (i.e., $1000 + 0.06*$1000). After two years, it is worth $1123.60 (i.e., $1060
+ 0.06*$1060). After three years, it is worth $1191.02 (i.e., $1123.60 + 0.06*$1123.60). In general, the
future worth of the present value of money can be calculated as follows:
F = P*(1+i)n
where F is the future worth, P is the present value, i is the interest rate as a fraction, and n is the number
of years. At 6% annual interest rate, $1000 dollars today would be worth $2396.56 after 15 years.
If a bank were to lend you $1000 today at 6% annual interest for 15 years, then the bank would charge
you $159.77 per year (i.e., $2396.56/15) to recoup the $1000 plus the compounded interest.
For a capital investment or cost of $1000 at 6% annual interest for 15 years, an annualizing factor can be
determined by taking $159.77 and divided it by $1000 to get 0.15977, which is roughly 1/6 per year. As
Appendix M
Page M-3
an economic heuristic rule, one sixth of the capital cost is the yearly amount to be charged for borrowing
the capital cost from a bank at 6% annual interest for 15 years.
What is the capital cost for a chemical process flowsheet? As an economic heuristic, the capital cost is
roughly equivalent to the sales of the product and byproducts for just one year. For the styrene flowsheet,
capital
cost
=
(
S33 product
styrene sales
$
=
(
$
+
S31 byproduct
ethylbenzene sales
)
*
one year
$
)
*
1 yr
+
yr
yr
annualized capital cost = capital cost / 6 in $/yr
In summary, the yearly cost to borrow the capital from a bank to build the plant for the styrene monomer
flowsheet is one-sixth of its capital investment, where the bank charges 6% annual interest for 15 years.
Electric Utility
The utility cost to run a pump or compressor is based on its power in kW, its mechanical and electrical
efficiency of 90%, and the cost of electricity, as follows:
electric
cost
=
$
=
yr
W
0.90
*
kW
*
unitless
electricity
price
$0.06
kW ⋅ h
*
*
onstream
time
8320 h
yr
where W is the shaft work for the process unit, as calculated from the HYSYS flowsheet simulation.
This cost equation is applied to each pump (P1, P2, P3, P4, P5, and P6) and to the compressor (K1). The
sum of their electric cost is the total electric utility for the styrene monomer flowsheet.
Natural Gas Utility
The utility cost to run the fired heater FH1 is based on its heat duty in kJ/h, the 90% thermal efficiency
of a furnace to burn the natural gas, and the cost of the natural gas, as follows:
natural gas
cost
$
yr
=
=
Q
0.90
kJ / h
unitless
*
*
natural gas
price
$12.10
M kJ
M kJ
106 kJ
*
*
onstream
time
8320 h
yr
Appendix M
Page M-4
where Q is the heat duty to increase the temperature of the feed stream to the reactor, as calculated from
the HYSYS flowsheet simulation.
Heater Utility
The utility cost to run a heater is based on the amount of high-pressure steam required to exchange
energy with the process stream that is being heated. The heating process takes place in a countercurrent
heat exchanger, depicted as follows:
Conceptual Model
Steam System Assumptions
F
feed
E
exit
process stream
Q H
metal
SO
sat’d liq
1.
2.
3.
4.
5.
barrier
42-bar steam
SI
sat’d vap
continuous process
no chemical reactions
neglect KE and PE changes
no shaft work
steam gives up only its latent heat
steam system
The steam is available as a saturated vapor at 42 bar and 253.2°C, with a latent heat of condensation
( ∆Hˆ cond ) equal to 1697.8 kJ/kg. The mass flow rate of steam required to heat the process stream can be
determined from an energy balance around the steam system, as follows:
Q H
m steam
=
kJ
kg
=
h
∆Hˆ cond
*
kJ
*
h
kg
The steam cost can be calculated from the following equation:
steam
cost
$
yr
=
=
Q H
∆Hˆ cond
kJ / h
kJ / kg
steam
price
*
*
$30.97
K kg
K kg
103 kg
*
*
onstream
time
8320 h
yr
where Q H is the heat duty needed to increase the temperature of the process stream, as calculated from
the HYSYS flowsheet simulation. This cost equation is applied to each heater unit (E1, E2, E4, E5, EC1,
and EC3), and the sum of their steam cost is the total heater utilities for the styrene monomer flowsheet.
Appendix M
Page M-5
Cooler Utility
The utility cost to run a cooler is based on the amount of cooling water required to exchange energy
with the process stream that is being cooled. The cooling process takes place in a countercurrent heat
exchanger, depicted as follows:
Conceptual Model
Water System Assumptions
F
feed
E
exit
process stream
Q C
metal
CO
water out
1.
2.
3.
4.
5.
6.
7.
8.
barrier
CI
water in
cooling water
water system
continuous process
no chemical reactions
neglect KE and PE changes
no shaft work
cooling water is available at 1 atm.
constant pressure process.
constant heat capacity for water
constant 1.0 kg/liter for water.
The cooling water is available at 31°C (TCI) and can be heated to only 41°C (TCO), with a constant heat
capacity ( Cˆ P , CW ) equal to 4.1852 kJ/(kg·∆°C). The mass flow rate of cooling water required to cool
the process stream can be determined from an energy balance around the water system, as follows:
Q C
=
kJ
=
h
m CW
kg
h
*
*
Cˆ P , CW
kJ
kg ⋅ ∆ C
*
(TCO − TCI )
*
∆ C
The cooling water cost can be calculated from the following equation:
cooling
cost
$
yr
=
=
m CW
ρ water
kg / h
kg / L
*
*
cooling water
price
*
KL
K L 103 L
*
$0.03
onstream
time
8320 h
yr
where Q C is the cooling duty needed to decrease the temperature of the process stream, as calculated
from the HYSYS flowsheet simulation. This cost equation is applied to each cooler unit (E3, E6, E7, E8,
and EC2), and the sum of their cooling cost is the total cooler utilities for the styrene monomer flowsheet.
Appendix M
Page M-6
Condenser Utility
The utility cost to run a condenser is based on the amount of cooling water required to exchange energy
with the overhead vapor in a distillation column. The cooling process takes place in a countercurrent
heat exchanger, similar to that used in the above Cooler Utility, where Q C is the cooling duty needed to
condense the overhead vapor, as calculated from the HYSYS flowsheet simulation.
The cost equation from the Cooler Utility is applied to each condenser unit in Columns C1, C2, and
C3, and the sum of their cooling cost is the total condenser utilities for the styrene monomer flowsheet.
Reboiler Utility
The utility cost to run a reboiler is based on the amount of high-pressure steam required to exchange
energy with the liquid in the reboiler of a distillation column. The heating process takes place in a
countercurrent heat exchanger, similar to that used in the above Heater Utility, where Q H is the heat
duty needed to vaporize the liquid in the reboiler, as calculated from the HYSYS flowsheet simulation.
The cost equation from the Heater Utility is applied to each reboiler unit in Columns C1, C2, and C3,
and the sum of their heating cost is the total reboiler utilities for the styrene monomer flowsheet.
HYSYS Spreadsheet Operator
The complete economic model to determine the net profit of the styrene monomer flowsheet for a
specific reactor inlet temperature is provided as the HYSYS spreadsheet operator named “net profit”.
The general content of this spreadsheet is presented in the last two pages of this appendix.
In Spreadsheet “net profit”, Columns A and C provide textual documentation. Column B contains
economic data, thermodynamic data, and imported quantities from the styrene monomer flowsheet.
Columns D, E, and F have formula cells that calculate the economics of the flowsheet. All formulae are
used to find the total sales, total costs, net profit, and annual % return, which are displayed in the
bottom right portion of the spreadsheet. The annual percent return on the investment to build the
chemical plant for making styrene monomer is the net profit divided by the capital cost.
For the Problem SM.7 simulation in Chapter 4 of this HYSYS manual, all of the flowsheet quantities in
Column B of Spreadsheet “net profit” have been imported for you, except for six of them. In order to
complete the net profit calculations, you need to import quantities in Cells B3, B30, B52, B72, B90, and
B102. Right click in one of these cells, chose the Import Variable option, and select the HYSYS
object and variable associated with that cell, as described in the two tables below.
Cell
B3
B30
B52
Object
Stream S33
Energy WP1
Unit E1
Variable
Mass Flow
Power
Duty
Cell
B72
B90
B102
Object
Unit E3
Energy QcC1
Energy QrC1
Variable
Duty
Heat Flow
Heat Flow
After you complete the six imports, what are the two largest costs on a percent basis? See Column F.
Appendix M
Page M-7
HYSYS Spreadsheet “net profit” (Part 1 of 2)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
A
Product Sales:
B
C
Economics:
D
E
Net Profit Terms:
F
Total Sales is
=e7+e13
S33 styrene, kg/h:
SM Price, $/kg:
S31 E-benz, kg/h:
EB Price, $/kg:
<import>
1.54
<import>
0.97
% thereof:
SM Sales, $/h:
EB Sales, $/h:
=b3*b4
=b5*b6
Product Sales, $/yr:
Fuel-Value Credit:
S13 off-gas, kgmol/h:
S13 LHV, kJ/kgmol:
Credit, $/M kJ:
Onstream, h/yr:
<import>
<import>
8.53
=(d4+d6)*d9
=e7/f2*100
8320
S17g and S23g off-gas ignored, only
Fuel Credit, $/yr:
2% of total off-gas
=((b11*b12*b13)/1e6)*d9
=e13/f2*100
Total Mat'ls, $/yr:
=(d18+d20)*d9
=e21/f2*100
=b25/6
=e26/f2*100
=d38*d9
=e39/f2*100
=d45*d9
=e46/f2*100
Raw Mat'l Costs:
S4 methanol, kg/h:
MeOH Price, $/kg:
S1 toluene, kg/h:
TL Price, $/kg:
<import>
0.35
<import>
0.65
MeOH Cost, $/h:
Toluene Cost, $/h:
=b17*b18
=b19*b20
Capital Investment:
Capital Cost, $:
Annualize, 1/yr:
Electric Utility:
WP1 Power, kW:
WP2 Power, kW:
WP3 Power, kW:
WP4 Power, kW:
WP5 Power, kW:
WP6 Power, kW:
WK1 Power, kW:
Total Power, kW:
Electricity, $/kW*h:
=(d4+d6)*d9
1/6
Annualized
Capital Cost, $/yr:
0.9
<------ electrical and
mechanical efficiency
<import>
<import>
<import>
<import>
<import>
<import>
<import>
=b30+ … +b36
6.00E-02
Electric Cost, $/h:
=(b37/b28)*b38
Electric Cost, $/yr:
Natural Gas Utility:
FH1 duty, kJ/h:
Thermal Efficiency:
Nat'l gas, $/M kJ:
<import>
0.9
12.10
Nat’l Gas Cost, $/h:
=(b43/b44)*b45/1e6
Nat’l Gas Cost, $/yr:
Heater Utilities:
Steam DH, kJ/kg:
Steam, $/K kg:
E1 Duty, kJ/h:
E1 Steam, kg/h:
E2 Duty, kJ/h:
E2 Steam, kg/h:
E4 Duty, kJ/h:
E4 Steam, kg/h:
1697.8
30.97
<import>
=b52/b50
P is 42 bar
T is 253.2 C
Steam Cost, $/h:
=b53*b51/1000
Steam Cost, $/h:
=b55*b51/1000
Steam Cost, $/h:
=b57*b51/1000
<import>
=b54/b50
<import>
=b56/b50
Appendix M
Page M-8
HYSYS Spreadsheet “net profit” (Part 2 of 2)
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
A
E5 Duty, kJ/h:
E5 Steam, kg/h:
EC1 Duty, kJ/h:
EC1 Steam, kg/h:
EC3 Duty, kJ/h:
EC3 Steam, kg/h:
B
<import>
=b58/b50
C
D
E
F
=(d53+d55+ … +d63)*d9
=e64/f2*100
=(d73+d75+ … +d81)*d9
=e82/f2*100
=(d91+d93+d95)*d9
=e96/f2*100
Reboiler Costs, $/yr:
=(d103+d105+d107)*d9
=e108/f2*100
Sales, $/yr:
Costs, $/yr:
Net Profit, $/yr:
=e7+e13
=e21+e26+ … +e108
=e111-e112
=e113/b25*100
Steam Cost, $/h:
=b59*b51/1000
Steam Cost, $/h:
=b61*b51/1000
<import>
=b60/b50
<import>
=b62/b50
Steam Cost, $/h:
=b63*b51/1000
Heater Costs, $/yr:
Cooler Utilities:
Cp, kJ/(kg C):
Temp Drop, C
Density, kg/L:
Cooling, $/K L:
E3 Duty, kJ/h:
E3 Water, kg/h:
E6 Duty, kJ/h:
E6 Water, kg/h:
E7 Duty, kJ/h:
E7 Water, kg/h:
E8 Duty, kJ/h:
E8 Water, kg/h:
EC2 Duty, kJ/h:
EC2 Water, kg/h:
4.1852
10
1
3.00E-02
<import>
=b72/(b68*b69)
cooling water
T = 31 C to 41 C
Cooling Cost, $/h:
=(b73/b70)*b71/1000
Cooling Cost, $/h:
=(b75/b70)*b71/1000
Cooling Cost, $/h:
=(b77/b70)*b71/1000
Cooling Cost, $/h:
=(b79/b70)*b71/1000
Cooling Cost, $/h:
=(b81/b70)*b71/1000
<import>
=b74/(b68*b69)
<import>
=b76/(b68*b69)
<import>
=b78/(b68*b69)
<import>
=b80/(b68*b69)
Cooler Costs, $/yr:
Condenser Utilities:
Cp, kJ/(kg C):
Temp Drop, C
Density, kg/L:
Cooling, $/K L:
Col. C1 Qc, kJ/h:
C1 Water, kg/h:
Col. C2 Qc, kJ/h:
C2 Water, kg/h:
Col. C3 Qc, kJ/h:
C3 Water, kg/h:
4.1852
10
1
3.00E-02
<import>
=b90/(b86*b87)
cooling water
T = 31 C to 41 C
Cooling Cost, $/h:
=(b91/b88)*b89/1000
Cooling Cost, $/h:
=(b93/b88)*b89/1000
Cooling Cost, $/h:
=(b95/b88)*b89/1000
<import>
=b92/(b86*b87)
<import>
=b94/(b86*b87)
Cond'r Costs, $/yr:
Reboiler Utilities:
Steam DH, kJ/kg:
Steam, $/K kg:
Col. C1 Qr, kJ/h:
C1 Steam, kg/h:
Col. C2 Qr, kJ/h:
C2 Steam, kg/h:
Col. C3 Qr, kJ/h:
C3 Steam, kg/h:
1697.8
30.97
<import>
=b102/b100
P is 42 bar
T is 253.2 C
Steam Cost, $/h:
=b103*b101/1000
Steam Cost, $/h:
=b105*b101/1000
<import>
=b104/b100
<import>
=b106/b100
Steam Cost, $/h:
=b107*b101/1000
% return
Appendix N
Bibliography
Page N-1
Chapter 0 – Preface
Bloom, B. S. (1956). Taxonomy of Educational Objectives, Handbook I: The Cognitive Domain.
David McKay, NY.
Felder, R. M. and Rousseau, R.W. (2005). Elementary Principles of Chemical Processes, 3rd Update
Ed. John Wiley & Sons, Inc., New York, NY. ISBN 978-0-471-68757-3.
Hanyak, M. E. and Raymond, T. M. (2009). "Teaching Material and Energy Balances to First-Year
Students using Cooperative Team-Based Projects and Labs”. Proceedings of the 2009
American Society for Engineering Education Annual Conference, Austin, TX, June 14-17.
Hanyak, M. E. (2011). Companion in Chemical Engineering: An Instructional Supplement. SelfPublished by Michael E. Hanyak, Chemical Engineering Department, Bucknell University,
Lewisburg, PA. Textbook distributed via On-Demand Publishing, LLC, Scotts Valley, CA
thru https://www.createspace.com/3574827.
Himmelblau, D. M. and Riggs, J. B. (2004). Basic Principles and Calculations in Chemical
Engineering, 7th Ed. Prentice Hall, Upper Saddle River, NJ. ISBN 978-0-13-140634-6.
Johnson, D. W., Johnson, R. T., and Smith, K. A. (1998). Active Learning: Cooperation in the
College Classroom. Interaction Book Co., Edina, MN. ISBN 0-0939603-14-4.
Murphy, R. M. (2007). Introduction to Chemical Processes: Principles, Analysis, Synthesis.
McGraw-Hill Companies, Inc., New York, NY. ISBN 978-0-07-284960-8.
Prince, M. J. (2004). “Does Active Learning Work? A Review of the Research”. Journal of
Engineering Education, 93(3), pp. 223-231.
Prince, M. J. and Felder, R. M. (2006). “Inductive Teaching and Learning Methods: Definitions,
Comparisons, and Research Bases”. Journal of Engineering Education, 95(2), pp. 123-128.
Taffe, P. (2008). “New Process may rescue Styrenics Industry ”. ICIS Chemical Business, Web
article at ICIS.com on 21 January 2008.
Chapter 1 – Styrene Monomer Production
AIChE (1984). “Student Contest Problem 1985: Styrene from Toluene and Methanol”. American
Institute of Chemical Engineers, New York, NY.
Halpern, D. F. (1989). Thought and Knowledge: An Introduction to Critical Thinking, Second
Edition. Lawrence Erlbaum Associates, Inc., Hillsdale, NJ.
Hanyak, M. E. (1995). “Optimum Diameter for a Cylindrical Storage Tank”. Chemical Engineering
Department, Bucknell University, Lewisburg, PA.
Appendix N
Bibliography
Page N-2
Hanyak, M. E. (2006). “Styrene Monomer Interactive Demo”. Chemical Engineering Department,
Bucknell University, Lewisburg, PA.
Hanyak, M. E. (2011). Companion in Chemical Engineering: An Instructional Supplement. SelfPublished by Michael E. Hanyak, Chemical Engineering Department, Bucknell University,
Lewisburg, PA. Textbook distributed via On-Demand Publishing, LLC, Scotts Valley, CA
thru https://www.createspace.com/3574827.
Hanyak, M. E. (2011b). “Reactor Data for Toluene Alkylation with Equimolar Methanol at 400 kPa to
produce Styrene Monomer and Ethylbenzene”. Chemical Engineering Department, Bucknell
University, Lewisburg, PA.
Woods, D. R. (2007). Rules of Thumb in Engineering Practice. Wiley-VCH Verlag GmbH & Co.,
KGaA, Weinheim, Germany. ISBN 978-3-527-31220-7.
Chapter 2 – HYSYS Simulation Tutorials
Hanyak, M. E. (2012a). “BEEF Logo Bit Map File”. Chemical Engineering Department, Bucknell
Hanyak, M. E. (2012b). “Starter File t2.02_intro.hsc for Tutorial 2.2”. Chemical Engineering
Hanyak, M. E. (2012c). “Starter File t2.03_replica.hsc for Tutorial 2.3”. Chemical Engineering
Hanyak, M. E. (2012d). “Starter File t2.04_heat.hsc for Tutorial 2.4”. Chemical Engineering
Hanyak, M. E. (2012e). “Starter File t2.05_conv.hsc for Tutorial 2.5”. Chemical Engineering
Hanyak, M. E. (2012f). “Starter File t2.06_pfdtools.hsc for Tutorial 2.6”. Chemical Engineering
Hanyak, M. E. (2012g). “Starter File t2.07_gibbs.hsc for Tutorial 2.7”. Chemical Engineering
Hanyak, M. E. (2012h). “Starter File t2.08_kinetic.hsc for Tutorial 2.8”. Chemical Engineering
Hanyak, M. E. (2012i). “Starter File t2.09_report.hsc for Tutorial 2.9”. Chemical Engineering
Hanyak, M. E. (2012j). “Starter File t2.10_spreadsheet.hsc for Tutorial 2.10”. Chemical Engineering
Appendix N
Bibliography
Page N-3
Chapter 3 – Process Unit Exercises
Hanyak, M. E. (2012a). “Starter Files HY1.A and HY1.B for Problem HY.1”. Chemical Engineering
Hanyak, M. E. (2012b). “Starter Files HY2.A and HY2.B for Problem HY.2”. Chemical Engineering
Hanyak, M. E. (2012c). “Starter Files HY3.A and HY3.B for Problem HY.3”. Chemical Engineering
Hanyak, M. E. (2012d). “Starter Files HY4.A and HY4.B for Problem HY.4”. Chemical Engineering
Hanyak, M. E. (2012e). “Starter Files HY5.A and HY5.B for Problem HY.5”. Chemical Engineering
Chapter 4 – Flowsheet Development Exercises
Hanyak, M. E. (2012a). “Starter Files SM1_465, SM1_480, SM1_495, SM1_510, SM1_525, and
SM1_540 for Problem SM.1”. Chemical Engineering Department, Bucknell University,
Lewisburg, PA.
Hanyak, M. E. (2012b). “Starter Files SM2_465, SM2_480, SM2_495, SM2_510, SM2_525, and
Lewisburg, PA.
Hanyak, M. E. (2012c). “Starter Files SM3_465, SM3_480, SM3_495, SM3_510, SM3_525, and
Lewisburg, PA.
Hanyak, M. E. (2012d). “Starter Files SM4_465, SM4_480, SM4_495, SM4_510, SM4_525, and
Lewisburg, PA.
Hanyak, M. E. (2012e). “Starter Files SM5_465, SM5_480, SM5_495, SM5_510, SM5_525, and
Lewisburg, PA.
Hanyak, M. E. (2012f). “Starter Files SM6_465, SM6_480, SM6_495, SM6_510, SM6_525, and
Lewisburg, PA.
Hanyak, M. E. (2012g). “Starter Files SM7_465, SM7_480, SM7_495, SM7_510, SM7_525, and
Lewisburg, PA.
Appendix N
Bibliography
Page N-4
Hanyak, M. E. (2012h). “Methanol Alkylation of Toluene to produce Styrene Monomer: A Flowsheet
Mathematical Model and Algorithm”. Chemical Engineering Department, Bucknell
Hanyak, M. E. (2012i). “Methanol Alkylation of Toluene to produce Styrene Monomer: The Iteration
Process on a Recycle Loop in the HYSYS Flowsheet Simulation”. Chemical Engineering
Appendices
Felder, R. M. and Rousseau, R.W. (2005). Elementary Principles of Chemical Processes, 3rd Update
Ed. John Wiley & Sons, Inc., New York, NY. ISBN 978-0-471-68757-3.
Hanyak, M. E. (2012a). “Appendix A: EZ Setup Solution for the Example Batch Simulation”.
Chemical Engineering Department, Bucknell University, Lewisburg, PA.
Hanyak, M. E. (2012b). “Appendix A: HYSYS Solution for the Example Batch Simulation”.
Hanyak, M. E. (2013). “Appendix C: TXY Diagram for a Binary System in Aspen HYSYS”.
Montgomery, S. (2001). Visual Encyclopedia of Chemical Engineering Equipment, Version 2.1.
Multimedia Educational Laboratory, Chemical Engineering Department, University of
Michigan, Ann Arbor, MI.

HYSYS manual - Academics

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