Techno-economical analysis of SNG production from

Technoeconomical study of bio-SNG
production from lignocellulosic
biomass
EGATEC
Conference 12-13.5.2011
GERG Network
Researcher Kristian Melin
Aalto University
School Of Chemical Technology
Bio and Chemical Technology
9.5.2011
Outline of presentation
• Different Lignocellulosic Biomass (Potential from a
Finnish perspective)
• Transport from site to plant
• Bio-SNG Conversion Technology
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Pre-Treatment for bio-SNG Production
Gasification
Synthesis gas Cleaning
Shift Reaction and Methanation
Economics of bio-SNG production
Sensitivity Analysis
Effect of Plant Scale on Economics
Conclusions
Acknowledgement
9.5.2011
Different Lignocellulostic Biomass
• Forest Chips
– branches, stumps, and small wood.
– logging residues per m3 of log usually 20-40 %
which is used in paper and pulp industry.
– Potential in Finland 23,5 TWh (Simola 2010)
0->40 m3/km2/y Ranta (2004)
– Logging Residues mostly available followed
by small wood and stumps.
• Agricultural Biomass
– Reed 30 MWh from 1 ha, 1t ~4,5 MWh density
very low 60-80m3 if not densified.
– With 10% use of available farming
land in Finland 6-9 TWh could be obtained
annually.
– Straw potential around 1 TWh and10 MWh/m3 Lötjönen (2007)
– Products from pulp and paper industry for example lignin
separated from black liqour could be used.
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Transport of biomass from site to plant
• Harvest of Energy Biomass from the forest.
• Transport :
– Truck transport of biomass
• The truck maximum weight in Finland for example 60t (40 t of load) and volume 145
m3 .
• Logging residues only compacted (volume limiting)
• Logging residues as Felling logs. (mass limiting)
• Chipped Biomass (mass limiting)
– rail transport .
– by ship.
• Estimation of transport costs
•
– Transport costs for logging residue as felling logs 2 € +0,07 x100 km for
biomass transport distance one way.
– Assumed that the average transport distance equals radius of harvest area
.
For agricultural biomass (reed, wheat straw the transport of 40 km transport cost of
9.5.2011
4 €/MWh
have been reported.
Pre-Treatment of biomass before
gasification
• Requirements for gasification
– Particle size:
• In Fluidized bed particle size up to 25-30
mm and chips tolerated Bridgwater(2002).
– Moisture Content:
• Less than 15 w-%.
• Heat released in the process can be utilized in drying of wet biomass with
flue gas, steam or low temperature air.
• Torrified biomass with very low moisture (3 w-%) content be pulverized
and gasified as dust in entrained bed gasifiers.
9.5.2011
Gasification Technology
– Oxygen and Steam
• Heat from combustion drive the
endothermic gasification reactions.
– Indirect Gasification Using Steam
• Two stage heat transfer agent and
remaining charcoal from gasification are
separated and combusted with air heating
the sand (heat transfer agent).
• In the second stage steam is added and required heat is obtained from the
hot sand.
– Hydrogasification
• Hydrogen reacts with carbon in an exothermic way giving methane with
high yield.
• The gasification reaction is slower than with steam or CO2.
– Supercritical Gasification (at critical conditions of water).
– Gasifier types: Bubbling fluidized Bed and Circulation Fluidized Bed.
9.5.2011
Synthesis gas clean-up
– For bio-SNG synthesis the raw synthesis gas
needs to be cleaned from following impurities.
• Tars can be destroyed by catalytic cracking using dolomite or
Nickel catalyst or thermally by adding oxygen to the gas so
that temperature is increased to <1000°C.
• Alkalis (Na and K)
– Exist in vapor phase at high temperatures are removed in wet
scrubbing system or by adsorption.
• Chlorine
– Can be removed by adsorption or water scrubbing etc.
• Sulphure
– Can be removed by scrubbing using an physical solvents, amines etc.
– removed somewhat by dolomite
– Low levels can be removed by ZnO beds.
• Nitrogen (NH3 and HCN)
– Ammonia readily dissolves in water can be removed by scrubbing.
– HCN can be hydrolysed into NH3 .
• Particulates
– Fine particles not removed by cyclone can be removed with ceramic filters.
9.5.2011
Synthesis gas reaction to form bio-SNG
Shift reactor
– If methanation catalyst do not have
water gas shift activity a separate shift reaction
stage might be needed.
–
High Temperature (300-500 ºC)Iron Chromium Oxide
–
Low Temperature shift (º180-270) sensitive to sulphur.
–
Raw Gas shift (200-500 ºC) cobalt and molybdenum
catalyst can withstand high amount of sulphur etc.
Methanation
–
–
–
–
CO and CO2 reacts with H2 into CH4 and H2O while large amount of heat is released.
• Catalyst for example Nickel is sensitive to sulphur impurities in the gas.
Lower temperature and higher pressure favorable for methane production
Carbon formation problem especially at high pressure and low temperature
Fixed bed methanation,
• Many reactors with intermediate cooling or gas recycle operated at elevated pressures.
• Temperatures up to 650 ºC (Rostrup-Nielsen et al., 2007)
can
be used
– Fluidized bed reactors
• Single reactor isothermal operation.
• Can be operated around 300ºC even at atmospheric pressures.
9.5.2011
Assumption for Techno-economic Calculation
Process parameters
• Direct oxygen blown gasification with gasifier outlet temperature 800 °C
• Biomass composition as ultimate composition of Spruce Biomass and
Lower Heating value as input and Biomass moisture content 15 w- %
(assumed to be dried to by steam generated)
• Gas purification 2 MJ/Kg of removed CO2
• The yield of SNG estimated from gasifier outlet composition and reaction
stoikiometrics for the Shift and Methanation reactor.
• Gas with H2/CO ratio 3 is produced and CO2 is removed before
methanation.
• Eletricity consumption estimated for synthesis gas compression and
oxygen manfucturing ( 80 kWh ton of biomass).
Economics
• Operation cost calculated based on simulation model
• Investment cost taken from VTT:s estimate 200 milj euros for300 MW
SNG plant and scaled according to capacity and corrected from time
McKeough (2005 )
Biomass
CO-SHIFT
H2/CO ratio 3
Biomass Gasification
5 bar and 800 C
Steam
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CO2 Separation
Gas
Compression
to 25 bar
Methanation at
350 C HP steam
produced in
reactor cooling
Flash To
Separate Water
SNG
Economics of total bio-SNG Process
Total Biomass Feed on LHV basis
(MW)
Efficiency to SNG on LHV basis %
300
67
Total electricity Consumption MW
Heat for amine Regeration MW
MP Steam Selling Price €/MWh
Electricity Price €/MWh
Annual operation h/a
Life Time of Invesment in years
Required rate on the capital%
13.2
38.4
13
40
8000
20
10
Production costs
Biomass Transport
Biomass
Annuity of inv. Cost
Electricity
Steam ( income)
Milj €/a
13.8
26.4
26.6
4.2
-0.8
70.1
% of total
19.6
37.7
37.9
6.0
-1.1
100.0
Logisctics
Biomass at Collection site
€/MWh
11
9.5.2011
Biomass
Transport cost Biomass at
by Truck
Plant
€/MWh
€/MWh
5.7
16.7
Average
Transport
distance
km
138
Yield
m3/a/km2
20
Sensitivy analysis of bio-SNG production
Sensitivity Analysis of bio-SNG Production
Production cost of bio-SNG (€/MWh)
60
50
40
Investment Cost
Biomass Costs
30
Transport Costs
SNG Yield
20
10
0
-60
-40
-20
0
20
Change on the variable in %
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40
60
Effect of plant scale on the economics
bio-SNG Production cost as function of Capacity
SNG Production cost [€/Mwh)
55
50
45
€/MWh
40
35
30
0
200
400
600
800
1000
Plant capacity Biomass Input [MW]
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1200
1400
Conclusions
• The yield of SNG affects the production
cost mostly of the studied variables.
• The Investment cost and raw material
effect the productions cost more whereas the transport cost
where less significant.
• Indirect steam gasification has been reported more
economically feasible compared with direct oxygen gasification.
• Hydrogasification combined with converting formed CO from
biomass into hydrogen should be studied more in detail due to
high efficiency of hydrogasification.
9.5.2011
Thank You!
• Special Thanks to:
– Colleagues at Plant Design:
– Markku Hurme, Raja
Mudassar and Jukka Koskinen.
– Sari Siitonen at Gasum for kind
invitation to GERG network
and valuable cooperation.
– Finnish Science academy:
Concepts of 2nd generation
biorefinery.
– Walter Ahlström foundation for funding.
9.5.2011