Slide 6

Débora Monteiro & Luis Sobral
Centre for Mineral Technology - CETEM/MCTI
Maio/2012
Pyrometallurgical process
T 10000C
CuFeS 22.5O 2  Cu 0  FeO  2SO 2
Hidrometallurgical processes
Direct chemical leaching
Pressure leaching
Acid rock drainage
2FeS 27O2 2H 2O  2FeSO 4 2H 2SO4
2FeSO 4 0.5O2  H 2SO4  Fe 2 (SO4 )3  H 2O
FeS 27 Fe 2 (SO4 )3 8H 2O  15FeSO 4 8H 2SO4
Microorganism isolation
(ARD, sludges and ore)
Strains from culture collection
(ATCC/USA and DSMZ/Germany)
In vitro cultivation
(contacting the M-os with nutrients and energy sources)
Bioleaching tests
Amenability testing
Cominution
Caracterization
Acid consumption
In vitro bioleaching tests
Results to be expected:
•To evaluate the maximum metals extraction as well as the
toxic effect of those metals and other heavy metals should
they are present and at what concentration;
•Evaluate the maximum acid consumption.
Bioleaching tests
Semi-pilot scale
Results to be expected:
•To foreseen the efficiency of the bioleaching process on each
operating temperatures;
•The viability of the used microorganisms during the bioleaching
process and the influence of the heterotrophic microorganisms
during the bioleaching process;
•The maximum extraction of the metals of interest bearing in
mind the ore particle size range used and the acid consumption in
such operating conditions, taking into consideration that not all
the gangue minerals will be available to such acid digestion;
•The evaluation of the metals extraction efficiencies bearing in
mind the different two ways of crushing the ore under study (Jaw
crusher, HPGR and Selfrag).
Bioleaching tests
Pilot scale
Results to be expected:
•The behaviour of used microorganisms in diverse pH, Eh and temperature
for different height of the ore bed;
•Identification of predominant microorganisms in the above mentioned
heights through molecular biology techniques;
•Whether or not will be necessary to re-inoculate the ore body as the
bioleaching process goes on;
•The leaching solution percolation and air blowing efficiencies while running
the bioleaching process;
•The necessity or not of an extra offer of CO2;
•The influence of the ever increasing metals concentration being released
into solution while running the bioleaching process through the dynamic
evaluation of the extraction of metals of interest (chemical analysis);
•The evaluation of axial flow of liquor and possible slumping of the ore bed.
Parameters
Effect
Temperature
Physicochemical
pH
Ferric ions
Oxygen
Microbial diversity cultures
Microbiological
Mineral
-affects leaching rate, microbial
composition and activity
- needs to be low to obtain the fastest
leaching rates and to keep ferric iron and
metals in solution
- electron acceptor needed in chemical
and biological oxidation
mixed cultures tend to be more robust and
efficient than pure ones
Population density
high population density tends to increase
the leaching rate
Metal tolerance
high metal concentrations may be toxic to
microorganisms
Composition
provides electron donor and trace
elements
Particle size
affects the available mineral/liquid contact
area
Surface area
leaching proportional to the increase in
mineral surface area
Porosity
cracks and pores in the particles give rise
to the internal area
Presence of other metal sulphides
mineral having the lowest potential is
generally oxidized first (galvanic couple)
GEOCOATTM Process
Solution Irrigation
Flotation concentrate
coating
Support rock
Void
Air flow
Column temperature (ºC)
Set point temperature (ºC)
Temperature ºC
Copper extraction (%)
Copper extraction (%)
Time(days)
Copper extraction vs. Time
Copper extraction: 90.06% (74 days)
 Caraíba Mining – Brazil
 Quebrada Blanca - Chile
 Talvivaara - Finland
 Agnes Gold Mine – South Africa
Caraíba Mining Co. - Brazil
– GEOCOAT™ Demonstration Plant
• Design
– 10,000 tpa crushed ore
- Sulphide copper Concentrate (28 % Cu)
– 4 months operation
up to 80 % Cu extraction
– 40 m x 40 m x 6 m heap
Concentrate
Chalcopyrite (58%)
CuFeS2
Bornite (38%)
Cu5FeS4
Pyrite (2% )
FeS2
Caraíba Mining Co. - Brazil
Demonstration Plant
Quebrada Blanca - Chile
– GEOLEACH™ Demonstration Plant
• Design
– 40,000 tpa crushed ore
• 1.35% Cu
• 2.8 % S(T)
– Chalcocite and Chalcopyrite
– 250 day demonstration
– $1.0 million capital
investment
– 60 m x 60 m heap
75% extraction
Quebrada Blanca - Chile
Quebrada Blanca - Chile
Talvivaara - Finland
Internationally significant base metals producer
with primary focus on nickel and zinc.
• Targeted full scale production from 2012
– Nickel 50,000 tonnes p.a.
– Zinc 90,000 tonnes p.a.
– Copper 15,000 p.a.
– Cobalt 1,800 tonnes p.a.
• Estimated mine life approx. 46 years
Talvivaara - Finland
The bacteria used in the Talvivaara process grow
naturally in the ore, and the company reports
recovery rates of up to 98% of metal from ore to
solution.
Reserves 257 Mt
0.27% Ni
0.02% Co
0.14% Cu
0.55% Zn
600 – 1200 m3/h
Talvivaara - Finland
Source: www.talvivaara.com
Talvivaara - Finland
Talvivaara - Finland
Raising the heap
Stacking operation
Agnes Gold Mine – South Africa
Heap 50m x 40m x 8m
65000 t of concentrate per year
Agnes Gold Mine – South Africa
Agnes Gold Mine – South Africa
Cil – Carbon in leaching
Gold-bearing activated
carbon (to elution
process)
• Low grade zinc ore (Zn + Pb)
• Low grade zinc ore (Zn, Cu and precious metals)
• Low grade copper ore (CuFeS2)
• Low grade nickel ore (Ni + Cu)
• And bioleaching of flotation process residue
High pressure grinding rolls (HPGR)
Polysius, Germany
HPGR
HPGR Product
Jaw Crusher
Ghorbani et al./Minerals Engineering 24 (2011) 1249-1257
Baum and Ausburn/Minerals and
Metallurgical Processing 28 (2011) 77-81
Selfrag- Electro-dynamic Fragmentation
www.selfrag.com
Selfrag
www.selfrag.com
Selfrag Lab, 2012
Selfrag
www.selfrag.com
Capacity: 35000 t/a
Value proposition: Selectivity continuous in
modules
Application: Mining, E-scrap Recycling,
Concrete Recycling etc.
Before such possibilities of bio-extracting metals out of ores, concentrates and tailings one can mention that:
The bioleaching process is far more environmentally friendly as the metals are put into
solution, which is easier to control their issues to ground water, although safety
measures have to be taken so as to avoid releasing metal ions to water streams;
Before such possibilities of bio-extracting metals out of ores, concentrates and tailings one can mention that:
As far as the use of autotrophic microorganisms is concerned we can assure that they
do not pose any risk for the human being and to any other living species;
Before such possibilities of bio-extracting metals out of ores, concentrates and tailings one can mention that:
Taking into consideration that the PLS being continuously produced has to go through
solvent extraction process, in order to get a metal of interest concentrated and free
of metallic impurities solution and ready for the electrowinning process, the raffinate
can return to the bioleaching process as it contains high acidity and high
microorganisms population. However, should such raffinate carries much extractant
micro-droplets it can be detrimental for its percolation down the heap as its top layer
can acts as a coalescence surface for such droplets causing the leaching solution to
by-pass the heap.
Thank you!
Débora Monteiro de Oliveira M.Sc.
Service of the Metallurgical and Biotechnological Processes
dmonteiro@cetem.gov.br
Luis Gonzaga Santos Sobral Ph.D
Head of the Metallurgical and Biotechnological Processes Division
Lsobral@cetem.gov.br
Centre for Mineral Technology CETEM/MCT
Av. Pedro Calmon, 900
Cidade Universitária
Rio de Janeiro - RJ
CEP: 21941-908
Tel: 55 21 3865-7246
Fax: 55 21 3865-7232