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Copper Refinery Operationin PT. Smelting
Electrorefining
• Application of electrical potential between copper anode and metal cathode in CuSO4-H2SO4-H2O electrolyte.
Refining process: Anode (99% Cu) Cathode (99.99% Cu)
SS-blank Cathode (-)
Fresh Anode (+)
Cuo = Cu++ + 2e-
Power supply
Cu++ + 2e- = Cuo
CuSO4 + H2SO4 + H2O
Electrorefining Process
• Electrochemically dissolving copper from impure copper anode to electrolyte
Cuoanode Cu++ + 2e- Eo = +0.34V
• Selectively electroplating pure copper without anode impurities from electrolyte onto cathodes
Cu++ + 2e- Cuocathode Eo = -0.34V
Standard Electrochemical (Reduction) Potentials
Au3+ + 3e- ---> Auo 1.50 voltsAg+ + e- ---> Ago 0.80 voltsCu2+ + 2e- ---> Cuo 0.34 voltsBiO+ + 2H+ + 3e- ---> Bio + H2O 0.32 voltsHAsO2 + 3H+ + 3e- ---> Aso
+ H2O 0.25 voltsSbO+ + 2H+ + 3e- ---> Sbo
+ H2O 0.21 volts2H+
+ 2e- ---> H2 0 (pH=0; pH2=1atm)Pb2+ + 2e- ---> Pbo -0.13 voltsNi2+ + 2e- ---> Nio -0.26 voltsCo2+ + 2e- ---> Coo -0.28 voltsFe2+ + 2e- ---> Feo -0.45 volts
Refining Target
• Production of pure copper, free from impurities (<65ppm)
• Separation of valuable impurities - precious metals Ag, Au, Pt - as slime (by-product)
PT SmeltingRefinery Plant
Element group
Element Symbol Max content (ppm)
Max content group (ppm)
Internal <= ppm
1 Selenium Se 2 2Tellurium Te 2 3 (Se, Te) 2Bismuth Bi 2 3 (Se, Te, Bi) 1
2 Chromium Cr -Mangan Mn -Antimony Sb 4 4Cadmium Cd -Arsenic As 5 5Phosphour P - 15
3 Lead Pb 5 5 3
4 Sulfur S 15* 15* 10
5 Tin Sn - 5Nickel Ni - 10Iron Fe 10 10Silicon Si -Zinc Zn -Cobalt Co - 20
6 Silver Ag 25 25 25
Total 65
* measured from cast sample
Data: British Standards Institute, BS 6017:1981
LME A-GRADE
(exclude oxygen)
Copper Cathode
Typical cathode analysis
DATEBiSeTe
<3SeTe
<3Ag <25
Pb <5
Fe <10
As <5
Sb <4
S <15 Bi <2
Se <2
Te <2 Ni
Impurities <65
Cu >99.9935
2004-08-25 0.3 0.2 6 0.7 1 0.3 0.1 3 0.1 0.1 0.1 0.2 11.7 99.99882004-08-24 0.3 0.2 7 0.6 1 0.3 0.1 5 0.1 0.1 0.1 0.3 14.7 99.99852004-08-23 0.3 0.2 7 0.9 1 0.4 0.1 5 0.1 0.1 0.1 0.3 15.1 99.99852004-08-22 0.3 0.2 7 1.1 1 0.3 0.1 4 0.1 0.1 0.1 0.1 14.0 99.99862004-08-21 0.3 0.2 7 0.9 1 0.5 0.1 5 0.1 0.1 0.1 0.4 15.3 99.99852004-08-20 0.3 0.2 6 0.7 1 0.2 0.1 5 0.1 0.1 0.1 0.2 13.6 99.99862004-08-19 0.3 0.2 7 1.2 1 0.3 0.1 3 0.1 0.1 0.1 0.2 13.2 99.99872004-08-18 0.3 0.2 7 1.4 1 0.4 0.1 4 0.1 0.1 0.1 0.4 14.7 99.99852004-08-17 0.4 0.3 7 1.2 1 0.3 0.1 4 0.1 0.2 0.1 0.2 14.3 99.9986
Typical anode analysis
Lot No.Au (96 gr/t)
Ag (114 gr/t)
Cu (>99.5
%)
PB (0.080
%)
S (0.004
%)
SB (0.001
%)
AS (0.047
%)
BI (0.011
%)
O (0.150
%)
SE (0.056
%)
TE (0.021
%) ZN % FE % AL %
NI (0.052
%) SN % CD %4214 99.4 272.0 99.140 0.265 0.005 0.003 0.106 0.026 0.070 0.067 0.005 0.002 0.002 0.001 0.012 0.001 0.0014215 95.7 277.0 99.090 0.268 0.002 0.003 0.110 0.030 0.070 0.076 0.007 0.001 0.001 0.001 0.011 0.001 0.0014216 92.7 268.0 99.280 0.249 0.003 0.003 0.109 0.030 0.370 0.072 0.008 0.001 0.002 0.001 0.010 0.001 0.0014217 87.4 263.0 99.470 0.247 0.003 0.003 0.097 0.025 0.120 0.107 0.009 0.002 0.002 0.001 0.009 0.001 0.0014218 95.3 276.0 99.060 0.167 0.004 0.002 0.066 0.022 0.080 0.077 0.008 0.001 0.002 0.001 0.008 0.001 0.0014219 105.1 277.0 99.450 0.126 0.001 0.002 0.061 0.012 0.050 0.067 0.008 0.001 0.003 0.001 0.008 0.001 0.0014220 111.2 272.0 99.380 0.170 0.007 0.002 0.048 0.011 0.070 0.069 0.007 0.002 0.004 0.001 0.009 0.001 0.0014221 120.2 286.0 99.360 0.146 0.003 0.001 0.051 0.012 0.070 0.066 0.007 0.001 0.002 0.001 0.007 0.001 0.0014222 121.1 287.0 99.050 0.187 0.001 0.002 0.081 0.015 0.070 0.061 0.007 0.001 0.004 0.001 0.007 0.001 0.0014223 115.5 282.0 99.560 0.187 0.004 0.002 0.083 0.016 0.170 0.068 0.007 0.001 0.003 0.001 0.008 0.001 0.0014224 104.3 272.0 99.260 0.222 0.001 0.003 0.113 0.019 0.140 0.061 0.007 0.001 0.004 0.001 0.008 0.001 0.0014225 94.7 271.0 99.470 0.222 0.001 0.003 0.099 0.022 0.080 0.078 0.007 0.001 0.004 0.001 0.009 0.001 0.0014226 94.8 272.0 99.030 0.286 0.003 0.003 0.095 0.027 0.070 0.090 0.008 0.002 0.001 0.001 0.010 0.001 0.001
Operation Control
• Electrodes flatness and alignment.
• Anode composition (Lead, Arsenic).
• Electrolyte parameter (Cu, FA, Cl-, Impurities, reagent, temperature, flow rate, and clarity).
• Cell monitoring (shorts inspection and breaking).
SS-blank Cathode
Fresh Anode
7th dayFinish20th day
50kgCathode 100kgCathode
Anode Scrap
Start0 day
Anode life
Crop Schedule• New anode + new SS blank insertion in cell• ER 7 days: Cathode stripping 50 kg/plate• Blank inserted again• ER 13 days: Cathode stropping 100 kg/plate• Anode scrap discharging• Electrolyte draining• Slime draining• New anode + blank insertion ...
Tankhouse
252,000762
Present
32,000108Diff
220,000Production (T/Y)654Cell Number (cells)
Before Exp.
SlimeTreatment Plant
TelluriumRecovery Plant Control Room Electrolyte Circulation Equipment
LiberatorCells Commercial Cells
ExpandedOriginal
LiberatorRectifiers
CommercialRectifiers
1
2
3
4
5
6
7
8
9
1011
12
13
14
15
16
17
18
19
20
21
AnodeAnodeScrap
Cathode
MachineArea
22
Plant Layout
Outside View
SIMPLIFIED PROCESS IN REFINERY
Rectifier
• 2 x 18 kA, 295 V• Thyristor• Power at maximum capacity = 10 MW• Current density 180~314 A/m2
Anode• Cu : 99.2~99.5%
• Continuous casting:
Hazelett Contilanod
• 380 kg/plate, 45 mm thick
• 970 x 938 mm area
• 20 Days anode life
Anode Preparation Machine
• Spacing 103.5 mm
• Lug brushing
• Anode verticality measurement, 5 mm
• 59 Anodes per cell
Cathode Mother Plate
• ISA Process Permanent Cathode
• SUS 316L• Surface 2B• 1 x 1 m deposit face• Bottom wax• ABS edge strip• 58 Cathodes per cell
Overhead Cranes
• 2 x 27T capacity
• Semi-automatic electrode bale
• Simultaneously 58 anodes and 58 cathodes lifting
• Manual positioning
Commercial Cells
• 762 cells• Polymer concrete• V-notch weir • Cell voltage 0.3 V/cell
Electrode Alignment
• Gap between anode and cathode must be uniform.
• One side lays on busbar and another side lays on insulator.
• Touching = short
Inside Tankhouse
Electrolyte
• Cu : 48-50 g/l
• H2SO4 : 170-180 g/l
• Cl- : 50-60 mg/l• Temp : 58-62oC• Flowrate : 35-40 l/m• Steam-heated by
plate heat exchanger
CELL
CIRCULATION TANK
HX
tankhead
overflowsteam
condensate
ELECTROLYTE FLOW
ELECTROLYTE FLOW DURING 2nd-CROP
CELL
Slime to leaching
area
Decant Tank
Leaf filter
Electrolyte Storage Tank
To electrolyte circulation tank
Heat Exchanger
• Plate type HX
• Less space than shell & tube type
• Higher heating efficiency
Reagents
• Glue: leveling agent
• Thiourea: grain refiner
• HCl: grain refiner
Some ER tankhouse add AVITON
Cropping activity
Cathode Washing & Stripping Machine
• Washing by hot water 86oC to melt wax
• Flexing to open• Chiseling to peel-off• Apply bottom waxing• Spacing 103.5 mm
Product Cathode
• 1st-crop = 50 kg/sheet
• 2nd-crop = 100 kg/sheet
• Size 1 x 1 m
• LME Grade-A
• Capa. 235,000 t/y
Current Efficiency
• Ratio between actual cathode deposited and theoretical deposition by Faraday’s law
• Simplified formula for theoretical deposit:
W (kg) = 1.185 x set kA x hour x cell
• Target CE = 96.0 %
Why CE drops?• Mainly by short circuit
between anode-cathode
• Checked by infra-red camera, or gaussmeter
• Short must be broken to avoid current loss
SHORT
Shorts/cell vs CE-1
y = -0.0112x + 0.9917
R2 = 0.8582
y = -0.0045x + 0.9721
R2 = 0.5746
90%91%92%93%94%95%96%97%98%99%
100%
0 1 2 3 4 5 6
CE1-DK185 CE1-DK312
Anode Scrap Washing Machine
• Washing anode scrap by hot water
• Anode scrap ratio 11~14%
Electrolyte Purification
• Dissolved Cu in electrolyte: 14 kg per ton Cathode.
• Soluble anode impurities build-up: Bi, Co, Fe, and Ni.
• Partially dissolved As and Sb.
• Dissolved Se and Te from slime leaching process.
Liberator Cells
• Electrowinning cell– Anode: H2O 2H+ + 1/2O2 + 2e-
– Cathode: Cu++ + 2e- Cu
• Using lead anode• Cell voltage = 2.4 volt• Total 32 cells (Primary, Secondary, Tertiary)• Used for stabilizing Cu in electrolyte as anode
dissolve is ~1.4% and reducing some impurities.
Liberato r S ludge
S m elter
L iberato r S ludgeT reatm ent A rea
P rim aryLiberato r
T ertiaryLiberato r
S eco ndaryLiberato r D eco pperizatio n
T ank
W W T P
Comm. Cell
3 m3/d
LIBERATOR ELECTROLYTE FLOW
Comm. Cell Head Tank
Decopperized Solution
Primary Liberator
• ISA blank cathode• Pb-Sn-Ca anode,
cold rolled• Reducing Cu from
50 40 g/l in the electrolyte
• Saleable liberator cathode product
Secondary Liberator
• Anode scrap as cathode
• Reducing Cu from 40 20 g/l in electrolyte
• Deposited cathode recycled in smelter
Tertiary Liberator
• Anode scrap as cathode
• Reducing Cu from 20 1 g/l , then deposited As, Sb and Bi.
• Sludge to be recycled to smelter
Anode Slime
• Insoluble elements in anode is accumulated at cell bottom (slime).
• Au, Pt, As, and Sb• Ag2Se, Ag2Te, Cu2Se,
Cu2S, PbSO4, Sn(OH)2SO4.
• Cu in slime must be controlled lower than 1%
S lim e S ettler
S lim e D ecant T ank
S lim e S lurry T ank
A uto c laves
S team
O xygen
H o ld ing T ank
C entrifuge
R epulp T ank
C entrifuge
Filter P ress
A uto c lave Feed T ank
H . W ater
D eco pperized S lim es
D ecant S lim es
S ulfuric A c id
Filtrate
Filtrate
Decant
Comm. Cell
SLIME DECOPPERIZING PROCESSING
Decopp. Solution
Comm. Cell
Te-Recovery
Leaching par: 115 deg.C 4.5 kg/cm2 3 hours 15-20% solid dens.
Slime Leaching
• Using autoclave
• High temperature
• High pressure
• Oxygen blowing
• Cu + H2SO4 + 1/2 O2 CuSO4 + H2O
• Cu2O + 2H2SO4 + 1/2 O2 2CuSO4 + 2H2O
• Decopperized slime : tankhouse by-product
Centrifugal Separator
• Used for dehydrating leached slime.
• Centrifugal force will separate fluid as filtrate
• Solid material remain on the screen
Slime analysis
0.03.06.09.0
12.015.018.021.024.027.030.033.036.039.042.045.048.051.054.057.0
Pb
Se
Ag
Bi
As
Au
Cu
Te
Sb
Fe
Ni
Sn
Pd
Pt
Elements
% (d
ry)
Sample-1 Ave. Aug-04 Typical (21-Jul-04)
Te Settlerto Commercial
Filtrate Tank
R1R2R5R6R7R8
R3R4
From Te Feed Tank
Filter PressCu2Te Byproduct
• Some Te in slime is leached and concentrated in solution• Te-recovery reactor is set at 94 deg.G• Reactor: 4 tanks with 6 cages each :
– 1 cage = 50 kg x 29 plates = 1.45 ton copper scrap• Treated solution is Te<50 ppm (design)• Cu2Te cropping: 1 tank/week
Tellurium Recovery
Tellurium Reactorfrom Slime area
to Commercial
1000~5000 ppm
<50 ppm
Tellurium Reactors
• Filtrate from slime area: high Te
• Te must be recovered before returned
• Use copper scrap for cementation of Cu2Te
Filter Press
• Used for Cu2Te dehydration
• Pneumatic air pressure will separate solid from liquid