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