An Overview of the Base Metal Removal Plant at

Northam Platinum Limited

Plant Manager BMRP

Presented by : Ashley Corbett

BMR Plant

Granulated Cu-Ni-PGM matte from Smelter

50% Ni, 29% Cu, 16% S <1.0% Fe and 0.4% 3 PGE’s + Au

Metallic Copper Cathode Plate (99.96% Cu)

Granulated Nickel Sulphate Hexahydrate crystals (22% Ni)

PGM Concentrate (45-50% 3PGE’s + Au)

Personnel

Operations Personnel Complement 51

Engineering Maintenance Complement 20

Control Room

Operator

Shift Supervisor

Process Control Analyst

Field Leader

Leach Operator

Crystallizer Operator

Mill Attendant

Operations Supervisor

4 shift rotating cycle giving coverage 24 hours /day and

7 days/week

Attendant

UHRA supervisor

Attendant

2 shift rotating cycle giving coverage 16 hours /day and

7 days/week

Plant Manager

Product Supervisor

Stripping T/leader

Cu. StripperCu. StripperCu. Stripper

Driver

Training Supervisor

Met. Clerk

Mechanical Foreman

FitterFitterFitter

Fitter AideFitter AideFitter Aide

B/makerB/maker

B/maker AideB/maker Aide

Electrician Snr.Instrument Tech.

TechnicianTechnician

Technician Aide

Technician Aide

Engineering Maintenance Personnel

Fitter Aide

Fitter

Matte Grinding

Atmospheric Leach

Pressure Leach

PGM filtration

Selenium Removal

Copper Electrowinning

Crystallizer

PGM concentrate

Copper cathodes

Spent Electrolyte

Granulated converter matte from Smelter

BMRP BLOCK DIAGRAM FLOWSHEET

Nickel Sulphate Crystals

Matte Grinding

Atmospheric Leach

Pressure Leach

PGM filtration

Selenium Removal

Copper Electrowinning

Crystallizer

PGM concentrate

Copper cathodes

Spent Electrolyte

Granulated converter matte from Smelter

Nickel Sulphate Crystals

Matte Grinding Circuit

Granulated Matte Surge

Bin

Biconical Ball Mill

Hydrocyclone

Flocculant

u/s

o/s

Grinds granulated matte to a size suitably fine for subsequent leaching to take place at an acceptable rate.

Ground Matte

Surge TankMill

discharge tank

SettlerMill

Return Tank

Grinding Objective

80 % minus 75 micron

Ground Matte

Surge Tank

Primary dilution water

Secondary dilution water

BMR Plant

Matte Grinding Circuit

Grinds granulated matte to a size suitably fine for subsequent leaching to take place at an acceptable rate.

Matte Grinding

Atmospheric Leach

Pressure Leach

PGM filtration

Selenium Removal

Copper Electrowinning

Crystallizer

PGM concentrate

Copper cathodes

Spent Electrolyte

Granulated converter matte from Smelter

Nickel Sulphate Crystals

Atmospheric Leaching Circuit

To leach Nickel & Iron from the ground matte and at the same time precipitate copper and PGM’s from the copper spent electrolyte.

OxygenOxygen

Ground Matte Slurry

Sulphuric AcidSpent

Electrolyte

pH 3.5

Recycle

Nickel Sulphate solution

Atmospheric leach

residue

Flocculant

pH 0.5pH 2.5

Typical Free acid concentrations

Tank 1 10 – 25 g/l H2SO4

Tank 2 0 g/l H2SO4

Thickener

Thickener U/F tank

12

34

5

Ni3S4 + H2SO4 + 0.5O2 à NiSO4 + 2NiS + H2O

Heazlewoodite reacts with sulphuric acid and oxygen to produce to millerite with the dissolution of 33 % of its

nickel content as nickel sulphate

Ni0 + H2SO4 + 0.5O2 à NiSO4 + H2O

The nickel alloy content reacts with sulphuric acid and oxygen to form nickel sulphate.

5NiS + CuSO4 à 2NiSO4 + Ni3S4 +Cu2S

Further leaching from the sulphide phase occurs by means of a metathesis reaction. Millerite is converted to

polydymite, heazlewoodite and copper is precipitated from solution as digenite.

Suggested Chemical Reactions in the first stage leaching circuit

BMR PlantAtmospheric Nickel

Leach

To leach Nickel & Iron from the ground matte and at the same time precipitate copper and PGM’s from

the copper spent electrolyte.

Typical Dry solids feed rate 500 kg/hr

Nickel extraction 70 – 75%

Iron dissolution 65 – 70 %

Matte Grinding

Atmospheric Leach

Pressure Leach

PGM filtration

Selenium Removal

Copper Electrowinning

Crystallizer

PGM concentrate

Copper cathodes

Spent Electrolyte

Granulated converter matte from Smelter

Nickel Sulphate Crystals

Condensed steam

steam

steam steam

Cooling Water

Cooling Water

Non condensibles

Process Water

Condensate Receiving

tank

Crystallizer

Nickel Sulphatesolution

Elutriation Pump Crystal

transfer Pump

Circulation pump

Crystal Slurry to centrifuge

The crystallizer circuit enables easily handled nickel sulphate hexahydrate crystals to be formed from nickel

sulphate solution

Crystallizer circuit

-82 Kpa Gauge

49 OC Heat Exchanger

Crystalizer

Produces easily handled Nickel

Sulphate hexahydrate crystal

from Nickel Sulphate solution

Moist nickel

sulphatecrystals

Induced Draught

Dry Nickel surge bin

Weigh flask

Condensate

Nickel crystal slurry

Nickel sulphate solution Returned

to crystallizer

Dryer vent to scrubber

Tube Conveyor

Dry nickel sulphate

crystals

Nickel Sulphate dryer

Steam

Heat exchangerRotary Dryer

Centrifuge

48OC

BMR Plant

Rotary Dryer

Nickel Sulphate Crystals are dried and packaged in 1 ton bulk bags

Daily production 28 tonnes (NiSO4.6H2O)

Matte Grinding

Atmospheric Leach

Pressure Leach

PGM filtration

Selenium Removal

Copper Electrowinning

Crystallizer

PGM concentrate

Copper cathodes

Spent Electrolyte

Granulated converter matte from Smelter

Nickel Sulphate Crystals

Extracts the Copper, Sulphur, Iron & remaining Nickel in the atmospheric leach residue, leaving a high grade PGM residue.

Pressure Leaching stage

Ground Matte Slurry

H.P. Air

Process Water

Sulphuric Acid

OxygenSpent Electrolyte

Spent electrolyte feed tank

Autoclave Discharge

Tank

Autoclave Flash Tank

Vent to Atmosphere

PGM slurry to PGM

Filtration

120 OC 119 OC 118 OC

Process control of Autoclave Discharge

100-110 g/l of Total Metals in solution

20-25 g/l of Free Sulphuric acid in Solution

Vent

Autoclave

Suggested Chemical Reactions within the Autoclave

The first stage leach residue typically contains nickel in the form of millerite, NiS, and polydymite, Ni3S4, and

copper in the form of the original Djurlite, Cu1.96S, and the precipitated digenite, Cu1.8S.These sulphides undergo total

oxidation to the corresponding sulphates in the second stage leach. Principle overall reactions are of the type

shown below.

Ni3S4 + 7.5 O2 + H2O à 3NiSO4 + H2SO4

NiS + 2O2 à NiSO4

Cu2S + H2SO4 + 0.5 O2 -à CuSO4 + CuS + H2O

CuS + O2 à CuSO4

BMR Plant

Autoclave

To extract the Copper, Sulphur, Iron & remaining Nickel in the atmospheric leach residue, leaving a high grade PGM residue.

Matte Grinding

Atmospheric Leach

Pressure Leach

PGM filtration

Selenium Removal

Copper Electrowinning

Crystallizer

PGM concentrate

Copper cathodes

Spent Electrolyte

Granulated converter matte from Smelter

Nickel Sulphate Crystals

Process Water

Autoclave discharge slurry

in

Clarified solution out

Mult-multi filament filter cloths

Filter Press

Frames

Filter Press Plates

PGM Filtration

Hydraulic Cylinder

To filter, wash and dry the 2nd stage leach discharge slurry to obtain a bone dry PGM rich residue.

BMR Plant

PGM Filtration circuit

To filter, wash and dry the 2nd stage leach discharge slurry to obtain a bone dry PGM rich residue.

Autoclave Residue 45 – 50% 3PGE’s + Au

Matte Grinding

Atmospheric Leach

Pressure Leach

PGM filtration

Selenium Removal

Copper Electrowinning

Crystallizer

PGM concentrate

Copper cathodes

Spent Electrolyte

Granulated converter matte from Smelter

Nickel Sulphate Crystals

Clarified autoclave

discharge solution

Cu-Ew Feed

Heat Exchanger

Sulphur dioxidesoluton

Selenium retention

tank

Pipe Reactor

Se-PGM cake

Selenium Filter press

Selenium Removal CircuitRemoval of Selenium from filtered autoclave solution to

prevent contamination of Copper cathode as well as recovery of dissolved PGM’s.

Process ChemistryThe second stage leach solution contains Nickel

Sulphate, Copper Sulphate, free sulphuric acid with low levels of Selenium , Tellurium, Palladium,

Rhodium and ruthenium.This solution is treated with sulphur dioxide solution to precipitate selenium as copper selenide and tellurium as coppper telluride together with most of the dissolved palladium and

rhodium.Overall chemistry can be represented by

CuSeO3 +CuSO4 + 4SO2 +5H2O ---àCu2Se + 5H2O

CuSeO4 +CuSO4 + 5SO2 +6H2O ---àCu2Se + 5H2O

Tellurium which is present as Te (IV) and Te (VI) behaves similarly.

BMR Plant

Se Removal

Removal of Selenium from filtered autoclave solution to prevent contamination of Copper

cathode as well as recovery of dissolved PGM’s.

Matte Grinding

Atmospheric Leach

Pressure Leach

PGM filtration

Selenium Removal

Copper Electrowinning

Crystallizer

PGM concentrate

Copper cathodes

Spent Electrolyte

Granulated converter matte from Smelter

Nickel Sulphate Crystals

Process Water

Process ChemistryIn Northam’s copper electrowinning circuit , metallic copper is

depositted at the cathode, and oxygen is liberated at the anode.The individual reactions are shown below

Cathode: 2CuSO4 +4e- -----à 2Cu0 + 2SO42-

Anode: 2H2O - 4e- --à O2 + 4H+

Overall: 2CuSO4 + 2H2O ---à 2Cu0 + 2H2SO4+ O2

4824Free H2SO4 (g/l)

<3Selenium (ppm)

4545Ni (g/l)

3248Cu (g/l)

Spent electrolyte

Electrolyte Feed

Component

Typical Analysis within the Electrowinning circuit

Electrowinning circuit

Electrowinning recycle tank

Electrolyte feed tank

Spent Electrolyte

tank

Guar Gum

Thiourea

To recover clean Copper cathode product free of PGM’s and to return a Copper spent electrolyte

for the operation of the leach stages.

Rectiformer rating up to 15KA with a

voltage of 25V

BMR Plant

Electro Winning

To recover clean Copper cathode product free of PGM’s and to return a Copper spent electrolyte for

the operation of the leach stages.

BMR Plant

Copper Stripping

Typical Production Rate: 4 t/day Quality:(99.96% Cu)

The End