An Overview of the Base Metal Removal Plant at Northam
Transcript of An Overview of the Base Metal Removal Plant at Northam
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)
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
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.
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.