Cu, Ni & Co Extraction

Extraction of Base Metals(Copper, Nickel and Cobalt)

S. K. SahuMetal Extraction & Forming Division

National Metallurgical Laboratory, Jamshedpur

Introduction

Copper Consumption

35%

5%7%10%8%

3%

32%

Electrical (35%) Telecommunications (5%)

Power Transmission (7%) Automobile industry (10%)

Building construction (8%) Railway equipment (3%)

Miscellaneous (32%)

Indian demand for Cu – 4.5 lakh tons i.e. ~ 3% of world copper market

Birla Copper, Sterlite Copper & Hindustan Copper Ltd. – three major Cu producers in India

Indian production of refined copper : 6.5 lakh tons

India is emerging as a net exporter of refined copper

Over 90% of concentrate requirement is imported

Copper – the most extensively used metal next only to steel & aluminium

Its chemical, physical & aesthetic properties make it suitable for wide range of domestic, industrial & technological applications

Global demand for Cu – 18 million tons (Primary production - 88% & secondary production - 12%)

Cu demand is growing by an avg. of 4% per year

Nickel

Cobalt

Nickel Consumption

65%

6%9%

20%

Stainless steel (65%)

Other steel and non-ferrous alloys & suoper alloys (20%)

Electroplating (9%)

Coins & nickel chemicals (6%)

Cobalt Consumption

22%11%

9%

8%

7%

11%

10% 22%

Batteries (22%) Superalloys (22%)

Catalysts (11%) Hardmetals (11%)

Pigments (9%) Tyre adhesives/driers (8%)

magnets (7%) others (10%)

Nickel is the most volatile owing to its strong demand and tight supply

Global demand for nickel – 1.3 million tons & consumption rate increasing @ 3% a year

About 65% Ni is used in manufacture of stainless steel

Due to lack of Ni reserves nickel market in India is import dependent

India imports ~30,000 tons of nickel

Cobalt is least abundant element compared to Cu & Ni

In terms of application, Co is regarded as a specialty metal

Global demand for Co – 60,000 tons

It lacks any primary cobalt resources

India consumes ~ 700 tons Co for application in the metallurgical & chemical sector

Year Ore Grade

(Mean Cu %)

1932 1.80

1939 1.23

1949 0.90

1960 0.73

1970 0.61

2000 0.48

Copper Ore Grades mined in USA Copper Ore Grades mined in USA World Copper Usage, 1900-2006World Copper Usage, 1900-2006Thousand metric tonnesSource: ICSG

Demand for refined copper increasing by an average of 4% per yearDemand for refined copper increasing by an average of 4% per year

Due to continuous mining and processing, mineral grades of promary Due to continuous mining and processing, mineral grades of promary resources are decliningresources are declining

However, newer & energy efficient processes are being developed to However, newer & energy efficient processes are being developed to recover metal from low grade ores & secondaries to meet the recover metal from low grade ores & secondaries to meet the requirement of the societyrequirement of the society

Extraction of Copper

Copper exists in nature mostly in the form of copper sulfide

Oxides or oxidised ores are found only in limited quantities

Some common minerals of copper are: Chalcopyrite (CuFeS2); Covelite (CuS); Chalcocite (Cu2S), Cuprite (Cu2O); etc.

Chalcopyrite is most abundant copper bearing mineral (70% of world Cu reserves)

Sulfide ore containing 0.5-2.0% Cu is considered satisfactory for Cu extraction by pyrometallurgy

From poor grade ores, Cu extracted by hydrometallurgical processes

Possible to roast sulfide ore of copper to oxide & then reduce it by carbon in the blast furnace

Concentrate also contains iron sulfide which form iron oxide

Cu2S does not oxidise until FeS is fully oxidised yielding Fe2O3

Fe2O3 is difficult to remove by slagging

Therefore, blast furnace smelting is not used for copper extraction

Cu extracted by matte smelting process without using any reductant

Conventional Process for extraction of Copper from sulfide concentrate

Ore (1-2% Cu)

Grinding

Flotation

Concentrate (15-35% Cu)

Hearth/fluid bed roasting

Reverberatory/electric furnace

smelting

Matte (35-60% Cu)

Converting

Anode slime for recovery of precious metals

Blister copper (98.5% Cu)

Cathode copper (99.99% Cu)

Discard slag

(0.3-0.8% Cu)

Slag

Conventional route

Refining Bleed electrolyte

Newer routes

Drying

Flash smelting

Matte

Converting

Continuous smelting

Slag for cleaning &

discard

Roasting Iron sulfide is partly converted to FeO for

subsequent removal by slagging

(g)SO2FeS(s)S(s)Cu(g)O(s)2CuFeS 2222

(g)SOFeO(s)(g)OFeS 2223

Smelting

FeO removed by slagging with silica (SiO2) at 1200-1300 OC in reverberatory furnace

Cu2S melt collected as matte

Converting

(g)SOFeO(l)(g)OFeS(l) 2223

(g)SOO(l)CuOS(l)Cu 22223

2

(g)SO6Cu(l)O(l)2CuS(l)Cu 222

FeO separated as slag

No external heat supply required – the reactions are exothermic

No reducing agent required for removal of oxygen from the oxide

ΔG01200 = -2.3 x 105

ΔG01200 = -0.5 x 105

(g)SO2Cu(l)(g)OS(l)Cu 222 ΔG01200 = -0.2 x 105

ΔH01200 = -2.2 x 105 kJ/kg mol

ΔH01200 = -5.1 x 105 kJ/kg mol

Flash smeltingConventional smelting operation is a melting

process rather than oxidation process

Its offgas – dilute in SO2 & difficult to remove

Energy intensive process because heat not generated during smelting

Controlled oxidation of Fe & S – offgas strong enough in SO2 for efficient recovery as H2SO4

Evolution of large amount of heat – making the process autogenous and energy efficient

Refining

Concentrate

Drying

Flash smelting

Matte

ConvertingSlag for

cleaning & discardBlister copper

Flux Air/O2

Copper cathode

Outokumpu process

Dry particulate feed and pre heated oxygen enriched air blown through the concentrate burners down into the furnace

Produce matte containing 45-65% Cu under autogenous condition depending on the quantity of fuel used & degree of oxygen enrichment employed

A closed process – captures upto 99% sulfur rich gases to produce H2SO4

INCO process

Uses commercial oxygen (95-98% O2), rather than oxygen enriched air

Oxygen blast & prticulate feed blown horizontally into the furnace

No external fuel is used – all of the energy comes from oxidation of Fe & S

The matte produced contains 45% Cu

Slag contains 05-06% Cu – discarded

Offgas containing 70-80% SO2 captured to produce H2SO4

Continuous smelting

Refining

Continuous smelting

Slag for cleaning &

discard

Blister copper

Copper concentrate

Copper cathode

Combines smelting & converting

in a single furnace

ConcentrateOil or coal

SiO2

Flux

WORCRA Furnace

Copper SlagBlowers

Air

Gas cleaner

Acid plant

Heat exchanger

WORCRA process

Combines smelting, converting & slag cleaning operations in separate but interconnected zones

Directly produces metal, rather than matte from a concentrate

In the converting zone, countermovement of slag & matte takes place, that leads to effective removal of impurities from the matte

Conserves energy by utilizing heat evolved during smelting and converting in the reactor itself

The Cu content of the slag is very low & can be discarded

Mitsubishi process Smelting furnace, slag cleaning furnace

& converting furnace - connected in cascade fashion

Concentrate & oxygen enriched air enter S-furnace through lances to produce matte and low Cu slag

In the C-furnace matte gets oxidised to blister copper

Main featuresMain features

All of the furnaces are stationary, driving mechanisms viz. furnace tilting, tuyere punching, hood driving etc. are not required

Molten products are transferred from one furnace to the next furnace under gravity

Molten products overflow continuously through the outlet hole of the furnace eliminating need for tapping and slag skimmig operations

IsaSmelt/Ausmelt processA high intensity smelting process producing matte from Cu-

concentrate & secondary materials

Uses an extremely efficient top-submerged lance & a simple stationary refractory-lined furnace

Air, oxygen & fuel are fed through the lance into the molten bath, creating a high turbulant environment that promotes rapid reaction of raw materials

Depending upon the grade of raw materials, matte containing upto 75% Cu can be produced

AdvantagesAdvantagesLow capital cost due to simple furnace construction & peripheral system arrangements

Flexibility to use various fuel types (coal, oil, gas)

Ability to produce high grade product from low grade materials

Small furnace foot-print

The table compares the energy requirements for seven smelter types, The table compares the energy requirements for seven smelter types, including the energy equivalents of the materials consumed by each including the energy equivalents of the materials consumed by each process.process.

Energy consumptio

n

Energy requirements vary for the different pyrometallurgical processes.

Flash furnaces make the most efficient use of the thermal energy released during the oxidation of sulfides; they generate sufficient

heat to provide a large proportion of the thermal energy for heating and melting the furnace charge.

Electric furnaces use electrical energy efficiently because of the low heat loss through the effluent gas, they make limited use of the heat produced during oxidation of the sulfide minerals, and their energy costs are high because of the high price of electricity.

Leaching Stripping EWExtraction

Cu loaded leach liquor

Ore or mine waste

Stripped organic

Aq. solution of Cu

Cu loaded organic

Solid waste

Acid make up

Spent electrolyte

Cu Cu cathodecathode

Simplified flow-chart Leach-SX-EW Process

Hydrometallurgical extraction of Cu

Environmental aspects

Exploitation of complex & low grade ores

Small isolated deposits

Hydrometallurgical Hydrometallurgical extraction of Cuextraction of Cu

Chalcopyrite is a very stable mineral, therefore it very hard to leach Cu from chalcopyrite concentrate

However, under oxidising condition Cu can be leached from chalcopyrite concentrate

CuFeS2 + 4FeCl3 CuCl2 + 5FeCl2 + 2S

CuFeS2 + 3CuCl2 4CuCl + FeCl2 + 2S

Produces elemental sulfur as a by-product – eliminates setting up of sulfuric acid plant

Ferric chloride leaching

Electrolysis

Half Cu is deposited cathodically

Cu+ + e Cuo at cathode

Rest half Cu is oxidised to Cu2+ at anode

Cu+ - e Cu2+ at anode

Pressure sulfuric acid leachingSulfide concentrates can be leached in

the acidic system under oxygen pressure

Iron ppt

Pressure Acid Leach

Solution purification

Sulphide concentrate

Cu Stripping

Cu Extraction

Co Extraction

LIX 84

Cu Solution

CuSO4/Cu

Co Solution Ni Solution

CoSO4/Co NiSO4/Ni

Leach liquor

CYANEX 272

CuFeS2 + 2H2SO4 CuSO4 + FeSO4 + 2S + 2H2O

FeSO4 +1/2H2SO4 + 1/4O2 1/2Fe2(SO4)3 + 1/2H2O

1/2Fe2(SO4)3 + 3H2O Fe(OH)3 + 3H2SO4

Extraction of nickel & cobalt

The principal ore of nickel is pentlandite [(NiFe)9S8]

Cobalt does not have any primary ore

Cobalt is extracted as a by-product of Cu, Ni, Zn or precious metals

Process flow sheet for extraction of nickelOre

(1.3% Cu, 1.2% Ni)

Grinding Flotation

Tailings (0.1% Cu, 0.2% Ni)

Bulk Cu-Ni Concentrate

(6% Ni, 7% Cu)

Copper cliff millCu concentrate

(30% Cu, 1% Ni)

Ni concentrate (10% Ni, 2% Cu)

Pyrrhotite concentrate (0.9% Ni)

Roasting Flux

Reverberatory furnace smelting

Slag discard

Matte (20% Ni, 7% Cu)

Converting

Matte (50% Ni, 25% Cu, 20% S)

Slag

1

Slow cooling Grinding Magnetic separation

Flotation

Metallics to precious metals

recovery (64% Ni, 16% Cu, 10% S)

Cu concentrate (70 % Cu, 5% Ni)

Low Cu (0.8%) Nickel sulfide

High Cu (3-4%) Nickel sulfide

Fluid bed roasting

Fluid bed roasting

Nickel oxide (low copper)

Nickel oxide (high copper)

Reduction

Metallic nickel (95% Ni)

Reduction Reduction smelting

ElectrolysisCarbonylation

Nickel pellets (99.95%)

Nickel powder (99.93%)

Electronickel (99.93%)

1

Extraction of nickel & cobalt from lateritic ore

Laterites are weathered, metal rich rocks (oxides) either in the form Laterites are weathered, metal rich rocks (oxides) either in the form of limonite or serpentineof limonite or serpentine

Limonites are mainly iron oxide containing Ni & Co & minor Limonites are mainly iron oxide containing Ni & Co & minor amount of magnesium silicateamount of magnesium silicate

Serpentine comprise nickel ferrous hydrated magnesium silicateSerpentine comprise nickel ferrous hydrated magnesium silicate

From such lateritic ores Ni & Co are extracted either by high-From such lateritic ores Ni & Co are extracted either by high-pressure acid leaching or by ammonia leaching (Caron process)pressure acid leaching or by ammonia leaching (Caron process)

Serpentines are not treated by high pressure acid leaching because Serpentines are not treated by high pressure acid leaching because high magnesium content results in excessive acid consumptionhigh magnesium content results in excessive acid consumption

LIMONITE

Pressure acid leaching

Filtration

Neutralisation

Precipitation

Filtration

Filtration

H2SO4

Residue to waste

H2S

Acid to waste

SERPENTINE

Reduction

Cooling

Leaching

Precipitation

Filtration

Filtration

CO

NH4HS

Acid to waste

CO2

NH3+(NH4)2CO3

Air

Residue to waste & NH3 recovery

CoS + NiS

CoS + NiS

H2SO4

India does not have any primary resource for Ni & Co

Indian refiners depend on imported feed materials

Type of materials imported to India for recovery of Co & Ni are sludges, scrap, metallic grinding dust, slags, etc.

Process for recovery of Ni & Co from scrap

Process for recovery of Ni & Co from sludge

Process for recovery of Ni & Co from slag