Nickel / Cobalt Laterite Processes

A short training for SPA GeologistsOctober 2004

By Boy AdhityaAdopted from ALTA 1997, Ni/Co Laterite Project Development Seminar

AndA presentation MS 2004-133rd Annual Meeting & Exhibition,

International Laterite Symposium – 2004 by Ashok Davi

Mineralogy And ore Composition

Idealized Orebody Profile

Cap-Lateritic soils and re-crystallized iron oxides formed by sequential leaching and re precipitation.-Generally has a low nickel grade, therefore classified as overburden.

Limonite-Main consituents are goethite, chromite, manganese wad (asbolane), silica and silicates.-Most of Nickel is in Goethite (Fe,Ni)O(OH) nH2O-Most of Cobalt is in the coarser grained wad, Mn, Fe, Co, Ni Oxide

Altered Peridotite-Generally called silicate or saprolite zone-In dry climates saprolite my contain upper clay rich zone.-Saprolite Zone can also contain wad and chromite to lesser degree than limonite.-Nickel is commonly present in silicates, clay goethite, and wad material.-Saprolite generally contains portion of reject low grade bed rock and silica boxwork. Nickel enriched rim may occur around rock pieces.

Bed Rock- Low grade Peridotite, which is not mined. However nickel enrichment can occur in upper cracks.

Metallurgical Implications- Physically upgrading for example by removing coarse silica.- Moisture content major energy consumer for processes -Ores are mineralogical and chemically complex-Various Zones differ significantly limit the applicability of a particular process -Processing routes must be able to reject the large Fe, Si and MgO contents.-High Fe content is a problem for acid leaching processes in general. Magnesia and alumina are also acid consumers.-Aggressive leaching conditions are required to take nickel into solution.-Si/Mg ratio has important implications for smelting processes.-Presence of clays generally has adverse impact on hydrometallurgical operations, e.g. settling, pumping, agitation.-Unlike sulphide ore treatment, sulphur is not released in the extraction of nickel and cobalt, which has environmental benefits.-Cobalt is potentially valuable by-product, which is a major consideration in selection of a processing route. Cobalt level is highest in the limonitic zone.-Chromite could be considered as a by-product in some cases, and its recovery by gravity separation would constitute minor upgrading

World’s Land Based Nickel Resourcesand Primary Nickel Production(Resources Distribution by Contained Nickel)

Primary Ni Production

Laterite Sulfide

World Ni Resource on Land

Laterite

Sulfide

Mt Resource

% Ni Mt Ni % of Total

Sulfide 10500 0.58 62 27.8%

Laterite 12600 1.28 161 72.2%

Total 23100 0.97% 223 100

Commercial Processes

Four basic process routes in current use for latterites :-Pyrometallurgical : - Ferronickel smelting - Matte smelting-Hydrometalurgical : - Pressure Acid Leach-Pyromet/hydromet : - Reduction roast – ammonia leach

Operating Plants-Ferronickel smelting is still the dominating process-Smelting is generally applied to higher grade feed, most are > 1.7% Ni. Hydrometallurgical plants generally process < 2% Ni.

World Nickel Laterite Resources(Distribution by Contained Nickel)

Mt of Resources %Ni Mt Ni

Laterites 12600 1.28 161

Typical Feed Compositions for Various Laterite Operations

Analysis, wt. %

Moa Bay Murrin Murrin

SLN Cerro Matoso

P.T. Inco

Process PAL PAL Fe-Ni Smelting

Fe-Ni Smelting

Matte Smelting

Ore Type Limonite Nontronite Garnierite Hi Silica

Saprolite

Saprolite

Ni 1.3 1.3 2.7 2.9 1.8

Co 0.15 0.09 0.07 0.07 0.07

Fe 47.5 22 14 14 18

Al 4.5 2.5

Mg 1.0 4 15 9 10

SiO2 3.7 42 37 46 34

Mn 0.75 0.4

Laterite Processes(Generalized Block Flow Diagram)

Drying

Calcine/Reduction Calcine & Reduction

CCD & Neutralization

Smelting

Refining or Converting

Ammoniacal leaching

Purification and Recovery

Drying High Pressure Leaching

Precipitation & Redesolution

(Optional)

Purification and Recovery

Laterite Ore Laterite OreLaterite Ore

FeNi or Matte Ni and Co Ni and Co

Smelting Caron Process PAL

Laterite Slag Melting Pointvs. S/M Ratio

81 2 3 4 5 6 7

1400

1300

1500

1600

1700

1600

1700

1800

1900

2000

T,KT,OC

20FeO 25FeO 30FeO

SiO2 / MgO

NO

TE

1

P.T

. IN

CO

CE

RR

O M

AT

OS

O

NOTE 1: Japanese FE-Ni Smelters and SLNNOTE 2: Cerro Matoso (FeO ~ 20%)

Electric Furnace Slag Compositions SuperimposedOn the FeO-MgO-SiO2 Phase Diagram

Process Description and ExamplesPyrometallurgical ProcessesFe-Ni Production

Ores suited for production of high carbon ferro-nickel have: High nickel grade (> 2.1 % Ni) Low Silica/Magnesia ratio, and Low iron content (Fe/Ni ratio <6)

Examples: SLN Doniambo, Pamco, Hyuga, P.T. Aneka Tambang

Ores suited for production of low carbon ferro-nickel have: Higher Fe/Ni ratio (6 to 12) Relatively high-melting point slags

(Either very high S/M ratio – Example: Cerro Matoso, or Low S/M ratio – Example: Falcondo)

Process Description and ExamplesPyrometallurgical ProcessesMatte Production

Ores suited for production of matte have: Relatively higher Fe/Ni ratio (6 to 12) Relatively low melting point slags

Example: P.T. Inco

Process Description and ExamplesCaron Process

Caron process could be used for limonitic ores or a mixture of limonite and saprolite

The process can tolerate a higher amount of Mg in the feed than the PAL processes

Examples: Nicaro, Punta Gorda, Yabulu, Nonoc (Closed)

Process Description and ExamplesPAL Processes

PAL processes use ore that: are predominantly limonitic, or nontronitic

in the case of dry laterites contain some saprolite have Mg generally limited to <4 % (At

higher Mg acid consumption is higher) require lower Al content

Examples: Moa Bay, Murrin Murrin

Smelting Process

Smelting process are governed by two basic chemical facts:-Separation of Nickel from Oxide gangue components such as silica and magnesia is readily achieved by smelting, due to large differences in the free energies of formation.

-Only partial separation of nickel from iron is possible by selective reduction of oxides. Reduction conditions can be set to completely reduce nickel oxide, but part of the iron oxide is co-reduced.

Two approaches have been adopted :-Minimise Fe/Ni ratio and accept a ferronickel product-Add sulphur to form a nickel/iron sulfide matte, then prefentially convert iron sulphide to oxide by blowing with air, to leave a low iron nickel suphide matte product (for further refining).

Ferronickel SmeltingMain reactions

Nickel and cobalt is almost totally reduced to metal by carbon monoxide (or Hydrogen):NiO + CO = Ni + CO2Iron is partially reduced in three stages. The extent depends on time, temperature, and reducing conditions3Fe2O3 + CO = 2Fe3O4 + CO2Fe3O4 + CO = 3FeO + CO2FeO + CO = Fe + CO2Iron reduction is the key control issue, as iron dilutes the product, and the ferrous iron content of slag affects slag properties and impurities in the product.

Ore Preparation

Depends on ore characteristics, but typically consists of coarse crushing and screening, with rejection of coarse barren material.

DryingUp to 250 C to drive off physically bound moisture to achieve a residual of about 15 – 20 % to avoid excessive dusting. Normally carried out in rotary dryer.

Screen and crushingTrend has been towards reducing ore to minus 10 mm and including pelletizing step. Additional coarse barren material may be rejected.

Calcination and Prereduction-Early practice was to limit the temperature to about 700 c, which is sufficient to drive off chemically bound moisture and preheat for smelting step.

INCOINCO

SIMPLIFIED FLOW SHEETPacking

E.L E.L E.LESP

THICKENER

Scr

ub

ber

500 TBIN

100 TBIN

ESPM.C

Slag to Disposal area (1550°C)

Furnace Matte (1380°C)Electric Furnace

Silica FluxScrap

Converter

Matte Cast

Hot Calcine (700°C)

Wet Ore StockpileDryer Kiln

Reduction Kiln

RecycleSlurry

Dry Dust

PugmillDust

Market

Stack

HSFOAir

Granulation

HSFOAirLiquid Sulphur

Dry Dust

DKP

Dried Ore Storage

RockWest Block (Reject)

East Block (Crushed)

DieselAir

Water (Hi pressure)

GranulatedMatte

Oversize (Recycle to Converter)

M.C

Air

Fluid Bed Drier

to dryer

PT INCO - IndonesiaPT INCO - Indonesia

SCREENINGSTATION PRODUCT

Dried Ore Storage 2

Dried Ore Storage 1 REDUCTION

KILNELECTRIC FURNACE

DRYER

CONVERTER

PRODUCTDRYER

Dryer 1

Dryer 2

Dryer 3

Kiln 1

Kiln 2

Kiln 3

Kiln 4

Kiln 5

Furnace 1

Furnace 2

Furnace 3

Furnace 4

PS2

PS3

PS4

Slag to Disposal

Revertsto Kiln

EB

WB

SHIPPING

INCOINCO PT INCO - IndonesiaPT INCO - Indonesia

CHEMICAL REACTIONS

REDUCTION:NiO + C Ni + CO

NiO + CO Ni + CO2

NiO + H2 Ni + H2O  CoO + C Co + CO

CoO + CO Co + CO2

CoO + H2 Co + H2O 

Fe2O3 + 3C 2Fe + 3CO

Fe2O3 + 3CO 2Fe + 3CO2

3Fe2O3 + H2 2Fe3O4 + H2O

Fe3O4 + H2 3FeO + H2O  SULFIDATION:

3Ni + S2 Ni3S2

Ni3S2 + S2 6NiS

2Fe+ S2 2FeS

2FeS+ S2 2FeS2

REDUCTION KILNS NiO + C Ni + CO

3FeS + 3NiO Ni3S2 + 3FeO

FeS + NiO NiS + FeO

Fe3O4 + C 3FeO + CO

FeO + C Fe + CO

Fe + NiO FeO + Ni

 

NiO + CO Ni + CO2

} Fe3O4 + CO FeO + CO2

FeO + CO Fe + CO2

  FeO + SiO2 FeO.SiO2

Fe3O4 + SiO2 Fe3O4.SiO2

NiO + SiO2 NiO.SiO2

CoO + SiO2 CoO.SiO2

ELECTRICAL FURNACES

DRYER FLOW SHEET

DKP

Dryer Kiln

Pugmill

Secondary Trommel

SymonCrusher

TrommelScreen

HSFO& AIR

BP

WBO

EBO

DKF

DKR

Wet Ore Stockpile (SSP)

Pugmill Dust

ESP

DKD

D 1,2+3

Reject rock

MultiClone

100T

BIN

Scale

AutoSampler

ROCK

INCOINCO PT INCO - IndonesiaPT INCO - Indonesia

Main functions of the Dryer

  To remove part of the moisture from the feed.

  To screen barren rocks in the case of WB.

  To crush ore grading rocks in the case of EB.

  To blend the recycled dust with the fresh ore

from the mine.

REDUCTION KILN FLOW SHEET

DRIED ORE STORAGE

HSFOAIR

LiquidSulphur

Scr

ubb

er

RK

1,2

,3

Coal

Dried Ore (DKP)

FeedBin

Stack

Pugmill Dust

Hot CalcineTo Furnace

Recycle

To Dryer

P.T.INCO

500 TBIN

MultiClone

ESPRK4 & 5

100 TBIN

PP

REDUCTION KILN

THICKENER

Main functions of Kiln

   To remove remaining free moisture of the blended ore.

   To remove crystalline water (LOI) of the blended ore.

   To pre-heat the charge to >700 °C.

   To partially reduce Ni, Co and Fe oxides to metallics.

   To blend the feed prior to smelting.

   To blend Carbon with the feed in controlled proportion to

control the composition of furnace matte and slag.

   To sulfidize calcine to control furnace matte sulfur content.

FURNACE FLOW SHEET

Hot Calcine (RKP)F

rom

Red

Kil

n

CALCINE

SLAG

MATTE

Ele

ctro

de

Ele

ctro

de

Ele

ctro

de

Feed Bin

ELECTRIC FURNACE

Slag To Dispossal area

Matte

To Converter

Quench Chamber

Dust

ToThickener

DustQuenchChamber

To Thickener

To Stack To Stack

Main functions of Furnace

  To remove remaining water crystal (LOI) of calcine.

  To complete reduction process using the carbon in calcine

  To melt sulfide and metallic phases to form a single liquid

matte phase.

  To melt the oxide phases to form a single liquid slag phase.

  To separate the matte and slag phase based on density

differences.

  To discard the slag containing only small amount of nickel.

  To tap matte containing most of nickel for further processing

in the converters.

CONVERTER FLOW SHEET

EFMSilica FluxScrapConv.Slag

Granulation Pit

MATTE CAST

Water(Hi Pressure)

Conv.Slag

To Disposal areaLow Nickel

High Nickel

Dust

Stack

Granulated Matte

Air

F

DropChamber ESP

CONVERTER

Recycle to System

Recycle to System

Fines Matte Lamela

Thikener

To Product Dryer

Main functions of Converter

  To reduce the iron content of furnace matte by

oxidizing the iron with silica flux   To separate the iron oxide (converter slag) and matte

based on density differences.   To discard the converter slag containing only small

amount of nickel.   To tap matte containing most of nickel for granulation

Adopted from :

- ALTA 1997, Ni/Co Laterite Project Development Seminar- A presentation MS 2004-133rd Annual Meeting & Exhibition, International Laterite Symposium – 2004 by Ashok Davi.- PTI _Plant flow sheet , a ppt by Agus Superiadi