Chloride Metallurgy

- Process Technology Development –

Edgar Peek

Xstrata Process Support

epeek@xstrataps.ca
February 27-March 3, 2011 – San Diego, California 2
Chloride Metallurgy
Few Successes –Why?

Economic Boundary Conditions

• Metal and sulphur prices
• Process capacity (throughput) versus capital costs
• Processing costs and maintenance expenditures
• Insufficient knowledge of market demand of a metal;
especially its physical properties (powder overvalued)
Psychological Factors
• Shortage of Chloride Practitioners (except TiO2)
– development costs tend to be higher; this can rapidly
discourage management.
– Perceived lack of suitable construction materials;
argument based on insufficient knowledge or higher
equipment costs compared to sulphate metallurgy.
Technological Challenges

February 27-March 3, 2011 – San Diego, California 3

 ORE

BENEFICIATION
crushing/grinding/screening
Outline gravity/magnetic/electrostatic separation
sintering/pelletisation
flotation

Chloride Metallurgy EXTRACTION

acidic leaching (H2SO4/HCl/HNO3)
• General Metallurgical Aspects base leaching (NH3/NaOH)
reduction (CO/H2)
• General Engineering Aspects sulphide roasting and smelting
(reduction) volatilisation

• Case Studies PURIFICATION

selective precipitation/cementation
– Chlor-Alkali Industry solvent extraction/ion exchange
fractional distillation
converting (oxidation)
– Steel Pickling & Pyrohydrolysis
– Ni/Cu/Co Matte Treatment
via chloride hydrometallurgy RECOVERY
electrowinning and refining
hydrogen reduction
carbonate/oxide precipitation

February 27-March 3, 2011 – San Diego, California METAL 4

Hydrometallurgical Aspects (I)

• Chloride System: operate over a wide

range of redox conditions and acidity (i.e.
a large portion of the Pourbaix diagram)
• Metal chlorides have high solubility; except
lead, silver and mercury. Thus, very
concentrated leach liquors can be made,
which reduces size of S/L equipment, SX/IX
equipment or other process equipment
– Example: leach tank with 230 g/L Ni and residence
time of 1 hour. For 60,000 tpy Ni or ~7 tph Ni you
need one ~30 m3 (ID 3.3m) or three 10 m3 tanks
(ID 2.3m) in series. Small affects maintainability!

February 27-March 3, 2011 – San Diego, California 5

Metal Chloride Solubility

• Why do we have sulphide ore bodies, if

>50% of the earth consist of sea water?
SULPHIDES CHLORIDES
Compound g/L Compound g/L
MnS 2.3*10
-6
ZnCl2 4320 Sea water:
-8
FeS 3.4*10 MnCl2 1510
ZnS 3.3*10
-10
CdCl2 1400
19% salinity
-12
NiS 9.0*10 CuCl2 770
CoS 4.0*10
-12

-12
FeCl3 750 Earth’s crust:
PbS 4.9*10 FeCl2 650
CdS 1.0*10
-12
NiCl2 640
~300 ppm S
Bi2S3 8.8*10
-13
CoCl2 450 ~130 ppm Cl
-14
Hg2S 5.9*10 HgCl2 36
Cu2S 2.7*10
-14
PbCl2 4.85
~75 ppm Ni
Ag2S 7.3*10
-15
Cu2Cl2 1.2*10
-1
~50 ppm Cu
-21 -4
8.8*10 3.8*10
CuS
4.0*10
-25
Hg2Cl2
AgCl 1.5*10
-3
~22 ppm Co
HgS
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Hydrometallurgical Aspects (II)

• HCl is a true lixiviant. Hydrogen ion has

very high activity compared to sulphate
solutions yielding fast leaching rates and
high unit capacities. Only moderate leach
temperatures needed, but closed (vented)
equipment are needed due to enhanced
HCl vapor pressure over solution.

• Tip: Basic Principles of Chloride

Hydrometallurgy, D.M. Muir, Chloride
Metallurgy 2002, Vol. 2, pp. 759-793

February 27-March 3, 2011 – San Diego, California 7

Hydrometallurgical Aspect (III)

• Selective metal solubilization possible due

to acidity and redox control
• In contrast to sulphate system a high redox
potential is possible across entire pH-range;
e.g. ferric and cupric chloride leaching

• Lixiviant (H+) and/or oxidant (e-)

regeneration (HCl, Cl2, CuCl2, FeCl3) is an
integral part of flow sheet.
• e.g. pyrohydrolysis and electrowinning

February 27-March 3, 2011 – San Diego, California 8

Hydrometallurgical Aspect (IV)

• Metal separation from solution by solvent

extraction or ion exchange is facilitated by
the fact that metals form anionic or
cationic complexes of differing stability
• e.g. CoCl42- SX by amine Alamine 336

• Due to high metal concentrations,

solutions will have high conductivity and
viscosity
• Lowers energy requirement in electrowinning
• Also plays a role in molten salt chemistry
February 27-March 3, 2011 – San Diego, California 9
Hydrometallurgical Aspects (V)

• Elemental sulphur can be produced “easily” in a

chloride leach. Pyrite hardly attacked by leaching.
Materials handling, like filtration, can be challenge.

MeS + Cl2 = MeCl2 + S0

MeS + 4Cl2 + 4H2O = MeSO4 + 8HCl
MeS + 4HCl + 2O2 = MeCl2 + H2SO4 + 2HCl

MeS + 2FeCl3 = MeCl2 + 2FeCl2 + S0

MeS + 2CuCl2 = MeCl2 + 2CuCl + S0
2MeS + 2FeCl2 + 1.5O2 = 2MeCl2 + Fe2O3 + 2S0

February 27-March 3, 2011 – San Diego, California 10

Chloride “Pyrometallurgy” (I)

• Metal chlorides, especially base metal

ones, are in general volatile at low
temperature. Metal sulphates decompose
• Selective volatilisation/fractional
distillation is possible for certain species
• Both chlorine and HCl (not dry) are very
reactive. It makes the use of reductants
(carbonaceous) obsolete in most cases;
exception Ti and Zr
• Every metal chloride has different
susceptibility to hydrolysis (=steam) or
oxygen. (selective oxidation)

February 27-March 3, 2011 – San Diego, California 11

Volatilisation –”Base Metals”

February 27-March 3, 2011 – San Diego, California 12

Chloride “Pyrometallurgy” (II)

• Hydrogen reduction of metal chlorides

may be perceived as an advantage;
reactor design is challenging though
• HCl gas can be used for salting out metal
chlorides and initiate crystallization
• HCl regeneration via pyrohydrolysis is a
proven technology
• Corrosion does occur at elevated
temperature, but very slow compared to
hydrometallurgy; watch for condensation
and protective oxide layer formation
February 27-March 3, 2011 – San Diego, California 13
Chloride Properties

Melting/Boiling Points
And Vapor Pressures
Properties –”Base Metals”

February 27-March 3, 2011 – San Diego, California 15

Properties -Alkaline

February 27-March 3, 2011 – San Diego, California 16

Properties –Other Elements

February 27-March 3, 2011 – San Diego, California 17

Volatilisation –”Base Metals”

February 27-March 3, 2011 – San Diego, California 18

Volatilisation -Alkaline

February 27-March 3, 2011 – San Diego, California 19

 Engineering Aspects

Some Highlights in Hydrometallurgy

Engineering Aspects

Hydrometallurgy -CHLORIDES
• Water balance; how to bleed water with impurities
from the system.
• Plant location: SEA or ARID CLIMATE preferred

Equipment Design & Reliability

• Driven by people (and their knowledge)
• A “MUST HAVE” for chloride metallurgy

Materials of Construction
• Workmanship component
• Actual ability of the material

February 27-March 3, 2011 – San Diego, California 21

Equipment Reliability Program

Reliability WORLD
CLASS
Hierarchy
RCM EQUIP SPECS

ENG & COST QA FOR NEW

ANALYSIS EQUIPMENT

WORKFORCE INTEGRATING EXTERNAL TOTAL

FLEXIBILITY MAINT & PROD BENCHMARKING MAINT & PROD

EQUIPMENT LIFE PERFECTING

PREDICTION WORKFORCE SKILLS
INTEGRATION OF PM FAILURE ANALYSIS EQUIPMENT
AND SOFTWARE AND PREVENTION RECORDS

PREVENTIVE MAINT WORK MGT. SYSTEMS MAINT. MGT. SOFTWARE

INITIATING WORK WORK PLANNING WORK EXECUTION MATERIAL CONTROL

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 Corrosion
Wear
Mech. Properties

Hoist Motor
Metals
Hoist Gear
Materials Plastics
Exhaust Fan Ceramics
Testing
Boiler Equipment Coatings
Root
Coatings
Cause Materials
Refractories Failure Selection
Analysis

Materials
Technology
Inspection &
Evaluation of Fabrication
in service Specification Tanks
RBI plant Reactors
Acid Plants equipment Quality
Process Vessels
Storage Tanks Assurance Process Piping
Concentrators in Machinery
Smelters Fabrication Linings & Coatings
Hoist Equipment Repairs
Dye Penetrant, MPI
UT, X-ray, Eddy Current
Hardness, PMI
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Testing & Selection of Materials
For Existing or new Equipment / Plants

Based on:
• Performance in identical process and equipment
Confidence Level

• Field testing in identical process and equipment

• Knowledge of performance in similar process and
equipment
• Pilot Plant Testing
• Laboratory Tests
• Published Materials Database
• Supplier Literature

February 27-March 3, 2011 – San Diego, California 24

 Example

Ni/Co/Cu Matte Treatment

in Chloride Hydrometallurgy
 Example
Ni/Cu/Co Matte Treatment

Why?
• Illustrate some basic “chloride” principles!
Skills
• Chloride metallurgy: Ni/Cu/Co/PGM/S
• Secret to success:
– highly-skilled stable work force
Engineering Sense: well developed
• Ni chloride refining technology: ~165 kton
– Xstrata Nikkelverk AS, Norway
– Sumitomo Metal Mining Co, Japan
– Eramet –Sandouville refinery, France
February 27-March 3, 2011 – San Diego, California 26
Ni/Co/Cu matte treatment

Why do we usually make matte?

• Smelter recovers PGM’s from concentrate
• Beside PGM’s also high recovery Ni/Co/Cu
• Smelter is Fe rejection unit; except 2%Fe
• Unlike in Cu smelting, not all the sulphur is rejected in
a Ni smelter
• Generally, smelter has lowest cost and lowest tailings
disposal risk in dealing with concentrates, which has
to meet certain specifications.

• These are hurdles hydrometallurgists have to

overcome to “compete” with a smelter

February 27-March 3, 2011 – San Diego, California 27

Ni/Cu/Co Matte Composition

Balance: sulphur
• ~20-25 wt% S

Table 1 – Typical Feed Materials into Falconbridge Nikkelverk AS (2000-2005)

Raw Material Ni (wt.%) Co (wt.%) Cu (wt.%) Fe (wt.%)
Ni matte (Canada) 54 - 56 1,7 - 2,2 17 - 20 2 - 2,5
Ni matte (Botswana) 39 - 41 0,5 - 0,9 33 - 35 2 - 2,5
Custom Feed (high Fe) 0–5 20 - 30 15 - 35 5 - 30
Custom Feed (low Fe) 10 - 20 15 - 30 10 - 20 0-5

February 27-March 3, 2011 – San Diego, California 28

Challenges in matte refining

• Nickel/Copper separation
• Cobalt/Nickel separation
• PGM recovery (slimes=inventory cost)

Historically, many different process routes

chosen, each with a distinct niche

• Tip: “Some Observations on the Chloride Based

Treatment of Ni-Cu-Co Mattes”, by G. Van
Weert, Chloride Metallurgy 2002 – Vol. 1, pp.
277-298.

February 27-March 3, 2011 – San Diego, California 29

Chloride Leach Criteria

Acid Leach (HCl) or Redox Leach (Cl2)

• HCl; process control pH-driven
• Chlorine; process control Eh-driven
• Both need: disposal of “salt water” (sea)
Lixiviant Regeneration Technique
• Pyrohydrolysis (HCl gas; 18-20 wt.% HCl)
– Needs preferably cheap natural gas
• Electrowinning (Cl2)
– DSA technology (from chlor-alkali industry)
– Needs preferably cheap electricity
– Needs floor space; well ventilated building
February 27-March 3, 2011 – San Diego, California 30
HCl vs. Cl2 Leach

Reductive Leach
Ni3S2 + 6HCl = 3NiCl2 + 2H2S + H2
(Cu insoluble; super azeotropic)

Oxidative Leach
Ni3S2 + 3Cl2 = 3NiCl2 + 2S0
Cu2S + Cl2 = CuS + CuCl2
(cementation: redox control with metallics,
e.g. matte, in separate process step for Cu
precipitation)

February 27-March 3, 2011 – San Diego, California 31

Chloride Leach Criteria -Matte

• Most valuable component (Ni) is

solubilized first, minimizing Ni inventories
and materials handling in refinery
• Achieve optimum Ni/Cu separation. The
less Ni follows the Cu, the higher the
upgrading factor for PGM’s.
• Create concentrated NiCl2 solutions;
allows removal of Co via SX based on
concentration and complexation difference
• Have a means to remove water from the
flow sheet.
February 27-March 3, 2011 – San Diego, California 32
HCl Azeotrope: Sub or Super?

• Azeotrope = constant boiling multi-

component mixture for which vapor and
liquid composition are identical; for HCl it
is 20.3 wt% HCl @108.6 Celsius or a
molarity of 6.13 mol/L

So what?
• H2O can be removed via boiling up to
about 5.5 M HCl economically from sub-
azeotropic acid
• HCl vapour can be removed from super-
azeotropic acid, but no water
February 27-March 3, 2011 – San Diego, California 33
Azeotrope

For process design

you have to chose
sub or super-
azeotropic, if HCl is
your active leaching
media.
Water balance and
dealing with weak
acid issues makes
super-azeotropic
more challenging
February 27-March 3, 2011 – San Diego, California 34
Xstrata Nikkelverk AS
Kristiansand, Norway

35
Xstrata Nikkelverk AS

Chlorine Leach Process

• Weakness: Ni/Cu separation
– Leaching mechanism: Cu(I)/Cu(II)
– Matte has to be used in cementation
– Autoclave needed to keep Ni in residue low
– Metallics in sulphur deficient matte (Ni & PGM) allow redox
control and precipitation of Cu
– Increases leach residue volume for Cu/PGM recovery
– It is costly to make copper in a nickel refinery
• Strengths
– Cl2 going to Cl-: ~1 tonne of water is boiled off per
tonne of Cl2; good for water balance
– Co-SX; excellent Ni/Co separation
February 27-March 3, 2011 – San Diego, California 36
Sunday afternoon
study material for
the enthusiastic
“chloride leach”
inspired engineer.

Be prepared for
more questions
than answers!

37
 Shorter possibly
“easier version”
Think process
design!!!
pH-Eh control
for various
impurity
removal steps

CHLORIDES
YES, WE CAN!
February 27-March 3, 2011 – San Diego, California 38
www.myxps.ca

Thank you

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