AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of...

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Autoclave Technology - Applications for Sulphide Concentrates and Laterite Ores CICITEM Annual Meeting, Antofagasta, Chile, 28 th and 29 th July 2010 Arthur Barnes

Transcript of AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of...

Page 1: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

Autoclave Technology -Applications for Sulphide

Concentrates and Laterite Ores

CICITEM Annual Meeting, Antofagasta, Chile,

28th and 29th July 2010

Arthur Barnes

Page 2: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

Introduction to Xstrata and Xstrata Process Support

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Xstrata Process Support

Falconbridge, Sudbury, Ontario, Canada

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Xstrata Process Support

History

Originally Falconbridge Technology Centre:• Initial research centre in Thornhill, Ontario.

• New centre opened in Sept. 1997, in memory of Frank Pickard (President & CEO of Falconbridge 1991 to 1996 who was a constantchampion of technological advancements with strategic vision.

• Built for a cost of $18m, following in-depth strategic planning.

• Incorporated Noranda Technology Centre in 2005 when Falconbridge

and Noranda merged.

• Acquired by Xstrata in 2007

• Now a fully independent consultancy and test centre, available to external clients as well as Xstrata

• ~55 employees, 4 divisions

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Background to Xstrata Plc.

Xstrata Plc is a major global diversified mining group.

Headquartered in Zug, Switzerland, Xstrata maintains a position in

the following major international commodity markets:

• copper, coal, ferrochrome, nickel, and zinc,

• recycling facilities,

• additional exposures to gold, lead, silver vanadium and

Platinum group metals

• suite of global technologies (Xstrata Technology).

The Group's operations and projects span 18 countries:

Argentina, Australia, Brazil, Canada, Chile, Colombia, Dominican

Republic, Germany, Jamaica, New Caledonia, Norway, Papua New

Guinea, Peru, South Africa, Spain, Tanzania, the USA and the UK.

Xstrata employs 43,000 people (including contractors).

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Process Control - Identify and deliver robust process control technology and engineering solutions.

Process Mineralogy - Design, implement and optimize mineral processing flow sheets by matching the flow sheet to the mineralogy.

Extractive Metallurgy – Provide high-end extractive metallurgy services. Flow sheet/project development using modeling, laboratory tests and piloting.

Materials Technology - Improve the reliability of critical equipment through appropriate implementation of well proven materials engineering practices at essential stages of design, procurement and operation.

XPS Specialist Services

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Applications of Pressure leaching to sulphides and oxides

Contents

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Contents

1 Introduction- Pressure Leaching

2 Overview- Sulphide & Laterite ore Leach Chemistry

3 Overview- Pressure Leach Reactors

4 Sulphide and Laterite Installations

5 Operational Challenges- Case Studies

6 Materials of Construction

7 Appendix: Design Principles (Not presented in this lecture)

Page 9: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

Pressure Leaching

Some Basic Principles -

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Introduction

• Leaching is a natural process of mineralogical alteration

(weathering) involving water. Most natural leaching involves

oxidation.

• The rate at which oxidation occurs can be increased by the

presence of reagents. e.g. acid; by increasing temperature

and by increasing concentrations of reagents, and by the

presence of solvents. The Arrhenius equation is a useful

guide:

k= A e –Q/RT where: k= rate;A= rate constant

R= gas constant; Q= Activation energy

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Introduction- continuedThe use of Pressure

• Increasing temperature alone leads to issues relating to boiling of reagents and volatility of solvents. The use of pressure permits increased concentrations and temperatures, allowing leaching of otherwise very unreactive minerals.

• Improved kinetics allow more compact reactors

• The operating conditions impose more demands on the equipment.

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The “Autoclave”

. •Strong walls- pressure vessel

•Maximum pressure controlled (or else dangerous!)

•Batch and continuous reactors need a pressure transition concept for loading and discharging

•Operating temperature above normal boiling point of water

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Continuous Autoclave Components

Impeller

Compartment Wall

(Air, Oxygen, Acid)

Compartment

Drive

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Typical Sulphide continuous pressure leach arrangement “Pox”

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Copper- Total Pressure oxidation

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Pressure Leach Applications-Some Examples

• Sherrit ammoniacal nickel sulphide concentrate leach

• Xstrata Nikkelverk matte chloride leach

• Laterite leaching (Moa bay, Goro, Murrin Murrin)

• Sherrit Sulphuric acid matte leach (RSA base metal ops)

• Norilsk pyrrhotite leach

• Refractory gold full pressure oxidation

• Kidd Zinc pressure leach

• Chambishi Metals cobalt matte-alloy leach

• Outotec DON process

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Typical Chemistry (Simplified)

Sulphide leaching: (Pressure oxidation)

Reaction sequences depend on pH and pO2

MS+ H2O+O2= MO + S0 + H+

S0 + O2= SO32-

SO32- + H2O= H2SO4

SO32- + MO= MSO4

“Water + Oxygen + sulphide= soluble metal + acid”

Laterite Leaching (Pressure acid leach)

2(Ni,Fe)OOH + H+ = Ni2+ + Fe2O3 +2H2O

via: 2NiO + 4H + = 2Ni2+ + 2H2O and

2FeOOH= Fe2O3 +H2O

(Note Ni in ore is not = Fe in ore)

“Ore + acid = soluble metal + residue + water”

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Poirbaix Diagram (Eh-pH)

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3.0

2.5

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

S - H2O - System at 25.00 C

C:\HSC4\S25HiOx.iep pH

Eh (Volts)

S

H2S(a)HS(-a)

HSO4(-a)SO4(-2a)

S2O8(-2a)Sulphur-water system

Increasingoxidation

IncreasingAcid

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1914121086420

2.0

1.5

1.0

0.5

0.0

-0.5

-1.0

-1.5

-2.0

+00

+00

+00+00

-03

-03-03

-06

-06-06

+00

+00

-03

-03

-03-06

-06

-06+00

+00

-03

-03

-06

-06

-03

-03

-06

-06

Zn - H2O - System at 25.00 C

pH

Eh (Volts)

Zn

ZnOZn(+2a)

ZnO2(-2a)

Pourbaix Diagram Zn-waterEffect of Zn concentration

Increasingdilution

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Differences between Sulphide Leaching and Laterite Leaching

SULPHIDES

• Minerals need oxidation, i.e. oxygen-slurry mixing. Oxygen transfer controls kinetics.

• Control of sulphur and passivation can be key at lower temperatures

• 110-170oC vessels –design lead lined steel vessels with acid resistant brick

•Temperature Control (exothermic)

•Diluted feed required

LATERITES

•Species already oxidised,

•Fe precipitation and Mg content in feed control sizing and economics

•>240oC vessels -design method commonly Ti cladding (no bricks)

•First order reaction kinetics r=k[H+]

•Temperature Control (endothermic)

Page 21: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

Examples of Pressure leach operations

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Vale Nickel Sulphide Pressure leachVoisey’s Bay)

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Typical Matte Leach circuit

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Case Study 1

Chalcopyrite leaching

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The Problem Of Chalcopyrite

• Chalcopyrite is the one of the most difficult sulfide minerals to leach.

• There are two INTERFACE problems in treatment of chalcopyrite

• Passive films of copper polysulfide form with mild leaching in sulfate

• Liquid sulfur occludes unleached chalcopyrite preventing complete extraction

• Passive films can be prevented by ultra fine grinding (5-15 um)

• How to solve the problem of liquid sulfur occlusion? Surfactants!

• Pressure leaching deals with both problems

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Chalcopyrite leach chemistry

Compare the simple leach chemistry:

MS+ H2O+O2= MO + S0 + H+

S0 + O2= SO32-

SO32- + H2O= H2SO4

SO32- + MO= MSO4

For chalcopyrite: The overall reaction

2CuFeS2 + 17/2O2 + H2O= 2CuSO4 + Fe2O3 + 2H2SO4

does not go to completion because the intermediate

S0 reaction results in an inert boundary layer

= “passivation”.

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Sulphur oxidation in acid medium

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Sulphide leaching challenges

Elemental sulphur melts in hot water

Above 160oC it becomes very viscous

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To be successful in leaching chalcopyrite at T < 119oCrequires avoidance of passivation of chalcopyrite by copper polysulfide

To be successful in leaching of chalcopyrite at 150o C in presence of elemental sulfur requires process conditions that prevent liquid sulfur occlusion of un-reacted sulfides and avoidance of passivation due to presence of copper polysulfide layer.

To be successful in leaching chalcopyrite at T > 200o C, requires managing the excess acid produced in the copper autoclave process.

Rules for Chalcopyrite Leaching in Sulfate Systems

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Sulphate Process Options For Chalcopyrite Leaching Typical Parameters

PROCESS TEMP PRESSURE P80 Special S Yield

(˚C) (ATM) (μm) (%)

ACTIVOX 110 12 7 70

ALBION 85 1 7 50

ANGLO-UBC 150 12 7 SURFACTANTS 70

BIOLEACH 45 1 7 MESOPHILES 0

BIOCOP 85 1 37 THERMOPHILES 0

CESL 150 12 37 12 g/L Cl 90

DYNATEC 150 12 37 COAL + RECYCLE 60

GALVANOX 85 1 37 VARIOUS 95

MT GORDON 90 8 100 CHALCOCITE

PLATSOL 225 30 15 10 g/L NaCl 0

SEPON-ATM 85 1 100 CHALCOCITE

SEPON-AC 225 30 100 PYRITE 0

TOTAL POX 225 30 40 0

Page 31: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

Case Study 2

Laterite High Pressure Acid Leach

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Laterite Ore Body -Description

SiO2

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EARTHY SAPROLITE

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FRESH PERIDOTITE

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40 – 45m

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TypicalHydroprocessing

TypicalPyroprocessing

Page 33: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

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HPAL for laterites

Page 34: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

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Xstrata Nickel – Strategic Options

Laterite Smelting

Pressure Acid Leaching

Improved Caron Process

Saprolite Ore Calcine FerronickelCalcinationReduction

SmeltingRefining

Limonite Ore Mixed Sulphide Mixed Oxide to FNALeachingPrecipitation

Roasting

Limonite Ore Calcine Mixed Oxide to FNACalcinationReduction

LeachingPrecipitation

Page 35: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

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Nickel Eh-pH chart

14121086420

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Ni - S - H2O - System at 25.00 C

C:\HSC4\NiS25.iep pH

Eh (Volts)

Ni3S4

Ni

NiSNi3S2

Ni3S2

NiONi(+2a)

Page 36: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

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SIX COMPARTMENT AUTOCLAVE

MIXEDSULPHIDES

TO REFINERY

HEATING TOWERS

TRIMHEATER

PARTIALNEUTRALIZATION

HEATER H2S PRECIPITATION THICKENER

FILTERPRESS

TAILINGS DAM

HP STEAM

HEAT RECOVERY

ACIDSULPHURICACID

PLANT

7 CCD'S

To TailingsDISPOSAL

WASHSOLUTION FILTRATE TO EFFLUENT

TREATMENT

BARREN SOLN TOCCD

SO2/LIMESTONE/ LIME

PREGNANTSOLUTION

SCREENS

WATERWATER

O/S TOBALL MILL

L-ORE

REPULP DRUM

PARTIALNEUTRALIZATION

LIMESTONE

HYDROGEN SULPHIDE

Mn FixationRoaster

Pressure Acid Leach (Generic)(Ivory Coast & Koniambo)

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Pilot Autoclave

Page 38: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

Materials Selection Issues

Corrosion of Components

Page 39: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

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Considerations for Material Selection

Specific process conditions:

T,P, pO2 pH, [Cl-], [S] etc.

Gangue minerals

Secondary elements

Precipitates

Site conditions ( Arid/ Humid/ Arctic/ Tropical)

Implication: every orebody is unique, every reactor must be designed for the specific ore and reagents available

Extended Piloting testwork and equipment evaluation is essential!

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Piloting testwork–Pressure Acid LeachCanada: ~$3.5 million, 1 year duration

96 L effective volume, 6 compartment

Ti-2 autoclave with Ti-7 inlay (Parr heads)

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Piloting –CCD CircuitCanada: $0.5m ½ year

6 stage CCD circuit (Ti-2) with external dilution wells (floc)

Page 42: AutoclaveTechnology- Applications for Sulphide ...€¢ Leaching is a natural process of mineralogical alteration (weathering)involving water. Most natural leaching involves oxidation.

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New Materials - HPAL

• Isolation Valves (material selection)

� VPS TiO2 no bond coat (corrosion, porosity, adhesion & wear)

� Life increased from 7 hours to 3 months!

� The limiting factor became coating delamination

− Delamination at edges (predominant mode in VPS TiO2)

− Corrosion of substrate (high porosity in coatings)

Cawse – Discharge Ball (10” Ti Gr 7 Cr2O3 Coated)

Xstrata – Discharge Ball (½” Ti Gr 7 TiO2 Coated)

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Thank you