DESIGN, DEVELOPMENT, AND CHALLENGES OF THE SART PROCESS

Humberto Estay and Francisco Arriagada - Arcadis Idesol, Chile

Sergio Bustos - Areva NC, France

CONTENTS

1. INTRODUCTION2. THE SART PROCESS

• DESCRIPTION OF THE SART PROCESS• SART PROCESS INTEGRATION WITH THE HEAP CYANIDATION CIRCUIT

3. DESIGN AND DEVELOPMENT OF THE SART PROCESS• OPTIMUM SART PLANT CAPACITY AND COPPER CONCENTRATION

CONTROL• COPPER RECOVERY, ADDITION CONTROL AND CONSUMPTION OF

NASH• ADDITION AND CONTROL OF ACID AND PH• SOLID-LIQUID SEPARATION PROCESSES• DESIGN FOCCUSED ON PERSONNEL SAFETY

4. SART PROCESS CHALLENGES5. CONCLUSIONS

1. INTRODUCTION

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Gold Projects• Pascua Lama• Peñón Expansion• Cerro Casale• Lobo Marte• Maricunga Expansion

CopperContent

Impacts

Presence of Cyanide SolubleCopper

• In some cases, contaminating dore metal

• Increases the cyanide consumption

• Gradual increment in the concentrationof copper in solution circuit

• Reducing Au extraction in carbonadsorption stage

• Increasing elusion cycle

1. INTRODUCTION

To eliminate copper of solution circuit is possible to incorporate the SART Process(Sulfidization-Acidification-Reciclyng-Thickening)

The SART Process is a new technology developed by Lakefield Research in Canada(MacPhail, P., Fleming, C., Sarbutt, K. 1998)

SART process has been applied in Telfer (40 m3/h), Lluvia de Oro (350 m3/h) y Yanacocha(1400 m3/h)

ARCADIS IDESOL has conducted the detail engineering design of SART plants forMaricunga (750 m3/h) and Mantos de Oro (250 m3/h) operations, owned by Kinross GoldCorporation in Chile

2. THE SART PROCESS - DESCRIPTION

NaSHSolution

H2SO4

SART Reactor

Lime

Cu2S

NaOH

TreatedSolution

Gypsum

WashWater

WashWater

Precipitate THK

Gypsum THK

NeutReactor

Dryer

Pp Filter

Gypsum Filter

Flocculant

Flocculant

2

442 )(22 SOacHCNSOHCN

)(6)(6)(2 2

22

3 acHCNsSCuHSCNCu

SART Rx, pH 4-5

OHCNCaOHCaacHCN 222 2)()()(2

OHsCaSOOHCaSO 2)()( 42

2

4

Neut Rx, pH 11

TreatedAir

NaOH

Scrubber

2. THE SART PROCESS - INTEGRATION

HEAP LEACH

ADR/EWPLS Pond

Barren Solution

Barren Pond

NaCN

SART

NaSH, H2SO4

Ca(OH)2

Cu2S

Gypsum

SART

NaSH, H2SO4

Ca(OH)2

Cu2S

Gypsum

PLS Option

Barren Solution Option

Dore Metal

Advantages• Increases CN-/Cu ratio• Reduces copper adsorptionRisks• Au Losses in Gypsum• Drag of Gypsum into carbon

adsorption

Advantages• Eliminate risk of gypsum

contamination in carbon stage• Possibility to incorporate the

AVR process to make possiblethe final washing of the heaps

3. DESIGN AND DEVELOPMENT OF THE SART PROCESSOptimum SART Plant Capacity and Copper Concentration Control

Q (SART) = f([Cu]eq)

Case30.000 ton/day of ore350 g/t CN-soluble Copper2.500 m3/h of PLS85% Copper Recovery in SART

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Heap leach flow fraction to SART, %

Mass Balance to IntegratedCircuit

To describe the time dependent evolution of copper effluents and instantaneous solutiondrainages or sinks arising from displacement of the active irrigation area, it’s necessary adynamic model of multi-lift heap leaching. These models have been addressed by ArcadisIdesol since 2003.

3. DESIGN AND DEVELOPMENT OF THE SART PROCESSCopper Recovery, Addition Control and Consumption of NaSH

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Co

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NaSH Addition wrt Stoichiometry , %

CMM Telfer Yanacocha

Rec (Cu) = f(NaSH/Cu ratio) Tests to Establish CopperRecovery

CMM: Ford et al., 2008Telfer: Barter et al., 2001Yanacocha: Botz & Acar, 2008

The control of NaSH addition is essential to ensure attainment of the target Cu recovery.There are three options: a) manual, b) ORP, c) gaseous H2S monitoring

3. DESIGN AND DEVELOPMENT OF THE SART PROCESSAddition and Control of Acid and pH

Copper precipitation requires a pH 5,0 or below

The design requiresdetermination of the curve ofacid consumption

The inflexion point at about pH near 3,0 must be identified. CuCN may precipitatecontaminating Cu2S product

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Acid Consumption, kg/m3

3. DESIGN AND DEVELOPMENT OF THE SART PROCESSSolid-Liquid Separation Process

Cu2Sformed

Thickening Process• Diluted slurry feeding (0,05-0,5% solids)• Low % of solids in underflow (10-15% solids)• High dosages of flocculant (0,25-4 mg/l)• Settling rate between 3-4 m/h

The design of solid-liquid separation process must ensure the correct velocity ofagitators, type of pumps and control philosophy

Colloidalprecipitate

Complex solid-liquidseparation process

Filtration Process• High moisture in filtration cake (50-65%)• High filtration cycles• It’s necessary additional stages• Cake is easy to handle in belts and bins

3. DESIGN AND DEVELOPMENT OF THE SART PROCESSDesign Focused on Personnel Safety

Slurries and solutions with CN-

Presence of sulphide in solutions

• The equipment operating under acid conditions must be sealed and connected to a gasscrubbing

Potential emission ofHCN and H2SLow pH

• The process must consider neutralization to pH 11-12 of the recycled solution and slurryfeeding filter

• HCN and H2S sensors must be placed in the process building and the operators mustuse portable sensors

• The design must be avoid leaks and spills and consider secondary contention per area

• The design should respond to Cyanide Code

• The operation must implement procedures of security and reagents handling

4. SART PROCESS CHALLENGES

SART process faces future challenges to improve or optimize theprocess, reduce opex or capex. The followings areas of development aresuggested:

• Optimize the performance of the process at a large scale. Generate operationalpractices and process control strategies

• Incorporation or combination of new engineering technologiesBioSulphide ® Process, (Lawrence, et al., 2008)EMS ® Process, (Lombardi, 2009)SART/AVR Process, (Botz & Acar, 2008)

• Ensure the correct handling of reagents by procedures which guarantee thesafety of the personnel

5. CONCLUSIONS

• The results provided by experimental and engineering studies havecontributed to support the design of the SART plant.

• The correct design of the SART process is based upon precise definitionof the plant flow capacity, definition of the control systems andexperimental determination of the solid-liquid separation parameters

• The design of a SART plant must be based on the results of a soundexperimental laboratory and pilot program

• The design must ensure the safety of the personnel, including correctunit operations and control systems

• The main challenge the SART process faces is to demonstrate itstechnical and economic feasibility processing large flow rates

Imagine the result

THANKS