Acknowledgement...iii. Editors...iii FOREWORD... v Practical limitations The ultimate objective THE DRIVERS...

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1 CONTENTS PREFACE... I Acknowledgement...iii Editors...iii FOREWORD... v INDUSTRY SPONSORS...vii 1 Introduction OBJECTIVES OF THE GUIDE BACKGROUND THE CURRENT SITUATION Practical limitations The ultimate objective THE DRIVERS CLOSURE CLASSIFICATION AND THE TAILINGS CONTINUUM ABOUT THE GUIDE...7 AUTHOR DETAILS The Tailings Continuum: Defining The Boundaries PREAMBLE THE TAILINGS CONTINUUM THE CURRENT SITUATION Conventional tailings slurry Thickened tailings slurry Paste Cake CLASSIFICATION SYSTEM BOUNDARIES Segregation threshold Initial settled density Liquid limit...16 ix

2 2.5 TRANSPORT OF TAILINGS TERMINOLOGY CONVENTION...17 AUTHOR DETAILS Rheological Concepts PREAMBLE INTRODUCTION RHEOLOGICAL ASPECTS OF PASTE AND THICKENED TAILINGS SYSTEM DESIGN Relevance of rheology to the overall system design Test sample preparation IMPORTANT RHEOLOGICAL CONCEPTS MEASUREMENT OF RHEOLOGICAL PROPERTIES The vane method The slump method Shear stress shear rate measurements The bucket rheometer VARIABLES AFFECTING THE RHEOLOGY OF FINE PARTICLE TAILINGS Particle concentration Particle size and particle-size distribution Particle shape Shear rate and shear history Clays Water chemistry ph and ionic strength Flocculation THICKENING AND COMPRESSION RHEOLOGY CONCLUSION...43 ACKNOWLEDGEMENT...43 AUTHOR DETAILS...43 Material Characterisation PREAMBLE PREPARATION Particle-size distribution...48 x

3 4.2.2 Specific gravity (also known as particle relative density) ph Mineralogy POST-TREATMENT Transport Deposition Beaching Settling and air drying Consolidation Water retention ability Stability Shear strength Liquefaction Post-liquefaction strength Geochemistry Acid-base accounting Erodibility Dust generation CONCLUSION...60 ACKNOWLEDGEMENT...61 AUTHOR DETAILS Slurry Chemistry PREAMBLE DISPERSED STATE COLLOIDAL SYSTEMS Hydrophobic colloid theory Surface charge potential Diffuse layer thickness Hydrophobic colloid particle interaction CLAY MINERAL PROPERTIES Clay classification and crystal structure Clay particle surface charge CLAY SLURRY BEHAVIOUR Suspended clay cation exchanged state Suspension ph Suspension ionic concentration CLAY SLURRY CONDITIONING AND FLOCCULATION...72 xi

4 5.6 SLURRY MEASUREMENTS Colour Composition and mineralogy Conductivity Density Particle size, shape and surface area ph Reduction potential (redox) Rheology Solids concentration Suspended solids Surface charge Total dissolved solids Turbidity (clarity)...80 AUTHOR DETAILS Reagents PREAMBLE FLOCCULANTS, COAGULANTS AND DISPERSANTS Flocculation versus coagulation Dispersion REAGENT CHEMISTRIES Coagulants Inorganic Synthetic Dispersants Inorganic Polymer Flocculants Natural Synthetic The evolution of synthetic flocculants BRIDGING TYPE POLYMERS Particle bridging Flocculant adsorption Adsorption of nonionic flocculants Adsorption of anionic flocculants...92 xii

5 Adsorption of cationic flocculants POLYMER CHAINS IN SOLUTION Solution state and dimensions The solution properties of flocculants PHYSICAL FORMS OF POLYMER PRODUCTS Solid phase Emulsion Dispersion Blocks Solution THEORY OF FLOCCULATION AND COAGULATION Aggregation kinetics Aggregate porosity Aggregate growth The impact of solids concentration Factors that affect particles in suspension Nature and size of the solids present Solids concentration Surface charge and slurry ph Type and quantity of dissolved ions present FACTORS AFFECTING POLYMER ACTIVITY Product life Solution make-up Flocculant transport Water quality Make-up equipment materials FACTORS AFFECTING POLYMER APPLICATION Reagent choice Flocculants Coagulants Reagent dilution Reagent dosage Dosing/addition conditions Dosing points Shear conditions Control INLINE POLYMER ADDITION REAGENT TESTING THE FUTURE OF REAGENTS AUTHOR DETAILS xiii

6 7 Thickening PREAMBLE DEVELOPMENT OF THICKENING Thickeners Filters SCIENCE OF THICKENING Thickening theory Thickening phases Factors affecting the thickening process Use of flocculants and coagulants in thickening Unit area sizing Rise rate sizing Compression zone sizing Sizing of rakeless high-rate thickeners Sizing of paste thickeners Underflow solids concentration and rheology Predicting underflow concentrations and rheology for paste thickeners Factors that affect underflow rheology and predicted solids Thickener sizing conclusions THICKENING EQUIPMENT TYPES Elevated tanks Bridge-mounted Column-mounted Caisson design THICKENER RAKES Single pipe rake arm Box truss rake arm Swing lift arm Thickening or dewatering pickets THICKENER DRIVE TYPES Centre drives Peripheral drives THICKENER DESIGN TYPES Conventional thickener High-rate thickener xiv

7 Feedwell design Dilution systems High-rate (rakeless) thickener High-density (paste) thickener THICKENER CONTROLS Conventional thickener controls High-rate (rakeless) thickeners Paste thickeners COMBINATION: THICKENERS AND FILTERS TRANSPORTATION CONSIDERATIONS THE SYSTEMATIC DESIGN APPROACH TO PASTE THICKENING CONCLUSION AND COMMENTS ON PASTE AND THICKENERS ACKNOWLEDGEMENT AUTHOR DETAILS Filtered Tailings PREAMBLE INTRODUCTION HISTORY FILTRATION BACKGROUND Introduction Cost of solid liquid separation Filtration methods Filtration dewatering continuum Filtration design considerations Filtration theory Flow through porous media The filtration cycle FILTRATION TEST-WORK Introduction Slurry characterisation and technology pre-selection Slurry characterisation Test-work strategies Experience Laboratory and pilot test-work Vacuum filtration test equipment xv

8 Pressure filtration test equipment Data collection Slurry properties Cake properties Time-dependent variables Sample preparation, cake and filtrate analysis Safety FILTRATION EQUIPMENT Introduction Vacuum filters Horizontal belt filter Horizontal pan filters Pressure filters Dewatering screens Capillary action filtration Hyperbaric filtration Filtration equipment comparison FILTRATION COSTS Introduction Flow sheeting considerations Traditional dewatering flow sheet Split dewatering flow sheet Cost example Capital costs Operating costs CONCLUSION AUTHOR DETAILS Thickening Plant Concepts PREAMBLE HYDROCYCLONES VIBRATORY SCREENING AUTHOR DETAILS xvi

9 10 High-Concentration Hydraulic Transport Systems PREAMBLE SLURRY PIPELINE FLOW BEHAVIOUR Heterogeneous slurries Homogeneous non-newtonian slurries Dense phase mixtures Mixed-regime slurries Minimum transport velocity PUMP TYPES Centrifugal pumps Effect of solids on pump performance in thickened tailings applications Effect of wear on pump performance Limiting centrifugal pump wear Positive displacement pumps Rotary pumps Reciprocating pumps Piston diaphragm pumps Valves in reciprocating pumps Suction requirements Operating characteristics of positive displacement pumps Comparison between centrifugal and positive displacement pumps ALTERNATIVE TRANSPORT OPTIONS Conveying options Trucking options DESIGN OF HIGH-CONCENTRATION SLURRY PIPELINE SYSTEMS Slurry flow modelling of thickened and paste tailings Pump and pipeline interaction Centrifugal pumps Positive displacement pumps Hydraulic grade line Pipeline mechanical design ECONOMIC EVALUATION OF THICKENED TAILINGS PUMPING SYSTEMS Capital costs: centrifugal versus positive displacement pumps Pressure Standby requirements xvii

10 Motor requirements Process considerations Capital costs: pipeline considerations Pressure considerations Pipe jointing Capital costs: other considerations Annual operating costs Annual costs: power and water Annual costs: maintenance Annual costs: personnel Annual costs: preparation Financial comparison CONCLUSIONS ACKNOWLEDGEMENT AUTHOR DETAILS Above Ground Disposal PREAMBLE INTRODUCTION TECHNIQUES FOR MANAGING SURFACE DEPOSITION OF THICKENED TAILINGS Central thickened discharge Down-valley discharge (DVD) Ring-dyke impoundment In-pit disposal PERCEIVED AND REALISED BENEFITS Reduced water usage Similar capital and reduced operating cost to wet disposal Increased deposit strength Decreased land footprint by at least doubling practical stacking height Decreased demand for borrow materials for construction Reduced risk of leachate seepage Reduction or elimination of ponding and low strength mud deposits Prompt creation of firm, concave draining surface at completion Earlier, better surface leaching and drainage xviii

11 Reduced potential for liquefaction Potentially reduced heating requirements, lower water demand Reduced reagent requirements Other key issues DESIGN CONSIDERATIONS Shape, layout and geometry Profiles of thickened tailings storage facilities Ensuring geotechnical stability Water management Strength and density Drying and consolidation Liquefaction potential OPERATIONS AND MANAGEMENT Facility operation and maintenance Risk management Environmental Seepage Wind erosion and dust generation Water erosion Closure considerations OPERATIONAL INTERVENTIONS TO IMPROVE PERFORMANCE Controlling and directing flow from CTD risers Enhancing the rate of gain on surface shear strength the concept of mud farming CONCLUSION AUTHOR DETAILS Beach Slope Prediction Approaches PREAMBLE BEACH SLOPE PREDICTION MODELS Lubrication theory Equilibrium channel slope Stream power RHEOLOGY/TESTING CONSIDERATIONS DISCUSSION OF FUNDAMENTAL PRINCIPLES OF BEACH FLOWS Non-Newtonian flow behaviour xix

12 Comparison of beach profile models Particle settling and sedimentation Turbulent settling Laminar segregation Assumptions regarding laminar or turbulent flow in the three main beach models Flow path Comparison of beach profile models THE FIELD EXPERIENCE CURRENT RESEARCH AUTHOR DETAILS Inline Flocculation PREAMBLE INTRODUCTION TAILINGS TYPES AND KEY MATERIAL PROPERTIES MECHANICS OF SLURRY AND POLYMER FLOWS Polymer dispersion and flocculation kinetics Floc growth Predictive modelling POLYMER INJECTION Injection techniques Flow regimes at injection CONDITIONING AND WATER RELEASE Additional factors influencing downstream pipe flow BEACHING DEPOSIT CONTROLS Observations of flow and beaching Homogeneous versus multiphase flows Rapidly dewatering tailings characteristics Considerations for beach modelling Beach management Beach profiles Drainage and surface runoff management CONCLUSION AUTHOR DETAILS xx

13 14 Mine Backfill PREAMBLE INTRODUCTION PREPARATION TRANSPORTATION AND PLACEMENT Transportation Placement IN SITU PERFORMANCE Barricade stability Stability upon exposure ENVIRONMENTAL CONSIDERATIONS ECONOMIC EVALUATION INTEGRATED APPROACH TO BACKFILL SELECTION AND DESIGN CONCLUSION AUTHOR DETAILS Closure Considerations PREAMBLE CLOSURE PLANNING PROCESS DESIGN STANDARDS FOR CLOSURE SAFETY STABILITY Embankments Upper surfaces AESTHETIC ACCEPTABILITY CONTROL OF ACID MINE DRAINAGE COVERS RECLAMATION/REHABILITATION OF TSFs REGULATION FINANCIAL ASPECTS CONCLUSION AUTHOR DETAILS xxi

14 16 Case Studies PREAMBLE Acknowledgement SAR CHESHMEH, IRAN MIDUK, IRAN DE BEERS COMBINED TREATMENT PLANT, SOUTH AFRICA Facility description Discharge riser pipes Perimeter wall raise Conclusion ASSMANG KHUMANI IRON ORE MINE, SOUTH AFRICA System description Facility description Deposition Facility operations Future wall raises Conclusion HILLENDALE, SOUTH AFRICA Introduction Mining process Primary wet plant Residue storage facility layout Fine residue properties Wall raising Operational comments Rehabilitation Conclusion QUEENSLAND ALUMINA, AUSTRALIA KIDD METALLURGICAL SITE TAILINGS MANAGEMENT AREA, CANADA GOLDCORP CANADA MUSSELWHITE MINE TAILINGS MANAGEMENT AREA FREEPORT INDONESIA BIG GOSSAN MINE PASTE BACKFILL PLANT Introduction Paste plant system Surface facilities Underground facilities xxii

15 Features of the paste plant system Tailings classification system Cement delivery and unloading system Paste distribution Conclusion USE OF RHEOMAX ETD TECHNOLOGY TO THICKEN BAUXITE RESIDUE SLURRY DURING SUPER THICKENER BYPASS OSBORNE MINE CASE STUDY, AUSTRALIA IMPLEMENTATION OF VIBRATORY DEWATERING SCREENS AT THE MANTOS BLANCOS MINE, CHILE Introduction Installation of second industrial unit AUTHOR DETAILS References 321 Glossary 339 Service Directory 347 Author Index 356 xxiii