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THE EXTRACTIVE METALLURGY OF GOLD IN SOUTH AFRICA
VOLUME 2
SAIMM PUBLICATIONS
THE MONOGRAPH SERIES
M1 Lognormal-De Wijsian Geostatistics for Ore Evaluation (2nd ed 1981) D.G. Krige
M2 An Introduction to Geostatistical Methods of Mineral Evaluation (2nd ed 1981) J.-M.M. Rendu
M3 Principles of Flotation (1982) Edited by R.P. King
M4 Increased Underground Extraction of Coal (1982) Edited by c.J. Fauconnier and R.W.O. Kersten
MS Rock Mechanics in Mining Practice (1983) (3rd imp. 1986) Edited by S. Budavari
M6 Assay and Analytical Practice in the South African Mining Industry (1986) W.C. Lenahan and R. de L. Murray-Smith
M7 The Extractive Metallurgy of Gold in South Africa, 2 volumes (1987) Edited by G. G Stanley
THE SPECIAL PUBLICATIONS SERIES
SP1 Proceedings, Underground Transport Symposium (1986) Edited by R.C.R. Edgar
SAIMM PUBLICATIONS
THE SYMPOSIUM SERlIES
SI Mathematical Statistics and Computer Applications in Ore Valuation (1966)
S2 Planning Open Pit Mines (1970) (4th imp.) Edited by P.W.J. van Rensburg
S3 Application of Computer Methods in the Mineral Industry (APCOM 1973) Edited by M.D.G. Salamon
S4 Infacon 1974 Edited by H. W. Glen
SS Proceedings of the 12th CMMI Congress, 2 volumes (1982) Edited by H. W. Glen
S6 Rockbursts and Seismicity in Mines (1984) Edited by N.C. Gay and E.H. Wainwright
S7 The Planning and Operation of Open Pit and Strip Mines (1986) Edited by J.P. Deetlefs
S8 GOLD 100: Proceedings of the International Conference on Gold (1986)
Volume 1: Gold Mining Technology Edited by H. Wagner and R.P. King Volume 2: Extractive Metallurgy of Gold Edited by e.E. Fivaz and R.P. King Volume 3: Industrial Uses of Gold Edited by G. Gafner and R.P. King
S9 APCOM 87: Proceedings of the Twentieth International Symposium on the Application of Computers and Mathematics in the Mineral Industries (1987)
Volume 1: Mining Edited by L. Wade, R.W.O. Kersten and J.R. Cutland Volume 2: Metallurgy Edited by R.P. King and LJ. Barker Volume 3: Geostatistics Edited by Le. Lemmer, H. Schaum and F.A.G.M. Cami
sani-Calzolari
The South African Institute of Mining and Metallurgy Monograph Series M7
The Extractive f 1 in S
Edited by G. G. Stanley
VOLUME 2
This book was commissioned by the Sub-Committee of Consulting Metallurgists of the Chamber of Mines of South Africa
Johannesburg 1987
Published by The South African Institute of Mining and Metallurgy
Kelvin House, 2 Hollard Street, Johannesburg, 2001
©The Chamber of Mines of South Africa, 1987 P.O. Box 809, Johannesburg, 2000
ISBN 0 620 10944 0 Volume 2 o 620 10109 1 Volume 1 o 620 10945 9 The Set
Typeset by Scientific and Technical Typesetting Kelvin House, 2 Hollard Street, Johannesburg 2001
Printed in the Republic of South Africa by National Book Printers, Goodwood
Outline of Contents
VOLUME 1
Preface .......................................................................... . Acknowledgements ........................................................... . Foreword by President, Chamber of Mines of South Africa ..... .
Chapter 1
Chapter 2 Chapter 3 Chapter 4 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9
Chapter 10 Chapter 11 Chapter 12 Chapter 13 Chapter 14 Chapter 15 Chapter 16 Chapter 17 Chapter 18
Geology and Mineralogy of the Principal Goldfields in South Africa ............................................. . Sorting and Crushing ...................................... . Milling and Classification ................................ . Gravity Concentration .................................... . Flotation ...................................................... . Cyanidation ................................................... . Recovery of Gold from Solution by Cementation .. Pyrometallurgy of Gold .................................. . Application of Activated Carbon to Gold Recovery
VOLUME 2
Refining of Gold at the Rand Refinery .............. . Disposal of Residues ...................................... . Retreatment of Residues and Waste Rock .......... . Process Evaluation ......................................... . Process Control ............................................. . The Chemistry of the Extraction of Gold ........... . Plant Design and Commissioning ...................... . Loss Control and Safety Management ............... . Laboratories and Pilot Plants ........................... .
page XXXI
xxxiii xxxvii
1 69
121 219 235 277 331 345 379
615 655 707 745 793 831 907 971
1013
Tables and Formulae ......................................................... 1053
Index .............................................................................. 1073
vu
Contents
VOLUME 2
page Chapter 10 Refining of Gold at the Rand Refinery, by
K.G. Fisher ... ........ ........ .......................... 615
10.1 Introduction .......................................................... 615 10.2 Historical Development ... .............. ........................... 615 10.3 Function ............................................................... 616 10.4 Metallurgical Operations ......... ................................. 618
10.4.1 Summary description .................................. 618 10.4.2 Gold Refining Branch .... ............................. 618
10.4.2.1 Flow sheet 618; 10.4.2.2 Melting and sampling 619; 10.4.2.3 Refining 621; 10.4.2.4 De-golding 626; 10.4.2.5 Electrolytic gold re-fining 626; 10.4.2.6 Fume recovery and sweep treatment 628
10.4.3 Silver Refining Branch ..... ..... ......... ... .......... 630 10.4.3.1 Flow sheet 630; 10.4.3.2 Leaching and reduction 630; 10.4.3.3 Electrolytic silver refining 633
10.4.4 Coin blank production .. .............................. 637 10.4.4.1 Historical 637; 10.4.4.2 Process description 638
10.4.5 Smelter ...... ....... ............................... ........ 641 10.4.5.1 Flow sheet 641; 10.4.5.2 Sampling 641; 10.4.5.3 Blending and sintering 643; 10.4.5.4 Blast furnace smelting 644; 10.4.5.5 Cupellation 648; 10.4.5.6 Pan furnace smelting 649; 10.4.5.7 Fume collection 651
10.4.6 Assaying and chemical analysis..................... 652 10.5 Future Developments. .............................................. 652 10.6 References ............................................................. 653
Chapter 11 Disposal of Residues, by G.1. MacPhail and J.C. Wagner ............................................ 655
11.1 Aim and Scope ...................................................... 655 11.2 Planning....... ......................................................... 656
ix
CONTENTS
x
11.2.1 11.2.2
Components of a residue disposal system ...... . Sizing ..................................................... . 11.2.2.1 Depositional area requirements 657; 11.2.2.2 Allowances for services 659; 11.2.2.3 Return water system 660; 11.2.2.4 Total area 660
656 657
11.2.3 Site selection ............................................. 660 11.2.4 Site exploration ......................................... 663 11.2.5 Pollution control considerations.................... 665
11.3 Statutory Requirements........... .......... ... ..... ............... 665 11.3.1 Legal considerations ................................... 665
11.3.1.1 The Water Act 665; 11.3 .1.2 The Mines
11.3.2 11.3.3
and Works Act 666 Licensing ................................................. . Environmental impact assessment ................. . 11.3.3.1 Methods of assessment 667; 11.3.3.2 Remedial measures 667; 11.3.3.3 Monitoring 667
666 666
11.4 Design, Specification and Construction ....................... 668 11.4.1 Operation... . .. .. . . . ... .. . .. . .. . ... . .. . . .. . . .. . . . . . . . . .. .. 668
11.4.2
11.4.3 11.4.4
11.4.5
11.4.1.1 General 668; 11.4.1.2 Method of formation of tailings dam 669 Tailings delivery ....................................... . 11.4.2.1 Pulp concentration 675; 11.4.2.2 Pumping and piping systems 676; 11.4.2.3 Pump and pipeline design 678; 11.4.2.4 Tailings distri-bution 678 Return water management .......................... . Stormwater management ............................ . 11.4.4.1 General 683; 11.4.4.2 Top surface of dam 684; 11.4.4.3 Side slopes 684 Slope stability .......................................... . 11.4.5.1 Influence of foundation soils 685; 11.4.5.2 Influence of tailings product 685; 11.4.5.3 Influence of rate of rise 687; 11.4.5.4 Influence of phreatic surface 687; 11.4.5.5 In-fluence of slope geometry 689; 11.4.5.6 Stability analysis 690
11.4.6 Repair and reinstatement of operational and aban-
675
678 683
685
doned impoundments .................................. 691 11.4.6.1 Common problems with old and aban-doned dams 691; Remedial measures 693
11.5 Observation and Control .......................................... 695 11.6 Closure Considerations ............................................ 698
11.6.1 11.6.2 11.6.3 11.6.4 11.6.5 11.6.6 11.6.7 11.6.8 11.6.9 11.6.10 11.6.11
CONTENTS
General ................................................... . Boundary fence ........................................ . Access roadways ....................................... . The underdrainage system .......................... .. The solution or effluent trench .................... . The slimes delivery pipeline ........................ .. Surface drainage ....................................... . Ground level catchment paddocks ................ . Berms or step-backs ................................. .. The dam surface ....................................... . Return water dam ...................................... .
698 698 700 700 701 701 701 701 701 703 706
11.7 References............................................................. 706
Chapter 12 Retreatment of Residues and Waste Rock, by D.W. Bosch ............................................ 707
12.1 Introduction .......................................................... 707 12.2 Origin of Residues .................................................. 707
12.2.1 Sand dumps and slimes dams ....................... 707 12.2.2 Rock dumps .............. ............................... 708
12.3 Sampling, Surveying and Valuation ............................ 709 12.3.1 Sampling .................................................. 709
12.3.1.1 Grab sampling 709; 12.3.1.2 Groove or channel sampling 709; 12.3.1.3 Drilling 710
12.3.2 Surveying ................................................. 711 12.3.2.1 Tacheometric surveys 711; 12.3.2.2 Electronic distance measuring 712; 12.3.2.3 Photogrammetry 712
12.4 Sand/Slime Retreatment Operations ........................... 715 12.4.1 Slime reclamation at Blyvooruitzicht Gold Mine 716
12.4.1.1 The bucket-wheel excavator 716; 12.4.1.2 Repulper feed conveyor 719; 12.4.1.3 Repulper 719
12.4.2 Slime reclamation at ERGO ......................... 719 12.4.2.1 Location of pump stations 720; 12.4.2.2 Reclamation operations 720; 12.4.2.3 Processing at ERGO 723
12.4.3 Sand and slime reclamation at Rand Mines and Milling ..................................................... 724 12.4.3.1 Process development for sand treatment 724; 12.4.3.2 Reclamation operations 726; 12.4.3.3 Plant operations 727
Xl
CONTENTS
12.4.4 The Anglo American Corporation Joint Operating Metallurgical Scheme .................................. 731
12.4.4.1 Historical overview 732; 12.4.4.2 Feed sources 733; 12.4.4.3 Flotation plants 733; 12.4.4.4 Treatment of flotation tailings 734; 12.4.4.5 Treatment of pyrite concentrates 735; 12.4.4.6 Treatment of calcine 735
12.5 Waste Rock Recovery and Treatment ......................... 736 12.5.1 Development waste ..................................... 736 12.5.2 Waste rejected from ore setting .................... 737 12.5.3 Radiometric sorting of waste rock................. 738 12.5.4 Waste rock reclamation at the Blyvooruitzicht
Gold Mine ................................................ 738 12.6 Heap Leaching of Dumps ........ ................................ 740 12.7 Bacterial Leaching of Dumps and Slimes Dams ............ 741
12.7.1 Theoretical aspects ..................................... 741 12.7.2 Dump leaching by bacteria .......................... 742 12.7.3 Slimes dam leaching by bacteria ................... 743
12.8 References........................................................ ..... 743
Chapter 13 Process Evaluation, by H.E. Bartlett and D.M. Hawkins ......................................... 745
13.1 Introduction........................................................ .. 745 13.2 Process Evaluation ............................................ ...... 745 13.3 Statistical Concepts ... .................... .......................... 746
13.3.1 Population, sample, increment and composite samples .................................................... 746
13.3.2 Accuracy and precision ............................... 746 13.3.3 Standard deviation, variance, coefficient of varia-
tion ......................................................... 746 13.3.4 Properties of variances and standard deviations 747 13.3.5 Normal and log-normal distribution .............. 748
13.4 Sampling Theory .................................................... 751 13.4.1 Calculation of the precision of sampling ......... 751 13.4.2 Theoretical calculation of sampling precision using
Gy's formulae ...................................... ..... 751 13.4.3 Gy's '50-piece' experiment ........................... 753 13.4.4 Precision of sampling using geostatistical methods 756
13.4.4.1 The semi-variogram 756; l3.4.4.2 Nug-get effect 757; l3.4.4.3 Estimates of variance from semi-variograms 757
13.5 Sampling Practice ................................................... 759 13.5.1 Run-of-mine ore feed - stop-belt sampling .... 761
13.5.2
13.5.3 13.5.4
13.5.5
13.5.6
13.5.7 13.5.8
CONTENTS
13.5.1.1 Calculation of precision of manual stopbelt sampling 762; 13.5.1.2 The effect of compositing increments into shift and daily samples 763; 13.5.1.3 Accuracy of the sampling procedures 765; 13.5.1.4 Crushing of the sample before sub-division 765
Automatic sampling of run-of-mine ore ........ .
13.5.2.1 Testing for bias in automatic sampling 766; 13.5.2.2 Examples of t-tests 768 Crusher product sampling .......................... .. Sampling of pulps .................................... ..
13.5.4.1 Cross-stream cutters 771; 13.5.4.2 Rotary samplers 773; 13.5.4.3 Precision of sampling with cross-stream cutters 774
Other sampling equipment of pulps .............. . 13.5.5.1 Pipe sampler 776; 13.5.5.2 Projector sampler 777
Sampling of loaded carbon, slag, flue dust and other secondary materials at Rand Refinery ... . Sampling of bullion .................................. .. Sampling of liquids .................................. ..
766
770 771
775
777 778 778
13.6 Sampling Preparation .............................................. 778 13.6.1 Sample preparation equipment and practice .... 778
13.6.1.1 Pulps 778; 13.6.1.2 High grade mate-rials 778; 13.6.1.3 Run-of-mine ore 780
13 .6.2 Statistical methods to quantify bias in sub-sampling .................................................. 780
13.7 Mass Measurement ................................................. 780
13 .7.1 Truck and train weighbridges ....................... 781 13.7.2 Electromechanical belt massmeters ................ 782 13.7.3 Nuclear belt massmeters .............................. 785 13.7.4 Moisture determination for mass measurement 785 13.7.5 Batch mass determination of pulps ................ 786 13.7.6 Batch tanks on load cells............................. 786 13.7.7 Mass of pulps using flow and density meters... 786
13.8 Chemical Analysis .................................................. 787 13.9 Metallurgical Accounting ......................................... 787
13.9.1 Call system ............................................... 788 13.9.2 Check-in/ check-out system .......................... 789
13.10 Further Developments ............................................. 790 13.11 References ............................................................. 791
Xlll
CONTENTS
Chapter 14 Process Control by I.M. MacLeod and H.E. Bartlett ................................................... 793
14.1 Introduction .......................................................... 793 14.2 Historical Background ............................................. 794 14.3 Principles of Continuous Process Control................... 795
14.3.1 Control objectives ...................................... 795 14.3.2 Classification of process variables ................. 796 14.3.3 Control system structuring ........................... 797 14.3.4 The standard three-term industrial controller .. , 800
14.4 Process Measurements ................. ............................ 801 14.4.1 Introduction .............................................. 801 14.4.2 Terminology of instrumentation systems ......... 802 14.4.3 The primary sensing element ........................ 803 14.4.4 Accuracy and calibration ............................. 803 14.4.5 Basic physical measurements ........................ 804
14.4.5.1 Flow rate of solids 804; 14.4.5.2 Flow rate of liquids 804; 14.4.5.3 Liquid level in a vessel 806; 14.4.5.4 The water content of a pulp 807; 14.4.5.5 One-line particle size measurement 807; 14.4.5.6 Basic chemical measurements 810; 14.4.5.7 Carbon and resin concentration meter 815; 14.4.5.8 Carbon activity meter 815
14.5 Actuators and Final Control Elements ........................ 817 14.5.1 14.5.2 14.5.3 14.5.4
Introduction ............................................. . Control valves .......................................... . Material feeders ........................................ . Variable-speed drives ................................. .
817 817 819 819
14.6 Process Control System Design Philosophies and Architec-tures .................................................................... 819 14.6.1 Introduction.............................................. 819 14.6.2 Manual control versus fully automatic control. 820 14.6.3 Hard-wired analogue control systems ............. 821 14.6.4 Centralized computer control systems ............ 822 14.6.5 Distributed computer control systems............. 823 14.6.6 Examples of current practice ........................ 824
14.7 References ............................................................. 829
Chapter 15 The Chemistry of the Extraction of Gold, by M.J. Nicol, C.A. Fleming and R.L. Paul...... 831
15.1 General Principles ................................................... 831 15.1.1 The chemistry of gold compounds ................. 831 15.1.2 An equilibrium approach to the hydrometallurgy
of gold .................................................... 836
xi'v
CONTENTS
15.1. 3 Electrochemical aspects ............................... 843 15.1.3.1 Anodic reactions of gold 843; 15.1.3.2 Anodic reactions of zinc 848; 15.1.3.3 Cathodic processes 849
15.2 The Dissolution of Gold .......................................... 854 15.2.1 The mechanism of cyanidation ..................... 854 15.2.2 The effect of other constituents of the pulp .... 857
15.2.2.1 Iron sulphide minerals 858; 15.2.2.2 Copper sulphide minerals 859; 15.2.2.3 Arsenic sulphide minerals 860; 15.2.2.4 Antimony sul-phide minerals 860; 15.2.2.5 Anions containing sulphur 861; 15.2.2.6 Cyanide complexes of various base metals 861; 15.2.2.7 Calcium ions 862; 15.2.2.8 Carbonaceous material 862; 15.2.2.9 Flotation reagents and other surface ac-tive reagents 863
15.2.3 Other leaching processes .............................. 863 15.2.3.1 Thiosulphate 864; 15.2.3.2 Thiourea 864; 15.2.3.3 Thiocyanate 865; 15.2.3.4 Chlo-ride 866
15.3 The Recovery of Gold from Solution ........... .............. 866 15.3.1 Cementation ................... , . .. .. . . . .. . . . . .. . .. .. .. . . 866 15.3.2 Extraction by activated carbon, ion-exchange
resins or organic solvents ............................. 869
15.3.3 15.3.4
15.3.2.1 The activated-carbon process 870; 15.3.2.2 The ion-exchange process 877; 15.3.2.3 The solvent-extraction process 885 Chemical precipitation ............................... . Electrowinning ......................................... . 15.3.4.1 Cell design 890; 15.3.4.2 Electrode reac-tions 893
889 890
15.4 Clean-up, Calcination and Smelting ........................... 894 15.4.1 Acid treatment .......................................... 895 15.4.2 Calcination............................................... 896 15.4.3 Smelting ................................................... 896
15.5 Acknowledgement ................................... , ............. " 899 15.6 References............................................................. 899
Chapter 16 Plant Design and Commissioning, by G.G. Stanley ..... ......... ..... ....... ....... ..... ............. 907
16.1 The Importance of Good Plant Design and Punctual Com-missioning ............................................................. 907
16.2 The Design and Construction Organization .................. 907
xv
CONTENTS
16.3 Status, Responsibilities and Qualities of the Design Metal-lurgist ................................................................... 908
16.4 General Procedure for Plant Design ........................... 908 16.4.1 The procedural plan ................................... 908 16.4.2 Ore testing ................................................ 909
16.4.2.1 Obtaining the sample 909; 16.4.2.2 Mineralogical examination 911; 16.4.2.3 Sample preparation 912; 16.4.2.4 Laboratory testing 913; 16.4.2.5 Pilot plant testing 917
16.4.3 Process design ...................................... ..... 917 16.4.3.1 Process design criteria 917; 16.4.3.2 Flowsheet design 917; 16.4.3.3 Quantified flow-sheet 918; 16.4.3.4 Equipment sizing and selec-tion 924; 16.4.3.5 Flowsheet evaluation and selection 926; 16.4.3.6 The conclusion of the pro-cess design phase 933
16.4.4 General arrangement .................................. 933 16.4.4.1 Site selection 934; 16.4.4.2 Elements of good layout 935; 16.4.4.3 Minimizing transpor-tation requirements 935; 16.4.4.4 Maximizing ease of operation 937; 16.4.4.5 Maximizing ease of maintenance 938; 16.4.4.6 Maximizing ease of supervision 938; 16.4.4.7 Maximizing security 939; 16.4.4.8 Maximizing safety 940; 16.4.4.9 Provision for expansion 940; 16.4.4.10 The use of CAD and models 941
16.4.5 Detailed design .......................................... 941 16.4.5.1 Plant layout and design details 941; 16.4.5.2 Construction details 953; 16.4.5.3 Piping and instrumentation diagrams 957; 16.4.5.4 The definitive and revised cost estimates 957
16.5 Plant Construction and Commissioning .............. ........ 957 16.5.1 Metallurgical involvement in the construction
phase ....................................................... 957 16.5.2 Preparation for commissioning ..................... 958 16.5.3 Commissioning .......................................... 958
16.5.3.1 Personnel 958; 16.5.3.2 Cold commis-sioning 958; 16.5.3.3 Hot commissioning 959; 16.5.3.4 Some practical commissioning tips 960; 16.5.3.5 Acceptance runs 961
16.6 Conclusion ............................................................ 961 16.7 References ............................................................. 961
Appendix 16.1 Pipeline Design............................................ 963 Appendix 16.2 Pump Selection ............................................ 967
xvi
CONTENTS
Chapter 17 Loss Control and Safety Management, by F.K. Vice and D.l. Nel ................ .............. 971
17.1 Introduction...... ........ ............................................ 971 17 .2 Loss Control Department ......................................... 971 17.3 Physical Condition Rating Programme ....................... 973 17.4 The Manager's Policy.............................................. 974 17.5 Training................................................................ 974 17.6 Planned Inspections ................................................ 974
17.6.1 The general inspection ................................ 974 17.6.2 Critical parts inspections ............................. 975
17.6.2.1 Pre-use inspection of equipment 975
17.7 Accident/Incident Investigation and Analysis ............... 975
17.7.1 The investigation ....................................... 977 17.7.2 Analysis.............................................. ..... 977
17.7.2.1 Statistical data 977
17.7.3 Benefits derived from accident investigations and analysis .................................................... 982
17.8 Communications....... ......................................... ..... 982 17.8.1 Group meetings ......................................... 982 17.8.2 Personal communication ............................. 983
17.9 Emergency Preparedness .......................................... 983 17.9.1 Care of the injured and ill ........................... 985 17.9.2 Hazardous chemicals .................................. 985 17.9.3 Fires........................................................ 985 17.9.4 Miscellaneous. . . . . . . . . . . .. . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . 986
17 .1 0 Physical Examination of Employees ........................... 987
17.10.1 Medical examinations ................................. 987 17.10.2 Eyesight examinations ................................. 987 17.10.3 Audiometric testing ...... .............................. 989
17.11 Personal Protective Equipment .................................. 991 17.12 Task Analysis and Procedures................................... 993
17.12.1 Identification of critical tasks ....................... 993
17.12.1.1 Severity 994; 17.12.1.2 Repetitiveness 994; 17.12.1.3 Probability 995; 17.12.1.4 Identification of tasks requiring procedures, standards or rules 995; 17.12.1.5 Task analysis 996; 17.12.1.6 Critical task inventory summary 996
17.13 Planned Task Observations ...................................... 999 17.14 Engineering and Purchasing Controls ......................... 1001 17.15 References............................................................. 1001
Appendix 17.1 Checklist for General Planned Inspection and Physi-cal Condition Ratings .............................................. 1002
XVll
CONTENTS
Chapter 18 Laboratories and Pilot Plants, by C. W.A. Muir 1013
18.1 Introduction .......................................................... 1013 18.2 Characteristics of Metallurgical Laboratories of the Gold
18.3
Mining Industry.................. ............................... .... 1015 18.2.1 On-mine laboratories ................................... 1015
18.2.1.1 Layout 1015; 18.2.1.2 Equipment 1017; 18.2.1.3 Functions 1019; 18.2.1.4 Staffing 1019; 18.2.1.5 Comment 1020
18.2.2 Group laboratories ..................................... 1020 18.2.2.1 Layout 1022; 18.2.2.2 Equipment 1022; 18.2.2.3 Functions 1023; 18.2.2.4 Staffing 1025
Mintek 1026
18.3.1 Introduction .............................................. 1026 18.3.2 Categories of sponsorship and conditions pertain-
ing to them ............................................... 1027 18.3.3 The facilities at Mintek ............................... 1028
18.4 Pilot Plants ........................................................... 1029 18.4.1 Reasons for piloting ................................... 1029 18.4.2 Types of pilot plants .................................. 1030 18.4.3 Scale-up factors ......................................... 1030 18.4.4 Design of pilot plants ................................. 1031 18.4.5 Operation of pilot plants ............................. 1031 18.4.6 Pilot plant location .................................... 1031 18.4.7 Type of investigation carried out in pilot plants 1032
18.5 References.. . .. . . .. .. . . .. . . .. ... . . ... . . . . .. . . .... . . . . ... .. ... . . . . .. ... . 1033 Appendix 18.1 Determination of Relative Grindability using a Labcr
ratory Batch Rod Mill ............................................. 1034 Appendix 18.2 Standard Procedure for Routine Size Analysis of
Finish-ground Products ............................................ 1036 Appendix 18.3 Determination of Thickener Area .................... 1041 Appendix 18.4 Filtration Rate Determination .............. ....... .... 1044 Appendix 18.5 Cyanidation Tests using Rolling Bottle Method.. 1047 Appendix 18.6 Muffle Roasting of Sulphide Concentrates ........ 1049 Appendix 18.7 Determination of Activated Carbon Parameters. 1050
Tables and Formulae, by W.R. Flook ........................... 1053 Note on conversion tables ........................................ 1054 Table 1 Conversion table: length ............................. 1055 Table 2 Conversion table: area ................................ 1056 Table 3 Conversion table: volume ............................ 1057 Table 4 Conversion table: velocity................ ........... 1058 Table 5 Conversion table: rate of flow...................... 1058 Table 6 Conversion table: mass ............................... 1059
X-'Vl11
CONTENTS
Table 7 Conversion table: pressure........................... 1060 Table 8 Conversion table: energy ............................. 1060 Table 9 Conversion table: power ............................. 1061 Table 10 Conversion table: density ............................ 1061 Table 11 Some fundamental constants ........................ 1062 Table 12 Moisture content, density, etc. of pulps ......... 1062 Table 13 Formulae ................................................. 1064 Table 14 Base units of the International System ........... 1067 Table 15 Derived units of the International System ....... 1067 Table 16 S I prefixes ..... ......... .... ........... ......... ......... 1068 Table 17 Critical speed of mills ................................. 1068 Table 18 Te~ting-sieve series ............... ......... ...... ... .... 1069 Table 19 The periodic table .. .... ...... ............... ........... 1071 Table 20 The Greek alphabet .................................... 1072
Index ...................................................................... 1073
VOLUME 1
Note: These contents have been abbreviated by omission of the third level of subheading.
Chapter 1 Geology and Mineralogy of the Principal Goldfields in South Africa, by C.R. Anhaeusser, C.E. Feather, W.R. Liebenberg, G. Smits and l.A. Snegg ............................................. .
1.1 Historical Background ............................................. 1 1.2 Gold in the Sediments of the Witwatersrand Triad ........ 5
1.2.1 Geological aspects ...................................... 5 1.2.2 Macroscopic description of the placers ........ ... 13 1.2.3 Mineral composition of the placers ..... ...... ..... 15 1.2.4 Nature and mode of occurrence of the gold .... 16 1.2.5 Distribution of gold and heavy minerals ......... 26 1.2.6 Chemical composition of the gold ................. 28 1.2.7 Gold in residues ......................................... 30 1.2.8 Other minerals of economic interest .............. 33
1.3 Gold in the Barberton Mountain Land ....................... 35 1.3.1 Introduction.............................................. 35 1.3.2 General geology......................................... 37 1.3.3 Gold distribution in the Barberton Mountain Land 41
xix
CONTENTS
1.3.4 1.3.5 1.3.6
Mineralogical aspects of the Barberton gold ores Refractory ores and their treatment .............. . Origin of the Barberton gold deposits ........... .
49 58 60
1.4 References........................................................... .. 60
Chapter 2 S0I1ing and Crushing, by G. G. Stanley ......... 69
2.1 Introduction .......................................................... 69 2.1.1 Mining methods ......................................... 69 2.1.2 Underground waste sorting .......................... 70 2.1.3 The nature of the run-of-mine ore ................. 70 2.1.4 The operations carried out in the sorting and
crushing plant ........................................... 72 2.2 Ore Transport to the Treatment Plant ........................ 75
2.2.1 Skip transport ........................................... 75 2.2.2 Endless rope haulages .................... ............. 75 2.2.3 Rail transport............................................ 75 2.2.4 Road transport ........ .................................. 76 2.2.5 Overhead ropeways .... ................................ 76 2.2.6 Belt conveyors........................................... 76
2.3 Ore Storage, Feeding and In-Plant Conveying .............. 76 2.3.1 Ore storage ............................................... 76 2.3.2 Feeders .................................................... 80 2.3.3 In-plant conveying ..................................... 85
2.4 Washing ............................................................... 91 2.4.1 Washing in chutes ...................................... 92 2.4.2 Washing on conveyor belts .......................... 92 2.4.3 Washing on grizzlies ................................... 92 2.4.4 Washing in trommels .................................. 92 2.4.5 Washing on vibrating screens ....................... 93 2.4.6 Dealing with washings ................................. 94
2.5 Sizing ................................................................... 94 2.5.1 Grizzlies ................................................... 94 2.5.2 Vibrating screens .............................. ......... 95
2.6 Crushing ............................................................... 98 2.6.1 Types of crusher ........................................ 98
2.7 Waste Sorting and Reef Picking ................................ 107 2.7.1 Definition of waste sorting .......................... 107 2.7.2 Manual sorting .......................................... 107 2.7.3 Mechanized sorting .................................... 108 2.7.4 Reef picking ............................................. 111 2.7.5 Disposal of reject rock ................................ 111 2.7.6 Economics of waste sorting .......................... 113
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CONTENTS
2.8 Selection of Grinding Media for Pebble Milling............ 114 2.8.1 Manual pebble selection .............................. 114 2.8.2 Pebble selection by grizzley or vibrating screen 114 2.8.3 Pebble selection by deflection of the entire ore
stream . ..................... ............... ......... ....... 115 2.8.4 Pebble storage and transport........................ 115
2.9 Mass Measurement, Sampling and Control.... .............. 115 2.9.1 Mass measurement ..................... ...... .......... 115 2.9.2 Sampling ....... .......... ...... ....................... .... 116 2.9.3 Control .................................................... 116
2.10 Safety and Health ................................................... 117 2.10.1 Regulations ............................................... 117 2.10.2 Dust suppression........................................ 117 2.10.3 Noise suppression ...................................... 119
2.11 References............................................................. 119
Chapter 3 Milling and Classification, by G. G. Stanley ... 121
3.1 Evolution of the Milling Techniques Used in the Treatment of South African Gold Ores ..................................... 121
3.2 Theory of Milling ................................................... 125 3.2.1 Terminology and definition.......................... 125 3.2.2 The reasons for grinding ............................. 125 3.2.3 The boundary between crushing and grinding.. 127 3.2.4 The process of brittle fracture resulting from com-
3.2.5
3.2.6
3.2.7 3.2.8
3.2.9 3.2.10 3.2.11 3.2.12
pression ............................. , .................... . The particle size distribution resulting from brittle fracture ................................................... . The determination and reporting of size distribu-tion ........................................................ . Mathematical descriptions of size distributions Mechanisms of size reduction and transport within tumbling mills .......................................... . Energy requirements of comminution ............ . Stage grinding ......................................... .. Closed circuiting ....................................... . Summary of basic milling theory ................ ..
128
129
129 131
135 139 143 147 152
3.3 Types of Tumbling Mill and their Characteristics .......... 152 3.3.1 General description .................................... 152 3.3.2 Rod mills ................................................. 157 3.3.3 Ball mills.................................................. 158 3.3.4 Autogenous mills ....................................... 160 3.3.5 Milling combinations .................................. 162
3.4 Mill Feeders .... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .... .. .. .. .. .. .. .. .. .. .. .. 163 3 .4.1 Scoop feeders ............................................ 163
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CONTENTS
3.4.2 3.4.3 3.4.4
Drum feeders ........................................... . Spout feeders .......................................... .. Hopper feeders ......................................... .
164 164 165
3.5 Mill Liners ............................................................ 166
3.5.1 3.5.2 3.5.3 3.5.4 3.5.5 3.5.6
Trunnion liners ........................................ .. Inlet end liners ......................................... . Outlet end liners ...................................... .. Shell liners .............................................. .. Summary of South African liner practice ...... .. Relining methods ..................................... ..
166 167 167 170 175 175
3.6 Grinding Media ...................................................... 178 3.6.1 Rods ....................................................... 178 3.6.2 Balls........................................................ 179 3.6.3 Pebbles.................................................... 179 3.6.4 Grinding medium size for given ore feed size.. 179 3.6.5 Nature of grinding medium wear .................. 181 3.6.6 The ball-wear theories of Davis and Prentice ... 182 3.6.7 Ball rationing ............................................ 183
3.7 Ancillary Equipment ............................................... 184 3 .7.1 Feeders. .. . . .. .. . .. . . . . .. . . .. . .. . .. .. . . . . . .. .. . . . . . . . . . .. .. 184 3.7.2 Massmeters ............................................... 187 3.7.3 Pumps ..................................................... 187 3.7.4 Pipes ....................................................... 188 3.7.5 Valves ...................................................... 188 3.7.6 Distributors .............................................. 188 3.7.7 Water reticulation ...................................... 189
3.8 Principles of Mill Operation .... ................................. 189 3.8.1 Basic objectives ......................................... 189 3.8.2 Maximizing energy availability...................... 189 3.8.3 The effect of feed size distribution in ROM and
SAG mills ................................................ 195 3.8.4 Maximizing utilization of the available power.. 196 3.8.5 Automatic control...................................... 199
3.9 References............................................................. 201 Appendix 3.1 Hydrocyclone classifier theory, modelling and design 204 Appendix 3.2 Classification formulae ................................... 209 Appendix 3.3 Pebble competence testing and autogenous grindabili-
ty determination.. ................................................... 210 Appendix 3.4 Mill design methods ....................................... 212 Appendix 3.5 Determining grinding energy requirements for
materials that are already finer than the feed size (3350 j-tm) specified for the Bond Grindability Test .. ................... 216
Appendix 3.6 Derivation of Equation 3.22 relating ball mass in load, daily ball feed rate, new ball diameter and daily ball wear rate ...................................................................... 217
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CONTENTS
Chapter 4 Gravity Concentration, by D.W. Penman ...... 219 4.1 Introduction ......... , . . . .. . . .. . .... . .. . . .. . . ... . . .. . . .. . . ... . . ... .... 219
4.1.1 Historical................................................. 219 4.1.2 The rationale of concentration ...................... 219 4.1.3 Historical background ................................. 220 4.1.4 Present philosophy and practice .................... 221
4.2 Advantages and Disadvantages of Gravity Concentration 221 4.3 Equipment ............................................................ 223
4.3.1 Corduroy blankets ..................................... 223 4.3.2 Johnson drum concentrator ......................... 224 4.3.3 Plane table ............................................... 225 4.3.4 Jigs ......................................................... 226 4.3.5 Endless riffle belts .................................. .... 226 4.3.6 Shaking tables ........................................... 227 4.3.7 Mill liners ............................................. .... 228
4.4 Concentrate Treatment ............................................ 228 4.4.1 Re-dressing and smelting ............................. 228 4.4.2 Roasting and cyanidation ............................ 228 4.4.3 Amalgamation ........................................... 229 4.4.4 Intensive cyanidation ...................... ............ 230 4.4.5 Iron removal............................................. 230
4.5 Gravity Concentration Circuits .................................. 231 4.5.1 President Steyn gravity circuit ...................... 231 4.5.2 Gravity concentration at Sheba ..................... 232
4.6 Development .......................................................... 233 4.7 References ............................................................. 234
Chapter 5 Flotation, by B.R. Broekman, L.A.C. Carter and R. C. Dunne ............................................. 235
5.1 Introduction ...................... , . .. . . .. . ... . ... .... . . . . .. .. . . . . . .. . 235 5.2 Flotation Processing ................................................ 236
5.2.1 Mineralogical aspects .................................. 236 5.2.2 Process aspects .............. ............................ 238 5.2.3 Flotation plant practice ............................... 251
5.3 Current Flotation Trends ......................................... 260
5.3.1 5.3.2 5.3.3 5.3.4 5.3.5
Equipment ............................................... . Design ................................................... .. Control ................................................... . Trouble-shooting methods .......................... . New flotation applications .......................... .
5.4 References
260 261 265 266 272
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CONTENTS
Chapter 6 Cyanidation, by G.J.C. Young .................... 277
6.1 Introduction .......................................................... 277 6.2 Thickening .... ..... ..... ...... .............. ..... ..... ........... ..... 277
6.2.1 Batch thickeners or collectors ....................... 277 6.2.2 Continuous thickeners. ....... ..... ..... ...... .... ..... 278 6.2.3 High-rate thickeners ......... ..... ..... ... ... .... ...... 290
6.3 Leaching ....... .... ... .............. ....... ...... .... .......... ........ 291
6.3.1 Leaching reagents ...................................... 291 6.3.2 Batch and continuous leaching ..................... 295 6.3.3 Leaching vessels ......................................... 301 6.3.4 Leaching conditions .................................... 303 6.3.5 Gold losses ............................................... 304
6.4 Liquid-solid Separation ............................................ 305
6.4.1 Filtration .................................................. 305 6.4.2 Filter practice........ ...... .............................. 312 6.4.3 Maintenance ............................................. 316 6.4.4 Capacities ................................................. 317
6.5 Clarification .......................................................... 317 6.5.1 Clarifier types .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 318
6.6 References ............................................................. 323 Appendix 6.1 Thickener design calculations ........................... 324 Appendix 6.2 Leaching design calculations ............ ................ 326 Appendix 6.3 A note on the development of an on-stream analyser
for cyanide concentration, pH and alkalinity ............... 328 Appendix 6.4 The determination of nett dissolved gold loss (DO
Nett) .................................................................... 328
Chapter 7 Recovery of Gold from Solution by Cementation, by D. Bosley ........................................... 331
7.1 Introduction.......................................................... 331
7.1.1 Characteristics of gold bearing solutions......... 331 7.1.2 Recovery methods ...................................... 331
7.2 Zinc Dust Precipitation............................ ................ 333
7.2.1 Solution preparation ................................... 333 7.2.2 Precipitation practice .................................. 337
7.3 References....................... ...................................... 343
Chapter 8 pyrometallurgy of Gold, by 0.1. Gossman.... 345
8.1 Introduction.......................................................... 345 8.2 Roasting of Concentrates ......................................... 345
8.2.1 Introduction.............................................. 345 8.2.2 Basic chemistry of the roasting process .......... 346
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CONTENTS
8.2.3 Roasting furnaces ...................................... 348 8.2.4 Roaster gas treatment ................................. 350 8.2.5 Status of roasting in South African gold metallurgy 351
8.3 Retorting of Gold Amalgam ........ ............................. 352
8.3.1 Introduction .............................................. 352 8.3.2 The retort furnace ...................................... 352 8.3.3 Mercury hazard ......................................... 353
8.3.3.1 Precautions when handling mercury 354
8.4 Calcining of Zinc-Gold Precipitate ............................. 354
8.4.1 Introduction .................................. ........ .... 354 8.4.2 Clean-up of zinc-gold precipitate................... 355 8.4.3 Acid treatment of zinc-gold precipitate ........... 356 8.4.4 Dewatering of gold slime. ........................ ..... 357 8.4.5 Calcining of gold slime ............................... 361
8.5 Smelting gold bearing Material.................................. 363 8.5.1 Introduction .............................................. 363 8.5.2 Fusion furnaces ......................................... 363 8.5.3 Direct smelting of gold concentrates .............. 369 8.5.4 Melting of sponge gold ............................... 369 8.5.5 Smelting of calcined slime ........................... 370 8.5.6 Smelting of steelwool cathodes ..................... 372 8.5.7 Cleaning and sampling gold bars ........ .......... 373 8.5.8 Slag handling ............................................ 375 8.5.9 Safety hazards in the smelthouse ................... 375
8.6 Dust and Fume Extraction .................................. ..... 376 8.7 Precautions against Gold Theft ................................. 376 8.8 Record Keeping ................................ ...................... 377
Chapter 9 Application of Activated Carbon to Gold Recovery, by P.R. Bailey...................... ..... 379
9.1 Introduction............................................ . ........... .. 379
9.1.1 Historical ................................................. 379 9.1.2 Gold recovery ........................................... 379 9.1.3 Process route comparisons ........................... 382
9.2 Activated Carbon .............................................. ..... 383
9.2.1 9.2.2
Physical and chemical properties .................. . Gold absorbing properties ........................... .
384 387
9.3 Absorption ............................................................ 393 9.3.1 Modelling ................................................. 393 9.3.2 Stage, loading and barren values ................... 399 9.3.3 Equilibrium effects ..................................... 417 9.3.4 Carbon activity .......................................... 429 9.3.5 Physical effects .................... ...................... 439
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CONTENTS
9.4
9.3.6 9.3.7 9.3.8 9.3.9 Elution
9.4.1 9.4.2 9.4.3 9.4.4
9.4.5 9.4.6
Operating considerations ............................ . Carbon-in-leach operations ........................ .. Other feed stocks ...................................... . Equipment ............................................... .
Introduction ............................................. . Physical and chemical effects ...................... . Kinetics of elution .................................... .. Anglo American Research Laboratory (AARL) elution .................................................... . Zadra elution ........................................... . Equipment ............................................... .
443 449 455 457 481 481 483 489
492 503 511
9.5 Regeneration .......................................................... 530
9.5.1 Introduction .............................................. 530 9.5.2 Thermal regeneration .................................. 530 9.5.3 Rotary kilns .............................................. 541 9.5.4 Rintoul kiln regeneration ............................. 547
9.6 Electrowinning ....................................................... 550
9.6.1 Electrochemical reactions ............................. 551 9.6.2 Cell design ................................................ 552 9.6.3 Electrowinning cells .................................... 554 9.6.4 Mintek cell - operational data .................... 561
9.7 Acid Treatment ...................................................... 570 9.7.1 Acid treatment conditions ............................ 571
9.8 Carbon Breakage .................................................... 575
9.8.1 Breakage by pumps .................................... 575 9.8.2 Breakage by eductors .................................. 581 9.8.3 Breakage by mixing .................................... 583 9.8.4 Breakage during regeneration ....................... 583 9.8.5 Plant carbon loss ....................................... 584
9.9 Carbon in Solution ................................................. 585
9.9.1 Adsorption systems .................................... 585 9.9.2 Design considerations ................................. 599
9.10 References ............................................................. 608
xxvi