Gold Ore Processing. Project Development and Operations

980 Pages·2016·74.63 MB·English

by  Mike D. Adams

Gold Ore Processing
Project Development and Operations
Second Edition
Edited by
Mike D. Adams
Fugue Pte Ltd, Singapore
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List of Contributors
S.Acar,AcarConsultingLLC,HighlandsRanch,CO,USA X. Díaz, University of Utah, Salt Lake City, UT, USA,
Escuela Politécnica Nacional, Quito, Ecuador
M.D. Adams, Fugue Pte Ltd, Singapore
D. Donato, Donato Environmental Services, Adelaide,
N. Ahern, AuTec Innovative Extractive Solutions Ltd.,
Australia
Vancouver, BC, Canada
D.B. Dreisinger, University of British Columbia,
A.U.Akcil,Suleyman DemirelUniversity, Isparta, Turkey
Vancouver, BC, Canada
C. Aldrich, Western Australian School of Mines, Perth,
R. Dunne, Western Australian School of Mines, Curtin
Australia
University (Gold Technology Group), Perth, WA,
J.E. Angove, AFT Metallurgy, North Beach, WA,
Australia
Australia
S. Ellis, Perth, WA, Australia
E. Asselin, The University of British Columbia,
C.J. Ferron, HydroProc Consultants, Peterborough, ON,
Vancouver, BC, Canada
Canada
M.G. Aylmore, John de Laeter Centre, Faculty of Science
S. Flatman, Previously AngloGold Ashanti, Ergo
and Engineering, Curtin University, Perth, WA,
Operation, Brakpan, South Africa
Australia
C.A. Fleming, SGS Minerals, Lakefield, ON, Canada
J.Y. Baron, Barrick Goldstrike Mines Inc., Carlin, NV,
USA M. Fullam, FLSmidth Ltd, Knelson Technologies,
Langley, BC, Canada
P. Bateman, International Cyanide Management Institute,
Washington, DC, USA A. Götz, Fraser Alexander, Boksburg, South Africa
G. Beale, Schlumberger, Denver, CO, USA S. Gray, Gekko Systems Pty Ltd, Ballarat, VIC, Australia
M.M. Botz, Elbow Creek Engineering, Sheridan, WY, B. Green, Retired (previously Mintek, Randburg, South
USA Africa)
P. Breuer, CSIRO, Perth, WA, Australia N. Greenwald, International Cyanide Management
Institute, Washington, DC, USA
N. Briggs, Sedgman Limited, Perth, WA, Australia
Y. Gu, Yingsheng Technology, Darra, Queensland,
A.R.G. Brown, Allan RG Brown & Associates Pty Ltd,
Australia
Booragoon, WA, Australia
J. Güntner, Outotec GmbH & Co. KG, Oberursel,
A. Charitos, Outotec GmbH & Co. KG, Oberursel,
Germany
Germany
F. Habashi, Department of Mining, Metallurgical, and
Y. Choi, Barrick Gold Corporation, Toronto, ON, Canada
Materials Engineering, Laval University, Québec City,
S.L. Chryssoulis, Amtel, London, ON, Canada
QC, Canada
A.P. Cole, Barrick Goldstrike Mines Inc., Elko, NV, USA
J.Hammerschmidt,OutotecGmbH&Co.KG,Oberursel,
M. Costello, Previously Lycopodium Ltd., Perth, WA, Germany
Australia
R.J.Holmes,CSIROMineralResources,Melbourne,VIC,
F.K. Crundwell, CM Solutions (Pty) Ltd, Johannesburg, Australia
South Africa
D.G. Hulbert, Retired (previously Mintek, Randburg,
G. Deschênes, BBA Inc., Toronto, ON, Canada South Africa)
ix
x List of Contributors
M. Jeffrey, Newmont, Denver, CO, USA A. Muir, Previously AngloGold Ashanti, Ergo Operation,
Brakpan, South Africa
E. Johanson, Lycopodium Engineering Pty Ltd., Perth,
WA, Australia J. Muller, Onkaparinga Mining & Metallurgy Pty Ltd,
Perth, WA, Australia
J. Johnson, WesTech Engineering, Inc., Salt Lake City,
UT, USA N.D. Overdevest, Donato Environmental Services,
Adelaide, Australia
D.W.Kappes,Kappes,Cassiday&Associates,Reno,NV,
USA M.S. Pearson, Autoclave Technology Group, Hatch Ltd,
Mississauga, ON, Canada
B. Kerstiens, Outotec GmbH & Co. KG, Oberursel,
Germany M. Reuter, Helmholtz Institute Freiberg for Resource
Technology, Freiberg, Germany
M. Kotze, Lanxess, South Africa (previously Mintek,
Randburg, South Africa) D.Rogers, Lycopodium EngineeringPty Ltd., Perth, WA,
Australia
G.Kyriakakis,ExtractiveResourcesLLC,Townville,SC,
USA P. Rohner, Core Resources, Brisbane, Australia
H. Lacy, MWH Global, Perth, WA, Australia A. Ryan, Lycopodium Engineering Pty Ltd., Perth, WA,
Australia
G. Lane, Ausenco Limited, Brisbane, QLD, Australia
C. Sabbagha, Previously AngloGold Ashanti, Ergo
G.T. Lapidus, Universidad Autónoma Metropolitana,
Operation, Brakpan, South Africa
Iztapalapa, Mexico
A. Laplante, Metallurgist (1953e2006) B. Sceresini, Australian Mining, Perth, WA, Australia
R. Shaw, Goldcorp Inc., Vancouver, BC, Canada
D. Lunt, Stirling Process Engineering Limited, Lincoln,
UK L. Simpson, Elemetal Refining, Jackson, OH, USA
J. Mackenzie, Murdoch Mackenzie Metallurgy, Perth, H. Smith, KWA Kenwalt Australia, Perth, WA, Australia
Australia
W.P. Staunton, Western Australian School of Mines,
T.J.Manning,Kappes,Cassiday&Associates,Reno,NV, Curtin University, Perth, WA, Australia
USA
D.Stephenson,AusencoLimited,Brisbane,QLD,Australia
M.L. McCaslin, WesTech Engineering, Inc., Salt Lake
K.G. Thomas, Ken Thomas & Associates Inc., Oakville,
City, UT, USA
ON, Canada
J. McMullen, J. McMullen & Associates (previously
A. van Schaik, MARAS, Material Recycling and
Barrick Gold Corporation), Toronto, ON, Canada
Sustainability, Den Haag, The Netherlands
P.Messenger,AusencoLimited,Brisbane,QLD,Australia
M. Virnig, BASF (previously Cognis Corporation),
M. Millard, Metallurgist (1951e2007) Tucson, AZ, USA
J.D. Miller, University of Utah, Salt Lake City, UT, USA R. Walton, Ray Walton Consulting Inc., Aurora, ON,
Canada
P.Miller,SulphideResourceProcessingPtyLtd,Hillarys,
WA, Australia R.-Y. Wan, Metallurgist (1932e2009)
J. Mitchell, Previously AngloGold Ashanti, Ergo Oper- J. Wates, Fraser Alexander, Boksburg, South Africa
ation, Brakpan, South Africa
B. Watson, Consep Pty, Perth, WA, Australia
M.B. Mooiman, Franklin Pierce University, Manchester,
T. Weeks, Aquila Ventures Pty Ltd, Perth, WA, Australia
NH, USA
D. Williams, Golder Associates, Perth, WA, Australia
J.B.Mosher,FreeportMcMoRanInc.,Phoenix,AZ,USA
J.Zhou,JoeZhouMineralogyLtd,Peterborough,Ontario,
T.I. Mudder, Times Ltd., Sheridan, WY, USA
Canada
Foreword
ThefirsteditionofAdvancesinGoldOreProcessingarrivedatatimewhenthegoldpricehadincreasedfromlowvalues
ofaroundUS$270/troyozin2001toanaverageof$444/troyozin2005.Sincethattime,thepricehassoared,reachingan
average of$1669/troy oz in2012 before softening tothe2015 levels of $1100/troy oz.This remarkableperformance has
led to a resurgence in primary gold production worldwide, as well as renewed interest in exploration, research, devel-
opment,andtechnologicalinnovationthroughouttheindustry.However,thishasbeentemperedtoasignificantextentbya
near-threefold increase in cash operating costs from $269/troy oz in 2005 to $750/troy oz in 2014 and similar increased
ratios in capital costs for new (Greenfield) and expansion production capacity. Capital cost intensity for new gold pro-
ductioncapacitynow ranges from $1500 to$4500/annualtroyozproduced,depending ontheorefeed grade, processing
method,byproducts,andorecomplexity.Thisleavesmuchoftheindustryfacingsignificantchallengestoprofitabilityfor
existing operations and for adding new capacity. A key part of this story is that average ore grades have decreased
significantly from about 1.8g/t in 2005 to approximately 1.3g/t in 2014. Ore deposits are being developed with
increasinglycomplexmineralogyandmetallurgicalpropertiesasthemoreeasilytreatableresourcesaredepleted.Thisnot
onlyaddstothecostofextraction,bothcapitalandoperatingbutalsoincreasesthedevelopmenttimeforprojectsandadds
technical risk.
Theglobalgoldproductionprofilewasverydifferentin2005.SouthAfricawasthetopproducerwith300metrictons,
followedbyAustralia,UnitedStates,China,andPeru.Totalglobalgoldproductionincreasedfromalmost2520metrictons
in 2005 to over 3100 metric tons in 2014; however, China increased its production to take the top position, followed by
Australia, Russia, United States, and Peru. Much of China’s production comes from small, distributed deposits, using
conventional technology that can be applied effectively at a small scale e for example, gravity concentration, flotation,
amalgamation,cyanidation,anddirectsmelting/processingofconcentrates.Inparallelwiththis,productionfrommanyofthe
majorproducingminesdroppedoffsignificantly,suchasYanacocha,Peru(NewmontGold),andDriefontein,SouthAfrica
(GoldFields).Thisservestounderscorethedramaticchangesthathaveoccurredwithintheindustryoverthepast10years.
Turning to the processing aspects of the industry, gold ore processing is dominated by the cyanidation process. Since
the inception of the process in the late 1800s, cyanide has been used widely to extract gold because of its relatively low
cost,greateffectivenessforgoldandsilverdissolution,selectivityforgoldandsilveroverothermetals,aswellasrelative
ease and efficiency of metal recovery from solution. Also, despite some concerns over the toxicity of cyanide, it can be
applied with little risk to human health and the environment. The oxidant most commonly used in cyanide leaching is
oxygen, usually supplied from air, which contributes to the attractiveness of the process.
Sincethemid-1970s,alternativeleachingreagentschemestocyanidehavebeeninvestigatedforanyorcombinationsof
the following reasons:
l Environmentalpressures,andinsomecasesrestrictionsorlimitations,maymaketheapplicationofcyanidedifficultin
certain locations;
l Some alternative reagent schemes provide faster gold (and/or silver) leaching kinetics;
l Several can be applied in acidic media, which may be more suitable for refractory ore treatment, and
l Some are more selective than cyanide for gold and silver over other metals, such as copper and zinc.
Some of the more important reagent systems that have been investigated (or reinvestigated) are chlorineechloride,
thiosulfate, thiocyanate, thiourea, ammonia, ammoniaecyanide, alkaline sulfide, and other halide combinations. Aside
from theadvantageslistedhere, all ofthe alternative reagent schemeshavedisadvantagescompared with cyanide and,at
thistime,noneappeartobewidelyapplicable,atleastnotwithoutfurthersignificantadvancesinthetechnology.However,
thiosulfate has emerged as the front runner of the alternative schemes for niche applications, and Barrick Gold has
xi
xii Foreword
advanced and implemented the commercial development of thiosulfate technology to treat carbonaceous ‘preg-robbing’
materialatGoldstrikeinNevada.Carbonaceous,preg-robbingoresaretheprimarypotentialapplicationforthisemerging
technology.
Theapplicationofultrafinegrindingtotreatoresandconcentratesbyliberatinggoldandsilvervaluesfromsulfideshas
gainedmomentumfollowingthedevelopmentofefficientfine-millingequipment,includingtheXstrataIsaMill,theMetso
SMDDetritor,andtheMetprotechmillasoptions.Thesedevelopmentspavedthewayformoreefficientgrindingdownto
finersizes,around80%passing10e15mmandbelowdhence,theterm“ultrafine”grinding. Also,furtherdevelopment
oftheMetsoVertimillfollowingmanysuccessfultertiarygrindingandregrindinginstallationshasledtoitsconsideration
forultrafinegrindingapplications(downtoabout80%lessthan15mm).Otherfinegrindingmillsareindevelopment.The
abilitytoeconomicallygrindtosuchfinesizespresentedtheopportunitytoliberatepreciousmetalsfromrefractorysulfide
ores and concentrates without the need for more costly oxidative treatment, such as roasting, pressure oxidation, and
biological oxidation. While not the first to use ultrafine grinding to treat concentrates, the application at Kalgoorlie
ConsolidatedGoldMines(KCGM,WesternAustralia)in2001totreatrefractorysulfidegoldoretosupplementtheroaster
capacity opened up the technology to the industry. The ultrafine milled product was cyanide leached, achieving a gold
recovery of over 90%. This was a significant development as it was the first major commercial application to avoid the
needforoxidativepretreatment.UltrafinegrindinghassubsequentlybeeninstalledatKumtor(Kyrgyzstan)in2005,Pogo
(Alaska)in2006,andLakeCowal(Australia)in2006.Theproductgrindsizeswere80%lessthan12mm,80%lessthan
10mm, and 80% less than 15mm, respectively, for these operations. In 2015, many other operations are considering or
using a similar processing approach, emphasizing the need for continued research and development in this area.
During the past 10years or so, significant innovations have occurred in process mineralogy. At the forefront of this
work has been the development of automated scanning electron microscopy techniques (e.g., QEMSCAN, provided by
FEI, and theMineral LiberationAnalyzer, developedby theJK Institute of Technology, Australia). These techniques are
nowwellknowntomostintheindustry,andthesignificanceofbeingabletoperformaccurate,quantitative,mineralogical
analysis on representative samples of ore, intermediate processing products, and residues from projects and operations
cannot be overstated. The individual mineral grain identification and quantification, size-by-size analysis, and mineral
liberation/locking analyses that can be generated have revolutionized the approach to design and optimization of mineral
and metal extraction worldwide. Other advanced mineralogical techniques are also now available that provide important
diagnostics for gold and silver recovery optimization, troubleshooting, and process design.
Other key areas of process developments that are covered within this volume include the following:
l Centrifugal gravity concentration equipment, with increasing volume treatment rates
l Intensive leaching equipment and systems to most effectively treat high-grade gravity and flotation concentrates
l Enhanced heap-leaching technology, especially cold climate and dry climate operations and the potential use of
high-pressure grinding rolls to prepare heap leach feed material
l Refractory ore processing, including improved pressure oxidation and roasting technology
l Continued and improved application of biological oxidation to treat flotation concentrates
l Goldecopper and copperegold oretreatment,including theuseofsulfidization, acidification, recycle, andthickening
(SART) technology and effective control of cyanide speciation
In parallel with these processing developments, a major effort with respect to the gold extraction industry was the
publicationoftheInternationalCyanideManagementCode(2002),towhichmostofthemajorgoldandsilverproducers
that use cyanide have committed to follow. This code was developed by the International Cyanide Management Institute
(ICMI), a nonprofit organization set up under the United Nations Environment Program (UNEP) and the International
Council on Metals and the Environment (ICME). All of this activity represented significantly increased emphasis on the
control and treatment of gold extraction byproducts and effluents, which should be considered as an integral part of gold
extractionprocesses.Detoxificationofcyanidesolutionsandslurriesisanimportantaspectofgoldoreprocessingglobally
andtherearemanyalternativesfordetoxificationofcyanide-containingsolutions.Whereapplicable,thepreferredmethod
istoallowthecyanideconcentrationtodecaynaturallythroughthecarbon-in-pulp/carbon-in-leach(CIP/CIL)circuittothe
pointatwhichitreacheslevelsacceptablefordischargetothetailingscontainmentfacility.Therearemanyoperationsthat
areabletomeetstrictdischargelimitstotailingsfacilitieswithouttheneedforanyformofcyanidedestructionotherthan
naturaldegradationovertime.However,theseoperationscarefullymanagecyanideconcentrationsdowntheleachingand
CIP/CIL circuit, as well as wash ratios in thickeners, using re-circulated, reclaimed or fresh water in the circuit. The
cyanidedegradesfurtherovertimeinthetailingsfacility,ultimatelytonon-toxicproducts,andtheunderstandingofsuch
degradation processes has improved significantly over the past 25e30years, including natural degradation of free, weak
acid-dissociable (WAD) and total cyanide species, thiocyanate, and cyanate. The use of tailings thickeners and, where
Foreword xiii
necessary,tailingsfiltrationcanassistwithrecoveringandrecyclingcyanide-bearingsolution.Allofthesepracticeshelpto
reduce cyanide naturally within the overall extraction circuit.
Where the above methods are not sufficient to meet the Cyanide Code guidelines (e.g., (cid:1)50mg/L WAD cyanide
dischargetotailingsstoragefacilities)and/orregulatoryenvironmentalrequirements,othermethodsofdetoxificationmust
be used, with the exception of some operations using the hypersaline process water in the Eastern Goldfields of Western
Australia,wherenaturalprocessesprovideaCode-certifiableprotectivemechanism.Afteralmost30yearsofapplicationat
operationsthroughouttheworld,theuseofsulfurdioxideeairhasbecomethepreferredandmostcost-effectivemethodof
cyanide destruction where natural degradation is not adequate. Many other methods have been tested and used
commercially;forexample,hydrogenperoxideandCaro’sacid(hydrogenperoxideandsulfuricacid)havebothbeenused
successfully at a variety of operations in various configurations.
Water conservation is, and will continue to be, an area for innovation and this is highlighted in this second edition.
Dry-stacked tailing, such as used at La Coipa (Chile), has additional benefits of cyanide recycling and reduced envi-
ronmentalconcernsforgroundwatercontamination.UseofbrackishandsalinewateriscommonplaceinWesternAustralia
and is currently extending to applications in Chile and Peru.
An important lesson from all of the major innovations in gold and silver extraction is that innovations are rarely
“eureka” moments, but rather they result from a sustained period of testing, investigating, modifying, and improving a
particulartechnologicalapproachtoaproblem.Inthecaseofcyanidation,carbonadsorption,heapleaching,andrefractory
oretreatmentprocesses,thetechnologyhadbeenknown,andversionsofeachprocesshadbeenpatented,testedandtried
for several decades. Those who successfully commercialized these innovations learned from the prior versions of the
technology, borrowed from other branches of the industry (and in some cases from other industries), and improved the
application of the technology with often simple modifications. The first-user recognized the benefit of the emerging
technologyovertheincumbentprocess;theywerepersistentandrelentlessintheirpursuitofsuccessfulcommercialization;
and in all cases they relied on innovative and tenacious process operators (not necessarily the inventor or researcher) to
implement the technology effectively. Success was not intuitively obvious in these efforts, and in most cases there were
several failures or, at best, marginal and/or small applications of the technology that preceded widespread
commercialization.
Assuch,thissecondeditionisparticularlytimelyandvalued.Theformatusedinthefirsteditionhasbeenretained,but
thenumberofchaptershasbeenexpandedtocoverimportantissuessuchasgeometallurgicaldevelopments,CyanideCode
compliance,alternativelixiviants,watermanagement,arsenicandmercurymanagement,goldrecoveryfrome-waste,and
emerging and transformational gold processing technologies d a significant enhancement and update to the previous
edition.Thecontributingauthorsrepresentanexcellentglobalcrosssectionofgoldmetallurgists,researchers,developers,
and experts in related fields. Mike D.Adams is tobe congratulated on bringing together this valuable contribution tothe
literature on gold extraction and processing.
JohnO.Marsden, PE
Phoenix,Arizona,USA
August21,2015
Preface to Second Edition
This second edition of Gold Ore Processing arrives a decade after the first edition was published in 2005 and has
established itself as a widespread reference work in the gold processing and mining industry. A revised and extended
edition was therefore timely. The 55 chapters in this second edition volume bring together many technical aspects of
relevance to gold ore processing, from project feasibility study stage, through operations stage to the closure and reha-
bilitationstage.Thevariousprocessflowsheetunitoperationsthatmaybeapplicabletoanyparticularoretypearecovered,
along with new emerging trends and potentially transformational technologies. In addition to updates of the existing
chapters,advancesinseveralfieldshavenecessitatedextensiverewrites,sometimeswithnewauthors.Ontheotherhand,
scantdevelopmentsinseveralmatureareasmeantthatrevisionwasnotwarranted,witheditorialcommentsprovidingsome
measure of update.
This edition incorporates 13 new chapters, including some 90 contributing authors, spanning environmental consid-
erations, modern instrumental techniques, and emerging technologies. Additional topics covered are as diverse as the
evaluation and funding ofcapital projects, solideliquidseparation,alternative lixiviants, gold refining, tailingstreatment,
andrecyclingofelectronicwasteinthecirculareconomy.Anewchapterongeometallurgyandautomatedmineralogyhas
beenincluded. Increasingemphasis on environmental aspects in gold mininghas resulted inadditional chapterscovering
management of arsenic and mercury, as well as water management. At the time of the first edition, the International
CyanideManagementCodewasinitsinfancydafteradecadeofprogress,twonewchaptershavenowbeencontributed,
covering perspectives from both regulator and auditor.
Existing chapters have been updated to include relevant new processes, flowsheets, technologies, and philosophies.
Examples andindicativedata, aswell asindustry profiles forparticulartechnologies,havebeenreviewed andrevised for
currency andrelevancy. Some chaptershave additional co-authors orlead authors.Sadly, first edition contributorsAndré
Laplante,DavidMuir,Rong-YuWan,andMartinMillardhavepassedonintheintervening10yearssincethefirstedition
was published.
This book should be of use across the gold industry, and it is hoped that metallurgists, geologists, chemists, mining
engineers, managers, financiers, operations, projects, and research staff alike will find the content both useful and
stimulating.
MikeD.Adams
2016
xv
Preface to First Edition
The gold-processing industry is experiencing change. As free-milling and oxide ores become depleted, more complex
polymetallic and refractory ores are being processed, coupled with increasing pressure for stricter environmental
compliance.Recentyearshavealsoseenasteadyreductioninmineralprocessingandmetallurgygraduatesandagradual
loss of older operating experience. A contribution to documenting current and future best practice in gold ore processing
seems timely.
Thefocusofthisvolumeisonadvancesincurrentgoldplantoperation,fromconceptiontoclosure;eachchapteralso
coversrecentinnovationsatthebenchandpilot-scalelevelthatwouldbeexpectedtofindcommercialapplicationatsome
stage. Coverage of essential chemistry and engineering aspects is included.
Part I of the book focuses on project development, with an emphasis on the various aspects of feasibility study
management andtakingthepaththroughcommissioning,safetyandenvironmentalmanagement inoperation, andfinally
closure of both plant and tailings storage facility. With increasing pressures on the resource company to ensure minimal
socioenvironmentalimpactthroughtheentirelifecycleofthemine,itisimportanttoaimatgettingit“rightthefirsttime.”
Part II centres on the process plant, sequentially probing the generic gold processing flowsheet for advances, best
practice, and potential future practical innovations. This is the heart of the book; there is coverage of the various unit
operations involved with comminution, concentration, oxidation, leaching, gold recovery, and disposal of residues and
effluents. Innovations described in the comminution chapter include those undertaken at Freeport, which is one of the
largestgoldmillsintheworld(despitebeingacoppermine).Concentrationofgoldbygravityhasseeninnovationdriven
partly by the development of new items of equipment and novel application within the milling circuit, such as is now
commonplaceinareassuchaswesternAustralia.Flotationhassimilarlybeeninfluencedbytheadventofflashandcolumn
flotation, as well as the application of differential floats for complex ores.
Treatment of refractory ores has necessarily become increasingly important, and the section covering pressure and
bacterial oxidation as well as roasting (both oxygenated and fluidized bed) has particular relevance to the modern gold
metallurgist. While these technologies can now be deemed as established, the recent advances outlined in the book are
clearly both novel and practical. Development of methods that increase recoveries while decreasing reagent consumption
by minimizing cyanicide formation are clearly at the forefront of these areas and further development is certain.
Again, in the leaching section, the emphasis is on treatment of problematic ores such as those arising from oxidation
processes. There has been a drive in recent years toward the development of alternative lixiviants for gold, mainly as a
result of environmental pressures. The most likely candidate for niche application is thiosulfate leaching; the amount of
recentworkinthisareahaswarrantedinclusionofthistopicasaseparatechapter.Cyanidehasseenpracticalapplication
formorethan100yearsnow,andthiswillcontinue,withtheongoingpositiveinitiativesincyanidemanagementsuchas
the Cyanide Code (which has also warranted a chapter in its own right) and the inherent benefits of a reagent that, in a
well-designed flowsheet, is low level and biodegradable.
Advancesintherecoveryofgoldfromleachsolutionareagaininfluencedbydevelopmentsinequipmentandreagents.
Ongoingimprovementsintherefiningofgoldarealsobeingmade.InnovationssuchastheAngloAmericanCorporation
(AAC)pumpcellcontactorandgold-selectiveresin-in-pulp(RIP)havefoundnicheapplicationatafewoperatingplants.
Theextentoftheirusewilldependonanumberoffactors,butthetrendtowardpolymetallicandrefractoryoresislikelyto
open up new applications that may require some innovative flowsheeting if the base-metal and precious-metal values are
both to be economically recovered.
Thereisanotherareathathasapositivebearingonthefutureofcyanideingoldprocessing.Theapplicationofcyanide
detoxification or recovery processes into flowsheets is becoming much more prevalent. This may well again reflect an
increasingsenseofenvironmentalstewardshipbyresourcecompanies,undoubtedlydrivenbytheneedforthetwoprongs
ofpublicandoperatorperceptiontomeetinacommonreality.Anumberofnewtechnologiesfortheeconomicrecovery
and recycle of cyanide from plant tailings have now been developed, and this may well be a key element to the ongoing
xvii
xviii Preface to First Edition
responsible use of cyanide. Perhaps the main area where public perception has been negatively influenced has been with
tailings storage facilities. Placement of paste or dry tailings using techniques such as centrally thickened discharge, for
example, is an innovation that addresses issues of dam stability and water recovery, while resulting in a more
natural-looking landform on closure.
Part III assesses the principles and developments outlined in the first two parts, by means of focused case studies of
typical flowsheets for the two major types of problematic gold ores that are being encountered e polymetallic and
refractory ores. A distinction is made on economic grounds between goldecopper ores and copperegold ores; process
flowsheets and issues differ between the two. Ores containing high silver, base-metal and platinum-group metal (PGM)
grades will continue to be more often in resource companies’ fields of view as the quest for pay dirt continues. As ore-
bodies become more complex, so, too, do the process flowsheets, with an increasing reliance on hydrometallurgical
treatmentsthat result inavarietyofproducts,notonly gold butalso copper, nickel,cobalt,silver,PGMs, andsometimes
lead and zinc.
Whilerefractorysulfideshavebeenaroundforsometime,anunderstandingisbeinggainedofthesubtlechemistrythat
can arise in high-pressure autoclaves treating a sometimes extensive mix of different sulfide minerals. As both the
knowledge base and the number of applications increase, so the risk of applying these processes becomes smaller. The
same can be said of other problematic ores, such as carbonaceous preg-robbing, tellurides, and antimonial ores.
Thegeneralprinciplebehindthestructureofthevolumeisthatofflowsheetingbasedonunitoperationsandappliedto
a mineralogical classification of gold ore types. Knowledge of the mineralogy of an orebody is the key to unlocking the
wealth contained within. The extensive chapter covering this aspect necessarily does so through process eyes; flowsheet
definition can then follow using the building blocks composing the unit operations described in the second part of the
volume.
Practical experience is vital to the successful development, operation, and closure of any operation. The 42 chapters
have been contributed by a total of 66 authors and coauthors who are experts from countries spanning the globe and
represent exhaustive practical knowledge covering many disciplines relevant to gold processing. Within the chapters are
numerous tidbits of practical personal experience, much of which is as yet unpublished. The content will be useful to
operators, engineers and researchers worldwide.
The original intention was to provide a selection of appendices covering SI units, conversion factors, pulp density
tables,andthelike.Thereadyavailabilityofthisinformationontheinternethasmadetheirinclusionredundant;however,
a periodic table kindly made available by Prof. Fathi Habashi has been included.
This book is intended for mineral-processing engineers, metallurgists, process mineralogists, mining engineers,
environmental engineers and consultants, and resource company managers. It will be of interest to professionals and
students alike.
MikeD.Adams
2005