cyanide control in the metallurgical process of gold extraction in anglogold (s.a.)

359The Journal of The South African Institute of Mining and Metallurgy OCTOBER 2001

Introduction

The ERGO CIL plant treats 3 million tons permonth reclaimed by hydraulic mining fromsurface slimes dams. A mix of up to 12individual dams is piped in 6 lines feeding theplant. The leach circuit comprises 22 tankswith a total volume of 44 000 m3 in twoparallel streams that allows for a totalretention time of 7 hours.

Calcium cyanide is added at an additionrate of approximately 350 g/t. Due to the large

tonnage multiplier, this equates to approxi-mately 1 000 (as 100% NaCN) tons of cyanideper month representing approximately 25% ofthe total operating cost. Consequently a largeamount of developmental work has beenconducted at Ergo in regards to determiningthe optimum cyanide addition and tominimizing deviations from the targetaddition.

More recently, increased environmentalawareness has further focused on thenecessity for tight control in order to minimizethe amount of cyanide added to the processand thus in residue streams whilst notcompromising leach performance.

Determination of the optimum cyanideaddition

Due to the high tonnage and commensurateshort leach residence time, the kinetics of theleach reaction, whilst important in anyoperation, are particularly important at Ergobecause the cyanide concentration is not highenough and insufficient time exists to dissolvethe gold. The situation is illustrated in Figure 1.

From Figure 1 it is noted that the optimumcyanide addition rate exists where themarginal gold revenue is equal to the marginalcyanide cost. To the left of this point themarginal revenue from the additional goldexceeds the marginal cost of cyanide, callingfor the addition of more cyanide. To the rightof this point, the opposite holds true andmarginal losses are incurred. This optimumcyanide rate is found in practice by monitoringthe response of the leachable gold lossesdetermined through daily laboratory leaches(500 g/t NaCN, 4 hours) and correlated withthe plant cyanide addition rate.

Cyanide control in the metallurgicalprocess of gold extraction in AngloGold (S.A.)by B.J. Vorster* and S.R. Flatman

Synopsis

AngloGold South Africa region currently consists of twelve goldplants. These plants use a combined total of $20 million of cyanideper annum. Of this, the major portion (60%) is consumed at twoErgo dump retreatment plants. Historically the primary motivationfor cyanide control at Ergo has been one of leach/cost optimization.However, more recently, with the increased public awareness ofcyanide in the environment, a secondary but increasingly importantmotivation for control has been to ensure that only the minimumamount of cyanide is added to the process whilst not compromisingleach performance.

Following a brief overview of the Ergo process, themethodology in determining the amount of cyanide to be added isdescribed. The paper then traces the developments in cyanidecontrol from very basic manual systems to the current automatedcontrol system. In line with the increasingly sophisticated controlsystems, developments also took place in regards to the method ofcyanide analysis. The development of these analysers is alsodiscussed. Whilst cyanide is one of the major drivers, if not themajor driver of gold dissolution, it cannot be viewed in isolationparticularly with respect to the relationship between cyanide andoxygen as ascertained from the Elsners well-known equation.Consequently, in order to control cyanide addition, knowledge ofthe relative cyanide/oxygen profiles is necessary. Various meansinvestigated at Ergo for pulp oxygenation have therefore beenincluded for the sake of completeness. Finally a comparison is madeof the control achieved from the current system compared to theoriginal manual system.

The knowledge and experience gained at Ergo is now beingused to draw up guidelines for the installation and optimizationwork at the other AngloGold plants. The net effect of this will bereduced cyanide consumption for the region, which also, apart fromthe obvious economic benefit, translates into a reduced environ-mental risk.

* AngloGold SA Metallurgical Technical Services. AngloGold SA ERGO CIL Plant. The South African Institute of Mining and

Metallurgy, 2001. SA ISSN 0038223X/3.00 +0.00. Paper received May 2001; revised paperreceived Sep. 2001.

Cyanide control in the metallurgical process of gold extraction in AngloGold (S.A.)

Influence of oxygen

Whilst cyanide is one of the major drivers if not the majordriver of gold dissolution, it cannot be viewed in isolationparticularly in respect to the relationship between cyanideand oxygen derived from Elsners equation:

[1]

From the Equation, it is apparent that both cyanide andoxygen are required in an aqueous solution in order to leachgold. For the leaching of pure gold, the stoichiometry ofElsners reaction gives the required molar ratio of freecyanide to oxygen as 8:1 (or 61/2:1 when expressed as a massratio). Since cyanide is the more expensive reagent, it isdesirable from a financial point of view to ensure thatcyanide is the rate-limiting reagent. Hence a cyanide-to-oxygen ratio that is less than the determined stoichiometricratio should be maintained throughout the tank farm.Maintaining a constant ratio of the reagents in each tank mayonly be achieved by ensuring that the cyanide and dissolvedoxygen profiles relate to one another.

Referring to Figure 2, the dissolved oxygen concentration(DO) at the Ergo CIL plant rises from about 6 to 8 ppm in thetop tank to about 18 to 20 ppm in the second to fourth stagesafter which it decays to about 9 ppm in the final stages. Thelow DO content in the first stage is indicative of the highinitial oxygen demand of the material. Considering this inconjunction with the stoichiometric ratio, it is clear that atleast two cyanide addition points should exist with the firsttwo stages being the obvious choice so as not to compromiseleaching efficiency. Furthermore, the highest cyanide concen-trations will exist but should be controlled in the second tofourth stages since this is where the maximum DO levels are.Comparing the cyanide profiles obtained for single stage anddual stage cyanide addition, the advantage of the latter isthat it ensures that the cyanide and oxygen profiles followone another more closely such that a more consistent ratio ismaintained. The various means investigated to increase thecircuit DO are discussed later.

Sampling system

Having established a control philosophy, the next challengeis implementation. The obvious starting point is to obtain arepresentative sample. In contrast to the pump/filter systemused in many operations and their associated disadvantages,

Ergo has found considerable success utilizing pipe samplersto produce a continuous clear solution sample. See Figure 3.

The samplers consist of a 6 m*15 mm steel pipe fittedwith a 1 m*100 mm filter bag pulled over a rolled up piece oflinear screen cloth to provide a void for the clear solution.Due to the difference in relative densities of the bulk slurryand solution inside the pipe, solution is forced up a 6 mmline fitted inside the pipe to provide a sample. A pulse ofcompressed air every 2 minutes for 10 seconds inflates thebag that breaks up the filter cake on the bag while pushingthe filtered solution through the sample line.

Having obtained a solution sample and analysed it forcyanide, the result is used to control cyanide addition to theleach. Various systems of increasing complexity have beendeveloped at Ergo over a period of time. The development ofthese control systems from manual control to the currentsystem is detailed below.

Control systems

Manual control system

The original cyanide control system was manual whereby theoperator adjusted the flow of cyanide to the process basedupon the results of a manual titration performed hourly.Some automated assistance by means of a flow-controlled

4 8 2

4 42 2

2

Au CN O H O

Au CN OH

+ + +

( ) +

.

360 OCTOBER 2001 The Journal of The South African Institute of Mining and Metallurgy

Figure 1Marginal gold revenue versus marginal cyanide cost

Cyanide Addition (g/t)

Optimization of the Gold Leach

Cost

(Ran

ds)

Figure 2Cyanide/oxygen profile at Ergo CIL plant

Figure 3Diagram of a pipe sampler

Air in Sample Out

Slurry Level

6 m

Pip

e

1 m

x 1

00 m

mFi

lter b

ag

valve was employed that dosed the cyanide at apredetermined volume based on the operator set point asshown in Figure 4. This made it easier for the operator sohe/she could calculate a required flow for the specific tonnagebeing processed through the plant to achieve a requiredaddition rate.

Variable tonnage control system

The major drawback of the manual system was that operatoraction was too infrequent to keep up with the rapid changesin throughput as shown by the graph in Figure 5. Since thesevariations in throughput were caused by external operationsand were not under the control of the operator, he/she wouldnot always be fully aware of the extent of the changesoccurring until a response was seen on the cyanide concen-tration.

The next stage of the optimization process involved theintegration of tonnage measurement utilizing the existingmass flow system and a PLC (see Figure 6). This feedforward system now handled variations in throughput whilststill maintaining a fixed addition rate. As opposed to manualcontrol whereby the operator was forced to estimate the effectof tonnage variations on the cyanide decay curve, the processwas now automatic. All that the operator needed to do wasstipulate a required addition rate. The PLC then calculated acyanide flow rate required to achieve the addition rate basedon the following formula:

[2]

Set Point (l/h) Volume of calcium cyanide requiredin litres per hour

Mass (tph) Mass flow of incoming material tothe plant in tons per hour

Set Point (g/t) Estimated cyanide consumption formaterial being treated

Cyanide (%NaCN) Active content of calcium cyanideexpressed as sodium cyanide

On-line cyanide analyser control system

Whilst the inclusion of tonnage measurement represented asignificant improvement in the overall control of cyanide,periods of poor control still regularly occurred. Continuous

changes in the cyanide demand of the feed material wereidentified as adversely influencing the cyanide control. Theoperators actions based on an hourly titration were too slowor inconsistent to adequately compensate for these variationsin cyanide demand. The manual titration of the operator was therefore replaced with an on-line cyanide analyser. This analyser provided regular and repeatable data aroundwhich a cyanide control system was designed to control to an operator-specified cyanide concentration as shown inFigure 7.

The feedback controller then adjusted the cyanide flow tocorrect for any deviation from set point caused by changes indemand. A significant amount of work was done to findbetter analysers to give faster analysis time so that controlcould be improved. These analysers are discussed in detaillater.

Advanced control system

Previously, when the density of the slurry decreased, a lowercyanide concentration would result due to increased dilution.An algorithm was therefore installed to pre-empt thesechanges by making use of the formula shown in [3]:

Cyanide control in the metallurgical process


Figure 5Plant throughput in dry tons per hour

Figure 4Manual control of cyanide into the process

Set PointMass Set Point

Cyanidehtph g t

NaCN

l//

%

*

( )( ) ( )

( )=

Figure 7On-line cyanide analyser control system

Figure 6Variable tonnage control system

ManualTitrationResult

CyanideFlowMeter

ValveLogic

Output(%)ControlValve

1 Week

Thro

ughp

ut (t

ph) 5000

4000

30002000

10000

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ManualTitrationResult

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Cyanide (%)Output(%)

Mass(tph)

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CyanideFlowMeter

RevisedSet Point(l/h) Valve

Logic

ControlValve

FeedForwardAdditionSet Point (g/t)

OperatorSet Point

(ppm)ProcessMassFlow

Cyanide (%) Output(%)

ProcessSolutionSample

On-lineCyanideAnalyser

Mass(tph)

FeedbackControl

Actual(ppm)

[3]

The algorithm now compensates for decreases in concen-tration by adding additional cyanide. In practice it was foundthat applying 50% of the calculated factor to the cyanide flowyielded the best response for a steady cyanide concentration.Returning to the main control system intervention by themetallurgist was still required at regular (daily) intervals tofine-tune the addition rate used by the feed-forwardcontroller to ensure the stability of the system. Realizing thatthe information used to do this was available in real timefrom the instrumentation a self-optimizing system wasdevised. The comparator in Figure 8 feeds back a fraction ofthe error that exists between the estimated addition rate andthe actual addition rate at a regular interval so that the feed-forward always uses the correct multiplier to calculate therequired flow rate. It does this very slowly so as not to causeoscillation in the feedback control loop or to interfere with theoverall control system.

Dual stage cyanide control system

Despite the various improvements made to cyanide control, amajor drawback still existed with the single-stage additionsystem. It was found necessary to maintain a higher thanmetallurgically optimum cyanide concentration in the firstleach stage to ensure that sufficient residual cyanide existedto fully utilize the residence time available. The cyanideconsumption was high due to the low dissolved oxygenlevels in the top tank resulting in cyanicides still beingavailable to complex the cyanide.

Figure 9 illustrates that the first stage cyanide concen-tration was reduced after a secondary dosing point wasinstalled to make up the difference required to ensure thedesired final stage cyanide tenor. The cyanide analyser

monitoring the last leach stage was relocated to analyse thesecond leach stage and a separate feedback-only controlsystem was installed. The first leach stage is run at a fixedcyanide concentration of 100 ppm [CN] while the secondstage is varied to obtain the correct final stage cyanide tenor.The second stage typically runs at about 110 ppm [CN]. Acloser correlation was now achieved between the desiredcyanide and oxygen profiles resulting in a reduction incyanide consumption of approximately 510%.

Controller hardware optimization

Instrumentation expertise was called upon to optimize thehardware installed for the dual-stage cyanide additionsystems. Using extensive modelling and the Pro-Tunersoftware, the system was successfully commissioned in1999. The controller settings were based on models createdon what was later discovered to be incorrect assumptions.After getting a better understanding of the process, in-housetuning greatly improved the controller performances on bothprimary and secondary controllers. It was found that highgain (high proportional) and short reset times (low integral)were used, as would be the normal trained response of anyinstrumentation technician. The setting cause a typical 1/4wave damping that results in a significant overshoot in aslow response system, as is the case here. It winds up rapidlyand becomes unstable after the smallest upset. Using reset(integral) times equivalent to the tanks retention time had asignificant stabilizing effect.

An inherent feature of the controller design was theseparated feed-forward and feedback components. Thisresulted in corrective action only affecting the feedbackcomponent. Any long duration error that would require achange to the addition rate causes instability and could onlybe corrected manually. In an attempt to reduce humanintervention a method to automate this action wasinvestigated and the result was the self-optimizing tooldiscussed earlier.

Density Correction Factor =

( ) ( )( ) ( )

( ) ( )

( ) ( )

2 7 1 7

1 7 2 7

. * .

. * .

Density Density

Density DensityReference Actual

Reference Actual



Figure 8Advanced control system with density compensation and self-optimization

OperatorSet

Point (ppm)

ControlValve

CyanideFlowMeter

Cyanide (%)Cyanide (RD)

LiquidSolidRatioSet Point(g/t)

ProcessDensityMeter

FeedForward

ProcessMassFlow

Mass(tph)

Set Point (l/h)

Actual(ppm)

RevisedSet Point(g/t)

RevisedSet Point(l/h)

Output(%)ReferenceDensity(kg/l)

FeedbackControl

ValveLogic

On-lineCyanideAnalyser


Self-OptimizationComparator

On-line cyanide analysers

In line with the developments in the cyanide control systemdevelopments were also made in the cyanide analysers usedto provide the control signal. These initiatives are discussedbelow and later compared in a Table (see Table I).

Kayton

This machine was developed by Anglo American ResearchLaboratories to perform on-line analysis of cyanide, pH andgold in solution every 40 minutes. The results were thenwired to the PLC for use in whatever control system wasimplemented there. It was designed for 8 sample streams butonly 4 were used to improve the sampling frequency to 40minutes. The first and last leach stages on both treatmentstreams were analysed. Cyanide detection was by means of apotentiometric analytical technique using an automatedtitration with silver nitrate. This became the standardanalytical technique used in nearly all cyanide analysers forthe next 10 years. The development of improved commercialanalysers by other companies combined with the Kaytonsuniqueness leading to problems with support and sparecomponents eventually prompted a decision to replace it withone of the commercially available analysers.

Cascon T

An Applikon 2015 cyanide analyser was selected for the firstleach stages and an Applikon 2011 cyanide analyser on thelast leach stages. The new control system was collectivelyreferred to as the Cascon T. These Applikon cyanideanalysers also use a potentiometric analytical technique todetect cyanide. Each device can analyse two sample streamsat around one analysis in 10 minutes. Changing the softwarelater enhanced them so that a sample could be analysed inless than 3 minutes.

Teklogic

The ERGO sister plant (Daggafontein) installed Teklogic

(TAC) cyanide analysers. The Teklogic is also a potentio-metric type analyser but includes as an option cyanidecontrol. Teklogic analysers are used worldwide on AngloGoldplants.

Anatech

An Anatech Flow Injector cyanide analyser was also tested atthe CIL plant, as its potential to improve cyanide control due



Figure 9Dual stage cyanide control with final tenor feedback

Table I

Comparison of successive cyanide analysers investigated

Advantages Disadvantages

KaytonFirst generation on-line analyser One of a kind that becameCapable of analysing 8 streams obsolete with no spares being

available. Slow sample frequency

of 40 minutesCascon TCommercially available Initial sample frequency low atRobust and reliable 10 minutes per sample prior to Upgraded to increase sampling upgrade. Regular maintenancefrequency to under 3 minutes requiredper sampleAnatech Flow InjectorFast analysis time of 90 seconds High running costsper sample Complex machine with Built-in calibration and multiple reagentsquality checking High maintenance and Capable of analysing maintenance costsix streams Specialized maintenanceHigh precision and accuracy High downtime due to aboveNo cross-stream contamination No signal output to PLC

Mintek CynoprobeVery fast analysis time Single stream capability onlyof 60 seconds Cannot be duplexed for Virtually no maintenance multiple streamsNo reagents used for analysis

FirstStage

Control

On-LineCyanideAnalyser



SecondStage

Control

Set Point(g/t)

finalStage

Control 1st 2nd ... ... FinalLeach Stages

Cya

nide

Con

cent

ratio

n (p

pm) 120

110

100

90

80

70

60

50


to its high sampling frequency of one in 90 seconds wasappealing. The analyser uses a colorimetric technique todetect the cyanide in a chemically prepared solution. Thedevice was decommissioned in favour of the existing titratorsthat are less complex, have better availability, and arecheaper to operate.

Mintek

A Mintek Cynoprobe was also tested. It uses an amperometrictechnique to detect the cyanide and requires no reagents inthe process. With a sample analysis time of less than 60seconds and robust enough for plant conditions, this unit isthe preferred analyser for new installations. However, itshould be noted that this unit is newly developed. With theremaining life of ERGO it is not viable to replace the existingtitrators but other plants that have a longer remaining lifecould pursue this option.

Oxygen equipment

As discussed earlier the dissolved oxygen concentration inthe pulp also influences the cyanide tenor and so, whilst theprimary focus has been towards cyanide control, considerablework has also been performed toward efficient oxygenationof the pulp. More recently this work has been performed atErgos sister plant Daggafontein. It should be noted thatcompressed air can only oxygenate to a dissolved concen-tration of approximately 8 ppm. Due to the high oxygendemand and high throughput at Ergo, gaseous oxygen isused to increase the concentration to a target of 20 ppm.Ergos experience with oxygen injection equipment aredetailed below.

Perforated ring

A donut shaped perforated pipe was fitted inside the leachtank just above the flat bottom. It was not very efficient andwas maintenance intensive. Different types of material,including porous cast pipe and plastic hoses, were evaluatedover time. The leach tank had to be taken off-line to domaintenance on the system.

Lances with ceramic tips

Lances measuring 15 mm in diameter fitted with ceramic tipswere inserted through the tank shell about 1/2 m from thebottom. The tip has a 6 mm hole and a taper rod that can bemanually adjusted from outside the tank. Ten lances arerequired on the first leach tank to achieve 8 ppm dissolvedoxygen in 40 minutes and is indicative of the high oxygendemand of the material. The second leach stage easilyachieves a dissolved oxygen concentration of up to 20 ppm.A system was developed to change these lances while thetank is on-line with the use of an isolation valve that thelance passes through. This system is still in use at the ERGOCIL plant.

Lances with variable gap tips

Alternative lance tips were evaluated that have a spring-loaded inverted cone-shaped tip that automatically adjustswith the oxygen flow. They are claimed to be more efficientand feature an automatic shut-off to prevent slurry choking

up the lance if the gas supply stopped. These tips wereunattractive because they lasted one month compared to thesix months achieved by the fixed type.

Water nozzles

The Daggafontein plant evaluated water nozzles that usewater at 6 bar and gaseous oxygen controlled up to 9 barinjected into a small reactor that allows the emulsion formedto escape sideways into the slurry. They are more efficientand have finer bubble dispersion and less bubble agglom-eration. It requires other auxiliary equipment including asource of clean pressurized water and various control valvesand sensors. They are well suited to yield high dissolvedoxygen concentrations quickly and efficiently but water-uselimits the number of units that can be installed in the leachtrain.

Shear reactor

A proprietary high shear reactor was tested at Daggafontein.The device injects gaseous oxygen into a special, formedceramic reactor through which slurry is pumped at 6 bar.Oxygenation is achieved through cross-shearing of theoxygen caused by the rapid flow direction changes in thespecially shaped patented reactor. With the existing lancesystem already achieving good results and being unable todetect any improvement, the additional costs of running theunit could not be justified.

EDR

This device used is similar to the high shear reactor butoperates at a lower pressure. Oxygenation of the slurry isachieved by injecting gaseous oxygen via a perforatedceramic venturi insert and making use of the formation ofturbulent eddy currents in the slurry pumped through thedevice. The device is currently on trial runs at Daggafontein.

Results

As can be clearly seen from Figure 10, the various initiativesundertaken at Ergo have resulted in a significantimprovement in cyanide control. Whilst an exact financialquantification of the benefits is complicated by changes in thefeed mix and mineralogy particularly as regards cyanide andoxygen demand, a conservative Figure of US $1 million perannum has been estimated. This value has been calculatedfrom a combination of savings in cyanide due to reducedover-dosage and reduction in leachable gold losses due tounder-addition. Over and above the economic considerations,the improved cyanide control has resulted in a reducedcyanide addition which inevitably contributes towardsreduced environmental exposure.

Conclusions and recommendations

A conventional gold plant should be able to achieveacceptable control of cyanide to the process by using thesystem depicted in Figure 11. Here the output from thefeedback controller that corrects for deviations in the cyanideconcentration is taken as the process demand. This demandis then manipulated by applying a mass flow percentage in abasic feed-forward calculation that, in turn, provides the set


point for the cyanide flow controller. The system is self-adjusting to changes in the process demand provided that thePID loop is correctly tuned for very slow process dynamics.

The on-line cyanide analyser should be able to sample atleast 8 times in a period equivalent to one leach tanksretention time with 99% repeatability. The more recentamperometric type analysers are well suited for thisapplication. If the control band is wider than +/- 10% thenadvanced system add-ons should be investigated such as asystem that compensates for changes in slurry density.

Multiple cyanide dosing stages should be investigatedwhere the cyanide concentration exceeds the optimum asdescribed by the cyanide:oxygen ratio of 8:1 expressed asmolar ratio. Oxygen addition is recommended in preferenceto air where leach kinetics is a constraint.

References

1. MOODLEY, S. Process Control Strategy at ERGOCIL Using On-lineEquipment (Anglogold SA Ergo CIL Plant 1995).

2. ARMSTRONG, C. Anatechs La Chat Flow Injector (Anglogold SA Ergo CILPlant 1997).

3. COOPER, R. Cyanide Control (Paper presented at the Anglogold SA SeniorMetallurgical Meeting September 1999).

4. VORSTER, B.J. Advanced Process Control (Paper presented at theMetallurgical Meeting Ergo 1999).

5. SCHWARZER, H. Oxygen Control at Daggafontein Plant (Paper presented atthe Anglogold SA Senior Metallurgical Meeting September 2000).

6. HEATH, A.R. and RUMBALL, J.A. Optimising cyanide:oxygen ratios in goldCIP/CIL circuits Minerals Engineering, vol. 11, issue 11, November 1998.pp. 9991010.



Figure 10Manual and automated cyanide control comparison graphs

Figure 11Minimum implementation automated cyanide control

Before After

24 Hours24 Hours

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Dr Roger Thompson, Associate Professor in the Departmentof Mining Engineering at the University of Pretoria, wasawarded a prestigious Fulbright Research Scholarship. TheFulbright Programme is recognized as the US Governmentsflagship programme in international exchange.

The annual award of a Fulbright Commission forEducational and Professional Exchanges South AfricanResearcher Scholarship is administered by the bi-nationalFulbright Commission and candidate selection is finallyratified by the J. William Fulbright Foreign ScholarshipBoard, appointed by the President of the United States.

Established in 1945 by freshman Senator J. WilliamFulbright, the programme was aimed at developing mutualunderstanding between people of the United States and thepeople of other countries of the world. Dr Thompson willwork in the United States with the Centres for DiseaseControl (CDC), National Institute of Occupational Safety andHealth, Spokane Research Laboratory (SRL), together withthe Western Mining Research Centre, at the Colorado Schoolof Mines (CSM). His project on characterizing mine haulroad functional defects as a causal factor in truck driverjolting and jarring injuries fulfils Fulbrights requirements ofhaving benefit and application in the mining industries ofSouth Africa and the United States.

An interdepartmental research field in mine haul roaddesign and management was established together with Prof.Alex Visser from the Department of Civil Engineering in themid-1990s and Dr Thompsons research in the United States

builds on their internationally recognized research. Over 34peer-reviewed and conference papers have been publishedat leading local and international conferences and symposia.The results of the research have already been adopted andapplied, not only in southern Africa, but also interna-tionally. Projects in Botswana, Namibia, the United Statesand Indonesia have been undertaken, and more recently, hehas been invited to co-author a book on mine road designwith academics in Canada.

Explains Dr Thompson the research programme withSRL and CSM fulfils the requirements of the Fulbrightprogramme in the sense that technology transfer in minehaul road design, specifically haul truck mine roadinteraction, is two-way and has benefit and application inthe mining industries of both countries.

Mine haul trucks are amongst the largest wheeledvehicles on earth with a mass of over 560 tons, tyres of 2,6m in diameter and 1 m width. It is a varied, challenging anddynamic field and the results of the work are particularlyimportant in the light of the ever-increasing size of trucks,road performance problems and the formidable health issuessurrounding driver exposure to poor ride quality.

* Contact: Sunel de Coning, Faculty of Engineering, BuiltEnvironment and Information Technology, Tel: (012)420 2482, Cell: 083 234 8782

Tukkies Mining Engineering awarded Fulbright scholarship*

cyanide control in the metallurgical process of gold extraction in anglogold (s.a.)

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