A metallurgical evaluation of a heavy mineral sand … metallurgical evaluation of a heavy mineral...

A METALLURGICAL EVALUATION OF A HEAVY MINERAL SAND DEPOSIT 139

IntroductionPart of the RBM ore reserve was known to be of lowerquality, containing a higher abundance of gangue mineralswhen compared to the rest of the orebody currently beingmined. Preliminary investigations on this lower grade oreindicated a potential difficulty in achieving a qualityilmenite product (hereafter referred to as roaster feedstock(RFS)) for feed into the roasting process to prepare smelterfeed.

Over the life of the current mining operation, the orebodyhas changed significantly in terms of grade and complexity.In recent years the importance of mineralogical andsubsequently metallurgical properties associated withdifferent geological units has therefore come under thespotlight. Consequently, an additional facet added to theinvestigation of the low grade orebody was the decision toprocess bulk samples of specific stratigraphic units insteadof taking random bulk samples of the deposit (as was thenorm during historic pilot scale work). This allowed thepinpointing of inferior performing units and the ability toquantify and mitigate their impact on operations over thelife of mine. Understanding the effect of different units onthe process can be useful in predicting metallurgicalperformance and allows the process metallurgist theopportunity to anticipate and react to metallurgical issues inthe plants during the beneficiation process.

The ultimate question to be answered by the investigationwas:

• Would mining the low grade area require thedevelopment of new plant flowsheets or additionalcircuits?

Being adjunct to the following:• How does one prove or disprove this need, using basic

techniques and resources within a limited timeframeand budget?

• How does one apply laboratory and pilot-scalesimulated test results to reflect and predict the reality inan already operating plant?

The paper will discuss the very basic approach devised toaddress these questions.

Test methodologies

Bulk sample processing to produce heavy mineralconcentrate (HMC)Approximately 20 tonnes of material was hauled from ninesites under the supervision of an experienced geologist. Thepositions of the bulk samples were chosen to berepresentative of the geological units occurring in the lowgrade area (Table I). Units are classified based on grade,slimes contents, relevant mineral ratios and colour loggedin the field.

The bulk samples were processed using a five- stage pilotscale spiral concentrator circuit to produce HMC for furtherprocessing (Figure 1).

BOSHOFF, L.I. and GRACIE, S. A metallurgical evaluation of a heavy mineral sand deposit based on stratigraphic unit classifications. The 6th InternationalHeavy Minerals Conference ‘Back to Basics’, The Southern African Institute of Mining and Metallurgy, 2007.

A metallurgical evaluation of a heavy mineral sand depositbased on stratigraphic unit classifications

L.I. BOSHOFF* and S. GRACIE**Richards Bay Minerals (RBM)

This paper discusses pilot and laboratory-scale metallurgical test work conducted on bulk samplesfrom a low grade heavy mineral deposit and provides an overview of basic practical metallurgicaltechniques applied to ascertain the suitability of existing production plants to process materialfrom this orebody. Previous investigations have shown this specific orebody to be morechallenging in terms of mineral beneficiation as it has a high gangue mineral content.

Test work was conducted on targeted stratigraphic units based on lithology and assay results toenable identification of the stratigraphic units portraying quality issues. Unit specific metallurgicalpilot work has never been conducted on any of the RBM orebodies and is a new field currentlybeing explored. During this investigation focus was placed on potential quality and yield issuesfor ilmenite product, with particular reference to CaO quality. A basic evaluation of zircon andrutile separability was also conducted.

The test work was conducted using a comparative baseline methodology with metallurgical testwork methods specifically aiming at mimicking the existing production plant as closely aspossible. This enabled not only the likely metallurgical performance to be assessed but alsoindicated whether current plant design would be suitable to process the low grade ore types intoproducts of acceptable quality at acceptable yields.

The methods and findings discussed in this paper indicate that although there is considerablevariation between different units, a blended feed can be successfully processed. With unit specificmetallurgical data applied to the existing geological block model, expected yields and recoveriesusing current plant designs could be predicted.

HEAVY MINERALS 2007140

Test work approachA simplified illustration of the plant circuit preparing HMCfrom the mining process into roaster feed (RFS) and drymill feed is provided in Figure 2. The circuit has severalscavenging circuits built into it, to ensure optimalrecoveries are maintained.

A pilot simulation of this type of production plant wouldrequire large quantities of test material. The final HMCproduced from each unit sample was ±300–800 kg makingit impractical to attempt conventional staged simulation ofthese circuits. Another approach therefore had to beadopted.

A basic test work programme was designed to give areasonably comparable outcome to actual plant results,within the practical limitations of basic pilot and lab scaletest work methods. To validate the success with which thelow grade material could be processed through the currentfeed preparation (Figure 2) and dry mill circuits, the testand evaluation methods were conducted using ‘baselinecomparison’. During the test work programme, current runof mine HMC was subjected to the same tests to produceresults that could be compared to that obtained for the lowgrade material. The premise for this approach was that ifthe products obtained from the low grade ore samples werecomparable or superior to that of the current baselinematerial, the potential to process the low grade materialwith similar success via the current plant would beconfirmed.

The actual results obtained for current run of mine HMCprocessed via the production plants was used to indicate apossible up or down scaling factor that could be applied tothe test work results.

Unit Contribution

5 3%

4B 20%4A

3 10%

2D 50%2C2B2A

1C 17%1B1A

Figure 1. Five stage gravity separation

Table IUnit types and their contribution to the low grade area

Figure 2. Conceptual flowsheet of current feed preparation plant circuit

CaO Gradecontrol

2 stage spiral

Quartz removal 3stage spiral

Linear Screen

CleanerWHIMS

Primary WHIMS

Secondary WHIMS

Ilm WHIMS

Scavenger plant

TAILS TAILS TAILSRFS Dry Mill Feed

Cone CleanerWHIMS


The test work programme incorporated two wet highintensity magnetic separation (WHIMS) stages and gravityseparation to upgrade to final product quality. Pilot andlaboratory scale test equipment was calibrated, usingcurrent plant feed, to achieve comparable performance tothe corresponding plant areas. The last leg of the testworkincluded a bench scale investigation on the separability ofthe dry mill feed produced into zircon and rutile products.Figure 3 illustrates the test work flowsheet.

Flowsheet development and calibration of equipmentusing baseline referencing

Before processing of the HMC could begin, a scopingexercise had to be conducted to establish optimal settingsand confirm the testing methodology. The scoping testsaimed to simulate the feed preparation process as closely aspractically possible on the pilot plant WHIMS machine.Subsequently material from each bulk sample could becompared with the run of mine baseline samples processed.The use of the baseline samples also allowed the accuracyand repeatability of the method to be assessed.

As the pilot WHIMS is a different model (8 pole, 68 mmrotor) to those used in the feed preparation plant (16 pole 120 mm rotor), determining the operating window for thepilot plant WHIMS involved running matrix tests withvarying feed rates and coil current settings. The settingsfinally chosen for the test work were based on the resultsobtained during the matrix tests that delivered the mostcomparable results to that of the plant (when processing thesame material).

Initial scoping tests where conducted on 20 kg batchsamples of HMC representing each bulk sample. The goalof this phase was to identify the need for a second stage andto identify bulk samples with potential quality or separabilityissues. During the scoping stage the need for furthercleaning of the non-mags using a second WHIMS stage wasidentified. The non-mags and mids from the first stage werecombined and fed to a second WHIMS stage set up tooptimize rejection of magnetics (mags). Mags product fromthe second stage was then combined with the mags productfrom the first stage for CaO grade control (Figure 3).

Upgrading WHIMS product to suitable roaster and drymill feedCalcium grade control in the preparation plant (refer toFigure 2) is achieved via a two-stage gravity (spiral)separation circuit (Figure 2). For the test work programmetable separation was opted for as CaO grade control methodas it operates using the same principles as spiral separationand the feed sample required for a representative test wouldbe much smaller (Figure 5). The set-up of the lab-scaleWilfley shaking table also allowed for better feed rate andvisual product split control when compared to the availablepilot-scale spiral set-up. In addition the mags productgenerated from the WHIMS stages was limited, thereforemaking the use of pilot-scale spiral test work unviable.

As this method could still not be directly compared tospiral separation, reference samples of actual feed to theproduction plants’ CaO control circuit were processed onthe table to compare the tables’ general performance withregard to mass yield and recovery. This stage also helpedwith optimizing the table settings for the CaO grade controlphase of the test work. The results were compared tosamples of the final concentrate produced by the plants’grade control circuits for that feed.

Figure 3. Test work flow sheet

Figure 4. Pilot plant WHIMS unit

BULK SAMPLES

Mags 1

Mags 2

Tails

Mids

Non Conductors

Conductors NonConductors

Mags & Oversize

Mids

Tails

N/M

N/M

HMC

Mags

BULK WHIMS(100 kg)

PILOT PLANT

WHIMS BULK 2

HT Separation

HIMS and screening(180 μm)

ESP

HIMS

Zircon

Dry Mill Feed

CaO Grade Control(Wilfley Table)

QTZ Removal(Wilfley Table)

Rutile

TAILS

RFS


The Wilfley table settings were chosen to maximize theamount of material going to concentrate to reduce anyexcessive loss of ilmenite product to tails.

During this stage the feed material was relativelyhomogeneous making the visible separation of the CaO richminerals difficult to observe during the test. Therefore, inmost cases, splitting aimed for a tails yield ofapproximately 5–10%. Where separation was clearly visiblethe aim was to reject CaO bearing minerals such as garnet(generally coarser grained pink to red coloured minerals,colours varying depending on elemental composition). Thenon-magnetic product from the WHIMS stages were alsoupgraded using the Wilfley shaking table to removeexcessive quartz and mag others (MO). To obtain optimalsettings for the tests the scoping exercise was conducted ina similar manner. In this case a visible quartz band helpedwith cutting the correct portion of material to tails.

Tabling was very effective in upgrading both the magsand non-mags product off the WHIMS stages, andproduced (with some sacrifice to mineral recovery) verycomparable products with only one stage of processingwhere two to three stages of spiral processing would beneeded. As the goal was to obtain a comparable product, thefractions were recombined to make up RFS and dry millfeed that resembled the desired specifications for theseproducts. The dry mill feed produced during the test workprogramme was used for further lab-scale tests to evaluateits separability into zircon and rutile products.

Lab-scale investigation into zircon and rutileseparabilityThe dry mill feed produced by the test work programmewas subjected to staged ESP (electrostatic screen plateseparation using a lab-scale MK III ESP machine) andstaged HT (high tension role separation using the bench-scale Coronastat HT machine) separation tests to generatezircon and rutile products. The basic principle applied wasone of multi-stage non-conductors (NC) cleaning using theElectrostatic screen plate (see Figure 6) and middlingrecycle on the HT separator (Figure 7).

The ESP testing method used has been proven to indicatedifferences in separation efficiency between different feedtypes. The test method was therefore to serve as acomparison method and was not intended to simulate thedry mill plant or products generated. During the ESP teststhe NC were passed through a number of cleaning stages toproduce a final NC. The cumulative conductors from this

test were then passed over the HT separator to yield a cleanconductor product and the middling stream recirculateduntil the yield to middlings reached negligible proportions.Unwanted mags and MO that could influence final productgrades were removed from the ESP NC (intended zirconproduct) and the HT conductors (intended rutile product) bya magnetic separation stage. The conductor products werealso screened at 180 micron to dispose of any quartz andother entrained gangues minerals present (Figure 8).

Results and discussion

Baseline sample results via test procedure compared toactual plant performanceThe test work programme results confirmed that themethods employed gave a fairly accurate prediction oflikely yield, grade and qualities obtainable when processinga specific material type through the plant. Figure 9illustrates selected test work results achieved for RFS. Theanalytical smelter feed (ASF) grades quoted in Figure 9 arederived via analytical lab analyses methods simulating theroasting and purification process the RFS would besubjected to. It therefore indicates the likely yield andquality of smelter feed the roaster plant would produce. Thebaseline material (sampled from each mining pond) and theactual plant average for the period in which the sampleswere collected are compared. Some degree of variabilitywas expected to exist between the test results of differentpond materials, depending on their unit composition;however, the average test results seemed to tie in with plantaverages reported.

Figure 5. Wilfley shaking table used for CaO grade control

Figure 7. High tension role separation

Source: Richards Bay Minerals, Dry Mills training Manual, 1995, Rev 2

Figure 6. Electrostatic screen plate

Source: Richards Bay Minerals, Dry Mills training Manual, 1995, Rev 2

D.Celectrode

H.T wire

+

Feed

Roll direction

A.C wiperelectrode

Nonconductors

Splitter

ConductorsMiddlings

Wiperbrush

Water addition

Dryfeed


Figure 8. Lab-scale separability comparison test work flow

Figure 9. RFS yield and ASF (analytical smelter feed) grade, recovery and quality

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Figure 10. Dry mill feed results via the test work procedure

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Conductors

ESP separation

HT separator Magnetic separation(HIMS)

Magnetic Separation(HIMS)

180 μ screen

Mids recycle

Zircon ‘Product’

Rutile ‘Product’

Conductors

Non-conductorsrecycle

Non-conductors


Variability in the results for the dry mill feed producedwas, however, more extensive, especially the variabilityevident concerning the grade and recovery of NM TiO2,grouped as rutile in Figure 10. This group could includeleucoxene and rutile minerals of varying elementalcomposition. These minerals can exhibit variations indensity, depending on the state of alteration. Some units canhave high proportions of low quality, low density NM TiO2

present. The low density NM TiO2 could be entrained withother gangue minerals that report to the middlings fractionduring gravity separation. During test work this specifictype of NM TiO2 can be difficult to recover withoutreducing the overall product quality in terms of final MOand quartz content. The test work programme couldtherefore amplify low recovery results for materials with anabundance of low quality NM TiO2. However, variations inNM TiO2 quality would also have occurred in the plantwith similar impacts on separation efficiency. This is

supported by the test results, which indicate a goodcomparison between the test method and the plant averagereported.

Unit specific results and identification of quality issues

It was expected that results for the unit specific materialwould vary to a larger degree and that it would be possibleto identify units portraying unfavourable characteristics interms of yield and quality. Unit correlation models forcurrent run of mine have shown that correlations existbetween achieved plant yields and units mined. During testwork the samples from unit 4 displayed problems withreaching acceptable RFS product yield and quality(therefore affecting likely smelter feed quality indicated byASF data in Figure 11) through the process. Focus wasplaced on various processing options to deal with only thismaterial to see if further optimization was possible.

Figure 11. Variation in yield and quality throughout unit types-roaster feed

Figure 12. Variation in yield and quality throughout unit types-dry mill feed

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DM1000N

1000M200N1

200H1200G

880R1

1430T/B

1430L/1A

1430L/1B DM1000N

1000M200N1

200H1200G

880R1

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1000M200N1

200H1200G

880R1

1430T/B

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DM1000N

1000M200N1

200H1200G

880R1

1430T/B

1430L/1A

1430L/1B

DM1000N

1000M200N1

200H1200G

880R1

1430T/B

1430L/1A

1430L/1BDM

1000N1000M

200N1200H1

200G880R1

1430T/B

1430L/1A

1430L/1B

DM1000N

1000M200N1

200H1200G

880R1

1430T/B

1430L/1A

1430L/1B


Elevated mags and quartz contents for some of the lowgrade samples were noted. This indicated possible difficultywith controlling the mags content in dry mill feed producedfrom the low grade ore and could pose operationaldifficulties in processing down the line. However, focuswas placed on RFS quality and further steps to improveASF CaO quality inferior performing units.

Mitigation attempts on high CaO materials and theblending hypothesesSeveral attempts at additional gravity separation stageswere made to determine if further rejection of the mediumdensity CaO bearing minerals could be achieved for the unit 4 material. A high proportion of garnets was observedfor unit 4 material, which, theoretically, should beremovable by gravity separation. These steps did notdeliver the desired results. This could be attributed to subtledifferences in the garnet minerals’ elemental composition(affecting density) or the abundance of these minerals in thelow grade ore samples.

Following this, dry drum rare earth magnetic (DDREM)separation was tested. This method visually indicated that agood separation could be achieved between the MOminerals and the magnetic material.

However, lab analysis indicated that the ASF CaOcontent of the mags product was still above specification. Amineral liberation analyser (MLA) was utilized toinvestigate this issue. Liberated grains of garnet could stillbe observed possibly causing high ASF CaO. Depending ontheir elemental composition some garnet grains can haveFe-rich rims or cores, increasing their density and magneticsusceptibility. This theory would explain the difficulty inseparating these minerals during gravity and DDREMstages.

The DDREM mags product was screened to determine ifthe garnet could be removed by sizing. A slight drop inASF CaO was observed in the finer grain sizes but ASF

CaO results stayed above the desired CaO contents. Thisindicates that there were gangue mineral grains reportingwith the ilmenite throughout the size distribution either asindividual grains or inclusions.

A second DDREM test was conducted, with the aim ofimproving the mags quality by reducing the yield to themags product. The mags product from this stage ofDDREM appeared to have very little garnet and other CaObearing minerals present, but still analyses indicated highASF CaO levels.

Normally the roasting process should reject anyremaining garnet mineral present, therefore the high ASFCaO levels in a seemingly pure ilmenite sample was notexpected. To confirm which minerals in the mags fraction,after roasting and magnetic separation, were contributing tothe CaO content, MLA analyses were conducted. With thebackground of previous investigations there was a strongpossibility that the high ASF CaO grade was as a result oftitanite inclusions associated with the ilmenite afterroasting.

The results of the MLA analysis conducted on theDDREM mags product confirmed the presence ofinclusions and some clay coatings. Titanite (CaTiSiO5) wasone of most abundant CaO bearing minerals present asinclusions, but not the sole contributor. Other CaO-bearingminerals present after roasting and magnetic separation(mostly as inclusions) included plagioclase, apatite,hornblende, garnet (almandine, pyrope, and grossularite),pyroxenes and altered magnetite.

The presence of inclusion type impurities, though not anew occurrence, seems to be of higher abundance in thelow grade orebody, specifically unit 4A. It was observedthat unit 4A also displayed a larger grain size whencompared to current run of mine units. This could be due toa difference in age and a lesser degree of reworking of thisgeological unit, hence a smaller degree of liberation ofincluded minerals within the ilmenite grains are seen.

Figure 13. Grade recovery curve from optimized DDREM stage

Figure 14. Distribution of CaO bearing minerals

Cu

m A

SF

CaO

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m A

SF

CaO

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AS

F g

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Cum Yield

Size distribution (micron)

AS

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Finally, blending was investigated as a possibility formitigating the effect of low quality units by dilution, beingthe most practically executable method available.Theoretical calculations show that the mere blending of thelow grade ore types should mitigate the effect units like 4Ahave on quality and yield. Applying blending ratios toactual results proved in most cases to mitigate qualityissues. Figure 15 shows selected theoretical blend resultsillustrating that a blended product would be within desiredyield and quality specifications. Blend A demonstrates aweighted average calculated by applying each unit’svolume fraction (based on geological block modelinformation) in the low grade orebody to the unit specificresults achieved during test work. Blend B and C areadjusted scenarios of blends that could be encounteredwhen mining different areas in the LG orebody asinterpreted by geologists familiar with the orebody(indicated in Table II). These blends were chosen to see ifthey would result in a major shift in theoretical materialbehaviour.

Proving the hypotheses—actual blended resultsTo confirm the relevance of the blending hypothesis the LGratio (see Table II) was used to make up an actual blendedmaterial with the HMC produced from the various units inthe low grade orebody and this blend was processed via thetest work programme. A theoretical blend result wascalculated using the ratios and compared to the actualoutcome of the tests. The LG blend ratio was chosen torepresent a worst case scenario assuming that 31% of theblended material will consist of high CaO material(although the unit 4 sample associated with high CaOduring test work only constitute 10–20% of this orebody).In reality this type of blend will rarely exist as mine andproduction planning can ensure that more acceptable unitblends are maintained throughout the life of mine.Examples of actual results compared to predicted

theoretical results show the relevance of the hypothesis.Most of the actual results were comparable or better thanwhat was predicted. In Figure 16 it can be assumed that thedifference in theoretical vs. actual results in terms ofilmenite grade and ASF grade are due to grade recoveryrelationships.

The blended material was also combined with some ofthe run of mine baseline samples tested to assess if blendingwith the low grade ore would negatively affect theirperformance.

The results indicated that blending the low grade ore withcurrent run of mine HMC has no significant negativeimpact on the potential performance through thepreparation plant. Blending with the low grade ore also didnot adversely affect the overall quality achieved. The needfor changes in plant design was therefore ruled out.

Separability comparison

The final area of investigation aimed at determining theease with which dry mill feed produced from the low gradeore could be separated into zircon and rutile. The test work

Theoretical blends used for hypothesisLG blend Blend A Blend B Blend C

DM 26.99 35.99 12.99 01000N 8.2 8.2 5.67 01000M 8.2 8.2 5.67 0200N1 11 10 11200H1 11 10 11200G 18.76 18.76 50 78880R1 6.85 6.85 5.67 01430T/b 31

Figure 15. Examples of theoretical blend results

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Table IIRatios for various blends


Figure 16. Examples of theoretical vs. actual blend results—roaster feed

Figure 17. Examples of theoretical blend vs. actual blend results—dry mill feed

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had to confirm if the separation efficiency of the geologicalunits in the low grade orebody compared with that ofcurrent run of mine. Electrostatic separability can beinfluenced by a number of variables. Under positivepolarity the ESP test method is extremely sensitive to theeffect of surface coatings and would indicate if suchproblems existed for a feed type. Variance introduced bytest work conditions, for example humidity, temperatureand so forth, was also a concern. To indicate if variance

introduced by environmental factors was significant, twoidentical samples were also tested during each test workrun. The results did not indicate any significant variancebetween the samples tested on different days, and it wasdeemed relevant to compare the results obtained during theseparate test runs.

The staged ESP test results indicated that, in terms ofTiO2 rejection, most of the low grade dry mill feed samplesproduced from units in the low grade orebody outperformed

Figure 18. Performance of blended samples—roaster feed

Figure 19. Performance of blended samples—dry mill feed

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the run of mine baseline sample used during these tests.When plotting TiO2 recovery to NC against zircon recovery(Figure 21), the low grade unit samples predominatelydisplayed a lower loss of zircon recovery for the samedegree of TiO2 rejection achieved for the run of minebaseline sample. The samples that did not perform as wellas the baseline sample were both from unit one in the lowgrade orebody.

Unit one material generally has higher slimes contentsand therefore particles are more likely to have surfacecoatings. These surface coatings can have an effect on separation and quality by masking or affectingelectrostatic properties of a grain (depending on theirmineralogy). Back scattered electron (BSE) images of thesesamples clearly show the presence of coatings on thematerial (predominantly typical clay coatings, Figure 20).

Figure 21 shows that a large degree of variability inseparability exists in dry mill feed produced from differentunit samples. This variability has also been observed whenprocessing current run of mine and it was expected that thelow grade orebody would display similar variation acrossgeological units.

Another way to evaluate the results obtained is to observethe zircon product yield obtained to reach a fixed TiO2grade (Figure 21 and Table III).

The yield obtained for the baseline sample to reach 1%TiO2 was lower than that obtained for most of the unitspecific samples. The cleaning steps involved to reach thisgrade were also less for most of the unit specific samples.This indicated once again that most of the low gradeorebody units separated more efficiently compared to thecurrent run of mine baseline material. This very basicmethodology supplied a lot of information regarding thepotential separability issues for various units in the lowgrade reserve and emphasized the high variance associatedwith electrostatic separation. Quantifying the effect of thesefactors, coatings for example, influencing the separation of

zircon and rutile is, however, not as obvious. Further testsare underway to ascertain possible reasons for the variationin separation efficiency of materials from different units.Most of the products produced during the separability testswere very close to or within product specification.

Conclusions

Back to basicsThe test work discussed emphasizes how a seeminglydifficult and cumbersome task (of simulating a fullyfunctional plant on pilot scale) can be completed by usingvery basic metallurgical techniques. The application of a

Figure 20. BSE image of 880R1 feed to ESP test stage

Figure 21. Staged separability of unit samples compared to baseline sample

Zircon recovery

TiO

2R

ec to

NC

DM 1000N 1000M 200N1 200H1 200G 880R1 Baseline test

Cleaning steps 5% TiO2 3 6 4 4 4 5 7 41% TiO2 10 9 8 9 10 15 16 13

0.50% TiO2 >16 11 11 16 14 >16 >16 16

NC yield 5% TiO2 60 50 65 71 73 67 46 681% TiO2 40 26 41 59 60 53 21 36

0.50% TiO2 <27 21 32 48 56 <40 <20 25

Table IIISeparability in terms of cleaning stages

ZirconRutileQuartz


baseline material and equipment calibration helped informulating a simple test programme that could helpidentify differences in performance for various feed types.It also allowed a more practical evaluation of potentialgrades and recovery results for the low grade orebody.Furthermore, the results were based on physical separationtechniques actually employed in the plant set-up. Althoughnot perfect, the basic programme can be applied to any oretype to ascertain its potential performance via the plant. Interms of electrostatic separability the mere nature of theprocessing plants makes it very difficult to simulate. Thebasic methods employed can, however, provide a goodindication of separation efficiency for different ore types. Itcan provide useful information when trying to understandvariances in a complex plant environment or pinpoint areasfor further investigation using more advanced analyticaltechniques.

Application of unit based information

Predicting how a blend could behave based on unit ratioscan be of value. It is important to understand both the unitsand their influence on each other to ensure opportunitiesaren’t overlooked and potential problems are prevented.Developing an understanding of the mineralogy and

metallurgy of specific geological units could support mineplanning optimization, forecasting and resultantly aid inplant control and metallurgical problem solving.

ReferencesBOSHOFF, L.I. and GRACIE, S. A Metallurgical

evaluation to ascertain RBM production plant circuitsuitability to process low grade ore types. RBMinternal report. Unpublished (RBM/MET/15/06).2006.

DEER, W.A., HOWIE, R.A., and ZUSSMAN, J. AnIntroduction to the Rock-forming minerals. 2ndedition. Prentice Hall. Pearson Education Limited,England. 1992.

MUNSAMI, R. Low grade flow sheet progress report.RBM internal report. Unpublished (MET/TI/18/99).1999.

PIETERSEN, K. The sources of ASF CaO in the low gradeorebody. RBM internal report. Unpublished(MET/TI/15/99). 1999.

WARD, M. A Mineralogical evaluation of the low gradeorebody by comparison with current run of mine.RBM internal report. Unpublished (MET/TI/01/90).1990.

Figure 22. TiO2 grade vs. cumulative non conductor yield

NC (zircon) yield

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