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Coal Flotation Washability: Development of anAdvanced ProcedureM.K. MOHANTY a , R.Q. HONAKER a & K. HO ba Department of Mining Engineering , Sourthern Illinois University , Carbondale, 11-62901b lllinois Clean Coal Institute , Carterville, ll-62918Published online: 27 Apr 2007.

To cite this article: M.K. MOHANTY , R.Q. HONAKER & K. HO (1998) Coal Flotation Washability: Development of an AdvancedProcedure, Coal Preparation, 19:1-2, 51-67, DOI: 10.1080/07349349808945573

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Coal Flotation Washability:Development of anAdvanced Procedure

M. K. MOHANTY·, R.Q. HONAKER· and K. HO b

"Department of Mining Engineering, Sourthem Illinois University,Carbondale, 11-62901; bllfinois Clean Coal Institute, Carterviffe 11-62918

(Received 30 May 1997; In final form 6 October 1997)

A modified coal flotation characterization procedure, referred to as the AdvancedFlotation Washability (AFW) technique, has been developed which, compared totraditional procedures, provides a more accurate prediction of the optimum separationperformance achievable by a froth flotation process. The AFW procedure uses a batch­operated flotation column packed with corrugated plates which provides enhancedselectivity among particles of varying degrees of hydrophobicity due to a selectivebubble-particle detachment mechanism. This mechanism is more pronounced in aflotation column operating under carrying-eapacity limited condition with a deep frothzone. In addition, the plug-flow environment resulting from the apparent high length-to­diameter ratio provides an improved performance over the near perfectly-mixedconventional cells used in the traditional procedures. The separation performanceprovided by the AFW procedure was superior to that obtained from multiple stagecleaning provided by commercially-available flotation columns under both kinetic andcarrying-capacity limiting conditions. The separation performance improvementprovided by the AFW technique has been illustrated using three different coal sampleshaving varying feed characteristics.

Keywords: Coal flotation; flotation characterization; column flotation; froth; selectivedetachment; reflux

INTRODUCTION

The traditional release and tree analysis procedures have beencommonly used by preparation plant operators and researchers forevaluating the efficiency of conventional flotation systems. However,

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52 M. K. MOHANTY et al.

several separation performance results reported in literature [1- 3]indicate that the recovery-grade relationship obtained from traditionalcoal flotation washability procedures can be inferior to that providedby continuously operated flotation columns. This finding may beexplained by an improvement in the flotation selectivity achievedamong particles having variable degrees of hydrophobicity usingcolumn flotation. Unlike the conventional flotation cells used in thetraditional procedures, the column flotation cells are characterized bya near plug flow environment provided by a larger length-to-diameterratio which facilitates an enhanced bubble-particle attachmentenvironment. In addition, cleaning in the froth phase is more feasiblein flotation columns due to their ability to support deeper froth zones.As a result, the recovery of hydraulically entrained material can beminimized while flotation selectivity among hydrophobic particles canbe enhanced by a selective detachment mechanism.

Improvement in the selectivity achieved in deep froth zones amongparticles varying in degrees of hydrophobicity has been reported byseveral investigators [4-8]. In a flotation cell, hydrophobic particlesreport to the froth zone at a rate that is dependent upon their degreeof hydrophobicity and the particle retention time within the collectionzone. However, upon entry into the froth zone, the bubbles tend tocoalscence as a result of the high air fraction which results in areduction in the amount of bubble surface area needed to carrythe hydrophobic particles reporting from the collection zone. If thebubble surface area remaining after bubble coalscence is less thanthe surface area required to carry the particles reporting fromthe collection zone, the excess particles are detached from the bubbleand return to the collection zone where re-attachment can occur. Thisaction is termed reflux and the flotation condition is generallyreferred to as carrying-capacity limited. The detachment process hasbeen found to be selective whereby the particles having a lowerdegree of hydrophobicity and, thus, a weaker bubble-particle bondingenergy, are detached and report back to the collection zone where re­flotation is subject to the differences in flotation kinetic rates [4-8].The degree of selective detachment achieved is enhanced withincreasing froth depths which indicates that the selectivity in flotationcolumns should be superior to the performances of conventionalflotation cells.

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COAL FLOTATION WASHABILITY II 53

In light of the above discussions, the use of flotation columns whileconducting the flotation characterization procedures appears to bemore appropriate. A fine particle characterization study using columnflotation was recently published after the inception of the investigation[9] leading to this publication. McClintock et al. [10] reported the useof a column flotation device in a continuous mode to characterize theflotation response of a stratiform copper ore. This 'column-releaseprocedure' has a potential for obtaining a separation performancesuperior to those obtained from the traditional release and treeprocedures. However, the more important issue of carrying capacitylimiting operation, which enhances the selectivity in the coal flotationprocess was not considered in the study. In fact, the 'column-releaseprocedure' was only recommended as an alternative method and wasnot described as a superior method for characterizing the flotationresponse of a given material.

This publication describes the development of a novel flotationcharacterization procedure, referred to as Advanced FlotationWashability (AFW), which uses a batch operated flotation columnin contrast to a conventional flotation cell used in the traditionalprocedures. A comparison of the traditional methods found that therelease analysis provides the best recovery-grade relationship for finecoal containing middling particles [9, II]. Thus, AFW performancecurve has been compared with those obtained from the traditionalrelease analysis technique as well as single and multiple stagecontinuous column operations. The experimental results obtainedfrom the AFW procedure on three different coal samples of varyingfeed characteristics are presented in this publication.

EXPERIMENTAL

Sample

The coal sample used extensively in this study originated from theIllinois No.5 coal seam, which is ranked as a bituminous high vol. Acoal. The run-of-mine sample was crushed to -180 11m and then splitinto representative lots of about 2.3 kg (5Ibs.) each and stored insample bags at -20°C to prevent surface oxidation of the coal

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54 M. K. MOHANTY et al.

particles. The size-by size wight, ash and total sulfur distributions forthe IIIionois No. 5 sample is provided in Table 1. The additionalsamples include a difficult-to-clean, Pittsburgh No. 8 coal samplecollected from the middlings stream of a three-product jig whichcontained 22.5 % ash and 2.32 % total sulfur. The middling samplewas ground from a top particle size of about 7.6 cm to 180 urn usinglaboratory jaw and hammer mills. A West Kentucky No. 9 coalsample collected from the fine circuit of an operating coal preparationplant was also treated and was found to contain 34.0 % ash and2.16 % total sulfur. Both Pittsburgh No.8 and West Kentucky No.9coal were ranked as bituminous high vol. A coal.

EXPERIMENTAL APPARATUS

The new apparatus for conducting the Advanced Flotation Wash­ability (AFW) procedure is shown in Figure I, which consistsessentially of a batch-operated, 5 cm (2-in.) diameter, 1.5 m (5 ft) tallflotation column. The flotation column is vertically-baffled withstainless steel corrugated packing material similar to that used bythe Packed-Column [12] with approximately a 0.64 em (0.25 in.)spacing. The packing inside the cell, in effect, produces a high length­to-diameter ratio providing a near-plug flow mixing environmentwhich is known to be highly congenial to the flotation process. Thefeed slurry is continuously re-circulated during the experiments toavoid deposition of solid particles in the cell and to provide a feed flowcounter-current to that of the air bubbles to allow efficient bubble­particle collision. The air is directly injected through a flow meter into

TABLE I Size-by-size reed characterization data or the nominally -150 urn IllinoisNo.5 coal sample used in the present investigation

Size fraction (mesh) Weight (%) Ash (%) Total sulfur (%)

+ 100 17.2 14.7 2.43100x200 29.7 15.2 2.62200x325 20.6 15.6 2.63325x400 2.50 16.4 2.99-400 30.1 26.9 2.87

Total 100.0 18.7 2.67

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COAL FLOTATION WASHABILITY II

..

Controller I29.S I

Air

55

FIGURE I A schematic of the experimental apparatus developed to conduct theadvanced flotation washability analysis.

the lower section of the cell. The cell is equipped with a PID controlledwash water system which is mainly used to mobilize (or lubricate) thedeep froth in the cell and to conveniently adjust the pulp level tooperate the cell at a desired froth depth. During the experiment, frothconcentrate continuously reports to the overflow launder which causesa reduction in the pulp level inside the cell. This reduction in the cellpulp level is indicated by a pressure transducer placed in the lowersection of the cell, which activates the PID controller to send aconstant analog signal to a peristaltic pump. The wash water flow rateentering the top of the froth zone is adjusted by the PID controller tomaintain the pulp level at the desired preset value.

EXPERIMENTAL PROCEDURE

Several possible approaches including the procedures used in thetraditional release and tree analyses were evaluated to establish an

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56 M. K. MOHANTY et 01.

appropriate procedure for the AFW analysis. The traditional releaseanalysis approach of removing all the hydrophilic mineral particles inthe first phase and collect concentrate samples having varying degreesof hydrophobicity in the second phase was also pursued in the AFWprocedure. It was found that the first phase of the procedure, whichseparates the hydrophobic material from the purely hydrophilicminerals, can be completed effectively in less time using the laboratoryDenver cell instead of the AFW apparatus. As shown in Figure 2, thetailings obtained from each step of the first stage were combined toform the final tailings. The froth concentrate collected from the firstphase, which was considered to be comprised of only hydrophobicparticles, was segregated into approximately seven different fractionsaccording to a decreasing order of hydrophobicity by varying theaeration rate from about 1.5 liters/min to nearly 2.5 liters/min andcollecting separate samples at each air setting. The sample stillremaining in the cell after the collection of the sixth concentratefraction forms the seventh fraction, which was collected by flushing theentire cell.

~ FEED Phase I Phase II

! • CONI• CON 2

!• CON3

• CON 4• CONS

• CON 6

TAIl.S

FIGURE 2 A schematic of the step-by-step procedure followed while conducting theadvanced flotation washability analysis.

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COAL FLOTATION WASHABILITY II 57

The reagents used for the AFW procedure were kerosene as thecollector and Dow Froth M-150, a polyglycol as the frother.Absolutely no collector was used in the second stage of the process.A few drops of frother was sometimes necessary to maintain a deepfroth of about 90 em throughout the second stage to facilitate aneffective column reflux action and prevent any possible by-pass of pulpwater to the product launder. One important difference fromtraditional procedures which renders this process less operatordependent is that the froth concentrate slowly flows to the productlaunder without the assistance of an operator. However, adjusting theairflow to the appropriate setting to allow a gentle flow of concentrateover the lip of the column is very crucial for the successful completionof a test with the AFW device. An excessively high aeration rate maylead to possible pulp water by-pass to the product launder which willaffect selectivity, whereas, a low aeration rate hinders the mobility ofthe froth and allows the coarser particles to adhere to the column wallor packing material, thereby, prohibiting a consistent froth flow to theproduct launder.

To compare the AFW performance with the best performanceachievable from the traditional procedures, release analysis wasconducted on all the three samples used in this study following theprocedure described by Dell (1964) [13]. As reported in a recentpublication [II], the release performance curve is significantlyimproved by conducting the procedure at a high initial feed solidscontent. Hence, the release procedures were conducted beginning witha feed solids content of about 20 % in a laboratory Denver flotationcell. The reagents used for the release procedure were kerosene as thecollector and Dow Froth M-150, a polyglycol as the frother.

The separation performance data were obtained from a continuousPacked-Column operating in rougher-only, rougher-cleaner androugher-cleaner-cleaner circuit arrangements to validate the AFWprocedure. Each of the coal samples was treated in a IO-cm (4-inch)diameter, 4.9 m (16 ft) tall Packed-Column. Typically, a froth depth of3 m (10ft), an aeration rate of4 cm/sec and wash water rate of0.4 em/secwere used to ensure an effective washing of entrainable materials. Thecorresponding bias factors were greater than 0.6 for all the testsconducted using the continuous column. The froth depth wasmaintained at the desired level by a PID controller, which upon

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58 M. K. MOHANTY er al.

receiving signal from a pressure transducer placed at the lower sectionof the column activated a peristaltic pump connected in the tailingstream.

RESULTS AND DISCUSSION

Through a series of tests conducted to establish the important processparameter values and an appropriate step-by-step procedure, the useof a wash water system was found to be necessary to ensure effectivemobility of the froth concentrate. Due to the need to operate undercarrying-capacity limited condition, the feed solid contents weremaintained relatively high at 20 % by weight or higher. As a result, thefroth zone was overloaded, thereby requiring the use of the washwater. The additional advantage obtained with the automated washwater system is that the flotation system operates under a zero biascondition in the froth zone meaning that the flow rate of the washwater addition is equal to the volume of solids and water recovered inthe froth concentrate. For the conventional cell used in the traditionalrelease procedure, the bias factor is negative indicating a non-selectiverecovery of entrained material including coal and middling particles tothe froth concentrate. Another important advantage which may be themost significant is that the automated wash water system allows theprocedure to be less operator dependent, which results in the excellentrepeatability of the procedure. As shown in Figure 3, five AFW testconducted under the similar experimental conditions produced nearlythe same separation performances.

The optimum separation performances achieved on the -180 urnIllinois No.5 coal sample using the AFW technique are compared inFigures 4(a) and (b) with the results obtained from the optimizedrelease analysis and the centrifugal gravity-based washability analysis.For each of the characterization techniques, the near horizontalportion of the curve represents the rejection of liberated ganguematerial while recovering nearly all of the combustible material. Onthe other hand, the vertical portion of the curve, which represents asharp decrease in recovery with decreasing product ash, is formedaccording to the manner in which the middling particles report to theclean coal concentrate. A comparison of the AFW and release analysis

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COAL FLOTATION WASHABILITY II 59

tOOM~~ '-"

Illinois No.5 Coal 0

Feed Ash: 18.7"10 •~

"<f. 80~

~

S~

;>-60 AFW Repeatability0

u~..!l .It. • Test IP- 40 0 o Test 2'§ 0.0

.~ • Test 3E

0 Test 40 20 ~u"I • Test 5

Cf0

0 2 4 6 10

ProductAsh(%)

FIGURE 3 Separation performance data obtained from 5 separate tests showing theexcellent repeatability of the AFW analysis.

procedures indicates that the separation performances on the basis ofash content are nearly equal along the horizontal portion of the curve.However, the AFW method provides a superior performance alongthe vertical portion, which indicates that the AFW procedure providesa more efficient treatment of middling particles.

As shown in Figure 4(a), the ash reduction obtained from the AFWprocedure at 80 % combustible recovery was from 18.7% to 4.5 % forthe -180 urn Illinois No.5 coal sample which corresponds to an ashrejection of nearly 85 %. However, this performance is substantiallyinferior to that of the gravity-based washability, which confirms thefact that gravity-based separations treat middling particles moreefficiently than surface-based separation. The separation performancedifferences were greater on the basis of product total sulfur content asshown in Figure 4(b). The AFW procedure provided product totalsulfur contents that were about 0.2 % weight units lower than that ofthe release procedure. This is likely due to the more efficient ability ofdeep froths to reject the floatable pyrite particles, both liberated andnon-liberated. The superior reflux action occurring as a result of thedeep froth, which also reduces the possibility of entrainment, and aheavy solids loading causes the enhanced rejection of the pyrite

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60 M. K. MOHANTY et al.

100

~ 80

~

Sj 60

Inro~ No.5 Coal.!l FeedAsh: 18.7%,e 40!§.0e -+25 urn Washability0

U 20 ----'-AFW~Release

02 6

(a) Product Ash (%)

(b) Product Total Sulfur (%)

FIGURE 4 A comparison of the separation performances obtained on the basis ofproduct <a) ash and (b) total sulfur contents from the AFW method, the traditionalrelease procedure and the gravity washability analysis conducted on the Illinois No.5coal sample.

particles. This separation performance was, however, substantiallyinferior to that of the gravity-based washability indicating a lowerdegree of selectivity for the treatment of middling particles.

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COAL FLOTATION WASHABILITY II

COMPARISON WITH CONTINUOUS COLUMN RESULTS

61

As described previously, flotation columns can be operated to providetwo different limiting conditions, which provide a variation inseparation performance. When the feed to the flotation columncontains a large amount of solids (e.g., > 15 % by weight) and/or theparticle size is very fine (e.g., 100 %-75 11m), the column tends tooperate under carrying-capacity limiting conditions in which insuffi­cient bubble surface area exists to float all of the hydrophobic particlesreporting to the froth zone. Thus, upon bubble coalescence, particlesselectively detach from the bubbles and report back to the pulp zonewhere the particles can re-attach to a bubble and report to the frothzone. On the other hand, if sufficient bubble surface area exists, thecolumn is considered to be kinetic-rate limited. Multiple stage cleaningunder kinetic rate limiting conditions (i.e., low feed solids contentand/or relatively large particle sizes) has been found to improve theoverall separation performance, whereas this finding was not realizedfor columns that were carrying-capacity limited [4].

Figures 5(a) and (b) compare the results obtained from a continuousPacked-Column operated under kinetic and carrying-capacity limitingconditions with those obtained from the AFW and improved releaseanalysis procedures. Under carrying capacity limited condition, arougher-cleaning stage was the only treatment step evaluated whereasrougher, rougher-cleaner, and rougher-cleaner-cleaner circuit arrange­ments were tested using the Packed-Column under kinetic limitingconditions. As shown, the separation performance provided by theextensive three stage cleaning (R-C-C) under kinetic limiting conditionsremained inferior to that of the AFW procedure on the basis of bothproduct ash (Fig. 5a) and total sulfur (Fig. 5b) contents, although theperformance approached the AFW curve with each subsequent cleaningstage. On the other hand, operating the Packed-Column under carrying­capacity limited condition provided a nearly equal separation perfor­mance on the basis of product ash content when compared to the AFWcurve and a superior performance when compared to the traditionalrelease results as shown in Figure 5(a). This finding is consistent with theexplanation of improved selectivity with carrying-capacity limitedcondition. However, in terms of the product total sulfur content, theperformance from the AFW procedure remained superior.

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62 M. K. MOHANTY et at.

100

fumisNo.5Call00

~ so Feed Ash:18.7%eS!> so

~..!! 0

0 R.g 4.

i0 R-C

" R-C-C

2. T Carrying Capacsyo ___AFW

-.-Release

o2

(a) Product Ash (%)

IDinois No. 5Call

°,rFeed Tctal Sulfur: 2.67"10

~80 ,,0 ,"0

° I

S ,. II

j 60,. AI

r/,..!! r 0.g 40

,0 R

!!l I>0 R-C,0 ,

a ,Ii R-C-C

0 ,o 20 ,

" Canying Capacsy,, __AFW

t-. -Release•0

1.0 J.S 2.0 2.5

(b) Product Tolal Sulfur (%)

FIGURE 5 A comparison of the separation performances achieved on the basis of a)product ash and b) total sulfur contents by the AFW and release analysis methods, thecontinuous Packed-Column under carrying-capacity limiting conditions and rougher R,rougher-cleaner (R-C), and rougher-cleaner-cleaner (R-C-C) arrangements of thePacked-Column under kinetic limiting conditions.

COMPARISONS USING ADDITIONAL COAL SOURCES

Test results on the basis of product ash content obtained from thetreatment of -180 urn Pittsburgh No.8 and West Kentucky No.9 finecoal samples are shown in Figures 6(a) and (b). For both coal samples,

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COAL FLOTATION WASHABILITY II 63

100,

o q.'",1,1 DO

~ 80 0~~ o ,

S o , ,

! 00 i Pinsburgh No.8,, Feed Ash: 22.5%,..Il ,

~40 , • AFW,

r • Release"E t, 0 Colurm8 20 •,,

:.0

6 10 12 14 16 18

(a) Product Ash (%)

100~.-------.-

~~ 80 0 1e o I

S 1

>00 o g~

_, Kenrucky No.9

J FeedAsh 34.0'10I,

JlI --AFW

oB 400 I --. - "Release] I

0E I Colurm0 ,U 20

00 6 10 12

(b) Product Ash (%)

FIGURE 6 Separation performances on the basis of product ash content achieved onthe a) Pittsburgh No.8 coal (feed ash: 22.5 %) and b) West Kentucky No.9 (feed ash:34.0 %) coal samples by the Advanced Flotation Washability (AFW), release analysisand a continuously operated Packed-Column.

AFW procedure produced the ultimate flotation response compared tothose obtained from the release analysis and a continuously operatedflotation column. The largest separation performance differenceoccurred from the treatment of the Pittsburgh No. 8 coal whichoriginated from the middlings stream of a three-product jig. Reducingthe ash content from 22.5% to 11.8% resulted in a combustible

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64 M. K. MOHANTY el al.

recovery of about 81 % for the AFW procedure whereas the recovery .achieved by the release analysis and continuous flotation column weresignificantly lower at 60% and 68%, respectively. Since the PittsburghNo. 8 coal was likely to contain a significant amount of middlingparticles, the superior performance provided by the AFW technique isindicative of the ability of the AFW procedure to achieve a betterseparation among particles varying in their degree of hydrophobicity.As explained previously, this improved selectivity is likely due to theextensive amount of selective bubble-particle detachment and reflux­ing that is strongly encouraged during the performance of the AFWprocedure by using a high feed solids content, and low aeration ratesas well as maintaining a deep froth depth.

For coal samples containing a relatively small amount of middlingparticles such as that expected for the Illinois No. 5 and WestKentucky No. 9 fine coal samples, the differences in separationperformance achieved on the basis of total sulfur content are greaterthan those achieved on the basis of ash content. From Figures 6 and 7,the differences between the ash and total sulfur rejections achieved bythe AFW and release analyses while recovering 80 % of thecombustibles in the Pittsburgh No. 8 coal sample was nearly equalat about 9.0 %. However, for the West Kentucky No.9 coal, thecorresponding improvement in total sulfur rejection at 80 % recoverywas 6.0 % while the difference in ash rejection was significantly lowerat 2.3 %. This finding indicates that the improvement in the separationperformance achieved by the AFW procedure at a given recoveryvalue is a function of the amount of middling and floatable coal pyriteparticles in the feed. In other words, for a coal containing no middlingor coal pyrite particles, the only improvement in separationperformance achieved by the AFW procedure would be a result ofthe selectivity obtained among the individual maceral particlescomprising the fine coal sample. For most U. S. coals which havehigh viritinite contents, this improvement would only be realized in thelow recovery region of the performance curve whereas Gondwanacoals in Southeast Asia and Africa would realize the improvement athigher recovery values due to the higher inertinite maceral contents.

One should also note that the continuous column results shown inFigures 6 and 7 were superior to the traditional release performancebut significantly inferior to the AFW performance for both fine coal

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COAL FLOTATION WASHABILITY II 65

40

20 •

o

,,,,,,,,,.It

o 0o

• AFW

• Releaseo CoIJmn

<aJ

(b)

o L-'---'~-----'~---'-~-'-~-L~---'--~

1.6 1.8 2.0 2.2. 2.4 2.6 2.8 3.0

Product Total Sulfur (%)

West Kentucky No.9FeedTool! Sulfur: 216%

_AFW

--.--Re!:ase

o CoIJmn

oL------'--'-~-'---'-_L..-...._____' _ _.J

1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0

Product Total Sulfur (%)

FIGURE 7 Separation performances on the basis of product total sulfur contentachieved on the a) Pittsburgh No.8 coal (feed total sulfur: 2.32 %) and b) WestKentucky No. 9 (feed total sulfur: 2.16 %) samples by the Advanced FlotationWashability (AFW), release analysis and a continuously operated Packed-Column.

samples. This finding has been the source of controversy in the pastbut is now realized to be the result of the advanced flotationmechanisms (i.e., selective detachment, refluxing, near plug-flowconditions, froth washing) extensively utilized in column flotation.

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66

CONCLUSIONS

M. K. MOHANTY et al.

The following conclusions were derived from the results presented inthis publication:

I. A new flotation characterization procedure referred to as AdvancedFlotation Washability (AFW) analysis described in this publicationfor predicting the optimum separation performance for frothflotation processes is superior to the traditional procedures. Thisfinding is due to the better utilization of advanced froth flotationmechanisms (i.e., nearly plug-flow environment, selective detach­ment, high refluxing action, etc.) in the AFW procedure.

2. Since the apparatus used in the AFW procedure is fully automated,the possibility of human error, which is a problem with thetraditional procedures, is substantially reduced. Thus, the AFWprocedure provides excellent test repeatability.

3. The improvement in separation performance achieved by the AFWanalysis over those obtained from traditional procedures is afunction of the proportion of middling and coal pyrite particlespresent in the fine coal sample. In the absence of middling and.pyrite particles, the selectivity improvement realized by the AFWprocedure will only be a result of the separation achieved amongthe individual coal maceral particles comprising the feed coal.

4. The separation performance achieved from the AFW procedurewas superior to multistage cleaning provided by a continuouslyoperated flotation column in both kinetically limiting and carryingcapacity limiting conditions. Thus, this finding is evidence that theseparation performance provided by the AFW analysis mayrepresent the ultimate recovery-grade relationship achievable byany froth flotation process.

Acknowledgements

The work presented in this publication was funded in part by grantsmade possible by the U. S. Department of Energy CooperativeAgreement Number DE-FC22-92PC92521 (Year 4) and the IllinoisDepartment of Commerce and Community Affairs through the Illinois

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COAL FLOTATION WASHABILITY II 67

Coal Development Board and the JIlinois Clean Coal Institute (ProjectNo. 95-1/1.2B-1P).

References

[1] R. Q. Honaker, M. K. Mohanty and K. Ho, "Comparison of column fiotationcells", Proceedings, J2th International Coal Preparation Exhibition and Conference(Lexington, Kentucky), pp. 175-189 (1995).

[2J B. K. Parekh, J. G. Groppo, F. Smit, M. C. Jha and T. Feely, "Column flotation toproduce ultra-clean coal", Proceedings, JI" Annual International Pittsburgh CoalConference, 2, 1261-1272 (1995).

13] D. Yang, Personal Communication (1995).[4] R. Q. Honaker and M. K. Mohanty, "Enhanced column flotation performance for

fine coal cleaning", Mineral Engineering, 9(9), 931-945 (1996).[5] J. A. Finch, J. Yianatos and G. Dobby, Column Froths, Mineral Processing and

Extractive Metallurgy Review, 5, 281-305 (1989).[6} J. B. Yianatos, J. A. Finch and A. R. Laplante, Selectivity in column flotation

froths, Int. J. Min. Processing, 23, 279 (1988).[7] J. B. Yianatos, J. A. Finch and A. R. Laplante, Cleaning action in column flotation

froths, Trans. Instn, Min. Metall. (Sec. C: Mineral Proc. Extr. Metall.), 96, Cl99(1987).

[8] M. H. Moys, A study of a plug-flow model for flotation froth behavior, Int. J. Min.Processing, 5, 21 (1978).

[9] R. Q. Honaker and M. K. Mohanty, "A modified release analysis procedure usingadvanced froth flotation mechanisms", 95-1/1.2B-IP, 1994 Proposal and 1995Final report, Illinois Clean Coal Institute, Carterville, Illinois, 1995.

[10] W. W. McClintock, D. E. Walsh and P. D. Rao, "Release analysis of a stratiformcopper sulfide ore using column flotation", Minerals and Metallurgical Processing,12,112-117 (1995).

[11] M. K. Mohanty, R. Q. Honaker, A. Patwardhan and K. Ho, "A ModifiedProcedure to Measure the Ultimate Flotation Response of Coal", Preprint No.97-178, SME Annual Meeting, Denver, Colorado, 1997.

[12] D. C. Yang, "Technical Advantages of Packed Flotation Columns", Proceedings,The International Conference on Column Flotation, Sudbury, Ontario, Canada,1991.

[13] C. C. Deli, "An improved release analysis procedure for determining coalwashability", Journal of the Institute of Fuel, 37, 149-150 (1964).D

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