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Coal Preparation Plant AdvancementsCoal Preparation Plant Advancements

R. Q. HonakerR. Q. HonakerUniversity of KentuckyUniversity of Kentucky

Department of Mining EngineeringDepartment of Mining Engineering

Kentucky Professional Engineers in Mining Seminar Lexington, Kentucky

August 29, 2007

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U. S. COAL PREPARATIONU. S. COAL PREPARATIONCoal preparationCoal preparationinvolves processing toinvolves processing toachieve the requiredachieve the requiredquality for end users.quality for end users.636 Mt of coal636 Mt of coal

processed annually.processed annually.Coal is sized andCoal is sized andcleaned in variouscleaned in variouscircuits.circuits.Fine (Fine ( --1 mm) coal1 mm) coaltypically accounts fortypically accounts for12%12% --15% of feed (7515% of feed (75

– – 95 Mt annually)95 Mt annually)

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Distribution Inefficiencies: DesignDistribution Inefficiencies: DesignImplicationsImplications

A number of major plant A number of major plant

design changes have beendesign changes have beenbased on poor distribution tobased on poor distribution tovarious process units.various process units.

Poor distribution results inPoor distribution results inunequal feed volumetric andunequal feed volumetric andmass flow rates.mass flow rates.

Unequal flow rates typicallyUnequal flow rates typicallylead to varying separationlead to varying separationperformances.performances.

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RulesRules --of of --ThumbThumb

For two or more separators having theFor two or more separators having thesame efficiency but different separationsame efficiency but different separationdensities, the overall efficiency is lowerdensities, the overall efficiency is lower

than the efficiency of the single unit.than the efficiency of the single unit.

For two or more separators havingFor two or more separators havingdifferent separation efficiencies, the overalldifferent separation efficiencies, the overallefficiency is the weighted average of theefficiency is the weighted average of the

efficiencies from the individual units.efficiencies from the individual units.

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Ramifications on Plant DesignRamifications on Plant DesignLarge Diameter DMCLarge Diameter DMC

vs. Standard DMC.vs. Standard DMC.Water Water --OnlyOnlyCyclone/Spiral CircuitCyclone/Spiral Circuitversus Spiral Circuit.versus Spiral Circuit.Teeter Teeter --Bed SeparatorsBed Separatorsversus Spiral Circuits.versus Spiral Circuits.Large (3Large (3 ’’) Diameter) DiameterClassifying CycloneClassifying Cycloneversus 15versus 15 ”” Cyclones.Cyclones.Banana Screen versusBanana Screen versusIncline Screen.Incline Screen.

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New Steam Coal Plant Design:New Steam Coal Plant Design:Reduced DistributionReduced Distribution

Clean CoalCyclones

Clean

Coal

WasteDisposal

DenseMedium Cyclones

D&R Screens

CircuitFeed

Raw Coal/DeslimeScreens

DewateringScreen

CentrifugalDryer

D&R Screens

Teeter-

Bed orSpirals

Thickener

Classifying

Cyclones

SIZING CLEANING DEWATERING

C O A R S E /

M

E D I U M

S M A L L /

F I N E

CentrifugalDryer

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Trend ProblemsTrend ProblemsThe efficiency of largeThe efficiency of large

units over a givenunits over a givenparticle size range mayparticle size range maybe lower than thatbe lower than thatachieved by smallerachieved by smaller

units.units.Efficiency of highEfficiency of highcapacity technologiescapacity technologiesmay be less than themay be less than thelower capacitylower capacityseparators that requireseparators that requirefeed distributors.feed distributors.

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Banana ScreensBanana Screens Australian technology Australian technologyUsed forUsed for deslimedeslime screeningscreeningandand drain&rinsedrain&rinse screenscreenapplications.applications.ScreenScreen --deck with multipledeck with multipleslopes (2 to 6) which reducesslopes (2 to 6) which reducesin inclination from the feedin inclination from the feedend.end.

As a result, the velocity of the As a result, the velocity of thematerial is fast at the feed endmaterial is fast at the feed endand slows toward theand slows toward thedischarge.discharge.The high inclinations provideThe high inclinations providea very thin particle bed whicha very thin particle bed whichallows the undersize materialallows the undersize materialto pass through the screento pass through the screenmore efficiently.more efficiently.

50% increase in feed50% increase in feedcapacity.capacity.

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Common U.S. FineCommon U.S. FineCoal CircuitCoal Circuit38cmClassifying

Cyclone

CompoundSpiral

Concentrator

CleanCoal

1 mmDeslimeScreenUnders

Thickener

SieveBend

ScreenBowlCentrifuge

HighFrequency

ScreenCoarse

Reject

ColumnFlotation

1 x 0.15 mm

Minus 0.15 mm

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Spiral ConcentratorsSpiral ConcentratorsFlowing film separator.Flowing film separator.Produces three product streams.Produces three product streams.

33--3.53.5 tphtph /start; 30/start; 30 gpmgpm /start./start.Three starts on one axis.Three starts on one axis.Separation density = 1.8 RD;Separation density = 1.8 RD; EpEp= 0.15= 0.15 – – 0.18.0.18.Typical 5Typical 5 --10% high density10% high densityparticle byparticle by --pass.pass.

S o r t i n g Z o n e

SpiralCoal

Rock

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Spiral Performance ImprovementsSpiral Performance Improvements

Luttrell et al. performed circuitLuttrell et al. performed circuitanalysis to reduce separationanalysis to reduce separation

density and improve efficiency.density and improve efficiency.Rougher Rougher --Cleaner arrangementCleaner arrangementwith middling recycle the mostwith middling recycle the mostpractical.practical.

Separation densities of aroundSeparation densities of around1.7 at1.7 at EpEp = 0.18.= 0.18.Significant economic gainsSignificant economic gains

have been reported from planthave been reported from plantinstallations.installations.Single units using Rougher Single units using Rougher --Cleaner cleaning action haveCleaner cleaning action have

been developed.been developed.Refuse

Feed

Primary-Secondary(Midds Only)

Product

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Water Water --Only/Spiral Fine Coal CircuitOnly/Spiral Fine Coal Circuit

38mmClassifying

Cyclone

CompoundSpiral

Concentrator

CleanCoal

1 mmDeslimeScreenUnders

Thickener

SieveBend

ScreenBowl

Centrifuge

HighFrequency

ScreenCoarse

Reject

Water-OnlyCyclone

ColumnFlotation

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Teeter Teeter --Bed SeparationsBed SeparationsHigh capacities (2 tph/ftHigh capacities (2 tph/ft 22 ))eliminates distributioneliminates distribution

problems associated withproblems associated withspirals.spirals.Low pressure waterLow pressure waterinjection at the bottom ofinjection at the bottom ofthe separation chamberthe separation chamberfluidizes the highfluidizes the high --densitydensityparticles.particles.Fluidized particle bed =Fluidized particle bed =autogenous medium.autogenous medium.Can be used as anCan be used as analternative or inalternative or inconjunction with spirals.conjunction with spirals.Effective over a particleEffective over a particle

size range 5:1.size range 5:1.

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Teeter Teeter --Bed InstallationBed Installation650 ton/hr plant650 ton/hr plantHMC/Teeter HMC/Teeter --bed/Flotation plantbed/Flotation plant140140 tphtph , 2 x 0.25, 2 x 0.25mm treated bymm treated byTeeter Teeter --Bed.Bed.3 x 3 m3 x 3 m 22 CrossflowCrossflowTeeter Teeter --Bed unitBed unitused.used.

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Teeter Teeter --Bed PerformanceBed PerformanceParametric evaluationParametric evaluationwas performed towas performed toimprove startimprove start --upupperformance.performance.9% ash product9% ash productachieved with organicachieved with organic

efficiency greaterefficiency greaterthan 95%.than 95%.

60

70

80

90

100

0 2 4 6 8 10 12 14 16 18 20Product Ash (%)

R e c o v e r y ( % )

Ken America WashabilityTest Set 3Test Set 2Test Set 1Start-Up

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ClassifyingCyclones

Reject

Reject

CleanCoal

ClassifyingCyclones

-1 mmFine

CircuitFeed

EnhancedGravity

Spirals

Ultrafine Gravity Circuit

- 0.250 mm

0.25 x 0.044 mm

1.0 x 0.25 mm

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Spiral Concentrator Application forSpiral Concentrator Application forUltrafine Coal CleaningUltrafine Coal Cleaning

Recent studies have foundRecent studies have found

that spirals such as the SX7that spirals such as the SX7can provide an effectivecan provide an effectivegravitygravity --based separationbased separationperformance forperformance for --100 mesh100 meshcoal.coal.

Required volumetric flowRequired volumetric flowrate is around 15rate is around 15 gpmgpm /start/startand feed solids contentand feed solids contentshould be nearly 15% byshould be nearly 15% byweight.weight.Currently, two U.S. coalCurrently, two U.S. coalpreparation plants usepreparation plants usespirals in this application.spirals in this application.

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Ultrafine Spiral Concentrator Ultrafine Spiral Concentrator Ash Rejection Performance Ash Rejection Performance

Weight (%) Ash (%) Weight (%) Ash (%) Weight (%) Ash (%) Weight (%) Ash (%) Weight (%) Ash (%)16 x 100 19.60 8.44 16.34 5.22 25.52 6.80 16.75 14.77 15.49 34.90

100 x 325 45.13 19.33 44.82 11.18 43.21 16.19 49.11 45.58 52.99 57.84-325 35.28 53.74 38.84 46.39 31.27 57.53 34.14 67.71 31.53 74.49Total 100 29.34 100 23.88 100 26.72 100 47.98 100 59.54

Spiral Mids 2 Spiral TailingsParticle Size(mesh)

Spiral Feed Spiral Product Spiral Mids 1

Test 1 Performance (Higher Yield)

Weight (%) Ash (%) Weight (%) Ash (%) Weight (%) Ash (%) Weight (%) Ash (%) Weight (%) Ash (%)16 x 100 19.60 8.44 17.50 4.94 25.26 5.99 21.92 6.80 20.16 36.87

100 x 325 45.13 19.33 58.26 10.71 42.27 12.00 47.18 16.19 52.56 56.33-325 35.28 53.74 24.24 47.13 32.47 51.64 30.91 57.53 27.29 68.68Total 100 29.34 100 18.53 100 23.35 100 26.91 100 55.78



Test 2 Performance (Lower Product Ash)

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Ultrafine Spiral Concentrator Ultrafine Spiral Concentrator Total Sulfur Rejection PerformanceTotal Sulfur Rejection Performance

Weight (%) T. Sulfur (%) Weight (%) T. Sulfur (%) Weight (%) T. Sulfur (%) Weight (%) T. Sulfur (%) Weight (%) T. Sulfur (%)16 x 100 19.60 2.64 16.34 2.43 25.52 2.67 16.75 3.34 15.49 4.34

100 x 325 45.13 3.37 44.82 2.7 43.21 3.07 49.11 4.77 52.99 5.62-325 35.28 5.77 38.84 2.31 31.27 5.19 34.14 7.31 31.53 8.48Total 100 4.07 100 2.50 100 3.63 100 5.40 100 6.32



Test 1 Performance

Weight (%) T. Sulfur (%) Weight (%) T. Sulfur (%) Weight (%) T. Sulfur (%) Weight (%) T. Sulfur (%) Weight (%) T. Sulfur (%)16 x 100 19.60 2.64 17.50 2.45 25.26 2.54 21.92 2.97 20.16 4.38

100 x 325 45.13 3.37 58.26 2.64 42.27 3.00 47.18 4.05 52.56 5.86-325 35.28 5.77 24.24 4.44 32.47 4.9 30.91 7.78 27.29 9.91Total 100 4.07 100 3.04 100 3.50 100 4.97 100 6.67



Test 2 Performance

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Dry Coal CleaningDry Coal CleaningDry coal cleaning was popular fromDry coal cleaning was popular from19301930 – – 1990.1990.Peak production was 25.4 million tonsPeak production was 25.4 million tonsannually in 1965.annually in 1965.

Largest allLargest all --air cleaning plant was 1400air cleaning plant was 1400tphtph in Pennsylvania (1968).in Pennsylvania (1968).Several commercial technologiesSeveral commercial technologiesdeveloped in the period of 1900developed in the period of 1900 – – 1950.1950.Decline was due to the need for efficientDecline was due to the need for efficient

low density cuts and environmentallow density cuts and environmentalhealth concerns (underground &health concerns (underground &surface).surface).Recent U.S. resurgence is in large partRecent U.S. resurgence is in large partdue to the need to reduce transportationdue to the need to reduce transportationcosts and clean western U.S coals.costs and clean western U.S coals.

Alminerals Alminerals modified the Stomp jig tomodified the Stomp jig toprovide a completely automatedprovide a completely automatedcommercial unit.commercial unit.

Allair Allair jig has been commercially jig has been commerciallysuccessful (Mining Engineering, 2007).successful (Mining Engineering, 2007).

Alminerals Allair Jig

FMC Separator (1940)

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Potential Dry Cleaning ApplicationsPotential Dry Cleaning ApplicationsDry coal cleaning technologiesDry coal cleaning technologieseffectively achieve densityeffectively achieve density

separations > 1.85 RD.separations > 1.85 RD.Separations at relatively highSeparations at relatively highdensities to removedensities to remove ‘ ‘nearlynearly ’ ’ purepurerock is referred to asrock is referred to asdeshaling deshaling ..DryDry deshalingdeshaling technologies aretechnologies areless expensive than wetless expensive than wetcleaning processes:cleaning processes: – – Capital Cost: $6,200/tph versusCapital Cost: $6,200/tph versus

$13,000/tph$13,000/tph

– – Operating Cost: $0.50/ton versusOperating Cost: $0.50/ton versus$1.95/ton.$1.95/ton.

DeshalingDeshaling can be applied at thecan be applied at themine site prior to loading andmine site prior to loading andtransportation to the end user.transportation to the end user.

ROM Coal

High-Density Rock

Dry Coal CleaningTechnology

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All All-- Air Jig: Density Air Jig: Density --Based SeparationBased SeparationThe AllThe All-- Air Jig is a unit Air Jig is a unitmodified from the Stompmodified from the StompJig.Jig.Coal is fluidized by aCoal is fluidized by aconstant flow of airconstant flow of airacross a perforatedacross a perforatedtable.table.Pulsating air providesPulsating air providesthe jigging action.the jigging action.Nuclear density gaugeNuclear density gaugeused to assist theused to assist thecontrol of reject rate.control of reject rate.Units up to 100Units up to 100 tphtph areareavailable.available.

Raw Coal

Pulsed Air Flow

Constant Air Flow

RejectClean Coal

Product

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100100 tphtph All All-- Air Jig Performance Air Jig Performance

49.8949.89

68.1268.12

Tailings AshTailings Ash(%)(%)

7.377.37

13.7313.73

Product AshProduct Ash(%)(%)

93.4993.49

81.1081.10

Mass YieldMass Yield(%)(%)

10.1410.14

23.9323.93

Feed AshFeed Ash(%)(%)

22

11

CoalCoalTypeType

22.7922.79

8.068.06

Tailings SulfurTailings Sulfur(%)(%)

3.173.17

3.773.77

Product SulfurProduct Sulfur(%)(%)

93.4993.49

81.1081.10

Mass YieldMass Yield(%)(%)

4.334.33

6.056.05

Feed SulfurFeed Sulfur(%)(%)

22

11

CoalCoalTypeType

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FGX Separator FGX Separator Separation based on riffling tableSeparation based on riffling tableprinciples with air as medium.principles with air as medium.Processes 75 x 6 mm coal;Processes 75 x 6 mm coal;however,however, --6 mm may cleaned6 mm may cleanedseparately.separately.10%10% --20% minus 6mm material20% minus 6mm materialneeded as anneeded as an autogenousautogenousmedium.medium.

Less than 7% surface moisture.Less than 7% surface moisture.High separation densities; ~2.0High separation densities; ~2.0Relative Density (RD).Relative Density (RD).Probable error (Probable error ( EpEp) values) valuesbetween 0.2between 0.2 – – 0.3.0.3.Chinese Technology based onChinese Technology based onprevious designs. (10previous designs. (10 – – 480480 tphtphunits).units).EriezEriez Manufacturing representsManufacturing representsthe technology in the U.S..the technology in the U.S..

240 tph Commercial Unit

ProductMiddlingsTailings

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FGXFGX DeshalingDeshaling PerformancePerformance

TestNo.

Feed Ash(%)

Product Ash(%)

Middlings Ash(%)

Reject Ash(%)

Yield(%)

1 50.00 19.46 83.38 89.03 53.52 51.69 34.05 87.08 89.51 66.53 54.88 29.09 78.19 87.75 48.44 48.27 25.75 80.42 89.92 55.95 51.58 25.97 78.41 91.37 58.8

6 46.70 17.87 68.21 88.34 44.57 50.84 16.84 55.11 87.30 34.68 54.33 15.53 62.70 87.02 34.09 38.05 29.02 82.04 89.80 58.5

10 50.18 19.69 78.26 90.09 51.111 45.88 34.50 86.30 91.09 66.712 49.93 12.88 72.51 90.13 46.113 47.14 13.96 57.02 88.90 37.314 51.69 14.78 71.90 87.95 43.415 47.87 12.63 73.30 89.38 42.9

Aver. 49.27 21.47 74.32 89.17 49.5

Note the abilityto reduce ashfrom 49.3% to

12.6%

DeshalingPerformance:33.5% Reject

Rate

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East Kentucky Underground CoalEast Kentucky Underground Coal(20 mile haul distance)(20 mile haul distance)

0

20

40

60

80

100

60 70 80 90 100

Cumulative Reject Ash (%)

R e j e c t

M a s s

Y i e l d ( % )

Test 11

Test 12Test 13Test 14Test 15Test 16

88% ash

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Central Appalachia Bituminous CoalCentral Appalachia Bituminous Coal(Site No. 2)(Site No. 2)

West Virginia underground coal containing around 60%West Virginia underground coal containing around 60%ash.ash.Yield to the reject & 1.6 RD floatYield to the reject & 1.6 RD float --sink performed.sink performed.

0.7836.42.7352.44

1.3236.63.7255.13

0.9033.02.8249.52

1.5135.93.7150.71

% Float 1.6 RD% Float 1.6 RD% of Feed% of Feed% Float 1.6 RD% Float 1.6 RD% of Feed% of Feed

Reject OnlyReject OnlyMiddlingsMiddlings & Reject Combined& Reject CombinedTestTest

NumberNumber

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Economic BenefitEconomic BenefitUnit Capacity = 500Unit Capacity = 500 tphtph

Yield to Reject = 36.4%Yield to Reject = 36.4%

Reject Amount = 500 x 0.364Reject Amount = 500 x 0.364= 182= 182 tphtph

Annual Operating Hours Annual Operating Hours= 6000 hrs/yr = 6000 hrs/yr

Total Reject left at mineTotal Reject left at mine= 182 tons/hr x 6000 hrs/yr= 182 tons/hr x 6000 hrs/yr= 1,092,000 tons= 1,092,000 tons

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Lost Coal CostLost Coal CostTotalTotal Deshaler Deshaler RejectReject

= 182 tons/hr = 182 tons/hr % 1.60 Float in Reject% 1.60 Float in Reject

= 0.78%= 0.78%Total Coal LossTotal Coal Loss

= 182 x 0.0078 = 1.42= 182 x 0.0078 = 1.42 tphtph Annual Coal Loss Annual Coal Loss

= 1.42 x 6000 hrs/yr = 1.42 x 6000 hrs/yr = 8518 tons= 8518 tons

Sales Price = $50/tonSales Price = $50/tonLost Coal CostLost Coal Cost= 8518 x 50 = $425,880/yr = 8518 x 50 = $425,880/yr

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Summary Economic BenefitSummary Economic BenefitFGX Operating CostFGX Operating Cost= $0.50/ton= $0.50/ton

Annual Operating Cost Annual Operating Cost= $0.50 x 500 x 6000= $0.50 x 500 x 6000= $1,500,000/yr = $1,500,000/yr

Summary:Summary:Transportation Savings = $6.55MTransportation Savings = $6.55MCoal Loss Cost = $0.43MCoal Loss Cost = $0.43M

Operating Cost = $1.50MOperating Cost = $1.50M

Net Profit Gain = $4.62MNet Profit Gain = $4.62M

Capitol Cost = $3200/tph500 tph unit = $1.6 M

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SummarySummaryThe most recentThe most recentchanges in coalchanges in coalprocessing plants areprocessing plants arelinked to two issueslinked to two issuesaffecting plantaffecting plantefficiency:efficiency: – – Maintaining constantMaintaining constant

incremental qualitiesincremental qualities

across each circuit.across each circuit. – – Reducing effects ofReducing effects of

distribution errors.distribution errors.

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SummarySummary

Higher capacity units areHigher capacity units arebeing employed which hasbeing employed which hasreduced circuit complexity.reduced circuit complexity.Performance problemsPerformance problems

have occurred with thehave occurred with thelarge single units.large single units.Various fine coalVarious fine coal

technologies and circuitstechnologies and circuitshave been commercializedhave been commercializedto reduce separationto reduce separation

density.density.

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SummarySummary A resurgence in dry coal A resurgence in dry coalcleaning has occurred duecleaning has occurred due

to the need to process lowto the need to process lowrank coals andrank coals and deshaledeshalehighhigh --ash eastern U.S.ash eastern U.S.coals.coals.

Separators haveSeparators havedemonstrated the ability todemonstrated the ability toremove material having anremove material having anash content > 88% whichash content > 88% whichrepresents up to 60% ofrepresents up to 60% ofthe feed.the feed.Current commercialCurrent commercialinstallations are successful.installations are successful.

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