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TypeofTechnology: _____Removal_ԀofPMbyreducingthegasvelocitytoenablethedusttosettleoutbythe xj  actionofgravity. ApplicablePollutants:  (    _Settling_ԀchambersareusedtocontrolPM,andprimarilyPMgreaterthan10micrometers_(XX<7Xs XXX378#X3X XXs?#8<81X XXX#1  X1X#1~  1m#1  1~##* 1^#m)in   aerodynamicdiameter.MostdesignsonlyeffectivelycollectPMgreaterthanapproximately50898%899XX*9<9Xs XXX39;#X3X XXs#;<;1X XXX#1  X1X#1~  1m#1  1~k##* 1)#m(Wark, {m  1981;Perry,1984;EPA,1998). *Xg X ;9 \N    ?+ 4 <DL!?#  XXg+ ##*  #*1~ 9;9m9;9#1  1~ ##* 1 #9;8m(Wark,1981;Perry,1984;EPA,1998).8;8 *Xg X 897  79?+ 4 <DL!X?__#  XXg #87  78#*  # *87#  #78 # #1~ 87m78#1  1~s ##* 1 #8m)_Ԁinaerodynamicdiameter.MostdesignsonlyeffectivelycollectPMgreaterthanapproximately50%m   (_Wark_,1981;Perry,1984;EPA,1998).8_ AchievableEmissionLimits/Reductions:   _The_Ԁcollectionefficiencyofsettlingchambersvariesasafunctionofparticlesizeandsettlingchamberdesign.Settlingchambersaremosteffectiveforlargeand/ordenseparticles.Gravitationalforcemaybeemployedtoremoveparticleswherethesettlingvelocityisgreaterthanabout13centimeterspersecond(cm/s)(25feetperminute(ft/min)).Ingeneral,thisappliestoparticleslargerthan50_?%??XX*Xg XXX?+ 4 <DL!X?#  XXg?# #^## # #!#1~ m#1  1~c##* 1#?m_Ԁiftheparticledensityislow,down  to10_@%@@XX*Xg XXX?+ 4 <DL!X?#  XXg# ### $# #f#1~ m#1  1~##* 1#@m_Ԁifthematerialdensityisreasonablyhigh.Particlessmallerthanthiswouldrequireexcessive  horizontalflowdistances,whichwouldleadtoexcessivechambervolumes.ThecollectionefficiencyforPMlessthanorequalto10_A%AAXX*Xg XXX?+ 4 <DL!X?#  XXg# ### $# #f#1~ m#1  1~##* 1#Am_Ԁinaerodynamicdiameter(PM10)istypicallylessthan10percent.Multipletray  w chambershavelowervolumerequirementsforthecollectionofparticlesassmallas15_B%BBXX*Xg XXX?+ 4 <DL!X?#  XXgL# #k## # #.#1~ m#1  1~p##* 1#Bm_Ԁ(_Wark_,1981; f!X _Mycock_,1995;EPA,1998). ApplicableSourceType: Point #  &  TypicalIndustrialApplications:  %! '%_Despite_Ԁlowcollectionefficiencies,settlingchambershavebeenusedextensivelyinthepast.Themetalsrefiningindustrieshaveusedsettlingchamberstocollectlargeparticles,suchasarsenictrioxidefromthesmeltingofarsenicalcopperores.Powerandheatingplantshaveusedsettlingchamberstocollectlargeunburnedcarbonparticlesfor_reinjection_Ԁintotheboiler.Theyareparticularlyusefulforindustriesthatalsoneedtocoolthegasstreampriortotreatmentinafabricfilter(_Mycock_,1995)._Settling_Ԁchambershavebeenusedtopreventexcessiveabrasionanddustloadinginprimarycollectiondevicesbyremovinglargeparticlesfromthegasstream,suchaseitherveryhighdustloadingsorextremelycoarseparticleswhichmightdamageadownstreamcollectorinserieswiththesettlingchamber.Theupstreamuseofsettlingchambershasdeclinedwithimprovementsinacceptableloadingofother,_moreefficient,controldevicesandincreasingspacerestrictionsatfacilities.Incaseswheresparksorheated o/a%-  TRY3'Avery 5162 AddressX3' Letter3'$Avery 5162 Address3'TX   materialispresentinthewastegas,settlingchambersarestillusedtoserveas sparktrapstopreventa  downstreambaghouseorfilterfromcatchingfire(Wark,1981;EPA,1998;Josephs,1999;Davis,1999).Thesedevicesaregenerallyconstructedforaspecificapplicationfromductmaterials,thoughalmostanymaterialcanbeused.Settlingchambershavebeenreplaced,formostapplications,bycyclonesprimarilyduetothelowerspacerequirementsandthehighercollectionefficiencyofcyclones.Multipletraysettlingchambershaveneverbeenwidelyusedbecauseofthedifficultyinremovingthesettleddustfromthehorizontaltrays(Mycock,1995;Josephs,1999).̀ EmissionStreamCharacteristics:   b    a.0 ` AirFlow: Thesimpledesignandconstructionofsettlingchambersallowsforalmostany   sizeandwastegasflowrate,butsizeisusuallyrestrictedtoa4.25meter(14foot)squareshippingsize.Unitsrestrictedbythisshippingconstraintwillgenerallyhaveflowrateswhichrangeupto50standardcubicmeterspersecond(sm3/sec)(106,000standardcubicfeetper 4  minute(scfm)).Typicalsettlingchamberwastegasflowcapacityis0.25to0.5sm3/secper V  cubicmeterofchambervolume(15to30scfmpercubicfootofchambervolume)(Wark,1981;Andriola,1999). ` (#` (#   b.0 ` Temperature: Inletgastemperaturesareonlylimitedbythematerialsofconstructionofthe N settlingchamber,andhavebeenoperatedattemperaturesashighas540C(1000F)(Wark,1981;Perry,1984). ` (#` (#   c.0 ` PollutantLoading: Wastegaspollutantloadingscanrangefrom20to4,500gramsper  standardcubicmeter(g/sm3)(9to1,970grainsperstandardcubicfoot(gr/scf)).Multipletray r settlingchamberscanonlyhandleinletdustconcentrationsoflessthanapproximately2.3g/sm3(1.0gr/scf)(Mycock,1995;Parsons,1999;Steinbach,1999;Josephs,1999).f` (#` (#   d.0 ` OtherConsiderations: Leakageofcoldairintoasettlingchambercancauselocalgas   quenchingandcondensation.Condensationcancausecorrosion,dustbuildup,andpluggingofthehopperordustremovalsystem.Theuseofthermalinsulationcanreduceheatlossandpreventcondensationbymaintainingtheinternaldevicetemperatureoftheabovethedewpoint(EPA,1982). ` (#` (#  EmissionStreamPretreatmentRequirements: Nopretreatmentisnecessaryforsettlingchambers.  "  & y CostInformation:  T"$ 'yT",Thefollowingarecostranges(expressedinthirdquarter1995dollars)forasingleconventionalexpansiontypesettlingchamberundertypicaloperatingconditions,developedusingamodifiedEPAcostestimatingspreadsheet(EPA,1996),andreferencedtothevolumetricflowrateofthewastestreamtreated.Forpurposesofcalculatingtheexamplecosteffectiveness,flowratesareassumedtobebetween0.25and50sm3/sec(530and106,000scfm),theinletPMloadingconcentrationisassumedtorangefromapproximately C'"* 20to4,500g/sm3(9to1,970gr/scf)andthecontrolefficiencyisassumedtobe50percent.Thecostsdonot (e#+ includecostsfordisposalortransportofcollectedmaterial.Capitalcostscanbehigherthanintherangesshownforapplicationswhichrequireexpensivematerials.Asarule,smallerunitscontrollingalowconcentrationwastestreamwillbemoreexpensive(perunitvolumetricflowrate)thanalargeunitcleaningahighpollutantloadflow.  a.0 ` CapitalCost: $330to$10,900persm3/sec($0.16to$5.10perscfm)-Q(1` (#` (#   b.0 ` O&MCost: $13to$470persm3/sec($0.01to$0.22perscfm),annually.)3` (#` (# Ї  c.0 ` AnnualizedCost: $40to$1,350persm3/sec($0.02to$0.64perscfm),annually` (#` (#   d.0 ` CostEffectiveness: $0.01to$3.90permetricton($0.01to$3.50pershortton),annualized Y costpertonperyearofpollutantcontrolled ` (#` (#  TheoryofOperation:  $ Settlingchambers,whichrelyongravitationalsettlingasacollectionmechanism,arethesimplestandoldestmechanicalcollectors.Settlingchambersaregenerallybuiltintheformoflong,horizontal,rectangularchamberswithaninletatoneendandanexitatthesideortopoftheoppositeend.Flowwithinthechambermustbeuniformandwithoutanymacroscopicmixing.Uniformflowisoftenensuredbyflowstraightenersattheinlettothechamber.Hoppersareusedtocollectthesettledoutmaterial,thoughdragscrapersandscrewconveyershavealsobeenemployed.Thedustremovalsystemmustbesealedtopreventairfromleakingintothechamberwhichincreasesturbulence,causesdustreentrainment,andpreventsdustfrombeingproperlydischargedfromthedevice(EPA,1982;Wark,1981;Corbitt,1990;Perry,1984;Mycock,1995;Avallone,1996;EPA,1998).Therearetwoprimarytypesofsettlingchambers:theexpansionchamberandthemultipletraychamber.Intheexpansionchamber,thevelocityofthegasstreamissignificantlyreducedasthegasexpandsinalargechamber.Thereductioninvelocityallowslargerparticlestosettleoutofthegasstream(EPA,1982;Wark,1981;Perry,1984;Mycock,1995;EPA,1998).Amultipletraysettlingchamberisanexpansionchamberwithanumberofthintrayscloselyspacedwithinthechamber,whichcausesthegastoflowhorizontallybetweenthem.Whilethegasvelocityisincreasedslightlyinamultipletraychamber,whencomparedtoasimpleexpansionchamber,thecollectionefficiencygenerallyimprovesbecausetheparticleshaveamuchshorterdistancetofallbeforetheyarecollected.Multipletraysettlingchambershavelowervolumerequirementsthanexpansiontypesettlingchambersforthecollectionofsmallparticles(YY15T%TT?+ 4 <DL!X?TT*1~ m#1  1~};##* 1;#TmZorgreaterZ)(EPA,1998). 3 Theefficiencyofsettlingchambersincreaseswithresidencetimeofthewastegasinthechamber.Becauseofthis,settlingchambersareoftenoperatedatthelowestpossiblegasvelocities.Inreality,thegasvelocitymustbelowenoughtopreventdustformbecomingreentrained,butnotsolowthatthechamberbecomesunreasonablylarge.Thesizeoftheunitisgenerallydrivenbythedesiredgasvelocitywithintheunit,whichshouldbelessthan3meterspersecond(m/s)(10feetpersecond(ft/sec)),andpreferablylessthan0.3m/s(1ft/sec)(Wark,1981;Corbitt,1990;Mycock,1995;EPA,1998). Advantages:  T"$ Advantagesofsettlingchambersinclude(Wark,1981;Corbitt,1990;Perry,1984;Mycock,1995;andEPA,1998):b Q(eh83Ib J3     J3?2eh  1  .3  0 `   Lowcapitalcost;J3??݌q&!)` (#` (# Ќ   J3     J3@2eh  2  .3  0 `   Verylowenergycost;J3@@݌'"+` (#` (# Ќ   J3     J3~A2eh  3  .3  0 `   Nomovingparts,therefore,fewmaintenancerequirementsandlowoperatingcosts;J3~AA݌(#-` (#` (# Ќ   J3     J3B2eh  4  .3  0 `   Excellentreliability;J3BB݌)%/` (#` (# Ќ   J3     J3C2eh  5  .3  0 `   Lowpressuredropthroughdevice;J3CC݌*9&1` (#` (# Ќ   J3     J3D2eh  6  .3  0 `   Devicenotsubjecttoabrasionduetolowgasvelocity;J3DD݌,W'3` (#` (# Ќ   J3     J3E2eh  7  .3  0 `   Provideincidentalcoolingofgasstream;J3EE݌%-u(5` (#` (# Ќ   J3     J3F2eh  8  .3  0 `   Drycollectionanddisposal;andJ3FF݌C.)7` (#` (# Ќ   J3     J3yG2eh  9  .3  0 `   Temperatureandpressurelimitationsareonlydependentonthematerialsofconstruction.J3yGG݌a/*9` (#` (# Ќ   Disadvantages:   Disadvantagesofsettlingchambersinclude(Wark,1981;Mycock,1995;andEPA,1998): b "(Uh88Qb J3   0  J3I2Uh  1  .3  0` (#(#  RelativelylowPMcollectionefficiencies,particularlyforPMlessthan50OXX*Xg XXXOPOJ3IJ݌` (#` (# Ќ  OPO?+ 4 <DL!X?#  XXgJ##* J#*1~ OQOmOQO#1  1~K##* 1K#OQXX*QTQXg XXXQR#XX XXgK#RTR1X XXX#1  X1XL#1~  1m#1  1~RM##* 1M#minsize; *Xg X RSQJ3+ItI݌` (#` (# Ќ  QSQ?+ 4 <DL!X?#  XXgM#QRQ QRQ#* M# *QRQ# L#QRQ ##O#1~ QRQmQRQ#1  1~O##* 1O#QRminsize;RJ3IJ݌` (#` (# Ќ   J3   0  J3P2Uh  2  .3  0` (#(#  Unabletohandlestickyortackymaterials;J3PP݌ P` (#` (# Ќ   J3   0  J3Q2Uh  3  .3  0` (#(#  Largephysicalsize;andJ3QQ݌ n ` (#` (# Ќ   J3   0  J3R2Uh  4  .3  0` (#(#  Traysinmultipletraysettlingchambermaywarpduringhightemperatureoperations.J3RR݌<  ` (#` (# Ќ  b G( 88"b &  OtherConsiderations: ',dT ,|  Themostcommonfailuremodeofsettlingchambersispluggingofthechamberwithcollecteddust.Inexpansionsettlingchambersthepluggingcanresultfromhopperbridgingorhopperdischargesealfailure.Multipletraysettlingchambersmayexperiencepluggingoftheindividualgaspassages.Suchfailurescanbepreventedorminimizedbyuseofhopperlevelindicatorsorbycontinuousmonitoringofthedustdischarge.Scheduledinternalinspectioncandetermineareasofairleakageandcondensation,bothofwhichmaycausehopperbridging.Normalinstrumentationforasettlingchambergenerallyincludesonlyanindicatorofdifferentialstaticpressure.Anincreaseinstaticpressuredropcanindicateplugging(EPA,1982). References:  c Andriola,1999.T.Andriola,FisherKlosterman,Inc.,(502)5724000,personalcommunicationwithEricAlbright,October14,1999.AWMA,1992.Air&WasteManagementAssociation,AirPollutionEngineeringManual,VanNostrand  Reinhold,NewYork,NY,1992.Avallone,1996. MarksStandardHandbookforMechanicalEngineers,editedbyEugeneAvalloneandTheodoreBaumeister,McGrawHill,NewYork,NY,1996.Corbitt,1990. StandardHandbookofEnvironmentalEngineering,editedbyRobertCorbitt,McGrawHill,NewYork,NY,1990.Davis,1999.W.Davis,ProfessorandCoordinator,EnvironmentalEngineeringProgram,DepartmentofCivilandEnvironmentalEngineering,UniversityofTennessee,(423)9747728,personalcommunicationwithE.Albright,October28,1999.EPA,1982.U.S.EPA,OfficeofAirQualityPlanningandStandards, ControlTechniquesforParticulateEmissionsfromStationarySourcesVolume1,EPA450/381005a,ResearchTrianglePark,NC,September,1982.EPA,1996.U.S.EPA,OfficeofAirQualityPlanningandStandards, OAQPSControlCostManual,FifthEdition,EPA453/B96001,ResearchTrianglePark,NC,February,1996.EPA,1998.U.S.EPA,OfficeofAirQualityPlanningandStandards, StationarySourceControlTechniquesDocumentforFineParticulateMatter,EPA452/R97001,ResearchTrianglePark,NC,October,1998.Josephs,1999.D.Josephs,EquipmentProductManager,AAFInternational,(502)6370313,personalcommunicationwithEricAlbright,October28,1999. /R*6 Mycock,1995.J.Mycock,J.McKenna,andL.Theodore, HandbookofAirPollutionControlEngineeringandTechnology,CRCPress,BocaRaton,FL,1995.Parsons,1999.B.Parsons,SterlingSystems,Inc.,(804)3165310,personalcommunicationwithE.Albright,October26,1999.Perry,1984. PerrysChemicalEngineersHandbook,editedbyRobertPerryandDonGreen,6thEdition,   McGrawHill,NewYork,NY,1984.Steinbach,1999.R.Steinbach,SolidsProcessingEquipmentCo.,(714)7799279,personalcommunicationwithE.Albright,October26,1999.Wark,1981.KennethWarkandCecilWarner, AirPollution:ItsOriginandControl,HarperCollins,NewYork,NY,1981.