ÿWPC7 ‹‘y2øðQ±InÁ‘ ¾²^ÝÙ¡ýMR¢’˜À/V‘öZÅM»?\VÞD7`û¬)4X¶‡ï-9úƒ»ÁZ…Ñ©d¯„‚äZ›]¿¨Qœ™½X éÆt¨;:ö™g‹0çåñ½˜q‚éýbòÒŠUÏñoÞ£´{ê ˵ÜƆìgYaƒV@_§÷x_y¥F©IàÐ&3ʉ-ñuä¡ ñ¥½^…ÁŠi`q”2¸â3Tz‡—ÖŠ¿ õ`ÓÝÛBT»äv§´{Ù–|³ZH ; 2öÁˆ0b“¶}õ|·§\Ó…¡y©æ~°V„‚J.®Ï•Ÿ«Ká‡íåûáÛ‘M}…j;Åñ¨P“ÉŒ„» ™ #'ˆõÌ£Œô¾GŽ˜}îBO—C;õV¸9Éý´Wè6€P¾Ø´‘Z¬:6*oµñ‹`1•¥ç#r¥‚pÈßVZ{,æFž¢¼ªê¥äì÷|"È<™Ê,$f¶qÆ6#âäww>%-›8CÒ,ï9€Ób‹¾H[$8D¬ÂZ¼}p]~SŽr+ªà½êÔâ­>ϤJL=ÄDkÞ„÷ ã¿âP¨2轊ËUnjûœZÛüÆfTU—ø¬Ò×A–ÖXèÓ_#!2BS %• 0R››^ íw@ù49 M \ m^ u Æ} fC aE E šY 0nóNa 0Çc 0Þ* D+M3 0n7U,¥U>Ñ 0nU*}U :§§§§§Eáááááãããã B-ppppp@ oû§§§§§§§§§§§§§§§§§§§§§§§§§§ A¢3 0n?4 D3­4 B à4 0ný4 0Kk5 AQ¶5Æ6 0DÍ6˜Acrobat DistillerØÚØÚÚØØÚ0 8Ñ°XÑÑÂÂÑÒ°°ÒÒ°°Ò(ò(*ÛL$¡¡Ó  ÓÓ °š…°œXÓÚ•ì.Æ ?UA£B£C£DEDFUGEHEJD2};.8Ü 3|xJÿU‹ÿÀÀÀ Level 1Level 2Level 3Level 4Level 5ˆÇTABLE A Ý ƒ3­'ÝÓ  ÓÓ °š…°œXÓÝ  ÝÔ_ÔÓ  Óßp€V;<,(`~0©è!! `ÀœœE°X!!!!eX··pßâ  (# (#°(#°(#âà @€ àà @ àà @Š àà @ àà @” àà @ àà @ž àà @# àà @¨ àà @- àà @² à€€Ô_ÔÔ‡'ò¶­òò(òÔÔ‡'ôoõò'ò¶­ÔEPA„Ô_Ô452/F„03„025Ô#†(ôoõõ'ôo‚#ÔÔ#†(ò¶­òõ(ôo¡#ÔÔ‡(X 8Xò(ò¶­ÔÔ‡%XZXX(X 8ÔÑ @ ÑÐ X ÐÓ  ÓÓ?+Ü Ü4Œ ä <”ìDœôL¤ü!°š…?ÓÔ#†%ò{‰òX%XZ&#ÔÔ#†(ò¶­òò%ò{‰E#ÔÌÌÓ  Óà @t àò òÔ‡$ò¶­òò(ò¶­ÔÔ‡$  ž!ò$ò¶­ÔAir€Pollution€Ô_ÔControl€TechnologyÔ_Ô€Ô_ÔÐ –> ÐFactÔ_Ô€Ô_ÔSheetó óÔ#†(  ž!!$  ž2#ÔÔ#†(ò¶­ò!(  žQ#ÔÔ_ÔÐ Êr ÐÓÓò òÓ  Óó ó(F33­$§§Ý ƒÛL!ÝÓ  ÓÓ °š…°œXÓÝ  Ý(OOÿÿ&p2Ó G ÓÓ  ÓÓ8.÷÷` ¸ hÀpÈ xÐ (#8ÓÓ  ÓÓ  ÓÓ8.°°` ¸ hÀpÈ xÐ (#8Ó*X[ÿÿ(p10Ó ° ÓÓ  ÓÓ5+` °` ¸ hÀpÈ xÐ (#5ÓÓ X ÓÓ  ÓÓ  ÓÓ8.°°` ¸ hÀpÈ xÐ (#8ÓÓ  Ó'ÈÈÈÈdxd<ÿÿ:Default ParaÔ‡XXXÔÔ‡XXXÔ,2ÇÝAZ‹Arial ô\  `&Times New Roman(F33­$©©Ý ƒÛL!ÝÓ  ÓÓ °š…°œXÓÝ  Ý%ä2¼A`Arial,æ«) AZ‹"Arial Regular ƒÝ ƒ&3­)ÝÓ  ÓÓ °š…°œXÓÝ  ÝÔ_ÔßA€Y-) °°xdÿÿE°WxAßÐ X ÐòòEPA„Ô_ÔCICAÔ_Ô€Fact€Sheetà€¶¶>(#àÔ‡(ôoõò(òÔFabric€FilterˆÐ g Ðà€005(#àPulse„Jet€Cleaned€TypeóóÔ#†(ò¶­òõ(ôoó#Ô)Hairline d< ÿWPC__††††††__ ÿÀoŠ™œÿÿÿ0T#4\;c-C~%L„0R,S-]–:^—;ižHjžIt¥Vu¦W€­d­eŒ´rŒµs—¼˜¼£Ã£Ä®Ë¯ËºÒ«ºÓ¬ÆÚºÑáÇÒâÈÜéÕÝéÖèðãéñäóøñôøò-Q.T0V2[4_6f8i:m@zDF„Gˆ-O%,M)0P.5^:6g0BdDTxQrŽtv•w…ŸŠ9XF>\KC_Q±¢¤¸±ºÇ¿ÚáÜZqlª®²½Á->š.?š1A›¬/ž]jlfƒD‚jJD‚jJiYND…jg˜«/ ]jlfi`VgNƒjƒjVR‚jlJTYdš-ª/œ`jjGG‚jVVƒjgdƒj]RjjTiž)©/.5œlƒjGT`dƒjd]ƒjdiVljlViœ-ˆ/.ˆ/.ˆ/.Š/(6œYJVd‚]VgƒjVVƒji‚gRjjlV›6'.†/+ˆ/)ˆ/'+ˆ/)$=› fDd]NJjƒjVTƒj…dJjjDg™=$'-„/,%%,…/.)$+…/.)$$)-„/'$%Œ" djVTjNjD‚jJJ‚jG‡`Djf‹ "ˆ&$%)++*'ƒ$'*‚+(%‚$%(‚+)%„$(‚+'‚$ˆ / djVVjgVjdJ‚jJJ‚jJdl‚jƒJTŒ„/  …6¨$=…  „/Ž jTVjdVjdJ‚jGJ‚jJfl‡jg‹ ‡/ ƒ@%¦$„ ‡/Ž jJiVjVVJjdTƒjƒjRƒfƒdV`‰/ ‚5¦$9‚ ‰/Žl‡j`VƒjƒjVi]„VTN` Š/ @&¤$ Š/N‚jJJNVYiVƒjƒjVY‡jDŒ/ 7£$%? …/‚/‘fddf‚Vƒjƒj VfRJTJjVVDj ƒ/„/5¢$6…/ #‚/iJjV`‚jJVƒjƒjV„TjJjŽ ‚/ƒ „/  $5 „/ „‚/  Tjl`VjGDjgVƒjƒjVƒdljdJjŽ‚/…ƒ/1ž$:ƒ/…#‚/  DlfVji]jYVƒjƒjTiV‚jRdljŽ"// †#ƒ/1œ$:„/#†‚/ jJYldjVVƒjJ‚jJiGjjTJ‚jJ‚/‡‚/2š$Aƒ/ˆ‚/ jG„VjYVƒjJ‚j Jdjl]fNjJf ‚/ˆ#ƒ/30–$09ƒ/ ˆ#‚/ ‘Gj]‚iljdJ‚jGJ‚j JdigYVV`‘‚/‰ƒ/;“$0Aƒ/ #‰‚/‘ `jjGTTDjGJ‚jJTƒj‚iR„jGi"//#‰‚/C<0Ž$0Ah‚/ #‰#//“Y„jGgD‚jJVƒj‚NjjGVTDjR‚/Š! ‚/ <0ˆ$2*™(#™(# ÐÌà  àò òb.à0 ™ àTemperature:ó ó€€€Typically,€gas€temperatures€up€to€about€260ððC€(500ððF),€with€surges€to€about€290ððCÐ ’â, Ð(550ððF)€can€be€accommodated€routinely,€with€the€appropriate€fabric€material.€€Spray€coolers€orÏdilution€air€can€be€used€to€lower€the€temperature€of€the€pollutant€stream.€€This€prevents€theÏtemperature€limits€of€the€fabric€from€being€exceeded.€€€Lowering€the€temperature,€however,Ïincreases€the€humidity€of€the€pollutant€stream.€€Therefore,€the€minimum€temperature€of€the€pollutantÏstream€must€remain€above€the€dew€point€of€any€condensable€in€the€stream.€€The€baghouse€andÏassociated€ductwork€should€be€insulated€and€possibly€heated€if€condensation€may€occur.€€(EPA,Ï1998b)Ð ™(#™(# ÐÌà  àò òc.à0 ™ àPollutant€Loading:ó ó€€€Typical€inlet€concentrations€to€baghouses€are€1€to€23€grams€per€cubic€meterÐ ù&I"5 Ð(g/mòò3óó)€(0.5€to€10€grains€per€cubic€foot€(gr/ftòò3óó)),€but€in€extreme€cases,€inlet€conditions€may€varyÐ Ð' #6 Ðbetween€0.1€to€more€than€230€g/mòò3óó€(0.05€to€more€than€100€gr/ftòò3óó).€€(EPA,€1998b)Т(ò#7™(#™(# ЀÌà  àò òd.à0 ™ àOther€Considerations:ó ó€€€Moisture€and€corrosives€content€are€the€major€gas€stream€characteristicsÐ F*–%9 Ðrequiring€design€consideration.€€Standard€fabric€filters€can€be€used€in€pressure€or€vacuum€service,Ïbut€only€within€the€range€of€about€ðð€640€millimeters€of€water€column€(25€inches€of€water€column).€ÏWell„designed€and€operated€baghouses€have€been€shown€to€be€capable€of€reducing€overallÏparticulate€emissions€to€less€than€0.05€g/mòò3óó€(0.010€gr/ftòò3óó),€and€in€a€number€of€cases,€to€as€low€asÐ “-ã(= Ð0.002€to€0.011€g/mòò3óó€(0.001€to€0.005€gr/ftòò3óó).€€(AWMA,€1992)Ðe.µ)>™(#™(# Їò òÔ& ï ÔEmission€Stream€Pretreatment€Requirements:ó óÐ ° ÐÌBecause€of€the€wide€variety€of€filter€types€available€to€the€designer,€it€is€not€usually€required€to€pretreat€a€wasteÏstreamððs€inlet€temperature.€€However,€in€some€high€temperature€applications,€the€cost€of€high€temperature„¼resistant€bags€must€be€weighed€against€the€cost€of€cooling€the€inlet€temperature€with€spray€coolers€or€dilutionÏair€(EPA,€1998b).€€When€much€of€the€pollutantÔ'ï°Ù"Ô€loading€consists€of€relatively€large€particles,€mechanicalÏcollectors€such€as€cyclones€may€be€used€to€reduce€the€load€on€the€fabric€filter,€especially€at€high€inletÏconcentrations€(EPA,€1998b).€ÌÌò òCost€Information:ó óÐ  e  ÐÌCost€estimates€are€presented€below€for€pulse„jet€cleaned€fabric€filters.€€The€costs€are€expressed€in€2002Ïdollars.€€The€cost€estimates€assume€a€conventional€design€under€typical€operating€conditions€and€do€notÏinclude€auxiliary€equipment€such€as€fans€and€ductwork.€€The€costs€for€pulse„jet€cleaned€systems€areÏgenerated€using€EPAððs€cost„estimating€spreadsheet€for€fabric€filters€(EPA,€1998b).€ÌÌCosts€are€primarily€driven€by€the€waste€stream€volumetric€flow€rate€and€pollutant€loading.€€In€general,€a€smallÏunit€controlling€a€low€pollutant€loading€will€not€be€as€cost€effective€as€a€large€unit€controlling€a€high€pollutantÏloading.€€The€costs€presented€are€for€flow€rates€of€470€mòò3óó/sec€(1,000,000€scfm)€and€1.0€mòò3óó/sec€(2,000€scfm),Ð zÊ Ðrespectively,€and€a€pollutant€loading€of€9€g/mòò3óó€€(4.0€gr/ftòò3óó).Ð Lœ ÐÌPollutants€that€require€an€unusually€high€level€of€control€or€that€require€the€fabric€filter€bags€or€the€unit€itselfÏto€be€constructed€of€special€materials,€such€as€Gore„Tex€or€stainless€steel,€will€increase€the€costs€of€theÏsystem€(EPA,€1998b).€€The€additional€costs€for€controlling€more€complex€waste€streams€are€not€reflected€inÏthe€estimates€given€below.€€For€these€types€of€systems,€the€capital€cost€could€increase€by€as€much€as€75%Ïand€the€€operational€and€maintenance€(O&M)€cost€could€increase€by€as€much€as€20%.ÌñBñÓ`ÓñBñÌà  àò òa.à0 ™ àCapital€Cost:ó ó€€$13,000€to€$55,000€per€smòò3óó/s€($6€to€$26€per€scfm)ÐÜ,™(#™(# ÐÌà  àò òb.à0 ™ àO€&€M€Cost:ó ó€€$11,000€to€$50,000€per€smòò3óó/s€($5€to€$24€per€scfm),€annuallyÐ…Õ™(#™(# ÐÌà  àò òc.à0 ™ àAnnualized€Cost:ó ó€€$13,000€to€$83,000€per€smòò3óó/s€($6€to€$39€per€scfm),€annuallyÐ.~™(#™(# ÐÌà  àò òd.à0 ™ àCost€Effectiveness:ó ó€€$46€to€$293€per€metric€ton€($42€to€$266€per€short€ton)Ð×'!™(#™(# ÐÌò òñAñÓ  ÓñAñTheory€of€Operation:ó óÐ €!Ð# ÐÌIn€a€fabric€filter,€flue€gas€is€passed€through€a€tightly€woven€or€felted€fabric,€causing€PM€in€the€flue€gas€to€beÏcollected€on€the€fabric€by€sieving€and€other€mechanisms.€€Fabric€filters€may€be€in€the€form€of€sheets,Ïcartridges,€or€bags,€with€a€number€of€the€individual€fabric€filter€units€housed€together€in€a€group.€€Bags€areÏmost€common€type€of€fabric€filter.€€The€dust€cake€that€forms€on€the€filter€from€the€collected€PM€can€significantlyÏincrease€collection€efficiency.€€Fabric€filters€are€frequently€referred€to€as€baghouses€because€the€fabric€isÏusually€configured€in€cylindrical€bags.€€Bags€may€be€6€to€9€m€(20€to€30€ft)€long€and€12.7€to€30.5€centimetersÏ(cm)€(5€to€12€inches)€in€diameter.€€Groups€of€bags€are€placed€in€isolable€compartments€to€allow€cleaning€ofÏthe€bags€or€replacement€of€some€of€the€bags€without€shutting€down€the€entire€fabric€filter.€(STAPPA/ALAPCO,Ï1996)ÌÌOperating€conditions€are€important€determinants€of€the€choice€of€fabric.€€Some€fabrics€(e.g.,€polyolefins,Ïnylons,€acrylics,€polyesters)€are€useful€only€at€relatively€low€temperatures€of€95€to€150ððC€(200€to€300ððF).€€ForÏhigh-temperature€flue€gas€streams,€more€thermally€stable€fabrics€such€as€fiberglass,€Teflonòòððóó,€or€Nomexòòððóó€mustÐ ÿ,O(1 Ðbe€used€(STAPPA/ALAPCO,€1996).ÌÐ £.ó)3 ÐPractical€application€of€fabric€filters€requires€the€use€of€a€large€fabric€area€in€order€to€avoid€an€unacceptableÏpressure€drop€across€the€fabric.€€Baghouse€size€for€a€particular€unit€is€determined€by€the€choice€of€air-to-clothÏratio,€or€the€ratio€of€volumetric€air€flow€to€cloth€area.€The€selection€of€air-to-cloth€ratio€depends€on€theÏparticulate€loading€and€characteristics,€and€the€cleaning€method€used.€€A€high€particulate€loading€will€requireÏthe€use€of€a€larger€baghouse€in€order€to€avoid€forming€too€heavy€a€dust€cake,€which€would€result€in€anÏexcessive€pressure€drop€€€As€an€example,€a€baghouse€for€a€250€MW€utility€boiler€may€have€5,000€separateÏbags€with€a€total€fabric€area€approaching€46,500€mòò2óó€(500,000€square€feet).€€(ICAC,€1999)Ð œ ì ÐÌDeterminants€of€baghouse€performance€include€the€fabric€chosen,€the€cleaning€frequency€and€methods,€andÏthe€particulate€characteristics.€Fabrics€can€be€chosen€which€will€intercept€a€greater€fraction€of€particulate,€andÏsome€fabrics€are€coated€with€a€membrane€with€very€fine€openings€for€enhanced€removal€of€submicronÏparticulate.€€Such€fabrics€tend€to€be€more€expensive.€ÌÌPulse„jet€cleaning€of€fabric€filters€is€relatively€new€compared€to€other€types€of€fabric€filters,€since€they€have€onlyÏbeen€used€for€the€past€30€years.€€This€cleaning€mechanism€has€consistently€grown€in€popularity€because€itÏcan€treat€high€dust€loadings,€operate€at€constant€pressure€drop,€and€occupy€less€space€than€other€types€ofÏfabric€filters.€€Pulse„jet€cleaned€fabric€filters€can€only€operate€as€external€cake€collection€devices.€€The€bagsÏare€closed€at€the€bottom,€open€at€the€top,€and€supported€by€internal€retainers,€called€cages.€€Particulate„ladenÏgas€flows€into€the€bag,€with€diffusers€often€used€to€prevent€oversized€particles€from€damaging€the€bags.€TheÏgas€flows€from€the€outside€to€the€inside€of€the€bags,€and€then€out€the€gas€exhaust.€€The€particles€are€collectedÏon€the€outside€of€the€bags€and€drop€into€a€hopper€below€the€fabric€filter.€€(EPA,€1998a)ÌÌDuring€pulse„jet€cleaning,€a€short€burst,€0.03€to€0.1€seconds€in€duration,€of€high€pressure€[415€to€830ÏkiloPascals€(kPa)€(60€to€120€pounds€per€square€inch€gage€(psig))]€air€is€injected€into€the€bags€(EPA,€1998a;ÏAWMA,€1992).€€The€pulse€is€blown€through€a€venturi€nozzle€at€the€top€of€the€bags€and€establishes€a€shockÏwave€that€continues€onto€the€bottom€of€the€bag.€€The€wave€flexes€the€fabric,€pushing€it€away€from€the€cage,Ïand€then€snaps€it€back€dislodging€the€dust€€cake.€€The€cleaning€cycle€is€regulated€by€a€remote€timer€connectedÏto€a€solenoid€valve.€€The€burst€of€air€is€controlled€by€the€solenoid€valve€and€is€released€into€blow€pipes€thatÏhave€nozzles€located€above€the€bags.€€The€bags€are€usually€cleaned€row€by€row€€(EPA,€1998a).ÌÌThere€are€several€unique€attributes€of€pulse„jet€cleaning.€€Because€the€cleaning€pulse€is€very€brief,€the€flowÏof€dusty€gas€does€not€have€to€be€stopped€during€cleaning.€€The€other€bags€continue€to€filter,€taking€on€extraÏduty€because€of€he€bags€being€cleaned.€€In€general,€there€is€no€change€in€fabric€filter€pressure€drop€orÏperformance€as€a€result€of€pulse„jet€cleaning.€€This€enables€the€pulse„jet€fabric€filters€to€operate€on€aÏcontinuous€basis€with€solenoid€valves€as€the€only€significant€moving€parts.€€Pulse„jet€cleaning€is€also€moreÏintense€and€occurs€with€greater€frequency€than€the€other€fabric€filter€cleaning€methods.€€This€intense€cleaningÏdislodges€nearly€all€of€the€dust€cake€each€time€the€bag€is€pulsed.€€As€a€result,€pulse„jet€filters€do€not€rely€onÏa€dust€cake€to€provide€filtration.€€Felted€(non„woven)€fabrics€are€used€in€pulse„jet€fabric€filters€because€theyÏdo€not€require€a€dust€cake€to€achieve€high€collection€efficiencies.€€It€has€been€found€that€woven€fabrics€usedÏwith€pulse„jet€fabric€filters€leak€a€great€deal€of€dust€after€they€are€cleaned.€€(EPA,€1998a)ÌÌSince€bags€cleaned€by€the€pulse„jet€method€do€not€need€to€be€isolated€for€cleaning,€pulse„jet€cleaned€fabricÏfilters€do€not€need€extra€compartments€to€maintain€adequate€filtration€during€cleaning.€€Also,€because€of€theÏintense€and€frequent€nature€of€the€cleaning,€they€can€treat€higher€gas€flow€rates€with€higher€dust€loadings.€ÏConsequently,€fabric€filters€cleaned€by€the€pulse„jet€method€can€be€smaller€than€other€types€of€fabric€filtersÏin€the€treatment€of€the€same€amount€of€gas€and€dust,€making€higher€gas„to„cloth€ratios€achievable.€€(EPA,Ï1998a)ÌÌò òAdvantagesñHñ/ProsñHñ:ó óÐ ,`'0 ÐÌFabric€filters€in€general€provide€high€collection€efficiencies€on€both€coarse€and€fine€(submicron)€particulates.€ÏThey€are€relatively€insensitive€to€fluctuations€in€gas€stream€conditions.€€Efficiency€and€pressure€drop€areÐ ‰.Ù)3 Ðrelatively€unaffected€by€large€changes€in€inlet€dust€loadings€for€continuously€cleaned€filters.€€Filter€outlet€airÏis€very€clean€and€may€be€recirculated€within€the€plant€in€many€cases€(for€energy€conservation).€€CollectedÏmaterial€is€collected€dry€for€subsequent€processing€or€disposal.€€Corrosion€and€rusting€of€components€areÏusually€not€problems.€€Operation€is€relatively€simple.€€Unlike€electrostatic€precipitators,€fabric€filter€systemsÏdo€not€require€the€use€of€high€voltage,€therefore,€maintenance€is€simplified€and€flammable€dust€may€beÏcollected€with€proper€care.€€The€use€of€selected€fibrous€or€granular€filter€aids€(precoating)€permits€the€high„¼efficiency€collection€of€submicron€smokes€and€gaseous€contaminants.€€Filter€collectors€are€available€in€a€largeÏnumber€of€configurations,€resulting€in€a€range€of€dimensions€and€inlet€and€outlet€flange€locations€to€suitÏinstallation€Ô& Ò Ôrequirements.€€(AWMA,€1992)Ô'Ò@ —HÔÌÌò òÔ& y ÔDisadvantagesñGñ/ConsñGñ:ó óÐ ä 4  ÐÌTemperaturesÔ'yä ÖHÔ€much€in€excess€of€290ñJñððñJñC€(550ððF)€require€special€refractory€mineral€or€metallic€fabrics,€whichÏcan€be€expensive.€€Certain€dusts€may€require€fabric€treatments€to€reduce€dust€seepage,€or€in€other€cases,Ïassist€in€the€removal€of€the€collected€dust.€€Concentrations€of€some€dusts€in€the€collector,€approximately€50Ïg/mòò3óó€(22€gr/ftòò3óó),€may€represent€a€fire€or€explosion€hazard€if€a€spark€or€flame€is€accidentally€admitted.€€FabricsÐ Q  Ðcan€burn€if€readily€oxidizable€dust€is€being€collected.€€Fabric€filters€have€relatively€high€maintenanceÏrequirements€(e.g.,€periodic€bag€replacement).€€Fabric€life€may€be€shortened€at€elevated€temperatures€andÏin€the€presence€of€acid€or€alkaline€particulate€or€gas€constituents.€€They€cannot€be€operated€in€moistÏenvironments;€hygroscopic€materials,€condensation€of€moisture,€or€tarry€adhesive€components€may€causeÏcrusty€caking€or€plugging€of€the€fabric€or€require€special€additives.€€Respiratory€protection€for€maintenanceÏpersonnel€may€be€required€when€replacing€fabric.€€Medium€pressure€drop€is€required,€typically€in€the€rangeÏof€100€to€250€mm€of€water€column€(4€to€10€inches€of€water€column).€€(AWMA,€1992)ÌÌA€specific€disadvantage€of€pulse„jet€units€that€use€very€high€gas€velocities€is€that€the€dust€from€the€cleanedÏbags€can€be€drawn€immediately€to€the€other€bags.€€If€this€occurs,€little€of€the€dust€falls€into€the€hopper€and€theÏdust€layer€on€the€bags€becomes€too€thick.€€To€prevent€this,€pulse„jet€fabric€filters€can€be€designed€withÏseparate€compartments€that€can€be€isolated€for€cleaning.€€(EPA,€1998a)ÌÌò òÔ& y ÔOther€Considerations:ó óÐ }Í ÐÌFabric€filters€are€useful€Ô'y}èOÔfor€collecting€particles€with€resistivities€either€too€low€or€too€high€for€collection€withÏelectrostatic€precipitators.€€Fabric€filters€therefore€may€be€good€candidates€for€collecting€fly€ash€from€low-sulfurÏcoals€or€fly€ash€containing€high€unburned€carbon€levels,€which€respectively€have€high€and€low€resistivities,€andÏthus€are€relatively€difficult€to€collect€with€electrostatic€precipitators.€€(STAPPA/ALAPCO,€1996)ñ?ñÌñ?ññAñÓj-ÓñAññDññ?ñÌÌñ?ñÌñDñÌò òReferences:ó óÐ >"Ž$ ÐÌAWMA,€1992.€€Air€&€Waste€Management€Association,€€òòAir€Pollution€Engineering€Manualóó,€Van€NostrandÐ å#5& ÐReinhold,€New€York.€ñEñÌñEññFñÌñFñÌEPA,€1997.€€U.S.€EPA,€Office€of€Air€Quality€Planning€and€Standards,€ð ðCompilation€of€Air€PollutantÏEmission€Factors,€Volume€I,€Fifth€Edition,€Research€Triangle€Park,€NC.,€October.ÌÌEPA,€1998a.€€U.S.€EPA,€Office€of€Air€Quality€Planning€and€Standards,€ð ðStationary€Source€ControlÏTechniques€Document€for€Fine€Particulate€Matter,ðð€EPA„452/R„97„001,€Research€Triangle€Park,€NC.,ÏOctober.ÌÌEPA,€1998b.€€U.S.€EPA,€Office€of€Air€Quality€Planning€and€Standards,€ð ðOAQPS€Control€Cost€Manual,ððÏFifth€Edition,€Chapter€5,€€EPA€453/B„96„001,€Research€Triangle€Park,€NC.€December.€Ìâ âÐ ½- )2 ÐICAC,€1999.€€Institute€of€Clean€Air€Companies€internet€web€page€www.icac.com,€Control€TechnologyÏâ âInformation€„€Fabric€Filters,€page€last€updated€January€11,€1999.ÌÌSTAPPA/ALAPCO,€1996.€€State€and€Territorial€Air€Pollution€Program€Administrators€and€Association€ofÏLocal€Air€Pollution€Control€Officials,€ð ðControlling€Particulate€Matter€Under€the€Clean€Air€Act:€A€Menu€ofÏOptions,ðð€July.€