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…/‚/‘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$2(#àFabric€FilterˆÐ g Ðà€rr-(#àMechanical€Shaker€Cleaned€Typeóó)Hairline d W[ I&mage <=8ÿÿÿÿÿÿÿÿÿÿCÿÿ HKKKK(F33­$££Ý ƒÛL!ÝÓ  ÓÓ °š…°œXÓÝ  ÝYYYY'ÿÿdxd d(F33­$¢¢Ý ƒÛL!ÝÓ  ÓÓ °š…°œXÓÝ  Ý( ±þ$’’ò òFigure€Ú  Ú1Ú  Úó ó]ZW^XCþÿ<<CÿÿƒLevel 1Level 2Level 3Level 4Level 5($$””ò òÚ  Ú1Ú  Úó óÝ ƒÛL!ÝÓ  ÓÓ °š…°œXÓÝ  ÝÔ_ÔÔ_ÔѰÑÑ  ÑÓ™ÓÑX°ÑÑ8€C®&òd¿dÉ8Ñò òÔ_ÔÖ€ÿÿÖÔ_ÔÑÈÑÔ_ÔÖ€0ÿÿÖÔ_ÔÑ€ÅÑÌName€of€Technologyó ó:à0 ( àFabric€Filter€„€Mechanical€Shaker€Cleaned€Ô_ÔTypeÔ_ÔÔ_ÔÔ_ÔÐã Õ( (#( (# Ðà0  àà0™(#(#àà0 ™(#™(#àà0£  (# (#àà0( £ (#£ (#àà0­ ( (#( (#àÔ_Ô€€€€€€€€€€€Ô_ÔÔ_ÔÔ_ÔÔ_ÔÔ_ÔÔ_ÔÔ_ÔÔ_Ô„Ô_Ô€Mechanical€Shaker€Cleaned€Type€Ô_ÔwithÔ_ÔÔ_ÔÔ_Ôà Z àÔ_ÔSonic€Horn€EnhancementÔ_Ôà ó" àà @ó" àà @ó" àà @ó" àà @ó" àà @ó" àà @ó" àÔ_ÔÔ_Ôк ¬­ (#­ (# Ðà  àà ™ àà  àà £ àà ( àà ­ àÔ_Ô€€€€€€Ô_ÔÔ_ÔÔ_Ô€€€€€€Ô_Ô(alsoÔ_Ô€referred€to€as€Ô_ÔBaghousesÔ_Ô)ÌÌò òType€of€Technology:ó óà0 ( àControl€Device€„€Capture/DisposalÐ0"( (#( (# ÐÌò òÔ_ÔÓ  ÓApplicableÔ_Ô€Pollutants:ó óà ( àParticulate€Matter€(PM),€including€particulate€matter€less€than€or€equal€to€10Ð ÙË Ðmicrometers€(Ô_ÔððmÔ_Ô)€in€aerodynamic€diameter€(PMòò10óó),€particulate€matter€less€than€or€equal€to€2.5€Ô_ÔððmÔ_Ô€inÐ °¢ Ðaerodynamic€diameter€(PMòò2.5óó),€and€hazardous€air€pollutants€(Ô_ÔHAPsÔ_Ô)€that€are€in€particulate€form,€such€as€mostÐ ‚t  Ðmetals€(except€mercury€is€the€notable€exception,€as€a€significant€portion€of€emissions€are€in€the€form€ofÏelemental€Ô_Ôvapor).Ô_ÔÌÌò òAchievable€Emission€Limits/Reductions:ó ó€Ð ʼ  ÐÌÔ_ÔTypicalÔ_Ô€new€equipment€design€efficiencies€are€between€99€and€99.9%.€€Older€existing€equipment€have€a€rangeÏof€actual€operating€efficiencies€of€95€to€99.9%.€€Several€factors€determine€fabric€filter€collection€efficiency.€ÏThese€include€gas€filtration€velocity,€particle€characteristics,€fabric€characteristics,€and€cleaning€mechanism.€ÏIn€general,€collection€efficiency€increases€with€increasing€filtration€velocity€and€particle€size.€€ÌÌÔ_ÔForÔ_Ô€a€given€combination€of€filter€design€and€dust,€the€effluent€particle€concentration€from€a€fabric€filter€is€nearlyÏconstant,€whereas€the€overall€efficiency€is€more€likely€to€vary€with€particulate€loading.€€For€this€reason,€fabricÏfilters€can€be€considered€to€be€constant€outlet€devices€rather€than€constant€efficiency€devices.€€ConstantÏeffluent€concentration€is€achieved€because€at€any€given€time,€part€of€the€fabric€filter€is€being€cleaned.€€As€aÏresult€of€the€cleaning€mechanisms€used€in€fabric€filters,€the€collection€efficiency€is€constantly€changing.€€EachÏcleaning€cycle€removes€at€least€some€of€the€filter€cake€and€loosens€particles€which€remain€on€the€filter.€€WhenÏfiltration€resumes,€the€filtering€capability€has€been€reduced€because€of€the€lost€filter€cake€and€loose€particlesÏare€pushed€through€the€filter€by€the€flow€of€gas.€€As€particles€are€captured,€the€efficiency€increases€until€theÏnext€cleaning€cycle.€€Average€collection€efficiencies€for€fabric€filters€are€usually€determined€from€tests€thatÏcover€a€number€of€cleaning€cycles€at€a€constant€inlet€loading.€€(EPA,€1998a)ÌÓÖÓÌò òApplicable€Source€Type:€€ó óPointÐ “#… ÐÌò òÔ& y ÔTypical€Industrial€Applications:ó óÐ <%.! ÐÌÓ  ÓÔ_ÔÔ_ÔÔ_ÔÔ'y<%NÔFabricÔ_Ô€filters€can€perform€very€effectively€in€many€different€applications.€€Common€applications€of€fabric€filterÏsystems€with€mechanical€shaker€cleaning€are€presented€in€Table€1,€however,€fabric€filters€can€be€used€in€mostÏany€process€where€dust€is€generated€and€can€be€collected€and€Ô_ÔductedÔ_Ô€to€a€central€location.€€Sonic€hornÏenhancement€of€mechanical€shaker€cleaning€is€generally€used€for€applications€with€dense€Ô_ÔparticulatesÔ_Ô€suchÏas€utility€boilers,€metal€processing,€and€mineral€products.Ìâ âÓ“ÓÐ ý*ï ( ÐÑÅÑâ âÑTRY3Ø'Avery 5162 AddressXà3Ø' Letter3Ø'$Avery 5162 Addressÿ3Ø'TÑѰXÑÑÂÂÑÒ°°ÒÒ°°Òâ âÑ  ÑÔ_ÔÖ€¶ÖÔ& ` Ôâ ââ âò òÓ  ÓTable€1.€€Typical€Industrial€Applications€of€Shaker€Cleaned€Fabric€Filters€(EPA,€1998a)ó óÐ ° ÐÓYÓÌÔ*‹ƒÜd dd Xdd Xdd X°(#°(#‹ÔÔ,Òdd ÔÔ,ø dd ÔÔ+  ÔÐ .€YY W§ ‚$‚ƒƒ„„.ÐApplicationÐ =€YY,!{ËYY „„=ÐSource€Category€Code€(SCC)Ð ;1'{Ë $ YY ‚$‚ƒƒ;ÐUtility€Boilers€(Coal)Ð  yÉ Ð1„01„002...003Ð #yÉ $ ‚$‚ƒƒ#ÐNon„Ferrous€Metals€Processing€Ì(Primary€and€Secondary):Ð  F – ÐÐ #tÄ  $ ‚$‚ƒƒ#ÐÓ  ÓCopperÐ A ‘ 0 Ð3„03„005,€3„04„002Ð #A ‘  $ ‚$‚ƒƒ#ÐÓ  ÓLeadÐ < Œ 0 Ð3„03„010,€3„04„004Ð #< Œ  $ ‚$‚ƒƒ#ÐÓ  ÓZincÐ 7 ‡0 Ð3„03„030,€3„04„008Ð #7 ‡ $ ‚$‚ƒƒ#ÐÓ  ÓAluminumÐ 2 ‚0 Ð3„03„000...002Ì3„04„001Ð #T  $ ‚$‚ƒƒ#ÐÓ  ÓOther€metals€productionÐ ÿO 0 Ð3„03„011...014Ì3„04„005...006Ì3„04„010...022Ð ,"£ó  $ ‚$‚ƒƒ„„,ÐFerrous€Metals€Processing:Ð žî 3 ÐÐ ,"žî  $ ‚$‚ƒƒ„„,ÐCokeÐ ™é 3 Ð3„03„003...004Ð ,"™é  $ ‚$‚ƒƒ„„,ÐFerroalloy€ProductionÐ ”ä3 Ð3„03„006...007Ð ,"”ä $ ‚$‚ƒƒ„„,ÐIron€and€Steel€ProductionÐ ß3 Ð3„03„008...009Ð ,"ß $ ‚$‚ƒƒ„„,ÐGray€Iron€FoundriesÐ @6ŠÚ3 ’@1188‰’@‰@Ð3„04„003Ð ND1ŠÚ  ’@1188 $ ’@ ‚$‚ƒƒ„„NÐSteel€FoundriesÐ …Õ!3 Ð3„04„007,„009Ð #…Õ" $ ‚$‚ƒƒ#ÐMineral€Products:Ð  €Ð# ÐÐ ,"€Ð$ $ ‚$‚ƒƒ„„,ÐCement€ManufacturingÐ {Ë%3 Ð3„05„006...007Ð ,"{Ë& $ ‚$‚ƒƒ„„,ÐCoal€CleaningÐ @6vÆ'3 $“@1225‰$“@‰@Ð3„05„010Ð ND1vÆ( $“@1225 $ $“@ ‚$‚ƒƒ„„NÐStone€Quarrying€and€ProcessingÐ @6qÁ)3 L“@1235‰L“@‰@Ð3„05„020Ð ND1qÁ* L“@1235 $ L“@ ‚$‚ƒƒ„„NÐOtherÐ l¼+3 Ð3„05„003...999Ð *€Yl¼, $ ‚$‚ƒƒ*ÐAsphalt€ManufactureÐ +€Yg·-Y +Ð3„05„001...002Ð.$"g·. $  Y .ÐÔ'`°6ÔÌÌò òEmission€Stream€Characteristics:ó óÐ â20 ÐÌÓ  Óà  àò òa.à0 ™ àAir€Flow:ó ó€€€Baghouses€are€separated€into€two€groups,€standard€and€custom,€which€are€furtherÐ ‰ Ù2 Ðseparated€into€low,€medium,€and€high€capacity.€€Standard€baghouses€are€factory„built,€off€the€shelfÏunits.€€They€may€handle€from€less€than€0.10€to€more€than€50€standard€cubic€meters€per€secondÏ(smòò3óó/sec)€(ð ðhundredsðð€to€more€than€100,000€standard€cubic€feet€per€minute€(scfm)).€€CustomÐ #T5 Ðbaghouses€are€designed€for€specific€applications€and€are€built€to€the€specifications€prescribed€byÏthe€customer.€€These€units€are€generally€much€larger€than€standard€units,€i.e.,€from€50€to€over€500Ïsmòò3óó/sec€(100,000€to€over€1,000,000€scfm).€€(EPA,€1998b)Ðz%Ê 8™(#™(# ÐÌà  àò òb.à0 ™ àTemperature:ó ó€€€Typically,€gas€temperatures€up€to€about€260ððC€(500ððF),€with€surges€to€about€290ððCÐ 'n": Ð(550ððF),€can€be€accommodated€with€the€appropriate€fabric€material.€€Spray€coolers€or€dilution€airÏcan€be€used€to€lower€the€temperature€of€the€pollutant€stream.€€This€prevents€the€temperature€limitsÏof€the€fabric€from€being€exceeded.€€€Lowering€the€temperature,€however,€increases€the€humidity€ofÏthe€pollutant€stream.€€Therefore,€the€minimum€temperature€of€the€pollutant€stream€must€remainÏabove€the€dew€point€of€any€condensable€in€the€stream.€€The€baghouse€and€associated€ductworkÏshould€be€insulated€and€possibly€heated€if€condensation€may€occur.€€(EPA,€1998b)Ð ™(#™(# Ðâ âÐ á,1(A Ðà  àò òc.à0 ™ àPollutant€Loading:ó ó€€€Typical€inlet€concentrations€to€baghouses€are€1€to€23€grams€per€cubic€meterÐ ° Ð(g/mòò3óó)€(0.5€to€10€grains€per€cubic€foot€(gr/ftòò3óó)),€but€in€extreme€cases,€inlet€conditions€may€varyÐ ‡× Ðbetween€0.1€to€more€than€230€g/mòò3óó€(0.05€to€more€than€100€gr/ftòò3óó).€€(EPA,€1998b)ÐY©™(#™(# Ðâ âÌà  àò òd.à0 ™ àOther€Considerations:ó ó€€€Moisture€and€corrosives€content€are€the€major€gas€stream€characteristicsÐ ýM 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€gr/mòò3óó€(0.010€gr/ftòò3óó),€and€in€a€number€of€cases,€to€as€low€asÐ J š Ð0.002€to€0.011€g/mòò3óó€(0.001€to€0.005€gr/ftòò3óó).€€(AWMA,€1992)Ð l ™(#™(# ÐÌò òÔ& ï ÔEmission€Stream€Pretreatment€Requirements:ó óÐ À   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'ïÀ ›)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 %u ÐÌCost€estimates,€expressed€in€2002€dollars,€are€presented€below€for€mechanical€shaker€cleaned€fabric€filtersÏand€for€sonic€horn€enhancement.€€Both€the€shaker€cleaned€and€sonic€horn€cost€estimates€assume€aÏconventional€design€under€typical€operating€conditions.€€The€costs€do€not€include€auxiliary€equipment€suchÏas€fans€and€ductwork.€€ÌÌThe€costs€for€shaker€cleaned€systems€are€generated€using€EPAððs€cost„estimating€spreadsheet€for€fabric€filtersÏ(EPA,€1998b).€€The€cost€estimate€for€sonic€horn€enhancement€is€obtained€from€the€manufacturer€quote€givenÏin€the€OAQPS€Control€Cost€Manual€(EPA,€1998b).€€Sonic€horns€are€presented€as€an€incremental€cost€to€theÏcapital€cost€for€a€shaker€cleaned€system.€€The€operational€and€maintenance€(O&M)€cost€for€shaker€cleanedÏsystems€are€reduced€by€1%€to€3%€with€the€sonic€horn€enhancement.€ÔÿÍ-ÔÌÌÔÿ­/ÔCosts€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 v!Æ# Ðrespectively,€and€a€pollutant€loading€of€9€g/mòò3óó€€(4.0€gr/ftòò3óó)€.Ð H"˜$ 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€30%Ïand€the€O&M€cost€could€increase€by€as€much€as€7%.ÌÓUÓÌà  àò òa.à0 ™ àCapital€Cost:ó ó€€€$17,000€to€$153,000€per€mòò3óó/sec€($8€to€$72€per€scfm)ÐØ(($,™(#™(# Ðà0  àà0™(#(#àà0 ™(#™(#àà0£  (# (#àà0( £ (#£ (#àà0­ ( (#( (#àà ( à$1,000€to€$1,300€per€mòò3óó/sec€($0.5ñvññmñ0ñmññvññwñ1ñwñ€to€$0.6ñxñ1ñxññyñ0ñyñ€€per€scfm),€additional€cost€for€Ð¯)ÿ$-­ (#­ (# Ðà  àà ™ àà  àà £ à€€€€€€€€sonic€hornsñzñà · àà < àà Á àà F àà Ë àà P àà Õ àñzñÐ *Ñ%. ÐÌà  àò òb.à0 ™ àO€&€M€Cost:ó óÔÿÔ€€Ôÿ.6Ô$9,ñpñ3ñpññpñ0ñpñ00€to€$51,000€per€mòò3óó/sec€($4€to€$24€per€scfm),€annuallyÐ%,u'0™(#™(# Ðâ âÐ ü,L(1 ÐÔ& À Ôâ ââ âà  àò òc.à0 ™ àAnnualized€Cost:ó ó€€$11,000€to€$95,000€per€mòò3óó/sec€($ñqñ5ñqññqñ7ñqñ€to€$4ñrñ5ñrññrñ3ñrñ€per€scfm),€annuallyà é àò òа™(#™(# ÐÌÓ €Óà  àd.à0 ™ àCost€Effectiveness:ó ó€€$41€to€$334€per€metric€ton€($ñsñ37ñsññsñ46ñsñ€to€$ñtñ303ñtññtñ290ñtñ€per€short€ton)Ð\¬™(#™(# ÐÔ'À°è6ÔÓ €Õ7ÓÌò òTheory€of€Operation:ó óÐ pÀ ÐÓ  Óà  àÌIn€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€13€to€31€centimeters€(cm)Ï(5€to€12€inches)€in€diameter.€€Groups€of€bags€are€placed€in€isolable€compartments€to€allow€cleaning€of€theÏbags€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 ï? Ðbe€used€(STAPPA/ALAPCO,€1996).ÌÌPractical€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€megawatt€(MW€)€utility€boiler€may€have€5,000Ïseparate€bags€with€a€total€fabric€area€approaching€46,500€mòò2óó€(500,000€square€feet).€€(ICAC,€1999)Ð Q¡ Ðà  àà ™ àà  àà £ àà ( àà ­ àà 2 àà · àà < àà Á àà F àà Ë àà P àà Õ àà Z àÌDeterminants€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.€€Cleaning€intensity€and€frequency€are€important€variablesÏin€determining€removal€efficiency.€€Because€the€dust€cake€can€provide€a€significant€fraction€of€the€fineÏparticulate€removal€capability€of€a€fabric,€cleaning€which€is€too€frequent€or€too€intense€will€lower€the€removalÏefficiency.€€On€the€other€hand,€if€removal€is€too€infrequent€or€too€ineffective,€then€the€baghouse€pressure€dropÏwill€become€too€high.€€(ICAC,€1999)ÌÌMechanical€shaking€has€been€a€popular€cleaning€method€for€many€years€because€of€its€simplicity€as€well€asÏits€effectiveness.€€In€typical€operation,€dusty€gas€enters€an€inlet€pipe€to€the€shaker€cleaned€fabric€filter€and€veryÏlarge€particles€are€removed€from€the€stream€when€they€strike€the€baffle€plate€in€the€inlet€duct€and€fall€into€theÏhopper.€€The€particulate„laden€gas€is€drawn€from€beneath€a€cell€plate€in€the€floor€and€into€the€filter€bags.€€TheÏgas€proceeds€from€the€inside€of€the€bags€to€the€outside€and€through€the€outlet€pipe.€€The€particles€areÏcollected€on€the€inside€surface€of€the€bags€and€a€filter€cake€accumulates.€€In€mechanical€shaking€units,€theÏtops€of€bags€are€attached€to€a€shaker€bar,€which€is€moved€briskly€(usually€in€a€horizontal€direction)€to€cleanÏthe€bags.€€The€shaker€bars€are€operated€by€mechanical€motors€or€by€hand,€in€applications€where€cleaning€isÏnot€required€frequently.€€(EPA,€1998a)ÌÌThe€vibration€cleaning€method€is€similar€to€mechanical€shaking€units.€€It€utilizes€a€pneumatically€driven€highÏfrequency,€low€amplitude€vibration€of€the€bag€frame€to€clean€the€bags.€€This€method€has€limited€applicationÏdue€to€its€low€cleaning€energy€and€smaller€baghouse€design€(Billings,€1970).€€Ð /.)3 ЇSonic€horns€are€increasingly€being€used€to€enhance€the€collection€efficiency€of€mechanical€shaker€andÏreverse„air€fabric€filters€(AWMA,€1992).€€Sonic€horns€utilize€compressed€air€to€vibrate€a€metal€diaphragm,Ïproducing€a€low€frequency€sound€wave€from€the€horn€bell.€€The€number€of€horns€required€is€determined€byÏfabric€area€and€the€number€of€baghouse€compartments.€€Typically,€1€to€4€horns€per€compartment€operatingÏat€150€to€200€hertz€are€required.€€Compressed€air€to€power€the€horns€is€supplied€at€275€to€620€kiloPascalsÏ(kPa)€(40€to€90€pounds€per€square€inch€gage€(psig)).€€Sonic€horns€activate€for€approximately€10€to€30€secondsÏduring€each€cleaning€cycle€(Carr,€1984)€.ÌÌSonic€horn€cleaning€significantly€reduces€the€residual€dust€load€on€the€bags.€€This€decreases€the€pressureÏdrop€across€the€filter€fabric€by€20€to€60%.€€It€also€lessens€the€mechanical€stress€on€the€bags,€resulting€inÏlonger€operational€life€(Carr,€1984).€€As€stated€previously,€this€can€decrease€the€O&M€cost€by€1€to€3%,Ïannually.€€Baghouse€compartments€are€easily€retrofitted€with€sonic€horns.€€Sonic€assistance€is€frequently€usedÏwith€fabric€filters€at€coal-burning€utilities€(EPA,€1998a).ÌÌò òAdvantages:ó óÐ ,|  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€areÏrelatively€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€Ô& ¤ Ôoutlet€flange€locations€to€suitÏinstallation€requirements.€€(AWMA,€1992)Ô'¤5¸RÔÌÌò òDisadvantages:ó óÐ «û ÐÌTemperatures€much€in€excess€of€290ððC€(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 È! 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)ÌÌò òÌÌÌOther€Considerations:ó óÐ ©)ù$- ÐÌFabric€filters€are€useful€for€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)ÌÓú8ÓÐ ˜.è)3 Ðò òReferences:ó óÐ ° ÐÌAWMA,€1992.€€Air€&€Waste€Management€Association,€€òòAir€Pollution€Engineering€Manualóó,€Van€NostrandÐ W§ ÐReinhold,€New€York.€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.€ÌÌBillings,€1970.€€Billings,€Charles,€et€al,€òòHandbook€of€Fabric€FIlter€Technology€Volume€I:€Fabric€FilterÐ ‹Û  ÐSystems€Studyóó,€GCA€Corp.,€Bedford€MA,€December.Ð ]­  ÐÌCarr,€1984.€€Carr,€R.€C.€and€W.€B.€Smith,€Fabric€Filter€Technology€for€Utility€Coal„Fired€Power€Plants,€PartÏV:€Development€and€Evaluation€of€Bag€Cleaning€Methods€in€Utility€Baghouses,€J.€Air€Pollution€ControlÏAssoc.,€34(5):584,€May.ÌÌICAC,€1999.€€Institute€of€Clean€Air€Companies€internet€web€page€www.icac.com,€Control€TechnologyÏInformation€„€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.