環(huán)境工程專業(yè)英語 課件 U2L2 Air Pollution Emission Control Devices for Stationary

ProfessionalEnglishforEnvironmentalEngineeringMainContents

IntroductiontoEnvironmentalEngineeringAirPollutionandControlWaterPollutionandControlSolidWasteandDisposalEnvironmentalImpactAssessmentEnvironmentalLaws，RegulationsandSustainableDevelopment

AirPollutionandControl

AirPollutionEmissionControlDevicesforStationary

ProfessionalEnglishforEnvironmentalEngineering

StationarysourcespowerplantssteelmillssmelterscementplantsrefineriesotherindustrialprocessesContaminantsparticulatesaerosolsvaporsgasesAirPollutionEmissionControlDevicesforStationaryStationarysourcesofairpollutionemission

CommonmethodsforeliminatingorreducinggaseouspollutantsDestroyingpollutantsbythermalorcatalyticcombustionChangingpollutantstolessharmfulformsthroughchemicalreactionsCollectingpollutantsusingairpollutioncontrolsystemsbeforetheyreachtheatmosphereAirPollutionEmissionControlDevicesforStationaryAirpollutioncontroldevices

Electrostaticprecipitators(wetanddrytypes)Fabricfilters(alsocalledbaghouses)WetscrubbersCyclones(ormulticlones)AirPollutionEmissionControlDevicesforStationary

ThemostcommonlyuseddevicesforcontrollingparticulateemissionsThermaloxidizersCatalyticreactorsCarbonadsorbersAbsorptiontowersBiofiltersAirPollutionEmissionControlDevicesforStationaryCommoncontroldevicesforgaseousandvaporpollutantsScrubbingScrubbingisaphysicalprocesswherebyparticulates,vapors,andgasesarecontrolledbyeitherpassingagasstreamthroughaliquidsolutionorsprayingaliquidintoagasstream.Wateristhemostcommonlyusedabsorbentliquid.Asthegasstreamcontactstheliquid,theliquidabsorbsthepollutants,inmuchthesamewaythatraindropletswashawaystrongodorsonhotsummerdaysAirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

WetScrubbingEquipment

GasabsorptionGasabsorptioniscommonlyusedtorecoverproductsortopurifygasstreamsthathavehighconcentrationsofwater-solublecompounds.Absorptionequipmentisdesignedtogetasmuchmixingbetweenthegasandliquidaspossible.Commontypesofgasabsorptionequipmentincludespraytowers,packedtowers,traytowers,andspraychambers.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

GasabsorptionPackedtowersarebyfarthemostcommonlyusedcontrolequipmentfortheabsorptionofgaseouspollutants.However,whenusedwithheavy,particulate-ladengas,theycanbepluggedbyparticulatematter(PM).WetcollectiondevicesusedforPMcontrolincludeventuriscrubbers,bubblingscrubbers,spraytowers,andinsomeinstances,wetelectrostaticprecipitators(ESPs).AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

PackedtowersAdsorptionTheprocessofadsorptioninvolvesthemolecularattractionofgasesorvapors[usuallyvolatileorganiccompounds(VOCs)]ontothesurfaceofcertainsolids(usuallycarbon,molecularsieves,and/orcatalysts).Thisattractionmaybechemicalorphysicalinnatureandispredominantlyasurfaceeffect.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

AdsorptionActivatedcarbon(charcoal),whichpossessesthelargeinternalsurfaceareaneededtoadsorblargequantitiesofgaseswithinitsstructure,isoftenusedtoremoveVOCsfromfluegases.AftertheactivatedcarbonissaturatedwithVOCs,itisoftentreated(byheatand/orsteam)tostripoffthecollectedVOCs.TheVOCsarethensentforfurthertreatment,andthecarbonisreusedintheadsorptionreactor.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

AdsorptionAdsorptionisaffectedbythetemperature,flowrate,concentration,andmolecularstructureofthegas.Adsorptioniscommonlyusedforremovinggasesfromcontaminatedsoil,oilrefineries,municipalwastewatertreatmentplants,industrialpaintshops,andsteelmills.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

AdsorptionTowerFabricFiltersorBagHousesFabricfilters,alsocommonlyreferredtoasbaghouses,areusedinmanyindustrialapplications.Theyoperateinamannersimilartoahouseholdvacuumcleaner.Dust-ladengasespassthroughfabricbagswherethedryparticulatesarecapturedonthefabricsurface.Afterenoughdusthasbuiltuponthefilters,asindicatedbyabuildupinpressureacrossthefabric,dustisperiodicallyremovedbyblowingairbackthroughthefabric,pulsingthefabricwithablastofair,orshakingthefabric.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

FabricFiltersorBagHousesBaghousesareusedtocontrolairpollutantsfromcoal-firedpowerplants,steelmills,foundries,andotherindustrialprocesses.Fabricfilerscancollectover99.9%oftheenteringparticulates,evenfinePM.Baghousesalsoaresometimesusedaspartofamultistagegascleaningsystemwheretheyareusedasareactoraswellasaparticulateremovaldevice,suchasinsemi-dryfluegasdesulphurizationsystems.Recentlysomebaghousesarebeingequippedwithcatalyticbagswheretheyalsoactasachemicalreactorwhiletheyarecollectingparticulate.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

CatalyticReactorsCatalyticreactors,referredtoasselectivecatalyticreduction(SCR)systems,areuseextensivelytocontrolNOx,emissionsarisingfromtheburningoffossilfuelsinindustrialprocesses.AmmoniaisinjectedandmixedwiththefluegasesupstreamoftheSCRreactor.IntheSCRreactor,ammoniaandNOx,reacttoformnitrogenandwater.Greaterthan90%NOx,removalispossiblewiththesesystems.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

CatalyticReactorsCatalyticreactorsalsoperformthermaldestructionfunctionslikeincinerators,butatlowertemperaturesandforselectedwastegasesonly.Theyincorporatebedsofsolidcatalyticmaterialthattheunwantedgasespassthrough,typicallyforoxidationorreductionpurposes.Catalyticreactorshavetheadvantageofloweringthethermalenergyrequirements.Destructionefficienciesof99.99%arepossiblewithsignificantlyreducedenergyandoperatingcostsascomparedtoanincinerator.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

CyclonesDust-ladengasiswhirledrapidlyinsideacollectorshapedlikeacylinder(orcyclone).Theswirlingmotioncreatescentrifugalforcesthatcausetheparticlestobethrownagainstthewallsofthecylinderanddropintoahopperbelow.Thegasleftinthemiddleofthecylinderafterthedustparticleshavebeenremovedmovesupwardandexitsthecylinder.CyclonesoperatetocollectrelativelylargesizePMfromagaseousstream,andcanoperateatelevatedtemperatures.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

CyclonesCyclonesaretypicallyusedfortheremovalofparticles50microns(μm)orlarger.Efficienciesgreaterthan90%forparticlesizesof10μmorgreaterarepossible,andefficiencyincreasesexponentiallywithparticlediameterandwithincreasedpressuredropthroughthecyclone.Cyclonesarewidelyused;theycontrolpollutantsfromcottongins,rockcrushers,andmanyotherindustrialprocessesthatcontainrelativelylargeparticulateinthegasstream.Heavydustattheinletofthecyclonecanalsoleadtopluggingofthecyclonehopper.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

ElectrostaticPrecipitators(ESPs)ESPsarerelativelylarge,lowvelocitydustcollectiondevicesthatremoveparticlesinmuchthesamewaythatstaticelectricityinclothingpicksupsmallpiecesoflint.Transformersareusedtodevelopextremelyhighvoltagedropsbetweenchargingelectrodesandcollectingplates.Theelectricalfieldproducedinthegasstreamasitpassesthroughthehighvoltagedischargeintroducesachargeontheparticles,whichisthenattractedtothecollectingplates.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

ElectrostaticPrecipitators(ESPs)Periodicallythecollecteddustisremovedfromthecollectingplatesbyahammerdevicestrikingthetopoftheplates(rapping)dislodgingtheparticulate,whichfallstoabottomhopperforremoval.Electrostaticprecipitatorsareoftenconfiguredasaseriesofcollectingplatestoimproveoverallcollectionefficiency.Efficienciesexceeding99%canbeachieved,andESPsareusedinmanyofthesameapplicationsasbaghouses,includingpowerplants,steelandpapermills,smelters,cementplants,andpetroleumrefineries.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

IncineratorsIncinerationinvolvesthehighefficiencycombustionofcertainsolid,liquid,orgaseouswastes.Thereactionsmaybeself-sustainingbasedonthecombustibilityofthewaste,ormayrequiretheadditionofauxiliaryfuels,suchasnaturalgasorpropane.Theymaybebatchoperationsorcontinuousaswithflaresusedtoburnoffmethanefromlandfills.Whennotburningsolids,theyarealsocalledthermaloxidizers,andthesedevicescanoperateatefficienciesof99.99%(aswithhazardouswasteincinerators).AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

IncineratorsThermaloxidizersareusedtodestroyodorousortoxicVOCs.Achievingtherequiredtemperatures(upto2000℉)requiresalargefuelusage,andcostscanbehigh.Regenerativethermaloxidizers,though,canachieveveryhighheatrecoveries(upto95%),greatlyreducingfuelcosts.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

BiofiltersBiofiltersoperatetodestroyVOCsandodorsbymicrobialoxidationoftheseproblemcompounds.Theyaremosteffectiveonwater-solublematerials.Thepollutedairispassedthroughawettedbed,whichsupportsabiomassofbacteriathatabsorbandmetabolizepollutants.Efficienciesover98%arepossiblewiththisapplication.AirPollutionEmissionControlDevicesforStationaryAbsorption&WetScrubbingEquipment

英語翻譯的詞義選擇

根據(jù)詞的單復(fù)數(shù)確定詞義(1)Electronicsisabranchofsciencethatdealswiththestudyandapplicationofelectrondevices.

譯文：電子學(xué)是有關(guān)電子裝置的研究和應(yīng)用的一門科學(xué)。(electronics看似為復(fù)數(shù)，實則單數(shù)，在句中為“電子學(xué)”的意思)Translation

英語翻譯的詞義選擇

根據(jù)詞的詞類確定詞義(1)Itistheatomsthatmakeupiron,water,oxygenandthelike.

譯文：正是原子構(gòu)成了鐵、水、氧等類物質(zhì)。(like在句中作為名詞，表示“相同之物”)Translation

英語翻譯的詞義選擇

根據(jù)詞的專業(yè)領(lǐng)域確定詞義

(1)Assumethattheinputvoltagefromthepowersupplyremainsconstant.

譯文：假定由電源輸入的電壓保持不變。(power在句中作“電源”)Translation

英語翻譯的詞義選擇

根據(jù)詞語境確定詞義

(1)Womenwhodrinkandsmokeheavilyarelikelytodevelopcancersoftheoralandtongueatayoungerage.

譯文：大量飲酒并吸煙的婦女很可能在年輕時就患上口腔癌和舌癌。(develop在句中表示“患病”)Translation

英語翻譯的詞義選擇

根據(jù)詞的漢語習(xí)慣搭配確定詞義

(1)Volcanicrocksfrominsidethefieldwerefoundtobenon-magnetic.

譯文1：熱田內(nèi)的火山巖以前被發(fā)現(xiàn)是非磁性的。

譯文2：以前的調(diào)查表明，這個熱田的火山巖為非磁性巖石。buildaship造船

buildabridge架橋universalmeter萬用表

universalmotor交直流兩用電動機(jī)universaldividingheading多用分度表頭universalconstant通用常數(shù)

universalrules一般法則Translation

英語翻譯的詞義選擇

根據(jù)詞的同義