大氣復(fù)習(xí)資含答案

1、大氣復(fù)習(xí)資料概念解釋(1) Globewarming:GlobalwarmingistheincreaseintheaveragemeasuredtemperatureoftheEarth'snear-surfaceairandoceanssincethemid-twentiethcentury,anditsprojectedcontinuation.(2) Temperatureinversions:Atemperatureinversionsisathinlayeroftheatmospherewherethedecreaseintemperaturewithheightismuc

2、hlessthannormal(orinextremecases,thetemperatureincreaseswithheight).(3) ESFPElectrostaticprecipitator,whichislikeagravitysetterorcentrifugalseparator,butelectrostaticforcedrivestheparticlestothewall.(4) HEPAHighEfficiencyParticulateAir(5) Leanbum:Leanburnreferstotheuseofleanmixturesinaninternalcombu

3、stionengine.Theair-fuelcanbeashighas65:1,sothemixturehasconsiderablylessfuelincomparisontothestoichiometriccombustionratio(14.7forpetrol,forexample).(6) Plumerise:theplumerisingadistanceAhabovethetopofthestackbeforelevelingout.(7) Wetscrubber:Adevicethatcollectsparticlesbycontactingthedirtygasstream

4、withliquiddrops.(8) Photochemicalsmog:(9) ThermalNOThermalNOreferstoNOformedthroughhightemperatureoxidationofthediatomicnitrogenfoundincombustionair.(10) A/Fratio:Airtofuelratioforautoengines.(11) PM2.5:particlewiththeaerodynamicdiameterlessthan2.5um,whichisalsocalledRespirableParticles.(Alternative

5、fuel:Severalotherfuelsexceptofconventionalgasolineanddiesel,whichhavebeenusedformanyyearsinslighutlymodifiedautomobileengines,forreasonsofcostandavailability.(13)VOCsVolatileorganiccompoundsarethoseorganicliquidsorsolidswhoseroomtemperaturevaporpressurearegreaterthanabout0.01psia(=0.0007atm)andwhose

6、atmosphericboilingpointsareuptoabout500F,whichmeansmostorganiccompoundswithlessthan12carbonatoms.(1)SCRandSNC:6NO+4NH5N+6HO,4NO+4NH+O-4N+6Ho2NOMNHH3N+6HO.Thesereactionscanbecarriedoutoveravarietyofcatalysts,thetemperatureisbetween1600Fand1800F,oncethetemperatureincreases,thedominantreactionisNH+Q-NO

7、+1.5HO,thecatalyticprocessesarecalledSCR,andthehigher-temperatureones,withoutcatalysts,callSNCR.2 Aerodynamicdiameter:Airborneparticleshaveirregularshapes,andtheiraerodynamicbehaviorisexpressedintermsofthediameterofanidealizedsphericalparticleknownasAerodynamicdiameter.3 PrimaryParticles:Particlesfo

8、undintheatmosphereintheforminwhichtheywereemitted,forexamples,NO,CO,SO24 4)PointSources:smallnumberoflargesourcesthatemitlargeramountspersource,athigherelevations(powerplants,smelters,cementplants,etc.)calledpointsourcesAnswerfollowingquestions（1） Whicharethemainconstituentsforthegroundlevelozonefor

9、mation?Ozoneisformedwhenthefollowingconstituentsarepresent.Nitrogenoxides,VolatileOrganic,Compounds,Sunlight,Hightemperature（18C）NO+VOC+Sunlight-NO+O（2） Pleaselistfivemajortypesofwetscrubbers.PlateScrubber（板式）PackedScrubber（填料式）PreformedSprayScrubber（噴霧式）Gas-AtomizedSprayScrubber（氣體霧化）CentrifugalScr

10、ubber（離心式）Impingement-EntrainmentScrubber,（沖擊夾帶式）MechanicallyAidedScrubber（機(jī)械輔助式）MovingBedScrubber（移動(dòng)床式）（3） HowtocontrolVOCspollutionbyprevention?Twoexamples.Substitution（代替），Replacinggasolineasamotorfuelwithcompressednaturalgasorpropaneisaformofsubstitution.ProcessModification（過程修改）,Replacinggasoli

11、ne-poweredvehicleswithelectric-poweredvehiclesisaformofprocessmodification.Leakage（滲漏）Control,Storinglargeamountsofgasolineinfloatingrooftanks.（4） Pleaseintroducetheprocessofforced-oxidationLimestoneWetScrubbingbriefly?（5） WhatarethemostdifferentpointsbetweenSCRandSNCR?（6） CanTWCbeappliedinthetreatm

12、entofdieselexhaust（=emissionofdieselengine）?Why? Thecharacteristicofemissionofdieselengine:AmplePMandExcessiveO2,Lowertemperature; Thedifficultyinthereactionofsolid-gas-solid.Key:Themixtureprocessoffuelandairforgasenginesisdistinguishedfromthatfordieselengines,hencethecharacterofonetypeengineisdiffe

13、rentfromtheotherone:therearemainlyfivegases(NOX,HC,COandO2,CO2)intheexhaustofgasmotors,whilethereareampleO2andfourothergasesmentionedaboveinthetailpipeemissionofdieselengine.AndthepresenceofabundantO2wouldinhibittheperformanceofTWC.Moreover,thecontactandreactionofsolid-solid-gasresultinginthedifficu

14、ltiesforcatalyststooxidationtheparticulateintheexhaustofdieselengine,whilethecontactandreactionofsolid-gas-gasoccurintheexhaustofgasolineengineandthelatterreactioniseasier.Whatkindsofindoorairpollutantsaremostlyconcernedbypublic?a) Randomb) Combustionby-products1. CO,CO2,SO2,Formaldehyde,Hydrocarbon

15、s,NOx2. Particulates,polyaromatichydrocarbonsc) Cigarettesd)Volatileorganiccompoundsf)Biologicalcontaminants(8) Listthetechnologystrategyforthecontrolofparticles.(9) Givenamesofthreetypicalkindsofcombustionreactors.Whichhaslowestoperatortemperatureamongthosereactors?1 .Directflameincineration2.Therm

16、alincineration3.Catalyticincineration(haslowestoperatortemperature)(10) WhatarethemajordevelopmentproblemsofForced-oxidationlimestonewetscrubbing?(11) Whatareprimaryairpollutantsandsecondaryairpollutants?Anyexample?primaryairpollutantsaredirectlyfromthesources,forexamples,NO,CO,SO2.Thesecondaryairpo

17、llutantsarefromtheprimarypollutants,suchasNO2,NO3,fineparticles.NO+CH+O2+sunlight-NO2+O3(12)Basicstrategyofcontrolforparticulatepollutants(threeaspects)?Impaction碰撞Interception截留Diffusion擴(kuò)散Byforcingtheindividualparticlestocontacteachother,Bycontactingthemwithdropsofwater,Bypreventingtheemissionofgas

18、eousPollutants.(13) HowtoreducetheformationofNOxinfluegasbymodifyingthecombustionprocesses?p459(14) Pleaseexplaintheformationofacidrain?SulfuroxidesandnitrogenoxidesNONO2HNO3nitricacidSO2H2SOsulfuricacid(15) WhatarebasicprinciplesofelectrostaticPrecipitators(sixactivities)? Ionization-Chargingofpart

19、icles Migration-Transportingthechargedparticlestothecollectingsurfaces Collection-Precipitationofthechargedparticlesontothecollectingsurfaces Chargedissipation-Neutralizingthechargedparticlesonthecollectingsurfaces Particledislodging-Removingtheparticlesfromthecollectingsurfacetothehopper Particlere

20、moval-Conveyingtheparticlesfromthehoppertoadisposalpoint、Calculation1) Estimatetheconcentrationofcarbonmonoxideatthedownwindedgeofacity.ci=0+(100*5000)/(3*400)=416.7gg/mcC1cC2qLuHqLuHThecitymaybeconsideredtoconsistofthreeparallelstrips,locatedperpendiculartothewind.Forallofthestripsthewindvelocityue

21、quals3m/s.ThepropertiesofNameofstripLength,kmEmissionrateq,g/skm2MixingheightH,mUpwindsuburbs5100400Downtownr215001500Downwindsuburbs5100400eachofthestripsaredescribedinthefollowingtable,solutioncb3qLuH,32=416.7+(500*2000)/(3*500)=1083.4gg/m,3c3=1083.4+(100*5000)/(3*400)=1500.1gg/m2) AnESPisdesigned

22、totrea540,000acfm(actualcubicfeetperminute)with99%efficiency.Assuminganeffectivedriftvelocityof0.12m/s,calculatetherequiredplateareaandthenumberofplates.Theplatesizeis5.4mtallby3mlong(A=QxIn(14)/cp,acfm=1ft3/min,1m=3.28ft,1m2=1550in2=10.7639ft2).solution1ft3/min=(1/3.28)3m3/min=0.0283m3/min540000acf

23、m=540000*0.028315282m3/min=254.7m3/sA=-(254.70.12)ln(1-0.99)=9774.47nfN=9774.47514.3=6043) Wewishtotreatanairstreamcontaining0.005molfraction(0.5%,5000ppm)toluene,movingataflowrate2240m3/hat0Cand1atm,soastoremove99%ofthetoluenebywaterabsorption.Estimatetherequiredwaterflowrate.HereHenrys'lawcons

24、tantis10000atm.Solution：4) Apowerplantfluegascontains1000ppmofSQandisemittedatarateof224m3/sat546Kand1atm.AForced-oxidationlimestonewetscrubbingsystemistobeusedtoachieve90%removaloftheSQ.CalculatetheamountofCaSO2H2Ocontainedinthefinalsolidproductint/d.-PV武Solution：n=(101325*224*1000*10-6)/(8.315*546

25、)=4.999mol/sSQCaSO2H2Oson(Caso4)=n(s&)=4.999mol/s*90%=4.4991mol/sm=4.4991mol/s*172g/mol*3600*24s/d*10-6t/d=66.86t/d5) Apowerplantemits36kg/hofSQatheightH=120mandthewindspeedis2m/s.DispersionCoefficients:0-y=40mand0-z=30m,Estimatetheground-levelconcentrationofSO?fromthissourceatadistance1kmdirectlydownwind?222cQ1y1zH1zHCx,y,zexpexp-exp2uyz2y2z2zSolution：u=2m/s,H=120m,Q=36kg/h=10g/s,y=0,z=