大气污染控制工程--Lecture 10 Control of Volatile OrganicCompounds

1、Prof. Jiakuan YangHuazhong University of Science and TechnologyControl of Volatile Organic Compounds (VOCs)Particulate pollutantsVolatile Organic Compounds (VOCs)(the second-most widespread and diverse)Sulfur OxidesNitrogen OxidesThe four major air pollutantsControl of Volatile Organic Compounds (VO

2、Cs) VOCs and Vapor Pressure Control by Prevention Control by Concentration and Recovery Control by Oxidation Summary VOCs and Vapor PressureVOCs are those organic liquids or solid whose room temperature vapor pressures are greater than about 0.01psia (=0.0007atm), and whose atmospheric boiling point

3、 are up to about 500 (=260), which means most organic compounds with less than about 12 carbon atoms.Page 336Definition VOCs and Vapor PressureVapor pressureLiquid, xigas, yi, pipPpxyiiiRaoults lawPage 333T, pi , atmyi VOCs and Vapor PressureVapor pressureLiquid, xigas, yi, pipPpxyiiiPage 333yiPyiTp

4、iyi VOCs and Vapor PressureExamplesHydrocarbon(HC)Acetone, CH3-CO-CH3MercuryMethyl chloride, CH3Cl Control by Prevention(1) substitution(2) Process modification(3) Leakage controlOil-based paintswater-based paintsGasoline-powered vehicleselectric-powered vehiclesBreathing losses Control by Preventio

5、nBreathing lossesTanks containing liquid VOCs can emit VOC vapors because of filling and emptying activities as well as changes in temperature and atmospheric pressure. These emissions are called filling or displacement losses, emptying losses, and breathing losses, working lossesPage 338 Control by

6、 PreventionVaporLiquidVapor outLiquid inHeadspacetank Control by PreventionFloating roof tankPage 345, Fig. 10.4 Control by PreventionUnderground storage tank having a vapor return systemPage 345, Fig. 10.5 Control by PreventionPage 347, Fig. 10.6Underground storage tank to a users vehicle using a v

7、apor return system Control by Concentration and Recovery(1) Condensation (冷凝法冷凝法)(2) Adsorption (固体吸附法固体吸附法)(3) Absorption (液体吸收法液体吸收法) Control by Concentration and Recovery(1) condensationOne can remove most of the VOCs from an air or gas stream by cooling the stream to a low enough temperature tha

8、t most of the VOCs are condensed as a liquid and then separated from the gas stream by gravity.Page 350 Control by Concentration and RecoveryPage 351, Fig. 10.8RefrigerantGas coolerPhase separatorRecovered liquid tolueneOut gas stream50 ppm tolueneinlet gas stream5000 ppm toluene Control by Concentr

9、ation and Recovery(2) AdsorptionAdsorption means the attachment of molecules to the surface of a solid.Adsorbent bedAdsorbentActivated carbonPage 354 Control by Concentration and Recovery(2) AdsorptionPage 355, Fig. 10.10Adsorbent bedAir with VOCsCleaned Air with few VOCs# 1# 2# 3Steam with high tem

10、peratureCondenserCooling waterseparatorSteam condensateRecovered HC乐凯胶片集团公司二氯甲烷尾气吸附回收装置乐凯胶片集团公司二氯甲烷尾气吸附回收装置活活性性炭炭纤纤维维有有机机废废气气吸吸附附回回收收装装置置齐鲁石化储运厂石脑油回收装置齐鲁石化储运厂石脑油回收装置活活性性炭炭纤纤维维有有机机废废气气吸吸附附回回收收装装置置南通农药厂混苯回收装置南通农药厂混苯回收装置活活性性炭炭纤纤维维有有机机废废气气吸吸附附回回收收装装置置常用吸附剂特性常用吸附剂特性吸附剂类型吸附剂类型活性炭活性炭活性氧化活性氧化铝铝硅胶硅胶沸石分子筛沸石分子

11、筛4A5A13x堆 积 密 度堆 积 密 度 /kg/kgm m-3-32006007501000800800800800热容热容/kJ(kgK)-1-10.8361.2540.8361.0450.920.7940.794操 作 温 度 上操 作 温 度 上限限/K423773673873873873平均孔径平均孔径/15251848224513再生温度再生温度 /K373413473523393423473573473573473573比表面积比表面积 / /g-16001600210360600吸附剂再生吸附剂再生(a)吸附吸附(b)解吸解吸 Control by Concentratio

12、n and Recovery(3) Absorption (scrubbing)If we can find a liquid solvent in which the VOC is soluble and in which the remainder of the contaminated gas stream is insoluble, then we can use absorption to remove and concentrate the VOC for recovery and re-use, or destruction. Control by Concentration a

13、nd Recovery(3) Absorption (scrubbing) Page 362, Fig. 10.15Absorption and stripping processFeed gas inCleaned gas outAbsorberLoadedsolventHeat exchangerSolute gas outStripperStrippedsolventReboiler气体吸收气体吸收吸收设备吸收设备填料塔填料塔喷淋塔喷淋塔吸收设备污污染染气气体体入入口口清清洁洁气气体体出出口口循循环环泵泵搅搅拌拌器器氧氧化化空空气气入入口口去去湿湿器器水水洗洗喷喷管管浆浆液液喷喷嘴嘴多多

14、孔孔板板污污染染气气体体入入口口清清洁洁气气体体出出口口循循环环泵泵搅搅拌拌器器氧氧化化空空气气入入口口去去湿湿器器水水洗洗喷喷管管浆浆液液喷喷嘴嘴多多孔孔板板填料塔填料塔Comparison between adsorption and absorption Control by Concentration and RecoveryAdsorptionAbsorptionLiquid solventwater Solid AdsorbentActivated carbontargetequipmentAdsorbent bedAbsorberregenerationstreamstrippe

15、refficiencyhighlowmechanismAttachment,adheresolution Control by Oxidation(1) combustion(Incineration) (焚烧法焚烧法)(2) Biological Oxidation(Biofiltration) (生物氧化法生物氧化法) Control by Oxidation(1) combustion(Incineration)Page 371 The final fate of VOCs is mostly to be oxidized to CO2 and H2O. Converting these

16、 materials from harmful or objectionable form to a harmless or less objectionable form by combustion may be the most economical and practical way of solving a VOC emission problem.(1) combustion(Incineration)Combustion may cause the secondary pollution.H2S + 3/2O2H2O + SO22(CH3)3N + 11.5O26CO2+9H2O+

17、 2NOCxHyCl +O2HClHg(L)Hg(G)(1) combustion(Incineration)(a) Simple thermal incinerator(b) Thermal incinerator with regenerative heat recovery(c) Catalytic incineratorPage 376, Fig. 10.17一般催化燃烧流程一般催化燃烧流程 废气入口热交换器预热室催化床排气补充能量有机废气的种类有机废气的种类烷烃类、苯及苯系物、烷烃类、苯及苯系物、醇类、酚类、酮类、醛类、醇类、酚类、酮类、醛类、酯类、胺类、腈、氰、金属酯类、胺类、腈、

18、氰、金属有机物、非金属有机物等。有机物、非金属有机物等。有机废气净化装置应用范围有机废气净化装置应用范围汽车制造业、自行车、摩托车、家用电汽车制造业、自行车、摩托车、家用电器、电线电缆、漆包线、电机及电机绝器、电线电缆、漆包线、电机及电机绝缘处、电器、仪表、电子、石油化工、缘处、电器、仪表、电子、石油化工、涂料、化工、印铁、印刷、家具、皮革、涂料、化工、印铁、印刷、家具、皮革、鞋业、玻璃、建材等行业。鞋业、玻璃、建材等行业。Catalytic combustion converter of exhausted gases from automobile SummaryChoosing a control technology according to the different concentration.Page 382, Fig. 10.19Would type of VOC matter?This Lectu