man-and-environment-5-ai教学讲解课件.ppt

1、 AIR POLLUTANTSTYPES OF AIR CLEANING EQUIPMENT.http:/e-stud.vgtu.lt/darb/3142.Listed below are the major air pollutants and their sourcesCarbon monoxide(CO)Carbon dioxide(CO2)Chloroflorocarbons(CFC)Lead(Pb)Nitrogen oxide(Nox)Suspended particulate matter(SPM)Sulphur dioxide(SO2).Men and the environme

2、nt4Fine Particulate Matter(PM2.5)nEXAMPLES OF SOURCES:nFuel combustion in motor vehicles,equipment,and industrial sources;residential and agricultural burning.Also formed from reaction of other pollutants(acid rain,NOx,SOx,organics).Particulate Matter(PM10:less than or equal to 10 microns)nEXAMPLES

3、OF SOURCES:nCars and trucks,especially diesels nFireplaces,woodstoves nWindblown dust,from roadways,agriculture and construction .Dust storm approaching Stratford,Texas.Ozone(O3)nEXAMPLES OF SOURCES:nFormed by chemical reactions of air pollutants in the presence of sunlight.Common sources:motor vehi

4、cles,industries,and consumer products .Men and the environment8Carbon Monoxide(CO)nEXAMPLES OF SOURCES:nAny source that burns fuel such as cars,trucks,construction and farming equipment,and residential heaters and stoves .Men and the environment9Nitrogen Dioxide(NO2)nEXAMPLES OF SOURCES:n Chest pain

5、 in heart patients nHeadaches,nausea nReduced mental alertness nDeath at very high levels .Burnig Field in Georgia.Men and the environment11Toxic Air Contaminants nEXAMPLES OF SOURCES:nCars and trucks,especially diesels nIndustrial sources such as chrome platers nNeighborhood businesses,such as dry

6、cleaners and service stations nBuilding materials and products .Air pollution from factories.Emission is increasing every year.Men and the environment13Lead nEXAMPLES OF SOURCES:nMetal smelters,resource recovery,leaded gasoline,deterioration of lead paint.Men and the environment14Sulfur Dioxide(SO2)

7、nEXAMPLES OF SOURCES:nCoal or oil burning power plants and industries,refineries,diesel engines.Men and the environment16Visibility Reducing Particles nEXAMPLES OF SOURCES:nFuel combustion in motor vehicles,equipment,and industrial sources;residential and agricultural burning.Smog in China in August

8、 2005.Looking down from the Hollywood Hills,with Griffith Observatory on the hill in the oreground,air pollution is visible in downtown Los Angeles on a late afternoon.Men and the environment19Sulfates nEXAMPLES OF SOURCES:nProduced by the reaction in the air of SO2,a component of acid rain.Hydrogen

9、 Sulfide nEXAMPLES OF SOURCES:nGeothermal power plants,petroleum production and refining,sewer gas.HEALTH EFFECTS nIncreased respiratory disease nLung damage nPremature death nCancer nChronic eye,lung,or skin irritation nNeurological and reproductive disorders .Prevention and Control nReduce motor v

10、ehicle reactive organic gas(ROG),volatile organic compounds(VOC)and nitrogen oxide emissions through emissions standards,reformulated fuels,inspections programs,and reduced vehicle use.Limit ROG emissions from commercial operations and consumer products.Limit ROG and NOx emissions from industrial so

11、urces such as power plants and refineries.Conserve energy nControl dust sources,industrial particulate emissions,wood burning stoves and fireplaces.Reduce secondary pollutants which react to form PM10.Conserve energy nControl emissions from geothermal power plants,petroleum production and refining,s

12、ewers,sewage treatment plants.Pollution control hardware,technologies and equipment that may be applicable to pollution prevention opportunities.METHODS OF PARTICULATE COLLECTIONMETHODS FOR CLEANING GASEOUS POLLUTANTS.METHODS OF PARTICULATE COLLECTIONSettling chambers,low-pressure-drop cyclones,and

13、dynamic precipitators are among the most common and important devices applied in end-of-pipe control applications for dust and particulate matter.GRAVITY SETTLING CHAMBERSRemoval of air pollutants through the mechanism of downward gravitational forces.In principle,pollutants are removed by reducing

14、the velocity of the gas stream sufficiently to allow particles to settle out under the influence of gravity.The simplest chamber is merely a horizontal duct in which large particles settle out on the floor.High-efficiency settling chambers are often fitted with baffles or deflectors to change the ga

15、s flow direction.This type of technology is a part of the group of air pollution ontrols collectively referred to as precleaners“.Particle ClassificationBefore selecting or sizing a specific control device,a careful evaluation of all aspects of the process and contaminants must be made.Liquid in Gas

16、Solid in Gas.Liquid in Gas:These include the following terminology:Mists and Sprays-There are numerous industrial chemical operations which involve liquid-in-gas dispersions.These operations generate mists and sprays that consist of particles in diameter ranges of:0.1 to 5,000 m.Liquid in Gas.Dusts-

17、Dusts are fine solid particles often formed in such operations aspulverizing,crushing,grinding,drilling,detonation,and polishing.Otherindustrial sources are conveying operations and screening.Particle diameters generally are in the range of 1.0 to 1,000 m.Dusts generally do not diffuse in air,but se

18、ttle out by gravity.Flyash-Flyashes are fiiely divided matter generally entrained in flue gases that arise from combustion.Particles range from 1 m in size on down.This is not within the operational range of gravity settling chambers.Wet scrubbers are generally employed in flyash control.In some app

19、lications high-efficiency electrostatic precipitators,baghouses,or cyclones are utilizedSolid in Gas.Fumes-Fumes are finely divided solid particles that are generated by thecondensation of vapors.Fumes are generated by sublimation,distillation,and molten metal processes.Particle diameters are genera

20、lly in the range of 0.1 to 1 m.Smoke-Smoke constitutes fine,solid,gasborne matters that are products ofincomplete combustion of organics(wood,coal,tobacco).Smoke particlesare extremely small,ranging in size from less than 0.01 m to 1 m.Solid in Gas.Smog-Smog refers to a mixture of natural fog and in

21、dustrial smoke.Aerosols-Aerosols are an assemblage of small particles,either solid orliquid,suspended in gas.Particle sizes range from 0.01 to 100 m.There are several classes of aerosols.Dispersion aerosols are a common class that are formed from processes such as grinding.Condensation aerosols are

22、formed when supersaturated vapors condense or when gases react chemically to form a nonvolatile product.Grit-The term grit is used to classify coarse particles that are are normally greater than 43 m in diameter and are within the operating efficiency of gravity settling chambers.Solid in Gas.Horizo

23、ntal simple gravity settling chamberAs a general guideline,linear gas velocities are kept below 300 cm/sec.This is satisfactory for most materials;however,some low-density particulates are reentrained at lower velocities.Most designs only effectively collect PM greater than approximately 50 m.Emissi

24、on Stream CharacteristicsAir Flow:The simple design and construction of settling chambers allows for almost any size and waste gas flow rate.Usualy flow rates range up to 50 m3/secTemperurure:Inlet gas temperatures are only limited by the materials ofconstruction of the settling chamber,and have bee

25、n operated at temperatures as high as 600 C.Pollutant Loading:Waste gas pollutant loadings can range from 20 to 4500 g/m3.Other Considerations:Leakage of cold air into a settling chamber can cause local gas condensation.Condensation can cause corrosion,dust buildup and plugging of the hopper or dust

26、 removal system.The use of thermal insulation can reduce heat loss and prevent condensation.Cost InformationCapital Cost:200 to 7,000 EUR per m3/sec0&M Cost:10 to 350 EUR per m3/sec.Horizontal simple gravity settling chamberSettling chambers have been used extensively in the pastSettling chambers ha

27、ve been replaced,formost applications,by cyclones primarily due to the lower space requirements andthe higher collection efficiency of cyclones.CYCLONE SEPARATORSThis type of technology is a part of the group of air pollution controls collectivelyreferred to as precleaners“.Cyclones are also referre

28、d to as cyclone collectors,cyclone separators,centrifugal separators,and inertial separators.Cyclones are used to control PM,greater than 10 m in aerodynamic diameter.Steps involved in particle separation.In applications where many small cyclones are operating in parallel,the entire system is called

29、 a multiple tube cyclone,multicyclone,or multiclone.Cyclones.Emission Limits and ReductionsThe control efficiency range for conventional single cyclones is estimated to be 70 to 90%for PM,30 to 90 percent for PM10,and 0 to 40%for PM2.5.Multicyclones are reported to achieve from 80 to 95 percent coll

30、ectionefficiency for 5 m particles.Note that this equipment is applicable only for stationary point source emission control.Emission Stream CharacteristicsAir Flow:Typical gas flow rates for a single cyclone unit are 0.5 to 12 m3/sec.Temperature:Inlet gas temperatures are only limited by the materia

31、ls ofconstruction of the cyclone,and have been operated at temperatures as high as 600 CPollutant Loading:Waste gas pollutant loadings typically range from 2.3 to 230 g/m3.Other Considerations:Cyclones perform more efficiently with higher pollutant loadings.Cost InformationCapital Cost:3 200 to 4 70

32、0 EUR per m3/sec0&M Cost:2 000 to 25 000 EUR per m3/sec.Typical Industrial ApplicationsCyclones are designed for manny applications.Cyclones themselves are generallynot adequate to meet stringent air pollution regulations,but they serve an important purpose as precleaners for more expensive final co

33、ntrol devices such as fabric filters or electrostatic precipitatorsCyclones are used extensively after spray drying operations in the food andchemical industries,and after crushing,grinding,and calcining operations in themineral and chemical industries to collect salable or useful material.Fossil-fu

34、el and wood-waste fired industrial and commercial fuel combustion unitscommonly use multiple cyclones(generally upstream of a wet scrubber,ESP,orfabric filter)which collect fine PM(C 2.5 m)with greater efficiency than a single cyclone.EXTENDED MEDIA CARTRIDGE FILTERSOlder existing cartridge collecto

35、r types have a range of actual operating efficiencies of 99 to 99.9%for PM10 and PM2,5.Typical new equipment design efficiencies are between 99.99 and 99.999%.In addition,commercially available designs are able to control submicron PM(0.8 m in diameter or greater)with a removal efficiency of 99.999%

36、.Several factors determine cartridge filter collection efficiency including gasfiltration velocity,particle characteristics,filter media characteristics,and cleaning mechanism.In general,collection efficiency increases with increasing filtration velocity and particle size.Types of Air Cleaning Proce

37、ssesMechanical Filters -Flat Filters -Pleated Filters -HEPA Filters -Fabric Filters.Flat Filters.Pocket,Cassete filters They can be maid from glass fiber or from syntetic material Application areas:wood industry,chemistry,glass industry,metal industry and others.Pleated Filters.High-Efficiency Parti

38、culate Air Filters.Emission Stream CharacteristicsAir Flow:Cartridge collectors are currently limited to low air flow capacity applications,Standard cartridge collectors are factory-built.They may handle airflow rates from less than 0.10 to more than 5 m3/sec.Temperature:Temperatures are limited by

39、the type of filter media and sealant used in the cartridges.Standard cartridges utilizing paper filter media can accommodate gas temperatures up to about 95 C.Cartridge filters utilizing synthetic,nonwoven media such as needle-punched felts fabricated of polyester can withstand temperatures of up to

40、 200C with the appropriate sealant material.Pollutant Loading:Typical inlet concentrations to cartridge collectors are 1 to 23 g/m3.Cartridge filters,which utilize synthetic,nonwoven media such as needle punched felts fabricated of polyester are able to handle inlet concentrations up to 60 g/m3.Othe

41、r Considerations:Moisture and corrosive content in the gas streams are the major design considerations.Standard cartridge filters can be used in pressure or vacuum service,but only within the range of about 640 millimeters of water column.Cost InformationCapital Cost:12 000 to 25 000 EUR per m3/sec0

42、&M Cost:15 000 to 45 000 EUR per m3/sec.n31 st October 8:30 nMiddle time examination.FABRIC FILTERS This equipment is used for the capture of Particulate Matter(PM),including particulate matter less than or equal to 10 micrometers in aerodynamic diameter(PM10),particulate matter less than or equal t

43、o 2.5 pm in aerodynamic diameter(PM2.5),and hazardous air pollutants(HAPS)that are in particulate form,such as most metals(mercury is the notable exception,as a significant portion of emissions are in the,form of elemental vapor).Typical new equipment design efficiencies are between 99 and 99.9%.Old

44、er existing equipment have a range of actual operating efficiencies of 95 to 99.9%.Several factors determine fabric filter collection efficiency.These include gas filtration velocity,particle characteristics,fabric characteristics,and cleaning mechanism.In general,collection efficiency increases wit

45、h increasing filtration velocity and particle size.Typical Industrial ApplicationsCommon applications using pulse-jet cleaning systems include:Utility Boilers(Coal)Industrial Boilers(Coal,Wood)Commercial/Institutional Boilers(Coal,Wood)Asphalt ManufacturingGrain MillingFerrous Metal Processing(e.g.,

46、Iron and Steel Production and Steel Foundries)Mineral Products(e.g.,Cement Manufacturing,Coal Cleaning,and StoneQuarrying and Processing).Emission Stream CharacteristicsAir Flow:Baghouses are separated into two groups,standard and custom,which are either separated into low,medium,and high capacity.S

47、tandard baghouses are factory-built,off the shelf units.They may handle from less than 0.10 to more than 50 m3/sec.Temperature:Typically,gas temperatures up to about 250C.Temperature can be accommodated with the appropriate fabric material.Pollutant Loading:Typical inlet concentrations to baghouses

48、are 1 to 23 g/m3,but in extreme cases,inlet conditions may vary between 0.1 to more than 230 g/m3.Other Considerations:Moisture and corrosives content are the major gas stream characteristics requiring design consideration.Standard fabric filters can be used in pressure or vacuum service,but only wi

49、thin the range of about 640 millimeters of water column.Cost InformationCapital Cost:10 000 to 50 000 EUR per m3/sec0&M Cost:10 000 to 45 000 EUR per m3/sec.DRY ELECTROSTATIC PRECIPITATOR(ESP)-WIRE-PIPE TYPE.Achievable Emission Limits ReductionsTypical new equipment design efficiencies are between 9

50、9 and 99.9%.Older existing equipment have a range of actual operating efficiencies of 90 to 99.9%.While several factors determine ESP collection efficiency,ESP size is most important.Collection efficiency is also affected by dust resistivity,gas temperature,chemical composition(of the dust and the g