air pollution control.pptx

7/26/2019 Air Pollution Control.pptx

http://slidepdf.com/reader/full/air-pollution-controlpptx 1/32

Air Pollution Control

Technology

http://www.epa.gov/oar/oaqps

/eog/course422/ce5.html



• All the data collected through the measurement o pollutants in the am!ient air and

rom emissions sources is used to develop emission inventories.

An emissions inventory is a quantitative list o the amounts and types o pollutants

that are entering the air rom all sources within a certain area.

The undamental elements in an emission inventory are the characteristics andlocations o the sources" as well as the amounts and types o pollutants emitted.

• An emission inventory can help identiy air pollution concerns and determine the air

quality goals that a certain region needs to meet.

An emissions inventory is one o the most !asic tools o air quality management.

The emission inventory data can !e used to simulate air pollution ormation and

transport" estimate potential pollutant concentrations in an area" and estimate the

e#ectiveness o potential emission reduction requirements.

Chemical transormation and computer dispersion models use emission data and

meteorological data to pro$ect how pollutants will orm and spread %disperse& across a

region.

'mission inventories are valua!le planning and evaluation tools in the air qualitymanagement system.

• 'PA encourages states to develop and maintain emission inventories" and provides

technical assistance to help the states achieve this goal.

'PA has pu!lished a num!er o documents to assist states and local agencies in

developing inventories.

(evelopment o an inventory is a tedious and detailed tas).



Source Control Technology (1)

• Air quality management sets the tools to control air pollutant emissions. This controltechnology or control measurements descri!es the equipment" processes or actionsused to reduce air pollution. The e,tent o pollution reduction varies amongtechnologies and measures. -n general" control technologies and measures that dothe !est $o! o reducing pollution will !e required in the areas with the worstpollution. The selection o control technologies depends on environmental"engineering" economic actors and pollutant type.

• +ome techniques to control air pollutant emissions do not require additionalequipment" while other techniques require addon controls. Addon controls are

equipment added to a pollution generating process to destroy or capture thepollutants. Techniques to cur! air pollutant emissions without using addon controlsinclude: process changes" changes in uel" good operating practices and plantshutdowns. These control methods wor) equally well or gaseous and particulatepollutants. An e,ample o a process change might !e the conversion rom a powersource using ossil uel to one using solar or hydroelectric power. +olar andhydroelectric power generators produce less air pollution than do generators that

!urn ossil uels. An e,ample o a change in uel would !e to use coal with low sulurcontent" rather than coal with high sulur content. This would reduce the amount osulur dio,ide emissions. Another e,ample o a uel change would !e to replace coalwith natural gas" a less polluting uel.

• 0ood operating practices include common sense measures" such as goodhouse)eeping and proper maintenance. An e,ample is the use o a regular inspection

and maintenance system to ensure that volatile organic compounds are not emitted!y lea)ing equipment in a chemical plant. 'quipment lea)s can !e a large source ovolatile organic compound emissions. A regular inspection program using simple lea)



Source Control Technology (2)

• 1inally" plant shutdowns are an e#ective pollution reduction technique. Plantshutdowns might !e necessary in e,treme cases" such as during an air pollutionepisode. eplacing old and outdated plants with moderni*ed acilities is also e#ectivein reducing air pollution.

• +ome techniques used to control PARTICULATES rom STATIONARY SOURCES:

– '+Ps %'lectrostatic Precipitators&

– 1a!ric 1ilter

– 3enturi +cru!!ers

– +ettling Cham!ers

– Cyclones• +ome techniques used to control GASEOUS POLLUTANTS rom STATIONARY

SOURCES:

– A!sorption

– Adsorption

– Condensation

– -ncineration

• +ome techniques used to control POLLUTANTS rom MOILE SOURCES:

– Cleaner 1uels

– Cleaner Cars

– -/ %-nspection/aintenance& Programs



SOURCE CONTROL TEC!NOLOGY " PARTICULATES

• Control o particulate pollutants rom stationary sources

• Control techniques or particles ocus on capturing the particlesemitted !y a pollution source. +everal actors must !e considered!eore choosing a particulate control device. Typically" particlesare collected and channeled through a duct or stac). Thecharacteristics o the particulate e,haust stream a#ect the choice

o the control device. These characteristics include the range oparticle si*es" the e,haust ow rate" the temperature" themoisture content" and various chemical properties such ase,plosiveness" acidity" al)alinity" and amma!ility.

•

The most commonly used control devices or controllingparticulate emissions include: electrostatic precipitators" a!ric6lters" venture scru!!ers" cyclones" and settling cham!ers. -nmany cases" more than one o these devices is used in a series too!tain the desired removal e7ciencies. 1or e,ample" a settlingcham!er can !e used to remove larger particles !eore a

pollutant stream enters an electrostatic precipitator.



P#rt$cul#te% " Electro%t#t$c Prec$&$t#tor%(ESP%)

• Control o particulates pollutants rom stationary

source.• An electrostatic precipitator %'+P& is a particle

control device that uses electrical orces to movethe particles out o the owing gas stream and

onto collector plates.• The '+P places electrical charges on the particles"

causing them to !e attracted to oppositelycharged metal plates located in the precipitator.

•

The particles are removed rom the plates !yrapping and collected in a hopper located !elowthe unit.

• The removal e7ciencies or '+Ps are highlyvaria!le8 however" or very small particles alone"the removal e7ciency is a!out 99 percent.



'$gure Electro%t#t$c Prec$&$t#tor (ESP)Co&onent%



P#rt$cul#te% " '#*r$c '$lter%

• Control o particulate pollutants rom stationarysources.

• 1a!ric 6lters" or !aghouses" remove dust rom agas stream !y passing the stream through aporous a!ric.

• The a!ric 6lter is e7cient at removing 6neparticles and can e,ceed e7ciencies o 99percent in most applications.

• The selection o the 6!er material and a!ric

construction is important to !aghouseperormance.

• The 6!er material rom which the a!ric is mademust have adequate strength characteristics at

the ma,imum gas temperature e,pected andade uate chemical com ati!ilit with !oth the



'$gure '#*r$c '$lter (#ghou%e) Co&onent%



P#rt$cul#te% " +entur$ Scru**er%

• Control o particulate pollutants rom stationary sources.

• 3enturi scru!!ers use a liquid stream to remove solidparticles.

• -n the venturi scru!!er" gas laden with particulate matterpasses through a short tu!e with ared ends and aconstricted middle.

• This constriction causes the gas stream to speed up whenthe pressure is increased.

• A water spray is directed into the gas stream either prior toor at the constriction in the tu!e.

• The di#erence in velocity and pressure resulting rom theconstriction causes the particles and water to mi, andcom!ine.

• The reduced velocity at the e,panded section o the throatallows the droplets o water containing the particles to dropout o the gas stream.

• 3enturi scru!!ers are e#ective in removing small particles"



'$gure +entur$ Scru**er Co&onent%



P#rt$cul#te% " Settl$ng Ch#*er%

• Control o particulate pollutants rom stationarysources.

• +ettling cham!ers use the orce o gravity toremove solid particles.

• The gas stream enters a cham!er where the

velocity o the gas is reduced.

• ;arge particles drop out o the gas and arerecollected in hoppers.

• <ecause settling cham!ers are e#ective in

removing only larger particles" they are used incon$unction with a more e7cient control device.



'$gure Settl$ng Ch#*er%



P#rt$cul#te% " Cyclone%

• Control o particulate pollutants rom stationary sources.

•Cyclones provide a lowcost" lowmaintenance method o removing largerparticulates rom a gas stream.

• The general principle o inertia separation is that the particulateladen gasis orced to change direction.

• As gas changes direction" the inertia o the particles causes them tocontinue in the original direction and !e separated rom the gas stream.

•

The walls o the cyclone narrow toward the !ottom o the unit" allowing theparticles to !e collected in a hopper.

• The cleaner air leaves the cyclone through the top o the cham!er" owingupward in a spiral vorte," ormed within a downward moving spiral.

• Cyclones are e7cient in removing large particles !ut are not as e7cientwith smaller particles.

•

1or this reason" they are used with other particulate control devices.• <ecause the particulate control devices discussed a!ove capture the

pollutants !ut don=t destroy them" proper disposal o the collected materialis needed.

• Collected solid particles are most oten disposed o in a land6ll. >astewatergenerated !y scru!!er must !e sent to a wastewater treatment acility.

•

>hen possi!le" collected particle matter is recycled and reused.



'$gure Cyclone Collector



GASEOUS POLLUTANTS

• Control o gaseous pollutants rom stationary

sources

• The most common method or controllinggaseous pollutants is the addition o addoncontrol devices to recover or destroy a pollutant.

• There are our commonly used controltechnologies or gaseous pollutants: a!sorption"adsorption" condensation" and incineration%com!ustion&.

• The choice o control technology depends on thepollutant%s& that must !e removed" the removale7ciency required" pollutant gas streamcharacteristics" and speci6c characteristics o the

site.• A!sor tion adsor tion and condensation all are



0aseous Pollutants A!sorption

• Control o gaseous pollutants rom stationary sources

•

The removal o one or more selected components rom a gas mi,ture !ya!sorption is pro!a!ly the most important operation in the control o gaseouspollutant emissions. A!sorption is a process in which a gaseous pollutant isdissolved in a liquid. >ater is the most commonly used a!sor!ent liquid. As thegas stream passes through the liquid" the liquid a!sor!s the gas" in much thesame way that sugar is a!sor!ed in a glass o water when stirred. A!sorption iscommonly used to recover products or to puriy gas streams that have high

concentrations o organic compounds. A!sorption equipment is designed to getas much mi,ing !etween the gas and liquid as possi!le.

• A!sor!ers are oten reerred to as scru!!ers" and there are various types oa!sorption equipment. The principal types o gas a!sorption equipment includespray towers" pac)ed columns" spray cham!ers" and venture scru!!ers. Thepac)ed column is !y ar the most commonly used or the a!sorption o gaseouspollutants. The pac)ed column a!sor!er has a column 6lled with an inert %non

reactive& su!stance" such as plastic or ceramic" which increases the liquidsurace area or the liquid/gas interace. The inert material helps to ma,imi*e thea!sorption capa!ility o the column. -n addition" the introduction o the gas andliquid at opposite ends o the column causes mi,ing to !e more e7cient !ecauseo the countercurrent ow through the column. -n general" a!sor!ers canachieve removal e7ciencies grater than 95 percent. ne potential pro!lem witha!sorption is the generation o wastewater" which converts an air pollution

pro!lem to a water pollution pro!lem.



'$gure A*%or&t$on " Ty&$c#l P#c,e-Colun .$#gr#



G#%eou% Pollut#nt% " A-%or&t$on

• Control o gaseous pollutants rom stationary sources.

•

>hen a gas or vapor is !rought into contact with a solid" part o it is ta)en up !y thesolid. The molecules that disappear rom the gas either enter the inside o the solid"or remain on the outside attached to the surace. The ormer phenomenon is termeda!sorption %or dissolution& and the latter adsorption. Adsorption is the !inding omolecules or particles to a surace. -n this phenomenon molecules rom a gas orliquid will !e attached in a physical way to a surace. The !inding to the surace isusually wea) and reversi!le. The most common industrial adsor!ents are activatedcar!on" silica gel" and alumina" !ecause they have enormous surace areas per unit

weight.• Activated car!on is the universal standard or puri6cation and removal o trace

organic contaminants rom liquid and vapor streams. Car!on adsorption usesactivated car!on to control and/or recover gaseous pollutant emissions. -n car!onadsorption" the gas is attracted and adheres to the porous surace o the activatedcar!on. emoval e7ciencies o 95 percent to 99 percent can !e achieved !y usingthis process. Car!on adsorption is used in cases where the recovered organics are

valua!le. 1or e,ample" car!on adsorption is oten used to recover perchloroethylene"a compound used in the dry cleaning process.

• Car!on adsorption systems are either regenerative or nonregenerative. Aregenerative system usually contains more than one car!on !ed. As one !ed activelyremoves pollutants" another !ed is !eing regenerated or uture use. +team is usedto purge captured pollutants rom the !ed to a pollutant recovery device. <yregenerating the car!on !ed" the same activated car!on particles can !e usedagain and again. egenerative systems are used when concentration o the pollutant

in the gas stream is relatively high. ?onregenerative systems have thinner !eds oactivated car!on. -n a nonregenerative adsor!er" the spent car!on is disposed o



'$gure A-%or&t$on " Regener#t$/e

C#r*on A-%or&t$on Sy%te

'$gure A-%or&t$on " NonRegener#t$/e

C#r*on A-%or&t$on Sy%te



G#%eou% Pollut#nt% " Con-en%#t$on

• Control o gaseous pollutants rom stationary sources.

• Condensation is the process o converting a gas or vapor to liquid. Any

gas can !e reduced to a liquid !y lowering its temperature and/orincreasing its pressure. The most common approach is to reduce thetemperature o the gas stream" since increasing the pressure o a gas can!e e,pensive. A simple e,ample o the condensation process is dropletso water orming on the outside o a glass o cold water. The coldtemperature o the glass causes water vapor rom the surrounding air topass into the liquid state on the surace o the glass.

• Condensers are widely used to recover valua!le products in a wastestream. Condensers are simple" relatively ine,pensive devices thatnormally use water or air to cool and condense a vapor stream.Condensers are typically used as pretreatment devices. They can !e usedahead o adsor!ers" a!sor!ers" and incinerators to reduce the total gasvolume to !e treated !y more e,pensive control equipment. Condensers

used or pollution control are contact condensers and suracecondensers. -n a contact condenser" the gas comes into contact with coldliquid. -n a surace condenser" the gas contacts a cooled surace in whichcooled liquid or gas is circulated" such as the outside o the tu!e.emoval e7ciencies o condensers typically range rom 5@ percent tomore than 95 percent" depending on design and applications.



'$gure Cont#ct

Con-en%er

'$gure Sur0#ce

Con-en%er



G#%eou% Pollut#nt% " Inc$ner#t$on

• Control o gaseous pollutants rom stationary sources

• -ncineration" also )nown as com!ustion" is most used to control the emissions o organic compoundsrom process industries. This control technique reers to the rapid o,idation o a su!stance through

the com!ination o o,ygen with a com!usti!le material in the presence o heat. >hen com!ustion iscomplete" the gaseous stream is converted to car!on dio,ide and water vapor. -ncompletecom!ustion will result in some pollutants !eing released into the atmosphere. +mo)e is oneindication o incomplete com!ustion. 'quipment used to control waste gases !y com!ustion can !edivided in three categories: direct com!ustion or aring" thermal incineration and catalyticincineration. Choosing the proper device depends on many actors" including type o ha*ardouscontaminants in the waste stream" concentration o com!usti!les in the stream" process ow rate"control requirements" and an economic evaluation.

• A direct com!ustor or are is a device in which air and all the com!usti!le waste gases react at the

!urner. Complete com!ustion must occur instantaneously since there is no residence cham!er.1lares are commonly used or disposal o waste gases during process upsets" such as those thatta)e place when a process is started or shut down. A are can !e used to control almost anyemission stream containing volatile organic compounds. +tudies conducted !y 'PA have shown thatthe destruction e7ciency o a are is a!out 9 percent.

• -n thermal incinerators the com!usti!le waste gases pass over or around a !urner ame into aresidence cham!er where o,idation o the waste gases is completed. 1or thermal incineration" it isimportant that the vapor stream directed to the thermal incinerator have a constant com!usti!le

gas concentration and ow rate. These devices are not wellsuited to vapor streams that uctuate"!ecause the e7ciency o the com!ustion process depends on the proper mi,ing o vapors and aspeci6c residence time in the com!ustion cham!er. esidence time is the amount o time the uelmi,ture remains in the com!ustion cham!er. ten" supplementary uel is added to a thermalincinerator to supplement the quantity o pollutant gases !eing !urned !y the incinerator. 'nergyand heat produced !y the incineration process can !e recovered and put to !ene6cial uses at aacility. Thermal incinerators can destroy gaseous pollutants at e7ciencies o greater than 99percent when operated correctly.

• Catalytic incinerators are very similar to thermal incinerators. The main di#erence is that ater

passing through the ame area" the gases pass over a catalyst !ed. A catalyst is a su!stance thatenhances a chemical reaction without !eing changed or consumed !y the reaction. A catalyst



'$gure Ther#l $nc$ner#tor gener#l c#%e

'$gure C#t#lyt$c $nc$ner#tor



MOILE SOURCES

• Control o pollutants rom mo!ile sources

• To achieve onroad mo!ile source emissioncontrol an integrated approach has !een used.

• This integrated approach includes technologicaladvances in vehicle and engine design together

with cleaner" highquality uels plus the additiono vapor and particulate recovery systems andthe development o auto inspection andmaintenance %-/& programs.



Mo*$le Source% " Cle#ner 0uel%• Control o pollutants rom mo!ile sources

• ne way to reduce air pollution rom cars and truc)s is to

use a gasoline that is designed to !urn clean. This cleaner!urning gasoline" called reormulated gasoline or 10" isrequired in cities with the worst smog pollution" !ut othercities with smog pro!lems may choose to use 10.eormulated gasoline contains less volatile organiccompounds %3Cs&" and will contain o,ygen additives toma)e the uel !urn more e7ciently. Also" all gasolines willhave to contain detergents" which" !y preventing !uildupo engine deposits" )eep engines wor)ing smoothly and!urning uel cleanly.

• ethyl tertiary!utyl ether %T<'& is the o,ygen additive

most commonly used !y the petroleum industry to satisythe two percent o,ygen mandate in the 10 program. T<'is used in appro,imately percent o 10" with ethanol!eing the second most commonly used additive.,ygenates increase the com!ustion e7ciency o gasoline"

there!y reducing vehicle emissions o car!on mono,ide. n



'$gure Methyl tert$#ry"*utyl ether (MTE)



Mo*$le Source% " Cle#ner C#r%


• -n response to tighter standards" manuacturers equipped new cars with even more

sophisticated emission control systems. These systems generally include a threeway catalyst %which converts car!on mono,ide and hydrocar!ons to car!ondio,ide and water" and also helps reduce nitrogen o,ides to elemental nitrogen ando,ygen&" plus an on!oard computer and o,ygen sensor. This equipment helpsoptimi*e the e7ciency o the catalytic converter. The catalytic converter is an antipollution device located !etween a vehicle=s engine and tailpipe. Catalyticconverters wor) !y acilitating chemical reactions that convert e,haust pollutantssuch as car!on mono,ide and nitrogen o,ides to normal atmospheric gases such asnitrogen" car!on dio,ide" and water.

• -n diesel e,haust" the addition o a particulate 6lter as an antipollution devicetraps particles in the e,haust !eore they can escape into the atmosphere. A vaporrecovery system" also an antipollution system" captures gasoline vapors thatwould otherwise escape into the atmosphere rom hot vehicle engines and ueltan)s.

•

1inally" auto ma)ers must !uild some cars that use clean uels" including alcohol"and that release less pollution rom the tailpipe through advanced engine design.'lectric cars" which are lowpollution vehicles" are currently !eing used as cleancars. 'lectric cars produce essentially no pollution rom the tailpipe or through uelevaporation. Car manuacturers are also !eginning to sell hy!rid vehicles thatcom!ine an electric motor with a separate gasoline or diesel engine. By!ridvehicles can more than dou!le the gas mileage o conventional gasoline or diesel

powered cars and can cut emissions signi6cantly.



Mo*$le Source% Auto In%&ect$on M#$nten#nce



Mo*$le Source% " Auto In%&ect$on M#$nten#nce(I3M) Progr#%


• Dnder the E99@ Clean Air Act" auto manuacturers will !uild

cleaner cars" and cars will use cleaner uels. Bowever" to get airpollution down and )eep it down" a third program is needed8vehicle inspection and maintenance %-/&" which ma)es surecars are !eing maintained adequately to )eep pollutionemissions %releases& low. The E99@ Clean Air Act includes very

speci6c requirements or inspection and maintenance programs.• Auto inspection and maintenance programs are designed to

ma)e sure that the cars we !uy and drive perorm their !estand live up to their pollution control promise. Auto inspectionand maintenance programs require the testing o motor vehiclesin parts o the country with unhealthy air and the repair o those

that do not meet standards. -/ tests use special equipment tomeasure the pollution in car e,haust. These tests chec) that thecar=s )ey emission controls are installed as designed and thenanaly*e the e,haust to chec) accepta!le control o car!onmono,ide and hydrocar!ons. Advanced tests also chec)

nitrogen o,ide emissions.



'$gure Current #uto $n%&ect$on #n-#$nten#nce &rogr#



En0orceent• Air pollution laws and regulations are monitored and enorced !y ederal" state" and local agencies.

The state and local agencies" however" usually !ear the !urden o most compliance andenorcement e#orts.

• 'norcement consists o actions ta)en in response to violations o environmental law or regulations!y a person or company. 'norcement actions depend primarily on the seriousness andcircumstances o the violation. -n choosing the most appropriate enorcement action" 'PA and stateagencies generally try to achieve several goals. These goals include:

– Correcting the violation as quic)ly as possi!le

– (eterring uture violations

– <eing air to the regulated community !y treating similar violations with similar enorcementactions

– Punishing serious violations through criminal sanctions

– '#ectively using enorcement resources to achieve environmental and health goals with theleast amount o spending in terms o time and money

• There are various types o enorcement mechanisms availa!le to a regulatory agency. These rangerom inormal responses" such as warning letters" to ormal responses that can include legal ordersand civil or criminal actions.

• The Clean Air Act Amendments o E99@ have greatly strengthened the authority o 'PA and otheragencies designated to enorce the provisions o the Act. 1or e,ample" 'PA is empowered to imposeadministrative penalties o up to F25"@@@ per day or violations o air pollution regulations.

Previously" only the $udicial !ranch o the government could esta!lish such penalties. Theamendments also authori*e 'PA to esta!lish a 6eld citation program or minor violations. Thisessentially allows inspectors to issue tic)ets o up to F5"@@@ or any violation discovered during aroutine inspection. -n addition" the amendments strengthen 'PA=s power to enorce !oth civil andcriminal sanctions.

• The amendments also authori*e private citi*ens to see) civil penalties against polluters in citi*ensuits. This provision has the potential to increase the num!er o citi*en suits related to air pollution.

The amendments allow courts to assess penalties and issue violations.

•

Another enorcement eature o the amendments is the use o mar)et orces to ensure emissionsreductions To address the pro!lem o acid rain the amendments esta!lished an emissions trading

air pollution control.pptx

Documents