Air Pollution Control Equipment - US EPA
Air Pollution Control Equipment1
Overall ProcessMonitorsTreatmentAir PollutionControl DeviceStackProcess2This module will focus on air pollution control equipment. The flow diagrampresented in this slide shows schematically a process that might be the subject ofMACT EEE, the hazardous waste combustor MACT. The process would be suchas a chemical process. The treatment would be the part of the air pollution controlthat combusted the hazardous waste, such as an incinerator, solid or liquid fuelboiler, or cement or light aggregate kiln. The air pollution control device would beone that follows the combustion device to remove hazardous constituents from thegas stream before being released to the atmosphere. This module will discussvarious air pollution control devices.2
MACT EEE Air Pollution Control (APC) Devices Function – HAP Control HAP – Organic, Acid, Particulate APC Devices:–––––Dry and Wet Particulate Control DeviceBaghouse (Fabric Filter)Wet and Dry Gas ScrubberElectrostatic Precipitator (ESP)Activated Carbon Adsorption, Bed and Injection3The function of air pollution control devices generally and for the MACT EEE rulespecifically is to control or remove hazardous air pollutants (HAP) from the off gasstream before being released to the atmosphere. The HAP to be controlled can beorganic, acidic, or a particulate. Some types of air pollution control devices that willbe discussed are Dry and Wet Particulate Control Devices, Baghouses (also calledFabric Filters), Wet and Dry Gas Scrubbers, Electrostatic Precipitators (ESP), andActivated Carbon Adsorption, Bed and Injection.3
Devices to Control Particulate Matter1.2.3.4.5.6.7.Cyclone SeparatorFabric FiltersCartridge FiltersElectrostatic Precipitators (ESPs)High-Efficiency Particulate Air (HEPA) FiltersVenturi ScrubberFiber-Bed Mist-Eliminator (used with WetScrubbers)4Air pollution control devices used to control particulate matter are: CycloneSeparators, Fabric Filters, Cartridge Filters, Electrostatic Precipitators (ESPs),High-Efficiency Particulate Air (HEPA) Filters, Venturi Scrubbers, and Fiber-BedMist-Eliminators (used with Wet Scrubbers).4
Devices to Control Gaseous Pollutants1. Wet Gas Scrubber2. Packed-Bed Scrubber3. Adsorbers (Activated Carbon)4. Selective Catalytic Reduction (SCR)5. Selective Non-Catalytic Reduction(SNCR)5Air pollution control devices used to control gaseous pollutants are: Wet GasScrubbers, Packed-Bed Scrubbers, Adsorbers (Activated Carbon), SelectiveCatalytic Reduction (SCR), and Selective Non-Catalytic Reduction (SNCR).5
APC Technical Considerations One type of APC device may be moreappropriate than another Incinerator is more appropriate than flarefor compounds containing halogensbecause acids formed by combustion maybe removed by scrubber followingincinerator, whereas flare cannot beequipped with scrubber to remove acidgas6There are technical considerations for air pollutant control devices since one type ofAPC device may be more appropriate than another. An Incinerator, for example, ismore appropriate than flare for compounds containing halogens because acidsformed by combustion may be removed by scrubber following incinerator, whereasflare cannot be equipped with scrubber to remove acid gas.6
APC Technical Considerations Table below provides qualitativedescription of different APC devices asthey apply to varying stream and flowcharacteristics Table only can be used as generalguideline because it only provides quickqualitative snapshots of APC devices andconditions All technical aspects should be consideredthoroughly when evaluating APC devices7The Tables shown in slide that follow provide a qualitative description of differentAPC devices as they apply to varying stream and flow characteristics. TheseTables only can be used as general guideline because they only provide quickqualitative snapshots of APC devices and conditions. All technical aspects shouldbe considered thoroughly when evaluating APC devices.7
Technical Considerations – Device ranking is from Excellent (A) to Poor (F)8The table compares the stream characteristics for a Cyclone, Baghouse, ESP, Scrubber, Carbon Adsorber, Condenser, Flare and Incinerator.For low concentration streams, a baghouse, ESP, carbon adsorber, flare or incinerator are shown a possible good candidates. For a highconcentration stream, a condenser and an incinerator are good candidates, for high temperature or high volume streams, all but scrubber,carbon adsorber and condenser are good candidates. For high moisture streams, a cyclone or a scrubber are the best choices.8
Technical Considerations – ContaminantsCondensibleParticulateSize A-CDeviceHalogenatedInorganicAcidsESPSize 10MicronsHigh B-DAABAADevice ranking is from Excellent (A) to Poor (F)* If followed by scrubber9The table compares the contaminant characteristics for a Cyclone, Baghouse, ESP, Scrubber, Carbon Adsorber, Condenser, Flare andIncinerator. For streams that are halogenated, a scrubber or carbon adsorber are good candidates. Note that an incinerator is a good choice iffollowed by a scrubber. For inorganic acids in the stream, a scrubber is the best choice. For condensible particulate, a flare or incinerator aregood choices. For particulate that is small, that is less than 10 microns, a baghouse, ESP, scrubber, or incinerator are good choices, whereasfor later particulate, a baghouse or scrubber are the best choices. For high vapor pressure contaminants in the stream, a scrubber, flare orincinerator are the best choices.9
Technical Considerations – Source Variable eratorCABDevice ranking is from Excellent (A) to Poor (F)10The table compares the characteristics of sources of contaminant for a Cyclone, Baghouse, ESP, Scrubber, Carbon Adsorber, Condenser,Flare and Incinerator. For non-continuous or batch processes, a cyclone, baghouse, and flare are good candidates. For continuous processes,all but a condenser could be considered for application. For a variable flow rate process and therefore variable contaminant concentration, acyclone, a baghouse and a flare are good candidates.10
Cyclone Separator11This slide shows how a cyclone separator works. As the schematic shows, dirtygas enters on the side at the top, normally at an angle, then swirls around theinterior of the cyclone spinning particulate to the sides of the cyclone. The removeddust slides to the bottom of the cyclone and exits at that point. The gas withreduced particulate exits the top of the cyclone.11
Cyclone Separator12This slide shows other schematics of cyclones with devices to aid the swirling actionof the cyclone.12
Cyclone Description Used for course particulate removal Typically used as pre-filter Can function at high temperatures withoutmoving parts Efficiency greatly depends on particle size Inlet swirling action moves suspendedparticles to walls then drops out13Cyclone separators are primarily used for course particulate removal. Mostly theyare used as a pre-filter to another filter to remove the smaller, finer particulate.Cyclones have no moving parts and typically can handle high temperatures withoutdifficulty. The efficiency of cyclones greatly depends on the size of the particulate,the larger particle being removed at higher efficiency than smaller particles. Theinlet swirling action, as discussed earlier, moves the particles that are suspended inthe gas to the walls of the cyclone where the velocity is lower and the particles willdrop out of the gas stream.13
Cyclone Advantages Low costSimple; no moving partsLow pressure drop compared to PMremovedWide temperature & pressure capabilitiesDry collection of PMRelatively small space requirement14The advantages of cyclones is that they are low cost, simple in operation becausethey have no moving parts, the pressure drop is low compared to the particlesremoved. Cyclones also can operate under wide ranges of temperature andpressure, they work well in dry gas streams for removal of particulate and arelatively small space is required for them.14
Cyclone Disadvantages Inefficient collection of small PMUnable to handle sticky or tacky PMIncrease in collection efficiency only withhigh pressure drop15The disadvantages of cyclones are that they are not highly efficient for collection ofsmall particulate, they do not operate well with sticky or tacky particles and toincrease their collection efficiency results in higher pressure drop across thecyclone.15
Fabric Filter – Baghouse16This slide depicts a fabric filter, commonly referred to as a baghouse because of thefilter bags it uses to collect particulate. In this schematic, the dirty gas enters from aplenum below the bags, flows through the bags from the outside to inside of thebags, then the cleaned gas exits from the top of the bags and the baghouse.Particulate that accumulates on the bags is removed by various means that will bediscussed later and falls to the bottom of the baghouse into a hopper for removal.16
Baghouse – Pulse Jet17This slide shows another schematic of a baghouse with a pulse jet to remove theparticulate from the bags. A blow pipe directs gas into the bag, reversing thedirection of gas through the bag, which blows the particulate off the bag and allowsit to drop to the hopper below. This process rotates between bags so that only afew bags are pulsed at a time.17
Baghouse - Shaker18This slide shows a shaker mechanism for particulate removal from bags. Here thebags are vibrated or moved back and forth to dislodge the particulate from the bagand allows the dust to settle in the bottom hopper.18
Baghouse SchematicThanks to MikroPul for use of pictures of their equipment19This slide shows another schematic view of a bag house.19
Baghouse Description Particles trapped on filter media, then removedEither interior or exterior filtration systemsUp to 99.9% efficiencyEfficiency increases with use; decreases aftercleaning 4 types of cleaning systems––––Shaker (off-line)Reverse air (low pressure, long time, off line)Pulse jet (60 to 120 psi air, on line)Sonic horn (150 to 550 Hz @ 120 to 140 dB, on line)20The fabric filter or baghouse as seen in the schematics previously presented trapsparticles on the filter media and then removes the particles by one of severalmeans. Although normally the collection side of the bag is the exterior, the interiorside can also be used. Some baghouses can remove particulate up to 99.9 percentefficiency. To clean the bags, four types of systems are used: shaker, normallydone while the baghouse is off-line; reverse air flow, which is low pressure, takes arather long time and must be done off-line; pulse jet with 60 to 120 psi air pressuredone while the baghouse is on-line; and use of a sonic horn to vibrate the bags.20
Factors Affecting Baghouse Efficiency Filter media– Abrasion– High temperature– Chemical attack Gas flowBroken or worn bagsBlindingCleaning system failureLeaksRe-entrainmentDamper or discharge equipment malfunctionCorrosion21Factors that affect a baghouse’s efficiency are filter media that can be affected byabrasion, high temperature or chemical attach; gas flow rate; broken or worn bagsthat allow particulate to pass through; blinding; cleaning system failure; leaksaround bag seals or other locations; re-entrainment of particulate after cleaningsystem operation; malfunction of a damper or discharge equipment; and corrosionof metal parts within the baghouse.21
Baghouse Performance Indicators Outlet PM concentrationBag leak detectorsOutlet opacityPressure differentialInlet temperatureTemperature differentialExhaust gas flow rate22Some performance indicators for baghouse operation are the outlet concentration ofparticulate; detectors of bag leaks; opacity of the outlet gas stream; pressuredifferential across the filter; inlet temperature; temperature differential; or exhaustgas flow rate.22
Baghouse Performance Indicators Cleaning mechanism operation Fan current Inspections and maintenance23Other baghouse performance indicators are the operation of the cleaningmechanism; current draw of the fan motor; and inspections and maintenance of theequipment.23
Baghouse Advantages Extremely high collection of coarse and finePMInsensitive to gas stream fluctuationsAvailable in large number of configurationsCollected material is recovered dryCollection efficiency not effected by PMresistivitySpecial catalyst-impregnated bags available24Advantages are a baghouse is has an extremely high collection of coarse and fineparticulate; the baghouse’s insensitivity to gas stream fluctuations within itsoperating range; a large number of configurations are possible; the collectedmaterial is dry; the resistivity of the particulate does not effect the collectionefficiency; and the bags can be made of special catalyst-impregnated material.24
Baghouse Disadvantages Limited to operating temperature 290 CCertain gas stream constituents can form dioxinConcentrations of some dusts susceptible to fireCare is required to prevent corrosionRelatively high maintenance requirementsFabric can plug with hygroscopic, tacky material25A baghouse’s disadvantages are: it is limited to an operating temperature of lessthan 290 degrees Celcius; certain gas stream constituents can form dioxin,concentrations of some dusts susceptible to fire, care is required to preventcorrosion, there are relatively high maintenance requirements, and the fabric canplug with hygroscopic, tacky material.25
Baghouse InstallationThanks to MikroPul for use of pictures of their equipment26This slide shows an installation of several large baghouse cells.26
Baghouse InstallationThanks to MikroPul for use of pictures of their equipment27Another baghouse installation is shown in this slide.27
Baghouse InstallationThanks to MikroPul for use of pictures of their equipment28This slide shows an extremely large baghouse installation.28
BagsThanks to MikroPul for use of pictures of their equipment29This slide shows several bag configurations and illustrates an installation without thesurrounding sides.29
Bag Materials Felt, TFE30Bags can be produced from a variety of materials such as woven felt, polyester,polypropylene, aramid, rayton, fiberglass and PTFE (teflon).30
Bag RetainersThanks to MikroPul for use of pictures of their equipment31This slide shows the retainers that hold the bags in place and the venturi nozzles atthe top of the bag retainers.31
Cartridge Filters Basically the same as a Baghouse withCartridges rather than bags Somewhat more sensitive to moisturedepending on the cartridge Can get higher collection efficiency thanBaghouse32A variation of the baghouse is a cartridge filter system, sometimes referred to asdust collectors. The cartridge filter system is basically the same as a baghouse anduses cartridges rather than bags. The cartridges are more sensitive to moisture,depending on the material of the cartridge. The cartridge system can provide higherdust collection efficiencies than a baghouse.32
Cartridge FilterThanks to Donaldson Torit for use of pictures of their equipment33This slide shows both a cartridge and the cartridge housing.33
Electrostatic Precipitator (ESP)34Another widely used particulate control device is the electrostatic precipitator,frequently referred to as an ESP. Dry gas enters the ESP and flows around theelectrodes and plates. The electrode is negatively charged and the collection plateis positively charged, making the particulate with high resistivity to be attracted tothe plate. The gas exiting the ESP has been cleaned of particulate and released tothe atmosphere. Particles that have been collected are released from the plates byseveral means and fall to the bottom of the housing into hoppers that allow forremoval of the collected particulate.34
ESP Principle of Operation35This slide further illustrates the principle of operation of the ESP. The particles inthe dust laden gas are attracted to the plate then later removed with the cleanedgas exiting the control device.35
Plate-type ESP36This slide provides a different view of a plate-type ESP. The illustration shows therapper for the collection plates and discharge electrodes.36
ESP Description Charged particles are attracted to plates andremoved from exhaust gas Two types– Dry type use mechanical action to clean plates– Wet type use water to pre-quench and to rinse plates High voltages are required Multiple sections (fields) may be used Efficiencies up to 99% can be obtained37The charged particles are attracted to plates and removed from the dust laden gasstream before exiting. The ESP has two types: either a dry type of system thatuses a mechanical action like rapping to clean plates or a wet type that uses waterto pre-quench and to rinse the particulate off the plates. An ESP operates with highvoltage to provide the charging and attraction of the particle to be removed. MostESPs are designed with multiple sections or fields. The ESP system can obtainparticulate removal efficiency to 99 percent.37
Factors Affecting ESP Efficiency Gas temperature, humidity, flow rateParticle resistivityFly ash compositionPlate lengthSurface area38The factors that affect an ESP’s efficiency are: the temperature, humidity and flowrate of the gas to be cleaned; the resistivity of the particle to be removed; thecomposition of the fly ash, that is the collected particles; the length of the collectionplate; and the total surface area of the collecting plates.38
ESP Performance Indicators Outlet PM concentrationOpacitySecondary corona power (current and voltage)Spark ratePrimary power (current and voltage)Inlet gas temperatureGas flow rateRapper operationFields in operationInlet water flow rate (wet type)Flush water solids content (wet type)39Performance indicators for an ESP are: the outlet concentration of the particulate;the opacity of the exhaust gas; the current and voltage of the primary andsecondary corona; the spark rate caused by arcing in the ESP; the inlet gastemperature; the flow rate of gas through the ESP; the rapper operation; the fields inoperation; the inlet water flow rate if a wet ESP; and the solids in the flush water if awet ESP.39
ESP Advantages High collection efficiency for small andlarge PMVery low pressure dropMinimum maintenance requirementsLow operating costs40Advantages of an ESP system are: the systems have a high collection efficiency forsmall and large particulate particles, the system normally has a very low pressuredrop, and maintenance requirements and operating costs are low.40
ESP DisadvantagesHigh capital costVery sensitive to fluctuations in gasstream flow rate, temperature, PMloadingInefficient on particles with high or lowresistivity – impractical for diversestreamsLarge space requiredLong weighted wires can oscillate(sparking)41Some disadvantages of an ESP are: the capital cost of the installation is high; theESP is sensitive to fluctuations in the gas flow rate, temperature and particulateloading; they are inefficient on particles with high or low resistivity making them notpractical for a stream with a diverse composition; a large space is required forinstallation; and on large systems the long weighted wires can oscillate and causesparking within the ESP.41
Dry ESP Advantages Can be designed for wide range of gas stream temperature (to700 C)Dry collection may lead to easier handling of captured PMDisadvantages Explosion hazard when treating combustible gases or PMCertain PM have too high or too low resistivity for effectivecollectionNot recommended for collection of sticky or moist materials42Advantages of a dry ESP are: that they can be designed for a wide range of gasstream temperature up to 700 degrees Celsius and collection of dry particles tend tobe easier to handle of the captured particles. Some disadvantages of a dry ESPsystem are: they can present an explosion hazard when the gases containcombustible materials; some particles have too high or too low resistivity for goodcollection; and a dry system is not recommended for collection of sticky or moistmaterials.42
Wet ESP Advantages Washing of collectors eliminates re-entrainment ofPM due to rappingHumid atmosphere allows collection of PM with highresistivity, sticky particles and mists, and absorptionof soluble gasesDisadvantages Inlet gas stream temperature 190 FConstruction of non-corrodible materialsCollected PM in form of slurry43Advantages of a wet ESP system are: that the washing of collectors eliminates there-entrainment of particles into the gas stream during rapping and the humidatmosphere inside the ESP allows for collection of particulate with high resistivity ,sticky particles, mists, and absorption of soluble gases. The wet ESP has thedisadvantages that the inlet gas stream must be below 190 degrees Fahrenheit, thematerials of construction must be non-corrodible, and the collected particulate formsa slurry in the effluent water.43
High-Efficiency Particulate Air (HEPA) Filters44This slide shows a High-Energy Particulate Air filter, called a HEPA filter, which is aparticulate collection device similar to a cartridge filter system.44
HEPA Filter Advantages Specifically designed for collection ofsubmicron PMInsensitive to major fluctuations in processstreamVery simple operationProvisions included for sensitive in-placetestingFilters are usually changed outside of housing45The advantages of the HEPA filter are that they are specifically designed forcollection of submicron particulate; they are insensitive to major fluctuations inprocess stream, their operation is very simple, provisions can be included forsensitive in-place testing, and the filters are usually changed outside of housing.45
HEPA Filter Disadvantages Media irreversibly damaged bymechanical stresses, high temperature,or high humidityFrequent filter changes are usual (filterscannot be cleaned)Spent filters may generate a largevolume of secondary waste with highdisposal restrictions46Disadvantages of the HEPA filter are that the media can be irreversibly damaged bymechanical stresses, high temperature or high humidity; frequent filter changes areusual and filters cannot be cleaned; and spent filters may generate a large volumeof waste with high disposal restrictions depending on the characteristics of theparticulate removed.46
Venturi Scrubber47This slide shows a schematic diagram of a venture scrubber. The dirty gas entersthe scrubber and the venturi, which is a reduction in area of the duct, increases thevelocity and turbulence. At the throat of the venturi the scrubbing liquid is injectedas an atomized droplets that cause the particles to interact and agglomerate. Fromthe throat the area of the duct increases, slowing the gas velocity as it enters acyclone separator that allows the velocity to be reduced further and theagglomerated particles to fall out.47
Venturi Scrubber Principle48This slide shows another schematic of the venturi scrubber principle.48
Fixed Throat Venturi Scrubber49This slide shows a variation on the vernturi scrubber type. The throat of the venturihas a fixed area.49
Variable Throat Venturi Scrubber50This slide shows a variable throat venturi.50
Two-Stage Scrubber51Some installations, such as the one presented in this slide, have the removal part ofthe scrubber separate from the venturi. The second stage can be a tray, packed orspray-type scrubber to allow for sorbent interaction with the gas stream.51
Scrubber with Tray Tower52This slide shows a venturi scrubber followed by a tray tower.52
Wet Scrubber Description Particles (and gases) get trapped in liquids– Inertial impaction and diffusion Liquids must contact pollutants and dirtyliquids must be removed from exhaust gas Chemical reaction occurs for reactantinjection (e.g. Cl2 reaction with NaOH) Four types: spray; venturi or orifice; sprayrotors; and moving bed or packed towers53The wet scrubber operates by particles, and gases to a degree, becoming trappedin the scrubber liquid due to the inertial impaction and diffusion created. The liquidmust contact the pollutants and the resulting dirty liquids in the gas stream must beremoved prior to release to the atmosphere. If the scrubber liquid has a chemicalreagent, such as sodium hydroxide or caustic, a chemical reaction will occur whenthe liquid is injected. Generally, there are four types of wet scrubbers: spray,venturi or orifice, spray rotors, and moving bed or packed towers.53
Factors Affecting Scrubber Efficiency Gas and liquid flow rate (saturated gasstream) Condensation of aerosols Poor liquid distribution High dissolved solids content in liquid Nozzle erosion or plugging Re-entrainment Scaling54Several factors affect the scrubber’s efficiency: the gas and liquid flow rate, thecondensation of aerosols, liquid distribution throughout the gas stream, highdissolved solids in the recirculated liquid, nozzle erosion or plugging, re-entrainmentof the pollutants, and scaling.54
Scrubber Performance Indicators Pressure differentialLiquid flow rateGas flow rateScrubber outlet gas temperatureMakeup / blowdown ratesScrubber liquid solids content (PM)Scrubber inlet gas, process exhaust gas temperature(PM)Scrubber liquid outlet concentration (Acid gas)Scrubber liquid pH (Acid gas)Neutralizing chemical feed rate (Acid gas)Scrubber liquid specific gravity (Acid gas)55Indicators of the scrubbers performance are: pressure differential across thescrubber, the liquid and gas flow rate, the scrubber outlet gas temperature, themakeup and blowdown rates, the solids content in the scrubber liquid, thetemperature of the gas entering the scrubber, the liquid outlet concentration ofpollutants, especially acid gases, the pH of the liquid, the neutralizing chemical feedrate, and the liquid density.55
Fiber-Bed Mist-Eliminator56This slide shows a fiber-bed mist eliminator. This device’s main function is toremove liquid droplets from the gas stream.56
Fiber-Bed Mist-Eliminator Advantages1. Highly efficient capture of submicronaerosols and mists2. Can handle acidic mists3. Moderate pressure drop4. Corrosive gases can be neutralized57Advantages of the fiber-bed mist eliminator are: it has a high efficiency for capturingsubmicron aerosols and mists, it can handle acid mists, it creates a moderatepressure drop, and corrosive gases can be neutralized within the mist eliminator.57
Fiber-Bed Mist-Eliminator Disadvantages Intolerant of PM in gas streamMust have corrosion resistantconstructionEffluent liquid must be handledLimited to gas stream inlet temperature 120 F58The mist eliminator’s principal disadvantages are: that it is not tolerant of particulatein the gas stream that would cause it to plug, the construction must be corrosionresistant, the effluent liquid must be addressed, and the inlet temperature of the gasstream is limited to about 120 degrees Fahrenheit.58
Mist Eliminator59This slide shows a schematic of a mist eliminator.59
Packed-Bed Scrubber60A packed bed scrubber operates such as illustrated in this slide. The gas enteringthe column generally vents upward through the column while the scrubbing liquiddrops downward through the column, providing a countercurrent flow of the liquidand gas. This countercurrent flow allows for interaction of the liquid with the gas toreact with pollutants such as acids.60
Packed-Bed Scrubber61This slide is a schematic of a packed bed scrubber. Also in this application, theliquid flows counter to the flow of gas through the scrubber. The scrubber is packedwith a media that allows for exposure of a large surface area that promotes theinteraction of the liquid and gas. The exit of the packed bed scrubber will have ademister to remove any liquid carryover.61
Packed-Bed Scrubber Advantages1. Highly efficient collection of acid gases2. Relatively low capital cost3. Small space requirements62The advantages of the packed bed scrubber are: it has a highly efficient collectionof acid gases, for a relatively low capital cost, and the space requirements arecomparatively minimal.62
Packed-Bed Scrubber Disadvantages1. Waste products collected wet2. Plugging of packing by high loading ofPM3. Gas stream inlet temperature limited to 190 F63The disadvantages of a packed bed scrubber are the waste products collected wet,plugging of packing by high loading of particulate, and the gas stream inlettemperature is limited to less than 190 degrees Fahrenheit.63
Hybrid Dry-Wet Scrubber64This slide shows a hybrid dray and wet scrubber system. The dirty gas first flowsthrough a spray dryer absorber in which an absorber is sprayed into the chamber.The gas with absorber is followed by a particulate collector to remove the sprayedabsorber material. The gas then enters the venturi scrubber as discussedpreviously then through a packed tower type scrubber before being exhausted tothe atmosphere.64
Adsorber65This slide illustrates a carbon bed adsorber. Gas from a process containing acontaminant enters one of two carbon beds that remove the contaminant byadsorption by the carbon. The carbon may be re-activated by injecti
4. Selective Catalytic Reduction (SCR) 5. Selective Non-Catalytic Reduction (SNCR) Air pollution control devices used to control gaseous pollutants are: Wet Gas Scrubbers, Packed-Bed Scrubbers, Adsorbers (Activated Carbon), Selective Catalytic Reduc
Unit 5 : Environmental Pollution Definition Cause, effects and control measures of :- a. Air pollution b. Water pollution c. Soil pollution d. Marine pollution e. Noise pollution f. Thermal pollution g. Nuclear hazards Solid waste Management : Causes, effects and control measures of urban and industrial wastes.
Secondary pollutants primary pollutant. air pollution. Objectives Name five primary air pollutants, and give sources for each. Name the two major sources of air pollution in urban areas. Describe the way in which smog forms. Explain the way in which a ther-mal inversion traps air pollution. Key Terms air pollution primary pollutant secondary .
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Because the main measure of air pollution we use is PM. 2.5, we use air pollution and PM. 2.5. interchangeably throughout the paper. Identifying the causal effect of air pollution on mental health illness is challenging for three reasons. First, air pollution is typically correlated with confounders such as income and . 3
Air pollution is the addition of harmful substances to the atmosphere. An air pollutant is anything in the air that can damage the environment or make people or other organisms sick. Some air pollution comes from natural sources. Other forms of air pollution are caused by things people do. There are two kinds of air pollutants: primary pollut-
Air Pollution Control Policy 12 Dr. Richard Ballaman, Swiss Federal Office for the Environment Key measures for successful Air Pollution Control in Switzerland Enforcement of Swiss Air pollution control policy through prescription, NOT subsidies �，而不是通过补贴
global scale and nested U.S. cities and quantify air pollution and health impacts, Conduct a detailed Northeast U.S. case study to validate the metamodel, Quantify air pollution and health impacts from transportation technology choices, Quantify air pollution and health impacts of coupled global climate and pollution policies.
and pollution sources in the Mongolian capital and conduct some air pollution analyses. Overall, the study indicates that the air pollution in Ulaanbaatar city is a very serious problem and for its reduction, rapid and thorough measures should be taken . Keywords Air Pollution; Pollutants; Ulaanbaatar City; Tho rough Measures 1. Introduction
