Air Pollution control for ch Lecture.pdf

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1. Environmental Pollution
Control (CH-411)
Engr. SM Tarique
Lecturer,
Chemical Engineering Department

2. Air Pollution
•Pureairisamixtureofgases,containing,onadry
volume(ormolar)basis,
•Ifthisispureair,thenitmaybeusefultodefineas
pollutantsthosematerials(gases,liquids,orsolids)
that,whenaddedtopureairatsufficientlyhigh
concentrations,willcauseadverseeffects.
•Presenceofunwantedandundesirableforeign
particleandgassesintheair,whichhaveadverse
effectsonhumanbeing,animal,plants,vegetation
andimportantstructures.
Constituent Percentage
Nitrogen 78.1%
Oxygen 20.9%
Argon 0.9%
Carbon dioxide0.04%
Neon 0.002%
Helium 0.0005%

3. Types/ Classification of Air Pollutants
According to origin
Primary pollutants:
Pollutants emitted directly from the sources and are found in the atmosphere in the form
in which they were emitted. E.g. Sulphur Oxides, Nitrogen Oxides, Hydrocarbons, ash,
dust, fumes and mist etc.
Secondary pollutants:
Pollutants formed in the atmosphere by chemical interactions between primary pollutants
and atmospheric constituents, usually formed by a photochemical reaction or by
hydrolysis or oxidation reactions in the atmosphere.E.g. Ozone, Sulphur trioxide, etc.
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4. According to chemical composition
Organic pollutants:
Organic compounds contain carbon and hydrogen and many also contain elements such
as oxygen, nitrogen, phosphorous and sulfur e.g. Hydrocarbons(Carbon & Hydrogen),
aldehydes & ketones(Oxygen, Carbon & Hydrogen), ethers, esters, amines, alcohols and
organic sulfur compounds.
Inorganic pollutants:
•Carbon compounds(e.g. CO)
•Nitrogen compounds(e.g. NOXand NH3)
•Sulphur compounds(e.g. H2S, SO2, SO3 and H2SO4 )
•Halogen compounds(e.g. HF and HCL)
•Oxidizing agents(e.g. O3)
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Types/ Classification of Air Pollutants

5. According to state of matter
Gaseous air pollutants: air pollutants:
Pollutants occurring in the gaseous state at normal temperature and pressure e.g. CO, CO2,
NOX, SOX, etc.
Particulate air pollutants:
All atmospheric substances that are not gases but may be suspended droplets, solid
particles or mixture of the two are generally referred to as particulates e.g. Aerosols, dust,
smoke, fumes, mist, fog, fly ash and soot etc.
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Types/ Classification of Air Pollutants

6. Sources of Air Pollution
Atmosphere is a dynamic system which absorbs pollutants from natural as
well as anthropogenic sources and acts as a natural sink like ocean.
Natural Sources
•They cause large scale air pollution which is beyond the control of man
•It includes
•Geogenic:Emitted from geological processes(from volcano -sulfur gases (SO2
and H2S), methane, carbon dioxide, particulates (minerals), chlorides and
petroleum gases)
•Biogenic:emitted from living organisms(from photosynthesis, decomposition of
living matter, etc)
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7. Natural Sources
•Photochemical and other reactions in the atmosphere, Salt sprays(aerosols formed from
ocean), CO from breakdown of methane, H2S and CH4from anaerobic decomposition of
organic wastes, radioactive minerals from the earth’s crust, hydrocarbons from trees;
Smoke and dust particles from forest fires, volcanic eruptions, dust storms etc.
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Sources of Air Pollution

8. Manmade or Anthropogenic Sources
•They pose problems severe enough to endanger life and property
•Rapid industrialization, automobile revolution and deforestation
•Chemical, metallurgical, coal fired power plant and petroleum refineries produce SO2
gas, NH3, NO2, HF, HCL gas and H2S gas besides dust, fumes and tar etc.
•Solid waste disposal (i.e., household and commercial refuse, coal refuse, and agricultural
burning)
•Automobiles results in emission of hazardous pollutants as by-products of the
combustion of fossil fuels.
•Advanced agricultural techniques like spraying of crops for pest and weed control
releases many pollutants like chlorinated hydrocarbons, organic Phosphates, Arsenic,
Fluorides and Lead etc.
•Nuclear explosives used in the war result in radioactive pollutants.
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Sources of Air Pollution

9. Characteristics of air pollution
Particulates
•Particulate pollutants can be further classified as dusts, fumes, mists, smoke, or spray.
•The EPA defines particulate matter as shown in Table
•Dustis defined as solid particles that are
•Entrained by process gases directly from the material being handled or processed
(e.g., coal, ash and cement)
•Direct offspring of a parent material undergoing a mechanical operation (e.g.,
sawdust from woodworking)
•Entrained materials used in a mechanical operation (e.g., sand from sandblasting)
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10. Characteristics of air pollution
Particulates
•A fumeis also a solid particle, frequently a metallic oxide, formed by the condensation
of vapors by sublimation, calcination, or chemical reaction processes.
•A mistis an entrained liquid particle formed by the condensation of a vapor
•Smokeis made up of entrained solid particles formed as a result of incomplete
combustion of carbonaceous materials.
•
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11. Air pollution Control Techniques
Basic approaches to control stationary source emissions
Source correction methods
Pollution control equipment
Diffusion of pollutants in air
Vegetation
Zoning
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12. Source correction method
Industriesmakeamajorcontributiontowardscausingairpollution.Formationof
pollutantscanbepreventedandtheemissioncanbeminimizedatthesourceitself.By
carefullyinvestigatingtheearlystagesofdesignanddevelopmentinindustrial
processese.g.thosemethodswhichhaveminimumairpollutionpotentialcanbe
selectedtoaccomplishairpollutioncontrolatsourceitself.Suchas:
Substitution of raw materials:
Iftheuseofparticularrawmaterialresultsinairpollutionthenitshouldbe
substitutedbyanotherpurergraderawmaterialwhichreducestheformationof
pollutants.Thus,lowsulfurfuelwhichislesspollutionpotentialcanbeusedasan
alternative,and,comparativelyliquidpetroleumgas(LPG)orliquefiednaturalgas
(LNG)canbeusedInsteadoftraditionalhighcontaminantsfuelssuchascoal.
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13. Source correction method
Process modification:
By using modified techniques to control emission at source e.g.
-Washing coal before pulverization to reduce fly ash emissions
•
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14. Source correction method
Process modification:
DoublecatalysisabsorptionprocessreducesS�
2emissionsintheproductionof
sulphuricacid---Caesiumascatalyst
•
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15. Source correction method
Modification of existing equipment:
Useofpropercombustiondevicesandmaintenance,reducestheoutputof
pollutants
Smoke,CO&fumescanbereducedifopenhearthfurnacesarereplacedwith
controlbasicoxygenfurnacesorelectricfurnaces
Inpetroleumrefineries,lossofhydrocarbonvaporsfromStorageTanks(STs)due
toevaporation,temperaturechangesetc.canbereducedbydesigningtheSTs
withfloatingroofcoversorpressurizingtheSTs
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16. Source correction method
Maintenanceofequipment:
Pollutioncausedduetopoormaintenanceofequipmentsuchasleakage
aroundducts,pipes,valvesandpumpsetc.
Emissionofpollutantsduetonegligencecanbeminimizedbyroutine
checkupofthesealsandgaskits.
•
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17. Pollution Control Equipment
Sometimesitbecomesnecessarytoinstallpollutioncontrolequipmenttoremove
thepollutantsfromthemaingasstream.
Pollutioncontrolequipmentaregenerallyclassifiedintotwotypes:
i.Control devices for particulate contaminants
ii.Control devices for gaseous contaminants
•
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18. Pollution Control Equipment
•
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Pollution Control
Equipment
Control Devices for
Particulate Contaminants
i. Gravitational settling
ii. Cyclone Separators
iii. Fabric Filters
iv. Electrostatic
Precipitators v. Wet
Scrubbers (Collectors)
Spray
Tower
Venturi
Scrubber
Cyclonic
Scrubber
Control Devices for
Gaseous Contaminants
Absorption Adsorption Condensation
Combustio
n

19. CONTROL OF SULFUR OXIDES
•
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LIMESTONE SCRUBBING

20. AIR QUALITY INDEX
•
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AQI is the EPA’s index for reporting the Air Quality.
AQI is in the range of 0-500.

21. AIR QUALITY INDEX
•
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22. AIR QUALITY INDEX
22
Calculate the AQI of air that contains 5mg/??????
3
CO (8-hour average), 300 ????????????/??????
3
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10(24-hours Average), and 50????????????/??????
3
S�
2(24-hours average)

23. INDOOR AIR QUALITY
•
23
•SOURCES OF INDOOR AIR POLLUTION
•Heating FurnacesCO
•Gas stove Nitrogen Oxides. CO, C�
2
•Glue, paints, solventsVOC
•Earth gas seepage radon
•Cigarette smokeCO, C�
2, PM(Multiple)

24. INDOOR AIR QUALITY MODEL
24
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25. INDOOR AIR QUALITY MODEL
25
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28. Assignment Question

29. CONTROL OF SULFUR OXIDES
•
29
LIMESTONE SCRUBBING

30. CONTROL OF SULFUR OXIDES
•
30
LIMESTONE SCRUBBING

31. Find the Following
•Calculate the amount of S�
2that must be removed by scrubber , and
the amount emitted to atmosphere. Assume the efficiency of
scrubber is 90%
•Calculate the limestone feed rate.
•Estimate the amount of water evaporated in the scrubber to
humidify the flue gas. Also, calculate the composition, temperature,
and volumetric flow rate of the cleaned flue gas leaving the
scrubber.
•Calculate the sludge production rate(100% solid basis) and the free
water composition in the sludge assuming 60% solids is achieved.
Calculate the total water makeup rate to the FGD system.