Sources of Air Pollution - WordPress.com€¦ · STATIONARY SOURCES OF AIR POLLUTION. A. Chemical and Allied Products The emissions from a chemical process can be related to the specific

SOURCES OF AIR POLLUTION

WHAT IS AN AIR POLLUTION??

SOURCE CLASSIFICATIONSOURCE

NATURAL SOURCE• Arising due to natural

causes like volcano, oceans, forest fire, dust storm, wind, etc.

ANTHRO-PROGENIC SOURCE• Arising due to man

made activities like industrial activities, vehicular emission, etc.

SOURCEPRIMARY SOURCE• Emitted directly from the

source

SECONDARY SOURCE• Formed in the

atmosphere due to chemical interaction between primary pollutants or between primary pollutants and atmosperic particles.

A. Natural Sources• Volcano• Accidental fire• Dust storms• Ocean• Plant and Trees

Volcano• An erupting volcano emits particulate matter.• SO2, H2S and methane are also emitted.• Harms the environment for a considerable distance

from the volcanic source• PM and Gases remains air born for a long period of

time.

Accidental fire• Fire emits large quantities of pollutants in the form of

smoke, unburned hydrocarbons, carbon monoxide,carbon dioxide, oxides of nitrogen, and ash.

• e.g. Forest fires in the Pacific Northwest of theUnited States have been observed to emit a plumewhich caused reduction in visibility and sunlight asfar away as 350 km from the actual fire.

Dust storms• Dust storms that entrain large amounts of particulate

matter.• Visibility reduction during major dust storms is cause

of severe highway accidents and can even affect airtravel.

• The particulate matter transferred by dust stormsfrom the desert to urban areas causes problems tohouseholders, industry, and automobiles.

• The materials removed by the air cleaner of anautomobile are primarily natural pollutants such asroad dust and similar entrained material.

Ocean• The ocean is continually emitting aerosols to the

atmosphere, in the form of salt particles, which arecorrosive to metals and paints.

• The action of waves on rocks reduces them to sand,which may eventually become airborne.

• Even the shells washed up on the beach are eroded bywave and tidal action until they are reduced to such asmall size that they too may become airborne.

Plant and Trees• Green plants play a large part in the conversion of

carbon dioxide to oxygen through photosynthesis;they are still the major source of hydrocarbons on theplanet.

• Blue haze over forested areas is nearly all from theatmospheric reactions of the volatile organics givenoff by the trees of the forest

Blue haze over forested areas

• Other natural sources, such as alkaline and saltwater lakes, Sulfurous gases from hot springs

ANTHROPROGENIC SOURCE

B. Anthropogenic sources• 1. Industrial Sources

• Industrial pollution comes from manufacturing products from raw materials—

(1) Iron from ore,(2) Lumber from trees, (3) Gasoline from crude oil, and(4) Stone from quarries.

• Industrial pollution is also emitted by industries that convert products to other products—

(1) Automobile bodies from steel, (2) Furniture from lumber,(3) Paint from solids and solvents, and (4) Asphaltic paving from rock and oil.• Industrial sources are stationary, and each emits

relatively consistent qualities and quantities ofpollutants. Eg. Paper Mill

• Industrial sources are stationary, and each emitsrelatively consistent qualities and quantities ofpollutants.

Utilities• An electric power plant generates electricity to heat

and light our homes in addition to providing power for the television, refrigerator

• If a large steam generating plant, producing 2000 MW, burns a million kilograms per hour of 4% ash coal, it must somehow dispose of 40,000 kg of ash per hour.

• Some will be removed from the furnaces by the ash-handling systems, but some will go up the stack with the flue gases.

• If 50% of the ash enters the stack and the fly ashcollection system is 99% efficient, 200 kg of ash perhour will be emitted to the atmosphere.

• For a typical generating plant, the gaseous emissionswould include 341,000 kg of oxides of sulfur per dayand 185,000 kg of oxides of nitrogen per day.

• For Control:(1) purchase lower-ash or lower-sulfur coal,(2) change the furnace so that more ash goes to the ash

pit and less goes up the stack, or(3) Install more efficient air pollution control

equipment.• In any case, the cost of operation will be increased

and this increase will be passed on to the consumer.

Personal sources▫ (1) automobiles, (2) home furnaces, (3) home fireplaces

and stoves, (4) open burning of refuse and leaves.

Control of Personal sources• Control of these personal sources of pollution takes

the form of• (1) regulation (fireplaces and stoves may be used

only when atmospheric mixing is favorable),• (2) change of lifestyle (sell the automobile and ride

public transportation),• (3) change from a more polluting to a less polluting

source (convert the furnace to natural gas), or• (4) change the form of pollution (instead of burning

leaves, haul them to the city dump).

• Whatever method is used for control of pollutionfrom personal sources, it will probably be difficultand unpopular to enforce.

• It is difficult to get citizens to believe that their new,highly advertised, shiny, unpaid-for automobiles areas serious a pollution problem as the smoking factorystack on the horizon.

• It is also a very ineffective argument to point out thatthe workers at that factory put more pollution into theair each day by driving their automobiles to and fromwork than does the factory with its visible plume ofsmoke.

II. COMBUSTION• Combustion is the most widely used, and yet one of

the least understood, chemical reactions at our disposal.

• Combustion is defined as the rapid union of a substance with oxygen accompanied by the evolution of light and heat.

• We use combustion primarily for heat by changing the potential chemical energy of the fuel to thermal energy.

• We do this in a fossil fuel-fired power plant, a home furnace, or an automobile engine.

• We also use combustion as a means of destruction forour unwanted materials.

• We reduce the volume of a solid waste by burning thecombustibles in an incinerator. We subjectcombustible gases, with undesirable properties suchas odors, to a high temperature in an afterburnersystem to convert them to less objectionable gases.

• The simple combustion equations are very familiar:C + O2 CO2

2H2 + O2 H2 O

• Products: carbon dioxide and water, which areodorless and invisible.

• Air pollutant: carbon monoxide, carbon dioxide,oxides of sulfur, oxides of nitrogen, smoke, fly ash,metals, metal oxides, metal salts, aldehydes, ketones,acids, polynuclear hydrocarbons, and many others.Combustion is extremely complicated but is generallyconsidered to be a free radical chain reaction.

• An automotive engineer, for example, was not overlyconcerned about the 1% of carbon monoxide in theexhaust of the gasoline engine.

• By getting this 1% to burn to carbon dioxide insidethe combustion chamber, the engineer could expectan increase in gasoline mileage of something lessthan one-half of 1%.

• This 1% of carbon monoxide, however, is 10,000ppm by volume, and a number of such magnitude cannot be ignored by an engineer dealing with airpollution.

• Combustion is extremely complicated but is generallyconsidered to be a free radical chain reaction.

• Several reasons exist to support the free radicalmechanism.

(1) Simple calculations of the heats of disassociation andformation for the molecules involved do not agree with theexperimental values obtained for heats of combustion.

(2) A great variety of end products may be found in the exhaustfrom a combustion reaction. Many complicated organicmolecules have been identified in the effluent from a systemburning pure methane with pure oxygen.

(3) Inhibitors, such as tetraethyl lead, can greatly change therate of reaction

• When visualizing a combustion process, it is useful to think of it in terms of the 3Ts: time, temperature, and turbulence.

• Time for combustion to occur is necessary. Acombustion process that is just initiated, and suddenlyhas its reactants discharged to a chilled environment,will not go to completion and will emit excessivepollutants.

• A high enough temperature must exist for thecombustion reaction to be initiated. Combustion is an

• exothermic reaction (it gives off heat), but it requires energy to be initiated.

• Turbulence is necessary to ensure that the reactingfuel and oxygen molecules in the combustion processare in intimate contact at proper instant, when thetemperature is high enough to cause the reaction tobegin.

• The physical state of the fuel for a combustionprocess dictates the type of system to be used forburning. A fuel may be composed of volatile material,fixed carbon, or both.

• The volatile material burns as a gas and exhibits avisible flame, whereas the fixed carbon burns withouta visible flame in a solid form. If a fuel is in thegaseous state, such as natural gas, it is very reactiveand can be fired with a simple burner.

• If a fuel is in the liquid state, such as fuel oil, most ofit must be vaporized to the gaseous state beforecombustion occurs.

• This vaporization can be accomplished by supplyingheat from an outside source, but usually the liquidfuel is first atomized and then the finely divided fuelparticles are sprayed into a hot combustion chamberto accomplish the gasification.

• With a solid fuel, such as coal or wood, a series ofsteps are involved in combustion. These steps occurin a definite order, and the combustion device mustbe designed with these steps in mind.

STATIONARY SOURCES OF AIR POLLUTION

A. Chemical and Allied Products▫ The emissions from a chemical process can be related

to the specific process.▫ A plant manufacturing a resin might be expected to

emit not only the resin being manufactured but alsosome of the raw material and some other productswhich may or may not resemble the resin.

▫ A plant manufacturing sulfuric acid can be expectedto emit sulfuric acid fumes and SO2.

▫ A plant manufacturing soap products could beexpected to emit a variety of odors.

▫ Depending on the process, the emission could be anyone or a combination of dust- aerosols, fumes, orgases.

B. Resins and Plastics▫ Resins are solid or semisolid, water-in-soluble,

organic substances with little or no tendency tocrystallize.

Application:▫ Basic components of plastics. Used for coatings on

paper, particleboard, and other surfaces that requirea decorative, protective, or special-purpose finish.The common characteristic of resins is that heat isused in their manufacture and application and gasesare exhausted from these processes. Some of thegases that are economically recoverable may becondensed, but large portions are lost to theatmosphere.

C. Varnish and Paints▫ In the manufacture of varnish, heat is

necessary for formulation and purification.The same may be true of operationspreparing paints, inks and other protective ordecorative coatings.

D. Acid Manufacture▫ Acids are used as basic raw materials for

many chemical processes and manufacturingoperations.

▫ Emission: gases including SO2and aerosolmists, containing SO3 and H2SO4, aerosolmists

▫ Other processes producing acids, such asnitric, acetic, and phosphoric acids, can beexpected to produce acid mists from theprocesses themselves as well as various toxicand nontoxic gases.

E. Soaps and Detergents▫ Soaps are made by reacting fats or oils with

a base. Soaps are produced in a number ofgrades and types. They may be liquid, solid,granules, or powder.

▫ The air pollution problems of soapmanufacture are primarily odors from thechemicals, greases, fats, and oils, althoughparticulate emissions may occur during andhandling operations.

F. Phosphate Fertilizers▫ Phosphate fertilizers are prepared by

beneficiation of phosphate rock to remove itsimpurities, followed by drying and grinding.The PO4 in the rock may then be reactedwith sulfuric acid to produce normalsuperphosphate fertilizer.

▫ Emission: The particulate and gaseousfluoride emissions.

G. Other Inorganic chemicalsMiscellaneous Inorganic Chemicals and Associated Air Pollution

Emissions

Inorganic Chemical Products

Major air pollution emissions

Calcium Oxide(lime) Lime dustSodium carbonate(soda ash) Ammonia-soda ash and dustSodium hydroxide(caustic

soda)Ammonia-caustic dust and

mistAmmonium nitrate Ammonia

Chlorine Chlorine gasBromine Chlorine gas

H. Petroleum▫ Petroleum products are obtained from crude oil.▫ Potential air pollutants from a petroleum

refinery could include Hydrocarbons from allsystems leaks, loading, and sampling;

▫ Sulfur oxides from boilers, treaters, andregenerators;

▫ Carbon monoxide from regenerators andincinerators;

▫ Nitrogen oxides from combustion sources andregenerators;

▫ Odors from air and steam blowing, condenser,drains, and vessels;

▫ Particulate matter from boilers, crackers,regenerators, cocking, and incinerators.

I. Primary Metals IndustryEmission: submicron-size dust and fumes.

1. Ferrous Metals▫ Air polluting emissions from steelmaking furnaces

include metal oxides, smoke, fumes, and dusts tomake up the visible aerosol plume. They also mayinclude gases, both organic and in organic.

▫ If steel scrap is melted, the charge may containappreciable amounts of oil, grease, and othercombustibles that further add to the organic gas andsmoke loadings.

▫ If the ore used has appreciable fluorideconcentrations, the emission of both gaseous andparticulate fluorides can be a serious problem.

2. Nonferrous Metals▫ Emissions from other non ferrous metal facilities

are primarily metal; fumes or metal oxides ofextremely small diameter.

▫ Arsenic, cadmium, bismuth, and other trace metalscan be emitted from many metallurgical processes.

J. Stone and Clay Products▫ These particulates may include fine minerals dusts

of a size to cause damage to the lungs.▫ In the production of clay, talc, cement, chalk, etc an

emission of particulate matter will usuallyaccompany each process.

▫ These processes may involve grinding, drying andsieving, which can be enclosed and controlled toprevent the emission of particles.

▫ In many cases, the recovered particles can bereturned to the process for a net economic gain.

▫ During the manufacture of glass, considerable dustwill be emitted. Some dusts may also be emittedfrom the handling of the raw materials involved.When glass is blown or formed into the product,smoke and gases can be released.

K. Forest Products Industry1. Wood Processing▫ Harvesting this resource can generate considerable

dust and particulates. Transportation over unpavedroads causes excessive dust generation .Visibilityreduction from such burning.

2. Pulp and Paper▫ Emissions from such recovery furnaces include

particulate matter, very odorous reduced sulfurcompounds, and oxides of sulfur.

• MOBILE SOURCES▫ A mobile source of air pollution can be defined as one

capable of moving from one place to another under its ownpower.

EMISSION FROM MOBILE SOURCESPower Plant Type Fuel Major Emissions Vehicle Type

Otto cycle Gasoline HC, CO, CO2, NOX

Auto, truck, bus

Two-stroke cycle Gasoline HC, CO, particulate, NOX

Motorcycle, outboard motor

Diesel Diesel oil NOX, SO2, CO2, particulate

Auto, truck, bus, railroad

Gas Turbine (jet) Turbine NOX, particulate Aircraft, marine, railroad

Steam Oil, Coal NOX, SO2, particulate

marine

Anthropogenic sources• Mostly related to burning different kinds of fuel.

• Stationary Sources include smoke stacks of power plants, manufacturingfacilities (factories) and waste incinerators, as well as furnaces and other typesof fuel-burning heating devices

• Mobile Sources include motor vehicles, marine vessels, aircraft and the effectof sound etc.

• Chemicals, dust and controlled burn practices in agriculture and forestrymanagement.

• Fumes from paint, hair spray, varnish, aerosol sprays and other solvents• Waste deposition in landfills, which generate methane. Methane is not toxic;

however, it is highly flammable and may form explosive mixtures with air.• Military, such as nuclear weapons, toxic gases, germ warfare and rocketry

Major pollutants from primary sources:• Sulfur oxides (SOx) • Nitrogen oxides (NOx) • Carbon monoxide • Carbon dioxide• H2S• HF• Volatile organic compounds • Particulate matter • Persistent free radicals• Toxic metals, such as lead, cadmium and copper. • Chlorofluorocarbons • Ammonia• Odors• Radioactive pollutants

Major pollutants from secondary sources:

• Photochemical smog • Ozone (O3)• Peroxyacetyl nitrate (PAN)• Aldehydes• Ketones• SO3

SOURCE CLASSIFICATIONTOTAL SOURCE

STATIONARY SOURCES

POINT SOURCE

Industrial processing, power plants, fuel combustion, solid waste disposal municipal incinerators, open burning, etc.

AREA SOURCE

Residential heating, coal, gas, oil, Institutional & Commercial heating, On site incineration, Open burning , Evaporative losses, etc.

MOBILE SOURCES

LINE SOURCE

Highwayvehicles,railroadlocomotives,channelvessels.

AREA SOURCE

Motor vehicles, railyardlocomotives, aircrafts, etc.

SOME SPECIFIC POLLUTANT AND THEIR SOURCE…