air pollution by industries

8/3/2019 Air Pollution by Industries

http://slidepdf.com/reader/full/air-pollution-by-industries 1/10

Air Pollution by Industries

Tikam chand

M.Tech. (Energy)

Deptt. of Mechanical Engg. , MNIT, Jaipur

(email: [email protected])

Abstract

Industries play major part of increasing air

pollution which effects the environment.

Today it is necessary to take action over

pollution and take some actions to reduce it.

This paper discuss the pollutants generate by

the industries, there effects. Control

techniques used in the some countries in their

industries of steel, cement, oil etc are also

discuss

1. Introduction

Air is an important natural resource

providing the basis of life on earth. Pollution

had been known to exist for centuries, but

it became an issue of serious concern only in

the last 200 years or so, mostly due to

the industrial revolution. Atmospheric

pollution occurs because the release of air

pollutants takes place at a rate much faster than they

can be accommodated by the environment and

removed from the atmosphere without causing

serious harm. Air pollution is a release into

the atmosphere of any substances, e.g.

Chemicals or airborne particles, which are

harmful both to the human and animal health

as well as the health of wider environment.

Air pollution is defined as the

addition of various hazardous chemicals,

particulate matter, toxic substances and biological

organisms into the Earth's atmosphere Industries

can discharge contaminants into the air.

Approximately 11% of public complaints

about air quality in the region are about

odour or dust from industry.

The problem with industrial air pollution is

that the release of toxins from plants and

industrial institutions is very high for the per

capita allowance. More air pollution problems are caused by industrial institutions

than anything else, and many of these

institutions are in chronic violation of air

pollution regulations. Industrial air

pollution is one of our biggest air pollution

problems in the world. In every country we

have problems with the toxic gases that are

released into the air every day while our

products are made and our trash is burned.

2. Origin of industrial pollution

Industrial air pollution can be from the

following:-

-Pollution from thermal power plants.

-Pollution due to chemical fertilizers, food, pesticide

and pharmaceutical industries.



-Pollution due to cement, steel, paper, sugar

industries.

-Pollution due to textile and textile related industries.

-Pollution due to petroleum and other industries.

-Pollution due to atomic units.

3. Types of air pollutants

Carbon Dioxide (CO2) – This is one of the

major gas pollutants in the atmosphere.

Major sources of CO2 are due to burning of

fossil fuels and deforestation. Industrially

developed countries like USA, Russia etc.,

and account for more than 65% of CO2

emission. Less developed countries with 80%

of world’s population responsible for about

35% of CO2 emission. Due to high growth

reported from less developed countries in last

decade, it is estimated that, the Carbon

dioxide emissions may rise from these areas

and by 2020 their contribution may become

50%. It has also been seen that, Carbon

dioxide emissions are rising by 4% annually.

As ocean water contains about 60 times more

CO2 than atmosphere; CO2 released by the

industry leads to disturbance of equilibriumof concentration of CO2 in the system. In

such a scenario, the oceans would absorb

more and more CO2 and atmosphere would

also remain excess of CO2. As water warms,

ocean’s ability to absorb CO2 is reduced.

CO2 is a good transmitter of sunlight, but

partially restricts infrared radiation going

back from the earth into space. This produces

the so-called “Greenhouse Effect” that

prevents a drastic cooling of the Earth during

the night. This so-called “Greenhouse Effect”

is responsible for GLOBAL WARMING.Currently Carbon Dioxide is responsible for

major portion of the global warming trend.

Nitrogen oxides (NOx) – They come mainly

from nitrogen based fertilizers, deforestation,

and biomass burning. Nitrogen oxides

contribute mostly as atmospheric

contaminants. These gases are responsible in

the formation of both acid precipitation and

photochemical smog and causes nitrogen

loading. These gases have a role in reducing

stratospheric ozone.

Sulfur Dioxide (SO2) – Sulfur dioxide is

produced by combustion of sulfur-containingfuels, such as coal and fuel oils. SO2 also

produced in the process of producing Sulfuric

Acid and in metallurgical process involving

ores that contain sulfur. Sulfur oxides can

injure man, plants and materials. As

emissions of sulfur dioxide and nitric oxide

from stationary sources are transported long

distances by winds, they form secondary pollutants such as nitrogen dioxide, nitric

acid vapor, and droplets containing solutions

of sulfuric acid, sulfate, and nitrate salts.

These chemicals descend to the earth’s

surface in wet form as rain or snow and in

dry form as a gases fog, dew, or solid

particles. This is known as acid deposition or

acid rain.



Chlorofluorocarbons(CFCs) –

Chlorofluorocarbons, also known as Freons,

are greenhouse gases that contribute to global

warming. CFCs are responsible for loweringthe average concentration of ozone in the

stratosphere.

Smog – Smog is the result from the

irradiation by sunlight of hydrocarbons

caused primarily by unburned gasoline

emitted by automobiles and other combustion

sources. Smog is created by burning coal and

heavy oil that contain mostly sulfur impurities.

Dust - Generation of fine particulates and

dust are inherent in the process of Cement

industries, but most are recovered and

recycled. The sources of dust emission

include clinker cooler, crushers, grinders and

material-handling equipments. Material-

handling operations such as conveyors result

in fugitive dust emission.

4. Effects of industrial pollution

Global Warming - Global warming is

largely considered one of the most hazardous

and serious complications associated with air

pollution caused by industries. The liberation

of certain gases such as methane, or CH4,

and carbon dioxide, or CO2, together known

as greenhouse gases, is often considered to be

prime factors causing global warming. These

greenhouse gases often result in an increase

in the atmospheric temperature, causing

global warming. Global warming has various

serious implications both on the ecological balance as well as human health. It often

results in the melting of glaciers and

snowcapped mountains, resulting in an

increase in the water levels of seas and rivers,

eventually increasing the risk of floods.

Apart from this, global warming also often

has numerous serious health risks on humans

such as increase in diseases like Lyme,malaria, cholera, dengue and plague, among

others.

Acid Rain - Industries often emit large

amounts of nitrogen and sulphur gases

into the Earth's atmosphere. When

these gases react with water vapors in

the atmosphere, they often change into

more aggressive gases, namely nitric

acid and sulphuric acid respectively.

The rain containing large amounts of

these acids is known as acid rain. Acid

rain has various health and natural

dangers. It results in the erosion of

monuments and buildings, makes the

soil acidic in nature, resulting in

reduction of plant and animal growth,

among other issues. Apart from these,

acid rain causes serious health

disorders such as cancer, skin

disorders and even death.



Respiratory Disorders - The emission of

various gases such as carbon

monoxide, or CO, often results in

various respiratory disorders such as bronchitis, asthma, chronic obstructive

pulmonary disease, or COPD, in

individuals. CO damages air passages

in individuals, leading to respiratory

disorders. However, if carbon

monoxide is present in increased levels

in the atmosphere, it can even cause

the death of the person, by inhibitingoxygen intake by combining with

hemoglobin.

Ozone Layer Depletion - The ozone layer is

a gaseous blanket that helps in

supporting and sustaining life on Earth

by protecting us from various

hazardous radiations such as UV rays.

Hence, the addition of some of the

above mentioned pollutants often

damages the atmosphere, thus causing

various health risks in humans such as

skin disorders like rashes, irritation

and even cancer in severe cases.

5. Control Techniques

Industrial activities are so different, one from

the other, it is impossible to arrive at any

single solution—or even any single set of

solutions—to the variety of pollution

challenges that they present. There are many

approaches that can be adopted, but generic

measures to provide financial or other

incentives at the plant level seem to work the

best. However, there are opportunities for

improving machines and other devices thatmany different factories and industries use.

Industrial Boilers and Motors

Industrial boilers burn coal, oil and other

fossil fuels or very often gases that are by products of the production process, to

generate hot water or steam used in a variety

of ways. Chemical plants, for example, use

the heat to change one substance into

another. Paper mills will use it to “pulp”

wood, which creates the raw material for

paper. Because boilers are common to so

many industrial processes, boosting their efficiency will sharply reduce emissions.

Similarly, electric motors are widely used in

industrial applications, so increasing their

efficiency will also reduce pollution. Motors

that have been used most commonly in the

past have efficiencies ranging from 60 to 90

percent, but versions are now available to

reach 95 percent.

Better Boilers- One specific way of

improving the efficiency of boilers deserves

special mention because is can be used so

widely, but isn’t in the U.S.



Cogeneration of heat and power-In the vast

majority of cases, the largest single

improvement in efficiency and reduction in

air pollution that can be made at an industrialfacility is through the adoption of

cogeneration—also known as combined heat

and power, distributed generation, or

recycled energy—which is the simultaneous

production of two or more forms of energy

from a single fuel source. Most often, fuel is

burned to generate electricity and the leftover

heat, which otherwise would simply bereleased into the air, is used to make

chemicals, process food or the like.

Cogeneration facilities can extract 80 to 85

percent of the energy in fuel, significantly

reducing the air pollution compared to

facilities where electricity and heat are

produced separately. The engine used to

generate electricity canvary from large

diesels to giant turbines, but the approach is

the same: make the electricity and use the

heat that would otherwise be wasted. The

heat can also be used to provide air

conditioning, using absorption chillers in

which heat is used to run a compressor

instead of electricity, in which case it is

called trigeneration. Whatever the name,

cogeneration is used widely in Europe, but is

the exception not the rule in the United

States. Most of the nation’s CHP stations are

small facilities, operated on college

campuses, military bases or offices, hospitals

and other commercial facilities.

Increasing boiler efficiency-Increasing

boiler efficiency, thus reducing air pollution,

can be accomplished in a variety of ways:

1.Proper maintenance, which can include awide range of options, such as blowing soot

from surfaces, tune ups, and reducing excess

air.

2.Reducing the need for steam and, thus use

of the boiler, by eliminating leaks, insulating

pipes, recovering heat. These can boost

system efficiency by 5 to 40 percent, and

costs are usually recovered in one to twoyears.

3. Improving the operating system by, for

example, installing devices that allow loads

to be automatically controlled, which also

saves money by reducing fuel consumption.

4. Switching from coal or oil to natural gas,

this reduces operating costs and extends the

plant’s lifetime by eliminating corrosion and

other damage from pollution-rich fuels.

Electric Motor System

Motors produce air pollution indirectly using

electricity, so the emission reductions that

result from improving efficiency will dependon the type of fuel used by the generator. The

amount of electricity consumed by these

motors can be huge. In California, for

example, one-third of the electricity is used

to move water. Standard motors operate with

an efficiency of 60 to 70 percent for small

devices of a few kilowatts, to 92 percent for

large motors of 100 or more kilowatts. High-



efficiency motors operate in the range of 83

to more than 95 percent.

Some of the opportunities lie in improving

the efficiency with which the output of a

motor is used, not in the motor itself. One

analysis of an industrial pumping system, for

example, found that only 49 percent of the

energy output of the electric motor was

actually converted into work to move the

liquid. Optimizing system design rather than

simply choosing components can lead to

improvements of 60 percent using existing

technology. One study found that replacing

traditional power-transmission “V” belts with

modern flat belts could improve efficiency

from 85 to 98 percent. Adjustable-speed

electronic drives that better match

mechanical load reduce electricity demand.1

An energy-efficient motor costs more to buy,

with a price typically 15 to 30 percent above

that of a standard motor. But over a typical

10-year operating life, a motor can easily

consume electricity valued at over 57 times

its initial purchase price. So, for example,

with the purchase of a $1,600 less-efficientmotor, a buyer may be committing much

larger electricity bills. In the case of the

$1,600 motor, paying a bit more up front—

say, $400—will reduce electricity

consumption by 3 percent, saving $2,760.

Purchasing new or replacement energy-

efficient motors makes good economic sense.

Now for a closer look at three specific

industrial sectors that are the largest

consumers of energy and sources of air

pollution: cement kilns, steel making and oil

refineries.

Cement Kilns

Cement production consumes vast amounts

of energy and raw materials, so what comes

out of the smoke stack is not pretty. The

pollutant emitted in largest quantity is carbon

dioxide. Cement accounts for roughly 22

percent of the carbon dioxide emitted by the

world’s industries. This is for two reasons:

First, the raw material for cement is

limestone, or calcium carbonate—seashells

deposited millions of years ago. One of the

first steps in cement production is to

“decarbonize” it, or drive off the carbondioxide that it contains by burning. Older

kilns do this in a huge rotating kiln in which

the mass of materials is so wet that the

process takes roughly 30 minutes and large

amounts of energy.

Second, producing the heat for baking burns

huge quantities of fuel, usually whatever is

the cheapest, which means it’s usually the

dirtiest as well. The owners will burn

whatever they get their hands on, everything

from coal and used tires to hazardous wastes

and city trash. As a result, for every ton of

Portland cement produced, roughly one ton

of carbon dioxide is emitted, as well as other



pollutants such as black carbon, dioxins,

mercury and the like. Because so much of

carbon dioxide comes from “decarbonizing”

the essential ingredient of cement, it mightseem likely that cutting emissions would be

tough. Not so. Emissions can also be sharply

reduced by substituting other materials for

limestone to produce so-called “blended”

cements. Substitute materials include blast

furnace slag from steel mills and fly ash from

coal-fired power plants. Blended cement sets

a bit more slowly, but produces a stronger and longer-lasting concrete. In some nations

(e.g., The Netherlands), all concrete is made

from blended cement. Individual states

determine how much pollution is emitted

from cement kilns because they are the

principal customers. The state highway

department sets specifications for concrete

used to build highways, and their

counterparts who build schools, courthouses

and the like do the same for them, and those

who write the building codes determine what

architects and contractors do. Requiring

blended cement might not be as simple as

snapping fingers, but it is certainly no

herculean task. Other pollution can be cut by

switching from a wet kiln to the more

efficient, and hence cleaner, dry process.

Then there’s the question of fuel: kiln

operators are willing to use any fuel that will

sustain a flame, but that needn’t be the case.

The kilns could just as easily burn natural gas

instead of coal, used tires or hazardous waste.

For that matter, burning isn’t required at all,

just heat. That can be provided by the sun’s

energy or electricity.

Dust in Cement Plant and CHP

Several mechanical equipments are used in

cement manufacturing plant to control /

collect dust. These are:

Dust collector - A dust collector (bag house)

is a typically low strength enclosure that

separates dust from a gas stream by passing

the gas through a media filter. The dust is

collected on either the inside or the outside of

the filter. A pulse of air or mechanical

vibration removes the layer of dust from the

filter. This type of filter is typically efficient

when particle sizes are in the 0.01 to 20

micron range.

Cyclone - Dust laden gas enters the chamber from a tangential direction at the outer wall

of the device, forming a vortex as it swirls

within the chamber. The larger articulates,

because of their greater inertia, move

outward and are forced against the chamber

wall. Slowed by friction with the wall

surface, they then slide down the wall into a

conical dust hopper at the bottom of thecyclone. The cleaned air swirls upward in a

narrower spiral through an inner cylinder and

emerges from an outlet at the top.

Accumulated particulate dust is deposited

into a hopper, dust bin or screw conveyor at

the base of the collector



Electrostatic Precipitator - In an

electrostatic precipitator, particles suspended

in the air stream are given an electric charge

as they enter the unit and are then removed by the influence of an electric field. A high

DC voltage (as much as 100,000 volts) is

applied to the discharge electrodes to charge

the particles, which then are attracted to

oppositely charged collection electrodes, on

which they become trapped. An electrostatic

precipitator can remove particulates as small

as 1 μm (0.00004 inch) with an efficiencyexceeding 99 percent.

Steel Making

The iron and steel industry is the largest

energy-consuming manufacturing industry in

the world, accounting for 10 to 15 percent of

the annual industrial energy consumption.

Annual world steel production has increased

from about 100 million tons in 1945 to about

770 million tons in 1990, and is expected to

grow further, by about 1.7 percent a year,

mainly because of an increase in steel

consumption in developing countries. Air

pollution, sometimes in prodigious amounts,

is produced at several stages in making steel.

Options for reducing pollution in each stage

are:

Coking: coke oven emissions are highly toxic

—is to assure that the oven doors are tightly

closed. But an even better option is to make

steel without coke, using a process nowemployed in South Africa and South Korea.

Casting: Continuous casting in which the

steel is rolled immediately, thus avoiding the

energy and pollution from reheating, is

employed widely in other countries,

especially Japan.

Cogeneration: Many of the gases produced

during the production of steel can themselves

be burned to generate electricity. Doing so

increases efficiency and eliminates air

pollution.

Oil Refineries

Refining is most energy intensive industry

and the source of immense amounts of air

pollution Refinery pollution and energy

consumption can both be reduced through a

variety of measures.

Process integration- So many streams of

different fluids are constantly passing

through a refinery, undergoing conversions



that are so complex and numerous that they

inevitably reach a point where there is a

“pinch” in the system that slows things down

and cuts efficiency. To avoid these, analystshave developed a methodology to optimize

the system called, not surprisingly “pinch

analysis.” In recent years, it has been

extended to virtually every aspect of refinery

operation, in part because it has greater

potential for increasing efficiency than any of

the more traditional measures, such as

cogeneration.

Energy recovery-At various points in the

refining process fluids are lost that could be

captured and used either in the refining

process itself or to generate electricity. Some

of these are burned, or flared, as they are

vented to the air. Capturing these and using

them, either by re injecting them into the

stream of refinery fluids or burning them for

electricity generation, increases efficiency

and reduces air pollution.

Heat recovery-In a modern refinery most

processes operate at high temperatures and

pressures alike. The crude oil that enters the process is loaded with contaminants that can

and do foul pipes, furnaces and other

components, reducing the efficiency with

heat. By one estimate the economic value of

these losses is roughly $2 billion a year.

Textile industries

Textile industry is the source of air pollutants

like Carbon dioxide, Aerosol fumes and

gases, Toxic gases, Smoke and Dust.

General control measure

-Use of Electrostatic precipitator

-Use of scrubber

-Use of oxidizer

-Height of chimneys: Chimneys height

should not be less than 30 meters and release

the pollutants not in the vicinity of livingorganism

-Gravitational & inertial separator: These are

working on gravitational and inertial

concepts of collecting, filtering etc of the

particulate matter. Eg. Settling chambers,

dynamic separator and wet cyclones &

multiple cyclones.

- Filters: Woven or sintered metal beds of

fibers, metal turning, fibrous mats &

aggregate bed filter, paper filters and fabric

filters are used for the filtration of particulate

matter like dust, lint and fumes

Conclusion

There are many techniques which can be

used to reduce the air pollution by industries.

Every industry has a potential to reduce the

emission. Developed countries are used these

techniques and getting good results. May

these techniques increase the overall cost and

having a high payback period but it is

essential to use these techniques in order to

reduce the pollution, these technique will



give profit in the future In India these

techniques must be use to make the

environment pollution free. As in every other

sector of the economy, ranging from herds of dairy cattle to fleets of cars,

there is no lack of solutions in the industrial

sector. They abound. But, just as in every

other sector, those charged with making

decisions are motivated only by making

profit, as much as possible and as quickly as

possible. They will not save us, so we must

save ourselves.

References

1. Bonneville Power Administration,

“Energy-Efficient Electric Motor

Selection Handbook,” Jan., 1993,

2. Price, L. & Worrell, “Global EnergyUse, CO2 Emissions and the Potential for

Reduction in the Cement Industry,”

Cement Energy Efficiency Workshop,

Organized by IEA in cooperation with

WBCSD, Paris, France, Sep.4-5, 2006,

3. Air Pollution Caused by Industries |

eHow.com http://www.ehow.com/about_540

7184_air-pollution-caused-

industries.html#ixzz1Jh4tke7oa

4. Zoidis, John D. (1999). "The Impact of Air

Pollution on COPD". RT: for Decision

Makers in Respiratory Care.

5. "EPA: Air Pollutants". Epa.gov. 2006-06-

28. Retrieved 2010-08-29.

6SINTEF Civil and Environmental

Engineering, Cement and Concrete, N-7465Trondheim, Norway. "Mechanism for

performance of energetically modified

cement EMC".

6. www.e-textile.org

http://www.ehow.com/about_5407184_air-pollution-caused-industries.html#ixzz1Jh4tke7o




air pollution by industries

Documents