Encyclopedia of Environmental Science and Engineering, Volume I and II

106 AIR POLLUTION SOURCES

Part 2. Major Air Pollution Sources (continued)

Chemicals manufacturing industry Nature of activity Type of air pollution problems

PRINTING INK Printing ink is produced by adding dyes to water

and then flushing it with an ink vehicle.

Particulate emissions result from the addition of pigments

to the vehicle while gases like terpenses, carbon

dioxide, and aldehydes are emitted into the atmosphere,

during the preliminary stages of ink production.

SOAP AND DETERGENTS Soap is manufactured by the catalytic hydrolysis

of various fatty acids with sodium or

potassium hydroxide to form a glycerol-soap

mixture. This mixture is separated by

distillation, neutralized and blended to

produce soap. In the manufacture of

detergents, a fatty alcohol is sulfated,

neutralized, and then sprayed dry to obtain

the product.

The main atmospheric pollution problem in the

manufacture of soap is odor from the spray drying

operation, storage of mixing tanks and particulate

emissions from the spray drying tower.

CHEMICAL INDUSTRY

SODIUM CARBONATE

The Solvay process is used to manufacture over

80% of all soda ash. In this process, the basic

raw materials of ammonia, cake, lime-stone

(calcium carbonate) and salt (sodium

chloride) are purified inabsorbent using

ammonia and CO 2 , to produce sodium

bicarbonate as a by-product.

The major emissions from the manufacture of soda ash is

ammonia. Small amounts of ammonia are emitted in

the vent gases from the brine purification system.

Traces of particulate emissions can result from rotary

drying, dry solids handling and processing of lime.

SULFURIC ACID The contact process is responsible for producing

90% of all the sulfuric acid in the United

States. In this process sulfuric acid is

produced from the contact of SO 2 and SO 3

with water.

The waste gas contains unreacted sulfur dioxide,

unabsorbent sulfur trioxide, as well as sulfuric acid

mist and spray. When the waste gas reaches the

atmosphere, sulfur trioxide is converted to acid mist.

Food and agricultural industry Nature of activity Type of air pollution problems

This section deals with the manufacture of food

and agricultured products and the

intermediate steps which present an air

pollution problem.

ALFALFA DEHYDRATING

COFFEE ROASTING

An alfalfa dehydrating plant produces an animal

feed from alfalfa. The dehydrating and

grinding of alfalfa constitute the bulk of the

manufacturing process of alfalfa meal. It is a

very dusty operation most commonly carried

out in rural areas.

Coffee, which is imported in the form of green

beans, must be cleaned, blended, roasted and

packaged before being sold.

Sources of dust emissions are the primary cyclone,

grinders and air-meal separators. Overall dust loss has

been reported as high as 7% by weight of the meal

produced. The use of a bag house as a secondary

collection system can greatly reduce emissions.

Dust, chaff, coffeebean oils (as mists), smoke, and odors

are the principal air contaminants emitted from coffee

processing. The major source of particulate emissions

and practically the only source of aldehydes, nitrogen

oxides and organic acids is the roasting process.

COTTON GINNING In separating the seed from the lint in raw seed

cotton, a large amount of trash is left over.

From one ton of cotton approximately one

500 pound bale of cotton can be made, the

rest is discarded as trash.

The major sources of particulates from cotton ginning are

the unloading fan, the cleaner and the stick and bur

machine. When cyclone collectors are used emissions

have been reported to be about 90% less.

FEED AND GRAIN MILLS AND

ELEVATORS

Grain elevators are primarily transfer and

storage units of various sizes. At grain

elevator locations the following might occur:

recewing, transfer and storages, cleaning,

drying and milling or grinding.

Almost all emissions emanating from grain mills are dust

particulates (minute grain particulates). The emissions

from grain elevator operations are dependent on the type

of grain, the moisture content of the grain, amount of

foreign material, and the loading and unloading areas.

FERMENTATION Fermentation occurs when various organisms (as

molds, yeast, certain bacteria, etc.) agitate or

excite substances into another form. The

fermentation industries include the food, beer,

whiskey, and wine categories.

Emissions from fermentation process are nearly all gases

and primarily consist of carbon dioxide, hydrogen,

oxygen, and water vapor, none of which present an air

pollution problem. However, particulate emissions can

occur in handling of the grain used as raw material,

while gaseous hydrocarbons can be emitted during the

drying of spent grains.

FISH PROCESSING The canning, dehydrating, smoking of fish, and

the manufacture of fish oil are the important

segments of fish processing.

The biggest problem from fish processing is emissions of

odors such as hydrogen sulfide and trimethylamine.

Some of the methods used to control odors include

activated carbon adsorbers, scrubbing with some

oxidizing solution and incineration.

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