The present air in atmosphere mainly consists of gases like O2 and N2 along with other gases in small proportions. During the manufacturing process pollutants are generated in the form of solid particles, liquid droplets or gases. The volume of pollutants after discharging from production unit, mix with the air and increase their heavy presence in the atmosphere than legally required, is termed as air pollution. A substance in the polluted air can cause harm to human beings and environment.Following are the two types of sources for generation of pollutants
Primary Pollutants :
- Primary Pollutants
- Secondary Pollutants
Primary Pollutants are directly emitted from the process such as ash or sulphur dioxide released from factories.Secondary Pollutants :
Secondary Pollutants are not emitted directly. Rather, they are formed in the air when primary pollutants react.Mainly man made Primary Pollutants are as under:
- Sulphur Oxides (SOx) - Sulphur oxide is a chemical compound with a formula S02 is produced in various industrial processes where coal and petroleum is used.
- Nitrogen Oxides (NOx) - Nitrogen Oxide is a chemical compound with a formula NO2 is emitted during a high temperature combustion in an industry.
- Carbon Monoxide - It is a product by incomplete combustion of fuel such as natural gas, coal or wood.
- Carbon Dioxide (CO2) - Carbon Dioxide is associated with oceanic acidification, emitted from sources such as combustion, cement production and respiration.
- Volatile Organic Compounds (VOCs) - Volatile Organic Compounds are important outdoor air pollutants and are another dangerous compound which is often associated with industries uses.
- Particulate Matter (PM) - Particulate Matter are tiny particles of solid or liquid suspended in gas. Sources of Particulate matter can be man-made or natural. Particulate Matter generated by human activities such as burning of fossil fuels in vehicles, power plants and various industrial processes.
- Toxic Metals - Toxic metals are lead cadmium and copper.
Particulate matter formed from gaseous primary pollutants and compounds in photochemical smog. Smog is a kind of air pollution, a mixer of smoke and fog. Smog results from large amount of coal burning in an area caused by a mixture of smoke and sulphur dioxide.Control Devices
- For the control of air pollution, industry uses mainly the following devices. They can either destroy contaminants or remove them from an exhaust stream before it is emitted into the atmosphere
- Particulate control
- Mechanical collectors i.e. Dust cyclones, Multi cyclones
- Electrostatic precipitators. An electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device and can easily remove fine particulate matter such as dust and smoke from the air stream.
- Baghouses designed to handle heavy dust loads, a dust collector consists of a blower, dust filter, a filter-cleaning system and a dust receptacle or dust removal system (distinguished from air cleaners which utilize disposable filters to remove the dust).