Air pollution is a major cause for concern these days with increasing awareness of its harmful effects on the environment. Here is a discussion about it as well as a few air pollution control systems.
Air pollution is caused by gases and particles, both liquid and solid, which contaminate the environment. Scientists link this kind of contamination of the air to adverse health effects such as respiratory diseases and even cancer. Some of the other harmful effects of air pollution are: damage to heritage buildings and artifacts, for example, due to air pollution in the city of Athens there is evidence of corrosion on the marble statues of the Parthenon; damage to agricultural products causing reduction in the growth of trees and crop yields; reduction in visibility in the atmosphere; and change in the climate, since particulate pollutants are absorbed by the gases in the atmosphere, resulting in global warming.
The Various Sources of Air Pollution
Some of the anthropogenic sources of air pollution are:
Power plants that are combustion fired
Controlled practices of burning carried out in forestry and agricultural management
Air pollution emissions generated by motorized vehicles; marine vessels like cruise ships and container ships; and airplanes
Air pollution created by incinerators, furnaces, stoves, fireplaces, and burning wood
General industrial activity, power plants, and oil refineries
Burning of crop waste in farming, and chemicals
Fumes from aerosol sprays, varnish, hair spray, paint, and other solvents
Waste deposits in landfills, which give off methane
Some of the natural sources of air pollution are:
Dust that is blown in large areas that have very little vegetation
Methane given off by cattle due to digestion of food
The radioactive gaseous element, radon, formed by radioactive decay that occurs in the Earth's crust
Carbon monoxide and smoke from wildfires
Volcanic eruptions, which produce ash particles, chlorine, and sulfur
Air Pollution is an International Problem
The trouble with air pollution and the problems caused by it is that it often does not remain confined to any geographical region. For instance, the radioactive cloud that resulted from the nuclear accident in Chernobyl, in 1986, spread as far as Ireland. According to a report by the United Nations, Southeast Asia is covered by a two-mile thick haze, called the Asian browncloud, which has been created by the burning of fossil fuels and wood. This haze could be responsible for thousands of death in the region due to respiratory problems.
Efforts to Reduce Air Pollution
These days there are many technologies available that can be used to control air pollution, which go hand-in-hand with strategies in urban planning that are designed to reduce air pollution. For example, there is debate ongoing worldwide about how to reduce the dependence we have on fossil fuels for our energy requirements and shift instead to using environmentally friendly renewable sources of energy. Regulations are already in place to use air pollution control systems at industrial plants, power plants, oil refineries, and so on.
Air Pollution Control Equipment
Here are a few air pollution control systems that are being used by vehicles and industries. They help to either remove pollutants from a stream of exhaust before they are emitted into the air or destroy them.
Air Pollution Control Systems To Reduce Particulate Matter
Wet Scrubbers: These include a number of devices that remove pollutants from furnace flue gas as well as other gas streams. The pollutants are removed by the polluted gas stream being forced through a scrubbing liquid or by using some other method of bringing it into contact with the liquid. Wet scrubbers are used in a number of industries like large power plants, asphalt plants, steel plants, fertilizer plants, and acid plants.
Electrostatic Precipitator (ESP): Also known as Electrostatic Air Cleaners, this air pollution control system is a particulate collecting device which uses the force created by an induced electrostatic charge to remove particulate matter from any flowing gas, e.g. air. These filtration devices are highly efficient and are very effective in removing fine particles like smoke and dust from the air stream. ESPs are used for controlling particulate emissions in various industries like oil refineries, pulp mills, and oil and coal fired utilities that generate electricity which produce smoke.
Dust Cyclones: These are used to remove particulate matter from a gas or air stream, without using filters, using vortex separation instead. Mixtures of fluids and solids are separated by using gravity and rotational effects. There is large-scale use of cyclones in oil refineries as well as the cement industry wherein they form a part of the kiln preheaters.
Air Pollution Control Systems To Reduce NOx (Nitrogen Dioxide and Nitrogen Oxide)
Exhaust Gas Recirculation (EGR): This is a technique used for reducing NOx that is used in most diesel and gasoline engines. A part of the exhaust of an engine is recirculated back into its cylinders. When the incoming air is intermixed with the recirculated exhaust gas, it results in diluting the mixture with inert gas, reducing the adiabatic flame temperature and also lowering the excessive oxygen in diesel engines. The peak combustion temperature is also lowered because the specific heat capacity of the mix is increased by the exhaust gas. Since high temperatures cause Nox to form much faster, EGR helps in limiting NOx from being generated. Nox is produced when a mixture of oxygen and nitrogen is subjected to high temperatures.
Catalytic Converter: This is a device that is used to diminish the toxicity of emissions that are produced by internal combustion engines. First introduced in 1975 in the US in order to comply with the tightening regulations by the Environmental Protection Agency, catalytic converters are still used most commonly in the exhaust systems of motor vehicles. Some of the other places they are use in are: trains, mining equipment, forklifts, generator sets, and other machines equipped with engines.
Air Pollution Control Systems To Decrease Volatile Organic Compounds (VOC):
Gas Flare: Also called a flare stack, this is a chimney that is erected on oil rigs or oil wells, as well as landfills, chemical plants, and refineries. When flammable gas or unusable waste gas plus liquids are discharged by pressure relief valves, this device is used to burn them off. This device is also used in landfills to burn and/or vent the waste gas that is produced by the decomposing materials.
Biofilters: This is a technique for pollution control which uses living matter to trap and biologically degrade pollutants. In air pollution control, the pollutants in the air are subjected to micro biotic oxidation. In other words, when it is applied in the filtration and purification of air, microorganisms, such as fungi and bacteria that are embedded in a biofilm, are used to degrade the air pollutant.