Control of the pollutants by process change methods

In controlling air pollution by process changes the method to be employed naturally depends upon the particular process involved. As a result no fixed set of rules can be applied on a universal basis.

Generally, four methods are available to control the pollutants by process changes.

 Substitution of raw materials or fuels

 Modification or replacement of process itself and also the process equipment.

 Changes in operational practices.

Substitution of raw materials or fuels

This method has been used successfully in many cases for controlling atmospheric pollution. For example use of low-volatile coals in place of high-volatile coals has proved quit effective in eliminating smoke and soot in many industrial and commercial heating application. Similarly, substitution of low-suphur fuels for high-sulphur has reduced considerably the SO2 discharge into the atmosphere. Another method of decreasing air pollution is subtracting bauxite flux for fluorspar in an open health furnace.

Process Change

While modifying a given process, a unit operation may be eliminated or altered or other unit operation may be substituted or added. For example, in disposing combustible refuse, the practice of incineration may be discontinued in favor of sanitary landfill. Another example is in brass-foundry practice, where an additional operational step has been used to reduce air

pollution. Here, a fluxing material is applied to the surface of the molten brass which serves as an evaporation barrier and consequently reduces the emission of brass flumes.

Replacement of the process equipment

This may include (a) modification of one or more items of the process equipment, (b) replacement or repair of faulty or repair of faulty or malfunctioning equipment or (c) substitution of one type of equipment for another type.

Change in operational practices

A good example for this is a thermal power plant. Here by using a low-sulphur fuel in place of high-sulphur fuel, the rate of release of SO2 from coal burning operations can be reduced, especially during the period of adverse meteorological conditions and consequently reduce the air pollution problems.