Mechanical devices generally work on the basis of the following:
(i) Gravity: In this process, the particles settle down by gravitational force.
(ii) Sudden change in direction of the gas flow. This causes the particles to separate out due to greater momentum.
2. Fabric Filters: The gases containing dust are passed through a porous medium. These porous media may be woven or filled fabrics.
The particles present in the gas are trapped and collected in the filters.
The gases freed from the particles are discharged.
3. Wet Scrubbers: Wet scrubbers are used in chemical, mining and metallurgical industries to trap SO2, NH3, metal fumes, etc.
4. Electrostatic Precipitators: When a gas or an air stream containing aerosols in the form of dust, fumes or mist, is passed between two electrodes, then, the aerosol particles get precipitated on the electrode.
C. Other practices in controlling air pollution -Apart from the above, following practices also help in controlling air pollution.
(i) Use of better designed equipment and smokeless fuels, hearths in industries and at home.
(ii) Automobiles should be properly maintained and adhere to recent emission-control standards.
(iii) More trees should be plantedalong road side and houses.
(iv) Renewable energy sources, such as wind, solar energy, ocean currents, should fulfill energy needs.
(v) Tall chimneys should be installed for vertical dispersion ofpollutants.
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