Method to control air pollution by rc vaisya

Method to control air pollution

1. METHODS TO CONTROL AIR POLLUTION Presented By- Registration no.- M.Tech (Env. Engg.) Presented to- Dr. R.C. Vaishya

2. Contents Introduction Major air pollutants Sources of air pollution Effects of air pollution Air pollution control methods Particulate pollution control Gaseous pollution control Conclusion References

3. Introduction Air pollution is a situation in which the outdoor atmosphere contains materials in concentrations which are harmful to people and their environment .

4. Major air pollutants Particulate matter Ozone Carbon monoxide Nitrogen dioxide Sulfur dioxide Lead Toxic air pollutants Greenhouse gases

5. Sources of air pollution

6. Effects of air pollution

7. Air pollution control methods 1. Dilution : dilution of contaminants in the atmosphere can be accomplished through the use of tall stacks. 2. Control at source : Substitution of raw materials Process modification Modification of existing equipment Maintenance of equipment Pollution control equipment

8. Particulate pollution control Devices for particulate pollutant control: a) Gravitational settling chamber- For removal of particles > 50µ Simple in design and operation. Settling chamber use the force of gravity to remove solid particles. Efficiency of removal is < 50%.

9. b) Centrifugal collectors /cyclones- Centrifugal force is utilized to separate the particulate matter. It can remove particle of size 5 to 25µm. Efficiency of removal is 50 to 90 %. Used mostly in industries such as feed and grain mills, cement plants etc.

10. c) Electrostatic precipitators Works on the principle of electrical charging of particulate matter (- ve ) and collecting it in a (+ ve ) charged surface. It can remove particle of size > 1µ. Removal efficiency is 95 to 99%.

11. d)Wet collectors or scrubbers Particulate matters are incorporated into liquid droplets and removed from the gas stream. Collection efficiency is a function of the energy consumed in the air to water contact process. Types of scrubbers- Spray tower Venturi scrubber Cyclone scrubber

12. Spray towers Water is introduced by means of spray nozzle. As the polluted gas flows upwards, the particulates present collide with the water droplets being sprayed, then under the influence of gravitational force, liquid droplets containing the particulates settle to the bottom of spray tower.

13. Venturi scrubbers Submicron particulates (size 0.5 to 5µm) associated with smokes and fumes are effectively removed. At a velocity from 60 to 180m/s, the contaminant gas passes through a duct that has a venturi shaped throat section. A coarse water spray is injected into the throat, where it is atomized by the high gas velocities. The liquid droplets collide with the particles in the gas stream, and the particles get entrained in the droplets and fall down to be removed later on.

14. Cyclone scrubbers High pressure spray nozzles generate a fine spray that intercepts the small particles entrained in the swirling gases. Particulate matter thrown to the wall by centrifugal force is then drained to the collection sump. For droplets of 100µm, efficiency approaches 100%, and 90 to 98% removal is achieved for droplets between 5 and 50µm.

15. e) Fabric filters ( Baghouse filters) In this device, the particulate laden gas stream passes through a woven fabric that filters out the particulate matter and allows the gas to pass through. After a dust mat has formed on the fabric, more efficient collection of submicron particles (99+percent) is accomplished by sieving.

16. Gaseous pollution control Methods of control include: a) Adsorption - Surface phenomenon Adsorption towers use adsorbents to remove the impurities from the gas stream. The impurities can bind either physically or chemically to the adsorbing material. It can remove low concentration of impurities from the flue gas stream. The most commonly used adsorbent is activated carbon.

17. b) Absorption In this process, gaseous pollutants removed by dissolution into a liquid solvent/absorbent such as water. The amount of gas that dissolves in a solvent depends upon the properties of both the gas and the solvent. Absorbents used to remove sulfur dioxide, oxides of nitrogen, hydrogen sulfide, chlorine, ammonia, hydrogen chloride and hydrocarbons.

18. c) Condensation Condensation is the process of converting a gas or vapor to liquid. Any gas can be reduced to liquid by lowering its temperature and/or increasing its pressure. Condensers are typically used as pretreatment devices. They can be used ahead of adsorbers, absorbers, and incinerators to reduce the total gas volume. Removal efficiency of condensers typically range from 50% to more than 95% depending upon design and applications.

19. d) Combustion This method used for the removal of VOCs since they can be decomposed to CO 2 and H 2 O. The combustion equipment is designed to push oxidation reactions as close as possible to completion, leaving a minimum of unburned compounds. For efficient combustion to occur ,it is necessary to have proper combination of four basic elements: oxygen, temperature, turbulence, and time.

20. Conclusion Air pollution is a major environmental issue .It can affect health and life support systems as well. Since clear air is an essential factor of life for respiration, it is necessary to prevent the sources of air pollution. Using appropriate controlling devices and processes, the pollutants in the air can be removed. There are five processes for the removal of particulate matters. Settling chambers, cyclone, electrostatic precipitators, wet scrubber, fabric filters. For gaseous matters, adsorption, absorption, condensation, and combustion processes are used .

21. References: Peavy, H.S., Rowe, D.R. and Tchobanoglous, G. (1985) Environmental Engineering. McGraw-Hill Book Company, New York, 696. https://www.yourarticlelibrary.com/air-pollution/5-effective-methods-to-control-air-pollution-explained-with-diagram/28360

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