CONTROL OF GASEOUS POLLUTANTS

The emission of gaseous pollutants can be controlled by the following methods:

i) Absorption, 

ii) Adsorption, and

iii) Combustion or incineration

i) Absorption: It is a process that involves the transfer of the pollutants from the gas phase to the liquid phase across the interface in response to a concentration gradient set up across the interface. The pollutants commonly controlled by absorption are sulphur dioxide, hydrogen sulphide, nitrogen oxides and light hydrocarbons. The equipment which works on this principle are spray towers, packed towers, venture-scrubbers.

ii) Adsorption: It is the process of capturing and retention of gas molecules from the gas phase by the surface of the solid adsorber or adsorbent. The commonly used adsorbers or adsorbents are activated carbon, activated alumina, molecular sieves such as dehydrated zeolites, silica gel, etc.

iii) Combustion or incineration: It may be used when the pollutants in the gas stream are oxidization to an inert gas.Pollutants like hydrocarbons and carbon monoxides can be easily burnt, oxidized and removed.

 SMOKE AND ITS CONTROL

Smoke is a product of incomplete combustion of fuel and hence contains mainly carbon particles. For estimating the density of smoke, the most commonly used method is the Ringlemann chart method.