4th lecture Envi engg

Electrostatic precipitator

Use electrical forces to kove the particle out of the following gas stream and onto collector plates

Fabric filter

Remove dust from a gas stream by passing the stream through a porous fabric

Venturi Scrubber

Use liquid to remove particle

Cyclone

Inertial separation

Settling chamber

Force of gravity

Thermal Oxidizer

Include device that use air and auxiliary fuel to produce a region of high temperature in which pollutants are oxidized

Temperature, time, turbulence

Design and operation are based on three T's

Selective Catalytic reactor

Used extensively to NOx emission arising from the burning of fossil fuels in industrial processes

70-90%

Efficiency of catalytic reactors

Adsorption

When gas vapor is brought into contact with a solid, part of it is taken up by the solid. The molecules that disappear from the gas either enter the inside of the solid, or remain on the outside attached to the surface. The former phenomenon is termed absorption and the latter adsorption

Regenerative system

Usually contains more than one carbon bed, as one bed actively removes pollutants another bed is being regenerated for future use

Non regenerative system

Have thinner bed of activated carbon. In a non regenerative adsorber, the spent carbon is disposed of when it becomes saturated with the pollutant

Absorption

Is a process in which a gaseous pollutant is dissolved in a liquid

Water

Most commonly use absorbent liquid

Biofilter

Essentially a reactor filled with a biological support medium

Condensation

the process by which a gas or vapor changes to a liquid, any gas can be reduce to a liquid by lowering its temperature and or increasing its pressure

Contact condensers

Gas comes into contact with cold liquid

Surface condenser

The gas contact a cooled surface in which coole dliquid or gas is circulated such as the outside of the tube

Incineration

Also known as combustion, is most used to control the emission of organic compound from proces industries

Direct combustor

Complete combustion must occur instantaneously since there is no residence chamber

98%

Direct combustor efficiency

thermal incinerators

The combustible waste gases pass over or around a burner flame into a residence chember where oxidation of the waste gases is completed

99%

thermal incinerators efficiency

Catalytic Incinerators

Are very similar to thermal incineration, the main difference is that after passing through the flame area, the gases pass over catalyst bed

95%

Catalytic Incinerators efficiency