Air Pollution Control: Stationary source Ms Sherina

Air Pollution Control approaches Gas Particulate

Gas Control Technologies Divided into 2 categories Process gases Volatilized organic compounds Solvents perchloroethylene Fuel vapors Propane, hexane Organic chemicals Acid gases HCl, HNO3, H2SO4, SO2, NO2 Toluene, methanol Combustion gases CO, Sulfur dioxides, NOx, product of incomplete combustion

Gas Control Technologies Absorbers Adsorbers Condenser

Absorbers Absorption is a gas-liquid contacting process that uses the preferentially solubility of the pollutant gas for the liquid phase Applications Gas streams containing Alcohols Acids Substituted aromatics Aldehydes esters

Adsorbers Work with the principle of molecular or atomic interaction at the surface of a sorbent Process is exothermic Application- gas phase air pollutants Composed of either natural or synthetic materials

Adsorbers Typical adsorbent materials Activated carbon Activated alumina Molecular sieves Silica gels

Condensers Operate by the removal of heat from the gas stream and provide a surface/medium for condensations from the gas phase to liquid to take place Two types Surface Coolant does not come into contact with the vapors/liquid condensate Contact The coolant, vapors and condensate are all intimately mixed

Condensers Used in gas streams containing: Aldehydes Alcohols Chlorinated compounds Fuel vapors Organic acids

Particulate control technologies Mechanical collectors Settling chambers Cyclones Fabric filters Wet scrubbers ESP

Wet scrubbers Provide control for a wide range of particulate emissions Used to control dry particulates in gas streams, equipped with a water spray system

Wet scrubbers Device that remove pollutants from a furnace flue gas or from other gas streams Applications: Gas streams containing emissions of dusts, metals, sticky particulates, soluble organic compounds

Wet scrubbers Advantages Relatively small space requirements Ability to collect gases as well as particulates Ability to handle high temperature, high humidity gas streams Minimal fire and explosion hazards Can neutralize corrosive gases Ability to achieve high collection efficiencies on fine particulates

Wet scrubbers Disadvantages Relatively high maintainance cost Must be protected from freezing Problem creation of water disposal problem Product collected wet Pressure drop and horsepower requirements possibly high

Dry scrubber does not saturate the flue gas stream that is being treated with moisture In some cases no moisture is added; while in other only the amount of moisture that can be evaporated in the flue gas without condensing is added do generally not have wastewater handling/disposal requirements Dry scrubbing systems are used to remove acid gases(such as SO2 and HCl) primarily from combustion sources

Dry scrubber Advantages No wet sludge to dispose of Relatively small space requirements Ability to collect acid gases at high efficiencies Ability to handle high temperature gas streams

Dry scrubber Acid gas control efficiency not as high as wet scrubber

END OF LECTURE