Industrial Air Pollution: Removal of Dilute Gaseous Vapors

Abstract

This article deals with the removal of volatile organic compounds (VOC) and odors from contaminated air generated by industrial operations. First, general information is given about air pollution: the main gaseous air pollutants are classified (NO_x, SO₂, CO, CO₂, etc.) according to the targeted receptive area and the nuisance created. A point is made on the principal manufacturing sources involved in this pollution.

Then, a state of the art on main removal techniques is given. Five cleaning processes are discussed: adsorption, scrubbing, condensation, biological removal and oxidizing systems. The principal fields of use, advantages and disavantages are studied for each of them.

Activated carbon adsorption is the most common technique for solvent removal thanks to an easy use and an economical way to recover a wide range of gas streams. But improvements must be made to reduce the slowness of operations, the treatment of mixtures, etc.

Scrubbing is seldom used for low VOC content, while it is very efficient for odor removals, with chemical oxidizing absorption. Major problems are linked with the oxidants use.

Condensation can be energy intensive and is generally used for gas streams with high levels of VOC contamination.

Biological processes can achieve very good efficiencies for very low VOC and inorganic compounds contents. Caking problems and slow residence time are the main disadvantages of this technique.

Thermal combustion and catalytic oxidation are total destruction methods. Low valuable VOC and high concentrations are required to be treated by these expensive processes.