AIR POLLUTION CONTROL

 EQUIPMENT SELECTION GUIDE

. Air pollution control can be generally described as a “separation” technology. The pollutants, whether they are gaseous, aerosol, or solid particulate, are Separated from a carrier gas, which is usually air. We separate these substances because, if we don’t, these pollutants may adversely affect our health and that of the environment. Of primary importance is the effect of the pollutants on our respiratory system, where the impact is most noticeable. Gaseous pollutants are compounds that exist as a gas at normal environmental conditions. Usually, “normal” is defined as ambient conditions. These gases may have, just moments before release, been in a liquid or even solid form. For the purposes of the air pollution device, however, the state they are in just prior to entering the control device is what is most important. Aerosols are finely divided solid or liquid particles that are typically under 0.5 m diameter. They often result from the sudden cooling (condensation) of a gaseous pollutant, through partial combustion, or through a catalytic effect in the gas phase. In the latter condition, a pollutant in the gas phase may combine to form an aerosol in the presence of, for example, a metal co-pollutant. Acid aerosols such as SO , for example, can form in the presence of vanadium particulate that may be evolved through the combustion of oil containing vanadium compounds. Solid metals in a furnace can sublime (change phase from solid directly to gaseous) in the heat of an incinerator, then cool sufficiently to form a finely divided aerosol.