ABSTRACT
This chapter describes the most important flue gas desulfurization (FGD) processes. Most FGD systems are nonregenerative. Major air pollutants are gases such as carbon monoxide, nitrogen oxides, sulfur oxides, and volatile organic compounds (VOCs). Generally, the pollutant concentrations in waste air streams are relatively low, but emissions can still exceed the regulatory limits. Removing air pollutants is achieved by the following methods: absorption by a liquid solution; condensation of pollutants by cooling the gas stream; adsorption on a porous adsorbent; and chemical conversion of pollutants into harmless compounds. Choosing the air pollutant removal method depends mostly on the physical and chemical properties of the pollutant and the conditions under which the pollutant is treated. Typically, a process in which the adsorbate is recovered uses temperature swing adsorption (TSA), pressure swing adsorption (PSA), or continuous or periodic removal of the adsorbent from the system. The TSA and PSA technologies are normally used only for the removal of high concentrations of adsorbate.
