Gaseous emissions, control adsorption

The removal of gaseous pollutants from dryer exhaust may be accomplished by several possible processes. Among these are absorption, adsorption, condensation, and incineration [11-16]. The choice of a given process is usually determined by physical and chemical characteristics of the dried product and by economic and environmental considerations. Table 53.3 summarizes some of the basic characteristics of the gaseous emission control equipment. 

There is now a larger range of potential gaseous and particulate emission control options, based on the use of catalytic, trapping and adsorption technologies, than at any time in the past. 

In order to illustrate the previous description, an industrial treatment used in VOC control in gaseous emissions is presented in Fig. 17 while the working procedure of adsorption and regeneration is displayed in Fig. 18. 

The technologies used in the control of gaseous organic compound emissions include destruction methods such as thermal and catalytic incineration and biological gas treatment and recovery methods such as adsorption, absorption, condensation, and membrane separation. The most common control methods are incineration, adsorption, and condensation, as they deal with a wide variety of emissions of organic compounds. The most common types of control equipment are thermal and fixed-bed catalytic incinerators with recuperative heat recovery, fixed-bed adsorbers, and surface condensers. The control efficiencies normally range between 90% and 99%. 

These results also allow deducing that despite the limestone increases the PAH emissions, its total performance is positive. Limestone not only abates SO emissions, but also PAH emissions on gas phase are avoided by adsorption, which means that gaseous PAH could be easily controlled by an effective particulate matter trapping system. 

In recent years considerable emphasis has been placed on energy conservation and environmental pollution control. As discussed earlier, the former problem is likely to be solved, at least in part, by the introduction or wider use of more efficient fuels such as biomass or nuclear fuel, coupled with more controlled application of what is at present waste heat from chemical reactions. This is now more than ever possible because of the improved and improving design of heat pumps, boilers, heat exchangers, etc., the use of which is more nearly optimized by computer control. Emissions of gaseous pollutants have been decreasing in recent years by improved methods of condensation, adsorption. 

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