subject: What Is A Recuperative Thermal Oxidizer? [print this page] In air pollution control processes, a catalytic or thermal oxidizer may be used to process and break down hot, hazardous gases by destroying the pollutants within. A thermal oxidizer operates on the principle of combustion and is used for the efficient destruction of hydrocarbon-based waste materials, by burning the exhaust gases before they are released into the air.
The recuperative thermal oxidizer consists of a primary heat exchanger, and in some cases, a secondary one, within the system. These heat exchangers are used to recover heat from the clean gases being discharged and heat the incoming stream of exhaust gases. Consequently, in some cases when the clean gases enter the secondary heat exchanger, it is used as an alternate source of thermal energy for other processes in the plant. These are conventional heat exchangers made from metal, commonly the shell and tube type.
The primary heat exchanger is used to preheat the incoming exhaust gases and is fitted immediately after the oxidization chamber and the thermal energy for preheating is recuperated from the exiting clean air. As the exhaust gases enter the heat exchanger and flow on one side of the tube or plate, the hot clean air from the oxidation chamber flows on the other side of the plate or tube. Thermal energy is transferred to the exhaust gases by conduction with the metal acting as the medium for heat transfer.
In some cases, a secondary heat exchanger is integrated into the system and usually positioned in series after the primary heat exchanger. Heat transfer in these secondary heat exchangers, as in the primary, occurs between two gases, but the fluid being heated by the exiting clean air stream is utilized in another part of the plant, and in most cases, as part of the process.
Thermal oxidizers utilizing this type of a heat recovery system normally have thermal efficiencies ranging from 50% to 75%. While this thermal efficiency is sufficient to offer significant energy and cost saving, it is still less as compared to the newer regenerative thermal oxidizers.
