A Thermal Oxidizer, also known as incinerator, relies on the use of auxiliary fuel, to pre-heat the waste gas to a temperature at which rapid oxidation of the VOC and malodorous hydrocarbon-based substances occur. Such an incinerator must also provide good mixing between the flue gases from the auxiliary fuel burner and the fuel and the air/solvent mixture to be oxidized to ensure a consistent final outlet temperature of the product gases.
Direct flame incineration is carried out in all metallic or refractory-lined carbon steel furnaces, depending on the final temperature required. Generally, a temperature of 760°C and a residence time of half a second are considered suitable, although temperatures of up to 1200°C may be required for destruction of materials such as chlorinated organics.
Retention time is as significant a parameter as temperature. Thermal oxidizers are normally designed to provide from 0.25 to 0.5 seconds’ retention time, although units have been designed large enough to provide a retention time of from 2 to 3 seconds.
The simplicity of automatic direct flame combustion make it an ideal VOC and malodorous hydrocarbon-based substances control technique in many cases. The configuration of this equipment lends itself to heat recovery. For heat recovery purpose, heat exchangers can be utilized to recover the high temperatures in the combustor exhaust to preheat the incoming combustion air and/or heat a stream for external use which can be gas or water for steam.