Enclosed Thermal Oxidizers Vapor Control Equipment
Thermal Oxidizer is a general term that can be correctly applied to most processes where a waste product is burned to inert or treatable products. Complex Thermal Oxidizers may include equipment to recover heats of combustion (a boiler to generate steam or a heat exchanger to preheat the waste gas or combustion air), acid gas scrubbers (to remove SO2, HCl, etc. from the flue gas) and particulate removal equipment (baghouse, venturi scrubber, etc.).
However, in terminal and storage applications, Thermal Oxidizers are relatively simple. Many times a Vapor Thermal Oxidizer is referred to as an Enclosed Flare. Generally, there are no solid or liquid waste streams. The waste to be burned is a gas or vapor. The products of combustion are generally inert, no acid gases or ash is produced. The feature that distinguishes a Thermal Oxidizer in this application from the Thermal Oxidizing Flare discussed above is the control of the combustion process.
Combustion of the waste gases in a Thermal Oxidizer can be tightly controlled. The combustion chamber is usually a closed, insulated vessel. Flue gas temperature is measured and auxiliary fuel and/or air flow are adjusted automatically to maintain desired chamber conditions. Operating temperatures can range from 1200°F to 2200°F (650°C to 1000°C) and flue gas residence time can range from 0.5 to 2.0 seconds. A flame detection device is used to shut off all streams should be flame disappear. Combustion air, if not supplied by the waste, may flow into the burner by natural draft or via an air blower. With tighter control of the combustion process, higher destruction efficiencies can be obtained.
Although standard models are available for some applications, typically, each Thermal Oxidizer is custom designed to handle a specific waste stream for specific site conditions. Standard systems can be used where the waste characteristics are always the same and only the flow varies, e.g. paint spray booth vent applications. Typical destruction efficiencies range from 99 to 99.99% depending on the application requirements.