What are Regenerative Thermal Oxidizers?

Kirsten C. Tynan

Regenerative thermal oxidizers are pollution control devices that destroy pollutants and then recycle the heat generated by burning them. The term thermal oxidizer refers to a machine that destroys pollutants through heat-producing combustion. Recovery and reuse of the energy generated in this way leads to these thermal oxidizers being described as regenerative. This recovered energy can be used to continue the pollution control process or for a secondary use, such as heating water or air.

Regenerative thermal oxidizers destroy pollutants and then recycle the heat generated by burning them.
Regenerative thermal oxidizers destroy pollutants and then recycle the heat generated by burning them.

Pollutants are destroyed in regenerative thermal oxidizers when exhaust streams from other industrial processes are drawn into them and burned. Waste gas containing toxins is directed into the inlet to the oxidizer by a fan. Valves direct the gas flow into energy recovery chambers where the exhaust is preheated in ceramic media beds.

From the ceramic media beds, the gas is then directed into the combustion chamber where it is burned to remove pollutants from it. Once the pollutants have been destroyed, the gas is much hotter and is routed back out through the ceramic media beds. Heat transfers from the gas to the ceramic media beds as it exits through them. As it loses heat, the gas cools down to a temperature that is not much higher than when it entered through the inlet.

Typically. hydrocarbons are the pollutants removed in this process. Hydrocarbons are chemical compounds consisting of atoms of hydrogen and carbon. Burning them is referred to as oxidizing them because adding oxygen causes a chemical reaction that breaks them down and releases heat. The byproducts of such a reaction are water vapor and carbon dioxide.

There are two primary measures by which regenerative thermal oxidizers are rated. Destruction efficiency refers to the percentage of volatile organic compounds (VOCs) removed by mass. This efficiency can easily be 99% or greater. Heat recovery efficiency refers to the percentage of available thermal energy that is recovered for reuse. It is common for heat recovery efficiency to exceed 95% with the use of regenerative thermal oxidizers.

Use of regenerative thermal oxidizers to recycle heat from the oxidation process can dramatically reduce the amount of fuel needed to burn exhaust emissions. The reduction in fuel required can represent a substantial operating cost reduction for a facility. Burning less fuel for this process also reduces the amount of pollutants produced in the process. These factors make regenerative thermal oxidizers a more cost-effective choice than other emission control methods in many instances.

Consequently, regenerative thermal oxidizers are used in many industrial applications to remove toxins in the exhaust they generate. They are best suited for processes with relatively low concentrations of VOCs. Paint spray booths, municipal waste processing facilities, and paper mills are a few examples of facilities that may utilize regenerative thermal oxidizers for emissions control.

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