Thermal oxidation is a process whereby most of the VOC's are broken down and recombined with oxygen to produce water vapor and carbon dioxide. The water vapor and carbon dioxide are naturally occurring and environmentally friendly and therefore can safely be vented to the atmosphere. Thermal oxidation is initiated by heating the polluted air to a temperature in the 1,300°F to 1,800°F range and retaining it at this temperature for a period of 0.5 to 1.0 seconds. At these temperature's the pollutant molecules spontaneously dis-associate and re-combine with available oxygen to create the carbon dioxide and water vapor.

Heating the polluted air stream to the oxidation temperature requires considerable thermal energy. The regenerative heat recovery system recovers the majority of this energy and reuses it to treat the incoming process air stream. This reduces the fuel consumption by the system to a small fraction of what would be required without the heat recovery system.

The regenerative heat recovery system uses multiple masses (beds) of heat resistant ceramic material to store and release thermal energy. The ceramic material is engineered to provide free airflow and maximum internal surface area to promote high heat transfer. The beds are housed in insulated towers and are connected to an insulated combustion chamber. A fuel fired burner is mounted to fire into the combustion chamber, and it is here that the thermal oxidation process takes place. A valve mechanism is provided to direct the VOC laden air into the beds and direct the clean air to the RTO exhaust stack.

The RTO operates as follows:

The VOC laden air is directed by the valve mechanism to flow through one or more beds into the combustion chamber. These beds have been previously heated and because of the intimate contact between the air and ceramic material, very high rates of heat transfer are produced. This results in the air being preheated very close to the required oxidation temperature by the time it reaches the combustion chamber. The air then enters the combustion chamber where a small amount of heat is added by a fuel fired burner to combustion temperatures.

The thermal oxidation process then takes place and the pollutants are destroyed. The clean air then exits the combustion chamber through another bed or beds that have been previously cooled. As the air passes through these beds it is cooled by the same heat transfer process. After passing through the cooled beds the air exits the RTO system at a temperature only slightly higher than the inlet temperature.

After several minutes the first set of beds (inlet) becomes depleted of heat while the second set of beds (outlet) becomes saturated with heat. At this point the flow of air through the beds is reversed with the formerly inlet beds acting as the outlet beds and the formerly outlet beds acting as the inlet beds. In this way each bed periodically extracts heat from the clean gas stream exiting the combustion chamber then releases this heat into the polluted gas entering the combustion chamber. This method is thermal regeneration.

The combination of thermal oxidation and regenerative heat recovery allows the RTO system to efficiently destroy VOC laden air with minimal operating costs.