Catalytic Oxidizers

Catalytic Oxidizers from The CMM Group are designed to destroy air pollutants emitted from process exhaust streams at temperatures ranging from 260°C (500 F) to 345°C (650 F). Catalytic oxidizers utilize a high-efficiency counter-flow plate type heat exchanger. Oxidation is achieved as pollutants pass through a heated bed of precious metal catalyst.

The basic design concept of catalytic oxidation is to utilize an industrial grade catalyst to promote the chemical reaction at lower temperatures as compared to thermal oxidation. The air pollutant is mixed with oxygen, heated to an elevated temperature and passed through a catalyst, thus destroying the pollutant in the air stream by converting it to CO2, H2O and heat. The rate of reaction is controlled by the temperature of the catalyst chamber and the amount of time that the pollutant spends within the catalyst itself. Catalytic oxidation commonly requires less energy to operate due to lower operating temperatures.

During operation, the process exhaust fumes are forced into the catalytic oxidizer inlet plenum (using a high pressure supply fan) and directed through the "cold" side of a high efficiency, counter-flow plate type heat exchanger. The VOC/HAP laden air then enters into the combustion chamber (typically at a temperature very close to that required for oxidation) where it is thoroughly mixed for temperature uniformity. To maintain set point temperature, auxiliary fuel is introduced if necessary. The preheated stream then passes through a fixed bed of industrial grade catalyst where air pollutant destruction takes place.

After passing through the catalyst chamber, the clean (hot) air is routed back through the "hot" side of the heat exchanger where it continuously preheats the incoming process air. Upon exiting the heat exchanger, the clean (cooled) air is routed to atmosphere through an exhaust chamber and ultimately through the exhaust stack. Heat exchangers in standard catalytic units are typically fabricated of heavy-duty stainless steel. Thermal recovery efficiencies (TRE) range from 50% to 80%. Internal chambers of a catalytic oxidizer are manufactured entirely of heavy gauge stainless steel. Thermal expansion joints are incorporated where necessary. To maintain low external shell temperatures and minimize radiant heat loss, the internal chambers are covered with blanket insulation and then clad, typically with embossed aluminum. Air pollutant destruction efficiencies of 99% can typically be guaranteed.

A brief description of the process emitting air pollutant. Hours of operation. Exhaust rates and temperature of process to be controlled. Types of air pollutants to be destroyed and in what quantity. Identify known compounds such as silicone, phosphorus, heavy metals, halogen, particulate and/or sulfur that may be present. Types of auxiliary fuel available (natural gas, propane, fuel oil, etc.). Electrical power requirements (voltage, hertz, phase). Installation supervision or complete turnkey installation requirements. Physical installation area and/or site space limitations. Production uses for energy that could be recovered (i.e., hot air, hot water, steam, hot oil).

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