How a Regenerative Catalytic Oxidizer Works

Regenerative Catalytic Oxidizer Process Explained

A regenerative catalytic oxidizer (RCO) heats polluted industrial exhaust to temperatures between 750°F and 850°F in a regenerative heat exchanger, passes the heated air through a catalyst bed to oxidize volatile organic compounds (VOCs), passes it through the regenerative heat exchanger again to recover heat, before exhausting the cleaned, cool air to atmosphere. The main stages of an RCO process include:

• Pre-heating incoming polluted air
• Final heating of polluted air to setpoint
• Catalytic oxidation of polluted air
• Cooling of clean air
• Exhausting of clean air
• Recycling captured heat to preheat incoming polluted air

The RCO Difference: Efficiency Through Regenerative Heat Exchange

What differentiates RCOs from other catalytic oxidizers is the regenerative heat exchange process. The defining characteristic of an RCO system is its ability to capture and release heat generated in the oxidation process and “regenerate” this heat to preheat incoming air. This method of heat transfer in a RCO provides exceptional thermal efficiencies. The RCO captures and releases heat from two or more “heat sinks” made up of ceramic media stored in “beds.”  This process is efficient and straightforward in operation.

RCO Preheating through Structured Ceramic Media

To enable this heat retention, the regenerative oxidation process incorporates ceramic media as a heat “sink” to store and then give off heat. These heat sinks are called “beds” in an RCO. The beds are filled with ceramic media that has been found to be the best heat sink material due to its excellent thermal conductivity, low thermal expansion and shock properties. The polluted air and the clean air pass through these beds alternately, giving off (or absorbing) heat in repeated cycles.

Heat Regeneration Cycle: Heat, Oxidize, Cool, Exhaust. Reverse & Repeat

To destroy VOCs in process emission airstreams, the air is raised to the optimal temperature for catalytic oxidation. Regenerative catalytic oxidizers use a regenerative heat exchanger that directs the process emissions through a ceramic heat-exchange media (bed #1), past a burner to drive it to a setpoint temperature, and into the catalyst bed where the pollutants oxidize at lower temperatures. The now hot, cleaned air passes through a second bed of ceramic heat exchange media (bed #2) which absorbs heat, cooling the air before it is finally exhausted into the atmosphere.

Flow Reversal and Heat Exchanger Role Reversal

After a few minutes, the airflow direction through the RCO is reversed with a series of opposing valves (poppet style, or possibly a rotary style). Heat stored in the ceramic media in bed #2 from the previous cycle now lends its temperature to the polluted airstream entering the bed. As the polluted air passes through bed #2, it absorbs heat from the ceramic media; the air rises in temperature, while the ceramic bed is cooled as it gives off heat.

The preheated and polluted air exits bed #2, travels past the burner to raise it to setpoint temperature, and passes into the catalyst bed. Held at the optimal temperature in the catalyst bed, the pollutants in the airstream are oxidized. The now hot, cleaned air passes through a second bed (bed #1 in this cycle) of ceramic heat exchange media which absorbs and stores much of the heat from the air, cooling it before it’s exhausted into the atmosphere as CO2 and water vapor in air.

Reversing the airflow direction is how the regenerative heat exchange process is able to achieve maximum thermal efficiency, while also achieving high VOC destruction.

The RCO Process: Step-by-Step VOC Destruction

1. A system fan draws a pollutant-laden (dirty) airstream from an industrial process and pushes the air through the oxidizer system.
2. Airflow direction through the system is controlled by a rotary valve (or poppet valves), directing the dirty air into one of two heat exchangers (chambers containing ceramic media beds).
3. As dirty air passes through the first media bed, the air absorbs heat from the hot ceramic media.
4. The pre-heated air is further heated by the burner in the combustion chamber.
5. In the catalyst bed, the dirty air is held at the optimal temperature for a specific dwell time. This oxidizes VOCs into CO2 and H2O.
6. The now clean, hot air then passes through the second ceramic media bed which absorbs/stores the heat from the air, cooling the air.
7. Cooled, clean air is then exhausted out of the exhaust stack and into the atmosphere.

Airflow Reversal

The RCO valve changes position every few minutes, reversing the flow direction and alternating heat transfer between the two ceramic media beds. This flow reversal gives RCOs their high fuel efficiency and low operating costs, making them highly desirable VOC abatement systems.

Why Regenerative Catalytic Oxidation?

Compared to other oxidizer technologies, regenerative catalytic oxidizers incorporate a repeated flow direction reversal to achieve exceptionally high performance in VOC destruction & thermal efficiency while using minimal fuel to keep the system at the correct temperature for pollutant oxidation.

Find Out More from VOC Oxidizer Specialists at Kono Kogs Inc.

KKI is the leading global supplier of high-quality refurbished RCOs and other air pollution control equipment. Our team has a 100% success rate meeting our performance guarantees and has consistently earned repeat business from our small to our Fortune 100 customers. Whether you’re looking to get more efficient service out of your existing RCO, or convert your RTO to an RCO, KKI can help.

Request a quote online or call 920.332.6692 for more information.

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