How Does an RTO Work?


The operation of a Regenerative Thermal Oxidizer (RTO) is based upon a chemical/thermal process and mechanical process.  The chemical/thermal process is the application of heat to a process exhaust stream that contains Volatile Organic Compounds (VOCs) and Hazardous Air Pollutants (HAPs).  This application of heat oxidizes these pollutants from their initial chemical state to two inert compounds; CO2 and H2O.

Examples of typical organic compounds:

Chemical Name Formula
Acetal C6H14O2
Acetone C3H6O
Benzene C6H6
Butanol C4H10O
Cyclohexanol C6H12O
Formaldehyde CH2O
Heptane C7H16
Isopentane C5H12

Examples of the conversion of VOCs to inert compounds:

Formaldehyde:   CH2O + O2 → CO2 + H2O

Heptane:           C7H16 + 11O2 → 7CO2 + 8H2O

Hexane:            2C6H14 + 19O2 → 12CO2 + 14H2O

The RTO mechanical process operates on the principle of alternating gas flow through multiple “beds” of ceramic heat exchange media.  The inlet gas is first drawn into the system and up through the inlet bed where the gas pre-heats by contact with ceramic heat media.  As the gas moves up through the ceramic media, it reaches temperatures of 1,400°F to 1,475°F.  The gas then enters the combustion chamber where a burner (typically natural gas fired) operates to increase the gas temperature to between 1,500°F to 1,750°F. 

This temperature is referred to as “combustion chamber set point” and is the point where nearly all VOC and HAP compounds are destroyed and converted to CO2 and H2O.  At this point the process gas, now cleaned of contaminants and heated, is directed downward through the outlet heat exchange media bed.  The gas at the combustion chamber temperature relinquishes its heat to the ceramic media as it travels downward through the outlet bed.  

After a two- to three-minute period, the RTO cycles so that valves reverse the airflow through the system (see below).  This back and forth process continues every two to three minutes while in operation. This process is what is referred to as a regenerative thermal process.

RTO mechanical process

This thermal process initiated through the cycling of the RTO valve system is typically referred to as Thermal Energy Recovery (TER) and is one of the key aspects of the RTO system.  This regenerative process allows for a very high percentage of heat recovery and is rated based upon the percent of heat recovered.  Typical TER values of the RTO will be in the 95-97% range. 

Industries That Utilize RTOs

  • Carbon Fiber
  • Chemical Manufacturing
  • Pharmaceutical
  • Automotive
  • Petrochemical
  • Foundry
  • Styrene
  • Wastewater Treatment
  • Printing & Flexography
  • Flooring
  • Fiber Manufacturing

  • Pulp & Paper
  • Rendering
  • Ethanol
  • Engineered Wood Products
  • Oil & Gas
  • Fiberglass / Mineral Wool Insulation
  • Surface Finishing / Coating
  • Semiconductor

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