What is a Regenerative Thermal Oxidizer (RTO)?

Regenerative Thermal Oxidizer (often referred to as RTO) destroys pollutants like Hazardous Air Pollutants (HAPs), Volatile Organic Compounds (VOCs), and odorous emissions that are often discharged during industrial processes.

Time, Temperature and Turbulence

Time, temperature and turbulence – Three T’s- are critical and co-dependent factors that determine oxidizer performance. VOC destruction of 99+% is routine, and the regenerative technology provides 95+% heat recovery as an industry standard.

It is possible for an RTO to operate with no auxiliary fuel use whatsoever if process VOC concentration levels are >/3-4% LFL.

How does a regenerative thermal oxidizer work?

A Regenerative Thermal Oxidizer (RTO) works by pushing a pollutant-filled airstream through the oxidizer, usually with a system fan (1). The flow of air is controlled by valves (2) that direct this airstream into one of two recovery (beds) chambers (3). In a regenerative oxidizer, a minimum of two beds of ceramic media (saddles, and/or structured media block) is utilized to capture heat and release heat to the polluted airstream.

As the dirty air passes through the first media bed, the air absorbs heat from the hot ceramic media beds. The air exits the first media bed and enters the combustion chamber (4) where oxidation occurs at high temperatures (>1500ºF), at a set temperature (>1500F) for a desired dwell time (>0.5 seconds) to convert over 98% of the VOCs to carbon dioxide and water vapor.  This hot, clean air then continues through a second ceramic media bed (5). As the air passes through the bed it releases heat into the ceramic media. The cooled, clean air is then exhausted to the atmosphere (6).

The valves change direction every few minutes reversing the flow direction through the RTO to transfer the heat to the other bed, which gives the RTO its high fuel efficiency and low operating costs

Questions to consider when purchasing a regenerative thermal oxidizer (RTO)

  • Is the RTO optimized for my exhaust airstream?
    • RTO’s typically treat airstreams with a 0-10% Lower Explosive Limit (LEL)
    • RTO systems can handle 25% Lower Explosive Limit (LEL) airstreams
      • Hot gas bypass systems and other features may be needed
  • Is the ceramic media in the RTO optimized for:
    • maximum thermal efficiency
    • lowest pressure drop
    • Ability to handle organic/inorganic particulates
  • Does the RTO main fan utilize a variable frequency drives (VFD)?
    • Important for volume turn-down and idle operation
  • Is the RTO skid mounted with little welding required in the field?
    • Ease of installation will result in lower turnkey cost
  • Are the PLC controls configured with remote access for troubleshooting?
    • Remote troubleshooting access  can reduce service visit frequency
  • Are process emissions visible to the naked eye?
    • A puff capture feature may be required to eliminate visible emissions
  • Would a fuel gas injection system be a wise choice for this application?
    • Fuel injection can provide significant fuel savings
  • Is there a used RTO system available with the features needed?
    • Quality-built used regenerative thermal oxidizer (RTO) systems have a long life, can save 40-60% vs. new units, and offer performance and parts warranties

Other Considerations:

  • Is there a risk of ceramic media plugging due to condensing VOCs?
    • A Bake-out feature can address organic build-up
  • Does the RTO have to address potentially corrosive emissions/halogens?
    • Special materials of construction may be required
  • Would an induced draft fan be a better choice than a forced draft fan?
    • High boiling point solvents can build up on fan wheel
  • Is there enough heat in the RTO exhaust (>250F) to consider secondary heat recovery
  • Is the process sensitive to pressure pulses that can occur with poppet valve technology?
    • Rotary valve technology may be a better option
  • Do your local government codes require Low NOX operation?
    • Low NOX burners can be retrofit for these applications.

Still unsure which technology is best? Call us or request a quote. Our cost-benefit analysis for your specific project will compare multiple technology options, recommend the most cost-effective option and clearly explain the trade-offs of each option.

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