Regenerative Thermal Oxidizer vs. Standard Thermal Oxidizer

Refurbished Regenerative Thermal Oxidizers (RTOs)

What are the Differences Between an RTO and a Thermal Oxidizer

The essential purpose for each of these systems is to remove or “oxidize” volatile organic compounds (VOC) and hazardous air pollutants (HAPs) from the exhausts of various manufacturing processes. The differences between them lie in their processes, their capacity and their efficiencies.

First, it’s important to note that a regenerative thermal oxidizer is actually a subcategory of thermal oxidizer. The general term “thermal oxidizer” encapsulates a range of oxidation systems like recuperative thermal oxidizers, catalytic recuperative oxidizers and more. Since the thermal recuperative (TRO) is the most common alternative to a RTO, we will compare TROs vs. RTOs only.

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Thermal Recuperative (TRO) vs.  Regenerative Thermal Oxidizer (RTO) Systems

A direct-fire thermal oxidizer (DFTO) does not utilize a heat exchanger to preheat the air/emission mix that enters the oxidizer, but simply fires a burner to heat the airstream to set point temperature. Alternatively, a thermal recuperative oxidizer (TRO) utilizes a heat exchanger, as does a regenerative thermal oxidizers (RTO). These heat exchangers reclaim heat from the airstream before it exits the oxidizer, and the heat is utilized to pre-heat the air/emission mix entering the RTO or TRO.

The TRO incorporates a pass-through heat exchanger made of metal, in either a plate configuration or a shell-and-tube configuration. While a regenerative thermal oxidizer (RTO) utilizes a ceramic heat exchanger and periodically-reversing airflow pattern to achieve regenerative heat exchange. This is done by incorporating heat exchange media in a regenerative heat exchanger. Once the air is preheated in the heat exchanger of an RTO or TRO, a burner provides any additional heat needed to raise the temperature to the setpoint temperature.

Efficiency: RTO vs. TRO

The main advantage of an RTO is the significant fuel savings compared to the TRO. Regenerative heat exchangers make these savings possible because they reclaim so much heat compared to other variations. The TRO reclaims heat, but much less efficiently than an RTO. The fuel savings in an RTO vs. TRO is nearly 80%.

An RTO achieves greater efficiency by re-claiming the heat from previous cycles to preheat the air prior to the combustion chamber, thus reducing the amount of fuel needed to achieve the desired combustion setpoint temperature. An RTO incorporates two heat exchange beds- typically made of ceramic media – to reclaim heat. These two heat-exchanging beds alternate as heating or cooling beds as the air flow is reversed periodically with switching valves.

TRO vs. RTO Characteristics

Thermal Recuperative Oxidizer (TRO) Air Flow
Regenerative Thermal Oxidizer heating cycle diagram
Regenerative Thermal Oxidizer (RTO) Air Flow

TYPE Thermal Recuperative Oxidizer (TRO) Regenerative Thermal Oxidizer (RTO)
Inlet Volume 1-50,000 Square Cubic Feet Measured (SCFM) 500-100,000+ SCFM
VOC Concentration 0-50+% / LFL 0-15% / LFL
Heat Exchange Material Metal - Stainless or exotic Ceramic
Thermal Efficiency 0-70% 80-97%
Operating Temp (°F) 1400-1600 1600
VOC Destruction Efficiency 99-99.99% 98-99+%

Regenerative Thermal Oxidizer or Thermal Recuperative Oxidizer – Which is Better?

Thanks to their fuel efficiency, regenerative thermal oxidizers are the oxidizer technology of choice for most industrial air emission control applications. In addition to high VOC destruction and low operating cost, RTOs  also have the longest life and the highest reliability when compared to other thermal oxidizer technologies. At low VOC concentrations, RTOs can operate at near-zero fuel consumption. Upfront capital costs for RTOs and TROs are comparable. For all these reasons most industrial applications are best served by an RTO.

Exceptions when a TRO may be a better option than an RTO

  • Exception #1 –  High VOC Destruction Efficiency: For applications requiring extremely high VOC destruction efficiency, a TRO may be the only option.
  • Exception #2 – Low Annual Run Time Applications: Manufacturers with batch processes or processes that have low annual run time may prefer a standard thermal oxidizer with no heat exchanger (Direct fired thermal oxidizer- DFTO) because of the low upfront capital cost. The fuel use will be extremely high (20X) for a DFTO vs. RTO, but for short run/batch applications it can make economic sense.

Contact the thermal oxidizer experts at Kono Kogs for more information on key differences between available pollution abatement systems.

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