Regenerative Thermal Oxidizer (RTO)

What is a Regenerative Thermal Oxidizer?

A Regenerative Thermal Oxidizer (RTO) is a combustion device that controls volatile organic compounds (VOCs), hazardous air pollutants (HAPs), and odors by converting (destroying) the emissions into CO2 and H2O through the use of heat before exhausting them to the atmosphere.

RTOs play a crucial role in promoting sustainable industrial practices by reducing emissions, conserving resources, and minimizing environmental impact.

Regenerative Thermal Oxidizers significantly reduce harmful emissions from industrial processes resulting in cleaner air and mitigating the impact on public health and the environment.

A Regenerative Thermal Oxidizer is designed to maximize energy efficiency through heat recovery methods. An RTO utilizes the heat generated during the oxidation process to preheat the incoming process streams, reducing the overall energy requirements of industrial processes.

With thermal efficiencies up to 97% and destruction efficiencies that can exceed 99%, Regenerative Thermal Oxidizers are the most efficient air pollution control device.



Regenerative Thermal Oxidizer (RTO) Questions:

How is a Regenerative Thermal Oxidizer Designed?

RTO oxidizers are considered among the world's most advanced thermal oxidation systems. With thermal efficiencies of up to 97%, and destruction efficiencies that can exceed 99%, a Regenerative Thermal Oxidizer (RTO) will give you the highest possible removal rates at the lowest full lifecycle cost relative to other thermal oxidizers

CPI Automotive Paint Shop RTO 60,000 SCFMAs a Regenerative Thermal Oxidizer (RTO) manufacturer, CPI engineers and builds to your specifications – matched to industry-leading construction and design features, all resulting in exceptional performance, substantially reduced operating costs, and industry-leading reliability.

We begin with three basic models that offer varying levels of VOC destruction and energy efficiency. We then take into consideration the particular characteristics of your air stream, such as quantity, temperature, composition of VOCs, and the possibility of incorporating energy conservation into the process.

These specially designed, cost-effective, proven systems combine the basic principles of thermal oxidizer design;  Time, Temperature, and Turbulence.

  • Time. Retention time, or residence time, is the length of time that a VOC/organic is at the appropriate oxidation temperature. Both retention time and residence time refer to time inside the thermal oxidizer's combustion chamber.
  • Temperature. Typical temperatures in the combustion chamber range between 1400°F and 1600°F and higher. For each organic, a specific temperature and a specific retention time is required to achieve the desired level of destruction.
  • Turbulence. Sufficient air mixing, also known as turbulence, must also be achieved in the combustion chamber.

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What is the Cost of a Regenerative Thermal Oxidizer?

The capital investment for an RTO includes the equipment cost, the cost of auxiliary equipment (e.g. ductwork, product options), and all direct and indirect installation costs. The higher capital costs of these units can be substantially offset by the substantial savings in auxiliary fuel costs.  The cost of an RTO is influenced by the exhaust stream volumetric flow rate, VOC loading and desired destruction rate efficiency.

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How does a Regenerative Thermal Oxidizer (RTO) work?

Thermal treatment of Volatile Organic Compounds (VOCs) and other air pollutants works by a simple oxidation reaction of the harmful air pollutants with oxygen and heat. In this environment, the VOCs are converted to harmless inert byproducts, water vapor (H2O), and usable heat. These harmless by-products are released into atmosphere or use an energy recovery technique to further lower the operational costs. 

See the below diagram for how an RTO works:

Diagram showing how an RTO works.

  1. Process exhaust air (with VOCs) enters the regenerative thermal oxidizer and is directed into the ceramic heat exchange media where it is preheated.
  2. Pre-heated air enters the combustion chamber where it is heated to the set-point temperature where oxidation of the VOCs are completed.

  3. Hot treated clean air is cooled as it passes through the heat exchange media and is exhausted from the stack into the atmosphere. 

  4. Every three (3) minutes the process of air flow reverses direction as the poppet valves switch positions, allowing the heat captured in the ceramic media from the exiting clean air stream to heat the incoming process air.  It is this regeneration of the ceramic heat exchanger media, with its high heat capacity, which enables a regenerative thermal oxidizer to deliver greater than 95% thermal efficiency. 


The CPI Regenerative Thermal Oxidizer (RTO) process begins with the touch of a button, which activates the system's hottest bed for damper positioning, opens the fresh air purge/idle damper, energizes the booster fan, purges the system with fresh air, ignites the burner, cycles the poppet valves, and gradually brings the system up to the correct operating set point temperature. The Temperature Safety System (TSS) also monitors the temperature in the regenerators, combustion chamber in three places, and in the valve assembly's inlet and outlet. This helps safeguard the system from extreme temperature fluctuations that cause thermal stress and overall system fatigue. 

As soon as the required operating set-point temperature is reached, the TSS enables the process lines to feed into the oxidizer, or holds the system in idle mode until production is ready. When production is ready the fresh air purge damper closes and one or more of the diverting dampers open to draw the volatile organic compounds (VOCs) off the process lines. 

A booster fan draws one or more VOC-laden exhausts from your process lines into the system. From there, VOCs are directed into one of the system's regenerators (an internally insulated vessel containing ceramic media). The contaminated gases are passed through the first regenerator, where energy is transferred from the ceramic RTO media to the gas in order to elevate the temperature. This elevated temperature approaches the ignition level for most solvents and then is directed from the ceramic bed into the combustion chamber. As the process stream exits the ceramic bed and travels through the internally lined combustion chamber, minimal heat is added. The oxidized gases are then directed to the second regenerator to absorb the heat energy. As the ceramic media loads with sufficient heat, the CPI Posi-Seal Valves switch, and the gases are reversed through the system where the second regenerator bed continues the energy transfer and oxidation cycle before being released to the atmosphere, or to auxiliary heating systems such as; secondary air to air recovery, air to water recovery, air to oil recovery, or directly back to the process in a closed loop direct recirculation process. 

The regenerative thermal oxidizer is in compliance with clean air regulations.

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What is the difference between a Regenerative Thermal Oxidizer and a Recuperative Thermal Oxidizer?

Regenerative Thermal Oxidizers are preferable for most industrial processes, especially for applications with large volume airflows and low VOC concentrations. Compared to other emission control technologies, Regenerative Thermal Oxidizers are more efficient, more reliable and provide low operating costs.

  • Regenerative Thermal Oxidizer
    Regenerative Thermal Oxidizers use ceramic media as heat exchangers and poppet valves which create airflow reversal. Rather than exhausting the clean, hot air to the atmosphere, the RTO system may capture up to 97% of the heat from the exiting stream to heat the incoming process air.
  • Recuperative Thermal Oxidizer
    Recuperative Thermal Oxidizers use metal plate or shell and tube heat exchangers to preheat the incoming process air using the clean “hot” air from the oxidizer combustion chamber. This primary heat recovery raises the temperature of the process gas before entering the combustion chamber, resulting in lower fuel requirements for the oxidizer burner system. Recuperative Thermal Oxidizers offer up to 80% thermal recovery efficiency.

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What are the features of a Regenerative Thermal Oxidizer?

Catalytic Products International has been designing, manufacturing, and installing the world's most innovative thermal oxidizers since 1969. Throughout our long history, we continually strive to offer the most advanced air pollution control equipment. These constant efforts have led us to the development of the CPI Regenerative Thermal Oxidizer (RTO). Each system is custom engineered to exceed all worldwide air compliance guidelines at the lowest overall costs.

CPI RTOs offer innovative design characteristics:

Modular Generator technology

t2_features1CPI RTOs are custom designed for the highest reliability with the lowest overall costs. The complete system is designed with a modular approach for the most cost-efficient solution. The typical CPI RTO is supplied as a 2-tower regenerator system fitted to our EvenFlo Valve Manifold. This modular approach satisfies your needs for a competitive installation cost and ensures that the Posi-Seal valves are properly installed and aligned prior to leaving the factory.

Cold Face Support

t2_features3Complementing the regenerator design is our unique cold face support system. While other systems merely rely on a perforated plate to support the ceramic media, CPI RTO systems use a superior supporting grid that allows the lowest pressure drops and highest structural integrity. Based on the application needs, the CPI RTO can be supplied with stainless steel metallurgy to resist chemical attack or added thermal stresses.

Posi-Seal Valves

t1_features5-696976-editedPosi-Seal valves are designed to take advantage of a vertical axis that allows for soft seating action with self-centering guidance. The innovative feature of all Posi -Seal valves is the air-tight machined seal that eliminates valve bypass and maintenance-intensive gaskets. The Posi-Seal valve will be pneumatically operated and will cycle open or closed based on the program logic called for in your application.

Posi-Seal Shaft Cooling

t2_features6CPI RTO systems incorporate shaft and bearing cooling systems. This simple yet often overlooked feature provides a cool supply of air in the bearing tube and on the bearings. This prevents leakage of the higher pressure air on the inside of the oxidizer from escaping to the atmosphere and helps cool the shaft and bearings for long life.

Internal Isolation Systems

t2_features8The CPI RTO is internally insulated with ceramic insulating modules. This system provides low shell temperatures and helps to retain heat for improved efficiency.


EvenFlo Manifold Insulation

t1_features8In some cases, the EvenFlo Manifold can be insulated to ensure that the pollutants that enter the oxidizer remain in a gaseous state. If the process constituents should condense at some point in the oxidizer, they can become a maintenance issue or worse yet, become a hazard to the equipment. Some pollutants will condense and collect on many of the surfaces of the oxidizers, leaving a sticky, tarry substance that is difficult to remove. Insulating our EvenFlo Manifold helps to prevent any condensation, and keeps your process air in a gaseous state.

Thermal Heat Transfer Ceramic Media

t1_features4Each CPI Regenerative Thermal Oxidizer system is designed around the particular ceramic heat transfer matrix recommended for the application. CPI RTO systems can be designed using a layered structural ceramic media or a mix of structured and random media (saddles), depending on your application's requirements. The thermal heat transfer model is the key to a well designed and efficient system. With thermal rate efficiencies (TRE) ranging from 85 percent to 97 percent, you can be assured that even the lowest VOC concentrations can be economically destroyed.

The CPI RTO also employs a bake-out feature that will allow periodic high temperature cleaning of condensate residue from the lower levels of the ceramic media beds and cold face support.

Learn more about RTO media maintenance and design by clicking here:  RTO Ceramic Media and Maintenance

Temperature Safety Systems

t2_features11Every CPI RTO system is integrated with our customized programmable logic controller PLC-control panel called Temperature Safety System (TSS) Control. TSS communicates with the CPI RTO system and your process for optimal performance, safety and reliability. We use our proprietary thermal control logic and multiple temperature inputs to maximize the regenerator's thermal efficiency. This unique control technique constantly adjusts valve timing to maximize thermal efficiency without compromise in destruction efficiency. No other supplier goes to these extremes to maximize the performance of their RTO.

Extensive Materials Selection

t2_features12Metallurgical conformity and assessment process to ensure corrosion, and thermally resistant materials are used throughout the regenerative thermal oxidizer system.


Complete Shop Assembly

t2_features10A drop-in-place installation has proven to be highly desirable. For some sizes this includes media loading, pre-wiring and extensive I/O quality control that ensures the control system is ready to operate.

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What are RTO OXidizer product OPTIONS?

Blue_Checkmark Hot Gas Bypass
Provides a method of controlling the RTO under high VOC conditions and ensures VOC destruction is maintained without cause for high-temperature shut-down.  


Secondary Heat Recovery
Solutions including direct or indirect heating system

Blue_Checkmark Induced Draft Systems
To keep booster fans clean of condensation
Blue_Checkmark Natural Gas Injection (NGI)
A means of adding auxiliary fuel (natural gas) when VOC loads are unusually low, or a means to assist with lowering the nitrogen oxide (NOx) byproducts of combustion. 
Blue_Checkmark SD (Severe Duty) Series
System for corrosive air streams, including halogenated  compounds such as chlorine, fluorine, and bromine. 
Blue_Checkmark PLC control and man-machine-interface options based on your needs
Blue_Checkmark Multiple fuel blends or oil fired combustion systems
Blue_Checkmark Footprint design flexibility to suit your space availability
Blue_Checkmark VOC Polishing Chamber
To enable +99% destruction efficiency with two-chamber RTO.
Blue_Checkmark Three Chamber or Multiple Chamber RTO


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