Which Thermal Oxidizer System Type is Best for You?

June 14, 2019

A thermal oxidizer is a machine that reduces air pollution and VOCs (Volatile Organic Compounds) from industrial exhaust airstreams by incinerating hazardous pollutants at extremely high temperatures until the VOCs are removed.

These pollutants are hydrocarbon-based, which means that when they are destroyed via thermal oxidizers, they chemically oxidize to form CO2, water vapor, and heat. Because of their extremely high operating temperatures, thermal oxidizers are able to destroy nearly all (99%) of air pollutants, HAPs, and VOCs to meet the strict environmental regulations for pollution control.

The Three T’s – Time, Temperature, and Turbulence

There are three main factors that determine the performance of a thermal oxidizer: Time, temperature, and turbulence.   The three are interrelated and co-dependent.  The higher the turbulence, temperature or time the greater the VOC destruction performance. The goal of the thermal oxidizer is to oxidize the hydrocarbons to create water vapor and carbon dioxide.  Oxidation is the term used to describe this process. Oxidation describes the breaking of the bonds that make up a hydrocarbon molecule. When raised to the operating temperature and held there for a length of time in a turbulent airstream, the molecule is broken apart into individual atoms. These atoms them re-combine with oxygen in the airstream to create water vapor and carbon dioxide. The clean airstream is then safely exhausted into the atmosphere.

Temperature

Thermal oxidizers typically expose the polluted airstream to temperatures of 1400-1800 F (760-982 degrees C) to ensure near complete (99+%) destruction of the pollutants.

Time

The thermal oxidizer maintains the polluted airstream at the high operating temperatures long enough to ensure that the oxidation is completed. This time span is called “Dwell Time”. Dwell times of 0.5-1 seconds convert over 99% of the VOCs to carbon dioxide and water vapor.

Turbulence

Turbulence in the airstream ensures proper mixing and heating of the airstream to fully oxidize the pollutants/VOCs.

Types of Thermal Oxidizers

Regenerative Thermal Oxidizers

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 from industrial processes.

Regenerative Thermal Oxidizers achieve the highest VOC destruction at the lowest operating cost, and highest reliability relative to other thermal oxidizer technologies. Regenerative thermal oxidizer systems utilize a special heat recovery method – regeneration– that has proven to be the most cost-effective approach for oxidizers in typical industrial applications.

RTOs capture and give off heat from beds of ceramic pieces (media) that act as a heat sink.  The heat absorption and release occur repeatedly in controlled, recurring cycles of about 2-4 minutes. This regenerative heat exchange has been proven to be a very energy efficient method of oxidizing pollutants, when compared with other oxidizer technologies. In fact, it is possible for RTOs to operate with little to no fuel at all, if the process’s VOC concentration levels are greater than 3-4% LFL.

Learn more about Regenerative Thermal Oxidizers.

Catalytic Thermal Oxidizers

A Catalytic Recuperative Oxidizer destroys pollutants like Hazardous Air Pollutants (HAPs), Volatile Organic Compounds (VOCs), and odorous emissions discharged during industrial processes.

As with all oxidizers, catalytic oxidizers destroy VOCs by heating pollutant airstreams at high temperatures for a specific dwell time. Catalytic systems are different in that they pass the polluted airstream over a bed of catalyst material. This catalyst material reduces the temperature needed for oxidation significantly compared to thermal oxidizer systems. The typical operating temperatures in a catalytic oxidizer are 600-700F.

Catalytic thermal oxidizers have a long lifespan compared to thermal recuperative oxidizers, because they operate at a much lower temperature.

Learn more about catalytic thermal oxidizers.

Recuperative Thermal Oxidizers

Recuperative thermal oxidizers are less thermal efficient (more fuel use) than RTOs or catalytic oxidizers. They are typically used only in high VOC concentration airstreams or when they can be configured with a secondary heat exchanger for process heating.  The metal heat exchangers have shorter life than regenerative thermal oxidizers and catalytic oxidizer due too the exposure of the metal to high temperatures.  

Like RTOs and catalytic oxidizers the polluted airstream is expose to high temperatures to break the hydrocarbon bonds in a thermal oxidizer. The heat needed to drive the airstream temperature to the 1400-1500F operating temperature is recovered by passing the hot, clean exhaust gas through a primary and/or secondary non-contact heat exchanger. The heat is passed to the incoming, dirty, cool airstream to pre-heat it before passing the burner chamber to bring the airstream to the final operating temperature, cleaning the airstream before passing it through the heat exchanger and out to the atmosphere.

A recuperative thermal oxidizer system can have a single heat recovery device or multiple heat recovery devices.

Learn more about Recuperative Thermal Oxidizers

Benefits of Working with Kono Kogs

The Kono Kogs philosophy is to provide innovative air pollution control technologies that provide the lowest cost, most reliable solution to our valued customers. We offer engineering, equipment manufacturing, installation, startup and post-sale service.

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