Air contaminated with pollutants is of no good. While pollution free air is required for a healthy living being, pollutants in air cause harmful health issues. The more the air is polluted, the more adverse effects it has on human and animal life as well as the plant life. With the advance inventions in science people are keen to know the methods or the devices by which they can get a pollution free air. One of the measures that can be taken for making the air pollution free is by treating the pollutants from the air and heat emitted by the industrial waste. A thermal oxidizer may help a lot in this case. It is an air pollution control device and in used in the manufacturing and other industrial process. A thermal oxidizer helps in reducing emissions of harmful air pollutants (HAPs), volatile organic solvents (VOCs) and other industrial emissions into non toxic CO2 and water vapor by undergoing thermal oxidization on the emitted air. They are also known as after burners and are used at many manufacturing facilities throughout the world. There are different thermal oxidizers out there and detailed description of each of them is sited below:
Direct-Fired Thermal Oxidizer
This is the most basic type of any thermal oxidizer and is also known as afterburner. This is the simplest type of thermal oxidizer and hence forth, it does not include any heat recovery, catalyst material, scrubber or absorbent. The upfront capital investment cost of this thermal oxidizer is the lowest, but it requires the most energy for its operation as it is thermally inefficient. This design is suitable for applications that emit a highly concentrated VOCs or applications that run for a short duration. This thermal oxidizer is often paired with a VOC concentrator and additionally they provide solvents that are highly concentrated. Their destruction efficiency lies between 98 to 99 percent respectively.
Recuperative Thermal Oxidizer
This is more thermally efficient than a direct fired thermal oxidizer and it passes the hot exhaust gas through an air-to-air exchanger and heats the incoming air to ~700 F. Then half the heat is provided by the burner for the combustion reaction to operate successfully. Due to its low energy cost, the recuperative thermal oxidizer is quite popular. Its operation cost is also lower as it reduces the required temperature to rise over the burner and it lowers the natural gas uses. This is a very common type of oxidizer in the industry as it can be used in high-use applications due to the favorable energy usage payback.
Catalytic Thermal Oxidizer
This is a more complex design and uses a precious metal in the catalytic oxidizer as a catalyst such as Platinum, Palladium or Rhodium. This helps in lowering the required reaction temperature within the combustion chamber. Compared to the direct fired oxidizer, where the temperature required was nearly 1400 F-1450 F, the catalytic thermal oxidizer requires a much lower temperature ranging from 600 to 650 Fahrenheit. The capital cost and the maintenance cost of the CTO is potentially high due to its precious metal catalyst, which is needed to be replaced when it fouls. The analysis of harmful air pollutants (HAPs), volatile organic solvents (VOCs) is required first prior to the choice of thermal oxidizer to determine how rapid the catalyst might foul.
Regenerative Thermal Oxidizer
This is best suited for large air volumes where the concentration of harmful air pollutants (HAPs) and volatile organic solvents (VOCs) are very high. RTOs provide the best thermal efficiency among all other thermal oxidizers. This captures waste heat using two or three beds of ceramic media. The captured waste heat is then used to heat the incoming air at 1350 F. When the reaction temperature rises to 1400 F, the air in the RTO burner is heated up to ~ 50 F. since the RTO captures waste heat using ceramic media, this oxidizer is 95% efficient thermally.