What is a thermal oxidizer?
A Thermal Oxidizer (often referred to as TOX, incinerator, or afterburner) destroys pollutants like Hazardous Air Pollutants (HAPs), Volatile Organic Compounds (VOCs), and odorous emissions that are often discharged from industrial processes.
The Three T’s of Thermal Oxidizers – Time, Temperature and Turbulence
The Three T’s are critical and co-dependent factors that determine oxidizer performance. Thermal oxidizers achieve very high VOC destruction efficiency by heating and maintaining a polluted airstream at high temperature for a set length of dwell time. Typical VOC destruction with these systems is 99+%. Thermal oxidizers can operate with an integral heat exchanger for fuel savings (or without, for capital cost savings). The diagram below includes an integral heat exchanger.
How does a thermal oxidizer work?
A pollutant-filled airstream is pushed through the oxidizer, usually with a system fan (1). When equipped with an air-to-air heat exchanger, the flow of air will pass air through the air-to-air heat exchanger (2) to preheat the air before entering the burner/combustion chamber (3). In the combustion chamber the air is heated to a sufficiently high (>1400F) temperature and held at this temperature, with some amount of turbulence, to ensure VOC destruction.
Typical operating temperatures are >1400F, with dwell times of 0.5-1.0 second, converting over 99% of the VOCs to carbon dioxide and water vapor. This hot, clean air then continues through the hot pass of the heat exchanger (4) (if heat exchanger is utilized). This cooled, clean air is then exhausted to the atmosphere. (5)
Questions to ask when considering a thermal oxidizer (TOX)
- Is a thermal oxidizer the most cost-effective oxidizer solution for my airstream?
- Would a heat exchanger be cost effective?
- Is a plate heat exchanger or shell and tube style heat exchanger a better choice?
- Shell and tube heat exchangers are more robust than plate style heat exchangers
- Is there a potential for particulates that could plug the heat exchanger?
- Shell and tube heat exchangers are better than plate for particulate applications
- Tube size is an important consideration when particulates are expected
- Is there a need for heat or steam in your plant?
- Secondary heat recovery has good payback with thermal oxidizers
- Do local codes require Low NOX operation?
- Low NOx burners can be retrofit for these applications.