Thermal Oxidizers by Type
Below is a description of the various thermal oxidizers OnQuest offers:
Direct-Fired Thermal Oxidizer (DFTO)
Direct-fired thermal oxidizers were the initial approach to a combustion-based technology for destroying volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). Originally, these units were called an incinerator, and often are still described as such.
The technology of a DFTO relies on diverting flue or waste gases into a combustion chamber instead of simply flaring them as exhaust at the top of a stack or chimney. Depending on design, the thermal oxidizer unit uses a burner flame in the combustion chamber to heat the gas stream to ~1600°F (870°C) to ensure complete destruction of organic chemicals. Effluent gases then pass through any other required treatments, such as a SOx scrubber with a quencher, NOx reduction, and particulate filtration, before being vented.
DFTOs present distinct advantages when the effluent stream to be treated is of relatively low volume and/or when concentrations of VOCs are high, thus reducing the fuel demand.
Regenerative Thermal Oxidizer (RTO)
With rising energy prices came the necessity to conserve fuel, prompting designs for thermal oxidizers that reduced fuel use and increased efficiency. Regenerative thermal oxidizers use a heat-recovery technique developed from blast furnace technology, alternately heating a bed of ceramic material, either randomly packed or in a structured medium, and then recover and recycle that heat to increase the temperature of the gas stream prior to combustion.
The original designs for RTOs included two chambers that held ceramic media, and achieved 98% destruction efficiency. Over time, some jurisdictions required 99% destruction efficiency, as well as and the prevention of spikes of emissions when the gas flow was switched between chambers. The result was a three-chamber RTO, where the flow is alternated smoothly in a firing order similar to the sparking of cylinders in an internal combustion engine, reducing the disruptions caused by changing the flow-pattern in the RTO.
The benefits of an RTO include lower fuel cost, a high destruction efficiency, and relatively low operational costs, since the units require only moderate maintenance.
Catalytic Regenerative Thermal Oxidizer (CRTO)
The design of a regenerative thermal oxidizer also lends itself to adding a chemical catalyst to the combustion chamber(s), along with the heat-transfer media. Using a catalyst allows oxidation to occur at around 600°F (315°C) instead of the usual 1600°F (~870°C), saving approximately 2/3 on fuel consumption.
Recuperative Thermal Oxidizer
The same drive to conserve fuel that prompted designs for regenerative thermal oxidizers also spurred the evolution of the recuperative thermal oxidizer, which uses a heat exchanger to preheat the incoming gas stream. Recuperative thermal oxidizers are best suited to operations which run at a steady state for long periods of time, providing an even heat load.
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