Regenerative Thermal Oxidizer (RTO)
One of today’s most widely accepted air pollution control technologies across industry is a Regenerative Thermal Oxidizer, commonly referred to as a RTO. They are very versatile and extremely efficient – thermal efficiency can reach 95%. They are regularly used for abating solvent fumes, odours, etc. from a wide range of industries. Regenerative Thermal Oxidizers are ideal in a range of low to high VOC concentrations up to 10 g/m3 solvent. There are currently many types Regenerative Thermal Oxidizer on the market with the capabitlity of 99.5+% Volatile Organic Compound (VOC) oxidisation or destruction efficiency. The ceramic heat exchanger(s) in the towers can be designed for thermal efficiencies as high as 97+%.
The VOC's are oxidised at high temperatures typically 800-850 degC for a period of 1–2 seconds where carbon molecules (VOC's) are bonded together with oxygen molecules prior to discharge to atmosphere. The energy efficiency is achieved storing heat ceramic media as the process air enters and exits the combustion chamber. The direction of airflow reverses every 1–3 minutes by a series of valves to alternately store and regenerate the heat - the inlet air gets pre-heated and the outlet air gives up the heat. The result is a very efficient operation. Solvent concentrations of 2-3 g/m3 and above allow the RTO to operate without support fuel using the energy within the solvent, i.e. auto-thermal or self-sustaining. At higher solvent concentrations of say 6-10g/m3, a high temperature bypass is necessary due to the excessive heat generated. Early RTO's had 2 towers or canisters which regularly satisfied the emission limits at the time of 150 mgVOC/m3 (average). However, there is a spike of VOC emitted as the valves change direction - the high VOC suddenly becomes the outlet for a few seconds. As emission limits have reduced to 50 mg/m3 and even 20 mg/m3, a third tower or an entrapment chamber is necessary to treat the spikes as well.
Variations in process airflow is usually controlled by the main fan being speed controlled to maintain a constant suction pressure. During times of no process airflow, the RTO would go into standby or idle mode to minimise energy consumption.
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