VOCs Treatment--Combustion Method
Direct Combustion
The temperature requirements of the direct combustion method are relatively high, generally above 1100 °C. Moreover, there are certain restrictions on the oxygen concentration. Low oxygen concentration will lead to incomplete combustion of VOCs, which is likely to cause secondary pollution; too high oxygen concentration will indirectly lead to the reduction of the concentration of combustibles, which will not reach the limit of ignition concentration.
The direct combustion method is easily operate, has no requirements on the type and nature of the treated gas, and the degradation rate can reach more than 98%. However, due to the high energy consumption and potential safety hazards, this method has been rarely used in recent years.
Thermal combustion method
Thermal combustion is generally used when the concentration of VOCs is low. The difference from the direct combustion method is that the organic waste gas needs to be preheated, and the combustion temperature is greatly reduced, generally at 350-600 °C, which belongs to flameless combustion, which reduces energy consumption and increases safety.
The equipment commonly used in the industry can be divided into thermal oxidizer without heat recovery, thermal oxidizer with partition heat exchanger, and regenerative thermal oxidizer (RTO).
Catalytic combustion
The catalytic combustion method refers to the use of catalysts to reduce the activation energy required for the oxidation of volatile organic compounds, increase the reaction rate, and make the oxidation reaction proceed at a lower temperature (200-400 °C).
According to different heat energy recovery methods, catalytic oxidizers can also be divided into non-heat recovery, partition type, and regenerative catalytic oxidizers (RCO). Compared with RTO, RCO has an additional layer of catalyst in the fixed bed of the regenerator.