Volatile organic compounds treatment technology（condensation technology, membrane separation technology and Biodegradation method)

Despite the adsorption and absorption discussed last time, there are still other treatment can help to realize the volatile treatment technology, including condensation technology, membrane separation technology and Biodegradation method. 

Condensation technology

Condensation recovery method is the process of condensing and separating volatile organic compounds in vapor state by changing the temperature or pressure of the system.

The operating system needs a low temperature and high pressure to achieve high recovery efficiency, so the equipment performance requirements and running costs are high.

Condensation technology is generally used in high concentration and high boiling point organic waste gas, usually combined with absorption, adsorption and other methods.

Membrane separation technology

Membrane separation technology can be divided into liquid separation and gas separation according to the state of the treatment.

Taking gaseous membrane separation as an example, the organic waste gas enters the condensation system after being pressurized by the compressor, and the condensed liquid VOCs can be recycled or processed in the next step.

Membrane separation system selectively allows the uncondensed gas to be enriched by VOCs, and the gas that cannot pass through the membrane can be discharged directly as the purified gas, while the exhaust gas that passes through the membrane is returned to the compressor for further cycle treatment.

Compared with the traditional VOCs processing technology, the membrane separation method has the advantages of high mass transfer efficiency, low energy consumption, small device size and simple operation.

The key of this technology lies in the selection of membrane. The selection of membrane material should consider the stability, mechanical properties, hydrophobicity and economy of the membrane. If the temperature of the treated exhaust gas is high, the high temperature resistance should also be considered.

Biodegradation method

The principle of biodegradation method is to use microorganisms to decompose organic matter contained in waste gas into CO2 and water, that is, organic matter in waste gas provides energy and nutrients for microorganisms. Biological treatment of volatile organic compounds generally involves the following steps:

(1) Volatile organic compounds diffuse from the main body of the gas phase to the gas-liquid interface, soluble in the liquid phase;

② The volatile organic compounds diffused from the liquid film to the biofilm under the promotion of concentration difference;

③ Volatile organic compounds are captured and degraded by microorganisms in the biofilm;

(4) Volatile organic compounds are decomposed as energy and nutrients in microbial life metabolism;

⑤ Some metabolites diffuse to the liquid phase, and gaseous substances diffuse to the gas phase.

Biological scrubber reaction conditions are mild, stable operation; However, the operation cost is high, and the treated VOCs need to be easily soluble in water. The main unit of waste gas treatment by biodegradation method is microorganism. It is one of the development trends of this technology to cultivate microorganism which can adapt to different environmental conditions, have short culture cycle and maintain high activity for a long time.