VOC exhaust gas is a volatile organic compound waste gas. The control technology of VOC exhaust gas treatment includes combustion method, photocatalysis method, activated carbon adsorption method, absorption method, condensation method, biological treatment method and the like. There are a variety of treatment technologies available for the treatment of VOC exhaust gases. The following is a description of several commonly used VOC exhaust gas treatment technologies:
- Adsorption method
The adsorption effect of the adsorption method mainly depends on the properties of the adsorbent, the gas phase pollutant species and the adsorption system process conditions (such as operating temperature, humidity, etc.), so the key problem of the adsorption method lies in the selection of the adsorbent. The adsorbent should have a dense pore structure, large internal surface area, good adsorption performance, stable chemical properties, acid and alkali resistance, water resistance, high temperature and high pressure resistance, not easy to be broken, and low air resistance. Commonly used adsorbents are mainly activated carbon (granular and fibrous), activated alumina, silica gel, artificial zeolite and the like.
2. Solvent absorption method
The liquid solvent is used as the absorbent, so that the harmful components in the exhaust gas are absorbed by the liquid, thereby purifying the liquid. The absorption process is based on the principle of similar organic matter, and the diesel oil and kerosene having higher boiling point and lower vapor pressure are often used as the solvent. The VOC is transferred from the gas phase to the liquid phase, and then the absorption liquid is desorbed to recover the VOC therein, and the solvent is regenerated. The method not only eliminates gaseous pollutants, but also recovers some useful substances. It can be used to treat VOCs with a gas flow rate of generally 3,000 to 15,000 m3/h and a concentration of 0.05% to 0.5% (volume fraction). The removal rate can reach 95%. ~98%.
The method has the advantages of being more effective and low-cost for treating large air volume, normal temperature and low concentration organic waste gas, and can convert pollutants into useful products. However, there are still some shortcomings in the solvent absorption method. Due to the large investment in the post-treatment of the absorbent, the selectivity to organic components is large, and secondary pollution is prone to occur. Therefore, when processing VOCs, it is necessary to select a plurality of different solvents for absorption, which greatly increases the cost and technical complexity.
3. Thermal destruction
The thermal destruction method is classified into a direct combustion method, a catalytic combustion method, and a concentrated combustion method. The thermal destruction method is suitable for small air volume and high concentration gas treatment. The use of the device is simple, the investment is small, the operation is convenient, the floor space is small, and the heat energy can be recycled and the gas purification is thorough.
4. Biological treatment
The application of biological treatment technology to the purification of organic waste gas has only begun in recent years and is an emerging technology. Common biological treatment processes include biological filtration, biological trickling, biological washing, membrane bioreactors, and rotary biofilter reactors.