Treatment of Organic Exhaust Gas in Automobile Coating

The production line of automobile painting is the most part of "three wastes" in the process of automobile manufacturing, and the exhaust gas of painting is the main part of "three wastes". The exhaust gas of painting workshop is mainly organic solvent contained in coating and decomposition of coating film during spraying and drying. It is collectively called volatile organic compounds (VOC). The main components of VOC are toluene and xylene. These ingredients are harmful to people's health and living environment, and have bad odor. If people inhale low concentration organic waste gas for a long time, it will cause chronic respiratory diseases such as cough, chest tightness, asthma and even emphysema. It is recognized as a strong carcinogen at present. In addition, organic exhaust gas plays a very important role in the formation of photochemical smog and acid rain. In order to reduce VOC in coatings, water-borne coatings and powder coatings have been developed, but water-borne coatings still contain a certain proportion of organic solvents. To this end, countries have promulgated corresponding decrees to limit the emission of such gases. In 1997, China promulgated and implemented GB16297 "Comprehensive Emission Standard of Air Pollution", which limits the emission of 33 pollutants, including benzene, toluene, xylene and other volatile organic solvents. In recent years, with the improvement of people's awareness of environmental protection, the improvement of environmental laws and regulations and the improvement of law enforcement, automobile manufacturers need to equip waste gas treatment equipment in the new painting line, and the old painting line is gradually supplemented with waste gas treatment equipment, which can be discharged only after the treatment reaches the standard. According to different painting exhaust gas, different manufacturers adopt different methods. The following is a preliminary analysis and discussion of automobile painting exhaust gas treatment technology.

According to the production process of automobile painting, painting exhaust gas mainly comes from spraying and drying process. The main pollutants discharged are paint mist and organic solvents produced during spraying and organic solvents produced during drying and volatilization. The paint mist mainly comes from the dispersed part of solvent-based coatings in air spraying operation, and its composition is consistent with the coatings used. Organic solvents mainly come from solvents and diluents in the use of coatings. Most of them are volatile emissions. The main pollutants are xylene, benzene, toluene and so on. Therefore, the main sources of harmful exhaust emissions in painting are spray room, air drying room and drying room.