The Exhaust Gas Treatment And Solution For Automotive Spraying Booth

The Exhaust Gas Treatment And Solution For Automotive Spraying Booth

Automotive spraying booth is used to paint the equipment surface and dye drying equipment, widely used in automotive, machinery, hardware, furniture, glass steel products, chemical equipment and other parts of the industry surface painting, paint construction operations. Due to the increasing use, the problem of exhaust pollution caused by it has gradually begun to attract attention.

The composition of the exhaust gas generated in the paint booth is more complicated and it has a certain degree of difficulty in handling. First of all, paint mist and exhaust gas will be generated when the equipment surface is sprayed. When the equipment is subjected to drying operation after spraying, it contains organic solvents, some plasticizers or resin monomers and other volatile components, and also includes thermal decomposition products and reaction generation. Things are more complex.

For the treatment of the paint room exhaust gas, due to the presence of particulate matter such as lacquer fog that may easily damage the equipment, the VOCs mixed exhaust gas is first subjected to operations such as paint mist removal and dust removal before being processed. In general, most of the VOCs are mixed using pre-spray towers.

Spray tower working principle: mixed exhaust gas is introduced into the purification tower through the air duct. After the filling layer, the exhaust gas and the absorbing liquid are in full contact with each other to absorb or chemically react to achieve the purpose of purification. After the exhaust gas is purified, it is dewatered by the defogging plate.

Remove the paint mist, dust VOCs exhaust gas for further purification. The methods that can be used include:

Photocatalytic Oxidation: Photocatalytic oxidation is catalyzed by external visible light. Photocatalytic oxidation reactions are semiconductors and air as a catalyst. With light as energy, organic matter is degraded into CO2 and H2O.

Heterogeneous Catalytic Oxidation: A collection of exhaust gas treatment technologies such as photocatalytic oxidation, UV photo-quantity photolysis, and advanced oxidants. It can improve the processing efficiency of organic materials, and this technology can react at normal temperature and pressure, with low operating cost, small equipment footprint, and high safety performance.

Plasma Catalytic Oxidation: After the organic exhaust gas is excited by plasma and dissociated and activated, the activated exhaust gas passes through high-energy rays on the surface of rare metal oxides and undergoes catalytic oxidation reaction with oxygen in the exhaust gas, and finally is converted into carbon dioxide and water.

RTO Regenerative Combustion: Using the heat storage combustion method, organic molecules are completely oxidized into carbon dioxide and water in a high-temperature environment to achieve discharge standards, which has a high purification efficiency.

As one of the major sources of atmospheric pollution, VOCs are not only one of the main substances that form PM2.5, but also an important precursor of ozone generation in the near-surface layer. Some environmental experts said that to solve ozone pollution, we must first solve the problem of VOCs. Therefore, the issue of VOCs has become an urgent environmental problem that needs to be solved. In addition to requiring companies that produce VOCs to install end-of-pipe facilities and corresponding monitoring equipment, they should use clean raw materials as much as possible to reduce VOC emissions at the source.

The furniture industry is one of the key industries for the treatment of organic waste gas. There are many exhaust gases and complex components. Among them, the output of wooden furniture, metal furniture and upholstered furniture is the largest (about 95% of the total furniture production). In the furniture manufacturing industry, the coating process is the main process for generating VOCs exhaust gas, including spraying, brushing, roller coating, shower coating and dip coating.

As far as the current furniture industry is concerned, VOCs mainly come from the volatilization of organic solvents and thinners in coatings during the painting process. Moreover, the types and contents of VOCs emitted during the use of different types of coatings are also different. When coating the same area, the use of oil paints produced the most VOCs, followed by waterborne coatings and powder coatings. In addition, because the furniture spraying workshop needs strong exhaust air, the generated exhaust gas has a large amount of air but a low concentration, generally lower than 200mg/m3; if it is a large-scale automatic spraying line, the emission concentration can reach 200mg/m3 due to the high spraying intensity. the above.

So, what should be done with the exhaust gas produced during the furniture manufacturing process?

At present, the treatment of VOCs in China's furniture industry is basically limited to the treatment of paint mist. Only a few companies have conducted adsorption treatment of VOCs in exhaust gas after the removal of paint mist.

The paint mist particles and wood dust generated by the furniture spraying process are mainly treated with water curtain filter. The total VOC removal efficiency is only 10% to 15%. The water absorption tower is adopted after the curtain wall cabinet, adding part of the flocculant can further improve the paint fog purification efficiency, and at the same time can remove part of the VOCs, but the VOCs purification efficiency does not exceed 30%. Wastewater from the absorption tower enters the company's wastewater treatment system.

Activated carbon adsorption recovery device is used for VOCs, and steam is used for regeneration of activated carbon to recover organic solvents in the exhaust gas;

Or activated carbon adsorption concentration - catalytic combustion control device, the use of hot air to regenerate activated carbon.

In some cases of governance in the current furniture industry, the operation of the activated carbon adsorption device is very poor and the operation rate is very low. The main reason is that the pretreatment of the paint mist is not thorough, resulting in failure of the activated carbon adsorber.

In addition, the low-temperature plasma technology is also very suitable for controlling the spraying exhaust gas of the furniture industry. It is characterized by simple equipment, convenient management, and low investment and operating costs. However, due to the design of this technology to the ignition process, it has a certain safety risk. At present, VOCs environmental protection facilities such as “low temperature plasma” and other ignition technologies have been suspended in some areas.

On the other hand, when the exhaust gas concentration is too high, the combination of heterogeneous catalytic oxidation can be considered for the treatment of VOCs. This technology integrates UV UV photolysis, UV photocatalytic oxidation, and advanced oxidizer technologies to improve the efficiency of organics. And this kind of technology can carry on the reaction under the normal temperature and the normal pressure, the operation cost is cheap, the equipment area is small, the safety performance is higher.