The selection of waste gas treatment processes in the coatings industry

During the production process in the coating industry, harmful gases such as xylene may escape. If the concentration of xylene in the workplace exceeds the national health standard (100 milligrams per cubic meter), it will seriously endanger the health of workers, and the emission of organic waste gas will cause harm to the environment. Therefore, it is of great significance to treat the organic waste gas from coating production.

1. Characteristics of coating production process and waste gas

The raw materials of coatings include nitrocellulose, xylene, ethyl acetate, ethanol, butyl ether, isopropyl acetate, octyl ester, diisobutyl ester, light calcium carbonate, etc. as solid and liquid raw materials. During the production process, the mixing machine and the three-roll grinding machine are open-type, emitting a large amount of organic waste gas mainly composed of xylene. Xylene is a flammable and volatile liquid at normal temperature and pressure, with a boiling point of 144℃ and a melting point of 25℃.

2. Selection of treatment methods

2.1 Catalytic oxidation treatment technology

The catalytic oxidation treatment technology (CO) involves heating the organic waste gas to above 280℃ and using a catalyst to oxidize and decompose the VOCs in the waste gas into CO2 and H2O. The high-temperature gas generated during catalytic oxidation passes through a heat exchanger and preheats the incoming organic waste gas, thereby saving the fuel consumption for heating the organic waste gas. This treatment technology is carried out.

2.2 Activated carbon adsorption + desorption

When a fluid comes into contact with a porous solid, a certain component or components in the fluid accumulate on the surface of the solid. This phenomenon is called adsorption. Based on this characteristic, an appropriate adsorbent can be selected according to the actual situation to recover and treat the pollutants (VOCs) in the organic waste gas for the purpose of recycling and protecting the environment.

2.3 Molecular sieve rotary wheel concentration

The molecular sieve rotary wheel concentrates the large volume and low-concentration organic waste gas (up to 10-20 times concentration). The high-concentration organic waste gas after passing through the molecular sieve enters the combustion chamber. With the assistance of fuel combustion, the temperature is raised to around 300℃, and then enters the catalytic bed for reaction. The catalyst in the catalytic bed reacts with the organic waste gas to generate carbon dioxide and water and release a large amount of heat. The released heat can be utilized to produce hot air, steam, etc. This treatment process has an去除 rate of over 99%， and once treated， there is no worry. Moreover， the residual heat can be used to heat boilers or produce hot air， which has positive benefits.