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How to deal with VOCs generated by the coating line?

How to deal with VOCs generated by the coating line?


In the spraying process to produce "three wastes" is inevitable, which is the main part of the "three wastes" spraying exhaust gas. Spraying exhaust from the thinner volatilization, organic solvents will not be attached to the surface of the paint with the paint, in the spraying and curing process will be released, the formation of volatile organic compounds (VOCs), the main components of benzene, toluene and xylene benzene and other non-methane hydrocarbons, these substances are extremely harmful, known as the human "invisible killer These substances are extremely harmful and are known as the "invisible killers" of human beings. Especially in the case of unprotected spraying, the concentration of benzene in the air of the workplace is quite high, which is also very harmful to the workers' bodies, such as aplastic anemia in mild cases and leukemia in severe cases. Direct emissions into the atmosphere can lead to acid rain, haze and photochemical smog and other pollution problems, endangering human health and ecological safety.
Spraying exhaust gas mainly comes from the spraying and drying process, and the sources occur in the spray paint room, drying room and drying room.
At present, the state for the control of VOCs emissions, the introduction of the policy of levying volatile organic compounds emission fee, according to the pound charge. Whether the company's emissions meet the standard or not, the emission fee is not escaped. Industry can not stop, so VOCs are bound to be generated, the most direct and effective way is: effective capture of released VOCs, and treatment.
Then the question arises, the concentration of VOCs in the exhaust gas from the paint booth and drying room is very low, but the air volume is particularly large, and the main components of the pollutants are aromatic hydrocarbons, alcohols and ethers and esters of organic substances. What methods are available to effectively treat VOCs generated from such places?
At present, the more mature method abroad is to first concentrate low concentration of large air volume gas into high concentration of small air volume gas, use adsorption method to adsorb low concentration of room temperature spray paint exhaust gas, use high temperature gas desorption, and the concentrated gas is treated by the process of RTO and RCO. In the whole process, the concentration device is very important, according to the composition of the exhaust gas and working conditions, the concentration device can choose activated carbon adsorption and zeolite rotor adsorption.
There are many zeolite rotors in the market, how to buy zeolite rotors?
1. Choose the one with high zeolite content rate
The zeolite content rate directly determines the adsorption efficiency, so the zeolite content rate is crucial.
2. Choose good hydrophobicity
The adsorption performance of zeolite depends not only on whether the specific surface area is large enough, but also on whether the hydrophobicity is excellent, especially in the environment where the humidity of the exhaust gas is greater than 60%, it is a test of the hydrophobicity of zeolite, poor hydrophobicity of zeolite easy to block the fine pores, thus reducing the adsorption efficiency. Therefore, in order to ensure the adsorption performance, the specific surface area and hydrophobicity are indispensable.
3. Choose the one with high desorption efficiency
The purification efficiency of zeolite is not high only by absorption, but also by desorption. If the desorption function cannot reach nearly complete, it will affect the adsorption efficiency of zeolite over time and directly affect the service life of zeolite. The zeolite is resistant to high temperatures, and the desorption temperature is high, so no reaction heat will occur.
We look at it, is not the feeling that the conditions are very harsh?
In fact, these problems can be solved by being able to meet the following conditions
Honeycomb shape
The zeolite structure is designed into a honeycomb shape, which is conducive to the adsorption of zeolite on VOCs components, and is suitable for low concentration and large air volume sites.
Applicable VOCs: benzene, toluene, xylene, styrene, hexane, cyclohexane, MEK, MIBK, acetone, ethyl acetate, NMP, THF, methanol, ethanol, propanol-1C, butanol and various chlorine system solvents, etc.]
Adsorption and concentration principle
When the exhaust gas containing low concentration of VOCs passes through the honeycomb zeolite, the VOCs components are adsorbed in the zeolite, and the purified gas is discharged to the atmosphere or discharged to the chamber for recycling, and heat energy is recovered through the recycling process. At this time, the honeycomb zeolite that has adsorbed VOCs is continuously rotated and regenerated by adsorption in the desorption module using a small amount of heated air, and this process is able to obtain highly concentrated gas from low concentration of exhaust gas.

Zeolite requirements
Natural zeolite (sodium aluminosilicate) is used. Combined with the actual application requirements, the zeolite is designed and processed into cylinder and disk types, and users can choose different forms of zeolite according to the properties, composition and air volume of VOCs in the exhaust gas.
The zeolite content rate must be high in order to make the zeolite's adsorption and concentration performance more excellent, especially for aromatic organic compounds, the adsorption capacity is stronger, and there is a clear advantage in dealing with waste gas with high relative humidity, without a sharp increase in water absorption.
In addition to the technical requirements, the service provider is required to have sufficient experience in VOCs treatment to make a precise and perfect solution to ensure that the solution is executable and meets the emission standards in the face of exhaust gases containing any components.


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