Application and post-treatment of zeolite in the t

2022-10-14
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Application and post-treatment of zeolite in spraying VOCs treatment

zeolite is an aluminosilicate mineral with water frame structure, which was first discovered in 1756. Swedish mineralogist cronstedt found that a kind of natural aluminosilicate ore would boil when burned, so it was named "zeolite" (Swedish zeolites). In Greek, it means "LITHOS" of "boiling" (Zeo). Since then, the research on zeolite has been deepened. Zeolite has the properties of adsorption, ion exchange, catalysis, acid resistance and heat resistance, so it is widely used as adsorbent, ion exchanger and catalyst, as well as gas drying, purification and sewage treatment

it is inevitable to produce "three wastes" in the spraying process, and the spraying exhaust gas is the main part of "three wastes". The spraying waste gas comes from the volatilization of diluent. The organic solvent will not adhere to the surface of the paint with the paint, and will be released completely during the painting and curing process to form volatile organic compounds (VOCs), which are mainly composed of benzene series such as benzene, toluene and xylene and other non methane total hydrocarbons. These substances are extremely harmful and are known as the "invisible killer" of mankind. Especially in the case of spraying without protection, the concentration of benzene in the air of the workplace is quite high, which is also very harmful to workers' health, ranging from aplastic anemia to leukemia. Directly discharged into the atmosphere will lead to pollution problems such as acid rain, haze and photochemical smog, which will endanger human health and ecological environment safety

the spraying waste gas mainly comes from the spraying and drying process, and the sources are paint spraying room, drying room and drying room

at present, the state has introduced the policy of levying volatile organic pollutant discharge fees according to the control of VOCs emissions, charging by catty. No matter whether the emission of enterprises reaches the standard or not, the sewage charge cannot be escaped. Industry cannot stop, so the most direct and effective way to generate VOCs is to effectively capture and control the released VOCs

then the problem comes. The concentration of VOCs in the exhaust gas from the paint spraying room and drying room is very low, but the problem of focusing on solving the problem of materials is that the air volume is particularly large, and the main components of pollutants are aromatic hydrocarbons, alcohol ethers and esters. What methods can be used to effectively control VOCs generated in such places

at present, the more mature method abroad is: first condense the low concentration gas with large air volume into a high concentration gas with small air volume, use the adsorption method to adsorb the low concentration waste gas from normal temperature painting, use the high-temperature gas to desorb, and use the RTO and RCO process to treat the concentrated gas. In the whole process, the concentration device is very important, which is within ± 0.5% of the set value according to the composition and operation of the waste gas; 15. Displacement control rate range: 0.001 ~ 500mm/min16. Displacement control rate accuracy: within ± 0.2% of the set value. 17. Constant stress, constant strain, constant displacement control range: 0.5% ~ 100% fs18. Constant stress, constant strain, constant displacement control accuracy: when the set value is ≥ 10% FS, the concentration device can choose activated carbon adsorption and zeolite runner adsorption

there are many zeolite runners on the market. How to choose zeolite runners

1. Selecting <2018/p>

zeolite with high zeolite content directly determines the adsorption efficiency, so the zeolite content is very important

2. The adsorption performance of zeolites with good hydrophobicity 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 exhaust gas humidity is greater than 60%, which tests the hydrophobicity of zeolites. Zeolites with poor hydrophobicity are easy to block the pores after experiments, thus reducing the adsorption efficiency. Therefore, in order to ensure the adsorption performance, specific surface area and hydrophobicity are indispensable

3. The purification efficiency of selecting

zeolite with high desorption efficiency is not high, so we can't just look at the absorption, and the desorption function is also very important. If the desorption function is not nearly complete, the adsorption efficiency of zeolite will be greatly affected over time, which will directly affect the service life of zeolite. However, zeolite has high temperature resistance and high desorption temperature, so no reaction heat will occur

after reading it, do you think the conditions are very harsh

in fact, these problems can be solved if the following conditions can be met

the structure of zeolite is designed into honeycomb, which is conducive to the adsorption of VOCs by zeolite, and is suitable for places with low concentration and large air volume

[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]

principle of adsorption concentration

when the waste gas containing low concentration 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 indoors for recycling treatment, Heat energy is recovered through recycling. At this time, the honeycomb zeolite that has adsorbed VOCs rotates continuously, and a small amount of heated air is used for adsorption regeneration in the desorption module. In this process, high concentrated gas can be obtained from low concentration waste gas

zeolite requirements

natural zeolite (sodium aluminosilicate) is used. Combined with the actual application needs, the zeolite is designed and processed into cylinder and disc. Users can choose different forms of zeolite according to the properties, composition and air volume of VOCs in waste gas

the content of zeolite must be high in order to make the adsorption and concentration performance of zeolite more excellent, especially aromatic organics, which have stronger adsorption capacity, and have obvious advantages in dealing with waste gas with high relative humidity, so that there will be no sharp increase in water absorption

in addition to technical requirements, service providers are also required to have sufficient experience in VOCs treatment, and be able to make accurate and perfect plans in the face of exhaust gas containing any component, so as to ensure the enforceability of the plan and meet the emission standards

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