Study on the Technology of Automotive Paint Spraying and Exhaust Gas Treatment

Abstract: With the improvement of people's awareness of environmental protection, the technical requirements for the treatment of automobile exhaust gas are getting higher and higher. This article explores the automotive paint spray exhaust treatment.

Automotive coating technology has a high technical content, plays a vital role in the car, but the coating process is the most exhausting link, for now, many companies do not understand the extent of its harm, even if To deal with, but also by its high prices and the high cost of technology collapsed, most companies in order to save costs, the direct discharge into the air. Harmful gas emissions generate new pollution during air integration, causing minor damage to the surrounding population. However, long-term exposure to such contaminated air can have irreversible consequences on the human body. Among the four major automobile production processes, the paint shop is the one with the most "three wastes", of which the coating gas is the main part of the painting "three wastes".

Many of the sources of waste gas from the car's load control room come from the spray-painted studio drying and drying room. Exhaust gas is now rigorously processed in many automobile plants and discharged only after it meets the standards. However, most of the harmful gases generated in paint shops and drying workshops are directly passed to the outside and there is no purification at all. This is not in conformity with the new Environmental Protection Law. Especially for new standards that have an important role, since paint spray exhaust is a sensitive indicator of the entire coating line, we have to make a budget assessment of the need for retrofitting ourselves, and we have to figure out the most reasonable area of ​​responsibility ourselves and at the same time do a good job with the tenderers Full communication, so as to fulfill the obligations of the enterprise. We need to upgrade the management of paint exhaust gas to a new level and adapt to the new era of development. This article has made an overall planning and adjustment of our disposal plan.

1 automotive paint spray booth exhaust characteristics

On the surface, the painting of a car is only used for decoration, but its deeper meaning is to protect the car body from corrosion and play a primary protective role in the car, and its related technology is also the key to the enterprise The weight. In the original production, organic dissolution reagents and dilution reagents were not able to form film-dissolving reagent-based coating solvent-based coatings, which eventually formed a waste gas that polluted the air. At present, the country has introduced the control measures for VOCs, but the implementation results in various regions are not satisfactory. Therefore, it is necessary to further strengthen the discussions on the VOCs treatment technology of VOCs for automobile painting and lay the foundation for improving the air quality.

In the car spray design, should ensure the quality of indoor air, in order to ensure the safety of indoor staff, the corresponding measure is to ensure continuous exchange of wind, but also to change the wind speed to ensure a certain wind speed. Spraying the main harmful components in the spray booth emission of volatile organic solvents in the painting process, including aromatic hydrocarbons, alcohol ethers and esters of organic solvents. Precisely because of the speed of air circulation in painted workstations, which results in low concentrations, typically less than 100 mg / m3, and the presence of a small amount of virgin paint gas in the spread of the paint shop, The painting workshop, in particular, is obviously dealing with problems that, in the light of this, its clarity should be clearly understood and prevented from affecting the effectiveness of the material concerned.

2 car coating exhaust gas treatment methods

When paint is applied to motor vehicles, there is a lot of work-shop associated with liquids of a similar nature, such as VOCs, which cause pollution especially when it is spread to the surroundings Large, it is recommended to take the relevant measures in the discharge. There are two core types of waste gas treatment methods: one is the type of damage removal methods, such as igniting or accelerating the ignition, so that VOCs into carbon dioxide and water; the other is the acquisition method, such as A method of absorbing and adhering, a method of absorbing, a method of cooling and condensing, and a method of leaving a liquid film.

2.1 Destructive elimination

A lot of VOCs can all be burned, can go through the heat to ignite or boost ignition method implementation. The benefits of using ignition methods are: VOCs purification efficiency, organic waste gas do not pre-treatment, you can rely on the nature of good. Inadequacies are: high temperature exhaust gas collection, for low density, low temperature gas, requires a lot of energy to burn; processed exhaust heat will be great, have to deal with high temperature gas equipment; a machine The capacity is not enough to support all the air volume, the excess gas for the wind, not only expensive to deal with, and the need for larger containers.

For the drying chamber of the exhaust gas, due to its VOCs concentration and temperature is high (concentration of 1000mg / m3, the temperature is between 150 and 200 degrees Celsius, the wind is very small hour of all exhaust gas is not enough 50000 cubic meters, more suitable for ignition For example, at present, the most widely used plants for vehicle painting and assembly are heat-storing incineration equipment and waste-gas-fired incineration equipment, however, when dealing with paint spray booths and air-drying rooms, The temperature is relatively low, the air volume is relatively large (general concentration <300mg / m3, temperature <30 ℃, air volume> 100,000 Nm3 / h), so the combustion method is not suitable.

2.2 secondary recovery treatment

In the decontamination of the corresponding pollutants, the gas-like use of other objects to absorb the way, but this way a bit hidden, smaller, dense, the implementation of cooling and solidification, the relevant material as a carrier, carrying pollutants for Temperature is not high and the flow rate of the situation. Especially in the important part of the adsorption method, because organic waste gas is a sensitive indicator of the progress of the whole project, we must make a budget assessment of temperature and humidity, and we have to predict the most reasonable pretreatment and at the same time do a good job of adsorbing VOCs Full communication, so as to achieve the maximization of business efficiency.

3 automotive paint spraying exhaust gas treatment technology

Adsorption treatment technology is the main method of exhaust gas treatment technology, the core is to rely on high-performance adsorbent, high performance adsorbent should have uniform pore, larger adsorption capacity, good hydrophobicity and easy regeneration and other characteristics. At present, among the industrial applications, the most commonly used adhesive for the waste attachment process is the two types of carbon molecules and zeolite molecular sieves.

3.1 Exhaust gas adsorption treatment commonly used adsorbent

Activated carbon has the advantages of rich pores and large specific surface area, which is suitable for adsorption purification of most VOCs. However, when the humidity of the exhaust gas is over 60%, the adsorption effect of the activated carbon will be greatly reduced. In addition, activated carbon often leads to safety problems when it is used in practice. Because of its instability, hot air can cause spontaneous combustion, so water vapor should be used for regeneration. In painted paint shops, the level of unwanted gas humidity, rh, ranges from 85% to 90%. Assuming that materials are being absorbed by activated carbon, these gases must first be stripped of moisture to operate The process is not very simple, so this method is not recommended.

Relative to the activated carbon, the characteristics of the zeolite adsorbent: non-flammable; temperature 1000 ℃, hot air can be high temperature regeneration; have a strong hydrophobic, when the exhaust humidity RH <90%, showing good VOCs adsorption.

3.2 use of molecules for adsorption