For modern coating lines, it can generally meet the requirements of constant temperature, constant humidity and clean air (air dust content<10mg/m3); but for relatively simple coating production lines, it is difficult to guarantee constant temperature, constant humidity and cleanliness In order to prevent the paint film from producing pinholes and orange peel, it is easy to cause the paint film to produce pinholes (shrinkage), orange peel, particles and other paint film defects. Improve the temperature and humidity in the spraying room so that the temperature and humidity in the spraying room meet the process requirements; secondly, the viscosity and thinner composition of the construction paint should be adjusted according to different temperatures and humidity; generally, the temperature of the spraying room must be controlled during the spray painting construction Below 35℃, the humidity is controlled below 80%.
In order to effectively control the amount of air dust in the coating production line, the environmental conditions outside the production line should be improved first, and the polishing and wiping processes should be separated from the painting process to prevent the dust generated by the polishing from entering the production line spraying room or drying (curing) furnace. Eliminate the impact of grinding dust on spraying; secondly, the air filter cloth should be replaced regularly to ensure that the dust in the air can be effectively removed. In recent years, with strict environmental protection requirements, environmentally friendly coatings such as water-based coatings, high-solid coatings, powder coatings, etc. have developed rapidly. According to reports, the annual output of powder coatings in my country has reached 60,000 tons, ranking fourth in the world after the United States, Italy and Germany. Since the 1980s, my country has successively introduced more than 500 powder coating production lines. According to the current situation, it should be said that it has basically reached saturation. And how to speed up the localization of powder coating equipment has become an urgent topic in my country's coating industry.
The pollution of the coating production line generally includes waste gas, waste water, waste residue and noise. At present, the exhaust gas from the coating production line in China mainly comes from the exhaust gas from the pretreatment, paint spraying room, leveling room, and drying furnace. The pollutants emitted are roughly as follows: organic solvents that can form photochemical smog, volatile paint that emits foul smell, Thermal decomposition products and reaction products, acid-base mist, dust generated during shot peening, and dust in paint mist. Using paints that do not contain organic solvents or have low organic solvent content is the most effective way to solve organic solvent pollution. Minimize the amount of organic solvents and reduce the amount of organic solvent waste gas treatment. The waste gas containing high-concentration organic solvents should be treated centrally. After dilution, it is discharged into the atmosphere; the high-concentration, low-volume organic solvent waste gas emitted by the drying and curing furnace in the production line is usually treated by combustion, catalytic combustion, and adsorption methods; low-concentration, high-volume waste gas discharged from the paint spray booth, In the past, paint mist flocculants or surfactants were mostly used for treatment, but now the activated carbon adsorption method is popularized, and the activated carbon fiber bee wheel method is used to treat organic waste gas.
The wastewater mainly comes from degreasing, phosphating, passivation wastewater produced by pre-painting treatment, and wastewater containing electrophoretic paint produced by cathodic electrophoresis. Waste water from the spray booth and cleaning of the water-based intermediate coating, and the waste water from the recycle water of the top paint spray booth. Generally, all wastewater is concentrated in the basement and treated separately according to the type of wastewater. Neutralization, precipitation, filtration, and discharge of acid-base wastewater; electrolysis and chemical reduction methods for wastewater containing hexavalent chromium (Cr6-); for spray booth wastewater, whether it is water-based paint or solvent-based paint Waste water is treated by adding flocculants, paint residue is automatically discharged, and the treated wastewater will continue to be recycled, and paint residue will be burned or treated together with other industrial waste.
Waste residues are mainly paint residues and sediments produced by wastewater treatment. Generally, they can be dehydrated by a plate and frame filter press and transported to a dedicated waste residue storage place. The noise source mainly comes from fans and transportation devices, so we must choose fans and transportation devices that meet the noise requirements on the production line. It is best to install sound-absorbing materials in the paint shop. The control system of the coating production line has been continuously improved with the development of the times, and the control system is required to be more and more reliable. Therefore, the electrical control of the coating production line is generally double control, which can be controlled by each electrical cabinet or the central room. The central control room and the drying tunnel are generally equipped with microcomputers, which can accurately control the temperature of each zone of the drying and curing furnace. The central control room can be equipped with a TV monitor to display and record the rising and falling temperature curve, and it can also set and modify the parameters at any time to adjust the temperature according to the size of various workpieces and different coating colors. The bath liquid can be controlled by thermocouple. At present, all motors on the painting production line are generally equipped with double protection and interlocked with the main control. If any motor fails, the sub-control cabinet and the central control room can alarm. If the equipment fails, the whole line can automatically stop. To ensure operational safety.