Application of the new dry paint mist separation device

0 Introduction: With
, people are paying more and more attention to environmental protection and energy conservation. Coating workshop as a car coating energy consumption and pollution of large households has long been the focus of industry attention. Coating of environmental protection and energy-saving new technologies are also emerging, more mature technology including silane pre-treatment, the use of RO (reverse osmosis) electrophoresis water zero-emission technology, low- and medium-temperature agents, water-based coatings, high solid sub-coating applications, oven waste heat recycling and other
China
. Dry paint mist separation technology for painting room has long been used, but the old-fashioned dry paint mist separation device uses paper filter materials to filter and separate paint mist, there are great fire hazards and environmental pollution, and there are frequent replacement of filter materials, non-reusable and other defects. Germany's Doyle, Italy's Jayco and other companies launched a new dry paint fog separation device to avoid the above shortcomings, in environmental protection, energy consumption, operating costs and other aspects have obvious advantages. The new dry paint mist separation device has been fully integrated with the paint room on the basis of previous technology, and the improved filter element is renewable and reused, eliminating safety hazards.
this paper discusses the application characteristics of the existing wet paint room and the new dry paint room.
1 Application features of wet paint room
Wet painting room mainly uses circulating water system for paint mist treatment, through the air conditioning of the paint room to send air away from the free paint fog, after contact with the circulating water flow to separate the air from the paint mist The air separated from the paint mist is discharged directly into the atmosphere, and the paint mist is carried into the circulating pool by circulating water with paint mist coagulants, and then floats under the role of a variety of agents, using artificial or automatic slag removal device to salvage the timed floating paint slag.
(1) Water
wet paint room is the biggest feature of the use of water, in order to improve the effect of paint spray treatment, the water quality of circulating water can not be too poor, slotting and use of water are industrial water. As there is no guarantee that all paint mist has floated, and with the production, the water quality of circulating water gradually deteriorates, such as slag, long bacteria, impurity ions and other pollution, not only will affect the treatment effect of paint mist, serious will also produce bad odor, the production environment and the surrounding environment caused a bad impact. As a result, an average of 3 to 6 months to carry out a tank cleaning, an annual output of 200,000 cars on the production line of up to 200 t of water per tank change. Daily production due to exhaust wind to take away moisture, the average daily rehydration of several tons. As a result, the annual water consumption of at least thousands of tons, in the increasingly tight water resources, this paint fog treatment will be limited.
(2) the
using paint mist coagulant to make the paint mist into the circulating water, and then floating separated, in order to achieve the reuse of circulating water. However, due to the complex composition of paint mist and paint mist condensant itself performance limit, not all of the over-spraying fog can be smoothly floating and normal removal, so the amount of potions, the mutual cooperation between agents, tank fluid parameters monitoring, over-spraying fog composition changes, etc. should be considered, the state of paint slag can only rely on the rich experience of technical personnel to judge, it is difficult to quantify, daily maintenance is very inconvenient.
(3) Equipment
The humid and impurity-rich environment has a great impact on the equipment, and equipment that operates for long periods of time is highly vulnerable to damage, with almost all pumps and lines being updated for up to 3 to 5 years. Environmentally harsh, the equipment anti-pollution capacity requirements are high, investment is large, equipment operation and need to repair, replacement costs have greatly increased production costs.
(4) paint slag
paint slag salvaged after treatment needs to be treated by environmentally qualified enterprises, must be placed for a period of time after drainage to be treated, even if the "dry paint slag" water content is as high as about 50%, not conducive to cost control. The operation effect of the "slag press" which removes the water from the paint residue is not satisfactory. Paint room bottom and the channel in the paint slag, slotting primer slag, etc. need to be manually cleaned, the working environment is harsh, labor intensity is high.
2 Application characteristics of the new dry paint chamber
The consumption medium of the new dry paint chamber is lime, the use of filtration device to make the paint mist deposited in its surface lime layer without polluting the filtration device, the air can be recycled after the filter device, the paint mist deposited to a certain amount after the use of compressed air recoil, so that the paint mist layer fell off to the bottom of the filter, and then was pumped to the waste tank to be removed.
(1) Lime Potion
In order to maximize the adsorption effect of paint mist, the fineness of the lime used needs to be controlled at about 8 m, the ratio of lime and over-spraying fog is 2 to 4:1, that is, the spray spray fog amount of each car is 2 kg, the production of 500 vehicles per day, the need for fresh lime 2 to 4 t. The price of new lime and the treatment price of waste lime after absorbing paint mist treated by a specially qualified environmental company are in the hundreds of yuan/t, i.e. the price of using and handling lime every day is several thousand yuan. Lime supply and waste lime storage tanks should be isolated from the workshop work area or placed directly outside the workshop. New lime needs to be kept dry and its storage environment should be kept dry to prevent lime from failing in wet conditions. Foreign environmental protection requirements are high, waste lime is used as raw materials for cement production, and China currently does not have such technology applications, can only be handled by qualified environmental protection companies. Lime is only used to filter the surface adsorption paint mist of the unit, there is no lime in the passages and lines from the bottom of the paint chamber to the filter, and the channels and lines are cleaned manually on a regular basis by spraying non-stick coatings or covering them directly with plastic sheeting. When spraying non-stick coatings, the manual maintenance cycle can be extended by 1 to 3 times, reducing labor, but the cost of non-stick coatings is high, and about every 3 years need to be re-sprayed. Specific design, the amount of labor and costs to be accounted for, choose the optimal scheme. Considering that lime may cause environmental pollution to the coating workshop, it is verified by testing the spray plate in areas that may be contaminated, and maintenance and maintenance are carried out in strict accordance with the maintenance points of the equipment on a daily basis to prevent the occurrence of lime leakage accidents caused by abnormal damage to the equipment. The adsorption of lime to paint mist is not affected by the paint type, and can be selectively adsorbed on water-based or solvent-based paint, so the difference between different coatings in paint mist treatment is not considered, which reduces the difficulty of technical maintenance.
(2) Equipment
Dry paint room equipment is simple, mainly composed of filters, filter units, pumps and lines to provide and recycle lime, circulating air return channels, etc., and the equipment working environment is dry, less pollution, so the amount of labor and cost of equipment maintenance is greatly reduced, investment and operating costs are also reduced simultaneously. The key equipment in the dry paint chamber is a rod-shaped filtration unit, made of special materials, which can be reused and has a service life of about 3 years. Each filter consists of dozens of filter units, which are produced by a lime supply pump to provide lime, forming a lime layer on the surface of the filtration unit, with a small portion of the paint mist in the circulating wind remaining in the bottom passages and parts of the lines of the paint chamber, most of which are absorbed by the lime on the surface of the filter unit. With the thickening of the paint mist layer, the filter pressure difference increases, reach the specified value or according to the production needs of regular use of pulsed compressed air to reverse the filter unit, the reverse reaction time only takes a few seconds, the use of spray gap can be, will not affect production. The reverse punch makes the paint mist layer fall off into the cone at the bottom of the filter, and then pumps it into the slag tank for centralized treatment. The reverse-flushing filtration unit is reseeded with a lime layer to continue normal operation. The bottom cone of the filter needs to be opened regularly to check and clean up to prevent clogging. The lime supply device is in a state of linkage with the paint room fan, which can effectively prevent the pollution of the paint room caused by the wind disorder, and also keep the fan in a state of operation when the pipe is cleaned, and prevent dust or lime pollution from the paint room during manual operation. Lime supply and waste lime recovery of the out and inlet are set up flow meters, through the flow difference to determine whether there is a lime leakage phenomenon. In the event of a lime leak, the alarm is automatically stopped to prevent contamination of the coating environment.
(3) Cycle air return
dry paint chamber after the circulation wind filtration can be reused, filtration accuracy of more than 99.9%, filtered air particle content of about 0.1 to 0.3 mg/m3. The reuse of circulating air can greatly reduce the heating and humidification power of air conditioners, and even meet the requirements without heating and humidification. However, the circulating wind in the process of continuous re-use by friction, equipment operating heat, the temperature will gradually increase by about 2 to 3 degrees C, therefore, the cycle wind re-use, air conditioning should have a certain cooling function. In the automatic spraying section, the circulating air return amount can reach more than 95%, only 5% of the fresh air, so that the solvent content in the air remains below a certain fixed value. However, the manual operation of the station, in order to protect personal safety and health, the amount of fresh air required is more than 30%, the reusable wind efficiency is reduced more. For water-based paint and solvent-based paint, due to the different solvent content, in the circulation of wind re-use need to be treated differently, through strict calculation and selection of reliable solutions to prevent pollution of the environment and personal injury accidents.
3 dry paint room and wet paint room compared to
dry paint room and wet paint room comparison can be seen in Table 1.
table 1 dry paint room and wet paint room comparison
Note: China does not yet have dry, wet paint room operation comparison data, foreign data show: dry paint room than wet paint room annual operating costs reduced by more than 40%.
4 Conclusion
In summary, with the maturity of technology and the use of new technologies, dry paint room has the necessary conditions to replace wet paint room, it is important to consider that the dry paint room technology is not enough localization, the full use of foreign technology will inevitably bring the use, maintenance costs remain high disadvantages, therefore, need to consider the company's current situation and reasonable budget after the selection of suitable spray room form. Dry paint room technology has been widely concerned, FAW-Volkswagen's new production line has successfully used dry paint room technology, more host plants have begun to study this technology. With the expansion of the application range of dry paint mist separation technology in China, as well as the improvement of localization and China's attention to environmental protection and energy conservation, the application of this technology in the paint spray room will be more and more, the research of this technology is conducive to the rapid application of coating environmental protection, energy saving and consumption reduction technology.