Views: 7 Author: China xicheng Publish Time: 2021-04-20 Origin: China xicheng
The primary sources of exhaust gas from furniture factories are from two aspects. One is from many used adhesives, which will produce a large amount of formaldehyde; the other is a large amount of toxic and harmful gases generated during the painting process. Organic waste gas containing harmful substances such as ketones and amines is also flammable and quickly causes fires, posing a threat to personal safety and property.
VOCs emissions from the furniture manufacturing process mainly have the following characteristics:
(1) VOCs emissions are related to the type of paint used. When the same area is painted, oil-based paint produces the most VOCs, followed by water-based paints, and powder paints are the least. Oil-based coatings are generally used in wooden furniture manufacturing, mainly including polyurethane coatings, nitro coatings, and alkyd coatings.
(2) VOCs emissions are related to coating technology. When painting the same area, air spraying technology produces more VOCs, while electrostatic spraying and brushing processes have fewer VOCs.
(3) Oil-based coatings generally used in the manufacturing process of wooden furniture mainly include polyurethane coatings, nitro coatings, and alkyd coatings. The air spraying method requires multiple primer and topcoat sprays on the table during the production process. The types of coatings used are varied, and the amount used is significant. The types and emissions of VOCs are ranked first in the furniture manufacturing industry.
(4) Upholstered furniture is mainly made of elastic materials and soft materials. The bending, armrests, and legs of the furniture are primarily made of wood. In the production process, primer and topcoat are also required. The painting process is similar to that of wooden furniture. The same, but the use of paint and VOCs emissions are less than wooden furniture.
(5) Metal furniture can be divided into electroplating furniture and baking varnish furniture. The types of coatings used include liquid coatings and solid powder coatings. Air spraying and electrostatic spraying can be used in the coating process.
(6) In the production process of plastic furniture, bamboo and rattan furniture, and glass furniture, VOCs are negligible, and pollution is low.
(7) Many furniture manufacturing companies have a wide variety of products and correspondingly use more types of coatings. The types and emissions of VOCs generated are not always stable but change with changes in product types.
(8) During the coating process, the types and emissions of VOCs produced by different coating processes are different.
The treatment of VOCs exhaust gas from the furniture manufacturing industry can be divided into two ways: prevention and treatment:
1. "Prevention" is mainly source control, that is, by increasing the proportion of environmentally friendly coatings (water-based coatings or powder coatings) with low organic solvent content and improving coating technology (rotary cup atomized electrostatic spraying, air atomized electrostatic spraying), Brushing, roller coating, etc.), research and development of intelligent coating test lines, fully airtight coating workshops and other methods to reduce the generation of VOCs.
2. "Treatment" is mainly to collect and purify the VOCs waste gas generated during the coating production process. At present, the VOCs emission control technology widely used in the market is mainly the control technology of the absorption method, the adsorption method, and the combination of the absorption method and the adsorption method.
(1) Wet spray equipment
Absorption method, that is, the use of wet scrubber equipment to capture the paint aerosol (paint mist) formed during the coating process. Its working principle is: under the action of the gravitational force of the exhaust fan, the air containing paint mist flows toward the inner wall of the water curtain machine, and a part of the paint mist directly contacts the water film on the water curtain plate and is absorbed, and a part of the paint mist is absorbed. It is washed away by the water curtain when passing through the water curtain, and the remaining paint mist that is not captured by the water film and the water curtain is washed away when passing through the water washing area and the cleaning area.
It should be pointed out that the paint mist treatment device installed in the water curtain machine can only treat the resin component in the paint mist. For organic solvents in the vapour state, because they are difficult to dissolve in water, they cannot be effectively treated and need to be combined with other exhaust gases—processing equipment for processing.
(2) Activated carbon adsorption equipment
The primary device used is the activated carbon adsorption device or the filter adsorption method with absorbent cotton. Its working principle is to use the windcatcher to collect the polluted air in the workshop and remove the pollutants in the air through the adsorbent such as activated carbon or absorbent cotton. Emission.
(3) Absorption-adsorption combination
The primary device is a water curtain cabinet + activated carbon adsorption box. The combination of absorption method and adsorption method means that a set of adsorption device is installed after the absorption method, which can prevent the aerosol from clogging the adsorbent and effectively remove the organic solvent in the vapour state.
At present, some wood furniture manufacturing enterprises adopt this method, but this method has significant drawbacks. After passing through the water curtain machine, the polluted air has an effective moisture content, and the adsorbent cannot be fully utilized.