How effective is the organic waste gas treatment equipment in Suzhou?

Coating refers to covering the metal and non-metal surfaces with protective or decorative coatings, which is the most basic technical means for product surface protection and decoration. The coating process can be simply summarized as follows: pretreatment spraying drying or curing. Pretreatment generally includes degreasing, rust removal and passivation (phosphating) processes. For different coatings and anti-corrosion requirements, oil removal, rust removal, phosphating and other treatment methods should be selected according to the status of the raw materials of the workpiece. In the pre-treatment rust removal process, sand blasting, shot blasting or grinding process are also selected according to the needs of different parts of different occupations.

With the rapid development of painting technology, the automatic production of painting has made remarkable progress, electrostatic spraying, electrophoretic painting, powder spraying technology has been used and promoted. However, all the coatings used now belong to organic solvent-based coatings.

According to the painting production process, the waste gas mainly comes from the pretreatment, spraying and drying process. The main pollutants discharged are dust or acid fog during the pretreatment process, paint fog and organic solvents during spraying, and organic solvents during drying and evaporation. Paint mist mainly comes from the dispersed part of solvent-based coatings in air spraying operation, and its components are in common with the coatings used. Organic solvents mainly come from solvents and diluents in the application of coatings. Most of them are evaporative emissions. The main pollutants are xylene, benzene, toluene and so on. The harmful exhaust gas discharged from painting mainly gathers on the spray paint production line, during which the spray paint room, drying room and drying room are the primary sources of exhaust gas.

2. Treatment of Painting Exhaust Gas

The management of painting waste gas can be divided into two ways: prevention and treatment. The first priority of prevention is to reduce the emission of exhaust gases, and the first priority of treatment is to purify and manage the unavoidable emission gases.

2.1 Reduction of Exhaust Gas Emissions

2.1.1 Source Control to Reduce the Use of Organic Solvents

In order to reduce the emission of exhaust gas in the process of painting, it is necessary to start from the source, and do not need or use less coatings containing organic solvents, such as powder coatings, water-borne coatings, coatings with high solid composition, etc. Powder coatings do not use organic solvents. In addition to coating dust, they do not emit harmful exhaust gases. Therefore, in recent years, they have developed rapidly and their scale of use has increased significantly. Water-soluble coatings and high-solid coatings can also be used to reduce harmful exhaust emissions in the painting process, which is the development trend of the paint industry. In the process of painting, high solid component coatings or coatings without organic solvents are selected. Although the price of coatings is relatively high, the emission of organic solvents is reduced, the difficulty of waste gas treatment and the scale of treatment equipment are reduced, which meets the requirements of clean production and energy saving and emission reduction.

2.1.2 Improve the use rate of coatings and reduce the amount of coatings used

Spraying is a common method in painting production. However, spraying occurs more paint mist, paint will evaporate into the air in the form of paint mist.

The coating efficiency is affected by many factors. When painting large area workpiece, the coating efficiency of these methods is very high. But as long as the large capacity low pressure air spraying gun (HVLP) and electrostatic spraying can meet 60% of the coating efficiency. In addition, spraying by manipulator and rotating atomization can improve the utilization rate of coatings.

2.2 Management of Emissions

For the exhaust gas discharged from painting, appropriate methods can be chosen to purify and manage. There are two ways of purification management, one is to recycle organic solvents in waste gas, the other is to differentiate organic solvents in waste gas into CO2 and H2O.

2.2.1 Recycling of Organic Solvents

Organic solvents which occur in paint mist and evaporation during painting process are the primary organic solvents that can be recovered and used. The recovery methods include activated carbon adsorption, liquid absorption and condensation.

2.2.2 Organic Solvent Differentiation

It refers to the differentiation of organic solvents into CO2 and H2O. The methods to differentiate organic solvents include incineration, catalytic incineration, ultraviolet-ozone and microbial differentiation.