Photochemical oxidation technology of Spray Booth

Photochemical oxidation technology uses light excitation oxidation to combine O2, H2O2 and other oxidants with light radiation. The light used is mainly UV light, including uv-H2O2, uv-O2 and other processes, and can be used to treat VOCs, odors, and other difficult-to-degrade substances.

 

Design criteria

<Integrated Emission Standard for Air Pollutants> GB16297-1996

Design range

It uses the exhaust outlets of auto paint booths as its boundary, including process design, processing equipment, electrical and high-altitude emissions.

 

Photocatalytic Catalysis Technology

Photo-Oxygen Catalysis

Photochemical oxidation technology uses light excitation oxidation to combine O2, H2O2 and other oxidants with light radiation. The light used is mainly UV light, including uv-H2O2, uv-O2 and other processes, and can be used to treat VOCs, odors, and other difficult-to-degrade substances.

In addition, in the system with ultraviolet light, there is a synergistic effect between the ultraviolet light and the iron ion, which greatly accelerates the rate of decomposition of H2O2 to produce hydroxyl radicals, and promotes the oxidation and removal of organic substances.

The so-called photochemical reaction is a chemical reaction that can only be performed under the action of light. In this reaction, the light energy absorbed by the molecule is excited to a high energy state, and then the electronically excited molecule reacts chemically.

Photochemical oxidation reduction using n-type semiconductors as catalysts, TiO2 because of chemical and photochemical properties are very stable, the absorption rate is the strongest, and non-toxic inexpensive, adequate supply, so the photocatalytic redox to remove pollutants usually TiO2 as light catalyst. The photocatalyst oxidation-reduction mechanism is mainly that the catalyst is irradiated with light, absorbs light energy, undergoes electron transitions, generates “electron-hole” pairs, directly oxidizes and reduces the pollutants adsorbed on the surface, or oxidizes the adsorbed hydroxyl OH- on the surface. The strong oxidizing hydroxyl radical OH is generated to oxidize the contaminants.

 

 

Source of Exhaust gas:

Automobile painting is the most frequent part of the “three wastes” in the automobile manufacturing process. The coating exhaust gas is the main part of the “three wastes”.Because people do not have enough knowledge of exhaust gas hazards, exhaust gas treatment technology is not mature enough, and exhaust gas treatment costs are high, coating exhaust gas is often discharged without treatment.

These exhaust gases are discharged into the atmosphere without treatment, and under certain conditions, photochemical pollution will be formed, affecting the quality of the atmosphere, affecting the growth of animals and plants and human health. Some toxic VOC exhausts are crippled, teratogenic, and carcinogenic and cause serious injury to humans exposed to them for a long time.

To this end, various countries have enacted corresponding laws and regulations to limit the emission of such gases. China's comprehensive emission standards for air pollution, GB 16297, promulgated and implemented in 1997, limit the emission limits of 33 pollutants, including benzene and toluene. The volatile organic solvent (VOC) spraying processes such as xylene and so on include spraying, leveling, and drying, each of which has VOC emissions. The amount of VOC produced in a spray booth, leveling chamber, and drying room is 60%, 35%, and 5%, respectively. The amount of varnish produced in the three processes is 50%, respectively. 20% and 30%.

The main pollutants in the spray booth or spraying process are VOC and paint mist (particles), and the main pollutants in the leveling and drying processes are VOC. Paint mist particles are small (most of which are below 10μm), high viscosity, easy to adhere to the surface of the material, must remove paint mist before purifying organic waste gas, and then further remove toluene and xylene in exhaust gas to maintain the spraying environment. According to the provisions of the Labor Safety and Health Act, during the spraying operation, the paint room shall be continuously replaced with air, and the air exchange speed shall be controlled within the range of (0.25 to 1) m/s.

The main components of the exhaust air for spray booths are volatile organic solvents for painting. The main components are aromatic hydrocarbons, alcohol ethers, and ester organic solvents. Because of the large amount of exhaust air in the paint booth, the organic exhaust gas is exhausted. The concentration is very low, usually below 100mg/m3. In addition, the exhaust of paint spray booths often contains a small amount of unfinished paint mist, especially the dry paint mist capture spray booth, and the paint mist in the exhaust is high, which may become an obstacle to the treatment of exhaust gas. deal with.

 

Exhaust gas parameters Exhaust gas components: toluene, xylene solvent, etc.;

Exhaust air volume: design accounting, a set of 16000m3/h;

Exhaust gas concentration: 150-400mg/m3; (analogous industry data)

Exhaust gas temperature: 25 °C;

Working hours: 8h/d, 300d/a;

Emission Standards

After the exhaust gas is treated, it meets the requirements in the "Integrated Emission Standard for Air Pollutants" (GB16297-1996).

Emissions standards (according to 15m chimneys). Secondary standards

Processing unit details

光 Photo-Oxygen Catalytic System

Equipment name Photocatalytic exhaust gas treatment system

Guangzhou Weilongda Mechanical and Electrical Equipment Co., Ltd.

Processing gas capacity/station 16000m3/h

Paint mist filter Two-layer drawer glass fiber cotton filter, filter area 2 m2

UV+ Plasma + Honeycomb Activated Carbon

20 pieces -UV catalysis lamps, each with 150W, 6 VOC exhaust gas treatment plasma oxidized high-energy ion lamp tubes, each with 60W, (each plasma tube generates ozone 3-5 times that of UV tubes)

Drag coefficient / table 150

Power / Voltage / Bench 5.5KW

Equipment size 1250*1250*2220

Air outlet flange size 740X740

Equipment material Galvanized sheet

Weight 250kg

Use power supply 220V

Technical features:

1. Efficient odor removal: highly effective removal of volatile organic compounds (VOC), inorganic alcohols and other major pollutants, as well as a variety of malodorous odor, deodorant efficiency of up to 80-95%, deodorant effect is much higher than the national odor pollution promulgated in 1993 Emission Standards (GB14554-93).

2. No need to add any substances: only need to set the corresponding exhaust ducts and exhaust power, so that odor gases through this equipment for deodorization decomposition purification

3. No need to add any substances to participate in chemical reactions.

4. No pretreatment is required: No special pretreatment is required for odorous gases, such as heating and humidification, and the working temperature of the equipment is at -30°C.

5. The equipment has a small footprint and light weight: it is suitable for special conditions such as compact layout and narrow space, and it can handle 16000m3/h air volume.

6. Strong adaptability: It can be used to deodorize and purify high-concentration, atmospheric air, and odor gas substances. It can work continuously for 24 hours a day, and the operation is stable and reliable.

7. Low operating costs: The equipment has no mechanical action, no noise, no special management and routine maintenance, only regular inspections, the equipment energy consumption is low (only consumes about 0.3 kWh per 1,000 cubic meters per hour) The extremely low wind resistance of the equipment is <300pa, which can save a lot of power consumption of exhaust wind power.