I'm Fang Liang, deputy general manager of Deqing Tianhao Environmental Protection Technology Co., Ltd. now I'm discussing the treatment of organic waste gas (VOCs) with qunyou based on the actual experience of our company. As we all know, the remediation of environmental pollution is very important and urgent. Environmental protection has attracted the attention of all countries and mankind all over the world. The International Olympic Committee assessment team inspected the bid cities and listed the improvement of the ecological environment as an important content. China attaches great importance to the environmental protection workbench, has issued many environmental protection policies and regulations, and carried out many environmental protection work and activities.

VOCs is one of the main sources of air pollution. VOCs waste gas is common in paint production, chemical fiber industry, metal coating, chemical coating, shoe and leather making, electroplating, plywood manufacturing, tire manufacturing, wastewater treatment plant and other industries. Harmful volatile organic compounds mainly include acetone, toluene, phenol, dimethylaniline, formaldehyde, ethyl acetate, ethanol, etc.

Since its establishment, the company has been aiming to build an influential domestic environmental protection enterprise, increasing R & D investment, strengthening technological innovation, and constantly improving the enterprise's independent core technology R & D and industrial development ability. The company now has advanced organic waste gas treatment technologies at home and abroad, such as th-dlz (plasma organic waste gas purifier), th-gcu (microwave photolysis organic purifier), and has mature market experience in VOCs waste gas treatment.

There are many technologies and processes that can be used for the treatment of industrial VOCs waste gas, such as absorption and hair method, oxidation method, adsorption method, biological method, low-temperature plasma and microwave photolysis. The most commonly used methods are combustion and adsorption. Absorption method is less used now. Photocatalysis, biological method and low-temperature plasma are the frontier and hot technologies of VOCs waste gas treatment at present.

The operation principle, application scope, advantages and disadvantages of each treatment method are briefly described below.

1. The masking method adopts the mixing of stronger aromatic smell and odor to mask the odor and make it acceptable. It is applicable to the occasions where the impact of low concentration odor gas needs to be eliminated immediately and temporarily. The odor intensity is about 2.5. There is no organized emission source, which can eliminate the odor impact as soon as possible. It has great flexibility and low cost. The odor components have not been removed

2. The dilution diffusion method discharges the odorous gas to the atmosphere through the chimney or dilutes it with odorless air to reduce the concentration of odorous substances to reduce the odor. It is suitable for the treatment of medium and low concentration odorous gases discharged in an organized way. The cost is low, the equipment is simple, and it is easy to be limited by meteorological conditions, and the odorous substances still exist

3. The thermal combustion method fully mixes the odorous substances and fuel gas at high temperature to realize complete combustion. It is suitable for the treatment of combustible gases with high concentration and small gas volume. The purification efficiency is high. The odorous substances are completely oxidized and decomposed. The equipment is easy to corrode, consume fuel, have high treatment cost and easy to form secondary pollution

4. The cost of catalytic combustion method is too high to be applied by enterprises

5. The water absorption method uses the characteristics that some substances in the odor are easily soluble in water to make the odor components directly contact with water, so as to dissolve in water to achieve the purpose of deodorization. The odor gas with water-soluble and organized emission source has the advantages of simple process, convenient management, low equipment operation cost and secondary pollution, so the washing solution needs to be treated; The purification efficiency is low, so it should be combined with other technologies, and the treatment effect of mercaptan and fatty acid is poor

6. Liquid medicine absorption method uses the chemical reaction characteristics of some substances and liquid medicine in the odor to remove some odor components. It is suitable for dealing with odor with large volume and high and medium concentration. It can deal with some odor components pertinently. The process is mature, the purification efficiency is not high, the absorbent is consumed, and it is easy to form secondary pollution

7. The adsorption method uses the adsorption function of the adsorbent to transfer the odor substances from the gas phase to the solid phase. It is suitable for the treatment of odor gases with low concentration and high purification requirements. The purification efficiency is very high. It can treat multi-component odor gases. The adsorbent is expensive and difficult to regenerate. The odor gases to be treated are required to have low temperature and dust content

8. Biofilter deodorization process: after pretreatment processes such as dust removal, humidification or cooling, the odor gas passes through the filter bed composed of filter material from bottom to top from the bottom of the filter bed. The odor gas is transferred from the gas phase to the water microbial mixed phase and decomposed through microbial metabolism fixed on the filter material. At present, it is the most studied, the most mature process and the most commonly used biological deodorization method in practice. It can also be subdivided into soil deodorization method, compost deodorization method and peat deodorization method. The treatment cost is low, the floor area is large, the filler needs to be replaced regularly, the deodorization process is not easy to control, problems are easy to occur after running for a period of time, and it is still difficult to deal with hydrophobic and difficult biodegradable substances

9. The principle of biological trickling filter is similar to that of biological filter, but the filter materials used are inert materials that cannot provide nutrients, such as polypropylene pellets, ceramics, charcoal and plastics. Only microorganisms degraded for some malodorous substances are attached to the filler, instead of mixing microbiota in the biological filter and consuming organic matter of the filter material at the same time, the number of microorganisms in the tank is large and can bear a greater pollution load than that of biological filter, The inert filter material can not be replaced, resulting in small pressure loss, and the operating conditions are very easy to control. It needs to add nutrients continuously, and the operation is complex, which limits its application

10. The washing activated sludge deodorization method fully contacts the malodorous substances with the mixed liquid of slurry containing suspended solids to remove them from the odor in the absorber, and the washing liquid is sent to the reactor. The dissolved malodorous substances are degraded through the metabolic activities of suspended microorganisms. It has a large scope of application, and can deal with a large amount of odor. At the same time, the operating conditions are easy to control, the floor area is small, and the equipment cost is large, The operation is complex and nutrients need to be added

11. The aeration activated sludge deodorization method disperses the malodorous substances into the mixed liquid containing activated sludge in the form of aeration, and degrades the malodorous substances through suspended microorganisms. At present, Japan has been used for odor treatment in fecal treatment plants and sewage treatment plants. After domestication, the removal rate of malodorous components that do not exceed the limit load can reach more than 99.5%, which is limited by the intensity of aeration, The application of this method has some limitations

12. The reaction tower of three-phase multi-media catalytic oxidation process is filled with special solid composite filler, and multi-media catalyst is compounded inside the filler. When the odor gas passes through the packing layer under the action of the induced draft fan and fully contacts with the liquid-phase compound oxidant ejected in a divergent mist through the special nozzle on the surface of the solid-phase packing, and under the catalysis of the multi-media catalyst, the pollution factors in the odor gas are fully decomposed. It has a wide range of applications, especially suitable for the treatment of large volume, medium and high concentration waste gas. It has a good removal rate of hydrophobic pollutants, small land occupation and low investment, Low operation cost; Convenient management, ready to use; It is resistant to impact load and is not easy to be affected by the change of pollutant concentration and temperature. A certain amount of reagent needs to be consumed

13. In the process of dielectric barrier discharge of low-temperature plasma technology, particles rich in high chemical activity are generated in the plasma, such as electrons, ions, free radicals and excited molecules. The pollutants in the waste gas react with these active groups with high energy and finally convert into CO2, H2O and other substances, so as to achieve the purpose of purifying the waste gas. It has a wide application range and high purification efficiency. It is especially suitable for multi-component odor gases that are difficult to be treated by other methods, such as chemical, pharmaceutical and other industries, which have high electronic energy and can interact with almost all odor gas molecules; Low operation cost; The reaction is fast, the equipment starts and stops very quickly, and the operation and maintenance are easy when used. It can avoid secondary pollution, the process is mature, save energy consumption and low treatment cost

Tianming-1: how about the effect of photocatalysis? Guangdong seems to be doing a lot?

Blue sky: photolysis equipment depends on which industry it is used in. Photolysis equipment is mainly used in food production, automobile manufacturing, bicycles, motorcycles, household appliances, wires and cables, enamelled wires, motor insulation, electrical appliances, instruments, electronics, petrochemical industry, coating, chemical industry, medicine, iron printing, printing, textile, furniture, synthetic wood, leather, casting, shoemaking industry, chemical factory, pharmaceutical factory, alcohol factory, feed factory Fish meal plants, sewage treatment plants, waste treatment stations, waste power plants, food factories and other industries that produce waste odor gas.

Aimee: what industry is photocatalysis suitable for? What industries and conditions are not applicable? What is the scope of inapplicability?

Blue sky: photocatalysis is not applicable to the treatment of high concentration organic waste gas, and the concentration of waste gas generally does not exceed 1200mg / m3.

Tianming-1: with such a high concentration, it may not be possible to rely on only photolysis or plasma. Do you need a combined process?

Blue sky: Yes, now double 90 is required, that is, the collection rate ≥ 90 and the removal rate ≥ 90. It is certainly difficult to meet the requirements by a separate process. In the textile and leather industry, we usually adopt the combined process of low temperature + photolysis + water spray.

Young brother Yang: Excuse me, can you list which substances can be decomposed by photolysis or isothermal plasma?

Blue sky: low temperature plasma equipment is used in paint production, chemical fiber industry, metal coating, chemical coating, shoe and leather making, electroplating, plywood manufacturing, tire manufacturing, wastewater treatment plant and other industries. Harmful volatile organic compounds mainly include acetone, toluene, phenol, dimethylaniline, formaldehyde, ethyl acetate, ethanol, etc. Low temperature and photolysis are suitable for large air volume and low concentration organic waste gas.

Tianming-1: is water spray pretreatment or post-treatment?

Blue sky: it depends on the content of dust or other solid impurities in the air.

Tianming-1: would you like to ask the general manager below if 185nm ultraviolet light has no effect on titanium dioxide catalyst?

Blue sky: the smaller the wavelength, the higher the efficiency. 365 and 254 are used more than 185. Many substances degrade significantly at this wavelength.

Aimee: what is the efficiency of a low temperature treatment? What is the efficiency of a photolysis process? What is the treatment efficiency of low temperature + photolysis?

Blue sky: low temperature treatment efficiency is generally 60% - 85%. The key to treatment efficiency depends on the composition of waste gas.

Zhou Baochang | China Environmental Protection hydrosphere initiative:   are there any cases to share?

Blue sky: case: leather waste gas, textile waste gas, painting waste gas and feed waste gas. Detection: the purification rate reaches more than 90%. Generally, the process is to cover the pool and enter the photolysis equipment through the pipeline. Leather textile industry, the general small enterprises can not afford to burn.

Aimee: can you share cases of 500, 1000 concentrations or large air volume?

Blue sky: the biggest thing in Haining is to achieve 100000 air volume, concentration of more than 700 points and power consumption of 40 kW. The waste gas is pretreated first, filtered out impurities, then treated at low temperature, and then sprayed with water. The wastewater is then discharged to the sewage treatment facilities of the enterprise for treatment.

Tianming-1: what is the power consumption of photolysis?

Blue sky: Microwave photolysis saves electricity, and ordinary photolysis consumes a lot of electricity.

Guo AVA:   photolysis mainly depends on fans and pumps.

Shuangjian Xiake: the design of fan and pump has been determined. It mainly depends on the running time.

Guo AVA: plasma was first used in oil fume treatment. Is the principle the same now?

Blue sky: plasma breaks down the exhaust gas factor through high pressure, changes the molecular structure of exhaust gas, and oil fume is adsorbed.

Aimee: the low-temperature plasma shared by the previous company said that 1000 air volume consumes about 2-5kw. Why is the difference so big? Where is it?

Blue sky: plasma is high voltage, generally at 20000-30000 volts.

Tianming-1:   as far as I know, the UV lamp also consumes a lot of power, because there are a lot of lamps needed.

Guo AVA: one 60-90W.

Blue sky: 60-90 is small. Our early product is 150W. However, the failure rate of photolysis equipment with rectifier is relatively high. The product design is different, and the industrial requirements are related. I met a customer whose waste gas volume is about 30000. The power consumption of my equipment is 6 kW. Another environmental protection company said that it can be treated as long as 1 kW. In the   treatment time, we play an edge ball. For general plasma equipment, our design is that the waste gas stays in the equipment for 3-5 seconds. In order to facilitate installation, it is now made into modularization, with a length of about 10-12m. Adjust the size of the equipment according to the actual situation, and the residence time of photolysis equipment or microwave is also the same.

Enterprises looking for talents:

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