VOCs waste gas treatment methods and advantages and disadvantages
What are the methods for VOCs governance? As we all know, the well-known VOCs treatment program is to preferentially select waste gas purification treatment methods with low cost, low energy consumption and no secondary pollution, and make full use of the waste heat of VOCs to realize the recycling of resources. Under normal circumstances, due to the special nature of its production activities, VOCs have high exhaust concentration, and use VOCs for condensation, absorption, and combustion. The various governance methods as well as the advantages and disadvantages are as follows:
1. Absorption method
In industrial production, the physical absorption method is often used for VOCs treatment, that is, the exhaust gas is introduced into the absorption liquid for absorption and purification, and the absorption liquid is saturated, and then heated, analyzed, condensed, etc., to recover waste heat. After recycling, the removal efficiency of VOCs can reach 50%-80%. The liquid absorbent is directly in contact with the exhaust gas. When the exhaust gas composition is complicated, it is difficult to select the absorbent, and industrial wastewater will be generated. In the case of low concentration, low temperature, and large air volume, the VOCs can be treated by treading absorption method, but a heating analysis and recovery device is required, and the investment amount is large. A method for absorbing paint mist by oil curtains and water curtains commonly used in paint painting enterprises, that is, a common organic waste gas absorption method.
2. Adsorption method
It belongs to the centralized treatment after recycling. It is often adsorbed by activated carbon. It needs to be replaced frequently, it is flammable, and it is necessary to pay for dangerous waste. Suitable for high air volume and low concentration. VOCs removal efficiency can reach 50%-90%.
3. Condensation recovery method
The condensation method is to directly introduce the industrially produced VOCs into the condenser, and through the action and reaction of adsorption, absorption, analysis and separation, recover valuable organic matter, recover the waste heat of the exhaust gas, purify the exhaust gas, and make the exhaust gas meet the discharge standard. After recycling, the removal efficiency of VOCs can reach 60%-90%. The exhaust gas needs to be cooled, so that the organic matter is condensed into droplets and separated from the exhaust gas. Applicable air volume is small, high concentration; high boiling point material recovery rate is high. Generally used in pharmaceutical and petrochemical enterprises. One or more other organic exhaust gas purification devices are usually installed behind the condensing recovery unit to achieve the target emission.
4. Decomposition method
The decomposition method includes a low temperature plasma method, a biological method, and a photolysis method.
(1.) Low temperature plasma method
It is a chemical reaction caused by high-energy electrons. It relies on the plasma to generate strong electric field energy for ionization and cracking in an instant, thereby destroying the molecular structure of the exhaust gas, and the processing range fluctuates greatly. VOCs removal efficiency can reach 50%-90%.
(2.) Biological law
It is the use of microorganisms on the reactor packing to decompose the exhaust gas in the metabolic process. It is rarely used in industrial waste gas, and is suitable for large air volume and low concentration. VOCs removal efficiency can reach 70%-90%.
(3.) Photolysis method
It is a photooxidant that oxidizes and decomposes exhaust gas, and is suitable for low-concentration exhaust gas, and is rarely used in industrial exhaust gas VOCs removal efficiency can reach 60%-90%.
5. Combustion method
It is a thermal destruction method, including direct combustion method and catalytic combustion method. The removal efficiency of VOCs can reach 90%-99.5%. The high-temperature oxidation decomposition of organic waste gas, the widely used and researched VOCs treatment method, is applicable to a wide range of exhaust gas volume and concentration.
(1.) Direct combustion method
The direct combustion method is to use an auxiliary material such as gas to ignite the exhaust gas, and to promote the harmful substances in the high-temperature combustion to be converted into harmless substances. The VOCs treatment method is easy to understand and learn, and has low investment, and is suitable for high concentration. Exhaust gas with small air volume, but its safety technology requirements are high.
(2.) Catalytic combustion method
The catalytic combustion method converts the exhaust gas into catalytically combusted gas and converts it into harmless carbon dioxide and water. The VOCs treatment method is suitable for the purification of organic waste gas with high temperature and high concentration. The method for treating VOCs has the advantages of low combustion temperature, high energy saving, high purification rate and small floor space, but the investment is large.
In the process of VOCs management, it is necessary to select the first VOCs treatment methods in different industries according to different organic waste gas components and different concentrations, and consider the maturity, economic practicability and equipment maintenance of China's VOCs treatment technology. The more widely used is the catalytic combustion method. Of course, China is also actively introducing new and more environmentally-friendly VOCs governance methods, which are expected to be widely used in technological transformation or new construction projects in the future.
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