VOCs are the acronym for volatile organic compounds. Common sense VOC refers to volatile organic compounds; however, the definition of environmentally friendly refers to a class of lively volatile organic compounds, ie, those that produce the hazard. This article details the main technologies for six VOC treatment.
ã€Technical Encyclopedia】 VOCs treatment of exhaust gas treatment technology analysis
First, the VOC exhaust gas treatment technology - thermal destructive method Thermal destructive method refers to the direct and auxiliary combustion of organic gases, which is VOC, or use a suitable catalyst to speed up the chemical reaction of VOC, and ultimately to reduce the concentration of organic matter so that it no longer has the hazard A method of treatment.
Thermal destruction method for the treatment of organic waste gas concentration is relatively good, therefore, in the treatment of low concentrations of waste gas has been widely used. This method is mainly divided into two kinds, namely, direct flame combustion and catalytic combustion. Direct flame combustion of organic waste heat treatment efficiency is relatively high, under normal circumstances can reach 99%. The catalytic combustion refers to the role of the catalytic bed to speed up the chemical reaction rate of organic waste gas. This method is less time consuming than direct combustion and is the preferred technology for purifying organic waste gases with high concentrations and low flow rates.
Second, the VOC waste gas treatment technology - adsorption method Organic waste gas adsorption method is mainly applied to low concentration, high-throughput organic waste gas. At this stage, this method of organic waste gas treatment has been quite mature, energy consumption is relatively small, but the treatment efficiency is very high, and can thoroughly clean the harmful organic waste gas. Practice has proved that this approach is worth promoting application.
However, this method also has some defects. It requires a relatively large volume of equipment and a complicated process. If there is a large amount of impurities in the exhaust gas, it can easily lead to staff poisoning. Therefore, the key to using this method to treat the exhaust gas is the adsorbent. At present, the use of adsorption treatment of organic waste gas, the more use of activated carbon, mainly because of activated carbon pore structure is better, strong adsorption.
In addition, activated carbon will have better adsorption performance through iron oxide or ozone treatment, and the treatment of organic waste gas will be safer and more effective.
Third, the VOC waste gas treatment technology - biological treatment of biological law Purification voc exhaust gas is developed in recent years, air pollution control technology, which is less investment than the traditional process, low operating costs, simple operation, wide range of applications, is the most promising alternative combustion method And adsorption purification of the new technology. From the basic principles of treatment, the use of biological treatment of organic waste gas is the use of microbial physiological processes to the organic waste gas into harmful substances such as simple inorganic matter, such as CO2, H2O and other simple inorganic and so on. This is a harmless way to treat organic waste gas. Biological purification method is actually the use of microbial life activities will be harmful substances in the exhaust gas into simple inorganic substances (such as carbon dioxide and water) and cell material, the main process of biological washing, biological filtration and biological filtration.
Different components, concentrations and gas pollutants have their own effective biological purification system. The biological scrubber is suitable for treating the exhaust gas with small purifying volume, large concentration, easily dissolved and low biological metabolic rate, and the biological filtration bed can be used for the exhaust gas with large gas volume and low concentration, while for the high load and after the pollutants are degraded Acid biotrickling filter bed is better.
Biological treatment of organic waste gas is a new technology. Due to the complicated and complicated influencing factors of gas, liquid, solid mass transfer and biodegradation, the relevant theoretical researches and practical applications are still not extensive enough. Many The issue needs further exploration and research.
Under normal circumstances, a complete biological treatment of organic waste gas process consists of three basic steps: a) organic waste organic pollutants in contact with water first, quickly dissolved in water; b) dissolved in the liquid film of organic matter, liquid In the case of low concentration, it can be gradually diffused into the biofilm and absorbed by the microorganisms attached to the biofilm. C) The organic waste gas absorbed by the microorganisms will be degraded in its own physiological metabolism and finally transformed into Chemical substances that do not harm the environment.
Fourth, VOC exhaust gas treatment technology - pressure swing adsorption separation and purification technology Pressure swing adsorption separation and purification technology is the use of gas components can be adsorbed on the characteristics of solid materials, organic waste gas and separation purification device, the gas pressure will appear A certain change, through the pressure changes to deal with organic waste gas.
PSA technology is the main application of the physical method, through the physical method to achieve organic waste gas purification, the use of materials mainly zeolite. Zeolite zeolite, in the adsorption selectivity and adsorption capacity has some advantages. Under certain temperature and pressure, the zeolite can adsorb the organic components in the organic waste gas and then transport the remaining gas to the next step. After the organic waste gas is adsorbed, it is converted into a certain process to maintain and enhance the regenerant capacity of the adsorbent so that the adsorbent can be put into use again. Then, the process steps are repeated and the process is repeated until the organic waste gas is purified.
In recent years, the technology began to be used in industrial production, with good results for gas separation. The main advantages of the technology are: less energy consumption, lower cost, automatic operation of the process and the purity of the mixture after separation and purification, and small environmental pollution. The use of this technology has good effect on the recovery and treatment of gas with certain value, and has a bright future in market development, which will become the development direction of organic waste gas treatment technology in the future.
V. VOC exhaust gas treatment technology - oxidation method For toxic, harmful, and do not need to recover the VOC, thermal oxidation method is the most suitable treatment techniques and methods. The basic principle of oxidation: VOC and O2 oxidation reaction, the formation of CO2 and H2O.
From the chemical reaction equation, the oxidation reaction is similar to the chemical combustion process, but due to the relatively low VOC concentration, no visible flame is produced in the chemical reaction. Under normal circumstances, the oxidation method by two ways to ensure the smooth oxidation reaction: a) Heating. The organic waste gas containing VOC is brought to the reaction temperature; b) The catalyst is used. If the temperature is relatively low, the oxidation reaction can be carried out on the catalyst surface. Therefore, the oxidation of organic waste gas treatment is divided into the following two methods:
a) Catalytic oxidation. At this stage, there are two kinds of catalysts used for catalytic oxidation, that is, precious metal catalysts and non-precious metal catalysts. The noble metal catalysts mainly include Pt, Pd and the like, which are in the form of fine particles attached to a catalyst support which is usually a metal or ceramic honeycomb or a bulk filler; the non-noble metal catalyst is mainly composed of a transition element metal oxide such as MnO2 and After a certain proportion of binder mixture, and then made of the catalyst. In order to effectively prevent the catalyst from losing catalytic activity after poisoning, the catalyst poisoning substances, such as Pb, Zn and Hg, must be completely eliminated before the treatment. VOCs should not be treated by this catalytic oxidation process if the catalyst poisons in the organic exhaust gas are unable to clear the cover material;
b) thermal oxidation method. Thermal oxidation is currently divided into three types: thermal combustion, partition, regenerative. The main difference between the three methods is the way of heat recovery. All three methods can be combined with the catalytic method to reduce the reaction temperature of the chemical reaction.
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