Population, resources and environment constitute the basic elements of the human ecosystem. Over the past century, the rapid development of the global economy and the dramatic increase in population have brought increasing pressure on the environment. Various pollution problems are emerging in an endless stream. Since pollutants can stay in the biosphere for a long time and proliferate and drift, Therefore, to take effective measures to solve environmental problems is imminent. In recent years, there have been many high and new technologies emerging in the world, such as ultrasound, photocatalytic oxidation, plasma, microwave, etc., which are environmentally friendly. Plasma, as an efficient, low-energy and simple environmental protection technology, Difficult to degrade material, is the hot spot of recent research. Low-temperature plasma has been used for ultra-fine particle production, exhaust gas treatment, metallurgical refining, etching and material surface treatment, many of which have been industrialized. However, the use of low-temperature plasma to treat VOCs and industrialize them is extremely rare. This paper comprehensively discusses the technology of low temperature plasma treatment of VOCs, the status quo of the commercialization of the technology at home and abroad, analyzes the existing problems and points out the research direction of the technology in the future, with a view to arousing the resonance of domestic counterparts. 1 Volatile Organic Compounds (VOCs) treatment technology status quo 1VOCs definition and source Volatile Organic Compounds (VOCs), generally refers to the standard state, the vapor pressure greater than 13.33Pa above organic compounds. VOCs mainly come from petrochemical (including plastics, rubber, film), printing, bonding, coating and other processes, paint, printing, molding of rubber and plastic products, photographic film and kinescope coating production process Use a large number of organic solvents, these organic solvents are mainly hydrocarbons, aromatic hydrocarbons, alcohols, ketones and other organic pollutants. 1.2VOCs treatment status The traditional methods of VOCs treatment are: absorption method, direct combustion method, catalytic combustion method, biological method, pollutant recovery method and photocatalytic method, their characteristics are as follows: (1) Adsorption removal efficiency, thorough purification, low energy consumption , Mature technology, easy to promote, but if the regenerated liquid can not be reused, these liquids must be processed, not only may cause secondary pollution, but also increase the cost of many processing, the other when the exhaust gas with aerosols or other impurities, the adsorbent easy Failure. (2) The direct combustion process is mature, and the treatment rate can reach 99% under suitable temperature and retention time. However, the energy consumption is high, investment is large, and it is easy to oxidize N2 in the air. (3) The catalytic combustion method treats 90% -95% of the reaction rate, only for the reaction of certain types of compounds, high energy consumption and large investment (precious metal catalyst needed). The catalyst is poisoned and dioxin may be produced. (4) The biological method is mainly wetland filtration, biological filtration and so on. The method has low energy consumption, but the equipment occupies a large area and the system has little flexibility. After treatment, the contaminated biological group needs to be reprocessed. If the continuous intake occurs and the pollutants in the exhaust gas The concentration and composition are stable and the cost of treatment with this method is very low, but the concentration and composition of pollutants in a typical industrial exhaust gas often fluctuate. (5) Recovery of pollutants This method is conducive to ecological recycling, but the high investment costs and high operating costs, the recovery of raw materials usually require further safe disposal. (6) Photocatalytic reaction process fast, high efficiency, and no secondary pollution problems, has a very large potential value. However, in the photocatalytic process, the higher the requirements of the catalyst, the catalyst activity is easy to reduce, how to solve the problem of catalyst deactivation has become the key technology. In recent years, the development of low temperature plasma treatment of VOCs, has its unique advantages: can be operated at room temperature and pressure; the final product of organic compounds CO2, CO and H2O, if the organic matter is chlorinated, the product should be added Chlorides, without intermediate by-products, reducing the toxicity of organic matter, while avoiding the other methods of post-processing problems; without having to consider the catalyst deactivation problems; process is simple, low operating costs, is the direct combustion of half; VOCs removal rate is high, VOCs adaptability. Domestic low-temperature plasma treatment VOCs commercial products blank because: (1) technology is not mature, the traditional treatment of VOCs is the use of adsorption, condensation, catalytic combustion, direct ionization and other technologies (these technologies have their own shortcomings) (2) Insufficient funds investment As a new technology, its technical achievements have not been recognized by the society, and enterprises are not willing to invest in R & D for this purpose. On the other hand, The invention of a new technology needs to be tested several times before it can be realized. Therefore, lack of funds is often the focus of research and development contradictions. (3) Insufficient cooperation in the fields of plasma technology involves electronic equipment, plasma chemistry, and high pressure resistant materials (4) high cost The current general industrial gas flow, air flow instability characteristics, which requires large-scale processing equipment, so the cost of equipment into the response also increased. In short, low temperature plasma treatment of VOCs due to its development is difficult, limited funding, involving a wide range, making the technology is difficult to mature and commercial application. Low-temperature plasma treatment of VOCs has drawn much attention due to its unique advantages. At present, the large-scale emission of industrial VOCs has an increasing demand for the commercialization of this technology. 2 low temperature plasma technology and its application 2.1 Definition and its characteristics Plasma refers to the ionization is greater than 0.1%, and its positive and negative charge equal ionized gas. It consists of a large number of electrons, ions, neutral atoms, excited atoms, photons and free radicals and other components, the charge of electrons and positive ions equal to the overall show neutral, it is different and substance 3 states (solid, liquid And gas), is the fourth form of material existence. Its main features are: (1) there is no net Coulomb force between the charged particles; (2) it is an excellent conducting fluid, and magnetic fluid power generation has been achieved using this feature; (3) there is no net magnetic force between the charged particles; ( 4) ionized gas has a certain thermal effect. According to the system energy state, temperature and ion density, the plasma can be divided into high-temperature plasma and low-temperature plasma. The former's ionization degree is close to 1, and the temperature of each kind of particle is almost the same. The system is in a macroscopically thermodynamic equilibrium state. Reached tens of thousands of degrees, mainly used in the controlled thermonuclear reaction research; and the latter is not the same temperature of various particles, the electron temperature is much larger than the ion temperature, the system in a macro thermodynamic imbalance, the apparent temperature of the system is still very Low, it is more closely related to the production of modern industry. 2.2 degradation mechanism Low-temperature plasma degradation of VOCs consists of two parts: (1) the recombination process of gas ions; (2) the reaction with gas molecules. General gas discharge plasma can be divided into glow discharge, corona discharge, radio frequency discharge and microwave discharge, and for the treatment of volatile organic compounds is mainly corona discharge, the degradation of the main mechanism is as follows: Under the action of an applied electric field, Electrons in the electrode space gain energy to start accelerating. The electrons collide with the gas molecules during the movement. As a result, the gas molecules ionize and excite or adsorb the electrons into negative ions. During the collision, the electrons may appear three kinds of situations. One is ionized neutral gas molecules to generate ions and derivative electrons, Derivative electrons are added to the ranks of ionized electrons to maintain the continuation of the discharge. The second one is collided with molecules with high electron affinity (such as O2, H2O, etc.) and absorbed by these molecules to form negative ions. The third one is collided with some gas molecules The excitated and excited molecules are extremely unstable, and quickly return to the ground state and radiate photons. Photons with sufficient energy irradiating onto the corona electrode may cause photoionization to generate photoelectrons, which are in favor of maintaining the discharge. After the electron collision of the gas molecules, the formation of highly active particles, these active particles on the VOCs molecules oxidation, degradation reaction, and ultimately the toxic and harmful pollutants into CO2, H2O and other non-toxic and harmless substances. Injection Moulding Machine Special For Garbage Can - Imported advanced computer systems, Chinese / English interface. Moulding Machine For Garbage Can, Trash Basket Mold Machine, Plastic Moulding Machine Garbage Can BOLE INTELLIGENT MACHINERY CO., LTD , https://www.bolemachinery.com
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