Removal of pollutants mechanism
Plasma chemical reaction process, plasma transfer of chemical energy in the reaction process energy transfer is roughly as follows:
(1) electric field + electrons → high-energy electrons
(2) high-energy electrons + molecules (or atoms) → (excited atoms, excited groups, free groups) active groups
( 3) active group + molecule (atom) → product + heat
(4) active group + active group → product + heat
From the above process, it can be seen that the electrons first obtain energy from the electric field, and then transfer the energy to the molecules or atoms through excitation or ionization, and the molecules or atoms that obtain the energy are excited, and at the same time some of the molecules are ionized, which becomes the active group; afterwards these active groups and molecules or atoms, active groups and active groups collide with each other to generate stable products and heat. In addition, high-energy electrons can also be captured by substances with strong electron affinity, such as halogens and oxygen, to become negative ions. These negative ions are chemically active and play an important role in chemical reactions.
Principle of removing pollutants
Low-temperature plasma technology to deal with pollutants is based on the following principle: under the action of an applied electric field, a large number of energy-carrying electrons generated by dielectric discharge bombard the pollutant molecules to ionize, dissociate, and excite, and then a series of complex physical and chemical reactions are triggered, so that the complex large-molecule pollutants are transformed into simple and small-molecule safe substances, or toxic and harmful substances are transformed into nontoxic and harmless substances. Harmful substances into non-toxic, harmless or low-toxicity and low-harm substances, so that the pollutants can be degraded and removed. Because of its ionization of the average energy of the electrons generated in 10ev, appropriate control of the reaction conditions can be realized in general difficult to achieve or slow chemical reaction becomes very fast. As a high-tech in the field of environmental pollution treatment with strong potential advantages, plasma has received a high degree of attention from the relevant disciplines at home and abroad.
Application in environmental engineering
Low-temperature plasma technology in exhaust gas treatment with the development of industrial economy, oil, pharmaceutical, paint, printing and coatings and other industries produce volatile organic waste gas is also increasing day by day, these exhaust gases not only will stay in the atmosphere for a long time, but also will diffuse and drift to a farther distance, to the environment to bring serious pollution, these These exhaust gases, when inhaled into the human body, are directly harmful to human health; in addition, the uncontrolled emission of industrial flue gases is deteriorating the global atmospheric environment, and the danger of acid rain (mainly from industrial emissions of sulfur oxides and nitrogen oxides) has attracted the attention of various countries. The acidification of the atmosphere due to pollution has led to the destruction of the ecological environment and the frequent occurrence of major disasters, which has caused great losses to mankind. Therefore, it is imperative to choose an economical and feasible treatment method.
Degradation of volatile organic pollutants (VOCs) traditional treatment methods such as absorption, adsorption, condensation and combustion are difficult to achieve for low concentrations of VOCs, and photocatalytic degradation of VOCs has the problem that catalysts are easy to be deactivated, the use of low-temperature plasma treatment of VOCs can be free of the above conditions, and has a potential advantage. However, plasma is a cross-discipline including discharge physics, discharge chemistry, chemical reaction engineering and vacuum technology. Therefore, there are very few units that can master this technology. Most of the publicity using low-temperature plasma technology to deal with exhaust gas publicity is not the true meaning of low-temperature plasma exhaust gas treatment technology.
Simple judgment method
Now, the media publicize the low-temperature plasma exhaust gas purification products and technologies, but most of these products are in the speculation of low-temperature plasma concept. How to determine whether it is the real sense of low-temperature plasma technology? You can use the following two simple rules to judge, even if you do not understand the low-temperature plasma technology can also determine whether it is true or false.
(1) The channel in the exhaust gas purification must be filled with low temperature plasma. This rule is very simple to judge, as long as the eyes to observe the treatment channel is filled with purple-blue discharge can intuitively understand whether the low-temperature plasma (need to pay attention to is not a variety of colors of light as an electric plasma discharge). If the channel in the exhaust gas treatment only sporadic distribution of a number of discharge points or lines, the effect of the treatment is very limited, because most of the (VOCs) gas did not enter the low-temperature plasma treatment area.
(2) Low-temperature plasma treatment system must have a certain discharge processing power. Usually need to be in 2 ~ 5 watt-hours / m 3. That is, 1000 m 3 / hour of wind volume need to deal with the electrical power of 2KW ~ 5KW. If the claimed 1000 m 3 / hour of wind volume only need a few dozens or a few hundred watts of electrical power, then at most it is also electrostatic (dust removal) processing or localized processing only. It is impossible to break down VOCs without a certain amount of energy.
Purification method
Plasma exhaust purifier adopts a unique adsorption-decomposition-carbonization centrifugal pumping installation of the latest process technology design, the use of standard modular design and other advantages, is a dry treatment of organic waste gas purification equipment. It has changed the process technology of using activated carbon material, no need to regenerate the raw material for treatment, no need to be responsible for it, no secondary pollution, easy to replace and maintain.
Low-temperature plasma is the fourth state of matter following the solid, liquid, gas, when the applied voltage reaches the discharge voltage of the gas, the gas is broken down, resulting in a mixture including electrons, various ions, atoms and free radicals. Although the temperature of electrons is very high during the discharge process, the temperature of heavy particles is very low, and the whole system presents a low-temperature state, so it is called low-temperature plasma. Low-temperature plasma degradation of pollutants is the use of these high-energy electrons, free radicals and other active particles and pollutants in the exhaust gas, so that the pollutant molecules in a very short period of time to decompose, and a variety of subsequent reactions in order to achieve the purpose of pollutant degradation. General gas discharge, will produce plasma, and this discharge phenomenon is through some mechanism to make one or more electrons from the gas principle or molecules separated from the formation of gas medium, this medium is called ionized gas, if the external electric field produced by the ionized gas, the conduction current is formed, this phenomenon is known as gas discharge. And this technology of purification equipment, is the latest kind of industrial exhaust gas treatment principle.