Desulphurization and denitrification equipment for FRP The basic principle of SCR method The selective catalytic reduction (SelectiveCatalyticReduction, SCR) means that under the action of the catalyst, the reduction agent (such as NH3) is used "selectively" to react with the NOx in the flue gas and produce non-toxic and pollution-free N2 and H2O. The principle was first discovered by Engelhard company and applied for a patent in 1957. Then, driven by the country's environmental policy, Japan successfully developed the widely used V2O5/TiO2 catalyst, and successfully put into commercial use in the fuel and coal-fired boilers in 1977 and 1979 respectively. SCR technology has a very significant effect on the NOx control of boiler flue gas and is more mature in technology. It has become one of the most effective and most effective flue gas denitrification technology in the world. In the process of SCR denitration, ammonia can be converted into natural nitrogen (N2) and water (H2O) contained in air by adding ammonia. The main chemical reactions are as follows: NOx: 4NO 4NH3 O2 to 4N2 6H2O (5-1) 6NO 4NH3 - 5N2 6H2O (5-2) 6NO2 8NH3 - 7N2 12H2O (5-3) 2NO2 4NH3 O2 to 3N2 6H2O (5-4) In the absence of catalyst, the chemical reaction is carried out only in a very narrow temperature range (850~1100 degrees C), and the activation energy of the reaction can be reduced after the use of the catalyst, which can be carried out at a lower temperature (300~400 degrees C). Selectivity refers to the preferential reaction of NH3 with NOx under the action of catalyst and oxygen, rather than the oxidation of oxygen in flue gas. In the selective catalytic reduction system, it is usually composed of ammonia storage system, ammonia and air mixing system, ammonia injection system, reactor system and monitoring control system. For thermal power plants, the SCR reactor is usually installed between the boiler economizer and the air preheater, because the smoke temperature in this interval is suitable for the reduction of SCR denitrification. In response, ammonia is injected in the flue between the economizer and the SCR reactor, and it is mixed with the flue gas to react with NOx in the reactor. The catalyst is placed in a box like a solid reactor. The catalyst unit is usually arranged vertically, and the flue gas flows upwards and downwards. Typical process layout and reaction. The principle of SCR flue gas denitrification SCR is currently the most widely applied, the most mature and the most effective flue gas denitration technology in the world. SCR technology has the following characteristics. (1) high efficiency of NOx removal According to the relevant documents and the monitoring data of engineering examples, the general NOx removal efficiency of SCR method can be maintained at 70%-90%, and the general NOx outlet concentration can be reduced to about 100mg/m3. It is a kind of efficient flue gas denitrification technology. Second, the two pollution is small The basic principle of the SCR method is to restore NOx to non-toxic and non polluting N2 and H2O by reducing agent. The two pollutants produced by the whole process are very few. Technology is more mature and widely used SCR flue gas denitrification technology has been widely applied in developed countries. For example, in Germany, the SCR method of flue gas denitration in thermal power plants accounts for about 95%. Most of the flue gas denitrification works that have been built or proposed in China are SCR. High cost of investment and high operating cost
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