Research On The Operation Of Flue Gas Denitration System Of Selective Catalytic Reduction In A Coal-fired Power Plant

Nitrogen oxides (NOx) can lead to acid rain and induce photochemical smog. NOx is also one of the main substances which can cause greenhouse effect and photochemical reactions. Hence NOx are serious threats to the ecological environment and human health, and reducing NOX emissions is important for environment and health. Coal-fired power plant is the main source of NOx emission, the system of flue gas denitrification will become the essential equipment installed for coal-fired units to strictly control NOx emission, and consequently, it is important to conduct an extensive and detailed research on the system of flue gas denitrification.Based on the performance of the flue gas denitration system of selective catalytic reduction (SCR) of the660MW units in the Huaneng Jinggangshan coal-fired power plant, the difficulty of accurately reflecting the reliability status of the SCR system, emitting excessive NOx, the uneven distribution of NOx in the outlet of SCR, the large pressure drop of the SCR system were studied in this paper.Based on the study, conclusions were drawn as following:1. SCR system is one of the most effective methods to control NOx emission, the performance of SCR system installed in Huaneng Jinggangshan coal-fired power plant indicated that SCR can greatly reduce the emission of NOx, the nitrogen removal efficiency was detected up to65.8%, and the concentration of discharged NOx amounted132mg/Nm3.2. The performance of SCR indicated that concentration of the emitted NOx is too high to reach the air pollutant emission standards for coal-fired power plants (GB13223-2011), namely<100mg/m3. In order to improve the nitrogen removal efficiency and reduce the emitted NOx concentration, more ammonia should be added and another layer of catalyst should be installed.3. The uneven distribution of Nox in the outlet of SCR reactor will affect the nitrogen removal efficiency and the emitted rate of ammonia. To overcome these difficulties, the amount of added ammonia should be adjusted, soot blowing should be strengthened, and the flow pattern should be modified. 4. Pressure drop of the SCR system is greater than the guarantee value of device performance. However another layer of catalyst installed to improve the nitrogen removal efficiency will result in the higher pressure drop and more energy consumption. To address this problem, the flow pattern in the SCR reactor and flue should be modified, ash clogging of SCR system should be controlled, and the interval of each layer of catalyst should be optimized.