Study On Energy Saving Optimization Of SCR Denitrification System Under Various Operating Conditions

Since the SCR denitrification system is gradually used in the national coal-fired power plant,problems in operation of denitration system have also exposed,which has a serious influence on the denitration efficiency of flue gas.Therefore,it is necessary to ensure the efficient,reliable and economical operation of SCR denitration system.This study mainly researches the optimization and verifies the applicability which aims at the problem of high ammonia escape rate and high energy consumption of dilution heating after the SCR denitration system is put into the operation in a 600MW coal-fired unit.Firstly,the SCR denitrification system is simulated and designed by using computational fluid dynamics software(CFD).According to the different numerical offset distance of the deflector,the uniformity of the flue gas velocity at the entrance of the SCR denitration catalyst was optimized.Compared with various schemes,the optimal flow rate of flue gas at the inlet of the reactor was selected when the deflector was offset at 0.5m.Under the conditions of 300MW,450MW and 600MW,the flow rates were 8.11m/s,8.65m/s and 9.99m/s,respectively.The experimental results are in accordance with the simulation,and basically meet the requirements of the best velocity(5-8m/s).The optimal adjustment of ammonia injection was carried out under the optimized guide plate scheme.The uniform ammonia injection scheme and uneven ammonia injection scheme were studied by simulation analysis.According to the simulation results,the iterative calculation is used to guide the regulation of ammonia injection rate of each ammonia injection valve in the operation unit.The relative standard deviation of 75.55%and 49.93%on both sides of A and B at 550MW were ameliorated to 27.22%and 27.10%respectively.And the relative standard deviation of 22.69%and 101.89%on both sides of A and B at 420MW were ameliorated to 52.64%and 23.42%respectively.The uniformity of NOx distribution at the outlet of the denitration reactor was effectively improved.Thus,the escape of ammonia in operation is reduced,and the efficiency of denitration is improved.Secondly,the heater technology of existing dilution wind in a factory was analyzed.The heating methods of diluted air were studied in domestic,followed by steam heating,flue gas heating and fuel heating.Through the economic research of each heating mode,the best way of saving energy is to take the heat exchange mode of flue gas.Compared with a plant reform,it is proved that the heat exchange mode of flue gas is the best way to save energy.