Study On Optimization Of SCR Ammonia Injection Based On Ammonia Escape Concentration Field

Nitrogen oxide is one kind of important pollutant to endanger the environment. It will lead to acid rain and photochemical smog. Also, it will destroy the ozone sphere and do harm to human’s health. Coal-fired power plant is a significant source of atmospheric pollutants emission. Selective catalytic reduction (SCR) technology could reduce nitrogen oxide efficiently and it has occupied more than90percent of all application. Ammonia is often used to be reductant and it lead to the existence of unreacted ammonia at the exit of SCR equipment, which is called ammonia escape. Escaped ammonia will react with sulfur trioxide in rear smoke channel to form ammonium sulfate and ammonium bisulfate, which will cause the corrosion, deposition and jam. Nonuniformity of ammonia use ratio is a key factor to lead to the large ammonia escape. The nonuniformity is resulted from many factors such as nonuniformity of ammonia injection, nonuniformity of flow field and nonuniformity of catalytic effect.Adjustment of ammonia injection has been done in a600MW coal-fired power plant. Factors of concentration field, temperature field, velocity field and catalytic performance have been considered synthetically. This research aim to improve the homogeneity of ammonia escape concentration field and to reduce the value of ammonia escape.First, multicomponent convey model is applied to research the concentration distribution when ammonia flows in the channel of SCR equipment. The variation trend of ammonia concentration in SCR reactor has been researched when ammonia injection changes.This result could offer the theoretical basis for actual test and guide the adjustment to be proceeded more effective.Second, test and analyze the flue gas concentration field, velocity field, temperature field and ammonia concentration field at catalyst entrance and exit under different working conditions. Refer to the ammonia flowing speciality got from simulation result, and then confirm the adjustment strategy to optimize the distribution of ammonia injection. Homogeneity of ammonia escape has been improved evidently and value of ammonia escape has been reduced after adjustment. The result changes from46.80%to16.67%for side A and50.65%to16.29%for side B of homogeneity. For the value of ammonia escape, the result changes from3.64ppm to1.31ppm for side A and2.02ppm to1.63ppm for side B.Finally, the factors for ammonia concentration at catalyst exit and denitration efficiency have been analyzed according to the result of the test. This could help to realize the influence degree and influence trend for different influence factors. Also, it could offer guidance and basis for optimization and adjustment.