Abstract: Constrained by the boiler layout, the compact installation of the denitrification system causes the flue gas concentration field unevenly distributed. As a result, some problems such as incomplete catalytic reduction reaction and unrepresentative sampling of outlet flue gas have commonly existed. In this paper, through the analysis on the measurement of SCR outlet NO_x distribution, the ammonia concentration in the SCR reaction area is improved by using the ammonia injection valve to adjust the ammonia injection volume. In this way, the unevenness degree of NO_x density concentration at the Outlets A and B is decreased to 20% and the utilization ratio of the catalyst is enhanced. By taking advantage of gaseous pollutants sampling method and uniform ventilation design method, the SCR outlet gas sampling method is improved and the uniform NO_x sampling is achieved, which effectively lowers the measurement deviation between the outlets of SCR and flue gas discharge systems. The ratio of NO_x concentration at the two outlets is reduced from 1.42 to 0.98. The study results can ensure stable ammonia injection volume control.

Key words: thermal power plant, SCR denitration, ammonia injection optimization, uniform sampling device, ammonia escape