By the end of 2021

over 95% of coal-fired thermal power units in China have achieved ultra-low emission of nitrogen oxides

with the remaining being W-flame boilers that burn anthracite. Due to the high mass concentration of nitrogen oxides generated

which often reaches 750～1 200 mg/m~3

achieving ultra-low emissions is difficult

making it the “last mile” for China to achieve ultra-low emission policies. At present

selective catalyst reduction(SCR) denitration flow field technology mainly includes “SCR partition hybrid dynamic leveling technology”

“full flue section mixing flow field technology”

and “conventional accurate ammonia injection technology”

etc. Taking a W-flame boiler of which the design denitration efficiency needs to be up to 95% as an example

this paper compares the performance indicators of various technologies through CFD simulation

and the indicators of the “SCR partition hybrid dynamic leveling technology” are significantly superior to other technologies. After the project transformation

when the mass concentration of nitrogen oxides at the denitration system inlet is 1 000 mg/m~3 and that at the system outlet is lower than 50 mg/m~3

the ammonia escape can be kept less than 3 μL/L

far exceeding the maximum design efficiency of the conventional SCR denitration system. The research provides a new technical route for ultra-low NOx emission of W-flame boilers.