Effect of biomass co‐firing position on combustion and NO X emission in a 300‐MWe coal‐fired tangential boiler

Co‐firing biomass in an existing coal combustion boiler is a promising way to mitigate carbon emission in the context of global carbon neutrality. This paper investigated the effect of biomass injection location on combustion and NO X formation characteristics in a 300‐MWe tangential boiler co‐firing with coal. Numerical models have been validated against experimental measurement for both pure coal firing and biomass/coal co‐firing cases. Compared to pure coal firing, co‐firing case with biomass injected into the highest layer can sustain a comparable temperature distribution profile along the furnace height, and generate a lower NO emission by around 20 ppm. By moving the biomass injection location downward, the temperature difference between co‐firing and pure coal firing cases becomes larger, and the final NO emission increases continually from 222 to 240 ppm. When biomass is injected through the lowest layer, N element in biomass volatile is oxidized to NO directly because of the abundant oxygen; thus, NO emission turns to be the highest among all co‐firing cases. Contrarily, when biomass is injected through the highest layer, the majority of N in biomass volatile is released as NH 3 , and it further acts as a reduction agent for NO, thus leading to the lowest NO emission.