In order to investigate the effects of re-burning nozzles of biomass gas at different heights on the combustion process of boiler

numerical simulation was carried out for re-burning process of a 660 MW coal-fired coupled biomass gas boiler

on the basis of establishing a model for the boiler using Fluent software. The effects of nozzle location of biomass gas on boiler temperature field

NO_x emissions and flue gas components were studied. The results show that

the biomass gas re-burning in coal-fired boiler will result in higher temperature at the furnace outlet

and the outlet temperature increases with the biomass gas nozzle height. The biomass gas re-burning can reduce the NO_x emissions

when the biomass gas nozzle is located in the upper

middle and lower parts of the reburning zone

the average mass concentration of NO_x emission is 228.32

210.19 mg/m3

239.58 mg/m3

respectively. When the biomass gas nozzle locates in the middle of the re-burning zone

it has the best NO_x reduction effect

which is 28.01% lower than the average mass concentration of NO_x emission(291.96 mg/m~3) under the original working condition. However

the biomass gas re-reburning increases the CO volume fraction

and the CO volume fraction increases with the biomass gas nozzle location height.