Numerical Research of Ammonia-Coal Mixing Combustion in a 650MW Coal-Fired Boiler Under Low Load: Influence of Ammonia-Mixing Ratio and Ammonia Injection Methods

Ammonia is a typical zero-carbon fuel, co-combustion of ammonia and coal in boilers can effectively reduce carbon emission, a three-dimensional numerical simulation of a 650 MW coal-fired boiler was studied to analyze the effects of different NH3 mixing ratios and different injection methods on temperature, component concentration, and emission of furnace exit. The results showed that the peak temperature of the main combustion zone decreased from 1741.3K to 1473.1K when the NH3 mixing ratio increased to 70%, and the O2 concentration decreased to form a better reduction atmosphere. Due to the reduction of coal consumption, the concentration of CO and CO2 is reduced, and the concentration of CO2 is reduced by 70% compared with the same load of coal combustion. However, with the increase of the NH3 mixing ratio, the concentration of H2O in the furnace increases, reducing the combustion temperature, which is unfavorable to stable combustion and may cause low-temperature corrosion. The H2O concentration in the furnace is higher when NH3 enters through the nozzle of the oil gun than when NH3 enters through the mixed with primary air, and the H2O concentration in the furnace is greatly reduced when the NH3 enters through the secondary air nozzle. When the mixing ratio increases (0% to 70%), the outlet NOx of the furnace decreases. When the mixing ratio is 30%, the NH3 enters the mixing NOx by the secondary air nozzle is lower.