CFD Analysis of Coal and Biomass Co-Firing Characteristics in a Tangentially Fired Boiler

Biomass co-firing is an effective approach for improving the low-carbon and flexible operation of coal-fired boilers under deep peak-shaving conditions. In this study, a 3D CFD model was established for a subcritical four-corner tangentially fired boiler to investigate the effects of biomass blending percentage, injection position, and boiler load on combustion characteristics and NO formation. The results show that increasing the biomass blending percentage improves the uniformity of the flow and temperature fields, promotes more complete pulverized coal combustion, and enhances boiler combustion efficiency. Among the investigated load conditions, the 70% load shows a relatively more favorable combustion state in terms of flow field distribution, temperature level, and species distribution. Compared with B-layer primary air injection, BC-layer secondary air injection shows a stronger tendency to reduce NO formation under the simulated conditions. These results indicate that proper biomass blending and optimization of the injection position can effectively improve combustion uniformity and suppress NO formation.