Research & Analysis
Gong Jian, Ma Dafu, Guan Yubao, Wang Mingyang, Ge Chengyong, Guo Kaiming, Yang Kun
In order to predict the influence of mixed biomass (after low temperature pyrolysis treatment) on the actual operation of coal-fired boiler, the combustion characteristics, flue gas composition, and heat flux distribution of a 350 MW corner tangentially fired boiler were simulated and analyzed through using FLUENT software. Following three working conditions were considered, such as pure coal combustion, biomass blending with a calorific value ratio of 20% and 40%. The simulation results show that, biomass blending with a calorific value ratio of 20% leads to an average temperature increase of 22 K in the furnace, 20 K in the primary combustion zone, and 37 K in the zone from the over-fire air to the furnace arch, as compared to the working condition of pure coal. When the calorific value ratio of blended biomass is increased from 20% to 40%, the temperature is almost unchanged. After blending biomass, there is an observed increase in the volume fraction of carbon monoxide (CO) within the primary combustion zone, ranging from 2.103×10-6 to 2.962×10-6. However, the volume fraction of CO within the over-fire air zone consistently remained in close proximity to zero. The volume fraction of oxygen (O2) in the primary combustion zone is decreased by 0.5% to 1.0%. At the elevation of 45 m, the volume fraction of O2 in three working conditions is measured to be 2.9%, 3.2%, and 3.6%, respectively. The mass concentration of nitrogen oxides (NOx) experiences a reduction ranging from 140 mg/m3 to 182 mg/m3. The heat flux does not change much and does not significantly affect the heat absorption of the water wall.
