秸秆直燃锅炉燃烧数值模拟

NUMERICAL SIMULATION OF COMBUSTION IN A STRAW-FIRED GRATE BOILER

对某75 t/h秸秆层燃锅炉进行数值模拟并用现场实测数据加以验证。计算结果与实测结果基本吻合,较好地反映出实际炉排炉稻杆层燃特性。通过对炉排炉一次风各风室比例的调整计算表明,一次风风量比例对床层稻杆的燃烧具有重要影响。针对该模型和设计燃料,当一次风4个风室风量比例为0.22∶0.32∶0.34∶0.12时运行综合效果最佳。在保证燃料水分析出段和挥发分析出燃烧段所需风量时,适当增加焦炭燃烧段的供风量有利于缩短燃烧时间,降低底灰含碳量。

The paper presents a computational fluid dynamics （CFD） analysis of a 75 t/h straw-fired boiler. Model predictions were compared with available gas temperature measurements showing grate good agreement. The variation in the ratio of primary air flow rate of different air chambers was studied and the operation conditions were further optimized. The calculated results show that the variation in the ratio of primary air flow rate of different chambers greatly affects straw combustion and furnace temperature. Based on the CFD analysis, it is suggested that the comprehensive performance of the grate-firing boiler is relatively good when the flow rate ratio is 0. 22：0. 32：0. 34：0. 12. When it is ensured that the air flow rate for straw drying and devolatilization stage is enough high, appropriate increase in the air flow rate for char oxidation stage can reduce the burning time of residual char and decrease the carbon content of the bottom ash.