煤改低浓度煤层气锅炉的燃烧及NOx排放特性

Characteristics of combustion and NOx emission in low concentration coal bed methane boiler retrofitted from coal-fired boiler

将燃煤链条炉改烧低浓度煤层气,运用数值模拟方法并结合实验对改造后的低浓度煤层气锅炉炉膛内的流动、燃烧及NOx排放特性进行了研究。结果表明,速度约在炉膛轴向距喷口0.5m处达到最大值,在炉膛宽度方向-0.4m<l<0.4m范围内剧烈衰减。随热负荷增加,炉膛轴线上最高温度后移,模拟与试验结果吻合较好。炉膛前部截面处沿炉膛宽度方向,低负荷下温度呈明显的双峰分布,100%负荷下呈单峰分布;但炉膛中后部温度均呈现双峰分布。炉膛出口烟温随热负荷的增加近似成线性增加,实验测量烟温略低于模拟值。NOx的生成主要集中在炉膛中后部的高温区,且NOx峰值位置远滞后于温度峰值。随过量空气系数的增大,炉内最高温度与NOx生成量均先增大后减小。

Coal-fired chain grate boiler is retrofitted to coal bed methane boiler.The flow,combustion and NOx emission characteristics of low concentrations methane in the boiler furnace are studied by the numerical simulation and experiments.The results show that the axial velocity reaches the maximum at 0.5 m from the nozzle and declines sharply in the range of-0.4~0.4 m on the width direction.With the heat load increases,the position of highest temperature moves to the rear of furnace and the simulation and experimental results agree well.At the front of the furnace,the obvious bimodal distribution of temperature at low heat load along the width direction is found,but it is a single peak distribution at 100% heat load.At the rear of the furnace,the temperature shows bimodal distribution at all kinds of heat loads.Gas temperature at boiler furnace outlet increases linearly with the increasing of heat load but the experimental results are slightly lower than the simulated results.The NOx is mainly produced in the middle and rear of furnace with high temperature,and the position of NOx peak lags far behind that of temperature peak.With the excess air coefficient increases,the highest furnace temperature and NOx generation increases and then decreases.