对29 MW燃煤链条炉排锅炉增加烟气循环系统，让烟气在风室中与新风混合，从而降低风室中氧浓度（体积分数），创造炉内低氮燃烧的氛围，促进NOx减排。通过试验与系统流程计算的两种方法，对比了改造前后链条炉锅炉出口的NOx和氧气浓度，从而得出了烟气循环的最佳循环量。研究表明:改造后，随着烟气循环比例增加，烟气中氧气浓度降低，伴随NOx排放浓度降低，在研究条件下，由实验得出最佳的烟气循环率约为12%；系统流程计算是基于系统质量守恒，将烟气循环、布袋除尘器内漏风等因素加以考虑，程序可预报烟气氧浓度变化的规律，证明与实测一致；烟气循环比率存在最大值，超过后会严重影响炉内火焰稳定性；该锅炉在12%烟气循环比率条件下，NOx排放浓度降低22%，是低氮燃烧获得较好效果的烟气循环工况。

A 29 MW chain grate furnace was retrofitted through adding a recycled flue-gas system,which contributed to the NOx emission reduction resulting from the reduced oxygen level (volume fraction)in flue gas inside the air box under chain grate.The experiments have been conducted to clarify the influence of retrofitted facility and determine the optimum condition of flue-gas recirculation.The main conclusions are drawn as follows: 1) After the retrofit,the oxygen in flue gas was decreased with the flue-gas flux increase.Under the conditions of this study,the optimum flue gas circulation rate is about 12%.2) Based on the mass conservation,a code was written to predict the relation of oxygen level and recycled-flue gas rate,which considered the gas circulation system and leakage problem in the filter bag.And the prediction has been verified well through the comparison between the calculated results and experimental data.3) There is a maximum ratio of gas recirculation,beyond which the combustion pattern would be worse.It was observed that the high reduction efficiency of NOx emission is decreased by 22% at the same time,the number of flue-gas circulation ratio is about 12%.

TK224

上海浦江人才计划（16PJ1407800）