超临界对冲旋流燃烧锅炉低氮改造

摘要

为了降低进入SCR(选择性催化还原)装置的NOx浓度,拟对某电厂600 MW超临界锅炉进行低氮燃烧器改造,在改造前对NOx排放浓度高的原因进行分析,同时提出3种备选改造方案并进行数值模拟研究,最后确定最优方案,即:保持原来燃烧器数量、位置不变,减小各次风的通流面积(风速不变),使主燃烧器区域过量空气系数为0.85,更换先进的低氮燃烧器,在原来的位于34.724 m标高位置的16只SOFA(分离燃尽风)风口中只保留两侧墙的6只,并在标高39.350 m处布置一层SOFA燃尽风(12个喷口).改造后进入SCR的NOx平均质量浓度约为400.7 mg/m3,与数值模拟计算结果误差为12.8％,说明数值模拟计算结果具有参考意义.%In order to reduce the NOx concentration entering the SCR (selective catalytic reduction),a 600 MW supercritical boiler was tentatively retrofitted to be a low nitrogen burner.Primarily,the factors causing high concentration NOx emission were investigated.Accordingly three kinds of retrofit schemes were made by a numerical simulation,and eventually,an optimized implementation scheme was selected.The detailed retrofit scheme is maintaining the original burner number and position,reducing the primary air flow area (constant wind speed) and obtaining the main burner region of excess air coefficient being 0.85.The replacement of advanced low NOx burners are recommended,and only 6 separation overfire air outlets (initial elevation 34.724 m) are left in the two sides of the wall,and a layer of separated overfire air (12 nozzle) is set at the elevation of 39.350 m.Over a period of operation after retrofitting,the average concentration of NOx entering SCR is about 400.7 mg/m3,which is about 12.8％ higher than the numerical simulation results indicating the appropriate significance of numerical simnlation.