超临界对冲旋流燃烧锅炉低氮改造

Low NO_x improvement scheme of supercritical swirling combustion boiler

为了降低进入SCR(选择性催化还原)装置的NO_x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NO_x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NO_x平均质量浓度约为400.7 mg/m^3,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. Accord- ingly three kinds of retrofit schemes were made by a numerical simulation, and eventually, an optimized implementation scheme was select- ed. 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 NO~ burners are recom- mended, 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/m^3 ,which is about 12. 8% higher than the numerical simulation results indicating the appropriate signifi- cance of numerical simulation.