某电厂1 000 MW锅炉在运行中，存在炉渣可燃物偏高、再热蒸汽温度偏低、燃烧稳定性差、炉膛四角一次风配风不均等问题。利用专业数值计算软件对该四角切圆燃烧锅炉改造前及改造后炉膛内燃烧工况进行数值模拟。计算结果表明：落入冷灰斗的煤粉量由改前的0.065 kg/m3减少为改造后的0.052 kg/m3，减少约20%，最下层二次风集中布置增强了对煤粉的托举能力。改造后在燃烧器截面方向，炉膛中心低温区减少，炉膛四周环形高温区增大，炉膛截面热负荷提高。沿炉膛高度方向，炉膛底部燃烧器区域截面平均温度提高约50~80 ℃，有利于煤粉气流的着火及燃烧；炉膛上部主燃区截面平均温度提高约20~30 ℃，有利于提高再热蒸汽温度。最下层燃烧器喷口四角煤粉碳转化率由改造前平均约为92.2%提高至改造后93.1%。提出了底部一、二次风喷口改造，下组燃烧器区域敷设卫燃带，在一次风管道加装可调缩孔等方案。改造完成后，该锅炉可在500 MW低负荷可不投油稳定燃烧，炉渣可燃物降低至2.5%~5.5%，再热蒸汽温度有一定提高，锅炉运行状态良好，锅炉效率提高0.3%。

A 1 000 MW boiler had some problems in actual operation,including high carbon content of furnace slag,low temperature of reheat steam,combustion instability and uneven primary air.Boiler furnace combustion conditions were numerically simulated by using professional numerical calculation software.The results showed that: the momentum of secondary air at the bottom increased,and pulverized coal into the dry bottom hopper dropped by 20%,from 0.065 kg/m3 to 0.052 kg/m3.After the modification,the lowtemperature zone in the center of the furnace decreased,the annular hightemperature zone around the furnace increased,and the thermal load of the furnace section increased.Along the furnace height direction,the burner area section average temperature increased about 50~80 ℃,which was conducive to the ignition and combustion of pulverized coal air flow.The main combustion zone section average temperature increased about 20~30 ℃,which was conducive to raise the temperature of reheat steam.The pulverized coal carbon conversion of the lowest primary air increased from an average of 92.2% to 93.1%.Some solutions were proposed,including transforming primary and secondary air nozzle at the bottom,adding refractory belt at the bottom of the burner area,equipping adjustable shrinkage cavity at the primary air pipe.By putting the transformation measures into practice,the boiler could combust stably at 500 MW,with carbon content of furnace slag reduced to 2.5%~5.5% and temperature of reheat steam increased.The operating parameters of the boiler were stable,and boiler efficiency was increased by 0.3 percent.

TK224.1