低NO_x燃烧器改造后飞灰可燃物高原因分析及优化调整

大修期间,某电厂对2号锅炉进行低NOx燃烧系统改造,为了将锅炉调整到最佳的运行状态,进行了改造后的优化调整试验。试验结果表明,燃烧器改造后,320 MW负荷下,不同磨煤机组合运行方式下,NOx排放浓度降低至306～355 mg/m3,相比于改造前,降幅达58.7%,改造效果明显;但由于改造后火焰中心上移,煤粉颗粒在炉内的停留时间缩短,煤粉颗粒未完全燃烧即进入尾部烟气通道,导致飞灰可燃物含量较高,约10%;针对这一问题,进行了燃烧系统的优化调整,调整后飞灰可燃物含量降至4%左右。

Analysis of the Causes for a High Combustible Content of the Flying Ash After a Reconstruction of a Low NO_x Burner and Its Optimization Adjustment

During an overhaul period,a reconstruction of No.2 boiler in a power plant was performed to reduce NOx emissions of the combustion system.To adjust the boiler to its optimum operating condition,an optimization and adjustment test was performed after the reconstruction.The test results show that after the reconstruction of the burner,at a load below 320 MW and various mill combination modes,the NOx emissions concentration can be lowered to 306 mg/Nm3-355 mg/Nm3,falling down by 58.7% compared with that before the reconstruction and achieving a remarkable reconstruction effectiveness.However,due to a shifting-upward of the flame center after the reconstruction,the residence time of the pulverized coal particles in the furnace is shortened and the pulverized coal particles enter into the flue gas passage at the tail portion,which having not yet burned out,leading to a comparatively high combustible content of the flying ash,around 10%.In the light of this problem,an optimization adjustment was made of the combustion system.After the adjustment,the combustible content of the flying ash went down to about 4%.