600 MW超临界对冲燃烧锅炉CO和NO_x排放特性的研究

Emission Characteristics of CO and NO_x from Opposed Firing Boiler in a 600 MW Supercritical Unit

采用现场试验研究和数值模拟的方法对布置前后墙对冲燃烧器的某600MW超临界锅炉CO和NOx的排放特性进行了研究.结果表明:锅炉尾部烟气中CO质量浓度为500～2 500mg/m3,当主燃烧区过量空气系数α1为0.86～0.90时,高于该锅炉低NOx排放的设计过量空气系数(0.80),对应的燃尽风占二次风的比例约为27%～32%,NOx排放质量浓度出现拐点;锅炉的NOx排放特性与HT-NR3燃烧器的低NOx设计有关,并与该锅炉的CO排放特性呈负相关关系;在负荷为600MW和总风量一定的工况下,当燃尽风比例从32%提高至49%时,CO排放质量浓度显著下降,飞灰可燃物浓度降低,氧气量对CO和NOx排放的影响明显减弱,但NOx排放质量浓度升高,主燃烧区侧墙高温腐蚀的风险增大.

Emission characteristics of CO and NOx from a 600 MW supercritical boiler with burners ar- ranged in front and back walls were studied by both field experiment and numerical simulation. Results show that the CO concentration in the flue gas is within 500-2 500 mg/m3. The turning point of NO, emis- sion appears when the excess air coefficient al is within 0.86-0.90 in main burning area, higher than the designed al （0.80） for tow NOx emission, in which case the corresponding ratio of overfire air to secondary air is about 27% -32%. NO, emission characteristics of the boiler are influenced by the design of its HT- NR3 burner for low NOx emission, indicating a negative correlation to CO emission. At the load of 600 MW and a constant total air volume, the rise of overfire air ratio from 32% to 49% would result in a sig- nificant reduction of CO concentration and combustible contents in fly ash, but an increase of NOx emis- sion, when the influence of oxygen content on CO and NOx emission weakens obviously, which may raise the possibility of high-temperature corrosion on side walls in the main burning area.