新型液排渣燃烧器内燃烧特性的数值模拟

NUMERICAL SIMULATION OF BURNING CHARACTERISTICS OF A NOVEL LIQUID SLAG-REMOVAL BURNER

通过数值模拟的方式,研究了新型液排渣燃烧器在不同过量空气系数下的速度、温度以及组分浓度的分布情况.结果表明,在较小的过量空气系数(α=0.7,0.8)时,煤的燃尽情况较差;α≥1.0时,煤粉燃烧更完全,但却不利于氮氧化物的控制.采用分级燃烧的方式,控制燃烧器内为欠氧燃烧(取α=0.9)以降低局部氧浓度,既能达到液态排渣要求,又可抑制NOx的生成,并在高温烟气进入炉膛降温之后再补充燃尽风,使得可燃成分在炉膛内再次燃烧,提高燃尽率.通过模拟与实验相结合的方式,对燃烧器进行三种不同负荷下的热态实验研究,该燃烧器负荷适应性好,模拟结果与实验结果相吻合.

Numerical simulation on a novel liquid slag-removal burner is performed to study the influence of excess air coefficient on velocity, temperature and component concentration distribution. Results show that small excess air coefficient （a= 0.7, 0.8） can result in low burnout rate of pulverized coal. When a is no lower than 1.0, pulverized coal can burn more completely, but NOx emission increases. In this paper, staged combustion is carried out in the burner with less oxygen （a=0.9） to reduce local oxygen concentration, which can not only realize liquid slag discharge, but also inhibit the generation of NOx. Over-fire air added into the furnace after high temperature flue gas gets cool makes the combustible components burn again, which improves the burn-out ratio. Thermal state experiment is conducted on the burner to investigate the influence of heat load by combining simulation with experiment, which shows the burner has good adaptability to variable heat load. The numerical simulation results tally with the experiment results.