骨料烘干煤粉燃烧器火焰的影响规律

Influence law of aggregate pulverized coal burner flame

受设备条件、燃料性质及工况参数的限制,骨料烘干煤粉燃烧器的火焰长度存在合理的变化范围,火焰长度不仅影响骨料烘干效果,并且影响煤粉燃烧效率和污染物排放特性。深入分析骨料烘干工艺及热力学需求,将理论分析与数值模拟计算相结合,通过研究煤粉燃烧机理及污染物生成机理,运用燃烧学、流体力学中反应、着火、燃烧、湍流流动、传质传热等相关理论,准确构建煤粉射流湍流流动、燃烧、辐射以及污染物生成等行为的控制模型,数值模拟煤粉燃烧行为。此外,火焰长度受燃烧器内部流场湍流扩散和混合作用的影响,明确火焰长度的影响因素,探究火焰长度的控制规律,且深入分析不同火焰长度下煤粉燃烧效率及污染物排放特性,在提升煤粉燃烧效率和降低污染物排放的目标下,结合骨料烘干工艺需求,探索煤粉燃烧过程中火焰长度的控制规律。研究结果表明:一次风预热温度、一次风煤粉浓度、一次风风速、二次风旋流强度均对骨料烘干煤粉燃烧器的火焰长度造成影响;影响火焰长度最显著的因素是一次风煤粉浓度,一次风煤粉浓度越高,火焰越长,火焰长度的变化在4.1~5.0 m,长度可提高22%,而火焰直径的变化在0.7~1.1 m;合理调节各物理因素,可扩大火焰径长比调节范围、达到1∶5~1∶9(通常为1∶4~1∶7);燃烧室内部温度、组分浓度以及内部流场状态影响骨料烘干煤粉燃烧器的燃烧效率和排放特性,并且在不同结构参数和控制参数下,随火焰长度的变化,燃烧效率以及污染物排放量的变化规律不同;在满足骨料烘干火焰长度需求的前提下,可通过减小一次风预热温度、减小煤粉浓度、增大旋流强度和各次风风速来提高燃烧效率的同时降低污染物的排放。

The flame length of aggregate drying pulverized coal burner has a reasonable range of variation due to equipment conditions,fuel properties and working condition parameters,which affects the aggregate drying effect as well as pulverized coal combustion efficiency and pollutant emission characteristics.In this study,the aggregate drying process and thermodynamic requirements were thoroughly analyzed,theoretical analysis and simulation calculations were combined.By studying the mechanism of pulverized coal combustion and the mechanism of pollutant formation,the control model of pulverized coal jet flow,combustion,radiation and other behaviors was constructed accurately and the numerical simulation of combustion behavior was conducted.In addition,the turbulent diffusion and mixing of the internal flow field of the burner affects the length of the flame.Thus,the influencing factors on the flame length of a pulverized coal burner were analyzed comprehensively,then the control law of flame length,pulverized coal combustion efficiency and pollutant emission characteristics were studied.Combined with aggregate drying process requirements,the flame length control rule in pulverized coal combustion was explored in order to improve the efficiency of combustion and reduce the emission of pollutants.The conclusion shows that the primary air preheating temperature,pulverized coal concentration of primary air,primary wind speed and swirling intensity of secondary air all affect the flame length of the aggregate drying pulverized coal burner.The most significant effect on the flame length is the pulverized coal concentration.The higher the pulverized coal concentration,the longer the flame length.The range of flame length is 4.15-5.0 m,with the longest increase of 22%,and the range of maximum flame width is 0.7-1.1 m.The range of flame diameter to length ratio can be extended to 1∶5-1∶9 by adjusting the physical factors reasonably(usually 1∶4-1∶7).Combustion efficiency and emission characteristics of pulverized coal burners are affected by combustion temperature,component concentration and internal flow field state.Under different structural parameters and control conditions,the variation of combustion efficiency and pollutant emission with the flame length are different.Under the premise of meeting the requirement of aggregate drying flame length,the combustion efficiency could be improved and the emission of pollutants could be reduced by reducing the primary air preheating temperature,reducing the pulverized coal concentration,increasing the swirling intensity and increasing the wind speed.