细颗粒无烟煤焦在CFB锅炉燃烧室内的燃尽特性研究

Modeling Research on the Burnout Characteristics of Fine Anthracite Char Particle in CFB Combustor

建立细颗粒无烟煤焦在CFB燃烧室的燃烧模型。模型考虑颗粒与烟气的能量交换、炉内的流体动力特性、炉膛中氧气浓度分布、分离器的分离特性和颗粒在炉内停留时间等因素的影响,能较好描述细无烟煤焦的燃烧行为,反映出CFB锅炉飞灰碳在50μm粒径档附近处出现峰值分布的特征,与工业实际运行结果吻合良好。模型求解结果表明:提高燃烧温度对于福建无烟煤细颗粒的燃尽有利,但当温度高于1000℃时,进一步提高燃烧温度对降低飞灰含碳意义不大。另外,提高过量空气系数、降低炉膛烟气流速、提高锅炉分离器分离效率等有利于细无烟煤焦的燃尽。

A model for the combustion of fine anthracite char particle in CFB was established. These factors such as the mass ＆ energy balance of particle, the hydrodynamic character of boiler, the distribution of oxygen concentration in furnace, the performance of cyclone and the residual time of particles were considered in model. The model was numerically resolved and compared with that from industrial measurement. It shown that the model can describe the combustion behavior of fine anthracite particle in CFB chamber well. The simulation result of the distribution of carbon content in fly ash is fits well to that from industrial measurement, and it can also explain this phenomena that there is a peak of carbon content distribution in fly ash particle which appears in the particle size nearby 50 micron, From the model, it can be predicted that increasing combustion temperature is good to the burnout of fine Longyan anthracite particle, but when the temperature is higher than 1000℃, continue to rise the combustion temperature will bring no more evident effect on the burnout of Longyan char. Besides, increasing the excess air coefficient, decreasing the gas velocity or increasing the collection efficiency of cyclone will help to reduce the carbon content in fly ash.