一次风量对煤粉分离器分离特性影响的研究

Study on Effects of Airflow Rate on Separation Characteristics of Pulverized Fuel Classifier

运用数值模拟与磨机工业采样相结合的方法研究一次风量对煤粉分离器分离特性的影响。采用欧拉κ-ε湍流模型对运用结构化网格划分的1/8分离器模型进行数值计算,结果显示:随着一次风速的增加,煤粉溢出分离器速度增加,未经分级作用而直接离开分离器的颗粒量增加;风速增加致使分离器分离比率降低,煤粉分离能力变差,并将导致循环倍率增加。对工业磨机进行开孔改造并完成2个风速条件下的采样试验,分析了风速对分离器入料、返料和合格煤粉粒度组成的影响。数质量平衡计算表明磨机循环倍率随风速的增加而增加,与基于数值模拟的计算结果呈良好的相关关系。

In this paper,the numerical simulation and industrial sampling tests for pulverizer were applied to study the effect of the primary airflow rate on the separation process of classifier. The Eulerian κ-ε turbulence model was utilized to conduct the numerical simulation of structural grid computing model of 1/8 classifier. Simulated results indicate that the overflow rate of pulverized fuel from the classifier increases with the primary airflow rate. Particles which leave the classifier without separation also see an increase. On the other hand,the segregation ratio decreases with the increase of airflow rate,which results in the lower separation efficiency for pulverized fuel and an increase of circulating ratio. Two industrial sampling tests,with different airflow rates,were made on the modified pulverizer,and the effects of airflow rate on the size composition of pulverized fuel,feed and reject of classifier are analyzed. Mass balance calculation indicates that the circulating ratio increases with the airflow rate,which shows a good liner relationship to the computed results based on numerical simulation.