高温气流干燥氧化铝对流传热传质分析

基于两相流理论,提出了一个描述含湿氧化铝颗粒气流干燥过程的一维数学模型.模型考虑了干燥管内气固两相间的传热和传质、气固两相温度和含湿量的变化.利用Bird等所提出的努赛尔数经验公式对该气流干燥模型进行了数值计算,得到了含湿氧化铝颗粒在不同气流干燥条件下的干燥曲线.整个干燥过程的数值模拟结果与实验数据吻合得很好,可以用来预测含湿氧化铝颗粒的干燥湿度.另外,对固气比、气流温度以及气流速度对颗粒湿度沿干燥管高度变化的影响也作了计算和分析,结果表明固气比和气流温度对颗粒湿度的变化影响较大.低固气比、高气流入口温度,干燥过程颗粒湿度变化大,有利于颗粒干燥.而气流速度对颗粒湿度变化的影响则可忽略不计.

Analysis on Heat and Mass Transfer of High Temperature Pneumatic Drying Alumina

A one-dimensional mathematical model for the pneumatic drying process of wet alumina particles based on two-phase flow theory was proposed. The model took into account mass and heat transfer between the gas and dispersed phase, variations of properties with humidity and the temperature during drying. It was solved under different initial conditions, and the numerical solution of the model showed that using Bird's correlation, the heat and mass transfer rates during the whole drying period are predicted very well. The developed model can be used to predict the final moisture content of wet alumina particles. Effects of mass flow ratio, velocity and temperature of air on moisture content of the particle along the pipe duct were also computed and analyzed. The results suggest that solid to air mass flow ratio and initial gas temperature have great effects on the change of moisture content of alumina. At the same time, water content of particle changes greatly with lower solid to air mass flow ratio and higher initial gas temperature. However, the gas velocity's effect is negligible.