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为了获得流态化干燥状态下的粉体干燥曲线,设计了一种小型流化床干燥装置用于粉体材料的干燥特性测定.应用该装置,实验研究了悬浮法PVC粉体的干燥特性.测定的PVC粉体在该流化床中流化参数为操作气速介于0.41 ~0.55m/s之间,即流化数ua/umf为1.24 ~1.67.实验测定了PVC粉体干燥动力学曲线,回归得到描述PVC干燥特性曲线的解析函数为(f=-0.622 6 +1.254 6exp(2.561 5Φ-0.707 2))/(1+exp(2.561 5Φ-0.7072)).确定了实验条件下PVC干燥的临界湿含量xc及传质系数K分别为0.02kg/kg和6.0×10-4kg/(m2.s).由于实验方法比较接近工业流态化干燥过程,获得的结果对于工程应用较为可靠,该方法可用于如PVC一样的粉体材料的干燥特性测定.
In order to obtain the powder drying curve in fluidized and dried state, a small fluidized bed drying device was designed for the determination of the drying properties of the powder material. The drying characteristics of the suspended PVC powder were experimentally studied. The measured fluidization parameters of the PVC powder in the fluidized bed are operating gas velocities ranging from 0.41 to 0.55 m / s, that is, the fluidized number ua / umf is 1.24 to 1.67. The drying kinetic curves of the PVC powders were measured , The analytical function describing the drying characteristic curve of PVC was obtained as (f = -0.622 6 +1.254 6exp (2.561 5Φ-0.707 2)) / (1 + exp (2.561 5Φ-0.7072)). The PVC dried The critical moisture content xc and mass transfer coefficient K are 0.02kg / kg and 6.0 × 10-4kg / (m2.s), respectively.As the experimental method is close to the industrial fluidization drying process, the obtained results are more reliable for engineering applications, The method can be used for the determination of the drying characteristics of powder materials like PVC.