加熱透過法による廃石膏粉体の乾燥特性の評価

Abstract

This study experimentally examined the drying characteristics of the waste gypsum powder using a permeation of heated air. The powder used was the waste gypsum which the particle diameter was classified into three kinds. As the experimental conditions, the particle diameter of dehydrate gypsum, the heating temperature, the initial mass of powder, the heating time and the mass flux of heated air were varied. When the initial mass of powder was an identical, it is found that the decrease in the time of change from the dehydrate gypsum to the hemihydrate gypsum depends on the increase in the particle diameter and the heating temperature. As the analysis of X-ray diffraction pattern, it can be confirmed a permeation test of heated air was an effectiveness for the evaluation of the change to hemihydrate gypsum. In addition, an effective thermal conductivity and heat flux of the packing bed of gypsum were estimated. It is found that a particle Reynolds number influenced to an effective thermal conductivity in the packing bed of waste gypsum. Also, an effective thermal conductivity including the flow of heated air was high in the case of large particle diameter. Furthermore, it is inferred that a high heat flux acting on the packing bed of gypsum influenced the time of change from the dehydrate gypsum to the hemihydrate gypsum.