Solid/liquid Mass Transfer Correlated to Mixing Pattern in a Mechanically-stirred Vessel

摘要

Cold model experiment on ion-exchange reaction between pearlite particles and HCI aq. was carried out in order to understand the effect of particles dispersion and operating factors on solid/liquid mass transfer rate in a mechanically-stirred vessel. Inner diameter of vessel was varied in conjunction with both bath depth as 400 (base) and 300 mm. Rotation speed and volume ratio of particles to liquid were changed between 0-240 rpm, 0.02-0.24 (-), respectively. When rotating speed increased, solid/liquid mass transfer rate increased moderately both in the regions Ⅰ and Ⅲ, whereas it increased in the region Ⅱ. When impeller depth decreased, it was kept almost constant in the region Ⅰ, increased in the region Ⅱ and increased moderately in the region Ⅲ. Solid/liquid mass transfer rate changed less than liquid/liquid one in the region Ⅱ when rotation speed and impeller height were changed, whereas both of solid/liquid and liquid/liquid mass transfer rates were kept almost constant in the region Ⅰ. The dimensionless equation on solid/liquid mass transfer rate of each region was given as a function of Sherwood number, Reynolds number, volume ratio of particles to liquid and bath depth normalized by vessel diameter. Dispersion ratio in the region Ⅱ was ranged by solid/liquid mass transfer coefficient and rotation speed or impeller height of the transitions Ⅰ-Ⅱ and Ⅱ-Ⅲ. Solid/liquid mass transfer rate of mechanical stirring was larger than that of gas injection practice for the same supplied rate of energy into bath.