濃厚スラリーの界面沈降速度と初高の影響
1987 年 103 巻 1188 号 p. 109-114
詳細
1987 年 103 巻 1188 号 p. 109-114
Zone settling rates of limestone, coal and kaolin-water slurrieswere investigated using vertical settling cylinders or a centrifuge. Zone settling was divided in dilute and intermediate modes depending on whether or not the aggregates were in contact and formed a network structure, and concentrate mode of intimate contact settling due to compression was followed. Although the higher initial height of slurry brought on the higher settling rate in the intermediate, it was found that in the region of rather lower initial height the settling rate became solely a function ofconcentration.
Comparing experimental values with known analytical derivations, Richardson and Zaki's equation modified by Michaels and Roberts' equation were effective for the dilute and the concentrate, respectively. And also, Michaels method of capillary model was impressive for the intermediate in which the settling rate was depended on both of concentration and initial height. It was demonstrated that when the initial height was low enough to correlate the settling rate only with concentration, settling rate of the intermediate was well coincided with predicted rate appling Kynch's theory on the dilute. Zone settling rates of rather wide range of concentration and initial height were able to be summerized as expressed in a figure.
If the initial composition is uniform the slurry concentration in centrifuge is independent of radius, but decreases everywhere within the suspension at the same rate with respect to time. Centrifugal settling rate was calculated on the basis of that it was able to be calculated from the settling rate in a gravitational field, field acceleration and slurry concentration accounting for the changingconcentration. Equilibrium thickness of centrifugal sediment waspredicted in the manner which took into account the relationshipbetween compressive pressure and porosity in the sediment. Usingthese values led to good correlation of experimental and calculated sedimentation process in centrifuge over the range of this investigation.
