ろ過方程式の実験による検証―定圧ケーキろ過―

Abstract

Introducing a thin permeation layer at the beginning of filtration, the governing differential equation for the filtration expressed in material coordinate derived in our previous papar (J. Soc. Powder Technol. Japan, Vol. 40, pp. 712-719) suggested that (i) the square of dry solid volume in a cake increases linearly with time, and (ii) there exists a similarity among the distributions of concentration, liquid pressure and liquid flow rate in the cake. In the present work, filtration experiments were carried out using four types of suspensions at low and high constant filtration pressures in order to examine the validity of (i) and (ii) as well as the consistency of the presented governing equation. As a result, the total solid volume and the wet to dry mass ratio of the cake were successfully predicted by the present model employing the average void ratio of the cake which was calculated theoretically, and (i) was found to hold for these suspensions. However, all of the filtration experiments showed that there was a time delay with a factor of 1.1 to 2.5 as those predicted by the present theory. The discrepancy may result from the viscous delay effect in thin cake layer near the filter medium, which was excluded in the present model. The effects of constitutive and permeation relation onto the distributions of concentration, liquid pressure and liquid flow rate in the cake were also presented.