Cake filtration in viscoelastic liquids

Abstract

The paper deals with the modeling of the constant-pressure cake filtration of suspensions in viscoelastic liquids. The filtration equations are presented based on the capillary hybrid model for power law fluid flow and comprising correction functions of the influence of dispersing liquid elasticity. The validity of these equations has been verified experimentally. The tests with suspensions of nearly spherical polystyrene particles Krasten in viscoelastic aqueous solutions of polyacrylamides Kerafloc and Praestol were performed at constant pressure in a laboratory cylindrical filtration unit. The rheological properties of liquids have been measured on a rotational rheometer Mars II and an extensional rheometer Caber 1. By analysing the experimental data, the filtration characteristics have been evaluated. The elastic effects manifest themselves predominantly at the early period of the filtration due to a higher filtration velocity which results in an evidently increased filtration resistance. The satisfactory agreement of the experimental dependences of the cumulative filtration volume on the time of filtration has been achieved when compared to those obtained by the numerical solution of the proposed differential equation of filtration. This confirms that the cake filtration from viscoelastic liquids can be predicted with a satisfactory accuracy, thus making the suggested filtration model applicable in practice.