Variable flow rate in compactible filter cakes

• Published in: Water research (Oxford) Vol. 33; no. 1; pp. 15 - 22
• Main Authors: Tiller, Frank M., Lu, Rong, Kwon, J.H., Lee, D.J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1999; Elsevier Science
• Subjects: Applied sciences; Chemical engineering; compactible cakes; Exact sciences and technology; Filtration; flow models; Liquid-liquid and fluid-solid mechanical separations; porosity; relative velocity; flow models; filtration; porosity; relative velocity; compactible cakes; Flow rate; Filtration; Theoretical study; Hydrodynamics; Porosity; Particle suspension; Compactibility; Mathematical model; Liquid solid; Modeling; Filter cake
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(98)00192-4

Traditional formulas used for design of filters and interpretation of experimental data depend upon a number of simplifications including negligible solid velocity u s and a superficial liquid flow rate q L which is assumed to be a function of time and independent of distance x through a filter cake. The extent of variation of u s and q L for highly compactible biosolids is discussed in this article. An approximate method based on well-known equations which rest on the assumption the q L is constant throughout a compressible cake at a given time is presented. Using previously available formulas, the assumption of constancy of q L is abandoned; and approximate equations yielding q L as a function of x are developed. Comparisons are made of the variation with distance of q L, u s, and relative velocities for cakes of different degrees of compactibility and slurries of varying concentrations. Problems related to verification of a given model are discussed.