A comparison of filtration characterisation devices for compressible suspensions using conventional filtration theory and compressional rheology

Abstract

Solid-liquid separation is carried out in many industries and plays a crucial role in overall process efficiency and product specification. The dewatering characteristics of solid-liquid mixtures, or particulate suspensions, have to be determined to compare filtration equipment performance or to design new equipment. Two theoretical frameworks used to describe solid-liquid separation, and therefore analyse experimental results, are the conventional filtration theory developed by Ruth, Tiller and Shirato and the compressional rheology framework developed by Buscall, White and Landman.In this paper, we compare the characterisation techniques that have developed over time based on these two approaches. This includes a comparison between an air-driven Nutsche Filter, a Compression-Permeability cell and a piston-driven Filtration Rig. The test material is calcium carbonate coagulated by attractive Van der Waals forces at its isoelectric point. We use three different particle sizes, leading to varying degrees of compressibility. The results show good agreement between the two theoretical frameworks for these compressible materials. Overall, this work highlights the differences and similarities between the theories and characterisation techniques alike and gives recommendations for good practice.