Influence of particle size uniformity on the filter cake resistance of physically and chemically modified fine particles

The filter cake resistance determines the flow rate in cake filtration. The resistance depends not only on the mean size of the particles but also on their overall distribution. An example of where we have insufficient understanding of the effect of particle size is lautering-a separation process used in beer production. In this type of filtration, a layer of biological fine particles (<500 mu m) with a high filter cake resistance forms on top of the cake and is responsible for a reduction in flow rate. Herein, differences in the resistance of fine particles based on alteration of their size distribution were investigated. An experimental setup was developed to isolate the fine particles from the filter cake, and their chemical and structural compositions were determined. To alter the particle size distribution, physical (heating, agitation) and chemical (prevention of oxidation, polyphenol addition, pH adjustment, ion concentration alteration) modifications were applied. The modifications affected the interparticle interactions, which influenced the size distribution and thus the resistance. The lowest resistance was achieved by heating (-88%) and the highest by agitation (+69%). Contrary to earlier findings, the results of this study show that not only the mean particle size determined resistance; low resistance also depended on high uniformity of the particle size distribution (R2 = 0.856). Compared with a uniform size distribution, a wide size distribution resulted in lower porosity, which was responsible for higher filter cake resistance. The universal validity of the results from the biological suspension was determined using glass beads as an inert model system.

Automated summary

This study investigated the impact of particle size distribution on filter cake resistance, finding that the uniformity of particle size distribution plays a crucial role in resistance, and that the mean particle size is not the sole determining factor.