Factors affecting cake resistance in non‐Newtonian filtration

Abstract

Abstract A methodology for evaluation of surface effects including polymer adsorption‐gel formation or slip within the pores of a filter cake has been developed and applied to constant pressure filtration of calcium carbonate in aqueous hydroxyethyl cellulose (Natrosol 250G, Hercules Powder Company) slurries. The fundamental framework of non‐Newtonian filtration is generalized to include the Blake, Kozeny‐Ergun and Kozeny‐Carman cake models and the cake resistances γ K and α R , in conjunction with the correction terms J RN and J gen , within a unified framework. Relationships are developed between the latter quantities and the effect of the bed model on the evaluations of the filtration characteristics is delineated. Significant polymer adsorption‐gel formation was found to take place in the constant pressure filtration of calcium carbonate in aqueous Natrosol 250G slurries. The resultant cake porosities were larger and the effective cake porosities lower than comparable porosities for cakes deposited from water slurries. The wide variation of J RN with the characteristic index N is attributed to the small size of the slurry particles. Polymer adsorption is shown to extend, and slip on the particle surface to reduce the variation of J RN with N .