Flow of Emulsions Stabilized by Polymers Through Packed Bed

Abstract

In this study, we present the results of measurements of pressure drops during the flow of emulsions stabilized by carboxymethylcellulose sodium salt (NaCMC), xanthan gum (XG) and poly(ethylene oxide) (PEO) through a packed bed of glass spheres. The concentration of dispersed phase ranged from 10 to 50 vol% and consisted of flocculated droplets with diameters much smaller than the pore size. Highly flocculated emulsions with the addition of NaCMC were yield-stress fluids whose flow curve can be described by the Herschel–Bulkley equation. An empirical model was formulated for Herschel–Bulkley fluids which allows predicting pressure losses during their flow through a packed bed. In this model, the friction factor was made dependent on the Reynolds number proposed by Kembłowski and Michniewicz (Rheol Acta 18:730–739, 1979. https://doi.org/10.1007/BF01533348) and generalized for yield-stress fluids. Also, a correlation was proposed which enables the prediction of values of the modified dimensionless plug size based on calculated values of the modified Herschel–Bulkley number. The viscosity curves obtained for the emulsions with added XG were described with the Carreau model. In the case of emulsions, the shift factor values necessary to calculate the shear rates depend on the concentration of the dispersed phase and the diameter of droplets. If the value of the shift factor is known, the friction factor can be determined from the Ergun equation. During the flow of the emulsion with added PEO through the packed bed, just as during the flow of the aqueous solution of this polymer, an apparent thickening region is noted. The relative increase in the apparent viscosity of the emulsion with added PEO is lower than the apparent viscosity of the aqueous PEO solution. This shows that elastic instability is suppressed by an increase in emulsion viscosity induced by the flocculation of droplets.