Performance of hydroclones for removing particles from viscous liquids

The performance of a 1-cm diam, Dorr-Oliver hydroclone with slurries containing approx. 5 wt % solids in water-glycerin solutions was studied to evaluate the effects of fluid viscosity. Micron-sized particles of low-density solids (aluminum oxide, test dust, fly ash, or kaolin) were removed from solutions with viscosities ranging from 1 to 85 cP. Pressure drop across the hydroclone increased with increasing feed rate and viscosity. Gross and centrifugal efficiencies were found to increase with flow rate and decrease with viscosity. Liquid viscosities >10 cP had deleterious effects on the pressure drop and efficiency; thus useful separations were not attained. The particle diameter, corresponding to a point efficiency of 50%, decreased as the product of the inlet Reynolds number and the solid-to-liquid density ratio increased. The reduced efficiency curve was found to characterize the hydroclone performance