Effect of slurry rheology on the performance of cross-flow filtration

Effects of slurry rheology and other operating conditions on the performance of cross-flow filtration are investigated. Aluminum oxide powders with a mean diameter of 34 gm are suspended in polyacrylamide (PAA) aqueous solution to prepare the viscoelastic slurry used in experiments. The filtration rate and the cake properties under various operating conditions, such as PAA concentration, filtration pressure and cross-flow velocity, are measured and discussed. The elastic behavior of permeating fluid plays an important role on the filtration performance as the Reynolds number exceeds a critical value that depends on the fluid rheology. The elastic effect is dominant at the beginning period of a filtration, which results in an extra filtration resistance and an excess cake compression. When the elastic effect vanishes, the permeating flow through the filter cake behaves as a pure viscous fluid, which can be modeled by the power law model. The pseudo-steady filtration rate increases with the increase of filtration pressure and cross-flow velocity, but with the decrease of PAA concentrations. These tendencies can be explained reasonably by the cake properties, e.g., the particle size distribution in the cake, the porosity and the specific filtration resistance of the cake under various conditions. The dynamic analysis method proposed by the authors is employed to estimate the cake properties. The calculated results agree fairly well with the experimental data.