The effect of a static mixer on the ultrafiltration of a two-phase flow

A new process which helps to reduce membrane fouling during ultrafiltration by a deposit of particles has been developed in our laboratory. It consists of injecting air in such a way as to obtain a two-phase gas-liquid flow that passes through a turbulence promoter (sulzer), placed upstream of the membrane, which creates a strong shearing stress on the surface of the membrane. Experiments have been performed with a polymer, sodium alginate. Various speed values of the gas, liquid and polymer concentrations have been examined, as well as the influence of the molecular weight cutoff of the membrane. The process of air injection in the presence of the turbulence promoter leads to a 180% improvement of the permeate flux. The shear stress exerted by the turbulent gas-liquid mixture prevents particles from depositing on the surface of the membrane and/or facilitates the detachment of the deposited polymer and thus improves mass transfer.