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 cut-off 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.