Intensification of microfiltration using a blade-type turbulence promoter

Abstract

Intensification of microfiltration has been accomplished using motionless mixers consisting of a series of pairs of semielliptical blades as turbulence promoters. Blade mixers of two aspect ratios 2.5 and 1.3 were tested in the microfiltration of milk (0.1μm membrane). The permeate fluxes are substantially increased by application of blade mixers due to a reduction of both reversible and irreversible fouling. The highest flux improvements of 500–650% for the same cross-flow rate (relative to the conventional operation) were obtained by application of the blade mixer of aspect ratio 1.3.When compared for the same hydraulic dissipated power mixer of aspect ratio 2.5 proved to be slightly more efficient because it causes the lower pressure drop. Despite to the increased pressure drop, the energy savings obtained by application of blade mixers are considerable compared to the conventional operation and to the operation using some other mixers. In the membrane fitted with a blade mixer the flow field changes in a manner which afford the intensive disruption of boundary layer, scouring and removal of fouling forming material. The flow field is characterized by the high cross-flow velocities at membrane wall, alternation of stream line path and swirling motion. Therefore, the application of blade mixers affords an operation under the several times lower initial cross-flow velocity.