Modeling and experimental study of microfiltration using a composite module

Microfiltration is usually conducted in either a dead-end or a cross-flow filtration mode, with a bundle of hollow fibers or a sheet of membrane as the filtration medium. This paper reports a development of microfiltration using a membrane screen-hollow fiber composite module involving both dead-end and cross-flow filtrations together. In the composite module, a cylindrical membrane screen of larger pores is installed outside a bundle of hollow fibers of smaller pores, and the suspension to be treated is passed through the membrane screen for pre-treatment before it is further treated through the hollow fibers. The membrane screen is operated in a cross-flow filtration mode whereas the hollow fibers are in a dead-end filtration mode. A simplified analysis was conducted for the prediction of permeation flux through the membrane screen-hollow fiber composite module, and the modular performance was evaluated through microfiltration experiments with kaolin suspensions. It was found that the addition of the membrane screen in the composite module largely improved microfiltration performance, and the theoretical model developed in the simplified analysis could be adequately fitted to the experimental permeation fluxes through the composite module under various operation conditions.