Performance Research Of Micro-Filtration Membrane Separator With Rotational Flow

The toughest problem of micro-filtration application is that filtration flux decreases sharply with time, which is caused by membrane contamination and concentration polarization. At present, a lot of improvements, such as modifying membrane material, adding an electric or sonic filed, have been made to enhance filtration and proved effectively in practice, but limited in application because of the high energy consumption and complex structure. However, the above problem can be solved by using rotational flow is used to enhance filtration in membrane separator. A new separator which combines with the hydro-cyclone and the tubular micro-filtration membrane separator is designed with some advantages such as simple structure and low energy consumption, and has a widely applied foreground.A set of experimental system of micro-filtration membrane separator combined with vortex generators is built in this study, and a series of experiments, theoretical calculations and simulations are conducted.As to experimental research, the influence of operation parameters such as concentration of suspension, inlet and outlet pressure and structure parameters such as the blade number of vortex generator and the number of vortex generators on the filtration flux. The results of experiments show that with the increase of concentration, filtration flux decreases sharply and static filtration flux decreases; the increase of the inlet pressure under an optimum value can enhance static filtration flux, but if it exceeds this value, the filtration flux will decrease; the increase of the outlet pressure can also enhance static filtration flux, but the effect is less remarkable. It is found that the rotational flow can be enhanced and filtration flux can be raised by decreasing the number of blades or increasing the number of vortex generators. The results verify that micro-filtration membrane with rotational flow has a greater filtration performance compared with tubular micro-filtration membrane separator with cross-flow.As to theory analysis, two mathematical models of filtration flux, an empirical equation for static filtration flux, and an empirical equation for dynamic filtration flux, are presented and verified by experimental data respectively. In the former, influence factors are summed up into some important dimensionless numbers like Re_g and Eu to obtain a feasible formula that provides basis for scale-up of the module. The latter which is a power function equation, based on the previous study, considering the influence of concentration of suspension, inlet and outlet pressure, describes the real variation of filtration flux with time and fits the experimental data well.As to simulation, using CFD software-Fluent, the simulation of micro-filtration membrane separator with vortex generator is presented in this study, in which a porous medium is introduced for the first time which can describes mass transfer process and resistance loss in filter medium accurately. Based on the simulation of fluid field in the gap between membrane separator and filter medium, an overall study is carded on.The results of above study demonstrate that a micro-filtration membrane separator with vortex generator might has great practical engineering value for its remarkable advantages such as homogeneous inlet fluid field, higher shear rate, lower pressure-drop through membrane and higher enhancement performance in filtration.