Field And Resistance Simulation Of Cross Flow Membrane Filtration Of Emulsified Oil

For heterogeneous mixing(emulsification) and unstable oil-water two-phase systems,traditional experiments are difficult to measure the flow field distribution.The use of traditional dead-end membrane filtration methods to treat emulsified oily wastewater is inefficient.For example,it is easy to cause membrane pollution and increase the difficulty of later membrane cleaning.The cross-flow membrane filtration of wastewater overcomes the shortcomings of dead-end filtering oil droplets that easily block the membrane pores.The use of the characteristic that the inflow direction of the original liquid and the outflow direction of the permeate are vertical can effectively slow down the process of membrane fouling,thereby increasing the membrane.Membrane flux and rejection index of the filtration process.The Euler multiphase flow model is used to numerically simulate the oil-water separation process in the forced cross-flow filter.The dynamic law of the movement of oil droplets on the material liquid side was analyzed,and the multi-stage membrane filtration experiment was combined to treat emulsified oily wastewater.The numerical simulation of the cross-flow film oil-water separation process in the device was realized,and the correctness of the model was verified through experimental data.The fluid velocity field and pressure field inside the oil-water treatment device were simulated,turbulence characteristic distribution,oil phase volume fraction distribution,and the influence of different parameter changes on membrane flux and rejection rate.Theoretically analyzed the dynamics of multi-directional diffusion,collision and coalescence between oil droplets in the feed liquid,and the shear stress generated by the stirring blade to reduce the nature of membrane fouling and filtration resistance.The process of emulsification of oily wastewater by cross-flow membrane filtration was analyzed by the method of simulation combined with experiment.The simulation results showed that:under the same rotational angular velocity,the oil droplets of the concentrate aggregated toward the center,and coalesced after the oil droplets collided.As the rotational angular velocity increases,the oil phase volume fraction at the permeate outlet and the upper surface of the filter membrane decreases.The controlled variable method is used to study the effects of different temperature of feed liquid,different porosity of porous media and different rotational angular velocity of stirring paddle on the membrane flux and rejection rate of oil-water separation process.The study found that:when the temperature of the feed liquid and the rotating speed of the stirring paddle are constant,with the increase of porosity,the membrane flux first increases and then remains unchanged,and the interception first remains unchanged and then decreases;Timing,with the increase of the rotational angular velocity,the membrane flux and retention rate will increase;when the porosity of the porous medium and the rotational angular velocity of the stirring paddle are constant,with the increase of the feed liquid temperature,the membrane flux will gradually increase,the interception increases first and then decreases gradually.The optimal solution for the experimental operation obtained from the simulation is a porosity of 0.4,a rotational angular velocity of 9 rad/s,and a temperature of 310 K.During the experiment,the method of mechanical stirring was used to prepare emulsified oil-containing wastewater.When the oil phase volume fraction was 0.2%,the non-ionic surfactant Tween 80 was added,and the volume averaged water was prepared at a rotation speed of 3000 r/min.Emulsion with particle size of 3.868μm.Under the simulated optimal conditions and the feed water pressure of 0.34 MPa,microfiltration was performed to treat the emulsified oily wastewater with a volume fraction of 0.2%.The membrane flux of the membrane filtration process is 155.92 L/(m~2·h),and the rejection rate can reach89.16%.A larger membrane flux can also ensure the separation effect.