Controlling Of Membrane Fouling By Micro-flow Field Of Membrane Module Based On Hydraulic Equilibrium

Nowadays,Membrane fouling is one of the main reasons that limit the ap plication of membrane technology in the field of water treatment.A lot of detailed researches on membrane fouling has been performed at home and abroad.Based on previous studies,the forces on micro-particles were analyzed,and a model based on hydraulic balance to regulate the micro-flow field of membra ne and to optimize the design of flat membrane module was established by co mbining the theory of ideal sedimentation tank and shallow tank.Compared wi th CFD software simulation and theoretical experiment,the design method of membrane module under certain operating conditions was discussed,and the siz e proportion equation of membrane module was defined.The main results were as follows:(1)Foundation and simulation of membrane module model based on hydraulic balance optimization: According to related equations and reasonable assumptions,a design model of membrane module based on hydraulic balance adjustment of Membrane micro-flow field was established.The advantages and disadvantages of each model and solution method in Fluent were compared and analyzed,and a set of parameters suitable for this research was optimized.(2)Verification of Membrane module model based on hydraulic balance optimization: Verification of Membrane module model based on hydraulic balance optimization: Dow 90 polyamide composite NF membrane was adopted when the influent flow rate was 15 L/h,20 L/h,25 L/h and the transmembrane pressure was 0.4 MPa,0.5 MPa and 0.6 MPa,respectively,the experiments were carried out at room temperature with potassium permanganate as the dye to investigate the characteristics of foulant accumulation on the membrane surface.The results were in good agreement with the simulated data.And the results show that when the influent flow rate is 20 L/h and the transmembrane pressure difference is 0.4 MPa,the error between the test and the simulated data was the smallest,only 0.7%.(3)Application of membrane module model based on hydraulic balance optimization: combined with membrane module design model and operation parameters,the dimension ratio of length: Width: Height of membrane module based on hydraulic balance optimization is 40:30:1,the inflow mode of membrane module was also optimized.The Velocity Cloud Diagram and particle passing through Membrane Diagram of membrane module and other five different size membrane module were optimized by Fluent simulation.The results showed the rationality of performance optimization based on hydraulic balance.(4)Performance evaluation of membrane module based on hydraulic balance optimization: The performance of membrane module was evaluated by residence time distribution test and characteristic foulants membrane flux decline test.The results show that the dead zone and vortex zone were reduced,and the overall flow field condition was better than that of the original membrane module.The results show that the optimization of micro-flow field in the module based on hydraulic balance was effective.(5)The specific flux decline rate of membrane module optimized by hydraulic balance was lower than that of original membrane module when the characteristic foulants were humic acid(HA),sodium alginate(SA)and bovine serum albumin(BSA),it decreased by 14%,9.3% and 7.9% respectively.The comparative analysis of membrane fouling resistance showed that the membrane fouling resistance of optimized membrane module based on hydraulic balance was smaller than that of unoptimized membrane module,which shows the effect of membrane module on flow field optimization and membrane fouling control.