| Membrane distillation is a new membrane technology which can make the utmost of low-grade heat source to realize the separation process.With the advantages of high separation efficiency and simple operation,it is one of the advanced technologies to realize the separation of low carbon and low energy consumption in the future.In this paper,the polypropylene blend membranes were prepared,the influence of the mixed diluent on the process of preparing membrane was investigated,and the experiment of vacuum membrane distillation was carried out.The process of membrane distillation was simulated and verified by using computational fluid dynamics(CFD)simulation software,and the optimized design of membrane distillation module amplification was explored.The main research contents and conclusions are as follows:(1)The addition of DOP in the mixed diluent reduces the interaction between the polymer and the diluent,forming a continuous cellular membrane pore structure and gradually eliminating the cracks on the membrane surface;As the DOP content in the diluent increases,the average pore size of the membrane increases from 0.154 ?m to 0.365 ?m,and gas permeability increases from 0.1641 L/(cm2·min)to 0.5925 L/(cm2·min).The change of membrane pore structure also affects the change of liquid entry pressure of the membrane.The liquid entry pressure first increases and then decreases,gradually increasing from 0.23 MPa to 0.33 MPa and then decreasing to 0.31 MPa.(2)Vacuum membrane distillation experiment was carried out on the prepared blend membrane to explore the influence of experimental operating conditions on permeation flux and interception rate of membrane distillation.It was found that the permeation flux of membrane distillation increased gradually from 12.68 kg/(m2·h)to 15.73 kg/(m2·h)with the increase of feed flow rate,and flow rate had smaller effect on flux.The permeation flux of the membrane increased from 0.26 kg/(m2·h)to 17.38 kg/(m2·h)with the increase of feed-liquid temperature from 30? to 80?,indicating that temperature has a great influence on permeation flux;As the vacuum degree on the permeation side increases from 0.05 MPa to 0.09 MPa,the permeation flux increases from 0.39 kg/(m2·h)to 13.75 kg/(m2·h).Within the tolerable range of the membrane,the higher the vacuum degree is,the larger the permeation flux will be.(3)The process of vacuum membrane distillation is simulated by using computational fluid dynamics simulation software.The experimental results were verified by self-written UDF.The simulation results show that under the influence of different feed temperature,feed flow rate and vacuum degree of permeation side,the simulated value and the experimental value are highly consistent and the correlation coefficients after fitting were all greater than 0.99,the prepared UDF could be used for the simulation of membrane module amplification.(4)After enlarging the design of the plate vacuum membrane distillation module,the simulation results show that when the effective filter area is 0.025 m2,the optimal length-width ratio of the plate membrane module is 1:2 and the height of the channel in the module is 7.5 mm,the permeation flux can be increased by 2.7%.The simulation results show that the optimum height of the separator is 3 mm and the distance between the separators is 40 mm,and permeation flux of the optimized membrane module was 6.53 kg/(m2·h),increased by 10.3%compared to the initial membrane module. |
PDF Full Text Request