Experimental And Simulation Study Of Joule Effect Intensified Membrane Distillation Process

Membrane distillation seawater desalination is one of the effective methods to solve the shortage of fresh water resources,but the process still has shortcomings such as low heat utilization rate and low flux,which limits its application in industrial production processes.How to strengthen the membrane distillation process and apply it to the industrial production of seawater desalination has become a problem worthy of attention.In this paper,the self-made conductive carbon membrane is used to carry out the Joule effect-enhanced membrane distillation of sodium chloride aqueous solution experiment and simulation research,and to explore the reliability of the Joule effect-enhanced membrane distillation process.The main research contents and results are as follows:(1)Preparation and performance characterization of conductive carbon membrane.With membrane distillation seawater desalination as the background,the membrane distillation conductive carbon membrane was prepared,and the membrane properties such as pore size,porosity,and electrical conductivity were characterized and tested.The results show that the prepared coal-based carbon membrane has good structural stability at 100oC;the introduction of weak current into the carbon membrane will not damage the entire carbon membrane and the structure of the PDMS hydrophobic layer on the surface,and the carbon membrane will not be oxidized after being energized Synergistic effects such as reduction.(2)Experimental study on the Joule effect intensified membrane distillation process of sodium chloride aqueous solution.On the basis of the conventional membrane distillation experiment,by applying direct current to the self-made conductive carbon membrane to produce the Joule effect,the membrane distillation sodium chloride aqueous solution process was strengthened experimental research,and the scanning electron microscope,X-ray photoelectron spectroscopy,Raman spectroscopy,etc.Methods The structural changes of the conductive carbon membrane before and after power-on were analyzed.The results show that,within the scope of the experiment,the carbon membrane has a good retention rate of sodium chloride(retention rate above 99.96%),the Joule effect can increase the permeation flux of membrane distillation up to 60%,and the Joule effect can affect the membrane at low temperatures.Distillation has a better strengthening effect and higher electrical conversion efficiency,indicating that the Joule effect is more suitable for the membrane distillation process at low temperatures;the introduction of the Joule effect will not cause additional membrane fouling,and the introduced Joule heat can be used for water vaporization.Feed liquid temperature,improve temperature polarization,increase the driving force of mass transfer;the influence law of the mass transfer coefficient in the Joule effect membrane distillation process is different,when the feed temperature is 50-80oC,it is affected by Knudsen diffusion and molecular diffusion,and the current is 1A The mass transfer coefficient value decreases,and the mass transfer coefficient value increases at 3A and 5A.(3)Numerical simulation of the Joule effect enhanced membrane distillation process of sodium chloride aqueous solution.On the basis of the conventional air-gap membrane distillation heat and mass transfer model,the Joule effect enhanced heat and mass transfer model of air-gap membrane distillation is established.Combined with the electric potential model,the permeation flux,temperature distribution,and pressure driving force under different current intensities are established.,Mass transfer coefficient,temperature polarization coefficient,etc.are calculated.The results show that the Joule effect can effectively compensate for the decrease in the temperature of the solution on the membrane surface caused by the vaporization of the solution on the membrane surface,increase the temperature of the inner surface of the membrane,increase the pressure driving force,and increase the thermal efficiency of the process to increase the temperature polarization coefficient;the solution temperature is not current at the same time The influence of intensity on the mass transfer coefficient is different: the mass transfer coefficient value at the feed temperature of 40? is proportional to the current intensity,and the mass transfer coefficient at the feed temperature of50-80? first decreases and then increases with the current intensity.Different law of the influence of intensity on mass transfer coefficient leads to different law of permeation flux.