Simulation And Optimization Of Seawater Desalination Components By Capacitive Deionization

At present,the shortage of fresh water resources,water pollution and other problems are aggravating,restricting the development of human society.The development of seawater desalination technology is an effective way to solve these problems.With the development of seawater desalination technology,multi-stage flash distillation,multi-effect distillation,reverse osmosis,electrodialysis and other technologies have been widely used.But because these traditional seawater desalination technology has the problem of high energy consumption and high cost,people begin to look for new seawater desalination technology.Compared with the traditional desalination technology,the Capacitive Deionization technology requires a lower working voltage,a simple device,and only produces concentrated seawater and fresh water in the process of desalination,which makes people pay more attention to this technology.With the development of science and technology,researchers have constructed porous materials with high porosity and carbon matrix composite electrode materials,and the process of preparing CDI electrode materials has also been developed.Through the breakthrough in the electrode material manufacturing,the seawater desalination performance of CDI device is getting stronger and stronger.There are many researches on improving the desalination ability of CDI cells by improving electrode materials,but few researches on the internal mechanism of CDI cells by using multi-physical field coupling numerical simulation,and the existing literatures on CDI modeling are really based on the classical GCS model.Therefore,for the capacitor deionization seawater desalination technology,CDI desalination process using porous materials as electrodes cannot be accurately simulated.Therefore,through the simulation study of CDI cell,this thesis deeply understands the solution flow and ion distribution in CDI cell with different configurations,finds out the influencing factors of the desalination capacity of CDI cell,and improves the desalination capacity of CDI cell by modifying the configuration.On this basis,a CDI component model was built to simulate the desalination process of CDI components with different parameters.Finally,the parameters were optimized.The main research work of this thesis is as follows:(1)Taking CDI unit as the analysis object,finite element analysis software COMSOL Multiphysics was adopted,combined with NNST-Planck equation and Navier-Stokes momentum conservation equation and cy’s law Poisson equation,the three-dimensional transient model of CDI unit was established based on the MD model The accuracy of the model was verified by experimental results.(2)Four CDI cells with different configurations were set,and the three-dimensional CDI cells with different configurations were studied by numerical simulation.The influences of different configurations on the solution flow and desalination performance in CDI cells were analyzed,and then the influences of different inlet flow rates on the desalination performance of CDI cells with different configurations were analyzed Through the comparison and analysis of the desalination performance of four types of CDI units(plate flow into outflow type plate,middle hole flow into two holes outflow type square plate,middle flow into surrounding outflow type disk,middle flow into surrounding outflow type)under the same inlet flow rate,and the degree of the influence of four types of CDI units on the desalination performance by inlet flow rate.(3)Through comparison and analysis on the performance of different configuration CDI unit desalination choice among the disc type into the flow around the CDI unit as the research object,and then different operation parameters and structure parameters on the influence law of CDI unit stripping absorption process and a conclusion that the optimized operation parameters and structure parameters,CDI unit plate voltage entrance velocity of plate thickness(4)On this basis,a desalination module composed of three CDI units was constructed.The seawater concentration was taken as the initial inlet concentration,and the distribution scheme of flow velocity at different inlet was analyzed and compared in detail In the flow channel spacing scheme and voltage scheme,the desalination rate of the CDI component and the time to reach adsorption saturation were determined,and then the working parameters of the CDI component were selected according to the results.