Study On Electrodeionization And Anti-scale Technology Based On Compound Bed

Electrodeionization?EDI?is a composite desalination process that combines ion exchange and electrodialysis to achieve continuous deionization.At present,it is widely used in the fields of electronics,electric power,medicine,desalination and chemical industry.However,the existing EDI device process has high requirements on the inlet water quality,low regeneration rate of ion exchange resin,high energy consumption,and in practical industrial applications,film stack is prone to scale,the long-term operation stability of the device is poor.Therefore,in this paper,a new type of compound bed structure was proposed,which realized the efficient regeneration of ion exchange resin and changed the process flow by circulating the concentrated water to make it show excellent anti-scale performance.First,the bed structure and process optimization of EDI device.First,a new type of compound bed structure in which the anion and cation exchange resins are packed in parallel layers was designed to make the anion and cation exchange resins close to the anion and cation exchange membranes.This improves the ion transport efficiency,reduces the energy consumption of the device and improves the regeneration efficiency of ion exchange resin.Then,the effect of different operating conditions on the desalination performance of the composite bed EDI device was investigated.The experimental results showed that the optimal membrane spacing of the compound bed EDI device was 10 mm,the current density was 9×10^-3 A/cm²,and the reaction time under the condition of 3 h,the regeneration rate of ion exchange resin can reach 67%,compared with the traditional EDI process,the regeneration rate increased by 2 to 3times,and even close to the level of chemical regeneration.Secondly,in view of the problem that the ion exchange membrane of the EDI device is prone to fouling under poor water quality,this paper proposed a new anti-scaling technology based on the in-depth analysis of the membrane fouling process and the resin regeneration mechanism:The process flow was changed by circulating the water in the concentration chamber of the EDI device,and the bed anion and cation exchange resin were optimized and the optimal operating current density was selected to make the concentrated chamber form an acidic environment,thereby effectively preventing the formation of precipitation.The experimental results show that:under the above process,even if the conductivity of the influent was about 1360?s/cm and the hardness is 400 ppm?calculated as CaCO₃?,no fouling will be generated after the device operates stably for 150 hours.The optimal filling ratio of ion exchange resin was cation exchange resin:anion exchange resin=2:3?mass ratio?and the optimal operating current density is 9×10^-3 A/cm² under the water quality conditions of this experiment.The structure and process of the new EDI device proposed in this study not only can realize the efficient regeneration of ion exchange resins,but also exhibit excellent anti-scaling performance,which broadens the restrictions of EDI water inlet conditions and ensures the long-term stable operation of EDI devices.The device technology has important practical significance for the industrial application of EDI technology.