Study on Ion-exchange Membrane of EDI and Simulation of Flow Field in the Dilute Chamber
|Keywords||EDI ion-exchange membrane dilute chamber CFD improvement|
EDI (electrodeionization) is a new separation technology which combines ion-exchange membrane and ion-exchange resin, and it can achieve continuous demineralization and resin regeneration. It has high efficiency, energy saving, environment-friendly and other significant advantages, and it is widely used in chemical, electrical, electronic, pharmaceutical, petrochemical and other fields of ultra-pure water production. In this paper, ion-exchange membrane used for EDI is studied, and flow field distribution modeling of dilute chamber with computational fluid dynamics (CFD) software is studied for the first time.As to continuous desalination of EDI, the ion-exchange membrane plays a vital role in the removal of ion, and it is an important component which is used to achieve hydrolysis of water to resin regenerate. In this paper, the performance of qianqiu membrane made in China is compared with AGC membrane from Japan by experiments. The changing resistivity of freshwater produced by the EDI filled with reducibility ion-exchange resin is observed after boot, as well as freshwater produced by EDI filled with salty ion-exchange resin. Experiments results show that the performance of AGC membrane is superior to qianqiu membrane, but it is more expensive. Therefore, we should choose a suitable ion-exchange membrane and EDI device according to different demands of dilute water quality.The design of dilute chamber plays an important role in the design of EDI device, and is also one of key EDI technologies. In this paper, the study on flow field distribution modeling of dilute chamber is conducted for the first time. First of all, porous media model is used to simulate the overall pressure drop of dilute water in the dilute chamber. Simulation results agree with experimental data, and it can predict the water pressure drop under different volume flow well. Then, the main target is to discuss the water distribution after diversion trench, distribution plate and fine draw. A comparison of water distribution and pressure drop is conducted, and the results of simulation show that the appropriate range of slit width is 0.3-0.4mm. The water distribution of two different structure of diversion trench is discussed, and a new improved structure of diversion trench is proposed by integrating the advantages of the two different diversion trenches. The results of simulation show that the new diversion trench can achieve a good water distribution and a lower pressure drop, and it also has a good supporting of plate cover which can be effective in preventing depressing of ion-exchange membrane. In a word,the new improved structure of diversion trench has excellent comprehensive performance. Finally, the operation problems and resolve method of EDI are summarized in this paper.