EDI technology

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EDI Technology I. Overview of EDI Technology Fill-bed electrodialysis, also known as electrode ionization and abbreviated as EDI, utilizes the polarization phenomenon that occurs during the electrodialysis process to electrochemically regenerate the ion-exchange fill bed. It combines the advantages of electrodialysis and ion-exchange methods while overcoming their respective disadvantages. EDI technology combines two established water treatment techniques: electrodialysis and ion exchange. In China, this is referred to as packed-bed electrodialysis or electro-deionization technology. It mainly replaces traditional ion exchange mixed beds for the production of high-purity water, and this technology has been widely adopted abroad in industries such as electronics, power generation, and chemicals for the preparation of high-purity water. It is foreseeable that such water treatment products will become the mainstream equipment in high-purity water production projects this century. The backward application of this technology and related technologies in half-width form will bring about fundamental changes to existing water treatment techniques, thereby limiting better environmental and economic benefits. 　　High-purity water is very important for many industrial and commercial applications, such as the semiconductor manufacturing industry and the pharmaceutical industry; in the past, the pure water used in these industries was obtained through ion exchange. However, membrane systems and membrane treatment processes are becoming increasingly popular as alternatives to pretreatment processes or ion exchange systems. Membrane systems such as the electro-deionization process (EDI) can remove minerals very effectively and operate continuously. Furthermore, the membrane treatment process is much simpler to operate than ion exchange systems, and it does not require the neutralization of waste water generated from acid or base regeneration. The EDI treatment process is one of the fastest-growing segments within the membrane treatment industry. EDI is a non-backflowing reverse electrodialysis (ED) system equipped with a special tank, whose flow channels are filled with mixed-bed ion exchange resin. EDI is mainly used to convert water with a total dissolved solids (TDS) level of 1–20 mg/L into pure water with a resistance of 8–17 MΩ. II. Advantages of the EDI pure water system: 1. It occupies less space, as it eliminates the need for mixed-bed and regeneration units ； 2. The water production is continuous and stable, with high water quality; whereas in mixed-bed systems, the water quality deteriorates as the resin approaches its end of life ； 3. Low operating costs: regeneration requires only electricity and no acids or bases, thus saving on material costs ； 4. It offers significant environmental benefits and enhances operational safety. http://www.china-qianqiu.com/UserFiles/Image/edi/image1.jpg III. Technical Performance The performance of EDI components depends on various operating conditions. The following are the minimum conditions to ensure the proper operation of EDI. To improve the system’s performance, these conditions should be appropriately increased during system design. 　　To prevent clogging of the device and extend its operational life, EDI has certain requirements regarding the quality of the incoming water; generally, RO-treated water is used as the input water. EDI feedwater parameters:
It parameter, unit: TEA, ppm – <25; Conductivity, µs/cm – 4–30; pH – 5–8; Hardness, ppm CaCO3 – <1.0; Active SiO2, ppm – <0.5; Total Organic Carbon (TOC), ppm – <0.5; Residual chlorine, ppm – <0.5; Fe, Mn, H2S, ppm – <0.01; SDI after 15 minutes – <1; Water temperature, °C – 5–35; Feedwater pressure, Psi/kg/cm2 – 25–60/1.5 kg/cm2–4 kg/cm2.

IV. Equipment performance:
Component, range: Quality of produced water – >10 MΩ·cm (at 25°C); Recovery rate – 90–95%; Power consumption – 0.12–1.06 kwh/m3; Water temperature – 5–38°C; Feedwater pressure – 0.31–0.68 MPa; Pressure difference between inlet and outlet water – 0.14–0.24 MPa.

V. Application areas: Chemical water treatment in power plants; Water supply for fine chemical industries and advanced scientific fields; Ultra-pure water for the electronics, semiconductor, and precision machinery industries; Process water for the pharmaceutical industry