EDI纯水设备系统的装置，作为反渗透技术之后的一步，已经取代了传统混合离子交换技术（MB-DI），以生产出稳定的去离子水。与混合离子交换技术相比，EDI纯水设备具有以下显著优势：①ED pure water device equipment ensures stable water quality;②it allows for easy automation control;③no need to shut down during regeneration;④no chemical regeneration required;⑤low operating costs;⑥smaller factory space needed; and ⑦zero wastewater discharge. The development history of high-purity water technology can be traced back to three stages: pre-treatment → ion exchange bed → mixed-bed, then pre-treatment → reverse osmosis (RO) + mixed-bed, and finally, pre-treatment → RO + EDI device. Although the reverse osmosis system can remove 95-98% of ions from the water, it is not enough to meet the requirements of industrial production. Therefore, subsequent processes must use ion exchange devices. In recent decades, mixed-bed ion exchange technology has been widely used as a standard process for producing pure water in industry. However, due to its periodic regeneration needs and large amounts of chemicals (acids and bases) used during this process along with a lot of pure water consumption in the regenerant solution preparation step itself, it is becoming increasingly difficult to achieve zero-acid-and-base systems.
Thus arose the need for new technologies that could overcome these limitations. The combined membrane-resin technology represented by EDI devices became a revolutionary innovation in water treatment technologies that replaced traditional methods like mixing beds or resin beds with their own unique advantages over them.
The working principle behind EDI devices involves several key steps:
Water enters an EDI system where most parts flow into resin/membrane internals while another part flows along membranes' outer sides to wash away ions leaked outside.
Ion-exchange resins within an EDI device capture dissolved ions from incoming feedwater.
Under electric field influence at electrodes inside an EDI device's chamber spaces,
Anions move towards positive electrode direction
Cations move towards negative electrode direction
4.The captured cations pass through selective cation membranes on one side & are flushed outwards.
5.The captured anions also pass through selective anion membranes on another side & are flushed outwards.
6.Concentrated removed salts leave via waste streams from spent brine return loop within each cell unit
7.Pure deionized product exits from internal reservoirs after completion of separation cycle
8.No residual salt or impurities remain upon completion.
Water quality requirements before entering such systems include:
TEA (CO2) <25mg/L as CaCO3
PH 5-9
Hardness <0·1 mg/L as CaCO3
Silica <0·5mg/L
Turbidity OC<0·5 mg/L Chloride Free Residual <0·05 mg/L Fe,Mn,H2S<0·01 mg/L Feed Pressure:30-100 PSI
