Electrodeionization (EDI) is a new water treatment technology that combines two mature water purification technologies, electrodialysis and ion exchange. When water passes through the EDI membrane stack, the anions and cations in the water are first adsorbed and conducted by the ion exchange resin, and at the same time, under the action of a direct current electric field, these anions and cations are respectively removed through the anion-cation exchange membrane into the concentrated water chamber. In this process, the ion exchange resin is continuously regenerated from the H+ and OH- produced by hydrolysis. The dissolved salt in the water can be removed under the condition of low energy consumption and no chemical regeneration, so that the high resistivity product water can have a large flow rate. , continuous production.
Primary EDI: EDI purified from RO pure water using only one stage of pure water is called primary EDI.
Secondary EDI: EDI purified from pure water in a two-stage pure water chamber is called secondary EDI.
The advancement of secondary EDI technology
3.3.2.1 Advantages of primary EDI technology
Compared with traditional ion exchange to prepare ultrapure water technology, EDI technology has the following advantages:
1 No need to use chemical regenerating agent, no pollution in the production process, it is clean production;
2 Regeneration does not require downtime, and it can continuously produce high-quality water with stable quality (5~10MΩ·cm);
3 low power consumption and high water utilization rate;
4 The equipment runs safely and reliably, with simple maintenance; low operating cost; small floor space and saving construction cost.
3.3.2.2 Advantages of secondary EDI technology
1 Two-stage EDI pure water chamber is connected in series, and the water production resistivity is extremely high and stable.
2 Secondary EDI concentrated water in parallel, shared by extreme water, saving water resources and high water utilization rate
3 Secondary EDI electrode plates are shared, using a set of regulated steady current DC power supply to save energy
4 Secondary EDI integration reduces equipment connection piping, instrumentation and control systems, greatly reducing equipment costs
5 Secondary EDI work at the same time, regenerate, and continuously supply water throughout the day
6 Secondary EDI does not require acid-base regeneration, no acid-base wastewater discharge
7 Secondary EDI ultrapure water without polishing mixed bed or fine mixing bed, no filter consumables
Advancement of monitoring and control technology
It adopts transmitters such as pressure, flow, liquid level, conductance, resistance and PH, and adopts A/D converter, PLC programmable controller and human-machine interface. Function: Man-machine interface displays data parameters such as flow, pressure, liquid level, conductance, resistance, etc. It can adjust two high and low control points of each parameter, and can store 360 ??days of work data for ready query and dynamic display of system workflow. Working parameters at various points, exceeding the standard alarm, the system is fully automatic control, no personnel is required to be on duty.
In summary, the first-stage RO+ secondary EDI purified water process is the most advanced laboratory purified water process for ultra-pure water machines. Its advanced nature is as follows:
1. The water quality is high, and the ultra-pure water with a resistivity of 18 MΩ·cm or more can be continuously produced.
2. It is not affected by the change of tap water, and is not affected by the decline of reverse osmosis rate. The water quality of the produced water is stable for a long time.
3. Pretreatment does not use conventional filter cartridge consumables, does not produce consumable garbage, and does not pollute the environment.
4. The refined part does not use the resin purification column, does not produce consumable garbage, and does not pollute the environment.
5. Save water, save electricity, and conserve resources, and truly achieve the goal of reducing consumption and reducing emissions and conserving resources.
6, no need for acid and alkali regeneration, to achieve zero discharge of sewage.
7. It is not only suitable for use in areas with low salt content in tap water, but also in areas with high salt content in tap water.
