Talking about the industrial application of two-stage reverse osmosis + EDI water treatment
1. Multimedia Filtration
The main task of this stage is to roughly filter the tap water to prepare for entering the reverse osmosis membrane, to ensure a certain water quality before entering the reverse osmosis membrane, so as to protect the use effect and service life of the reverse osmosis membrane. The process is to filter the tap water of the raw water tank through fine sand, activated carbon and precision filters to remove impurities, organic matter, colloids, suspended solids, etc. After coarse filtration, the water quality has been improved to a certain extent. and allowed to proceed to the next link.
Two, one-stage reverse osmosis
The coarsely filtered water passes through the reverse osmosis membrane, which is the first-level reverse osmosis. The reverse osmosis membrane is a semi-permeable membrane, which can prevent the passage of large ions such as Ga2+, Mg2+, Fe-2, SO4-2, Cl-1, Na+, etc. To ensure the effect of reverse osmosis and protect the reverse osmosis membrane, it is necessary to continuously add scale inhibitors to the reverse osmosis container, and at the same time, it must ensure that the water temperature is above 25 ℃, (use a steam heat exchanger in winter) and ensure a certain water pressure, (use vertical Pump) Under a certain pressure, the ion-containing water is squeezed through the reverse osmosis membrane, thereby forming two kinds of water, all the water that passes through the reverse osmosis membrane, that is, the finished water enters the next link, and the water that does not pass through the reverse osmosis membrane is discharged. , the water treated by the first-level reverse osmosis will enter the next link - the second-level reverse osmosis.
Three, two reverse osmosis
The principle of secondary reverse osmosis is the same as that of primary reverse osmosis. Its function is to further remove salt in water, (Ga2+, Mg2+, Fe-2, SO4-2, Cl-1, Na+ plasma) to further improve water quality. After reverse osmosis, the water conductivity can be close to 1MΩ.CM. After the first and second reverse osmosis pretreatment, the remaining water becomes the feed water of EDI, and the water (concentrated water) that has not passed through the reverse osmosis membrane is discharged in time, and the ratio is generally 1:3, that is, every ton of production Qualified water, about 3 tons of concentrated water (reclaimed water) will be discharged.
4. EDI (Electro deionization) processing
The water after the secondary reverse osmosis is stored in the intermediate water tank, and more than 99% of its ions have been removed. However, in order to further improve the water quality, produce ultrapure water, and remove trace elements and CO2 dissolved in the water, it must also pass electricity. Dialysis, that is, EDI treatment, the principle is as follows, EDI is continuous electric desalination, which uses mixed ion exchange resin to adsorb the anions and cations in the feed water. the process of removing the membrane. In this process, the ion exchange resin is continuously regenerated by electricity, so there is no need to use acid and alkali to regenerate it. This technology can replace traditional ion exchange devices and produce ultrapure water with resistivity up to 18MΩ.CM. This process technology is known as a revolution in the water treatment industry. Compared with traditional ion exchange, EDI has the following advantages: EDI does not need chemical regeneration; EDI does not need to be shut down during regeneration; provides more stable water quality; low energy consumption; convenient operation, low labor intensity; low operating costs.
5. Preservation and water supply of pure water
The water after EDI treatment can be finished water, which can be stored in the pure water tank. In order to ensure the water quality, nitrogen sealing is generally adopted, that is, nitrogen is filled from the top of the pure water tank. After the water is supplied, the liquid level solenoid valve cooperates with the PLC. When the water level of the pure water tank is lower than the low water level, the PLC starts the water production program, and the whole system starts to produce water until the water level of the pure water tank reaches the high water level, and the system stops water production, so The cycle is repeated, and there is always a certain water level in the pure water tank.
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