Reverse Osmosis System Design
Grade: refers to the number of times of raw water infiltration, that is, the number of times of produced water passing through reverse osmosis membrane elements. The desalination rate of primary reverse osmosis can reach 98 99 percent , so multi-stage reverse osmosis can achieve a desalination rate of more than 99.5 percent .
Section: refers to the number of times that the raw water flows through the pressure vessel, that is, the number of times that the concentrated shrinkage flows through different pressure vessels.
As required, multiple membrane modules can be arranged into one stage, two stages or even multiple stages, and the membrane modules in each stage can be arranged into one stage, two stages or even multiple stages. The so-called first stage means that the feed liquid is separated by primary pressurized reverse osmosis, the second stage means that it is separated by secondary pressurized reverse osmosis, and so on; In the same stage, the same membrane modules are arranged into a segment.
The basic arrangement and combination of reverse osmosis membrane can be divided into the following six ways:
1. One stage one section continuous type
After membrane treatment, the permeated water and concentrated liquid are continuously led out of the system. This method is characterized by low water recovery.
2. One stage one stage circulating type
Return part of the concentrated liquid to the feed liquid storage tank, mix it with the feed liquid, and separate it again through the reverse osmosis membrane module. Characteristics: the water quality of permeate has decreased.
3. One stage multi-stage continuous type
The concentrated liquid of the previous section is used as the raw material liquid of the next two sections, which is cut and continuously discharged through water. It is suitable for occasions with large water treatment capacity. The recovery rate is high and the number of concentrated solution is reduced, but the proportion of solute in concentrated solution is high.
4. One stage multi-stage circulating type
The permeated water of the next section is used as the feed liquid of the previous section for separation. In this way, the concentrate can obtain higher concentration, which is suitable for separation with concentration as the main purpose.
5. Multi section conical arrangement
Since the sections are connected in parallel and the sections are connected in series, it can not only meet the water recovery requirements of the reverse osmosis system, but also ensure that there is roughly the same flow state in each component in the device. A high-pressure pump is required to prevent the decline of production efficiency.
6. Multi stage and multi-stage configuration of reverse osmosis membrane module
The multi-stage and multi-stage configuration of the reverse osmosis membrane module also has a circulating type, which separates the permeated water of the first stage as the feed water of the next stage again, so as to lead the permeated water of the last stage out of the system. The concentrated liquid is mixed with the feed liquid from the later stage to the front stage, and then separated. This method improves the recovery rate and water quality, but the pump consumption increases and can be divided into continuous type.
