What do you know about the art of reverse osmosis desalination? Detailed explanation. Desalination refers to the skill and process of obtaining fresh water from seawater. There are many desalination techniques, including distillation, membrane process (reverse immersion, electrodialysis membrane transpiration, etc.), ion exchange, etc., but only distillation and reverse immersion are suitable for large-scale desalination. At present, reverse immersion is one of the main treatment skills of seawater desalination. Reverse immersion is the separation of seawater and fresh water by a semi-permeable membrane that allows only the passage of the solvent but not the penetration of the solute. In general, fresh water diffuses to one side of the seawater through a semi-permeable membrane. Because of the resistance of the semi-permeable film, the liquid level on the seawater side gradually rises until it stops rising to a certain height. At this time, the side of the water column where the static pressure is higher than that of seawater is called penetration pressure. If an external pressure higher than the penetration pressure of seawater is applied to one side, the purified water in seawater will penetrate into the fresh water.

Characteristics of reverse immersion desalination equipment

1. Reverse immersion desalination equipment has good water quality, less energy consumption and low cost of water production;

2. Compact structure, diverse forms, suitable for different equipment space;

3. Easy equipment and operation;

4. Perfect pretreatment system, suitable for different water quality conditions;

5. Mature production skills of anti-permeable film data and film components, and high function of film and film components;

6. International first-class anti-permeable membrane components and high pressure pumps, quality, safety and reliability;

7. Seawater desalination is a unit combination type, and the construction scale can be gradually expanded, which is easy to promote and apply.

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Overview of reverse immersion desalination process

Seawater disinfection and algae killing, there are many microorganisms, bacteria and algae in seawater. The proliferation of bacteria and algae and the growth of microorganisms in seawater not only bring a lot of trouble to water intake equipment, but also directly affect the normal operation of desalination equipment and process pipelines. Therefore, chemical agents such as liquid chlorine, sodium hypochlorite and copper sulfate are often used in desalination projects to kill bacteria and algae.

Coagulation filtration

In order to further improve the inlet water quality and reduce the turbidity of the inlet water, multimedia filters are generally installed after condensation filtration to further remove trace suspended solids and particles in the water to ensure further reverse penetration. Improve water quality.

Scale inhibitors and reducing agents

In order to better adhere to the water quality of the system, it is necessary to add anti-scale agents to the system to adhere to better water quality. In addition, because oxidizing agents are added to the pretreatment of anti-immersion sterilization, it is necessary to add reducing agents to reduce the residual chlorine in the water of the anti-immersion system, and then make the residual chlorine in the water of the anti-immersion system less than 0.1ppm (or ORP <200mV), which meets the requirements of the anti-immersion system for the content of oxidizing substances in the water.

Safety filter

Because of the high salt content in sea water, the safety filter must be made of 316L data. The aperture of the filter element is generally 5μM. Prior to the filtration of the high-pressure pump, the seawater will block the impurities in the seawater with a diameter greater than 5μm, and then ensure the safe, long-term, stable operation of the high-pressure pump, the energy recovery equipment and the composition of the anti-immersion membrane elements.

High pressure pump and energy recovery equipment

High pressure pump and energy recovery equipment are important equipment to provide energy conversion and energy saving for reverse immersion desalination equipment. According to the flow and pressure required by the reverse immersion desalination equipment, the energy recovery equipment has a turbine structure, which can use the pressure of the concentrated seawater discharged by the reverse immersion to improve the inlet pressure by 30%, and then effectively use the energy of the concentrated water, reduce energy consumption, and then effectively reduce the operating cost.

Anti-penetration elements and equipment

The back permeation membrane element is the core component of the back permeation desalination equipment. The desalination film corresponding to the desalination equipment system should be selected. According to the different planning of the system, different membrane elements can be selected. The anti-permeable membrane element has a high desalting rate, outstanding pressure resistance, oxidation resistance and pollution resistance. The data of the desalination anti-penetration equipment system should be made of 316L stainless steel in the high pressure part to prevent the corrosion of the high pressure pipeline caused by the high salinity water quality of the seawater.

System control

The control system of anti-saturating desalination equipment generally uses PLC to constitute a control system of decentralized sampling control and centralized monitoring operation. Set high and low voltage maintenance switches and active switching equipment according to process parameters. When the conductivity, flow and pressure are abnormal, active switching, active interlock alarm and shutdown can be completed to maintain the high pressure pump and anti-permeable membrane elements. High pressure pump start and stop frequency control, complete the soft operation of the high pressure pump, save energy, prevent water hammer or back pressure on the high pressure pump and membrane assembly damage. The program can be programmed to complete low-pressure active flushing before and after starting and closing the anti-saturating equipment. Especially when the equipment is closed, the metastable state of the thick seawater will be transformed into deposition and contaminate the membrane surface. The active flushing of low-pressure desalinated water can replace concentrated seawater, maintain the membrane surface from pollution, and extend the service life of the membrane. System temperature, flow, water quality, water yield and other relevant parameters can be displayed, stored, counted, tabulated and printed. The dynamic process picture in the monitoring operation is clear and intuitive, and the system control simplifies the manual operation, ensuring the active, safe and reliable operation of the system.