Device and method for improving desalination efficiency of desalination membrane by using in-situ nanobubbles

Abstract

The invention relates to the technical field of membrane separation, in particular to a device and method for improving desalination efficiency of a desalination membrane by using in-situ nanobubbles, and the device comprises one or more than one gas-liquid mixing and dissolving device and one or more than one membrane desalination device; desalted water sequentially passes through one or more gas-liquid mixing and dissolving devices and one or more membrane desalting devices, gas dissolution saturation of water is realized by arranging the gas-liquid mixing and dissolving device on a pipeline at the front section of the membrane desalting device, and after the water enters the membrane desalting device, a salting-out effect is formed in a high-salinity area on the surface of a desalting membrane, so that the desalting effect is realized. The dissolved gas molecules are separated out and gathered to form a large number of nano bubbles, the salt crystallization process is dispersed, the number of crystals is increased, but the sizes of the crystals are reduced, the blockage degree of salt crystallization to a membrane is relieved, the desalination efficiency is improved, the follow-up membrane cleaning difficulty is reduced, and the device is simple in structure, low in energy consumption and very suitable for reverse osmosis desalination and pervaporation desalination processes.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation, and in particular to a device and a method for improving the desalination efficiency of a desalination membrane by utilizing in-situ nanobubbles. Background Art

[0002] Membrane technology is a highly efficient separation technology, among which membrane processes used in the desalination process include reverse osmosis membrane desalination, pervaporation and other processes. Among them, reverse osmosis membrane desalination mainly uses high pressure to force water molecules to pass through the reverse osmosis membrane, intercepting soluble salt ions to achieve the desalination process; pervaporation is mainly driven by the vapor pressure difference on both sides of the membrane, water molecules flow through the liquid in the membrane, undergo phase change, and finally pass through the membrane in gaseous form and condense and collect.

[0003] Due to the high ion concentration formed on the membrane surface during the above process, salt precipitation occurs, causing membrane blockage and greatly affecting membrane efficiency. The use of bubbles to disturb the membrane surface to interfere with the salt precipitation process on the membrane surface and reduce the degree of membrane contamination is a membrane cleaning technology that has emerged in recent years. Patent 201910393332.3 provides a solution for improving the cleaning effect of reverse osmosis membranes by combining micro-nano bubbles with ultrasonic technology. However, the membrane surface containing a large number of microporous structures has a very strong inhibitory effect on ultrasound. At the same time, micron-sized bubbles are mostly used as fluid tracers in water because they flow with water in water, so it is difficult to enter the boundary layer, and membrane contamination is in the boundary layer; on the other hand, the size of nanobubbles is generally around 100nm, which is much smaller than the length of conventional ultrasonic waves, so traditional ultrasound cannot couple with nanobubbles.

[0004] The solubility of gas in aqueous solution decreases with the increase of ion concentration, which is usually called "salting out effect". The increase of ions leads to the increase of solvation degree of water molecules, which in turn weakens the attraction between gas molecules and water molecules, and then "releases" a large number of "dissolved" gas molecules. The above-mentioned "dissolved" gas molecules are squeezed by the solvated water molecules, and then aggregated to form nanobubbles through hydrophobic force. The charged nanobubbles can act as crystallization nuclei in high-concentration salt solutions. Due to the appearance of a large number of new "crystallization nuclei", the salt crystallization process can be dispersed, the number of crystals increases but the size decreases, and the blockage of the membrane by salt crystallization is alleviated, thereby improving the efficiency and effect of the subsequent membrane cleaning process.

[0005] In view of this, the present invention provides a device and method for improving the desalination efficiency of a desalination membrane by utilizing in-situ nanobubbles. The device achieves gas dissolution saturation of water by arranging a liquid mixing and dissolving device in the front-end pipeline of the membrane desalination equipment. After entering the membrane desalination equipment, a "salting-out effect" is formed in the high-salinity area on the surface of the desalination membrane, and dissolved gas molecules are precipitated and aggregated to form a large number of nanobubbles, which disperse the salt crystallization process, increase the number of crystals but reduce their size, alleviate the degree of blockage of the membrane by salt crystallization, improve the desalination efficiency, and reduce the difficulty of subsequent membrane cleaning. The device has a simple structure and low energy consumption, and is very suitable for use in reverse osmosis desalination and pervaporation desalination processes. Summary of the invention

[0006] The object of the present invention is to provide a device and method for improving the desalination efficiency of a desalination membrane by using in-situ nanobubbles, so as to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A device and method for improving the desalination efficiency of a desalination membrane by using in-situ nanobubbles, characterized in that it comprises one or more gas-liquid mixed dissolution devices and one or more membrane desalination devices; salt water passes through one or more gas-liquid mixed dissolution devices and one or more membrane desalination devices in sequence;

[0009] Wherein, the membrane desalination device includes a reverse osmosis desalination device or a pervaporation desalination device;

[0010] Among them, the function of the gas-liquid mixed dissolution device is to achieve gas-water mixed dissolution and gas-liquid phase equilibrium through mechanical stirring and hydraulic stirring;

[0011] Among them, the gas-liquid mixing and dissolving device includes a gas source, a gas supply pipeline, and a gas-liquid mixer; the gas-liquid mixer can be a combination of one or more of a venturi water ejector, a static mixer, an absorption tower, and a gas-liquid mixing pump.

[0012] Furthermore, the gas-liquid mixing pressure of the gas-liquid mixing and dissolving device is not less than the operating pressure of the membrane desalination device;

[0013] Furthermore, the gas source used in the gas-liquid mixed dissolution process can be compressed air, cylinder nitrogen, or cylinder oxygen.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: the device realizes gas dissolution saturation of water by arranging a liquid mixing and dissolving device in the front-end pipeline of the membrane desalination equipment. After entering the membrane desalination equipment, a "salting-out effect" is formed in the high-salinity area on the surface of the desalination membrane, and the dissolved gas molecules are precipitated and aggregated to form a large number of nanobubbles, which disperse the salt crystallization process, increase the number of crystals but reduce their size, alleviate the blockage of the membrane by salt crystallization, improve the desalination efficiency, and reduce the difficulty of subsequent membrane cleaning. The device has a simple structure and low energy consumption, and is very suitable for use in reverse osmosis desalination and pervaporation desalination processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an overall schematic diagram of the present invention.

[0016] The serial numbers in the figure are: 1 is the water inlet pipeline, 2 is the gas-liquid mixing pump, 3 is the nitrogen cylinder, 4 is the air inlet pipeline, 5 is the gas-water separation tank, 6 is the automatic exhaust valve, 7 is the reverse osmosis water inlet pipeline, 8 is the reverse osmosis membrane assembly, 9 is the water outlet pipeline, and 10 is the concentrated water pipeline. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0019] In the description of this patent, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", and "set" should be understood in a broad sense. For example, it can be fixedly connected or set, or it can be detachably connected or set, or connected or set in one piece. For ordinary technicians in this field, the specific meanings of the above terms in this patent can be understood according to specific circumstances. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically limited.

[0020] See also Figure 1As shown, the present invention provides an embodiment of a device and method for improving the desalination efficiency of a desalination membrane by using in-situ nanobubbles:

[0021] The nitrogen in the nitrogen cylinder 3 enters the gas-liquid mixing pump 2 through the air inlet pipe 4, and the salt water enters the gas-liquid mixing pump 2 through the water inlet pipe 1. The blades in the gas-liquid mixing pump 4 rotate at a high speed to produce a mechanical cutting effect. The nitrogen and the salt water are fully mixed in the pump, and the gas-liquid phase equilibrium is achieved under a pressure of 8 Bar. The undissolved nitrogen is separated from the salt water in the gas-water separation tank 56 and discharged through the automatic exhaust valve 6; the dissolved saturated salt water enters the reverse osmosis membrane assembly 8 with an operating pressure of 8 Bar through the reverse osmosis water inlet pipe 7. Due to the proximity to the reverse osmosis membrane surface, the saturated salt water enters the reverse osmosis membrane assembly 8 with an operating pressure of 8 Bar. The salt concentration in the surface area is high. Due to the "salting out effect", the dissolved nitrogen molecules are precipitated and aggregated in the brine near the membrane surface to form a large number of nanobubbles. The charged nanobubbles on the surface can act as crystallization nuclei in the high-concentration salt solution. Due to the appearance of a large number of new "crystallization nuclei", the number of crystals increases but the size decreases, which alleviates the blockage of the membrane by salt crystallization, improves the desalination efficiency, and reduces the difficulty of subsequent membrane cleaning. The desalted water is discharged from the reverse osmosis membrane assembly 8 through the outlet pipe 9, and the concentrated brine is discharged from the reverse osmosis membrane assembly 8 through the concentrated water pipe 10.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: the device realizes gas dissolution saturation of water by arranging a liquid mixing and dissolving device in the front-end pipeline of the membrane desalination equipment. After entering the membrane desalination equipment, a "salting-out effect" is formed in the high-salinity area on the surface of the desalination membrane, and the dissolved gas molecules are precipitated and aggregated to form a large number of nanobubbles, which disperse the salt crystallization process, increase the number of crystals but reduce their size, alleviate the blockage of the membrane by salt crystallization, improve the desalination efficiency, and reduce the difficulty of subsequent membrane cleaning. The device has a simple structure and low energy consumption, and is very suitable for use in reverse osmosis desalination and pervaporation desalination processes.

[0023] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A device and method for improving the desalination efficiency of a desalination membrane using in-situ nanobubbles, characterized in that: It includes one or more gas-liquid mixed dissolution devices and one or more membrane desalination devices; the salt water passes through one or more gas-liquid mixed dissolution devices and one or more membrane desalination devices in sequence; Wherein, the membrane desalination device includes a reverse osmosis desalination device or a pervaporation desalination device; Among them, the function of the gas-liquid mixed dissolution device is to achieve gas-water mixed dissolution and gas-liquid phase equilibrium through mechanical stirring and hydraulic stirring; Among them, the gas-liquid mixing and dissolving device includes a gas source, a gas supply pipeline, and a gas-liquid mixer; the gas-liquid mixer can be a combination of one or more of a venturi water ejector, a static mixer, an absorption tower, and a gas-liquid mixing pump.

2. The device and method for improving the desalination efficiency of a desalination membrane by using in-situ nanobubbles according to claim 1, characterized in that: The gas-liquid mixing pressure of the gas-liquid mixing dissolution device shall not be less than the operating pressure of the membrane desalination device.

3. The device and method for improving the desalination efficiency of a desalination membrane by using in-situ nanobubbles according to claim 1, characterized in that: The gas source used in the gas-liquid mixed dissolution process can be compressed air, cylinder nitrogen, or cylinder oxygen.

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