Microbubble generation method and device

Abstract

According to the microbubble generation method and device, high-speed liquid jet impacts gas, the constraint effect of a rotary body structure on bubbles is utilized, the bubbles are frequently sheared and broken by the liquid jet to generate a large number of microbubbles, and meanwhile, the high-speed liquid jet impacts wall face jet constructed by a flat plate to promote uniform dispersion of the microbubbles. The microbubble generation method and device have the advantages of simple structure, good microbubble generation effect, large gas treatment capacity, low energy consumption, good bubble dispersing and mixing effect and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of petrochemical industry, and in particular relates to a method and device for generating microbubbles. Background Art

[0002] Compared with macrobubbles with a size greater than 1000 μm, microbubbles have a larger internal pressure and specific surface area, a slow floating speed, a high interphase mass transfer rate, and strong adsorption. They are widely used in sewage treatment, mineral flotation, and nanoparticle preparation. Commonly used microbubble preparation methods include dissolved gas precipitation, electrochemical precipitation technology, microfluidics, and air-entrained dispersion.

[0003] Compared with other methods, the air-entrained dispersion method has the advantages of low equipment cost, easy to scale up, and simple operation, so it is widely used. Among them, the Venturi microbubble generator is the most widely used, which has the advantages of small bubble size and large bubble output, but it has the disadvantages of easy clogging, high energy consumption, and uneven bubble size; the ultra-gravity microbubble generator is also used in the field of chemical synthesis. The bubble size it produces is small and easy to scale up in parallel, but it has high energy consumption, poor bubble dispersion, and high equipment costs.

[0004] In summary, the existing microbubble generation methods have the disadvantages of low energy utilization and high generator manufacturing cost. Therefore, it is urgent to develop a microbubble generation method with high energy utilization, simple structure, high gas-liquid ratio, and small bubble size, and apply it to the field of industrial production. Summary of the invention

[0005] In order to develop a microbubble generation technology with good microbubble generation effect, high energy utilization rate and large processing capacity, the present invention first provides a microbubble generation method, which comprises the following steps: a liquid jet collides with a gas distributor to form an impact jet field including an impact zone, a free jet zone and a wall jet zone; a rotating shell structure is arranged in the impact jet field to regulate the bubble movement trajectory; gas is introduced from the impact zone to cause the gas to be initially broken under the action of high pulsating pressure, and a part of the generated bubbles with larger sizes are confined in the free jet zone by the local negative pressure formed by the rotating shell structure, and a large number of microbubbles are generated through frequent shearing and breaking by the liquid jet; another part of the generated bubbles with smaller sizes and the microbubbles escape from the rotating body structure under the transportation of the wall jet in the wall jet zone and are fully dispersed, thereby finally generating a large number of microbubbles with uniform size distribution.

[0006] In the present invention, "microbubbles" refer to bubbles having a diameter of 1 mm or less.

[0007] In the present invention, a "surface of revolution" geometrically refers to a shape formed by rotating 360 degrees around an axis with an arbitrary curve as a generatrix, and a "revolution shell" geometrically refers to a shell composed only of a surface of revolution or a surface of revolution and a plane.

[0008] In the present invention, the arrangement method of the liquid nozzle, the gas distributor and the rotating shell structure satisfies: the central axes of the gas distributor, the liquid nozzle and the rotating shell structure are in a straight line, the outlets of the gas distributor and the liquid nozzle are opposite, and the liquid nozzle and the rotating shell structure are arranged above the gas distributor; when there is a gas distributor, there must be a liquid nozzle and a rotating shell structure at the same time, that is, in the microbubble generator, the number of gas distributors, liquid nozzles and rotating shell structures is the same.

[0009] According to a preferred embodiment of the present invention, the generatrix of the rotating shell structure is an arc whose curvature and curvature change rate are not always 0, and the cross-sectional diameter of the end connected to the liquid inlet pipe is the smallest, and the cross-sectional diameter of the open end is the largest.

[0010] In order to implement the aforementioned method, the present invention provides a microbubble generating device, which includes: a liquid injection device composed of a liquid nozzle and a liquid inlet pipe connected thereto, a gas injection component composed of a gas distributor and an air inlet pipe connected thereto, and a rotating shell structure with a hole at one end and an open end at the other end; the liquid injection device passes through the hole at the end of the rotating shell structure so that the liquid nozzle is located in the rotating shell structure; the centers of the liquid injection device, the gas injection component and the rotating shell structure are on the same axis, and the liquid nozzle and the rotating shell structure are located above the gas distributor; the liquid injection device and the gas injection component are arranged opposite to each other; there is a distance between the gas distributor and the open end cross-section of the rotating shell.

[0011] According to a preferred embodiment of the present invention, the gas distributor may be a disc-shaped structure. The contact angle between the material of the rotating shell structure and the liquid phase is greater than 90° and the gas cannot be completely adsorbed.

[0012] According to a preferred embodiment of the present invention, at least one pore is provided on the gas distributor, wherein the diameter of the pore is 50 μm-6 mm, preferably 200 μm-2 mm. According to some embodiments of the present invention, the pores on the gas distributor are arranged within the range from the center to a circle 0.5 times the diameter of the gas distributor, and there is at least one pore with a diameter of 50 μm-6 mm. According to some embodiments of the present invention, the gas transported by the air inlet pipe is ejected from the pores, and the outlet diameter of the air inlet pipe is sized so that the outlet of the air inlet pipe completely covers the pores on the gas distributor, and the outlet diameter of the air inlet pipe is less than or equal to the diameter of the gas distributor.

[0013] According to a preferred embodiment of the present invention, the liquid nozzle can be selected from a straight tube of equal diameter and a straight tube of reduced diameter. The straight tube selected is centrally symmetrical and easy to assemble with the rotating body structure.

[0014] According to a preferred embodiment of the present invention, the distance between the gas distributor and the liquid nozzle is 0.5-50 mm, preferably 1-30 mm; the distance between the open end of the rotary shell structure and the gas distributor is 0.5-20 mm, preferably 0.5-15 mm.

[0015] According to a preferred embodiment of the present invention, the ratio of the diameter of the open end section of the rotating shell structure to the diameter of the gas distributor is 0.5-4, preferably 0.5-2, and is selected according to the physical properties of the continuous phase liquid.

[0016] According to a preferred embodiment of the present invention, the cross-sectional diameter of the open end of the rotary shell is 2-15 times, preferably 6-10 times, the cross-sectional diameter of the liquid nozzle outlet.

[0017] According to a preferred embodiment of the present invention, the cross-sectional diameter of the gas distributor is 3-15 times, preferably 6-10 times, the cross-sectional diameter of the liquid nozzle outlet.

[0018] According to a preferred embodiment of the present invention, the flow rate of the liquid flowing out of the liquid nozzle (calculated based on the cross-sectional area of ​​the liquid nozzle outlet) is greater than 1.2 m / s, preferably greater than 2.2 m / s, and the ratio of the volume flow rate of the liquid phase input by the liquid nozzle to the volume flow rate of the gas phase flowing out of the gas distributor (calculated based on the cross-sectional area of ​​the gas outlet) is 0.5-5, preferably 1-3.

[0019] The present invention also provides a microbubble generation method based on the above device, which effectively improves the utilization rate of unit liquid input energy and regulates the bubble movement trajectory to make it break multiple times. The method includes: liquid is transported by a liquid inlet pipe, and a liquid jet is sprayed out through a liquid nozzle; gas is transported by an air inlet pipe and distributed through a gas distributor; gas and liquid interact in the microbubble generation device to generate microbubbles with uniform size distribution; the outlet flow rate of the liquid nozzle is controlled to be greater than 1.2m / s; by adjusting the outlet flow rate u (m / s) of the liquid nozzle, the distance H (m) between the liquid nozzle and the gas distributor, the distance l (m) from the open end of the rotor to the gas distributor, and the diameter D of the cross section of the open end of the rotor 0 (m), liquid nozzle diameter d j (m), gas outlet velocity u g (m / s), gas outlet diameter d g (m) can adjust the average size of the bubble 32 (m) and maximum bubble size d m (m):

[0020]

[0021] Among them, ρ g , l (kg / m 3 ) are gas density and liquid density respectively, μ g , μ l (Pa·s) is the gas viscosity and liquid viscosity, g (m / s 2 ) is the acceleration due to gravity, k 1 , k 2 The value of is only related to physical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the microbubble generator provided by the present invention.

[0023] Figure 2 It is a structural schematic diagram of the cylindrical gas distributor provided by the present invention.

[0024] Figure 3 It is a verification diagram of the maximum bubble size relationship formula provided by the present invention.

[0025] Figure 4 It is a verification diagram of the Sauter average size relationship equation provided by the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0027] The following combination Figure 1-2 The microbubble generator provided by the present invention is described in detail.

[0028] In some embodiments of the present invention, the structure of the microbubble generator is as follows Figure 1As shown, it includes a liquid inlet pipe 1, a rotating shell structure 2, a liquid nozzle 3, a gas distributor 4 and an air inlet pipe 5. The air inlet pipe and the liquid inlet pipe are cylindrical, the outlet end of the air inlet pipe is connected to the gas distributor, the center of the gas distributor and the center of the rotating shell structure are on the same axis, one end of the liquid inlet pipe is connected to the liquid nozzle, and the liquid outlet of the liquid nozzle is inside the rotating shell structure. The liquid nozzle and the rotating shell structure are located above the gas distributor. The liquid nozzle is a circular tube, wherein the diameter of the circular tube outlet is 3-18mm. The gas distributor structure is disc-shaped (with a diameter of 15-40mm, a height-to-diameter ratio of 0.02-0.1, and a disc diameter greater than or equal to the diameter of the outlet end of the air inlet pipe), and the disc is symmetrically arranged with holes within a range of 0.5 times the diameter of the disc with the center of the circle as the center, and the aperture is 0.5-4mm; the rotating shell structure is made of a sparse continuous phase material to ensure that the liquid phase does not adhere to the material, and the diameter of the cross section of the rotating body structure and the open end is 15-50mm. The distance l between the liquid outlet and the outlet end of the gas distributor is 0.5-30 mm. The distance between the open end of the rotary structure and the gas distributor is 0.5-20 mm. The liquid flow rate of the liquid inlet pipe makes the liquid velocity flowing out of the liquid nozzle above 1.2 m / s, and the ratio of the liquid phase volume flow rate flowing out of the liquid nozzle to the gas phase volume flow rate input by the gas distributor is 1-3.

[0029] Example 1

[0030] The structure of the microbubble generator is as follows Figure 1 As shown, it includes a liquid inlet pipe 1, a rotating shell structure 2, a liquid nozzle 3, a gas distributor 4 and an air inlet pipe 5. The air inlet pipe and the liquid inlet pipe are cylindrical, the outlet end of the air inlet pipe is connected to the gas distributor, the gas distributor completely covers the outlet end of the air inlet pipe, the center of the gas distributor is on the same axis as the center of the rotating shell structure, one end of the liquid inlet pipe is connected to the liquid nozzle, and the liquid outlet of the liquid nozzle is inside the rotating shell structure. The liquid nozzle and the rotating body structure are located above the gas distributor. The liquid nozzle adopts a circular tube with an outlet diameter of 4mm, and the gas distributor is disc-shaped (diameter 25mm), with a 2mm hole in the center of the disc. The rotating body structure is made of hydrophobic material (PMMA), and the diameter of the open end section is 30mm. The distance H between the liquid nozzle outlet and the gas distributor is 20mm, and the distance l between the open end of the rotating body and the gas distributor is 5mm. The liquid velocity of the liquid flowing out of the liquid nozzle is 1.66m / s, and the ratio of the gas phase volume flow rate to the liquid phase volume flow rate is 0.23. Using air as the gas experimental medium and water as the liquid experimental medium, a high-speed camera is used to measure the bubble size and distribution generated by the microbubble generator. Figure 3 , Figure 4 As shown, the bubble size generated is 500-1300 μm, the microbubble number fraction is 65%, and the bubble radial dispersion width is 30 mm (1.2 times the diameter of the gas distribution disk).

[0031] Example 2

[0032] The only difference from Example 1 is that the liquid velocity of the liquid flowing out of the liquid nozzle is 2.66 m / s, and a high-speed camera is used to photograph the bubbles generated by the micro-bubble generator, such as Figure 3 , Figure 4 As shown, the bubble size generated is 300-1000 μm, the microbubble number fraction is 76%, the ratio of gas volume flow rate to liquid volume flow rate is 0.14, and the radial dispersion width of the bubbles is 33 mm (1.32 times the diameter of the gas distribution disk).

[0033] Example 3

[0034] The only difference from Example 1 is that the liquid velocity of the liquid flowing out of the liquid nozzle is 3.55 m / s, and a high-speed camera is used to photograph the bubbles generated by the micro-bubble generator, such as Figure 3 , Figure 4 As shown, the bubble size generated is 200-900 μm, the microbubble number fraction is 100%, the ratio of gas volume flow rate to liquid volume flow rate is 0.11, and the radial dispersion width of the bubbles is 38 mm (1.52 times the diameter of the gas distribution disk).

[0035] Example 4

[0036] The only difference from Example 3 is that four pores with a diameter of 1 mm are evenly distributed on the disc-shaped gas distributor, and the center of the pores is 3 mm away from the center of the gas distributor. A high-speed camera is used to photograph the bubbles generated by the microbubble generator. The size of the generated bubbles is 200-1000 μm, the microbubble number fraction is 100%, the ratio of gas volume flow rate to liquid volume flow rate is 0.11, and the radial dispersion width of the bubbles is 39 mm (1.56 times the diameter of the gas distribution disk).

[0037] Example 5

[0038] The only difference from Example 3 is that the distance H between the liquid nozzle outlet and the gas distributor is 15 mm, and a high-speed camera is used to photograph the bubbles generated by the microbubble generator. The size of the generated bubbles is 200-1100 μm, the microbubble number fraction is 96%, the ratio of the gas volume flow rate to the liquid volume flow rate is 0.11, and the radial dispersion width of the bubbles is 43 mm (1.72 times the diameter of the gas distribution disk).

[0039] Example 6

[0040] The only difference from Example 3 is that the cross-sectional diameter of the flow field connecting end of the rotating body component is 45 mm, and the bubbles generated by the microbubble generator are photographed with a high-speed camera. The bubble size generated is 200-1000 μm, the microbubble number fraction is 100%, the ratio of gas volume flow rate to liquid volume flow rate is 0.11, and the radial dispersion width of the bubbles is 45 mm (1.8 times the diameter of the gas distribution disk).

[0041] Comparative Example 1:

[0042] The only difference from Example 1 is that the distance H between the liquid nozzle outlet and the gas distributor is 60 mm (more than 50 mm), the distance l between the open end of the rotor and the gas distributor is 40 mm, and a high-speed camera is used to photograph the bubbles generated by the microbubble generator. The size of the generated bubbles is 1300-2900 μm, the microbubble number fraction is 0%, the ratio of the gas volume flow rate to the liquid volume flow rate is 0.23, and the radial dispersion width of the bubbles is 51 mm (2.04 times the diameter of the gas distribution disk).

[0043] Comparative Example 2:

[0044] The only difference from Example 3 is that the distance H between the liquid nozzle outlet and the gas distributor is 60 mm (more than 50 mm), the distance l between the open end of the rotor and the gas distributor is 40 mm, and a high-speed camera is used to photograph the bubbles generated by the microbubble generator. The size of the generated bubbles is 1100-2300 μm, the microbubble number fraction is 0%, the ratio of the gas volume flow rate to the liquid volume flow rate is 0.11, and the radial dispersion width of the bubbles is 57.5 mm (2.3 times the diameter of the gas distribution disk).

[0045] Comparative Example 3:

[0046] The only difference from Example 3 is that the air holes on the gas distributor are arranged on a circle from the center to 0.8 times the diameter of the gas distributor (exceeding the range of 0.5 times the diameter of the gas distributor), and the bubbles generated by the microbubble generator are photographed with a high-speed camera. The size of the generated bubbles is 900-1900μm, the microbubble number fraction is 15%, the ratio of gas volume flow rate to liquid volume flow rate is 0.11, and the radial dispersion width of the bubbles is 38mm (1.52 times the diameter of the gas distribution disk).

[0047] Comparative Example 4:

[0048] The only difference from Example 3 is that the cross-sectional diameter of the flow field connecting end of the rotating body component is 75 mm (larger than 15 times the cross-sectional diameter of the liquid nozzle outlet), and the bubbles generated by the microbubble generator are photographed with a high-speed camera. The bubble size generated is 1600-4500 μm, the microbubble number fraction is 0%, the bubble aggregation is serious, and the ratio of gas volume flow rate to liquid volume flow rate is 0.11.

[0049] It should be noted that the embodiments and comparative examples described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A method for generating microbubbles, characterized in that The invention comprises the following steps: a liquid jet collides with a gas distributor to form an impact jet field including an impact zone, a free jet zone and a wall jet zone; a rotating shell structure is arranged in the impact jet field to regulate the bubble movement trajectory; gas is introduced from the impact zone to cause the gas to be initially broken under the action of high pulsating pressure, and a part of the generated bubbles with larger sizes are confined in the free jet zone by the local negative pressure formed by the rotating shell structure, and a large number of microbubbles are generated through frequent shearing and breaking by the liquid jet; another part of the generated bubbles with smaller sizes and the microbubbles escape from the rotating body structure under the transportation of the wall jet in the wall jet zone and are fully dispersed, and finally a large number of microbubbles with uniform size distribution are generated.

2. A microbubble generating device, characterized in that: include: A liquid injection device consisting of a liquid nozzle and a liquid inlet pipe connected thereto, a gas injection component consisting of a gas distributor and an air inlet pipe connected thereto, and a rotating shell structure with a hole at one end and an open end at the other end; the liquid injection device passes through the hole at the end of the rotating shell structure so that the liquid nozzle is located in the rotating shell structure; the centers of the liquid injection device, the gas injection component and the rotating shell structure are on the same axis, and the liquid nozzle and the rotating shell structure are located above the gas distributor; the liquid injection device and the gas injection component are arranged opposite to each other; there is a distance between the gas distributor and the open end cross-section of the rotating shell.

3. The microbubble generating device according to claim 2, characterized in that: The generatrix of the rotating shell structure is an arc, the curvature and curvature change rate of the arc are not always 0, and the cross-sectional diameter of the end connected to the liquid inlet pipe is the smallest, and the cross-sectional diameter of the open end is the largest.

4. The microbubble generating device according to claim 2, characterized in that: The gas distributor structure is a disc-shaped structure.

5. The microbubble generating device according to claim 2, characterized in that: The contact angle between the material of the rotating shell structure and the liquid phase is greater than 90° and the gas cannot be completely adsorbed.

6. The microbubble generating device according to claim 2, characterized in that: The air holes on the gas distributor are arranged within the range from the center to a circle 0.5 times the diameter of the gas distributor, and there is at least one air hole with a diameter of 50 μm-6 mm.

7. The microbubble generating device according to any one of claims 2 to 6, characterized in that: The distance between the liquid nozzle outlet and the gas distributor is 0.5-50 mm; the distance between the open end of the rotary shell structure and the gas distributor is 0.5-30 mm.

8. The microbubble generating device according to any one of claims 2 to 6, characterized in that: The cross-sectional diameter of the open end of the rotating shell structure is 2-15 times the cross-sectional diameter of the liquid nozzle outlet, the cross-sectional diameter of the gas distributor is 3-15 times the cross-sectional diameter of the liquid nozzle outlet, and the cross-sectional diameter of the open end of the rotating shell is 0.5-4 times the cross-sectional diameter of the gas distributor.

9. A method for generating microbubbles based on the microbubble generating device according to any one of claims 2 to 6, characterized in that: include: The liquid is transported by the liquid inlet pipe and ejected as a liquid jet through the liquid nozzle; The gas is transported by the inlet pipe and distributed through the gas distributor; The gas and liquid interact in the microbubble generating device to produce microbubbles with uniform size distribution; The liquid nozzle outlet flow rate is controlled to be greater than 1.2 m / s; the ratio of the liquid phase volume flow rate input by the liquid injection device to the gas phase volume flow rate input by the gas injection component is 0.5-10; by adjusting the liquid nozzle outlet flow rate u, the distance H between the liquid nozzle and the gas distributor, the distance l between the open end of the rotating body and the gas distributor, the diameter D0 of the cross section of the open end of the rotating body, and the diameter d of the liquid nozzle j , gas outlet flow rate u g , Gas outlet diameter d g Ability to adjust the average bubble size d 32 and the maximum bubble size d m : Among them, ρ g , l They are respectively the gas density and the liquid density, in kg / m 3 , μ g , μ l is the gas viscosity and liquid viscosity, in Pa·s, g is the gravitational acceleration, in m / s 2 , k1, k2 are constants, and their values ​​are only related to physical properties. g The unit is m / s, H, l, D0, d j ,d g ,d 32 ,d m The unit is m.

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