Microbubble generating device and method

Abstract

According to the microbubble generating device and method, a high-speed jet flow is restrained by using a limited space composed of an impact flat plate and a semi-closed cavity, and a wall jet flow formed after the high-speed jet flow impacts the flat plate is restrained to form local circulating flow. During continuous parallel flow air inlet, a section of air column is formed in the cavity, the jet flow main body impacts the flat plate to entrain surrounding air, and a large number of microbubbles are generated; during intermittent parallel-flow air inlet, bubbles are broken for multiple times along with the movement of circulating fluid; and the generated microbubbles are conveyed by the wall jet flow, penetrate through the gap of the local closed space and are uniformly dispersed. The method has the advantages of simplicity in implementation, high utilization rate of microbubble generation energy, large gas treatment capacity and good bubble dispersing and mixing effects.

Description

Technical Field

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

[0002] Microbubbles have the advantages of small size, high stability, long residence time, large specific surface area and self-pressurization effect, which can significantly increase the contact area and contact time between gas and liquid phases and enhance the mass transfer rate between gas and liquid phases. The unique advantages of microbubbles in the field of chemical synthesis have gradually developed the application of microbubble enhancement technology in the field of chemical processes.

[0003] From the perspective of industrial application, the generation of microbubbles currently adopts the pressurized dissolution method, microporous aeration method and Venturi method. The pressurized dissolution method uses the high pressure of the pressurized gas dissolving tank to dissolve a large amount of gas in the liquid phase, and then the pressure is sharply reduced through the releaser, so that the supersaturated gas is released from the liquid phase in the form of microbubbles. In this method, the gas dissolving tank determines the microbubble yield, but the equipment cost of this method is high; the microporous aeration method ventilates the liquid through a perforated plate or porous medium, which can form a large number of bubbles with low energy consumption. In order to reduce the particle size of microbubbles, a smaller pore size can be used, or external forces such as shear flow field and mechanical vibration can be used to make microbubbles fall off from the orifice more easily. This method has a good microbubble generation effect, but the application range is narrow; the Venturi method mainly uses the shearing and collision effects of the flow field to break up larger cavitations to form microbubbles. The particle size is relatively large and the monodispersity is poor, but the yield and energy efficiency are high, which has advantages in large-scale applications. In summary, it is of great significance to develop a microbubble generation method that can be applied on a large scale, has good generation effect and high energy utilization rate. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a microbubble generating device and method.

[0005] The microbubble generator provided by the present invention comprises a liquid input component consisting of a liquid inlet pipe and a liquid nozzle interconnected with the liquid inlet pipe; a gas input component consisting of a gas nozzle and a matching gas inlet pipe; an incompletely closed space consisting of a cavity structure with one end open and an impact plate, wherein the open end of the cavity structure is located above the impact plate and there is a certain gap between the cavity structure and the impact plate; the liquid input component and the gas input component penetrate into the cavity structure, the liquid nozzle and the gas nozzle are both located inside the cavity body, the liquid nozzle is opposite to the impact plate and there is a certain distance between the two.

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

[0007] In the present invention, a "cavity structure" refers to a geometric body surrounded by multiple planes or curved surfaces and at least one plane is not closed. These planes or curved surfaces are called the walls of the cavity.

[0008] According to a preferred embodiment of the present invention, the liquid inlet pipe is vertically downward, and the liquid nozzle is directly opposite to the impact plate; the gas input component can enter the cavity structure from the top surface or side surface of the cavity structure.

[0009] According to a preferred embodiment of the present invention, the shape of the cavity structure can be a shell-column structure, a hollow platform or a hollow cone.

[0010] According to a preferred embodiment of the present invention, the impact plate structure may be a column or a platform column.

[0011] According to a preferred embodiment of the present invention, the center of the impact plate, the liquid nozzle and the central axis of the cavity structure are in a straight line; the gas input from the gas inlet is in parallel flow contact or cross flow contact with the liquid input from the liquid nozzle.

[0012] According to a preferred embodiment of the present invention, the cavity structure has at least one air hole for gas input component to inlet gas, wherein the diameter of the air hole is 50 μm-6 mm, preferably 200 μm-2 mm. Preferably, the outlet (gas inlet position) of the gas nozzle is downstream of the liquid jet.

[0013] According to a preferred embodiment of the present invention, the liquid nozzle may be a straight tube of equal diameter or a straight tube of reduced diameter. The shape of the straight tube is highly related to the shape of the cavity structure, and a circular tube of equal diameter is preferred.

[0014] According to a preferred embodiment of the present invention, the adjustment range of the gap width h1 between the cavity structure and the impact plate is related to the unit volume input work E of the input flow field. k , the volume of the cavity body V, and the distance l between the liquid nozzle and the impact plate satisfy:

[0015]

[0016] Where k is a constant related to the physical properties of the liquid, h1 and l are in m, and E k The unit is J / m 3 , V in m 3 .

[0017] The present invention further provides a method for generating microbubbles, comprising the following steps: a liquid jet ejected from a liquid nozzle collides with an impact plate to form an impact jet field including an impact zone, a free jet zone and a wall jet zone; a wall jet in the wall jet zone passes through a gap formed by an open end of the cavity structure and the plate; a gas is continuously or intermittently introduced into the cavity structure through a gas nozzle;

[0018] When gas is continuously introduced into the cavity structure, an air chamber is formed in the cavity structure, and the impact jet entrains the gas in the air chamber to generate a large number of microbubbles; the size of the formed microbubbles is further reduced and fully dispersed under the shearing, crushing and transportation of the liquid jet in the wall jet area, and finally a large number of microbubbles with uniform size distribution are generated;

[0019] When gas is intermittently introduced into the cavity structure, the impact jet carries the gas to form a circulating flow in the cavity, frequently shearing the gas to generate a large number of microbubbles; the size of the formed microbubbles is further reduced and fully dispersed under the shearing, crushing and transportation of the liquid jet in the wall jet area, and finally a large number of microbubbles with uniform size distribution are generated.

[0020] According to a preferred embodiment of the present invention, the liquid flow rate out of the liquid nozzle is greater than u j,min ,u j,min Liquid nozzle diameter d j , liquid viscosity coefficient μ, liquid surface tension σ, and liquid density ρ satisfy the following relationship:

[0021]

[0022] In the formula, u j,min The unit is m / s, d j The unit is m, μ is m 3 , μ is in Pa·s, σ is in N / m, ρ is in kg / m 3 .

[0023] According to a preferred embodiment of the present invention, when gas is intermittently introduced into the cavity structure, the distance h2 between the gas nozzle and the liquid nozzle cannot exceed the initial section range of the jet, and the specific relationship satisfies:

[0024]

[0025] Where l is the distance between the liquid nozzle and the impact plate, in m, and u j is the liquid nozzle inlet speed, u j,min 、u j The unit is m / s, and the unit of h2 is m.

[0026] The equivalent circumscribed circle diameter of the open end cross section of the cavity structure is 9-225 times, preferably 36-100 times, the cross section diameter of the liquid nozzle outlet.

[0027] The cross-sectional area of ​​the impact plate is 1-2 times, preferably 1 times, the cross-sectional area of ​​the equivalent circumscribed circle of the open end of the cavity structure.

[0028] According to a preferred embodiment of the present invention, the cross-sectional area of ​​the impact plate is 9-225 times, preferably 36-100 times, the cross-sectional area of ​​the liquid nozzle outlet.

[0029] According to a preferred embodiment of the present invention, the ratio of the volume flow rate of the liquid input by the liquid nozzle to the volume flow rate of the gas input by the gas nozzle is 0.05-5. When the gas is continuously introduced into the cavity structure, the average size of the microbubbles finally generated is d 32 The distance h1 between the open end of the cavity body and the impact plate, the distance l between the liquid nozzle and the impact plate, and the liquid nozzle liquid inlet speed u j , Liquid nozzle diameter d j , cavity volume V, gas volume flow rate Q g The relationship between them is:

[0030]

[0031] Where a is a constant related only to physical properties.

[0032] When gas is intermittently introduced into the cavity structure, the microbubbles finally generated have an average size d 32 The relationship between the work per unit volume of the jet input, the cavity volume, and the distance h1 between the open end of the cavity body and the impact plate is:

[0033]

[0034] Where b is a constant related only to physical properties. j The unit is m / s, l, d 32 、h1、d j Unit: m, Q g Unit: m 3 / s, V in m3, E k The unit is J / m 3 .

[0035] The microbubble generating method provided by the present invention is simple to use, convenient to install and use, has a high gas processing capacity and low energy consumption, has a good bubble dispersion effect, and can ensure full mixing of gas and liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural schematic diagram of the microbubble generator provided by the present invention.

[0037] Figure 2 It is a schematic structural diagram of the impact plate provided by the present invention.

[0038] Figure 3 The continuous air intake time d provided by the present invention 32 Verification diagram of equation (4).

[0039] Figure 4 The intermittent air intake time d provided by the present invention is 32 Verification diagram of equation (5) (20 times / min, 1s / time, interval 2s). DETAILED DESCRIPTION

[0040] The present invention is described in detail below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0041] The following combination Figure 1-2 The microbubble generator provided by the present invention is described in detail.

[0042] In some embodiments of the present invention, the structure of the microbubble generator is as follows Figure 1 As shown, it includes a liquid inlet pipe 1, a cavity 2, a liquid nozzle 3, an impact plate 4 and an assembly 5 of an air inlet pipe and a gas nozzle. The air inlet pipe and the liquid inlet pipe are cylindrical, the air inlet pipe is installed at the end or side of the cavity, and enters the cavity structure through the air hole. The liquid nozzle is arranged at the end of the liquid inlet pipe, and the central axis of the liquid nozzle coincides with the central axis of the cavity body. The outlet of the air inlet pipe is connected to the gas nozzle and (the air inlet position) is downstream of the liquid jet, and the air is in parallel or cross-flow. The liquid nozzle is a circular tube of equal diameter, wherein the diameter of the circular tube outlet is 4-16mm. In some embodiments of the present invention, a plurality of air inlets are evenly distributed around the top of the cavity body around the liquid inlet pipe for installing the air inlet pipes respectively, and the aperture of the air inlet is 0.5-4mm; the cavity is made of PMMA, stainless steel or ceramic, and its shape is cylindrical with a diameter of 15-40mm. The impact plate is a disc with a diameter of 15-45mm. The distance l between the outlet end of the liquid nozzle and the outlet end of the gas is 0.5-10mm. The distance between the outlet end of the liquid nozzle and the impact plate is 5-50 mm. The gap between the open end of the cavity and the impact plate is 0.5-5 mm. The liquid velocity flowing out of the liquid nozzle is above 1.5 m / s, and the ratio of the liquid volume flow rate of the liquid input to the gas volume flow rate of the pore input is 1-3.

[0043] Example 1

[0044] The structure of the microbubble generator is as follows Figure 1As shown, it includes a liquid inlet pipe 1, a cavity 2, a liquid nozzle 3, an impact plate 4 and a combination of an air inlet pipe and a gas nozzle 5. The air inlet pipe and the liquid inlet pipe are cylindrical. The air inlet pipe is installed at the end of the cavity and enters the cavity body through the air hole. The liquid nozzle is arranged at the end of the liquid inlet pipe. The central axis of the liquid nozzle coincides with the central axis of the cavity body. The air inlet position is downstream of the liquid jet and flows into the air. The liquid nozzle adopts a round tube with an outlet diameter of 4mm, and the impact plate is a disc (diameter 15mm). The cavity is made of hydrophobic material, and its shape is cylindrical, with a diameter of 15mm, and a 2mm diameter air hole is opened on the top. The distance between the liquid nozzle outlet and the gas outlet end is 3mm, the distance between the liquid nozzle and the impact plate is 30mm, and the gap between the cavity body and the impact plate is 3mm. Under the operating condition of continuously introducing gas into the cavity structure, the liquid velocity of the liquid flowing out of the liquid nozzle is 1.66m / s. Air is used as the gas experimental medium and water is used as the liquid experimental medium. In this system, k in the following formula (1) is 372100. The gap width h1 between the cavity structure and the impact plate of each embodiment of the present invention satisfies the formula (1). The liquid flow rate out of the liquid nozzle satisfies u greater than the formula (2). j,min , the distance h2 between the gas nozzle and the liquid nozzle satisfies equation (3). A high-speed camera is used to measure the size and distribution of the bubbles generated by the microbubble generator, such as Figure 3 As shown, the bubble size generated is 500-1600 μm, the microbubble number fraction is 56%, the ratio of gas volume flow rate to liquid volume flow rate is 0.4 (higher than 0.05), and the radial dispersion width of the bubbles is 20 mm (1.33 times the diameter of the impact plate).

[0045] Example 2

[0046] 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 As shown, the bubble size generated is 300-1200 μm, the microbubble number fraction is 73%, the ratio of gas volume flow rate to liquid volume flow rate is 0.25 (higher than 0.05), and the radial dispersion width of the bubbles is 25 mm (1.67 times the diameter of the impact plate).

[0047] Example 3

[0048] 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 As shown, 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 0.19 (higher than 0.05), and the bubble radial dispersion width is 28 mm (1.87 times the diameter of the impact plate).

[0049] Example 4

[0050] The only difference from Example 1 is that the liquid velocity of the liquid flowing out of the liquid nozzle is 4.33 m / s, and a high-speed camera is used to photograph the bubbles generated by the micro-bubble generator, such as Figure 3 As shown, the bubble size generated is 100-900 μm, the microbubble number fraction is 100%, the ratio of gas volume flow rate to liquid volume flow rate is 0.15 (higher than 0.05), and the radial dispersion width of the bubbles is 31 mm (2.06 times the diameter of the impact plate).

[0051] Example 5

[0052] The only difference from Example 4 is that four air holes with a diameter of 1 mm are evenly distributed around the liquid inlet pipe on the top of the cavity body (corresponding to four air inlet pipes), and the bubbles generated by the microbubble generator are photographed with a high-speed camera. The size of the generated bubbles is 100-950 μm, the number fraction of microbubbles is 100%, the ratio of the gas volume flow rate to the liquid volume flow rate is 0.165 (higher than 0.05), and the radial dispersion width of the bubbles is 28 mm (1.87 times the diameter of the impact plate).

[0053] Example 6

[0054] The only difference from Example 4 is that the distance l between the liquid nozzle outlet and the impact plate is 15 mm, and the bubbles generated by the microbubble generator are photographed with a high-speed camera. The bubble size generated is 150-1000 μm, the microbubble number fraction is 100%, the ratio of gas volume flow rate to liquid volume flow rate is 0.15 (higher than 0.05), and the radial dispersion width of the bubbles is 35 mm (2.33 times the diameter of the impact plate).

[0055] Example 7

[0056] The only difference from Example 6 is that the gap between the cavity body and the impact plate is 1 mm, and the bubbles generated by the microbubble generator are photographed with a high-speed camera. The bubble size generated is 80-500 μm, the microbubble number fraction is 100%, the ratio of gas volume flow rate to liquid volume flow rate is 0.15 (higher than 0.05), and the radial dispersion width of the bubbles is 26 mm (1.73 times the diameter of the impact plate).

[0057] Example 8

[0058] The only difference from Example 6 is that the operating conditions are changed to intermittently (20 times / min, 1s / time, interval 2s) passing gas into the cavity structure, and the bubbles generated by the microbubble generator are photographed with a high-speed camera, such as Figure 4As shown, the bubble size generated is 80-500 μm, the microbubble number fraction is 100%, the ratio of gas volume flow rate to liquid volume flow rate is 0.15 (higher than 0.05), and the bubble radial dispersion width is 29 mm (1.67 times the diameter of the impact plate).

[0059] Comparative Example 1

[0060] The only difference from Example 1 is that the liquid velocity of the liquid flowing out of the liquid nozzle is 0.66 m / s<0.9025 m / s, which does not meet the condition of formula (2). The bubbles generated by the microbubble generator are photographed using a high-speed camera. The bubble size generated is 2600-3700 μm, the microbubble number fraction is 0%, and the ratio of gas volume flow rate to liquid volume flow rate is 1.77 (higher than 0.05).

[0061] Comparative Example 2

[0062] The only difference from Example 2 is that the gap between the cavity body and the impact plate is 30 mm, which does not meet the condition of formula (1). The bubbles generated by the microbubble generator are photographed using a high-speed camera. The bubble size is 900-2500 μm, the microbubble number fraction is 17%, the ratio of gas volume flow rate to liquid volume flow rate is 0.15 (higher than 0.05), and the radial dispersion width of the bubbles is 36 mm (2.4 times the diameter of the impact plate).

[0063] Comparative Example 3

[0064] The only difference from Example 2 is that the distance between the gas nozzle and the liquid nozzle is 15 mm, which does not meet the condition of formula (3). The bubbles generated by the microbubble generator are photographed with a high-speed camera. The bubble size is 800-1800 μm, the microbubble number fraction is 29%, the ratio of the gas volume flow rate to the liquid volume flow rate is 0.15 (higher than 0.05), and the radial dispersion width of the bubbles is 25 mm (1.67 times the diameter of the impact plate).

[0065] Comparative Example 4

[0066] The only difference from Example 2 is that the distance between the liquid nozzle and the impact plate is 60 mm, which does not meet the requirement of 5-50 mm. A high-speed camera is used to photograph the bubbles generated by the microbubble generator. The bubble size is 1100-2400 μm, the microbubble number fraction is 0%, the ratio of gas volume flow rate to liquid volume flow rate is 0.15 (higher than 0.05), and the radial dispersion width of the bubbles is 13 mm (0.87 times the diameter of the impact plate).

[0067] It should be noted that the embodiments 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 microbubble generating device, characterized in that: include: A liquid input component consisting of a liquid inlet pipe and a liquid nozzle interconnected with the liquid inlet pipe; a gas input component consisting of a gas nozzle and a matching air inlet pipe; an incompletely closed space consisting of a cavity structure with one end open and an impact plate, the open end of the cavity structure is located above the impact plate, and there is a certain gap between the open end and the impact plate; the liquid input component and the gas input component penetrate into the cavity structure, the liquid nozzle and the gas nozzle are both located inside the cavity body, the liquid nozzle is opposite to the impact plate, and there is a certain distance between the two.

2. The microbubble generating device according to claim 1, characterized in that: The cavity structure is a cylindrical shell structure, a hollow platform or a hollow cone.

3. The microbubble generating device according to claim 1, characterized in that: The structure of the impact plate is a column or a platform column.

4. The microbubble generating device according to claim 1, characterized in that: The distance between the liquid nozzle and the impact plate is 5-50 mm.

5. The microbubble generating device according to claim 1, characterized in that: The adjustment range of the gap h1 between the open end of the cavity structure and the impact plate and the unit volume input work E of the input flow field k , the volume of the cavity body V, and the distance l between the liquid nozzle and the impact plate satisfy: Where k is a constant related to the physical properties of the liquid, h1 and l are in m, and E k The unit is J / m 3 , V in m 3 .

6. The microbubble generating device according to claim 1, characterized in that: The equivalent circumscribed circle diameter of the open end section of the cavity structure is 9-225 times the diameter of the liquid nozzle outlet section, and the cross-sectional area of ​​the impact plate is 1-10 times the cross-sectional area of ​​the equivalent circumscribed circle of the open end of the cavity structure.

7. A method for generating microbubbles according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: a liquid jet ejected from a liquid nozzle collides with an impact plate to form an impact jet field including an impact zone, a free jet zone and a wall jet zone; a wall jet in the wall jet zone passes through a gap formed by an open end of the cavity structure and the plate; and a gas is continuously or intermittently introduced into the cavity structure through a gas nozzle; When gas is continuously introduced into the cavity structure, an air chamber is formed in the cavity structure, and the impact jet entrains the gas in the air chamber to generate a large number of microbubbles; the size of the formed microbubbles is further reduced and fully dispersed under the shearing, crushing and transportation of the liquid jet in the wall jet area, and finally a large number of microbubbles with uniform size distribution are generated; When gas is intermittently introduced into the cavity structure, the impact jet carries the gas to form a circulating flow in the cavity, frequently shearing the gas to generate a large number of microbubbles; the size of the formed microbubbles is further reduced and fully dispersed under the shearing, crushing and transportation of the liquid jet in the wall jet area, and finally a large number of microbubbles with uniform size distribution are generated.

8. The microbubble generating method according to claim 7, characterized in that: Control the liquid flow rate from the liquid nozzle to be greater than u j，min ,u j，min Liquid nozzle diameter d j , liquid viscosity coefficient μ, liquid surface tension σ, and liquid density ρ satisfy the following relationship: In the formula, u j，min The unit is m / s, d j The unit is m, μ is m 3 , μ is in Pa·s, σ is in N / m, ρ is in kg / m 3 .

9. The microbubble generating method according to claim 8, characterized in that: When gas is intermittently introduced into the cavity structure, the distance h2 between the liquid nozzle and the gas nozzle cannot exceed the initial section range of the jet, and the specific relationship satisfies: Where l is the distance between the liquid nozzle and the impact plate, in m, and u j is the liquid nozzle inlet speed, u j，min 、u j The unit is m / s, and the unit of h2 is m.

10. The microbubble generating method according to claim 7, characterized in that: The ratio of the liquid volume flow rate input by the liquid nozzle to the gas volume flow rate input by the gas nozzle is 0.05-5; When gas is continuously introduced into the cavity structure, the average size of the microbubbles finally generated is d 32 The distance h1 between the open end of the cavity structure and the impact plate, the distance l between the liquid nozzle and the impact plate, and the liquid nozzle liquid inlet speed u j , Liquid nozzle diameter d j , cavity volume V, gas volume flow rate Q g The relationship between them is: Where a is a constant related only to physical properties; When gas is intermittently introduced into the cavity structure, the microbubbles finally generated have an average size d 32 The work E per unit volume of the liquid jet input k , the cavity volume, and the distance h1 between the open end of the cavity structure and the impact plate are as follows: Where b is a constant related only to physical properties, j The unit is m / s, l, d 32 、h1、d j Unit: m, Q g Unit: m 3 / s, V in m 3 , E k The unit is J / m 3 .

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