Microbubble generator, gas-liquid bubbling bed reaction device and reaction method thereof

Abstract

The present application relates to the field of gas-liquid mixing reaction, disclose a kind of microbubble generator, gas-liquid bubble bed reaction device and its reaction method, wherein, the microbubble generator includes Venturi tube (1), the Venturi tube (1) includes taper section (3), throat straight section (4) and gradually expanding section (7), first spiral flow gas hole (13) is provided on the throat straight section (4) and the first spiral flow gas hole (13) is through the wall of tube and is angled with radial direction, the size of the bubble formed in liquid can be reduced by the above technical solution, the residence time of bubble in throat straight section and gradually expanding section is prolonged, so that gas and liquid are mixed uniformly.

Description

Technical Field

[0001] This invention relates to the field of gas-liquid mixing reactions, specifically to a microbubble generator, and to a gas-liquid bubbling bed reaction apparatus and reaction method thereof. Background Technology

[0002] Gas-liquid bubbling bed reactors are important multiphase reactors where gas and liquid phases flow upwards in parallel. The liquid phase is the continuous phase, and the gas phase is the dispersed phase, dispersed in the liquid phase as bubbles. Bubble size is crucial for mass transfer between the gas and liquid phases; smaller bubbles result in a larger gas-liquid interphase area, which is more conducive to mass transfer and improves reactor performance. However, in traditional gas-liquid bubbling bed reactors, the bubbles generated by the gas distributor are typically larger than millimeters, which is particularly detrimental to mass transfer under low gas-liquid ratio conditions. Besides their small specific surface area and low mass transfer rate, millimeter-sized bubbles easily cause liquid-phase turbulence and backmixing, and the interactions between bubbles become more severe, adversely affecting reactor performance. Therefore, developing microbubble-based gas-liquid bubbling reactors offers advantages such as safety, high efficiency, and energy saving, with broad application prospects.

[0003] Microbubbles, characterized by their large specific surface area, high gas holdup, slow rise rate, and rapid dissolution rate, are crucial for enhancing mass transfer and are widely used in gas-liquid two-phase mass transfer processes in the petrochemical industry, wastewater treatment, brewing, and aerobic aquaculture. Currently, microbubble generation is primarily achieved through microbubble generators, which can be categorized into several methods: shear contact type (e.g., Venturi microbubble generators); dissolved gas release type (e.g., pressure dissolution microbubble generators); microporous dispersion type (e.g., microporous plastic, rubber, and ceramic tubes); ultrasonic bubble generation; and electrolytic bubble generation.

[0004] Patent CN201910238708.3 discloses a Venturi-type microbubble generator and a gas-liquid generator. The invented Venturi-type microbubble generator consists of a swirling device, an air inlet, and a Venturi tube. The swirling device within the gradually expanding section of the Venturi tube enhances the liquid shear force. The high-speed, highly turbulent liquid causes secondary breakage of the bubbles, generating a large number of microbubbles. It has advantages such as compact structure, low energy consumption, good microbubble generation effect, and convenient maintenance. Using this microbubble generator in a gas-liquid reactor enhances the dispersion effect of bubbles in the reactor and strengthens the gas-liquid mass transfer efficiency.

[0005] Patent CN109550418A proposes a swirling microbubble generator and a gas-liquid reactor containing the microbubble generator. The microbubble generator consists of a liquid inlet pipe, a gas inlet pipe, and a venturi tube. The outer diameter of the liquid inlet pipe is tangent to the outer diameter of the tapered section of the venturi tube. After the high-speed liquid entering through the liquid inlet pipe collides with each other, the turbulent kinetic energy increases. The strong shearing action causes the bubbles to break up multiple times and generate a large number of microbubbles. It has the characteristics of compact structure, simple operation, and low maintenance cost.

[0006] The aforementioned microbubble generator still suffers from problems such as inconsistent bubble size, excessively large bubble size, and insufficient liquid-phase gas dissolution rate. Therefore, it is necessary to optimize the design of the microbubble generator to improve its microbubble generation effect, meet the requirements of high gas-liquid ratio and high mass transfer efficiency, and make it more widely applicable.

[0007] o-Toluic acid is an important organic synthesis intermediate and chemical raw material, widely used in pesticides, fragrances, dyes, and other fine chemicals. Currently, the production of o-toluic acid mostly employs a liquid-phase air oxidation method using cobalt naphthenate as a catalyst. However, due to the low activity of cobalt naphthenate, the low mass transfer efficiency of existing gas-liquid bubbling devices, the slow oxidation rate, and the long oxidation time, the reaction residence time is too long, resulting in a large accumulation of oxidation byproducts and high raw material consumption, which restricts the development of this production technology. Summary of the Invention

[0008] The purpose of this invention is to provide a microbubble generator to solve problems such as excessively large bubble size and insufficient gas dissolution rate in the liquid phase.

[0009] To achieve the above objectives, the present invention provides a microbubble generator, wherein the microbubble generator includes a venturi tube, the venturi tube includes a tapering section, a throat straight section and a tapering section, and the throat straight section is provided with a first swirling air hole that penetrates the tube wall at an angle to the radial direction.

[0010] Optionally, the first swirling air hole can penetrate the pipe wall along the tangential direction of a concentric circle with a radius smaller than the inner circumference of the straight section of the throat.

[0011] Alternatively, the microbubble generator includes a first air chamber surrounding the throat straight section at the first swirling air hole.

[0012] Optionally, the microbubble generator includes an outlet straight pipe connected to the expanding section, and the outlet straight pipe is provided with a second swirling air hole that penetrates the pipe wall at an angle to the radial direction.

[0013] Optionally, the second swirling air hole penetrates the pipe wall tangentially.

[0014] Alternatively, the microbubble generator may include a second chamber surrounding the outlet straight pipe at the second swirling air hole.

[0015] Optionally, the first swirling air hole and / or the second swirling air hole are tapered holes along the airflow direction.

[0016] Optionally, the microbubble generator includes an accelerator disposed in the outlet straight pipe, and an acceleration annular gap is formed between the accelerator and the inner circumferential surface of the outlet straight pipe.

[0017] Optionally, the second swirling air hole is located at the position where the acceleration annular gap cross section is the smallest.

[0018] Optionally, corrugations may be provided on the inner wall of the expanding section, the inner wall of the outlet straight pipe, and the outer wall of the rear part of the accelerating member.

[0019] Alternatively, the microbubble generator may include a mesh or grid-like bubble-breaking plate disposed at one end of the outlet straight pipe away from the diffuser section.

[0020] Optionally, the microbubble generator includes an inlet straight pipe connected to the tapered section.

[0021] In addition, the present invention also provides a gas-liquid bubbling bed reaction device, wherein the gas-liquid bubbling bed reaction device includes a bubbling bed and a circulation pipeline. The bubbling bed is provided with a gas phase outlet at the top, a liquid phase outlet at the bottom, a raw material inlet at the side, a circulation outlet at the top, and a circulation inlet at the bottom. The circulation pipeline is connected to the circulation outlet and the circulation inlet, and a microbubble generator as described in the above scheme is provided on the circulation pipeline.

[0022] Optionally, the circulation pipeline is equipped with a power component and a heat exchange unit.

[0023] In addition, the present invention also provides a reaction method for a gas-liquid bubbling bed reactor, wherein the gas-liquid bubbling bed reactor is the gas-liquid bubbling bed reactor described in the above scheme.

[0024] The above technical solution can reduce the size of bubbles formed in the liquid and prolong the residence time of bubbles in the straight section and the gradually expanding section of the throat, so that the gas and liquid are mixed evenly. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the microbubble generator according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of the swirling air hole described in an embodiment of the present invention;

[0027] Figure 3This is a schematic diagram of the accelerating component according to an embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of the gas-liquid bubbling bed reactor according to an embodiment of the present invention.

[0029] Explanation of reference numerals in the attached figures

[0030] 1-Venturi tube, 2-Inlet straight pipe, 3-Converging section, 4-Throat straight section, 5-First inlet pipe, 6-First air chamber, 7-Diverging section, 8-Second inlet pipe, 9-Second air chamber, 10-Accelerator, 11-Outlet straight pipe, 12-Bubble breaking plate, 13-First swirling air hole, 14-Second swirling air hole, 20-Raw material inlet, 21-Microbubble generator, 22-Circulation inlet, 23-Bubble bed, 24-Circulation outlet, 25-Heat exchange unit, 26-Power component, 27-Gas phase outlet, 28-Liquid phase outlet. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0032] The present invention provides a microbubble generator, wherein the microbubble generator includes a venturi tube 1, the venturi tube 1 includes a tapering section 3, a throat straight section 4 and a tapering section 7, and the throat straight section 4 is provided with a first swirling air hole 13 that penetrates the tube wall at an angle to the radial direction.

[0033] The Venturi tube 1 comprises a converging section 3 with a gradually decreasing inner diameter, a straight throat section 4 with a basically constant inner diameter, and a diverging section 7 with a gradually increasing inner diameter. These three sections are connected sequentially along the flow direction. The fluid, such as a liquid, is introduced into the Venturi tube 1 through the converging section 3.

[0034] The throat section 4 has a first swirling air hole 13. The first swirling air hole 13 extends at a certain angle to the radial direction, that is, there is an angle between its extension direction and the radial direction. The airflow entering the throat section 4 from the first swirling air hole 13 has an angle with the radial direction, so that a swirling flow can be formed in the throat section 4. This can reduce the size of the bubbles formed in the liquid, prolong the residence time of the bubbles in the throat section 4 and the gradually expanding section 7, and make the gas and liquid mix evenly.

[0035] In this design, the swirling orifice allows the gas to swirl within the venturi tube, forming smaller bubbles and improving the uniformity of gas-liquid mixing.

[0036] Optionally, the first swirling air hole 13 penetrates the pipe wall tangentially along a concentric circle with a radius smaller than the inner circumference of the straight throat section 4. For example... Figure 2As shown, the extension direction of the first swirling air hole 13 forms an angle with the radial direction of the throat straight section 4, and the circle tangent to its extension direction is a concentric circle of the throat straight section 4. The radius of this concentric circle is smaller than the inner radius, thereby allowing the swirling gas to form a swirling flow inside the throat straight section 4.

[0037] The first swirling air hole 13 is located within 1 / 4 to 3 / 4 of the length of the throat straight section 4, and is provided in 2 to 5 layers. Each layer is provided with at least 4 swirling air holes. The swirling air holes are tangent to the radius of a concentric circle of the throat straight section 4, and the radius of tangency (the radius of the concentric circle tangent to the extension direction of the swirling air hole) is 1 / 3 to 2 / 3 of the radius of the throat straight section 4 (inner circumference).

[0038] The tangent radius refers to the radius of a concentric circle that is tangent to the extension direction of the swirling vent.

[0039] Additionally, the microbubble generator includes a first air chamber 6 surrounding the throat straight section 4 at the first swirling air hole 13. For example... Figure 1 As shown, the first air chamber 6 surrounds the portion of the throat straight section 4 where the first swirling air hole 13 is located. The first air chamber 6 can contain gas, forming a relatively stable air pressure environment for injecting swirling gas into the throat straight section 4. Furthermore, the first air chamber 6 is connected to a first air inlet pipe 5, which can be connected to a gas supply device to provide the corresponding gas to the first air chamber 6. The first air chamber 6 provides a communication medium between the first air inlet pipe 5 and the first swirling air hole 13, and in particular, it can act as a pressure buffer chamber to ensure air pressure stability.

[0040] In addition, the microbubble generator includes an outlet straight pipe 11 connected to the diffuser section 7. The outlet straight pipe 11 has a second swirling air hole 14 that penetrates the pipe wall at an angle to the radial direction. The outlet straight pipe 11 extends the flow path of the gas and liquid, allowing for further mixing and causing the bubbles to break down into smaller sizes. The second swirling air hole 14 has a structure and function basically similar to the first swirling air hole 13, and will not be described again here.

[0041] Similar to the first swirling air hole 13, the second swirling air hole 14 penetrates the pipe wall along the tangential direction of a concentric circle smaller than the inner circumferential radius of the outlet straight pipe 11.

[0042] The second swirling air hole 14 is located at the front of the outlet straight pipe 11, within the range of 0 to 1 / 3 of the length of the outlet straight pipe 11. It is provided with 1 to 3 layers of swirling air holes, with at least 8 swirling air holes in each layer. The swirling air holes are tangent to the radius of a concentric circle of the outlet straight pipe 11, and the tangent radius is 1 / 2 to 1 / 3 of the inner circumference radius of the outlet straight pipe 11.

[0043] Additionally, the microbubble generator includes a second air chamber 9 surrounding the outlet straight pipe 11 at the second swirling air hole 14. The second air chamber 9 can be connected to a second air inlet pipe 8. The second air inlet pipe 8 and the first air inlet pipe 5 can be connected to the same air supply device, or they can be connected to different air supply devices. The structure and function of the second air chamber 9 and the second air inlet pipe 8 are basically similar to those of the first air chamber 6 and the first air inlet pipe 5 described above, and will not be repeated here.

[0044] In this design, swirling air holes are provided at both the venturi tube 1 and the outlet straight pipe 11, allowing airflow to be injected sequentially at both locations, thus ensuring thorough mixing between the airflow and the liquid.

[0045] The first swirling orifice 13 and / or the second swirling orifice 14 are tapered orifices along the airflow direction. The tapered orifice structure reduces the size of bubbles formed in the liquid, allowing for more thorough mixing of the bubbles with the liquid. The tapering angle of the swirling orifice can be 0–45°.

[0046] Additionally, the microbubble generator includes an accelerator 10 disposed within the outlet straight pipe 11, forming an accelerating annular gap between the accelerator 10 and the inner circumferential surface of the outlet straight pipe 11. The accelerator 10 can be spherical, elliptical, spherical-conical, conical, etc., or can be composed of combinations thereof. Figure 1 and Figure 3 As shown, the accelerator 10 includes a hemispherical front portion and a conical rear portion. The annular gap formed between the accelerator 10 and the outlet straight pipe 11 can increase the fluid flow velocity and achieve secondary breakup of bubbles, forming smaller bubbles; in addition, the gas provided by the second swirling gas hole increases the gas-liquid ratio, thereby increasing the dissolved gas rate.

[0047] The second swirling air hole 14 is located at the position where the acceleration annular gap cross-section is smallest. For example... Figure 1 As shown, the size of the cross-section of the annular gap between the accelerating member 10 and the outlet straight pipe 11 varies in the axial direction, wherein the area of ​​the minimum annular gap is 0.03 to 0.2 of the cross-sectional area of ​​the outlet straight pipe.

[0048] The accelerator 10 is located at the front of the outlet straight pipe 11, within 0 to 1 / 3 of the length of the outlet straight pipe 11.

[0049] In addition, corrugations are provided on the inner wall of the expanding section 7, the inner wall of the outlet straight pipe 11, and the outer wall of the rear part of the accelerator 10. The corrugated structure enhances the turbulence intensity, forms a large number of small eddies, and deepens the breakup of bubbles. The corrugated structure can be a concave-convex platform with a triangular, circular, or trapezoidal cross-sectional shape, or it can be formed by combining different shapes.

[0050] Additionally, the microbubble generator includes a mesh or grid-like bubble-breaking plate 12 disposed at the end of the outlet straight pipe 11 away from the diffuser section 7. The small holes formed on the bubble-breaking plate 12 can break up bubbles present in the liquid to form smaller bubbles.

[0051] Additionally, the microbubble generator includes an inlet straight pipe 2 connected to the converging section 3. The ratio of the cross-sectional area of ​​the throat straight section 4 to that of the inlet straight pipe 2 is 0.05–0.3, the ratio of the cross-sectional area of ​​the throat straight section 4 to that of the outlet straight pipe 11 is 0.05–0.3, and the ratio of the cross-sectional area of ​​the inlet straight pipe 2 to that of the outlet straight pipe 11 is 0.8–1.2. The cone angle of the converging section 3 is 10–60°, and the cone angle of the expanding section 7 is 5–50°.

[0052] The microbubble generator enhances gas-liquid mixing and breaks up the gas by incorporating features such as swirling air holes, corrugated wall structures, gas-liquid annular gap acceleration components, and bubble-breaking plates, thereby increasing the gas-liquid ratio.

[0053] In addition, the present invention also provides a gas-liquid bubbling bed reaction device, wherein, as Figure 4 As shown, the gas-liquid bubbling bed reactor includes a bubbling bed 23 and a circulation pipeline. The bubbling bed 23 is provided with a gas phase outlet 27 at the top, a liquid phase outlet 28 at the bottom, a raw material inlet 20 on the side, a circulation outlet 24 at the top, and a circulation inlet 22 at the bottom. The circulation pipeline is connected to the circulation outlet 24 and the circulation inlet 22. The microbubble generator 21 described in the above scheme is provided on the circulation pipeline.

[0054] In addition, a power unit 26 and a heat exchange unit 25 are provided on the circulation pipeline. The power unit 26 can be a pressure pump to provide circulation power for the fluid in the circulation pipeline. The heat exchange unit 25 can dissipate heat from the fluid in the circulation pipeline.

[0055] The swirling flow and external circulation formed by the circulation pipeline in the gas-liquid bubbling bed enhance the transfer efficiency within the gas-liquid bubbling bed and improve the homogeneous distribution of gas and liquid.

[0056] On the other hand, the present invention also provides a reaction method for a gas-liquid bubbling bed reactor, wherein the gas-liquid bubbling bed reactor is the gas-liquid bubbling bed reactor described in the above scheme.

[0057] In this process, liquid raw material enters the gas-liquid bubble bed 23 through raw material inlet 20. When the liquid level is higher than the circulation outlet 24, the liquid raw material enters the circulation pipe and, under the action of the power component 26, enters the microbubble generator 21 at high speed. It mixes with air from the first air inlet pipe 5 and the second air inlet pipe 8 to generate a liquid rich in microbubbles, which then swirls into the gas bubble bed 23. The liquid raw material in the gas-liquid bubble bed 23 is driven by the swirling flow, rotating and reacting with the microbubble air in the liquid raw material to generate liquid-phase oxidation products and gas-phase products, releasing heat. The heated liquid-phase oxidation products flow through the circulation pipe again, are cooled by the heat exchange unit, and then circulate as liquid to generate microbubbles again.

[0058] In this process, the liquid raw material passes through the liquid inlet 1, the straight inlet pipe 2, and the converging section 3 of the microbubble generator 21. The liquid velocity increases as it enters the throat section 4. Air enters the first air inlet pipe 5, is evenly distributed through the first air chamber 6, and then rotates into the throat section 4 through the first swirling air hole 13. It is drawn into the throat section 4 by the high-speed, low-pressure liquid, where it mixes thoroughly with the liquid raw material. After being sheared and broken by the high-speed liquid, coarse bubbles are formed. The liquid containing coarse bubbles enters the expanding section 7, where the liquid velocity decreases and the pressure increases, further breaking down the coarse bubbles. Furthermore, the corrugated structure on the inner wall of the expanding section 7 increases the turbulence intensity near the wall, forming numerous small eddies, further deepening the bubble breakage to the microbubble level. Liquid containing microbubbles enters the outlet straight pipe 11 and is accelerated and broken up by secondary decompression under the action of the accelerator 10. Air enters the second inlet pipe 8, is evenly distributed in the second air chamber 9, and then rotates into the front of the outlet straight pipe 11 through the second swirling air hole 14. It is entrained by the high-speed, low-pressure liquid in the annular gap and fully mixed with the liquid containing microbubbles. After being broken up by the high-speed liquid shearing, the liquid enters the middle and rear of the outlet straight pipe 11 and is decelerated and pressurized. Under the turbulent action of the corrugated structure on the rear outer wall of the accelerator 10 and the inner wall of the outlet straight pipe 11, a high gas-liquid ratio bubble-rich liquid is formed. Finally, after passing through the bubble-breaking plate 12, uniformly distributed microbubbles are obtained.

[0059] Among them, the liquid velocity at the liquid inlet of the inlet straight pipe 2 is greater than 0.5 m / s, the ratio of the gas volume flow rate to the liquid volume flow rate at the first air inlet pipe 5 is 0.01 to 0.2, and the ratio of the gas volume flow rate to the liquid volume flow rate at the liquid inlet of the second air inlet pipe 8 is 0.005 to 0.1.

[0060] In addition, the gas velocity through the first swirling air hole 13 is 0.01 to 0.01 m / s, and the gas velocity through the second swirling air hole 14 is 0.005 to 0.005 m / s.

[0061] The following will describe various embodiments of the gas-liquid bubbling bed reactor of this scheme.

[0062]

Example 1

[0063] o-Xylene enters the microbubble generator from the liquid feed inlet of the gas-liquid bubbling bed reactor. After passing through the inlet straight pipe and the converging section, the liquid accelerates into the throat straight section. Gas feed air enters the first swirling orifice and is entrained by high-speed negative pressure into the throat straight section, mixing with the high-speed liquid. The bubbles are sheared and broken up by the high-speed liquid, forming coarse bubbles. Further breaking down into microbubbles is achieved by the corrugated structure on the inner wall of the expanding section. The liquid containing microbubbles enters the outlet straight pipe and is accelerated and broken up again by the accelerator. Another stream of feed air enters the second gas chamber and is entrained by the high-speed, low-pressure liquid in the annular gap, mixing thoroughly with the microbubble-containing liquid. After being sheared and broken up by the high-speed liquid, the liquid enters the middle and rear parts of the outlet straight pipe, where it is decelerated and pressurized. Under the turbulent action of the corrugated structure on the outer wall of the accelerator and the inner wall of the outlet straight pipe, a high gas-liquid ratio bubble-rich liquid is formed. Finally, after passing through the bubble-breaking plate, uniformly distributed microbubbles are obtained and enter the bubbling bed, where a gas-liquid reaction takes place under the action of a catalyst.

[0064] The first swirling air orifice is located within half the length of the throat straight section, and consists of two layers, with four swirling air orifices in each layer. These orifices are tangent to the radial direction of the throat straight section, with a tangent radius of one-third of the throat straight section's radius. The convergence angle of the swirling air orifices is 30°. The second swirling air orifice consists of two layers, with eight swirling air orifices in each layer. These orifices are also tangent to the radial direction of the throat straight section, with a tangent radius of one-third of the throat straight section's radius. The convergence angle of the swirling air orifices is 30°. The ratio of the cross-sectional area of ​​the throat straight section to that of the inlet straight pipe is 0.1. The accelerator is spherical, and the area of ​​the minimum annular gap is 0.08 times the cross-sectional area of ​​the outlet straight pipe. The corrugations on the inner wall of the diffuser section and the outlet straight pipe, as well as the outer wall of the rear part of the accelerator, are triangular cross-sectional convex and concave platforms. The gas-to-liquid volumetric flow rate ratio at the first inlet pipe 5 is 0.1, and the gas-to-liquid volumetric flow rate ratio at the second inlet pipe is 0.01. The gas holdup in the gas-liquid bubbling bed is 0.31, the average bubble diameter is 300 μm, and the single-pass yield of o-methylbenzoic acid is 61.2%. The results are detailed in Table 1.

[0065]

Example 2

[0066] The method is the same as in Example 1, except that the number of layers of the first swirling air pores is 3. The results of gas holdup, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubbling bed are detailed in Table 1.

[0067]

Example 3

[0068] The method is the same as in Example 1, except that the first swirl reduction angle is 30°. The gas content, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubbling bed are detailed in Table 1.

[0069]

Example 4

[0070] The method is the same as in Example 1, except that the ratio of the cross-sectional area of ​​the throat straight section to the inlet straight pipe is 0.7. The results of the gas content, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubble bed are detailed in Table 1.

[0071]

Example 5

[0072] The method is the same as in Example 1, except that the accelerator is a spherical cone shape. The gas content, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubbling bed are detailed in Table 1.

[0073]

Example 6

[0074] The method is the same as in Example 1, except that the ratio of the area of ​​the minimum annular gap to the cross-sectional area of ​​the outlet straight pipe is 0.05. The results of gas holdup, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubbling bed are detailed in Table 2.

[0075]

Example 7

[0076] The method is the same as in Example 1, except that the corrugations on the inner wall of the diffuser section, the outlet straight pipe and the outer wall of the rear part of the accelerator are semi-circular. The gas holdup, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubbling bed are detailed in Table 2.

[0077]

Example 8

[0078] The method is the same as in Example 1, except that the ratio of gas to liquid volume flow rate at the first inlet pipe is 0.15. The results of gas holdup, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubble bed are detailed in Table 2.

[0079]

Example 9

[0080] The method is the same as in Example 1, except that the ratio of gas volume flow rate in the second inlet pipe to liquid volume flow rate in the liquid inlet is 0.02. The results of gas content, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubble bed are detailed in Table 2.

[0081]

Example 10

[0082] The method is the same as in Example 1, except that the grid is in the form of a mesh. The results of gas content, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubble bed are detailed in Table 2.

[0083]

Comparative Example 1

[0084] The method is the same as in Example 1, except that the second swirling air hole is not set. The gas content, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubbling bed are detailed in Table 3.

[0085] [Comparative Example 2]

[0086] Following the method of Example 1, except that no accelerator is set, the gas holdup, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubbling bed are detailed in Table 3.

[0087] [Comparative Example 3]

[0088] The method is the same as in Example 1, except that the corrugated form on the inner wall of the outlet straight pipe and the outer wall of the rear part of the accelerator is not set. The gas holdup, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubbling bed are detailed in Table 3.

[0089] [Comparative Example 4]

[0090] The results of the gas holdup, average bubble diameter and single-pass yield of o-methylbenzoic acid in the gas-liquid bubble bed using the existing Venturi bubble generator and gas-liquid bubbling device are detailed in Table 3.

[0091] Table 1

[0092]

[0093]

[0094] Table 2

[0095]

[0096]

[0097] Table 3

[0098]

[0099] This invention increases the gas-liquid contact area, improves the dissolved gas rate, and enhances the transfer process by using a bubble generator, a gas-liquid bubbling reactor, and a reaction method. This increases the reaction rate, effectively reduces the reaction time, and significantly improves the product yield and economy of o-methylbenzoic acid.

[0100] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A microbubble generator, characterized in that, The microbubble generator includes a venturi tube (1), which includes a tapering section (3), a throat straight section (4), and a expanding section (7). The throat straight section (4) is provided with a first swirling air hole (13) that penetrates the tube wall at an angle to the radial direction. The microbubble generator includes an outlet straight pipe (11) connected to the expanding section (7). The outlet straight pipe (11) is provided with a second swirling air hole (14) that penetrates the pipe wall at an angle to the radial direction. The first swirling air hole (13) and the second swirling air hole (14) are gradually narrowing holes along the airflow direction. The microbubble generator includes an accelerator (10) disposed in the outlet straight pipe (11). The accelerator (10) includes a hemispherical shape at the front and a conical shape at the rear. An acceleration annular gap is formed between the inner circumferential surface of the accelerator (10) and the outlet straight pipe (11). The second swirling air hole (14) is located at the position where the cross-section of the acceleration annular gap is the smallest. Corrugations are provided on the inner wall of the expanding section (7), the inner wall of the outlet straight pipe (11), and the outer wall of the rear part of the accelerator (10). The corrugations are concave and convex platforms with triangular, circular, or trapezoidal cross-sections.

2. The microbubble generator according to claim 1, characterized in that, The first swirling air hole (13) penetrates the pipe wall along the tangential direction of a concentric circle with a radius smaller than the inner circumference of the straight throat section (4).

3. The microbubble generator according to claim 1, characterized in that, The microbubble generator includes a first air chamber (6) surrounding the throat straight section (4) at the first swirling air hole (13).

4. The microbubble generator according to claim 1, characterized in that, The second swirling air hole (14) penetrates the pipe wall along the tangential direction of a concentric circle with a radius smaller than the inner circumference of the outlet straight pipe (11).

5. The microbubble generator according to claim 1, characterized in that, The microbubble generator includes a second chamber (9) surrounding the outlet straight pipe (11) at the second swirling air hole (14).

6. The microbubble generator according to claim 1, characterized in that, The microbubble generator includes a mesh or grid-like bubble-breaking plate (12) disposed at one end of the outlet straight pipe (11) away from the diffuser section (7).

7. The microbubble generator according to claim 6, characterized in that, The microbubble generator includes an inlet straight pipe (2) connected to the tapered section (3).

8. A gas-liquid bubbling bed reactor, characterized in that, The gas-liquid bubbling bed reactor includes a bubbling bed (23) and a circulation pipeline. The bubbling bed (23) is provided with a gas phase outlet (27) at the top, a liquid phase outlet (28) at the bottom, a raw material inlet (20) on the side, a circulation outlet (24) at the top, and a circulation inlet (22) at the bottom. The circulation pipeline is connected to the circulation outlet (24) and the circulation inlet (22). A microbubble generator (21) as described in any one of claims 1-7 is provided on the circulation pipeline.

9. The gas-liquid bubbling bed reactor according to claim 8, characterized in that, The circulation pipeline is equipped with a power component (26) and a heat exchange unit (25).

10. A reaction method for a gas-liquid bubbling bed reactor, characterized in that, The gas-liquid bubbling bed reactor is the gas-liquid bubbling bed reactor as described in claim 8 or 9.

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