A method for generating multi-stage bubbles in a slurry bed reactor

Abstract

This invention proposes a method for generating multi-stage bubbles in a slurry bed reactor. The slurry enters a microbubble generator, where a low-pressure zone is formed through a special structure. Gas is self-absorbed into the microbubble generator and sheared and broken to generate microbubbles. Gas that is not drawn into the microbubble generator generates large bubbles through a gas distribution plate. The bubbles exiting the microbubble generator and the gas distribution plate enter the slurry bed, resulting in a wide distribution of bubbles within the reactor. This not only improves the gas-liquid mass transfer rate but also achieves uniform dispersion and mixing of the gas, liquid, and solid phases, significantly enhancing reaction efficiency.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals, specifically relating to a method for generating multi-stage bubbles in a slurry bed reactor. Background Technology

[0002] Slurry bed reactors are widely used in gas-liquid-solid three-phase reactions, including residue hydrotreating. Gas enters the slurry bed from a gas distributor at the bottom of the reactor, while solids exist in suspension within the reactor. The mass transfer performance in a slurry bed reactor depends to a large extent on the bubble size. The liquid phase volumetric mass transfer coefficient k... L a can be decomposed into k L The parameters are k and 'a'. Undoubtedly, for the same gas volume, the smaller the bubble size, the larger the specific surface area 'a'. However, k... L Related to the turbulent kinetic energy of the liquid phase, in still water, the smaller the bubble size, the smaller its disturbance to the liquid phase, k L Smaller bubbles are less conducive to gas-liquid mixing. Therefore, simply reducing bubble size has limited effect on enhancing mass transfer. In the reaction, it is necessary not only to generate microbubbles but also to generate some larger bubbles to increase liquid-phase turbulence, enhance liquid-phase renewal around the microbubbles, and improve the liquid-phase mass transfer coefficient k. L Therefore, a multi-level distribution of bubble size in the reactor is more conducive to enhancing gas-liquid mass transfer, thereby improving reaction efficiency. Currently, bubble generators mostly produce bubbles with a single-peak size distribution, and structures that produce a small number of bubbles of different sizes are achieved by arranging multiple bubble generators in combination. This multi-scale bubble generation method is relatively complex, occupies a lot of space in the reactor, and is prone to flow dead zones. Summary of the Invention

[0003] The purpose of this invention is to provide a method for generating multi-stage bubbles in a slurry bed reactor, which can obtain bubbles with multi-stage size distribution and improve the liquid phase volume mass transfer coefficient.

[0004] To achieve the above objectives, the present invention provides a method for generating multi-stage bubbles in a slurry bed reactor. The slurry bed reactor includes a shell, with a bubble generator located at the bottom of the shell. The bubble generator includes a gas chamber, a microbubble generator located within the gas chamber, and a gas distribution plate located at the top of the gas chamber. The microbubble generator is a Venturi structure including a contraction section, a throat, and a diffusion section. An air inlet is provided at the throat. The gas distribution plate is connected to the outer wall of the diffusion section, and the outlet end of the diffusion section communicates with the interior of the shell. The bottom plate of the gas chamber is connected to the outer wall of the contraction section. The gas chamber is connected to a gas inlet pipe, and the contraction section is connected to a slurry inlet pipe. Gas enters the gas chamber through the gas inlet pipe, and slurry enters the microbubble generator through the slurry inlet pipe. Under the negative pressure generated by the microbubble generator, part of the gas in the gas chamber enters the microbubble generator through the air inlet and forms microbubbles by liquid shearing. Another part of the gas enters the shell in the form of large bubbles through the gas distribution plate under the action of the gas pressure in the gas chamber. The average liquid velocity at the throat of the microbubble generator is greater than or equal to 0.5 m / s, and the diameter of the air outlet on the gas distribution plate is 1-8 mm.

[0005] The method for generating multi-stage bubbles in a slurry bed reactor described in this invention has a gas flow rate ratio of 1:9 to 1:1 between the gas flow rate through the microbubble generator and the gas flow rate through the gas distribution plate in the gas chamber.

[0006] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention, wherein the diameter of solid particles in the slurry is less than or equal to 2 mm, and the particle / liquid specific gravity ρ s / ρ l Less than or equal to 5, and solid content less than or equal to 30 wt%.

[0007] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention has gas outlets on the gas distribution plate that are equidistantly distributed in a circular pattern from the center to the outer edge, with the diameter of the inner ring gas outlets being less than or equal to the diameter of the outer ring gas outlets.

[0008] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention has an outlet hole diameter of 2-4 mm on the gas distribution plate, and the diameter of the outlet hole from the inner ring to the outer ring increases by a ratio of 1.2-1.5.

[0009] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention has 1-3 air inlets.

[0010] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention includes a built-in swirl guide vane in the diffusion section channel.

[0011] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention comprises 1-4 swirling guide vanes with a bending angle of 270°-360°.

[0012] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention includes a liquid chamber connected below the gas chamber, the inlet end of the contraction section located inside the liquid chamber, the liquid chamber being connected to the slurry feed pipe, and the outer wall of the inlet end of the contraction section having multiple tangential inlets connected to the contraction section.

[0013] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention includes an upper end cap, a lower end cap, and a cylindrical body, wherein the bubble generator is located at the bottom of the lower end cap.

[0014] The method for generating multi-stage bubbles in a slurry bed reactor according to the present invention has the slurry feed pipe inlet end and the gas feed pipe inlet end both located outside the shell.

[0015] Beneficial effects of this invention:

[0016] This invention provides a method for generating multi-stage bubbles in a slurry bed reactor. The slurry bed reactor employs an integrated combination of a microbubble generator and a gas distribution plate to generate bubbles, resulting in the simultaneous presence of bubbles with multiple size distributions within the reactor. Specifically, the average liquid velocity at the throat of the microbubble generator is greater than or equal to 0.5 m / s. This ensures sufficient shear strength between the liquid and the bubbles within the microbubble generator, facilitating better microbubble generation. The microbubbles generated by the microbubble generator have a slow rising velocity, a longer residence time in the liquid phase, and a larger specific surface area, which is beneficial for improving the liquid phase volumetric mass transfer coefficient. The gas distribution plate has 1-8 mm diameter vents, primarily used to generate millimeter- or even centimeter-sized large bubbles. The large bubbles generated by the gas distribution plate have a fast rising velocity, causing strong liquid phase turbulence, which is conducive to the radial uniform distribution of the gas, liquid, and solid phases. Together, these two components promote gas-liquid mixing and enhance gas-liquid mass transfer. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a slurry bed reactor that generates multi-stage bubbles, provided by the present invention.

[0018] Figure 2 This is a schematic diagram of the structure of a microbubble generator and a gas distribution plate provided by the present invention;

[0019] Figure 3 This is a schematic diagram of another microbubble generator and gas distribution plate provided by the present invention.

[0020] In the attached figures, the following labels are used:

[0021] 1. Cylindrical shell; 2. Lower head; 3. Upper head; 4. Gas feed pipe; 5. Slurry feed pipe; 6. Bubble generator; 7. Discharge port; 61. Gas chamber; 62. Microbubble generator; 621. Liquid inlet; 6211. Liquid chamber; 6212. Tangential inlet; 622. Contraction section; 623. Air inlet; 624. Diffusion section; 625. Outlet end; 63. Gas distribution plate; 631. Air outlet. Detailed Implementation

[0022] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0023] Please refer to Figure 1 The slurry bed reactor that generates multi-stage bubbles includes a cylindrical body 1, a lower head 2, an upper head 3, and a bubble generator 6. The bubble generator 6 includes a gas chamber 61, a gas distribution plate 63 located at the top of the gas chamber, a microbubble generator 62 located inside the gas chamber, a gas feed pipe 4 connected to the gas chamber 61, and a slurry feed pipe 5 connected to the microbubble generator. A discharge port 7 is provided on the upper side wall of the cylindrical body 1.

[0024] Please refer to Figure 2 The diagram shows the structure of a microbubble generator and a gas distribution plate. The microbubble generator is a venturi structure, including a contraction section 622 and a throat. The throat is provided with an air inlet 623 and a diffuser section 624. The outer wall of the outlet end 625 of the diffuser section 624 is connected to the gas distribution plate. The outer wall of the contraction section 622 is connected to the bottom plate of the gas chamber. The inlet end of the contraction section 622 is directly connected to the liquid inlet 621 of the slurry feed pipe.

[0025] Please refer to Figure 3 This is another structural schematic diagram of a microbubble generator and a gas distribution plate. The microbubble generator also includes a liquid chamber 6211, located below the gas chamber 61. The inlet end of the contraction section 622 is located inside the liquid chamber 6211, which is connected to the inlet 621 of the slurry feed pipe 5. The outer wall of the inlet end of the contraction section 622 has multiple tangential inlets 6212 communicating with the contraction section 622. Under the action of liquid negative pressure, a portion of the gas in the gas chamber is drawn into the microbubble generator 62 through the inlet 623, forming a large number of microbubbles under the shearing action of the liquid phase swirling flow. Another portion of the gas is cut into multiple large bubbles through the outlet 631 and enters the slurry bed reactor.

[0026] In one specific embodiment, the gas outlets 631 on the gas distribution plate are equidistantly distributed circumferentially from the center to the outer edge, with the diameter of the inner ring of gas outlets 631 being smaller than the diameter of the outer ring of gas outlets 631, such as... Figure 2As shown, preferably, the diameter of the air outlet on the gas distribution plate is 2-4 mm, and the diameter of the inner ring air outlet increases from the diameter of the outer ring air outlet by a ratio of 1.2-1.5.

[0027] In one specific embodiment, the gas outlets 631 on the gas distribution plate are equidistantly distributed circumferentially from the center to the outer edge, and the diameter of the inner ring of gas outlets 631 is equal to the diameter of the outer ring of gas outlets 631, such as... Figure 3 As shown.

[0028] In one specific embodiment, the number of air inlets 623 is 1 to 3, such as 1, 2 or 3, and the height of the air inlets is preferably equal to or close to the height of the center of the air chamber.

[0029] In one specific embodiment, the diffusion section channel has built-in swirl guide vanes. Preferably, the number of swirl guide vanes is 1-4, and the bending angle is 270°-360°.

[0030] In one specific embodiment, the housing includes an upper end cap 3, a lower end cap 2, and a cylindrical body 1, with the bubble generator 6 located at the bottom of the lower end cap 2.

[0031] In one specific embodiment, the feed end of the slurry feed pipe 5 and the air inlet end of the gas feed pipe 4 are both located outside the housing. Slurry and gas are transported into the bubble generator 6 through the slurry feed pipe 5 and the gas feed pipe 4, and the gas is dispersed in the slurry by the bubble generator 6.

[0032] Example 1

[0033] Adopting such Figure 1 The slurry bed reactor shown has a reactor body 10m high and 1.2m in diameter. The upper and lower end caps are hemispherical, each 1.2m in diameter. The reactor liquid level is 8.5m. A bubble generator is included. Figure 2 As shown, there is an air inlet at the throat. The diameter of the solid particles in the slurry is less than or equal to 2 mm, and the particle / liquid specific gravity ρ s / ρ lThe slurry has a viscosity of 1.5 and a solid content of 20 wt%. The slurry enters the contraction section, throat, and diffusion section sequentially through the inlet. Under the influence of the gradually contracting / diffusion structure, a negative pressure is created, and the average liquid velocity at the throat is 3 m / s. Part of the gas in the gas chamber is drawn into the microbubble generator through the inlet under the negative liquid pressure. It is subjected to liquid-phase shearing, forming numerous microbubbles. These microbubbles are carried by the liquid through the diffusion section and its outlet, exiting the microbubble generator and entering the slurry bed reactor. The remaining gas, not drawn into the microbubble generator, passes through a gas distribution plate under pressure. The gas distribution plate has three rings of outlet holes. The diameter of the inner ring outlet holes is 4 mm, and the diameter increases from the inner ring to the outer ring at a ratio of 1.2. Under the shearing action of the outlet holes, multiple large bubbles are formed and enter the slurry bed reactor. The ratio of the gas flow rate through the microbubble generator to the gas flow rate through the gas distribution plate in the gas chamber is 1:1. The bubble size and liquid volumetric mass transfer coefficient in the reactor were detected by high-speed imaging and dynamic dissolved oxygen method. The results showed that the bubble size distribution exhibited a bimodal distribution, with bubbles of 200-500 μm in diameter accounting for 70% and bubbles of 2-15 mm in diameter accounting for 30%. The liquid volumetric mass transfer coefficient was 0.023 s⁻¹. -1 .

[0034] Comparative Example 1

[0035] Under the same operating conditions as in Example 1, the only difference was that all gas entered the slurry bed reactor through a microbubble generator. The results showed that the bubble size distribution exhibited a unimodal pattern, with bubble sizes concentrated in the 200-1200 μm range (number fraction 80%), and the liquid-phase volumetric mass transfer coefficient was 0.018 s⁻¹. -1 .

[0036] Example 2

[0037] Adopting such Figure 1 The slurry bed reactor shown has a reactor body 10m high and 1.2m in diameter. The upper and lower end caps are hemispherical, each 1.2m in diameter. The reactor liquid level is 8.5m. A bubble generator is included. Figure 2 As shown, there are two air inlets at the throat, and four swirl vanes with a bending angle of 270° are built into the diffuser channel. The solid particles in the slurry have a diameter of less than or equal to 2 mm, and the particle / liquid specific gravity ρ... s / ρ lThe solid content is 20 wt%. The slurry enters the contraction section, throat, and diffusion section sequentially through the inlet. Under the action of the gradually contracting / diffusion structure, a negative pressure is formed, and the average liquid velocity at the throat is 0.5 m / s. Part of the gas in the gas chamber is drawn into the microbubble generator through the inlet under the negative liquid pressure. It is subjected to liquid-phase shearing, forming a large number of microbubbles. These microbubbles are carried by the liquid through the diffusion section and its outlet, exiting the microbubble generator and entering the slurry bed reactor. The remaining gas, not drawn into the microbubble generator, passes through a gas distribution plate under pressure. The gas distribution plate has three rings of 8mm vent holes. Under the shearing action of the vent holes, multiple large bubbles are formed and enter the slurry bed reactor. The ratio of the gas flow rate through the microbubble generator to the gas flow rate through the gas distribution plate is 1:9. By detecting the bubble size and liquid phase volumetric mass transfer coefficient within the reactor, the results showed that the bubble size distribution exhibited a bimodal pattern, with bubbles of diameter 100-600 μm comprising 75% of the total number of bubbles and bubbles of diameter 4-20 mm comprising 25%. The liquid phase volumetric mass transfer coefficient was 0.027 s⁻¹. -1 .

[0038] Example 3

[0039] Under the same operating conditions as in Example 1, the only difference from Example 1 is the use of... Figure 3 The bubble generator shown has three rings of vents on the gas distribution plate, each with a diameter of 2 mm, and four tangential inlets on the converging section. The results show that the bubble size distribution exhibits a bimodal pattern, with bubbles of 100-400 μm diameter comprising 85% of the total number of bubbles, and bubbles of 1-10 mm diameter comprising 15%. The liquid-phase volumetric mass transfer coefficient is 0.031 s⁻¹. -1 .

[0040] Comparative Example 2

[0041] Similar to Example 1, the difference lies in the average liquid velocity at the throat cross-section being 0.3 m / s. The resulting bubble size distribution exhibits a bimodal distribution, with 50% of the bubbles having a diameter of 400-800 μm and 50% having a diameter of 2-15 mm. The liquid phase volumetric mass transfer coefficient is 0.016 s². -1 .

[0042] Comparative Example 3

[0043] Similar to Example 2, the difference lies in the pore size of the gas outlet on the gas distribution plate being 0.5 mm. The resulting bubble size distribution exhibits a bimodal distribution, with 70% of the bubbles having a diameter of 100-500 μm and 30% having a diameter of 2-10 mm. The liquid phase volumetric mass transfer coefficient is 0.021 s². -1 .

[0044] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for generating multi-stage bubbles in a slurry bed reactor, characterized in that, The slurry bed reactor includes a shell, with a bubble generator located at the bottom of the shell. The bubble generator includes a gas chamber, a microbubble generator located within the gas chamber, and a gas distribution plate located at the top of the gas chamber. The microbubble generator is a Venturi structure including a contraction section, a throat, and a diffusion section. An air inlet is provided at the throat. The gas distribution plate is connected to the outer wall of the diffusion section, and the outlet end of the diffusion section communicates with the interior of the shell. The bottom plate of the gas chamber is connected to the outer wall of the contraction section, and a gas feed pipe is connected to the gas chamber. The contraction section is connected to a slurry feed pipe. Gas enters the gas chamber through the gas feed pipe, and slurry enters the microbubble generator through the slurry feed pipe. Under the negative pressure generated by the microbubble generator, part of the gas in the gas chamber enters the microbubble generator through the air inlet and forms microbubbles by liquid shearing. Another part of the gas enters the shell in the form of large bubbles through the gas distribution plate under the action of the gas pressure in the gas chamber. The average liquid velocity at the throat section of the microbubble generator is greater than or equal to 0.5 m / s, and the diameter of the air outlet holes on the gas distribution plate is 1-8 mm.

2. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 1, characterized in that, The ratio of the gas flow rate through the microbubble generator to the gas flow rate through the gas distribution plate in the gas chamber is 1:9-1:

1.

3. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 1, characterized in that, The solid particles in the slurry have a diameter of less than or equal to 2 mm, and the particle / liquid specific gravity ρ s / ρ l Less than or equal to 5, and solid content less than or equal to 30 wt%.

4. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 1, characterized in that, The gas outlets on the gas distribution plate are equidistantly distributed in a circle from the center to the outer edge, and the diameter of the inner circle of gas outlets is less than or equal to the diameter of the outer circle of gas outlets.

5. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 4, characterized in that, The diameter of the air outlet on the gas distribution plate is 2-4 mm, and the diameter of the inner ring air outlet increases by a ratio of 1.2-1.5 from the outer ring air outlet diameter.

6. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 1, characterized in that, The number of air inlets is 1-3.

7. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 1, characterized in that, The diffuser channel has a built-in swirl guide vane.

8. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 7, characterized in that, The number of swirl guide vanes is 1-4, and the bending angle is 270°-360°.

9. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 1, characterized in that, A liquid chamber is connected below the gas chamber. The inlet end of the contraction section is located inside the liquid chamber. The liquid chamber is connected to the slurry feed pipe. The outer wall of the inlet end of the contraction section is provided with multiple tangential inlets that are connected to the contraction section.

10. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 1, characterized in that, The shell includes an upper end cap, a lower end cap, and a cylindrical body, with the bubble generator located at the bottom of the lower end cap.

11. The method for generating multi-stage bubbles in a slurry bed reactor according to claim 1, characterized in that, The feed end of the slurry feed pipe and the air inlet end of the gas feed pipe are both located outside the housing.

Images