A fixed bed reactor

Abstract

The application discloses a fixed bed reactor, which is characterized in that heat-conducting cylinders one and two are arranged in the upper shell and the lower shell of the fixed bed reactor respectively, the material in the shell is precisely controlled in temperature through a heat-conducting medium, the catalyst is located outside the heat-conducting cylinder, a baffle is arranged to form a multilayer structure of the catalyst, the contact time of the material and the catalyst is increased, the catalytic effect is improved, the waste heat in the upper shell can be transferred to the lower shell through the heat-conducting fins, the power consumption is reduced, energy is saved, and the environment is protected, the cold material entering the feeding port in the middle is preheated, the temperature of the discharged material of the upper shell can be controlled, the temperature is prevented from rising too fast, the setting of the wake hole can prevent the reaction from being incomplete due to the laminar flow in the reaction with high single-pass conversion rate, the fixed bed reactor of the technical scheme can be provided with multiple stages according to the single-pass conversion rate, and the feeding pipe between the multiple stages can feed or not feed according to requirements, and the fixed bed of the technical scheme can be used for the catalytic reaction, high conversion rate can be achieved, the temperature can be precisely controlled, energy can be saved, the environment can be protected, and the fixed bed is suitable for promotion.

Description

Technical Field

[0001] This invention relates to the field of fixed-bed reactor technology, specifically to a fixed-bed reactor. Background Technology

[0002] A fixed-bed reactor is filled with granular solid catalysts or solid reactants to form a stacked bed of a certain height. While the material or liquid material flows through the gaps between the particles through the stationary fixed bed, a heterogeneous reaction is achieved. Fixed-bed reactors can be used for gas-phase or liquid-phase reactions in which the catalyst is in the solid phase. The reactants are injected from the top or bottom, react through the catalyst bed, and are discharged from the bottom.

[0003] Currently, most fixed-bed reactors do not have internal guiding structures. The catalyst is directly fixed in the reactor through the grid plate, and the material is discharged after passing through the catalyst. The contact time with the catalyst is short. In order to ensure sufficient contact between the material and the catalyst bed, the fixed-bed reactor needs to be made very large. This also leads to slow temperature conduction in the fixed-bed reactor, making it difficult to initiate the reaction or difficult to control the temperature runaway after the reaction is initiated. The single-pass conversion rate of the reaction is low or there are many by-products, and even production accidents may occur. Summary of the Invention

[0004] The purpose of this invention is to provide a fixed-bed reactor to solve the problems mentioned in the background art. Most of the fixed-bed reactors used in the above-mentioned art do not have a guiding structure inside. The catalyst is directly fixed in the reactor through the grid plate. The material is discharged after passing through the catalyst. The contact time with the catalyst is short. In order to ensure sufficient contact between the material and the catalyst bed, the fixed-bed reactor needs to be made very large. This also leads to slow temperature conduction in the fixed-bed reactor, making it difficult to initiate or control the reaction after it is initiated, resulting in temperature runaway, low single-pass conversion rate, or many by-products, and even production accidents.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a fixed-bed reactor, comprising an upper shell, a lower shell fixedly installed at the lower end of the upper shell, a partition fixedly installed between the upper shell and the lower shell, a feed pipe fixedly installed at the upper end of the upper shell, a grid plate fixedly installed on the inner side of the upper shell, an oil inlet pipe and an oil outlet pipe fixedly installed on the side of the upper shell, a heat-conducting cylinder fixedly installed at one end of the oil inlet pipe and the oil outlet pipe located inside the upper shell, a heat-conducting pipe fixedly installed inside the heat-conducting cylinder, a third heat-conducting pipe fixedly installed inside the heat-conducting cylinder, a distribution plate fixedly installed at the upper end of the third heat-conducting pipe, and a distribution plate fixedly installed on the outer side of the heat-conducting cylinder. The upper shell has a baffle plate 1. A discharge pipe 1 and a feed pipe 2 are fixedly installed on the side of the upper shell. A grid plate 2 is fixedly installed on the inner side of the feed pipe 2. A grid plate 3 is fixedly installed on the inner side of the lower shell. An oil inlet pipe 2 and an oil outlet pipe 2 are fixedly installed on the side of the lower shell. A heat-conducting cylinder 2 is fixedly installed at one end of the oil inlet pipe 2 and the oil outlet pipe 2 located inside the lower shell. A heat-conducting pipe 2 is fixedly installed inside the heat-conducting cylinder 2. A baffle plate 2 is fixedly installed on the outer side of the heat-conducting cylinder 2. A discharge pipe 2 is fixedly installed on the side of the lower shell. A heat-conducting fin is fixedly installed on the inner side of the upper shell. A heat-conducting pipe 4 is fixedly installed inside the heat-conducting fin. A manhole is fixedly installed on the side of the upper shell and the lower shell.

[0006] Preferably, the feed pipe is located at the center of the upper end of the upper shell and is connected to the interior of the upper shell. Two grid plates are arranged vertically and vertically, and a catalyst is placed between the grid plates. The manhole is opened and the catalyst is added to the outside of the heat-conducting cylinder. The grid plates are used to fix the catalyst, and the material is injected into the upper shell through the feed pipe.

[0007] Preferably, the first oil inlet pipe is located below the first oil outlet pipe. The first oil inlet pipe and the first oil outlet pipe are respectively connected to the interior of the first heat-conducting cylinder. The center of the first heat-conducting cylinder and the center of the upper shell are located on the same vertical line. The upper and lower ends of the first heat-conducting cylinder are respectively fixedly connected to the first grid plate. The heat-conducting medium is transported to the first heat-conducting cylinder through the first oil inlet pipe. The first heat-conducting cylinder heats the heat-conducting medium in the first heat-conducting cylinder, and the heat is transferred to the interior of the upper shell to improve the reaction efficiency in the upper shell.

[0008] Preferably, the heat pipe three has a "7" shaped structure, with its upper end extending to the outside of the heat pipe one. Six heat pipes are arranged in a ring around the vertical center line of the heat pipe one. The center of the distribution plate is located on the same vertical line as the center of the heat pipe one. The heat of the heat-conducting medium is transferred to the heat pipe one, which preheats the material. The distribution plate distributes the material entering the upper shell.

[0009] Preferably, the first baffle is a semi-circular structure, and five baffles are arranged vertically. The first baffle is distributed in a cross pattern. The first discharge pipe is located below the first grid plate. A catalyst is arranged between the partition and the third grid plate. The first baffle creates a multi-layer structure inside the upper shell, and the material is transported in a serpentine path inside the upper shell, increasing the contact time between the material and the catalyst.

[0010] Preferably, the second feed pipe has a "7" shaped structure, with its lower end extending into the interior of the lower shell. The third grid plate is located below the partition. The upper and lower ends of the second heat-conducting cylinder are fixedly connected to the partition and the third grid plate, respectively. The second oil inlet pipe is located below the second oil outlet pipe. The second oil inlet pipe and the second oil outlet pipe are connected to the interior of the second heat-conducting cylinder. The center of the second heat-conducting cylinder and the center of the lower shell are on the same vertical line. Another set of materials is injected into the lower shell through the second feed pipe. The heat-conducting medium is transported to the second heat-conducting cylinder through the second oil inlet pipe. The second heat-conducting cylinder heats the heat-conducting medium, and the heat is transferred to the interior of the lower shell, improving the reaction efficiency in the lower shell.

[0011] Preferably, the second baffle is a semi-circular structure, and four baffles are arranged vertically and crosswise. The second discharge pipe is located below the third grid plate. The second baffle creates a multi-layer structure inside the lower shell, and the material is transported in a serpentine path inside the lower shell, increasing the contact time between the material and the catalyst.

[0012] Preferably, multiple heat-conducting fins are evenly spaced and are attached to the outer side of the second feed pipe. Two heat-conducting pipes are symmetrically arranged and have a "7"-shaped structure. The lower end of the heat-conducting pipe extends into the interior of the second heat-conducting cylinder. The reacted material in the upper shell comes into contact with the heat-conducting fins, and the residual heat is transferred to the heat-conducting fins, and then transferred to the second feed pipe and the second heat-conducting pipe to preheat the material in the lower shell. The heat from the second heat-conducting pipe is then transferred to the heat-conducting medium in the second heat-conducting cylinder to assist in heating the heat-conducting medium, reducing the power consumption of the second heat-conducting pipe, recovering and utilizing waste heat, and improving environmental protection.

[0013] Preferably, the baffle has a tail flow hole on the edge near the upper shell and the baffle has a tail flow hole on the edge near the lower shell. The tail flow hole can effectively prevent some material from sticking to the dead corner of the reactor caused by laminar flow.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This fixed-bed reactor is provided with an upper shell and a lower shell for processing two streams of materials. A heat-conducting cylinder I and a heat-conducting cylinder II are respectively installed inside the upper and lower shells. The temperature of the materials inside the shells is precisely controlled by a heat-conducting medium. The catalyst is located outside the heat-conducting cylinders. Baffles I and II are respectively installed on the outer sides of the two sets of heat-conducting cylinders, forming a multi-layered structure of the catalyst, increasing the contact time between the materials and the catalyst, and further improving the catalytic effect. Heat-conducting fins are installed between the upper and lower shells to transfer residual heat from the upper shell to the lower shell, reducing power consumption and saving energy and protecting the environment. Simultaneously, the cold material entering through the central feed inlet is preheated, effectively controlling the temperature of the material exiting from the upper shell and preventing overheating. The tail flow orifice prevents incomplete reactions caused by laminar flow in reactions with high single-pass conversion rates. Furthermore, the fixed-bed reactor of the present invention can be configured with multiple stages according to the single-pass conversion rate. The feed pipes between the multiple stages can be used for feeding or not feeding as needed. The fixed-bed reactor of the present invention can achieve high conversion rates, precise temperature control, and is energy-saving and environmentally friendly for catalytic reactions, making it suitable for widespread application. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0016] Figure 2 This is a front view structural diagram of the present invention;

[0017] Figure 3 This is a top view of the structure of the present invention;

[0018] Figure 4 This is a schematic diagram of the internal structure of the present invention;

[0019] Figure 5 For the present invention Figure 4 Enlarged structural diagram at point A in the middle;

[0020] Figure 6 For the present invention Figure 4 Enlarged structural diagram at point B;

[0021] Figure 7 This is a three-dimensional structural diagram of the heat-conducting cylinder of the present invention;

[0022] Figure 8 This is a schematic diagram of the two-dimensional structure of the heat-conducting cylinder of the present invention.

[0023] The components are as follows: 1. Upper shell; 2. Lower shell; 3. Baffle plate; 4. Feed pipe 1; 5. Grille plate 1; 6. Oil inlet pipe 1; 7. Oil outlet pipe 1; 8. Heat-conducting cylinder 1; 9. Heat-conducting pipe 1; 10. Heat-conducting pipe 3; 11. Distribution plate; 12. Baffle plate 1; 13. Discharge pipe 1; 14. Feed pipe 2; 15. Grille plate 2; 16. Grille plate 3; 17. Oil inlet pipe 2; 18. Oil outlet pipe 2; 19. Heat-conducting cylinder 2; 20. Heat-conducting pipe 2; 21. Baffle plate 2; 22. Discharge pipe 2; 23. Heat-conducting fins; 24. Heat-conducting pipe 4; 25. Manhole; 26. Tailhole. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figure 1-8This invention provides a technical solution: a fixed-bed reactor, comprising an upper shell 1, a lower shell 2 fixedly installed at the lower end of the upper shell 1, manholes 25 fixedly installed on the sides of the upper shell 1 and the lower shell 2, a partition 3 fixedly installed between the upper shell 1 and the lower shell 2, a feed pipe 4 fixedly installed at the upper end of the upper shell 1, a grid plate 5 fixedly installed on the inner side of the upper shell 1, the feed pipe 4 being located at the center of the upper end of the upper shell 1 and communicating with the interior of the upper shell 1, two grid plates 5 arranged vertically, a catalyst placed between the grid plates 5, and an oil inlet pipe 6 and an oil outlet pipe 7 fixedly installed on the sides of the upper shell 1. A heat-conducting cylinder 8 is fixedly installed at one end of the oil outlet pipe 7 inside the upper housing 1. A heat-conducting pipe 9 is fixedly installed inside the heat-conducting cylinder 8. An oil inlet pipe 6 is located below the oil outlet pipe 7. The oil inlet pipe 6 and the oil outlet pipe 7 are respectively connected to the interior of the heat-conducting cylinder 8. The center of the heat-conducting cylinder 8 is on the same vertical line as the center of the upper housing 1. The upper and lower ends of the heat-conducting cylinder 8 are fixedly connected to the grid plate 5. A heat-conducting pipe 10 is fixedly installed inside the heat-conducting pipe 9. A distribution plate 11 is fixedly installed at the upper end of the heat-conducting pipe 10. The heat-conducting pipe 10 has a "7" shaped structure, and its upper end extends to the outside of the heat-conducting cylinder 8. Six rings are arranged around the vertical centerline of the heat-conducting cylinder 10. The center of the distribution plate 11 is on the same vertical line as the center of the heat-conducting cylinder 18. A baffle 12 is fixedly installed on the outside of the heat-conducting cylinder 18. A discharge pipe 13 and a feed pipe 14 are fixedly installed on the side of the upper shell 1. The baffle 12 has a semi-circular structure, and five baffles 12 are arranged vertically and crosswise. The discharge pipe 13 is located below the grid plate 5. The manhole 25 is opened to add the catalyst to the outside of the heat-conducting cylinder 18. The grid plate 5 is used to fix the catalyst. The material is injected into the upper shell 1 through the feed pipe 4. The heat transfer medium is transported to the heat-conducting cylinder 1 through the oil inlet pipe 6. In cylinder 8, heat pipe 9 heats the heat transfer medium in the heat transfer cylinder 8, and the heat is transferred to the interior of the upper shell 1 to improve the reaction efficiency in the upper shell 1. The heat of the heat transfer medium is transferred to heat pipe 10, which preheats the material. Distribution plate 11 distributes the material entering the upper shell 1. Baffle 12 forms a multi-layer structure inside the upper shell 1, and the material is transported in a serpentine path inside the upper shell 1 to increase the contact time between the material and the catalyst. The edge of baffle 12 near the upper shell 1 is provided with tail flow hole 26, which can effectively prevent some material caused by laminar flow from sticking in the dead corner of the reactor.

[0026] A catalyst is placed between the partition 3 and the grid plate 16. A grid plate 15 is fixedly installed inside the feed pipe 14. A grid plate 16 is fixedly installed inside the lower shell 2. An oil inlet pipe 17 and an oil outlet pipe 18 are fixedly installed on the side of the lower shell 2. A heat-conducting cylinder 19 is fixedly installed at one end of the oil inlet pipe 17 and the oil outlet pipe 18 inside the lower shell 2. A heat-conducting pipe 20 is fixedly installed inside the heat-conducting cylinder 19. The feed pipe 14 has a "7"-shaped structure, with its lower end extending into the lower shell 2. The grid plate 16 is located below the partition 3. The upper and lower ends of the heat-conducting cylinder 19 are fixedly connected to the partition 3 and the grid plate 16, respectively. The oil inlet pipe 17 is located below the oil outlet pipe 18. The oil inlet pipe 17 and the oil outlet pipe 18 are connected to the interior of the heat-conducting cylinder 19. The center of the heat-conducting cylinder 19 and the center of the lower shell 2 are on the same vertical line. Above, a baffle 21 is fixedly installed on the outer side of the heat-conducting cylinder 2 19, and a discharge pipe 22 is fixedly installed on the side of the lower shell 2. The baffle 21 has a semi-circular structure, and four baffles 21 are arranged vertically. The discharge pipe 22 is located below the grid plate 3 16. Another set of materials is injected into the lower shell 2 through the feed pipe 2 14. The heat-conducting medium is transported to the heat-conducting cylinder 2 19 through the oil inlet pipe 2 17. The heat-conducting pipe 20 heats the heat-conducting medium, and the heat is transferred to the interior of the lower shell 2 to improve the reaction efficiency in the lower shell 2. The baffle 21 makes the interior of the lower shell 2 form a multi-layer structure. The material is transported in a serpentine path inside the lower shell 2, which increases the contact time between the material and the catalyst. The edge of the baffle 21 near the lower shell 2 is provided with a tail flow hole 26. The tail flow hole 26 can effectively prevent some material caused by laminar flow from sticking in the dead corner of the reactor.

[0027] A heat-conducting fin 23 is fixedly installed on the inner side of the upper shell 1. A heat-conducting pipe 24 is fixedly installed inside the heat-conducting fin 23. Multiple heat-conducting fins 23 are equidistantly arranged. The heat-conducting fins 23 are attached to the outer side of the feed pipe 14. Two heat-conducting pipes 24 are symmetrically arranged. The heat-conducting pipes 24 have a "7" shaped structure. The lower end of the heat-conducting pipes 24 extends into the interior of the heat-conducting cylinder 19. The reacted material in the upper shell 1 comes into contact with the heat-conducting fins 23. The residual heat is transferred to the heat-conducting fins 23 and then to the feed pipe 14 and the heat-conducting pipes 24 to preheat the material in the lower shell 2. The heat from the heat-conducting pipes 24 is then transferred to the heat-conducting medium in the heat-conducting cylinder 19 to provide auxiliary heating for the heat-conducting medium, reduce the power consumption of the heat-conducting pipe 20, recover and utilize the waste heat, and improve environmental protection.

[0028] Working principle: First, open manhole 25 and add the catalyst to the outside of heat-conducting cylinder 1 (8) and heat-conducting cylinder 2 (19). Grille plate 1 (5) and grille plate 2 (15) are used to fix the catalyst. The heat transfer medium is conveyed to heat-conducting cylinder 1 (8) and heat-conducting cylinder 2 (19) through oil inlet pipe 1 (6) and oil inlet pipe 2 (17), respectively. Heat-conducting pipe 1 (9) and heat-conducting pipe 2 (20) heat the heat transfer medium, and the heat is transferred to heat-conducting pipe 3 (10). The material is injected into the upper shell 1 through feed pipe 1 (4). Distribution plate 11 distributes the material, and heat-conducting pipe 3 (10) preheats the material. The preheated material comes into contact with the catalyst in the upper shell 1. Baffle plate 1 (12) creates a multi-layered structure inside the upper shell 1. The material is transported in a serpentine path inside the upper shell 1, increasing the contact between the material and the catalyst. During the contact time, the material is discharged from the discharge pipe 13. The residual heat in the material is transferred to the heat-conducting fins 23, and then the heat is transferred to the feed pipe 14 and the heat-conducting pipe 24. Another group of material is injected into the lower shell 2 through the feed pipe 14. The heat from the feed pipe 14 preheats the material. The heat from the heat-conducting pipe 24 is then transferred to the heat-conducting medium in the heat-conducting cylinder 19 to assist in heating the heat-conducting medium, reduce the power consumption of the heat-conducting pipe 20, recover and utilize the waste heat, and improve environmental protection. The baffle 21 has the same function as the baffle 12, increasing the contact time between the material and the catalyst. The reacted material is discharged from the discharge pipe 22. A small amount of material stuck in the dead corner of the reactor due to laminar flow enters the next reaction layer through the tail hole 26.

[0029] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A fixed bed reactor comprising an upper housing (1), characterized in that: The lower end of the upper shell (1) is fixedly installed with a lower shell (2), the upper shell (1) and the lower shell (2) are fixedly installed with a partition plate (3), the upper end of the upper shell (1) is fixedly installed with a feeding pipe one (4), the inner side of the upper shell (1) is fixedly installed with a grating plate one (5), the side of the upper shell (1) is fixedly installed with an oil inlet pipe one (6) and an oil outlet pipe one (7), one end of the oil inlet pipe one (6) and the oil outlet pipe one (7) inside the upper shell (1) is fixedly installed with a heat conducting cylinder one (8), the inside of the heat conducting cylinder one (8) is fixedly installed with a heat conducting pipe one (9), the inside of the heat conducting cylinder one (8) is also fixedly installed with a heat conducting pipe three (10), the upper end of the heat conducting pipe three (10) is fixedly installed with a distribution plate (11), the outer side of the heat conducting cylinder one (8) is fixedly installed with a baffle one (12), the side of the upper shell (1) is fixedly installed with a discharge pipe one (13) and a feeding pipe two (14), the inner side of the feeding pipe two (14) is fixedly installed with a grating plate two (15), the inner side of the lower shell (2) is fixedly installed with a grating plate three (16), the side of the lower shell (2) is fixedly installed with an oil inlet pipe two (17) and an oil outlet pipe two (18), one end of the oil inlet pipe two (17) and the oil outlet pipe two (18) inside the lower shell (2) is fixedly installed with a heat conducting cylinder two (19), the inside of the heat conducting cylinder two (19) is fixedly installed with a heat conducting pipe two (20), the outer side of the heat conducting cylinder two (19) is fixedly installed with a baffle two (21), the side of the lower shell (2) is fixedly installed with a discharge pipe two (22), the inner side of the upper shell (1) is fixedly installed with a heat conducting fin (23), the inside of the heat conducting fin (23) is fixedly installed with a heat conducting pipe four (24), the side of the upper shell (1) and the lower shell (2) is fixedly installed with a manhole (25).

2. A fixed bed reactor according to claim 1, characterized in that: The feeding pipe one (4) is located at the center of the upper end of the upper shell (1), the feeding pipe one (4) and the inside of the upper shell (1) are mutually connected, the grating plate one (5) is provided with two from top to bottom, and the catalyst is arranged between the grating plate one (5).

3. The fixed bed reactor of claim 1, wherein: The oil inlet pipe one (6) is located below the oil outlet pipe one (7), the oil inlet pipe one (6) and the oil outlet pipe one (7) are respectively connected with the inside of the heat conducting cylinder one (8), the center of the heat conducting cylinder one (8) and the center of the upper shell (1) are located on the same vertical line, and the upper and lower ends of the heat conducting cylinder one (8) are respectively fixedly connected with the grating plate one (5).

4. The fixed bed reactor of claim 1, wherein: The heat conducting pipe three (10) is a "7" type structure, the upper end of the heat conducting pipe three (10) extends to the outer side of the heat conducting cylinder one (8), the heat conducting pipe three (10) is annularly provided with six about the vertical center line of the heat conducting cylinder one (8), and the center of the distribution plate (11) and the center of the heat conducting cylinder one (8) are located on the same vertical line.

5. The fixed bed reactor of claim 1, wherein: The first baffle (12) has a semi-circular structure. Five baffles (12) are arranged vertically. The first baffles (12) are arranged in a cross pattern. The first discharge pipe (13) is located below the first grid plate (5). A catalyst is arranged between the partition plate (3) and the third grid plate (16).

6. The fixed bed reactor of claim 1, wherein: The feed pipe 2 (14) has a "7" shaped structure. The lower end of the feed pipe 2 (14) extends into the interior of the lower shell (2). The grid plate 3 (16) is located below the partition plate (3). The upper and lower ends of the heat-conducting cylinder 2 (19) are fixedly connected to the partition plate (3) and the grid plate 3 (16) respectively. The oil inlet pipe 2 (17) is located below the oil outlet pipe 2 (18). The oil inlet pipe 2 (17) and the oil outlet pipe 2 (18) are respectively connected to the interior of the heat-conducting cylinder 2 (19). The center of the heat-conducting cylinder 2 (19) and the center of the lower shell (2) are located on the same vertical line.

7. The fixed bed reactor of claim 1, wherein: The second baffle (21) is a semi-circular structure. There are four baffles (21) arranged vertically. The second baffle (21) is distributed in a cross pattern. The second discharge pipe (22) is located below the third grid plate (16).

8. The fixed bed reactor of claim 1, wherein: Multiple heat-conducting fins (23) are equidistantly arranged. The heat-conducting fins (23) are attached to the outer side of the feed pipe two (14). Two heat-conducting pipes four (24) are symmetrically arranged. The heat-conducting pipes four (24) have a "7" shaped structure. The lower end of the heat-conducting pipes four (24) extends into the interior of the heat-conducting cylinder two (19).

9. The fixed bed reactor of claim 1, wherein: The edge of the first baffle (12) near the upper housing (1) is provided with a tail flow hole (26), and the edge of the second baffle (21) near the lower housing (2) is provided with a tail flow hole (26).

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