Gas-liquid separation reflux device

Abstract

The utility model provides a kind of gas-liquid separation backflow device, the utility model belongs to gas-liquid separation field, including backflow pipe, block backflow device, connecting pipe, three ways and open-closed ware, air inlet pipe and air outlet pipe, the upper end of backflow pipe is connected with air outlet pipe, the lower end of backflow pipe is connected with air inlet pipe, the upper end of open-closed ware is connected with the middle part of backflow pipe, the first end of three ways is connected with the lower end of backflow pipe, the second end of three ways is connected with air inlet pipe, the third end of three ways is connected with the lower end of open-closed ware by connecting pipe, one block backflow device is connected between the upper end of backflow pipe and air outlet pipe and between the lower end of backflow pipe and the first end of three ways respectively.The purpose is to solve the problem of water resource waste caused by electrolytic hydrogen production.The technical effect achieved is:good backflow effect, prevent alkali mist volatilization, reduce the rate of concentration reduction of potassium hydroxide solute while reducing water consumption, save water resources.

Description

Technical Field

[0001] This utility model relates to the field of gas-liquid separation technology, and in particular to a gas-liquid separation reflux device. Background Technology

[0002] Electrolysis of water for hydrogen production is considered one of the most promising hydrogen production technologies due to its ability to be coupled with renewable intermittent energy sources such as wind and solar power. However, the high-temperature heating of the electrolyte during electrolysis experiments leads to the generation of large amounts of water vapor and alkaline mist, which evaporate outside the system through the exhaust pipe, exacerbating electrolyte loss within the experimental apparatus. This method also increases the burden on water resources in water-scarce regions. Current experiments typically utilize condensers for reflux condensation to reduce water evaporation and potassium hydroxide solute loss; however, this also increases the consumption of water, electricity, and human resources. Utility Model Content

[0003] This invention provides a gas-liquid separation and reflux device to solve the above-mentioned problems in the prior art.

[0004] This utility model provides a gas-liquid separation reflux device, including a reflux pipe, a gas-blocking reflux device, a connecting pipe, a tee and a switch, an inlet pipe and an outlet pipe. The upper end of the reflux pipe is connected to the outlet pipe, and the lower end of the reflux pipe is connected to the inlet pipe. The upper end of the switch is connected to the middle of the reflux pipe. The first end of the tee is connected to the lower end of the reflux pipe, the second end of the tee is connected to the inlet pipe, and the third end of the tee is connected to the lower end of the switch through the connecting pipe. A gas-blocking reflux device is connected between the upper end of the reflux pipe and the outlet pipe, and between the lower end of the reflux pipe and the first end of the tee.

[0005] In addition, the gas-liquid separation reflux device according to this utility model may also have the following additional technical features:

[0006] In some embodiments of this utility model, each gas-blocking reflux device includes a gas-blocking shell and multiple first gas-blocking baffles. A gas-blocking shell is connected between the upper end of the reflux pipe and the outlet pipe, and between the lower end of the reflux pipe and the first end of the tee. Multiple first gas-blocking baffles are arranged in each gas-blocking shell from top to bottom.

[0007] In some embodiments of this utility model, each gas-blocking backflow device further includes multiple second gas-blocking baffles. Multiple second gas-blocking baffles are spaced apart from top to bottom in each gas-blocking shell. Multiple first gas-blocking baffles and multiple second gas-blocking baffles are arranged alternately in sequence. Each first gas-blocking baffle is disposed on the first side of the gas-blocking shell, and each second gas-blocking baffle is disposed on the second side of the gas-blocking shell. The first side of the gas-blocking shell and the second side of the gas-blocking shell are opposite to each other.

[0008] In some embodiments of this utility model, the opener includes an outer shell and a movable cover plate. The upper end of the outer shell is connected to the middle of the return pipe, and the lower end of the outer shell is connected to the connecting pipe. The movable cover plate is rotatably connected to the outer shell.

[0009] In some embodiments of this utility model, the opening and closing device further includes an inner shell and a fixed cover plate. The inner shell is connected to the outer shell, the fixed cover plate is installed inside the inner shell, and the movable cover plate is rotatably connected to the fixed cover plate. The movable cover plate and the fixed cover plate cooperate to seal the cross-section of the receiving cavity of the inner shell.

[0010] In some embodiments of this utility model, the opening and closing device further includes a bushing ring, and the fixed cover plate includes a rotating shaft part and a baffle part. The rotating shaft part is rotatably connected to the fixed cover plate through the bushing ring, and the baffle part is connected to the rotating shaft part.

[0011] In some embodiments of this utility model, the opening and closing device further includes a first magnet and a second magnet. The first magnet is provided on one side of the movable cover plate, and the second magnet is provided on the inner side wall of the inner shell. The second magnet is located below the fixed cover plate, and the opposing surfaces of the first magnet and the second magnet have the same magnetic properties.

[0012] In some embodiments of this utility model, each first air-blocking baffle and each second air-blocking baffle are provided with mesh holes.

[0013] In some embodiments of this utility model, the return pipe includes a first bend section, a second bend section, and an open section. The first end of the first bend section is connected to one of the gas-blocking return devices. The first end of the second bend section is connected to the second end of the first bend section. The second end of the second bend section is connected to another gas-blocking return device. An open section is provided in the middle of the second bend section, and the upper end of the opener is connected to the open section.

[0014] In some embodiments of this utility model, the return pipe further includes an outlet pipe section and an inlet pipe section. The inlet pipe section is connected between one of the gas-blocking return devices and the first bend pipe section, and the outlet pipe section is connected between another gas-blocking return device and the second bend pipe section.

[0015] In summary, this application includes the following beneficial technical effects: By coordinating the gas-blocking reflux device and the opening and closing device, when there is only a small amount of liquid at the bottom of the reflux pipe, the opening and closing device will not open. At this time, a liquid surface is formed, and the discharged gas will not return to the water electrolysis hydrogen production device through the opening and closing device. Water vapor and alkaline mist will also not directly enter the reflux pipe through the three-way valve and the opening and closing device, thus making the reflux effect better. This can prevent the volatilization of alkaline mist, slow down the rate of decrease in the concentration of potassium hydroxide solute, reduce water consumption, and save water resources. Attached Figure Description

[0016] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0017] Figure 1 A schematic diagram of the structure of a gas-liquid separation and reflux device according to some embodiments of the present invention is shown.

[0018] Figure 2 A schematic diagram of the opening and closing mechanism of a gas-liquid separation reflux device according to some embodiments of the present invention is shown.

[0019] Figure 3 A schematic diagram of the structure of the gas-blocking reflux device of the gas-liquid separation reflux device according to some embodiments of the present invention is shown.

[0020] Figure 4 A schematic diagram of the structure of the movable cover plate of a gas-liquid separation reflux device according to some embodiments of the present invention is shown.

[0021] Figure label:

[0022] 1. Return pipe; 11. First bend section; 12. Outlet pipe section; 13. Second bend section; 14. Inlet pipe section; 15. Opening section; 2. Air-blocking and return device; 21. Air-blocking shell; 22. First air-blocking baffle; 23. Second air-blocking baffle; 3. Opener / closer; 31. Outer shell; 32. Inner shell; 33. Fixed cover plate; 34. Bushing ring; 35. First magnet; 36. Movable cover plate; 361. Rotating shaft; 362. Baffle; 37. Inlet / outlet pipe; 38. Second magnet; 4. Tee; 5. Connecting pipe; 6. Inlet pipe; 7. Outlet pipe. Detailed Implementation

[0023] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0024] It should be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” used herein may also refer to the plural forms. The terms “comprising,” “including,” “containing,” and “having” are inclusive and therefore indicate the presence of the stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein are not construed as requiring them to be performed in a specific order described or illustrated unless the order of performance is explicitly indicated. It should also be understood that additional or alternative steps may be used.

[0025] Although terms such as first, second, third, etc., may be used in this document to describe multiple elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms may be used only to distinguish one element, component, region, layer, or segment from another. Unless the context clearly indicates otherwise, terms such as "first," "second," and other numerical terms used herein do not imply order or sequence. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0026] For ease of description, spatial relative terms may be used in the text to describe the relationship of one element or feature relative to another element or feature, as shown in the figure. These relative terms include, for example, "inside," "outside," "middle," "outer," "below," "below," "above," "over," etc. Such spatial relative terms are intended to include different orientations of the device in use or operation, other than those depicted in the figure. For example, if the device in the figure is flipped, an element described as "below other elements or features" or "below other elements or features" would subsequently be oriented "above other elements or features" or "above other elements or features." Therefore, the example term "below" can include both upper and lower orientations. The device may also be rotated 90 degrees or in other orientations, and the spatial relative descriptors used in the text will be interpreted accordingly.

[0027] like Figures 1 to 4As shown, according to an embodiment of the first aspect of this utility model, a gas-liquid separation reflux device is proposed, including a reflux pipe 1, a gas-blocking reflux device 2, a connecting pipe 5, a tee 4 and a valve 3, an inlet pipe 6 and an outlet pipe 7. The upper end of the reflux pipe 1 is connected to the outlet pipe 7, the lower end of the reflux pipe 1 is connected to the inlet pipe 6, the upper end of the valve 3 is connected to the middle part of the reflux pipe 1, the first end of the tee 4 is connected to the lower end of the reflux pipe 1, the second end of the tee 4 is connected to the inlet pipe 6, and the third end of the tee 4 is connected to the lower end of the valve 3 through the connecting pipe 5. A gas-blocking reflux device 2 is connected between the upper end of the reflux pipe 1 and the outlet pipe 7, and between the lower end of the reflux pipe 1 and the first end of the tee 4.

[0028] In the above embodiments, it should be noted that the reflux pipe 1 is S-shaped, the end of the air inlet pipe 6 away from the tee 4 is connected to the exhaust port of the existing water electrolysis hydrogen production device, and the bottom of the switch 3 is equipped with a switch valve.

[0029] The gas-blocking reflux device 2 is used to block the gas from passing through from top to bottom while allowing water vapor to adhere as much as possible. When the water vapor condenses and refluxes, it flows back to the opening and closing device 3. When a certain amount of liquid accumulates in the opening and closing device 3, the switch valve of the opening and closing device 3 opens, and the liquid flows out through the three-way valve 4 back to the water electrolysis hydrogen production device for secondary electrolysis hydrogen production.

[0030] The technical effect achieved by the above embodiment is as follows: the gas reflux device 2 and the opening and closing device 3 are combined to achieve the following: when there is only a small amount of liquid at the bottom of the reflux pipe 1, the opening and closing device 3 will not open. At this time, a liquid surface is formed, and the discharged gas will not return to the water electrolysis hydrogen production device through the opening and closing device 3. Water vapor will also not directly enter the reflux pipe 1 through the three-way valve 4 and the opening and closing device 3. This results in a better reflux effect, which can prevent the evaporation of alkaline mist, slow down the rate of decrease in the concentration of potassium hydroxide solute, reduce water consumption, and save water resources.

[0031] Optional, such as Figures 1 to 4 As shown, each gas-blocking reflux device 2 includes a gas-blocking shell 21 and multiple first gas-blocking baffles 22. A gas-blocking shell 21 is connected between the upper end of the reflux pipe 1 and the outlet pipe 7, and between the lower end of the reflux pipe 1 and the first end of the tee 4. Multiple first gas-blocking baffles 22 are arranged in each gas-blocking shell 21 from top to bottom.

[0032] In the above optional embodiments, it should be noted that each first air-blocking baffle 22 is connected to the air-blocking shell 21 by means of screwing, welding, snapping, or bonding. Each first air-blocking baffle 22 has multiple holes in a circular or rectangular array. The air-blocking shell 21 is connected to the first end of the tee 4 by means of screwing, welding, snapping, or bonding. The air-blocking shell 21 is connected to the lower end of the return pipe 1 by means of screwing, welding, snapping, or bonding. The upper end of the return pipe 1 is connected to the air-blocking shell 21 by means of screwing, welding, snapping, or bonding. The vent pipe 7 is connected to the air-blocking shell 21 by means of screwing, welding, snapping, or bonding.

[0033] Optional, such as Figures 1 to 4 As shown, each gas-blocking backflow device 2 also includes multiple second gas-blocking baffles 23. Multiple second gas-blocking baffles 23 are arranged at intervals from top to bottom in each gas-blocking shell 21. Multiple first gas-blocking baffles 22 and multiple second gas-blocking baffles 23 are arranged alternately in sequence. Each first gas-blocking baffle 22 is arranged on the first side of the gas-blocking shell 21, and each second gas-blocking baffle 23 is arranged on the second side of the gas-blocking shell 21. The first side of the gas-blocking shell 21 is opposite to the second side of the gas-blocking shell 21.

[0034] In the above optional embodiments, it should be noted that each second air-blocking baffle 23 is connected to the air-blocking shell 21 by means of screwing, welding, snapping, or bonding, and each second air-blocking baffle 23 has multiple holes in a circular array or rectangular array, etc.; each adjacent first air-blocking baffle 22 and second air-blocking baffle 23 have overlapping portions.

[0035] The beneficial effects of the above optional embodiments are as follows: the combined arrangement of multiple first gas-blocking baffles 22 and multiple second gas-blocking baffles 23 not only blocks the backflow of gas but also allows water vapor to adhere and form water. When a certain amount of water droplets adhere, they will fall off from the corresponding first gas-blocking baffles 22 and the corresponding second gas-blocking baffles 23 due to gravity. The liquid in the gas-blocking backflow device 2 located between the upper end of the return pipe 1 and the outlet pipe 7 falls into the opening and closing device 3 and accumulates to a certain amount. After the opening and closing device 3 is opened, the liquid flows into the tee 4 and then enters the water electrolysis hydrogen production device for secondary use through the inlet pipe 6. The liquid in the gas-blocking backflow device 2 between the lower end of the return pipe 1 and the first end of the tee 4 directly enters the tee 4 and then enters the water electrolysis hydrogen production device for secondary use through the inlet pipe 6. This reduces water consumption and alkali mist volatilization, realizing the secondary use of water resources while reducing the consumption of electricity or human resources.

[0036] Optional, such as Figures 1 to 4 As shown, each of the first air-blocking baffles 22 and each of the second air-blocking baffles 23 is provided with mesh holes.

[0037] Optional, such as Figures 1 to 4 As shown, the opener 3 includes an outer shell 31 and a movable cover plate 36. The upper end of the outer shell 31 is connected to the middle of the return pipe 1, and the lower end of the outer shell 31 is connected to the connecting pipe 5. The movable cover plate 36 is rotatably connected inside the outer shell 31.

[0038] In the above optional embodiments, it should be noted that the movable cover plate 36 can be connected to the outer shell 31 by means of a rotating shaft and a torsion spring; it also includes an inlet / outlet port 37, with an inlet / outlet port 37 connected to the upper and lower ends of the outer shell 31 respectively; the upper end of the outer shell 31 is connected to the middle of the return pipe 1 through an inlet / outlet port 37, and the lower end of the outer shell 31 is connected to the connecting pipe 5 through an inlet / outlet port 37.

[0039] Optional, such as Figures 1 to 4 As shown, the opening and closing device 3 also includes an inner housing 32 and a fixed cover plate 33. The inner housing 32 is connected inside the outer housing 31, and the fixed cover plate 33 is installed inside the inner housing 32. The movable cover plate 36 is rotatably connected to the fixed cover plate 33. The movable cover plate 36 and the fixed cover plate 33 cooperate to seal the cross section of the receiving cavity of the inner housing 32.

[0040] Optional, such as Figures 1 to 4 As shown, the opening and closing device 3 also includes a bushing ring 34, and the fixed cover plate 33 includes a rotating shaft part 361 and a baffle part 362. The rotating shaft part 361 is rotatably connected to the fixed cover plate 33 through the bushing ring 34, and the baffle part 362 is connected to the rotating shaft part 361.

[0041] Optional, such as Figures 1 to 4 As shown, the opener 3 also includes a first magnet 35 and a second magnet 38. The first magnet 35 is provided on one side of the movable cover plate 36, and the second magnet 38 is provided on the inner side wall of the inner housing 32. The second magnet 38 is located below the fixed cover plate 33, and the opposing surfaces of the first magnet 35 and the second magnet 38 have the same magnetic properties.

[0042] In the above optional embodiments, it should be noted that the cooperation between the movable cover plate 36 and the fixed cover plate 33 to seal the cross-section of the receiving cavity of the inner shell 32 refers to the cross-section of the receiving cavity that is perpendicular to the vertical direction of the opening and closing device 3; a first magnet 35 is provided on one side of the movable cover plate 36 by means of screwing or bonding, and a second magnet 38 is provided on the inner sidewall of the inner shell 32 by means of screwing or bonding.

[0043] The advantages of the above optional embodiments are that the effective opening and closing of the movable cover 36 is achieved through the cooperative arrangement of the first magnet 35 and the second magnet 38.

[0044] Optional, such as Figures 1 to 4As shown, the return pipe 1 includes a first bend section 11, a second bend section 13, and an open section 15. The first end of the first bend section 11 is connected to one of the gas-blocking return devices 2. The first end of the second bend section 13 is connected to the second end of the first bend section 11. The second end of the second bend section 13 is connected to another gas-blocking return device 2. An open section 15 is provided in the middle of the second bend section 13. The upper end of the opener 3 is connected to the open section 15.

[0045] In the above optional embodiments, it should be noted that the shapes of the first bend section 11 and the second bend section 13 are both "U" shaped.

[0046] Optional, such as Figures 1 to 4 As shown, the return pipe 1 also includes an outlet pipe section 12 and an inlet pipe section 14. The inlet pipe section 14 is connected between one of the gas-blocking return devices 2 and the first bend pipe section 11, and the outlet pipe section 12 is connected between the other gas-blocking return device 2 and the second bend pipe section 13.

[0047] The working principle of this device is as follows: The exhaust port of the water electrolysis hydrogen production device is connected to the air inlet 6 of this device, allowing water vapor to enter the return pipe 1 through the air inlet pipe 6. The gas in the water vapor flows out sequentially through one of the gas-blocking return devices 2, the return pipe 3, and another gas-blocking return device 2. Multiple first gas-blocking baffles 22 and multiple second gas-blocking baffles 23 are set to block the gas flow while ensuring that the water vapor adheres to these baffles as much as possible. An opening section 15 is provided at the bottom of the return pipe 1 to facilitate the return of water vapor from the return pipe 1 and the exhaust pipe 7 into the cover device. When a certain amount of liquid accumulates in the opening section 15 at the bottom of the return pipe 1, the weight of the liquid exceeds the repulsive force between the first magnet 35 and the second magnet 38, causing the movable cover plate 36 to open, and the liquid flows back to the water electrolysis hydrogen production device through the three-way valve 4.

[0048] Due to the repulsive force between the first magnet 35 and the second magnet 38, when there is only a small amount of liquid at the bottom of the reflux pipe 1, the movable cover 36 will not open. At this time, a liquid surface is formed, and the discharged gas will not return to the reaction device through the opener 3. Water vapor and alkali mist will also not directly enter the reflux pipe 1 through the three-way valve 4 and then through the opener 3, thus avoiding a weakening of the reflux effect. This achieves the purpose of preventing alkali mist volatilization, slowing down the rate of decrease in the concentration of potassium hydroxide solute, reducing water consumption, and saving water resources.

[0049] The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A gas-liquid separation reflux device, characterized in that, It includes a return pipe (1), an air-blocking return device (2), a connecting pipe (5), a tee (4) and a switch (3), an air inlet pipe (6) and an air outlet pipe (7). The upper end of the return pipe (1) is connected to the air outlet pipe (7), the lower end of the return pipe (1) is connected to the air inlet pipe (6), the upper end of the switch (3) is connected to the middle part of the return pipe (1), the first end of the tee (4) is connected to the lower end of the return pipe (1), the second end of the tee (4) is connected to the air inlet pipe (6), and the third end of the tee (4) is connected to the lower end of the switch (3) through the connecting pipe (5). An air-blocking return device (2) is connected between the upper end of the return pipe (1) and the air outlet pipe (7) and between the lower end of the return pipe (1) and the first end of the tee (4).

2. The gas-liquid separation reflux device according to claim 1, characterized in that, Each of the gas-blocking return devices (2) includes a gas-blocking shell (21) and a plurality of first gas-blocking baffles (22). A gas-blocking shell (21) is connected between the upper end of the return pipe (1) and the outlet pipe (7) and between the lower end of the return pipe (1) and the first end of the tee (4). A plurality of first gas-blocking baffles (22) are arranged in each gas-blocking shell (21) from top to bottom.

3. The gas-liquid separation reflux device according to claim 2, characterized in that, Each of the gas-blocking backflow devices (2) further includes a plurality of second gas-blocking baffles (23). Each of the gas-blocking shells (21) is provided with a plurality of second gas-blocking baffles (23) spaced from top to bottom. A plurality of first gas-blocking baffles (22) and a plurality of second gas-blocking baffles (23) are arranged alternately in sequence. Each first gas-blocking baffle (22) is provided on the first side of the gas-blocking shell (21), and each second gas-blocking baffle (23) is provided on the second side of the gas-blocking shell (21). The first side of the gas-blocking shell (21) is opposite to the second side of the gas-blocking shell (21).

4. The gas-liquid separation reflux device according to claim 1, characterized in that, The opening / closing device (3) includes an outer shell (31) and a movable cover plate (36). The upper end of the outer shell (31) is connected to the middle part of the return pipe (1), and the lower end of the outer shell (31) is connected to the connecting pipe (5). The movable cover plate (36) is rotatably connected inside the outer shell (31).

5. The gas-liquid separation reflux device according to claim 4, characterized in that, The opening and closing device (3) also includes an inner shell (32) and a fixed cover plate (33). The inner shell (32) is connected to the outer shell (31). The fixed cover plate (33) is installed in the inner shell (32). The movable cover plate (36) is rotatably connected to the fixed cover plate (33). The movable cover plate (36) and the fixed cover plate (33) cooperate to seal the cross section of the receiving cavity of the inner shell (32).

6. The gas-liquid separation reflux device according to claim 5, characterized in that, The opening and closing device (3) also includes a bushing ring (34), and the fixed cover plate (33) includes a rotating shaft part (361) and a baffle part (362). The rotating shaft part (361) is rotatably connected to the fixed cover plate (33) through the bushing ring (34), and the baffle part (362) is connected to the rotating shaft part (361).

7. The gas-liquid separation reflux device according to claim 6, characterized in that, The opening and closing device (3) also includes a first magnet (35) and a second magnet (38). The first magnet (35) is provided on one side of the movable cover plate (36), and the second magnet (38) is provided on the inner side wall of the inner shell (32). The second magnet (38) is located below the fixed cover plate (33), and the first magnet (35) and the second magnet (38) have the same surface magnetism.

8. The gas-liquid separation reflux device according to claim 3, characterized in that, Each of the first air-blocking baffles (22) and each of the second air-blocking baffles (23) is provided with a grid hole.

9. The gas-liquid separation reflux device according to claim 1, characterized in that, The return pipe (1) includes a first bend section (11), a second bend section (13), and an open section (15). The first end of the first bend section (11) is connected to one of the gas-blocking return devices (2). The first end of the second bend section (13) is connected to the second end of the first bend section (11). The second end of the second bend section (13) is connected to the other gas-blocking return device (2). The open section (15) is provided in the middle of the second bend section (13). The upper end of the opener (3) is connected to the open section (15).

10. The gas-liquid separation reflux device according to claim 9, characterized in that, The return pipe (1) further includes an outlet pipe section (12) and an inlet pipe section (14). The inlet pipe section (14) is connected between one of the gas-blocking return devices (2) and the first bend pipe section (11). The outlet pipe section (12) is connected between the other gas-blocking return device (2) and the second bend pipe section (13).

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