Tank system and gas replacement method

Abstract

A tank system according to the present disclosure comprises: a tank that is capable of retaining gas; a first pipe that has a plurality of openings provided along the upper wall surface in the tank, and that causes a first gas to flow into and out of the tank through the openings; and a second pipe that has a plurality of openings provided along the lower wall surface in the tank, and that causes a second gas having a density higher than that of the first gas to flow into and out of the tank through the openings. Accordingly, replacement between the first gas and the second gas in the tank can be easily performed by simple equipment.

Description

Tank system and gas replacement method

[0001] This application claims priority to Japanese Patent Application No. 2023-210546, filed on December 13, 2023, the contents of which are incorporated herein by reference.

[0002] For example, Patent Document 1 discloses a tank structure capable of replacing gases with different densities. In this tank structure, when the density of the replacement gas is lower than the density of the gas to be replaced, the replacement gas is supplied upward from an upper nozzle ring located at the top of the tank. The gas to be replaced is then discharged through a lower exhaust pipe located at the bottom of the tank. On the other hand, when the density of the replacement gas is higher than the density of the gas to be replaced, the replacement gas is supplied downward from a lower nozzle ring located at the bottom of the tank. The gas to be replaced is then discharged through an upper exhaust pipe located at the top of the tank.

[0003] Japanese Patent Application Laid-Open No. 2001-32998

[0004] However, the tank structure described in Patent Document 1 requires two nozzle rings for supplying replacement gas into the tank, as well as two exhaust pipes, one above the other, for discharging the gas to be replaced from inside the tank, which results in a complex piping structure.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a tank system and a gas replacement method that can avoid the piping structure from becoming complicated.

[0006] In order to solve the above problems, the tank system of the present disclosure includes a tank capable of storing gas, a first pipe having a plurality of openings arranged along an upper wall surface of the tank, through which a first gas flows in and out of the tank, and a second pipe having a plurality of openings arranged along a lower wall surface of the tank, through which a second gas having a density greater than that of the first gas flows in and out of the tank.

[0007] A gas replacement method according to the present disclosure is a gas replacement method using the tank system described above, and includes a step of discharging the first gas from the tank through an opening of the first piping while supplying the second gas into the tank in which the first gas is stored through an opening of the second piping.

[0008] The gas replacement method according to the present disclosure is a gas replacement method using the tank system described above, and includes a step of supplying the first gas into the tank in which the second gas is stored through an opening of the first piping, while discharging the second gas from the tank through an opening of the piping.

[0009] According to the tank system and gas replacement method according to the present disclosure, maintainability can be improved.

[0010] FIG. 1 is an overall view showing an overview of a tank system according to a first embodiment of the present disclosure. FIG. 2 is an overall view showing an overview of a tank system according to a second embodiment of the present disclosure. FIG. 3 is an overall view showing an overview of a tank system according to a modified example of the second embodiment of the present disclosure. FIG. 4 is an enlarged view of a main part showing the structure of a header of a tank system according to a third embodiment of the present disclosure. FIG. 5 is an enlarged view of a main part showing the structure of a header and branch pipes of a tank system according to a fourth embodiment of the present disclosure. FIG. 6 is an enlarged view of a main part showing the structure of a header and branch pipes of a tank system according to a fifth embodiment of the present disclosure. FIG. 7 is an enlarged view of a main part showing the structure of a header and branch pipes of a tank system according to a sixth embodiment of the present disclosure. FIG. 8 is an enlarged view of a main part showing the structure of a header and branch pipes of a tank system according to a seventh embodiment of the present disclosure. FIG. 9 is an enlarged view of a main part showing the structure of a header and branch pipes of a tank system according to an eighth embodiment of the present disclosure.

[0011] First Embodiment Next, a first embodiment of a tank system 1 according to an embodiment of the present disclosure will be described with reference to Fig. 1. Tank System As shown in Fig. 1, the tank system 1 includes a rectangular tank 10 as a tank, a first pipe 20, a second pipe 30, a first gas supply / discharge unit 40, a second gas supply / discharge unit 50, an inert gas supply unit 60, and a gas sensor 70.

[0012] <Rectangular Tank> The rectangular tank 10 is a tank having a rectangular parallelepiped shape and an interior that defines a gas storage space R. The top surface of the inner surface 11 of the rectangular tank 10 is an upper wall surface 12. The upper wall surface 12 is flat and extends horizontally. The bottom surface of the inner surface 11 of the rectangular tank 10 is a lower wall surface 13. The lower wall surface 13 is flat and extends horizontally. The upper wall surface 12 and the lower wall surface 13 are arranged parallel to each other and are arranged opposite each other in the vertical direction.

[0013] <First piping> The first piping 20 is piping provided in the upper part of the storage space R inside the rectangular tank 10, close to the top wall surface 12. The first piping 20 has a first header 21 and a plurality of first branch pipes 22. The first header 21 extends horizontally along the top wall surface 12 at a height position below and close to the top wall surface 12 in the storage space R. The first header 21 is fixed to the rectangular tank 10 via, for example, a bracket (not shown).

[0014] The first branch pipe 22 is a pipe that communicates with the first header 21. A plurality of first branch pipes 22 are provided at intervals in the extension direction of the first header 21. The first branch pipe 22 extends upward from a base end where the first branch pipe 22 is connected to the first header 21. A first opening 23 that opens upward is formed at the tip, which is the upper end of the first branch pipe 22. The first opening 23 allows the first gas to flow in and out between the first piping 20 and the storage space R. The heights of the first openings 23 of each first branch pipe 22 are the same. The first openings 23 of each first branch pipe 22 face the upper wall surface 12 of the rectangular tank 10 from below. The vertical distance between the first openings 23 and the upper wall surface 12 is set to, for example, a range of 30 mm to 200 mm, and preferably a range of 50 mm to 150 mm.

[0015] <Second piping> The second piping 30 is provided in the lower part of the storage space R inside the rectangular tank 10, close to the bottom wall surface 13. The second piping 30 has a second header 31 and a plurality of second branch pipes 32. The second header 31 extends horizontally along the bottom wall surface 13 at a height position above the bottom wall surface 13, close to the bottom wall surface 13 in the storage space R. The second header 31 is fixed to the rectangular tank 10 via a bracket (not shown), for example.

[0016] The second branch pipe 32 is a pipe that communicates with the second header 31. A plurality of second branch pipes 32 are provided at intervals in the extension direction of the second header 31. The second branch pipe 32 extends downward from a base end where the second branch pipe 32 is connected to the second header 31. A second opening 33 that opens downward is formed at the lower end of the second branch pipe 32. The second opening 33 allows the second gas to flow in and out between the second piping 30 and the storage space R. The heights of the second openings 33 of each second branch pipe 32 are the same. The second openings 33 of each second branch pipe 32 face the bottom wall surface 13 of the rectangular tank 10 from above. The vertical distance between the second opening 33 and the bottom wall surface 13 is set to, for example, a range of 50 mm to 200 mm, and preferably a range of 50 mm to 150 mm.

[0017] <First Gas Supply and Discharge Unit> The first gas supply and discharge unit 40 supplies the first gas to the first piping 20 and discharges the first gas from the first piping 20. The first supply and discharge unit has a first gas tank 41, a first gas pipe 42, a first supply and discharge pipe 43, a first gas valve 44, and a first exhaust valve 45.

[0018] The first gas tank 41 is a tank disposed outside the rectangular tank 10 independently of the rectangular tank 10, and stores a first gas in a compressed state. The first gas pipe 42 is a pipe connected to the first gas tank 41. That is, one end of the first gas tank 41 is connected in communication with the first gas tank 41. The other end of the first gas tank 41 is connected to the outside of the system.

[0019] The first supply / discharge pipe 43 is a pipe that extends through the rectangular tank 10 to connect the first gas pipe 42 and the first piping 20. One end of the first supply / discharge pipe 43 is arranged to communicate with the first gas pipe 42. The other end of the first supply / discharge pipe 43 is connected to the first header 21 of the first piping 20.

[0020] The first gas valve 44 is an on-off valve provided on the first gas pipe 42. The first gas valve 44 is provided at a position on the first gas pipe 42 closer to the first gas tank 41 than the connection point between the first gas pipe 42 and the first supply and exhaust pipe 43. The first exhaust valve 45 is an on-off valve provided on the first gas pipe 42. The first exhaust valve 45 is provided at a position on the first gas pipe 42 on the opposite side from the first gas tank 41 than the connection point between the first gas pipe 42 and the first supply and exhaust pipe 43. In other words, the connection point between the first gas pipe 42 and the first supply and exhaust pipe 43 is located between the first gas valve 44 and the first exhaust valve 45.

[0021] <Second Gas Supply and Discharge Unit> The second gas supply and discharge unit 50 supplies the second gas to the second piping 30 and discharges the second gas from the second piping 30. The second gas supply and discharge unit 50 has a second gas tank 51, a second gas pipe 52, a second supply and discharge pipe 53, a second gas valve 54, and a second exhaust valve 55.

[0022] The second gas tank 51 is a tank provided outside the rectangular tank 10 and independent of the rectangular tank 10, and stores the second gas in a compressed state.

[0023] Here, the density of the second gas in the atmosphere is greater than the density of the first gas. Various gases can be used as the first gas and the second gas as long as there is the above-mentioned density difference. Assuming there is the above-mentioned density difference, for example, ammonia gas or the like can be used as the first gas, and carbon dioxide gas, LNG gas, LPG gas, or the like can be used as the second gas. Specific examples of combinations of the first gas and the second gas include ammonia / dry air, dry air / carbon dioxide, methane / carbon dioxide, and propane / nitrogen.

[0024] The second gas pipe 52 is a pipe connected to the second gas tank 51. That is, one end of the second gas tank 51 is connected in communication with the gas tank, and the other end of the second gas tank 51 is connected to the outside of the system.

[0025] The second supply / discharge pipe 53 is a pipe that extends through the rectangular tank 10 to connect the second gas pipe 52 and the second piping 30. Two ends of the second supply / discharge pipe 53 are arranged to communicate with the second gas pipe 52. The other end of the second supply / discharge pipe 53 is connected to the second header 31 of the second piping 30.

[0026] The second gas valve 54 is an on-off valve provided on the second gas pipe 52. The second gas valve 54 is provided at a position on the second gas pipe 52 closer to the second gas tank 51 than the connection point between the second gas pipe 52 and the second supply / discharge pipe 53. The second exhaust valve 55 is an on-off valve provided on the second gas pipe 52. The second exhaust valve 55 is provided at a position on the second gas pipe 52 on the opposite side from the second gas tank 51 than the connection point between the second gas pipe 52 and the second supply / discharge pipe 53. In other words, the connection point between the second gas pipe 52 and the second supply / discharge pipe 53 is located between the second gas valve 54 and the second exhaust valve 55.

[0027] <Inert Gas Supply Unit> The inert gas supply unit 60 is capable of supplying inert gas into the rectangular tank 10. The inert gas supply unit 60 includes an inert gas source 61, a first inert pipe 62, a first inert valve 63, a second inert pipe 64, and a second inert valve 65.

[0028] The inert gas source 61 is a device capable of generating an inert gas. The density of the inert gas in the atmosphere is greater than that of the first gas and less than that of the second gas. The inert gas is a gas that is interposed between the first gas and the second gas when the first gas is replaced with the second gas. In this embodiment, the inert gas is defined to include air as well as inert gases such as nitrogen. Air can also be used as the inert gas as long as it does not react with either the first gas or the second gas.

[0029] The first inert pipe 62 connects the inert gas source 61 and the first pipe 20. One end of the first inert pipe 62 is connected to and communicates with the inert gas source 61. The other end of the first inert pipe 62 is connected to and communicates with the first gas pipe 42. That is, in this embodiment, the first inert pipe 62 is connected to the first pipe 20 via the first gas pipe 42.

[0030] The first inert valve 63 is an on-off valve provided on the first inert pipe 62. The first inert valve 63 opens and closes to allow or restrict the supply of inert gas to the first pipe 20.

[0031] The second inert pipe 64 connects the inert gas source 61 and the second pipe 30. One end of the second inert pipe 64 is connected to and communicates with the inert gas source 61. The other end of the second inert pipe 64 is connected to and communicates with the second gas pipe 52. That is, in this embodiment, the second inert pipe 64 is connected to the second pipe 30 via the second gas pipe 52.

[0032] The second inert valve 65 is an on-off valve provided on the second inert pipe 64. The second inert valve 65 opens and closes to allow or restrict the supply of inert gas to the second pipe 30.

[0033] <Gas Sensor> The gas sensor 70 is a sensor capable of detecting the components of gas inside the rectangular tank 10. The gas sensor 70 is capable of detecting the components of gases that it comes into contact with. The gas sensor 70 of this embodiment can detect the components of the first gas, the second gas, and the inert gas. Note that the gas sensor 70 may be configured to detect the presence of the first gas, the second gas, and the inert gas by detecting the concentration of a specific gas component, such as oxygen.

[0034] A plurality of gas sensors 70 are provided at intervals in the vertical direction inside the rectangular tank 10. The positions of the gas sensors 70 in the figure indicate the positions at which the gas sensors 70 detect gas. The uppermost gas sensor 70 among the plurality of gas sensors 70 is installed at the same height as the first opening 23 of the first pipe 20, at a height position where it contacts the upper wall surface 12, or at a height position between the first opening 23 of the first pipe 20 and the upper wall surface 12. The lowermost gas sensor 70 among the plurality of gas sensors 70 is installed at the same height as the second opening 33 of the second pipe 30, at a height position where it contacts the lower wall surface 13, or at a height position between the second opening 33 of the second pipe 30 and the lower wall surface 13. The plurality of gas sensors 70 may be provided not only in the vertical direction but also in the horizontal direction.

[0035] <Operation and Effect> Next, the operation and effect of this embodiment will be described. By using the tank system 1, it is possible to replace the first gas and the second gas via an inert gas.

[0036] <Replacing a Low-Density Gas with a High-Density Gas> First, a procedure for replacing the first gas filled in the rectangular tank 10 with an inert gas will be described. With all valves closed, the second inert valve 65 and the first exhaust valve 45 are opened. As a result, the inert gas stored in the inert gas source 61 is guided to the second piping 30 via the second inert pipe 64, the second gas pipe 52, and the second supply / discharge pipe 53. The inert gas passes through the second header 31 of the second piping 30, reaches each second branch pipe 32, and then reaches the inside of the rectangular tank 10 via the second opening 33 of the second piping 30.

[0037] Because the inert gas has a higher density than the first gas, it accumulates in the lower part of the storage space R of the rectangular tank 10. As a result, as the pressure inside the rectangular tank 10 increases, the first gas, which is lighter than the inert gas, has nowhere to go inside the rectangular tank 10, and as a result, it enters each of the first branch pipes 22 through each of the first openings 23 of the first piping 20 and circulates inside the first piping 20. In this way, the first gas circulating inside the first piping 20 flows through the first supply / exhaust pipe 43, the first gas pipe 42, and the first exhaust valve 45, and is led outside the system, where the pressure is lower than the internal pressure of the rectangular tank 10. This progresses the replacement of gas inside the rectangular tank 10.

[0038] As the gas replacement progresses, the inert gas occupies the lower region of the accommodation space R, and the first gas is driven upward into the accommodation space R. That is, the boundary surface between the inert gas and the first gas gradually transitions upward into the accommodation space R. Such transition of the boundary surface can be confirmed by the detected components of the multiple gas sensors 70.

[0039] The first gas collected near the upper wall surface 12 of the storage space R is then discharged from the storage space R through the first opening 23 of the first piping 20, and as a result, the inert gas occupies the entire area of ​​the storage space R. This completes the replacement of the first gas with the inert gas. The completion of the replacement can be confirmed by the detection result of the gas sensor 70.

[0040] Next, after all the valves are closed, the second gas valve 54 and the first exhaust valve 45 are opened. As a result, the inert gas is replaced with the second gas from the bottom to the top within the accommodation space R of the rectangular tank 10, as described above, and the inert gas or the mixed gas of the inert gas and the second gas is discharged outside the rectangular tank 10 system.

[0041] When replacing the inert gas with the second gas in this manner, the supply pressure of the second gas needs to be greater than the internal pressure of the rectangular tank 10. For this reason, a blower for pressure-feeding the second gas may be provided.

[0042] <Replacing a High-Density Gas with a Low-Density Gas> Next, a procedure for replacing the second gas filled in the rectangular tank 10 with an inert gas will be described. With all valves closed, the first inert valve 63 and the second exhaust valve 55 are opened. As a result, the inert gas supplied from the inert gas source 61 is guided to the first piping 20 via the first inert pipe 62, the first gas pipe 42, and the first supply / discharge pipe 43. The inert gas passes through the first header 21 of the first piping 20, reaches each of the first branch pipes 22, and reaches the inside of the rectangular tank 10 via the second opening 33 of the first piping 20.

[0043] Because the inert gas has a lower density than the second gas, it accumulates in the upper part of the storage space R of the rectangular tank 10. As a result, as the pressure inside the rectangular tank 10 increases, the second gas, which is heavier than the inert gas, has nowhere to go inside the rectangular tank 10, and enters each second branch pipe 32 through each second opening 33 of the second pipe 30, and circulates inside the second pipe 30. The second gas circulating inside the second pipe 30 in this way flows through the second supply / exhaust pipe 53, the second gas pipe 52, and the second exhaust valve 55, and is led outside the system, where the pressure is lower than the internal pressure of the rectangular tank 10. This progresses the gas replacement inside the rectangular tank 10.

[0044] As the gas replacement progresses, the inert gas occupies the upper region of the storage space R, and the second gas is driven downward into the storage space R. That is, the boundary surface between the inert gas and the second gas gradually transitions downward into the storage space R. As described above, the transition of the boundary surface can be confirmed by the multiple gas sensors 70.

[0045] The second gas collected near the lower wall surface 13 of the storage space R is then discharged from the storage space R through the second opening 33 of the second piping 30, resulting in the inert gas occupying the entire area of ​​the storage space R. This completes the replacement of the second gas with the inert gas. Note that the replacement of the inert gas in the rectangular tank 10 with the first gas can also be carried out by appropriately operating the valve, as described above. The replacement of the first gas with the second gas may also be carried out directly without using the inert gas.

[0046] As described above, in this embodiment, when replacing the gas in the rectangular tank 10, both the first piping 20 and the second piping 30 are used for both supplying and discharging the gas. Therefore, for example, there is no need to provide separate supply and discharge pipes for the first gas and the second gas, and the piping configuration can be simplified. As a result, material and construction costs during manufacturing can be reduced, and various benefits can be obtained, such as a simplification of the equipment, a reduction in the number of monitoring points during operation, a reduction in the number of objects to be operated, a reduction in the number of objects to be inspected during maintenance, and a reduction in the number of objects to be repaired.

[0047] Furthermore, the first opening 23 of the first piping 20 is disposed close to and along the upper wall surface 12, and the second opening 33 of the second piping 30 is disposed close to and along the lower wall surface 13, so that gas that accumulates in the upper or lower part of the storage space R can be smoothly discharged. This allows gas replacement using the difference in specific gravity to be performed quickly, and also minimizes the amount of gas to be replaced remaining in the rectangular tank 10. This not only improves work efficiency, but also reduces the amount of gas that is discharged before replacement is complete.

[0048] The vertical distance between the first opening 23 and the upper wall surface 12 and the vertical distance between the second opening 33 and the lower wall surface 13 are preferably set appropriately depending on the outflow speed of the gas discharged during gas replacement. For example, when the average flow speed is 20 m / s, the distance is preferably set to 150 mm or less. On the other hand, if the distance is too small, the first pipe 20, the second pipe 30, and the rectangular tank 10 may come into contact with each other due to differences in thermal expansion among them. Therefore, the distance is preferably set to, for example, 30 mm or more, more preferably 50 mm or more.

[0049] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to FIG. 2. In the second embodiment, components similar to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. The tank in the second embodiment is a spherical tank 110, and accordingly, the configurations of the first piping 20 and the second piping 30 differ from those in the first embodiment. Furthermore, the second embodiment includes a first internal valve 24 and a second internal valve 34 in addition to the configuration of the first embodiment.

[0050] The spherical tank 110 is a spherical tank, and has a gas storage space R formed inside. The upper part of the inner surface 111 of the spherical tank 110 is an upper wall surface 112, and the lower part is a lower wall surface 113.

[0051] The upper wall surface 112 forms the upper part of the inner surface 111 of the spherical tank 110. The upper wall surface 112 may be in the range above the center of the vertical height of the inner surface 111 of the spherical tank 110, preferably in the range of the upper one-third, more preferably in the range of the upper one-quarter, or even in the range of the upper one-fifth including the upper end of the inner surface 111. The upper wall surface 112 is a concave curved surface that is concave upward.

[0052] The lower wall surface 113 forms the lower part of the inner surface 111 of the spherical tank 110. The lower wall surface 113 may be in a range below the center of the vertical height of the inner surface 111 of the spherical tank 110, preferably in a range of the upper one-third including the lower end of the inner surface 111, more preferably in a range of one-fourth, or even one-fifth. The lower wall surface 113 is a concave curved surface that is concave downward.

[0053] The first header 21 of the first piping 20 is arranged so as to curve along the concavely curved upper wall surface 112. The first header 21 has a top portion corresponding to the top portion of the upper wall surface 112, and curves downward from the top portion toward both sides in the horizontal direction. A first supply / discharge pipe 43 is connected to the first header 21 near the top portion.

[0054] The first branch pipes 22 of the first piping 20 extend upward from the first header 21, with their first openings 23 facing the concavely curved upper wall surface 112. The vertical distance between each first branch pipe 22 and the upper wall surface 112 is constant. The vertical dimensions of each first branch pipe 22 are identical. One of the first branch pipes 22 is located at the center of the top of the first header 21. The first opening 23 of the central first branch pipe 22 is located at the top, and the heights of the first openings 23 of the first branch pipes 22 decrease with increasing horizontal distance from the central first branch pipe 22. As a result, the heights of the first openings 23 of adjacent first branch pipes 22 are different from each other. In this embodiment, one first branch pipe 22 is located at the center of the first header 21, and two first branch pipes 22 are located on each horizontal side of the top first branch pipe 22, for a total of five first branch pipes 22. The number of first branch pipes 22 is not limited to this and can be changed as appropriate.

[0055] The second header 31 of the second piping 30 is disposed so as to curve along the concavely curved lower wall surface 113. The second header 31 has a bottom that corresponds to the bottom of the lower wall surface 113, and curves upward from the bottom toward both sides in the horizontal direction. A second supply / discharge pipe 53 is connected to the second header 31 near the bottom.

[0056] The second branch pipes 32 of the second piping 30 extend downward from the second header 31 described below, and each second opening 33 faces the concavely curved bottom wall surface 113. The vertical distance between each second branch pipe 32 and the bottom wall surface 113 is constant. The vertical dimensions of each second branch pipe 32 are the same. One of the second branch pipes 32 is located at the center of the bottom of the second header 31. The second opening 33 of the central second branch pipe 32 is located lowest, and the heights of the second openings 33 of the second branch pipes 32 increase with increasing distance from the central second branch pipe 32 on both sides in the horizontal direction. As a result, the heights of the second openings 33 of adjacent second branch pipes 32 are different from each other. In this embodiment, one second branch pipe 32 is located in the center of the second header 31, and two second branch pipes 32 are located on each horizontal side of the first branch pipe 22 at the bottom, i.e., a total of five second branch pipes 32 are provided. The number of second branch pipes 32 is not limited to this and can be changed as appropriate.

[0057] The first internal valves 24 are on-off valves provided in a pair in the first header 21 of the first piping 20. The first internal valves 24 are provided between adjacent first branch pipes 22 in the first header 21. That is, the first internal valves 24 are provided between adjacent first openings 23. In this embodiment, of the total five first branch pipes 22, a first internal valve 24 is provided at a location between the first branch pipes 22 at both ends farthest from the center and the first branch pipes 22 adjacent to these first branch pipes 22 and closer to the top.

[0058] The second internal valves 34 are on-off valves provided in a pair in the second header 31 of the second piping 30. The second internal valves 34 are provided between adjacent second branch pipes 32 in the second header 31. That is, the second internal valves 34 are provided between adjacent second openings 33. In the present embodiment, of the total five second branch pipes 32, the second internal valves 34 are provided at locations between the second branch pipes 32 at both ends farthest from the center and the second branch pipes 32 adjacent to these second branch pipes 32 near the top.

[0059] In the second embodiment, similarly to the first embodiment, a plurality of gas sensors 70 are provided spaced apart in the vertical direction.

[0060] One of the gas sensors 70 (referred to as the upper specified gas sensor 70) arranged in the upper part of the accommodation space R is provided at a height position between a pair of adjacent first openings 23 arranged to sandwich the first internal valve 24 from above and below. That is, the upper specified gas sensor 70 is provided at a height position between the first openings 23 of the first branch pipes 22 at both ends that are farthest from the center of the first header 21 and the first openings 23 of the first branch pipes 22 that are one branch closer to the center than either end.

[0061] One of the gas sensors 70 (referred to as the lower specified gas sensor 70) arranged in the lower part of the accommodation space R is provided at a height position between a pair of adjacent second openings 33 arranged to sandwich the second internal valve 34 from above and below. That is, the lower specified gas sensor 70 is provided at a height position between the second openings 33 of the second branch pipes 32 at both ends that are farthest from the center of the second header 31 and the second openings 33 of the second branch pipes 32 that are one end closer to the center than the both ends.

[0062] <Effects> In this embodiment, gas replacement is performed in the same procedure as in Embodiment 1. However, because the height positions of the plurality of first openings 23 and the height positions of the plurality of second openings 33 are different, the following procedure is added to avoid inadvertent gas leakage.

[0063] <Replacing a Gas with a Low Density with a Gas with a High Density> When the first gas in the spherical tank 110 is replaced with the second gas, the boundary surface between the first gas and the second gas gradually rises within the accommodation space R. If the boundary surface exceeds the height of the lowest first opening 23 in the first piping 20, the second gas, which should not be discharged, will be discharged through the first opening 23.

[0064] Therefore, in this embodiment, when the gas boundary surface exceeds the height position of the lowest first opening 23, the upper specific gas sensor 70 detects a change in the gas composition. This causes the operator to change the first internal valve 24 from an open state to a closed state. If the first internal valve 24 is maintained in the open state, the discharge of the second gas, which is the replacement gas, will begin when the gas boundary surface exceeds the height of the lowest first opening 23. In contrast, by closing the first internal valve 24 as in this embodiment, the discharge of the second gas can be avoided. Incidentally, when replacing the first gas with an inert gas, the same procedure as described above can be used to avoid the inadvertent discharge of the inert gas.

[0065] <Replacing a High-Density Gas with a Low-Density Gas> Meanwhile, when the second gas in the spherical tank 110 is replaced with the first gas, the boundary surface between the first gas and the second gas gradually descends within the accommodation space R. If the boundary surface falls below the height of the uppermost second opening 33 in the second piping 30, the first gas, which should not be discharged, will be discharged through the second opening 33.

[0066] Therefore, as described above, when the gas boundary surface falls below the height position of the uppermost second opening 33, the lower specific gas sensor 70 detects a change in the gas component. This causes the operator to change the second internal valve 34 from an open state to a closed state. If the second internal valve 34 is maintained in the open state, the discharge of the first gas, which is the replacement gas, will begin when the gas boundary surface falls below the height of the uppermost second opening 33. In contrast, by closing the second internal valve 34 as in this embodiment, the discharge of the first gas can be avoided. Incidentally, when replacing the second gas with an inert gas, the same procedure as described above can be used to avoid the inadvertent discharge of the inert gas.

[0067] For example, as shown in Fig. 3, as a modification of the second embodiment, the first header 21 and the second header 31 may be straight pipes extending horizontally. In this case, the vertical dimensions of the plurality of first branch pipes 22 are different from one another, and the vertical dimensions of the plurality of second branch pipes 32 are different from one another. That is, the vertical dimensions of the first branch pipe 22 and the second branch pipe 32 increase toward the center. This also achieves the same effects as the second embodiment.

[0068] Furthermore, the location of the first internal valve 24 in the first header 21 is not limited to the above, and it may be provided, for example, between the central first branch pipe 22 in the first header 21 and the first branch pipe 22 adjacent to the central first branch pipe 22. In this case, too, by providing the upper specific gas sensor 70 at a height position between the first opening 23 of the central first branch pipe 22 and the second opening 33 of the first branch pipe 22 adjacent to the central first branch pipe 22, it is possible to suppress the discharge of gas that should not be discharged, as described above. Furthermore, the first internal valves 24 may be provided in all of the spaces between adjacent first branch pipes 22 in the first header 21.

[0069] Similarly, the location of the second internal valve 34 in the second header 31 is not limited to the above, and may be provided, for example, between the central second branch pipe 32 in the second header 31 and the second branch pipe 32 adjacent to the central second branch pipe 32. In this case, too, by providing the lower specific gas sensor 70 at a height position between the second opening 33 of the central second branch pipe 32 and the second opening 33 of the second branch pipe 32 adjacent to the central second branch pipe 32, it is possible to suppress the emission of gas that should not be emitted, as described above.

[0070] Third Embodiment Next, a third embodiment of the present disclosure will be described with reference to FIG. 4 . In the third embodiment, components similar to those in the other embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. The first piping 20 of the third embodiment does not have a first branch pipe 22, and a first opening 23 is formed in the first header 21. That is, the first header 21 is formed with a plurality of first openings 23 that penetrate the inside and outside of the first header 21 at intervals in the extension direction of the first header 21. Each of the first openings 23 opens upward at an upper portion of the first header 21.

[0071] The first header 21 of the third embodiment is disposed closer to the upper wall surface 12 than in the first and second embodiments. That is, in order to bring the first opening 23 closer to the upper wall surface 12, the first header 21 itself is located at the same height as the tip of the first branch pipe 22 of the first and second embodiments. This also makes it possible to smoothly discharge gas remaining near the upper wall surface 12, as in the first and second embodiments.

[0072] A similar configuration can also be applied to the second piping 30. That is, the second opening 33 may be formed directly in the second header 31 without providing the second branch pipe 32 in the second piping 30. Also, the third embodiment may be applied to the second embodiment, and a configuration may be provided in which the first internal valve 24 and the second internal valve 34 are provided.

[0073] Fourth Embodiment Next, a fourth embodiment of the present disclosure will be described with reference to Fig. 5. In the fourth embodiment, components similar to those of the other embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. The first branch pipe 22 in the fourth embodiment has a tapered tubular shape in which the inner and outer circumferential surfaces increase in diameter from the base end to the tip end. As a result, the opening area of ​​the first opening 23 is larger than in the first and second embodiments.

[0074] The enlargement of the first opening 23 slows down the flow rate of gas sucked into the first opening 23. This makes it possible to prevent the gas from being accidentally sucked in from a location distant below the upper wall surface 12. Furthermore, by increasing the contact area of ​​the first opening 23 with the gas accumulating near the upper wall surface 12, it is possible to collect gas from a wider range.

[0075] A similar configuration may be applied to the second branch pipe 32 of the second pipe 30. That is, the second branch pipe 32 may be formed as a tapered pipe whose diameter increases from the base end to the tip end.

[0076] Fifth Embodiment Next, a fifth embodiment of the present disclosure will be described with reference to Fig. 6. In the fifth embodiment, components similar to those of the other embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. In addition to the configuration of the fourth embodiment, the fifth embodiment includes a helical structure 22a on the inner circumferential surface of the first branch pipe 22. The helical structure 22a is a ridge that protrudes from the inner circumferential surface of the first branch pipe 22 and is formed so as to twist around the axis of the first branch pipe 22 as it extends in the axial direction of the first branch pipe 22.

[0077] As a result, the sucked gas flows in a vortex shape according to the spiral structure 22a within the first branch pipe 22. This reduces the pressure within the first branch pipe 22, and induces a flow in the sucking direction of the gas around the first opening 23. This allows for smoother gas collection.

[0078] The helical structure 22a may not only be a ridge, but also, for example, a groove recessed from the inner circumferential surface of the first branch pipe 22 and twisting around the axis of the first branch pipe 22 as it extends in the axial direction of the first branch pipe 22. This also provides the same advantageous effects. A similar configuration may also be applied to the second branch pipe 32 of the second piping 30. That is, the helical structure 22a may be provided on the inner circumferential surface of the second branch pipe 32. Furthermore, the helical structure 22a may be adopted for the first branch pipe 22 and the second branch pipe 32 that are straight pipes as in the first and second embodiments.

[0079] Sixth Embodiment Next, a sixth embodiment of the present disclosure will be described with reference to FIG. 7 . In the sixth embodiment, components similar to those in the other embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. In addition to the first configuration, the sixth embodiment includes a flange 22b on the first branch pipe 22. The flange 22b is formed so as to extend radially outward from the tip of the first branch pipe 22 over the entire circumferential length of the first branch pipe 22 relative to the axis of the first branch pipe 22. The flange 22b has a plate shape extending horizontally. The surface of the flange 22b that faces the upper wall surface 12 is spaced apart from the upper wall surface 12 and is positioned along the upper wall surface 12.

[0080] This makes it possible to avoid the intake of gas from a location spaced below the upper wall surface 12. Therefore, it is possible to suppress the emission of gas that should not be emitted. When this embodiment is applied to the second embodiment, the flange 22b is arranged so as to follow the concavely curved upper wall surface 12. That is, the opposing surface of the flange 22b faces along the curved surface of the upper wall surface 12. This makes it possible to avoid the inadvertent emission of gas. Furthermore, a similar configuration may be applied to the second branch pipe 32 of the second piping 30. That is, the flange 22b may be provided at the tip of the second branch pipe 32.

[0081] Seventh Embodiment Next, a seventh embodiment of the present disclosure will be described with reference to FIG. 8 . In the seventh embodiment, components similar to those in the other embodiments are denoted by the same reference numerals, and detailed description thereof will be omitted. In addition to the other embodiments, the sixth embodiment includes a convex portion 22c on the upper wall surface 12 facing the first opening 23. The convex portion 22c is formed so as to protrude from the upper wall surface 12 toward the first opening 23 of the first branch pipe 22. The convex portion 22c has a tapered shape that reduces in diameter toward the first opening 23 at the tip of the first branch pipe 22. The tip of the convex portion 22c is spaced apart from the first branch pipe 22 in the up-down direction. The tip of the convex portion 22c is positioned so as to overlap the first opening 23 in a plan view. The diameter of the proximal end of the convex portion 22c is set to be larger than the diameter of the first opening 23.

[0082] This makes it possible to induce a flow along the outer peripheral surface of the protrusion 22c when gas is sucked through the first opening 23. Therefore, it is possible to increase the suction flow rate of gas accumulating on the upper wall surface 12, and to smoothly discharge the gas. Note that the protrusion 22c may be provided so as to face the second opening 33 of the second branch pipe 32 of the second piping 30.

[0083] Eighth Embodiment Next, an eighth embodiment of the present disclosure will be described with reference to FIG. 9 . In the eighth embodiment, components similar to those in the other embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. In the eighth embodiment, an elastic tube 22d is provided at the distal end of a first branch pipe 22. The elastic tube 22d is made of an elastic material such as rubber. The proximal end of the elastic tube 22d is attached to the distal end of the first branch pipe 22 so as to cover the distal end from the outer periphery. The elastic tube 22d extends upward from the distal end of the first branch pipe 22 and is bent horizontally by contacting the upper wall surface 12. As a result, the opening at the distal end of the elastic tube 22d faces horizontally. In this embodiment, the opening of the elastic tube 22d serves as a first opening 23 in the first piping 20.

[0084] This allows the first opening 23 to be as close as possible to the upper wall surface 12. Therefore, it is possible to efficiently and reliably collect gas remaining on the upper wall surface 12. Furthermore, even if thermal expansion of the first branch pipe 22 occurs, it is possible to avoid contact between the first branch pipe 22 and the upper wall surface 12.

[0085] Other Embodiments Although the embodiments of the present disclosure have been described above in detail with reference to the drawings, the specific configuration is not limited to these embodiments, and design modifications and the like are also included within the scope of the gist of the present disclosure. For example, the third to eighth embodiments may be applied to the spherical tank 110 of the second embodiment. Furthermore, a cylindrical tank may be used instead of the rectangular tank or spherical tank. In this case, the first piping 20 is provided along the top of the upper wall surface, and the second piping 30 is provided along the bottom of the lower wall surface.

[0086] <Additional Notes> The tank system 1 and gas replacement method according to this embodiment can be understood as follows: (1) The tank system 1 includes a tank capable of storing gas, a first pipe 20 having a plurality of openings provided along an upper wall surface 12, 112 of the tank and allowing a first gas to flow in and out of the tank via these openings, and a second pipe 30 having a plurality of openings provided along a lower wall surface 13, 113 of the tank and allowing a second gas having a density greater than the first gas to flow in and out of the tank via these openings.

[0087] This allows the first gas to be easily replaced with the second gas in the tank using simple equipment.

[0088] The tank system 1 of (2) is the tank system 1 of (1), in which the first piping 20 has a header extending horizontally within the tank and a plurality of branch pipes arranged at intervals in the extension direction of the header of the first piping 20, extending from a base end communicating with the header of the first piping 20 toward the upper wall surface 12, 112 and having the opening of the first piping 20 at its tip, and the second piping 30 has a header extending horizontally within the tank and a plurality of branch pipes arranged at intervals in the extension direction of the header of the second piping 30, extending from a base end communicating with the header of the second piping 30 toward the lower wall surface 13, 113 and having the opening of the second piping 30 at its tip.

[0089] This allows the first gas and the second gas to be smoothly supplied and discharged.

[0090] The tank system 1 of (3) is the tank system 1 of (2), in which the branch pipe has an inner circumferential surface whose diameter increases from the base end to the tip end.

[0091] This increases the opening area of ​​the opening, allowing gas remaining on the upper wall surfaces 12, 112 and the lower wall surfaces 13, 113 of the tank to be sucked in smoothly.

[0092] The tank system 1 of (4) is the tank system 1 of (2) or (3) having a spiral structure 22a that protrudes from the inner peripheral surface of the branch pipe and twists in the extension direction of the branch pipe.

[0093] This induces a spiral gas flow in the branch pipe, reducing the pressure inside the branch pipe, allowing the gas to be sucked in smoothly.

[0094] The tank system 1 of (5) is a tank system 1 of (2) to (4) having a flange 22b provided at the tip of the branch pipe and extending radially from the branch pipe.

[0095] This allows gas remaining on the upper wall surfaces 12, 112 and the lower wall surfaces 13, 113 of the tank to be smoothly sucked in.

[0096] (6) The tank system 1 is any of the tank systems 1 (2) to (5) having a convex portion 22c provided on the inner surface 11, 111 of the tank, protruding toward the tip of the branch pipe and decreasing in diameter as it approaches the tip.

[0097] This allows a gas flow to be formed toward the opening of the branch pipe.

[0098] (7) The tank system 1 is any of the tank systems 1 (2) to (6) having an elastic tube 22d connected to the tip of the branch pipe, extending in a direction away from the tip of the branch pipe, and formed from an elastic material.

[0099] This allows the opening to be in contact with the upper wall surface 12, 112 or the lower wall surface 13, 113.

[0100] The tank system 1 of (8) is the tank system 1 of (1), in which the first pipe 20 extends horizontally within the tank and has a header in which a plurality of openings of the first pipe 20 are formed at intervals in the extension direction, and the second pipe 30 extends horizontally within the tank and has a header in which a plurality of openings of the second pipe 30 are formed at intervals in the extension direction.

[0101] This also allows the first gas and the second gas to be smoothly supplied and discharged.

[0102] The tank system 1 of (9) is a tank system 1 of any of (1) to (8) in which the upper wall surface 112 is a concave curved surface that is recessed upward, and the multiple openings of the first piping 20 are arranged so that adjacent first openings 23 are at different heights from each other, along the concave curved upper wall surfaces 12, 112.

[0103] This makes it possible to easily replace the second gas with the first gas in a spherical tank, for example, using simple equipment.

[0104] The tank system 1 of (10) is a tank system 1 of any of (1) to (9), in which the lower wall surface 113 is a concave curved surface that is recessed downward, and the multiple second openings 33 are arranged so that adjacent second openings 33 are at different heights, along the concave curved lower wall surfaces 13, 113.

[0105] This also makes it possible to easily replace the first gas with the second gas in, for example, a spherical tank using simple equipment.

[0106] The tank system 1 of (11) is the tank system 1 of (9) or (10), further comprising an internal valve provided between adjacent openings at different heights in the header.

[0107] By switching the internal valve from an open state to a closed state at the appropriate timing, unintentional inhalation of gas can be avoided.

[0108] (12) The tank system 1 is any of the tank systems 1 of (1) to (11), further comprising a plurality of gas sensors 70 arranged at intervals in the vertical direction within the tank and capable of detecting the gas components within the tank.

[0109] This makes it possible to check the progress of gas replacement.

[0110] (13) The tank system 1 is the tank system 1 of (11), further comprising a plurality of gas sensors 70 arranged at intervals in the vertical direction within the tank and capable of detecting the gas components within the tank, and at least one of the plurality of gas sensors 70 is arranged at a height position between a pair of adjacent openings arranged to sandwich the internal valve from above and below.

[0111] This makes it possible to avoid unintentional inhalation of gas.

[0112] (14) The tank system 1 is any of the tank systems 1 of (1) to (13), comprising a first gas supply / discharge unit 40 capable of supplying the first gas to the first piping 20 and discharging the gas in the tank via the first piping 20, and a second gas supply / discharge unit 50 capable of supplying the second gas to the second piping 30 and discharging the gas in the tank via the second piping 30.

[0113] This allows the first gas to be appropriately replaced with the second gas.

[0114] The tank system 1 of (15) is the tank system 1 of (14), further comprising an inert gas supply unit 60 capable of supplying an inert gas as the first gas to the first piping 20 and an inert gas as the second gas to the second piping 30.

[0115] This allows replacement of the first gas with the inert gas, or replacement of the second gas with the inert gas.

[0116] The gas replacement method (16) is a gas replacement method using any of the tank systems 1 (1) to (15), and includes a step of supplying the second gas into the tank in which the first gas is stored through an opening of the second piping 30, while discharging the first gas from the tank through an opening of the first piping 20.

[0117] The gas replacement method (17) is a gas replacement method using any of the tank systems 1 (1) to (15), and includes a step of supplying the first gas into the tank in which the second gas is stored through an opening of the first piping 20, while discharging the second gas from the tank through an opening of the second piping.

[0118] The gas replacement method of (18) is a gas replacement method using the tank system 1 of (13), and includes the steps of: supplying the first gas into the tank in which the second gas is stored through an opening of the first piping 20, while discharging the second gas from the tank through an opening of the piping; and closing the internal valve provided in the second piping 30 when the gas component detected by the gas sensor 70 changes from the second gas to the first gas.

[0119] The gas replacement method of (19) is a gas replacement method using the tank system 1 of (13), and includes the steps of: discharging the first gas from the tank through an opening of the first piping 20 while supplying the second gas into the tank in which the first gas is stored through an opening of the second piping 30; and closing the internal valve provided in the second piping 30 when the gas component detected by the gas sensor 70, which is provided at a height position between a pair of adjacent openings arranged to sandwich the internal valve from above and below, changes from the first gas to the first gas.

[0120] According to the tank system and gas replacement method according to the present disclosure, maintainability can be improved.

[0121] REFERENCE SIGNS LIST 1 Tank system 10 Rectangular tank 11 Inner surface 12 Upper wall surface 13 Lower wall surface 20 First piping 21 First header 22 First branch pipe 22a Spiral structure 22b Flange 22c Convex portion 22d Elastic pipe 23 First opening 24 First internal valve 30 Second piping 31 Second header 32 Second branch pipe 33 Second opening 34 Second internal valve 40 First gas supply and exhaust section 41 First gas tank 42 First gas pipe 43 First supply and exhaust pipe 44 First gas valve 45 First exhaust valve 50 Second gas supply and exhaust section 51 Second gas tank 52 Second gas pipe 53 Second supply and exhaust pipe 54 Second gas valve 55 Second exhaust valve 60 Inert gas supply section 61 Inert gas source 62 First inert pipe 63 First inert valve 64 Second inert pipe 65 Second inert valve 70 Gas sensor 110 Spherical tank 111 Inner surface 112 Upper wall surface 113 Lower wall surface R Storage space

Claims

1. A tank system comprising: a tank capable of storing gas; a first pipe having a plurality of openings provided along an upper wall surface of the tank, for allowing a first gas to flow in and out of the tank via these openings; and a second pipe having a plurality of openings provided along a lower wall surface of the tank, for allowing a second gas having a higher density than the first gas to flow in and out of the tank via these openings.

2. The tank system described in claim 1, wherein the first piping has a header extending horizontally within the tank, and a plurality of branch pipes arranged at intervals in the extension direction of the header of the first piping, extending from a base end communicating with the header of the first piping toward the upper wall surface and having the opening of the first piping at a tip thereof; and the second piping has a header extending horizontally within the tank, and a plurality of branch pipes arranged at intervals in the extension direction of the header of the second piping, extending from a base end communicating with the header of the second piping toward the lower wall surface and having the opening of the second piping at a tip thereof.

3. A tank system according to claim 2, wherein the branch pipe has an inner circumferential surface that expands in diameter from the base end to the tip end.

4. A tank system as described in claim 3, having a spiral structure that protrudes or is recessed from the inner peripheral surface of said branch pipe and that is twisted in the extension direction of said branch pipe.

5. A tank system according to claim 2, further comprising a flange provided at the tip of said branch pipe and extending radially outward from said branch pipe.

6. A tank system as set forth in claim 2, further comprising a convex portion provided on the inner surface of said tank, protruding toward the tip of said branch pipe and tapering in diameter as it approaches said tip.

7. The tank system according to claim 2, further comprising an elastic tube made of an elastic material, connected to the tip of said branch pipe and extending in a direction away from the tip of said branch pipe.

8. A tank system as described in claim 1, wherein the first pipe extends horizontally within the tank and has a header in which a plurality of openings for the first pipe are formed at intervals in the extension direction, and the second pipe extends horizontally within the tank and has a header in which a plurality of openings for the second pipe are formed at intervals in the extension direction.

9. A tank system as described in claim 2, wherein the upper wall surface is a concave curved surface that is recessed upward, and the multiple openings of the first pipe are arranged so that adjacent openings are at different heights and along the concave curved upper wall surface.

10. A tank system as described in claim 2, wherein the lower wall surface is a concave curved surface that is recessed downward, and the multiple openings of the second piping are arranged so that adjacent openings are at different heights and along the concave curved lower wall surface.

11. The tank system of claim 9 or 10, further comprising an internal valve disposed between said openings in said header.

12. A tank system as described in any one of claims 1 to 10, further comprising a plurality of gas sensors arranged at intervals in the vertical direction within the tank and capable of detecting gas components within the tank.

13. The tank system described in claim 11, further comprising a plurality of gas sensors arranged at intervals in the vertical direction within the tank and capable of detecting gas components within the tank, wherein at least one of the plurality of gas sensors is arranged at a height position between a pair of the openings arranged to sandwich the internal valve from above and below.

14. The tank system described in claim 1, comprising: a first gas supply and exhaust unit capable of supplying the first gas to the first piping and discharging the gas in the tank via the first piping; and a second gas supply and exhaust unit capable of supplying the second gas to the second piping and discharging the gas in the tank via the second piping.

15. The tank system according to claim 14, further comprising an inert gas supply unit capable of supplying an inert gas as the first gas to the first pipe and an inert gas as the second gas to the second pipe.

16. A gas replacement method using a tank system according to any one of claims 1 to 10, comprising the steps of: supplying the second gas into the tank in which the first gas is stored via the opening of the second piping; and discharging the first gas from within the tank via the opening of the first piping.

17. A gas replacement method using a tank system according to any one of claims 1 to 10, comprising the steps of: supplying the first gas into the tank in which the second gas is stored through the opening of the first piping; and discharging the second gas from within the tank through the opening of the second piping.

18. A gas replacement method using the tank system described in claim 13, comprising the steps of: discharging the first gas from within the tank through the opening of the first piping while supplying the second gas into the tank in which the first gas is stored through the opening of the second piping; and closing the internal valve provided in the first piping when the gas component detected by the gas sensor located at a height position between a pair of adjacent openings arranged so as to sandwich the internal valve provided in the first piping from above and below changes from the first gas to the first gas.

19. A gas replacement method using the tank system described in claim 13, comprising the steps of: discharging the second gas in the tank through the opening of the second piping while supplying the first gas into the tank in which the second gas is stored through the opening of the first piping; and closing the internal valve provided in the second piping when the gas component detected by the gas sensor at a height position between a pair of adjacent openings arranged so as to sandwich the internal valve provided in the second piping from above and below changes from the second gas to the second gas.

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