Method for transporting flammable gases, and system for transporting flammable gases

Abstract

This suppresses the expansion of the combustion area of ​​leaked flammable gas. [Solution] The flammable gas transport method is a transport method using a transport route for transporting flammable gas from a flammable gas supply unit to a flammable gas supply destination, wherein the transport route has a first piping section connecting the flammable gas supply unit and the flammable gas supply destination, and a second piping section connecting an inert gas supply unit and the first piping section, wherein the flammable gas supply unit supplies the flammable gas to the first piping section, and the inert gas supply unit supplies the inert gas to the first piping section via the second piping section, and a mixed gas of the flammable gas and the inert gas flows through the portion of the first piping section between the connection section connected to the second piping section and the flammable gas supply destination.

Description

Technical Field

[0001] The present invention relates to a method for transporting combustible gas and a combustible gas transport system.

Background Art

[0002] In recent years, for the purpose of forming a decarbonized society, technological innovations such as manufacturing technologies and transport technologies for combustible gases such as hydrogen gas and biogas containing methane gas have been accelerating. For example, Patent Document 1 discloses a water electrolysis system that stores hydrogen gas generated in a water electrolysis device in a hydrogen tank.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above water electrolysis system, if a crack occurs in the pipe connecting the water electrolysis device and the hydrogen tank and combustible gas leaks from such a crack, for example, when the leaked combustible gas burns with static electricity generated by the friction between the combustible gas and the pipe as an ignition source. When the combustible gas is hydrogen gas, the combustible gas is easily ignited and the combustion range easily spreads. Therefore, there is a demand for a method for transporting combustible gas that can suppress the spread of the combustion range of the combustible gas even when the combustible gas leaks from a crack in the pipe. [[ID=3,6]]

[0005] The present invention has been made in consideration of the above points, and one of the objects is to provide a method for transporting combustible gas and a combustible gas transport system that can suppress the spread of the combustion range of the leaked combustible gas.

Means for Solving the Problems

[0006] (1) One aspect of the present invention is a method for transporting flammable gas using a transport route for transporting flammable gas from a flammable gas supply unit to a flammable gas supply destination, wherein the transport route comprises a first piping section connecting the flammable gas supply unit and the flammable gas supply destination, and a second piping section connecting an inert gas supply unit and the first piping section, wherein the flammable gas supply unit supplies the flammable gas to the first piping section, the inert gas supply unit supplies the inert gas to the first piping section via the second piping section, and a mixed gas of the flammable gas and the inert gas flows through the portion of the first piping section between the connection section connected to the second piping section and the flammable gas supply destination.

[0007] (2) One aspect of the present invention is the method for transporting a flammable gas described in (1) above, wherein the flammable gas is a carbon-neutral fuel gas.

[0008] (3) One aspect of the present invention is the method for transporting a flammable gas described in (1) or (2) above, wherein the flammable gas is hydrogen gas and the inert gas is carbon dioxide gas.

[0009] (4) In one aspect of the present invention, in the flammable gas transport method described in (3) above, the volume ratio of the inert gas in the mixed gas is 30% or more and 50% or less.

[0010] (5) One aspect of the present invention is a method for transporting flammable gas as described in (1) or (2) above, wherein the flammable gas comprises hydrogen gas and biogas containing methane gas and carbon dioxide gas, and the inert gas is carbon dioxide gas.

[0011] (6) In one aspect of the present invention, in the flammable gas transport method described in (5) above, the volume ratio of the hydrogen gas in the flammable gas is 40% or more and 60% or less, and the volume ratio of the inert gas in the mixed gas is 20% or more and 40% or less.

[0012] (7) In one aspect of the present invention, in a flammable gas transport method described in any of (1) to (6) above, the second piping section is provided with a first flow rate adjustment section for adjusting the flow rate of the inert gas supplied from the inert gas supply section to the first piping section.

[0013] (8) One aspect of the present invention is a flammable gas transport system comprising a transport route for transporting flammable gas from a flammable gas supply unit to a flammable gas supply destination, wherein the transport route comprises a first piping section connecting the flammable gas supply unit and the flammable gas supply destination, and a second piping section connecting an inert gas supply unit and the first piping section, wherein the flammable gas supply unit supplies the flammable gas to the first piping section, the inert gas supply unit supplies the inert gas to the first piping section via the second piping section, and a mixed gas of the flammable gas and the inert gas flows through the portion of the first piping section between the connection section connected to the second piping section and the flammable gas supply destination.

[0014] (9) One aspect of the present invention is a flammable gas transport system as described in (8) above, comprising an imaging device for imaging at least the first piping section and a control unit capable of communicating with the imaging device, wherein the control unit is capable of detecting flames based on the image captured by the imaging device.

[0015] (10) One aspect of the present invention is a flammable gas transport system as described in (8) above, comprising: an imaging device for imaging at least the first piping section; and a control unit capable of communicating with the imaging device, wherein the control unit has a processing unit for generating an evaluation image based on an image captured by the imaging device; and a storage unit for storing a learning model that has been trained to recognize the correspondence between a plurality of previously acquired evaluation images and flames generated when the mixed gas Gm burns, wherein the processing unit inputs the evaluation image to the learning model, and the learning model can determine whether or not the input evaluation image includes an image of a flame.

[0016] (11) In one aspect of the present invention, in the flammable gas transport system described in (10) above, the storage unit stores the captured images at predetermined intervals, and when N is a natural number, the evaluation image is a difference image obtained by subtracting the (N-1)th captured image stored in the storage unit from the Nth captured image stored in the storage unit.

[0017] (12) One aspect of the present invention is a flammable gas transport system according to any one of (9) to (11) above, comprising a first flow rate adjustment unit provided in the second piping section for adjusting the flow rate of the inert gas supplied from the inert gas supply section to the first piping section, wherein the control unit is able to communicate with the first flow rate adjustment unit, and when the control unit detects the flame, it increases the flow rate of the inert gas supplied from the inert gas supply section to the first piping section by the first flow rate adjustment unit.

[0018] (13) In one aspect of the present invention, in a flammable gas transport system according to any one of (9) to (12) above, the control unit is capable of communicating with the flammable gas supply unit, the flammable gas is hydrogen gas, the flammable gas supply unit is a flammable gas production apparatus that produces the flammable gas, and when the control unit detects the flame, it stops the operation of the flammable gas supply unit.

[0019] (14) One aspect of the present invention is a flammable gas transport system according to any one of (9) to (13) above, comprising: a third piping section connecting a nitrogen gas supply section containing nitrogen gas to the first piping section; and a second flow rate adjustment section provided in the third piping section for adjusting the flow rate of the nitrogen gas supplied from the nitrogen gas supply section to the first piping section, wherein the control unit is able to communicate with the second flow rate adjustment section, and when the control unit detects the flame, the second flow rate adjustment section supplies the nitrogen gas from the nitrogen gas supply section to the first piping section.

[0020] (15) One aspect of the present invention is in the combustible gas transportation system described in (13) above, wherein the imaging device is capable of imaging at least light in the visible region, the inert gas is carbon dioxide gas, and the volume ratio of the inert gas in the mixed gas is 30% or more and 50% or less.

Advantages of the Invention

[0021] According to the present invention, it is possible to provide a combustible gas transportation method and a combustible gas transportation system that can suppress the spread of the combustion range of leaked combustible gas.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic diagram showing a combustible gas transportation system of the first embodiment. [Figure 2] It is a schematic diagram showing a combustion experiment apparatus of the first embodiment. [Figure 3] It is a diagram showing the measurement results of the flame height of the first embodiment. [Figure 4] It is a diagram showing the measurement results of the maximum temperature within the flame region of the first embodiment. [Figure 5] It is a diagram showing the results of the visibility of the flame of the first embodiment. [Figure 6] It is a schematic diagram showing a combustible gas transportation system of a modified example of the first embodiment. [Figure 7] It is a diagram showing the results of the detection rate of a modified example of the first embodiment. [Figure 8] It is a schematic diagram showing a combustible gas transportation system of the second embodiment. [Figure 9] It is a diagram showing the measurement results of the flame height of the second embodiment. [Figure 10] It is a diagram showing the results of the visibility of the flame of the second embodiment.

Modes for Carrying Out the Invention

[0023] The following description will explain a flammable gas transport method and a flammable gas transport system according to embodiments of the present invention, with reference to the drawings. Note that the scope of the present invention is not limited to the following embodiments, and modifications can be made as appropriate within the scope of the technical concept of the present invention. Furthermore, in the following drawings, the scale and number of components in each structure may differ from the actual structure in order to make the configurations easier to understand.

[0024] <First Embodiment> Figure 1 is a schematic diagram showing the flammable gas transport system 10 of this embodiment. The flammable gas transport system 10 of this embodiment uses a flammable gas transport method in which flammable gas Gf is transported from the flammable gas supply unit 31 to the flammable gas supply destination 33 via a transport path 20 connecting the flammable gas supply unit 31 and the flammable gas supply destination 33. The flammable gas transport system 10 comprises a transport path 20, a flammable gas supply unit 31, a flammable gas supply destination 33, an inert gas supply unit 35, a control unit 41, and an imaging device 43.

[0025] As described above, the transport route 20 transports flammable gas Gf from the flammable gas supply unit 31 to the flammable gas supply destination 33. The transport route 20 is composed of multiple pipes through which gas flows. In this embodiment, the transport route 20 has a first piping section 21 and a second piping section 22.

[0026] The first piping section 21 is a pipe connecting the flammable gas supply section 31 and the flammable gas supply destination 33. In this embodiment, the first piping section 21 is made of metal. Therefore, the strength and durability of the first piping section 21 can be increased compared to the case where the first piping section 21 is made of rubber and resin. The material constituting the first piping section 21 may be a material other than metal, such as rubber and resin. Flammable gas Gf and mixed gas Gm, which is a mixture of flammable gas Gf and inert gas Gi, flow inside the first piping section 21. In the first piping section 21, the flammable gas Gf and the mixed gas Gm each flow from the flammable gas supply section 31 toward the flammable gas supply destination 33. The first piping section 21 has one end 21a, the other end 21c, and a connecting section 21d.

[0027] One end 21a is the upstream end of the first piping section 21. One end 21a is connected to the flammable gas supply section 31. The other end 21c is the downstream end of the first piping section 21. The other end 21c is connected to the flammable gas supply destination 33. The connection section 21d is the part that connects to the second piping section 22. The connection section 21d is provided on the part of the first piping section 21 on the side of one end 21a.

[0028] The second piping section 22 is a pipe connecting the inert gas supply section 35 and the connection section 21d of the first piping section 21. In this embodiment, the second piping section 22 is made of metal. Therefore, the strength and durability of the second piping section 22 can be increased compared to cases where the second piping section 22 is made of rubber or resin. Inert gas Gi flows inside the second piping section 22. In the second piping section 22, the inert gas Gi flows from the inert gas supply section 35 toward the connection section 21d. The second piping section 22 has one end 22a and the other end 22c. The second piping section 22 is provided with a first flow rate adjustment section 22d. That is, the flammable gas transport system 10 is equipped with a first flow rate adjustment section 22d.

[0029] One end 22a is the upstream end of the second piping section 22. This end 22a is connected to the inert gas supply section 35. The other end 22c is the downstream end of the second piping section 22. This end 22c is connected to the connection section 21d. As a result, the connection section 21d is connected to the second piping section 22, and inert gas Gi is supplied to the first piping section 21. The first flow rate adjustment section 22d adjusts the flow rate of the inert gas Gi supplied from the inert gas supply section 35 to the first piping section 21. In this embodiment, the first flow rate adjustment section 22d is, for example, a solenoid valve.

[0030] The combustible gas supply unit 31 supplies combustible gas Gf to the first piping unit 21. In this embodiment, the combustible gas Gf is hydrogen gas. That is, the combustible gas Gf is a carbon-neutral fuel gas that does not emit carbon dioxide when burned. The combustible gas Gf may also be fossil fuel gas such as liquefied natural gas (LNG) and propane gas. In this embodiment, the combustible gas supply unit 31 is a combustible gas production apparatus that produces combustible gas Gf. More specifically, the combustible gas supply unit 31 is a water electrolysis apparatus that produces hydrogen gas by electrolyzing water. The combustible gas supply unit 31 may also be a container such as a tank that contains the combustible gas Gf. In this case, the combustible gas supply unit 31 contains combustible gas Gf produced in a combustible gas production unit (not shown). The combustible gas supply unit 31 supplies combustible gas Gf to the first piping unit 21 via one end 21a.

[0031] Combustible gas Gf is supplied to the combustible gas supply destination 33. In this embodiment, the combustible gas supply destination 33 may be, for example, a tank and trailer containing combustible gas Gf or mixed gas Gm, or it may be a combustion device such as a boiler that burns combustible gas Gf or mixed gas Gm to generate thermal energy. In this embodiment, the combustible gas supply destination 33 is a boiler. Combustible gas Gf or mixed gas Gm is supplied to the combustible gas supply destination 33 via the other end 21c.

[0032] The inert gas supply unit 35 supplies inert gas Gi to the first piping unit 21 via the second piping unit 22. In this embodiment, the inert gas Gi is carbon dioxide gas. As will be described later, the inert gas Gi suppresses the expansion of the combustion range of the combustible gas Gf even if the combustible gas Gf leaks from the transport line 20 and burns, and also reduces the temperature of the flame generated when the combustible gas Gf burns. In addition, the inert gas Gi plays a role in improving the visibility of the flame generated when the mixed gas Gm burns.

[0033] In this embodiment, the inert gas supply unit 35 is a storage container such as a tank that contains inert gas Gi. The inert gas supply unit 35 contains inert gas Gi produced in an inert gas production unit (not shown). The inert gas supply unit 35 may also be a gas production apparatus that produces inert gas Gi. The inert gas supply unit 35 supplies inert gas Gi to the second piping unit 22 via one end 22a. The inert gas Gi supplied to the second piping unit 22 flows into the first piping unit 21 via the connection part 21d. As a result, a mixed gas Gm, which is a mixture of flammable gas Gf and inert gas Gi, flows through the portion of the first piping unit 21 between the connection part 21d and the flammable gas supply destination 33. In this embodiment, the first ratio R1, which is the volume ratio of inert gas Gi in the mixed gas Gm, is 30% or more and 50% or less. The first ratio R1 may be less than 30% or greater than 50%.

[0034] The imaging device 43 images each part that constitutes the flammable gas transport system 10. More specifically, the imaging device 43 images at least the first piping section 21 among the parts that constitute the flammable gas transport system 10. The imaging device 43 images the flame generated when the mixed gas Gm leaking from the first piping section 21 burns. The number of imaging devices 43 provided in the flammable gas transport system 10 is not particularly limited and may be one or multiple. In addition to the first piping section 21, the imaging device 43 may also image the flammable gas supply section 31 that produces the flammable gas Gf and the flammable gas supply destination 33 that burns the flammable gas Gf. As the imaging device 43, any imaging device capable of capturing at least visible light can be used, such as a surveillance camera that monitors the inside of the building in which the flammable gas transport system 10 is installed, and a general-purpose digital video camera. In this embodiment, the imaging device 43 is the surveillance camera described above. The imaging device 43 may also be an imaging device capable of capturing light outside the visible region, such as the infrared and ultraviolet regions.

[0035] In this embodiment, the control unit 41 controls the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d. The control unit 41 can communicate with the flammable gas supply unit 31, the first flow rate adjustment unit 22d, and the imaging device 43. The control unit 41 may be connected to the flammable gas supply unit 31, the first flow rate adjustment unit 22d, and the imaging device 43 via cables or the like, or via wireless communication means. In this embodiment, the control unit 41 is a computer that controls the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d. The control unit 41 has a control program installed that performs control of the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d. At least part of the functions of each component of the control unit 41 are realized, for example, by a processor such as a CPU (Central Processing Unit) executing a control program, i.e., software, stored in a storage unit (not shown).

[0036] At least some of the functions of each component of the control unit 41 may be implemented by hardware including circuit sections such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and GPU (Graphics Processing Unit), or by the cooperation of software and hardware. The control unit 41 may also include a storage unit (not shown). In this case, the storage unit (not shown) may be implemented by a storage medium such as RAM, ROM, HDD (hard disk drive), and flash memory. The control method by which the control unit 41 controls the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d will be described in detail later.

[0037] The flammable gas transport system 10 may also include a separation section 37, shown by a dashed line in Figure 1. The transport path 20 may also have a fourth piping section 25, shown by a dashed line in Figure 1. The separation section 37 is located in the downstream portion of the first piping section 21. Preferably, the separation section 37 is located near the other end 21c of the first piping section 21. The separation section 37 separates the mixed gas Gm flowing through the first piping section 21 into a flammable gas Gf and an inert gas Gi. For example, a separation membrane that selectively permeates carbon dioxide gas can be used as the separation section 37. In this embodiment, as described above, the flammable gas Gf is hydrogen gas and the inert gas Gi is carbon dioxide gas, so the difference between the density of the flammable gas Gf and the density of the inert gas Gi is large. Therefore, the flammable gas Gf and the inert gas Gi can be easily separated in the separation section 37.

[0038] The flammable gas Gf separated in the separation unit 37 is supplied to the flammable gas supply destination 33. This makes it possible to increase the flammability of the gas supplied to the flammable gas supply destination 33 compared to when the flammable gas transport system 10 does not have a separation unit 37, i.e., when a mixed gas Gm is supplied to the flammable gas supply destination 33.

[0039] The fourth piping section 25 is a pipe that connects the separation section 37 and the inert gas supply section 35. Therefore, the inert gas Gi separated in the separation section 37 can be returned to the inert gas supply section 35 via the fourth piping section 25. This allows the inert gas Gi to be reused, thereby reducing the amount of inert gas Gi used in the flammable gas transport system 10.

[0040] Figure 2 is a schematic diagram showing the combustion experiment apparatus 50 of this embodiment. Next, the results of the combustion experiment of the mixed gas Gm of this embodiment, conducted using the combustion experiment apparatus 50, will be described. As shown in Figure 2, the combustion experiment apparatus 50 has a first flow path 51, a second flow path 52, a combustible gas containment section 53, an inert gas containment section 54, a slit burner 56, and an imaging device 58.

[0041] The first flow path 51 is a pipe connecting the flammable gas containment section 53 and the slit burner 56. Flammable gas Gf and a mixed gas Gm, which is a mixture of flammable gas Gf and inert gas Gi, flow through the first flow path 51. In the first flow path 51, the flammable gas Gf and the mixed gas Gm each flow from the flammable gas containment section 53 toward the slit burner 56. The first flow path 51 has a connection section 51a. The first flow path 51 is provided with a first valve 51d. The first valve 51d adjusts the flow rate of the flammable gas Gf supplied from the flammable gas containment section 53 toward the slit burner 56. In this embodiment, the first valve 51d is, for example, a solenoid valve.

[0042] The second flow path 52 is a pipe connecting the inert gas containment section 54 and the connection section 51a. Inert gas Gi flows through the second flow path 52. In the second flow path 52, the inert gas Gi flows from the inert gas containment section 54 towards the connection section 51a. As a result, inert gas Gi is supplied to the first flow path 51, and a mixed gas Gm, which is a mixture of flammable gas Gf and inert gas Gi, is supplied to the slit burner 56. A second valve 52d is provided in the second flow path 52.

[0043] The second valve 52d adjusts the flow rate of the inert gas Gi supplied from the inert gas containment section 54 to the first flow path 51. In this embodiment, the second valve 52d is, for example, a solenoid valve. In this embodiment, by appropriately adjusting the opening degrees of the first valve 51d and the second valve 52d, the flow rate of the flammable gas Gf supplied to the slit burner 56, the flow rate of the inert gas Gi, and the first ratio R1, which is the volume ratio of the inert gas Gi in the mixed gas Gm, can be adjusted.

[0044] The flammable gas containment section 53 supplies flammable gas Gf to the first flow path 51. As described above, in this embodiment, the flammable gas Gf is hydrogen gas. The flammable gas containment section 53 is a containment container such as a tank that contains the flammable gas Gf.

[0045] The inert gas containment section 54 supplies inert gas Gi to the first channel 51 via the second channel 52. As described above, in this embodiment, the inert gas Gi is carbon dioxide gas. The inert gas containment section 54 is a containment container such as a tank that contains the inert gas Gi.

[0046] A mixed gas Gm is supplied to the slit burner 56. The slit burner 56 is a combustion device that flows the mixed gas Gm to the outside through a slit 56a that opens upward and burns the mixed gas Gm. The flame F generated by the combustion of the mixed gas Gm spreads upward from the slit 56a. In this embodiment, the shape of the slit 56a is approximately rectangular with a long side dimension of 5 mm and a short side dimension of 1 mm.

[0047] The imaging device 58 images the flame F from a horizontal direction. In this embodiment, a Nikon D5600 digital camera was used as the imaging device 58. The imaging device 58 is capable of imaging light in the visible region. In the combustion experiment of the mixed gas Gm, the height Hf of the flame F, the maximum temperature Tmax within the flame F region, and the visibility of the flame F were confirmed with respect to the first ratio R1, which is the volume ratio of the inert gas Gi in the mixed gas Gm. The flow rate of the combustible gas Gf supplied to the slit burner 56 was set to 10 L / min.

[0048] The height Hf of the flame F was calculated by binarizing the image of the flame F captured by the imaging device 58 and using image analysis software. The shutter speed when the imaging device 58 captured the flame F was set to 0.125 seconds. The ISO sensitivity of the imaging device 58, as specified in ISO 12232, was set to 3200. The illuminance around the combustion experiment apparatus 50 was set to 0 lux. In other words, the flame F was imaged in darkness. This makes the outline of the flame F clearer, thereby improving the accuracy of measuring the height Hf of the flame F.

[0049] The maximum temperature Tmax within the flame F region was measured directly by bringing an R-type thermocouple into contact with the flame F. The maximum temperature Tmax within the flame F region is the highest temperature measured at multiple points on the flame F.

[0050] The visibility of flame F was visually determined by the inventors from the image of flame F captured by the imaging device 58. The shutter speed when the imaging device 58 captured flame F was set to 0.125 seconds. The ISO sensitivity of the imaging device 58, as defined in ISO 12232, was set to 1600. The illuminance around the combustion experiment apparatus 50 was set to 480-500 lux. This illuminance range is typical for a room where the flammable gas transport system 10 is installed. Therefore, the visibility of flame F in this combustion experiment is evaluated based on whether or not the flame F can be imaged by the imaging device 43 of the flammable gas transport system 10 in a room with lighting fixtures etc. turned on.

[0051] Figure 3 shows the measurement results of the flame height Hf in the combustion test of this embodiment. The horizontal axis of Figure 3 is the first ratio R1 [%]. The vertical axis of Figure 3 is the flame height Hf [mm]. As shown in Figure 3, the flame height Hf decreases as the first ratio R1 increases. In other words, by increasing the first ratio R1, which is the volume ratio of the inert gas Gi in the mixed gas Gm, it is possible to suppress the expansion of the combustion range of the combustible gas Gf. This is because the mixed gas Gm becomes less combustible as the proportion of the inert gas Gi, which is less combustible than the combustible gas Gf, increases. When the first ratio R1 was greater than 55%, the mixed gas Gm did not combust. This is because the concentration of the combustible gas Gf near the slit 56a was lower than the lower limit of the combustible concentration of the combustible gas Gf.

[0052] As described above, in the flammable gas transport system 10 of this embodiment, the first proportion R1 of the mixed gas Gm is preferably 30% or more and 50% or less. As shown in Figure 3, when the first proportion R1 of the mixed gas Gm is set to 30% or more and 50% or less, the flame height Hf is lower compared to the case where inert gas Gi is not supplied to the first piping section 21, i.e., when the first proportion R1 of the mixed gas Gm is 0%, and the combustion range of the flammable gas Gf can be reduced to about 30% to 45%.

[0053] Figure 4 shows the measurement results of the maximum temperature Tmax in the flame F region during the combustion test of this embodiment. The horizontal axis of Figure 4 represents the first proportion R1 [%]. The vertical axis of Figure 4 represents the maximum temperature Tmax [°C] in the flame F region. As shown in Figure 4, the maximum temperature Tmax in the flame F region decreases as the first proportion R1 increases. This is because, as described above, as the proportion of the inert gas Gi, which is less combustible than the flammable gas Gf, increases, the mixed gas Gm becomes less combustible.

[0054] As described above, in the flammable gas transport system 10 of this embodiment, the first proportion R1 of the mixed gas Gm is preferably 30% or more and 50% or less. As shown in Figure 4, when the first proportion R1 of the mixed gas Gm is 30% or more and 50% or less, the maximum temperature Tmax in the flame F region can be reduced by approximately 200°C to 420°C compared to when the first proportion R1 of the mixed gas Gm is 0%.

[0055] Figure 5 shows the results of the visibility of flame F in the combustion test of this embodiment. As shown in Figure 5, when the first proportion R1 is 16.7% or less, flame F is difficult to see. As described above, the combustible gas Gf in this embodiment is hydrogen gas. The wavelength range of light produced during the combustion reaction of hydrogen gas is the ultraviolet region (278 nm to 320 nm) and the near-infrared to infrared region (900 nm or more). Therefore, when a mixed gas Gm with a large proportion of combustible gas Gf and a first proportion R1 of 9.1% or less burns, flame F is difficult to see. In contrast, with a mixed gas Gm where the first proportion R1 is 28.6% or more and 52.4% or less, flame F can be suitably seen. As described above, the inert gas Gi in this embodiment is carbon dioxide gas. When carbon dioxide gas burns, CH radicals emit light. The light emitted by the emission of CH radicals is blue light with a wavelength of about 500 nm. Therefore, the flame F generated when a mixed gas Gm with a first proportion R1 of 28.6% or more and 52.4% or less, where the proportion of inert gas Gi is large, can be clearly observed. However, when the first proportion R1 is 54.6% or more, the proportion of inert gas Gi in the mixed gas Gm becomes too large, making it difficult for the mixed gas Gm to burn. Therefore, the flame F generated when a mixed gas Gm with a first proportion R1 of 54.6% or more burns is difficult to observe.

[0056] As described above, in the flammable gas transport system 10 of this embodiment, the first proportion R1 of the mixed gas Gm is 30% or more and 50% or less. Therefore, in this embodiment, the flame generated when the mixed gas Gm burns can be suitably visualized. Accordingly, in this embodiment, the flame generated when the mixed gas Gm burns can be imaged by the imaging device 43 described above in a room with lighting fixtures etc. The control unit 41 detects the flame based on the image captured by the imaging device 43. Accordingly, in this embodiment, the control unit 41 can quickly detect the flame.

[0057] Next, a control method will be described in which the control unit 41 shown in Figure 1 controls the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d. If a crack (not shown) occurs in the first piping unit 21 due to deterioration of the first piping unit 21, the mixed gas Gm may leak from the inside of the first piping unit 21 to the outside of the first piping unit 21 through the crack. Also, if the first piping unit 21 is composed of multiple pipes connected to each other, the mixed gas Gm may leak from the parts connecting the pipes due to loosening of the parts connecting the pipes. Furthermore, when the mixed gas Gm leaks from the first piping unit 21, static electricity is generated by drawing in dust inside the first piping unit 21 and around the outlet of the first piping unit 21. As a result, when the mixed gas Gm leaks from the first piping unit 21, the leaked mixed gas Gm may burn using the static electricity as an ignition source.

[0058] In contrast, in this embodiment, the first proportion R1 of the mixed gas Gm is 30% or more and 50% or less. Therefore, as described above, the imaging device 43 can image the flame generated when the mixed gas Gm burns. When the control unit 41 detects a flame, it increases the flow rate of the inert gas Gi supplied from the inert gas supply unit 35 to the first piping unit 21 by increasing the opening of the first flow rate adjustment unit 22d. In other words, the control unit 41 increases the flow rate of the inert gas Gi supplied from the inert gas supply unit 35 to the first piping unit 21 by the first flow rate adjustment unit 22d. This makes it possible to increase the first proportion R1 of the mixed gas Gm, thereby suppressing the expansion of the combustion range of the leaked flammable gas Gf and reducing the maximum temperature within the flame region. Furthermore, by making the first proportion R1 of the mixed gas Gm greater than 55%, the combustion of the mixed gas Gm can be stopped.

[0059] As described above, in this embodiment, the combustible gas supply unit 31 is a combustible gas production device that produces combustible gas Gf, i.e., hydrogen gas. In this embodiment, when the control unit 41 detects a flame, it stops the operation of the combustible gas supply unit 31. This stops the supply of combustible gas Gf from the combustible gas supply unit 31 to the first piping unit 21, and thus the combustion of the mixed gas Gm can be stopped quickly.

[0060] Furthermore, when the control unit 41 detects a flame, it may warn the administrator or other person managing the flammable gas transport system 10 that a flame has occurred. In this case, the control unit 41 may illuminate or flash a warning lamp (not shown), or generate an alarm sound using an audible device such as a buzzer (not shown). The control unit 41 may also notify the administrator or other person that a fire has occurred via email or other means. In this way, the control unit 41 can promptly notify the administrator or other person that a flame has occurred, so that the administrator or other person can promptly carry out firefighting operations. Therefore, in this embodiment, the combustion of the mixed gas Gm can be stopped quickly.

[0061] According to this embodiment, the flammable gas transport method is a flammable gas transport method using a transport route 20 for transporting flammable gas Gf from a flammable gas supply unit 31 to a flammable gas destination 33, wherein the transport route 20 has a first piping section 21 connecting the flammable gas supply unit 31 and the flammable gas destination 33, and a second piping section 22 connecting the inert gas supply unit 35 and the first piping section 21, the flammable gas supply unit 31 supplies flammable gas Gf to the first piping section 21, the inert gas supply unit 35 supplies inert gas Gi to the first piping section 21 via the second piping section 22, and a mixed gas Gm, which is a mixture of flammable gas Gf and inert gas Gi, flows in the portion of the first piping section 21 between the connection section 21d connected to the second piping section 22 and the flammable gas destination 33. Therefore, as described above, even if the mixed gas Gm leaks from the first piping section 21 through a crack or the like in the first piping section 21 and the mixed gas Gm burns, because the mixed gas Gm contains the inert gas Gi, as described above, the expansion of the combustion range of the leaked flammable gas Gf can be suppressed and the flame temperature can be reduced. Thus, the risk of fire due to the leakage of flammable gas Gf can be reduced.

[0062] According to this embodiment, the combustible gas Gf is a carbon-neutral fuel gas. Therefore, when the combustible gas Gf is burned at the combustible gas supply destination 33, etc., the emission of carbon dioxide can be suppressed. Consequently, the environmental burden can be reduced compared to when the combustible gas Gf is a fossil fuel such as liquefied natural gas.

[0063] In this embodiment, the flammable gas Gf is hydrogen gas, and the inert gas Gi is carbon dioxide gas. As described above, the wavelength range of light produced during the combustion reaction of hydrogen gas is in the ultraviolet region (278 nm to 320 nm) and the near-infrared to infrared region (900 nm or higher), so the flame generated when hydrogen gas burns is difficult to see. Also, as described above, the light emitted by the emission of CH radicals when carbon dioxide gas burns is blue light. Since the mixed gas Gm in this embodiment is a mixture of hydrogen gas and carbon dioxide gas, as described above, the visibility of the flame generated when the mixed gas Gm burns can be improved. As a result, for example, an administrator managing the flammable gas transport system 10 can see the flame directly or indirectly via the imaging device 43. Therefore, the administrator can quickly increase the flow rate of carbon dioxide gas supplied to the first piping section 21 and stop the operation of the flammable gas supply section 31. Therefore, since the rapid spread of the flammable gas Gf can be suppressed, the risk of fire due to the leakage of flammable gas Gf can be reduced.

[0064] According to this embodiment, the first ratio R1, that is, the volume ratio of the inert gas Gi in the mixed gas Gm, is 30% or more and 50% or less. Therefore, as described above, the flame generated when the mixed gas Gm burns can be clearly seen. Consequently, managers and others can easily see the flame, and thus quickly suppress the expansion of the burning area of ​​the leaked flammable gas Gf.

[0065] Furthermore, in this embodiment, since the first ratio R1 is 30% or more and 50% or less, as described above, the combustion range of the flammable gas Gf can be reduced to about 30% to 45% of the combustion range of the flammable gas Gf when inert gas Gi is not supplied to the first piping section 21. Therefore, the expansion of the combustion range of leaked flammable gas Gf can be suitably suppressed. Also, as described above, the maximum temperature Tmax in the flame region can be reduced to about 200°C to 420°C compared to the maximum temperature Tmax in the flame region when inert gas Gi is not supplied to the first piping section 21. Therefore, the flame temperature can be suitably reduced. As a result, the risk of fire due to leakage of flammable gas Gf can be suitably reduced.

[0066] Furthermore, in this embodiment, the volume ratio of the combustible gas Gf in the mixed gas Gm is 50% or more. This prevents the ratio of the combustible gas Gf in the mixed gas Gm from becoming too small. Therefore, it is possible to prevent the transport efficiency of the combustible gas Gf in the combustible gas transport system 10 from becoming too small.

[0067] According to this embodiment, the second piping section 22 is provided with a first flow rate adjustment section 22d that adjusts the flow rate of the inert gas Gi supplied from the inert gas supply section 35 to the first piping section 21. Therefore, when a flame is observed, the manager or other person can easily increase the flow rate of the inert gas Gi supplied to the first piping section 21 by adjusting the opening of the first flow rate adjustment section 22d. This makes it possible to more quickly suppress the expansion of the combustion range of leaked flammable gas Gf, and thus more effectively reduce the risk of fire due to the leakage of flammable gas Gf.

[0068] Furthermore, in this embodiment, the flow rate of inert gas Gi supplied to the first piping section 21 can be adjusted according to the flow rate of combustible gas Gf supplied from the combustible gas supply section 31 to the first piping section 21. This allows the first ratio R1 of the mixed gas Gm to be stabilized. Therefore, the expansion of the combustion range of leaked combustible gas Gf can be stably suppressed, and the flame temperature can be stably reduced. In addition, the visibility of the flame can be stably improved. Therefore, the risk of fire due to the leakage of combustible gas Gf can be more effectively reduced.

[0069] According to this embodiment, the flammable gas transport system 10 is a transport system 10 that includes a transport path 20 for transporting flammable gas Gf from a flammable gas supply unit 31 to a flammable gas destination 33, wherein the transport path 20 has a first piping section 21 connecting the flammable gas supply unit 31 and the flammable gas destination 33, and a second piping section 22 connecting the inert gas supply unit 35 and the first piping section 21, wherein the flammable gas supply unit 31 supplies flammable gas Gf to the first piping section 21, and the inert gas supply unit 35 supplies inert gas Gi to the first piping section 21 via the second piping section 22, and a mixed gas Gm, which is a mixture of flammable gas Gf and inert gas Gi, flows through the portion of the first piping section 21 between the connection section 21d connected to the second piping section 22 and the flammable gas destination 33. Therefore, as described above, even if the mixed gas Gm leaks from the first piping section 21 through a crack or the like in the first piping section 21 and the mixed gas Gm burns, it is possible to suppress the expansion of the combustion range of the leaked flammable gas Gf and reduce the flame temperature. Consequently, the risk of fire due to leakage of flammable gas Gf can be reduced.

[0070] According to this embodiment, the flammable gas transport system 10 includes an imaging device 43 that images at least the first piping section 21, and a control unit 41 that can communicate with the imaging device 43. The control unit 41 can detect flames based on the images captured by the imaging device 43. Therefore, as described above, even if the mixed gas Gm leaks from the first piping section 21 through a crack or the like and the mixed gas Gm burns, the control unit 41 can quickly detect the flames. As a result, as described above, the control unit 41 can quickly notify the administrator or others that a flame has occurred. Therefore, the administrator or others can quickly carry out firefighting operations. Consequently, in this embodiment, the combustion of the mixed gas Gm can be stopped quickly.

[0071] According to this embodiment, the flammable gas transport system 10 includes a first flow rate adjustment unit 22d provided in the second piping section 22, which adjusts the flow rate of the inert gas Gi supplied from the inert gas supply section 35 to the first piping section 21. The control unit 41 can communicate with the first flow rate adjustment unit 22d, and when the control unit 41 detects a flame, it increases the flow rate of the inert gas Gi supplied from the inert gas supply section 35 to the first piping section 21 by the first flow rate adjustment unit 22d. Therefore, as described above, when the mixed gas Gm leaked from the first piping section 21 burns, the control unit 41 can quickly increase the first ratio R1 of the mixed gas Gm. Consequently, the expansion of the combustion range of the leaked flammable gas Gf can be more effectively suppressed, and the maximum temperature within the flame region can be more effectively reduced.

[0072] According to this embodiment, the control unit 41 can communicate with the flammable gas supply unit 31, the flammable gas Gf is hydrogen gas, the flammable gas supply unit 31 is a flammable gas production device that produces flammable gas Gf, and when the control unit 41 detects a flame, it stops the operation of the flammable gas supply unit 31. Therefore, as described above, when the mixed gas Gm leaking from the first piping unit 21 burns, the control unit 41 can stop the supply of hydrogen gas, i.e., flammable gas Gf, from the flammable gas supply unit 31 to the first piping unit 21. This allows the combustion of the mixed gas Gm to be stopped more quickly.

[0073] According to this embodiment, the imaging device 43 is capable of imaging light in at least the visible region, the inert gas Gi is carbon dioxide gas, and the first proportion R1, i.e., the volume ratio of the inert gas Gi in the mixed gas Gm, is 30% or more and 50% or less. Therefore, as described above, even if the imaging device 43 is, for example, a surveillance camera or a general-purpose digital video camera that monitors the inside of a building in which the flammable gas transport system 10 is installed, the imaging device 43 can image the flame generated when the mixed gas Gm burns. Therefore, compared to the case where the imaging device 43 is an imaging device capable of imaging light outside the visible region, such as an infrared camera, an increase in the manufacturing cost of the imaging device 43 can be suppressed. Consequently, an increase in the manufacturing cost of the flammable gas transport system 10 can be suppressed.

[0074] <Modified form of the first embodiment> Figure 6 is a schematic diagram showing the flammable gas transport system 110 of this modified example. In the following description, components that are the same as those in the first embodiment described above are denoted by the same reference numerals, and their descriptions are omitted. The flammable gas transport system 110 of this modified example comprises a transport path 20, a flammable gas supply unit 31, a flammable gas supply destination 33, an inert gas supply unit 35, a control unit 141, and an imaging device 43.

[0075] In this modified example, the control unit 141 controls the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d. The control unit 141 can communicate with the flammable gas supply unit 31, the first flow rate adjustment unit 22d, and the imaging device 43. The control unit 141 may be connected to the flammable gas supply unit 31, the first flow rate adjustment unit 22d, and the imaging device 43 via cables or the like, or via wireless communication means. The control unit 141 is a computer that controls the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d. The control unit 141 has a processing unit 141a and a storage unit 141c.

[0076] In this modified example, the control unit 141 is a personal computer. The control unit 141 may also be a communication device such as a tablet terminal or a smartphone. At least some of the functions of each component of the control unit 141 may be realized by hardware including circuit parts such as LSIs, ASICs, FPGAs, and GPUs, or by the cooperation of software and hardware.

[0077] The processing unit 141a is, for example, a processor such as a CPU. The processing unit 141a controls the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d. In this modified example, the processing unit 141a generates an evaluation image Ie based on the image captured by the imaging device 43. The evaluation image Ie will be described in detail later.

[0078] The memory unit 141c is, for example, a storage medium such as RAM, ROM, HDD, and flash memory. The memory unit 141c has a control program installed that controls the operation of the flammable gas supply unit 31 and the first flow rate adjustment unit 22d. The memory unit 141c stores the images captured by the imaging device 43. The memory unit 141c stores the images captured by the imaging device 43 at predetermined intervals. That is, multiple images are stored in the memory unit 141c. In this modified example, the predetermined interval is, for example, 7 seconds. The predetermined interval may be shorter or longer than 7 seconds. Furthermore, the memory unit 141c stores a learning model 141e that has been trained to learn the correspondence between multiple evaluation images Ie acquired in advance and the flame generated when the mixed gas Gm burns.

[0079] In this modified example, the learning model 141e is a learning model in AI (Artificial Intelligence). The learning model 141e in this modified example is a learning model that has learned the correspondence between multiple pre-acquired evaluation images Ie and flames generated when a mixed gas Gm burns, and is a learning model that can determine whether or not a newly input evaluation image Ie contains an image of a flame. In this modified example, the multiple pre-acquired evaluation images Ie are images generated based on images captured by the imaging device 43 of flames generated when a mixed gas Gm burns in each of multiple first proportions R1. In this modified example, the number of evaluation images Ie in one first proportion R1 is, for example, 50.

[0080] When the evaluation image Ie generated by the processing unit 141a is input to the learning model 141e, the learning model 141e compares the input evaluation image Ie with the learned data to determine whether or not the evaluation image Ie contains an image of a flame. As a result, the control unit 141 can detect a flame based on the image captured by the imaging device 43. The other configurations of the flammable gas transport system 110 of this modified example are the same as the other configurations of the flammable gas transport system 10 of the first embodiment described above.

[0081] Next, the procedure by which the control unit 141 detects a flame in this modified example will be described. First, the processing unit 141a generates an evaluation image Ie from the captured images stored in the storage unit 141c. As described above, multiple captured images are stored in the storage unit 141c. When N captured images are stored in the storage unit 141c, the processing unit 141a generates an evaluation image Ie by removing the (N-1)th captured image I(N-1) stored in the storage unit 141c from the (N)th captured image I(N) stored in the storage unit 141c. That is, in this modified example, the evaluation image Ie is a difference image obtained by performing a difference process to remove the (N-1)th captured image I(N-1) stored in the storage unit 141c from the (N)th captured image I(N) stored in the storage unit 141c. Therefore, the evaluation image Ie is an image from which images of each part of the flammable gas transport system 110, such as the first piping section 21, have been removed. Note that N is a natural number. In this modified example, captured image I(N) is the most recent captured image stored in the memory unit 141c, and captured image I(N-1) is the next most recent captured image after captured image I(N).

[0082] If no flames are generated between the timing T(N-1) when image I(N-1) is captured and the timing T(N) when image I(N) is captured, then neither image I(N-1) nor image I(N) will contain images of flames. Furthermore, as described above, evaluation image Ie is an image that does not contain images of any part of the flammable gas transport system 110, such as the first piping section 21. Therefore, if no flames are generated between the timing T(N-1) and the timing T(N), the evaluation image Ie generated by the processing unit 141a will, for example, be an entirely black image and will not contain images of flames.

[0083] If, between the timing T(N-1) when captured image I(N-1) was taken and the timing T(N) when captured image I(N) was taken, the mixed gas Gm gas leaking from the first piping section 21 burns and generates a flame, captured image I(N-1) will not include an image of the flame, while captured image I(N) will include an image of the flame. Furthermore, as described above, evaluation image Ie is an image that does not include images of each part of the flammable gas transport system 110, such as the first piping section 21. Therefore, if a flame occurs between timing T(N-1) and timing T(N), the evaluation image Ie generated by the processing unit 141a will be an image that includes only the flame.

[0084] Next, the processing unit 141a inputs the generated evaluation image Ie to the learning model 141e. If the evaluation image Ie is an image that does not contain an image of flames, the learning model 141e determines that the evaluation image Ie does not contain an image of flames. If the evaluation image Ie is an image that contains an image of flames, the learning model 141e determines that the evaluation image Ie contains an image of flames. In this way, the learning model 141e can determine whether or not the evaluation image Ie contains an image of flames.

[0085] If the learning model 141e determines that the evaluation image Ie does not contain an image of a flame, the control unit 141 does not detect a flame. If the control unit 141 does not detect a flame, the process of generating the evaluation image Ie by the processing unit 141a and determining whether or not the evaluation image Ie contains an image of a flame is repeated.

[0086] If the learning model 141e determines that the evaluation image Ie contains an image of a flame, the control unit 141 detects the flame. In this modified example, when the control unit 141 detects a flame, it increases the flow rate of the inert gas Gi supplied from the inert gas supply unit 35 to the first piping unit 21 by the first flow rate adjustment unit 22d, similar to the first embodiment described above. This increases the first proportion R1 of the mixed gas Gm, thereby suppressing the expansion of the combustion range of the leaked flammable gas Gf and reducing the maximum temperature within the flame region. Furthermore, by making the first proportion R1 of the mixed gas Gm greater than 55%, the combustion of the mixed gas Gm can be stopped.

[0087] Furthermore, similar to the first embodiment described above, when the control unit 141 detects a flame, it stops the operation of the flammable gas supply unit 31. This stops the supply of flammable gas Gf from the flammable gas supply unit 31 to the first piping unit 21, thereby quickly stopping the combustion of the mixed gas Gm.

[0088] Furthermore, similar to the first embodiment described above, when the control unit 141 detects a flame, it may warn the administrator or other relevant person that a flame has occurred using a warning lamp (not shown) and an audible device such as a buzzer (not shown). This allows the control unit 41 to promptly notify the administrator or other relevant person that a flame has occurred, enabling them to quickly carry out firefighting operations. Therefore, the combustion of the mixed gas Gm can be stopped quickly.

[0089] In this modified example, the processing unit 141a may perform noise reduction processing on the difference image after performing the difference processing described above, and use the difference image after noise reduction processing as the evaluation image Ie. For example, if the illumination in the room where the flammable gas transport system 110 is installed is high, depending on the arrangement of each part of the flammable gas transport system 110, such as the first piping section 21, and the imaging device 43, the reflected light from the first piping section 21, etc., included in the imaging image may become too large. In this case, the difference processing described above may not be able to completely remove the reflected light, and the reflected light may become noise that reduces the judgment accuracy of the learning model 141e in determining whether or not an image of flames is included in the evaluation image Ie. Therefore, by using the difference image after noise reduction processing to remove such reflected light, etc., as the evaluation image Ie, it is possible to suppress a decrease in the judgment accuracy of the learning model 141e. The noise reduction processing method is not particularly limited, and for example, a method of setting a filter on at least one of the hue, saturation, and brightness of the difference image can be employed.

[0090] Figure 7 shows the results of the flame detection rate Rd in a flame detection experiment of the flammable gas transport system 110 of this modified example. The horizontal axis of Figure 7 is the first proportion R1 [%]. The vertical axis of Figure 7 is the detection rate Rd [%]. In this flame detection experiment, the flame detection rate Rd was measured for mixed gas Gm at 13 levels of the first proportion R1. The number of flame detections at each level was 100. As shown in Figure 7, the detection rate Rd is significantly low when the first proportion R1 is 20.0% or less. The flammable gas Gf in this modified example is hydrogen gas. As mentioned above, the wavelength range of light produced during the combustion reaction of hydrogen gas is in the ultraviolet, near-infrared, and infrared regions. Therefore, when the first proportion R1 of the mixed gas Gm is 20.0% or less, the proportion of flammable gas Gf is large, and the saturation of the flame image included in the evaluation image Ie becomes low. Therefore, it is difficult for the learning model 141e to improve the accuracy of flame detection. In contrast, when the first proportion R1 of the mixed gas Gm was between 30.0% and 50.0%, the detection rate Rd was 100%. In this modified example, the inert gas Gi is carbon dioxide. As mentioned above, when carbon dioxide burns, it emits blue light with a wavelength of about 500 nm. Therefore, when the first proportion R1 is between 30.0% and 50.0%, the proportion of inert gas Gi is large, and the saturation of the flame image included in the evaluation image Ie is high. Thus, the accuracy of flame detection by the learning model 141e can be suitably improved. However, when the first proportion R1 is greater than 50.0%, as mentioned above, the proportion of inert gas Gi in the mixed gas Gm becomes too large, making it difficult for the mixed gas Gm to burn. Therefore, when the first proportion R1 of the mixed gas Gm is greater than 50.0%, the saturation of the flame image included in the evaluation image Ie is low. Therefore, when the first proportion R1 of the mixed gas Gm is greater than 50.0%, the detection rate Rd decreases because the learning model 141e has difficulty improving its accuracy in detecting flames.

[0091] Similar to the first embodiment described above, in this modified flammable gas transport system 110, the first proportion R1 of the mixed gas Gm is 30% or more and 50% or less. Therefore, in this modified version, the accuracy of flame detection by the control unit 141 can be suitably improved.

[0092] As described above, in this modified example, the control unit 141 detects flames using a machine learning model 141e. Therefore, compared to the case where an administrator or the like visually determines the presence or absence of flames based on the captured images taken by the imaging device 43, the flame detection rate Rd can be suitably increased. Furthermore, in this modified example, the evaluation image Ie is a difference image generated by removing the captured image I(N-1) from the captured image I(N). Therefore, as described above, the evaluation image Ie is an image that does not include images of each part of the flammable gas transport system 110, such as the first piping section 21, and is an image in which flames are accurately extracted. Therefore, compared to the case where the captured image I(N) is used as the evaluation image Ie as is, the accuracy of the learning model 141e in detecting flames can be suitably increased. Thus, the flame detection rate Rd can be more suitably increased.

[0093] According to this modified example, the flammable gas transport system 110 includes an imaging device 43 that images at least the first piping section 21, and a control unit 141 that can communicate with the imaging device 43. The control unit 141 includes a processing unit 141a that generates an evaluation image Ie based on the image captured by the imaging device 43, and a storage unit 141c that stores a learning model 141e that has been trained to recognize the correspondence between a plurality of previously acquired evaluation images Ie and the flame generated when the mixed gas Gm burns. The processing unit 141a inputs the evaluation image Ie to the learning model 141e, and the learning model 141e determines whether or not the input evaluation image Ie contains an image of a flame. Therefore, as described above, the detection rate Rd, which is the accuracy with which the control unit 141 detects a flame, can be suitably increased compared to when an administrator or the like visually confirms the flame based on the image captured by the imaging device 43. Therefore, the control unit 141 can reliably and quickly stop the combustion of the mixed gas Gm by controlling the operation of the first flow rate adjustment unit 22d or the combustible gas supply unit 31. Consequently, the expansion of the combustion range of the leaked combustible gas Gf can be effectively suppressed, and the risk of fire due to the leakage of combustible gas Gf can be effectively reduced.

[0094] According to this modified example, the memory unit 141c stores captured images at predetermined intervals, and when N is a natural number, the evaluation image Ie is a difference image obtained by removing the N-1st captured image I(N-1) stored in the memory unit 141c from the Nth captured image I(N) stored in the memory unit 141c. Therefore, as described above, compared to the case where the captured image I(N) is used directly as the evaluation image Ie, the accuracy of flame detection by the learning model 141e can be suitably improved. This allows for a more favorable improvement in the flame detection rate Rd. As a result, the control unit 141 can more reliably and quickly stop the combustion of the mixed gas Gm by controlling the operation of the first flow rate adjustment unit 22d or the flammable gas supply unit 31. Therefore, the expansion of the combustion range of the leaked flammable gas Gf can be more favorably suppressed, and the risk of fire due to the leakage of flammable gas Gf can be more favorably reduced.

[0095] <Second Embodiment> Figure 8 is a schematic diagram showing the combustible gas transport system 210 of this embodiment. In this embodiment, the combustible gas Gf includes hydrogen gas and biogas containing methane gas and carbon dioxide gas. The combustible gas transport system 210 of this embodiment uses a combustible gas transport method in which combustible gas Gf is transported from the combustible gas supply unit 231 to the combustible gas supply destination 33 by a transport path 220 connecting the combustible gas supply unit 231 and the combustible gas supply destination 33. In the following description, components that are the same as those in the first embodiment described above are denoted by the same reference numerals and their descriptions are omitted. The combustible gas transport system 210 comprises a transport path 220, a combustible gas supply unit 231, a combustible gas supply destination 33, an inert gas supply unit 35, a nitrogen gas supply unit 239, a control unit 241, and an imaging device 43.

[0096] The transport route 220 transports flammable gas Gf from the flammable gas supply unit 231 to the flammable gas supply destination 33. In this embodiment, the transport route 220 includes a first piping section 221, a second piping section 22, and a third piping section 223.

[0097] The first piping section 221 is a pipe connecting the flammable gas supply section 231 and the flammable gas supply destination 33. Flammable gas Gf, a mixed gas Gm (a mixture of flammable gas Gf and inert gas Gi), and nitrogen gas Gn flow through the first piping section 221. The first piping section 221 has one end 21a, the other end 21c, a connection section 21d, and a second connection section 221f.

[0098] One end 21a is connected to the flammable gas supply unit 231. The other end 21c is connected to the flammable gas supply destination 33. The connection part 21d is the part that connects to the second piping unit 22. The second connection part 221f is the part that connects to the third piping unit 223. The second connection part 221f is provided on the other end 21c side of the connection part 21d of the first piping unit 221. The second connection part 221f may also be provided on the one end 21a side of the connection part 21d of the first piping unit 221.

[0099] The third piping section 223 is a pipe that connects the nitrogen gas supply section 239 and the second connection section 221f of the first piping section 221. In other words, the third piping section 223 connects the nitrogen gas supply section 239 and the first piping section 221. In this embodiment, the third piping section 223 is made of metal. Therefore, the strength and durability of the third piping section 223 can be increased compared to cases where the third piping section 223 is made of rubber or resin. Nitrogen gas Gn flows inside the third piping section 223. In the third piping section 223, the nitrogen gas Gn flows from the nitrogen gas supply section 239 toward the second connection section 221f. The third piping section 223 has one end 223a and the other end 223c. The third piping section 223 is provided with a second flow rate adjustment section 223d. That is, the flammable gas transport system 210 is equipped with a second flow rate adjustment section 223d.

[0100] One end 223a is the upstream end of the third piping section 223. This end 223a is connected to the nitrogen gas supply section 239. The other end 223c is the downstream end of the third piping section 223. This end 223c is connected to the second connection section 221f. This allows nitrogen gas Gn to be supplied to the first piping section 221. The second flow rate adjustment section 223d adjusts the flow rate of nitrogen gas Gn supplied from the nitrogen gas supply section 239 to the first piping section 221. In this embodiment, the second flow rate adjustment section 223d is, for example, a solenoid valve. The second flow rate adjustment section 223d opens when flammable gas Gf leaked from the first piping section 221 burns. That is, under normal conditions, the second flow rate adjustment section 223d is closed. Therefore, under normal conditions, nitrogen gas Gn is not supplied to the first piping section 221. The other configurations of the transport route 220 in this embodiment are the same as the other configurations of the transport route 20 in the embodiment described above.

[0101] The combustible gas supply unit 231 supplies combustible gas Gf to the first piping unit 221. In this embodiment, the combustible gas Gf includes hydrogen gas and biogas containing methane gas and carbon dioxide gas. In this embodiment, methane gas is a gas synthesized by reacting hydrogen gas and carbon dioxide gas. Therefore, the combustible gas Gf is a carbon-neutral fuel gas. The combustible gas Gf may also be fossil fuel gas such as liquefied natural gas and propane gas. In this embodiment, the volume proportion of methane gas in the biogas is 70%. In this embodiment, the volume proportion of hydrogen gas in the combustible gas Gf is 40% or more and 60% or less. That is, the volume proportion of biogas in the combustible gas Gf is 40% or more and 60% or less. Methane gas is a gas that is difficult to burn on its own. In this embodiment, the flammable gas Gf is mixed with hydrogen gas, which has a low ignition temperature and is easily combustible, and methane gas, thereby enabling stable combustion of methane gas. Therefore, the combustion efficiency of the flammable gas Gf can be increased.

[0102] In this embodiment, the flammable gas supply unit 231 is a container such as a tank that contains flammable gas Gf. The flammable gas supply unit 231 contains flammable gas Gf manufactured in a flammable gas manufacturing unit (not shown). The flammable gas supply unit 231 supplies flammable gas Gf to the first piping unit 221 via one end 21a.

[0103] The inert gas supply unit 35 supplies inert gas Gi to the first piping unit 221 via the second piping unit 22. In this embodiment, the inert gas Gi is carbon dioxide gas. In this embodiment, the second ratio R2, which is the volume ratio of inert gas Gi in the mixed gas Gm obtained by mixing flammable gas Gf and inert gas Gi, is 20% or more and 40% or less. The second ratio R2 may be less than 20% or greater than 40%.

[0104] The imaging device 43 images at least the first piping section 221 among the various parts constituting the flammable gas transport system 210. The imaging device 43 also images the flame generated when the mixed gas Gm leaking from the first piping section 221 burns. As the imaging device 43, any imaging device capable of capturing at least visible light can be used, such as a surveillance camera that monitors the inside of the building where the flammable gas transport system 210 is installed, or a general-purpose digital video camera.

[0105] In this embodiment, the control unit 241 controls the operation of the first flow rate adjustment unit 22d and the second flow rate adjustment unit 223d. The control unit 241 can communicate with the first flow rate adjustment unit 22d, the second flow rate adjustment unit 223d, and the imaging device 43, respectively. The control unit 241 may be connected to the first flow rate adjustment unit 22d, the second flow rate adjustment unit 223d, and the imaging device 43 via cables or the like, or via wireless communication means. The other configurations of the control unit 241 are the same as the other configurations of the control unit 41 in the first embodiment described above. The other configurations of the flammable gas transport system 210 in this embodiment are the same as the other configurations of the flammable gas transport system 10 in the first embodiment described above.

[0106] Next, the results of the combustion experiment of the mixed gas Gm of this embodiment will be described. The combustion experiment of the mixed gas Gm of this embodiment was conducted using the combustion experiment apparatus 50 shown in Figure 2, similar to the combustion experiment of the mixed gas Gm of the first embodiment described above. In the combustion experiment of the mixed gas Gm of this embodiment, the height Hf of the flame F and the visibility of the flame F were confirmed in relation to the second ratio R2, which is the volume ratio of the inert gas Gi in the mixed gas Gm. The flow rate of the combustible gas Gf supplied to the slit burner 56 was set to 5 L / min.

[0107] Figure 9 shows the measurement results of the flame height Hf in the combustion test of this embodiment. The horizontal axis of Figure 9 is the second proportion R2 [%]. The vertical axis of Figure 9 is the flame height Hf [mm]. As shown in Figure 9, the flame height Hf decreases as the second proportion R2 increases. In other words, by increasing the second proportion R2, which is the volume ratio of the inert gas Gi in the mixed gas Gm, it is possible to suppress the expansion of the combustion range of the combustible gas Gf. Note that when the second proportion R2 was greater than 45%, the mixed gas Gm did not burn. This is because the concentration of the combustible gas Gf near the slit 56a was lower than the lower limit of the combustible concentration of the combustible gas Gf.

[0108] As described above, in this embodiment, the second proportion R2 of the mixed gas Gm is 20% or more and 40% or less. Therefore, in this embodiment, the combustion range of the combustible gas Gf can be reduced to about 50% to 70% of the combustion range of the combustible gas Gf when inert gas Gi is not supplied to the first piping section 221, i.e., when the second proportion R2 of the mixed gas Gm is 0%.

[0109] Figure 10 shows the results of the visibility of flame F in the combustion test of this embodiment. As shown in Figure 10, in this embodiment, flame F can be suitably visible in mixed gas Gm where the second proportion R2 is 16.7% or more. This is because, as mentioned above, the light emitted by the emission of CH radicals when carbon dioxide gas burns is blue light. Furthermore, the lower limit of the second proportion R2 for which flame F can be suitably visible in the combustible gas Gf of this embodiment is smaller than the lower limit of the first proportion R1 for which flame F can be suitably visible in the combustible gas Gf of the first embodiment described above. This is because the combustible gas Gf of this embodiment contains methane gas, whose flame color is blue when it burns. Note that when the second proportion R2 is 44.4% or more, the proportion of inert gas Gi in the mixed gas Gm becomes too large, making it difficult for the mixed gas Gm to burn. Therefore, the flame F generated when mixed gas Gm with a second proportion R2 of 44.4% or more burns is difficult to see.

[0110] As described above, in this embodiment, the second proportion R2 of the mixed gas Gm is 20% or more and 40% or less. Therefore, in this embodiment, the flame generated when the mixed gas Gm burns can be suitably visualized. Accordingly, in this embodiment, the flame generated when the mixed gas Gm burns can be imaged by the imaging device 43 in a room with lighting fixtures etc. The control unit 241 detects the flame based on the image captured by the imaging device 43. Accordingly, in this embodiment, the control unit 241 can quickly detect the flame.

[0111] Next, a control method will be described in which the control unit 241 shown in Figure 8 controls the operation of the first flow rate adjustment unit 22d and the second flow rate adjustment unit 223d. As described above, if the mixed gas Gm leaks from the first piping unit 221, the leaked mixed gas Gm may burn using static electricity as an ignition source. In contrast, in this embodiment, the second proportion R2 of the mixed gas Gm is 20% or more and 40% or less. Therefore, as described above, the imaging device 43 can image the flame generated when the mixed gas Gm burns. When the control unit 241 detects a flame, the first flow rate adjustment unit 22d increases the flow rate of the inert gas Gi supplied from the inert gas supply unit 35 to the first piping unit 221. This makes it possible to increase the second proportion R2 of the mixed gas Gm, thereby suppressing the expansion of the combustion range of the leaked flammable gas Gf. Furthermore, by making the second proportion R2 of the mixed gas Gm greater than 45%, the combustion of the mixed gas Gm can be stopped.

[0112] Furthermore, in this embodiment, when the control unit 241 detects a flame, the second flow rate adjustment unit 223d supplies nitrogen gas Gn from the nitrogen gas supply unit 239 to the first piping unit 221. Nitrogen gas Gn is a gas that is neither flammable nor a combustion-supporting gas. Therefore, by supplying nitrogen gas Gn to the mixed gas Gm, the expansion of the combustion range of the leaked flammable gas Gf can be more effectively suppressed.

[0113] According to this embodiment, the flammable gas Gf includes hydrogen gas and biogas containing methane gas and carbon dioxide gas, and the inert gas Gi is carbon dioxide gas. Therefore, since the mixed gas Gm contains carbon dioxide gas, the visibility of the flame generated when the mixed gas Gm burns can be improved. As a result, managers can see the flame and quickly increase the flow rate of carbon dioxide gas, i.e., inert gas Gi, supplied to the first piping section 221. Managers can also quickly supply nitrogen gas Gn to the first piping section 221. Therefore, the spread of the combustion range of the leaked flammable gas Gf can be quickly suppressed, and the risk of fire due to the leakage of flammable gas Gf can be suitably reduced.

[0114] Furthermore, in this embodiment, since the flammable gas Gf contains methane gas, as described above, the visibility of the flame generated when the mixed gas Gm burns can be more favorably improved. Therefore, managers and others can more easily see the flame, and thus the spread of the flammable gas Gf that has leaked can be suppressed more quickly.

[0115] According to this embodiment, the volume ratio of hydrogen gas in the flammable gas Gf is 40% or more and 60% or less, and the volume ratio of inert gas Gi in the mixed gas Gm is 20% or more and 40% or less. Therefore, as described above, managers can easily see the flame generated when the mixed gas Gm burns. Consequently, managers can more easily see the flame, and thus can more quickly suppress the expansion of the burning area of ​​the leaked flammable gas Gf.

[0116] Furthermore, in this embodiment, the volume ratio of the combustible gas Gf in the mixed gas Gm is 50% or more. This prevents the ratio of the combustible gas Gf in the mixed gas Gm from becoming too small. Therefore, it is possible to prevent the transport efficiency of the combustible gas Gf in the combustible gas transport system 210 from becoming too small.

[0117] According to this embodiment, the flammable gas transport system 210 includes a third piping section 223 connecting a nitrogen gas supply section 239 containing nitrogen gas Gn to a first piping section 221, and a second flow rate adjustment section 223d provided in the third piping section 223 for adjusting the flow rate of nitrogen gas Gn supplied from the nitrogen gas supply section 239 to the first piping section 221. The control unit 241 can communicate with the second flow rate adjustment section 223d, and when the control unit 241 detects a flame, the second flow rate adjustment section 223d supplies nitrogen gas Gn from the nitrogen gas supply section 239 to the first piping section 221. Therefore, when a mixed gas Gm leaking from the first piping section 221 burns, the control unit 241 can supply nitrogen gas Gn from the nitrogen gas supply section 239 to the first piping section 221. As described above, nitrogen gas Gn is a gas that is neither flammable nor a combustion-supporting gas. Therefore, by supplying nitrogen gas Gn to the mixed gas Gm, the expansion of the combustion range of the leaked flammable gas Gf can be more effectively suppressed.

[0118] The configuration of the control unit 241 in this embodiment may be the same as the configuration of the control unit 141 in the modified version of the first embodiment described above. In this case, the control unit 241 detects the flame using a machine learning model, which allows for a favorable increase in the flame detection rate Rd. Furthermore, by making the evaluation image Ie a difference image generated by removing the captured image I(N-1) from the captured image I(N), the accuracy of the learning model in detecting the flame can be further favorably increased. As a result, the flame detection rate Rd can be favorably increased. Consequently, the expansion of the combustion range of the leaked flammable gas Gf can be favorably suppressed, thus favorably reducing the risk of fire due to the leakage of flammable gas Gf.

[0119] Although embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention.

[0120] The configuration of the main body is not limited to the embodiment described above. For example, the flammable gas transport system may include multiple flammable gas supply units. In this case, the flow rate of the flammable gas supplied to the first piping unit can be increased, thereby increasing the flow rate of transportable flammable gas. [Explanation of Symbols]

[0121] 10,110,210…Flammable gas transport system, 20,220…Transport route, 21,221…First piping section, 21d…Connection section, 22…Second piping section, 22d…First flow rate adjustment section, 31,231…Flammable gas supply section, 33…Flammable gas supply destination, 35…Inert gas supply section, 41,141,241…Control section, 43…Imaging device, 141a…Processing section, 141c…Storage section, 141e…Learning model, 223…Third piping section, 223d…Second flow rate adjustment section, 239…Nitrogen gas supply section, Ie…Evaluation image, I(N-1),I(N)…Imaging image, Gf…Flammable gas, Gi…Inert gas, Gm…Mixed gas, Gn…Nitrogen gas

Claims

1. A method for transporting flammable gas using a transport route that transports flammable gas from a flammable gas supply unit to a flammable gas supply destination, The aforementioned transport route is A first piping section connecting the flammable gas supply unit and the flammable gas supply destination, A second piping section connecting the inert gas supply section and the first piping section, It has, The flammable gas supply unit supplies the flammable gas to the first piping unit. The inert gas supply unit supplies inert gas to the first piping unit via the second piping unit. A method for transporting combustible gas, wherein a mixed gas, which is a mixture of the combustible gas and the inert gas, flows through the portion of the first piping section between the connection section that connects to the second piping section and the combustible gas supply destination.

2. The method for transporting a combustible gas according to claim 1, wherein the combustible gas is a carbon-neutral fuel gas.

3. The aforementioned flammable gas is hydrogen gas. The method for transporting a flammable gas according to claim 1 or 2, wherein the inert gas is carbon dioxide gas.

4. The method for transporting flammable gas according to claim 3, wherein the volume ratio of the inert gas in the mixed gas is 30% or more and 50% or less.

5. The aforementioned combustible gas includes hydrogen gas and biogas containing methane gas and carbon dioxide gas. The method for transporting a flammable gas according to claim 1 or 2, wherein the inert gas is carbon dioxide gas.

6. The proportion of hydrogen gas by volume in the aforementioned combustible gas is 40% or more and 60% or less. The method for transporting flammable gas according to claim 5, wherein the volume ratio of the inert gas in the mixed gas is 20% or more and 40% or less.

7. The method for transporting flammable gas according to claim 1 or 2, wherein the second piping section is provided with a first flow rate adjustment section for adjusting the flow rate of the inert gas supplied from the inert gas supply section to the first piping section.

8. A flammable gas transport system comprising a transport route for transporting flammable gas from a flammable gas supply unit to a flammable gas supply destination, The aforementioned transport route is A first piping section connecting the flammable gas supply unit and the flammable gas supply destination, A second piping section connecting the inert gas supply section and the first piping section, It has, The flammable gas supply unit supplies the flammable gas to the first piping unit. The inert gas supply unit supplies inert gas to the first piping unit via the second piping unit. A flammable gas transport system wherein a mixed gas, which is a mixture of the flammable gas and the inert gas, flows through the portion of the first piping section between the connection section that connects to the second piping section and the destination of the flammable gas.

9. An imaging device for imaging at least the first piping section, A control unit capable of communicating with the aforementioned imaging device, Equipped with, The flammable gas transport system according to claim 8, wherein the control unit is capable of detecting a flame based on an image captured by the imaging device.

10. An imaging device for imaging at least the first piping section, A control unit capable of communicating with the aforementioned imaging device, Equipped with, The control unit, A processing unit that generates an evaluation image based on the captured image captured by the imaging device, A storage unit that stores a learning model that has been trained to recognize the correspondence between multiple evaluation images acquired in advance and the flame generated when the mixed gas burns, It has, The processing unit inputs the evaluation image to the learning model, The flammable gas transport system according to claim 8, wherein the learning model is capable of determining whether or not the input evaluation image includes an image of a flame.

11. The storage unit stores the captured images at predetermined intervals. When N is a natural number, The flammable gas transport system according to claim 10, wherein the evaluation image is a difference image obtained by removing the (N-1)th captured image stored in the storage unit from the Nth captured image stored in the storage unit.

12. The second piping section is provided with a first flow rate adjustment unit that adjusts the flow rate of the inert gas supplied from the inert gas supply unit to the first piping section, The control unit is capable of communicating with the first flow rate adjustment unit. The flammable gas transport system according to any one of claims 9 to 11, wherein the control unit, upon detecting the flame, increases the flow rate of the inert gas supplied from the inert gas supply unit to the first piping unit by the first flow rate adjustment unit.

13. The control unit is capable of communicating with the flammable gas supply unit, The aforementioned flammable gas is hydrogen gas. The aforementioned flammable gas supply unit is a flammable gas manufacturing apparatus that manufactures the aforementioned flammable gas, The flammable gas transport system according to any one of claims 9 to 11, wherein the control unit stops the operation of the flammable gas supply unit when it detects the flame.

14. A third piping section connects the nitrogen gas supply section containing nitrogen gas and the first piping section, A second flow rate adjustment unit is provided in the third piping section and adjusts the flow rate of the nitrogen gas supplied from the nitrogen gas supply unit to the first piping section, Equipped with, The control unit is capable of communicating with the second flow rate adjustment unit. The combustible gas transport system according to any one of claims 9 to 11, wherein when the control unit detects the flame, the second flow rate adjustment unit supplies the nitrogen gas from the nitrogen gas supply unit to the first piping unit.

15. The imaging device is capable of capturing light in at least the visible region. The inert gas is carbon dioxide gas. The flammable gas transport system according to claim 13, wherein the volume ratio of the inert gas in the mixed gas is 30% or more and 50% or less.

Images