Hydrogen gas conveyance system and marine vessel engine

Abstract

A hydrogen gas conveyance system according to one form of the present disclosure comprises: a double-walled pipe including an inner pipe through which hydrogen gas flows and an outer pipe which covers the inner pipe; an inert gas supply device which supplies an inert gas to an annulus between the inner pipe and the outer pipe; and an exhaust ventilation fan which performs ventilation by discharging the inert gas from the annulus.

Description

Hydrogen gas transport system and marine engine

[0001] The present disclosure relates to a hydrogen gas delivery system and a marine engine.

[0002] A hydrogen gas transport system is installed, for example, on a ship that uses hydrogen gas as fuel. In this case, however, the portion of the piping that transports hydrogen gas located in the ship's engine room must be double-piped. Patent Document 1 listed below discloses a technology in which the gas piping is double-piped and an inert gas is sealed in the outer pipe at a pressure higher than the gas pressure in the inner pipe, although the gas piping is for a fuel gas whose main component is methane gas rather than hydrogen gas.

[0003] Japanese Patent Application Laid-Open No. 2002-54800

[0004] Even in double piping for transporting hydrogen gas, if an inert gas with a higher pressure than the hydrogen gas in the inner pipe is sealed in the annular section between the inner and outer pipes, hydrogen gas is less likely to leak into the annular section, which has a higher pressure than the inner pipe, and even if hydrogen gas does leak into the annular section, an explosion is less likely to occur in the annular section filled with inert gas.

[0005] However, if a high-pressure inert gas is sealed in the annular section, the pressure inside the annular section will be higher than the pressure outside the double piping. Furthermore, hydrogen gas has the smallest molecules of any substance, and is more likely to pass through even the smallest gaps than methane gas and other gases. Therefore, if hydrogen gas leaks into the annular section, there is a risk that the hydrogen gas will leak from the annular section to the outside of the double piping.

[0006] Therefore, an object of the present disclosure is to provide a hydrogen gas transportation system that is less likely to leak hydrogen gas outside the double pipe.

[0007] A hydrogen gas transport system according to one aspect of the present disclosure includes a double pipe including an inner pipe through which hydrogen gas flows and an outer pipe covering the inner pipe, an inert gas supply device that supplies inert gas to an annular portion between the inner pipe and the outer pipe, and an exhaust ventilation fan that exhausts the inert gas from the annular portion to perform ventilation.

[0008] According to the above hydrogen gas transportation system, hydrogen gas is less likely to leak outside the double pipe.

[0009] FIG. 1 is a schematic diagram of a hydrogen gas delivery system.

[0010] A hydrogen gas transport system 100 according to an embodiment will now be described. FIG. 1 is a schematic diagram of the hydrogen gas transport system 100. The hydrogen gas transport system 100 is a system for transporting hydrogen gas. The hydrogen gas transport system 100 of this embodiment is installed on a ship and transports hydrogen gas to an engine 102 in an engine room 101. The engine 102 is a marine engine that may directly drive a propeller (mechanical propulsion) or may drive a propeller via a generator and a motor (electric propulsion). The engine 102 may also be an Otto cycle two-stroke or four-stroke reciprocating engine. Of these, the reciprocating engine may be a diesel cycle or a Sabaté cycle. The engine 102 may also be a gas turbine engine. In particular, a diesel cycle hydrogen gas engine (with a pressure of 20-30 MPaG for the hydrogen gas supplied to the engine 102) is preferred. However, the destination of the hydrogen gas transported by the hydrogen gas transport system 100 is not limited. For example, the hydrogen gas transport system 100 may transport hydrogen gas to a fuel cell, a steam boiler, etc. Furthermore, the hydrogen gas transport system 100 may be installed in a facility other than a ship. In other words, the hydrogen gas transport system 100 may transport hydrogen gas to a hydrogen gas consuming device other than the engine 102.

[0011] 1, the hydrogen gas transportation system 100 according to this embodiment includes a double pipe 10, an inert gas supply device 20, an exhaust ventilation fan 30, and a gas leak detection device 40. These components will be described below in order.

[0012] <Double Pipe> The double pipe 10 of this embodiment is located in an engine room 101 and connected to an engine 102 in the engine room 101. The double pipe 10 includes an inner pipe 11 and an outer pipe 12. The inner pipe 11 is a pipe through which hydrogen gas flows. In this embodiment, hydrogen gas flows inside the inner pipe 11 toward the right of the page in FIG. 1 . The outer pipe 12 is a pipe that covers the inner pipe 11. An annular section 13 having a circular cross section is formed between the inner pipe 11 and the outer pipe 12. As will be described in detail later, an inert gas flows through the annular section 13. In this embodiment, the downstream portion of the double pipe 10 in the direction of hydrogen gas flow is located within the engine 102. Similarly, when the double pipe 10 supplies hydrogen gas to a hydrogen gas consuming device other than the engine 102, the downstream portion of the double pipe 10 in the direction of hydrogen gas flow may be located within the hydrogen gas consuming device. In other words, the downstream portion of the double pipe 10 in the direction of hydrogen gas flow may form part of the hydrogen gas consuming device. In this embodiment, hydrogen gas is directly supplied from the double pipe 10 to each cylinder 103 of the engine 102 .

[0013] The outer pipe 12 has a supply port 14 that supplies inert gas to the annular portion 13 and a discharge port 15 that discharges the inert gas from the annular portion 13. In this embodiment, the supply port 14 is located in a downstream portion of the outer pipe 12 in the direction of hydrogen gas flow (which may be the downstream end), and the discharge port 15 is located in an upstream portion of the outer pipe 12 in the direction of hydrogen gas flow. In other words, the discharge port 15 is located upstream of the supply port 14 in the direction of hydrogen gas flow. Therefore, the inert gas flows in the opposite direction to the flow direction of hydrogen gas. However, the positions of the supply port 14 and the discharge port 15 are not limited to those described above.

[0014] <Inert Gas Supply Device> The inert gas supply device 20 is a device that supplies inert gas to the annular section 13. In this embodiment, the supply port 14 of the outer pipe 12 and the inert gas supply device 20 are connected by a supply pipe 21. The inert gas supply device 20 supplies inert gas to the annular section 13 via this supply pipe 21. The supply pipe 21 is also provided with an inert gas supply flow rate adjustment valve 22 and an inert gas supply ON-OFF valve 23. Of these, the inert gas supply flow rate adjustment valve 22 adjusts the flow rate of inert gas supplied to the annular section 13 so that the inside of the annular section 13 becomes negative pressure (slight negative pressure). Furthermore, the inert gas supply flow rate adjustment valve 22 and the inert gas supply ON-OFF valve 23 may be formed as a single valve. Note that although the inert gas supply device 20 in this embodiment is located inside the engine room 101, it may also be located outside the engine room 101.

[0015] The inert gas supply device 20 of this embodiment acquires nitrogen gas and air and mixes the acquired nitrogen gas with the air to generate a mixed gas. The nitrogen gas can be acquired from a device that generates nitrogen gas from air, such as a membrane nitrogen generator or a PSA (Pressure Swing Adsorption) nitrogen generator, or from a nitrogen gas cylinder. Air can also be acquired from outside the engine room 101. The inert gas supply device 20 then supplies the generated mixed gas to the annular section 13 as an inert gas.

[0016] As described above, in this embodiment, the inert gas is not a gas composed of only nitrogen gas, but a mixed gas of nitrogen gas and air. Therefore, the amount of nitrogen gas used in the hydrogen gas transportation system 100 can be reduced. Furthermore, because the nitrogen gas is mixed with air, the nitrogen gas used does not need to be highly pure, and there is no need for equipment to generate high-purity nitrogen gas with a purity of, for example, 99% vol. or higher.

[0017] However, the inert gas supply device 20 mixes nitrogen gas and air so that the oxygen concentration of the mixed gas is 9% vol. or less. For example, when nitrogen gas consisting of 97% vol. nitrogen and 3% vol. oxygen is mixed with air consisting of 79% vol. nitrogen and 21% vol. oxygen to generate a mixed gas, if the proportion of nitrogen gas in the mixed gas is 67% vol. or more, a mixed gas with an oxygen concentration of 9% vol. or less can be generated. The effect of setting the oxygen concentration of the mixed gas to 9% vol. or less will be described later.

[0018] Furthermore, the inert gas supply device 20 may mix nitrogen gas and air so that the oxygen concentration of the mixed gas is 5% vol. or less. At room temperature and normal pressure, the explosive limit oxygen concentration in a three-component system of hydrogen, nitrogen, and oxygen is 5% vol. Therefore, if the oxygen concentration of the inert gas is 5% vol. or less, even if hydrogen gas leaks into the annular portion 13 filled with inert gas, the hydrogen gas will not ignite or explode in the annular portion 13.

[0019] <Exhaust Ventilation Fan> The exhaust ventilation fan 30 is a fan for ventilating the inside of the annular section 13. An exhaust pipe 31 extending toward the outside of the engine room 101 is connected to the exhaust port 15 of the outer pipe 12. The exhaust ventilation fan 30 is provided on this exhaust pipe 31. Therefore, the exhaust ventilation fan 30 sucks in inert gas inside the annular section 13 through the exhaust pipe 31 and exhausts it outside the engine room 101 (to the atmosphere outside the ship in this embodiment). The exhaust ventilation fan 30 of this embodiment operates constantly while the hydrogen gas transportation system 100 supplies hydrogen gas to the engine 102, that is, while hydrogen gas is flowing through the inner pipe 11 of the double pipe 10, and continuously sucks in and exhausts the inert gas inside the annular section 13.

[0020] The exhaust type ventilation fan 30 is driven by electricity supplied from a power supply device 32. The exhaust type ventilation fan 30 of this embodiment has an induction motor. The power supply device 32 supplies electricity of a constant frequency to the exhaust type ventilation fan 30 (induction motor), thereby maintaining a constant rotation speed of the exhaust type ventilation fan 30. Under these circumstances, if the specific gravity (density) of the gas sucked into the exhaust type ventilation fan 30 decreases, the workload of the exhaust type ventilation fan 30 decreases, and as a result, the current value of the electricity supplied to the exhaust type ventilation fan 30 decreases.

[0021] Furthermore, as described above, the exhaust ventilation fan 30 of this embodiment continuously sucks in the inert gas within the annular section 13 and exhausts it to the atmosphere. Therefore, the pressure inside the annular section 13 is lower than atmospheric pressure, resulting in a negative pressure (slight negative pressure). On the other hand, the internal pressure of the engine room 101 is the same as or slightly higher than atmospheric pressure. Therefore, the pressure inside the annular section 13 is lower than the pressure inside the engine room 101, i.e., the space outside the outer pipe 12. Therefore, according to this embodiment, even if hydrogen gas leaks from the inner pipe 11 to the annular section 13, the hydrogen gas leaking from the inner pipe 11 is unlikely to leak outside the double pipe 10, where the pressure is higher than the pressure inside the annular section 13.

[0022] Here, it has been demonstrated that in double piping for transporting methane gas, a structure (air ventilation structure) that continuously flows air into the annular section can prevent ignition and explosion of methane gas leaked into the annular section. Furthermore, if the oxygen concentration of the inert gas flowing through the annular section 13 is 9% vol. or less as in this embodiment, from the perspective of the minimum ignition energy of flammable gases, the likelihood of ignition, i.e., the risk of ignition, is the same or smaller (the minimum ignition energy is the same or larger) when methane gas leaks into the annular section 13 where air consisting of 79% vol. nitrogen and 21% vol. oxygen flows continuously and when hydrogen gas leaks into the annular section 13 where inert gas consisting of 91% vol. or more nitrogen and 9% vol. or less oxygen flows continuously. Therefore, according to this embodiment, even if hydrogen gas leaks from the inner pipe 11 into the annular portion 13, the risk of the hydrogen gas igniting or exploding in the annular portion 13 can be reduced to the same level as or less than when methane gas is transported through a double pipe with an air ventilation structure.

[0023] In the hydrogen gas transport system 100 according to the present embodiment, instead of sealing an inert gas in the annular portion 13, the inert gas is continuously flowed in the annular portion 13. Therefore, for example, when a general gas detector is installed in the annular portion 13, even if hydrogen gas leaks into the annular portion 13, the leaked hydrogen gas is likely to reach the gas detector, and internal gas leaks can be detected early. Furthermore, by continuously flowing the inert gas in the annular portion 13, hydrogen gas is less likely to stagnate in the annular portion 13, and the risk of hydrogen gas ignition or explosion can be reduced. Furthermore, since the hydrogen gas transport system 100 according to the present embodiment does not seal a high-pressure inert gas in the annular portion 13, the strength required for the inner pipe 11 and the outer pipe 12 is relatively low, and the manufacturing cost of the double pipe 10 can be reduced.

[0024] The inert gas supply device 20 of this embodiment mixes nitrogen gas and air to generate a mixed gas, and supplies the generated mixed gas as an inert gas to the annular portion 13. However, the inert gas supply device 20 may supply the generated or stored nitrogen gas directly as an inert gas to the annular portion 13. In this case, the inert gas supply device 20 may be the device that generates nitrogen gas from air described above or a nitrogen gas cylinder.

[0025] <Gas Leak Determination Device> The gas leak determination device 40 is a device that determines whether or not hydrogen gas has leaked from the inner pipe 11 to the annular portion 13. Hereinafter, the phenomenon in which hydrogen gas leaks from the inner pipe 11 to the annular portion 13 will be referred to as an "internal gas leak."

[0026] The gas leak determination device 40 of this embodiment acquires the current value of the electricity supplied to the exhaust type ventilation fan 30 from the ammeter 41, and determines whether or not an internal gas leak has occurred based on the acquired current value. As described above, in this embodiment, when the specific gravity of the gas sucked into the exhaust type ventilation fan 30 decreases, the current value of the electricity supplied to the exhaust type ventilation fan 30 decreases. Therefore, when hydrogen gas leaks from the inner pipe 11 and the specific gravity of the gas in the annular portion 13 decreases, the current value of the electricity supplied to the exhaust type ventilation fan 30 decreases. Therefore, when the current value of the exhaust type ventilation fan 30 falls below a predetermined reference current value, it can be determined that an internal gas leak has occurred.

[0027] However, the configuration of the gas leak determination device 40 is not limited to the above. For example, the gas leak determination device 40 may determine whether an internal gas leak has occurred based on the differential pressure between the inlet pressure and the outlet pressure of the exhaust ventilation fan 30. When hydrogen gas leaks from the inner pipe 11 and the specific gravity of the gas in the annular portion 13 decreases, the differential pressure between the inlet pressure and the outlet pressure of the exhaust ventilation fan 30 decreases. Therefore, the leak determination device 40 can determine that an internal gas leak has occurred when the differential pressure between the inlet pressure and the outlet pressure of the exhaust ventilation fan 30 falls below a predetermined reference differential pressure.

[0028] Furthermore, the gas leak detection device 40 may determine whether an internal gas leak has occurred based on the aperture of the inert gas supply flow rate adjustment valve 22. In this embodiment, the inert gas supply flow rate adjustment valve 22 adjusts its aperture so that the internal pressure of the annular portion 13 remains constant (slightly negative pressure). Therefore, when hydrogen gas leaks from the inner pipe 11, the internal pressure of the annular portion 13 temporarily increases, but the inert gas supply flow rate adjustment valve 22 reduces its aperture to return the internal pressure of the annular portion 13 to its original value. Therefore, the leak detection device 40 can determine that an internal gas leak has occurred when the aperture of the inert gas supply flow rate adjustment valve 22 falls below a predetermined reference aperture.

[0029] In the hydrogen gas transport system 100 according to this embodiment, if the gas leak determination device 40 determines that an internal gas leak has occurred, the transport of hydrogen gas is stopped and an alarm is issued by the alarm device.

[0030] (Summary) The first item disclosed in this specification is a hydrogen gas transportation system comprising a double pipe having an inner pipe through which hydrogen gas flows and an outer pipe covering the inner pipe, an inert gas supply device that supplies inert gas to an annular section between the inner pipe and the outer pipe, and an exhaust ventilation fan that exhausts the inert gas from the annular section to ventilate.

[0031] This configuration allows the internal pressure of the annular portion to be kept low, so that even if hydrogen gas leaks from the inner pipe into the annular portion, the hydrogen gas is less likely to leak outside the double pipe, where the pressure is higher than that of the annular portion.

[0032] The second item disclosed in this specification is the hydrogen gas transportation system described in the first item, in which the inert gas supply device mixes nitrogen gas and air to generate a mixed gas having an oxygen concentration equal to or lower than a predetermined value, and supplies the generated mixed gas to the annular portion as the inert gas.

[0033] According to this configuration, the amount of nitrogen gas used can be reduced, and there is no need for equipment to generate high-purity nitrogen gas.

[0034] A third item disclosed in the present specification is the hydrogen gas transportation system according to the second item, wherein the oxygen concentration of the mixed gas is 9% vol. or less.

[0035] With this configuration, even if hydrogen gas leaks from the inner pipe into the annular section, the risk of the hydrogen gas igniting or exploding within the annular section can be reduced to the same level as or lower than when methane gas is transported through double piping with an air ventilation structure.

[0036] A fourth item disclosed in the present specification is the hydrogen gas transportation system according to the second item, wherein the oxygen concentration of the mixed gas is 5% vol. or less.

[0037] With this configuration, even if hydrogen gas leaks from the inner pipe into the annular portion, the hydrogen gas will not ignite or explode within the annular portion.

[0038] A fifth item disclosed in this specification is a hydrogen gas transportation system described in any one of the first to fourth items, further comprising a gas leak determination device that determines whether an internal gas leak has occurred, in which hydrogen gas leaks from the inner pipe to the annular portion, wherein electricity is supplied to the exhaust ventilation fan so that the rotation speed is constant, and the gas leak determination device determines that the internal gas leak has occurred when the current value of the exhaust ventilation fan falls below a predetermined reference current value.

[0039] According to this configuration, it is possible to determine whether or not an internal gas leak has occurred, despite the simple configuration.

[0040] A sixth item disclosed in this specification is a hydrogen gas transportation system according to any one of the first to fourth items, further comprising a gas leak determination device that determines whether an internal gas leak has occurred, in which hydrogen gas leaks from the inner pipe to the annular portion, and the gas leak determination device determines that the internal gas leak has occurred when the differential pressure between the inlet pressure and the outlet pressure of the exhaust ventilation fan falls below a predetermined reference differential pressure.

[0041] According to this configuration, it is possible to determine whether or not an internal gas leak has occurred, despite the simple configuration.

[0042] A seventh item disclosed in this specification is a hydrogen gas transportation system described in any one of the first to fourth items, further comprising an inert gas supply flow rate adjustment valve that adjusts the flow rate of inert gas supplied to the annular portion so that the internal pressure of the annular portion remains constant, and a gas leak determination device that determines whether an internal gas leak has occurred, in which hydrogen gas leaks from the inner pipe to the annular portion, and the gas leak determination device determines that the internal gas leak has occurred when the opening degree of the inert gas supply flow rate adjustment valve falls below a predetermined reference opening degree.

[0043] According to this configuration, it is possible to determine whether or not an internal gas leak has occurred, despite the simple configuration.

[0044] An eighth item disclosed in this specification is a marine engine to which hydrogen gas is supplied from the hydrogen gas transportation system according to any one of the first to seventh items.

[0045] With this configuration, hydrogen gas is less likely to leak from the outside of the double pipe that supplies hydrogen gas to the marine engine.

[0046] REFERENCE SIGNS LIST 10 Double piping 11 Inner pipe 12 Outer pipe 13 Annular section 14 Supply port 15 Discharge port 20 Inert gas supply device 21 Supply piping 22 Inert gas supply flow rate adjustment valve 23 Inert gas supply ON-OFF valve 30 Exhaust ventilation fan 31 Discharge piping 32 Electricity supply device 40 Gas leak detection device 41 Ammeter 100 Hydrogen gas transport system 101 Engine room 102 Engine 103 Cylinder

Claims

1. A hydrogen gas transport system comprising: a double pipe including an inner pipe through which hydrogen gas flows and an outer pipe covering the inner pipe; an inert gas supply device that supplies inert gas to an annular section between the inner pipe and the outer pipe; and an exhaust ventilation fan that exhausts the inert gas from the annular section to ventilate the area.

2. The hydrogen gas transportation system according to claim 1, wherein the inert gas supply device mixes nitrogen gas and air to generate a mixed gas having an oxygen concentration below a predetermined value, and supplies the generated mixed gas to the annular portion as the inert gas.

3. The hydrogen gas transportation system according to claim 2, wherein the oxygen concentration of the mixed gas is 9% vol. or less.

4. The hydrogen gas transportation system according to claim 2, wherein the oxygen concentration of the mixed gas is 5% vol. or less.

5. A hydrogen gas transport system as described in claim 1, further comprising a gas leak determination device that determines whether an internal gas leak has occurred, in which hydrogen gas leaks from the inner pipe to the annular portion, wherein electricity is supplied to the exhaust ventilation fan so that the rotation speed is constant, and wherein the gas leak determination device determines that the internal gas leak has occurred when the current value of the exhaust ventilation fan falls below a predetermined reference current value.

6. A hydrogen gas transportation system as described in claim 1, further comprising a gas leak determination device that determines whether an internal gas leak has occurred, in which hydrogen gas leaks from the inner pipe to the annular portion, and the gas leak determination device determines that the internal gas leak has occurred when the differential pressure between the inlet pressure and the outlet pressure of the exhaust ventilation fan falls below a predetermined reference differential pressure.

7. A hydrogen gas transportation system as described in claim 1, further comprising: an inert gas supply flow rate adjustment valve that adjusts the flow rate of inert gas supplied to the annular portion so that the internal pressure of the annular portion remains constant; and a gas leak determination device that determines whether an internal gas leak has occurred, in which hydrogen gas leaks from the inner pipe to the annular portion, wherein the gas leak determination device determines that the internal gas leak has occurred when the opening degree of the inert gas supply flow rate adjustment valve falls below a predetermined reference opening degree.

8. A marine engine to which hydrogen gas is supplied from the hydrogen gas transportation system according to any one of claims 1 to 7.

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