Shipboard fuel gas supply system and liquefied gas fuel ship

Abstract

A shipboard fuel gas supply system according to the present invention comprises a tank that has a liquid-phase area that stores a liquefied gas and a gas-phase area that stores a vaporized gas of the liquefied gas, a high-pressure gas supply line that supplies a high-pressure fuel gas obtained by forcibly vaporizing liquefied gas extracted from the liquid-phase area of the tank to a high-pressure gas–consuming apparatus, a low-pressure gas supply line that supplies vaporized gas from the gas-phase area of the tank to a low-pressure gas–consuming apparatus as a low-pressure fuel gas, and a pressure adjustment device that adjusts the pressure inside the tank to a pressure setting value that corresponds to a usage pressure or a required pressure for the low-pressure gas–consuming apparatus.

Description

Marine fuel gas supply system and liquefied gas fueled ship

[0001] The present disclosure relates to a ship fuel gas supply system and a liquefied gas fuelled ship equipped with the ship fuel gas supply system.

[0002]

[0003] Conventionally, ships equipped with tanks storing liquefied gas are known that are equipped with a gas supply system having both a line for extracting the liquefied gas from the tank, vaporizing it, and supplying it to gas-consuming devices, and a line for extracting the vaporized gas from the tank and supplying it to gas-consuming devices. Examples of gas-consuming devices include a propulsion system and a power generation system installed on the ship. Patent Document 1 discloses this type of gas supply system.

[0003] The gas supply system of Patent Document 1 includes a tank storing liquefied gas at atmospheric pressure, a first gas supply line for supplying gas from a liquid phase compartment of the tank to one or more gas consumers, and a second gas supply line for supplying gas from a vapor phase compartment of the tank to one or more gas consumers. The first gas supply line includes a cryogenic pump that pressurizes the liquefied gas extracted from the tank to a gas pressure required by the gas consumers, and a first heat exchanger that vaporizes the liquefied gas and heats it to the operating temperature of the gas consumers. The second gas supply line includes a second heat exchanger that heats the vaporized gas extracted from the tank to the operating temperature of the gas consumers, and a compressor that pressurizes the vaporized gas to the operating pressure of the gas consumers.

[0004] Special Publication No. 2021-516749

[0005] In a gas supply system installed on a ship, in order to enable greater energy supply within the limited installation space on the ship, it is preferable to increase the capacity of the tank that stores fuel and reduce the space occupied by the gas supply line from the tank to the gas consuming equipment.

[0006] The present disclosure has been made in consideration of the above circumstances, and its purpose is to propose a technology for reducing the space occupied by the fuel gas supply line while ensuring a large tank volume in a marine fuel gas supply system that has both a gas supply line that extracts liquefied gas from a tank that stores the liquefied gas, vaporizes it, and supplies it to a gas consuming device, and a gas supply line that extracts vaporized gas from the tank and supplies it to a gas consuming device, and in a liquefied gas-fueled ship on which the system is installed.

[0007] In order to solve the above problems, a fuel gas supply system for a ship according to one aspect of the present disclosure comprises: a tank having a liquid phase region in which liquefied gas is stored and a gas phase region in which vaporized gas of the liquefied gas is accommodated; a high-pressure gas supply line that supplies high-pressure fuel gas obtained by forcibly vaporizing the liquefied gas extracted from the liquid phase region of the tank to one or more high-pressure gas consuming appliances having a fuel gas operating pressure of more than 1 MPaG; a low-pressure gas supply line that supplies the vaporized gas from the gas phase region of the tank as low-pressure fuel gas to one or more low-pressure gas consuming appliances having a fuel gas operating pressure of 1 MPaG or less; and a pressure regulating device that adjusts the pressure in the tank so that the pressure in the tank or the pressure in the low-pressure gas supply line becomes a predetermined pressure set value corresponding to the operating pressure or required pressure of the low-pressure gas consuming appliances, wherein the low-pressure gas supply line has a low-pressure gas heater that heats the vaporized gas to the operating temperature of the low-pressure gas consuming appliances, The high-pressure gas supply line has a pump that pressurizes the liquefied gas to the operating pressure of the high-pressure gas consumer, and a high-pressure gas heater that heats the liquefied gas to the operating temperature of the high-pressure gas consumer.

[0008] Furthermore, a liquefied gas fuelled ship according to one aspect of the present disclosure comprises: a hull; a tank mounted on the hull for storing liquefied gas; one or more high-pressure gas consuming equipment mounted on the hull, including a gas engine that generates propulsion energy for the hull, the fuel gas operating pressure of which exceeds 1 MPaG; one or more low-pressure gas consuming equipment mounted on the hull, the fuel gas operating pressure of which is 1 MPaG or less; and the marine fuel gas supply system.

[0009] According to the present disclosure, a technology can be proposed for a marine fuel gas supply system that includes both a gas supply line that extracts liquefied gas from a tank that stores the liquefied gas, vaporizes it, and supplies it to a gas consuming device, and a gas supply line that extracts vaporized gas from the tank and supplies it to a gas consuming device, and for a liquefied gas-fueled ship on which the system is installed, that reduces the space occupied by the fuel gas supply line while ensuring a large tank volume.

[0010] Fig. 1 is a diagram showing a schematic configuration of a liquefied gas fuelled ship equipped with a boat fuel gas supply system according to an embodiment of the present disclosure. Fig. 2 is a diagram showing the configuration of the boat fuel gas supply system. Fig. 3 is a diagram showing the configuration of a boat fuel gas supply system according to a first modified example of the embodiment. Fig. 4 is a diagram showing the configuration of a boat fuel gas supply system according to a second modified example of the embodiment. Fig. 5 is a diagram showing the configuration of a boat fuel gas supply system according to a third modified example of the embodiment.

[0011] Next, an embodiment of the present disclosure will be described with reference to the drawings. Note that, hereinafter, unless otherwise specified, "-" indicating a numerical range means "greater than or equal to" or less than. FIG. 1 is a diagram showing a schematic configuration of a liquefied gas fueled ship 10 equipped with a marine fuel gas supply system 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the liquefied gas fueled ship 10 according to this embodiment includes a hull 11, a liquefied gas tank 2 (hereinafter simply referred to as the "tank 2") equipped on the hull 11, and a marine fuel gas supply system 1 that supplies liquefied gas from the tank 2 to low-pressure gas consuming equipment 6 and high-pressure gas consuming equipment 7.

[0012] The type of liquefied gas fuelled ship 10 is not particularly limited, and various ships can be used as long as they are propelled by energy generated using liquefied gas as fuel. The fuel gas supplied to the gas consumers 6, 7 by the marine fuel gas supply system 1 according to this embodiment is a vaporized liquefied gas, and the liquefied gas is liquefied hydrogen. However, the liquefied gas is not limited to liquefied hydrogen, and may be a liquefied hydrocarbon gas such as LNG (Liquefied Natural Gas) or LPG (Liquefied Petroleum Gas), or liquefied ammonia.

[0013] The low-pressure gas consuming equipment 6 is equipment that consumes fuel gas and has a pressure of fuel gas during use, i.e., a working pressure, of 1 MPaG or less. The working pressure is defined as the pressure when the equipment or system is actually used. Non-limiting examples of the low-pressure gas consuming equipment 6 include a fuel cell, a generator, a boiler, etc. installed on the liquefied gas-fueled ship 10. The fuel cell, for example, converts the chemical energy of fuel and oxidizer into electricity, and the generated electricity is sent to the onboard power system for use on the ship. The pressure of the fuel gas of the fuel cell during use is, for example, about 0.5 MPaG. The fuel cell is preferably combined with a battery that stores the generated electricity, which allows for flexible increase or decrease in fuel consumption independent of the onboard power demand. The generator, for example, is a four-stroke dual-fuel reciprocating engine capable of gas combustion using an Otto cycle when using gas fuel, and converts the rotational power of the generator into electrical energy. The generated electricity is sent to the onboard power system for use on the ship. The pressure of fuel gas used in the generator's reciprocating engine is, for example, about 0.7 MPaG. The boiler burns at least one of fuel oil and fuel gas to generate steam, which is used, for example, as a heat source for hot water on board a ship or a heat source for heating fuel gas. The pressure of fuel gas used in the boiler is, for example, about 0.1 MPaG.

[0014] The high-pressure gas consuming equipment 7 refers to equipment that consumes fuel gas, and the pressure of the fuel gas when in use exceeds 1 MPaG. A non-limiting example of the high-pressure gas consuming equipment 7 is a dual-fuel engine that can use fuel gas and fuel oil as fuel. The dual-fuel engine is, for example, a two-stroke reciprocating engine of a diesel cycle or an Otto cycle. The power generated by the dual-fuel engine is transmitted to the propeller via a propeller shaft. The power generated by the dual-fuel engine may also be used in a shaft generator that generates electricity using the rotation of the propeller shaft. The pressure of the fuel gas when in use in a dual-fuel engine is, for example, 20-30 MPaG for a diesel cycle and 1-2 MPaG for an Otto cycle.

[0015] <Configuration of the boat fuel gas supply system 1> The configuration of the boat fuel gas supply system 1 will be described in detail. Figure 2 is a diagram showing the configuration of the boat fuel gas supply system 1. As shown in Figure 2, the boat fuel gas supply system 1 includes a tank 2 that stores liquefied gas as fuel, a low-pressure gas supply line 60 that supplies fuel gas from the tank 2 to a low-pressure gas consuming device 6, a high-pressure gas supply line 70 that supplies fuel gas from the tank 2 to a high-pressure gas consuming device 7, and a pressure regulating device 8 that adjusts the pressure inside the tank 2.

[0016] The tank 2 according to this embodiment is a vacuum double-shelled container for storing low-temperature liquefied gas. The tank 2 has a double-shelled structure consisting of an inner shell that stores the liquefied gas and an outer shell that surrounds the inner shell, with a vacuum insulation layer formed between the inner and outer shells. However, the tank 2 may have a single-shelled structure covered with insulation material, or a multi-shelled structure with three or more shells.

[0017] Due to the heat input to the tank 2, a portion of the liquefied gas in the tank 2 is vaporized to form a vaporized gas. Within the tank 2, a liquid phase region 21 below the liquid level of the liquefied gas and a gas phase region 22 above the liquid level of the liquefied gas are formed.

[0018] The low-pressure gas supply line 60 is a conduit that sends vaporized gas in the tank 2 to one or more low-pressure gas consumers 6 as "low-pressure fuel gas." By supplying the vaporized gas in the tank 2 to the low-pressure gas consumers 6, the vaporized gas generated in the tank 2 can be actively consumed while suppressing a pressure increase in the tank 2. The low-pressure gas supply line 60 is composed of piping or the like. The low-pressure gas supply line 60 is connected to the gas phase region 22 of the tank 2. Specifically, the low-pressure gas supply line 60 is connected to the top of the tank 2 or to a side of the tank 2 above the liquid level of the liquefied gas at the tank loading limit. However, the connection position of the low-pressure gas supply line 60 to the tank 2 may be lower than the liquid level of the liquefied gas at the tank loading limit, as long as the opening end that is the starting point of the low-pressure gas supply line 60 is in the gas phase region 22 of the tank 2. This allows the vaporized gas in the tank 2 to flow into the low-pressure gas supply line 60 as low-pressure fuel gas.

[0019] The low-pressure gas supply line 60 is provided with a low-pressure gas heater 61 that heats the low-pressure fuel gas to the operating temperature of the low-pressure gas consumer 6. The low-pressure gas heater 61 may be a known heating means such as a heat exchanger that exchanges heat between the low-pressure fuel gas and a heat medium or an electric heater. When there are multiple low-pressure gas consumers 6 to which the low-pressure fuel gas is supplied, a supply valve 63 that distributes the low-pressure fuel gas to the low-pressure gas consumers 6 and adjusts the supply amount, or a regulator 64 that adjusts the pressure to the operating pressure of each low-pressure gas consumer 6 may be provided downstream of the low-pressure gas heater 61 on the low-pressure gas supply line 60. Note that the low-pressure gas supply line 60 is not provided with a pump or compressor that pressurizes the low-pressure fuel gas.

[0020] The high-pressure gas supply line 70 is a pipeline that forcibly vaporizes and pressurizes the liquefied gas in the tank 2 and sends it as "high-pressure fuel gas" to one or more high-pressure gas consuming devices 7. The high-pressure gas supply line 70 is composed of piping or the like. The high-pressure gas supply line 70 is connected to the liquid phase region 21 of the tank 2. Specifically, the high-pressure gas supply line 70 is connected to the bottom of the tank 2 or the lower side of the tank 2. This allows the liquefied gas to flow from the tank 2 into the high-pressure gas supply line 70.

[0021] The high-pressure gas supply line 70 is provided with a pump 71 that pressurizes the liquefied gas. The pump 71 is a cryogenic fluid pump that can pressurize low-temperature liquefied gas to the operating pressure of the high-pressure gas consumer 7. A high-pressure gas heater 73 that heats the pressurized liquefied gas is provided downstream of the pump 71 on the high-pressure gas supply line 70. The high-pressure gas heater 73 may be a known heating means, such as a heat exchanger that exchanges heat between the liquefied gas and a heat medium or an electric heater. The liquefied gas that flows into the high-pressure gas supply line 70 passes through the pump 71 and the high-pressure gas heater 73 and becomes high-temperature, high-pressure fuel gas. When there are multiple high-pressure gas consumers 7 to which the high-pressure fuel gas is supplied, a supply valve 74 that distributes the high-pressure fuel gas to the high-pressure gas consumers 7 and adjusts the supply amount, a regulator 75 that finely adjusts the operating pressure of each high-pressure gas consumer 7, and the like may be provided downstream of the high-pressure gas heater 73 on the high-pressure gas supply line 70.

[0022] The pressure adjustment device 8 is a device that maintains the pressure inside the tank 2 at a predetermined level. The pressure adjustment device 8 may, for example, utilize a heat exchanger 81, also known as a PBU (Pressure Build-up Unit). The pressure adjustment device 8 is composed of a pressure sensor 86, a pressure adjustment line 80, and a controller 84. The pressure adjustment line 80 is composed of the heat exchanger 81, a liquid supply pipe 82, and an air supply pipe 83. The liquid supply pipe 82 is connected to the liquid phase region 21 of the tank 2 and sends liquefied gas from the liquid phase region 21 of the tank 2 to the heat exchanger 81. The heat exchanger 81 heats the liquefied gas to forcibly vaporize it. The air supply pipe 83 is connected to the gas phase region 22 of the tank 2 and sends the vaporized gas generated in the heat exchanger 81 to the gas phase region 22 of the tank 2. The vaporized gas sent to the gas phase region 22 of the tank 2 through the pressure adjustment line 80 in this manner pressurizes the inside of the tank 2. The gas supply pipe 83 is provided with a shutoff valve 85 that switches between supplying and stopping the supply of vaporized gas to the tank 2. Instead of the shutoff valve 85, a flow rate adjustment valve may be provided.

[0023] A pressure sensor 86 that detects the pressure of the low-pressure fuel gas supplied from the low-pressure gas supply line 60 to the low-pressure gas consuming equipment 6 is provided downstream of the low-pressure gas heater 61 on the low-pressure gas supply line 60. The controller 84 is electrically connected to the heat exchanger 81, the shut-off valve 85, and the pressure sensor 86. The controller 84 adjusts the pressure in the tank 2 by operating the pressure adjustment line 80 based on the detection value of the pressure sensor 86.

[0024] <<Operation Method of Marine Fuel Gas Supply System 1>> Here, we will explain the operation method of the marine fuel gas supply system 1 configured as described above. During operation of the marine fuel gas supply system 1, the pressure regulating device 8 adjusts the pressure in the tank 2 so that the pressure of the low-pressure fuel gas detected by the pressure sensor 86 becomes a predetermined pressure setting value. Normally, during operation, the pressure in the tank 2 gradually decreases due to the supply of fuel gas to the low-pressure gas consuming equipment 6 and the high-pressure gas consuming equipment 7.

[0025] The controller 84 of the pressure regulating device 8 acquires the detection value of the pressure sensor 86 and compares the detection value with the set pressure value. The set pressure value is the operating pressure of the low-pressure gas consuming equipment 6 or a numerical value obtained by adding an allowable error range and pressure loss to the operating pressure, and is stored in advance in the controller 84. Taking into account the action of the regulator 64, the set pressure value may be slightly higher than the operating pressure of the low-pressure gas consuming equipment 6. If there are multiple low-pressure gas consuming equipment 6, the set pressure value may be the highest value among the operating pressures of the multiple low-pressure gas consuming equipment 6, or a numerical value obtained by adding an allowable error range and pressure loss to the highest value. Furthermore, the set pressure value may be a value corresponding to the required pressure instead of the operating pressure of the low-pressure gas consuming equipment 6. Here, the required pressure is the pressure required for normal operation of the gas consuming equipment. The required pressure is input from the low-pressure gas consuming equipment 6 to the controller 84 of the fuel gas supply system 1, and the controller 84 controls the pressure of the low-pressure gas supply line 60 or the tank 2 to the required pressure.

[0026] The operating pressure of the low-pressure gas consuming equipment 6 is standard atmospheric pressure, i.e., greater than 0 MPaG, equal to or less than 1 MPaG, and equal to or less than the maximum operating pressure of the tank 2. The maximum operating pressure is defined as the highest usable pressure of the equipment or system. Therefore, the pressure setting value is set to a value greater than 0 MPaG, equal to or less than 1 MPaG, and equal to or less than the maximum operating pressure of the tank 2, according to the operating pressure of the low-pressure gas consuming equipment 6. To give a non-limiting numerical example, if the low-pressure gas consuming equipment 6 is a fuel cell with an operating pressure of 0.5 MPaG, a generator with an operating pressure of 0.7 MPaG, and a boiler with an operating pressure of 0.1 MPaG, the pressure setting value is set to 0.7 MPaG, which is greater than the operating pressure of the generator. The low-pressure gas supply line 60 reduces the pressure of 0.7 MPaG low-pressure fuel gas to 0.5 MPaG using a regulator 64 before supplying it to the fuel cell, supplies the 0.7 MPaG low-pressure fuel gas to the generator without reducing the pressure, and reduces the 0.7 MPaG low-pressure fuel gas to 0.1 MPaG before supplying it to the boiler. In such a case, the maximum operating pressure of the tank 2 is set to be higher than 0.7 MPaG.

[0027] In addition, when the liquefied gas is liquefied hydrogen, the critical pressure of hydrogen is approximately 1.3 MPa.abs (approximately 1.2 MPaG), which is lower than that of LNG, which is conventionally used as marine fuel. Therefore, it is preferable to set the maximum operating pressure of the tank 2 to a pressure not exceeding, for example, 1 MPaG. For example, by setting the pressure to 0.7 MPaG, which is lower than the maximum operating pressure of the tank 2 but higher than the operating pressure of the generator, and adjusting the pressure of the tank 2 to this pressure setting, liquefied hydrogen in the liquid phase region 21 and hydrogen gas in the gas phase region 22 exist inside the tank 2. In this case, the liquefied hydrogen in the lower layer of the tank 2 is pressurized by the pump 71 and supplied to the high-pressure gas consuming equipment 7 through the high-pressure gas supply line 70, and the hydrogen gas in the upper layer of the tank 2 is supplied to the low-pressure gas consuming equipment 6 through the low-pressure gas supply line 60 using the pressure of the tank 2. As a result, the hydrogen gas is sent from the tank 2 to the low-pressure gas consuming equipment 6 or the high-pressure gas consuming equipment 7 and effectively used as fuel, without being disposed of by incineration or atmospheric release.

[0028] When the detection value of the pressure sensor 86 becomes smaller than the pressure set value, the controller 84 starts using the heat exchanger 81 and opens the shutoff valve 85 to start supplying vaporized gas to the gas phase region 22 of the tank 2. When the detection value of the pressure sensor 86 exceeds the pressure set value, the controller 84 stops using the heat exchanger 81 and closes the shutoff valve 85 to end the supply of vaporized gas to the gas phase region 22 of the tank 2. In this way, the pressure of the low-pressure fuel gas supplied to the low-pressure gas consuming equipment 6 is maintained at or above the pressure set value, i.e., the operating pressure of the low-pressure gas consuming equipment 6. Note that, since the low-pressure gas supply line 60 and the gas phase region 22 of the tank 2 are connected, there is almost no difference between the pressure of the low-pressure fuel gas in the low-pressure gas supply line 60 and the pressure in the gas phase region 22 of the tank 2, even when pressure loss is taken into account. For this reason, the pressure sensor 86 may be provided in the tank 2 instead of the low-pressure gas supply line 60.

[0029] With the pressure of the tank 2 adjusted by the pressure adjustment device 8 as described above, fuel is supplied from the tank 2 to the low-pressure gas consumer 6 and the high-pressure gas consumer 7. In the high-pressure gas supply line 70, the pump 71 operates to cause liquefied gas in the liquid phase region 21 of the tank 2 to flow into the high-pressure gas supply line 70, and the liquefied gas is pressurized by the pump 71 and heated by the high-pressure gas heater 73 to become high-pressure fuel gas at the operating pressure and temperature of the high-pressure gas consumer 7, which is then supplied to the high-pressure gas consumer 7. In the low-pressure gas supply line 60, as low-pressure fuel gas is consumed in the low-pressure gas consumer 6, vaporized gas flows from the gas phase region 22 of the tank 2 into the low-pressure gas supply line 60, and the vaporized gas is heated by the low-pressure gas heater 61 to become low-pressure fuel gas at the operating pressure and temperature of the low-pressure gas consumer 6, which is then supplied to the low-pressure gas consumer 6.

[0030] In the fuel gas supply system 1 for a boat having the above configuration, the pressure in the tank 2 is maintained at or above the operating pressure of the low-pressure gas consuming equipment 6, high-pressure fuel gas pressurized by the pump 71 is supplied to the high-pressure gas consuming equipment 7, and low-pressure fuel gas is supplied directly from the tank 2 to the low-pressure gas consuming equipment 6 without going through a compressor or pump. In other words, the fuel gas supply system 1 for a boat according to the present disclosure can omit elements such as compressors and pumps for pressurizing vaporized gas, which are provided in conventional fuel gas supply systems. Therefore, compared to conventional fuel gas supply systems, the occupied space and equipment costs for the omitted elements can be reduced, and operating energy and operating costs can also be reduced.

[0031] [Modification 1] Next, Modification 1 of the above embodiment will be described. Figure 3 is a diagram showing the configuration of a boat fuel gas supply system 1 according to Modification 1 of the embodiment. In the description of this modification, the same or similar members as those in the above embodiment will be denoted by the same reference numerals in the drawings, and descriptions thereof will be omitted.

[0032] The boat fuel gas supply system 1 according to Modification 1 shown in Figure 3 is substantially the same as the boat fuel gas supply system 1 according to the above embodiment, except for the addition of a pre-pump 72. In the boat fuel gas supply system 1 according to Modification 1, the high-pressure gas supply line 70 is equipped with a two-stage pump: a pump 71 which is a main pump, and a pre-pump 72 which is arranged upstream of the pump 71. In the boat fuel gas supply system 1 shown in Figure 3, the pre-pump 72 is arranged midway through the high-pressure gas supply line 70, but the pre-pump 72 may also be arranged at the inlet of the high-pressure gas supply line 70 which penetrates the tank 2 and is led to the inside and bottom of the tank 2, i.e., inside the tank 2.

[0033] The liquefied gas that flows out from the tank 2 into the high-pressure gas supply line 70 is first pressurized by the pre-pump 72. The pre-pump 72 pressurizes the liquefied gas in the tank 2, which has a predetermined set pressure value greater than 0 MPaG and equal to or less than 1 MPaG, to approximately 0.5-1 MPaG. The liquefied gas pressurized by the pre-pump 72 is further pressurized by the pump 71. The pump 71 pressurizes the liquefied gas, which has been pressurized to approximately several MPaG by the pre-pump 72, to several tens of MPaG, which corresponds to the operating pressure of the high-pressure gas consuming equipment 7.

[0034] In the marine fuel gas supply system 1 according to Modification 1, the pre-pump 72 and the pump 71 gradually pressurize the liquefied gas in the high-pressure gas supply line 70, thereby suppressing the occurrence of cavitation at the suction ports of the pre-pump 72 and the pump 71. In particular, when the liquefied gas is liquefied hydrogen, pressurizing the liquefied hydrogen in two stages, by the pre-pump 72 and the pump 71, is useful from the perspective of ensuring a large NPSH (net positive suction head), because it allows the liquefied hydrogen to be pressurized in a liquid phase while maintaining a low temperature. Generally, if the NPSH is sufficiently large, the occurrence of cavitation in the pump is suppressed, and the pump can exhibit high performance.

[0035] [Modification 2] Next, Modification 2 of the above embodiment will be described. Figure 4 is a diagram showing the configuration of a boat fuel gas supply system 1 according to Modification 2 of the embodiment. In the description of this modification, the same or similar members as those in the above embodiment will be denoted by the same reference numerals in the drawings, and descriptions thereof will be omitted.

[0036] The boat fuel gas supply system 1 according to Modification 2 shown in Figure 4 is substantially the same as the boat fuel gas supply system 1 according to the above embodiment, except for the addition of a pre-pump 72 and a return line 51. In the boat fuel gas supply system 1 according to Modification 2, like the boat fuel gas supply system 1 according to Modification 1, the high-pressure gas supply line 70 is equipped with a two-stage pump consisting of a pre-pump 72 and a pump 71. The explanation of the two-stage pump will be omitted, and the explanation of Modification 1 will be cited.

[0037] Generally, in a submerged pump used as the pre-pump 72, the motor that drives the pump is integrally formed with the pump. Because the pump and motor are immersed in the working fluid, energy lost in the pump itself and heat dissipated by the motor are input into the working fluid. In a submerged pump, this heat input vaporizes a portion of the liquefied gas, generating vaporized gas. Furthermore, a reciprocating pump used as the pump 71 generally requires a large amount of power, i.e., driving energy, to pressurize the liquefied gas to a high pressure. Some of the large driving energy transmitted to the pump is lost, i.e., becomes heat input to the liquefied gas, vaporizing a portion of the liquefied gas and generating vaporized gas. Therefore, the marine fuel gas supply system 1 according to the second modification is configured to return the vaporized gas generated by the pre-pump 72 and the pump 71 to the gas phase region 22 of the tank 2, enabling effective fuel utilization. Because liquefied hydrogen has a lower latent heat of vaporization than LNG, a larger amount of vaporization occurs for the same amount of heat input. Therefore, the configuration of the fuel gas supply system 1 according to the second modification is particularly useful when the liquefied gas is liquefied hydrogen.

[0038] The boat fuel gas supply system 1 according to the second modification includes a return line 51 that returns the vaporized gas generated by the pre-pump 72 and the pump 71 to the gas phase region 22 of the tank 2. The return line 51 is a pipe that connects the vaporized gas outlets of the pre-pump 72 and the pump 71 to the gas phase region 22 of the tank 2. However, the return line 51 may be configured to return the vaporized gas to the tank 2 independently from each of the pre-pump 72 and the pump 71, or may be configured to return the vaporized gas to the tank 2 from one of the pre-pump 72 and the pump 71.

[0039] As described above, by returning the vaporized gas produced by the pre-pump 72 and the pump 71 to the tank 2 through the return line 51, the load on the heat exchanger 81 of the pressure regulating device 8 can be reduced, and more active use can be made of the vaporized gas produced in the marine fuel gas supply system 1. Furthermore, by returning the vaporized gas of the liquefied gas in the high-pressure gas supply line 70 to the tank 2 through the return line 51, it is possible to adjust the supply amount of high-pressure fuel gas supplied to the high-pressure gas consuming equipment 7.

[0040] Next, Modification 3 of the above embodiment will be described. Figure 5 is a diagram showing the configuration of a boat fuel gas supply system 1 according to Modification 3 of the embodiment. In the description of this modification, the same or similar members as those in the above embodiment will be denoted by the same reference numerals in the drawings, and descriptions thereof will be omitted.

[0041] The boat fuel gas supply system 1 according to Modification 3 shown in Figure 5 is substantially the same as the boat fuel gas supply system 1 according to the above embodiment, except that it adds a pre-pump 72 and a return line 52. In the boat fuel gas supply system 1 according to Modification 3, like the boat fuel gas supply system 1 according to Modification 1, the high-pressure gas supply line 70 is equipped with a two-stage pump consisting of a pre-pump 72 and a pump 71. The explanation of the two-stage pump will be omitted, and the explanation of Modification 1 will be cited.

[0042] If an abnormality occurs in the high-pressure gas consuming equipment 7, such as a sudden decrease in load or a gas supply cutoff, the fuel gas may be temporarily oversupplied to the high-pressure gas supply line 70, resulting in a surplus of fuel gas. Furthermore, depending on the operating range of the pump 71, the fuel gas may be continuously oversupplied. Therefore, the fuel gas supply system 1 according to Modification 3 is provided with return lines 52a, 52b that return the surplus fuel gas generated in the high-pressure gas supply line 70 to the tank 2. Note that although the fuel gas supply system 1 shown in FIG. 5 is provided with two return lines 52a, 52b, it may also be provided with at least one of the two return lines 52a, 52b.

[0043] A return line 52a is connected to the flow path connecting the pre-pump 72 and the pump 71. A flow rate adjustment valve 53a is provided in the return line 52a. This return line 52a extracts the liquefied gas discharged from the pre-pump 72 before it is sucked into the pump 71 and sends it to the tank 2. The amount of liquefied gas returned to the tank 2 through the return line 52a is adjusted by the flow rate adjustment valve 53a.

[0044] In addition, a return line 52b is connected between the pump 71 and the supply valve 74. A flow rate adjustment valve 53b is provided on the return line 52b. This return line 52b extracts the liquefied gas discharged from the pump 71 before it is sent to the high-pressure gas consuming equipment 7 and sends it to the tank 2. The amount of liquefied gas returned to the tank 2 through the return line 52b is adjusted by the flow rate adjustment valve 53b. The return line 52b is preferably connected to the high-pressure gas supply line 70 downstream of the pump 71 and upstream of the high-pressure gas heater 73 so that liquefied gas before being heated by the high-pressure gas heater 73 can be extracted. However, the return line 52b may also be connected to the high-pressure gas supply line 70 so that vaporized liquefied gas after being heated by the high-pressure gas heater 73 can be extracted.

[0045] In the fuel gas supply system 1 according to the third modification, surplus liquefied gas or its vaporized gas in the high-pressure gas supply line 70 is returned to the tank 2 via the return lines 52a and 52b. Therefore, the excess fuel in the high-pressure gas supply line 70 is not disposed of by incineration or atmospheric release, but is instead sent from the tank 2 to the low-pressure gas consumer 6 or the high-pressure gas consumer 7, where it can be effectively utilized as fuel. The return line 52b is particularly useful when the liquefied gas is liquefied hydrogen. Compared to LNG, liquefied hydrogen experiences a significantly greater increase in enthalpy when pressurized to several tens of MPaG by the pump 71. When the excess liquefied hydrogen whose enthalpy has increased after pressurization by the pump 71 is sent to the tank 2 via the return line 52b, most of the liquefied hydrogen decompressed to the pressure within the tank 2 becomes vaporized gas and is returned to the tank 2. The vaporized liquefied hydrogen gas, i.e., low-pressure hydrogen gas, returned to the tank 2 via the return line 52b in this manner is effectively utilized in the low-pressure gas consumer 6. That is, even in cases where it is unavoidable to return some excess liquefied hydrogen, which has been pressurized to several tens of MPaG and has a high enthalpy, to tank 2, much of the vaporized gas generated by reducing the pressure to the pressure inside tank 2 can be effectively used in low-pressure gas consuming equipment 6 via tank 2, thereby suppressing an increase in pressure in tank 2. In this way, tank 2 can be used within a range that does not exceed its maximum operating pressure, without disposing of liquefied hydrogen or its vaporized gas by incineration or atmospheric release.

[0046] [Summary] A marine fuel gas supply system 1 according to a first item of the present disclosure comprises: a tank 2 having a liquid phase region 21 in which liquefied gas is stored and a gas phase region 22 in which vaporized gas of the liquefied gas is accommodated; a high-pressure gas supply line 70 for supplying high-pressure fuel gas obtained by forcibly vaporizing the liquefied gas extracted from the liquid phase region 21 of the tank 2 to one or more high-pressure gas consuming appliances 7 in which the fuel gas usage pressure exceeds 1 MPaG; a low-pressure gas supply line 60 for supplying vaporized gas from the gas phase region 22 of the tank 2 as low-pressure fuel gas to one or more low-pressure gas consuming appliances 6 in which the fuel gas usage pressure is 1 MPaG or less; and a pressure regulating device 8 for adjusting the pressure in the tank 2 so that the pressure in the tank 2 or the pressure in the low-pressure gas supply line 60 becomes a predetermined pressure set value corresponding to the usage pressure or required pressure of the low-pressure gas consuming appliances 6, wherein the low-pressure gas supply line 60 has a low-pressure gas heater 61 for heating the vaporized gas to the usage temperature of the low-pressure gas consuming appliances 6, The high-pressure gas supply line 70 has a pump 71 that pressurizes the liquefied gas to the operating pressure of the high-pressure gas consumer 7, and a high-pressure gas heater 73 that heats the liquefied gas to the operating temperature of the high-pressure gas consumer 7.

[0047] According to the marine fuel gas supply system 1 having the above configuration, the low-pressure gas supply line 60 does not require a pressure-boosting means such as a pump or compressor for pressurizing the vaporized gas extracted from the tank 2. Therefore, the space occupied by the vaporized gas pressurizing means provided in conventional fuel gas supply systems can be reduced, so the space occupied by the low-pressure gas supply line 60 is reduced, and the volume of the tank 2 can be increased accordingly.

[0048] A marine fuel gas supply system 1 according to a second item of the present disclosure is the marine fuel gas supply system 1 according to the first item, wherein the pressure adjustment device 8 includes a pressure sensor 86 that detects the pressure of the low-pressure fuel gas supplied to the low-pressure gas consuming equipment 6, a pressure adjustment line 80 that pressurizes the inside of the tank 2 by forcibly vaporizing the liquefied gas in the tank 2 and returning it to the gas phase region 22 of the tank 2, and a controller 84 that controls the operation of the pressure adjustment line 80 based on the detection value of the pressure sensor 86.

[0049] According to the fuel gas supply system 1 for a boat configured as described above, the pressure of the low-pressure fuel gas supplied to the low-pressure gas consuming equipment 6 can be controlled with higher accuracy.

[0050] The marine fuel gas supply system 1 according to the third item of the present disclosure is the marine fuel gas supply system 1 according to the first or second item, wherein the high-pressure gas supply line 70 has a pre-pump 72 arranged upstream of the pump 71, and the liquefied gas in the tank 2 is pressurized to the operating pressure of the high-pressure gas consuming equipment 7 in two stages, by the pre-pump 72 and the pump 71.

[0051] According to the fuel gas supply system for a ship 1 having the above configuration, the occurrence of cavitation can be suppressed by gradually increasing the pressure of the liquefied gas using the two-stage pumps of the pre-pump 72 and the pump 71.

[0052] The ship fuel gas supply system 1 according to the fourth item of the present disclosure is the ship fuel gas supply system 1 according to the third item, which is provided with a first return line 51 that sends vaporized gas generated by at least one of the pump 71 and the pre-pump 72 to the gas phase region 22 of the tank 2.

[0053] According to the fuel gas supply system for a boat 1 having the above-described configuration, the vaporized gas generated in the fuel gas supply system for a boat 1 can be more actively utilized.

[0054] The fuel gas supply system 1 relating to the fifth item of the present disclosure is a fuel gas supply system 1 relating to either the third or fourth item, which is provided with second return lines 52a, 52b that return to the tank 2 at least one of the excess liquefied gas sent from the pre-pump 72 to the pump 71 and the excess liquefied gas sent from the pump 72 to the high-pressure gas consuming equipment 7.

[0055] According to the fuel gas supply system 1 having the above-described configuration, excess liquefied gas or its vaporized gas in the high-pressure gas supply line 70 is returned to the tank 2, so that the excess fuel in the high-pressure gas supply line 70 is not disposed of by incineration or release into the atmosphere, but is sent from the tank 2 to the low-pressure gas consuming equipment 6 or the high-pressure gas consuming equipment 7 and can be effectively used as fuel.

[0056] The liquefied gas fuelled ship 10 according to the sixth item of the present disclosure comprises a hull 11, a tank 2 for storing liquefied gas mounted on the hull 11, one or more high-pressure gas consuming equipment 7 mounted on the hull 11, including a gas engine for generating propulsion energy for the hull 11, the fuel gas operating pressure of which exceeds 1 MPaG, one or more low-pressure gas consuming equipment 6 mounted on the hull 11, the fuel gas operating pressure of which is 1 MPaG or less, and a marine fuel gas supply system 1 according to any one of the first to fifth items.

[0057] The marine fuel gas supply system 1 configured as described above reduces the space occupied by the low-pressure gas supply line 60, thereby enabling the volume of the tank 2 to be increased, making it suitable as a marine fuel gas supply system 1 for a liquefied gas fueled ship 10.

[0058] The functions performed by the controller 84 described herein may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (Central Processing Units), conventional circuits, and / or combinations thereof, programmed to perform the described functions. Processors include transistors and other circuits and are considered circuitry or processing circuitry. A processor may also be a programmed processor that executes a program stored in memory. In this specification, a circuit, unit, or means is hardware that is programmed to perform or executes the described functions. The hardware may be any hardware disclosed herein or any hardware known to be programmed to perform or execute the described functions. If the hardware is a processor, which is considered a type of circuitry, the circuit, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0059] The foregoing discussion of the present disclosure has been presented for purposes of illustration and description and is not intended to limit the present disclosure to the form disclosed herein. For example, in the foregoing detailed description, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure, but some of the features may also be combined. Furthermore, the features included in the present disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above.

[0060] DESCRIPTION OF SYMBOLS 1: Marine fuel gas supply system 2: Tank (liquefied gas tank) 6: Low-pressure gas consuming equipment 6: Gas consuming equipment 7: Gas consuming equipment 7: High-pressure gas consuming equipment 8: Pressure regulating device 10: Liquefied gas fuelled ship 11: Hull 21: Liquid phase region 22: Gas phase region 51: Return line (first return line) 52a, 52b: Return lines (second return lines) 60: Low-pressure gas supply line 61: Low-pressure gas heater 70: High-pressure gas supply line 71: Pump 72: Pre-pump 73: High-pressure gas heater 80: Pressure regulating line 84: Controller 86: Pressure sensor

Claims

1. A system comprising: a tank having a liquid phase region in which liquefied gas is stored and a gas phase region in which vaporized gas of the liquefied gas is stored; a high-pressure gas supply line for supplying high-pressure fuel gas obtained by forcibly vaporizing the liquefied gas extracted from the liquid phase region of the tank to one or more high-pressure gas consuming equipment whose fuel gas operating pressure exceeds 1 MPaG; a low-pressure gas supply line for supplying the vaporized gas from the gas phase region of the tank as low-pressure fuel gas to one or more low-pressure gas consuming equipment whose fuel gas operating pressure is 1 MPaG or less; and a pressure regulating device for adjusting the pressure in the tank so that the pressure in the tank or the pressure in the low-pressure gas supply line becomes a predetermined pressure set value corresponding to the operating pressure or required pressure of the low-pressure gas consuming equipment, wherein the low-pressure gas supply line has a low-pressure gas heater for heating the vaporized gas to the operating temperature of the low-pressure gas consuming equipment, A fuel gas supply system for a ship, wherein the high-pressure gas supply line has a pump that pressurizes the liquefied gas to the operating pressure of the high-pressure gas consuming equipment, and a high-pressure gas heater that heats the liquefied gas to the operating temperature of the high-pressure gas consuming equipment.

2. A marine fuel gas supply system as set forth in claim 1, wherein the pressure regulating device comprises: a pressure sensor that detects the pressure of the low-pressure fuel gas supplied to the low-pressure gas consuming equipment; a pressure regulating line that pressurizes the inside of the tank by forcibly vaporizing the liquefied gas in the tank and returning it to the gas phase region of the tank; and a controller that controls the operation of the pressure regulating line based on the detection value of the pressure sensor.

3. A fuel gas supply system for a ship as set forth in claim 1, wherein the high-pressure gas supply line has a pre-pump arranged upstream of the pump, and the liquefied gas in the tank is pressurized to the operating pressure of the high-pressure gas consuming equipment in two stages, by the pre-pump and the pump.

4. The fuel gas supply system for a boat according to claim 3, further comprising a first return line that delivers vaporized gas produced by at least one of the pump and the pre-pump to the vapor phase region of the tank.

5. A marine fuel gas supply system as described in claim 3, further comprising a second return line that returns to the tank at least one of the excess liquefied gas sent from the pre-pump to the pump and the excess liquefied gas sent from the pump to the high-pressure gas consuming equipment.

6. A liquefied gas fuelled ship comprising: a hull; a tank mounted on the hull for storing liquefied gas; one or more high-pressure gas consuming equipment mounted on the hull, including a gas engine that generates propulsion energy for the hull, the fuel gas operating pressure of which exceeds 1 MPaG; one or more low-pressure gas consuming equipment mounted on the hull, the fuel gas operating pressure of which is 1 MPaG or less; and a marine fuel gas supply system according to any one of claims 1 to 5.

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