Fuel supply system

Abstract

To provide a fuel supply system that has good energy efficiency when utilizing ammonia as fuel in a ship.SOLUTION: A fuel supply system for supplying fuel to a main engine or auxiliary engine of a ship carrying ammonia, includes: a plurality of devices that includes the main engine and the auxiliary engine, and discharges heat when consuming fuel; a decomposer that uses waste heat discharged from at least one of the plurality of devices as a heat source to decompose a portion of ammonia heated to a decomposition temperature to produce hydrogen. The fuel supply system supplies the hydrogen as at least a portion of the fuel to any one of the plurality of devices.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Relates to a fuel supply system that supplies hydrogen obtained by decomposing ammonia as fuel.

Background Art

[0002] In the trend of carbon neutrality, decarbonized fuels such as ammonia and biogas are supplied to devices such as fuel cells, gas turbines, and engines to extract energy. Depending on the specifications and characteristics of these devices, it may be more convenient to supply the decarbonized fuel after reforming it into hydrogen. Therefore, a device for reforming decarbonized fuel into hydrogen is required according to the specifications and characteristics of the device.

[0003] As a method for reforming ammonia into hydrogen, a method of decomposing ammonia by contacting it with a catalyst to generate hydrogen is known. Since the decomposition reaction of ammonia is an endothermic reaction, a heat source is required to promote the decomposition. Patent Document 1 describes heating a catalyst using an electric heater and contacting it with ammonia.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the method described in Patent Document 1, energy is required to create a heat source, so the energy efficiency when using decarbonized fuel as fuel is poor.

[0006] An object of the present invention is to provide a fuel supply system with good energy efficiency when using ammonia as fuel in a ship.

Means for Solving the Problems

[0007] This disclosure includes the following aspects: Appearance 1 A fuel supply system for supplying fuel to the main engine or auxiliary engine of a ship equipped with ammonia, The main engine and the auxiliary engines include a plurality of devices that discharge heat when consuming fuel, The apparatus comprises a decomposer that uses waste heat discharged from at least one of the aforementioned plurality of devices as a heat source to decompose a portion of the ammonia heated to a decomposition temperature to produce hydrogen, A fuel supply system that supplies hydrogen as at least a portion of the fuel to any of the plurality of devices.

[0008] Appearance 2 The fuel supply system according to embodiment 1, wherein the decomposer has a catalyst that decomposes a portion of the ammonia when it comes into contact with a portion of the ammonia heated to the decomposition temperature.

[0009] Appearance 3 At least one of the aforementioned plurality of devices is A combustion section that burns the aforementioned fuel and discharges exhaust gas accompanied by the aforementioned heat, The exhaust gas flow section is connected to the combustion section and has a flow path for flowing the exhaust gas discharged from the combustion section, The fuel supply system according to embodiment 1 or 2, wherein the decomposer is located within the flow path.

[0010] Pattern 4 The aforementioned exhaust gas flow section is An exhaust receiver having an internal space that forms part of the flow path and receives the exhaust gas discharged from the combustion section, The system comprises a denitrification section which forms part of the flow path downstream of the internal space and has a denitrification space into which the exhaust gas is introduced for denitrification, The fuel supply system according to embodiment 3, wherein the decomposer is located within the internal space or the denitrification space.

[0011] Appearance 5 The exhaust gas flow portion is a part of the flow path, and an exhaust receiver having an internal space for receiving the exhaust gas discharged from the combustion portion; and a branch line connected to the exhaust receiver and branching at least a part of the exhaust gas in the internal space and guiding it to the downstream side. The fuel supply system according to Aspect 3, wherein the decomposer is disposed in the branch line. The fuel supply system according to Aspect 3, wherein the decomposer is disposed in the branch line.

[0012] Aspect 6 The fuel supply system according to any one of Aspects 3 to 5, wherein the decomposer has a container surrounding the flow paths of a part of the ammonia and the hydrogen so as to isolate the part of the ammonia and the hydrogen from the exhaust gas in the flow path.

[0013] Aspect 7 The decomposer has a catalyst that decomposes a part of the ammonia by contacting a part of the ammonia heated to the decomposition temperature, and a structure made of metal that supports the catalyst and is held in the container so as to be disposed on the flow paths of a part of the ammonia and the hydrogen. The fuel supply system according to Aspect 6.

[0014] Aspect 8 The fuel supply system according to any one of Aspects 1 to 7, wherein the concentration of hydrogen in the decomposition gas containing hydrogen generated in the decomposer is 5 to 75%.

[0015] Aspect 9 The fuel supply system according to any one of Aspects 1 to 8, wherein the concentration of hydrogen in the decomposition gas containing hydrogen generated in the decomposer is 30 to 60%.

[0016] Aspect 10 The fuel supply system according to Aspect 2 or 7, wherein the exhaust heat of the main machine is used as the heat source, and the catalyst includes at least a catalyst made of a noble metal.

[0017] Aspect 11 The fuel supply system according to embodiment 2 or 7, wherein waste heat of the auxiliary machine is used as the heat source, and the catalyst includes at least a catalyst made of base metal.

[0018] Embodiment 12 The fuel supply system according to any one of Embodiments 1 to 11, wherein waste heat of the main engine is used as the heat source, and the hydrogen is supplied to the auxiliary machine.

[0019] Embodiment 13 A part of the ammonia is heated to the decomposition temperature using waste heat of a first device among the plurality of devices. When the decomposer is referred to as a first decomposer, the fuel supply system further includes a second decomposer that decomposes the residual ammonia contained in the decomposition gas including the hydrogen and the undissolved residual ammonia generated in the first decomposer and heated to the decomposition temperature using waste heat of a second device different from the first device among the plurality of devices to generate hydrogen. The fuel supply system according to any one of Embodiments 1 to 12.

Advantages of the Invention

[0020] According to the fuel supply system of the above aspect, the energy efficiency when using ammonia as fuel in a ship is good.

Brief Description of Drawings

[0021] [Figure 1] It is a diagram showing an example of a fuel supply system of an embodiment. [Figure 2] It is a diagram showing another example of a fuel supply system of an embodiment. [Figure 3] It is a diagram showing a decomposer arranged in a denitrification unit. [Figure 4] It is a diagram showing an example of the structure of a decomposer. [Figure 5] (a) and (b) are diagrams showing examples of the form of a decomposer. [Figure 6] It is a diagram showing an example of a device that generates waste heat serving as a heat source. [Figure 7] This figure shows another example of the fuel supply system of the embodiment. [Modes for carrying out the invention]

[0022] The fuel supply system of an embodiment will be described below. Figure 1 shows a fuel supply system 1 according to one embodiment.

[0023] The fuel supply system 1 is a system for supplying fuel to the main engine 3 or auxiliary engine 5 of a ship equipped with ammonia.

[0024] Ammonia is carried on ships as either fuel or cargo. As fuel, ammonia is used for ship propulsion, generating electricity needed by the ship (electricity generation), and as a raw material for decomposition into hydrogen (reformation). Since ammonia does not emit carbon dioxide when consumed as fuel, it contributes to achieving carbon neutrality. Ammonia carried as cargo may also be partially used as fuel. In the following explanation, we will use a ship that carries ammonia as fuel (ammonia-fueled ship) as an example.

[0025] The fuel supply system 1 comprises multiple devices and a decomposer 7.

[0026] The multiple devices include a main engine 3 and multiple auxiliary engines 5, and are devices that dissipate heat when consuming fuel. The main engine 3 is a device that consumes fuel to generate power to propel the ship. The power generated by the main engine 3 is transmitted to the propeller. One or more main engines 3 are installed on the ship. In the following description, the case in which there is one main engine 3 included in the multiple devices will be used as an example. Auxiliary engine 5 is a device that consumes fuel to generate electricity used on the ship, such as for onboard equipment. In other words, in this specification, "auxiliary engine" means an auxiliary generator. The electricity generated by auxiliary engine 5 is supplied to onboard equipment and electrical equipment necessary for the operation of multiple devices. Multiple auxiliary engines 5 (for example, two or three or more) are installed on the ship to ensure redundancy. The figure shows only one of the multiple auxiliary engines 5 as a representative example.

[0027] Each of the multiple devices uses one or more of the following as fuel: ammonia, hydrogen, methanol, ethanol, and fossil fuels such as heavy oil, liquefied natural gas (LNG), and liquefied petroleum gas (LPG). In an ammonia-fueled ship, it is preferable that at least ammonia is used as fuel for the main engine 3, and at least hydrogen is used as fuel for the auxiliary engine 5.

[0028] Each of the multiple devices preferably includes a device body 30, 50 composed of an internal combustion engine such as an engine or gas turbine, or a fuel cell. The main unit 30 of the main engine 3 is preferably composed of an internal combustion engine. In the illustrated example, the main unit 30 is a two-stroke low-speed diesel engine that uses ammonia as the main fuel and heavy oil or hydrogen as a pilot fuel to ignite the ammonia. However, the main unit 30 is not limited to this and may be, for example, a gas turbine. The main unit 50 of the auxiliary equipment 5 is preferably composed of an internal combustion engine or a fuel cell. The main unit 50 in the illustrated example is a 4-stroke medium-speed diesel engine that uses hydrogen or decomposition gas as fuel, but the main unit 50 is not limited to this and may be a dual-fuel engine that switches between an operating mode using liquefied ammonia as liquid fuel and an operating mode using liquefied ammonia as liquid fuel and hydrogen or decomposition gas as gaseous fuel, or it may be a gas turbine. The main unit 50 may also be composed of a fuel cell. As the fuel cell, a solid oxide fuel cell (SOFC) or a polymer electrolyte fuel cell (PEFC) is used. For a solid oxide fuel cell (SOFC), the fuel gas used is hydrogen or decomposition gas (described later) obtained by the decomposition of ammonia. The decomposition gas may be a mixed gas containing at least hydrogen and nitrogen, and further containing ammonia. For a polymer electrolyte fuel cell (PEFC), hydrogen is used as the fuel gas. Of these fuel cells, the solid oxide fuel cell (SOFC) is preferred because it does not degrade the power generation performance even when the ammonia concentration in the fuel gas supplied to the fuel cell is high. Furthermore, among the multiple auxiliary devices 5, the main unit 50 may be of the same type, or it may be of two or three different types.

[0029] The decomposer 7 is a device that generates hydrogen by decomposing (cracking) a portion of ammonia heated to a decomposition temperature using waste heat discharged from at least one of multiple devices as a heat source. The decomposition temperature is the temperature at which the ammonia decomposition reaction occurs in the decomposer 7. Since the ammonia decomposition reaction is an endothermic reaction, a heat source is necessary to promote the decomposition of ammonia. As this heat source, the fuel supply system 1 utilizes waste heat from at least one of the multiple devices. In this way, by procuring the heat source necessary for ammonia decomposition from the waste heat of multiple devices, it is not necessary to procure a heat source from an external source for ammonia decomposition. In other words, the fuel supply system 1 is energy efficient when using ammonia as fuel on a ship. Energy saving effects are obtained by utilizing waste heat that would normally be discarded.

[0030] The fuel supply system 1 supplies the hydrogen produced in this manner to one of the multiple devices (hereinafter also referred to as the receiving device) as at least part of the fuel. The receiving device is preferably a device that uses ammonia reformed into hydrogen, or a device for which it is convenient to use ammonia together with reformed hydrogen. Depending on the specifications and characteristics of each of the multiple devices, it may be more convenient to use ammonia reformed into hydrogen by cracking, or to use ammonia together with reformed hydrogen, rather than using ammonia alone as fuel. For example, a high-speed rotating engine (e.g., a 4-stroke medium-speed diesel engine) preferably uses hydrogen or a cracked gas (mixed gas) containing ammonia as fuel. Also, a device whose power generation performance may deteriorate due to the supply of ammonia (e.g., a polymer electrolyte fuel cell (PEFC)) preferably uses hydrogen as fuel. Furthermore, a low-speed rotating engine (e.g., a 2-stroke low-speed diesel engine) that uses pilot fuel together with the main fuel preferably uses hydrogen or a cracked gas (mixed gas) containing ammonia as pilot fuel, along with the main fuel, ammonia. In fuel supply system 1, ammonia is effectively utilized as fuel by generating hydrogen supplied to such devices using a portion of the ammonia carried on board the ship.

[0031] The fuel supply system 1, as shown in Figure 1, preferably further comprises an ammonia tank 11, an ammonia supply line 13, a decomposition gas supply line 15, and a heavy oil supply line 19, in addition to the multiple devices and the decomposer 7.

[0032] The ammonia tank 11 is a container for storing ammonia. For example, liquefied ammonia is stored in the ammonia tank 11, and the gas phase space above the liquefied ammonia is filled with ammonia gas (boil-off gas of liquefied ammonia).

[0033] The ammonia supply line 13 is a line that connects the ammonia tank 11, the decomposer 7, and the main unit of each of the devices that use ammonia as fuel among the multiple devices. The devices that use ammonia as fuel among the multiple devices are devices that generate waste heat which serves as a heat source for the ammonia decomposition reaction in the decomposer 7 (hereinafter also referred to as heat source devices). In the example shown in Figure 1, the heat source device is the main unit 3. The ammonia supply line 13 extends from the ammonia tank 11 and branches off along the way, having a first supply line 13a connected to the decomposer 7 and a second supply line 13b connected to the heat source device 3. Preferably, the ammonia supply line 13 is equipped with a blower or pump (not shown) for sending ammonia to the decomposer 7 and the heat source device 3, and the operation of the blower or pump causes ammonia gas or liquefied ammonia in the ammonia tank 11 to flow through the ammonia supply line 13. Preferably, the ammonia supply line 13 is equipped with a vaporizer and a flow regulator (neither shown). The vaporizer heats and vaporizes the liquefied ammonia. The flow regulator adjusts the flow rate of ammonia flowing toward the decomposer 7 or the main unit 3 to a desired range. A booster (not shown) for pressurizing the ammonia is also provided in the second supply line 13b. In this specification, lines include piping and may include valves and the like provided in the piping. Each line is indicated by an arrow.

[0034] The decomposition gas supply line 15 is a line that connects the decomposer 7 to a supply destination device among the multiple devices. In the example shown in Figure 1, the supply destination device is one of the auxiliary devices 5, but any other auxiliary device 5 can also be used as the supply destination device. The decomposition gas generated in the decomposer 7 flows through the decomposition gas supply line 15 and is supplied to the main body 50 of the auxiliary device 5. Preferably, the decomposition gas supply line 15 is provided with a pressurizer (not shown) for pressurizing the decomposition gas.

[0035] The heavy oil supply line 19 is a line connecting a heavy oil tank (not shown) provided by the fuel supply system 1 to the main unit 30 of the main engine 3. The heavy oil is used as pilot fuel for the main engine 3 shown in Figure 1. Preferably, the heavy oil supply line 19 is provided with a pump (not shown) for flowing the heavy oil towards the main unit 30 of the main engine 3, and the operation of the pump causes the heavy oil in the heavy oil tank to flow through the heavy oil supply line 19.

[0036] The fuel supply system 1 preferably further includes a control device (not shown). The control device is connected to a plurality of devices and to various parts of each line, such as valves, blowers, pumps, vaporizers, flow regulators, and boosters, and controls the operation of each device and part to operate the plurality of devices while the fuel supply system 1 is running, and also supplies ammonia to the decomposer 7, where it is heated to the decomposition temperature and decomposed, and the resulting decomposition gas is supplied as fuel to one of the plurality of devices.

[0037] The fuel supply system 1 may further include a line for supplying ammonia from the ammonia tank 11 to a denitrification reducing agent manufacturing apparatus that uses ammonia as a raw material to produce ammonia water used in the denitrification section described later.

[0038] According to one embodiment, it is preferable that the decomposer 7 has a catalyst that decomposes a portion of the ammonia when it comes into contact with a portion of the ammonia heated to the decomposition temperature. Using such a catalyst allows for a lower required decomposition temperature, thus reducing the amount of heat required for the decomposition reaction.

[0039] On the other hand, according to one embodiment, it is also preferable that the decomposer 7 does not have the catalyst. That is, it is also preferable that the ammonia decomposition in the fuel supply system 1 is carried out without using a catalyst. This can reduce the cost associated with the catalyst.

[0040] According to one embodiment, as shown in Figure 1, at least one of a plurality of devices comprises a device body 30, 50 and an exhaust gas flow section 33, 53. Each of the device bodies 30, 50 has a plurality of combustion sections 31, 51, and each of the plurality of combustion sections 31, 51 comprises a piston and a cylinder. For convenience, only one of the combustion sections 31, 51 is shown in the illustration.

[0041] The combustion sections 31 and 51 are parts of the main body 30 and 50 of the device that burn fuel and discharge exhaust gas accompanied by heat.

[0042] The exhaust gas flow sections 33 and 53 are connected to the combustion sections 31 and 51 and have flow paths for the exhaust gas discharged from the combustion sections 31 and 51. The decomposer 7 is preferably located within the flow paths of the exhaust gas flow sections 33 and 53. By exposing the decomposer 7 to high-temperature exhaust gas, the heat source necessary for the ammonia decomposition reaction can be efficiently procured and the decomposition reaction can be maintained. The exhaust gas that has flowed through the exhaust gas flow sections 33 and 53 is further directed towards the ship's chimney.

[0043] According to one embodiment, the exhaust gas flow sections 33, 53 preferably include exhaust receivers 35, 55 and denitrification sections 37, 57, as shown in Figure 1. The exhaust receivers 35, 55 and the denitrification sections 37, 57 are shown connected to each other, but they may be spaced apart from each other.

[0044] The exhaust receivers 35 and 55 are the parts where exhaust gases discharged from the cylinders of the combustion sections 31 and 51 collect, and form part of the flow path of the exhaust gas flow sections 33 and 53. The exhaust receivers 35 and 55 have internal spaces 35a and 55a that receive the exhaust gases discharged from the combustion sections 31 and 51. All of the exhaust gases discharged from the combustion sections 31 and 51 flow downstream through the internal spaces 35a and 55a of the exhaust receivers 35 and 55.

[0045] The denitrification sections 37 and 57 are parts into which exhaust gas is introduced and denitrified. The denitrification sections 37 and 57 preferably perform denitrification by selective catalytic reduction (SCR), but may also perform denitrification by, for example, non-catalytic reduction (SNCR). The denitrification sections 37 and 57 form part of the flow path of the exhaust gas flow sections 33 and 53, downstream from the internal spaces 35a and 55a of the exhaust receivers 35 and 55. The denitrification sections 37 and 57 have denitrification spaces 37a and 57a into which exhaust gas is introduced and denitrified. All of the exhaust gas discharged from the combustion sections 31 and 51 flows downstream through the denitrification spaces 37a and 57a of the denitrification sections 37 and 57.

[0046] Figure 2 shows another example of the fuel supply system 1. The decomposer 7 is preferably located either within the internal spaces 35a, 55a of the exhaust receivers 35, 55, as shown in Figure 2, or within the denitrification spaces 37a, 57a of the denitrification sections 37, 57, as shown in Figure 1. As described above, all of the exhaust gas from the combustion sections 31, 51 passes through these spaces 35a, 55a, 37a, 57a, ensuring that sufficient heat is available for the decomposition reaction in the decomposer 7. Furthermore, since these spaces 35a, 55a, 37a, 57a have a larger flow path cross-section and volume compared to other parts of the exhaust gas flow sections 33, 53, they do not obstruct the flow of exhaust gas within the exhaust gas flow sections 33, 53, and the overall temperature drop of the exhaust gas can be suppressed by localizing the temperature drop. Since the volumes of the denitrification spaces 37a and 57a in the denitrification sections 37 and 57 are usually larger than the volumes of the internal spaces 35a and 55a of the exhaust receivers 35 and 55, as shown in the figure, it is more preferable to place the decomposer 7 within the denitrification spaces 37a and 57a.

[0047] Figure 3 shows the decomposer 7 located within the denitrification sections 37 and 57. The symbols in parentheses in Figure 3 indicate elements related to the auxiliary equipment 5. The rightward arrows in Figure 3 indicate the direction of exhaust gas flow. In the denitrification spaces 37a and 57a of the denitrification sections 37 and 57, it is preferable to place the decomposer 7 in the downstream space region, as shown in Figure 3. The temperature of the exhaust gas in the denitrification sections 37 and 57 is slightly lower than the temperature of the exhaust gas in the exhaust receivers 35 and 55 located upstream. However, since the denitrification reaction is an exothermic reaction, the decomposer 7 can be exposed to a higher temperature exhaust gas if placed in the downstream space region. The denitrification sections 37 and 57 shown are apparatuses that perform denitrification by selective catalytic reduction (SCR), and the decomposer 7 is located in the space region downstream of the catalyst and support indicated by reference numerals 37c and 57c.

[0048] Furthermore, within the denitrification spaces 37a and 57a of the denitrification sections 37 and 57, it is preferable to place the decomposer 7 in the upper spatial region, as shown in the figure. Since the volume of the denitrification sections 37 and 57 is particularly large within the exhaust gas flow sections 33 and 53, the temperature of the exhaust gas in the upper spatial region is slightly higher than that of the exhaust gas in the lower spatial region due to the rising airflow generated within the denitrification spaces 37a and 57a. For this reason, by placing the decomposer 7 in the upper spatial region of the denitrification spaces 37a and 57a, the decomposer 7 can be exposed to higher temperature exhaust gas.

[0049] Furthermore, within the denitrification spaces 37a and 57a of the denitrification sections 37 and 57, it is preferable to position the decomposer 7 in contact with or near the inner wall of the container indicated by reference numerals 37b and 57b of the denitrification sections 37 and 57, as shown in the figure. This simplifies the structure for connecting the ammonia supply line 13 to the decomposer 7 in the denitrification sections 37 and 57.

[0050] Figure 4 shows an example of the structure of the decomposer 7. The rightward arrow in Figure 4 indicates the direction in which the exhaust gas flows. According to one embodiment, the decomposer 7 preferably has a container 7b surrounding the flow path of a portion of ammonia and hydrogen so as to isolate it from the exhaust gas in the flow paths of the exhaust gas flow sections 33 and 53. The container 7b is preferably made of stainless steel, and more preferably of stainless steel or nickel steel with a high nickel content, such as SUS310S. This prevents the exhaust gas from mixing with the decomposition gas containing hydrogen produced by decomposition, and prevents gas components other than the decomposition gas from being supplied to the receiving device. Patent document 1 describes supplying ammonia and oxygen to the decomposer, oxidizing the ammonia to generate oxidation heat, and using the oxidation heat to decompose the ammonia. When ammonia is decomposed in this way, impurities such as water, nitrogen oxides, and unreacted oxygen mix with the hydrogen. It is undesirable for such impurities to be supplied to the device mixed with the fuel. Also, since ammonia is consumed in order to oxidize ammonia, the ammonia that should be used as fuel cannot be effectively utilized.

[0051] According to one embodiment, the decomposer 7 preferably includes a catalyst and a structure. In Figure 4, the catalyst and structure are the parts indicated by reference numeral 7a. The structure supports the catalyst and is made of metal, and is held in a container 7b so as to be positioned on the flow path for some ammonia and hydrogen in the decomposer 7. The metal of the structure is preferably stainless steel. The decomposer 7 is prone to vibration because vibrations generated by the operation of the main engine 3 and auxiliary engine 5 are transmitted to the exhaust gas flow sections 33 and 53. If the carrier supporting the catalyst is ceramic, it is easily damaged by vibration. It is undesirable for fragments of the damaged ceramic carrier to flow along with the exhaust gas in the flow path of the exhaust gas flow section 33. In contrast, the above structure is more resistant to vibration and less prone to damage than a ceramic carrier. Furthermore, since the metal structure has excellent thermal conductivity, it can efficiently receive heat from the container 7b exposed to the exhaust gas and transfer it to the catalyst. The structure preferably has a honeycomb structure. This ensures strength against vibration while also ensuring the flow path for exhaust gas.

[0052] On the other hand, the form of the catalyst support in the decomposer 7 is not limited to the above structure, and may be, for example, granular or pelletized. The granular or pelletized support carrying the catalyst is packed and arranged to block a portion of the flow path in the decomposer 7. The size of the granular or pelletized support is, for example, 0.5 to 5 mm.

[0053] Figure 5 shows an example of the configuration of the decomposer 7. The rightward arrow in Figure 5 indicates the direction in which the exhaust gas flows. Preferred configurations for the decomposer 7 include, for example, the donut-shaped (annular) configuration shown in Figure 5(a) and the flat plate-shaped configuration shown in Figure 5(b). Such configurations of the decomposer 7 can efficiently transfer the heat absorbed from the exhaust gas by being exposed to the exhaust gas to the ammonia and catalyst in the flow path of the decomposer 7. The donut-shaped decomposer 7 is positioned so as to abut the inner wall of the flow path of the exhaust gas flow section 33, 53 from the inner circumference. The flat plate-shaped decomposer 7 is held against the inner wall of the exhaust gas flow section 33, 53 so as to be parallel to the flow path of the exhaust gas.

[0054] Figure 6 shows an example of a device that generates waste heat to serve as a heat source. The symbols in parentheses in Figure 6 indicate elements related to auxiliary equipment 5. According to one embodiment, the exhaust gas flow sections 33 and 53 preferably include exhaust receivers 35 and 55 and branch lines 39 and 59, as shown in Figure 6. The exhaust receivers 35 and 55 are configured in the same manner as the exhaust receivers 35 and 55 described above. The device shown in Figure 6 includes denitrification sections 37 and 57 configured in the same manner as the denitrification sections 37 and 57 described above.

[0055] The branch lines 39 and 59 extend downstream from the exhaust receivers 35 and 55, and are lines that branch off at least a portion of the exhaust gas in the internal spaces 35a and 55a of the exhaust receivers 35 and 55 and guide it downstream. As shown in the figure, the branch lines 39 and 59 merge with the portions of the exhaust gas flow sections 33 and 53 downstream of the denitrification sections 37 and 57. It is also preferable that the decomposer 7 be located within the branch lines 39 and 59, as shown in Figure 6. By exposing the decomposer 7 to the exhaust gas flowing through the branch lines 39 and 59, the amount of heat required for the decomposition reaction can be secured. In order to place the decomposer 7 within the exhaust receivers 35 and 55 or the denitrification sections 37 and 57, it is necessary to connect the ammonia supply line 13 and the decomposition gas supply line 15 to the placed decomposer 7 while positioning the decomposer 7 so as not to impair the original functions of the exhaust receivers 35 and 55 or the denitrification sections 37 and 57. In contrast, the configuration shown in Figure 6, in which the decomposer 7 is placed within the branch lines 39 and 59 and connected to the ammonia supply line 13 and the decomposition gas supply line 15, has fewer design constraints and greater design flexibility. Part of the exhaust gas from the exhaust receivers 35 and 55 may be led to the branch lines 39 and 59, or all of it may be led to them. This allows for adjustment of the amount of exhaust gas flowing through the branch lines 39 and 59, and thereby the amount of heat supplied to the decomposer 7.

[0056] According to one embodiment, the hydrogen concentration in the decomposition gas is preferably 5 to 75%. This range of hydrogen concentration includes a range in which combustion efficiency equivalent to that of natural gas can be easily obtained when the supplying device is an internal combustion engine. Furthermore, when the decomposition gas is a mixed gas containing ammonia as a gas component other than hydrogen, a hydrogen concentration of 5% or more in the decomposition gas makes it easier to ignite ammonia using hydrogen as a combustion aid. A hydrogen concentration in the decomposition gas is more preferably 30 to 60%. When the hydrogen concentration in the decomposition gas is 60% or less, it is not necessary to make the ammonia decomposition rate (reformation rate) in the decomposer 7 excessively high, and the amount of heat required for the decomposition reaction can be reduced. In this specification, unless otherwise specified, the percentage representing concentration means volume percent.

[0057] The hydrogen concentration in the decomposition gas can be controlled by adjusting the flow rate of ammonia flowing through the decomposer 7 and the temperature of the ammonia supplied to the decomposer 7, thereby adjusting the ammonia decomposition rate. Alternatively, the hydrogen concentration can be controlled by additionally supplying ammonia from the ammonia tank 11 to the decomposition gas to dilute the hydrogen. If the decomposer 7 is equipped with the catalyst described above for the decomposition reaction, the flow rate of ammonia flowing through the decomposer 7 can be determined according to the amount of catalyst. The ammonia concentration in the decomposition gas is preferably 90% or less.

[0058] Furthermore, the fuel supplied to the receiving equipment may be a hydrogen-dominant gas obtained by removing gas components other than hydrogen from the decomposition gas and increasing the hydrogen concentration. The concentration of the hydrogen-dominant gas (hydrogen-dominant gas) is, for example, 80% or more, or 90% or more. Removal of gas components other than hydrogen can be carried out, for example, by selectively permeating hydrogen through a separation membrane having many micropores using differential pressure, or by using pressure fluctuation adsorption (PSA) or cryogenic separation.

[0059] The receiving device may be supplied with hydrogen obtained using the waste heat of other devices as a heat source, as explained below, or it may be supplied with hydrogen obtained using the waste heat of the receiving device itself as a heat source. In other words, the receiving device does not have to be the heat source device described above, or it may be the heat source device described above.

[0060] According to one embodiment, it is preferable that the waste heat of the main engine 3 is used as the heat source, and hydrogen is supplied to the auxiliary engine 5. By using the waste heat of the main engine 3, which has a large amount of waste heat among the multiple devices, as the heat source to decompose ammonia and supply the hydrogen obtained to the auxiliary engine 5, which has a small fuel consumption, it is possible to generate enough hydrogen necessary for the operation of the auxiliary engine 5 and supply it stably. The inventors of the present invention calculated an example of the amount of waste heat of the main engine 3 and the amount of heat absorbed by the decomposer 7 in the following manner and found that the amount of waste heat of the main engine 3 is about 20 times the amount of heat absorbed by the decomposer 7. (A) Heat dissipation amount of main unit 3 Exhaust gas density 1.3 kg / m³ 3The specific heat is 2 J / kg·K, and the flow path cross-sectional area of ​​the portion within the denitrification section 37 of the main unit 3, where the decomposer 7 is installed, is 0.03 m². 2 Assuming a flow velocity of 2000 m / s and a temperature difference of 200°C between the downstream and upstream ends of the denitrification section 37, the heat dissipation rate of the exhaust gas from the main engine 3 is 934 kJ / s. (B) Heat absorption of decomposer 7 Assuming an ammonia flow rate of 3000 L / min, a decomposition rate (reformation rate) of 50%, and an energy requirement of 50 kJ / mol(NH3) for decomposition without a catalyst, the heat absorption rate of decomposer 7 is 51 kJ / s.

[0061] Furthermore, if the device that generates the waste heat that serves as the heat source (heat source device) among the multiple devices is, for example, an engine equipped with a supercharger, then if the amount of heat removed by the decomposer 7 increases and the amount of waste heat decreases, the temperature of the exhaust gas will drop, the energy supplied to the supercharger will decrease, and the output may decrease. In order to suppress the occurrence of such problems, as described above, it is preferable to use the waste heat of the main engine 3 as the heat source and supply hydrogen to the auxiliary engine 5.

[0062] On the other hand, for example, if the engine of the receiving device uses hydrogen as pilot fuel, the amount of hydrogen supplied to the receiving device is small, making it easier to obtain the necessary hydrogen using the waste heat of the receiving device itself as a heat source. Furthermore, when supplying hydrogen generated using the waste heat of the receiving device itself as a heat source to the receiving device, it is preferable to generate hydrogen using not only the waste heat of the receiving device itself but also the waste heat of one or more other devices in the group as a heat source to compensate for any shortage of heat from the heat source.

[0063] In one embodiment, the waste heat from the main engine 3 is used as a heat source to bring the ammonia to a decomposition temperature, and the catalyst in the decomposer 7 preferably contains at least a catalyst made of a precious metal. Regarding the exhaust gas of the internal combustion engine, the temperature of the exhaust gas from the main engine 3 is lower than the temperature of the exhaust gas from the auxiliary engine 5. Using a catalyst made of a precious metal increases the ammonia decomposition rate even at low temperatures, making it suitable as a catalyst when the waste heat from the main engine 3 is used as the heat source. In this respect, it is preferable that all of the catalyst in the decomposer 7 is made of a precious metal. The temperature of the exhaust gas from the main engine 3, which is an internal combustion engine, is, for example, 300 to 450°C in the denitrification section 37. Examples of precious metals that can be used in the catalyst include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), and ruthenium (Ru), among which ruthenium (Ru) is preferably used.

[0064] In another embodiment, the waste heat from the auxiliary engine 5 is used as a heat source to bring the ammonia to the decomposition temperature, and the catalyst preferably includes at least a catalyst made of a base metal. Regarding the exhaust gas of the internal combustion engine, the temperature of the exhaust gas from the auxiliary engine 5 is higher than the temperature of the exhaust gas from the main engine 3. Using a catalyst made of a base metal increases the ammonia decomposition rate at high temperatures, making it suitable as a catalyst when the waste heat from the auxiliary engine 5 is used as the heat source. In this respect, it is preferable that all of the catalyst in the decomposer 7 is made of base metal. The temperature of the exhaust gas from the auxiliary engine 5, which is an internal combustion engine, is, for example, 400 to 550°C in the denitrification section 57. Examples of base metals that can be used in the catalyst include iron (Fe), aluminum (Al), copper (Cu), nickel (Ni), zinc (Zn), tin (Sn), cobalt (Co), molybdenum (Mo), and magnesium (Mg), among which iron (Fe), nickel (Ni), and cobalt (Co) are preferably used.

[0065] The catalyst for the decomposer 7 can preferably be one that is supported on the surface of a metal or metal oxide carrier in the form of ultrafine particles or the like.

[0066] Figure 7 shows another example of the fuel supply system 1. According to one embodiment, as shown in Figure 7, the fuel supply system 1 preferably includes a decomposer 7 (hereinafter also referred to as the first decomposer 7) and, in addition, another decomposer 17 (hereinafter also referred to as the second decomposer 17). The second decomposer 17 decomposes residual ammonia contained in the decomposition gas to produce hydrogen. The decomposition gas is a decomposition gas containing hydrogen produced in the first decomposer 7 and undecomposed residual ammonia, and is heated to a decomposition temperature using the waste heat of a second device, which is different from the first device in which the first decomposer 7 is located, among the multiple devices. In the example shown in Figure 7, the first device is the main unit 3, and the second device is the auxiliary unit 5. The temperature of the waste heat from the multiple devices fluctuates depending on the load on each device, operating conditions, ambient temperature, etc., and may be insufficient. The amount of waste heat from the main unit 3 is sufficient compared to the amount of waste heat from the auxiliary unit 5, but if the temperature of the waste heat from the main unit 3 is low, the decomposition reaction may not proceed sufficiently, and the decomposition rate may not be high. If the decomposition rate is not high, a sufficient amount of hydrogen to be supplied as fuel to the receiving device will not be produced. Therefore, the decomposition gas generated in the first decomposition unit 7 is used in the second decomposition unit 17, utilizing the waste heat from the auxiliary unit 5, which has a higher temperature than the waste heat from the main unit 3, to decompose the undecomposed ammonia in the decomposition gas, thereby generating additional hydrogen and supplementing the amount of hydrogen supplied to the receiving device.

[0067] If the decomposers 7 and 17 use catalysts to decompose ammonia, it is preferable to select the catalysts for the decomposers 7 and 17 according to the temperature of the waste heat from the main unit 3 and auxiliary unit 5 and the desired decomposition rate. For example, as described above, it is preferable to use a catalyst containing a noble metal for the catalyst in the first decomposer 7 and a catalyst containing a base metal for the catalyst in the second decomposer 17.

[0068] According to one embodiment, the ammonia supplied to the decomposer 7 may be preheated in order to achieve a desired decomposition rate. In this case, it is preferable that boil-off gas from the ammonia tank 11 is supplied to the decomposer 7. If the amount of boil-off gas is insufficient, it is preferable to vaporize liquefied ammonia. It is also preferable that both ammonia gases are heated and their temperatures are adjusted. As a heat source for vaporizing liquefied ammonia and heating the ammonia gas, for example, heat generated by a boiler or gas combustion unit (GCU) installed on the ship can be used. Since the ammonia tank 11 is usually located outside the engine room of the ship, the temperature of the ammonia supplied to the decomposer 7 is prone to fluctuations. Therefore, the ammonia may not be sufficiently heated in the decomposer 7, and the decomposition rate may not be high. On the other hand, liquefied ammonia may be supplied to the decomposer 7 without vaporization.

[0069] According to one embodiment, the fuel supplied to the receiving device is preferably the mixed gas described above, which contains hydrogen in addition to gaseous components other than hydrogen. The gaseous components other than hydrogen are, for example, ammonia and nitrogen. The mixed gas is preferably a decomposition gas containing hydrogen and nitrogen, produced by the decomposition of ammonia in the decomposition unit 7. Such a mixed gas can be supplied directly from the decomposition unit 7 to the receiving device, which is efficient. Furthermore, when the receiving device is a solid oxide fuel cell (SOFC), the heating of the fuel gas can be omitted by supplying high-temperature decomposition gas as the fuel gas.

[0070] The fuel supply system of the present invention has been described above, but the present invention is not limited to the above embodiments, and various improvements and modifications may be made without departing from the spirit of the present invention. For example, the multiple devices may include devices other than the main unit 3 and auxiliary unit 5. For example, they may include a gas combustion unit (GCU), etc. Furthermore, among the multiple devices, the heat source supply device may be a device that does not use ammonia or hydrogen as fuel, but rather uses fossil fuels such as heavy oil as fuel. [Explanation of symbols]

[0071] 1. Fuel supply system 3 Main engine 5. Auxiliary equipment 7, 17 Decomposer 7a Catalysts and Structures 7b container 11 Ammonia tank 13 Ammonia supply line 13a First supply line 13b Second supply line 15. Decomposition gas supply line 19. Heavy fuel oil supply line 30, 50 Main unit of the device 31, 51 Combustion section 33, 53 Exhaust gas flow section 35, 55 Exhaust receiver 35a, 55a interior space 37, 57 Denitration section 37a, 57a Denitrification space 37b, 57b container 37c, 57c Catalysts and Supports 39, 59 Branch Line

Claims

1. A fuel supply system for supplying fuel to the main engine or auxiliary engine of a ship equipped with ammonia, The main engine and the auxiliary engines include a plurality of devices that discharge heat when consuming fuel, The apparatus comprises a decomposer that uses waste heat discharged from at least one of the aforementioned plurality of devices as a heat source to decompose a portion of the ammonia heated to a decomposition temperature to produce hydrogen, The hydrogen is supplied to any of the aforementioned devices as at least a portion of the fuel. At least one of the aforementioned plurality of devices is A combustion section that burns the aforementioned fuel and discharges exhaust gas accompanied by the aforementioned heat, The exhaust gas flow section is connected to the combustion section and has a flow path for flowing the exhaust gas discharged from the combustion section, The disintegrator is located within the flow path, The aforementioned exhaust gas flow section is An exhaust receiver having an internal space that forms part of the flow path and receives the exhaust gas discharged from the combustion section, The system comprises a denitrification section which forms part of the flow path downstream of the internal space and has a denitrification space into which the exhaust gas is introduced for denitrification, The decomposer is a fuel supply system located within the denitrification space.

2. The fuel supply system according to claim 1, wherein the decomposer has a catalyst that decomposes a portion of the ammonia when it comes into contact with a portion of the ammonia heated to the decomposition temperature.

3. The fuel supply system according to claim 1, wherein the decomposer has a container surrounding the flow path for a portion of the ammonia and hydrogen so as to isolate the portion of the ammonia and hydrogen from the exhaust gas in the flow path.

4. The aforementioned disassembly device is A catalyst that decomposes a portion of the ammonia by coming into contact with a portion of the ammonia heated to the aforementioned decomposition temperature, The fuel supply system according to claim 3, comprising a metal structure supporting the catalyst, the structure being held in the container so as to be positioned on the flow path for a portion of the ammonia and the hydrogen.

5. The fuel supply system according to claim 1 or 2, wherein the concentration of hydrogen in the decomposition gas containing hydrogen produced in the decomposition apparatus is 5 to 75%.

6. The fuel supply system according to claim 1 or 2, wherein the concentration of hydrogen in the decomposition gas containing hydrogen produced in the decomposition apparatus is 30 to 60%.

7. The fuel supply system according to claim 2 or 4, wherein the waste heat of the main engine is used as the heat source, and the catalyst comprises at least a catalyst made of a precious metal.

8. The fuel supply system according to claim 2 or 4, wherein the waste heat from the auxiliary equipment is used as the heat source, and the catalyst comprises at least a catalyst made of a base metal.

9. The fuel supply system according to claim 1 or 2, wherein the waste heat of the main engine is used as the heat source, and the hydrogen is supplied to the auxiliary engine.

10. A fuel supply system for supplying fuel to the main engine or auxiliary engine of a ship equipped with ammonia, The main engine and the auxiliary engines include a plurality of devices that discharge heat when consuming fuel, The apparatus comprises a decomposer that uses waste heat discharged from at least one of the aforementioned plurality of devices as a heat source to decompose a portion of the ammonia heated to a decomposition temperature to produce hydrogen, The hydrogen is supplied to any of the aforementioned devices as at least a portion of the fuel. At least one of the aforementioned plurality of devices is A combustion section that burns the aforementioned fuel and discharges exhaust gas accompanied by the aforementioned heat, The exhaust gas flow section is connected to the combustion section and has a flow path for flowing the exhaust gas discharged from the combustion section, The disintegrator is located within the flow path, A portion of the ammonia is heated to the decomposition temperature using the waste heat from the first of the multiple devices. When the decomposer is referred to as the first decomposer, the fuel supply system further comprises a second decomposer that decomposes the residual ammonia contained in the decomposition gas, which contains the hydrogen and undecomposed residual ammonia generated in the first decomposer, and is heated to the decomposition temperature using the waste heat of a second device, which is different from the first device among the plurality of devices, to produce hydrogen.

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