Ammonia decomposition system, internal combustion engine system, and ammonia decomposition method

Abstract

To provide an ammonia decomposition system, an internal combustion engine system, and an ammonia decomposition method, capable of easily controlling the amount of hydrogen being generated.SOLUTION: An ammonia decomposition system 10 comprises a decomposer 1 and a controller 2. The decomposer 1 decomposes ammonia. The controller 2 controls the decomposition ratio of ammonia in the decomposer 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ammonia decomposition system, an internal combustion engine system, and an ammonia decomposition method for decomposing ammonia. [Background technology]

[0002] As a related technology, an ammonia decomposition system (ammonia cracker device) is known that includes a catalyst for decomposing ammonia (ammonia cracker catalyst) and decomposes ammonia to produce hydrogen (see, for example, Patent Document 1). In this related technology, the combustion of ammonia is insufficient during low-load and high-load operation of an ammonia-fueled engine (ammonia engine) due to the poor ignition properties of ammonia, and hydrogen obtained by decomposing ammonia is used as a combustion aid.

[0003] In this related technology, an ammonia oxidation device is installed between the engine and the ammonia decomposition system, making it possible to raise the temperature of the exhaust gas by the heat of oxidation from the ammonia oxidation reaction. This makes it possible to maintain the temperature of the catalyst above its operating temperature even during low-load operation when the temperature of the exhaust gas from the engine is low, enabling stable engine operation. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2010-121509 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in ammonia decomposition systems related to this technology, the amount of hydrogen produced is determined arbitrarily by the temperature of the (heated) exhaust gas, making it difficult to properly adjust the fuel combustion efficiency in the engine.

[0006] The object of the present invention is to provide an ammonia decomposition system, an internal combustion engine system, and an ammonia decomposition method that allow for easy adjustment of the amount of hydrogen generated. [Means for solving the problem]

[0007] An ammonia decomposition system according to one aspect of the present invention comprises a decomposition unit and a control unit. The decomposition unit decomposes ammonia. The control unit controls the rate of ammonia decomposition in the decomposition unit.

[0008] An internal combustion engine system according to one aspect of the present invention comprises the ammonia decomposition system and an engine. The engine is driven by a supply of gas output from the ammonia decomposition system.

[0009] An ammonia decomposition method according to one aspect of the present invention comprises decomposing ammonia in a decomposition unit and controlling the decomposition rate of ammonia in the decomposition unit. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an ammonia decomposition system, an internal combustion engine system, and an ammonia decomposition method that allow for easy adjustment of the amount of hydrogen generated. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram showing the configuration of an internal combustion engine system according to Embodiment 1. [Figure 2] Figure 2 is a schematic diagram showing the configuration of the ammonia decomposition system according to Embodiment 1. [Figure 3] Figure 3 is a graph showing an example of the actual ammonia decomposition rate when the catalyst temperature is changed in the ammonia decomposition system according to Embodiment 1. [Figure 4] Figure 4 is a graph showing an example of the actual ammonia decomposition rate when the current value flowing through the catalyst is changed in the ammonia decomposition system according to Embodiment 1. [Figure 5] FIG. 5 is a graph showing an example of the actual value of the ammonia decomposition rate when the current value flowing through the catalyst is changed in the ammonia decomposition system according to Embodiment 1. [Figure 6] FIG. 6 is a graph showing an example of the actual value of the ammonia decomposition rate when the flow rate of ammonia is changed in the ammonia decomposition system according to Embodiment 1. [Figure 7] FIG. 7 is a graph showing an example of the actual value of the ammonia decomposition rate when the catalyst material is changed in the ammonia decomposition system according to Embodiment 1. [Figure 8] FIG. 8 is a graph showing an example of the actual value of the ammonia decomposition rate when the flow rate of ammonia is changed in the ammonia decomposition system according to Embodiment 1. [Figure 9] FIG. 9 is a graph showing an example of the actual value of the ammonia decomposition rate when the catalyst material is changed in the ammonia decomposition system according to Embodiment 1. [Figure 10] FIG. 10 is a graph showing an example of the actual value of the ammonia decomposition rate when the catalyst material is changed in the ammonia decomposition system according to Embodiment 1. [Figure 11] FIG. 11 is an explanatory diagram schematically showing how ammonia is decomposed by the catalyst in the ammonia decomposition system according to Embodiment 1. [Figure 12] FIG. 12 is a schematic diagram showing the configuration of the internal combustion engine system according to Embodiment 2.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiments are an example of embodying the present invention and are not intended to limit the technical scope of the present invention. In the accompanying drawings, illustrations of the detailed shapes of each part are appropriately omitted.

[0013] (Embodiment 1) [1] Overall Configuration of the Internal Combustion Engine System First, the overall configuration of the internal combustion engine system 100 according to this embodiment will be described with reference to Figure 1. In Figure 1, the configuration of each part of the internal combustion engine system 100 is schematically shown, with thick arrows indicating the flow of gas or liquid and dotted arrows indicating the flow of heat.

[0014] As shown in Figure 1, the internal combustion engine system 100 according to this embodiment includes an engine 101, which is the main component of the internal combustion engine system 100. Here, "engine" refers to a heat engine that generates mechanical energy (power) by burning fuel, and includes an internal combustion engine, which is a prime mover in which the combustion of fuel takes place inside the engine and the combustion gas is used as a working gas to convert thermal energy into mechanical energy. In other words, the engine 101 generates power (mechanical energy) using the supplied fuel.

[0015] In this embodiment, an internal combustion engine system 100 used in a ship will be described as an example. That is, the internal combustion engine system 100 is mounted on the hull of the ship. The engine 101 of the internal combustion engine system 100 is used as a drive source to generate thrust to propel the ship forward. In this embodiment, the engine 101 of the internal combustion engine system 100 can also be used as a drive source to drive a generator that generates electrical energy (electricity) used in the ship. That is, the engine 101 of the internal combustion engine system 100 is used as a drive source for generating thrust in the ship or for driving a generator in the ship. The electrical energy generated by the generator may be stored in an energy storage device.

[0016] A ship is a moving object that navigates (sails) on water such as the sea, lake, or river. In this embodiment, as an example, the ship is a vessel that can travel relatively long distances on a single refueling, such as an ocean-going vessel. The ship's hull has a propeller. The propeller is connected to the engine 101 of the internal combustion engine system 100 by a propeller shaft. The ship generates thrust to move its hull forward or backward by receiving power generated by the engine 101 and rotating the propeller around the propeller shaft.

[0017] Furthermore, in this embodiment, the vessel is configured to operate in response to human (pilot) operation (including remote operation), and in particular, it is a manned type in which a pilot can board. For this reason, the vessel has a control panel on the hull that receives pilot input, and drives the engine 101 of the internal combustion engine system 100 in response to the operation on the control panel. As a result, the vessel can move forward or backward by driving the engine 101 in response to pilot input and rotating the propeller. The hull is also further equipped with various onboard facilities, including a rudder mechanism, display device, communication device, and lighting equipment.

[0018] Incidentally, the engine 101 according to this embodiment is an engine that uses at least hydrogen as fuel or combustion aid. In other words, in the internal combustion engine system 100, the engine 101 is driven by supplying hydrogen stored in the hydrogen tank 102 to the engine 101 via the hydrogen fuel supply device 103. In particular, in this embodiment, the engine 101 is described as a co-fired engine that burns a fuel gas mixed with hydrogen (H2) and ammonia (NH3). Furthermore, the engine 101 is assumed to be a lean-burn engine that burns at a leaner (excess air) ratio than the stoichiometric air-fuel ratio. Therefore, in the internal combustion engine system 100 according to this embodiment, ammonia stored in the ammonia tank 104 is supplied to the engine 101 via the ammonia fuel supply device 105. As a result, hydrogen and ammonia are supplied to the engine 101, and the engine 101 is driven using hydrogen and ammonia as fuel.

[0019] Engine 101 is a type of ammonia engine that uses ammonia as its primary fuel, and it has the advantage of being able to reduce carbon dioxide emissions compared to engines that use fossil fuels (such as diesel or gasoline) as their primary fuel. Moreover, in engine 101, both hydrogen and ammonia are used as fuel (or combustion aids), so the weakness of ammonia, which is difficult to ignite and burn, can be compensated for by hydrogen. In other words, by using a mixture of ammonia and hydrogen gas, engine 101, while using ammonia as fuel, has improved combustibility compared to when ammonia is used as fuel alone, making it easier to use in a wide range of operating conditions (load ranges). Furthermore, compared to when hydrogen is used as fuel alone, it is easier to appropriately control the combustion efficiency of engine 101, thus suppressing the occurrence of abnormal combustion and making it easier to achieve high output.

[0020] In this embodiment of the internal combustion engine system 100, hydrogen obtained by decomposing ammonia is supplied to the engine 101 as fuel (or combustion aid). For this purpose, an ammonia decomposition system 10 is used to decompose ammonia. The ammonia decomposition system 10 decomposes ammonia to obtain hydrogen and nitrogen. That is, when ammonia (NH3) is supplied to the ammonia decomposition system 10, hydrogen (H2), nitrogen (N2), and residual ammonia (NH3) that remains undecomposed are output from the ammonia decomposition system 10. Thus, the internal combustion engine system 100 according to this embodiment comprises an ammonia decomposition system 10 and an engine 101. The engine 101 is driven by the supply of gas (hydrogen) output from the ammonia decomposition system 10.

[0021] Specifically, the internal combustion engine system 100 includes an engine 101, a hydrogen tank 102, a hydrogen fuel supply device 103, an ammonia tank 104, and an ammonia fuel supply device 105, as well as an ammonia decomposition system 10 and a vaporizer 106. Liquid ammonia (liquefied ammonia) is stored in the ammonia tank 104. The vaporizer 106 vaporizes the liquefied ammonia in the ammonia tank 104 and supplies the gaseous ammonia to the ammonia decomposition system 10. The ammonia decomposition system 10 outputs the gas (hydrogen) obtained by decomposing ammonia to the hydrogen tank 102. As a result, the hydrogen supplied as fuel to the engine 101 is produced from ammonia in the ammonia decomposition system 10 and (temporarily) stored in the hydrogen tank 102.

[0022] The internal combustion engine system 100 with the above configuration makes it possible to efficiently and safely supply hydrogen as fuel for the engine 101. In other words, ammonia has a higher volumetric energy density than hydrogen, for example, and liquefies under milder conditions. Therefore, in the internal combustion engine system 100, by decomposing the ammonia stored in the ammonia tank 104 in the ammonia decomposition system 10 each time to obtain hydrogen as fuel, it is possible to improve the volumetric energy density of the stored material compared to when hydrogen as fuel is stored in a compressed gas or liquid state. Consequently, if the capacity of the tank (ammonia tank 104) is the same, more fuel can be stored, and if the same amount of fuel (hydrogen) is to be stored, a smaller tank (ammonia tank 104) is sufficient. Thus, the ability to efficiently (with a smaller tank) and safely supply hydrogen as fuel is particularly useful for ships that sail relatively long distances on a single refueling, such as ocean-going vessels.

[0023] More specifically, the internal combustion engine system 100 includes an engine 101, a hydrogen tank 102, a hydrogen fuel supply device 103, an ammonia tank 104, an ammonia fuel supply device 105, an ammonia decomposition system 10, and a vaporizer 106, in addition to a compressor 107 and a heat exchanger 108. The compressor 107 compresses air (atmosphere) drawn in from around the internal combustion engine system 100 and supplies the compressed air to the engine 101 along with fuel (hydrogen and ammonia). The heat exchanger 108 performs heat exchange between the exhaust gas discharged from the engine 101 and a heat transfer medium (refrigerant), recovering the thermal energy of the exhaust gas to cool it.

[0024] Furthermore, the thermal energy recovered in the heat exchanger 108 is sent to the ammonia supplied to the ammonia decomposition system 10. In other words, the ammonia vaporized in the vaporizer 106 and supplied to the ammonia decomposition system 10 is heated by the waste heat from the engine 101 recovered in the heat exchanger 108. The heated ammonia is then supplied to the decomposition section 1 of the ammonia decomposition system 10, so the waste heat from the engine 101 recovered in the heat exchanger 108 indirectly heats the decomposition section 1. Thus, in the internal combustion engine system 100 according to this embodiment, the waste heat from the engine 101 is used to heat the decomposition section 1. In this embodiment, the decomposition section 1 has a catalyst 11 (see Figure 2), and the decomposition rate of ammonia in the decomposition section 1 (catalyst 11) is improved by heating the catalyst 11.

[0025] In this way, by effectively utilizing the waste heat from the engine 101, it is possible to reduce the energy required to heat the decomposition unit 1 (catalyst 11). Moreover, by using the waste heat from the engine 101 to heat the decomposition unit 1, the exhaust gas is also cooled. Here, the internal combustion engine system 100 is not limited to a configuration that indirectly heats the decomposition unit 1 using the waste heat from the engine 101, but may also directly heat the decomposition unit 1 by directly sending the waste heat from the engine 101 to the decomposition unit 1. Furthermore, the waste heat from the engine 101 referred to here is not limited to the heat of the exhaust gas, but may also be the heat of, for example, coolant or lubricating oil. In other words, the heat exchanger 108 may, in addition to or instead of the exhaust gas, perform heat exchange between, for example, the coolant or lubricating oil heated by the engine 101 and the heat transfer medium, and recover thermal energy from the coolant or lubricating oil.

[0026] As described above, in the internal combustion engine system 100 according to this embodiment, the engine 101 utilizes hydrogen obtained in the decomposition section 1 (of the ammonia decomposition system 10) as at least part of its fuel. This makes it possible to efficiently and safely supply hydrogen as fuel to the engine 101.

[0027] Furthermore, the engine 101 utilizes hydrogen obtained in the decomposition section 1 (of the ammonia decomposition system 10) and ammonia as fuel. This allows for lower carbon dioxide emissions compared to engines that primarily use fossil fuels (such as diesel or gasoline). Moreover, by using ammonia and hydrogen as fuel, the engine 101 improves combustibility compared to when ammonia alone is used as fuel, making it easier to use in a wide range of operating conditions (load ranges). Compared to when hydrogen alone is used as fuel, it suppresses abnormal combustion and makes it easier to achieve higher output.

[0028] Furthermore, in this embodiment, the ammonia used as fuel for the engine 101 is stored in a common tank (ammonia tank 104) with the ammonia that is decomposed in the decomposition unit 1 (of the ammonia decomposition system 10). In other words, the ammonia stored in the single ammonia tank 104 is supplied to the engine 101 as fuel by the ammonia fuel supply device 105, while at the same time it is supplied to the decomposition unit 1 of the ammonia decomposition system 10 by the vaporizer 106 to be decomposed. Therefore, even though hydrogen and ammonia are used as fuel for the engine 101, the source of these two types of fuel can be stored in a single tank (ammonia tank 104), making the tank more compact and simplifying the tank replenishment process.

[0029] [2] Definition In this disclosure, "decomposition" refers to a type of chemical reaction in which a compound is broken down into its constituent elements or simpler compounds, which is the reverse process of chemical synthesis. Decomposition usually requires an external energy supply, and depending on the energy source, there are various types of decomposition, such as thermal decomposition, photodecomposition, electrolysis, or radiolysis. In this embodiment, as an example, the ammonia decomposition system 10 uses a catalyst 11 to decompose ammonia (NH3) into hydrogen (H2) and nitrogen (N2). However, the ammonia decomposition system 10 only needs to decompose at least a portion of the supplied ammonia into hydrogen and nitrogen, and is not limited to decomposing the entire amount. The ammonia that is supplied to the ammonia decomposition system 10 but remains undecomposed is also called "residual ammonia."

[0030] In this disclosure, "catalyst" refers to a substance that, in a chemical reaction such as decomposition, does not change itself but promotes the chemical reaction. More precisely, the "catalyst" interacts with the reaction in some way, and sometimes the "catalyst" itself changes, thereby altering the reaction pathway and promoting the reaction. After the reaction, the "catalyst" returns to its original state, and as a result, the "catalyst" itself remains unchanged. In this embodiment, as an example, the decomposition unit 1 of the ammonia decomposition system 10 has a catalyst 11 (ammonia decomposition catalyst) that decomposes ammonia, and the catalyst 11 is used to decompose ammonia.

[0031] In this disclosure, "decomposition rate" refers to the ratio of the amount of compound actually decomposed to the total amount of the compound during decomposition. For the same amount of compound, a higher decomposition rate results in a larger amount of the compound being decomposed, while a lower decomposition rate results in a smaller amount of the compound being decomposed. In this embodiment, as an example, the decomposition rate for ammonia decomposition in the ammonia decomposition system 10 is expressed as a percentage from "0%" to "100%". For example, if the decomposition rate is "0%", the ammonia supplied to the ammonia decomposition system 10 is not decomposed at all, and the entire amount becomes residual ammonia. Conversely, if the decomposition rate is "100%", the entire amount of ammonia supplied to the ammonia decomposition system 10 is decomposed, and no residual ammonia is produced. If the decomposition rate is "50%", half of the ammonia supplied to the ammonia decomposition system 10 is decomposed, and the remaining half becomes residual ammonia.

[0032] [3] Configuration of the ammonia decomposition system Next, the configuration of the ammonia decomposition system 10 according to this embodiment will be described with reference to Figure 2. Figure 2 is a schematic diagram showing the configuration of the decomposition unit 1.

[0033] As a related technology, a technique has been proposed that involves installing an ammonia oxidation device between the engine and the ammonia decomposition system, enabling the exhaust gas to be heated by the heat of oxidation from the ammonia oxidation reaction. This makes it possible to maintain the catalyst temperature above its operating temperature even during low-load operation when the exhaust gas temperature from the engine is low, thus enabling stable engine operation.

[0034] However, in ammonia decomposition systems related to the technology described above, the amount of hydrogen produced is determined arbitrarily by the temperature of the (heated) exhaust gas, making it difficult to appropriately adjust the fuel combustion efficiency in the engine. Therefore, the ammonia decomposition system 10 according to this embodiment adopts the configuration described below in order to make it easier to adjust the amount of hydrogen produced.

[0035] In other words, the ammonia decomposition system 10 according to this embodiment comprises a decomposition unit 1 and a control unit 2. The decomposition unit 1 is a device that decomposes ammonia. The control unit 2 controls the rate of ammonia decomposition in the decomposition unit 1. That is, the ammonia decomposition system 10 decomposes ammonia supplied to the decomposition unit 1 from an external source (vaporizer 106) in the decomposition unit 1. In this embodiment, as an example, the decomposition unit 1 decomposes ammonia into hydrogen and nitrogen, and outputs the hydrogen to a hydrogen tank 102 (see Figure 1). That is, the ammonia decomposition system 10 (temporarily) stores the gas (hydrogen) obtained by decomposing ammonia in the hydrogen tank 102.

[0036] In the ammonia decomposition system 10 according to this embodiment, the ammonia decomposition rate in the decomposition unit 1 is not fixed, but can be controlled (adjusted) by the control unit 2. For example, the control unit 2 changes the ammonia decomposition rate (ammonia decomposition rate) within a variable range of "0%" to "100%". If the control unit 2 controls the decomposition rate to "0%", no ammonia is decomposed at all in the decomposition unit 1, so the amount of hydrogen generated from the decomposition of ammonia is minimized (0). Conversely, if the control unit 2 controls the decomposition rate to "100%", the entire amount of ammonia is decomposed in the decomposition unit 1, so the amount of hydrogen generated from the decomposition of ammonia is maximized.

[0037] According to the configuration described above, the ammonia decomposition system 10 according to this embodiment allows for variable ammonia decomposition rate in the decomposition unit 1, and therefore the amount of hydrogen produced by decomposing ammonia can also be adjusted. Thus, it becomes possible to provide an ammonia decomposition system 10 that allows for easy adjustment of the amount of hydrogen produced.

[0038] Furthermore, in the ammonia decomposition system 10 according to this embodiment, as described above, the decomposition unit 1 has a catalyst 11 for decomposing ammonia. In addition, the decomposition unit 1 has electrodes 12 and 13 for applying an electric field to the catalyst 11. In short, in this embodiment, the decomposition unit 1 has, for example, a pair of electrodes 12 and 13 provided so as to sandwich the catalyst 11, and an electric field is applied to the catalyst 11 from this pair of electrodes 12 and 13. As a result, compared to the case in which no electric field is applied to the catalyst 11, the decomposition of ammonia in the catalyst 11 can be promoted, especially in environments where the temperature of the catalyst 11 is low.

[0039] Specifically, as shown in Figure 2, the ammonia decomposition system 10 includes a decomposition unit 1 containing a catalyst 11 and electrodes 12 and 13, a control unit 2, and a power supply unit 3. The power supply unit 3 is electrically connected to the pair of electrodes 12 and 13 in the decomposition unit 1 and is a device that applies a DC voltage between the pair of electrodes 12 and 13. When a DC voltage is applied from the power supply unit 3 between the pair of electrodes 12 and 13, an electric field is applied from the pair of electrodes 12 and 13 to the catalyst 11. The power supply unit 3 generates a DC voltage of, for example, several hundred volts and applies it between the pair of electrodes 12 and 13.

[0040] In this embodiment, as an example, the power supply unit 3 applies a DC voltage between a pair of electrodes 12 and 13, with electrode 12 as the negative electrode and electrode 13 as the positive electrode. This causes the power supply unit 3 to apply a DC voltage between the pair of electrodes 12 and 13, with electrode 12 on the low potential side and electrode 13 on the high potential side. Here, the power supply unit 3 uses electrode 13, which is the positive electrode, as the reference potential point (ground) and applies a negative voltage between the pair of electrodes 12 and 13. However, the configuration is not limited to this; as long as an electric field is applied to the catalyst 11, the power supply unit 3 may, for example, apply a positive voltage between the pair of electrodes 12 and 13 by setting the low-potential electrode 12 to ground and the high-potential electrode 13 to a positive potential.

[0041] More specifically, as shown in Figure 2, the decomposition unit 1 includes, in addition to the catalyst 11 and a pair of electrodes 12 and 13, an inlet 14, an outlet 15, a cylindrical body 16, a catalyst stationary layer 17, a mesh 18, and a temperature sensor 19.

[0042] The inlet 14 is an opening through which the gas (ammonia) to be decomposed in the decomposition section 1 is introduced. The outlet 15 is an opening through which the gas obtained by decomposing ammonia in the decomposition section 1 is discharged. The cylindrical body 16 is formed, for example, in a cylindrical shape and contains at least the catalyst 11. The inlet 14 is provided at one end of the cylindrical body 16 in the longitudinal direction, and the outlet 15 is provided at the other end of the cylindrical body 16 in the longitudinal direction. As a result, the gas introduced from the inlet 14 can pass through the cylindrical body 16 and be discharged from the outlet 15. The gas (ammonia) is decomposed by the catalyst 11 contained in the cylindrical body 16, so it is decomposed as it passes through the cylindrical body 16.

[0043] The cylindrical body 16 houses a catalyst stationary layer 17 and a mesh 18. The catalyst 11 is stacked on the catalyst stationary layer 17 via the mesh 18. Here, a pair of electrodes 12 and 13 are rod-shaped electrodes, inserted into the catalyst 11 from both ends in the longitudinal direction of the cylindrical body 16. Furthermore, a temperature sensor 19, for example a thermocouple, is inserted into the catalyst from the other end in the longitudinal direction of the cylindrical body 16, and measures the reaction field temperature (catalyst temperature) in real time. The measured catalyst temperature value from the temperature sensor 19 is output to the control unit 2.

[0044] In this embodiment, an inert gas (argon, for example) is introduced into the decomposition unit 1 along with ammonia. Therefore, as shown in Figure 2, ammonia (NH3) and argon (Ar) are introduced from the inlet 14, the ammonia is decomposed by the catalyst 11 in the decomposition unit 1, and hydrogen (H2), nitrogen (N2), (residual) ammonia (NH3) and argon (Ar) are discharged from the outlet 15. However, the inert gas is not essential for the decomposition of ammonia.

[0045] As explained above, the decomposition unit 1 of the ammonia decomposition system 10 is configured such that an electric field is applied to the catalyst 11 from a pair of electrodes 12 and 13. Therefore, the decomposition of ammonia in the catalyst 11 can be promoted, especially in environments where the temperature of the catalyst 11 is low. In particular, in environments where the exhaust heat from the engine 101 of the internal combustion engine system 100 is insufficient, it is necessary to supply additional ammonia to raise the temperature of the catalyst 11, which can worsen the fuel efficiency of the internal combustion engine system 100. In contrast, in this embodiment, where the decomposition of ammonia in the catalyst 11 is promoted even in low temperature ranges by applying an electric field to the catalyst 11, it is not necessary to raise the temperature of the catalyst 11 to that extent in the first place, making it easier to suppress the deterioration of fuel efficiency of the internal combustion engine system 100.

[0046] Furthermore, the ammonia decomposition system 10 according to this embodiment further includes a heating unit 4 for heating the catalyst 11. The heating unit 4 sets the temperature of the catalyst 11 in the range of 50°C to 600°C. That is, in order to increase the ammonia decomposition rate of the catalyst 11, the heating unit 4 heats the catalyst 11 so that its temperature is in the range of 50°C to 600°C. The heating unit 4 may indirectly heat the catalyst 11 by heating the ammonia that has been vaporized in the vaporizer 106 and supplied to the ammonia decomposition system 10, or it may directly heat the catalyst 11 using a heater or the like. Moreover, in this embodiment, as described above, an electric field is applied to the catalyst 11, so the heating unit 4 does not need to heat the catalyst 11 to a high temperature such as 300°C or higher to sufficiently achieve ammonia decomposition in the catalyst 11.

[0047] However, the lower limit of the temperature of the catalyst 11 heated by the heating unit 4 is not limited to 50°C, but may be less than 50°C, or it may be 100°C, 150°C, 200°C, 250°C, or 300°C, etc. Similarly, the upper limit of the temperature of the catalyst 11 heated by the heating unit 4 is not limited to 600°C, but may be higher than 600°C, or it may be 350°C, 400°C, 450°C, 500°C, or 550°C, etc. As an example, it is more preferable for the heating unit 4 to heat the catalyst 11 so that the temperature of the catalyst 11 is in the range of 100°C or more and 400°C or less.

[0048] Furthermore, in this embodiment, as described above, the decomposition unit 1 is heated using the waste heat of the engine 101, so the heating unit 4 may heat the catalyst 11 using at least the waste heat of the engine 101. In this way, by effectively utilizing the waste heat of the engine 101, it is possible to reduce the energy required to heat the catalyst 11 in the heating unit 4. In particular, when the catalyst 11 is used in a low temperature range of 300°C or less, the catalyst 11 can be sufficiently heated by the waste heat of the engine 101 alone, so there is no need to provide a separate heating device, and it is easy to miniaturize and simplify the ammonia decomposition system 10.

[0049] Incidentally, in the ammonia decomposition system 10 according to this embodiment, as described above, the ammonia decomposition rate (ammonia decomposition rate) in the decomposition unit 1 can be controlled (adjusted) by the control unit 2. Here, the control unit 2 changes the decomposition rate by changing at least one of the following: the temperature of the catalyst 11, the current value flowing through the catalyst 11, and the flow rate of ammonia passing through the catalyst 11. In other words, the ammonia decomposition rate changes by changing at least one of the three parameters: the temperature of the catalyst 11, the current value flowing through the catalyst 11, and the flow rate of ammonia passing through the catalyst 11. In this embodiment, as an example, the control unit 2 is configured to control all of the following: the temperature of the catalyst 11, the current value flowing through the catalyst 11, and the flow rate of ammonia passing through the catalyst 11.

[0050] For example, the control unit 2 changes the decomposition rate (of ammonia) by at least the current value, such that the decomposition rate (of ammonia) increases as the current value flowing through the catalyst 11 increases. Specifically, the control unit 2 is configured to control the power supply unit 3, and controls the magnitude (current value) of the current flowing through the catalyst 11 by controlling the magnitude (current value) of the current supplied from the power supply unit 3 to the decomposition unit 1 (between the pair of electrodes 12 and 13). In other words, the power supply unit 3 does not have a constant output current, but rather a variable output current, and that current value is controlled by the control unit 2. The control unit 2 may change the current value flowing through the catalyst 11 continuously, or it may change it in steps (discontinuously).

[0051] Basically, when the output current of the power supply unit 3 increases, the current flowing through the catalyst 11 increases, the ammonia decomposition rate increases, and the amount of hydrogen produced from the decomposition of ammonia increases. Conversely, when the output current of the power supply unit 3 decreases, the current flowing through the catalyst 11 decreases, the ammonia decomposition rate decreases, and the amount of hydrogen produced from the decomposition of ammonia decreases. As a result, the ammonia decomposition rate can be controlled (adjusted) with a relatively simple configuration, and since the response of the ammonia decomposition rate to changes in the current value is relatively high, the control unit 2 can easily control the ammonia decomposition rate in real time.

[0052] Furthermore, the control unit 2 changes the decomposition rate (of ammonia) at least by the temperature of the catalyst 11, such that the decomposition rate (of ammonia) increases as the temperature of the catalyst 11 increases (higher temperature). Specifically, the control unit 2 is configured to control the heating unit 4, and controls the temperature of the catalyst 11 by controlling the amount of thermal energy supplied to the catalyst 11 from the heating unit 4. In other words, the heating unit 4 does not have a constant output, but a variable output, and its output (thermal energy) is controlled by the control unit 2. The control unit 2 may change the temperature of the catalyst 11 continuously or in steps (discontinuously).

[0053] Basically, as the temperature of catalyst 11 increases, the ammonia decomposition rate increases, and thus the amount of hydrogen produced by the decomposition of ammonia increases. Conversely, as the temperature of catalyst 11 decreases, the ammonia decomposition rate decreases, and thus the amount of hydrogen produced by the decomposition of ammonia decreases. As a result, the ammonia decomposition rate can be controlled (adjusted) with a relatively simple configuration, and since the response of the ammonia decomposition rate to temperature changes of catalyst 11 is relatively high, the control unit 2 can easily control the ammonia decomposition rate in real time.

[0054] Furthermore, the control unit 2 changes the decomposition rate of ammonia by controlling at least the flow rate (velocity) of ammonia passing through the catalyst 11, such that the decomposition rate increases as the flow rate (velocity) of ammonia passing through the catalyst 11 decreases. Specifically, the control unit 2 is configured to control the flow rate of ammonia supplied to the decomposition unit 1, and controls the flow rate (velocity) of ammonia passing through the catalyst 11 by controlling the flow rate of ammonia supplied to the decomposition unit 1. In other words, the flow rate (velocity) of ammonia passing through the catalyst 11 is not constant but variable, and its value (flow rate) is controlled by the control unit 2. The control unit 2 may continuously change the flow rate of ammonia passing through the catalyst 11, or it may change it in steps (discontinuously).

[0055] Basically, if the flow rate of ammonia passing through catalyst 11 decreases, the ammonia decomposition rate increases, and therefore the concentration of hydrogen obtained by decomposing ammonia increases. Conversely, if the flow rate of ammonia passing through catalyst 11 increases, the ammonia decomposition rate decreases, and therefore the concentration of hydrogen obtained by decomposing ammonia decreases. As a result, the ammonia decomposition rate can be controlled (adjusted) with a relatively simple configuration, and since the response of the ammonia decomposition rate to the flow rate of ammonia passing through catalyst 11 is relatively high, the control unit 2 can easily control the ammonia decomposition rate in real time.

[0056] Here, catalyst 11 comprises an active metal and an oxide. The active metal is one of ruthenium (Ru), nickel (Ni), iron (Fe), or cobalt (Co), and the oxide mainly contains one of cerium (Ce), zirconium (Zr), Ba (barium), or Sr (strontium). In other words, catalyst 11 comprises an active metal such as ruthenium and a catalyst support made of an active metal such as cerium. In such catalyst 11, the control unit 2 can change the ammonia decomposition rate by changing, for example, the temperature of catalyst 11, the current value flowing through catalyst 11, and the flow rate of ammonia passing through catalyst 11.

[0057] More specifically, in this embodiment, the oxide used as the catalyst support is CeO2,Ce x Zr (1-x) O2, BaZrO3, Sr x Ba (1-x) It is one of ZrO3. Here, "x" is any value in the range of "0" to "1" (i.e., "0≦x≦1"), for example, Ce x Zr (1-x) For example, if it's O2, then Ce 0.5 Zr 0.5 Contains O2, etc.

[0058] The ammonia decomposition system 10 with the above configuration embodies an ammonia decomposition method that includes decomposing ammonia in the decomposition unit 1 and controlling the decomposition rate of ammonia in the decomposition unit 1. Such an ammonia decomposition method may be implemented without using the ammonia decomposition system 10.

[0059] [4] Actual values Below, with reference to Figures 3 to 10, we will describe the actual values ​​of the ammonia decomposition rate when the temperature of the catalyst 11, the current value flowing through the catalyst 11, or the flow rate of ammonia passing through the catalyst 11 are changed in the ammonia decomposition system 10 according to this embodiment. Figures 3 to 10 are graphs showing an example of actual values, with various parameters such as the temperature of the catalyst 11 plotted on the horizontal axis and the ammonia decomposition rate (ammonia decomposition rate) plotted on the vertical axis. Furthermore, since the ammonia decomposition rate also changes depending on the amount of catalyst 11 and the material (components) of catalyst 11, we will also describe the actual values ​​of the ammonia decomposition rate when the material of catalyst 11 is changed below.

[0060] Figure 3 is a graph showing the actual values ​​of ammonia decomposition rate when the temperature (horizontal axis) of catalyst 11 is changed. The test conditions other than the temperature of catalyst 11 in Figure 3 are: the current flowing through catalyst 11 (when an electric field is present) is "6mA", the material of catalyst 11 is "5wt%Ru / CeO2", the amount of catalyst 11 is "100mg", the ammonia flow rate is "50mL / min", and the reaction pressure is "atmospheric pressure". In Figure 3, the black circle plot P1 shows the data when an electric field is applied to catalyst 11 ("with electric field"), and the black triangle plot P2 shows the data when an electric field is not applied to catalyst 11 ("without electric field").

[0061] As is clear from Figure 3, the ammonia decomposition rate tends to increase as the temperature of catalyst 11 increases. Furthermore, in the range where the temperature of catalyst 11 is "300°C" or lower, the effect of promoting ammonia decomposition and increasing the ammonia decomposition rate is significantly greater with an electric field than without an electric field. For example, in the low temperature range of catalyst 11 at "100°C", the ammonia decomposition rate is approximately "0%" without an electric field, while it exceeds "20%" with an electric field.

[0062] Figure 4 is a graph showing the actual ammonia decomposition rate when the current value (horizontal axis) flowing through catalyst 11 is changed. The test conditions other than the current value in Figure 4 are: catalyst 11 temperature of "150°C", catalyst 11 material of "5wt%Ru / CeO2", amount of catalyst 11 of "300mg", ammonia flow rate of "10mL / min", and reaction pressure of "atmospheric pressure".

[0063] As is clear from Figure 4, the ammonia decomposition rate tends to increase as the current flowing through catalyst 11 increases. For example, when the current value is around "10 mA", the ammonia decomposition rate rises to around "100%", even though the temperature of catalyst 11 is in the low range of "150°C".

[0064] Figure 5 is a graph showing the actual ammonia decomposition rate when the current value (horizontal axis) flowing through catalyst 11 is changed, under conditions different from those in Figure 4, such as the amount of catalyst 11 and the ammonia flow rate. The test conditions other than the current value in Figure 5 are: catalyst 11 temperature of "125°C", catalyst 11 material of "5wt%Ru / CeO2", amount of catalyst 11 of "100mg", ammonia flow rate of "50mL / min", and reaction pressure of "atmospheric pressure". In other words, the actual values ​​in Figure 5, regarding the amount of catalyst 11 and the ammonia flow rate, are set to result in a lower ammonia decomposition rate than those in Figure 4.

[0065] As is clear from Figure 5, even if various conditions such as the amount of catalyst 11 and the ammonia flow rate change, the tendency for the ammonia decomposition rate to increase as the current flowing through catalyst 11 increases remains the same. In other words, even if the amount of catalyst 11 is reduced, for example, it is possible to achieve the same ammonia decomposition rate as before reducing the amount of catalyst 11 by increasing the electric field (power) applied to catalyst 11 from power supply 3 and increasing the current value flowing through catalyst 11.

[0066] Figure 6 is a graph showing the actual values ​​of ammonia decomposition rates when the ammonia flow rate is varied. In Figure 6, the horizontal axis represents the "catalyst size," which is the amount of catalyst 11 divided by the ammonia flow rate. In other words, the catalyst size increases as the ammonia flow rate decreases. The test conditions in Figure 6 are: the current flowing through catalyst 11 (with an electric field) is "6mA," the material of catalyst 11 is "5wt%Ru / CeO2," the amount of catalyst 11 is "300mg," and the reaction pressure is "atmospheric pressure." In this case, the horizontal axis represents the catalyst size when the ammonia flow rate is varied in the range from "5mL / min" to "50mL / min." In Figure 6, plot P1 (white circle) shows data when an electric field is applied to catalyst 11 ("with electric field") and the temperature of catalyst 11 is between "130°C" and "140°C", plot P2 (black circle) shows data when an electric field is applied and the temperature of catalyst 11 is "45°C", plot P3 (black square) shows data when an electric field is applied and the temperature of catalyst 11 is "70°C", and plot P4 (black triangle) shows data when no electric field is applied to catalyst 11 ("without electric field").

[0067] As is clear from Figure 6, the ammonia decomposition rate tends to increase as the flow rate (velocity) of ammonia passing through catalyst 11 decreases, that is, as the catalyst size increases. Moreover, even when the temperature of catalyst 11 is in the low temperature range of "150°C" or "100°C" or below, ammonia decomposition is sufficiently promoted under the condition of "with an electric field," and in particular, when the temperature of catalyst 11 is between "130°C" and "140°C," the ammonia decomposition rate rises to around "100%." ​​Furthermore, even when the temperature of catalyst 11 is "45°C," the ammonia decomposition rate reaches approximately "75%," and even when the temperature of catalyst 11 is "70°C," the ammonia decomposition rate reaches approximately "80%." On the other hand, in the case of "no electric field," ammonia decomposition is not promoted even if the ammonia flow rate changes.

[0068] Figure 7 is a graph showing the actual values ​​of ammonia decomposition rates when the material (components) of catalyst 11 is changed. In Figure 7, the temperature of catalyst 11 is on the horizontal axis. The test conditions in Figure 7 are: the current flowing through catalyst 11 (when an electric field is present) is "6 mA", the amount of catalyst 11 is "100 mg", the ammonia flow rate is "50 mL / min", and the reaction pressure is "atmospheric pressure". In this case, Figure 7 shows the actual values ​​for catalyst 11 materials of "5 wt% Ru / CeO2", "3 wt% Ni / CeO2", and "3 wt% Fe / CeO2". In addition, in Figure 7, the data for when the temperature of catalyst 11 is "100°C" is extracted and the results are shown as bar graphs for each active metal of catalyst 11 (ruthenium (Ru), nickel (Ni), or iron (Fe)) in the nozzle.

[0069] In Figure 7, plot P1 (black circle) shows the data when an electric field is applied to catalyst 11 ("with electric field") and catalyst 11 containing ruthenium (Ru) as the active metal (5wt%Ru / CeO2). Plot P2 (white circle) shows the data when no electric field is applied to catalyst 11 ("without electric field") and catalyst 11 containing ruthenium as the active metal. Additionally, plot P3 (black diamond) shows the data when an electric field is applied and catalyst 11 containing nickel (Ni) as the active metal (3wt%Ni / CeO2). Plot P4 (white diamond) shows the data when no electric field is applied and catalyst 11 containing nickel as the active metal. Furthermore, plot P5, represented by a black triangle, shows the data when an electric field is present and catalyst 11 (3wt%Fe / CeO2) containing iron (Fe) as the active metal is used, while plot P6, represented by a white triangle, shows the data when an electric field is absent and catalyst 11 containing iron as the active metal is used.

[0070] As is clear from Figure 7, in the high-temperature range of catalyst 11 around "500°C", ruthenium has the highest ammonia decomposition rate, followed by nickel, and iron has the lowest. However, under the condition of "electric field present", even though the temperature of catalyst 11 is in the low-temperature range of "100°C", ammonia decomposition rates of around "20%" are achieved not only with ruthenium, but also with nickel and iron. From this, it can be seen that the sensitivity of the catalyst 11 material to the promotion of ammonia decomposition differs depending on the material.

[0071] Figure 8 is a graph showing the actual values ​​of ammonia decomposition rates when the ammonia flow rate is varied, with catalyst material 11 being "3wt%Ni / CeO2". In Figure 8, the horizontal axis represents the "catalyst size," which is the amount of catalyst 11 divided by the ammonia flow rate. The test conditions in Figure 8 are: catalyst temperature 11 is "100°C", current flowing through catalyst 11 is "6mA", amount of catalyst 11 is "300mg", and reaction pressure is "atmospheric pressure". In this case, the horizontal axis represents the catalyst size when the ammonia flow rate is varied from "5mL / min" to "50mL / min".

[0072] As is clear from FIG. 8, even when nickel, which is easier to adopt than ruthenium, is used as the active metal, as the flow rate (flow velocity) of ammonia passing through the catalyst 11 decreases, that is, as the catalyst size increases, the ammonia decomposition rate tends to increase. Moreover, even though the temperature of the catalyst 11 is in the low temperature range of "100 ° C", under the condition of "with electric field", the decomposition of ammonia is sufficiently promoted, and the ammonia decomposition rate rises to around "80%". Thus, even when nickel is used as the active metal, the ammonia decomposition rate can be controlled by changing the flow rate (flow velocity) of ammonia passing through the catalyst 11.

[0073] FIG. 9 is a graph showing the actual values of the ammonia decomposition rate when the material (component) of the catalyst 11 is changed. In FIG. 9, the temperature of the catalyst 11 is taken as the horizontal axis. The test conditions in FIG. 9 are that the current value flowing through the catalyst 11 (in the case of "with electric field") is "6 mA", the amount of the catalyst 11 is "100 mg", the flow rate of ammonia is "50 mL / min", and the reaction pressure is "atmospheric pressure". In this case, the actual values when the material of the catalyst 11 is "5 wt% Ru / Sr x Ba (1-x) ZrO3 (x = 0.125)", "5 wt% Ru / CeO2" are shown in FIG. 9. In FIG. 9, the black circle plot P1 shows the data when an electric field is applied to the catalyst 11 in "with electric field" and the catalyst 11 contains "Sr x Ba (1-x) ZrO3 (x = 0.125)" as the oxide, and the black diamond plot P2 shows the data when the catalyst 11 containing "CeO2" as the oxide is adopted in "with electric field". The black triangle plot P3 in FIG. 9 shows the data of "without electric field" where no electric field is applied to the catalyst 11.

[0074] <000029l>As is clear from FIG. 9, even when only the oxide is changed without changing the active metal of the catalyst 11, in the low temperature range where the temperature of the catalyst 11 is "100 ° C", under the condition of "with electric field", the decomposition of ammonia is sufficiently promoted. <0-000293> Figure 10 is a graph showing the actual values ​​of ammonia decomposition rate when the material (components) of catalyst 11 is changed. In Figure 10, the horizontal axis represents the ratio of ruthenium (Ru) as the active metal in catalyst 11, i.e., the amount of active metal supported (wt%). The test conditions in Figure 10 are: catalyst 11 temperature of "100°C", current flowing through catalyst 11 of "6mA", amount of catalyst 11 of "100mg", ammonia flow rate of "50mL / min", and reaction pressure of "atmospheric pressure". In this case, Figure 10 shows the actual values ​​for catalyst 11 materials of "1wt%Ru / CeO2", "3wt%Ru / CeO2", "5wt%Ru / CeO2", and "7wt%Ru / CeO2".

[0076] As is clear from Figure 10, even at a low temperature of "100°C" for catalyst 11, the ammonia decomposition rate tends to increase as the amount of active metal supported on catalyst 11 increases.

[0077] [5] Mechanism Next, the mechanism for promoting ammonia decomposition in the ammonia decomposition system 10 according to this embodiment will be explained with reference to Figure 11. Figure 11 schematically shows how ammonia is decomposed by the catalyst 11. The upper panel shows the case without an electric field applied to the catalyst 11 as a comparative example ("no electric field"), and the lower panel shows the case with an electric field applied to the catalyst 11 ("with electric field").

[0078] First, in a comparative example where no electric field is applied to catalyst 11, ions such as hydrogen (H) are released from ammonia (NH3) adsorbed on the catalyst metal (active metal). + ) or atoms (H) may be abstracted. However, these ions will remain on the surface of the oxide acting as a catalyst support and will not actively move.

[0079] In contrast, when an electric field is applied to the catalyst 11 as in this embodiment, ions such as hydrogen (H +) are pulled by the electric field and move across the surface of the oxide that serves as the catalyst support. More specifically, there are two possible mechanisms for ion movement: the "Vehicle Mechanism," in which the charged ions themselves move, and the "Grotthuss Mechanism," in which ions appear to move through proton hopping via water adsorbed on the surface of catalyst 11, for example. In particular, proton hopping involves protons (H) in which hydrogen atoms carry a positive charge. + When ions combine with water molecules, the bonds between the original oxygen and hydrogen atoms are broken, and protons are repeatedly transferred to adjacent water molecules. This causes the protons to appear to move rapidly across the surface of the catalyst 11, much like a bucket brigade. In either transfer mechanism, it is presumed that the actively moving ions physically collide with molecules such as ammonia, thereby promoting the decomposition of ammonia (NH3) into hydrogen and nitrogen. As a result, compared to the case where no electric field is applied to the catalyst 11, the decomposition of ammonia in the catalyst 11 is promoted, especially in environments where the temperature of the catalyst 11 is low.

[0080] However, the mechanism of decomposition acceleration described here is only one theory and is not intended to limit the composition of the ammonia decomposition system 10.

[0081] [6] Variant The following lists some modifications of Embodiment 1. The modifications described below can be combined and applied as appropriate.

[0082] The ammonia decomposition system 10 in this disclosure includes a computer system as a control unit 2. The computer system mainly consists of one or more processors and one or more memories as hardware. The functions of the control unit 2 in this disclosure are realized by the execution of a program recorded in the memory of the computer system by the processor. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided on a non-temporary recording medium such as a memory card, optical disk, or hard disk drive that can be read by the computer system. Furthermore, some or all of the functional parts included in the control unit 2 may be composed of electronic circuits.

[0083] Furthermore, it is not essential for the ammonia decomposition system 10 to have at least some of its functions integrated into a single housing; the components of the ammonia decomposition system 10 may be distributed across multiple housings. Conversely, functions that are distributed across multiple devices in Embodiment 1 may be integrated into a single housing.

[0084] Furthermore, at least a portion of the internal combustion engine system 100 is not limited to being mounted on the hull, but may be provided separately from the hull. For example, if the control unit 2 of the ammonia decomposition system 10 is implemented by a server device provided separately from the hull, the control unit 2 can control the internal combustion engine system 100 through communication between the server device and the hull (its communication device). At least a portion of the functions of the control unit 2 may be realized by the cloud (cloud computing), etc.

[0085] Furthermore, the vessels on which the internal combustion engine system 100 is installed are not limited to ocean-going vessels that can travel relatively long distances on a single refueling, but may also include, for example, small vessels used for sports or recreation at sea, such as "pleasure boats." In addition, the vessels on which the internal combustion engine system 100 is installed may include merchant ships, such as cargo ships and passenger-cargo ships; workboats, such as tugboats and salvage vessels; special vessels, such as weather observation vessels and training vessels; fishing vessels; and warships. Moreover, the vessels are not limited to manned vessels with an operator on board, but may also be unmanned vessels that can be remotely operated by a person (operator) or that can operate autonomously. Furthermore, in addition to the engine 101, the vessels may be equipped with one or more power sources such as motors (electric motors) in addition to the engine 101. The internal combustion engine system 100 may also be used in applications other than vessels, such as work machinery, vehicles, or flying objects.

[0086] Furthermore, the ammonia decomposition system 10 may be used in applications other than the internal combustion engine system 100. In other words, the use of the gas (hydrogen) obtained from the ammonia decomposition system 10 as fuel for the engine 101 is not an essential component of the ammonia decomposition system 10, and the gas (hydrogen or nitrogen) obtained by decomposing ammonia in the ammonia decomposition system 10 may be used in applications other than the engine 101. In this case, a tank (such as a hydrogen tank 102) for storing the gas obtained by decomposing ammonia in the ammonia decomposition system 10 may or may not be provided. Alternatively, the ammonia decomposition system 10 may be used for the purpose of decomposing ammonia, in which case the gas (hydrogen or nitrogen) obtained by decomposing ammonia may be exhausted.

[0087] Furthermore, it is sufficient for an electric field to be applied to the catalyst 11, and it is not essential that the decomposition unit 1 has a pair of electrodes 12 and 13; for example, the decomposition unit 1 may have only a single electrode 12. Moreover, it is not essential that the power supply unit 3 be included as a component of the ammonia decomposition system 10; a voltage may be applied to the catalyst 11 (between the pair of electrodes 12 and 13) from a power supply unit outside the ammonia decomposition system 10.

[0088] Furthermore, the inclusion of a control unit 2 for controlling the ammonia decomposition rate in the decomposition unit 1 is not an essential configuration for the ammonia decomposition system 10, and the control unit 2 may be omitted. Also, the presence of a catalyst 11 and electrodes 12 and 13 in the decomposition unit 1 is not an essential configuration for the ammonia decomposition system 10. The control unit 2 changing the decomposition rate by changing at least one of the temperature of the catalyst 11, the current value flowing through the catalyst 11, and the flow rate of ammonia passing through the catalyst 11 is also not an essential configuration for the ammonia decomposition system 10. The control unit 2 changing the decomposition rate by at least the current value such that the decomposition rate increases as the current value increases is also not an essential configuration for the ammonia decomposition system 10.

[0089] Furthermore, the heating section 4 for heating the catalyst is not an essential component of the ammonia decomposition system 10, and the heating section 4 may be omitted. The fact that the active metal of the catalyst 11 is one of Ru, Ni, Fe, or Co, and that the oxide of the catalyst 11 contains one of Ce, Zr, Ba, or Sr, is also not an essential component of the ammonia decomposition system 10. The fact that the oxide is one of CeO2, CexZr(1-x)O2, BaZrO3, or SrxBa(1-x)ZrO3 is also not an essential component.

[0090] Furthermore, using the waste heat from the engine 101 to heat the decomposition unit 1 is not an essential configuration for the internal combustion engine system 100. It is also not an essential configuration for the internal combustion engine system 100 that the engine 101 utilizes the hydrogen obtained in the decomposition unit 1 as at least part of its fuel. It is also not essential that the ammonia used as fuel for the engine 101 and the ammonia decomposed in the decomposition unit 1 are stored in a common tank; they may be stored in separate tanks.

[0091] (Embodiment 2) As shown in Figure 12, the internal combustion engine system 100A according to this embodiment differs from the internal combustion engine system 100 according to Embodiment 1 in that it does not use ammonia as fuel for the engine 101, but uses only hydrogen as fuel for the engine 101. Hereinafter, components similar to those in Embodiment 1 will be denoted by common reference numerals and their descriptions will be omitted as appropriate.

[0092] In other words, in this embodiment, the ammonia fuel supply device 105 (see Figure 1) for supplying ammonia to the engine 101 is omitted, and only hydrogen is supplied to the engine 101 as fuel. Therefore, in this embodiment, the engine 101 is a hydrogen-fueled internal combustion engine that generates power using hydrogen supplied from the hydrogen fuel supply device 103 as fuel. With this engine 101, compared to the case where a mixture of ammonia and hydrogen is used as fuel, the generation of unburned ammonia or greenhouse gases is suppressed, resulting in cleaner exhaust gas.

[0093] In the internal combustion engine system 100A according to this embodiment, the hydrogen used as fuel is obtained by decomposing ammonia in the ammonia decomposition system 10. Therefore, in this embodiment as well, fuel can be produced from (liquefied) ammonia stored in the ammonia tank 104, similar to Embodiment 1, making it possible to efficiently and safely supply hydrogen as fuel for the engine 101.

[0094] As a modification of Embodiment 2, the engine of the internal combustion engine system 100A may be a so-called dual-fuel engine (DF engine) that can accommodate either a premixed combustion method in which gaseous fuel (hydrogen) is mixed with air before being introduced into the combustion chamber of the engine 101, or a diffusion combustion method in which liquid fuel is injected into the combustion chamber of the engine 101 and burned. Here, the liquid fuel is, as an example, a fossil fuel (diesel oil or gasoline, etc.), a biofuel, or a synthetic fuel. More specifically, by using diesel oil, etc. as the liquid fuel, the internal combustion engine system 100 can accommodate either a gas mode using hydrogen as fuel or a diesel mode using diesel oil, etc. as fuel. Here, in the gas mode, a small amount of liquid fuel (diesel oil, etc.) may be used as ignition fuel.

[0095] The configuration according to Embodiment 2 (including modified versions) can be adopted in appropriate combination with the various configurations (including modified versions) described in Embodiment 1.

[0096] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0097] <Note 1> A decomposition unit that breaks down ammonia, The system includes a control unit that controls the ammonia decomposition rate in the decomposition unit, Ammonia decomposition system.

[0098] <Note 2> The aforementioned disassembly unit is A catalyst that decomposes ammonia, The catalyst has an electrode for applying an electric field, The ammonia decomposition system described in Appendix 1.

[0099] <Note 3> The control unit changes the decomposition rate by changing at least one of the temperature of the catalyst, the current value flowing through the catalyst, and the flow rate of ammonia passing through the catalyst. The ammonia decomposition system described in Appendix 2.

[0100] <Note 4> The control unit changes the decomposition rate at least according to the current value such that the decomposition rate increases as the current value increases. The ammonia decomposition system described in Appendix 3.

[0101] <Note 5> The system further comprises a heating section for heating the catalyst, The heating section sets the temperature of the catalyst in a range of 50°C or higher and 600°C or lower. An ammonia decomposition system as described in any of the appendices 2 to 4.

[0102] <Note 6> The catalyst comprises an active metal and an oxide, The active metal is one of Ru, Ni, Fe, or Co. The aforementioned oxide contains one of Ce, Zr, Ba, or Sr. An ammonia decomposition system as described in any of the appendices 2 to 5.

[0103] <Note 7> The aforementioned oxide is CeO2,Ce x Zr (1-x) O2, BaZrO3, Sr x Ba (1-x) It is one of the following ZrO3 The ammonia decomposition system described in Appendix 6.

[0104] <Note 8> An ammonia decomposition system described in any of Appendix 1 to 7, The system comprises an engine that is driven by a supply of gas output from the ammonia decomposition system, Internal combustion engine system.

[0105] <Note 9> The disassembly section is heated using the exhaust heat from the engine. The internal combustion engine system described in Appendix 8.

[0106] <Note 10> The engine utilizes the hydrogen obtained in the decomposition section as at least part of its fuel. An internal combustion engine system as described in Appendix 8 or 9.

[0107] <Note 11> The engine uses hydrogen obtained in the decomposition section and ammonia as fuel. The internal combustion engine system described in Appendix 10.

[0108] <Note 12> The ammonia used as fuel for the engine consists of ammonia decomposed in the decomposition unit and ammonia stored in a common tank. The internal combustion engine system described in Appendix 11. [Explanation of symbols]

[0109] 1 Disassembly part 2 Control Unit 4 Heating section 10 Ammonia decomposition system 11 Catalyst 12,13 electrode 100, 100A Internal Combustion Engine System 101 Engine 104 Ammonia tank (tank)

Claims

1. A decomposition unit that breaks down ammonia, The system comprises a control unit for controlling the ammonia decomposition rate in the decomposition unit, The aforementioned disassembly unit is A catalyst that decomposes ammonia, The catalyst has an electrode for applying an electric field, The control unit changes the decomposition rate by changing at least the current value flowing through the catalyst. Ammonia decomposition system.

2. The control unit further changes the decomposition rate by changing at least one of the temperature of the catalyst and the flow rate of ammonia passing through the catalyst. The ammonia decomposition system according to claim 1.

3. The control unit changes the decomposition rate at least according to the current value such that the decomposition rate increases as the current value increases. The ammonia decomposition system according to claim 1 or 2.

4. The system further comprises a heating section for heating the catalyst, The heating section sets the temperature of the catalyst in the range of 50°C or higher and 600°C or lower. The ammonia decomposition system according to claim 1 or 2.

5. The catalyst comprises an active metal and an oxide, The active metal is one of Ru, Ni, Fe, or Co. The oxide comprises any of Ce, Zr, Ba, or Sr. The ammonia decomposition system according to claim 1 or 2.

6. The oxide is CeO ２ Ce ｘ Zr （１－ｘ） O ２ , BaZrO ３ , Sr ｘ Ba （１－ｘ） ZrO ３ It is one of the following: The ammonia decomposition system according to claim 5.

7. The ammonia decomposition system according to claim 1, The system comprises an engine that is driven by a supply of gas output from the ammonia decomposition system, Internal combustion engine system.

8. The disassembly section is heated using the exhaust heat from the engine. The internal combustion engine system according to claim 7.

9. The engine utilizes the hydrogen obtained in the decomposition section as at least part of its fuel. The internal combustion engine system according to claim 7 or 8.

10. The engine uses hydrogen obtained in the decomposition section and ammonia as fuel. The internal combustion engine system according to claim 9.

11. The ammonia used as fuel for the engine consists of ammonia decomposed in the decomposition unit and ammonia stored in a common tank. The internal combustion engine system according to claim 10.

12. Decomposing ammonia in a decomposition unit having a catalyst for decomposing ammonia and an electrode for applying an electric field to the catalyst, The method involves controlling the ammonia decomposition rate in the decomposition section by changing the current value flowing through the catalyst, Methods for decomposing ammonia.

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