Ammonia synthesis system, method for synthesizing ammonia, and computer program

Abstract

This ammonia synthesis system comprises: a catalytic reactor that houses a first catalyst and a second catalyst for synthesizing ammonia from hydrogen and nitrogen, the temperatures of the first catalyst and the second catalyst being different from each other; and a gas supply unit that supplies a first starting material gas that contains hydrogen and nitrogen to the catalytic reactor. The catalytic reactor is connected to the gas supply unit and has a gas inlet through which the first starting material gas flows into the catalytic reactor. The first catalyst is disposed closer to the gas inlet side than the second catalyst and synthesizes ammonia using the first starting material gas supplied through the gas inlet. The second catalyst synthesizes ammonia using a second starting material gas that includes the gas supplied via the first catalyst.

Description

Ammonia synthesis system, ammonia synthesis method, and computer program

[0001] The present invention relates to an ammonia synthesis system, an ammonia synthesis method, and a computer program.

[0002] Conventionally, an ammonia synthesis system that synthesizes ammonia from hydrogen and nitrogen using a catalyst has been known (for example, Patent Documents 1 to 4).

[0003] Japanese Patent Publication No. 2023-526396, Japanese Patent Publication No. 2022-552632, Japanese Patent Publication No. 2023-508225, Japanese Unexamined Patent Application Publication No. 2023-37606

[0004] However, even with prior arts such as Patent Documents 1 to 4, there was still room for improvement in the technology for adjusting the amount of ammonia synthesized in the ammonia synthesis system.

[0005] The present invention has been made to solve the above-described problems, and an object thereof is to provide a technology for adjusting the amount of ammonia synthesized in an ammonia synthesis system.

[0006] The present invention has been made to solve at least part of the above-described problems and can be realized in the following forms.

[0007] (1) According to one aspect of the present invention, an ammonia synthesis system is provided. This ammonia synthesis system is a catalytic reactor that houses a first catalyst and a second catalyst that each synthesize ammonia from hydrogen and nitrogen, and the temperatures of the first catalyst and the second catalyst are different from each other. A catalytic reactor, and a gas supply unit that supplies a first raw material gas containing hydrogen and nitrogen to the catalytic reactor, the catalytic reactor is connected to the gas supply unit, and has a gas inlet for flowing the first raw material gas into the inside of the catalytic reactor. The first catalyst is disposed on the gas inlet side of the second catalyst, synthesizes ammonia from the first raw material gas supplied through the gas inlet, and the second catalyst synthesizes ammonia from a second raw material gas containing the gas supplied through the first catalyst.

[0008] In this configuration, a catalytic reactor for synthesizing ammonia from hydrogen and nitrogen contains a first catalyst and a second catalyst, each at a different temperature. Due to the difference in temperature, even when supplied with gases containing the same ratio of nitrogen to hydrogen, the amount of ammonia synthesized differs between the first and second catalysts, and the change in the amount of ammonia synthesized in response to a change in the nitrogen-to-hydrogen ratio also differs. The first catalyst is positioned closer to the gas inlet of the catalytic reactor than the second catalyst, where the first raw material gas containing hydrogen and nitrogen flows in. As a result, by changing the ratio of nitrogen to hydrogen in the first raw material gas supplied to the catalytic reactor, the amount of ammonia synthesized from the first raw material gas in the first catalyst and the amount of ammonia synthesized from the second raw material gas in the second catalyst are both changed. Therefore, by changing the ratio of nitrogen to hydrogen in the first raw material gas, the total amount of ammonia synthesized in the catalytic reactor can be adjusted.

[0009] (2) The ammonia synthesis system of the above form may further include a flow regulator that adjusts at least one of the amount of hydrogen and the amount of nitrogen contained in the first raw material gas, and a control unit that changes the ratio of nitrogen to hydrogen in the first raw material gas by controlling the flow regulator. With this configuration, the control unit can change the ratio of nitrogen to hydrogen in the first raw material gas by controlling the flow regulator that adjusts at least one of the amount of hydrogen and the amount of nitrogen contained in the first raw material gas. This makes it possible to adjust the amount of ammonia synthesized in the entire catalytic reactor.

[0010] (3) In the ammonia synthesis system of the above form, the control unit may control the flow rate regulator to change the ratio of nitrogen to hydrogen in the first raw material gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. With this configuration, the control unit controls the flow rate regulator to change the ratio of nitrogen to hydrogen in the first raw material gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. This makes it possible to adjust the amount of ammonia synthesized in the entire catalytic reactor in response to fluctuations in the flow rate of hydrogen supplied by the gas supply unit.

[0011] (4) In the ammonia synthesis system of the above form, the control unit may control the flow rate regulator so that the flow rate of the first raw material gas is reduced when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. With this configuration, the control unit controls the flow rate regulator to reduce the flow rate of the first raw material gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. This expands the range over which the amount of ammonia synthesized in the entire catalytic reactor can be adjusted.

[0012] (5) The ammonia synthesis system of the above form further includes a pressure regulator connected to the gas supply unit for adjusting the pressure of the first raw material gas, and the control unit may control the pressure regulator so that the pressure of the first raw material gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. With this configuration, the control unit controls the pressure regulator to decrease the pressure of the first raw material gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. This expands the range over which the amount of ammonia synthesized in the entire catalytic reactor can be adjusted.

[0013] (6) The ammonia synthesis system of the above form further includes a temperature controller connected to the gas supply unit for adjusting the temperature of the first raw material gas, and the control unit may control the temperature controller so that the temperature of the first raw material gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. With this configuration, the control unit controls the temperature controller to decrease the temperature of the first raw material gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. This expands the range over which the amount of ammonia synthesized in the entire catalytic reactor can be adjusted.

[0014] (7) In the ammonia synthesis system of the above form, the catalytic reactor has a gas outlet that discharges the synthesis gas containing ammonia released from the second catalyst from inside the catalytic reactor, and the ammonia synthesis system further includes a separator connected to the gas outlet that separates hydrogen and nitrogen contained in the synthesis gas from the synthesis gas, a recycle gas line that supplies the recycle gas containing the hydrogen and nitrogen separated in the separator to the catalytic reactor as part of the first raw material gas, and a hydrogen concentration detector that detects the hydrogen concentration of the recycle gas, and the control unit may control the flow regulator using the hydrogen concentration of the recycle gas detected by the hydrogen concentration detector. This allows for highly precise adjustment of the ratio of nitrogen to hydrogen in the first raw material gas supplied to the catalytic reactor, thereby enabling precise control of the amount of ammonia synthesized throughout the catalytic reactor.

[0015] (8) The ammonia synthesis system of the above form may further include a synthesis gas concentration detector for detecting the ammonia concentration of the synthesis gas, and the control unit may control the nitrogen flow regulator using the ammonia concentration of the synthesis gas detected by the synthesis gas concentration detector. With this configuration, the ammonia synthesis system includes a synthesis gas concentration detector for detecting the ammonia concentration of the synthesis gas. The control unit controls the flow regulator using the ammonia concentration of the synthesis gas detected by the synthesis gas concentration detector. This makes it possible to change the ratio of nitrogen to hydrogen in the first raw material gas supplied to the catalytic reactor with even greater precision, and thus the amount of ammonia synthesized in the entire catalytic reactor can be adjusted with high precision.

[0016] (9) In the ammonia synthesis system of the above form, the catalytic reactor comprises a gas outlet for discharging synthesis gas containing ammonia released from the second catalyst from the inside of the catalytic reactor, and an intermediate gas outlet for discharging the second raw material gas from the inside of the catalytic reactor, and the ammonia synthesis system further comprises a synthesis gas line connected to the gas outlet, a first control valve connected to the synthesis gas line for controlling the flow of the synthesis gas in the synthesis gas line, an intermediate synthesis gas line connected to the intermediate gas outlet, a second control valve connected to the intermediate synthesis gas line for controlling the flow of the second raw material gas in the intermediate synthesis gas line, and a control unit for controlling the first control valve and the second control valve, respectively, which blocks the flow of the synthesis gas in the synthesis gas line and allows the flow of the second raw material gas in the intermediate synthesis gas line. In this configuration, the catalytic reactor includes a gas outlet that allows synthesis gas containing ammonia released from the second catalyst to flow out from the inside of the catalytic reactor, and an intermediate gas outlet that allows a second raw material gas containing ammonia released from the first catalyst to flow out. The control unit controls the first control valve and the second control valve respectively, and by allowing the second raw material gas to flow out from the intermediate gas outlet, the synthesis of ammonia by the second catalyst is suppressed. As a result, the amount of ammonia synthesized in the catalytic reactor as a whole can be reduced, and thus the amount of ammonia synthesized in the catalytic reactor as a whole can be adjusted.

[0017] (10) In the ammonia synthesis system of the above form, the catalytic reactor includes an intermediate gas inlet for introducing a divided gas containing either hydrogen or nitrogen supplied by the gas supply unit between the first catalyst and the second catalyst inside the catalytic reactor, and a gas outlet for introducing a synthesis gas containing ammonia released from the second catalyst out from inside the catalytic reactor, and the ammonia synthesis system may further include a divided gas line connected to the intermediate gas inlet, a divided gas control valve connected to the divided gas line for controlling the flow of the divided gas in the divided gas line, and a control unit for controlling the divided gas control valve, which allows the flow of the divided gas in the divided gas line. According to this configuration, the catalytic reactor includes a gas outlet for introducing a synthesis gas containing ammonia released from the second catalyst out from inside the catalytic reactor, and an intermediate gas inlet for introducing a divided gas containing either hydrogen or nitrogen between the first catalyst and the second catalyst. The control unit controls the split gas control valve to change the ratio of nitrogen to hydrogen in the first or second raw material gas, thereby controlling the synthesis of ammonia in the first or second catalyst. This allows for adjustment of the total amount of ammonia synthesized throughout the catalytic reactor.

[0018] (11) The ammonia synthesis system of the above form further includes a temperature controller connected to the divided gas line for adjusting the temperature of the divided gas, and the control unit may control the temperature controller so as to reduce the temperature of the divided gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. With this configuration, the control unit reduces the temperature of the divided gas by controlling the temperature controller for adjusting the temperature of the divided gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. This expands the range over which the amount of ammonia synthesized in the entire catalytic reactor can be adjusted.

[0019] (12) According to another embodiment of the present invention, a method for synthesizing ammonia is provided, which synthesizes ammonia using an ammonia synthesis system. This method for synthesizing ammonia comprises the steps of supplying a first raw material gas containing hydrogen and nitrogen to a catalytic reactor, and synthesizing ammonia from hydrogen and nitrogen using a first catalyst and a second catalyst housed in the catalytic reactor, each having different temperatures, wherein the first catalyst synthesizes ammonia from the first raw material gas, and the second catalyst synthesizes ammonia from a second raw material gas containing the gas supplied via the first catalyst. With this configuration, the catalytic reactor for synthesizing ammonia from hydrogen and nitrogen houses a first catalyst and a second catalyst, each having different temperatures. As a result, by changing the ratio of nitrogen to hydrogen in the first raw material gas, the amount of ammonia synthesized by the first catalyst and the amount of ammonia synthesized by the second catalyst are changed, and the total amount of ammonia synthesized in the catalytic reactor can be adjusted.

[0020] (13) According to yet another embodiment of the present invention, a computer program is provided which causes a computer to perform the synthesis of ammonia using an ammonia synthesis system. The computer program causes the computer to perform the following functions: supplying a first raw material gas containing hydrogen and nitrogen to a catalytic reactor; and synthesizing ammonia from hydrogen and nitrogen using a first catalyst and a second catalyst housed in the catalytic reactor, each having different temperatures, wherein the first catalyst synthesizes ammonia from the first raw material gas, and the second catalyst synthesizes ammonia from a second raw material gas containing the gas supplied via the first catalyst. With this configuration, the catalytic reactor for synthesizing ammonia from hydrogen and nitrogen houses a first catalyst and a second catalyst, each having different temperatures. As a result, by changing the ratio of nitrogen to hydrogen in the first raw material gas, the amount of ammonia synthesized by the first catalyst and the amount of ammonia synthesized by the second catalyst are changed, and the total amount of ammonia synthesized in the catalytic reactor can be adjusted.

[0021] Furthermore, the present invention can be realized in various forms, for example, as a catalytic reactor included in an ammonia synthesis system, an ammonia synthesis method for synthesizing ammonia using the catalytic reactor, a control method for the ammonia synthesis system, a computer program for executing ammonia synthesis in the catalytic reactor and the ammonia synthesis system, a server device for distributing the computer program, and a non-temporary storage medium storing the computer program.

[0022] This is a schematic diagram showing the general configuration of the ammonia synthesis system of the first embodiment. This is a diagram illustrating the characteristics of the Ru-based catalyst. This is a flowchart of the ammonia synthesis method of the first embodiment. This is a diagram illustrating the ammonia synthesis method of the first embodiment. This is the first diagram illustrating the ammonia synthesis method of the second embodiment. This is the second diagram illustrating the ammonia synthesis method of the second embodiment. This is a schematic diagram showing the general configuration of the ammonia synthesis system of the third embodiment. This is the first diagram illustrating the ammonia synthesis method of the third embodiment. This is the second diagram illustrating the ammonia synthesis method of the third embodiment. This is a schematic diagram showing the general configuration of the ammonia synthesis system of the fourth embodiment. This is the first diagram illustrating the ammonia synthesis method of the fourth embodiment. This is the second diagram illustrating the ammonia synthesis method of the fourth embodiment. This is a schematic diagram showing the general configuration of the ammonia synthesis system of the fifth embodiment. This is a flowchart of the ammonia synthesis method of the fifth embodiment. This is the first diagram illustrating the ammonia synthesis method of the fifth embodiment. This is the second diagram illustrating the ammonia synthesis method of the fifth embodiment. This is a schematic diagram showing the general configuration of the ammonia synthesis system of the sixth embodiment. This is a diagram illustrating the ammonia synthesis method of the sixth embodiment. This is a schematic diagram showing a general configuration of a modified example of the ammonia synthesis system of the first embodiment.

[0023] <First Embodiment> Figure 1 is a schematic diagram showing the general configuration of the ammonia synthesis system of this embodiment. The ammonia synthesis system 1 of this embodiment uses hydrogen (H ２ ) and nitrogen (N ２ ) and ammonia (NH ３The system comprises a catalytic reactor 10 for synthesizing ammonia, a separator 20 for separating ammonia from the synthesis gas extracted from the catalytic reactor 10, a control unit 30 for controlling each part of the ammonia synthesis system 1, and a plurality of gas lines (gas piping) connecting the catalytic reactor 10 and the separator 20.

[0024] A raw material gas line 41 is connected to the catalytic reactor 10, supplying a gas containing hydrogen and nitrogen to the catalytic reactor 10. As shown in Figure 1, the raw material gas line 41 is connected to the water electrolysis device 40a and the nitrogen tank 40b, respectively. A hydrogen flow detector 41a, which detects the flow rate of hydrogen supplied by the water electrolysis device 40a, and a nitrogen flow regulator 41b, which controls the flow rate of nitrogen supplied by the nitrogen tank 40b are connected to the raw material gas line 41a. The hydrogen flow detector 41a and the nitrogen flow regulator 41b are each electrically connected to the control unit 30. The hydrogen flow detector 41a outputs the flow rate of hydrogen supplied by the water electrolysis device 40a to the control unit 30. The nitrogen flow regulator 41b controls the flow rate of nitrogen supplied by the nitrogen tank 40b in response to a command from the control unit 30. A compressor 41c is connected to the raw material gas line 41, which compresses the gas flowing through the raw material gas line 41 to a predetermined pressure. The raw material gas line 41 corresponds to the "gas supply section" in the claims.

[0025] The water electrolyzer 40a that supplies hydrogen to the ammonia synthesis system 1 of this embodiment uses electricity generated by sunlight or wind power to electrolyze water and produce hydrogen. Therefore, the flow rate of hydrogen supplied by the water electrolyzer 40a is easily affected by weather and tends to fluctuate. In the ammonia synthesis system 1 of this embodiment, the control unit 30 controls the nitrogen flow regulator 41b according to the flow rate of hydrogen supplied by the water electrolyzer 40a, and adjusts the flow rate of nitrogen supplied by the nitrogen tank 40b. Details of the control by the control unit 30 will be described later.

[0026] The catalytic reactor 10 houses a first catalyst 11 and a second catalyst 12. Each of the first catalyst 11 and the second catalyst 12 synthesizes ammonia from hydrogen and nitrogen. The catalytic reactor 10 is connected to a raw material gas line 41 and has a gas inlet 10a that allows the gas flowing through the raw material gas line 41 to flow into the inside of the catalytic reactor 10, and a gas outlet 10b that allows the gas containing ammonia synthesized by each of the first catalyst 11 and the second catalyst 12 to flow out. In the catalytic reactor 10 of this embodiment, the first catalyst 11 is positioned on the gas inlet 10a side of the second catalyst 12 inside the catalytic reactor 10. That is, in the gas flow inside the catalytic reactor 10, the first catalyst 11 is positioned upstream and the second catalyst 12 is positioned downstream. As a result, the first catalyst 11 synthesizes ammonia using a gas containing hydrogen and nitrogen supplied through the gas inlet 10a. The second catalyst 12 synthesizes ammonia using a gas supplied via the first catalyst 11, which contains ammonia synthesized by the first catalyst 11 and unreacted hydrogen and nitrogen. The gas supplied to the second catalyst 12, which contains ammonia synthesized and released by the first catalyst 11 and unreacted hydrogen and nitrogen in the first catalyst 11, corresponds to the "second raw material gas" in the claims.

[0027] In this embodiment, the first catalyst 11 and the second catalyst 12 are both Ru-based catalysts containing ruthenium (Ru). In the catalytic reactor 10, when hydrogen and nitrogen are supplied, ammonia is synthesized by the chemical reaction shown in the following formula (1) involving the Ru-based catalyst. In the catalytic reactor 10 of this embodiment, not all of the hydrogen and nitrogen entering the catalytic reactor 10 is converted into ammonia at once. Therefore, the synthesis gas containing ammonia, which is taken out from the gas outlet 10b of the catalytic reactor 10, contains unreacted hydrogen and nitrogen in addition to ammonia. ２ +3H ２ = 2NH ３ ... (1)

[0028] Figure 2 illustrates the characteristics of Ru-based catalysts. Figure 2 shows the relationship between the ratio of hydrogen atom concentration to nitrogen atom concentration (hereinafter simply referred to as the "hydrogen ratio") and the amount of ammonia synthesized in the ammonia synthesis reaction using a Ru-based catalyst. In Figure 2, the horizontal axis represents the hydrogen ratio as "H / N," and the vertical axis represents the amount of ammonia synthesized. Figure 2 shows the relationship between the hydrogen ratio and the amount of ammonia synthesized when the Ru-based catalyst temperature is relatively high (400-500°C) with the solid line H0, and the relationship between the hydrogen ratio and the amount of ammonia synthesized when the Ru-based catalyst temperature is relatively low (300-400°C) with the solid line L0. Figure 2 also shows the equilibrium concentration for the above-mentioned equation (1) when the Ru-based catalyst temperature is relatively high, represented by the dashed line Deq. Note that the equilibrium concentration when the Ru-based catalyst temperature is relatively low is not shown in Figure 2, but it is greater than the equilibrium concentration Deq.

[0029] Ru-based catalysts exhibit different catalytic activity depending on the hydrogen ratio. Specifically, because hydrogen molecules readily adsorb to the surface of ruthenium atoms, the catalytic activity of Ru-based catalysts improves when the hydrogen partial pressure is low, i.e., when the hydrogen ratio is small. Furthermore, when the Ru-based catalyst's temperature is relatively high, the amount of ammonia synthesized reaches the equilibrium concentration (the dashed line Deq shown in Figure 2), so the catalytic activity does not increase significantly in the range of relatively low hydrogen ratios. Therefore, the catalytic activity of Ru-based catalysts at relatively high temperatures is maximized at the hydrogen ratio Rsp, as shown by the solid line H0 in Figure 2. On the other hand, when the temperature is relatively low, the catalytic activity is lower than at relatively high temperatures, and as mentioned above, the equilibrium concentration is higher than at relatively high temperatures, making it difficult for the amount of ammonia synthesized to reach the equilibrium concentration. Therefore, the catalytic activity of Ru-based catalysts at relatively low temperatures increases as the hydrogen ratio decreases, as shown by the solid line L0 in Figure 2.

[0030] In the catalytic reactor 10 of this embodiment, the temperature of the first catalyst 11 is set to be higher than the temperature of the second catalyst 12. In this embodiment, for example, the temperature of the first catalyst 11 is set to 450°C, and the temperature of the second catalyst 12 is set to 350°C. As a result, the first catalyst 11 synthesizes an amount of ammonia corresponding to the solid line H0 shown in Figure 2, and the second catalyst 12 synthesizes an amount of ammonia corresponding to the solid line L0 shown in Figure 2, corresponding to the hydrogen ratio in the gas flowing into the catalytic reactor 10 through the gas inlet 10a. Therefore, the amount of ammonia removed from the inside of the catalytic reactor 10 through the gas outlet 10b is the sum of the amount of ammonia synthesized by the first catalyst 11 and the amount synthesized by the second catalyst 12. In this embodiment, the first catalyst 11 and the second catalyst 12 are heated by the heat of the gas supplied to the catalytic reactor 10. Note that the temperatures of the first catalyst 11 and the second catalyst 12 are not limited to those caused by the heat of the supplied gas. The catalytic reactor 10 may have temperature controllers that can adjust the temperatures of the first catalyst 11 and the second catalyst 12, respectively.

[0031] The catalytic reactor 10 and the separator 20 are connected by a synthesis gas line 42. A gas concentration detector 42a is connected to the synthesis gas line 42. The gas concentration detector 42a detects the ammonia concentration of the synthesis gas flowing through the synthesis gas line 42. The gas concentration detector 42a is electrically connected to a control unit 30, which will be described later. The gas concentration detector 42a outputs the ammonia concentration detection result to the control unit 30.

[0032] The separator 20 is a so-called gas-liquid separator. In the separator 20, the synthesis gas extracted from the catalytic reactor 10 is cooled and the ammonia contained in the synthesis gas is liquefied. As a result, the synthesis gas is separated into liquid ammonia and gaseous hydrogen and nitrogen. The liquid ammonia is compressed by a compressor (not shown) and supplied to an ammonia use site (not shown) via an external supply line 43. The gaseous hydrogen and nitrogen flow through a recycle gas line 44 connected to the separator 20.

[0033] The recycle gas line 44 is a gas line capable of returning at least a portion of the recycle gas, which contains gaseous hydrogen and nitrogen, back to the raw gas line 41. The recycle gas line 44 is connected to the separator 20 and the raw gas line 41. Specifically, the recycle gas line 44 is connected upstream of the compressor 41c in the raw gas line 41. A recycle gas flow regulator 44a is connected to the recycle gas line 44. The recycle gas flow regulator 44a is electrically connected to the control unit 30. The recycle gas flow regulator 44a controls the flow rate of the recycle gas flowing through the recycle gas line 44 in response to commands from the control unit 30.

[0034] A purge gas line 45 is connected to the recycle gas line 44, which purges at least a portion of the recycle gas from the ammonia synthesis system 1. A gas concentration detector 45a is connected to the purge gas line 45. The gas concentration detector 45a detects the hydrogen concentration of the purge gas flowing through the purge gas line 45. Since the purge gas is a portion of the recycle gas discharged by the separator 20, the hydrogen concentration of the purge gas detected by the gas concentration detector 45a is the same as the hydrogen concentration of the recycle gas. The gas concentration detector 45a is electrically connected to a control unit 30, which will be described later. The gas concentration detector 45a outputs the hydrogen concentration detection result to the control unit 30.

[0035] The control unit 30 is a computer comprising ROM, RAM, and CPU. The control unit 30 is electrically connected to the hydrogen flow detector 41a, nitrogen flow regulator 41b, recycled gas flow regulator 44a, gas concentration detectors 42a and 45a, etc. The control unit 30 is constantly input with the hydrogen flow rate detected by the hydrogen flow detector 41a, the ammonia concentration detected by the gas concentration detector 42a, and the hydrogen concentration detected by the gas concentration detector 45a. The control unit 30 loads a computer program stored in a ROM (Read Only Memory) (not shown) into the RAM (Random Access Memory) and executes it using this information to produce ammonia using the ammonia synthesis system 1.

[0036] Next, a method for synthesizing ammonia using the ammonia synthesis system 1 of this embodiment will be described. In the ammonia synthesis system 1 of this embodiment, ammonia is synthesized in the catalytic reactor 10 using hydrogen supplied by the water electrolysis device 40a and nitrogen supplied by the nitrogen tank 40b. When ammonia synthesis by the ammonia synthesis system 1 is performed in steady-state operation, the ratio of the amount of hydrogen supplied from the water electrolysis device 40a to the amount of nitrogen supplied from the nitrogen tank 40b is 3, which is the same as the ratio of hydrogen atoms to nitrogen atoms in ammonia. On the other hand, since the conversion rate of the ammonia synthesis reaction shown in equation (1) is relatively low, the ammonia synthesis system 1 returns unreacted hydrogen and nitrogen to the raw material gas line 41 via the recycling gas line 44. As a result, in this embodiment, the hydrogen ratio in the gas supplied to the catalytic reactor 10 is a hydrogen ratio Rh0 which is less than 3. Here, for convenience, the raw material gas line 41 is defined as the raw material gas supply line 411, located on the side of the water electrolysis device 40a and the nitrogen tank 40b from the confluence point P1 (see Figure 1) where unreacted hydrogen and nitrogen from the recycle gas line 44 merge, and the raw material gas line 41 located on the side of the catalytic reactor 10 from the confluence point P1. The raw material gas supply line 411 carries hydrogen supplied by the water electrolysis device 40a and nitrogen supplied by the nitrogen tank 40b. Hereinafter, the gas flowing through the raw material gas supply line 411 will be referred to as "raw material gas". The raw material gas mixing line 412 carries a gas which is the raw material gas plus hydrogen and nitrogen from the recycle gas line 44. The gas flowing through the raw material gas mixing line 412 is the gas supplied to the catalytic reactor 10 and is the gas that passes through the gas inlet 10a of the catalytic reactor 10. Hereinafter, the gas flowing through the raw material gas mixing line 412 will be referred to as "reactor inlet gas". The reactor inlet gas is a gas containing hydrogen and nitrogen that flows into the catalytic reactor 10 through the gas inlet 10a as described above. The reactor inlet gas corresponds to the "first raw material gas" in the claims.

[0037] In the ammonia synthesis system 1 of this embodiment, as described above, the electricity supplied to the water electrolyzer 40a is generated using sunlight or wind power, so the flow rate of hydrogen supplied by the water electrolyzer 40a is prone to change depending on the weather and time of day. When the control unit of the water electrolyzer 40a (not shown), which controls the water electrolyzer 40a, plans to change the amount of electricity supplied to the water electrolyzer 40a based on weather forecasts such as weather reports, it also changes the hydrogen supply plan that can be supplied from the water electrolyzer 40a to the ammonia synthesis system 1. When the control unit 30 receives the changed hydrogen supply plan from the control unit of the water electrolyzer 40a, it changes the ammonia production plan in the ammonia synthesis system 1. In other words, in the ammonia synthesis system 1 of this embodiment, if there is a prediction that the amount of hydrogen supplied by the water electrolyzer 40a will decrease in the future, the amount of ammonia synthesized can be systematically reduced even if the amount of hydrogen supplied by the water electrolyzer 40a at present has not fallen below a preset threshold. The ammonia synthesis method using the ammonia synthesis system 1 of this embodiment is performed by the control unit 30 changing the ammonia production plan in the ammonia synthesis system 1.

[0038] Figure 3 is a flowchart of the ammonia synthesis method of this embodiment. In the ammonia synthesis method of this embodiment, first, it is determined whether or not to change the hydrogen ratio (H / N) of the reactor inlet gas (step S11). In step S11, the control unit 30 uses information regarding the operating state of the ammonia synthesis system 1 to determine whether or not to change the hydrogen ratio of the reactor inlet gas. In this embodiment, the control unit 30 uses information regarding the hydrogen supply plan input from the control unit of the water electrolysis device 40a to determine whether or not to change the hydrogen ratio of the reactor inlet gas supplied to the catalytic reactor 10. In the hydrogen supply plan input from the control unit of the water electrolysis device 40a, if the flow rate (supply amount) of hydrogen supplied by the water electrolysis device 40a to the ammonia synthesis system 1 becomes smaller than a preset threshold, the operation of the ammonia synthesis system 1 may become unstable. Therefore, the ammonia synthesis system 1 of this embodiment reduces the amount of ammonia synthesized in the catalytic reactor 10 by changing the hydrogen ratio of the reactor inlet gas. This makes it possible to suppress the ammonia synthesis system 1 from becoming unstable. If the control unit 30 determines that the hydrogen ratio of the reactor inlet gas should be changed (step S11: YES), the process proceeds to step S12. If the control unit 30 determines that the hydrogen ratio of the reactor inlet gas should not be changed (step S11: NO), the flow of the ammonia synthesis method shown in Figure 3 is terminated.

[0039] In step S11, if the control unit 30 determines that the hydrogen ratio of the reactor inlet gas should be changed, it changes the hydrogen ratio (H / N) of the raw material gas (step S12). In step S12, the control unit 30 controls the nitrogen flow regulator 41b to change the hydrogen ratio of the raw material gas. As a result, the hydrogen ratio of the reactor inlet gas is ultimately changed, and the amount of ammonia synthesized in the catalytic reactor 10 is changed. In this embodiment, the control unit 30 has map A showing the relationship between the hydrogen ratio of the reactor inlet gas and the amount of ammonia synthesized in the catalytic reactor 10, and map B showing the relationship between the hydrogen ratio of the reactor inlet gas and the hydrogen ratio of the raw material gas.

[0040] Figure 4 is a diagram illustrating the ammonia synthesis method of this embodiment. Figure 4 shows a portion of Map A, which illustrates the relationship between the hydrogen ratio of the reactor inlet gas and the amount of ammonia synthesized in the catalytic reactor 10 in the ammonia synthesis method of this embodiment. In Figure 4, the horizontal axis shows the hydrogen ratio of the reactor inlet gas as "H / N", and the vertical axis shows the amount of ammonia synthesized. In Figure 4, the amount of ammonia synthesized by the first catalyst 11 is shown by the solid line MC1, the amount of ammonia synthesized by the second catalyst 12 is shown by the solid line MC2, and the amount of ammonia synthesized in the catalytic reactor 10 is shown by the solid line Mtotal. The amount of ammonia synthesized in the catalytic reactor 10, Mtotal, is the sum of the amount of ammonia synthesized by the first catalyst 11 (MC1) and the amount of ammonia synthesized by the second catalyst 12 (MC2). Figure 4 also shows the equilibrium concentration Deq of equation (1) when the ambient temperature is relatively high (400-500°C), as also shown in Figure 2.

[0041] As described above, in the ammonia synthesis system 1 during steady-state operation, the hydrogen ratio of the reactor inlet gas is Rh0. As a result, in the ammonia synthesis system 1 of this embodiment, the total amount of ammonia synthesized in the catalytic reactor 10 is maximized. In contrast, as explained in Figure 2, if the hydrogen ratio of the reactor inlet gas is set to a hydrogen ratio Rh11, which is lower than Rh0, the amount of ammonia synthesized in the second catalyst 12, which has a relatively small ammonia synthesis rate, increases, but the amount of ammonia synthesized in the first catalyst 11, which has a relatively large ammonia synthesis rate, decreases. Therefore, the total amount of ammonia synthesized in the catalytic reactor 10 decreases. Also, if the hydrogen ratio of the reactor inlet gas is set to a hydrogen ratio Rh12, which is greater than Rh0, the amount of ammonia synthesized in both the first catalyst 11 and the second catalyst 12 decreases, so the total amount of ammonia synthesized in the catalytic reactor 10 decreases. In the ammonia synthesis method of this embodiment, a map A, as shown in Figure 4, is used to calculate the hydrogen ratio of the reactor inlet gas to reduce the amount of ammonia synthesized in the catalytic reactor 10, using a map that shows the relationship between the hydrogen ratio of the reactor inlet gas and the amount of ammonia synthesized in the catalytic reactor 10 as Map A.

[0042] The ammonia synthesis system 1 of this embodiment includes a recycle gas line 44 that returns at least a part of the recycle gas in a gaseous state, in which hydrogen and nitrogen separated from the synthesis gas in the separator 20 are mixed, to the raw material gas line 41. Therefore, the hydrogen ratio of the reactor inlet gas is a value considering the hydrogen ratio of the raw material gas and the hydrogen ratio of the recycle gas. Thus, in step S12, the control unit 30 uses the hydrogen ratio of the reactor inlet gas for reducing the synthesis amount of ammonia calculated using map A and map B showing the relationship between the hydrogen ratio of the reactor inlet gas and the hydrogen ratio of the raw material gas to calculate the hydrogen ratio of the raw material gas.

[0043] In step S12, the control unit 30 calculates the hydrogen ratio of the reactor inlet gas (hereinafter referred to as "target hydrogen ratio") suitable for the flow rate of hydrogen supplied from the water electrolysis device 40a using map A and map B. The control unit 30 controls the nitrogen flow rate regulator 41b using the calculated target hydrogen ratio to change the hydrogen ratio of the raw material gas flowing through the raw material gas supply line 411. When the hydrogen ratio of the raw material gas flowing through the raw material gas supply line 411 is changed, the hydrogen ratio of the reactor inlet gas temporarily changes, so the hydrogen ratio of the synthesis gas flowing through the synthesis gas line 42 also changes. When the hydrogen ratio of the synthesis gas changes, the hydrogen ratio of the recycle gas flowing through the recycle gas line 44 also changes, so the hydrogen ratio of the recycle gas flowing through the recycle gas line 44 also changes, and the hydrogen ratio of the reactor inlet gas flowing through the raw material gas mixing line 412 changes.

[0044] In the ammonia synthesis system 1 of the present embodiment, when the flow rate of hydrogen supplied from the water electrolysis device 40a becomes smaller than a preset threshold value, the nitrogen flow rate regulator 41b is controlled to reduce the flow rate of nitrogen supplied from the nitrogen tank 40b, thereby increasing the hydrogen ratio of the reactor inlet gas. In the present embodiment, the control unit 30 also controls the recycle gas flow rate regulator 44a to increase the flow rate of the recycle gas so as to compensate for the reduction in the flow rate of the reactor inlet gas due to the control of the nitrogen flow rate by the nitrogen flow rate regulator 41b. As a result, the flow rate of the reactor inlet gas supplied to the catalytic reactor 10 does not change significantly, and it is possible to suppress the operation of the ammonia synthesis system 1 from becoming unstable.

[0045] Next to step S12, the composition of the recycle gas is analyzed (step S13). In step S13, the control unit 30 calculates the hydrogen ratio of the recycle gas using the detection result of the hydrogen concentration of the gas concentration detector 45a connected to the purge gas line 45. Also in step S13, the control unit 30 calculates the amount of ammonia synthesized in the catalytic reactor 10 using the detection result of the ammonia concentration of the gas concentration detector 42a connected to the synthesis gas line 42.

[0046] Following step S13, step S14 determines whether the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio (H / N). In step S14, the control unit 30 uses the results of the compositional analysis of the synthesis gas and recycled gas in step S13 to determine whether the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio. The control unit 30 checks the flow rate of hydrogen supplied by the water electrolysis device 40a using the hydrogen flow rate detector 41a, and detects the hydrogen concentration of the recycled gas flowing through the recycled gas line 44 using the gas concentration detector 45a. The hydrogen concentration of the recycled gas is a value related to the amount of ammonia synthesized in the catalytic reactor 10, that is, the hydrogen ratio of the reactor inlet gas. Therefore, the control unit 30 uses the hydrogen concentration of the recycled gas flowing through the recycled gas line 44 to determine whether the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio. If the control unit 30 determines that the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio (step S14: YES), the process proceeds to step S15. As the hydrogen ratio of the reactor inlet gas reaches the target hydrogen ratio, the amount of ammonia synthesized in the catalytic reactor 10 becomes smaller than in the state before the change in the hydrogen ratio of the reactor inlet gas (steady state). If the control unit 30 determines that the hydrogen ratio of the reactor inlet gas is not the target hydrogen ratio (step S14: NO), the process returns to step S12, and the hydrogen ratio of the raw material gas is further changed (step S12).

[0047] In step S14, when it is determined that the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio, the hydrogen ratio (H / N) of the raw material gas is set to 3 (step S15). The control unit 30's determination that the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio means that the synthesis of ammonia in the catalytic reactor 10 is proceeding stably. Therefore, by setting the hydrogen ratio of the raw material gas to 3, the ammonia synthesis system 1 is brought into a steady-state operation state. In this way, the ammonia synthesis system 1 of this embodiment can adjust the amount of ammonia synthesized without significantly changing the flow rate or pressure of the gas supplied to the catalytic reactor 10.

[0048] Ammonia can sometimes be continuously synthesized using the Haber-Bosch process, which employs a catalyst, from hydrogen and nitrogen produced by the reforming reaction of natural gas. However, the Haber-Bosch process is ideally suited to continuous operation at 100% load, and fluctuations in the supply of hydrogen and nitrogen significantly alter the amount of ammonia synthesized. This makes the pressure and temperature within the catalytic reactor unstable and difficult to control, and rapid changes in pressure and temperature can damage the catalyst and the catalytic reactor containing it. On the other hand, when synthesizing ammonia using hydrogen produced by the electrolysis of water using renewable energy, which can suppress carbon dioxide emissions, the amount of hydrogen produced fluctuates significantly due to weather conditions. Therefore, to prevent fluctuations in hydrogen production from affecting the amount of ammonia synthesized, for example, a relatively large intermediate hydrogen storage tank is required, which adds further space and cost.

[0049] The ammonia synthesis system 1 of this embodiment includes a first catalyst 11 and a second catalyst 12 that operate at different temperature ranges for ammonia synthesis, such that the change in the amount of ammonia synthesized differs depending on the change in the hydrogen ratio of the gas supplied to the catalytic reactor 10. Specifically, as explained with reference to Figure 2, the first catalyst 11, which operates at a relatively high temperature, has catalytic activity that changes to have a maximum value at a specific hydrogen ratio, while the second catalyst 12, which operates at a relatively low temperature, has catalytic activity that decreases as the hydrogen ratio increases. The ammonia synthesis system 1 of this embodiment can adjust the amount of ammonia synthesized in the catalytic reactor 10 by changing the hydrogen ratio of the reactor inlet gas, even when the amount of hydrogen produced in the water electrolysis device 40a changes.

[0050] As described above, in the ammonia synthesis system 1 of this embodiment, the catalytic reactor 10 for synthesizing ammonia from hydrogen and nitrogen contains a first catalyst 11 and a second catalyst 12, each having a different temperature. Due to the difference in temperature, even when supplied with gases having the same hydrogen ratio, the first catalyst 11 and the second catalyst 12 not only produce different amounts of ammonia, but also experience different changes in the amount of ammonia produced in response to changes in the hydrogen ratio. In the catalytic reactor 10, the first catalyst 11 is positioned closer to the gas inlet 10a than the second catalyst 12. As a result, by changing the hydrogen ratio in the reactor inlet gas supplied to the catalytic reactor 10, the amount of ammonia synthesized in the first catalyst 11 from the reactor inlet gas and the amount of ammonia synthesized in the second catalyst 12 from the gas released from the first catalyst 11 are both changed. Therefore, by changing the hydrogen ratio in the reactor inlet gas, the total amount of ammonia synthesized in the catalytic reactor 10 can be adjusted.

[0051] Furthermore, according to the ammonia synthesis system 1 of this embodiment, the control unit 30 can change the hydrogen ratio in the reactor inlet gas by controlling the nitrogen flow regulator 41b, which adjusts the amount of nitrogen contained in the reactor inlet gas. This makes it possible to adjust the amount of ammonia synthesized throughout the catalytic reactor 10.

[0052] Furthermore, according to the ammonia synthesis system 1 of this embodiment, the control unit 30 controls the nitrogen flow regulator 41b to change the hydrogen ratio in the reactor inlet gas when the flow rate of hydrogen supplied by the water electrolyzer 40a falls below a preset threshold. This makes it possible to adjust the amount of ammonia synthesized in the entire catalytic reactor 10 in accordance with fluctuations in the flow rate of hydrogen supplied by the water electrolyzer 40a.

[0053] Furthermore, according to the ammonia synthesis system 1 of this embodiment, the ammonia synthesis system 1 includes a recycle gas line 44 that separates hydrogen and nitrogen contained in the synthesis gas and returns them to the catalytic reactor 10 as part of the reaction inlet gas. A gas concentration detector 45a for detecting the hydrogen concentration of the recycle gas is connected to a purge gas line 45 that is connected to the recycle gas line 44. The control unit 30 controls the nitrogen flow regulator 41b using the hydrogen concentration of the recycle gas detected by the gas concentration detector 45a. This makes it possible to change the hydrogen ratio in the reactor inlet gas supplied to the catalytic reactor 10 with high precision, and thus the amount of ammonia synthesized in the catalytic reactor 10 as a whole can be adjusted with high precision.

[0054] Furthermore, according to the ammonia synthesis system 1 of this embodiment, the ammonia synthesis system 1 is equipped with a gas concentration detector 42a for detecting the ammonia concentration of the synthesis gas. The control unit 30 controls the nitrogen flow regulator 41b using the ammonia concentration of the synthesis gas detected by the gas concentration detector 42a. This makes it possible to change the hydrogen ratio in the reactor inlet gas supplied to the catalytic reactor 10 with even greater precision, and thus the amount of ammonia synthesized throughout the catalytic reactor 10 can be adjusted with high precision.

[0055] Furthermore, according to the ammonia synthesis method of this embodiment, in step S12 of the flow shown in Figure 3, the amount of ammonia synthesized by the first catalyst 11 and the amount of ammonia synthesized by the second catalyst 12 are changed by changing the hydrogen ratio in the reactor inlet gas. This makes it possible to adjust the total amount of ammonia synthesized in the catalytic reactor 10.

[0056] Furthermore, according to the computer program of this embodiment, the control unit 30 can control the nitrogen flow regulator 41b and change the hydrogen ratio in the reactor inlet gas, thereby changing the amount of ammonia synthesized by the first catalyst 11 and the amount of ammonia synthesized by the second catalyst 12. This makes it possible to adjust the total amount of ammonia synthesized in the catalytic reactor 10.

[0057] <Second Embodiment> Figure 5 is the first diagram illustrating the ammonia synthesis method of the second embodiment. The ammonia synthesis system of the second embodiment differs from the ammonia synthesis system of the first embodiment (Figure 1) in that the flow rate of the gas supplied to the catalytic reactor is changed.

[0058] The ammonia synthesis system of this embodiment has the same configuration as the ammonia synthesis system 1 of the first embodiment. Specifically, the ammonia synthesis system of this embodiment comprises a catalytic reactor 10, a separator 20, a control unit 30, and a plurality of gas lines (gas piping) connecting these.

[0059] In the ammonia synthesis method using the ammonia synthesis system of this embodiment, when the hydrogen ratio of the reactor inlet gas is set to the target hydrogen ratio, the hydrogen ratio of the raw material gas is changed, and the flow rate of the reactor inlet gas supplied to the catalytic reactor 10 is also changed. In Figure 5, the amount of ammonia synthesized in the first catalyst 11, as shown in Figure 4, is shown by the dashed line MC1, and the amount of ammonia synthesized in the first catalyst 11 when the flow rate of the reactor inlet gas is reduced is shown by the solid line MC1g.

[0060] In the ammonia synthesis method of this embodiment, similar to the first embodiment, the amount of ammonia synthesized in the first catalyst 11 can be reduced from synthesis amount P20 to synthesis amount P21 by setting the hydrogen ratio of the raw material gas to a hydrogen ratio greater than Rh0, for example, Rh21. Furthermore, in the ammonia synthesis method of this embodiment, the amount of ammonia synthesized in the first catalyst 11 can be reduced from synthesis amount P21 to synthesis amount P21g by reducing the flow rate of the reactor inlet gas supplied to the catalytic reactor 10 (white arrow F21 shown in Figure 5). In the ammonia synthesis system of this embodiment, the control unit 30 can change the flow rate of the reactor inlet gas by controlling the nitrogen flow regulator 41b and the recycle gas flow regulator 44a. Although only the first catalyst 11 is shown in Figure 5, the second catalyst 12 shows a similar trend.

[0061] Figure 6 is a second diagram illustrating the ammonia synthesis method of the second embodiment. Figure 6 shows the amount of ammonia synthesized in the catalytic reactor 10 in the ammonia synthesis method of this embodiment. In Figure 6, the amount of ammonia synthesized before changing the flow rate of the reactor inlet gas is shown by the dashed line Mtotal, and the amount of ammonia synthesized after reducing the flow rate of the reactor inlet gas is shown by the solid line Mtotal_g. As shown in Figure 6, by setting the hydrogen ratio of the raw material gas to a hydrogen ratio Rh21 which is greater than the hydrogen ratio Rh0, the amount of ammonia synthesized in the catalytic reactor 10 decreases from a synthesis amount Pt20 to a synthesis amount Pt21. Furthermore, by reducing the flow rate of the reactor inlet gas supplied to the catalytic reactor 10, the amount of ammonia synthesized in the catalytic reactor 10 can be reduced from a synthesis amount Pt21 to a synthesis amount Pt21g (white arrow F22 shown in Figure 6).

[0062] As described above, in the ammonia synthesis system of this embodiment, the catalytic reactor 10 contains a first catalyst 11 and a second catalyst 12, each having different temperatures. Therefore, by changing the hydrogen ratio in the reactor inlet gas, the amount of ammonia synthesized throughout the catalytic reactor 10 can be adjusted.

[0063] Furthermore, according to the ammonia synthesis system of this embodiment, when the flow rate of hydrogen supplied by the water electrolyzer 40a falls below a preset threshold, the control unit 30 controls the recycle gas flow regulator 44a connected to the recycle gas line 44 to reduce the flow rate of the reactor inlet gas. This expands the range over which the amount of ammonia synthesized throughout the catalytic reactor 10 can be adjusted.

[0064] <Third Embodiment> Figure 7 is a schematic diagram showing the general configuration of the ammonia synthesis system of the third embodiment. The ammonia synthesis system of the third embodiment differs from the ammonia synthesis system of the first embodiment (Figure 1) in that the pressure of the gas supplied to the catalytic reactor is changed.

[0065] The ammonia synthesis system 3 of this embodiment comprises a catalytic reactor 10, a separator 20, a control unit 30, a plurality of gas lines (gas piping) connecting these, and a pressure regulator 41d. The pressure regulator 41d is connected to the raw material gas mixing line 412. The pressure regulator 41d is electrically connected to the control unit 30 and changes the pressure of the reactor inlet gas in response to commands from the control unit 30.

[0066] Figure 8 is the first diagram illustrating the ammonia synthesis method of this embodiment. In the ammonia synthesis method using the ammonia synthesis system 3, in order to change the amount of ammonia synthesized in the catalytic reactor 10, the hydrogen ratio of the reactor inlet gas is changed, and the pressure of the reactor inlet gas is also changed. In Figure 8, the amount of ammonia synthesized in the first catalyst 11, as shown in Figure 4, is shown by the dashed line MC1, and the amount of ammonia synthesized in the first catalyst 11 when the pressure of the reactor inlet gas is reduced is shown by the solid line MC1p.

[0067] In the ammonia synthesis method of this embodiment, similar to the first embodiment, the amount of ammonia synthesized in the first catalyst 11 can be reduced from synthesis amount P30 to synthesis amount P31 by setting the hydrogen ratio of the raw material gas to a hydrogen ratio greater than Rh0, for example, Rh31. Furthermore, in the ammonia synthesis method of this embodiment, the amount of ammonia synthesized in the first catalyst 11 can be reduced from synthesis amount P31 to synthesis amount P31p by reducing the pressure of the reactor inlet gas supplied to the catalytic reactor 10 (white arrow F31 shown in Figure 8). In the ammonia synthesis system 3 of this embodiment, the control unit 30 can change the pressure of the reactor inlet gas by controlling the pressure regulator 41d. Although only the first catalyst 11 is shown in Figure 8, the second catalyst 12 shows a similar trend.

[0068] Figure 9 is a second diagram illustrating the ammonia synthesis method of this embodiment. Figure 9 shows the amount of ammonia synthesized in the catalytic reactor 10 in the ammonia synthesis method of this embodiment. In Figure 9, the amount of ammonia synthesized before changing the pressure of the reactor inlet gas is shown by the dashed line Mtotal, and the amount of ammonia synthesized after reducing the pressure of the reactor inlet gas is shown by the solid line Mtotal_p. As shown in Figure 9, by setting the hydrogen ratio of the raw material gas to a hydrogen ratio Rh31 which is greater than the hydrogen ratio Rh0, the amount of ammonia synthesized in the catalytic reactor 10 decreases from synthesis amount Pt30 to synthesis amount Pt31. Furthermore, by reducing the pressure of the reactor inlet gas supplied to the catalytic reactor 10, the amount of ammonia synthesized in the catalytic reactor 10 can be reduced from synthesis amount Pt31 to synthesis amount Pt31p (white arrow F32 shown in Figure 9).

[0069] As described above, according to the ammonia synthesis system 3 of this embodiment, the catalytic reactor 10 contains a first catalyst 11 and a second catalyst 12, each having different temperatures. Therefore, by changing the hydrogen ratio in the reactor inlet gas, the amount of ammonia synthesized throughout the catalytic reactor 10 can be adjusted.

[0070] Furthermore, according to the ammonia synthesis system 3 of this embodiment, the control unit 30 controls the pressure regulator 41d to reduce the pressure of the reactor inlet gas when the flow rate of hydrogen supplied by the water electrolyzer 40a falls below a preset threshold. This expands the range over which the amount of ammonia synthesized in the entire catalytic reactor 10 can be adjusted.

[0071] <Fourth Embodiment> Figure 10 is a schematic diagram showing the general configuration of the ammonia synthesis system of the fourth embodiment. The ammonia synthesis system of the fourth embodiment differs from the ammonia synthesis system of the first embodiment (Figure 1) in that a temperature controller for adjusting the gas temperature is connected to the raw material gas line.

[0072] The ammonia synthesis system 4 of this embodiment includes a catalytic reactor 10, a separator 20, a control unit 30 that controls each part of the ammonia synthesis system 1, a plurality of gas lines (gas piping) connecting these, and a temperature controller 41e. The temperature controller 41e is connected to the raw material gas mixing line 412. The temperature controller 41e is electrically connected to the control unit 30 and changes the temperature of the reactor inlet gas flowing through the raw material gas mixing line 412 in response to commands from the control unit 30.

[0073] Figure 11 is the first diagram illustrating the ammonia synthesis method of the fourth embodiment. In the ammonia synthesis method using the ammonia synthesis system 4, in order to change the amount of ammonia synthesized in the catalytic reactor 10, the hydrogen ratio of the reactor inlet gas is changed, and the temperature of the reactor inlet gas is also changed. In Figure 11, the amount of ammonia synthesized in the first catalyst 11, as shown in Figure 4, is shown by the dashed line MC1, and the amount of ammonia synthesized in the first catalyst 11 when the temperature of the reactor inlet gas is lowered is shown by the solid line MC1t.

[0074] In the ammonia synthesis method of this embodiment, similar to the first embodiment, the amount of ammonia synthesized in the first catalyst 11 can be reduced from synthesis amount P40 to synthesis amount P41 by setting the hydrogen ratio of the raw material gas to a hydrogen ratio Rh0 greater than, for example, a hydrogen ratio Rh41. Furthermore, in the ammonia synthesis method of this embodiment, the amount of ammonia synthesized in the first catalyst 11 can be reduced from synthesis amount P41 to synthesis amount P41t by lowering the temperature of the reactor inlet gas supplied to the catalytic reactor 10 (white arrow F41 shown in Figure 11). In the ammonia synthesis system 4 of this embodiment, the control unit 30 can change the temperature of the reactor inlet gas by controlling the temperature controller 41e. Although only the first catalyst 11 is shown in Figure 11, the second catalyst 12 shows a similar trend.

[0075] Figure 12 is a second diagram illustrating the ammonia synthesis method of this embodiment. Figure 12 shows the amount of ammonia synthesized in the catalytic reactor 10 in the ammonia synthesis method of this embodiment. In Figure 12, the amount of ammonia synthesized before changing the temperature of the reactor inlet gas is shown by the dashed line Mtotal, and the amount of ammonia synthesized after reducing the temperature of the reactor inlet gas is shown by the solid line Mtotal_t. As shown in Figure 12, by setting the hydrogen ratio of the raw material gas to a hydrogen ratio Rh31 which is greater than the hydrogen ratio Rh0, the amount of ammonia synthesized in the catalytic reactor 10 decreases from a synthesis amount Pt40 to a synthesis amount Pt41. Furthermore, by reducing the temperature of the reactor inlet gas supplied to the catalytic reactor 10, the amount of ammonia synthesized in the catalytic reactor 10 can be reduced from a synthesis amount Pt41 to a synthesis amount Pt41t (white arrow F42 shown in Figure 12).

[0076] As described above, according to the ammonia synthesis system 4 of this embodiment, the catalytic reactor 10 contains a first catalyst 11 and a second catalyst 12, each having different temperatures. Therefore, by changing the hydrogen ratio in the reactor inlet gas, the amount of ammonia synthesized throughout the catalytic reactor 10 can be adjusted.

[0077] Furthermore, according to the ammonia synthesis system 4 of this embodiment, the control unit 30 controls the temperature controller 41e to lower the temperature of the reactor inlet gas when the flow rate of hydrogen supplied by the water electrolyzer 40a falls below a preset threshold. This makes it possible to adjust the amount of ammonia synthesized throughout the catalytic reactor 10.

[0078] <Fifth Embodiment> Figure 13 is a schematic diagram showing the general configuration of the ammonia synthesis system of the fifth embodiment. The ammonia synthesis system of the fifth embodiment differs from the ammonia synthesis system of the first embodiment (Figure 1) in that it has two gas lines connecting the catalytic reactor and the separator.

[0079] The ammonia synthesis system 5 of this embodiment includes a catalytic reactor 10, a separator 20, a control unit 30 that controls each part of the ammonia synthesis system 5, and a plurality of gas lines connecting them. As shown in Figure 13, the ammonia synthesis system 5 of this embodiment includes a synthesis gas line 46 and an intermediate synthesis gas line 47 as gas lines connecting the catalytic reactor 10 and the separator 20.

[0080] The synthesis gas line 46 supplies the synthesis gas released by the second catalyst 12 and extracted from the gas outlet 10b of the catalytic reactor 10 to the separator 20. In other words, the synthesis gas line 46 has the same function as the synthesis gas line 42 provided in the ammonia synthesis system 1 of the first embodiment. A gas concentration detector 42a and a first control valve 46a are connected to the synthesis gas line 46. The first control valve 46a is electrically connected to the control unit 30. The first control valve 46a controls the flow of synthesis gas in the synthesis gas line 46 in response to commands from the control unit 30.

[0081] The intermediate synthesis gas line 47 is connected to the intermediate gas outlet 10c, which discharges the gas released by the first catalyst 11. The intermediate synthesis gas line 47 takes the gas released by the first catalyst 11 from the catalytic reactor 10 and sends it to the separator 20. The intermediate synthesis gas line 47 is connected to the synthesis gas line 46 between the first control valve 46a and the gas concentration detector 42a. A second control valve 47a is connected to the intermediate synthesis gas line 47. The second control valve 47a is electrically connected to the control unit 30. The second control valve 47a controls the flow of synthesis gas in the intermediate synthesis gas line 47 in response to commands from the control unit 30. Here, the synthesis gas flowing through the intermediate synthesis gas line 47 is called "intermediate synthesis gas".

[0082] Next, the details of the ammonia synthesis method using the ammonia synthesis system 5 of this embodiment will be described. In the ammonia synthesis method of this embodiment, the amount of ammonia synthesized in the catalytic reactor 10 is adjusted by switching between two synthesis gas lines 46 and 47 and adjusting the hydrogen ratio of the reactor inlet gas.

[0083] Figure 14 is a flowchart of the ammonia synthesis method of this embodiment. In the ammonia synthesis method of this embodiment, first, a gas line for extracting ammonia from inside the catalytic reactor 10 is selected (step S51). In step S51, the control unit 30 uses the operation information of the ammonia synthesis system 5 to select a gas line for extracting the ammonia synthesized in the catalytic reactor 10 from the catalytic reactor 10. In the ammonia synthesis system 5 of this embodiment, the synthesis gas flowing through the synthesis gas line 46 contains ammonia synthesized in both the first catalyst 11 and the second catalyst 12, and therefore contains a relatively large amount of ammonia. On the other hand, the intermediate synthesis gas flowing through the intermediate synthesis gas line 47 contains only ammonia synthesized in the first catalyst 11, and therefore contains less ammonia than the synthesis gas flowing through the synthesis gas line 46. Therefore, in this embodiment, the control unit 30 uses the hydrogen supply plan information input from the control unit of the water electrolysis device 40a to select the intermediate synthesis gas line 47 when it is necessary to reduce the amount of ammonia produced by a relatively large amount, thereby reducing the amount of ammonia synthesized in the catalytic reactor 10. This prevents the ammonia synthesis system 5 from becoming unstable. In the input hydrogen supply plan, the control unit 30 selects the synthesis gas line 46 if the flow rate of hydrogen supplied from the water electrolyzer 40a is above a preset threshold. When the synthesis gas line 46 is selected, the control unit 30 opens the first control valve 46a and closes the second control valve 47a. In the input hydrogen supply plan, the control unit 30 selects the intermediate synthesis gas line 47 if the flow rate of hydrogen supplied from the water electrolyzer 40a is below a preset threshold. When the intermediate synthesis gas line 47 is selected, the control unit 30 closes the first control valve 46a and opens the second control valve 47a.

[0084] Following step S51, it is determined whether or not to change the hydrogen ratio (H / N) of the reactor inlet gas (step S52). In step S52, the control unit 30, similar to step S11 of the ammonia synthesis method of the first embodiment, uses information regarding the operating state of the ammonia synthesis system 5 to determine whether or not to change the hydrogen ratio of the reactor inlet gas. In the ammonia synthesis method of the fifth embodiment, if the amount of ammonia synthesized in the catalytic reactor 10 has already been reduced by selecting the intermediate synthesis gas line 47 in step S51, this is also taken into consideration when determining whether or not to change the hydrogen ratio of the reactor inlet gas. If the control unit 30 determines to change the hydrogen ratio of the reactor inlet gas (step S52: YES), the process proceeds to step S53. If the control unit 30 determines not to change the hydrogen ratio of the reactor inlet gas (step S52: NO), the flow of the ammonia synthesis method shown in Figure 14 is terminated.

[0085] In step S52, if the control unit 30 determines that the hydrogen ratio of the reactor inlet gas should be changed, it changes the hydrogen ratio (H / N) of the raw material gas (step S53). In step S53, similar to step S12 of the ammonia synthesis method of the first embodiment, the control unit 30 uses a map A, which has a prior relationship between the hydrogen ratio of the reactor inlet gas and the amount of ammonia synthesized in the catalytic reactor 10, and a map B, which has a relationship between the hydrogen ratio of the reactor inlet gas and the hydrogen ratio of the raw material gas, to calculate the target hydrogen ratio of the reactor inlet gas.

[0086] Following step S53, the composition of the synthesis gas and recycled gas is analyzed (step S54). In step S54, the control unit 30 calculates the hydrogen ratio of the recycled gas using the hydrogen concentration detection result from the gas concentration detector 45a connected to the recycled gas line 44, similar to step S13 of the ammonia synthesis method of the first embodiment. Also in step S54, the control unit 30 calculates the amount of ammonia synthesized in the catalytic reactor 10 using the ammonia concentration detection result from the gas concentration detector 42a connected to the synthesis gas line 46.

[0087] Following step S54, step S55 determines whether the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio (H / N). In step S55, the control unit 30 uses the results of the compositional analysis of the synthesis gas and recycled gas in step S54 to determine whether the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio. If the control unit 30 determines that the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio (step S55: YES), the process proceeds to step S56. If the control unit 30 determines that the hydrogen ratio of the reactor inlet gas has not reached the target hydrogen ratio (step S55: NO), the process returns to step S53 and further changes the hydrogen ratio of the raw material gas (step S53).

[0088] In step S55, if it is determined that the hydrogen ratio of the reactor inlet gas has reached the target hydrogen ratio, the hydrogen ratio (H / N) of the raw material gas is set to 3 (step S56). In step S56, similar to step S15 of the ammonia synthesis method of the first embodiment, the control unit 30 sets the hydrogen ratio of the raw material gas to 3 and puts the ammonia synthesis system 5 into a steady-state operation state.

[0089] Figure 15 is the first diagram illustrating the ammonia synthesis method of this embodiment. Figure 15 shows the relationship between the hydrogen ratio of the reactor inlet gas and the amount of ammonia synthesized in the catalytic reactor 10 when the synthesis gas line 46 is selected as the gas line that sends the synthesis gas extracted from the catalytic reactor 10 to the separator 20. In the relationship between the hydrogen ratio of the reactor inlet gas and the amount of ammonia synthesized in the catalytic reactor 10 shown in Figure 15, the amount of ammonia synthesized in the catalytic reactor 10 (solid line Mtotal in Figure 15) is the sum of the amount of ammonia synthesized by the first catalyst 11 (solid line MC1 in Figure 15) and the amount of ammonia synthesized by the second catalyst 12 (solid line MC2 in Figure 15). Specifically, as shown in Figure 15, when the hydrogen ratio is Rh0, the amount of ammonia synthesized in the catalytic reactor 10 Pt50 is the sum of the amount of ammonia synthesized by the first catalyst 11 P51 and the amount of ammonia synthesized by the second catalyst 12 P52. Furthermore, by changing the hydrogen ratio of the reactor inlet gas, both the amount of ammonia synthesized by the first catalyst 11 and the amount of ammonia synthesized by the second catalyst 12 change, and therefore the amount of ammonia synthesized in the catalytic reactor 10 also changes (for example, the hydrogen ratios Rh51 and Rh52 shown in Figure 15).

[0090] Figure 16 is a second diagram illustrating the ammonia synthesis method of this embodiment. Figure 16 shows the relationship between the hydrogen ratio of the reactor inlet gas and the amount of ammonia synthesized in the catalytic reactor 10 when the intermediate synthesis gas line 47 is selected as the gas line that sends the synthesis gas extracted from the catalytic reactor 10 to the separator 20. For reference, Figure 16 shows the amount of ammonia synthesized by the second catalyst 12 as the dashed line MC2, and the amount of ammonia synthesized in the catalytic reactor 10 when the synthesis gas line 46 shown in Figure 15 is selected as the dashed line Mtotal. When the intermediate synthesis gas line 47 is selected as the gas line that sends the synthesis gas to the separator 20, the intermediate synthesis gas flowing through the intermediate synthesis gas line 47 is the gas released by the first catalyst 11, so the amount of ammonia synthesized in the catalytic reactor 10 is only the ammonia synthesized by the first catalyst 11. As a result, the amount of ammonia synthesized in the catalytic reactor 10 when the intermediate synthesis gas line 47 is selected is the same as the amount of ammonia synthesized by the first catalyst 11 P51. Therefore, even without changing the hydrogen ratio of the raw material gas, the amount of ammonia synthesized in the catalytic reactor 10 when the intermediate synthesis gas line 47 is selected is smaller than the amount of ammonia synthesized in the catalytic reactor 10 when the synthesis gas line 46 is selected. Furthermore, by changing the hydrogen ratio of the raw material gas, the amount of ammonia synthesized in the catalytic reactor 10 can be further reduced (for example, the hydrogen ratios Rh51 and Rh52 shown in Figure 16).

[0091] As described above, according to the ammonia synthesis system 5 of this embodiment, the catalytic reactor 10 contains a first catalyst 11 and a second catalyst 12, each having different temperatures. Therefore, by changing the hydrogen ratio in the reactor inlet gas, the amount of ammonia synthesized throughout the catalytic reactor 10 can be adjusted.

[0092] Furthermore, according to the ammonia synthesis system 5 of this embodiment, the catalytic reactor 10 includes a gas outlet 10b for releasing synthesis gas containing ammonia released from the second catalyst 12 out of the catalytic reactor 10, and an intermediate gas outlet 10c for releasing intermediate synthesis gas containing ammonia released from the first catalyst 11. The control unit 30 controls the first control valve 46a and the second control valve 47a respectively to extract the ammonia synthesized in the catalytic reactor 10 from the intermediate gas outlet 10c. This makes it possible to adjust the amount of ammonia synthesized in the catalytic reactor 10 as a whole.

[0093] Furthermore, according to the ammonia synthesis system 5 of this embodiment, the amount of ammonia synthesized can be adjusted by changing the line from the synthesis gas line 46 to the intermediate synthesis gas line 47 without changing the hydrogen ratio in the reactor inlet gas. This makes it possible to adjust the amount of ammonia synthesized relatively easily.

[0094] <Sixth Embodiment> Figure 17 is a schematic diagram showing the general configuration of the ammonia synthesis system of the sixth embodiment. The ammonia synthesis system of the sixth embodiment differs from the ammonia synthesis system of the first embodiment (Figure 1) in that it is equipped with a gas line that supplies a portion of the raw material gas between the first catalyst and the second catalyst.

[0095] The ammonia synthesis system 6 of this embodiment includes a catalytic reactor 10, a separator 20, a control unit 30 that controls each part of the ammonia synthesis system 5, and a plurality of gas lines connecting them. The ammonia synthesis system 6 of this embodiment includes a raw material gas line 41 and a split gas line 48 as gas lines that supply hydrogen and nitrogen to the catalytic reactor 10.

[0096] The divided gas line 48 is connected to the raw material gas supply line 411 and the catalytic reactor 10. One end of the divided gas line 48 is connected to the raw material gas supply line 411 that is connected to the nitrogen tank 40b. As a result, nitrogen flows through the divided gas line 48. The other end of the divided gas line 48 is connected to the divided gas inlet 10d of the catalytic reactor 10. The divided gas inlet 10d is provided to supply nitrogen between the first catalyst 11 and the second catalyst 12 inside the catalytic reactor 10. Here, the gas flowing through the divided gas line 48 is called "divided gas". Alternatively, one end of the divided gas line 48 may be connected to the raw material gas supply line 411 that is connected to the water electrolyzer 40a.

[0097] A flow regulator 48a and a temperature regulator 48b are connected to the divided gas line 48. The flow regulator 48a is electrically connected to the control unit 30 and controls the flow of divided gas in the divided gas line 48 in response to commands from the control unit 30. The temperature regulator 48b is electrically connected to the control unit 30 and controls the temperature of the divided gas flowing through the divided gas line 48 in response to commands from the control unit 30.

[0098] Next, a method for synthesizing ammonia using the ammonia synthesis system 6 of this embodiment will be described. In the ammonia synthesis method of this embodiment, the amount of ammonia synthesized in the catalytic reactor 10 is adjusted by using a combination of supplying divided gas through the divided gas line 48 and adjusting the hydrogen ratio of the reactor inlet gas.

[0099] Figure 18 illustrates the ammonia synthesis method of this embodiment. Figure 18 shows the relationship between the hydrogen ratio of the gas supplied to the first catalyst 11 and the second catalyst 12, both housed in the catalytic reactor 10, and the amount of ammonia synthesized in each catalyst. In Figure 18, the horizontal axis shows the hydrogen ratio supplied to each catalyst as "C_H / N", and the vertical axis shows the amount of ammonia synthesized in each catalyst. In Figure 18, the amount of ammonia synthesized by the first catalyst 11 is shown by the solid line MC1, and the amount of ammonia synthesized by the second catalyst 12 is shown by two solid lines MC2 and MC2t. The amount of ammonia synthesized by the second catalyst 12, represented by the solid line MC2, represents the amount of ammonia synthesized when the temperature of the second catalyst 12 is, for example, 350°C. The amount of ammonia synthesized by the second catalyst 12, represented by the solid line MC2t, represents the amount of ammonia synthesized when the temperature of the second catalyst 12 is lower than the temperature of the second catalyst 12 shown by the solid line MC2.

[0100] In the ammonia synthesis method of this embodiment, when the hydrogen ratio supplied to the catalyst is hydrogen ratio Rh0, as shown in Figure 18, the amount of ammonia synthesized in the first catalyst 11 is synthesis amount P61, and the amount of ammonia synthesized in the second catalyst 12 is synthesis amount P62. Therefore, the amount of ammonia synthesized in the catalytic reactor 10 is synthesis amount (P61 + P62). If the hydrogen ratio supplied to the catalyst is set to a hydrogen ratio Rh61, which is greater than hydrogen ratio Rh0, the amount of ammonia synthesized in both the first catalyst 11 and the second catalyst 12 decreases, similar to the first embodiment. As a result, the amount of ammonia synthesized in the first catalyst 11 becomes synthesis amount P611, and the amount of ammonia synthesized in the second catalyst 12 becomes synthesis amount P621, so the amount of ammonia synthesized in the catalytic reactor 10 becomes synthesis amount (P611 + P621), which is smaller than the synthesis amount (P61 + P62).

[0101] In the ammonia synthesis method of this embodiment, a portion of the nitrogen in the raw material gas, when the hydrogen ratio of the reactor inlet gas is Rh61, is introduced into the catalytic reactor 10 as a split gas via the split gas inlet 10d. As a result, the hydrogen ratio of the reactor inlet gas entering the catalytic reactor 10 from the gas inlet 10a increases, and the amount of ammonia synthesized in the first catalyst 11 changes from the synthesis amount P611 to, for example, the ammonia synthesis amount P61d in the first catalyst 11 at a hydrogen ratio of Rh62 as shown in Figure 18 (white arrow F61 shown in Figure 18). On the other hand, the second catalyst 12 is supplied with ammonia synthesized by the first catalyst 11, a gas containing unreacted hydrogen and nitrogen from the first catalyst 11, and nitrogen supplied as a split gas. That is, the gas supplied to the second catalyst 12 has a hydrogen ratio of Rh61, so the amount of ammonia synthesized in the second catalyst 12 remains at the synthesis amount P621. Therefore, by using the divided gas line 48, the amount of ammonia synthesized in the catalytic reactor 10 becomes an even smaller amount (P61d + P621) than the total amount synthesized (P611 + P621).

[0102] In the ammonia synthesis method of this embodiment, the amount of ammonia synthesized in the second catalyst 12 can be further reduced by cooling the divided gas with the temperature controller 48b. Specifically, by cooling the divided gas with the temperature controller 48b before it is supplied to the inside of the catalytic reactor 10 via the divided gas inlet 10d, the temperature of the second catalyst 12 is reduced. As a result, as shown in Figure 18, the amount of ammonia synthesized in the second catalyst 12 changes from the synthesis amount P621 to, for example, the ammonia synthesis amount P62t represented by the solid line MC2t (white arrow F62 shown in Figure 18). Consequently, in the ammonia synthesis method of this embodiment, by dividing the raw material gas and cooling the divided gas, the amount of ammonia synthesized in the catalytic reactor 10 (P611 + P621) becomes an even smaller synthesis amount (P61d + P62t) than the synthesis amount (P61d + P621).

[0103] As described above, according to the ammonia synthesis system 6 of this embodiment, the catalytic reactor 10 contains a first catalyst 11 and a second catalyst 12, each having different temperatures. Therefore, by changing the hydrogen ratio in the reactor inlet gas, the amount of ammonia synthesized throughout the catalytic reactor 10 can be adjusted.

[0104] Furthermore, according to the ammonia synthesis system 6 of this embodiment, the catalytic reactor 10 is equipped with a divided gas inlet 10d that allows a portion of the nitrogen contained in the raw material gas to flow between the first catalyst 11 and the second catalyst 12. The control unit 30 controls the flow regulator 48a connected to the divided gas line 48 to change the hydrogen ratio in the reactor inlet gas supplied to the first catalyst 11, thereby controlling the ammonia synthesis in the first catalyst 11. This makes it possible to adjust the amount of ammonia synthesized throughout the catalytic reactor 10.

[0105] Furthermore, according to the ammonia synthesis system 6 of this embodiment, the control unit 30 reduces the temperature of the divided gas by controlling the temperature controller 48b, which adjusts the temperature of the divided gas, when the flow rate of hydrogen supplied by the water electrolyzer 40a falls below a preset threshold. This expands the range over which the amount of ammonia synthesized in the entire catalytic reactor 10 can be adjusted.

[0106] <Modifications of this Embodiment> The present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0107] [Modification 1] In the above embodiment, the temperature of the first catalyst 11 was set to be higher than the temperature of the second catalyst 12. However, the relationship between the temperature of the first catalyst 11 and the temperature of the second catalyst 12 in the catalytic reactor 10 is not limited to this. It is sufficient that the temperatures of the first catalyst 11 and the second catalyst 12 are different from each other.

[0108] [Modification 2] In the above embodiment, the hydrogen supplied to the ammonia synthesis system was produced by a water electrolysis device using renewable energy, and the nitrogen was produced by a nitrogen tank. The method of producing the hydrogen and nitrogen supplied to the ammonia synthesis system is not limited to this. For example, hydrogen produced by a reforming reaction of natural gas may be supplied.

[0109] [Modification 3] In the above embodiment, when increasing the hydrogen ratio of the reactor inlet gas, the flow rate of nitrogen supplied by the nitrogen tank 40b was reduced by controlling the nitrogen flow rate regulator 41b. However, the method for increasing the hydrogen ratio of the reactor inlet gas is not limited to this. The hydrogen ratio of the reactor inlet gas may also be increased by increasing the flow rate of hydrogen contained in the reactor inlet gas.

[0110] Figure 19 is a schematic diagram showing a general configuration of a modified example of the ammonia synthesis system of the first embodiment. Hydrogen is supplied to the ammonia synthesis system 1 shown in Figure 19 from a hydrogen tank 40c that stores hydrogen. In addition to a hydrogen flow detector 41a, a hydrogen flow regulator 41f is connected to the raw material gas supply line 411 connected to the hydrogen tank 40c. The hydrogen flow regulator 41f is electrically connected to the control unit 30 and can change the flow path of hydrogen supplied by the hydrogen tank 40c in response to a command from the control unit 30. As a result, if the amount of nitrogen supplied falls below a preset threshold due to a malfunction of the nitrogen tank 40b or the like, the hydrogen flow regulator 41f can be controlled to increase the hydrogen ratio of the reactor inlet gas and reduce the amount of ammonia synthesized in the catalytic reactor 10, thereby suppressing an unstable operating state of the ammonia synthesis system 1.

[0111] [Modification 4] In the above embodiment, the control unit 30 changes the hydrogen ratio in the reactor inlet gas when the flow rate of hydrogen supplied by the water electrolyzer 40a falls below a preset threshold. However, the control contents of the control unit 30 are not limited to this. The hydrogen ratio in the reactor inlet gas may also be changed when the flow rate of nitrogen supplied by the nitrogen tank 40b falls below a preset threshold. Therefore, when changing the amount of ammonia synthesized in the catalytic reactor, the hydrogen ratio in the reactor inlet gas may be changed by changing at least one of the flow rate of hydrogen supplied by the water electrolyzer 40a and the flow rate of nitrogen supplied by the nitrogen tank 40b.

[0112] [Modification 5] In the above embodiment, the amount of ammonia synthesized in the catalytic reactor 10 as a whole was reduced by increasing the hydrogen ratio of the reactor inlet gas. As shown in Figure 2, the amount of ammonia synthesized in the catalytic reactor 10 as a whole can also be reduced by decreasing the hydrogen ratio of the reactor inlet gas.

[0113] [Modification 6] In the above-described embodiment, the timing for changing the hydrogen ratio in the reactor inlet gas is not limited to when the flow rate of supplied hydrogen or nitrogen falls below a preset threshold. If changes in the flow rate of supplied hydrogen or nitrogen are planned, the amount of ammonia synthesized in the entire catalytic reactor 10 may be reduced by systematically changing the hydrogen ratio in the reactor inlet gas.

[0114] [Modification 7] In the second embodiment, the control unit 30 changes the flow rate of the reactor inlet gas by controlling the nitrogen flow regulator 41b and the recycle gas flow regulator 44a. The method for changing the flow rate of the reactor inlet gas is not limited to this. It may also be done by controlling either the nitrogen flow regulator 41b or the recycle gas flow regulator 44a. In the case of the ammonia synthesis system 1 shown in Figure 19 above, the flow rate of the reactor inlet gas may also be changed by controlling the hydrogen flow regulator 41f.

[0115] [Modification 8] In the second embodiment, the amount of ammonia synthesized in the catalytic reactor 10 was changed by changing the flow rate of the reactor inlet gas. In the third embodiment, the amount of ammonia synthesized in the catalytic reactor 10 was changed by changing the pressure of the reactor inlet gas. In the fourth embodiment, the amount of ammonia synthesized in the catalytic reactor 10 was changed by changing the temperature of the reactor inlet gas. These changes may be made all at once. That is, the amount of ammonia synthesized in the catalytic reactor 10 may be changed by changing at least one of the flow rate, pressure, and temperature of the reactor inlet gas.

[0116] [Modification 9] In the above embodiment, a recycling gas line is provided to return the gaseous hydrogen and nitrogen separated from the synthesis gas in the separator back to the raw material gas line. The recycling gas line is not required. The hydrogen ratio of the gas supplied to the catalytic reactor may be changed by controlling the flow rate of nitrogen supplied from the nitrogen tank according to the flow rate of hydrogen supplied from the water electrolysis device.

[0117] [Modification 10] In the fifth embodiment, the amount of ammonia synthesized in the catalytic reactor 10 is adjusted by using a combination of switching between two synthesis gas lines 46 and 47 and adjusting the hydrogen ratio of the reactor inlet gas. In the sixth embodiment, the amount of ammonia synthesized in the catalytic reactor 10 is adjusted by using a combination of supplying divided gas through a divided gas line 48 and adjusting the hydrogen ratio of the reactor inlet gas. The amount of ammonia synthesized in the catalytic reactor 10 may also be adjusted by using a combination of switching between two synthesis gas lines 46 and 47 and supplying divided gas through a divided gas line 48. Furthermore, in each of the fifth and sixth embodiments, the amount of ammonia synthesized in the catalytic reactor 10 may also be adjusted by changing at least one of the flow rate, pressure, and temperature of the reactor inlet gas.

[0118] [Modification 11] In the sixth embodiment, nitrogen produced by a nitrogen tank flows through the divided gas line connected to the raw material gas line and the catalytic reactor. The type of gas flowing through the divided gas line is not limited to this. It may be hydrogen supplied by a water electrolysis device, or a gas mixture of hydrogen and nitrogen may flow through it.

[0119] [Modification 12] In the above embodiment, the catalyst was a Ru-based catalyst containing ruthenium. The catalyst used for the synthesis of ammonia is not limited to this. For example, an Fe-based catalyst may also be used.

[0120] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0121] <Application Example 1> An ammonia synthesis system comprising: a catalytic reactor containing a first catalyst and a second catalyst, each for synthesizing ammonia from hydrogen and nitrogen, wherein the temperatures of the first catalyst and the second catalyst are different from each other; and a gas supply unit for supplying a first raw material gas containing hydrogen and nitrogen to the catalytic reactor, wherein the catalytic reactor is connected to the gas supply unit and has a gas inlet for introducing the first raw material gas into the inside of the catalytic reactor, the first catalyst is positioned closer to the gas inlet than the second catalyst, and ammonia is synthesized using the first raw material gas supplied through the gas inlet, and the second catalyst synthesizes ammonia using a second raw material gas containing the gas supplied through the first catalyst. <Example 2> An ammonia synthesis system according to claim 1, further comprising: a flow regulator for adjusting at least one of the amount of hydrogen and the amount of nitrogen contained in the first raw material gas; and a control unit for changing the ratio of nitrogen to hydrogen in the first raw material gas by controlling the flow regulator. <Example 3> An ammonia synthesis system according to Example 1 or Example 2, wherein the control unit controls the flow regulator to change the ratio of nitrogen to hydrogen in the first raw material gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. <Example 4> An ammonia synthesis system according to any one of Examples 1 to 3, wherein the control unit controls the flow regulator to reduce the flow rate of the first raw material gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. <Application Example 5> An ammonia synthesis system as described in any one of Application Examples 1 to 4, further comprising a pressure regulator connected to the gas supply unit for adjusting the pressure of the first raw material gas, wherein the control unit controls the pressure regulator so that the pressure of the first raw material gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold.<Application Example 6> An ammonia synthesis system described in any one of Application Examples 1 to 5 further comprises a temperature controller connected to the gas supply unit for adjusting the temperature of the first raw material gas, and the control unit controls the temperature controller so that the temperature of the first raw material gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. <Application Example 7> An ammonia synthesis system according to any one of Application Examples 1 to 6, wherein the catalytic reactor has a gas outlet that discharges synthesis gas containing ammonia released from the second catalyst from the inside of the catalytic reactor, the ammonia synthesis system further comprises: a separator connected to the gas outlet that separates hydrogen and nitrogen contained in the synthesis gas from the synthesis gas; a recycle gas line that supplies the recycle gas containing the hydrogen and nitrogen separated in the separator to the catalytic reactor as part of the first raw material gas; and a hydrogen concentration detector that detects the hydrogen concentration of the recycle gas, the control unit controls the flow regulator using the hydrogen concentration of the recycle gas detected by the hydrogen concentration detector. <Application Example 8> An ammonia synthesis system according to any one of Application Examples 1 to 7, further comprising: a synthesis gas concentration detector that detects the ammonia concentration of the synthesis gas, the control unit controls the flow regulator using the ammonia concentration of the synthesis gas detected by the synthesis gas concentration detector.<Application Example 9> An ammonia synthesis system according to any one example from Application Example 1 to Application Example 8, wherein the catalytic reactor comprises a gas outlet for discharging synthesis gas containing ammonia released from the second catalyst from the inside of the catalytic reactor, and an intermediate gas outlet for discharging the second raw material gas from the inside of the catalytic reactor, and the ammonia synthesis system further comprises: a synthesis gas line connected to the gas outlet, a first control valve connected to the synthesis gas line for controlling the flow of the synthesis gas in the synthesis gas line, an intermediate synthesis gas line connected to the intermediate gas outlet, a second control valve connected to the intermediate synthesis gas line for controlling the flow of the second raw material gas in the intermediate synthesis gas line, and a control unit for controlling the first control valve and the second control valve, respectively, which blocks the flow of the synthesis gas in the synthesis gas line and allows the flow of the second raw material gas in the intermediate synthesis gas line. <Application Example 10> An ammonia synthesis system according to any one of Application Examples 1 to 9, wherein the catalytic reactor comprises: an intermediate gas inlet for introducing a divided gas containing either hydrogen or nitrogen supplied by the gas supply unit between the first catalyst and the second catalyst inside the catalytic reactor; and a gas outlet for releasing synthesis gas containing ammonia released from the second catalyst from inside the catalytic reactor, the ammonia synthesis system further comprises: a divided gas line connected to the intermediate gas inlet; a divided gas control valve connected to the divided gas line for controlling the flow of the divided gas in the divided gas line; and a control unit for controlling the divided gas control valve, which allows the flow of the divided gas in the divided gas line.<Application Example 11> An ammonia synthesis system described in any one of Application Examples 1 to 10 further comprises a temperature controller connected to the divided gas line for adjusting the temperature of the divided gas, wherein the control unit controls the temperature controller so that the temperature of the divided gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. <Application Example 12> An ammonia synthesis method for synthesizing ammonia using an ammonia synthesis system, comprising the steps of: supplying a first raw material gas containing hydrogen and nitrogen to a catalytic reactor; and synthesizing ammonia from hydrogen and nitrogen using a first catalyst and a second catalyst housed in the catalytic reactor, each having different temperatures, wherein the first catalyst synthesizes ammonia using the first raw material gas, and the second catalyst synthesizes ammonia using a second raw material gas containing gas supplied via the first catalyst. <Application Example 13> A computer program that causes a computer to perform the synthesis of ammonia using an ammonia synthesis system, the computer program that causes the computer to perform the following functions: supplying a first raw material gas containing hydrogen and nitrogen to a catalytic reactor; and synthesizing ammonia from hydrogen and nitrogen using a first catalyst and a second catalyst housed in the catalytic reactor, each having different temperatures, wherein the first catalyst synthesizes ammonia using the first raw material gas, and the second catalyst synthesizes ammonia using a second raw material gas containing the gas supplied through the first catalyst.

[0122] 1, 3, 4, 5, 6…Ammonia synthesis system 10…Catalytic reactor 10a…Gas inlet 10b…Gas outlet 10c…Intermediate gas outlet 10d…Split gas inlet 11…First catalyst 12…Second catalyst 20…Separator 30…Control unit 41b…Nitrogen flow regulator 41d…Pressure regulator 41e, 48b…Temperature regulator 41f…Hydrogen flow regulator 41…Raw material gas line 42a, 45a…Gas concentration detector 42, 46…Synthesis gas line 44…Recycle gas line 46a…First control valve 47…Intermediate synthesis gas line 47a…Second control valve 48…Split gas line 48a…Flow regulator

Claims

an ammonia synthesis system, A catalytic reactor containing a first catalyst and a second catalyst for synthesizing ammonia from hydrogen and nitrogen, wherein the temperatures of the first catalyst and the second catalyst are different from each other. The catalytic reactor comprises a gas supply unit that supplies a first raw material gas containing hydrogen and nitrogen, The catalytic reactor is connected to the gas supply unit and has a gas inlet for introducing the first raw material gas into the inside of the catalytic reactor. The first catalyst is It is positioned closer to the gas inlet than the second catalyst, Ammonia is synthesized using the first raw material gas supplied through the gas inlet. The second catalyst synthesizes ammonia using a second raw material gas, which includes the gas supplied via the first catalyst. Ammonia synthesis system. 　 The ammonia synthesis system according to claim 1 further, A flow regulator that adjusts at least one of the amounts of hydrogen and nitrogen contained in the first raw material gas, The system includes a control unit that controls the flow regulator to change the ratio of nitrogen to hydrogen in the first raw material gas, Ammonia synthesis system. 　 The ammonia synthesis system according to claim 2, The control unit controls the flow regulator to change the ratio of nitrogen to hydrogen in the first raw material gas when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. Ammonia synthesis system. 　 The ammonia synthesis system according to claim 2, The control unit controls the flow regulator so that the flow rate of the first raw material gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. Ammonia synthesis system. 　 The ammonia synthesis system according to claim 2 further, It is connected to the gas supply unit and includes a pressure regulator that adjusts the pressure of the first raw material gas, The control unit controls the pressure regulator so that the pressure of the first raw material gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. Ammonia synthesis system. 　 The ammonia synthesis system according to claim 2 further, It is connected to the gas supply unit and includes a temperature controller for adjusting the temperature of the first raw material gas, The control unit controls the temperature controller so that the temperature of the first raw material gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. Ammonia synthesis system. 　 An ammonia synthesis system according to any one of claims 2 to 6, The catalytic reactor has a gas outlet that allows the synthesis gas containing ammonia released from the second catalyst to flow out from the inside of the catalytic reactor. The ammonia synthesis system further, A separator connected to the gas outlet separates hydrogen and nitrogen contained in the synthesis gas from the synthesis gas, A recycling gas line supplies the recycled gas containing hydrogen and nitrogen separated in the separator to the catalytic reactor as part of the first raw material gas, The system includes a hydrogen concentration detector for detecting the hydrogen concentration of the recycled gas, The control unit controls the flow regulator using the hydrogen concentration of the recycled gas detected by the hydrogen concentration detector. Ammonia synthesis system. 　 The ammonia synthesis system according to claim 7 further, The system includes a synthesis gas concentration detector for detecting the ammonia concentration of the synthesis gas, The control unit controls the flow regulator using the ammonia concentration of the synthesis gas detected by the synthesis gas concentration detector. Ammonia synthesis system. 　 The ammonia synthesis system according to claim 1, The catalytic reactor is, A gas outlet for releasing the synthesis gas containing ammonia released from the second catalyst from the inside of the catalytic reactor, The reactor comprises an intermediate gas outlet for releasing the second raw material gas from the inside of the catalytic reactor, The ammonia synthesis system further, A synthesis gas line connected to the aforementioned gas outlet, A first control valve connected to the synthesis gas line and controlling the flow of the synthesis gas in the synthesis gas line, An intermediate synthesis gas line connected to the aforementioned intermediate gas outlet, A second control valve connected to the intermediate synthesis gas line and controlling the flow of the second raw material gas in the intermediate synthesis gas line, A control unit that controls the first control valve and the second control valve, comprising a control unit that shuts off the flow of the synthesis gas in the synthesis gas line and allows the flow of the second raw material gas in the intermediate synthesis gas line, Ammonia synthesis system. 　 The ammonia synthesis system according to claim 1, The catalytic reactor is, An intermediate gas inlet is provided to allow a divided gas containing either hydrogen or nitrogen, supplied by the gas supply unit, to flow between the first catalyst and the second catalyst inside the catalytic reactor. The reactor comprises a gas outlet for discharging the synthesis gas containing ammonia released from the second catalyst from the inside of the catalytic reactor, The ammonia synthesis system further, A divided gas line connected to the intermediate gas inlet, A divided gas control valve connected to the divided gas line and controlling the flow of the divided gas in the divided gas line, A control unit for controlling the divided gas control valve, comprising a control unit for allowing the flow of the divided gas in the divided gas line, Ammonia synthesis system. 　 The ammonia synthesis system according to claim 10 further, It is equipped with a temperature controller connected to the divided gas line and for adjusting the temperature of the divided gas, The control unit controls the temperature controller so that the temperature of the divided gas decreases when the flow rate of hydrogen supplied by the gas supply unit falls below a preset threshold. Ammonia synthesis system. 　 A method for synthesizing ammonia using an ammonia synthesis system, A step of supplying a first raw material gas containing hydrogen and nitrogen to a catalytic reactor, A step of synthesizing ammonia from hydrogen and nitrogen using a first catalyst and a second catalyst, each having a different temperature, housed in the catalytic reactor, comprising: a step in which the first catalyst synthesizes ammonia using a first raw material gas; and a step in which the second catalyst synthesizes ammonia using a second raw material gas that includes a gas supplied via the first catalyst. Methods for synthesizing ammonia. 　 A computer program that causes a computer to perform the synthesis of ammonia using an ammonia synthesis system, The function of supplying a first raw material gas containing hydrogen and nitrogen to a catalytic reactor, The computer is instructed to perform the following functions using a first catalyst and a second catalyst, each having a different temperature, housed in the catalytic reactor, to synthesize ammonia from hydrogen and nitrogen, wherein the first catalyst synthesizes ammonia using a first raw material gas, and the second catalyst synthesizes ammonia using a second raw material gas that includes the gas supplied through the first catalyst. Computer program.

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