Ammonia production system and ammonia production method

Abstract

An ammonia production system (1A) is provided with at least one reactor (40) to which a raw material gas containing nitrogen and hydrogen is supplied and in which heat accumulation bodies (50a, 50b) are provided, and produces ammonia by using the reactor (40). This ammonia production method involves producing ammonia by using at least one reactor to which a raw material gas containing nitrogen and hydrogen is supplied and in which heat accumulation bodies are provided. The production method comprises a heating step for supplying the raw material gas to the reactor and heating the raw material gas by causing heat in the heat accumulation bodies to be released, and a heat accumulation step for accumulating, in the heat accumulation bodies, heat of a reaction gas passing inside the reactor. The heating step and the heat accumulation step are alternately repeated.

Description

Ammonia production system and ammonia production method

[0001] The present disclosure relates to an ammonia production system and an ammonia production method.

[0002] Ammonia (NH ３ ), which is used as a raw material for fertilizers and various chemical products, can be synthesized from nitrogen and hydrogen. Conventionally, there has been known an ammonia production system that performs heat exchange between a high-temperature reaction gas and a low-temperature raw material gas before reaction by means of an indirect heat exchanger provided outside a reactor. Patent Document 1 discloses an ammonia production apparatus that suppresses destabilization of ammonia production by heating a raw material gas using an indirect heat exchanger separately provided outside a reactor.

[0003] International Publication No. WO 2022 / 162759

[0004] Even when an indirect heat exchanger is separately provided as in Patent Document 1, it is necessary to transfer heat via a heat medium or the like, so the structure of the entire ammonia production system is complicated and inefficient. Therefore, it has been a problem to stably produce ammonia while efficiently performing heat exchange between a high-temperature reaction gas and a low-temperature raw material gas.

[0005] Accordingly, an object of the present disclosure is to provide an ammonia production system and an ammonia production method that achieve improved efficiency and stability.

[0006] The ammonia production system according to the present disclosure is supplied with a raw material gas containing nitrogen and hydrogen, includes at least one reactor having a heat storage body provided therein, and produces ammonia by the reactor.

[0007] The heat storage body may include a first heat storage body and a second heat storage body. At least one reactor may comprise a first reactor having the first heat storage body inside, and a second reactor connected to the first reactor via an intermediate product gas flow path and having the second heat storage body inside. The raw material gas may be supplied to the first reactor or the second reactor. When the raw material gas is supplied to the first reactor, the intermediate product gas that has passed through the first reactor may be supplied to the second reactor via the intermediate product gas flow path. When the raw material gas is supplied to the second reactor, the intermediate product gas that has passed through the second reactor may be supplied to the first reactor via the intermediate product gas flow path.

[0008] A heater may be provided in the intermediate product gas flow path.

[0009] A first catalyst layer for promoting ammonia production may be provided inside the first reactor, and a second catalyst layer for promoting ammonia production may be provided inside the second reactor. A raw material gas may be supplied between the first heat storage body and the first catalyst layer in the first reactor, between the second heat storage body and the second catalyst layer in the second reactor, and between the first catalyst layer and the second catalyst layer.

[0010] At least one of the first heat storage body and the second heat storage body may contain ceramics.

[0011] The ammonia production method according to this disclosure produces ammonia in at least one reactor, which is supplied with a raw material gas containing nitrogen and hydrogen and has a heat storage body inside. The ammonia production method includes a heating step of supplying the raw material gas to the reactor and heating the raw material gas by releasing heat from the heat storage body, and a heat storage step of storing the heat of the reaction gas passing through the reactor in the heat storage body. The ammonia production method alternately repeats the heating step and the heat storage step.

[0012] The ammonia production method according to this disclosure produces ammonia from a raw material gas containing nitrogen and hydrogen using a reactor comprising a first reactor and a second reactor. A first heat storage body and a first catalyst layer for promoting ammonia production are provided inside the first reactor, and a second heat storage body and a second catalyst layer for promoting ammonia production are provided inside the second reactor. The ammonia production method includes a first heating step in which raw material gas is supplied to the first reactor and the raw material gas is heated by releasing heat from the first heat storage body. The ammonia production method includes a first heat storage step in which the intermediate product gas that has passed through the first reactor is supplied to the second reactor and the heat of the reaction gas passing through the second reactor is stored in the second heat storage body. The ammonia production method includes a second heating step in which raw material gas is supplied to the second reactor and the raw material gas is heated by releasing heat from the second heat storage body. The ammonia production method includes a second heat storage step in which the intermediate product gas that has passed through the second reactor is supplied to the first reactor, and the heat of the reaction gas passing through the first reactor is stored in the first heat storage body. The ammonia production method repeats the first heating step, the first heat storage step, the second heating step, and the second heat storage step in this order.

[0013] The ammonia production method may include a first switching step of switching the supply destination of the raw material gas from the first reactor to the second reactor, and a second switching step of switching the supply destination of the raw material gas from the second reactor to the first reactor.

[0014] The ammonia production method may include a catalyst temperature control step in which the temperature of at least one of the first catalyst layer and the second catalyst layer is controlled by supplying a raw material gas to at least one of the following: between the first heat storage body and the first catalyst layer in the first reactor, between the heat storage body and the second catalyst layer in the second reactor, and between the first catalyst layer and the second catalyst layer.

[0015] This disclosure provides an ammonia production system and ammonia production method that are more efficient and stable.

[0016] Figure 1 is a schematic diagram showing an ammonia production system according to the first embodiment. Figure 2 is a schematic diagram showing the state during steady-state operation of the ammonia production system according to the first embodiment. Figure 3 is a schematic diagram showing the state during steady-state operation of the ammonia production system according to the first embodiment. Figure 4 is a schematic diagram showing an ammonia production system according to the second embodiment. Figure 5 is a schematic diagram showing the state during steady-state operation of the ammonia production system according to the second embodiment. Figure 6 is a schematic diagram showing the state during steady-state operation of the ammonia production system according to the second embodiment. Figure 7 is a schematic diagram showing an ammonia production system according to the third embodiment.

[0017] Several exemplary embodiments will be described below with reference to the drawings. Note that the dimensional ratios in the drawings are exaggerated for illustrative purposes and may differ from the actual ratios.

[0018] [First Embodiment] The ammonia production system is supplied with a raw material gas containing nitrogen and hydrogen, and comprises at least one reactor equipped with a heat storage body. The reactor produces ammonia from the raw material gas containing nitrogen and hydrogen.

[0019] First, an ammonia production system 1A according to the first embodiment will be described using Figure 1. The ammonia production system 1A is supplied with a raw material gas containing nitrogen and hydrogen, and includes a reactor 40 equipped with heat storage bodies 50a and 50b inside. The reactor 40 then produces ammonia from the raw material gas containing nitrogen and hydrogen.

[0020] The ammonia production system 1A may also include a hydrogen supply unit 10, a nitrogen supply unit 20, a raw material compressor 31, a condenser 90, a separator 100, a circulation compressor 110, and an ammonia tank 200, in addition to the reactor 40.

[0021] The hydrogen supply unit 10 is installed to supply hydrogen contained in the raw material gas to the reactor 40, and a shut-off valve 11 may be provided in the hydrogen supply channel that supplies hydrogen from the hydrogen supply unit 10. Furthermore, the hydrogen supply unit 10 is not particularly limited, but may be a water electrolysis device that decomposes water into hydrogen and oxygen. In other words, the hydrogen supply unit 10 may store the hydrogen produced by the water electrolysis device.

[0022] The nitrogen supply unit 20 is installed to supply nitrogen contained in the raw material gas to the reactor 40, and a shut-off valve 21 may be provided in the nitrogen supply channel that supplies nitrogen from the nitrogen supply unit 20. The nitrogen supply unit 20 is not particularly limited, but may be a nitrogen gas production device using the pressure swing adsorption (PSA) method. The PSA method is a method that can continuously extract nitrogen gas from compressed air by using an adsorbent that selectively adsorbs oxygen molecules. In other words, the nitrogen supply unit 20 may store nitrogen produced by a PSA type nitrogen gas generator.

[0023] The hydrogen supplied from the hydrogen supply unit 10 and the nitrogen supplied from the nitrogen supply unit 20 combine to form the raw material gas 30, which is then sent to the raw material compressor 31. The raw material compressor 31 then pressurizes the raw material gas 30, which contains nitrogen and hydrogen. The raw material gas 30 pressurized by the raw material compressor 31 is then supplied to the reactor 40. The raw material gas 30 contains nitrogen and hydrogen as essential components, but may also contain unreacted nitrogen and hydrogen, as well as residual gaseous ammonia, which are sent from the circulating compressor 110 as residual gas 83, as described later.

[0024] During steady-state operation of the ammonia production system 1A, a raw material gas 30 containing nitrogen and hydrogen is supplied to the reactor 40 to produce ammonia. Inside the reactor 40, there are heat storage bodies 50a and 50b, and catalyst layers 60a and 60b that promote ammonia production. The order in which the heat storage bodies 50a and 50b and catalyst layers 60a and 60b are arranged inside the reactor 40 is not particularly limited, but from the viewpoint of heat exchange efficiency, it is preferable that the catalyst layers 60a and 60b are arranged so as to be sandwiched between the heat storage bodies 50a and 50b. In Figures 1 to 3, there are two catalyst layers 60a and 60b, but there may be one layer or three or more layers. Furthermore, the reactor 40 may be vertically arranged with the raw material gas and reaction gas flowing vertically, or horizontally arranged with the raw material gas and reaction gas flowing horizontally.

[0025] In the ammonia production system 1A, heat exchange between the high-temperature reaction gas and the low-temperature raw material gas is alternately performed by heat storage bodies 50a and 50b installed inside the reactor 40. Therefore, it functions as a regenerative heat exchanger. By repeatedly switching the raw material gas supply channel through which the raw material gas 30 is supplied to the reactor 40, the high-temperature reaction gas and the low-temperature raw material gas alternately pass through the heat storage bodies 50a and 50b, and heat exchange between the reaction gas and the raw material gas alternately takes place. In other words, in the ammonia production system 1A, the raw material gas supply channel is repeatedly switched alternately between the state in Figure 2 and the state in Figure 3. Note that in Figure 2, the on-off valves 11, 21, 32a and the raw material compressor 31 are blacked out to indicate that the raw material gas 30 is supplied as raw material gas 30a from one of the raw material gas supply channels, that is, the raw material gas supply channel on the lower side of the reactor 40. In Figure 3, the on / off valves 11, 21, 32b and the raw material compressor 31 are colored black to indicate that the raw material gas 30 is supplied as raw material gas 30b from the other raw material gas supply channel, that is, the raw material gas supply channel on the upper side of the reactor 40.

[0026] First, as shown in Figure 2, when the raw material gas 30a is supplied from one of the raw material gas supply channels, the low-temperature raw material gas 30a passes through the heat storage body 50a and reacts in the catalyst layers 60a and 60b, while the high-temperature reaction gas passes through the heat storage body 50b. At this time, the heat storage body 50b, through which the high-temperature reaction gas has passed, is heated to a temperature similar to that of the reaction gas. After that, the raw material gas supply channels are switched to achieve the state shown in Figure 3. The temperature of the low-temperature raw material gas 30a before passing through the heat storage body 50a is, for example, 50°C, and the temperature of the high-temperature reaction gas is, for example, 400°C to 500°C.

[0027] As shown in Figure 3, when the raw material gas 30b is supplied from the other raw material gas supply channel, the low-temperature raw material gas 30b passes through the heat storage body 50b and reacts in the catalyst layers 60b and 60a, while the high-temperature reaction gas passes through the heat storage body 50a. At this time, the temperature of the low-temperature raw material gas 30b is raised to approximately the same temperature as the reaction gas by the heat storage body 50b, which has already been heated to approximately the same temperature as the reaction gas. Then, the heat storage body 50a, through which the high-temperature reaction gas has passed, is heated to approximately the same temperature as the reaction gas. After that, the raw material gas supply channels are switched to the state shown in Figure 2. When the raw material gas 30a is supplied again from one of the raw material gas supply channels, the low-temperature raw material gas 30a is raised to approximately the same temperature as the reaction gas by the heat storage body 50a, which has already been heated to approximately the same temperature as the reaction gas. Note that the temperature of the low-temperature raw material gas 30b before passing through the heat storage body 50b is, for example, 50°C, and the temperature of the high-temperature reaction gas is, for example, 400°C to 500°C.

[0028] In conventional ammonia production systems, a heat exchanger located outside the reactor was used to exchange heat between the high-temperature reaction gas and the low-temperature raw material gas before the reaction. In the ammonia production system 1A according to this embodiment, by repeatedly switching the raw material gas supply channel alternately, the low-temperature raw material gas and the high-temperature reaction gas alternately pass through the heat storage bodies 50a and 50b, enabling efficient heat exchange. Compared to the case where an indirect heat exchanger is used, the heat exchange in the heat storage bodies 50a and 50b has a larger heat transfer area per unit volume and higher heat exchange efficiency. Therefore, the heat storage bodies 50a and 50b can be compactly installed inside the reactor 40, and the high heat exchange efficiency allows for a shorter heating time for the raw material gases 30a and 30b. In addition, since the introduction of raw material gases 30a and 30b into the catalyst layers 60a and 60b is switched alternately, the entire catalyst layers 60a and 60b become a uniform reaction field.

[0029] In recent years, in order to achieve carbon neutrality, the synthesis of ammonia using hydrogen produced by a water electrolysis device powered by renewable energy has been considered. When using electricity from renewable energy sources, it is expected that the flow rate of the raw material gas will change due to load fluctuations. As a result, the heat exchange efficiency will fluctuate, which may prevent proper control of the temperature of the raw material gas and lead to an unstable reaction. Ammonia production system 1A can stably raise the temperature of raw material gases 30a and 30b by releasing heat from heat storage elements 50a and 50b, even when the flow rate of raw material gases 30a and 30b changes due to load fluctuations of electricity from renewable energy sources, thus exhibiting excellent load-following capabilities.

[0030] The constituent materials of the heat storage bodies 50a and 50b are not particularly limited, and examples include ceramics or metals. From the viewpoint of heat resistance and cost, it is preferable that the heat storage bodies 50a and 50b are made of ceramics. Furthermore, the form of the heat storage bodies 50a and 50b is preferably a form in which ceramic balls are filled or a form in which ceramics are arranged in a honeycomb shape.

[0031] A heater 35 may be provided in the center of the reactor 40 to heat the inside of the reactor 40. Specifically, the heater 35 may be provided between the heat storage bodies 50a, 50b and the catalyst layers 60a, 60b. Furthermore, a raw material gas supply channel may be provided in the center of the reactor 40 to supply raw material gas, and raw material gas may be supplied from the raw material gas supply channel between the heat storage bodies 50a, 50b and the catalyst layers 60a, 60b. In addition, an on / off valve 33 may be provided to open and close the raw material gas supply channel.

[0032] When the ammonia production system 1A is started, nitrogen is supplied to the reactor 40 using the raw material gas supply channel, and the catalyst layers 60a, 60b and the heat storage bodies 50a, 50b can be heated by the heater 35 to a predetermined temperature. Here, "startup of the ammonia production system 1A" refers to the state before steady-state operation of the ammonia production system 1A begins, that is, the state before raw material gases 30a, 30b are supplied to the reactor 40. By preheating the catalyst layers 60a, 60b and the heat storage bodies 50a, 50b when the ammonia production system 1A is started, the system can smoothly transition to steady-state operation. The type of heater 35 is not particularly limited, and an electric heater may be used. Furthermore, the raw material gas supply channel used to supply nitrogen may be the raw material gas supply channel below the reactor 40, or the raw material gas supply channels below and above the reactor 40, or the raw material gas supply channels below and in the center of the reactor 40.

[0033] Furthermore, during steady-state operation of the ammonia production system 1A, the temperature of the catalyst layers 60a and 60b can be adjusted by supplying low-temperature raw material gases 30a and 30b between the heat regenerators 50a and 50b and the catalyst layers 60a and 60b from the raw material gas supply channel in the center of the reactor 40. Since ammonia production is an exothermic reaction, the reaction ratio tends to decrease if the temperature of the catalyst layers 60a and 60b rises too high. Therefore, the reaction can be controlled by adjusting the temperature of the catalyst layers 60a and 60b by supplying low-temperature raw material gases 30a and 30b. Note that in Figures 2 and 3, the on-off valves 11, 21, and 33 and the raw material compressor 31 are blacked out to indicate that the raw material gases 30a and 30b are supplied between the heat regenerators 50a and 50b and the catalyst layers 60a and 60b.

[0034] Alternatively, in the central part of the reactor 40, an indirect heat exchanger (not shown) may be provided between the heat storage bodies 50a, 50b and the catalyst layers 60a, 60b instead of a raw material gas supply channel to adjust the temperature of the catalyst layers 60a, 60b. Specifically, the flow path from the raw material compressor 31 to the reactor 40, i.e., the raw material gas supply channel through which the low-temperature raw material gases 30a, 30b flow, may be passed through the indirect heat exchanger installed between the heat storage bodies 50a, 50b and the catalyst layers 60a, 60b. By using such an indirect heat exchanger, during steady-state operation of the ammonia production system 1A, heat exchange can be performed between the raw material gases 30a, 30b before they are supplied to the reactor 40 and the reaction gases in the reactor. In this way, by using an indirect heat exchanger, the reaction can be controlled by adjusting the temperature of the catalyst layers 60a, 60b without directly supplying the low-temperature raw material gases 30a, 30b into the reactor. On the other hand, the raw material gases 30a and 30b can be preheated before being supplied to the reactor 40.

[0035] The reaction gas generated in reactor 40 is cooled by storing heat in heat storage bodies 50a and 50b, and sent to condenser 90 as reaction gases 80a and 80b containing gaseous ammonia. The refrigerant passes through refrigerant channel 91 to condenser 90. The reaction gases 80a and 80b are then condensed by the refrigerant and sent to separator 100 as product 82 containing liquid ammonia. In Figures 2 and 3, the on-off valves 81b and 81a are colored black to indicate that the reaction gases 80b and 80a are sent to condenser 90. The temperature of the reaction gas generated in reactor 40 is, for example, 400°C to 500°C, and the temperature of the reaction gases 80a and 80b cooled by storing heat in heat storage bodies 50a and 50b is, for example, 100°C to 200°C.

[0036] In the separator 100, liquid ammonia 84 may be separated from the product 82 and sent to the ammonia tank 200 for storage. A shut-off valve 101 may be provided in the supply channel that supplies liquid ammonia 84 to the ammonia tank 200. In Figures 2 and 3, the shut-off valve 101 is colored black to indicate that liquid ammonia 84 is sent to the ammonia tank 200.

[0037] On the other hand, in the separator 100, residual gas 83 containing unreacted nitrogen and hydrogen is separated from the product 82, and the residual gas 83 may be sent to the circulating compressor 110 and pressurized. The residual gas 83 may also contain gaseous ammonia. The residual gas 83 pressurized in the circulating compressor 110 then joins the raw material gas supply channel through which the raw material gases 30a and 30b flow, and is supplied back to the reactor 40. An on-off valve 111 may be provided to send the residual gas 83 to the raw material gas supply channel. Note that in Figures 2 and 3, the on-off valve 111 and the circulating compressor 110 are colored black to indicate that the residual gas 83 is sent to the raw material gas supply channel.

[0038] Furthermore, the separator 100 may separate the exhaust gas 85 from the product 82, and the exhaust gas 85 may be sent to a gas treatment facility (not shown). A shut-off valve 102 may be provided to send the exhaust gas 85. The exhaust gas 85 is, for example, an impurity or a gas with the same components as the residual gas 83. In Figures 2 and 3, the shut-off valve 102 is blacked out to indicate that the exhaust gas 85 is being discharged.

[0039] When nitrogen produced by a PSA-type nitrogen gas generator is used as the raw material gas, impurities such as argon contained with the nitrogen become concentrated as the reaction progresses, so it is preferable to discharge them as exhaust gas 85. On the other hand, in order to treat excess ammonia, the exhaust gas 85 may be sent to a gas treatment facility. Examples of gas treatment facilities include flare stack facilities and vent stack facilities. By installing a flare stack facility, ammonia can be burned. By installing a vent stack facility, the treated gas from which ammonia has been neutralized can be released into the atmosphere.

[0040] As described above, the ammonia production system 1A according to this embodiment is supplied with a raw material gas containing nitrogen and hydrogen, and comprises at least one reactor 40 equipped with heat storage bodies 50a and 50b, and produces ammonia in the reactor 40. By repeatedly switching the raw material gas supply flow path alternately, low-temperature raw material gas and high-temperature reaction gas alternately pass through the heat storage bodies 50a and 50b, enabling efficient heat exchange. Furthermore, even if the flow rate of the raw material gases 30a and 30b changes due to load fluctuations of electricity derived from renewable energy, the raw material gases 30a and 30b can be stably heated up by releasing heat from the heat storage bodies 50a and 50b, thus exhibiting excellent load-following capabilities. In this way, the ammonia production system 1A of this embodiment leads to the realization of small-scale, highly efficient, and stable ammonia production, thus providing an ammonia production system that is both efficient and stable.

[0041] Next, the ammonia production method in ammonia production system 1A will be explained using Figures 1 to 3.

[0042] First, hydrogen supplied from the hydrogen supply unit 10 and nitrogen supplied from the nitrogen supply unit 20 merge and are sent to the raw material compressor 31. The raw material compressor 31 pressurizes the raw material gas 30 containing nitrogen and hydrogen. When starting up the ammonia production system 1A, it is preferable to perform a preheating step in which nitrogen is supplied to the reactor 40 via a raw material gas supply passage, and the nitrogen is heated by a heater 35 provided at the center of the reactor 40. By performing the preheating step, the catalyst layers 60a, 60b and the heat storage bodies 50a, 50b can be heated to a predetermined temperature, and a smooth transition to steady operation of the ammonia production system 1A can be achieved.

[0043] During steady operation of the ammonia production system 1A, as shown in FIG. 2, the raw material gas 30a is supplied to the reactor 40 from one supply passage, or as shown in FIG. 3, the raw material gas 30b is supplied to the reactor 40 from the other supply passage.

[0044] First, as shown in FIG. 2, when the raw material gas 30a is supplied to the reactor 40 from one supply passage, the low-temperature raw material gas 30a passes through the heat storage body 50a. Then, a heating step is performed in which heat is radiated from the heat storage body 50a that has been heated by the aforementioned preheating step to heat the raw material gas 30a. Note that, as described later, this step may be performed after carrying out a switching step of switching the supply from the raw material gas 30b to the raw material gas 30a. When this step is performed after the switching step, the raw material gas 30a is heated by radiating heat from the heat storage body 50a that has been heated by the heat storage step described later.

[0045] The raw material gas 30a heated by the aforementioned heating step reacts in the catalyst layers 60a and 60b that have been heated by the aforementioned preheating step, and the high-temperature reaction gas passes through the heat storage body 50b. Then, a heat storage step is performed in which the heat of the reaction gas passing through the reactor 40 is stored in the heat storage body 50b. At this time, the heat storage body 50b is heated to a temperature approximately equal to that of the high-temperature reaction gas. On the other hand, the reaction gas generated in the reactor 40 is cooled by storing its heat in the heat storage body 50b, and is sent to the condenser 90 as the reaction gas 80b containing gaseous ammonia.

[0046] After a predetermined time has elapsed, a switching step is performed to switch the raw material gas supply channel through which the raw material gas 30 is supplied to the reactor 40 from one supply channel to the other supply channel. That is, through this switching step, the raw material gas supply channel is switched from the state shown in FIG. 2 to the state shown in FIG. 3, and the raw material gas is switched from the raw material gas 30a to the raw material gas 30b.

[0047] As shown in FIG. 3, when the raw material gas 30b is supplied to the reactor 40 from the other supply channel, the low-temperature raw material gas 30b passes through the heat storage body 50b. Then, a heating step is performed in which heat is dissipated from the heat storage body 50b that has been heated in the aforementioned heat storage step to heat the raw material gas 30b. Note that this step may be performed after the aforementioned preheating step is carried out. When this step is performed after the preheating step, heat is dissipated from the heat storage body 50b that has been heated in the preheating step to heat the raw material gas 30b.

[0048] The raw material gas 30b heated by the aforementioned heating step reacts in the catalyst layers 60b and 60a, and the high-temperature reaction gas passes through the heat storage body 50a. Then, a heat storage step is performed in which the heat of the reaction gas passing through the reactor 40 is stored in the heat storage body 50a. At this time, the temperature of the heat storage body 50a is raised to a temperature approximately equal to that of the high-temperature reaction gas. On the other hand, the reaction gas generated in the reactor 40 is cooled by having its heat stored in the heat storage body 50a, and is sent to the condenser 90 as reaction gas 80a containing gaseous ammonia.

[0049] After a predetermined time has elapsed, a switching step is performed to switch the raw material gas supply channel through which the raw material gas 30 is supplied to the reactor 40 from the other supply channel back to the one supply channel. That is, through this switching step, the raw material gas supply channel is switched from the state shown in FIG. 3 to the state shown in FIG. 2, and the raw material gas is switched from the raw material gas 30b back to the raw material gas 30a. Then, as described above, the heating step is performed again when the raw material gas 30a is supplied to the reactor 40 from the one supply channel.

[0050] As described above, the heating step is a step in which raw material gases 30a and 30b are supplied to the reactor 40 and heat is released from the heat storage bodies 50a and 50b to heat the raw material gases 30a and 30b. On the other hand, the heat storage step is a step in which the heat of the reaction gas passing through the reactor 40 is stored in the heat storage bodies 50a and 50b. In this way, the ammonia production method can efficiently exchange heat by alternately repeating the heating step and the heat storage step, allowing low-temperature raw material gas and high-temperature reaction gas to pass alternately through the heat storage bodies 50a and 50b. Furthermore, the ammonia production method may also include the preheating step and switching step described above.

[0051] Furthermore, during steady-state operation of the ammonia production system 1A, a catalyst temperature control step may be included, in which the temperature of the catalyst layers 60a and 60b is adjusted by supplying low-temperature raw material gases 30a and 30b between the heat storage bodies 50a and 50b and the catalyst layers 60a and 60b. Since ammonia production is an exothermic reaction, the reaction rate tends to decrease if the temperature of the catalyst layers 60a and 60b rises too high. Therefore, the reaction can be controlled by adjusting the temperature of the catalyst layers 60a and 60b through the catalyst temperature control step. Thus, the ammonia production method may include the catalyst temperature control step described above.

[0052] As described above, the ammonia production method according to this embodiment produces ammonia in at least one reactor equipped with a heat storage body, to which raw material gases containing nitrogen and hydrogen are supplied. The production method includes a heating step of supplying raw material gases to the reactor and heating the raw material gases by releasing heat from the heat storage body, and a heat storage step of storing the heat of the reaction gas passing through the reactor in the heat storage body, and the heating step and the heat storage step are repeated alternately. By repeating the heating step and the heat storage step alternately, the low-temperature raw material gas and the high-temperature reaction gas alternately pass through the heat storage bodies 50a and 50b, enabling efficient heat exchange. Furthermore, even if the flow rate of the raw material gas changes due to load fluctuations of electricity derived from renewable energy, the raw material gas can be stably heated by releasing heat from the heat storage bodies 50a and 50b, thus providing excellent load-following capabilities. In this way, the ammonia production system of this embodiment leads to the realization of small-scale, highly efficient, and stable ammonia synthesis, and thus provides an ammonia production method that improves the efficiency and stability of the reaction.

[0053] [Second Embodiment] The ammonia production system 1B according to the second embodiment will be described with reference to Figure 4. In the description of the second embodiment, the same parts as in the first embodiment will be omitted or simplified.

[0054] The ammonia production system is supplied with a raw material gas containing nitrogen and hydrogen, and comprises at least one reactor equipped with a heat storage body. The reactor then produces ammonia from the raw material gas containing nitrogen and hydrogen. In ammonia production system 1B, the heat storage body includes a first heat storage body 50c and a second heat storage body 50d. The at least one reactor comprises a first reactor 40c equipped with the first heat storage body 50c, and a second reactor 40d connected to the first reactor 40c via an intermediate product gas flow path 71, and equipped with a second heat storage body 50d. Ammonia production system 1B differs from ammonia production system 1A according to the first embodiment in that it comprises a first reactor 40c and a second reactor 40d instead of a reactor 40. In other words, ammonia production system 1B produces ammonia from a raw material gas 30 containing nitrogen and hydrogen using a reactor equipped with a first reactor 40c and a second reactor 40d. Other than the points mentioned, the ammonia production system 1A according to the first embodiment is the same and will therefore not be explained.

[0055] During steady-state operation of the ammonia production system 1B, the raw material gas 30 is supplied to either the first reactor 40c or the second reactor 40d. The raw material gas 30c is supplied to the first reactor 40c as raw material gas 30c, and the raw material gas 30d is supplied to the second reactor 40d as raw material gas 30d. When raw material gas 30c is supplied to the first reactor 40c, the intermediate product gas 70c that has passed through the first reactor 40c via the intermediate product gas flow path 71 is supplied to the second reactor 40d. Similarly, when raw material gas 30d is supplied to the second reactor 40d, the intermediate product gas 70d that has passed through the second reactor 40d via the intermediate product gas flow path 71 is supplied to the first reactor 40c.

[0056] A first heat storage body 50c and a first catalyst layer 60c for promoting ammonia production are provided inside the first reactor 40c. A second heat storage body 50d and a second catalyst layer 60d for promoting ammonia production are provided inside the second reactor 40d. In the first reactor 40c, the order in which the first heat storage body 50c and the first catalyst layer 60c are arranged is not particularly limited, but from the viewpoint of heat exchange efficiency, it is preferable to place the first heat storage body 50c at the position through which the raw material gas 30c passes first. Similarly, in the second reactor 40d, the order in which the second heat storage body 50d and the second catalyst layer 60d are arranged is not particularly limited, but from the viewpoint of heat exchange efficiency, it is preferable to place the second heat storage body 50d at the position through which the raw material gas 30d passes first. In Figures 4 to 6, the first catalyst layer 60c and the second catalyst layer 60d each have two layers, but they may be one layer or three or more layers. Furthermore, the first reactor 40c and the second reactor 40d may be arranged vertically so that the raw material gas and reaction gas flow in the vertical direction, or they may be arranged horizontally so that the raw material gas and reaction gas flow in the horizontal direction.

[0057] In the ammonia production system 1B, the first heat storage body 50c, located inside the first reactor 40c, and the second heat storage body 50d, located inside the second reactor 40d, alternately exchange heat between the high-temperature reaction gas and the low-temperature raw material gas. Therefore, it functions as a regenerative heat exchanger. By repeatedly switching the raw material gas supply channel through which the raw material gas 30 is supplied to the first reactor 40c or the second reactor 40d, the high-temperature reaction gas and the low-temperature raw material gas alternately pass through the first heat storage body 50c and the second heat storage body 50d, and heat exchange alternately occurs between the reaction gas and the raw material gas. In other words, in the ammonia production system 1B, the raw material gas supply channel is repeatedly switched alternately between the state in Figure 5 and the state in Figure 6. Note that in Figure 5, the on-off valves 11, 21, 32c and the raw material compressor 31 are blacked out to indicate that the raw material gas 30 is supplied as raw material gas 30c from the raw material gas supply channel below the first reactor 40c. In Figure 6, the on-off valves 11, 21, 32d and the raw material compressor 31 are colored black to indicate that the raw material gas 30 is supplied as raw material gas 30d from the raw material gas supply channel below the second reactor 40d.

[0058] First, as shown in Figure 5, when the raw material gas 30c is supplied from the raw material gas supply channel below the first reactor 40c, the low-temperature raw material gas 30c passes through the first heat storage body 50c, reacts in the first catalyst layer 60c, and generates an intermediate product gas 70c. Then, via the intermediate product gas channel 71, the intermediate product gas 70c that has passed through the first reactor 40c is supplied to the second reactor 40d. Subsequently, it reacts in the second catalyst layer 60d, and the high-temperature reaction gas passes through the second heat storage body 50d. At this time, the second heat storage body 50d, through which the high-temperature reaction gas has passed, is heated to a temperature similar to that of the reaction gas. After that, the raw material gas supply channel is switched to achieve the state shown in Figure 6. Note that the temperature of the low-temperature raw material gas 30c before passing through the first heat storage body 50c is, for example, 50°C, and the temperature of the high-temperature reaction gas is, for example, 400°C to 500°C.

[0059] As shown in Figure 6, when the raw material gas 30d is supplied from the raw material gas supply channel below the second reactor 40d, the low-temperature raw material gas 30d passes through the second heat storage body 50d. At this time, the temperature of the low-temperature raw material gas 30d is raised to approximately the same temperature as the reaction gas by the second heat storage body 50d, which has already been heated to approximately the same temperature as the reaction gas. Then, it reacts in the second catalyst layer 60d to produce an intermediate product gas 70d. The intermediate product gas 70d that has passed through the second reactor 40d is then supplied to the first reactor 40c via the intermediate product gas channel 71. Subsequently, it reacts in the first catalyst layer 60c, and the high-temperature reaction gas passes through the first heat storage body 50c. At this time, the first heat storage body 50c, through which the high-temperature reaction gas has passed, is heated to approximately the same temperature as the reaction gas. After that, the raw material gas supply channel is switched to achieve the state shown in Figure 5. When the raw material gas 30c is again supplied from the raw material gas supply channel below the first reactor 40c, the temperature of the low-temperature raw material gas 30c is raised to approximately the same temperature as the reaction gas by the first heat storage body 50c, which has already been heated to approximately the same temperature as the reaction gas. The temperature of the low-temperature raw material gas 30d before passing through the second heat storage body 50d is, for example, 50°C, and the temperature of the high-temperature reaction gas is, for example, 400°C to 500°C.

[0060] In the ammonia production system 1B according to this embodiment, by repeatedly switching the raw material gas supply channel alternately, the first heat storage body 50c and the second heat storage body 50d are alternately passed through with low-temperature raw material gas and high-temperature reaction gas, enabling efficient heat exchange. Compared to the case where an indirect heat exchanger is used, the heat exchange in the first heat storage body 50c and the second heat storage body 50d has a larger heat transfer area per unit volume and higher heat exchange efficiency. Therefore, the first heat storage body 50c and the second heat storage body 50d can be compactly installed inside the first reactor 40c and the second reactor 40d, and the high heat exchange efficiency allows for a shorter heating time for the raw material gases 30c and 30d. In addition, since the introduction of raw material gases 30c and 30d into the first catalyst layer 60c and the second catalyst layer 60d is alternately switched, the entire first catalyst layer 60c and the second catalyst layer 60d become a uniform reaction field. Furthermore, even if the flow rates of the raw material gases 30c and 30d change due to load fluctuations of electricity derived from renewable energy, the raw material gases 30c and 30d can be stably heated up by releasing heat from the first heat storage body 50c and the second heat storage body 50d, resulting in excellent load-following capabilities.

[0061] A heater 35 may be provided in the intermediate product gas flow path 71. Furthermore, raw material gases 30c and 30d may be supplied to the first reactor 40c and the second reactor 40d from a raw material gas supply flow path provided between the first catalyst layer 60c and the second catalyst layer 60d. The raw material gas supply flow path may be provided in the intermediate product gas flow path 71 located between the first catalyst layer 60c and the second catalyst layer 60d. An on / off valve 34 for opening and closing the raw material gas supply flow path may also be provided.

[0062] Furthermore, a raw material gas supply channel may be provided between the first heat storage body 50c and the first catalyst layer 60c in the first reactor 40c, and between the second heat storage body 50d and the second catalyst layer 60d in the second reactor 40d. Raw material gases 30c and 30d may be supplied from this raw material gas supply channel. On-off valves 33c and 33d for opening and closing the raw material gas supply channel may also be provided.

[0063] In Figure 4, when the ammonia production system 1B is started, nitrogen is preferably supplied to the first reactor 40c and the second reactor 40d using the raw material gas supply channel, and the nitrogen is heated by the heater 35 provided in the intermediate product gas channel 71. Here, "startup of the ammonia production system 1B" refers to the state before steady-state operation of the ammonia production system 1B begins, that is, the state before raw material gases 30c and 30d are supplied to the first reactor 40c or the second reactor 40d. By supplying nitrogen to the first reactor 40c and the second reactor 40d and heating them when the ammonia production system 1B is started, the first catalyst layer 60c and the second catalyst layer 60d and the first heat storage body 50c and the second heat storage body 50d can be heated to a predetermined temperature. By preheating the first catalyst layer 60c and the second catalyst layer 60d and the first heat storage body 50c and the second heat storage body 50d when the ammonia production system 1B is started, the ammonia production system 1B can smoothly transition to steady-state operation. The raw material gas supply channel used to supply nitrogen may be the raw material gas supply channel below the first reactor 40c, or it may be the raw material gas supply channel below the second reactor 40d. Alternatively, nitrogen may be supplied using at least one of the raw material gas supply channel below the first reactor 40c and the raw material gas supply channel below the second reactor 40d, and a raw material gas supply channel provided between the first catalyst layer 60c and the second catalyst layer 60d. Alternatively, nitrogen may be supplied using at least one of the raw material gas supply channel below the first reactor 40c and the raw material gas supply channel below the second reactor 40d, and a raw material gas supply channel provided between the first heat storage body 50c and the first catalyst layer 60c in the first reactor 40c. Nitrogen may be supplied using at least one of the raw material gas supply channel below the first reactor 40c and the raw material gas supply channel below the second reactor 40d, and a raw material gas supply channel provided between the second heat storage body 50d and the second catalyst layer 60d in the second reactor 40d.

[0064] The heater 35 may also be provided between the first heat storage body 50c and the first catalyst layer 60c in the first reactor 40c, or between the second heat storage body 50d and the second catalyst layer 60d in the second reactor 40d. The heater 35 installed in the above-mentioned positions may be used to heat the nitrogen supplied when the ammonia production system 1B is started up.

[0065] During steady-state operation of the ammonia production system 1B, when the raw material gas 30c is supplied to the first reactor 40c, the temperature of the first catalyst layer 60c can be adjusted by supplying the raw material gas 30c between the first heat regenerator 50c and the first catalyst layer 60c in the first reactor 40c. Similarly, during steady-state operation of the ammonia production system 1B, when the raw material gas 30d is supplied to the second reactor 40d, the temperature of the second catalyst layer 60d can be adjusted by supplying the raw material gas 30d between the second heat regenerator 50d and the second catalyst layer 60d in the second reactor 40d. Since ammonia production is an exothermic reaction, if the temperatures of the first catalyst layer 60c and the second catalyst layer 60d rise too high, the reaction ratio tends to decrease. Therefore, by supplying low-temperature raw material gases 30c and 30d as described above, the temperatures of the first catalyst layer 60c and the second catalyst layer 60d can be adjusted, thereby controlling the reaction. In Figures 5 and 6, the on-off valves 11, 21, 33c, 33d and the raw material compressor 31 are colored black to indicate that the raw material gases 30c and 30d are supplied to at least one of the first reactor 40c and the second reactor 40d.

[0066] Furthermore, during steady-state operation of the ammonia production system 1B, raw material gases 30c and 30d may be supplied to the first reactor 40c or the second reactor 40d from a raw material gas supply channel provided between the first catalyst layer 60c and the second catalyst layer 60d. For example, when raw material gas 30c is supplied to the first reactor 40c, the temperature of the second catalyst layer 60d can be adjusted by supplying the raw material gas to the second reactor 40d from the raw material gas supply channel provided between the first catalyst layer 60c and the second catalyst layer 60d. Also, when raw material gas 30d is supplied to the second reactor 40d, the temperature of the first catalyst layer 60c can be adjusted by supplying the raw material gas to the first reactor 40c from the raw material gas supply channel provided between the first catalyst layer 60c and the second catalyst layer 60d.

[0067] Thus, the raw material gas may be supplied to at least one of the following locations: between the first heat storage body 50c and the first catalyst layer 60c in the first reactor 40c, between the second heat storage body 50d and the second catalyst layer 60d in the second reactor 40d, or between the first catalyst layer 60c and the second catalyst layer 60d. During steady-state operation of the ammonia production system 1B, the supply of raw material gases 30c and 30d to the first reactor 40c or the second reactor 40d as described above allows for the temperature of at least one of the first catalyst layer 60c and the second catalyst layer 60d to be adjusted, thereby controlling the reaction.

[0068] An indirect heat exchanger (not shown) may be provided in at least one of the following locations: between the first heat storage body 50c and the first catalyst layer 60c in the first reactor 40c, between the second heat storage body 50d and the second catalyst layer 60d in the second reactor 40d, or between the first catalyst layer 60c and the second catalyst layer 60d. The indirect heat exchanger may be provided in the intermediate product gas flow path 71 located between the first catalyst layer 60c and the second catalyst layer 60d. Furthermore, a flow path connecting the raw material compressor 31 to the first reactor 40c or the second reactor 40d, that is, a raw material gas supply flow path through which low-temperature raw material gases 30c and 30d flow, may be passed to the indirect heat exchanger installed in the above-mentioned location.

[0069] During steady-state operation of the ammonia production system 1B, when the raw material gas 30c is supplied to the first reactor 40c, the low-temperature raw material gas 30c is passed through an indirect heat exchanger installed between the second heat storage body 50d and the second catalyst layer 60d in the second reactor 40d. As a result, the temperature of the second catalyst layer 60d can be adjusted by exchanging heat between the raw material gas 30c before it is supplied to the first reactor 40c and the reaction gas in the second reactor 40d. Furthermore, during steady-state operation of the ammonia production system 1B, when the raw material gas 30c is supplied to the first reactor 40c, the low-temperature raw material gas 30c is passed through an indirect heat exchanger installed between the first catalyst layer 60c and the second catalyst layer 60d. As a result, the temperature of the second catalyst layer 60d can be adjusted by exchanging heat between the raw material gas 30c before it is supplied to the first reactor 40c and the reaction gas that has passed through the first catalyst layer 60c.

[0070] During steady-state operation of the ammonia production system 1B, when the raw material gas 30d is supplied to the second reactor 40d, the low-temperature raw material gas 30d is passed through an indirect heat exchanger installed between the first heat storage body 50c and the first catalyst layer 60c in the first reactor 40c. As a result, the temperature of the first catalyst layer 60c can be adjusted by exchanging heat between the raw material gas 30d before it is supplied to the second reactor 40d and the reaction gas inside the first reactor 40c. Also, during steady-state operation of the ammonia production system 1B, when the raw material gas 30d is supplied to the second reactor 40d, the low-temperature raw material gas 30d is passed through an indirect heat exchanger installed between the first catalyst layer 60c and the second catalyst layer 60d. As a result, the temperature of the first catalyst layer 60c can be adjusted by exchanging heat between the raw material gas 30d before it is supplied to the second reactor 40d and the reaction gas that has passed through the second catalyst layer 60d.

[0071] In this way, by using an indirect heat exchanger, the reaction can be controlled by adjusting the temperature of the first catalyst layer 60c and the second catalyst layer 60d without directly supplying the low-temperature raw material gases 30c and 30d into the reactor. On the other hand, the raw material gases 30c and 30d can be preheated before being supplied to the first reactor 40c or the second reactor 40d.

[0072] The reaction gas produced in the first reactor 40c is cooled by storing heat in the first heat storage body 50c and sent to the condenser 90 as reaction gas 80c containing gaseous ammonia. Similarly, the reaction gas produced in the second reactor 40d is cooled by storing heat in the second heat storage body 50d and sent to the condenser 90 as reaction gas 80d containing gaseous ammonia. Then, a refrigerant passes through the refrigerant channel 91 to the condenser 90. The reaction gases 80c and 80d are condensed by the refrigerant and sent to the separator 100 as product 82 containing liquid ammonia. Note that in Figures 5 and 6, the on-off valves 81d and 81c are colored black to indicate that the reaction gases 80d and 80c are sent to the condenser 90. The temperature of the reaction gas generated in the first reactor 40c and the second reactor 40d is, for example, 400°C to 500°C, and the temperature of the reaction gas 80c and 80d, which are cooled by storing heat in the first heat storage body 50c and the second heat storage body 50d, is, for example, 100°C to 200°C.

[0073] In the separator 100, liquid ammonia 84 may be separated from the product 82, and the liquid ammonia 84 may be sent to the ammonia tank 200 for storage.

[0074] On the other hand, in the separator 100, residual gas 83 containing unreacted nitrogen and hydrogen is separated from the product 82, and the residual gas 83 may be sent to the circulating compressor 110 and pressurized. The residual gas 83 may also contain gaseous ammonia. The residual gas 83 pressurized in the circulating compressor 110 then joins the raw material gas supply channel through which the raw material gases 30c and 30d flow, and is supplied again to the first reactor 40c or the second reactor 40d.

[0075] Furthermore, the separator 100 may separate the exhaust gas 85 from the product 82, and the exhaust gas 85 may be sent to a gas treatment facility (not shown).

[0076] As described above, the ammonia production system 1B according to this embodiment includes a first reactor 40c having a first heat storage body 50c inside, and a second reactor 40d connected to the first reactor 40c via an intermediate product gas flow path 71 and having a second heat storage body 50d inside. The raw material gases 30c and 30d are supplied to either the first reactor 40c or the second reactor 40d. When the raw material gas 30c is supplied to the first reactor 40c, the intermediate product gas 70c that has passed through the first reactor 40c is supplied to the second reactor 40d via the intermediate product gas flow path 71. When the raw material gas 30d is supplied to the second reactor 40d, the intermediate product gas 70d that has passed through the second reactor 40d is supplied to the first reactor 40c via the intermediate product gas flow path 71.

[0077] Ammonia production system 1B produces ammonia from raw material gases 30c and 30d containing nitrogen and hydrogen using a reactor equipped with a first reactor 40c and a second reactor 40d. By repeatedly switching the raw material gas supply flow path alternately, low-temperature raw material gas and high-temperature reaction gas alternately pass through the first heat storage body 50c and the second heat storage body 50d, enabling efficient heat exchange. Furthermore, even if the flow rate of raw material gases 30c and 30d changes due to load fluctuations of electricity derived from renewable energy, the raw material gases 30c and 30d can be stably heated up by releasing heat from the first heat storage body 50c and the second heat storage body 50d, thus providing excellent load-following capabilities. In this way, ammonia production system 1B can provide an ammonia production system that is efficient and stable, leading to the realization of small-scale, highly efficient, and stable ammonia production.

[0078] Next, the ammonia production method in ammonia production system 1B will be explained using Figures 4 to 6.

[0079] First, the hydrogen supplied from the hydrogen supply unit 10 and the nitrogen supplied from the nitrogen supply unit 20 are combined and sent to the raw material compressor 31. The raw material compressor 31 pressurizes the raw material gas 30 containing nitrogen and hydrogen.

[0080] When starting up the ammonia production system 1B, it is preferable to perform a preheating step in which nitrogen is supplied to the first reactor 40c and the second reactor 40d, and the nitrogen is heated by a heater 35 provided in the intermediate product gas flow path 71. By performing the preheating step, the first catalyst layer 60c and the second catalyst layer 60d and the first heat storage body 50c and the second heat storage body 50d can be raised to a predetermined temperature, and the ammonia production system 1B can smoothly transition to steady-state operation.

[0081] During steady-state operation of the ammonia production system 1B, raw material gas 30c is supplied to the first reactor 40c from the raw material gas supply channel below the first reactor 40c, or raw material gas 30d is supplied to the second reactor 40d from the raw material gas supply channel below the second reactor 40d.

[0082] First, as shown in Figure 5, when the raw material gas 30c is supplied to the first reactor 40c, the low-temperature raw material gas 30c passes through the first heat storage body 50c. Then, a first heating step is performed in which the raw material gas 30c is heated by releasing heat from the first heat storage body 50c, which has been heated up by the preheating step described above.

[0083] The raw material gas 30c, heated by the first heating step described above, reacts in the first catalyst layer 60c, which has been heated by the preheating step described above, to produce an intermediate product gas 70c. The intermediate product gas 70c then passes through the first reactor 40c via the intermediate product gas flow path 71 and is supplied to the second reactor 40d. Subsequently, it reacts in the second catalyst layer 60d, and the high-temperature reaction gas passes through the second heat storage body 50d. Then, the first heat storage step is performed to store the heat of the reaction gas passing through the second reactor 40d in the second heat storage body 50d. At this time, the second heat storage body 50d is heated to a temperature similar to that of the high-temperature reaction gas. Meanwhile, the reaction gas produced in the second reactor 40d is cooled by storing heat in the second heat storage body 50d and sent to the condenser 90 as a reaction gas 80d containing gaseous ammonia.

[0084] After a predetermined time has elapsed, a first switching process is performed to switch the supply destination of the raw material gases 30c and 30d from the first reactor 40c to the second reactor 40d. In other words, this first switching process switches the raw material gas supply path from the state shown in Figure 5 to the state shown in Figure 6, and switches from raw material gas 30c to raw material gas 30d.

[0085] As shown in Figure 6, when the raw material gas 30d is supplied to the second reactor 40d, the low-temperature raw material gas 30d passes through the second heat storage body 50d. Then, a second heating step is performed in which heat is released from the second heat storage body 50d, which has been heated by the first heat storage step described above, to heat the raw material gas 30d.

[0086] The raw material gas 30d heated by the second heating step described above reacts in the second catalyst layer 60d to produce an intermediate product gas 70d. The intermediate product gas 70d then passes through the second reactor 40d via the intermediate product gas flow path 71 and is supplied to the first reactor 40c. Subsequently, it reacts in the first catalyst layer 60c, and the high-temperature reaction gas passes through the first heat storage body 50c. A second heat storage step is then performed to store the heat of the reaction gas passing through the first reactor 40c in the first heat storage body 50c. At this time, the first heat storage body 50c is heated to a temperature similar to that of the high-temperature reaction gas. Meanwhile, the reaction gas produced in the first reactor 40c is cooled by storing heat in the first heat storage body 50c and sent to the condenser 90 as a reaction gas 80c containing gaseous ammonia.

[0087] After a predetermined time has elapsed, a second switching step is performed to switch the supply destination of the raw material gases 30c and 30d from the second reactor 40d to the first reactor 40c. In other words, this second switching step switches the raw material gas supply path from the state shown in Figure 6 to the state shown in Figure 5, and switches from raw material gas 30d to raw material gas 30c. Then, as described above, the first heating step is performed again when the raw material gas 30c is supplied to the first reactor 40c.

[0088] Thus, the ammonia production method, by repeating the first heating step, the first heat storage step, the second heating step, and the second heat storage step in this order, allows the low-temperature raw material gas and the high-temperature reaction gas to pass alternately through the first heat storage body 50c and the second heat storage body 50d, enabling efficient heat exchange. Furthermore, the ammonia production method may also include the preheating step, the first switching step, and the second switching step described above.

[0089] The ammonia production method may include a catalyst temperature control step of supplying a low-temperature raw material gas to at least one of the following: between the first heat regenerator 50c and the first catalyst layer 60c in the first reactor 40c, and between the second heat regenerator 50d and the second catalyst layer 60d in the second reactor 40d. During steady-state operation of the ammonia production system 1B, when the raw material gas 30c is supplied to the first reactor 40c, the temperature of the first catalyst layer 60c can be adjusted by supplying a low-temperature raw material gas 30c between the first heat regenerator 50c and the first catalyst layer 60c in the first reactor 40c. Similarly, when the raw material gas 30d is supplied to the second reactor 40d, the temperature of the second catalyst layer 60d can be adjusted by supplying a low-temperature raw material gas 30d between the second heat regenerator 50d and the second catalyst layer 60d in the second reactor 40d. Since ammonia production is an exothermic reaction, if the temperatures of the catalyst layers 60a and 60b rise too high, the reaction ratio tends to decrease. Therefore, by performing a catalyst temperature control step, the temperature of at least one of the first catalyst layer 60c and the second catalyst layer 60d can be adjusted to control the reaction.

[0090] Furthermore, the ammonia production method may include a catalyst temperature control step in which a low-temperature raw material gas is supplied between the first catalyst layer 60c and the second catalyst layer 60d during steady-state operation of the ammonia production system 1B. When the raw material gas 30c is supplied to the first reactor 40c, the temperature of the second catalyst layer 60d can be controlled by supplying the raw material gas to the second reactor 40d through a raw material gas supply channel provided between the first catalyst layer 60c and the second catalyst layer 60d. Also, when the raw material gas 30d is supplied to the second reactor 40d, the temperature of the first catalyst layer 60c can be controlled by supplying the raw material gas to the first reactor 40c through a raw material gas supply channel provided between the first catalyst layer 60c and the second catalyst layer 60d. Therefore, by performing the catalyst temperature control step, the temperature of at least one of the first catalyst layer 60c and the second catalyst layer 60d can be adjusted to control the reaction.

[0091] In the catalyst temperature control step, a raw material gas is supplied to at least one of the following locations: between the first heat storage body 50c and the first catalyst layer 60c in the first reactor 40c, between the second heat storage body 50d and the second catalyst layer 60d in the second reactor 40d, and between the first catalyst layer 60c and the second catalyst layer 60d. The catalyst temperature control step then adjusts the temperature of at least one of the first catalyst layer 60c and the second catalyst layer 60d. The ammonia production method may include the catalyst temperature control step described above.

[0092] As described above, the ammonia production method according to this embodiment is an ammonia production method that produces ammonia from a raw material gas containing nitrogen and hydrogen using a reactor equipped with a first reactor 40c and a second reactor 40d. Inside the first reactor 40c is provided a first heat storage body 50c and a first catalyst layer 60c that promotes the production of ammonia, and inside the second reactor 40d is provided a second heat storage body 50d and a second catalyst layer 60d that promotes the production of ammonia. The production method includes a first heating step in which raw material gas 30c is supplied to the first reactor 40c and the raw material gas 30c is heated by releasing heat from the first heat storage body 50c. The production method includes a first heat storage step in which the intermediate product gas 70c that has passed through the first reactor 40c is supplied to the second reactor 40d and the heat of the reaction gas passing through the second reactor 40d is stored in the second heat storage body 50d. The manufacturing method includes a second heating step in which raw material gas 30d is supplied to a second reactor 40d, and heat is released from a second heat storage body 50d to heat the raw material gas 30d. The manufacturing method also includes a second heat storage step in which the intermediate product gas 70d that has passed through the second reactor 40d is supplied to a first reactor 40c, and the heat of the reaction gas passing through the first reactor 40c is stored in the first heat storage body 50c. The manufacturing method repeats the first heating step, the first heat storage step, the second heating step, and the second heat storage step in this order. By alternately repeating the heating step and the heat storage step, the first heat storage body 50c and the second heat storage body 50d are alternately passed through by the low-temperature raw material gas and the high-temperature reaction gas, enabling efficient heat exchange. Furthermore, even if the flow rates of the raw material gases 30c and 30d change due to load fluctuations of electricity derived from renewable energy, the raw material gases 30c and 30d can be stably heated up by releasing heat from the first heat storage body 50c and the second heat storage body 50d, thus providing excellent load-following capabilities. In this way, the ammonia production system of this embodiment leads to the realization of small-scale, highly efficient, and stable ammonia synthesis, thus providing an ammonia production method that is both efficient and stable.

[0093] [Third Embodiment] The ammonia production system 1C according to the third embodiment will be described with reference to Figure 7. In the description of the third embodiment, the same parts as those in the first and second embodiments will be omitted or simplified.

[0094] As shown in Figure 7, the ammonia production system 1C according to this embodiment differs from the ammonia production system 1B according to the second embodiment in that it is equipped with an indirect heat exchanger 120. Other aspects are the same as those of the ammonia production system 1B according to the second embodiment unless otherwise specified, and therefore will not be described.

[0095] The type of indirect heat exchanger 120 is not particularly limited; for example, it may be vertical or horizontal. Furthermore, the indirect heat exchanger 120 may be a shell-and-tube type heat exchanger (multi-tube heat exchanger).

[0096] As shown in Figure 7, the indirect heat exchanger 120 is installed in the flow path connecting the raw material compressor 31 to the first reactor 40c or the second reactor 40d, that is, in the raw material gas supply flow path through which the low-temperature raw material gases 30c and 30d flow. The indirect heat exchanger 120 is also installed in the flow path connecting the first reactor 40c or the second reactor 40d to the condenser 90, that is, in the flow path through which the high-temperature reaction gases 80c and 80d pass.

[0097] The indirect heat exchanger 120 exchanges heat between the raw material gas 30c before it is supplied to the first reactor 40c and the reaction gas 80d that has passed through the second reactor 40d, for example, when the raw material gas 30c is supplied from the raw material gas supply channel below the first reactor 40c. On the other hand, the indirect heat exchanger 120 also exchanges heat between the raw material gas 30d before it is supplied to the second reactor 40d and the reaction gas 80c that has passed through the first reactor 40c, for example, when the raw material gas 30d is supplied from the raw material gas supply channel below the second reactor 40d. The temperature of the low-temperature raw material gases 30c and 30d is, for example, 50°C, the temperature of the reaction gases 80c and 80d that have passed through the first reactor 40c or the second reactor 40d is, for example, 200°C, and the temperature of the reaction gas after passing through the indirect heat exchanger 120 is, for example, 100°C.

[0098] In this embodiment, the ammonia production system 1C can preheat the raw material gas before supplying it to the first reactor 40c or the second reactor 40d, while precooling the reaction gas before sending it to the condenser 90, using the indirect heat exchanger 120. Furthermore, the ammonia production system 1C can perform heat exchange between the low-temperature raw material gas and the high-temperature reaction gas not only in the first heat storage body 50c and the second heat storage body 50d, but also in the indirect heat exchanger 120, thus enabling even more efficient heat exchange. Thus, the ammonia production system 1C can perform heat exchange between the low-temperature raw material gas and the high-temperature reaction gas not only in the first heat storage body 50c and the second heat storage body 50d, but also in the indirect heat exchanger 120. Therefore, the ammonia production system 1C can provide an ammonia production system that is more efficient and stable.

[0099] Although several embodiments have been described, it is possible to modify or transform the embodiments based on the above disclosure. All components of the above embodiments, and all features described in the claims, may be taken individually and combined, provided that they do not conflict with each other.

[0100] This disclosure can contribute, for example, to United Nations-led Sustainable Development Goals (SDGs) Goal 2, "End hunger, achieve food security and improved nutrition and promote sustainable agriculture," Goal 7, "Ensure access to affordable, reliable, and sustainable energy for all," and Goal 13, "Take urgent action to combat climate change and its impacts."

[0101] The entire contents of Japanese Patent Application No. 2025-040227 (Filing Date: March 13, 2025) are incorporated herein by reference.

[0102] 1A, 1B, 1C Ammonia production system 30, 30a, 30b, 30c, 30d Raw material gas 35 Heater 40 Reactor 40c First reactor 40d Second reactor 50a, 50b Heat storage 50c First heat storage 50d Second heat storage 60a, 60b Catalyst layer 60c First catalyst layer 60d Second catalyst layer 70c, 70d Intermediate product gas 71 Intermediate product gas flow path

Claims

1. An ammonia production system comprising at least one reactor to which raw material gases containing nitrogen and hydrogen are supplied and which has a heat storage body inside, wherein ammonia is produced by the reactor.

2. The ammonia production system according to claim 1, wherein the heat storage body comprises a first heat storage body and a second heat storage body, the at least one reactor comprises a first reactor having the first heat storage body inside, and a second reactor connected to the first reactor via an intermediate product gas flow path and having the second heat storage body inside, the raw material gas is supplied to the first reactor or the second reactor, when the raw material gas is supplied to the first reactor, the intermediate product gas that has passed through the first reactor is supplied to the second reactor via the intermediate product gas flow path, and when the raw material gas is supplied to the second reactor, the intermediate product gas that has passed through the second reactor is supplied to the first reactor via the intermediate product gas flow path.

3. The ammonia production system according to claim 2, wherein a heater is provided in the intermediate product gas flow path.

4. An ammonia production system according to claim 2 or 3, wherein a first catalyst layer for promoting the production of ammonia is provided inside the first reactor, a second catalyst layer for promoting the production of ammonia is provided inside the second reactor, and the raw material gas is supplied to at least one of the following: between the first heat storage body and the first catalyst layer in the first reactor, between the second heat storage body and the second catalyst layer in the second reactor, and between the first catalyst layer and the second catalyst layer.

5. The ammonia production system according to any one of claims 2 to 4, wherein at least one of the first heat storage body and the second heat storage body includes ceramics.

6. A method for producing ammonia, comprising supplying a raw material gas containing nitrogen and hydrogen and producing ammonia in at least one reactor equipped with a heat storage body, the method comprising: a heating step of supplying the raw material gas to the reactor and heating the raw material gas by releasing heat from the heat storage body; and a heat storage step of storing the heat of the reaction gas passing through the reactor in the heat storage body, wherein the heating step and the heat storage step are repeated alternately.

7. A method for producing ammonia from a raw material gas containing nitrogen and hydrogen using a reactor comprising a first reactor and a second reactor, wherein a first heat storage body and a first catalyst layer for promoting the production of ammonia are provided inside the first reactor, a second heat storage body and a second catalyst layer for promoting the production of ammonia are provided inside the second reactor, a first heating step of supplying the raw material gas to the first reactor and heating the raw material gas by releasing heat from the first heat storage body, a first heat storage step of supplying the intermediate product gas that has passed through the first reactor to the second reactor and storing the heat of the reaction gas passing through the second reactor in the second heat storage body, and a second heating step of supplying the raw material gas to the second reactor and heating the raw material gas by releasing heat from the second heat storage body, A method for producing ammonia, comprising: a second heat storage step of supplying the intermediate product gas that has passed through the second reactor to the first reactor, thereby storing the heat of the reaction gas passing through the first reactor in the first heat storage body, and repeating the first heating step, the first heat storage step, the second heating step, and the second heat storage step in this order.

8. The ammonia production method according to claim 7, comprising: a first switching step of switching the supply destination of the raw material gas from the first reactor to the second reactor; and a second switching step of switching the supply destination of the raw material gas from the second reactor to the first reactor.

9. The ammonia production method according to claim 7 or 8, comprising a catalyst temperature control step of adjusting the temperature of at least one of the first catalyst layer and the second catalyst layer by supplying the raw material gas to at least one of the following: between the first heat storage body and the first catalyst layer in the first reactor, between the second heat storage body and the second catalyst layer in the second reactor, and between the first catalyst layer and the second catalyst layer.

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