ammonia synthesis system

Abstract

To improve a synthetic ability of a catalyst for synthesis of ammonia from hydrogen and nitrogen.SOLUTION: An ammonia synthesis system used in an ammonia production plant assembled with circulation equipment where a gas after reaction is reused is assembled with a catalyst group where a plurality of catalysts for synthesis of ammonia from hydrogen and nitrogen are arranged in tandem, a gas supply part for supplying a split gas involving at least one of hydrogen and nitrogen to an intermediate synthesis gas obtained between each catalyst constituting the catalyst group, and a control part for controlling a composition of the intermediate synthesis gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an ammonia synthesis system.

Background Art

[0002] A system for synthesizing ammonia from nitrogen (N2) and hydrogen (H2) using reaction means including a plurality of catalysts arranged in series is known (for example, Patent Document 1). In the system described in Patent Document 1, purge gas purged from an ammonia production plant is used to cool intermediate product gas obtained between the plurality of catalysts. Patent Document 2 discloses a technique for temperature control in a reactor containing a catalyst. In the ammonia synthesis technique disclosed in Patent Document 3, a gas rich in oxygen is introduced into a natural gas reformer that generates H2 in the stage prior to the ammonia synthesis reaction, and N2 is supplied into the synthesis loop of the ammonia synthesis reaction. Thereby, the reaction proceeds with a composition advantageous for reforming and ammonia synthesis reactions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in Fe catalysts and Ru catalysts often used for ammonia synthesis, the adsorption of N2 is inhibited by the adsorption of H2 (H2 poisoning). Therefore, ammonia is synthesized in a state where the gas ratio of H2 to N2 (H2 / N2 ratio) is 3 or less. Further, in the Ru catalyst, since H2 poisoning is stronger than in the Fe catalyst, it is preferable that the H2 / N2 ratio is smaller.

[0005] In ammonia synthesis, the reaction proceeds at a stoichiometric ratio of H2 / N2 of 3. Therefore, if the reaction proceeds with an H2 / N2 ratio of less than 3 in the gas, the H2 / N2 ratio after the reaction will be lower than the ratio before the reaction. In the ammonia synthesis system described in Patent Document 1, where multiple catalysts are arranged in series, the H2 / N2 ratio of the gas is less than 3, so the optimal H2 / N2 ratio for each catalyst cannot be maintained, and the catalyst's capacity cannot be fully utilized. Furthermore, if the types of catalysts arranged in series are different, there is an optimal H2 / N2 ratio for each catalyst, so it is necessary to control the H2 / N2 ratio of the gas supplied to each catalyst in order to utilize the catalyst's capacity. In this respect, Patent Documents 1 to 3 do not consider the control of the H2 / N2 ratio at all.

[0006] The present invention aims to improve the synthesis capacity of a catalyst for synthesizing ammonia from hydrogen and nitrogen. [Means for solving the problem]

[0007] This invention was made to solve the above-mentioned problems and can be realized in the following forms.

[0008] (1) According to one embodiment of the present invention, an ammonia synthesis system is provided for use in an ammonia production plant equipped with a circulation system for reusing the gas after the reaction. This ammonia synthesis system comprises a catalyst group in which a plurality of catalysts for synthesizing ammonia from hydrogen and nitrogen are arranged in series, a gas supply unit that supplies a divided gas containing at least one of hydrogen and nitrogen to the intermediate product gas obtained between each of the catalysts constituting the catalyst group, and a control unit that controls the composition of the intermediate product gas.

[0009] In this configuration, a portion of the raw material gas supplied from the gas supply unit is supplied to the intermediate product gas as a split gas, thereby controlling the gas composition of the gas supplied to the catalyst located upstream and the gas composition of the gas supplied to the catalyst located downstream to which the intermediate product gas is supplied. By adjusting the gas composition of the gas supplied to each catalyst and the type of catalysts arranged in series to a gas composition that allows each catalyst to perform to its full potential, the process efficiency of ammonia synthesis is improved. In other words, the ammonia synthesis system of this embodiment can improve the synthesis capacity of the catalyst group that synthesizes ammonia (NH3) from hydrogen (H2) and nitrogen (N2). Furthermore, even if the optimal gas composition for the catalyst to perform to its full potential changes due to catalyst degradation, the gas composition of the gas supplied to each catalyst is controlled by adjusting the split gas, thereby improving the synthesis capacity of each catalyst.

[0010] (2) In the ammonia synthesis system according to the above embodiment, the divided gas supplied from the gas supply unit may be nitrogen or hydrogen. With this configuration, the split gas supplied to the intermediate product gas is not a mixed gas containing N2 and H2, making it easier to adjust the gas composition of the intermediate product gas.

[0011] (3) In the ammonia synthesis system according to the above embodiment, the divided gas contains hydrogen and nitrogen, and the control unit may set the gas ratio of hydrogen to nitrogen in the divided gas to less than 2.5 or greater than 3. With this configuration, by adjusting the gas composition of the divided gas, the gas composition of the intermediate product gas can be adjusted to the optimal gas composition for the catalyst used to synthesize ammonia from the intermediate product gas.

[0012] (4) In the ammonia synthesis system according to the above embodiment, the control unit may set the gas ratio of hydrogen to nitrogen in the divided gas to less than 1. With this configuration, by adjusting the gas ratio of the divided gases, the gas composition of the intermediate product gas can be adjusted to the optimal gas composition corresponding to the catalyst for synthesizing ammonia from the intermediate product gas.

[0013] (5) In the ammonia synthesis system of the above form, the system may further include a detection unit that detects at least one gas composition of the gas supplied to the catalyst group, the gas discharged from the catalyst group, and the gas of the intermediate product gas, and the control unit may control the composition of the intermediate product gas using the gas composition detected by the detection unit. In this configuration, the detected gas composition is used to control the flow rate of N2 supplied to the intermediate product gas. As a result, the gas composition of the intermediate product gas is more precisely adjusted, and the synthesis capacity of each catalyst in the catalyst group is improved.

[0014] (6) In the ammonia synthesis system of the above form, each catalyst forming the catalyst group may be of a different type. If multiple catalysts arranged in series are of different types, the optimal gas composition for each catalyst to exert its synthesis capacity will also differ. In this configuration, the optimal gas composition for each catalyst differs compared to a system where each catalyst is of the same type. Therefore, by selecting different catalysts according to the type of divided gas and flow rate control, the synthesis capacity of the catalyst group as a whole is improved.

[0015] (7) In the ammonia synthesis system of the above form, a heater may be provided for heating the divided gas supplied from the gas supply unit. With this configuration, by controlling the temperature of the split gas, the ammonia synthesis in a catalyst supplied with an intermediate product gas at an inappropriate temperature is prevented from reaching equilibrium. In other words, in this configuration, in addition to adjusting the gas composition of the intermediate product gas, the temperature of the intermediate product gas is adjusted by controlling the temperature of the split gas. This prevents the ammonia synthesis in the catalyst supplied with the intermediate product gas from reaching equilibrium, thereby further improving the synthesis capacity.

[0016] (8) In the ammonia synthesis system of the above form, the reactor may further include a reactor housing the catalyst group, which has a heat exchange channel inside that supplies the raw material gas used in the reaction by the catalyst group to the catalyst group without reacting it with the catalyst group, while exchanging heat with the catalyst group. Since the ammonia synthesis reaction is exothermic, the temperature of each catalyst constituting the catalyst group tends to be high. With this configuration, the raw material gas can be heated through heat exchange with the catalyst group before being used in the ammonia synthesis reaction by the catalyst group. Therefore, it is possible to suppress the decrease in the reaction rate in the synthesis reaction caused by a low temperature of the raw material gas supplied to the catalyst group. In addition, since the heat generated by the synthesis reaction is reused to heat the raw material gas, the process efficiency in ammonia synthesis can be improved.

[0017] (9) In the ammonia synthesis system of the above form, the system further comprises a supply pipe connected to the heat exchange channel and supplying the raw material gas to the heat exchange channel, wherein the reactor has an inner pipe housing the catalyst group and an outer pipe covering the inner pipe, the heat exchange channel is the space between the inner pipe and the outer pipe, and the raw material gas supplied from the supply pipe is supplied via the heat exchange channel to the catalyst located at one end of the catalyst group arranged in series in the inner pipe. In this configuration, the raw material gas is heated through heat exchange with the catalyst group, which is separated by an inner pipe, as it flows through the heat exchange channel, and then supplied to the catalyst located at one end of the catalyst group for use in the ammonia synthesis reaction. Therefore, it is possible to suppress the decrease in the reaction rate in the synthesis reaction caused by a low temperature of the raw material gas supplied to the catalyst group. In addition, since the heat generated by the synthesis reaction is reused to raise the temperature of the raw material gas, the process efficiency in ammonia synthesis can be improved.

[0018] (10) In the ammonia synthesis system of the above form, the catalyst group includes a first catalyst and a second catalyst, and a first supply pipe connected to the portion of the heat exchange channel on the side of the first catalyst and supplying the raw material gas to the heat exchange channel, a second supply pipe connected to the portion of the heat exchange channel on the side of the second catalyst and supplying the raw material gas to the heat exchange channel, a first discharge pipe connected to the portion of the outer piping on the side in the direction from the second catalyst to the first catalyst and discharging the post-reaction gas after the reaction by the catalyst group, and a portion of the outer piping on the side in the direction from the first catalyst to the second catalyst The system may also include a second discharge pipe for discharging the post-reaction gas after the reaction by the catalyst group, and a path switching unit for switching between a first path in which the raw material gas is supplied to the heat exchange channel and then discharged as the post-reaction gas from the first discharge pipe, and a second path in which the raw material gas is supplied to the first catalyst from the second supply pipe and then discharged as the post-reaction gas from the second discharge pipe, and then discharged as the post-reaction gas from the second discharge pipe, and is supplied to the first catalyst from the second supply pipe and then discharged as the post-reaction gas from the second discharge pipe, and is supplied to the first catalyst from the second catalyst. If ammonia synthesis continues with the first catalyst upstream (i.e., if the raw material gas is supplied to the catalyst group via the second pathway), more ammonia is synthesized by the first catalyst than by the second catalyst. As a result, the first catalyst heats up at a higher rate than the second catalyst, reaching a higher temperature. Consequently, the ammonia synthesis reaction is subject to equilibrium constraints at high temperatures, increasing the likelihood of the ammonia synthesis reaction by the first catalyst being inhibited. On the other hand, with this configuration, the pathway for ammonia synthesis can be switched between the first and second pathways. By periodically switching between the first and second pathways and swapping the catalyst positioned upstream between the first and second catalysts, it is possible to suppress the inhibition of the ammonia synthesis reaction in one of the catalysts due to equilibrium constraints at high temperatures. As a result, the process efficiency of ammonia synthesis can be improved in the ammonia synthesis system. Furthermore, since the heat generated by the synthesis reaction is reused to heat the raw material gas, the process efficiency of ammonia synthesis can also be improved from this perspective. Furthermore, since the raw material gas is heated through heat exchange with the catalyst group as it flows through the heat exchange channel before being used in the ammonia synthesis reaction by the catalyst group, it is possible to suppress the decrease in the reaction rate in the synthesis reaction caused by a low temperature of the raw material gas supplied to the catalyst group.

[0019] (11) In the ammonia synthesis system of the above form, the catalyst group further includes a first catalyst and a second catalyst, the heat exchange channel has two or more heat exchange sections capable of exchanging heat with the catalyst group, the two or more heat exchange sections include a first heat exchange section located furthest upstream of the two or more heat exchange sections and capable of exchanging heat with the first catalyst, and a second heat exchange section located next to the first heat exchange section in the direction from upstream to downstream of the two or more heat exchange sections and capable of exchanging heat with the second catalyst, the system includes a first introduction pipe for introducing the raw material gas into the first heat exchange section, and the first heat exchange The system includes a second introduction pipe for introducing the raw material gas into the second heat exchange section from a downstream side of the section, a downstream introduction pipe for introducing the raw material gas into the heat exchange flow path from a downstream side of the second heat exchange section, and a flow rate adjustment unit for adjusting the flow rate of the raw material gas introduced from the first introduction pipe, the flow rate of the raw material gas introduced from the second introduction pipe, and the flow rate of the raw material gas introduced from the downstream introduction pipe, wherein the raw material gas introduced from the first introduction pipe, the second introduction pipe, and the downstream pipe may be supplied via the heat exchange flow path to the catalyst located at one end of the catalyst group arranged in series. With this configuration, if the temperature of the first catalyst is higher than the target temperature, the flow rate of the raw material gas introduced from the first introduction pipe is increased to promote heat exchange between the raw material gas and the first catalyst. If the temperature of the second catalyst is higher than the target temperature, the flow rate of the raw material gas introduced from the second introduction pipe is increased to promote heat exchange between the raw material gas and the second catalyst. This prevents the progression of the ammonia synthesis reaction by each catalyst from being inhibited by equilibrium constraints at high temperatures. Furthermore, if the temperature of the first catalyst is lower than the target temperature, the flow rate of the raw material gas introduced from the first introduction pipe is reduced to suppress heat exchange between the raw material gas and the first catalyst. If the temperature of the second catalyst is lower than the target temperature, the flow rate of the raw material gas introduced from the second introduction pipe is reduced to suppress heat exchange between the raw material gas and the second catalyst. This prevents each catalyst from being cooled down by heat exchange with the raw material gas. Furthermore, if there are no other heat exchange sections downstream of the second heat exchange section in the heat exchange flow path, increasing the flow rate of the raw material gas introduced from the downstream inlet pipe can promote the ammonia synthesis reaction by each catalyst while suppressing the cooling of each catalyst due to heat exchange with the raw material gas, thereby promoting the heating of each catalyst. In this way, by adjusting the flow rate of the raw material gas introduced from the first inlet pipe, the second inlet pipe, and the downstream inlet pipe, the temperature of each catalyst can be adjusted, and the process efficiency in ammonia synthesis can be improved.

[0020] Furthermore, the present invention can be realized in various forms, for example, in the form of an ammonia synthesis system, an ammonia production plant, an ammonia production apparatus, apparatus and systems comprising these, a method for producing ammonia, a method for synthesizing ammonia, a computer program for executing these apparatus and methods, a server device for distributing this computer program, and a non-temporary storage medium storing the computer program. [Brief explanation of the drawing]

[0021] [Figure 1] This is a schematic block diagram of an ammonia synthesis system in an embodiment of the present invention. [Figure 2] This is an explanatory diagram illustrating the relationship between gas composition and the catalytic activity of a catalyst. [Figure 3] This is an explanatory diagram illustrating the process efficiency of the ammonia synthesis system in the first embodiment. [Figure 4] This is an explanatory diagram illustrating the process efficiency of the ammonia synthesis system in the first embodiment. [Figure 5] This is an explanatory diagram illustrating the process efficiency of the ammonia synthesis system in the second embodiment. [Figure 6] This is an explanatory diagram illustrating the process efficiency of the ammonia synthesis system in the second embodiment. [Figure 7] This is a schematic block diagram of the ammonia synthesis system of the third embodiment. [Figure 8] This is a cross-sectional view showing the internal structure of the reactor in the third embodiment. [Figure 9] This is a cross-sectional view showing the internal structure of the reactor in the third embodiment. [Figure 10] This is a schematic block diagram of the ammonia synthesis system of the fourth embodiment. [Figure 11] This is a cross-sectional view showing the internal structure of the reactor in the fourth embodiment. [Figure 12] This is a cross-sectional view showing the internal structure of the reactor in the fourth embodiment. [Figure 13] This is a cross-sectional view showing the internal structure of the reactor in the fourth embodiment. [Figure 14] This is a perspective view of a portion of the reactor in the fourth embodiment, viewed through a transparent lens. [Figure 15] This is a cross-sectional view showing the internal structure of a reactor in another embodiment. [Figure 16] This is a schematic block diagram of the ammonia synthesis system of the fifth embodiment. [Figure 17] This is a cross-sectional view showing the internal structure of the reactor in the fifth embodiment. [Figure 18] This is a cross-sectional view showing the internal structure of the reactor in the fifth embodiment. [Figure 19] This is a cross-sectional view showing the internal structure of the reactor in the sixth embodiment. [Figure 20]This is a cross-sectional view showing the internal structure of the reactor in the sixth embodiment. [Figure 21] This is a cross-sectional view showing the internal structure of the reactor in the seventh embodiment. [Figure 22] This is a cross-sectional view showing the internal structure of the reactor in the seventh embodiment. [Figure 23] This is a cross-sectional view showing the internal structure of the reactor in the eighth embodiment. [Figure 24] This is a cross-sectional view showing the internal structure of the reactor in the eighth embodiment. [Modes for carrying out the invention]

[0022] <Embodiment> 1. Configuration of the ammonia synthesis system: Figure 1 is a schematic block diagram of an ammonia synthesis system 100 in an embodiment of the present invention. In the ammonia synthesis system 100 shown in Figure 1, not all of the nitrogen (N2), which is the raw material gas for ammonia (NH3), is supplied to the first catalyst 11, and some of the N2 is divided into gas G SP As such, it is supplied to the intermediate product gas discharged from the first catalyst 11. This allows the gas ratio Rg (=H2 / N2 ratio) of hydrogen (H2) to the reaction gas N2 supplied to the first catalyst 11 and the intermediate product gas supplied to the second catalyst 12 to be optimally adjusted according to the types of catalysts forming the first catalyst 11 and the second catalyst 12.

[0023] The ammonia synthesis system 100 of this embodiment is a system used in an ammonia production plant equipped with a circulation system for reusing the gas after the reaction. As shown in Figure 1, the ammonia synthesis system 100 includes a reactor (catalyst group) 10 for synthesizing ammonia, a gas supply unit 25 for supplying raw material gas, a gas divider 20 for dividing a portion of the supplied gas, a division control unit 30, a gas-liquid separator 40, a tank 50 for storing NH3, a gas sensor (detection unit) 60, a first mixer 71 and a second mixer 72, a first compressor 81 and a second compressor 82 for compressing the gas, a heat exchanger 91, a cooler 92, and heaters 93, 94.

[0024] The gas supply unit 25 supplies N2 and H2, which are raw material gases for ammonia. The gas supply unit 25 includes an N2 tank for storing N2 (not shown) and an H2 tank for storing H2. The gas supply unit 25 supplies N2 to the gas divider 20 and H2 to the first mixer 71. The raw material H2 gas G supplied to the first mixer 71 is H2. H2 The flow rate is regulated by a control valve (not shown).

[0025] The gas divider 20 is a mass flow controller that adjusts and supplies the gas flow rates to the first mixer 71 and the reactor 10, respectively. The splitting control unit 30 controls the gas divider 20 using the gas composition detected by the gas sensor 60, which will be described later. The gas divider 20 supplies raw material H2 gas G to the first mixer 71 under the control of the splitting control unit 30. H2 Depending on the flow rate, the raw material N2 gas G supplied to the first mixer 71 is N2 N2 The flow rate and the divided gas G of N2 supplied to the intermediate product gas described later. SP The flow rates of each are controlled. In other words, the gas supply unit 25 supplies divided gas to the intermediate generated gas via the gas divider 20. The gas divider 20 and the division control unit 30 are both control units.

[0026] In this embodiment, the gas divider 20 divides a portion of N2 into divided gas G SP In one embodiment, it is supplied as an intermediate product gas, but in another embodiment, a portion of H2 is used as the split gas G instead of N2. SP It may be supplied as an intermediate product gas. Alternatively, the gas divider 20 divides a portion of the mixed gas containing H2 and N2 into divided gas G SP It may also be supplied as an intermediate product gas.

[0027] The first mixer 71 mixes the H2 supplied from the gas supply unit 25 with the N2 supplied from the gas divider 20. The first compressor 81 compresses the raw material gas containing N2 and H2 mixed by the first mixer 71, and supplies the compressed raw material gas to the second mixer 72. In addition to the raw material gas from the first compressor 81, the second mixer 72 is supplied with the recycle gas G CY that is supplied. The recycle gas G CY is the gas after removing NH3 from the post-reaction gas of the reactor 10. The recycle gas G CY contains unreacted H2, N2, and NH3 that was not removed by the gas-liquid separator 40.

[0028] The heat exchanger 91 performs heat exchange between the raw material gas supplied from the second mixer 72 and the post-reaction gas discharged from the reactor 10. The synthesis of ammonia represented by the following formula (1) is an exothermic reaction. Therefore, the heat exchanger 91 uses the heat of the post-reaction gas discharged from the reactor 10 to heat the raw material gas supplied from the second mixer 72. The raw material gas heated by the heat exchanger 91 is further heated by the heater 94. The raw material gas is heated by the heat exchanger 91 and the heater 94, and is heated to a temperature suitable for the ammonia synthesis reaction.

Number

[0029] Reactor 10 is equipped with a first catalyst 11 and a second catalyst 12 for synthesizing ammonia from H2 and N2. As shown in Figure 1, the first catalyst 11 and the second catalyst 12 are arranged in series within reactor 10 with space SP in between. As the first catalyst 11 and the second catalyst 12, well-known catalysts for ammonia synthesis, such as Fe catalysts and Ru catalysts that synthesize NH3 from raw material gases, can be used. The first catalyst 11 synthesizes NH3 from the raw material gas supplied from heat exchanger 91 via heater 94. The intermediate product gas that flows into space SP after passing through the first catalyst 11 contains unreacted H2 and N2 in addition to the NH3 synthesized by the first catalyst 11. As shown in Figure 1, the N2 divided gas G is supplied to the intermediate product gas from gas divider 20. SP It is supplied. Split gas G SP It is heated by the heater 93 before being supplied to the intermediate product gas in the reactor 10.

[0030] The second catalyst 12 synthesizes NH3 from the supplied intermediate product gas. The post-reaction gas discharged from the reactor 10 is cooled by heat exchange in the heat exchanger 91 and further cooled by the cooler 92. The gas-liquid separator 40 liquefies the NH3 contained in the post-reaction gas by cooling and stores the liquid NH3 in the tank 50. The recycled gas G is obtained by separating NH3 from the post-reaction gas in the gas-liquid separator 40. CY It is compressed in the second compressor 82 and then supplied to the second mixer 72.

[0031] The gas sensor 60 of this embodiment, as shown in Figure 1, detects recycled gas G CY The split control unit 30 detects the gas composition of the fuel gas supplied from the heat exchanger 91 to the reactor 10, the gas composition of the intermediate product gas, and the gas composition of the post-reaction gas discharged from the reactor 10. The split control unit 30 acquires the gas compositions of the various gases obtained by the gas sensor 60. The split control unit 30 controls the gas composition of the intermediate product gas using the acquired gas compositions. In this embodiment, the split control unit 30 uses the gas splitter 20 to select the fuel N2 gas G supplied to the first mixer 71 from the N2 supplied from the gas supply unit 25. N2And the divided gas G supplied to the intermediate product gas SP The raw material gas supplied to reactor 10 is adjusted by adjusting the ratio of these two elements.

[0032] 2. Evaluation of process efficiency: The optimal gas composition for ammonia synthesis differs depending on the type of catalyst used in the first catalyst 11 and the second catalyst 12. Therefore, optimizing the gas composition of the gas flowing into the first catalyst 11 and the second catalyst 12 improves the process efficiency EP of the ammonia synthesis system 100, as shown in equation (2) below.

number

[0033] Figure 2 is an explanatory diagram of the relationship between gas composition and catalytic activity of the catalyst. Figure 2 shows the change in catalytic activity A for Ru-based catalysts and Fe-based catalysts, respectively, depending on the gas composition of the supplied gas. Ru ,A Fe This is shown. The horizontal axis of Figure 2 shows the gas ratio Rg, which is the ratio of H2 to N2, one of the gas compositions. Catalytic activity A shown in Figure 2 Ru Therefore, the gas ratio Rg at which Ru-based catalysts are most active is around 1.1. On the other hand, catalytic activity A Fe Therefore, the gas ratio Rg at which Fe-based catalysts are most active is approximately 1.3 to 3.0. More precisely, catalytic activity A Fe The gas ratio Rg gradually increases from approximately 1.3 to a peak of approximately 2.0, and then gradually decreases. Thus, since the gas ratio Rg at which each catalyst is activated differs depending on the type of catalyst, it is preferable to control the gas composition of the gas supplied to the catalyst in order to improve process efficiency EP.

[0034] Figures 3 and 4 are explanatory diagrams regarding the process efficiency EP of the ammonia synthesis system 100A of the first embodiment. In the ammonia synthesis system 100A of the first embodiment, an Fe-based catalyst is used as the first catalyst 11 in the ammonia synthesis system 100 of the embodiment, and a Ru-based catalyst is used as the second catalyst 12. In the first embodiment, when a raw material gas with a gas ratio Rg of 2.5 is supplied from the gas supply unit 25, the divided gas G SP The process efficiency EP was evaluated when the following was changed. Specifically, the divided gas G supplied to the intermediate product gas from the raw material gas supplied from the gas supply unit 25 was evaluated. SP However, there are cases where it is 20% H2, 20% mixed gas, 20% N2, and divided gas G SP We evaluated four different process efficiencies (EP) under the assumption that the system itself was absent. In all four cases, the total flow rate of the raw material gas supplied to the ammonia synthesis system 100A was the same.

[0035] Figure 3 shows a bar graph of the evaluated process efficiency EP. Figure 4 shows, in addition to the evaluated process efficiency EP, the outlet temperatures of the first catalyst 11 and the second catalyst 12, and the gas ratio Rg of the gas supplied to the first catalyst 11 and the second catalyst 12, respectively, in a table. Note that the divided gas G of the first embodiment SP It is heated to 150°C by the heater 93.

[0036] As shown in Figures 3 and 4, the intermediate product gas is divided into gas G SP The three types of process efficiency EP supplied were divided gas G SP The process efficiency EP (58.26) was higher than when it was absent. Split gas G SP Of the three types of process efficiency EP supplied, N2 was the split gas G SPThe process efficiency EP when supplied as is is 59.26, which is the highest. In this case, the gas ratio Rg of the gas supplied to the second catalyst 12 is 1.08, which is almost the same as the other three gas ratios. On the other hand, the gas ratio Rg of the gas supplied to the first catalyst 11 is 1.45, which is higher than the other three gas ratios Rg. Referring to Figure 2, the catalytic activity of the Fe-based catalyst peaks when the gas ratio Rg is approximately 2.0. Therefore, the split gas G SP When N2 was supplied, the gas ratio Rg was closer to 2.0 than in other cases, suggesting that the synthesis efficiency of the first catalyst 11 was improved.

[0037] Figures 5 and 6 are explanatory diagrams regarding the process efficiency EP of the ammonia synthesis system 100B of the second embodiment. In the ammonia synthesis system 100B of the second embodiment, Ru-based catalysts are used as the first catalyst 11 and the second catalyst 12 in the ammonia synthesis system 100 of the embodiment. In the second embodiment, when a raw material gas with a gas ratio Rg of 2.7 is supplied from the gas supply unit 25, the divided gas G SP The process efficiency EP was evaluated when the following was changed. Specifically, the divided gas G supplied to the intermediate product gas from the raw material gas supplied from the gas supply unit 25 was evaluated. SP However, there are cases where it is 20% H2, 20% mixed gas, 20% N2, and divided gas G SP The process efficiency EP for four different cases, including the absence of the substance itself, was evaluated. As with the first embodiment, the total flow rate of the raw material gas supplied to the ammonia synthesis system 100B was the same in all four cases. Figure 5 shows a bar graph of the process efficiency EP for the second embodiment, corresponding to Figure 3. Figure 6 shows a table for the second embodiment, corresponding to Figure 4. The divided gas G of the second embodiment... SP It is heated to 150°C by the heater 93, as in the first embodiment.

[0038] As shown in Figures 5 and 6, the intermediate product gas is divided into gas G SP The three types of process efficiency EP supplied were divided gas G SPThe process efficiency EP (58.35) was higher than when it was absent. Split gas G SP Of the three types of process efficiency EP supplied, H2 was the split gas G SP When supplied as such, the process efficiency EP is 58.86, which is the highest. In this case, the gas ratio Rg of the gas supplied to the second catalyst 12 is approximately 1.60, which is almost the same as the other three gas ratios. On the other hand, the gas ratio Rg of the gas supplied to the first catalyst 11 is 1.63, which is lower than the other three gas ratios Rg. Referring to Figure 2, the peak catalytic activity of the Ru-based catalyst occurs when the gas ratio Rg is approximately 1.1. Therefore, the split gas G SP When N2 was supplied, the gas ratio Rg was closer to 1.1 than in other cases, suggesting that the synthesis efficiency of the first catalyst 11 improved.

[0039] As described above, in the ammonia synthesis system 100 of this embodiment, N2 and H2, which are the raw materials for ammonia, are supplied from the gas supply unit 25 to the reactor 10 which houses the first catalyst 11 and the second catalyst 12 arranged in series. The splitting control unit 30, via the gas splitter 20, supplies splitting gas G from the gas supply unit 25 to the intermediate product gas obtained between the first catalyst 11 and the second catalyst 12. SP It is supplied. A portion of the gas supplied from the raw material gas is divided gas G SP By supplying it as an intermediate product gas, the gas composition of the gas supplied to the first catalyst 11 and the gas composition of the intermediate product gas supplied to the second catalyst 12 are controlled. The gas ratio Rg supplied to each catalyst 11 and 12 is adjusted to a gas ratio that allows each catalyst 11 and 12 to exert its capabilities, according to the type of first catalyst 11 and second catalyst 12, thereby improving the process efficiency EP of the ammonia synthesis systems 100A and 100B, as shown in Figures 3 to 6. In other words, the ammonia synthesis system 100 can improve the synthesis capacity of the reactor 10 that synthesizes NH3 from H2 and N2. Furthermore, even if the optimal gas ratio Rg for each catalyst 11 and 12 to exert its synthesis capacity changes due to the degradation of each catalyst 11 and 12, the divided gas G SPBy adjusting the gas ratio Rg of the gas supplied to each catalyst 11 and 12, the synthesis capacity of each catalyst 11 and 12 is improved.

[0040] Furthermore, in the ammonia synthesis system 100 of this embodiment, the divided gas G supplied from the gas supply unit 25 to the intermediate product gas is also used. SP This is N2. The split gas G is supplied to the intermediate product gas. SP Since it is not a mixed gas containing N2 and H2, the split control unit 30 can easily adjust the gas composition of the intermediate product gas.

[0041] Furthermore, the ammonia synthesis system 100 of this embodiment is equipped with a gas sensor 60 that detects the gas composition of the intermediate product gas. The split control unit 30 uses the detected gas composition to control the flow rate of N2 supplied to the intermediate product gas. As a result, the gas composition of the intermediate product gas is adjusted more precisely, and the synthesis capacity of each catalyst 11, 12 is improved.

[0042] Furthermore, in the ammonia synthesis system 100A of the first embodiment, the first catalyst 11 is an Fe-based catalyst, and the second catalyst 12 is a Ru-based catalyst, which is different from the Fe-based catalyst. If the types of catalysts forming the first catalyst 11 and the second catalyst 12 are different, the optimal gas ratio Rg for each catalyst 11 and 12 to exert their synthesis capacity will also be different. In other words, in the ammonia synthesis system 100A of the first embodiment, the optimal gas ratio Rg for each catalyst 11 and 12 is different from that of a system in which the first catalyst 11 and the second catalyst 12 are formed by the same type of catalyst. Therefore, the divided gas G SP By selecting different catalysts 11 and 12 depending on the type and flow rate control, the synthesis capacity of the reactor 10 is improved.

[0043] Furthermore, in the ammonia synthesis system 100 of this embodiment, the heater 93 supplies divided gas G to the intermediate product gas in the reactor 10. SPThe mixture is heated. This prevents the temperature of the intermediate product gas from being appropriate, thus suppressing the ammonia synthesis of the second catalyst 12 from reaching equilibrium. In other words, in the ammonia synthesis system 100 of this embodiment, in addition to adjusting the gas composition of the intermediate product gas, the divided gas G SP The temperature of the intermediate product gas is adjusted by adjusting the temperature of the catalyst. This suppresses the ammonia synthesis in the second catalyst 12 from reaching equilibrium, thereby further improving the synthesis capacity of the second catalyst 12.

[0044] Figure 7 is a schematic block diagram of the ammonia synthesis system 100C of the third embodiment. The ammonia synthesis system 100C of the third embodiment differs from the ammonia synthesis system 100 shown in Figure 1 mainly in that it does not have a heat exchanger 91 and has a reactor 10c which is different from reactor 10.

[0045] Figures 8 and 9 are cross-sectional views showing the internal structure of reactor 10c. Figure 8 shows mutually orthogonal X, Y, and Z axes. These X, Y, and Z axes are common to all subsequent figures. The cross-section shown in Figure 8 corresponds to the XZ cross-section of reactor 10c. The cross-sections shown in Figures 9(A) and 9(B) correspond to the YZ cross-section of reactor 10c in the F9A-F9A and F9B-F9B cross-sections shown in Figure 8, respectively. The arrows shown in Figures 8 and 9 indicate the gas flow within reactor 10c.

[0046] As shown in Figure 8, reactor 10c houses a catalyst group consisting of a first catalyst 11 and a second catalyst 12. The first catalyst 11 and the second catalyst 12 are housed in reactor 10c in a series arrangement. Reactor 10c has an inner pipe 13 and an outer pipe 15, as shown in Figure 8. The inner pipe 13 is cylindrical in shape and houses the catalyst group inside. Specifically, the first catalyst 11 is housed in the first housing portion 13L, which is the portion of the inner pipe 13 on the -X axis side, and the second catalyst 12 is housed in the second housing portion 13R, which is the portion on the +X axis side. The outer pipe 15, which covers the inner pipe, consists of hemispherical portions 15L and 15R and a cylindrical portion 15M. The hemispherical portions 15L and 15R are connected to the cylindrical portion 15M from the -X axis side and the +X axis side, respectively. The cylindrical portion 15M covers the inner pipe 13. The cylindrical portion 15M includes a first opposing portion 15ML facing the first housing portion 13L and a second opposing portion 15MR facing the second housing portion 13R. In reactor 10c, the space between the inner piping 13 and the outer piping 15 corresponds to the heat exchange channel HF1. ​​That is, reactor 10c has a heat exchange channel HF1 inside.

[0047] The supply pipe 16 connects the second mixer 72 (see Figure 7) and the reactor 10c, and supplies the raw material gas from the second mixer 72 between the inner pipe 13 and the outer pipe 15. A heater 94 (see Figure 7) for heating the raw material gas is provided in the supply pipe 16. In the third embodiment, the supply pipe 16 supplies the raw material gas between the inner pipe 13 and the outer pipe 15 from the end of the second opposing section 15MR on the +X axis side.

[0048] The raw material gas supplied from the supply pipe 16 flows through the heat exchange channel HF1. ​​The heat exchange channel HF1 is a channel that supplies the raw material gas used in the reaction by the catalyst group to the catalyst group without reacting it with the catalyst group, while simultaneously exchanging heat with the catalyst group. In other words, the raw material gas flows through the heat exchange channel HF1 around the catalyst group separated by the inner pipe 13, performing heat exchange between the catalyst group and the raw material gas, and then the raw material gas is supplied to the first catalyst 11, which is located at one end of the catalyst group arranged in series in the inner pipe 13. For example, heat exchange between the second catalyst 12 and the raw material gas is performed by flowing the raw material gas around the second catalyst 12, which is separated by the second containment section 13R, as shown in Figure 9(A). The same applies to heat exchange between the first catalyst 11 and the raw material gas. Thus, in reactor 10c, the raw material gas flows through the portion of the heat exchange channel HF1 defined by the first containment portion 13L and the second containment portion 13R, and the first opposing portion 15ML and the second opposing portion 15MR, and then flows through the portion defined by the hemispherical portion 15L before being supplied to the first catalyst 11. The end of the second containment portion 13R on the +X axis side and the end of the second opposing portion 15MR on the +X axis side of the heat exchange channel HF1 are connected by a connecting wall 14 that extends along the YZ plane, thereby blocking them.

[0049] The raw material gas supplied to the first catalyst 11 passes through the first catalyst 11 while being subjected to the ammonia synthesis reaction, and flows into the space SP as an intermediate product gas. The intermediate product gas that flows into space SP is divided into divided gas G from the gas divider 20 (see Figure 7). SP The gas is supplied via the supply pipe 17 (see Figure 9(B)). The supply pipe 17 connects the gas divider 20 and the reactor 10c, and supplies the raw material gas from the gas divider 20 to the space SP. Divided gas G SP A heater 93 (see Figure 7) for heating is provided in the supply piping 17. The intermediate generated gas is divided gas G. SPAfter being mixed with the other substances, the mixture passes through the second catalyst 12 while being subjected to the ammonia synthesis reaction, and is discharged as a post-reaction gas from the reactor 10c via the discharge pipe 18. The discharge pipe 18 connects the hemispherical section 15R to the cooler 92 (see Figure 7), and discharges the post-reaction gas from the reactor 10c towards the cooler 92.

[0050] Since the ammonia synthesis reaction is an exothermic reaction, the temperature of each catalyst constituting the catalyst group tends to be high. In the ammonia synthesis system 100C of the third embodiment, the raw material gas can be heated by heat exchange with such a catalyst group before being used in the ammonia synthesis reaction by the catalyst group. Therefore, it is possible to suppress the decrease in the reaction rate in the synthesis reaction caused by a low temperature of the raw material gas supplied to the catalyst group. In addition, since the heat generated by the synthesis reaction is reused to heat the raw material gas, the process efficiency in ammonia synthesis can be improved. In particular, when a large amount of heat is easily generated by the exothermic reaction associated with the ammonia synthesis reaction due to the relatively large amount of Fe, Ru, etc. supported in the first catalyst 11 and the second catalyst 12, the structure shown in the ammonia synthesis system 100C of the third embodiment is effective because that heat can be reused.

[0051] Furthermore, in the ammonia synthesis system 100C of the third embodiment, the raw material gas is heated by heat exchange with the catalyst group separated by the inner piping 13 while flowing through the heat exchange channel HF1, and then supplied to the first catalyst 11 for use in the ammonia synthesis reaction. This configuration suppresses the decrease in the reaction rate during the synthesis reaction and improves the process efficiency in ammonia synthesis.

[0052] Figure 10 is a schematic block diagram of the ammonia synthesis system 100D of the fourth embodiment. The ammonia synthesis system 100D of the fourth embodiment differs from the ammonia synthesis system 100C shown in Figure 7 mainly in that it has a reactor 10d that is different from reactor 10c. Reactor 10d has a heat exchange channel HF2 (not shown) inside, which has a different structure from the heat exchange channel HF1. ​​The heat exchange channel HF2 is a channel that supplies the raw material gas used in the reaction by the catalyst group to the catalyst group without reacting it with the catalyst group, while exchanging heat with the catalyst group, and is the space between the inner pipe 13 and the outer pipe 15, similar to the heat exchange channel HF1. ​​The channels HFa, HFb, and HFc shown in Figures 11 to 14, which will be described later, are parts of the heat exchange channel HF2.

[0053] Figures 11-13 are explanatory diagrams showing the internal structure of reactor 10d. Figure 11 shows the XZ cross-section of reactor 10d. More specifically, Figure 11 shows the XZ cross-section of reactor 10d passing through the second supply pipe 16R and supply pipe 17, which will be described later. Figures 12(A), (B), and (C) show the YZ cross-sections of reactor 10d in the F12A-F12A, F12B-F12B, and F12C-F12C cross-sections shown in Figure 11, respectively. Figure 13 shows the internal structure of reactor 10d viewed through from the +Z axis side. The arrows shown in Figures 11-13 (except Figure 12(C)) indicate the direction of the gas flowing through the second path, which will be described later, in reactor 10d. Note that the arrow shown in Figure 12(B) indicates the direction of the gas flowing in the -X axis direction (towards the viewer in the drawing).

[0054] As shown in Figure 11, reactor 10d includes a first supply pipe 16L, a second supply pipe 16R, a first discharge pipe 18L, and a second discharge pipe 18R. Each of the first supply pipe 16L and the second supply pipe 16R connects the second mixer 72 (see Figure 10) to reactor 10d. More specifically, each of the first supply pipe 16L and the second supply pipe 16R, which branch off from a single pipe connected to the second mixer 72 (see Figure 10), is connected to reactor 10d. A heater 94 (see Figure 10) for heating the raw material gas is provided on this single pipe. The first supply pipe 16L is connected to the portion of the heat exchange channel HF2 on the side of the first catalyst 11 and supplies the raw material gas to the heat exchange channel HF2 (not shown). More specifically, the first supply pipe 16L is connected to the -X axis side end of the first opposing section 15ML. The second supply pipe 16R is connected to the portion of the heat exchange flow path HF2 on the side of the second catalyst 12, and supplies the raw material gas to the heat exchange flow path HF2. More specifically, the second supply pipe 16R is connected to the end of the second opposing portion 15MR on the +X axis side, and supplies the raw material gas to the flow path HFa described later.

[0055] The first discharge pipe 18L is connected to the portion of the outer pipe 15 (hemispherical section 15L) on the side in the direction from the second catalyst 12 to the first catalyst 11 (the -X axis direction in Figure 11), and discharges the post-reaction gas, which has undergone the reaction by the catalyst group, to the outside of the reactor 10d. The second discharge pipe 18R is connected to the portion of the outer pipe 15 (hemispherical section 15R) on the side in the direction from the first catalyst 11 to the second catalyst 12 (the +X axis direction in Figure 11), and discharges the post-reaction gas, which has undergone the reaction by the catalyst group, to the outside of the reactor 10d. The first discharge pipe 18L and the second discharge pipe 18R each connect the hemispherical sections 15L and 15R to the cooler 92 (see Figure 10), and discharge the post-reaction gas from the reactor 10d toward the cooler 92.

[0056] Valves B1, A1, B2, and A2 are provided in the first supply pipe 16L, the second supply pipe 16R, the first discharge pipe 18L, and the second discharge pipe 18R, respectively. Valves B1, A1, B2, and A2 are shut-off valves capable of blocking the flow of gas within the pipes in which they are installed.

[0057] In reactor 10d, the pathways through which the raw material gas is supplied to the heat exchange channel HF2 and then discharged outside reactor 10d as post-reaction gas include a first pathway and a second pathway. The second pathway is the pathway through which gas flows when valves A1 and A2 are open and valves B1 and B2 are closed. As described above, the arrows shown in Figures 11-13 (excluding Figure 12(C)) indicate the direction of the gas flowing through the second pathway. As shown in Figure 11, the second pathway is the pathway through which the raw material gas is supplied from the second supply pipe 16R to the first catalyst 11 via the heat exchange channel HF2 (including channels HFa, HFb, and HFc described later), and then discharged as post-reaction gas from the second discharge pipe 18R after passing through the second catalyst 12.

[0058] Figure 14 shows a perspective view of a portion of reactor 10d, viewed through a transparent lens. The portion of reactor 10d shown in Figure 14 is the portion of reactor 10d shown in Figure 11, excluding the hemispherical sections 15L,R and the first and second discharge pipes 18L,R. In Figure 14, in order to make the arrangement of the second pathway within reactor 10d easier to see, the area where the first pathway is located is hatched, and only a portion of the internal structure of reactor 10d viewed through a transparent lens is shown.

[0059] The process by which the raw material gas reaches the first catalyst 11 from the second supply pipe 16R via the second pathway will be described in detail. In this process, the raw material gas flows through three pathways HFa, HFb, and HFc of the heat exchange flow path HF2. As shown in Figures 11, 12(A), 13, and 14, the flow path HFa is defined by the second containment portion 13R and the second opposing portion 15MR, and is a cylindrical flow path surrounding the second catalyst 12. As shown in Figures 11, 12(B), 13, and 14, the flow path HFb is mainly defined by the first containment portion 13L and the first opposing portion 15ML, and is a narrow cylindrical flow path extending along the X-axis on the +Z-axis side of the first catalyst 11. The structure defining the flow path HFb includes, in addition to the first containment section 13L and the first opposing section 15ML, connecting walls 14C and 14CB that connect the first containment section 13L and the first opposing section 15ML, as shown in Figures 12(B), 13, and 14. As shown in Figures 13 and 14, connecting wall 14C connects to the outer pipe 15 along the entire length of the inner pipe 13 in the X-axis direction, and connecting wall 14CB connects to the outer pipe 15 along the length of the inner pipe 13 from the center in the X-axis direction toward the X-axis direction. The flow path HFc is a hemispherical flow path defined by the hemispherical section 15L, as shown in Figures 11 and 13. In the second path, the raw material gas sent from the second supply pipe 16R reaches the first catalyst 11 via the flow paths HFa, HFb, and HFc.

[0060] As shown in Figure 11, the raw material gas supplied to the first catalyst 11 passes through the first catalyst 11 while being subjected to the ammonia synthesis reaction, similar to the third embodiment, and flows into the space SP as an intermediate product gas. The intermediate product gas that flows into the space SP is divided into divided gas G from the gas divider 20 (see Figure 7). SP It is supplied via the supply pipe 17. In the fourth embodiment, divided gas G SP As shown in Figure 12(C), the gas is supplied from the supply pipe 17 to the space SP via a cylindrical flow path SF that surrounds the space SP. In space SP, the intermediate product gas is divided gas G SP After being mixed with the other substances, it passes through the second catalyst 12 while being subjected to the ammonia synthesis reaction, and is discharged as a post-reaction gas from the reactor 10d via the second discharge pipe 18R.

[0061] On the other hand, the first path is the path through which gas flows when valves A1 and A2 are closed and valves B1 and B2 are open. The first path is arranged symmetrically with the second path in reactor 10d (see the hatched areas in Figures 13 and 14), and is the path through which the raw material gas is supplied from the first supply pipe 16L to the second catalyst 12 via the heat exchange channel HF2, and then discharged as post-reaction gas from the first discharge pipe 18L after passing through the first catalyst 11. When the raw material gas travels from the first supply pipe 16L to the second catalyst 12 via the first path, it passes through three sections of the heat exchange channel HF2: a cylindrical channel surrounding the first catalyst 11 (corresponding to channel HFa included in the second path), a narrow cylindrical channel extending along the X-axis on the +Z-axis side of the second catalyst 12 (corresponding to channel HFb included in the second path), and a hemispherical channel defined by the hemispherical section 15R (corresponding to channel HFc included in the second path). As described above, depending on the open / closed state of valves B1, A1, B2, and A2, the path through which the raw material gas is supplied to the heat exchange channel HF2 and then discharged outside the reactor 10d as post-reaction gas is switched between the first and second paths. Therefore, valves B1, A1, B2, and A2 each act as path switching sections.

[0062] The switching between the first and second pathways is controlled by a pathway control unit (not shown). The pathway control unit instructs the pathway switching based on the outlet gas temperature, which is the gas temperature immediately after passing through the first catalyst 11 and the second catalyst 12, and the elapsed time after the pathway switching. For example, the pathway switching is restarted when the temperature difference between the outlet gas temperature of the first catalyst 11 and the outlet gas temperature of the second catalyst 12 is 50°C or more, and 30 minutes or more have elapsed since the last pathway switching was performed. A temperature difference of 50°C or more indicates, for example, that the supply of raw material gas to the first catalyst 11 via the second pathway continues, and a large amount of ammonia is synthesized in the first catalyst 11 upstream of the second catalyst 12, causing the first catalyst 11 to heat up at a higher rate than the second catalyst 12 and reach a higher temperature. If the temperature difference becomes even larger than 50°C, the possibility of the ammonia synthesis reaction being inhibited in the first catalyst 11 due to equilibrium constraints at high temperatures increases, so it is preferable to switch the direction of raw material gas supply to the first pathway. Furthermore, the gas temperature used as the reference for the temperature difference may be the internal temperature of the first catalyst 11 and the second catalyst 12, rather than the outlet gas temperature.

[0063] As described above, if ammonia synthesis is continued with the first catalyst 11 as the upstream side of the first catalyst 11 and the second catalyst 12 (if the supply of raw material gas to the catalyst group via the second pathway is continued), more ammonia is synthesized in the first catalyst 11 than in the second catalyst 12. As a result, the first catalyst 11 is heated at a higher rate than the second catalyst 12 and reaches a higher temperature. Consequently, the ammonia synthesis reaction is subject to equilibrium constraints at high temperatures, increasing the likelihood that the ammonia synthesis reaction by the first catalyst 11 will be inhibited. On the other hand, according to the ammonia synthesis system 100D of the fourth embodiment, since the pathway for executing ammonia synthesis can be switched between the first pathway and the second pathway, by periodically switching between the first pathway and the second pathway and swapping the catalyst placed on the upstream side of the first catalyst 11 and the second catalyst 12, it is possible to suppress the inhibition of the ammonia synthesis reaction in one of the catalysts due to equilibrium constraints at high temperatures. As a result, the process efficiency of ammonia synthesis can be improved in the ammonia synthesis system 100D. In particular, when the amount of Fe, Ru, etc., supported on the first catalyst 11 and the second catalyst 12 is relatively large, and a large amount of heat is easily generated by the exothermic reaction associated with the ammonia synthesis, the switching of the pathway shown in the ammonia synthesis system 100D of the fourth embodiment is effective. Furthermore, since the heat generated by the synthesis reaction is reused to raise the temperature of the raw material gas, the process efficiency in ammonia synthesis can be improved from this viewpoint as well. In addition, since the raw material gas is heated by heat exchange with the catalyst group while flowing through the heat exchange channel HF2 before being used in the ammonia synthesis reaction by the catalyst group, it is also possible to suppress the decrease in the reaction rate in the synthesis reaction due to the low temperature of the raw material gas supplied to the catalyst group.

[0064] Figure 16 is a schematic block diagram of the ammonia synthesis system 100E of the fifth embodiment. The ammonia synthesis system 100E of the fifth embodiment differs from the ammonia synthesis system 100C of the third embodiment shown in Figure 7 mainly in that it is equipped with a gas divider 95 and a gas divider control unit 96, and has a reactor 10e that is different from reactor 10c. Reactor 10e has a heat exchange channel HF3 (not shown) inside, which has a different structure from the heat exchange channels HF1 and 2. The heat exchange channel HF3, like the heat exchange channels HF1 and 2, is a channel that supplies the raw material gas used in the reaction by the catalyst group to the catalyst group without reacting it with the catalyst group, while exchanging heat with the catalyst group. The first heat exchange section EX1, the second heat exchange section EX2, and the downstream section EXT shown in Figure 17, which will be described later, are each parts of the heat exchange channel HF3.

[0065] Figure 17 is an explanatory diagram showing the internal structure of reactor 10e. Figure 17 shows the XZ cross-section of reactor 10e. Figures 18(A) to (D) show the YZ cross-section of reactor 10e in the F18A to D-F18A to D cross-sections shown in Figure 17, respectively. The XYZ axes shown in the lower right of Figure 18 are shared in each of Figures 18(A) to (D). The arrows shown in Figures 17 and 18 indicate the gas flow within reactor 10e.

[0066] As shown in Figure 17, reactor 10e, like reactors 10c and d in the third and fourth embodiments (see Figures 8 and 11), has an inner piping 13 and an outer piping 15, and houses the catalyst group consisting of the first catalyst 11 and the second catalyst 12. That is, the catalyst group of the fifth embodiment includes the first catalyst 11 and the second catalyst 12. The first catalyst 11 and the second catalyst 12 are housed in reactor 10e in a series arrangement, as in the embodiments described above, but in this embodiment, the first catalyst 11 is housed in the second housing portion 13R of the inner piping 13, and the second catalyst 12 is housed in the first housing portion 13L of the inner piping 13.

[0067] In reactor 10e, the space between the inner piping 13 and the outer piping 15 corresponds to the heat exchange channel HF3. That is, reactor 10e has a heat exchange channel HF3 inside. The heat exchange channel HF3 has two heat exchange sections that can exchange heat with the catalyst group, as shown in Figure 17: a first heat exchange section EX1 and a second heat exchange section EX2.

[0068] The first heat exchange section EX1 is located furthest upstream of the two heat exchange sections and is capable of heat exchange with the first catalyst 11. The first heat exchange section EX1 is defined by the second containment section 13R and the second opposing section 15MR. On the other hand, the second heat exchange section EX2 is located next to the first heat exchange section EX1 in the direction from upstream to downstream of the two heat exchange sections and is capable of heat exchange with the second catalyst 12. The second heat exchange section EX2 is defined by the first containment section 13L and the first opposing section 15ML.

[0069] Furthermore, as shown in Figure 17, reactor 10e includes a first inlet pipe 16e1, a second inlet pipe 16e2, and a downstream inlet pipe 16eT. Each of the first inlet pipe 16e1, the second inlet pipe 16e2, and the downstream inlet pipe 16eT connects the gas divider 95 (see Figure 16) to reactor 10e. More specifically, each of the first inlet pipe 16e1, the second inlet pipe 16e2, and the downstream inlet pipe 16eT, which branch off from a single pipe connected to the gas divider 95 (see Figure 16), is connected to reactor 10e. Each of the first inlet pipe 16e1, the second inlet pipe 16e2, and the downstream inlet pipe 16eT is a pipe that introduces the raw material gas supplied from the gas divider 95 into reactor 10e.

[0070] As shown in Figure 17, the first introduction pipe 16e1 is connected to the +X-axis side end of the second opposing section 15MR and introduces the raw material gas into the first heat exchange section EX1. As shown in Figures 17 and 18(A), the raw material gas introduced from the first introduction pipe 16e1 flows around the second containment section 13R and moves toward the -X-axis side (flows within the first heat exchange section EX1), exchanging heat with the first catalyst 11. In this embodiment as well, as shown in Figure 17, the +X-axis side end of the second containment section 13R and the +X-axis side end of the second opposing section 15MR are connected by a connecting wall 14 that extends along the YZ plane, thus creating a closure.

[0071] The second introduction pipe 16e2 is connected to the central part of the cylindrical section 15M in the X-axis direction, and introduces the raw material gas into the second heat exchange section EX2 from downstream of the first heat exchange section EX1. As shown in Figures 17 and 18(B), the raw material gas introduced from the second introduction pipe 16e2 flows around the inner pipe 13 (near the central part in the X-axis direction) and moves toward the X-axis direction (flowing through the second heat exchange section EX2), exchanging heat with the second catalyst 12.

[0072] The downstream introduction pipe 16eT is connected to the -X-axis side end of the first opposing section 15ML and introduces the raw material gas into the heat exchange flow path HF3 from downstream of the second heat exchange section EX2. The raw material gas introduced from the downstream introduction pipe 16eT flows around the first containment section 13L and heads toward the downstream section EXT (the section defined by the hemispherical section 15L), as shown in Figures 17 and 18(D).

[0073] The gas divider 95 is a mass flow controller that adjusts the flow rate of the raw material gas heated by the heater 94 and supplies it to the first inlet pipe 16e1, the second inlet pipe 16e2, and the downstream inlet pipe 16eT, respectively. The splitting control unit 96 controls the gas divider 95 using the temperatures of the first catalyst 11 and the second catalyst 12, which are obtained by a temperature sensor (not shown). The specific control by the splitting control unit 96 will be described later. The gas divider 95 and the splitting control unit 96 correspond to the flow rate adjustment unit. The flow rate adjustment unit referred to here is a configuration that has the function of adjusting the flow rate of the raw material gas introduced from the first inlet pipe 16e1, the flow rate of the raw material gas introduced from the second inlet pipe 16e2, and the flow rate of the raw material gas introduced from the downstream inlet pipe 16eT.

[0074] If the temperature of the first catalyst 11 is higher than the target temperature (a predetermined desired temperature), the splitting control unit 96 controls the gas divider 95 to increase the flow rate of the raw material gas introduced from the first introduction pipe 16e1 (first introduction amount). At the same time, the splitting control unit 96 controls the gas divider 95 to decrease at least one of the flow rate of the raw material gas introduced from the second introduction pipe 16e2 (second introduction amount) and the flow rate of the raw material gas introduced from the downstream introduction pipe 16eT (downstream introduction amount). On the other hand, if the temperature of the first catalyst 11 is lower than the target temperature, the splitting control unit 96 controls the gas divider 95 to decrease the first introduction amount while increasing at least one of the second introduction amount and the downstream introduction amount.

[0075] If the temperature of the second catalyst 12 is higher than the target temperature, the split control unit 96 controls the gas divider 95 to increase the second introduction amount while decreasing at least one of the first introduction amount and the downstream introduction amount. On the other hand, if the temperature of the second catalyst 12 is lower than the target temperature, the split control unit 96 controls the gas divider 95 to decrease the second introduction amount while increasing at least one of the first introduction amount and the downstream introduction amount. The above-described increase or decrease of the first introduction amount in accordance with the temperature of the first catalyst 11 and the resulting increase or decrease of at least one of the second introduction amount and the downstream introduction amount, and the increase or decrease of the second introduction amount in accordance with the temperature of the second catalyst 12 and the resulting increase or decrease of at least one of the first introduction amount and the downstream introduction amount may be performed in parallel.

[0076] The raw material gas introduced into the reactor 10e from the first inlet pipe 16e1, the second inlet pipe 16e2, and the downstream inlet pipe 16eT reaches the downstream section EXT, and then passes through the second catalyst 12 while being subjected to the ammonia synthesis reaction, and flows into space SP as an intermediate product gas. The intermediate product gas that flows into space SP is divided into divided gas G from the gas divider 20 (see Figure 16). SP It is supplied via supply pipe 17 (see Figure 18(C)). The intermediate product gas is divided gas G SP After being mixed with the other substances, the mixture passes through the first catalyst 11 while being subjected to the ammonia synthesis reaction, and is discharged as a post-reaction gas from the reactor 10e via the discharge pipe 18. The discharge pipe 18 connects the hemispherical section 15R to the cooler 92 (see Figure 16), and discharges the post-reaction gas from the reactor 10e towards the cooler 92.

[0077] According to the ammonia synthesis system 100E of the fifth embodiment described above, when the temperature of the first catalyst 11 is higher than the target temperature, the flow rate of the raw material gas introduced from the first introduction pipe 16e1 is increased to promote heat exchange between the raw material gas and the first catalyst 11. When the temperature of the second catalyst 12 is higher than the target temperature, the flow rate of the raw material gas introduced from the second introduction pipe 16e2 is increased to promote heat exchange between the raw material gas and the second catalyst 12. This suppresses the inhibition of the ammonia synthesis reaction by each catalyst due to equilibrium constraints at high temperatures. Furthermore, when the temperature of the first catalyst 11 is lower than the target temperature, the flow rate of the raw material gas introduced from the first introduction pipe 16e1 is reduced to suppress heat exchange between the raw material gas and the first catalyst 11. When the temperature of the second catalyst 12 is lower than the target temperature, the flow rate of the raw material gas introduced from the second introduction pipe 16e2 is reduced to suppress heat exchange between the raw material gas and the second catalyst 12. This suppresses the cooling of each catalyst by heat exchange with the raw material gas. Furthermore, in the ammonia synthesis system 100E of the fifth embodiment, since there are no other heat exchange sections downstream of the second heat exchange section EX2 in the heat exchange channel HF3, increasing the flow rate of the raw material gas introduced from the downstream introduction pipe 16eT suppresses the cooling of the first and second catalysts 11 and 12 due to heat exchange with the raw material gas while promoting the ammonia synthesis reaction by the first and second catalysts 11 and 12, thus promoting the heating of each catalyst. In this way, by adjusting the flow rate of the raw material gas introduced from the first introduction pipe 16e1, the second introduction pipe 16e2, and the downstream introduction pipe 16eT, and adjusting the temperature of the first and second catalysts 11 and 12, the process efficiency in ammonia synthesis can be improved.

[0078] Figure 19 is an explanatory diagram showing the internal structure of reactor 10f in the ammonia synthesis system 100F of the sixth embodiment. Figures 20(A) to (D) show the YZ cross-sections of reactor 10f in the F20A to D-F20A to D cross-sections shown in Figure 19, respectively. The XYZ axes shown in the lower right of Figure 20 are shared in each of the figures 20(A) to (D). The ammonia synthesis system 100F of the sixth embodiment differs from the ammonia synthesis system 100E of the fifth embodiment shown in Figure 17 in that it has a reactor 10f which is different from reactor 10e. Reactor 10f has an internal heat exchange channel HF4 (not shown) which has a different structure from the heat exchange channels HF1 to 3 described above. The first heat exchange section EX1f, the second heat exchange section EX2f, and the downstream section EXT shown in Figure 19, which will be described later, are each parts of the heat exchange channel HF4.

[0079] As shown in Figure 19, reactor 10f has an inner pipe 13f and an outer pipe 15. The inner pipe 13f is cylindrical in shape and its outer surface is covered with a catalyst group. Specifically, the outer surface of the second cylindrical portion 13fR, which is the portion of the inner pipe 13f on the +X axis side, is covered with the first catalyst 11, and the outer surface of the first cylindrical portion 13fL, which is the portion on the -X axis side, is covered with the second catalyst 12. That is, in the sixth embodiment, the shape of the first catalyst 11 and the shape of the second catalyst are annular.

[0080] The outer piping 15 has a cylindrical shape, covers the inner piping 13f, and houses the catalyst group inside. Specifically, the first catalyst 11 is housed inside the second opposing portion 15MR (opposite the second cylindrical portion 13fR in the sixth embodiment) of the outer piping 15, and the second catalyst 12 is housed inside the first opposing portion 15ML (opposite the first cylindrical portion 13fL in the sixth embodiment).

[0081] Furthermore, the inner piping 13f has a first heat exchange section EX1f and a second heat exchange section EX2f, which are part of the heat exchange flow path HF4. The first heat exchange section EX1f is defined by the second cylindrical section 13fR. On the other hand, the second heat exchange section EX2f is defined by the first cylindrical section 13fL.

[0082] Furthermore, as shown in Figure 19, reactor 10f is equipped with a first introduction pipe 16f1, a second introduction pipe 16f2, and a downstream introduction pipe 16fT. The first introduction pipe 16f1 is connected to the +X-axis side end of the second cylindrical section 13fR. As shown in Figures 19 and 20(A), the raw material gas introduced from the first introduction pipe 16f1 exchanges heat with the first catalyst 11 as it flows through the inside of the second cylindrical section 13fR toward the -X-axis direction (through the first heat exchange section EX1f).

[0083] The second introduction pipe 16f2 is connected to the inner pipe 13f near its center in the X-axis direction. As shown in Figures 19 and 20(B), the raw material gas introduced from the second introduction pipe 16f2 flows through the inside of the first cylindrical section 13fL (through the second heat exchange section EX2f) from near its center in the X-axis direction towards the X-axis direction of the inner pipe 13f, and exchanges heat with the second catalyst 12.

[0084] The downstream introduction pipe 16fT is connected to the -X-axis side end of the first cylindrical section 13fL. As shown in Figures 19 and 20(D), the raw material gas introduced from the downstream introduction pipe 16fT flows from the first cylindrical section 13fL in the -X-axis direction before reaching the downstream section EXT (the section defined by the hemispherical section 15L).

[0085] The raw material gas introduced into reactor 10f from the first inlet pipe 16f1, the second inlet pipe 16f2, and the downstream inlet pipe 16fT reaches the downstream section EXT, then passes through the second catalyst 12, space SP, and first catalyst 11 while being subjected to the ammonia synthesis reaction, and is then discharged from the discharge pipe 18. When passing through space SP, the raw material gas is divided gas G supplied via the supply pipe 17. SP It is mixed with (see Figure 20(C)). The ammonia synthesis system 100F of the sixth embodiment described above can achieve the same effects as the fifth embodiment.

[0086] Figure 21 is an explanatory diagram showing the internal structure of reactor 10g in the ammonia synthesis system 100G of the seventh embodiment. Figures 22(A) to (E) show the YZ cross-sections of reactor 10g in the F22A to D and F22A to E cross-sections shown in Figure 21, respectively. The XYZ axes shown in the lower right of Figure 22 are shared in each of the figures 22(A) to (E). The ammonia synthesis system 100G of the seventh embodiment differs from the ammonia synthesis system 100F of the sixth embodiment shown in Figures 19 and 20 in that it has a reactor 10g that is different from reactor 10f. Reactor 10g has an internal heat exchange channel HF5 (not shown) with a different structure from the heat exchange channels HF1 to 4 described above. The first to fourth heat exchange sections EX1g to 4g and the downstream section EXT shown in Figure 21, which will be described later, are each part of the heat exchange channel HF5.

[0087] As shown in Figure 21, the reactor 10g includes a central pipe 5g, an inner pipe 13g, and an outer pipe 15. The central pipe 5g is cylindrical in shape, and its outer surface is covered with a catalyst group. More specifically, the outer surface of the first central cylindrical portion 5gL, which is the part of the central pipe 5g on the -X axis side, is covered with a first catalyst 11, while the outer surface of the second central cylindrical portion 5gR, which is the part on the +X axis side, is covered with a second catalyst 12. That is, in the seventh embodiment, the shapes of the first catalyst 11 and the second catalyst are annular.

[0088] The inner piping 13g has a cylindrical shape, covers the central piping 5g, and houses the catalyst group inside. Specifically, the first catalyst 11 is housed in the first housing portion 13gL, which is the -X-axis side of the inner piping 13g, and the second catalyst 12 is housed in the second housing portion 13gR, which is the +X-axis side. The outer piping 15 has a cylindrical shape and covers the inner piping 13g.

[0089] In reactor 10g, the space between the inner piping 13g and the outer piping 15 constitutes part of the heat exchange channel HF5. This space includes a first heat exchange section EX1g and a second heat exchange section EX2g. The first heat exchange section EX1g is defined by a first containment section 13gL and a first opposing section 15ML (opposite the first containment section 13gL in the seventh embodiment). On the other hand, the second heat exchange section EX2 is defined by a second containment section 13gR and a second opposing section 15MR (opposite the second containment section 13gR in the seventh embodiment).

[0090] Furthermore, as shown in Figure 21, the reactor 10g is equipped with a first introduction pipe 16g1, a second introduction pipe 16g2, and a downstream introduction pipe 16gT. The first introduction pipe 16g1 is connected to the -X-axis side end of the first opposing section 15ML. As shown in Figures 21 and 22(A), the raw material gas introduced from the first introduction pipe 16g1 flows around the first containment section 13gL and moves toward the +X-axis side (flowing through the first heat exchange section EX1), exchanging heat with the first catalyst 11. In this embodiment, the -X-axis side end of the first containment section 13gL and the -X-axis side end of the first opposing section 15ML are connected by a connecting wall 14g extending along the YZ plane, thus creating a blockage.

[0091] The second introduction pipe 16g2 is connected to the outer pipe 15 near its center in the X-axis direction. As shown in Figures 21 and 22(C), the raw material gas introduced from the second introduction pipe 16g2 flows around the second containment section 13gR and moves towards the +X-axis direction (flowing through the second heat exchange section EX2), exchanging heat with the second catalyst 12.

[0092] The downstream introduction pipe 16gT is connected to the end of the second opposing section 15MR on the +X axis side. The raw material gas introduced from the downstream introduction pipe 16gT flows in the +X axis and -Z axis directions from the second opposing section 15MR, as shown in Figures 21 and 22(D).

[0093] Furthermore, the central pipe 5g has a third heat exchange section EX3g and a fourth heat exchange section EX4g inside, which are part of the heat exchange channel HF5. The third heat exchange section EX3g is a section defined by the second central cylindrical section 5gR. That is, since the third heat exchange section EX3g is covered by the second catalyst 12, it is a section in which heat exchange with the second catalyst 12 is possible. On the other hand, the fourth heat exchange section EX4g is a section defined by the first central cylindrical section 5gL. That is, since the fourth heat exchange section EX4g is covered by the first catalyst 11, it is a section in which heat exchange with the first catalyst 11 is possible. In other words, since the reactor 10g has four heat exchange sections, the first heat exchange section EX1g is the heat exchange section located furthest upstream of the four heat exchange sections, and the second heat exchange section EX2g is the heat exchange section located after the first heat exchange section EX1g in the direction from upstream to downstream of the four heat exchange sections.

[0094] As shown in Figure 21, connecting pipe 9g is the pipe that defines the connecting section CN, which connects the second heat exchange section EX2g and the third heat exchange section EX3g (see also Figure 22(E)).

[0095] The raw material gas introduced into reactor 10g from the first inlet pipe 16g1, the second inlet pipe 16g2, and the downstream inlet pipe 16gT passes through the connection section CN, the third heat exchange section EX3g, and the fourth heat exchange section EX4g, before reaching the downstream section EXT. Furthermore, the raw material gas passes through the first catalyst 11, space SP, and second catalyst 12 while being subjected to the ammonia synthesis reaction, and is then discharged from the discharge pipe 18. Note that when passing through space SP, the raw material gas is divided into gases G supplied via the supply pipe 17. SP It is mixed with (see Figure 22(B)).

[0096] The ammonia synthesis system 100G of the seventh embodiment described above can achieve the same effects as the fifth and sixth embodiments. Furthermore, in the ammonia synthesis system 100G of the seventh embodiment, the raw material gas flows through the first and second heat exchange sections EX1g and EX2g to exchange heat with the first and second catalysts 11 and EX2, and then flows through the third and fourth heat exchange sections EX3g and EX4g to exchange heat again with the first and second catalysts 11 and EX2. Therefore, since the raw material gas is heated by heat exchange with the catalyst group while flowing through the four heat exchange sections before being used in the ammonia synthesis reaction by the catalyst group, it is possible to further suppress the decrease in the reaction rate in the synthesis reaction caused by a low temperature of the raw material gas supplied to the catalyst group.

[0097] Figure 23 is an explanatory diagram showing the internal structure of reactor 10h in the ammonia synthesis system 100H of the 8th embodiment. Figures 24(A) to (E) show the YZ cross-sections of reactor 10h in the F24A to E and F22A to E cross-sections shown in Figure 23, respectively. The XYZ axes shown in the lower right of Figure 24 are shared in each of the figures 24(A) to (E). The ammonia synthesis system 100H of the 8th embodiment differs from the ammonia synthesis system 100G of the 7th embodiment shown in Figures 21 and 22 in that it has a reactor 10h that is different from reactor 10g. Reactor 10h has an internal heat exchange channel HF6 (not shown) with a different structure from the heat exchange channels HF1 to 5 described above. The 1st to 4th heat exchange sections EX1f to 4f and the downstream section EXT shown in Figure 23, which will be described later, are each part of the heat exchange channel HF6.

[0098] Reactor 10h, like reactor 10g in the 7th embodiment (see Figure 21), has a central pipe 5g, an inner pipe 13g, and an outer pipe 15. Also, in reactor 10h, the shape of the first catalyst 11 and the second catalyst are annular, the first catalyst 11 covers the outer surface of the first central cylindrical portion 5gL and is housed in the first housing portion 13gL, and the second catalyst 12 covers the outer surface of the second central cylindrical portion 5gR and is housed in the second housing portion 13gR, which is also the same as reactor 10g in the 7th embodiment (see Figure 21).

[0099] In reactor 10h, the central pipe 5g has a first heat exchange section EX1h and a second heat exchange section EX2h, which are part of the heat exchange channel HF6. The first heat exchange section EX1h is defined by the first central cylindrical section 5gL. That is, since the first heat exchange section EX1h is covered by the first catalyst 11, it is a section in which heat exchange with the first catalyst 11 is possible. On the other hand, the second heat exchange section EX2h is defined by the second central cylindrical section 5gR. That is, since the second heat exchange section EX2h is covered by the second catalyst 12, it is a section in which heat exchange with the second catalyst 12 is possible.

[0100] Furthermore, as shown in Figure 23, reactor 10h is equipped with a first introduction pipe 16h1, a second introduction pipe 16h2, and a downstream introduction pipe 16hT. The first introduction pipe 16h1 is connected to the -X-axis side end of the first central cylindrical section 5gL. As shown in Figures 23 and 24(A), the raw material gas introduced from the first introduction pipe 16g1 exchanges heat with the first catalyst 11 as it flows through the first central cylindrical section 5gL toward the +X-axis direction (through the first heat exchange section EX1h).

[0101] The second introduction pipe 16h2 is connected to the central pipe 5g near its center in the X-axis direction. As shown in Figures 23 and 24(C), the raw material gas introduced from the second introduction pipe 16h2 flows through the second central cylindrical section 5gR (through the second heat exchange section EX2h) from near its center in the X-axis direction towards the +X-axis direction, and exchanges heat with the second catalyst 12.

[0102] The downstream inlet pipe 16hT is connected to the +X-axis side end of the second opposing section 15MR. The raw material gas introduced from the downstream inlet pipe 16hT flows around the second containment section 13gR and the first containment section 13gL, as shown in Figures 23 and 24(D), towards the downstream section EXT.

[0103] Furthermore, in reactor 10h, the space between the inner piping 13g and the outer piping 15 constitutes part of the heat exchange channel HF6. This space includes the third heat exchange section EX3h and the fourth heat exchange section EX4h. The third heat exchange section EX3h is defined by the second containment section 13gR and the second opposing section 15MR. That is, the third heat exchange section EX3h is located in a position that covers the second catalyst 12, and therefore is a section in which heat exchange with the second catalyst 12 is possible. On the other hand, the fourth heat exchange section EX4h is defined by the first containment section 13gL and the first opposing section 15ML. That is, the fourth heat exchange section EX4h is located in a position that covers the first catalyst 11, and therefore is a section in which heat exchange with the first catalyst 11 is possible. In other words, reactor 10h, like reactor 10g (see Figure 21), has four heat exchange sections. Therefore, the first heat exchange section EX1h is the heat exchange section located furthest upstream of the four heat exchange sections, and the second heat exchange section EX2h is the heat exchange section located after the first heat exchange section EX1h in the direction from upstream to downstream of the four heat exchange sections.

[0104] In reactor 10h, the connection section CN defined by connecting pipe 9g connects the second heat exchange section EX2h and the third heat exchange section EX3h, as shown in Figure 23 (see also Figure 24(E)).

[0105] The raw material gas introduced into reactor 10h from the first inlet pipe 16h1, the second inlet pipe 16h2, and the downstream inlet pipe 16hT passes through the third heat exchange section EX3h and the fourth heat exchange section EX4h, and reaches the downstream section EXT. Furthermore, the raw material gas passes through the first catalyst 11, space SP, and second catalyst 12 while being subjected to the ammonia synthesis reaction, and is then discharged from the discharge pipe 18. Note that when passing through space SP, the raw material gas is divided into divided gas G supplied via the supply pipe 17. SP It is mixed with (see Figure 24(B)).

[0106] The ammonia synthesis system 100H of the 8th embodiment described above can achieve the same effects as the 5th to 7th embodiments. Furthermore, in the ammonia synthesis system 100H of the 8th embodiment, similar to the 7th embodiment, the raw material gas flows through the 1st and 2nd heat exchange sections EX1g and 2g to exchange heat with the 1st and 2nd catalysts 11 and 12, and then flows through the 3rd and 4th heat exchange sections EX3g and 4g to exchange heat again with the 1st and 2nd catalysts 11 and 12. Therefore, similar to the 7th embodiment, the raw material gas is heated by heat exchange with the catalyst group while flowing through the four heat exchange sections before being used in the ammonia synthesis reaction by the catalyst group. This further suppresses the decrease in the reaction rate in the synthesis reaction caused by a low temperature of the raw material gas supplied to the catalyst group.

[0107] <Modified examples of embodiments> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit, for example, the following modifications are also possible.

[0108] The ammonia synthesis system 100 in the above embodiment is just one example, and the configuration and control of the ammonia synthesis system 100 can be modified in various ways. For example, the ammonia synthesis system 100 does not have a gas-liquid separator 40 and a tank 50, and another system connected to the ammonia synthesis system 100 may have a gas-liquid separator 40, etc. The ammonia synthesis system 100 does not have a first mixer 71 and a second mixer 72, and various gases may be mixed in the piping that forms the flow path. The ammonia synthesis system 100 does not have heaters 93, 94, and divided gas G SP It may be mixed with the intermediate product gas without being heated.

[0109] The gas sensor 60 in the above embodiment uses recycled gas G CYIt is sufficient to detect at least one of the following: the gas composition of the fuel gas supplied from the heat exchanger 91 to the reactor 10, the gas composition of the intermediate product gas, and the gas composition of the post-reaction gas discharged from the reactor 10. Furthermore, the ammonia synthesis system 100 does not necessarily have to be equipped with a gas sensor 60.

[0110] The reactor 10 in the above embodiment was equipped with two catalysts, a first catalyst 11 and a second catalyst 12, arranged in series, but it may be equipped with three or more catalysts. In this case, a split gas G containing at least one of N2 and H2 is added to the intermediate product gas obtained between at least two catalysts. SP However, it is sufficient if it is supplied from the gas supply unit 25.

[0111] In the ammonia synthesis system 100A of the first embodiment shown in Figures 3 and 4, N2 is divided gas G SP The process efficiency EP is highest when supplied as such. In other words, in the first embodiment, the divided gas G SP The higher the concentration of N2 contained in the gas, the better the process efficiency EP. Therefore, the divided gas G in the first embodiment SP The gas ratio Rg is preferably small, specifically less than 2.5. On the other hand, in the ammonia synthesis system 100B of the second embodiment shown in Figures 5 and 6, H2 is divided gas G SP The process efficiency EP is highest when supplied as such. In other words, in the second embodiment, the divided gas G SP The higher the concentration of H2 contained, the better the process efficiency EP. Therefore, the split gas G in the second embodiment SP The gas ratio is preferably large, and specifically, preferably greater than 3. That is, the divided gas G supplied from the gas supply unit 25 to the intermediate product gas. SP The gas ratio Rg is preferably less than 2.5 or greater than 3. Furthermore, the divided gas G SP The gas ratio Rg is preferably less than 1 or greater than 3. Thus, the divided gas G SP By adjusting the gas ratio Rg, the gas composition of the intermediate product gas can be adjusted to the optimal gas composition corresponding to the second catalyst 12.

[0112] The heat exchange channels HF1 and HF2 in reactors 10c (Figure 8) and 10d (Figure 11) of the above embodiment are examples, and the structure of the heat exchange channels can be modified. For example, the heat exchange channels may have a structure as shown in Figure 15. Reactor 10j shown in Figure 15 differs from reactor 10d (Figure 11) in that it has a channel HFB instead of a channel HFb. Channel HFB is defined by a pipe 19R that connects the second opposing section 15MR and the hemispherical section 15L outside the outer pipe 15. In reactor 10j, when the raw material gas reaches the first catalyst 11 from the second supply pipe 16R via the second path, the raw material gas reaches the first catalyst 11 via channels HFa, HFB, and HFc. At this time, the raw material gas is heated by heat exchange with the second catalyst 12 separated by the inner pipe 13, and then supplied to the first catalyst 11 without heat exchange with the first catalyst 11 to be used in the ammonia synthesis reaction. On the other hand, piping 19L is a pipe that connects the first opposing section 15ML and the hemispherical section 15R outside of the outer piping 15. Piping 19L is positioned in contrast to piping 19R and defines the flow path through which the raw material gas travels from the first supply piping 16L to the second catalyst 12 via the first path.

[0113] In the reactor 10d of the above embodiment (Figure 11), the first supply pipe 16L and the second supply pipe 16R were both connected to the outer pipe 15 from the same direction (the side in the +Z axis direction in Figure 11), but this is not limited to this. For example, the first supply pipe 16L and the second supply pipe 16R may each be connected to the outer pipe 15 from different directions (for example, the side in the +Z axis direction and the side in the -Z axis direction). Even in such a case, as long as the first and second paths are arranged symmetrically within the reactor, the same effects as in the fourth embodiment can be achieved.

[0114] In the reactors 10e to h described above, the heat exchange channels HF3 to HF6 had two or four heat exchange sections. However, as long as the first and second introduction pipes for introducing the raw material gas into the first and second heat exchange sections are provided, the heat exchange channels may have any number of heat exchange sections, two or more.

[0115] In the reactors 10e to h described above, the catalyst group included a first catalyst 11 and a second catalyst 12, but is not limited to this. For example, the catalyst group may further include a third catalyst and a fourth catalyst. In such a case, the heat exchange channel may include a third heat exchange section capable of heat exchange with the third catalyst and a fourth heat exchange section capable of heat exchange with the fourth catalyst, and further third and fourth introduction pipes may be provided to introduce the raw material gas into these third and fourth heat exchange sections.

[0116] In the reactors 10e to h described above, the flow rate of the raw material gas introduced from each inlet pipe was adjusted by the gas divider 95, but this is not limited to it. For example, instead of the gas divider 95, valves may be provided in each inlet pipe. The division control unit 96 may then adjust the flow rate of the raw material gas introduced from each inlet pipe by adjusting the opening of these valves according to the temperature of the first catalyst 11 and the temperature of the second catalyst 12.

[0117] 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.

[0118] The present invention can also be realized in the following forms. [Application Example 1] An ammonia synthesis system used in an ammonia production plant equipped with a circulation system for reusing the gas after the reaction, A group of catalysts arranged in series, which synthesize ammonia from hydrogen and nitrogen, A gas supply unit supplies a divided gas containing at least one of hydrogen and nitrogen to the intermediate product gas obtained between each of the catalysts constituting the catalyst group. A control unit for controlling the composition of the intermediate product gas, An ammonia synthesis system equipped with the following features. [Application Example 2] The ammonia synthesis system described in Application Example 1, An ammonia synthesis system in which the divided gas supplied from the gas supply unit is nitrogen or hydrogen. [Application Example 3] An ammonia synthesis system as described in Application Example 1 or Application Example 2, The divided gas comprises hydrogen and nitrogen. The control unit is configured to set the gas ratio of hydrogen to nitrogen in the divided gas to less than 2.5 or greater than 3, in an ammonia synthesis system. [Application Example 4] An ammonia synthesis system as described in any of Application Examples 1 to 3, The control unit is an ammonia synthesis system in which the gas ratio of hydrogen to nitrogen in the divided gas is less than 1. [Application Example 5] An ammonia synthesis system according to any of Application Examples 1 to 4, further comprising: The system includes a detection unit that detects at least one gas composition of the gas supplied to the catalyst group, the gas discharged from the catalyst group, and the gas of the intermediate product gas. The control unit controls the composition of the intermediate product gas using the gas composition detected by the detection unit in an ammonia synthesis system. [Application Example 6] An ammonia synthesis system as described in any of Application Examples 1 to 5, The ammonia synthesis system is composed of catalysts of different types, each forming part of the catalyst group. [Application Example 7] An ammonia synthesis system according to any of Application Examples 1 to 6, further comprising: An ammonia synthesis system comprising a heater for heating the divided gas supplied from the gas supply unit. [Application Example 8] An ammonia synthesis system according to any of Application Examples 1 to 7, further comprising: An ammonia synthesis system comprising a reactor housing the catalyst group, the reactor having an internal heat exchange channel for supplying the raw material gas used in the reaction by the catalyst group to the catalyst group without reacting it with the catalyst group, while exchanging heat with the catalyst group. [Application Example 9] An ammonia synthesis system described in any of Application Examples 1 to 8, further comprising: The system includes a supply pipe connected to the heat exchange channel and for supplying the raw material gas to the heat exchange channel, The reactor is, An internal piping housing the catalyst group, It has an outer pipe that covers the inner pipe, The heat exchange channel is the space between the inner pipe and the outer pipe. An ammonia synthesis system wherein the raw material gas supplied from the supply pipe is supplied via the heat exchange channel to the catalyst located at one end of the group of catalysts arranged in series in the inner pipe. [Application Example 10] An ammonia synthesis system as described in any of Application Examples 1 to 9, The catalyst group includes a first catalyst and a second catalyst, A first supply pipe connected to the portion of the heat exchange channel on the side of the first catalyst, which supplies the raw material gas to the heat exchange channel, A second supply pipe connected to the portion of the heat exchange channel on the side of the second catalyst, which supplies the raw material gas to the heat exchange channel, A first discharge pipe is connected to the portion of the outer piping on the side in the direction from the second catalyst to the first catalyst, and discharges the reaction gas after the reaction by the catalyst group, A second discharge pipe is connected to the portion of the outer piping on the side in the direction from the first catalyst to the second catalyst, and discharges the reaction gas after the reaction by the catalyst group, An ammonia synthesis system comprising: a path switching unit that switches the path through which the raw material gas is supplied to the heat exchange channel and then discharged as the post-reaction gas between a first path in which the raw material gas is supplied from the first supply pipe to the second catalyst via the heat exchange channel and then discharged as the post-reaction gas from the first discharge pipe via the first catalyst and a second path in which the raw material gas is supplied from the second supply pipe to the first catalyst via the heat exchange channel and then discharged as the post-reaction gas from the second discharge pipe via the second catalyst. [Application Example 11] An ammonia synthesis system described in any of Application Examples 1 to 10, further comprising: The catalyst group includes a first catalyst and a second catalyst, The heat exchange channel has two or more heat exchange sections that can exchange heat with the catalyst group, Two or more of the heat exchange sections include: A first heat exchange section is located furthest upstream of two or more heat exchange sections and is capable of exchanging heat with the first catalyst, The system includes a second heat exchange section, which is located next to the first heat exchange section in the direction from upstream to downstream among two or more heat exchange sections and is capable of exchanging heat with the second catalyst, A first introduction pipe for introducing the raw material gas into the first heat exchange section, A second introduction pipe for introducing the raw material gas into the second heat exchange section from downstream of the first heat exchange section, A downstream introduction pipe for introducing the raw material gas into the heat exchange flow path from a downstream side of the second heat exchange section, An ammonia synthesis system comprising a flow rate adjustment unit that adjusts the flow rate of the raw material gas introduced from the first introduction pipe, the flow rate of the raw material gas introduced from the second introduction pipe, and the flow rate of the raw material gas introduced from the downstream introduction pipe. [Explanation of symbols]

[0119] 5g... Central piping 5gL…1st center cylinder part 5gR…Second central cylinder part 9g…connecting pipe 10… Reactor (catalyst group) 10°C~H, 10°J… Reactor 11…First catalyst 12…Second catalyst 13, 13f, 13g... Internal piping 13L…1st storage part 13R…Second containment area 13fL…First cylindrical section 13fR…Second cylindrical section 13gL…First storage section 13gR…Second storage section 14, 14C, 14CB, 14g…connection wall 15…Outside piping 15L,15R…Hemisphere part 15M...Cylindrical part 15ML…1st opposing part 15MR…Second opposing part 16…Supply piping 16L…1st supply piping 16R…Second supply piping 16e1,16f1,16g1,16h1...1st introduction pipe 16e2, 16f2, 16g2, 16h2… Second introduction piping 16eT, 16fT, 16gT, 16hT… Downstream inlet piping 17…Supply piping 18…Discharge piping 18L…1st discharge pipe 18R…Second discharge pipe 19L...piping 19R... Piping 20...Gas divider (control unit) 25…Gas Supply Department 30…Divided control unit (control unit) 40…Gas-liquid separator 50... Tank 60...Gas sensor (detection unit) 71...First mixer 72…Second mixer 81...First Compressor 82... Second compressor 91...Heat exchanger 92...Cooler 93,94…heater 95...Gas splitter 96...Division Control Unit 100, 100A~H... Ammonia synthesis system A Fe ...catalytic activity of Fe-based catalysts A Ru ...catalytic activity of Ru-based catalysts EP…Process Efficiency G CY ...recycled gas G H2 ...raw material: H2 gas G N2 ...raw material: N2 gas G SP ...divided gas Rg...Gas ratio SP…Space

Claims

1. An ammonia synthesis system used in an ammonia production plant equipped with a circulation system for reusing the gas after the reaction, A group of catalysts arranged in series, which synthesize ammonia from hydrogen and nitrogen, A gas supply unit supplies a divided gas containing at least one of hydrogen and nitrogen to the intermediate product gas obtained between each of the catalysts constituting the catalyst group. A control unit for controlling the composition of the intermediate product gas, An ammonia synthesis system equipped with the following features.

2. The ammonia synthesis system according to claim 1, An ammonia synthesis system in which the divided gas supplied from the gas supply unit is nitrogen or hydrogen.

3. The ammonia synthesis system according to claim 1, The divided gas comprises hydrogen and nitrogen. The control unit is configured to set the gas ratio of hydrogen to nitrogen in the divided gas to less than 2.5 or greater than 3, in an ammonia synthesis system.

4. The ammonia synthesis system according to claim 3, The control unit is an ammonia synthesis system in which the gas ratio of hydrogen to nitrogen in the divided gas is less than 1.

5. An ammonia synthesis system according to any one of claims 1 to 4, further comprising: The system includes a detection unit that detects at least one gas composition of the gas supplied to the catalyst group, the gas discharged from the catalyst group, and the gas of the intermediate product gas, The control unit controls the composition of the intermediate product gas using the gas composition detected by the detection unit in an ammonia synthesis system.

6. An ammonia synthesis system according to any one of claims 1 to 4, The ammonia synthesis system is composed of catalysts of different types, each forming part of the catalyst group.

7. An ammonia synthesis system according to any one of claims 1 to 4, further comprising: An ammonia synthesis system comprising a heater for heating the divided gas supplied from the gas supply unit.

8. The ammonia synthesis system according to claim 1, further, An ammonia synthesis system comprising a reactor housing the catalyst group, the reactor having an internal heat exchange channel for supplying the raw material gas used in the reaction by the catalyst group to the catalyst group without reacting it with the catalyst group, while exchanging heat with the catalyst group.

9. The ammonia synthesis system according to claim 8, further, The system includes a supply pipe connected to the heat exchange channel and for supplying the raw material gas to the heat exchange channel, The reactor is, An internal piping housing the catalyst group, It has an outer pipe that covers the inner pipe, The heat exchange channel is the space between the inner pipe and the outer pipe. An ammonia synthesis system wherein the raw material gas supplied from the supply pipe is supplied via the heat exchange channel to the catalyst located at one end of the group of catalysts arranged in series in the inner pipe.

10. The ammonia synthesis system according to claim 8, The reactor is, An internal piping housing the catalyst group, It has an outer pipe that covers the inner pipe, The heat exchange channel is the space between the inner pipe and the outer pipe. The catalyst group includes a first catalyst and a second catalyst, A first supply pipe connected to the portion of the heat exchange channel on the side of the first catalyst, which supplies the raw material gas to the heat exchange channel, A second supply pipe is connected to the portion of the heat exchange channel on the side of the second catalyst and supplies the raw material gas to the heat exchange channel. A first discharge pipe is connected to the portion of the outer piping on the side in the direction from the second catalyst to the first catalyst, and discharges the reaction gas after the reaction by the catalyst group, A second discharge pipe is connected to the portion of the outer piping on the side in the direction from the first catalyst to the second catalyst, and discharges the reaction gas after the reaction by the catalyst group, An ammonia synthesis system comprising: a path switching unit that switches the path through which the raw material gas is supplied to the heat exchange channel and then discharged as the post-reaction gas between a first path in which the raw material gas is supplied from the first supply pipe to the second catalyst via the heat exchange channel and then discharged as the post-reaction gas from the first discharge pipe via the first catalyst and a second path in which the raw material gas is supplied from the second supply pipe to the first catalyst via the heat exchange channel and then discharged as the post-reaction gas from the second discharge pipe via the second catalyst.

11. The ammonia synthesis system according to claim 8, further, The catalyst group includes a first catalyst and a second catalyst, The heat exchange channel has two or more heat exchange sections that can exchange heat with the catalyst group, Two or more of the heat exchange sections include: A first heat exchange section is located furthest upstream of two or more heat exchange sections and is capable of exchanging heat with the first catalyst, The system includes a second heat exchange section, which is located next to the first heat exchange section in the direction from upstream to downstream among two or more heat exchange sections, and which is capable of exchanging heat with the second catalyst, A first introduction pipe for introducing the raw material gas into the first heat exchange section, A second introduction pipe for introducing the raw material gas into the second heat exchange section from downstream of the first heat exchange section, A downstream introduction pipe for introducing the raw material gas into the heat exchange flow path from a downstream side of the second heat exchange section, An ammonia synthesis system comprising a flow rate adjustment unit that adjusts the flow rate of the raw material gas introduced from the first introduction pipe, the flow rate of the raw material gas introduced from the second introduction pipe, and the flow rate of the raw material gas introduced from the downstream introduction pipe.

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