Gas manufacturing system and its operation method

Abstract

The gas manufacturing system (100) includes a switching unit (21, 22) for regulating the flow path (L1, L4) and a hollow reaction unit (40A) connected to the flow path and containing a reducing agent inside. The reaction unit is connected via the flow path to a first supply unit (11) supplying a first gas (G1A) containing carbon dioxide and oxygen, and a second supply unit (13) supplying a reducing gas. The switching unit is configured to switch between the following contacts: contact between the first gas (G1A) supplied from the first supply unit and a first reducing agent containing a metal oxide as a reducing agent; contact between a second reducing agent (G3) that has contacted the first reducing agent and the reducing gas; and contact between a third reducing agent (G1B) that has contacted the second reducing agent and the first gas (G1B) that has contacted the first reducing agent.

Description

Technical Field

[0001] This disclosure pertains to gas manufacturing systems and methods of operating such systems. Prior Technology

[0002] In recent years, research and development of technologies for recovering carbon dioxide (CO2) from exhaust gases and the atmosphere, and for converting recovered CO2 into valuable substances, has been carried out in order to prevent global warming and realize a carbon cycle society. For example, a product gas containing carbon monoxide (CO) is produced by contacting a feed gas containing CO2 with a reducing agent containing a metal oxide that reduces CO2. Increasing the CO2 concentration in the feed gas is important to improve the efficiency of product gas production. To this end, gas production apparatuses, including those for removing unwanted gaseous components, primarily O2, contained in the feed gas, have been disclosed.

[0003] In other words, conventional gas manufacturing apparatuses include a concentration adjustment unit for an oxygen removal device, such as a separator using a cryogenic separation method, a pressure swing adsorption method, or a temperature swing adsorption method, in order to remove oxygen contained in the feed gas. The feed gas, having passed through this concentration adjustment unit and with oxygen removed, is then contacted in a reactor with a reducing agent containing metal oxides to produce a generated gas containing carbon monoxide. (For example, please refer to Patent Document 1.) [Preliminary Technology Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-75447 Summary of the Invention

[0005] [The problem the invention aims to solve] In the aforementioned conventional gas manufacturing apparatus, in order to remove unwanted gaseous components, mainly oxygen (O2) contained in the feed gas, an oxygen removal device, such as a low-temperature separator, is included in the upstream section of the reactor. However, such oxygen removal devices are relatively expensive and consume a large amount of electricity. Therefore, conventional gas manufacturing apparatuses suffer from energy losses when driving the oxygen removal device and low gas manufacturing efficiency.

[0006] This disclosure discloses a technique for solving the aforementioned problems, with the aim of providing a low-cost, high-efficiency gas production system and a method for operating the gas production system. [Methods used to solve problems]

[0007] The gas manufacturing system disclosed herein includes: A switching unit, provided in the flow path, adjusts the switching of the aforementioned flow path; and The hollow reaction section is connected to the aforementioned flow path and contains a reducing agent inside; The aforementioned reaction system, The flow path is connected to a first supply unit that supplies gas 1A containing carbon dioxide and oxygen, and a second supply unit that supplies reducing gas. By adjusting the switching of the aforementioned flow path through the switching unit, the aforementioned reaction unit is configured to switch to the following contacts respectively: The contact between the aforementioned first A gas supplied from the aforementioned first supply unit and the first reducing agent containing a metal oxide as the aforementioned reducing agent, the contact between the second reducing agent which has been in contact with the aforementioned first A gas and the aforementioned reducing gas, the contact between the third reducing agent which has been in contact with the aforementioned reducing gas and the first B gas which has been in contact with the aforementioned first reducing agent, the contact between the first A gas and the aforementioned reducing gas. Furthermore, the operating method of the gas manufacturing system disclosed herein includes: In the oxygen reaction step, a first A gas containing carbon dioxide and oxygen is contacted with a first reducing agent containing a metal oxide to generate a first B gas from the aforementioned first A gas, in which the oxygen has been removed. The hydrogen reaction step involves contacting the second reducing agent, which is the first reducing agent oxidized by the oxygen in the aforementioned gas 1A, with a reducing gas containing hydrogen to generate a third reducing agent that reduces the aforementioned second reducing agent; and In the carbon dioxide reaction step, the aforementioned third reducing agent is brought into contact with the aforementioned first B gas, causing the aforementioned carbon dioxide in the aforementioned first B gas to be reduced to generate a product gas containing carbon monoxide, while the aforementioned third reducing agent is oxidized and the aforementioned first reducing agent is used in the aforementioned oxygen reaction step. [Invention Benefits]

[0008] Based on the gas manufacturing system and its operation method disclosed herein, a low-cost, high-efficiency gas manufacturing system and its operation method can be obtained. Simple Explanation of the Diagram

[0009] Figure 1 is a block diagram showing the general structure of the gas manufacturing system according to Example 1. Figure 2 is a flowchart illustrating the operation method of the gas manufacturing system according to Example 1. Figure 3 is a block diagram showing other schematic configurations of the gas manufacturing system according to Example 1. Figure 4 is a diagram showing the hardware configuration of the control unit of the gas manufacturing system according to Embodiment 1. Figure 5 is a block diagram showing the general configuration of the gas manufacturing system according to Example 2. Figure 6 is a diagram illustrating the reaction states of each switching reactor in the first step of the gas manufacturing system according to Example 2. Figure 7 is a diagram illustrating the reaction states of each switching reactor in the second step of the gas manufacturing system according to Example 2. Figure 8 is a diagram illustrating the reaction states of each switching reactor in the third step of the gas manufacturing system according to Example 2. Implementation

[0010] Example 1. Figure 1 is a block diagram showing the general configuration of the gas manufacturing system 100 according to Embodiment 1. The gas manufacturing system 100 of this embodiment converts raw material gases, such as exhaust gases containing carbon dioxide (CO2) and oxygen (O2), into a generated gas containing valuable substances, such as carbon monoxide (CO), using a reducing agent.

[0011] As shown in Figure 1, the gas manufacturing system 100 comprises a first reactor 41 as a first reaction unit, a second reactor 42 as a second reaction unit, and a third reactor 43 as a third reaction unit, which are hollow reaction units containing reducing agents. Furthermore, in the following descriptions, there is no need to distinguish between the first reactor 41, the second reactor 42, and the third reactor 43; they may simply be referred to as reactors.

[0012] Furthermore, the reaction section of this gas manufacturing system 100 is connected to: a raw material gas supply section 11, which supplies the raw material gas G1A as the first supply section; a hydrogen generator 13, which generates a gas containing hydrogen as the reducing gas G3 as the second supply section; a generated gas discharge section 12, which discharges the generated gas G2; and a water vapor discharge device 14, which discharges water vapor G4.

[0013] Specifically, the raw material gas supply unit 11 and the first reactor 41 are connected by a raw material gas pipe L1, which serves as a flow path for supplying raw material gas G1A to the first reactor 41. The first reactor 41 and the second reactor 42 are connected by an oxygen removal pipe L2, which serves as a flow path. The generated gas discharge section 12 and the second reactor 42 are connected by a generated gas pipe L3, which serves as the flow path for discharging the generated gas G2. The hydrogen generator 13 and the third reactor 43 are connected by a reducing gas pipe L4, which serves as a flow path for supplying reducing gas G3 to the third reactor 43. The steam discharge device 14 and the third reactor 43 are connected by a steam discharge pipe L5, which serves as the flow path for discharging steam.

[0014] Furthermore, the gas manufacturing system 100 includes circulation piping for circulating the reducing agent between the reactors. Specifically, the gas manufacturing system 100 includes circulation piping L6A, which serves as a first transfer section for transferring the reducing agent from the first reactor 41 to the third reactor 43; circulation piping L6B, which serves as a second transfer section for transferring the reducing agent from the third reactor 43 to the second reactor 42; and circulation piping L6C, which serves as a third transfer section for transferring the reducing agent from the second reactor 42 to the first reactor 41. With this configuration, the reducing agent can flow in the order of first reactor 41, third reactor 43, second reactor 42, and first reactor 41.

[0015] In addition, the gas manufacturing system 100 series has adjustment valves in the front and rear sections of each reactor, which are used as switching units to control the switches of each pipeline. Specifically, an adjustment valve 21 serving as a first switching unit is provided between the raw material gas supply unit 11 and the first reactor 41. Furthermore, an adjustment valve 22 serving as a second switching unit is provided between the hydrogen generator 13 and the third reactor 43.

[0016] Furthermore, an adjusting valve 23 is provided on the oxygen removal piping L2 between the first reactor 41 and the second reactor 42. Also, an adjusting valve 24 is provided on the generator gas piping L3 between the second reactor 42 and the generator gas discharge section 12. Furthermore, an adjusting valve 25 is provided on the steam discharge piping L5 between the third reactor 43 and the steam discharge device 14. Furthermore, regulating valves 31 and 32 are provided in the circulation piping L6A. Furthermore, regulating valves 33 and 34 are provided in the circulation piping L6B. Furthermore, regulating valves 35 and 36 are provided in the circulation piping L6C. Furthermore, although two regulating valves 31 and 32 are provided in the circulation piping L6A, it is also possible to have only one of them. Similarly, although two regulating valves 33 and 34 are provided in the circulation piping L6B, it is also possible to have only one of them. Likewise, although two regulating valves 35 and 36 are provided in the circulation piping L6C, it is also possible to have only one of them.

[0017] In the following explanations, it is not necessary to distinguish between the cases of each regulating valve 21~25 and 31~36; they can be simply referred to as regulating valves. Furthermore, the gas manufacturing system 100 includes a control unit 50 that controls the on / off state of each of these regulating valves, and controls each regulating valve according to the modes described later.

[0018] Furthermore, an unshown blower is provided in the raw material gas supply section 11 for pressurizing and conveying the raw material gas G1A. Also, a heater 1 for heating the raw material gas G1A is provided in the raw material gas piping L1. Furthermore, a heater 2 for heating the gas supplied via the first reactor 41 is provided in the oxygen removal piping L2. Furthermore, a heater 3 for heating the reducing gas G3 is provided in the reducing gas piping L4.

[0019] Here, the reducing agent is a material that is oxidized by carbon dioxide and reduced by hydrogen. Such a material can be, for example, a metallic element belonging to at least one class from Group 3 to Group 12. In particular, iron-containing metal oxides and complex oxide systems are preferred because they have particularly good conversion efficiency from carbon dioxide (CO2) to carbon monoxide (CO).

[0020] Furthermore, the reducing agent is preferably in the form of granules, flakes, or pellets. Reducing agents of these shapes can increase the filling rate inside each reactor and improve the contact efficiency between the reducing agent and the gas. Alternatively, the reducing agent can be placed on a carrier.

[0021] Each reactor system is maintained at a temperature suitable for the oxidation reaction caused by carbon dioxide (the reducing agent) and the reduction reaction caused by hydrogen (the oxidized reducing agent). The temperature of each reactor is set, for example, depending on the material of the reducing agent; for example, 600–1000°C is preferable when it contains iron-containing metal oxides or complex oxides. Because the higher the temperature of each reactor, the greater the reaction rate, the greater the gas throughput.

[0022] On the other hand, the lower the temperature of each reactor, the less heat energy is required to raise the temperature, and the lower the heat resistance required for the components of each reactor, thus reducing the manufacturing and operating costs of the gas production system. Furthermore, the temperature of each reactor can be changed or left unchanged during oxidation and reduction reactions. When oxidation and reduction reactions are carried out at the same temperature, the usable energy loss caused by temperature changes in each reactor is reduced, thereby improving the energy efficiency of the gas production system.

[0023] The aforementioned hydrogen generating device 13, although generating hydrogen as a reducing gas G3, can be configured in various ways, such as by using a solid oxide electrolytic cell or methane steam reforming. In particular, it is preferable to use a solid oxide electrolytic cell because hydrogen can be generated using only steam as a feedstock.

[0024] The temperature of the hydrogen generator 13 is set to a suitable temperature for hydrogen generation, depending on the method. For example, 600-800°C is preferred in the case of a solid oxide electrolytic cell, and 500-1000°C is preferred in the case of methane steam reforming. The lower the temperature of the hydrogen generator 13, the less heat energy is required for heating, and the lower the heat resistance required for the components of the hydrogen generator 13, thus reducing the manufacturing and operating costs of the gas production system. Furthermore, the closer the temperature of the hydrogen generator 13 is to the temperature of each reactor, the less usable energy loss caused by temperature changes in the reducing gas G3, thereby improving the energy efficiency of the gas production system. Furthermore, in this embodiment, hydrogen is supplied by generating hydrogen through hydrogen generator 13, but hydrogen generator 13 is not required; for example, hydrogen obtained by purchase can also be supplied.

[0025] The operation of the gas manufacturing system 100 with the above-described configuration will now be explained. Figure 2 is a flowchart illustrating the operation method of the gas manufacturing system 100 according to Embodiment 1. Furthermore, in cases where the reducing agent included in each reactor contains Fe (iron), the case where the first reducing agent Fe3O4 (iron tetraoxide) is included as a reducing agent in the first reactor 41 will be described. Furthermore, before the gas manufacturing system 100 is activated, all regulating valves are controlled to be closed.

[0026] <Mode 1: Oxygen Reaction Step S1> First, the control unit 50 controls the adjusting valve 21 between the raw material gas supply unit 11 and the first reactor 41 to the open state. Hereby, raw material gas G1A, containing carbon dioxide (CO2) and oxygen (O2), is supplied from the raw material gas supply unit 11 into the first reactor 41. After the raw material gas G1A is supplied into the first reactor 41, the control unit 50 controls the adjusting valve 21 to the closed state.

[0027] Inside the first reactor 41, the raw material gas G1A reacts with the oxidized first reducing agent Fe3O4, as shown in Equation 1 below. The oxygen O2 in the raw material gas G1A is removed, and the first reducing agent Fe3O4 is completely oxidized to Fe2O3 (iron oxide). There is no particular limitation on the oxygen concentration in the feed gas after this reaction, but the lower the concentration, the better. Here, the oxygen concentration in the feed gas after the reaction depends on various conditions such as the amount of the first reducing agent Fe3O4, the oxygen concentration in the feed gas G1A at the time it is supplied to the first reactor 41, and the contact time between the first reducing agent Fe3O4 and the feed gas G1A. Therefore, it is also possible to adjust the oxygen concentration to achieve the optimal overall system efficiency by taking all these conditions into account.

[0028] [Formula 1]

[0029] <Mode 2: First Transfer Step S2> The control unit 50 controls the regulating valves 31 and 32 located in the circulation pipe L6A to be in the open state, and transfers the completely oxidized Fe2O3 as the second reducing agent Fe2O3 to the third reactor 43 through the circulation pipe L6A. After the second reducing agent Fe2O3 is transferred into the third reactor 43, the control unit 50 controls the adjusting valves 31 and 32 to the closed state.

[0030] <Mode 3: Hydrogen Reaction Step S3> The control unit 50 controls the regulating valve 22 between the hydrogen generator 13 and the third reactor 43 to be in the open state. This allows reducing gas G3, containing hydrogen, to be supplied from the hydrogen generator 13 into the third reactor 43. After the reducing gas G3 is supplied into the third reactor 43, the control unit 50 controls the regulating valve 22 to be in the closed state. Inside the third reactor 43, a reducing gas G3 containing hydrogen reacts with a second reducing agent Fe2O3 that has been completely oxidized, as shown in Equation 2 below. The second reducing agent Fe2O3 is reduced to Fe, and water vapor G4 is generated at the same time.

[0031] [Formula 2]

[0032] The control unit 50 controls the regulating valve 25 between the third reactor 43 and the steam discharge device 14 to be in the open state, and controls the regulating valve 25 to be in the closed state after the generated steam G4 is discharged through the steam discharge device 14.

[0033] <Mode 4: Second Transfer Step S4> The control unit 50 controls the regulating valves 33 and 34 located in the circulation pipe L6B to be in the open state, and uses the Fe that has been reduced by contact with the reducing gas G3 as the third reducing agent Fe to be transferred to the second reactor 42 through the circulation pipe L6B. After the third reducing agent Fe is transferred into the second reactor 42, the control unit 50 controls the adjusting valves 33 and 34 to the closed state.

[0034] <Mode 5: Carbon Dioxide Reduction Step S5> The control unit 50 controls the adjustment valve 23 between the first reactor 41 and the second reactor 42 to be in the open state. Hereby, the raw material gas G1B, which has been in contact with the first reducing agent Fe3O4 and whose oxygen has been removed, is supplied from the first reactor 41 to the second reactor 42. After the raw material gas G1B is supplied into the second reactor 42, the control unit 50 controls the regulating valve 23 to be closed.

[0035] Inside the second reactor 42, the raw material gas G1B, whose oxygen has been removed, reacts with the third reducing agent Fe, as shown in Equation 3 below. The third reducing agent is oxidized to Fe3O4, and at the same time, carbon dioxide CO2 in the raw material gas G1B is reduced to carbon monoxide CO, and the generated gas G2 is produced.

[0036] [Formula 3]

[0037] The control unit 50 controls the adjustment valve 24 between the generated gas discharge unit 12 and the second reactor 42 to the open state, and after the generated gas G2 is discharged through the generated gas discharge unit 12, controls the adjustment valve 24 to the closed state.

[0038] <Mode 6: Third Transfer Step S6> The control unit 50 controls the regulating valves 35 and 36 located in the circulation pipe L6C to be in the open state, and transfers the Fe3O4 that has been oxidized by contact with the raw material gas G1B as the first reducing agent Fe3O4 into the first reactor 41. After the first reducing agent Fe3O4 is transferred into the first reactor 41, the control unit 50 controls the adjusting valves 35 and 36 to the closed state.

[0039] By repeating the above steps from Mode 1 to Mode 6, expensive and power-intensive devices such as oxygen removal equipment can be used to efficiently remove oxygen from the feed gas. This allows for the production of the generated gas at a low cost and with high efficiency. In particular, because the exhaust gas of the reducing agent can be directly treated, and the reducing agent can be circulated between reactors using redox reactions, the reducing agent can be effectively utilized in each reactor, thus reducing costs and further improving gas production efficiency.

[0040] Furthermore, at the beginning of the manufacturing steps from Mode 1 to Mode 6, for example, if the third reducing agent Fe is already present in the second reactor 42, then the carbon dioxide reduction step of Mode 5 can be performed after the oxygen reaction step of Mode 1. The above-mentioned modes can be implemented by appropriately adjusting the opening and closing sequence of each regulating valve, in which the redox reaction system that circulates the reducing agent is carried out in each reactor. Furthermore, while the above description states that the control unit 50 controls the opening and closing of each regulating valve, it is not limited to this. The control unit 50 may not be required; the operator may manually open and close each regulating valve. Furthermore, when the feed gas contains substances such as nitrogen oxides and sulfur oxides that corrode reducing agents, it is desirable to reduce the levels of these substances in the feed gas in advance using emission reduction equipment or the like.

[0041] The following description pertains to a gas manufacturing system 100A, which has a different configuration from the gas manufacturing system 100 shown in Figure 1 above. Figure 3 is a block diagram showing the general configuration of the gas manufacturing system 100A according to Example 1.

[0042] The gas manufacturing system 100 shown in Figure 1 includes three reactors, namely, a first reactor 41, a second reactor 42, and a third reactor 43, which are each independently configured. In this gas manufacturing system 100A, only one reactor 40A is included as the reaction section. Furthermore, this reactor 40A does not have a circulation piping for circulating the reducing agent. Then, the raw material gas supply unit 11, the generated gas discharge unit 12, the hydrogen generator 13, and the water vapor discharge unit 14 are respectively connected to this reactor 40A.

[0043] The operating modes 1, 3, and 5 described below are the same as those shown in Figure 2. During gas supply in each mode, the supply of gases other than the reactants is stopped by adjusting the valve, thus initiating the reaction. Specifically, the gas generation system 100A performs the following general operations. Furthermore, within reactor 40A, the case of the first reducing agent, Fe3O4, as a reducing agent will be explained. Also, before the operation of gas generation system 100A, all regulating valves are controlled to the closed state.

[0044] <Mode 1: Oxygen Reaction Steps> First, the control unit 50 controls the regulating valve 21 between the raw material gas supply unit 11 and the reactor 40A to the open state. Hereby, raw material gas G1A, containing carbon dioxide (CO2) and oxygen (O2), is supplied from the raw material gas supply unit 11 into the reactor 40A. After the raw material gas G1A is supplied into the reactor 40A, the control unit 50 controls the regulating valve 21 to the closed state.

[0045] Inside reactor 40A, the raw material gas G1A reacts with the oxidized first reducing agent Fe3O4, removing oxygen O2 and simultaneously oxidizing the first reducing agent Fe3O4 to the second reducing agent Fe2O3. The raw material gas G1B system, which has been removed by contact with the first reducing agent Fe3O4, is mainly retained in the oxygen removal piping L2 from reactor 40A.

[0046] <Mode 3: Hydrogen Reaction Steps> The control unit 50 controls the regulating valve 22 between the hydrogen generator 13 and the reactor 40A to be in the open state. This allows reducing gas G3, containing hydrogen, to be supplied from the hydrogen generator 13 into the reactor 40A. After the reducing gas G3 is supplied into the reactor 40A, the control unit 50 controls the regulating valve 22 to be in the closed state. Inside reactor 40A, a reducing gas G3 containing hydrogen reacts with a second reducing agent Fe2O3 that has been completely oxidized. The second reducing agent Fe2O3 is reduced to a third reducing agent Fe, and water vapor G4 is generated at the same time.

[0047] The control unit 50 controls the regulating valve 25 between the reactor 40A and the steam discharge device 14 to the open state, and after the generated steam G4 is discharged through the steam discharge device 14, controls the regulating valve 25 to the closed state.

[0048] <Mode 5: Carbon Dioxide Reduction Steps> The control unit 50 controls the regulating valve 23 to the open state. Hereby, the raw material gas G1B, which has been in contact with the first reducing agent Fe3O4 and has had its oxygen removed, is supplied from the oxygen removal pipe L2 to the reactor 40A. Inside reactor 40A, the raw material gas G1B, whose oxygen has been removed, reacts with the third reducing agent Fe. The third reducing agent Fe is oxidized to the first reducing agent Fe3O4, and at the same time, carbon dioxide CO2 in the raw material gas G1B is reduced to carbon monoxide CO, and the resulting gas G2 is generated.

[0049] The control unit 50 controls the adjustment valve 24 between the generated gas discharge unit 12 and the reactor 40A to the open state, and after the generated gas G2 is discharged through the generated gas discharge unit 12, controls the adjustment valve 24 to the closed state.

[0050] Here, the regulating valve 23 functions as a partition wall separating the raw material gas G1B from the second reducing agent Fe2O3 and the reducing gas G3 during the contact between them. This improves the gas production efficiency. The diameter and length of the oxygen removal pipe L2 are adjusted in such a way that they can temporarily retain the raw material gas G1B, which is the first gas (1B), after contact with the first reducing agent Fe3O4 to remove oxygen.

[0051] Furthermore, as another example of a configuration where the feed gas G1B, which has been deoxygenated by contacting the first reducing agent Fe3O4, is removed from the reducing gas G3 by a partition wall, it is also possible to have the wall located inside the reactor 40A. In the aforementioned gas manufacturing system 100, the wall system constituting the containers of the second reactor 42 and the third reactor 43 functions as the aforementioned partition wall. However, even with a configuration that does not include the aforementioned partition wall, the oxygen reaction step, the hydrogen reaction step, and the carbon dioxide reduction step can be performed separately.

[0052] By adopting the above configuration, compared to a configuration with three separate reactors and piping between the reactors for circulating the reducing agent, the manufacturing cost of the reactors can be reduced, which is also the overall cost of the gas production system. At the same time, the control of the regulating valve in the control unit 50 is also simplified.

[0053] The gas manufacturing system of this embodiment, configured as described above, includes: A switching unit, provided in the flow path, adjusts the switching of the aforementioned flow path; and The hollow reaction section is connected to the aforementioned flow path and contains a reducing agent inside; The aforementioned reaction system, The flow path is connected to a first supply unit that supplies gas 1A containing carbon dioxide and oxygen, and a second supply unit that supplies reducing gas. By adjusting the switching of the aforementioned flow path through the switching unit, the aforementioned reaction unit is configured to switch to the following contacts respectively: The contact between the aforementioned first A gas supplied from the aforementioned first supply unit and the first reducing agent containing a metal oxide as the aforementioned reducing agent, the contact between the second reducing agent which has been in contact with the aforementioned first A gas and the aforementioned reducing gas, the contact between the third reducing agent which has been in contact with the aforementioned reducing gas and the first B gas which has been in contact with the aforementioned first reducing agent, the contact between the first A gas and the aforementioned reducing gas. Furthermore, the operation method of the gas manufacturing system of this embodiment, configured as described above, includes: In the oxygen reaction step, a first A gas containing carbon dioxide and oxygen is contacted with a first reducing agent containing a metal oxide to generate a first B gas from the aforementioned first A gas, in which the oxygen has been removed. The hydrogen reaction step involves contacting the second reducing agent, which is the first reducing agent oxidized by the oxygen in the aforementioned gas 1A, with a reducing gas containing hydrogen to generate a third reducing agent that reduces the aforementioned second reducing agent; and In the carbon dioxide reaction step, the aforementioned third reducing agent is brought into contact with the aforementioned first B gas, causing the aforementioned carbon dioxide in the aforementioned first B gas to be reduced to generate a product gas containing carbon monoxide, while the aforementioned third reducing agent is oxidized and the aforementioned first reducing agent is used in the aforementioned oxygen reaction step.

[0054] Therefore, since expensive and power-consuming devices such as oxygen removal equipment are not required, oxygen in the raw material gas can be removed efficiently, thus enabling the production gas to be manufactured at a low cost and with high production efficiency. In particular, because the exhaust gas from the reducing agent can be directly treated, and the reducing agent can be effectively utilized in the reactor through redox reaction, the cost can be reduced, and the gas production efficiency can be further improved.

[0055] Furthermore, in the gas manufacturing system of this embodiment configured as described above, The aforementioned reaction system has: The partition wall separates the first gas (Gas 1B) from the second reducing agent and the reducing gas during the contact between the second reducing agent and the reducing gas. Furthermore, in the operation method of the gas manufacturing system of this embodiment configured as described above, Before the aforementioned hydrogen reaction step in which the second reducing agent is brought into contact with the reducing gas. This separates the aforementioned gas 1B from the aforementioned second reducing agent and the aforementioned reducing gas.

[0056] This can improve the reaction efficiency in the hydrogen reaction step and the carbon dioxide reduction step, and also increase the gas production efficiency.

[0057] Furthermore, in the gas manufacturing system of this embodiment configured as described above, The aforementioned reaction system includes: The first reaction section brings the first gas A supplied from the first supply section into contact with the first reducing agent; The second reaction section is connected to the rear section of the first reaction section via the aforementioned flow path, so that the first gas B is supplied while the third reducing agent comes into contact with the first gas B; The third reaction section brings the aforementioned second reducing agent into contact with the aforementioned reducing gas; The first transfer section moves the aforementioned second reducing agent from the aforementioned first reaction section to the aforementioned third reaction section; The second transfer section moves the aforementioned third reducing agent from the aforementioned third reaction section to the aforementioned second reaction section; and The third transfer section moves the aforementioned first reducing agent, which has been in contact with the aforementioned third reducing agent, from the aforementioned second reaction section to the aforementioned first reaction section. Furthermore, the operation method of the gas manufacturing system of this embodiment, configured as described above, further includes: In the first transfer step, after the oxygen reaction step described above in the first reaction section where the aforementioned gas A comes into contact with the aforementioned first reducing agent, the aforementioned second reducing agent in the aforementioned first reaction section is transferred to the third reaction section where the aforementioned second reducing agent comes into contact with the aforementioned reducing gas; The second transfer step involves, after the aforementioned hydrogen reaction step, transferring the aforementioned third reducing agent from the aforementioned third reaction section to the second reaction section where the aforementioned third reducing agent comes into contact with the aforementioned first B gas; and The third transfer step involves transferring the first reducing agent from the second reaction section to the first reaction section after the aforementioned carbon dioxide reaction step.

[0058] Thus, by using redox reactions to circulate the reducing agent between reactors, the reducing agent is effectively utilized in each reactor, thereby reducing costs and further improving gas production efficiency.

[0059] The following describes the hardware configuration of the control unit 50. Figure 4 is a diagram showing one example of the hardware configuration of the control unit 50 as a control device. As shown in Figure 4, the control device consists of a processor 51 and a memory device 52. The memory device series 52 includes volatile memory devices such as random access memory (not shown) and non-volatile auxiliary memory devices such as flash memory. Alternatively, an auxiliary memory device, including a hard drive, may be used instead of flash memory. The processor 51 executes a program input from the memory device 52. In this case, the program is input to the processor 51 from the auxiliary memory device via a volatile memory device. Furthermore, the processor 51 may output data such as calculation results to the volatile memory device of the memory device 52, or it may store data in the auxiliary memory device via the volatile memory device.

[0060] Example 2. Hereinafter, this embodiment 2 will be described with reference to the figures, focusing on the differences from embodiment 1 described above. The same parts as in embodiment 1 are given the same symbols and are omitted from the description. Figure 5 is a block diagram showing the general configuration of the gas manufacturing system 200 according to Embodiment 2. The gas production system 200 series, as a hollow reaction section containing a reducing agent, is a switching reaction section that is constructed independently, including switching reactor 245A, switching reactor 245B, and switching reactor 245C. Furthermore, in the following descriptions, there is no need to distinguish between switching reactor 245A, switching reactor 245B, and switching reactor 245C; they may simply be referred to as switching reactors.

[0061] The raw material gas supply unit 11 is connected to the switching reactors 245A, 245B, and 245C respectively via the raw material gas piping L201, which serves as a flow path. The hydrogen generator 13 is connected to the switching reactors 245A, 245B, and 245C respectively via the reducing gas piping L204, which serves as the flow path. Furthermore, although the generated gas exhaust section 12 is not shown in Figure 5, it is provided in the same manner as in Embodiment 1, and this generated gas exhaust section 12 is connected to the switching reactors 245A, 245B, and 245C via the generated gas piping L203. Furthermore, although the steam exhaust device 14 is not shown in Figure 5, it is provided in the same manner as in Embodiment 1, and this steam exhaust device 14 is connected to the switching reactors 245A, 245B, and 245C respectively via steam exhaust pipes L205. In addition, the switching reactors 245A, 245B, and 245C are interconnected via oxygen removal piping L202.

[0062] In addition, the gas production system 200 series has adjustment valves in the front and rear sections of each switching reactor, which are used to control the switches of each pipeline as the switching section. Specifically, between the raw material gas supply unit 11 and the switching reactors 245A, 245B, and 245C, adjustment valves 261, 262, and 263, which serve as the first switching unit, are respectively provided. Furthermore, between the hydrogen generator 13 and the switching reactors 245A, 245B, and 245C, adjustment valves 264, 265, and 266, respectively, are provided as the second switching section. Furthermore, between the switching reactors 245A, 245B, and 245C, there are regulating valves 267, 268, and 269 serving as a third switching section.

[0063] Furthermore, in Figure 5, the heaters 1, 2, 3, and control unit 50 shown in Embodiment 1 are omitted. Also, even on the generator gas piping L203 and steam exhaust piping L205 connected to each switching reactor, there is an adjustment valve (not shown) serving as a switching unit.

[0064] The operation of the gas manufacturing system 200 configured as described above will now be explained. Figure 6 is a diagram illustrating the reaction states of each switching reactor in the first step of the gas production system 200 according to Example 2. Figure 7 is a diagram illustrating the reaction states of each switching reactor in the second step of the gas production system 200 according to Example 2. Figure 8 is a diagram illustrating the reaction states of each switching reactor in the third step of the gas production system 200 according to Example 2.

[0065] Furthermore, when the reducing agent included in each switching reactor contains Fe, the following will be described: the first reducing agent Fe3O4 is included in the switching reactor 245A, the third reducing agent Fe is included in the switching reactor 245B, and the second reducing agent Fe2O3 is included in the switching reactor 245C. Furthermore, before the gas manufacturing system 200 is activated, all regulating valves are controlled to be closed.

[0066] First, in the first step shown in Figure 6, the control unit 50 controls the regulating valve 261 between the raw material gas supply unit 11 and the switching reactor 245A to be open, and simultaneously controls the regulating valves 267 and 268 between the switching reactor 245A and the switching reactor 245B to be open. At the same time, the control unit 50 controls the regulating valve 266 between the hydrogen generator 13 and the switching reactor 245C to be open.

[0067] Thus, as shown by the solid line in Figure 6, the feed gas G1A containing carbon dioxide (CO2) and oxygen (O2) is supplied from the feed gas supply unit 11 to the switching reactor 245A. Inside the switching reactor 245A, the raw material gas G1A reacts with the first reducing agent Fe3O4 through contact. The oxygen O2 in the raw material gas G1A is removed, and the first reducing agent Fe3O4 is completely oxidized into the second reducing agent Fe2O3. Furthermore, the raw material gas G1B, which has had its oxygen removed by contacting the first reducing agent Fe3O4, is supplied from the switching reactor 245A to the switching reactor 245B via the oxygen removal pipe L202.

[0068] Inside the switching reactor 245B, the feed gas G1B reacts with the third reducing agent Fe, until the third reducing agent Fe is oxidized to the first reducing agent Fe3O4. Simultaneously, carbon dioxide CO2 in the feed gas G1B is reduced to carbon monoxide CO, and a product gas G2 is generated. The product gas G2 is discharged from the product gas discharge section 12 via the product gas pipe L203.

[0069] Furthermore, as shown by the dashed line in Figure 6, the reducing gas G3 containing hydrogen is supplied from the hydrogen generator 13 to the switching reactor 245C. Inside the switching reactor 245C, a reducing gas G3 containing hydrogen reacts with a second reducing agent, Fe2O3, until the second reducing agent Fe2O3 is reduced to a third reducing agent Fe. Simultaneously, water vapor G4 is generated. The water vapor G4 is discharged from the water vapor discharge device 14 via the water vapor discharge pipe L205.

[0070] As described above, in the first step, by adjusting the opening and closing of each regulating valve caused by the control unit 50, reactor 245A is switched to function as the first reaction unit for the oxygen reaction step in which the raw material gas G1A contacts the first reducing agent Fe3O4. Reactor 245B is switched to function as the second reaction unit for the carbon dioxide reaction step in which the raw material gas G1B, after oxygen has been removed, contacts the third reducing agent Fe. Reactor 245C is switched to function as the third reaction unit for the hydrogen reaction step in which the reducing gas G3 contacts the second reducing agent Fe2O3. After the implementation of this first step, the control unit 50 will control all the regulating valves to the closed state.

[0071] By implementing this first step, the switching reactor 245A becomes a state in which the second reducing agent Fe2O3 can be included, the switching reactor 245B becomes a state in which the first reducing agent Fe3O4 can be included, and the switching reactor 245C becomes a state in which the third reducing agent Fe can be included.

[0072] Next, in the second step shown in Figure 7, the control unit 50 controls the regulating valve 262 between the raw material gas supply unit 11 and the switching reactor 245B to the open state, and simultaneously controls the regulating valves 268 and 269 between the switching reactor 245B and the switching reactor 245C to the open state. At the same time, the control unit 50 controls the regulating valve 264 between the hydrogen generator 13 and the switching reactor 245A to the open state.

[0073] Thus, as shown by the solid line in Figure 7, the feed gas G1A, which contains carbon dioxide (CO2) and oxygen (O2), is supplied from the feed gas supply unit 11 to the switching reactor 245B. Inside the switching reactor 245B, the raw material gas G1A reacts with the first reducing agent Fe3O4 through contact. The oxygen O2 in the raw material gas G1A is removed, and the first reducing agent Fe3O4 is completely oxidized into the second reducing agent Fe2O3. Furthermore, the raw material gas G1B system, which has had its oxygen removed by contacting the first reducing agent Fe3O4, is supplied from the switching reactor 245B via the oxygen removal pipe L202 into the switching reactor 245C.

[0074] Inside the switching reactor 245C, the feed gas G1B reacts with the third reducing agent Fe, until the third reducing agent Fe is oxidized to the first reducing agent Fe3O4. Simultaneously, carbon dioxide CO2 in the feed gas G1B is reduced to carbon monoxide CO, and a product gas G2 is generated. The product gas G2 is discharged from the product gas discharge section 12 via the product gas pipe L203.

[0075] Furthermore, as shown by the dashed line in Figure 7, the reducing gas G3 containing hydrogen is supplied from the hydrogen generator 13 to the switching reactor 245A. Inside the switching reactor 245A, a reducing gas G3 containing hydrogen reacts with a second reducing agent, Fe2O3, until the second reducing agent Fe2O3 is reduced to a third reducing agent, Fe. Simultaneously, water vapor G4 is generated. The water vapor G4 is discharged from the water vapor discharge device 14 via the water vapor discharge pipe L205.

[0076] As described above, in the second step, by adjusting the opening and closing of each regulating valve caused by the control unit 50, reactor 245B is switched to function as the first reaction unit for the oxygen reaction step in which the raw material gas G1A contacts the first reducing agent Fe3O4. Reactor 245C is switched to function as the second reaction unit for the carbon dioxide reaction step in which the oxygen-removed raw material gas G1B contacts the third reducing agent Fe. Reactor 245A is switched to function as the third reaction unit for the hydrogen reaction step in which the reducing gas G3 contacts the second reducing agent Fe2O3. After the implementation of this second step, the control unit 50 will control all the regulating valves to the closed state.

[0077] By implementing this second step, the state in which the third reducing agent Fe can be included inside the switching reactor 245A becomes the state in which the second reducing agent Fe2O3 can be included inside the switching reactor 245B becomes the state in which the first reducing agent Fe3O4 can be included inside the switching reactor 245C.

[0078] Next, in the third step shown in Figure 8, the control unit 50 controls the regulating valve 263 between the raw material gas supply unit 11 and the switching reactor 245C to the open state, and simultaneously controls the regulating valves 267 and 269 between the switching reactor 245C and the switching reactor 245A to the open state. At the same time, the control unit 50 controls the regulating valve 265 between the hydrogen generator 13 and the switching reactor 245B to the open state.

[0079] Thus, as shown by the solid line in Figure 8, the feed gas G1A, which contains carbon dioxide (CO2) and oxygen (O2), is supplied from the feed gas supply unit 11 to the switching reactor 245C. Inside the switching reactor 245C, the raw material gas G1A reacts with the first reducing agent Fe3O4 through contact. The oxygen O2 in the raw material gas G1A is removed, and the first reducing agent Fe3O4 is completely oxidized into the second reducing agent Fe2O3. Furthermore, the raw material gas G1B system, which has had its oxygen removed by contacting the first reducing agent Fe3O4, is supplied from the switching reactor 245C to the switching reactor 245A via the oxygen removal pipe L202.

[0080] Inside the switching reactor 245A, the feed gas G1B reacts with the third reducing agent Fe, until the third reducing agent Fe is oxidized to the first reducing agent Fe3O4. Simultaneously, carbon dioxide CO2 in the feed gas G1B is reduced to carbon monoxide CO, and a product gas G2 is generated. The product gas G2 is discharged from the product gas discharge section 12 via the product gas pipe L203.

[0081] Furthermore, as shown by the dashed line in Figure 8, the reducing gas G3 containing hydrogen is supplied from the hydrogen generator 13 to the switching reactor 245B. Inside the switching reactor 245B, a reducing gas G3 containing hydrogen reacts with a second reducing agent, Fe2O3, until the second reducing agent Fe2O3 is reduced to a third reducing agent, Fe. Simultaneously, water vapor G4 is generated. The water vapor G4 is discharged from the water vapor discharge device 14 via the water vapor discharge pipe L205.

[0082] As described above, in the third step, by adjusting the opening and closing of each regulating valve caused by the control unit 50, reactor 245C is switched to function as the first reaction unit for the oxygen reaction step in which the raw material gas G1A contacts the first reducing agent Fe3O4. Reactor 245A is then switched to function as the second reaction unit for the carbon dioxide reaction step in which the raw material gas G1B, after oxygen has been removed, contacts the third reducing agent Fe. Reactor 245B is then switched to function as the third reaction unit for the hydrogen reaction step in which the reducing gas G3 contacts the second reducing agent Fe2O3. After the implementation of this third step, the control unit 50 will control all the regulating valves to the closed state.

[0083] By implementing this third step, the state in which the first reducing agent Fe3O4 can be included inside the switching reactor 245A becomes the state in which the third reducing agent Fe can be included inside the switching reactor 245B becomes the state in which the second reducing agent Fe2O3 can be included inside the switching reactor 245C.

[0084] After the implementation of the third step above, the first step as shown in Figure 6 is performed. As described above, the switching of the various regulating valves, resulting in a switch from the first step to the second step, from the second step to the third step, and from the third step back to the first step, is called a switching step. In other words, a switching step refers to the switching of the regulating valves that function as the third reaction unit when the switching reaction unit, which was previously functioning as the first reaction unit, functions as the first reaction unit when it was previously functioning as the second reaction unit, and vice versa. By using redox reactions, the reducing agent can be effectively utilized in each switching reactor, thus reducing costs and further improving gas production efficiency.

[0085] Furthermore, although this embodiment describes the control unit 50 controlling the opening and closing of each regulating valve, it is not limited to this; the operator may also manually open and close each regulating valve.

[0086] In the gas production system of this embodiment configured as described above, The aforementioned reaction system is configured to have three independent switching reaction sections; The aforementioned switching reaction units are respectively connected to the aforementioned first supply unit and the aforementioned second supply unit via the aforementioned flow path, and the aforementioned switching reaction units are interconnected with each other via the aforementioned flow path; The aforementioned switching unit adjusts the switching of the aforementioned flow path. Each of the aforementioned switching reaction units is configured to function as a reaction unit that can function as any of the following: A first reaction section that brings the first A gas supplied from the first supply section into contact with the first reducing agent; a second reaction section that brings the third reducing agent into contact with the first B gas while the first B gas is supplied; and a third reaction section that brings the second reducing agent into contact with the reducing gas.

[0087] In this way, the same effect as in Example 1 can be achieved because it does not require expensive and power-consuming devices such as oxygen removal devices, and can efficiently remove oxygen from the raw material gas. Therefore, the generated gas can be produced at a low cost and with high production efficiency. Furthermore, by adjusting the switching of each flow path through the switching unit, each switching reaction unit can function almost simultaneously as a first reaction unit for the oxygen reaction step, which involves contacting the raw gas containing carbon dioxide and oxygen with the first reducing agent; a second reaction unit for the carbon dioxide reaction step, which involves contacting the raw gas with oxygen removed with the third reducing agent; and a third reaction unit for the hydrogen reaction step, which involves contacting the reducing gas with the second reducing agent. This makes it possible to improve gas production efficiency.

[0088] Furthermore, the operation method of the gas manufacturing system of this embodiment, configured as described above, further includes: After the step of making the aforementioned switching reaction section function as any one of the aforementioned first reaction section, the aforementioned second reaction section, and the aforementioned third reaction section, the following is included: The switching step involves adjusting the switching of the aforementioned flow path by means of the aforementioned switching unit, so that the aforementioned switching reaction unit, which has been functioning as the aforementioned first reaction unit, functions as the aforementioned third reaction unit, the aforementioned switching reaction unit, which has been functioning as the aforementioned second reaction unit, functions as the aforementioned first reaction unit, and the aforementioned switching reaction unit, which has been functioning as the aforementioned third reaction unit, functions as the aforementioned second reaction unit.

[0089] This allows for efficient use of the reducing agent within each switching reactor through redox reactions, thereby reducing costs and further improving gas production efficiency.

[0090] This disclosure describes various exemplary embodiments and examples. However, the features, forms, and functions of one or more embodiments are not limited to specific embodiments, but can be applied to embodiments individually or in various combinations. Therefore, numerous variations not illustrated are assumed to be within the technical scope disclosed in this patent specification. This also includes, for example, cases where at least one structural element is added or omitted, or even cases where at least one structural element is extracted and combined with structural elements of other embodiments.

[0091] 1,2,3: Heaters 11: Raw Material Gas Supply Department (First Supply Department) 12: Generated Gas Discharge Section 13: Hydrogen Generating Unit (Second Supply Section) 14: Steam exhaust device 21, 261, 262, 263: Adjusting valve (first switching unit) 22, 264, 265, 266: Adjusting valve (second switching unit) 23,24,25,31,32,33,34,35,36: Adjusting valve 40A: Reactor (Reaction Section) 41: First reactor (first reaction section) 42: Second reactor (second reaction section) 43: Third reactor (third reaction section) 50: Control Department 51: Processor 52: Memory device 100, 100A, 200: Gas manufacturing system 245A, 245B, 245C: Switching reactors (switching reaction sections) 267, 268, 269: Adjusting valve (third switching unit) G1A: Feed gas (Gas 1A) G1B: Feed Gas (Gas 1B) G2: Generated gas G3: Reducing gas G4: Water vapor L1, L201: Raw material gas piping (flow path) L2, L202: Oxygen removal piping (flow path) L3, L203: Generative gas piping (flow path) L4, L204: Reducing gas piping (flow path) L5, L205: Water vapor exhaust piping (flow path) L6A, L6B, L6C: Circulation piping (flow path) S1: Oxygen Reaction Steps S2: First transfer step S3: Hydrogen reaction steps S4: Second transfer step S5: Carbon Dioxide Reduction Step S6: Third Transfer Step

Claims

1. A gas production system, comprising: A switching unit is provided in the flow path to regulate the switching of the flow path; A hollow reaction section is connected to the flow path and contains a reducing agent that reduces carbon dioxide by means of hydrogen. The reaction section is connected via the flow path to a first supply section that supplies a first gas containing carbon dioxide and oxygen (Gas 1A) and a second supply section that supplies a reducing gas containing hydrogen. By adjusting the switching of the flow path by the switching section, the reaction section is configured to switch to the following contacts respectively: contact between the Gas 1A supplied from the first supply section and the first reducing agent containing a metal oxide as the reducing agent; contact between the second reducing agent that has contacted the Gas 1A and the reducing gas; contact between the third reducing agent that has contacted the reducing gas and the Gas 1B that has contacted the Gas 1A.

2. The gas manufacturing system as described in claim 1, wherein, The reaction section has a partition wall that separates the first gas (Gas 1B) from the second reducing agent and the reducing gas during contact between the second reducing agent and the reducing gas.

3. The gas manufacturing system as described in claim 1 or 2, wherein, The reaction system includes: a first reaction unit that contacts the first A gas supplied from the first supply unit with the first reducing agent; a second reaction unit connected to the downstream section of the first reaction unit via the flow path that contacts the third reducing agent with the first B gas while the first B gas is supplied; a third reaction unit that contacts the second reducing agent with the reducing gas; a first transfer unit that moves the second reducing agent from the first reaction unit to the third reaction unit; a second transfer unit that moves the third reducing agent from the third reaction unit to the second reaction unit; and a third transfer unit that moves the first reducing agent, which is the third reducing agent that has been contacted with the first B gas, from the second reaction unit to the first reaction unit.

4. The gas manufacturing system as described in claim 1 or 2, wherein, The reaction system is configured to have three independent switching reaction units. Each switching reaction unit is connected to the first supply unit and the second supply unit via the flow path, and the switching reaction units are interconnected with each other via the flow path. By adjusting the opening and closing of the flow path caused by the switching unit, each switching reaction unit is configured to function as a reaction unit that can function as any of the following: a first reaction unit that contacts the first A gas supplied from the first supply unit with the first reducing agent; a second reaction unit that contacts the third reducing agent with the first B gas while the first B gas is supplied; and a third reaction unit that contacts the second reducing agent with the reducing gas.

5. A method for operating a gas production system, comprising: The oxygen reaction step involves contacting a first gas, 1A, containing carbon dioxide and oxygen, with a first reducing agent containing a metal oxide to generate a first gas, 1B, in which the oxygen has been removed from the first gas; the hydrogen reaction step involves contacting a second reducing agent, which is the first reducing agent oxidized by the oxygen in the first gas, with a reducing gas containing hydrogen to generate a third reducing agent that reduces the second reducing agent; and the carbon dioxide reaction step involves contacting the third reducing agent with the first gas, reducing the carbon dioxide in the first gas to generate a product gas containing carbon monoxide, while simultaneously generating the first reducing agent used in the oxygen reaction step after the third reducing agent has been oxidized.

6. The method of operating the gas production system as described in claim 5, wherein, Prior to the hydrogen reaction step in which the second reducing agent comes into contact with the reducing gas, the first B gas is separated from both the second reducing agent and the reducing gas.

7. The method of operating the gas production system as described in claim 5 or 6 further includes: In the first transfer step, after the oxygen reaction step in the first reaction section where the first A gas comes into contact with the first reducing agent, the second reducing agent in the first reaction section is transferred to the third reaction section where the second reducing agent comes into contact with the reducing gas; in the second transfer step, after the hydrogen reaction step, the third reducing agent in the third reaction section is transferred to the second reaction section where the third reducing agent comes into contact with the first B gas; and in the third transfer step, after the carbon dioxide reaction step, the first reducing agent in the second reaction section is transferred to the first reaction section.

8. A method of operating a gas manufacturing system as described in claim 4, wherein, After the step of making the switching reaction section function as any one of the first reaction section, the second reaction section, and the third reaction section, the method includes: a switching step in which the switching reaction section adjusts the switching of the flow path to make the switching reaction section that was functioning as the first reaction section function as the third reaction section, the switching reaction section that was functioning as the second reaction section function as the first reaction section, and the switching reaction section that was functioning as the third reaction section function as the second reaction section.

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