Gas manufacturing system and its operation method

Abstract

This invention provides a gas manufacturing system with high energy efficiency. The invention comprises: a reactor 2, a hydrogen generator 3, a raw material gas supply path 41, a reducing gas supply path 42, a generated gas discharge path 43, a reused gas discharge path 44, a supply gas switching unit 60, and a discharge gas switching unit 70; wherein the reactor 2 has a reducing agent that reduces the raw material gas to generate the generated gas; the hydrogen generator 3 generates a reducing gas containing hydrogen for reducing the reducing agent; the raw material gas supply path 41 supplies the raw material gas to the reactor; and the reducing gas supply path 42 supplies the reducing gas from the hydrogen generator to the reactor. The reactor is equipped with a generator; the generated gas discharge path 43 discharges the generated gas produced by the reactor; the reuse gas discharge path 44 discharges the reuse gas containing water vapor generated by the reducing agent reduced by the reducing gas from the reactor and then delivers it to the hydrogen generator; the supply gas switching unit 60 switches the path of the gas supplied to the reactor to one of the raw material gas supply path and the reducing gas supply path; the discharge gas switching unit 70 switches the path of the gas discharged from the reactor to one of the generated gas discharge path and the reuse gas discharge path.

Description

Technical Field

[0001] This invention relates to a gas manufacturing system and a method for operating a gas manufacturing system. Prior Technology

[0002] In recent years, in the trend of preventing global warming and realizing a carbon-circular society, there has been progress in the research and development of technologies that recover carbon dioxide from exhaust gases or the atmosphere and then convert the recovered carbon dioxide into valuable substances. For example, there are gas manufacturing systems that disclose the production of carbon monoxide-containing gas from carbon dioxide-containing feedstock gases (see, for example, Patent Document 1). [Preliminary Technology Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2021-75447 Summary of the Invention

[0004] [The problem that the invention aims to solve] Conventional gas production systems condense water vapor generated in a reactor into liquid water, which is then temporarily stored in a tank and supplied to a hydrogen generation device. The hydrogen generation device, which may consist of a solid oxide electrolysis cell, a steam methane reformer, or a steam reformer using an oxygen carrier such as a metal oxide, converts the water stored in the tank into water vapor and supplies it to the hydrogen generation device. Therefore, conventional gas production systems require energy not only to convert the carbon dioxide-containing feed gas into the carbon monoxide-containing product gas, but also energy for condensing the water vapor and for converting the water into water vapor, resulting in low energy efficiency.

[0005] This invention was developed to address the aforementioned issues and aims to provide a gas manufacturing system with high energy efficiency. [Technical means to solve the problem]

[0006] The gas manufacturing system of the present invention comprises: a reactor, a hydrogen generator, a raw material gas supply path, a reducing gas supply path, a generated gas discharge path, a reused gas discharge path, a supply gas switching unit, and a discharge gas switching unit. The reactor has a reducing agent that reduces carbon dioxide contained in the raw material gas to generate a generated gas containing carbon monoxide. The hydrogen generator generates a reducing gas containing hydrogen for reducing the reducing agent. The raw material gas supply path supplies the raw material gas to the reactor. The reducing gas supply path supplies the reducing gas from the hydrogen generator to the reactor. The generated gas discharge path discharges the generated gas from the reactor. The reused gas discharge path discharges reused gas containing water vapor generated from the reducing agent reduced by the reducing gas from the reactor and then supplies it to the hydrogen generator. The supply gas switching unit switches the path supplying gas to the reactor to either the raw material gas supply path or the reducing gas supply path. The discharge gas switching unit switches the path discharging gas from the reactor to either the generated gas discharge path or the reused gas discharge path. [Invention Effects]

[0007] The gas manufacturing system of the present invention has an energy efficiency improvement because it has a reuse gas discharge path that discharges the reuse gas containing water vapor generated by the reducing agent reduced by the reducing gas from the reactor and then delivers it to the hydrogen generator. Simple Explanation of the Diagram

[0008] Figure 1 is a schematic diagram of the gas production system in Embodiment 1; Figure 2 is an operational diagram illustrating the gas production system of Embodiment 1; Figure 3 is an operational diagram illustrating the gas production system of Embodiment 1; Figure 4 is a schematic diagram of the gas production system in Embodiment 2; Figure 5 is an operational diagram illustrating the gas production system of Embodiment 2; Figure 6 is an operational diagram illustrating the gas production system of Embodiment 2; Figure 7 is a schematic diagram of the gas production system in Embodiment 3; and Figure 8 is an operational diagram illustrating the gas production system of Embodiment 3. Implementation

[0009] The following is a detailed description of the gas manufacturing system for implementing the present invention, with reference to the accompanying drawings. Furthermore, the same element symbols in the drawings represent the same or equivalent parts.

[0010] Implementation Form 1. Figure 1 shows a configuration diagram of the gas manufacturing system according to Embodiment 1. The gas manufacturing system 1 of this embodiment includes a reactor 2 and a hydrogen generator 3. The reactor 2 has a reducing agent that reduces a raw material gas containing carbon dioxide to generate a product gas containing carbon monoxide. The hydrogen generator 3 generates a reducing gas containing hydrogen for reducing the reducing agent. Furthermore, the gas manufacturing system 1 of this embodiment includes a raw material gas supply path 41, a reducing gas supply path 42, a product gas discharge path 43, and a reuse gas discharge path 44. The raw material gas supply path 41 supplies the raw material gas to the reactor 2. The reducing gas supply path 42 supplies the reducing gas from the hydrogen generator 3 to the reactor 2. The product gas discharge path 43 discharges the product gas generated by the reactor 2 from the reactor 2. The reuse gas discharge path 44 discharges the reuse gas containing water vapor generated from the reducing agent reduced by the reducing gas from the reactor 2 and then supplies it to the hydrogen generator 3. Furthermore, the gas manufacturing system 1 of this embodiment includes a gas supply switching unit 60 and a gas discharge switching unit 70. The gas supply switching unit 60 switches the path of gas delivery to reactor 2 to one of a raw material gas supply path 41 and a reducing gas supply path 42. The gas discharge switching unit 70 switches the path of gas discharge from reactor 2 to one of a generated gas discharge path 43 and a reused gas discharge path 44.

[0011] The raw material gas supply path 41 supplies carbon dioxide-containing raw material gas from the external raw material gas supply unit 4. The raw material gas supply path 41 includes a blower 51 for pressurizing the raw material gas and a raw material gas heater 31 for heating the raw material gas. The raw material gas heater 31 heats the raw material gas to a temperature close to that of the reactor 2 described later. Alternatively, if the temperature of the raw material gas supplied from the raw material gas supply unit 4 is high, or if the heat capacity of the reactor 2 is sufficiently greater than that of the raw material gas, the raw material gas heater 31 may not be necessary.

[0012] The reducing gas supply path 42 supplies hydrogen-containing reducing gas from the hydrogen generator 3. The reducing gas supply path 42 includes a blower 52 for pressurizing the reducing gas and a reducing gas heater 32 for heating the reducing gas. The reducing gas heater 32 heats the reducing gas to a temperature close to that of the reactor 2 described later. Alternatively, if the temperature of the reducing gas supplied from the hydrogen generator 3 is high, or if the heat capacity of the reactor 2 is sufficiently greater than that of the reducing gas, the reducing gas heater 32 may not be necessary.

[0013] The generated gas discharge path 43 is connected to the generated gas discharge section 5 for discharging the generated gas to the outside. The reused gas discharge path 44 includes a blower 53 for pressurizing the reused gas from the reactor 2 to the hydrogen generator 3. Alternatively, when the airflow of the blower 53 pressurizing the reused gas to the hydrogen generator 3 is large, the blower 52 installed in the reducing gas supply path 42 may not be necessary.

[0014] The gas supply switching unit 60 consists of a raw material gas switching valve 61 located between the raw material gas supply path 41 and the reactor 2, and a reducing gas switching valve 62 located between the reducing gas supply path 42 and the reactor 2. When either the raw material gas switching valve 61 or the reducing gas switching valve 62 is opened, the gas supply switching unit 60 closes the other valve. In this way, the gas supply switching unit 60 switches the path supplying gas to the reactor 2 to either the raw material gas supply path 41 or the reducing gas supply path 42.

[0015] The exhaust gas switching unit 70 consists of a generator gas switching valve 71 located between the generator gas exhaust path 43 and the reactor 2, and a reuse gas switching valve 72 located between the reuse gas exhaust path 44 and the reactor 2. When either the generator gas switching valve 71 or the reuse gas switching valve 72 is opened, the exhaust gas switching unit 70 closes the other valve. In this way, the exhaust gas switching unit 70 switches the path from which gas is discharged from the reactor 2 to one of the generator gas exhaust path 43 or the reuse gas exhaust path 44.

[0016] The reducing agent in reactor 2 is composed of a material that is easily oxidized by carbon dioxide and easily reduced by hydrogen. This material can be selected from those containing at least one metallic element belonging to Groups 3 to 12. For example, iron is preferred because it has a high conversion efficiency in reducing carbon dioxide to carbon monoxide. The reducing agent is preferably in the form of granules, flakes, or particles. This shape increases the filling rate into reactor 2 and increases the contact area with the feed gas. Alternatively, the reducing agent can also be supported on carriers such as alumina, silica, or activated carbon.

[0017] Reactor 2 utilizes a temperature adjustment mechanism (not shown) to maintain a temperature suitable for the redox reaction of the reducing agent. When the reducing agent is, for example, iron, the temperature of reactor 2 is preferably 600-1000°C. This is because a higher temperature in reactor 2 increases the reaction rate of the redox reaction, thus increasing the amount of gas generated per unit time. Conversely, a lower temperature in reactor 2 requires less energy for the temperature adjustment mechanism and lowers the heat resistance requirements on the components of reactor 2. Therefore, the operating cost of gas production system 1 and the manufacturing cost of reactor 2 can be reduced. Furthermore, the temperature of reactor 2 can be varied according to the oxidation and reduction reactions of the reducing agent. However, if the temperature does not change with the oxidation and reduction reactions of the reducing agent, the energy loss due to heating and cooling is less.

[0018] Hydrogen generator 3 has the function of generating hydrogen from water vapor. Hydrogen generators with this function can use, for example, solid oxide electrolysis cells or water vapor methane reformers. Because solid oxide electrolysis cells can generate hydrogen using only water vapor as feedstock, hydrogen generator 3 is preferably made of solid oxide electrolysis cells. Hydrogen generator 3 uses a temperature adjustment mechanism (not shown) to maintain a suitable temperature for hydrogen generation. When hydrogen generator 3 is a solid oxide electrolysis cell, the temperature of hydrogen generator 3 is preferably 600~800°C. When hydrogen generator 3 is a water vapor methane reformer, the temperature of hydrogen generator 3 is preferably 500~1000°C. The lower the temperature of hydrogen generator 3, the less energy is required for the temperature adjustment mechanism, and the lower the heat resistance requirement for the components of hydrogen generator 3. Therefore, the operating cost of gas production system 1 and the manufacturing cost of hydrogen generator 3 can be reduced. Furthermore, the smaller the temperature difference between hydrogen generator 3 and reactor 2, the less energy loss is caused by temperature changes in the reducing gas and recycled gas.

[0019] The recycled gas discharge path 44 is maintained at a high temperature that suppresses the condensation of water vapor contained in the recycled gas. The temperature of the water vapor generated inside the reactor 2 is the same as the temperature of the reactor 2, 600~1000°C. In the gas manufacturing system 1 of this embodiment, the temperature of the water vapor flowing in the recycled gas discharge path 44 is preferably above the temperature of the hydrogen generator 3. If the temperature of the water vapor flowing in the recycled gas discharge path 44 is above the temperature of the hydrogen generator 3, the heating capacity of the hydrogen generator 3 can be suppressed, which is preferable. In order to keep the temperature of the water vapor flowing in the recycled gas discharge path 44 above the temperature of the hydrogen generator 3, the recycled gas discharge path 44 is preferably covered with an insulating material. Also, a heater may be installed if necessary.

[0020] Next, the operation of the gas manufacturing system 1 in this embodiment will be explained. Figures 2 and 3 are operational diagrams of the gas manufacturing system 1 of this embodiment. In Figures 2 and 3, thick lines indicate the state where there is gas flow in the path, and dashed lines indicate the state where there is no gas flow in the path.

[0021] The gas manufacturing system 1 of this embodiment has two operating modes: a reducing agent regeneration mode, in which the reducing agent in the reactor 2 is reduced and regenerated, and a gas generation mode, in which the raw material gas is reduced by the reducing agent to generate a useful gas. The gas manufacturing system 1 of this embodiment generates the desired product gas from the raw material gas by repeating these two modes.

[0022] Figure 2 shows an operational diagram illustrating the reductive regeneration mode of reactor 2. In this mode, the reductive is assumed to be oxidized in the gas generation mode. In this mode, the feed gas switch valve 61 of the supply gas switching unit 60 is closed, while the reducing gas switch valve 62 is opened. Similarly, the generator gas switch valve 71 of the exhaust gas switching unit 70 is closed, while the reuse gas switch valve 72 is opened. In this mode, hydrogen is supplied from the hydrogen generator 3 to reactor 2 via the reducing gas supply path 42. The oxidized reductive is then regenerated using this hydrogen. Water vapor is generated during the reduction of the oxidized reductive. The water vapor generated inside reactor 2 is sent to the hydrogen generator 3 via the reuse gas exhaust path 44. Thus, the oxidized reductive can be regenerated in the gas generation mode.

[0023] Figure 3 shows an operational diagram illustrating the gas generation mode in which the raw material gas is reduced to generate a useful gas using the reducing agent provided in reactor 2. In this mode, the raw material gas switching valve 61 of the supply gas switching unit 60 is opened, while the reducing gas switching valve 62 is closed. Similarly, the generator gas switching valve 71 of the discharge gas switching unit 70 is opened, while the reuse gas switching valve 72 is closed. In this mode, a raw material gas containing carbon dioxide is supplied to reactor 2 from the external raw material gas supply unit 4 via the raw material gas supply path 41. The reducing agent provided in reactor 2 reduces the carbon dioxide in the supplied raw material gas, converting it into a generator gas containing carbon monoxide. During this process, the reducing agent is oxidized. The generator gas generated inside reactor 2 is then discharged to the external generator gas discharge unit 5 via the generator gas discharge path 43. Thus, in the gas generation mode operation, the gas manufacturing system 1 of this embodiment generates a generator gas containing carbon monoxide from a raw material gas containing carbon dioxide.

[0024] The gas generation system 1 constructed in this way can deliver the water vapor generated in the reducing agent regeneration mode to the hydrogen generator 3 without condensation, thus eliminating the need for energy to convert water into water vapor and improving energy efficiency.

[0025] Furthermore, in this embodiment of the gas manufacturing system, a heat exchanger can also be installed between the raw material gas supply path 41 and the generated gas discharge path 43. By using this heat exchanger, the heat energy of the generated gas flowing in the generated gas discharge path 43 can be used to increase the temperature of the raw material gas flowing in the raw material gas supply path 41. Alternatively, a heat exchanger can also be installed between the raw material gas supply path 41 and the reused gas discharge path 44. By using this heat exchanger, the heat energy of the reused gas flowing in the reused gas discharge path 44 can be used to increase the temperature of the raw material gas flowing in the raw material gas supply path 41.

[0026] Furthermore, in the reducing agent regeneration mode, when there are residual reducing agents and unreacted hydrogen, the residual hydrogen, along with water vapor, is transported to hydrogen generator 3 as a reuse gas and, together with the hydrogen produced by hydrogen generator 3, is reused for reducing agent regeneration. Therefore, compared to the case where the gas produced in the reducing agent regeneration mode is not recycled, the hydrogen utilization efficiency can be improved. Even if the gas produced in the reducing agent regeneration mode is not recycled, although hydrogen can still be separated and purified from the gas produced in the reducing agent regeneration mode and reused for reducing agent regeneration, it is still quite difficult to separate and purify 100% hydrogen from the gas in this case. Therefore, compared to the case where hydrogen is separated and purified, the hydrogen utilization efficiency can still be improved.

[0027] Furthermore, when components that are easily oxidized by water vapor are used inside the hydrogen generator 3, the deterioration of the internal components of the hydrogen generator 3 can be prevented by setting the gas flow rate according to the fact that a certain amount of hydrogen is always present in the recycled gas.

[0028] Implementation Form 2. In the gas production system of Embodiment 1, when operating in the reducing agent regeneration mode, the feed gas cannot be converted into the product gas, thus preventing continuous production of the product gas. In the gas production system of Embodiment 2, because it has multiple reactors, at least one reactor can be operated in the gas production mode at any given time. Therefore, the gas production system of this embodiment can continuously produce the product gas.

[0029] Figure 4 shows a configuration diagram of the gas manufacturing system of this embodiment. As shown in Figure 4, in the gas manufacturing system 1 of this embodiment, the first reactor 21 and the second reactor 22 are connected in parallel between the raw material gas supply path 41 (and the reducing gas supply path 42) and the generated gas discharge path 43 (and the reused gas discharge path 44). Furthermore, in the gas manufacturing system 1 of this embodiment, a first heat exchanger 81 is provided between the raw material gas supply path 41 and the generated gas discharge path 43, and a second heat exchanger 82 is provided between the raw material gas supply path 41 and the reused gas discharge path 44. The first heat exchanger 81 uses the heat energy of the generated gas flowing in the generated gas discharge path 43 to increase the temperature of the raw material gas flowing in the raw material gas supply path 41. The second heat exchanger 82 uses the heat energy of the reused gas flowing in the reused gas discharge path 44 to increase the temperature of the raw material gas flowing in the raw material gas supply path 41.

[0030] Furthermore, in the gas manufacturing system 1 of this embodiment, a gas-water separator 80 and a water vapor measuring unit 84 are provided between the second heat exchanger 82 and the hydrogen generator 3 in the recycled gas discharge path 44. The gas-water separator 80 separates water vapor and liquid water contained in the recycled gas flowing in the recycled gas discharge path 44. The water separated by the gas-water separator 80 is discharged to the outside through the drainage discharge unit 6. Also, in the gas manufacturing system 1 of this embodiment, the hydrogen generator 3 is connected to the water vapor supply unit 85, and the water vapor measuring unit 84 is connected to the water vapor control unit 86. The water vapor control unit 86 controls the amount of water vapor supplied from the water vapor supply unit 85 to the hydrogen generator 3 based on the amount of water vapor measured by the water vapor measuring unit 84.

[0031] The gas supply switching unit 60 comprises: a raw material gas switching valve 61 disposed between the raw material gas supply path 41 and the first reactor 21; a reducing gas switching valve 62 disposed between the reducing gas supply path 42 and the first reactor 21; a raw material gas switching valve 63 disposed between the raw material gas supply path 41 and the second reactor 22; and a reducing gas switching valve 64 disposed between the reducing gas supply path 42 and the second reactor 22. The gas supply switching unit 60 closes the other valve when one of the raw material gas switching valve 61 or the reducing gas switching valve 62 is opened. In this way, the gas supply switching unit 60 switches the gas path supplied to the first reactor 21 to one of the raw material gas supply path 41 or the reducing gas supply path 42. Furthermore, the gas supply switching unit 60 closes the other valve when one of the raw material gas switching valve 63 or the reducing gas switching valve 64 is opened. Accordingly, the gas supply switching unit 60 switches the gas path supplied to the second reactor 22 to one of the raw material gas supply path 41 and the reducing gas supply path 42.

[0032] The exhaust gas switching unit 70 comprises: a generator gas switching valve 71 disposed between the generator gas exhaust path 43 and the first reactor 21; a reuse gas switching valve 72 disposed between the reuse gas exhaust path 44 and the first reactor 21; a generator gas switching valve 73 disposed between the generator gas exhaust path 43 and the second reactor 22; and a reuse gas switching valve 74 disposed between the reuse gas exhaust path 44 and the second reactor 22. When one of the generator gas switching valves 71 and the reuse gas switching valve 72 is opened, the other valve is closed. Thus, the exhaust gas switching unit 70 switches the path of the gas discharged from the first reactor 21 to one of the generator gas exhaust path 43 and the reuse gas exhaust path 44. Furthermore, when one of the generator gas switching valves 73 and the reuse gas switching valve 74 is opened, the other valve is closed. Accordingly, the exhaust gas switching unit 70 will switch from the path of the gas discharged from the second reactor 22 to one of the generated gas discharge path 43 and the reused gas discharge path 44.

[0033] The gas production system 1 constructed in this way can effectively utilize the heat energy of the generated gas by using the heat energy of the generated gas discharged to the outside by the first heat exchanger 81 to raise the temperature of the feed gas. Furthermore, as shown in Figure 4, the first heat exchanger 81 is preferably positioned upstream of the second heat exchanger 82 in the feed gas supply path 41. By positioning the first heat exchanger 81 upstream of the second heat exchanger 82, the temperature difference between the generated gas and the feed gas can be increased, thus enabling the first heat exchanger 81 to perform heat exchange more efficiently.

[0034] Furthermore, in the gas manufacturing system 1 of this embodiment, the steam control unit 86 controls the amount of steam supplied from the steam supply unit 85 to the hydrogen generator 3 based on the amount of steam measured by the steam measuring unit 84. Therefore, even if the amount of steam flowing in the reused gas discharge path 44 decreases, steam can still be replenished to the hydrogen generator 3. Thus, the hydrogen generator 3 can operate stably for a long time.

[0035] Furthermore, because the gas-water separator 80 removes liquid water contained in the reused gas, it can prevent the reused gas discharge path 44 from becoming blocked or inhibit the deterioration of the blower 53 and the hydrogen generator 3. In addition, the water separated by the gas-water separator 80 can also be supplied to the steam supply unit 85 and reused as steam instead of being discharged to the outside through the drain discharge unit 6.

[0036] Furthermore, since the gas production system 1 of this embodiment has two reactors, each reactor can operate in different modes. Figures 5 and 6 are operational diagrams of the gas manufacturing system 1 of this embodiment. In Figures 5 and 6, thick lines indicate the state where gas flows in the path, and dashed lines indicate the state where there is no gas flow in the path. In addition, to achieve the gas flow shown in Figures 5 and 6, the opening and closing of each switch valve of the gas supply switching unit 60 and the gas discharge switching unit 70 are controlled.

[0037] Figure 5 illustrates the operation of reactor 21 in reductant regeneration mode and reactor 22 in gas generation mode. As shown in Figure 5, reducing gas is supplied to reactor 21 from hydrogen generator 3 via reducing gas supply path 42. Inside reactor 21, the reducing gas is used to regenerate the reductant. The water vapor generated during the reduction of the reductant is supplied to hydrogen generator 3 via reuse gas discharge path 44. In this way, reactor 21 can regenerate the reductant that was oxidized in gas generation mode.

[0038] Furthermore, as shown in Figure 5, raw material gas is supplied to the second reactor 22 via the raw material gas supply path 41. Inside the second reactor 22, a reducing agent is used to reduce the carbon dioxide contained in the raw material gas, generating a product gas containing carbon monoxide. The product gas generated inside the second reactor 22 is transported to the external product gas discharge section 5 via the product gas discharge path 43. In this way, the second reactor 22 can generate a product gas containing carbon monoxide from a raw material gas containing carbon dioxide.

[0039] Figure 6 shows an operational diagram illustrating the operation of the first reactor 21 in gas generation mode and the second reactor 22 in reducing agent regeneration mode. As shown in Figure 6, raw material gas is supplied to the first reactor 21 from the raw material gas supply path 41. Inside the first reactor 21, the carbon dioxide contained in the raw material gas is reduced using a reducing agent to generate a product gas containing carbon monoxide. The product gas generated inside the first reactor 21 is transported to the external product gas discharge unit 5 via the product gas discharge path 43. In this way, the first reactor 21 can generate a product gas containing carbon monoxide from a raw material gas containing carbon dioxide.

[0040] Furthermore, as shown in Figure 6, reducing gas is supplied from the hydrogen generator 3 to the second reactor 22 via the reducing gas supply path 42. Inside the second reactor 22, the reducing agent is regenerated using the reducing gas. The water vapor generated during the reduction of the reducing agent is supplied to the hydrogen generator 3 via the reused gas discharge path 44. In this way, the second reactor 22 can regenerate the reducing agent that was oxidized in the gas generation mode.

[0041] In this gas production system, one of the two reactors can operate continuously in gas generation mode, thus continuously generating the product gas. Furthermore, in this embodiment of the gas production system, it is not necessary for the two reactors to operate in different modes. Typically, both reactors operate in gas generation mode, but one reactor can also operate in reducing agent regeneration mode as needed. Additionally, this embodiment of the gas production system can also have three or more reactors.

[0042] The gas generation system 1 constructed in this way can deliver the water vapor generated in the reducing agent regeneration mode to the hydrogen generator 3 without condensation, thus eliminating the need for energy to convert water into water vapor and improving energy efficiency. Furthermore, even if the amount of water vapor generated in the reducing agent regeneration mode is insufficient, only the insufficient amount of water vapor needs to be supplied from the water vapor supply unit 85, thus suppressing energy increases.

[0043] Furthermore, in the gas production system of this embodiment, when the hydrogen generator uses a solid oxide electrolytic cell, oxygen-containing gas is generated from the oxygen electrode of the solid oxide electrolytic cell. Although not shown in the figure, a heat exchanger can be installed between the path through which the oxygen-containing gas is discharged and the raw material gas supply path to raise the temperature of the raw material gas flowing in the raw material gas supply path 41 using the heat energy of the oxygen-containing gas. This further improves the energy efficiency of the gas production system.

[0044] Implementation Form 3. When the reducing agent inside the reactor reduces the raw material gas, carbon, organic matter, etc., may adhere to its surface. If these deposits are present on the surface of the reducing agent, the contact area between the reducing agent and the raw material gas will be reduced, thus decreasing the reducing capacity of the reducing agent. In Embodiment 3, the gas production system supplies oxygen generated by a hydrogen generator to the reactor, which then combusts and removes the deposits adhering to the surface of the reducing agent.

[0045] Figure 7 shows a configuration diagram of the gas manufacturing system of this embodiment. The gas manufacturing system 1 of this embodiment includes three reactors. As shown in Figure 7, in the gas manufacturing system 1 of this embodiment, the first reactor 21, the second reactor 22, and the third reactor 23 are connected in parallel between the raw material gas supply path 41 (and the reducing gas supply path 42) and the generated gas discharge path 43 (and the reused gas discharge path 44). Furthermore, in this embodiment, the hydrogen generator 3 is composed of a solid oxide electrolytic cell. The solid oxide electrolytic cell generates hydrogen at the hydrogen electrode and oxygen-containing gas at the oxygen electrode. To supply this oxygen-containing gas to the first reactor 21, the second reactor 22, and the third reactor 23, the gas manufacturing system 1 of this embodiment is provided with an oxygen supply path 45. The oxygen supply path 45 is equipped with a blower 54 for pressurizing the oxygen-containing gas. Oxygen switch valves 67, 68, and 69 are respectively provided between the oxygen supply path 45 and the first reactor 21, the second reactor 22, and the third reactor 23. In addition, when the air force of the blower 53 that pressurizes and recycles gas to the hydrogen generator 3 is large, the blower 54 provided by the oxygen supply path 45 may not be installed.

[0046] Furthermore, in the gas manufacturing system 1 of this embodiment, a combustion gas discharge path 46 is provided to discharge the combustion gas generated when oxygen is used to burn off the deposits on the surface of the reducing agent. The combustion gas flowing in the combustion gas discharge path 46 is discharged to the outside from the combustion gas discharge section 7. Combustion gas switching valves 77, 78, and 79 are respectively provided between the combustion gas discharge path 46 and the first reactor 21, the second reactor 22, and the third reactor 23. Also, in the gas manufacturing system 1 of this embodiment, the oxygen supply path 45 and the combustion gas discharge path 46 are connected via a bypass valve 87.

[0047] The gas supply switching unit 60 consists of: a raw gas switching valve 61 installed between the raw gas supply path 41 and the first reactor 21; a reducing gas switching valve 62 installed between the reducing gas supply path 42 and the first reactor 21; a raw gas switching valve 63 installed between the raw gas supply path 41 and the second reactor 22; a reducing gas switching valve 64 installed between the reducing gas supply path 42 and the second reactor 22; a raw gas switching valve 65 installed between the raw gas supply path 41 and the third reactor 23; a reducing gas switching valve 66 installed between the reducing gas supply path 42 and the third reactor 23; oxygen switching valves 67, 68, and 69; and a bypass valve 87.

[0048] The exhaust gas switching unit 70 consists of a generator gas switching valve 71 installed between the generator gas exhaust path 43 and the first reactor 21, a reuse gas switching valve 72 installed between the reuse gas exhaust path 44 and the first reactor 21, a generator gas switching valve 73 installed between the generator gas exhaust path 43 and the second reactor 22, a reuse gas switching valve 74 installed between the reuse gas exhaust path 44 and the second reactor 22, a generator gas switching valve 75 installed between the generator gas exhaust path 43 and the third reactor 23, a reuse gas switching valve 76 installed between the reuse gas exhaust path 44 and the third reactor 23, and combustion gas switching valves 77, 78, and 79.

[0049] Furthermore, in the gas manufacturing system 1 of this embodiment, a third heat exchanger 83 is provided between the raw material gas supply path 41 and the combustion gas discharge path 46. The third heat exchanger 83 uses the heat energy of the combustion gas flowing in the combustion gas discharge path 46 to raise the temperature of the raw material gas flowing in the raw material gas supply path 41. Also, the gas manufacturing system 1 of this embodiment, like the gas manufacturing system of embodiment 2, is provided with: a gas-water separation unit 80, a water vapor measuring unit 84, a water vapor supply unit 85, and a water vapor control unit 86.

[0050] In the gas manufacturing system 1 of this embodiment, the reactor operates in a mode that includes a gas generation mode, a reducing agent regeneration mode, and an adhering substance removal mode. Figure 8 is an operational diagram illustrating the gas generation system 1 of this embodiment. In Figure 8, thick lines indicate states where gas flows along the path, and dashed lines indicate states where there is no gas flow along the path. Figure 8 is an operational diagram illustrating the following scenarios: the first reactor 21 operates in gas generation mode, the second reactor 22 operates in reducing agent regeneration mode, and the third reactor 23 operates in deposit removal mode. Furthermore, to achieve the gas flow shown in Figure 8, the opening and closing of each switch valve in the supply gas switching unit 60 and the discharge gas switching unit 70 are controlled.

[0051] As shown in Figure 8, raw material gas is supplied to the first reactor 21 via raw material gas supply path 41. Inside the first reactor 21, a reducing agent is used to reduce the carbon dioxide contained in the raw material gas, generating a product gas containing carbon monoxide. The product gas generated inside the first reactor 21 is transported to the external product gas discharge unit 5 via product gas discharge path 43. In this way, the first reactor 21 can generate a product gas containing carbon monoxide from a raw material gas containing carbon dioxide.

[0052] Furthermore, as shown in Figure 8, reducing gas is supplied from the hydrogen generator 3 to the second reactor 22 via the reducing gas supply path 42. Inside the second reactor 22, the reducing agent is regenerated by reducing the reducing gas. The water vapor generated during the reduction of the reducing agent is supplied to the hydrogen generator 3 via the reused gas discharge path 44. In this way, the second reactor 22 can regenerate the reducing agent that has been oxidized according to the gas generation mode.

[0053] Furthermore, as shown in Figure 8, oxygen is supplied to the third reactor 23 from the hydrogen generator 3 via the oxygen supply path 45. Inside the third reactor 23, the oxygen is used to burn off the residues adhering to the surface of the reducing agent. The combustion gases produced during the combustion of the residues are sent to the combustion gas discharge section 7 via the combustion gas discharge path 46.

[0054] The gas generation system constructed in this way can deliver the water vapor generated in the reducing agent regeneration mode to the hydrogen generator 3 without condensation, thus eliminating the need for energy to convert water into water vapor and improving energy efficiency. Furthermore, even if the amount of water vapor generated in the reducing agent regeneration mode is insufficient, only the insufficient amount of water vapor needs to be supplied from the water vapor supply unit 85, thus suppressing energy increases and ensuring stable operation of the gas generation system.

[0055] Furthermore, the gas production system constructed in this way can continuously generate gas because at least one of the multiple reactors can operate in gas generation mode at all times. Also, in this embodiment of the gas production system, because it can operate in deposit removal mode, the gas production system can operate stably for a long time. Furthermore, since oxygen is not supplied from outside the gas production system, but rather high-temperature oxygen generated by the hydrogen generator 3 is used, the energy efficiency of the gas production system can be further improved.

[0056] Furthermore, the gas generation system shown in Figure 8 operates by having the three reactors operate in different modes, but the three reactors do not necessarily have to operate in their own distinct modes. Typically, the three reactors can operate in gas generation mode, and then, as needed, one or two of the reactors can operate in reducing agent regeneration mode or deposit removal mode. Additionally, each reactor can either perform deposit removal mode after each gas generation mode operation, or it can only intermittently perform deposit removal mode operation when the reducing agent's reducing capacity decreases.

[0057] Furthermore, the gas manufacturing system of this embodiment has three reactors, but it is not limited to this. In the gas manufacturing system of this embodiment, one or more reactors are sufficient. Also, since the combustion gas contains carbon dioxide, the combustion gas can also be supplied from the combustion gas discharge unit to the raw material gas supply unit.

[0058] When at least one reactor operates in the reducing agent regeneration mode, hydrogen generator 3 produces hydrogen, which is then supplied to the reactor operating in the reducing agent regeneration mode. At this time, when no other reactor is operating in the deposit removal mode, the oxygen produced by hydrogen generator 3 becomes unnecessary. In this case, in the gas production system of this embodiment, by closing oxygen switch valves 67, 68, and 69, but opening bypass valve 87, the unnecessary oxygen produced by hydrogen generator 3 can be directly sent to the combustion gas discharge path 46.

[0059] Although the present invention describes various exemplary embodiments and examples, the various features, forms and functions described in one or more embodiments are not only applicable to specific embodiments, but can also be applied to embodiments individually or in various combinations. Therefore, numerous variations not illustrated are expected, but all of these are covered within the technical scope disclosed in this specification. For example, variations (additions, omissions) of at least one constituent element, or even the extraction of at least one constituent element and its combination with constituent elements of other embodiments, are all covered within the technical scope disclosed in this specification.

[0060] 1: Gas Manufacturing System 2: Reactor 3: Hydrogen generator 4: Raw Material Gas Supply Department 5: Generated gas discharge section 6: Drainage outlet 7: Combustion gas exhaust section 21: Reactor No. 1 22: Reactor No. 2 23: Reactor No. 3 31: Raw material gas heater 32: Reducing Gas Heater 41: Raw material gas supply route 42: Reducing gas supply path 43: Generated gas discharge path 44: Reuse gas exhaust path 45: Oxygen Gas Supply Pathway 46: Combustion gas exhaust path 51, 52, 53, 54: Blower 60: Gas Supply Switching Unit 61, 63, 65: Raw material gas switching valve 62, 64, 66: Reducing gas switching valve 67, 68, 69: Oxygen switch valve 70: Exhaust Gas Switching Unit 71, 73, 75: Gas generating switch valve 72, 74, 76: Reusing gas switching valves 77, 78, 79: Combustion gas switching valve 80: Gas-water separation section 81: First heat exchanger 82: Second heat exchanger 83: Third heat exchanger 84: Water Vapor Measurement Department 85: Steam Supply Department 86: Steam Control Department 87: Bypass valve

Claims

1. A gas production system comprising: a reactor having a reducing agent that reduces carbon dioxide contained in a raw material gas to generate a product gas containing carbon monoxide; a hydrogen generator that generates a reducing gas containing hydrogen for reducing the reducing agent; a raw material gas supply path that supplies the raw material gas to the reactor; a reducing gas supply path that supplies the reducing gas from the hydrogen generator to the reactor; a product gas discharge path that discharges the product gas generated by the reactor from the reactor; a reuse gas discharge path that discharges reuse gas containing water vapor generated from the reducing agent reduced by the reducing gas from the reactor and then supplies it to the hydrogen generator; a supply gas switching unit that switches the path of supplying gas to the reactor to one of the raw material gas supply path and the reducing gas supply path; and a discharge gas switching unit that switches the path of discharging gas from the reactor to one of the product gas discharge path and the reuse gas discharge path.

2. The gas manufacturing system as described in claim 1, wherein, The above-mentioned raw material gas supply path is provided with a raw material gas heater for heating the raw material gas; the above-mentioned reducing gas supply path is provided with a reducing gas heater for heating the reducing gas.

3. As in the gas manufacturing system of claim 1, wherein, A first heat exchanger is provided between the aforementioned raw material gas supply path and the aforementioned generated gas discharge path, and a second heat exchanger is provided between the aforementioned raw material gas supply path and the aforementioned reused gas discharge path.

4. The gas manufacturing system as described in claim 3, wherein, The first heat exchanger is located upstream of the second heat exchanger in the raw material gas supply path.

5. A gas manufacturing system as described in any of claims 1 to 4, wherein, The aforementioned recycled gas discharge path is provided with a water vapor measuring unit that measures the amount of water vapor contained in the recycled gas; further, it is provided with a water vapor supply unit that supplies water vapor to the hydrogen generator based on the amount of water vapor contained in the recycled gas measured by the water vapor measuring unit.

6. A gas manufacturing system as described in any of claims 1 to 4, wherein, The aforementioned reactors are provided in a plurality of units; and the plurality of aforementioned reactors are connected in parallel between the aforementioned raw material gas supply path and the aforementioned reducing gas supply path, and between the aforementioned generated gas discharge path and the aforementioned reuse gas discharge path; the aforementioned supply gas switching unit switches the gas path supplied to each of the aforementioned reactors to one of the aforementioned raw material gas supply path and the aforementioned reducing gas supply path, and the aforementioned discharge gas switching unit switches the gas discharge path from each of the aforementioned reactors to one of the aforementioned generated gas discharge path and the aforementioned reuse gas discharge path.

7. A gas manufacturing system as described in any of claims 1 to 4, wherein, The aforementioned hydrogen generator is composed of a solid oxide electrolytic cell with a hydrogen electrode and an oxygen electrode. Hydrogen is generated by the hydrogen electrode and oxygen is generated by the oxygen electrode.

8. The gas manufacturing system as described in claim 7, wherein, Furthermore, it includes: an oxygen gas supply path that supplies oxygen generated by the oxygen electrode of the hydrogen generator to the reactor; and a combustion gas discharge path that discharges the combustion gas generated when the adhering material to the reducing agent is combusted using the oxygen supplied to the reactor; the gas supply switching unit switches the gas path supplied to the reactor to one of the raw material gas supply path, the reducing gas supply path, and the oxygen gas supply path; and the gas discharge switching unit switches the gas discharge path from the reactor to one of the generated gas discharge path, the reused gas discharge path, and the combustion gas discharge path.

9. A gas manufacturing system as described in any of claims 1 to 4, wherein, The aforementioned recycled gas system contains hydrogen.

10. A gas manufacturing system as described in any of claims 1 to 4, wherein, The temperature of the water vapor contained in the reclaimed gas flowing in the aforementioned reclaimed gas discharge path is maintained above the temperature of the aforementioned hydrogen generator.

11. A method of operating a gas production system comprising: a reactor and a hydrogen generator; the reactor having a reducing agent that reduces carbon dioxide contained in a raw material gas to generate a product gas containing carbon monoxide; the hydrogen generator generating a reducing gas containing hydrogen for reducing the reducing agent; comprising: a gas generation mode in which the raw material gas is fed to the reactor and the reducing agent is used to reduce the raw material gas to generate the product gas; and a reducing agent regeneration mode in which the reducing gas generated by the hydrogen generator is fed to the reactor, the reducing agent is regenerated, and the water vapor generated during the reduction of the reducing agent is fed to the hydrogen generator.

12. The method of operating the gas production system as described in claim 11, wherein, The aforementioned hydrogen generator is composed of a solid oxide electrolytic cell having a hydrogen electrode and an oxygen electrode; it further includes an adhering substance removal mode, which involves supplying oxygen generated by the oxygen electrode of the aforementioned hydrogen generator to the aforementioned reactor, thereby burning away the adhering substances attached to the aforementioned reducing agent.

13. The method of operating the gas production system as described in claim 11 or 12, wherein, When operating in the above-mentioned reducing agent regeneration mode, the temperature of the water vapor supplied to the hydrogen generator is maintained above the temperature of the hydrogen generator.

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