Gas production apparatus

Abstract

To provide a gas production apparatus that can use an oxidation gas including carbon dioxide and a reduction gas including reduction substance to efficiently produce carbon valuable substance.SOLUTION: There is provided a gas production apparatus. The gas production apparatus has a plurality of reactors. Each of the reactors is configured to house a reducer and alternately supply an oxidation gas including carbon dioxide and a reduction gas including reduction substance. The reducer includes at least one of metal alone and metal oxide producing carbon valuable substance by reducing the carbon dioxide, and is brought into contact with the reduction substance after being placed in an oxidation state by contacting the carbon dioxide to achieve reduction. A part or all of at least one of the oxidation gas and the reduction gas that have passed through each reactor are returned again to the upstream side of the same reactor.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a gas production device. [Background technology]

[0002] In recent years, the atmospheric concentration of carbon dioxide (CO2), a type of greenhouse gas, has been increasing. The increase in the concentration of carbon dioxide in the atmosphere contributes to global warming. Therefore, it is important to capture carbon dioxide emitted into the atmosphere, and if the captured carbon dioxide can be converted into carbon valuables and reused, a carbon circulation society can be realized. As a global policy, the Kyoto Protocol of the United Nations Framework Convention on Climate Change stipulates that each developed country must set its own reduction rate for carbon dioxide, the cause of global warming, using 1990 as a base year, and that they must jointly achieve reduction targets within the commitment period.

[0003] In order to achieve this reduction target, exhaust gases containing carbon dioxide generated from steel mills, smelters, and thermal power plants are also included, and various technological improvements are being made to reduce carbon dioxide in these industries. One example of such a technology is carbon capture and storage (CCS). However, this technology has physical limitations in terms of storage, and is not a fundamental solution. For example, Patent Document 1 discloses a carbon dioxide reduction system equipped with a chemical looping reactor. This chemical looping reactor has two reactors filled with a metal oxide catalyst, and a first reaction in which carbon dioxide is reduced to carbon monoxide is carried out in one reactor, and a second reaction in which hydrogen is oxidized to water is carried out in the other reactor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 163968 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there remains room for further improvement in order to produce carbon monoxide (a carbon valuable product) from carbon dioxide more efficiently on an industrial scale. In view of the above circumstances, the present invention provides a gas production apparatus capable of efficiently producing carbon valuables by using an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance. [Means for solving the problem]

[0006] According to one aspect of the present invention, a gas production apparatus is provided. The gas production apparatus has a plurality of reactors. Each reactor is configured to accommodate a reducing agent and to be able to switch between supplying an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance. The reducing agent contains at least one of an elemental metal and a metal oxide that produces carbon valuables by reducing carbon dioxide, and is oxidized by contact with carbon dioxide and then reduced by contact with the reducing substance. At least one of the oxidizing gas and the reducing gas that have passed through each reactor is returned, in whole or in part, to the upstream side of the same reactor.

[0007] According to this aspect, carbon valuables can be efficiently produced by using an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing an overall configuration of a gas production system using a gas production apparatus of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration of a reaction unit in the first embodiment. [Diagram 3] FIG. 11 is a schematic diagram showing the configuration of a reaction unit in a second embodiment. [Figure 4] FIG. 11 is a schematic diagram showing the configuration of a reaction unit in a third embodiment. [Diagram 5]FIG. 13 is a schematic diagram showing the configuration of a reaction unit in a fourth embodiment. [Figure 6] FIG. 13 is a schematic diagram showing the configuration of a reaction unit in a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a gas production apparatus according to the present invention will be described in detail with reference to preferred embodiments shown in the accompanying drawings. First, the overall configuration of the gas production system will be described. First Embodiment Fig. 1 is a schematic diagram showing the overall configuration of a gas production system using a gas production apparatus of the present invention, Fig. 2 is a schematic diagram showing the configuration of a reaction section of a first embodiment. The gas production system 100 shown in FIG. 1 includes a furnace 20 that generates exhaust gas (oxidizing gas) containing carbon dioxide, and a gas production device 1 that is connected to the furnace 20 via a connection part 2. In this specification, the upstream side with respect to the gas flow direction is also simply referred to as the "upstream side", and the downstream side is also simply referred to as the "downstream side".

[0010] The furnace 20 is not particularly limited, but may be, for example, a furnace attached to a steelworks, a smelter, or a thermal power plant, and preferably includes a combustion furnace, a blast furnace, a converter, etc. In the furnace 20, exhaust gas is generated (generated) when the contents are burned, melted, refined, etc. In the case of a combustion furnace (incinerator) in a waste incineration plant, the contents (waste) include, for example, plastic waste, food waste, municipal solid waste (MSW), discarded tires, biomass waste, household waste (futons, paper), building materials, etc. These wastes may contain one type alone or two or more types.

[0011] Exhaust gas usually contains, in addition to carbon dioxide, other gas components such as nitrogen, oxygen, carbon monoxide, water vapor, methane, etc. The concentration of carbon dioxide contained in the exhaust gas is not particularly limited, but considering the production cost of the generated gas (conversion efficiency to carbon monoxide), it is preferably 1 vol% or more, and more preferably 5 vol% or more. Exhaust gas from the combustion furnace at a waste incineration plant contains 5 to 15 volume percent carbon dioxide, 60 to 70 volume percent nitrogen, 5 to 10 volume percent oxygen, and 15 to 25 volume percent water vapor.

[0012] Exhaust gas from a blast furnace (blast furnace gas) is a gas generated when pig iron is produced in a blast furnace, and contains 10 to 15 volume % carbon dioxide, 55 to 60 volume % nitrogen, 25 to 30 volume % carbon monoxide, and 1 to 5 volume % hydrogen. In addition, exhaust gas from a converter (converter gas) is a gas generated when steel is produced in a converter, and contains 15 to 20 volume % carbon dioxide, 50 to 60 volume % carbon monoxide, 15 to 25 volume % nitrogen, and 1 to 5 volume % hydrogen. The oxidizing gas is not limited to exhaust gas, and a pure gas containing 100% by volume of carbon dioxide may be used.

[0013] However, if exhaust gas is used as the oxidizing gas, carbon dioxide that has conventionally been discharged into the atmosphere can be effectively utilized, and the burden on the environment can be reduced. Among these, from the viewpoint of carbon circulation, exhaust gas containing carbon dioxide generated in a steelworks or a smelter is preferred. In addition, the blast furnace gas and converter gas may be untreated gas discharged from the furnace as is, or treated gas after treatment to remove carbon monoxide, for example, may be used. Untreated blast furnace gas and converter gas each have the gas composition described above, and treated gas has a gas composition close to the gas composition shown for the exhaust gas from the combustion furnace. In this specification, all of the above gases (gases before being supplied to the gas production apparatus 1) are referred to as exhaust gas.

[0014] The gas production apparatus 1 produces a product gas (synthetic gas) containing carbon monoxide by contacting exhaust gas (oxidizing gas containing carbon dioxide) discharged from the furnace 20 and supplied via a connection part 2 with a reducing agent 4R that reduces the carbon dioxide contained in the exhaust gas. In this specification, carbon monoxide is used as a representative example of a carbon valuable. However, the carbon valuable is not limited to carbon monoxide, and may be, for example, methane, methanol, etc., and may be a single substance or a mixture of two or more of these. The type of carbon valuable generated varies depending on the type of reducing agent described later.

[0015] The gas manufacturing apparatus 1 mainly includes a connection section 2, a reducing gas supply section 3, a reaction section 4 having two reactors 4a, 4b, a gas line GL1 connecting the connection section 2 and the reaction section 4, a gas line GL2 connecting the reducing gas supply section 3 and the reaction section 4, and a gas line GL4 connected to the reaction section 4. In this embodiment, the connection part 2 constitutes an exhaust gas supply part (oxidizing gas supply part) that supplies exhaust gas to the reaction part 4. If necessary, pumps for transferring gas may be provided at predetermined positions along the gas lines GL1, GL2, and GL4. For example, when the pressure of the exhaust gas is adjusted to a relatively low value in the compression section 6 described below, the gas can be transferred smoothly within the gas production apparatus 1 by providing the pumps.

[0016] One end of the gas line GL1 is connected to the connection part 2. On the other hand, the other end of the gas line GL1 is connected to the inlet ports of the reactors 4a and 4b in the reaction part 4 via the gas switching part 8 and two gas lines GL3a and GL3b, as shown in FIG. With this configuration, the exhaust gas supplied from the furnace 20 through the connection part 2 passes through the gas line GL1 and is supplied to each of the reactors 4a and 4b. The gas switching unit 8 can be configured to include, for example, a branch gas line and a flow path opening and closing mechanism such as a valve provided midway along the branch gas line.

[0017] As shown in Fig. 2, each of the reactors 4a and 4b is a multi-tube type reactor (fixed-bed type reactor) including a plurality of tubes 41 each filled with (accommodating) a reducing agent 4R and a housing 42 accommodating the plurality of tubes 41. Such a multi-tube type reactor can ensure sufficient opportunities for the reducing agent 4R to come into contact with the exhaust gas and the reducing gas. As a result, the production efficiency of the generated gas can be improved. The reducing agent 4R of the present embodiment is preferably in the form of, for example, particles (granules), flakes, pellets, etc. The reducing agent 4R in such a shape can increase the filling efficiency into the pipe 41, and can further increase the contact area with the gas supplied into the pipe 41.

[0018] When the reducing agent 4R is particulate, its volume average particle size is not particularly limited, but is preferably 1 to 50 mm, and more preferably 3 to 30 mm. In this case, the contact area between the reducing agent 4R and the exhaust gas (carbon dioxide) can be further increased, and the conversion efficiency of carbon dioxide to carbon monoxide can be further improved. Similarly, regeneration (reduction) of the reducing agent 4R by the reducing gas containing the reducing substance can be performed more efficiently. The particulate reducing agent 4R is preferably a compact produced by rolling granulation, since this increases the sphericity.

[0019] The reducing agent 4R may be supported on a carrier. The constituent material of the carrier may be any material that is not easily denatured by contact with exhaust gas (oxidizing gas) or by reaction conditions, and examples of such materials include carbon materials (graphite, graphene, etc.), carbides such as Mo2C, zeolites, montmorillonite, oxides such as ZrO2, TiO2, V2O5, MgO, CeO2, Al2O3, and SiO2, and composite oxides containing these.

[0020] Among these, zeolite, montmorillonite, ZrO2, TiO2, V2O5, MgO, Al2O3, SiO2, and composite oxides containing these are preferred as the constituent material of the carrier. Carriers made of such materials are preferred in that they do not adversely affect the reaction of the reducing agent 4R and have excellent supporting ability for the reducing agent 4R. Here, the carrier does not participate in the reaction of the reducing agent 4R, but simply supports (holds) the reducing agent 4R. One example of such a configuration is one in which at least a portion of the surface of the support is coated with the reducing agent 4R.

[0021] The reducing agent 4R contains at least one of a metal element and a metal oxide (oxygen carrier). At least one of the metal element and the metal oxide is not particularly limited as long as it can reduce carbon dioxide, but it preferably contains at least one selected from metal elements belonging to groups 3 to 12, more preferably contains at least one selected from metal elements belonging to groups 4 to 12, and further preferably contains at least one of titanium, vanadium, iron, copper, zinc, nickel, manganese, chromium, cerium, etc., and is particularly preferably a metal oxide or composite metal oxide containing iron. These metal oxides are useful because they have particularly good conversion efficiency of carbon dioxide to carbon monoxide.

[0022] In particular, iron oxide, cerium oxide, etc. are suitable as metal oxides that convert carbon dioxide to carbon monoxide. For example, zirconia, alumina, titania, silica, etc. that support or contain at least one of nickel and ruthenium are suitable as metal oxides that convert carbon dioxide to methane. For example, zirconia, alumina, silica, etc. that support or contain at least one of copper and zinc are suitable as metal oxides that convert carbon dioxide to methanol.

[0023] In each of the reactors 4a and 4b, the tube (cylindrical molded body) 41 may be made of the reducing agent 4R (at least one of a simple metal and a metal oxide) itself. Furthermore, a molded body such as a block or lattice (e.g., a mesh or honeycomb) may be made of the reducing agent 4R and placed in the housing 42. In these cases, the reducing agent 4R as a filler may be omitted or may be used in combination.

[0024] Among these, a preferred configuration is one in which a mesh body is made of the reducing agent 4R and placed in the housing 42. In the case of such a configuration, it is possible to prevent an increase in the passage resistance of the exhaust gas and the reducing gas in each of the reactors 4a, 4b, while also ensuring a sufficient opportunity for the reducing agent 4R to come into contact with the exhaust gas and the reducing gas. The volumes of the two reactors 4a, 4b are set to be approximately equal to each other and are appropriately set according to the amount of exhaust gas to be treated (the size of the furnace 20 and the size of the gas production device 1). The volume of at least one of the two reactors 4a, 4b may be made different according to the types of exhaust gas and reducing gas, the performance of the reducing agent 4R, etc.

[0025] In the middle of the gas line GL1, a concentration adjusting section 5, a compression section 6, a minor component removing section 7, and an exhaust gas heating section (oxidizing gas heating section) 10 are provided in this order from the connecting section 2 side. The concentration adjusting unit 5 adjusts the concentration of carbon dioxide contained in the exhaust gas to increase it (in other words, to concentrate carbon dioxide). The exhaust gas also contains unnecessary gas components such as oxygen. By increasing the concentration of carbon dioxide contained in the exhaust gas with the concentration adjusting unit 5, the concentration of the unnecessary gas components contained in the exhaust gas can be relatively lowered. This makes it possible to prevent or suppress the unnecessary gas components from adversely affecting the efficiency of conversion of carbon dioxide to carbon monoxide by the reducing agent 4R.

[0026] The concentration adjusting section 5 is preferably configured with an oxygen removing device that removes oxygen contained in the exhaust gas. This makes it possible to reduce the amount of oxygen brought into the gas production apparatus 1 (i.e., adjust the concentration of oxygen contained in the exhaust gas to be lower). This makes it possible to move the gas composition of the exhaust gas away from the explosion range and prevent the exhaust gas from igniting. Note that, since the oxygen removing device in the gas production apparatus 1 consumes a large amount of electric energy, it is effective to use electricity as a renewable energy source as described below.

[0027] In this case, the concentration of oxygen contained in the exhaust gas is preferably adjusted to less than 1% by volume, more preferably less than 0.5% by volume, and even more preferably less than 0.1% by volume, based on the total volume of the exhaust gas. This can reliably prevent the formation of detonation gas due to oxygen and reducing gas in the exhaust gas. The oxygen removal device that removes oxygen contained in exhaust gas can be constructed using one or more of the following separators: a low-temperature separation type (cryogenic type), a pressure swing adsorption (PSA) type separator, a membrane separation type separator, a temperature swing adsorption (TSA) type separator, a chemical absorption type separator, a chemical adsorption type separator, etc. Incidentally, in the concentration adjusting section 5, carbon dioxide may be added to the exhaust gas to adjust the concentration of carbon dioxide to a high level.

[0028] The compression section 6 increases the pressure of the exhaust gas before it is supplied to the reactors 4a and 4b. This increases the amount of exhaust gas that can be treated at one time in the reactors 4a and 4b. This further improves the efficiency of converting carbon dioxide into carbon monoxide in the reactors 4a and 4b. The compression section 6 can be composed of, for example, a volumetric compressor such as a centrifugal compressor, a turbo compressor such as an axial compressor, a reciprocating compressor, a diaphragm compressor, a single screw compressor, a twin screw compressor, a scroll compressor, a rotary compressor, a rotary piston type compressor, or a slide vane type compressor, a Roots blower (two-blade blower) capable of handling low pressure, a centrifugal blower, or the like.

[0029] Of these, from the viewpoint of easiness in scaling up the gas production system 100, it is preferable that the compression section 6 be configured with a centrifugal compressor, and from the viewpoint of reducing the manufacturing costs of the gas production system 100, it is preferable that the compression section 6 be configured with a reciprocating compressor. The pressure of the exhaust gas after passing through the compression section 6 is not particularly limited, but is preferably 0 to 1 MPaG, more preferably 0 to 0.5 MPaG, and even more preferably 0.01 to 0.5 MPaG. In this case, the efficiency of converting carbon dioxide to carbon monoxide in the reactors 4a and 4b can be further improved without increasing the pressure resistance of the gas production apparatus 1 more than necessary.

[0030] The minor component removal section 7 removes minor components (such as trace amounts of unnecessary gas components) contained in the exhaust gas. The fine component removing section 7 can be composed of at least one type of treatment device among, for example, a gas-liquid separator, a guard reactor, and a scrubber (absorption tower). When multiple treatment devices are used, the order of their arrangement is arbitrary, but when a gas-liquid separator and a protective device are used in combination, it is preferable to arrange the gas-liquid separator upstream of the protective device. In this case, the efficiency of removing trace components from the exhaust gas can be further increased, and the service life (life) of the protective device can be extended.

[0031] The gas-liquid separator separates, for example, condensed water (liquid) generated when the exhaust gas is compressed in the compression section 6 from the exhaust gas. In this case, unnecessary gas components remaining in the exhaust gas are also dissolved in the condensed water and removed. The gas-liquid separator can be configured, for example, as a simple container, a swirl-flow separator, a centrifugal separator, a surface tension separator, etc. Among these, it is preferable that the gas-liquid separator is configured as a simple container because of its simple configuration and low cost, etc. In this case, a filter that allows the passage of gas but prevents the passage of liquid may be disposed at the gas-liquid interface in the container.

[0032] In this case, a liquid line may be connected to the bottom of the container, and a valve may be provided on the way. With this configuration, the condensed water stored in the container can be discharged to the outside of the gas production apparatus 1 through the liquid line by opening the valve. The liquid line may be connected to a tank 30, which will be described later, so that the discharged condensed water can be reused.

[0033] The exhaust gas from which condensed water has been removed in the gas-liquid separator may be configured to be supplied to, for example, a protector. Such a protector preferably includes a substance capable of capturing minor components contained in exhaust gas that reduce the activity of the reducing agent 4R (inactivating components) by coming into contact with the reducing agent 4R. According to this configuration, when exhaust gas passes through the protector, the substance in the protector reacts (captures) with the inactivated components, thereby preventing or suppressing the exhaust gas from reaching the reducing agent 4R in the reactors 4a and 4b, thereby protecting the exhaust gas (i.e., preventing a decrease in activity). Therefore, it is possible to prevent or suppress a drastic decrease in the efficiency of conversion of carbon dioxide to carbon monoxide by the reducing agent 4R due to the adverse effect of the inactivated components.

[0034] Such a substance can be a substance having a composition contained in the reducing agent 4R that reduces the activity of the reducing agent 4R by contacting with an inactivating component, specifically, a substance that is the same as or similar to at least one of the simple metal and metal oxide contained in the reducing agent 4R. Here, a similar metal oxide refers to a metal oxide that contains the same metal element but has a different composition, or a metal oxide that contains different types of metal elements but belongs to the same group in the periodic table of the elements.

[0035] The inactivating component is preferably at least one selected from sulfur, mercury, a sulfur compound, a halogen compound, an organic silicone, an organic phosphorus, and an organic metal compound, and more preferably at least one selected from sulfur and a sulfur compound. If such an inactivating component is removed in advance, the activity of the reducing agent 4R can be effectively prevented from decreasing rapidly. The above-mentioned substance may be any substance whose activity is reduced by the same component as the inactivating component of the reducing agent 4R, and metal oxides such as iron oxide and zinc oxide are preferred because of their excellent ability to capture the above-mentioned inactivating components.

[0036] The protective device can be configured in such a way that a mesh material is placed within a housing and particles of the above-mentioned material are placed on the mesh material, or that a honeycomb-shaped filter member or a cylindrical or granular molded body made of the above-mentioned material is placed within the housing. In particular, when the protective device is disposed between the compression section 6 (gas-liquid separator) and the exhaust gas heating section 10, it is possible to improve the efficiency of removing the inactivated components while preventing deterioration of the above-mentioned substances due to heat.

[0037] The exhaust gas heating section 10 heats the exhaust gas before it is supplied to the reactors 4a and 4b. By preheating the exhaust gas before the reaction (before reduction) in the exhaust gas heating section 10, the conversion (reduction) reaction of carbon dioxide to carbon monoxide by the reducing agent 4R can be further promoted in the reactors 4a and 4b. The exhaust gas heating section 10 can be composed of, for example, an electric heater and a heat exchanger (economizer). The heat exchanger is configured by bending a part of the piping constituting the gas line GL4, which discharges the gas (mixed gas) after passing through the reactors 4a and 4b, and bringing it close to the piping constituting the gas line GL1. With this configuration, the heat of the high-temperature gas (mixed gas) after passing through the reactors 4a and 4b is used to heat the exhaust gas before being supplied to the reactors 4a and 4b by heat exchange, so that the heat can be effectively utilized.

[0038] Such a heat exchanger can be configured, for example, as a jacket type heat exchanger, an immersed coil type heat exchanger, a double-pipe type heat exchanger, a shell-and-tube type heat exchanger, a plate type heat exchanger, a spiral type heat exchanger, or the like. In addition, in the exhaust gas heating section 10, either the electric heater or the heat exchanger may be omitted. In the exhaust gas heating section 10, a combustion furnace or the like can be used instead of an electric heater. However, if an electric heater is used, electricity (electrical energy) as a renewable energy source can be used as its power source, thereby reducing the burden on the environment. As the renewable energy, electric energy utilizing at least one selected from photovoltaic power generation, wind power generation, hydroelectric power generation, wave power generation, tidal power generation, biomass power generation, geothermal power generation, solar heat, and geothermal heat can be used.

[0039] In addition, an exhaust gas line may be branched off from the gas line GL1 upstream of the exhaust gas heating section 10 (for example, between the gas-liquid separator and the protector midway through the microcomponent removal section 7), and a vent section provided outside the gas manufacturing apparatus 1 may be connected to the end of the exhaust gas line. In this case, a valve is preferably provided in the exhaust gas line. If the pressure in the gas production device 1 (gas line GL1) rises more than necessary, the valve can be opened to discharge (release) part of the exhaust gas from the vent through the exhaust gas line, thereby preventing damage to the gas production device 1 due to an increase in pressure.

[0040] One end of the gas line GL2 is connected to the reducing gas supply unit 3. On the other hand, the gas line GL2 is connected to the inlet ports of reactors 4a and 4b provided in the reaction unit 4 via a gas switching unit 8 and two gas lines GL3a and GL3b, respectively. The reducing gas supply unit 3 supplies a reducing gas containing a reducing substance that reduces the reducing agent 4R oxidized by contact with carbon dioxide. The reducing gas supply unit 3 in this embodiment is composed of a hydrogen generation device that generates hydrogen by electrolysis of water, and a tank (reducing gas raw material storage unit) 30 that stores water and is outside the gas production apparatus 1 is connected to this hydrogen generation device. With this configuration, the reducing gas containing hydrogen (reducing substance) supplied from the hydrogen generation device (reducing gas supply unit 3) passes through the gas line GL2 and is supplied to each of the reactors 4a, 4b.

[0041] The hydrogen generation device can generate a large amount of hydrogen relatively cheaply and easily. Another advantage is that the condensed water generated in the gas production device 1 can be reused. Since the hydrogen generation device consumes a large amount of electric energy in the gas production device 1, it is effective to use electricity as a renewable energy source as described above.

[0042] In addition, a device that generates by-product hydrogen can also be used as the hydrogen generating device. In this case, a reducing gas containing by-product hydrogen is supplied to each of the reactors 4a and 4b. Examples of devices that generate by-product hydrogen include devices that electrolyze sodium chloride aqueous solution, devices that steam reform petroleum, and devices that manufacture ammonia. Also, the gas line GL2 may be connected to a coke oven outside the gas production apparatus 1 via a connection part, and the exhaust gas from the coke oven may be used as the reducing gas. In this case, the connection part constitutes a reducing gas supply part. This is because the exhaust gas from the coke oven is mainly composed of hydrogen and methane, and contains 50 to 60 volume % of hydrogen.

[0043] A reducing gas heating unit 11 is provided in the gas line GL2. This reducing gas heating unit 11 heats the reducing gas before it is supplied to the reactors 4a and 4b. By preheating the reducing gas before reaction (before oxidation) in the reducing gas heating unit 11, the reduction (regeneration) reaction of the reducing agent 4R by the reducing gas in the reactors 4a and 4b can be further promoted.

[0044] The reducing gas heating section 11 can be configured in the same manner as the above-mentioned exhaust gas heating section 10. The reducing gas heating section 11 is preferably configured with only an electric heater, only a heat exchanger, or a combination of an electric heater and a heat exchanger, and more preferably configured with only a heat exchanger, or a combination of an electric heater and a heat exchanger. If the reducing gas heating section 11 is equipped with a heat exchanger, the heat of the high-temperature gas (e.g., mixed gas) after passing through the reactors 4a, 4b is utilized to heat the reducing gas by heat exchange before being supplied to the reactors 4a, 4b, thereby enabling effective use of heat.

[0045] According to the above-mentioned configuration, by switching the gas lines (flow paths) in the gas switching unit 8, for example, exhaust gas can be supplied via the gas line GL3a to the reactor 4a containing the reducing agent 4R before oxidation, and reducing gas can be supplied via the gas line GL3b to the reactor 4b containing the reducing agent 4R after oxidation. At this time, the reaction of the following formula 1 proceeds in the reactor 4a, and the reaction of the following formula 2 proceeds in the reactor 4b.

[0046] In the following formulas 1 and 2, the reducing agent 4R is iron oxide (FeO x-1 ) is shown as an example. Formula 1: CO2+ FeO x-1 → CO + FeO x Formula 2: H2+ FeO x → HO + FeO x-1 Thereafter, by switching the gas lines in the opposite direction at gas switching section 8, the reaction of formula 2 above can be caused to proceed in reactor 4a, and the reaction of formula 1 above can be caused to proceed in reactor 4b.

[0047] That is, the reducing agent 4R generates carbon monoxide (carbon value) by reducing carbon dioxide. At this time, the reducing agent 4R is oxidized by contact with carbon dioxide, but is then reduced by contact with hydrogen (reducing substance) and returns to its original state. In this specification, the reducing agent 4R is considered as the main focus, and the side where the reducing agent 4R is oxidized by carbon dioxide is referred to as the "oxidation side", and the side where the oxidized reducing agent 4R is reduced by hydrogen is also referred to as the "reduction side".

[0048] The reactions shown in the above formulas 1 and 2 are both endothermic reactions. For this reason, the gas production device 1 preferably further includes a reducing agent heating unit (not shown in FIG. 1) that heats the reducing agent 4R when the exhaust gas or reducing gas is brought into contact with the reducing agent 4R (i.e., when the exhaust gas or reducing gas reacts with the reducing agent 4R). By providing such a reducing agent heating section, the temperature in the reaction between the exhaust gas or reducing gas and the reducing agent 4R can be maintained at a high temperature, thereby suitably preventing or suppressing a decrease in the conversion efficiency of carbon dioxide to carbon monoxide, and further promoting the regeneration of the reducing agent 4R by the reducing gas.

[0049] However, depending on the type of reducing agent 4R, the reactions shown in the above formulas 1 and 2 may be exothermic reactions. In this case, the gas production device 1 preferably has a reducing agent cooling unit that cools the reducing agent 4R instead of the reducing agent heating unit. By providing such a reducing agent cooling unit, it is possible to suitably prevent deterioration of the reducing agent 4R during the reaction between the exhaust gas or reducing gas and the reducing agent 4R, suitably prevent or suppress a decrease in the conversion efficiency of carbon dioxide to carbon monoxide, and further promote the regeneration of the reducing agent 4R by the reducing gas. That is, the gas production device 1 is preferably provided with a reducing agent temperature adjustment unit that adjusts the temperature of the reducing agent 4R depending on the type of reducing agent 4R (exothermic reaction or endothermic reaction).

[0050] Gas lines GL4a and GL4b are connected to the outlet ports of the reactors 4a and 4b, respectively, and merge at a gas junction J4 to form the gas line GL4. In addition, valves (not shown) are provided midway along the gas lines GL4a and GL4b, respectively, as necessary. For example, by adjusting the opening of the valve, the passing speed of the exhaust gas and the reducing gas passing through the reactors 4a, 4b (i.e., the treatment speed of the exhaust gas by the reducing agent 4R and the treatment speed of the reducing agent 4R by the reducing gas) can be set. In this embodiment, the reaction section 4 is mainly composed of the reactors 4a, 4b and the gas switching section 8.

[0051] A produced gas discharge unit 40 that discharges the produced gas to the outside of the gas production apparatus 1 is connected to the end of the gas line GL4 opposite to the reactors 4a, 4b. Further, a gas purification section 9 is provided in the middle of the gas line GL4. In the gas purification unit 9, carbon monoxide is purified from the mixed gas, and a product gas containing a high concentration of carbon monoxide is recovered. Note that, if the concentration of carbon monoxide in the mixed gas is sufficiently high, the gas purification unit 9 may be omitted.

[0052] The gas purification section 9 can be composed of at least one type of treatment device among, for example, a cooler, a gas-liquid separator, a gas separator, a separation membrane, and a scrubber (absorption tower). When multiple treatment devices are used, the order of arrangement of the devices may be arbitrary, but when a cooler, a gas-liquid separator, and a gas separator are used in combination, it is preferable to arrange them in this order, which can further increase the efficiency of purifying carbon monoxide from the mixed gas.

[0053] The cooler cools the mixed gas, which produces condensed water (liquid). Such a cooler can be configured to include a jacket-type cooling device in which a jacket is arranged around a pipe for passing a refrigerant, a multi-tube cooling device having a configuration similar to that of the reactors 4a, 4b (see Figure 2) and passing the mixed gas through a tube 41 and the refrigerant through the space 43 around the tube 41, an air fin cooler, or the like.

[0054] The gas-liquid separator separates the condensed water generated when the mixed gas is cooled in the cooler from the mixed gas. The condensed water has the advantage that it can dissolve and remove unnecessary gas components (especially carbon dioxide) remaining in the mixed gas.

[0055] The gas-liquid separator can be configured similarly to the gas-liquid separator of the microconstituent removing section 7, and can preferably be configured as a simple container. In this case, a filter that allows the passage of gas but prevents the passage of liquid may be disposed at the gas-liquid interface in the container. In this case, a liquid line may be connected to the bottom of the container, and a valve may be provided on the way. With this configuration, the condensed water stored in the container can be discharged (released) to the outside of the gas production apparatus 1 through the liquid line by opening the valve.

[0056] Furthermore, it is preferable to provide a drain trap downstream of the valve in the liquid line. This makes it possible to prevent carbon monoxide or hydrogen from being discharged outside the gas production apparatus 1, even if the valve malfunctions and carbon monoxide or hydrogen flows into the liquid line. Instead of or in addition to this drain trap, a valve malfunction detection function and redundancy measures in case of valve malfunction may be provided. The liquid line may be connected to the tank 30 described above so that the discharged condensed water can be reused.

[0057] The gas separator may be constructed using one or more of the following: a low-temperature separation type (cryogenic type) separator, a pressure swing adsorption (PSA) type separator, a membrane separation type separator, a temperature swing adsorption (TSA) type separator, a separator using a porous coordination polymer (PCP) that combines a metal ion (e.g., copper ion) with an organic ligand (e.g., 5-azidoisophthalic acid), and a separator that uses amine absorption. A valve may be provided between the gas-liquid separator and the gas separator in the gas line GL4. In this case, the processing speed of the mixed gas (the production speed of the generated gas) can be adjusted by adjusting the opening of the valve.

[0058] In this embodiment, the concentration of carbon monoxide contained in the mixed gas discharged from the gas-liquid separator is 75 to 90% by volume with respect to the entire mixed gas. Therefore, in fields where a product gas containing a relatively low concentration of carbon monoxide (75 to 90% by volume) can be used, the carbon monoxide can be directly supplied to the next process without being purified from the mixed gas, i.e., a gas separator can be omitted. Such fields include, for example, the field of synthesizing carbon valuables (e.g., ethanol, etc.) from generated gas by fermentation with microorganisms (e.g., Clostridium, etc.), the field of producing steel using generated gas as a fuel or reducing agent, the field of producing electric devices, and the field of synthesizing chemicals (phosgene, acetic acid, etc.) using carbon monoxide as a synthetic raw material.

[0059] On the other hand, in fields where it is necessary to utilize a product gas containing carbon monoxide at a relatively high concentration (over 90% by volume), carbon monoxide is purified from the mixed gas to obtain a product gas containing carbon monoxide at a high concentration. Such fields include, for example, a field in which the generated gas is used as a reducing agent (blast furnace), a field in which the generated gas is used as fuel to generate electricity by thermal power, a field in which the generated gas is used as a raw material to manufacture chemicals, and a field in which the generated gas is used as fuel for fuel cells.

[0060] In this embodiment, as shown in Fig. 2, return gas lines GL5a and GL5b are provided which branch off from the gas lines GL4a and GL4b and are connected to the gas lines GL3a and GL3b. That is, the exhaust gas which has passed through the oxidation-side reactor 4a and been discharged from the outlet port is returned again to the inlet port (upstream side) of the same oxidation-side reactor 4a, and the reduction gas which has passed through the reduction-side reactor 4b and been discharged from the outlet port is returned again to the inlet port (upstream side) of the same reduction-side reactor 4b.

[0061] As described above, the reactors 4a and 4b to which the exhaust gas and the reducing gas are supplied are switched at a predetermined timing, so that the reactors 4a and 4b are switched between the oxidation side and the reduction side. According to this configuration, unreacted carbon dioxide (CO2) and unreacted hydrogen (H2) can be reused to convert carbon dioxide into carbon monoxide and reduce (regenerate) the reducing agent 4R in an oxidized state with hydrogen (reducing substance). This makes it possible to further increase the efficiency of generating carbon dioxide (carbon valuables).

[0062] However, it is not necessary to return both the exhaust gas and the reducing gas to the same reactor 4a, 4b, and only the gas having a lower reaction rate with the reducing agent 4R may be returned to the same reactor 4a, 4b. In this case, it is preferable to configure the system so that the oxidizing gas discharged from the outlet port is not returned to the inlet port (exhaust gas in the reactors 4a, 4b on the oxidation side) and the reducing gas discharged from the outlet port is returned to the inlet port (reducing gas in the reactors 4a, 4b on the reduction side). In general, the efficiency of reduction of the reducing agent 4R in an oxidized state by hydrogen (reducing substance) (in other words, the efficiency of using hydrogen) is lower than the efficiency of conversion of carbon dioxide to carbon monoxide. Therefore, the above-mentioned configuration is preferable from the viewpoint of further improving the efficiency of generating carbon dioxide, since it is possible to smoothly regenerate the reducing agent 4R.

[0063] Next, the method of using (functioning) the gas production system 100 will be described. [1] First, the gas line (flow path) is switched in the gas switching unit 8 to communicate the connection unit 2 with the reactor 4a, and the reducing gas supply unit 3 with the reactor 4b. [2] Next, in this state, the supply of exhaust gas from the furnace 20 via the connection part 2 is started. [3] Next, the exhaust gas passes through an oxygen removal device (concentration adjustment unit 5), which removes oxygen from the exhaust gas and increases the concentration of carbon dioxide contained in the exhaust gas.

[0064] [4] The exhaust gas then passes through compression section 6, which increases the pressure of the exhaust gas. [5] Next, the exhaust gas passes through the fine component removal section 7. This removes condensed water generated when the exhaust gas is compressed in the compression section 6 and inactive components that reduce the activity of the reducing agent 4R from the exhaust gas. [6] Next, the exhaust gas passes through the exhaust gas heating section 10, whereby the exhaust gas is heated. [7] Next, the exhaust gas is supplied to the reactor 4a. In the reactor 4a, the carbon dioxide in the exhaust gas is reduced to carbon monoxide by the reducing agent 4R. At this time, the reducing agent 4R is oxidized by contact with the carbon dioxide.

[0065] The temperature (reaction temperature) of the reactor 4a (exhaust gas, reducing agent 4R) in the above step [7] is preferably 600° C. or higher, more preferably 650 to 1100° C., and even more preferably 700 to 1000° C. If the reaction temperature is set within the above range, for example, a sudden decrease in temperature of the reducing agent 4R due to an endothermic reaction when carbon dioxide is converted to carbon monoxide can be prevented or suppressed, so that the reduction reaction of carbon dioxide in the reactor 4a can proceed more smoothly.

[0066] [9] Exhaust gas is discharged from reactor 4a into gas line GL4a.

[10] Next, the exhaust gas is returned through the return gas line GL5a, mixed with the exhaust gas supplied from the gas line GL3a, and supplied again to the reactor 4a. As described above, in the reactor 4a, the carbon dioxide in the exhaust gas is reduced to carbon monoxide by the reducing agent 4R. At this time, the reducing agent 4R is oxidized by contact with the carbon dioxide. The conditions in reactor 42a can be similar to those in reactor 41a. In addition, only a part of the exhaust gas discharged from the reactor 4a to the gas line GL4a may be returned via the return gas line GL5a, in which case the remaining part of the exhaust gas is discharged to the gas line GL4.

[0067]

[11] In parallel with the above steps [2] to

[10] , water (reducing gas raw material) is supplied from the tank 30 to the hydrogen generation device (reducing gas supply unit 3), and hydrogen is generated from the water.

[12] Next, the reducing gas containing hydrogen passes through the reducing gas heating section 11. This causes the reducing gas to be heated.

[13] Next, the reducing gas is supplied to the reactor 4b. In the reactor 4b, the reducing agent 4R in an oxidized state is reduced (regenerated) by contact with the reducing gas (hydrogen). At this time, water is produced.

[0068] The temperature (reaction temperature) of the reactor 4b (reducing gas, reducing agent 4R) in the above step

[13] is preferably 600° C. or higher, more preferably 650 to 1100° C., and even more preferably 700 to 1000° C. If the reaction temperature is set within the above range, for example, a rapid temperature drop of the reducing agent 4R due to an endothermic reaction when reducing (regenerating) the reducing agent 4R in an oxidized state can be prevented or suppressed, so that the reduction reaction of the reducing agent 4R in the reactor 4b can proceed more smoothly.

[0069]

[14] The reducing gas is discharged from reactor 4b into gas line GL4b.

[15] Next, the reducing gas is returned through the return gas line GL5b, mixed with the reducing gas supplied from the gas line GL3b, and supplied to the reactor 4b. As in the above, in the reactor 4b, the oxidized reducing agent 4R is reduced (regenerated) by contact with the reducing gas (hydrogen). At this time, water is produced. The conditions in reactor 4b can be similar to those in reactor 4b.

[0070]

[16] Next, the gases that have passed through the reactors 4a and 4b are joined together to generate a mixed gas. At this point, the temperature of the mixed gas is usually 600 to 650°C. If the temperature of the mixed gas at this point is within the above range, it means that the temperature inside the reactors 4a and 4b is maintained at a sufficiently high temperature, and it can be determined that the conversion of carbon dioxide to carbon monoxide by the reducing agent 4R and the reduction of the reducing agent 4R by the reducing gas are proceeding efficiently.

[17] Next, the mixed gas is cooled to 100 to 300° C. before reaching the gas purification section 9.

[0071]

[18] Next, the mixed gas passes through the gas purification unit 9. This removes, for example, the generated condensed water and carbon dioxide dissolved in the condensed water. As a result, carbon monoxide is purified from the mixed gas, and a product gas containing a high concentration of carbon monoxide is obtained. The temperature of the resulting produced gas is 20 to 50°C.

[19] Next, the produced gas is discharged from the produced gas discharge section 40 to the outside of the gas production apparatus 1 and is used for the next process. The gas lines GL4a and GL4b do not have to be joined at the gas junction J4. In this case, the exhaust gas and the reducing gas that have passed through the reactors 4a and 4b may be independently supplied to the next process via the gas lines GL4a and GL4b.

[0072] <Second embodiment> The reaction section 4 can also be configured as follows. FIG. 3 is a schematic diagram showing the configuration of a reaction unit according to the second embodiment. The reaction unit 4 of the second embodiment will be described below, focusing on the differences from the reaction unit 4 of the first embodiment, and a description of the similarities will be omitted.

[0073] In the reaction section 4 of the second embodiment, a separation section 19 is provided at a branching section (connecting section) between the gas lines GL4a, GL4b and the return gas lines GL5a, GL5b. This separation section 19 is connected to the outlet port of each of the reactors 4a, 4b, and is configured to separate a product of the reaction with the reducing agent 4R contained in the gas (exhaust gas or reducing gas) that has passed through the reactors 4a, 4b. In this embodiment, for example, the separation unit 19 on the reduction side is configured to separate water (a product of the reaction with the reducing agent 4R) contained in the reduction gas that has passed through the reactor 4b. The separation unit 19 on the oxidation side may also be configured to separate carbon monoxide (a product of the reaction with the reducing agent 4R) contained in the exhaust gas that has passed through the reactor 4a.

[0074] In this embodiment, for example, the reactor 4b on the reduction side is configured to separate water (a product of the reaction with the reducing agent 4R) contained in the reducing gas that has passed through it. In this case, the amount of water contained in the returning reducing gas (separated gas) is reduced, so that even when the reducing gas is returned, it is possible to prevent the reduction efficiency of the reducing agent 4R from decreasing. In addition, the amount of water contained in the mixed gas can also be reduced. The water separated in the separation unit 19 is discharged from the gas line GL19b. The gas discharged from the gas line GL19b may contain gas components other than water.

[0075] On the other hand, in this embodiment, the exhaust gas that has passed through the oxidation-side reactor 4a is discharged to the gas line GL4 via the gas line GL4a. The separation section 19 connected to the oxidation-side reactor 4a may also be configured to separate carbon monoxide (a product of the reaction with the reducing agent 4R) contained in the exhaust gas.

[0076] The separation section 19 may be composed of a condenser that condenses water (product) by cooling, or may be composed of a separation membrane that allows water (product) molecules to pass through and prevents other molecules from passing through, or may be composed of a capture material that physically or chemically captures water (product), or may be composed of any combination of two or more of a cooler, a separation membrane, and a capture material. The condenser can be configured, for example, as a low-temperature separation type (cryogenic type) condenser, a temperature swing adsorption (TSA) type condenser, or the like. The separation membrane may be made of a metal, an inorganic oxide, or a metal organic framework (MOF).

[0077] Examples of the metal include titanium, aluminum, copper, nickel, chromium, cobalt, and alloys containing these metals. When a metal is used, the separation membrane is preferably a porous body having a porosity of 80% or more. Examples of inorganic oxides include silica and zeolite. Examples of the metal-organic framework include a framework of zinc nitrate hydrate and a terephthalic acid dianion, and a framework of copper nitrate hydrate and a trimesic acid trianion.

[0078] The separation membrane is preferably made of a porous body having continuous pores (pores penetrating the cylindrical wall) in which adjacent pores are connected to each other. A separation membrane having such a configuration can increase the permeability of water or carbon monoxide, and can more smoothly and reliably separate water and hydrogen and / or carbon monoxide and carbon dioxide. The porosity of the separation membrane is not particularly limited, but is preferably 10 to 90%, and more preferably 20 to 60%, which makes it possible to prevent the mechanical strength of the separation membrane from decreasing excessively while maintaining a sufficiently high permeability to water or carbon monoxide. The shape of the separation membrane is not particularly limited, and examples thereof include a cylindrical shape, a rectangular shape, and a rectangular tube shape such as a hexagon.

[0079] From the viewpoint of further increasing the efficiency of conversion of carbon dioxide to carbon monoxide, it is effective to increase the reduction (regeneration) efficiency of the reducing agent 4R in an oxidized state. In this case, the average pore size of the separation membrane is preferably 600 pm or less, and more preferably 400 to 500 pm, which can further improve the efficiency of separation of water and hydrogen. The separation membrane is usually used in a state where it is housed in a housing. In this case, the space outside the separation membrane in the housing may be depressurized, or a carrier gas (sweep gas) may be passed through it. Examples of the carrier gas include inert gases such as helium and argon.

[0080] In addition, the separation membrane is preferably hydrophilic. If the separation membrane has hydrophilic properties, the affinity of water to the separation membrane increases, and water can more easily permeate the separation membrane. Methods for imparting hydrophilicity to a separation membrane include a method for improving the polarity of the separation membrane by changing the ratio of metal elements in the inorganic oxide (e.g., increasing the Al / Si ratio), a method for coating the separation membrane with a hydrophilic polymer, a method for treating the separation membrane with a coupling agent having a hydrophilic group (polar group), and a method for subjecting the separation membrane to plasma treatment, corona discharge treatment, etc. Furthermore, the affinity for water may be controlled by adjusting the surface potential of the separation membrane.

[0081] On the other hand, in the case where the separation membrane is used to prioritize separation of carbon monoxide and carbon dioxide from the exhaust gas that has passed through the oxidation side reactor 4a, and in the case where the separation membrane is used to simultaneously separate water and hydrogen, and carbon monoxide and carbon dioxide from the exhaust gas and reducing gas that have passed through both reactors 4a and 4b, the constituent materials, porosity, average pore size, degree of hydrophilicity or hydrophobicity, surface potential, etc. of the separation membrane may be set in an appropriate combination. It is possible to form the tubular body 41 of the reactors 4a, 4b using such a separation membrane, but in this case, the temperature (reaction temperature) of the reactors 4a, 4b cannot be set to a high temperature because the separation membrane would deteriorate due to heat. In contrast, by disposing the separation membrane outside the reactors 4a and 4b, the temperature of the reactors 4a and 4b can be set to a relatively high temperature, and therefore the efficiency of converting carbon dioxide into carbon monoxide and the efficiency of regenerating (reducing) the reducing agent 4R by the reducing gas can be further increased.

[0082] Furthermore, examples of trapping materials that physically or chemically trap water include zeolite, silica gel, decyl clay (clay-based desiccant), calcium chloride, and calcium oxide. On the other hand, examples of scavenger materials that physically or chemically capture carbon monoxide include a complex of copper ion and 5-azidoisophthalic acid, a copper ammine complex, and a copper aluminum chloride complex.

[0083] <Third embodiment> The reaction section 4 can also be configured as follows. FIG. 4 is a schematic diagram showing the configuration of a reaction unit according to the third embodiment. The reaction section 4 of the third embodiment will be described below, focusing on the differences from the reaction section 4 of the first or second embodiment, and a description of the similar points will be omitted.

[0084] In the reaction section 4 of the third embodiment, vent lines (vent sections) VL6a and VL6b are connected to the return gas lines GL5a and GL5b of the second embodiment. In this embodiment, for example, the reduction-side vent line VL6b is configured to exhaust a portion of the hydrogen (separated gas) separated in the separation unit 19. The oxidation-side vent line VL6a may also be configured to exhaust a portion of the carbon dioxide (separated gas) separated in the separation unit 19. By connecting such vent lines VL6a and VL6b and discharging a part of the separated gas on the reduction side, the amounts of carbon monoxide, carbon dioxide, by-product methane, etc. present in the recycle system can be reduced. This reduces the cost required for heating and / or cooling, and enables accurate evaluation of the hydrogen conversion rate. As a result, the operation of the gas production apparatus 1 (gas production system 100) becomes easier.

[0085] <Fourth embodiment> The reaction section 4 can also be configured as follows. FIG. 5 is a schematic diagram showing the configuration of a reaction unit according to the fourth embodiment. The reaction section 4 of the fourth embodiment will be described below, focusing on the differences from the reaction section 4 of the first to third embodiments, and a description of the similar points will be omitted.

[0086] The reaction section 4 of the fourth embodiment further includes a heat exchanger (economizer) 18. This heat exchanger 18 is connected between the reactors 4a, 4b and the separation section 19, and is configured by bending some of the piping that constitutes the return gas lines GL5a, GL5b and bringing it close to the piping that constitutes the gas lines GL4a, GL4b. According to this configuration, heating is performed by heat exchange between the separated gas separated in the separation section 19 and returned to the inlet port and the gas that passes through the reactors 4a, 4b and is discharged from the outlet port, thereby making it possible to effectively utilize heat. The heat exchanger 18 can be configured as, for example, a jacket type heat exchanger, an immersed coil type heat exchanger, a double-pipe type heat exchanger, a shell-and-tube type heat exchanger, a plate type heat exchanger, a spiral type heat exchanger, or the like.

[0087] <Fifth embodiment> The reaction section 4 can also be configured as follows. FIG. 6 is a schematic diagram showing the configuration of a reaction unit according to the fifth embodiment. The reaction section 4 of the fifth embodiment will be described below, focusing on the differences from the reaction section 4 of the first to fourth embodiments, and a description of the similar points will be omitted. In FIG. 6, the oxidation side and the reduction side are shown without distinction.

[0088] In the reaction section 4 of the fifth embodiment, two or more (at least one) reactors 4a, 4b are provided between the most downstream reactors 4a, 4b and the most upstream location where the oxidizing gas or reducing gas is returned. Specifically, in the configuration shown in Fig. 6(a), multiple reactors 4a, 4b are connected in series, and a separation unit 19 is connected to the outlet port of the most downstream reactors 4a, 4b. In addition, return gas lines GL5a, GL5b are connected to the inlet port of the most upstream reactors 4a, 4b, the inlet port of the intermediate reactors 4a, 4b, and the inlet port of the most downstream reactors 4a, 4b. The separated gas can be returned to any desired location.

[0089] On the other hand, in the configuration shown in Fig. 6(b), multiple reactors 4a, 4b are connected in series, and the outlet ports of each of the reactors 4a, 4b are connected to a separation section 19. In addition, each of the return lines GL5a, GL5b join together and are connected to the inlet ports of the most upstream reactors 4a, 4b. Additionally, optional return lines GL5a, GL5b may be used to return oxidizing or reducing gas from a given reactor 4a, 4b. The configuration shown in FIG. 6(a) and the configuration shown in FIG. 6(b) can also be combined.

[0090] In the configuration shown in FIG. 6(a) and FIG. 6(b), this line includes a separation section 19 connected between adjacent reactors 4a, 4b. The separation section 19 separates carbon monoxide or water (product) generated by the reaction with the reducing agent 4R contained in the exhaust gas (oxidizing gas) or reducing gas that has passed through each reactor 4a, 4b, to generate a separated gas with an increased purity of carbon dioxide or hydrogen (reducing substance) that has not reacted with the reducing agent 4R, and the separated gas is returned to the upstream side of the reactors 4a, 4b. In this case, the separated gas can be returned in part or in whole. When returning a part of the separated gas, a vent line as shown in FIG. 4 is connected to the return gas line GL5a, GL5b, and a part of the separated gas is exhausted through the vent line. According to the gas production apparatus 1 (gas production system 100) as described above, carbon valuables can be efficiently produced by using an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance.

[0091] Furthermore, it may be provided in the following aspects: The gas manufacturing apparatus further includes a separation unit connected to each of the reactors and configured to separate a product of a reaction with the reducing agent contained in the gas that has passed through the reactors. In the gas production apparatus, the separation section includes a condenser that condenses the product by cooling. In the gas production apparatus, the separation section includes a separation membrane that allows the product molecules to pass through and prevents other molecules from passing through. In the gas production apparatus, the separation section includes a capture material that physically or chemically captures the product. The gas manufacturing apparatus further comprises a heat exchanger, the heat exchanger being connected between the reactor and the separation section and configured to exchange heat between a separated gas that is separated in the separation section and returned to the upstream side of the reactor and a gas that has passed through the reactor. The gas production apparatus further comprises a vent section, the vent section being configured to exhaust a portion of the separated gas separated in the separation section and returned to the upstream side of the reactor. In the gas manufacturing apparatus, at least one of the reactors is provided between the reactor and an upstream location where the oxidizing gas or the reducing gas is returned. The gas manufacturing apparatus further includes a separation unit connected between adjacent reactors, and the separation unit is configured to separate a product of reaction with the reducing agent contained in the oxidizing gas or reducing gas that has passed through each of the reactors, thereby returning a part or all of the carbon dioxide that has not reacted with the reducing agent or the separated gas in which the purity of the reducing substance has been increased to the upstream side of the reactors. The gas production apparatus is configured not to return the oxidizing gas that has passed through the reactor, but to return the reducing gas that has passed through the reactor. Of course, this is not the case.

[0092] As described above, various embodiments of the present invention have been described, but these are presented as examples and do not limit the scope of the invention in any way. The novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. The embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0093] For example, the gas manufacturing apparatus of the present invention may have any other additional configuration compared to the above-described embodiment, may be replaced with any configuration that performs a similar function, or some configurations may be omitted. Furthermore, any of the configurations of the first to fifth embodiments may be combined. In the above embodiment, the reactor has been described as a multi-tube type reaction device, but the reactor may be configured such that the tube body 41 is omitted and the reducing agent 4R is directly filled in the housing . In the above embodiment, a gas containing hydrogen has been described as a representative reducing gas. However, the reducing gas may also be a gas containing at least one selected from hydrocarbons (e.g., methane, ethane, acetylene, etc.) and ammonia as a reducing substance instead of or in addition to hydrogen. [Explanation of symbols]

[0094] 1: Gas production equipment 2: Connection part 3: Reducing gas supply section 4: Reaction section 41: Body 42: Housing 43: Space 4R: Reducing agent 4a: Reactor 4b: Reactor 5:Density adjustment section 6: Compression section 7: Fine component removal section 8: Gas switching section 8a: First gas switching section 8b: Second gas switching section 9: Gas purification section 10: Exhaust gas heating section 11: Reducing gas heating section 18: Heat exchanger 19: Separation part 20: Furnace 30: Tank 40: Produced gas exhaust section 100: Gas production system GL1: Gas line GL2: Gas line GL3a: Gas line GL3b: Gas line GL3c: Gas Line GL3d: Gas Line GL4: Gas line GL4a: Gas line GL4b: Gas line GL4c: Gas Line GL4d: Gas Line GL5a: Return gas line GL5b: Return gas line GL19a: Gas line GL19b: Gas line VL6a: Vent line VL6b: Vent line J4: Gas junction

Claims

1. A gas production apparatus comprising: A reactor is provided. Each of the reactors is configured to accommodate a reducing agent and to be capable of switching between an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance, the reducing agent includes at least one of a metal element and a metal oxide that generates a carbon valuable by reducing the carbon dioxide, and is oxidized by contact with the carbon dioxide and then reduced by contact with the reducing substance; A gas producing apparatus configured to return a part or all of at least one of the oxidizing gas and the reducing gas that have passed through each of the reactors to the upstream side of the same reactor.

2. The gas production apparatus according to claim 1, Further, the separator includes: The separation unit is connected to each of the reactors and configured to separate a product of a reaction between the reducing agent and the gas that has passed through the reactor.

3. The gas production apparatus according to claim 2, The gas production apparatus, wherein the separation section includes a condenser that condenses the product by cooling.

4. The gas production apparatus according to claim 2 or 3, The gas production apparatus, wherein the separation section is provided with a separation membrane that allows the product molecules to pass through and prevents other molecules from passing through.

5. The gas production apparatus according to any one of claims 2 to 4, The gas production apparatus, wherein the separation section includes a capture material that physically or chemically captures the product.

6. The gas production apparatus according to any one of claims 2 to 5, Further, the apparatus has a heat exchanger, The heat exchanger is connected between the reactor and the separation section and configured to exchange heat between a separated gas that is separated in the separation section and returned to the upstream side of the reactor and a gas that has passed through the reactor.

7. The gas production apparatus according to any one of claims 2 to 6, Further, the device has a vent portion, The gas producing apparatus, wherein the vent section is configured to exhaust a portion of the separated gas that is separated in the separation section and returned to the upstream side of the reactor.

8. The gas production apparatus according to any one of claims 1 to 7, A gas production apparatus, wherein at least one of the reactors is provided between the reactor and an upstream location where the oxidizing gas or the reducing gas is returned.

9. The gas production apparatus according to claim 8, Further, a separation section is connected between adjacent reactors, The separation section is configured to separate products of reaction with the reducing agent contained in the oxidizing gas or reducing gas that has passed through each of the reactors, and to return a part or all of the carbon dioxide that has not reacted with the reducing agent or the separated gas in which the purity of the reducing substance has been increased to the upstream side of the reactors.

10. The gas production apparatus according to any one of claims 1 to 9, The gas production apparatus is configured not to return the oxidizing gas that has passed through the reactor, but to return the reducing gas that has passed through the reactor.

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