Oxygen carrier, method of producing oxygen carrier, method of producing gas, and device of producing gas

Abstract

To provide an oxygen carrier or the like capable of efficiently producing a carbon valuable material using raw material gas including carbon dioxide, and reductive gas including a reduction substance.SOLUTION: There is provided an oxygen carrier comprising a metal compound, according to one aspect of the present invention. The metal compound in the oxygen carrier comprises a cation moiety and an anion moiety. The cation moiety at least includes a metal element. The anion moiety at least includes an oxygen element. At least one of the cation moiety and the anion moiety includes another element other than the metal element and the oxygen element. The other element is an element belonging to the groups 14 to 17 and the periods 2 to 5 in the periodic table.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an oxygen carrier, a method for producing an oxygen carrier, a method for producing a gas, and a gas production apparatus. [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 Brochure 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 an oxygen carrier or the like that can efficiently generate carbon valuables by using a raw material gas containing carbon dioxide and a gas having reducing properties that contains a reducing substance. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided an oxygen carrier having a metal compound. The metal compound in this oxygen carrier has a cation moiety and an anion moiety. The cation moiety contains at least a metal element. The anion moiety contains at least an oxygen element. At least one of the cation moiety or the anion moiety contains another element different from the metal element and the oxygen element. The other element is an element belonging to Groups 14 to 17 and Periods 2 to 5.

[0007] According to this aspect, carbon valuables can be efficiently produced by using a raw material gas containing carbon dioxide and a gas having reducing properties 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 according to an embodiment 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 a method for switching the gas to be passed through the reactor in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[0010] <Oxygen Carrier> First, the oxygen carrier of the present embodiment will be described. The oxygen carrier of the present embodiment is as follows. An oxygen carrier having a metal compound, The metal compound has a cation portion and an anion portion, The cation moiety contains at least a metal element, The anion portion contains at least an oxygen element, At least one of the cation moiety and the anion moiety contains an element different from the metal element and the oxygen element, The other element is an oxygen carrier, which is an element belonging to Groups 14 to 17 and Periods 2 to 5.

[0011] The oxygen carrier of this embodiment has a metal compound, and is typically used in the reduction reaction of gas such as carbon dioxide (a reaction in which the reduced oxygen carrier is brought into contact with carbon dioxide to produce carbon valuables such as carbon monoxide) and the oxidation reaction of gas such as hydrogen (a reaction in which water is produced by contacting with hydrogen). That is, since this metal compound functions as an oxygen carrier, the above-mentioned reduction reaction or oxidation reaction can be promoted.

[0012] The metal compound has a cation moiety and an anion moiety, and the cation moiety has at least a metal element. The metal element can be appropriately selected, and as an example, the metal element contained in the cation moiety may be a transition metal element. The metal element contained in the cation moiety may contain at least one type selected from the metal elements belonging to groups 3 to 12, or may contain at least one type selected from the metal elements belonging to groups 4 to 12. The metal element contained in the cation portion may contain at least one of indium, lanthanum, aluminum, titanium, vanadium, zirconium, iron, copper, zinc, nickel, manganese, chromium, cerium, and the like.

[0013] Moreover, the metal element may be appropriately selected depending on the process in which the oxygen carrier is applied. In particular, when the oxygen carrier is used in the process of converting carbon dioxide to carbon monoxide, the metal element preferably includes iron, cerium, etc. When the oxygen carrier is used in the process of converting carbon dioxide to methane, the metal element preferably includes at least one of nickel and ruthenium. When the oxygen carrier is used in the process of converting carbon dioxide to methanol, the metal element preferably includes at least one of copper and zinc.

[0014] In addition, the metal compound has at least an oxygen element as an anion portion. As described above, the oxygen carrier of the present embodiment is typically used for converting carbon dioxide to carbon monoxide and hydrogen to water, and such various conversions can be performed through the release or absorption of the oxygen element.

[0015] In addition, the metal compound contained in the oxygen carrier of this embodiment contains other elements different from the above-mentioned metal element and oxygen element, where the other elements belong to Groups 14 to 17 and Periods 2 to 5. That is, the other element is any of: a Group 14 element selected from carbon, silicon, germanium, and tin; a Group 15 element selected from nitrogen, phosphorus, arsenic, and antimony; a Group 16 element selected from sulfur, selenium, and tellurium; and a Group 17 element selected from fluorine, chlorine, bromine, and iodine.

[0016] The oxygen carrier of the present embodiment contains such other elements in the metal compound, and therefore the efficiency of various reactions is improved. Although the reason is not necessarily limited to the following, the oxygen carrier subjected to the oxidation reaction or reduction reaction may become a non-stoichiometric compound composition (typically, a composition in which the oxygen element is deficient relative to the metal element, or a composition in which the metal element is deficient relative to the oxygen element) in the reaction process. At that time, it is presumed that the presence of other elements in the oxygen carrier makes it easier to compensate for the deficient portion in the non-stoichiometric compound composition, thereby improving the efficiency of various reactions.

[0017] The other element may be selected depending on the reaction to be carried out, and in the metal compound, the other element may form part of the cation moiety or part of the anion moiety.

[0018] Among the above, the other elements preferably contain at least one element belonging to Groups 15 and 16, and more preferably contain at least one element belonging to Group 16.

[0019] The content of the other elements can be appropriately selected depending on the purpose, but as an example, the content of the other elements is preferably 0.001% by mass or more and 10% by mass or less, more preferably 0.005% by mass or more and 8% by mass or less, and even more preferably 0.01% by mass or more and 5% by mass or less, relative to the metal compound (all components of the metal compound). Setting the content of the other elements within such a range makes it easier to contribute to the targeted improvement of reaction efficiency.

[0020] Such a metal compound can be obtained, for example, by heating a metal element, alloy, or metal oxide containing the metal element in contact with a compound containing another element, which may be in the form of a solid, liquid, or gas when brought into contact with the metal element. In this way, by heating a raw material containing a metal element and a compound containing another element while contacting them, the other element is incorporated into the raw material, and the metal compound of this embodiment can be formed. When the raw material for this reaction is a simple metal or an alloy, the heating reaction may be carried out in an oxygen atmosphere in order to incorporate an oxygen element into the resulting metal compound.

[0021] Taking an example where the other element is sulfur, examples of the compound to be brought into contact with the metal element, alloy, or metal oxide containing the metal element include elemental sulfur, hydrogen sulfide, sulfuric acid, sulfur dioxide, sulfur trioxide, sulfur hexafluoride, sulfur dichloride, carbon disulfide, metal sulfides (lithium sulfide, iron sulfide, zinc sulfide, lanthanum sulfide, etc.), and sulfates (barium sulfate, sodium sulfate, etc.), but are not limited to these, and any known compound containing sulfur as a constituent atom may be used as appropriate.

[0022] The heating temperature when obtaining the metal compound can be appropriately set depending on the metal compound to be produced. As an example, the heating temperature is preferably 200°C or more and 1600°C or less, more preferably 350°C or more and 1400°C or less, and even more preferably 500°C or more and 1200°C or less. By setting such a temperature range, it is possible to control the energy used and perform efficient compound conversion.

[0023] The oxygen carrier of the present embodiment may be a metal compound supported on a carrier. The constituent material of the support is preferably one that is not easily denatured by contact with exhaust gas (raw material gas) or by reaction conditions, etc., and examples thereof include carbon materials (graphite, graphene, etc.), carbides such as Mo2C, zeolite, montmorillonite, oxides such as ZrO2, TiO2, V2O5, MgO, CeO2, Al2O3, and SiO2, and composite oxides containing these.

[0024] 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 because they do not adversely affect oxidation and reduction reactions and have excellent ability to support metal compounds. In the oxygen carrier of this embodiment, at least a part of the surface of the carrier may be coated with the above-mentioned metal compound.

[0025] <Gas production system> Next, the overall configuration of a gas production system to which the oxygen carrier of this embodiment can be applied will be described.

[0026] (First embodiment of gas production system) Fig. 1 is a schematic diagram showing the overall configuration of a gas production system using a gas production apparatus according to the present embodiment, Fig. 2 is a schematic diagram showing the configuration of a reaction section of the first embodiment. The gas production system 100 shown in FIG. 1 includes a furnace 20 that produces exhaust gas (raw material 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 in the gas flow direction is simply referred to as the "upstream side," and the downstream side is simply referred to as the "downstream side." Furthermore, each component provided in this gas production system is not necessarily required to be installed, and may be omitted or replaced as appropriate depending on the process to be constructed.

[0027] 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.

[0028] 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.

[0029] Exhaust gas from a blast furnace (blast furnace gas) is a gas generated when pig iron is produced in a blast furnace, and contains 20 to 30 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 raw material gas is not limited to exhaust gas, and a pure gas containing 100% by volume of carbon dioxide may be used.

[0030] However, if exhaust gas is used as the raw material 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.

[0031] The gas production apparatus 1 produces a product gas (synthetic gas) containing carbon monoxide by contacting exhaust gas (raw material 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.

[0032] The gas manufacturing apparatus 1 mainly includes a connection section 2, a reducing gas supply section 3, a reaction section 4 having four reactors 41a, 42a, 41b, 42b (hereinafter collectively referred to as "reactors 4ab"), 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 (raw material 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.

[0033] 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 41a and 41b 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 via the connection part 2 passes through the gas line GL1 and is supplied to each of the reactors 41a, 41b. 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.

[0034] As shown in Fig. 2, each reactor 4ab 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.

[0035] Here, the reducing agent 4R accommodated in each reactor 4ab contains an oxygen carrier containing the above-mentioned metal compound. That is, the gas containing carbon dioxide (raw material gas) supplied into the tube body 41 is reduced by contacting with the oxygen carrier and converted into a gas containing carbon monoxide (product gas). At this time, the oxygen carrier is oxidized by contacting with the raw material gas (oxidizing gas).

[0036] 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.

[0037] 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.

[0038] Here, in each reactor 4ab, the reducing agent 4R itself may be used to prepare a tube (cylindrical molded body) 41. Furthermore, the reducing agent 4R may be used to prepare a molded body having a block shape, a lattice shape (for example, a mesh shape, a honeycomb shape), or the like, and the molded body may be disposed in the housing 42.

[0039] 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 reactor 4ab, 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 four reactors 41a, 42a, 41b, and 42b 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). Furthermore, the volume of at least one of the four reactors 41a, 42a, 41b, and 42b may be made different according to the types of exhaust gas and reducing gas, etc.

[0040] In 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 (raw material gas heating section) 10 are provided in this order from the connection 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.

[0041] 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.

[0042] 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, relative to the total volume of the exhaust gas, thereby making it possible to more reliably prevent the exhaust gas from igniting. 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.

[0043] The compression section 6 increases the pressure of the exhaust gas before it is supplied to the reactor 4ab. This increases the amount of exhaust gas that can be treated at one time in the reactor 4ab. This further improves the efficiency of converting carbon dioxide into carbon monoxide in the reactor 4ab. 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.

[0044] 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 conversion efficiency of carbon dioxide to carbon monoxide in the reactor 4ab can be further improved without increasing the pressure resistance of the gas production apparatus 1 more than necessary.

[0045] 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. Although the gas production system 100 in FIG. 1 is provided with such a configuration, the minor component removing section 7 may be omitted depending on the composition of the material used as the raw material.

[0046] 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.

[0047] 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. It is also possible to connect a liquid line to a tank so that the discharged condensed water can be reused.

[0048] 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. If necessary, such a protector can also be provided with a substance capable of capturing trace components (inactivating components) contained in the exhaust gas that reduce the activity of the reducing agent 4R upon 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 reactor 4ab, 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.

[0049] 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. 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.

[0050] 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.

[0051] The exhaust gas heating section 10 heats the exhaust gas before it is supplied to the reactor 4ab. 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 in the reactor 4ab can be further promoted. 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 that discharges the gas (mixed gas) after passing through the reactor 4ab, 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 reactor 4ab is used to heat the exhaust gas before being supplied to the reactor 4ab by heat exchange, so that the heat can be effectively utilized.

[0052] 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.

[0053] 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.

[0054] 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 41a and 41b 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 configured with a hydrogen generation device that generates hydrogen by electrolysis of water, for example, 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 reactor 4ab.

[0055] 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.

[0056] 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 reactor 4ab. 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.

[0057] 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 reactor 4ab. 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 reactor 4ab can be further promoted.

[0058] 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 reactor 4ab is utilized to heat the reducing gas by heat exchange before being supplied to the reactor 4ab, thereby enabling effective use of heat.

[0059] According to the above-mentioned configuration, by switching the gas line (flow path) in the gas switching unit 8, for example, exhaust gas (carbon dioxide, etc.) is supplied to the reactors 41a, 42a containing the oxygen carrier before oxidation through the gas line GL3a, and the oxygen carrier is brought into contact with the exhaust gas, thereby performing a reduction reaction on the exhaust gas. Also, a gas having a reducing property (reducing gas) is supplied to the reactors 41b, 42b containing the oxidized carrier after the generation of the product gas (carbon monoxide, etc.) through the gas line GL3b, and the oxygen carrier is brought into contact with the gas having a reducing property (reducing gas), thereby performing an oxidation reaction on the reducing gas. Note that the step of contacting the gas having a reducing property (reducing gas) may be provided before the generation of the product gas (carbon monoxide, etc.).

[0060] Then, by switching the gas lines in the gas switching section 8 in the opposite direction to the above, an oxidation reaction of the reducing gas can be carried out in the reactors 41a and 42a, and a reduction reaction of the exhaust gas can be carried out in the reactors 41b and 42b.

[0061] It is preferable that the gas manufacturing apparatus 1 further includes a reducing agent heating section (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.

[0062] In addition, when the reaction to be carried out is an exothermic reaction, the gas production device 1 preferably has a reducing agent cooling unit for cooling 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 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).

[0063] Gas lines GL4a and GL4b are connected to the outlet ports of the reactors 42a and 42b, respectively, and merge at a gas junction J4 to form the gas line GL4. In addition, valves (not shown in FIG. 2) 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 reactor 4ab (that is, 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 reactor 4ab and the gas switching section 8.

[0064] 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 42a, 42b. 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.

[0065] 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.

[0066] 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 reactor 4ab (see Figure 2) and passing the mixed gas inside tube 41 and the refrigerant through space 43 around tube 41, an air fin cooler, or the like.

[0067] 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.

[0068] 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.

[0069] 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. It is also possible to connect a liquid line to a tank so that the discharged condensed water can be reused.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Next, a description will be given of an example of a method of using (action of) the gas production system 100. Note that the method of using the gas production system 100 of this embodiment is not limited to the following, and steps can be added, replaced, or omitted as appropriate. [1] First, the gas line (flow path) is switched in the gas switching unit 8 to communicate the connection unit 2 with the reactor 41a and to communicate the reducing gas supply unit 3 with the reactor 41b. [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.

[0074] [4] The exhaust gas then passes through compression section 6, which increases the pressure of the exhaust gas. [5] Next, if necessary, the exhaust gas is transferred and passed 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 41a. In the reactor 41a, 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.

[0075] The temperature (reaction temperature) of the reactor 41a (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 41a can proceed more smoothly.

[0076] [8] Exhaust gas is discharged from reactor 41a to gas line GL5a. [9] Next, the exhaust gas is supplied to the reactor 42a. In the reactor 42a, 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.

[0077]

[10] In parallel with the above steps [2] to [9], water (reducing gas raw material) is supplied to the hydrogen generation device (reducing gas supply unit 3) to generate hydrogen from the water.

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

[12] Next, the reducing gas is supplied to the reactor 41b. In the reactor 41b, the reducing agent 4R in an oxidized state is reduced (regenerated) by contact with the reducing gas (hydrogen). At this time, water is produced.

[0078] The temperature (reaction temperature) of the reactor 41b (reducing gas, reducing agent 4R) in the above step

[12] 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 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 41b can proceed more smoothly.

[0079]

[13] The reducing gas is discharged from reactor 41b to gas line GL5b.

[14] Next, the reducing gas is supplied to the reactor 42b. In the reactor 42b, the reducing agent 4R in the oxidized state is reduced (regenerated) by contact with the reducing gas (hydrogen). At this time, water is produced. The conditions in reactor 42b can be similar to those in reactor 41b.

[0080]

[15] Next, the gases that have passed through the reactors 42a and 42b 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 reactor 4ab 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.

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

[0081]

[17] 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.

[18] 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.

[0082] (Second embodiment of gas production system) The reaction section 4 of the above-mentioned gas production system can also be configured as follows (second embodiment). Fig. 3 is a schematic diagram showing the configuration of a reaction section in the second embodiment. Fig. 4 is a schematic diagram showing a method for switching the gas passed through the reactor in 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.

[0083] The reaction section 4 of the second embodiment has a first gas switching section 8a, four reactors 4a to 4d, and a second gas switching section 8b. The first gas switching unit 8a is connected to the inlet ports of the reactors 4a to 4d via gas lines GL3a to GL3d, respectively. Gas lines GL4a to GL4d are connected to the outlet ports of the reactors 4a to 4d, respectively, and merge at a second gas switching section 8b to form a gas line GL4. The first gas switching unit 8a and the second gas switching unit 8b are connected by four gas lines GL5a to GL5d.

[0084] With this configuration, by switching the gas lines (flow paths) between the first gas switching section 8a and the second gas switching section 8b, for example, exhaust gas (oxidizing gas) can be supplied to and passed through one of the reactors 4a to 4d, while reducing gas can be continuously supplied to and passed through the remaining three reactors 4a to 4d in this order.

[0085] That is, in the second embodiment, among the multiple reactors 4a to 4d, one reactor to which exhaust gas is supplied constitutes a first reactor, and three reactors to which reducing gas is continuously supplied when exhaust gas is supplied to the first reactor can constitute a second reactor.

[0086] Specifically, in the first turn shown in FIG. 4(I), exhaust gas (carbon dioxide) is supplied to the reactor (first reactor) 4a via the gas line GL3a, and the exhaust gas (carbon monoxide) that has passed through it can be discharged via the gas line GL4a.

[0087] On the other hand, for the remaining reactors 4b to 4d, first, reducing gas (hydrogen) is supplied to the reactor (first second reactor) 4b via the gas line GL3b, and then the reducing gas (residual hydrogen) that has passed through this can be supplied to the reactor (second second reactor) 4c via the gas line GL4b, the gas line GL5c, and the gas line GL3c. Although not shown, a mechanism for removing water may be provided midway through the gas line GL5c, and the generated water may be discharged outside the system as appropriate. Thereafter, the reducing gas (residual hydrogen) that has passed through the reactor 4c is supplied to the reactor (third second reactor) 4d via the gas line GL4c, the gas line GL5d, and the gas line GL3d, and the reducing gas (water) that has passed through it can be discharged via the gas line GL4d. In this case, too, the generated water may be discharged to the outside of the system by a water removal mechanism provided in the middle of the gas line GL5d.

[0088] Next, in the second turn shown in FIG. 4(II), exhaust gas is supplied to and passed through the reactor (first reactor) 4b, while reducing gas is continuously supplied to and passed through the reactors (second reactors) 4c, 4d, and 4a in this order. Next, in the third turn shown in FIG. 4(III), exhaust gas is supplied to and passed through the reactor (first reactor) 4c, while reducing gas is continuously supplied to and passed through the reactors (second reactors) 4d, 4a, and 4b in this order. Next, in the fourth turn shown in FIG. 4(IV), exhaust gas is supplied to and passed through the reactor (first reactor) 4d, while reducing gas is continuously supplied to and passed through the reactors (second reactors) 4a, 4b, and 4c in this order.

[0089] In the second embodiment, a series of operations from the first turn to the fourth turn is regarded as one cycle, and by repeating multiple cycles, it is possible to continuously and stably convert carbon dioxide to carbon monoxide. For example, when using a reducing agent 4R in which the reduction efficiency of the oxidized reducing agent 4R by hydrogen (reducing substance) is lower than the conversion efficiency of carbon dioxide to carbon monoxide, if the reducing gas is passed through one reactor only once, the hydrogen (residual hydrogen) that was not used in the reduction of the oxidized reducing agent 4R will be wasted. In contrast, in this embodiment, the reducing gas can be passed through three reactors in succession, in other words, it can be passed through one reactor three times. This makes it possible to prevent hydrogen (reducing gas) from being wasted.

[0090] In addition, by using three or more reactors, it is possible to provide a reactor that does not allow exhaust gas and reducing gas to pass through. Therefore, while continuing normal operation to produce product gas (carbon monoxide), other operations can be performed on the reactor that is not being used for normal operation. For example, when carbon dioxide is converted to carbon monoxide (carbon value), carbon may accumulate on the surface of the reducing agent 4R, decreasing the conversion efficiency. In this case, if oxygen is supplied to a reactor that is not normally used, the carbon accumulated on the surface of the reducing agent 4R can be removed by combustion, and the reducing agent 4R can be regenerated.

[0091] In this case, the reactor may be purged with an inert gas (e.g., nitrogen gas) before and after supplying oxygen to the reactor, thereby preventing the reducing gas and oxygen from accidentally coming into contact with each other and causing an explosive reaction. 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.

[0092] (Third embodiment of gas production system) In the gas production systems of the first and second embodiments, the oxygen carrier having the metal compound containing the other elements described above is used as the reducing agent 4R. However, instead of this, the following aspect can be adopted. The process for producing the generated gas in the third embodiment will be described below, focusing on the differences from the first and second embodiments, and a description of the similarities will be omitted.

[0093] That is, as the reducing agent 4R to be accommodated in each reactor (reactor 4ab, etc.), an oxygen carrier precursor containing a metal element may be selected, and a raw material gas containing a compound containing an element other than oxygen element (other element) belonging to Groups 14 to 17 and Periods 2 to 5 may be brought into contact with this oxygen carrier precursor. In this case, a product gas can be obtained while adding an element other than oxygen (other element) belonging to Groups 14 to 17 and Periods 2 to 5 to the oxygen carrier precursor.

[0094] In other words, in the first and second embodiments, the oxygen carrier having a metal compound containing other elements is prepared in advance, but in the third embodiment, the introduction of other elements is performed within the gas production system. This configuration also makes it possible to realize a reducing agent 4R with improved reaction efficiency.

[0095] In addition, the oxygen carrier precursor in the third embodiment may be a metal oxide containing a metal element and an oxygen element. On the other hand, this oxygen carrier precursor may be a metal element or an alloy that does not substantially contain an oxygen element. Even if the metal element or alloy does not substantially contain an oxygen element, the raw material gas that is contacted has an oxidation function, so that it is possible to convert it into the target oxygen carrier.

[0096] The source gas containing the compound containing the other element may be used continuously throughout the entire operation time of the gas production system, or may be used only at the beginning of the operation of the gas production system. In addition, a mode in which the source gas containing the compound containing the other element is intermittently used during the operation of the gas production system while monitoring the composition of the generated gas, etc., may also be adopted. When a compound containing another element is contained in the source gas, the type and amount of the compound may be appropriately selected depending on the type of source gas and the process design.

[0097] After the product gas is obtained in this manner, a gas having reducing properties can be brought into contact with an oxygen carrier, and then the gas can be brought into contact with a raw material gas (oxidizing gas) to obtain carbon valuables, as in each of the above-mentioned embodiments, and a gas having reducing properties can be brought into contact with an oxygen carrier before the product gas is obtained.

[0098] Furthermore, it may be provided in the following aspects: The oxygen carrier, wherein the metal element contained in the cation moiety is a transition metal element. The oxygen carrier, wherein the other element contains at least one element belonging to Groups 15 and 16. The oxygen carrier produces water by contacting with hydrogen, and produces carbon values ​​by contacting the reduced oxygen carrier with carbon dioxide. The oxygen carrier, wherein the content of the other element contained in the metal compound is 0.001 mass % or more. The oxygen carrier, wherein the content of the other element contained in the metal compound is 10 mass % or less. A method for producing the oxygen carrier, comprising the step of heating an elemental metal, alloy or metal oxide containing the metal element while contacting it with a compound containing the other element. In the method for producing the oxygen carrier, the heating step is a step of heating the metal, the alloy or the metal oxide while contacting it with a gas containing the compound containing the other element. A method for producing a gas, comprising a step of contacting the oxygen carrier or the oxygen carrier obtained by the method for producing an oxygen carrier with a raw material gas to obtain a product gas. The method for producing the gas comprises a step of contacting a gas having reducing properties with the oxygen carrier before or after the step of obtaining a product gas. A gas production method comprising the steps of: preparing an oxygen carrier precursor containing a metal element; and a raw material gas containing a compound containing an element other than oxygen element belonging to Groups 14 to 17 and Periods 2 to 5; and contacting the oxygen carrier precursor with the raw material gas to obtain a product gas while imparting the element other than oxygen element belonging to Groups 14 to 17 and Periods 2 to 5 to the oxygen carrier precursor. The method for producing the gas comprises a step of contacting a gas having reducing properties with the oxygen carrier before or after the step of obtaining a product gas. A gas production apparatus comprising a reactor, the oxygen carrier being accommodated in the reactor. Of course, this is not the case.

[0099] 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.

[0100] 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. In each of the above embodiments, the metal compound functions as a reducing agent that reduces carbon dioxide, but the metal compound can also function as a catalyst that promotes the reaction between carbon dioxide and a reducing substance. In this case, the catalyst is accommodated in a reactor, and exhaust gas and a reducing gas are simultaneously supplied to the reactor to carry out the reverse water gas shift reaction.

[0101] In addition, in each of the above embodiments, a gas containing hydrogen has been described as a representative reducing gas, but 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. In addition, in the first embodiment, the number of reactors connected in series may be three or more, and in the second embodiment, the number of reactors in series used as the second reactor (reactors on the reduction side that reduce the reducing agent 4R) may be two or four or more. Furthermore, the present invention is not limited to the above-described embodiments, and the number of reactors used for gas production may be one. EXAMPLES

[0102] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0103] <Preparation of oxygen carrier (reducing agent)> The oxygen carrier (reducing agent) used in this example was prepared as follows.

[0104] (Example 1-1: CeO2_La2S3-3wt%) First, 1.94 g of cerium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.06 g of lanthanum sulfide (manufactured by Kojundo Chemical Laboratory Co., Ltd.) were weighed as precursors of the reducing agent and mixed in a crucible. The mixture was heated to 450°C over 1 hour, held at 450°C for 4 hours, then heated to 950°C over 1 hour, and fired at 950°C for 8 hours. Finally, the fired mass was mechanically pulverized to obtain the target reducing agent. The reducing agent was granular.

[0105] (Example 1-2: CeO2_La2S3-5wt%) A reducing agent was produced in the same manner as in Example 1-1, except that 1.90 g of cerium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.10 g of lanthanum sulfide (manufactured by Kojundo Chemical Laboratory Co., Ltd.) were weighed as precursors of the reducing agent. The reducing agent was in granular form.

[0106] (Comparative Example 1: CeO2) First, 2.00 g of cerium oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was heated to 450°C over 1 hour, held at 450°C for 4 hours, then heated to 950°C over 1 hour, and held at 950°C for 8 hours. Finally, the fired mass was mechanically pulverized to obtain the target reducing agent. The reducing agent was in granular form.

[0107] (Example 2: Ce 0.9 Zr 0.1 O2_La2S3-5wt%) First, 0.32 g of zirconium(II) oxynitrate dihydrate (Kishida Chemical Co., Ltd., purity: 99.0%) and 4.67 g of cerium(III) nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%) were weighed out as precursors of the reducing agent. Next, 5.03 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%) was weighed and dissolved in 100 mL of deionized water to obtain an aqueous citric acid solution. After that, the precursor (metal nitrate salt) was added to the aqueous citric acid solution at 65° C. while stirring. After 30 minutes had passed, 1.78 g of ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%) was added to the aqueous citric acid solution, and the temperature was raised to 80° C. The molar ratio of metal:citric acid:ethylene glycol was 1:2:1.2. The temperature was maintained at 80°C with continuous stirring until a viscous gel was formed. The gel was then transferred to a drying oven. The gel was dried at 120°C for 8 hours. The resulting swollen mass of organic and inorganic compounds was crushed and calcined by increasing the temperature to 450°C over 1 hour, holding at 450°C for 4 hours, then increasing the temperature to 950°C over 1 hour, and holding at 950°C for 8 hours. Finally, the calcined mass was mechanically crushed to obtain metal oxides. 1.90 g of the obtained metal oxide and 0.10 g of lanthanum sulfide (manufactured by Kojundo Chemical Laboratory Co., Ltd.) were weighed and mixed in a crucible. The mixture was heated to 450°C over 1 hour, held at 450°C for 4 hours, then heated to 950°C over 1 hour, and fired at 950°C for 8 hours. Finally, the fired mass was mechanically crushed into fine particles to obtain the target reducing agent. The reducing agent was granular.

[0108] (Comparative example 2: Ce 0.9 Zr 0.1 O2) The target metal oxide was obtained in the same manner as in Example 2, except that lanthanum sulfide was not added.

[0109] (Example 3: Ce 0.9 Zr 0.1 After O2_S gas reaction) Ce, a precursor of the reducing agent, was added to the fixed-bed flow-type reactor. 0.9 Zr 0.1 The reactor was then filled with O2. After that, the reactor was heated to 850°C, H2 gas was introduced, and then CO2 gas mixed with 1% H2S was introduced. This cycle was repeated 20 times or more. After cooling to room temperature, the target reducing agent was obtained.

[0110] (Comparative example 3: Ce 0.9 Zr 0.1 O2) The target metal oxide was obtained in the same manner as in Comparative Example 2.

[0111] For each of the oxygen carriers (reducing agents) obtained above, the amount of sulfur (sulfur element) contained therein is quantified using the following device and method. 1: Equipment ICP-AES: Agilent Technologies Agilent 5110 VDV Microwave digestion equipment: Anton Paar MultiWave3000 2: Method The acid and the sample were placed in a decomposition vessel, which was then sealed, and the sample was decomposed by heating using microwaves. The volume was then adjusted with ultrapure water to obtain the test solution. The quantitative analysis of S in the sample was then performed using ICP-AES (standard addition method).

[0112] The sulfur content of each oxygen carrier is shown in Table 1 below.

[0113] [Table 1]

[0114] <Evaluation of oxygen carriers (reducing agents)> The performance of the obtained oxygen carrier (reducing agent) was evaluated based on its reactivity with hydrogen and carbon dioxide.

[0115] (Reactivity with hydrogen (1)) Thermogravimetry (TG) was carried out for each oxygen carrier (reducing agent) under a hydrogen atmosphere. The specific procedure is as follows. First, 50 to 100 mg of each oxygen carrier was loaded onto the sample stage in the reactor. Next, helium gas was passed through the sample at a flow rate of 50 mL / min for 5 minutes, and then hydrogen gas was passed through the sample at a flow rate of 50 mL / min, and the sample was heated from room temperature to 900°C. The mass change rate was measured in the range of 400°C to 900°C. The heating rate during the thermogravimetric measurement was 10°C / min. The evaluation was performed based on the amount of change when the mass at room temperature was taken as 100%, and Examples 1-1 and 1-2 were shown as relative values ​​when the amount of change in Comparative Example 1 was taken as "1." Moreover, Example 2 was shown as a relative value when the amount of change in Comparative Example 2 was taken as "1." The results of the mass change rate are shown in Table 2.

[0116] (Reactivity with carbon dioxide (1)) The measurements were carried out using a rapid catalyst evaluation system equipped with a fixed-bed flow reactor and a gas chromatograph mass spectrometer (GC / MS) directly connected to the reactor. Specifically, a quartz reaction tube with an inner diameter of 4 mm was prepared and filled with cylindrical oxygen carriers molded to a major axis of 3 mm so that the stack height was 30 mm. After that, while flowing helium gas at a flow rate of 20 mL / min, the temperature was increased to 850°C at a heating rate of 40°C / min, and the tube was heated at the same temperature for 20 minutes. Next, in order to activate the oxygen carrier, hydrogen gas (reducing gas) was flowed at a flow rate of 20 mL / min for 5 minutes to carry out a reduction reaction (first process) of the oxygen carrier, thereby reducing the oxygen carrier. At this time, the gas discharged from the outlet contained water vapor. After that, for gas exchange, helium gas was flowed at a flow rate of 20 mL / min for 5 minutes, and then carbon dioxide gas was flowed at a flow rate of 20 mL / min for 5 minutes to carry out a reduction reaction (second process) of carbon dioxide, thereby reducing the carbon dioxide gas (raw material gas). At this time, the product gas discharged from the outlet contained carbon monoxide. Next, the following process was carried out for this test. First, for gas exchange, helium gas was flowed at a flow rate of 20 mL / min for 5 minutes. Next, hydrogen gas (reducing gas) was flowed at a flow rate of 3 mL / min for 4 minutes to carry out a reduction reaction of the reducing agent (first process) and reduce the reducing agent. At this time, the gas discharged from the exhaust port contained water vapor. After that, for gas exchange, helium gas was flowed at a flow rate of 3 mL / min for 5 minutes, and then carbon dioxide gas was flowed at a flow rate of 3 mL / min for 4 minutes to carry out a reduction reaction of carbon dioxide (second process) and reduce the carbon dioxide gas (raw material gas). At this time, the product gas discharged from the exhaust port contained carbon monoxide. In the above process, the temperature of the oxygen carrier was maintained at 850° C. and the process was carried out under atmospheric pressure conditions when any of the gases was flowing. The reaction rate of carbon dioxide by the oxygen carrier was calculated as the molar amount (mmol) of carbon monoxide produced when carbon dioxide gas was flowing divided by the weight (g) of the filled oxygen carrier (mmol / g). The results of the amount of carbon monoxide produced are shown in Table 2. The amounts of carbon monoxide produced in Examples 1-1 and 1-2 are shown as relative values ​​when the amount produced in Comparative Example 1 is set to "1." The amount of carbon monoxide produced in Example 2 is shown as a relative value when the amount produced in Comparative Example 2 is set to "1."

[0117] [Table 2]

[0118] (Reactivity with hydrogen (2)) Thermogravimetry (TG) was carried out under a hydrogen atmosphere for the oxygen carriers (reducing agents) of Example 3 and Comparative Example 3. The specific procedure was as follows. First, 50 to 100 mg of each oxygen carrier was loaded onto the sample stage in the reactor. Next, helium gas was passed through the sample at a flow rate of 50 mL / min for 5 minutes, and then hydrogen gas was passed through the sample at a flow rate of 50 mL / min, and the sample was heated from room temperature to 900°C. The mass change rate was measured in the range of 400°C to 700°C. The heating rate during the thermogravimetric measurement was 10°C / min. The evaluation was performed based on the amount of change when the mass at room temperature was taken as 100%, and the amount of change in Example 3 was shown as a relative value when the amount of change in Comparative Example 3 was taken as "1".

[0119] (Reactivity with carbon dioxide (2)) The measurements were carried out using a rapid catalyst evaluation system equipped with a fixed-bed flow reactor and a gas chromatograph mass spectrometer (GC / MS) directly connected to the reactor. Specifically, a quartz reaction tube with an inner diameter of 4 mm was prepared and filled with cylindrical oxygen carriers molded to a major axis of 3 mm so that the stack height was 30 mm. After that, while flowing helium gas at a flow rate of 20 mL / min, the temperature was raised to 700°C at a heating rate of 40°C / min and heated for 20 minutes. Next, in order to activate the oxygen carrier, hydrogen gas (reducing gas) was flowed at a flow rate of 20 mL / min for 5 minutes to carry out a reduction reaction (first process) of the oxygen carrier, thereby reducing the oxygen carrier. At this time, the gas discharged from the outlet contained water vapor. After that, for gas exchange, helium gas was flowed at a flow rate of 20 mL / min for 5 minutes, and then carbon dioxide gas was flowed at a flow rate of 20 mL / min for 5 minutes to carry out a reduction reaction (second process) of carbon dioxide, thereby reducing the carbon dioxide gas (raw material gas). At this time, the product gas discharged from the outlet contained carbon monoxide. Next, the following process was carried out for this test. First, for gas exchange, helium gas was flowed at a flow rate of 20 mL / min for 5 minutes. Next, hydrogen gas (reducing gas) was flowed at a flow rate of 3 mL / min for 4 minutes to carry out a reduction reaction of the reducing agent (first process) and reduce the reducing agent. At this time, the gas discharged from the exhaust port contained water vapor. After that, for gas exchange, helium gas was flowed at a flow rate of 3 mL / min for 5 minutes, and then carbon dioxide gas was flowed at a flow rate of 3 mL / min for 4 minutes to carry out a reduction reaction of carbon dioxide (second process) and reduce the carbon dioxide gas (raw material gas). At this time, the product gas discharged from the exhaust port contained carbon monoxide. In the above process, the temperature of the oxygen carrier was maintained at 700° C. and the process was carried out under atmospheric pressure conditions when any of the gases was flowing. The reaction rate of carbon dioxide by the oxygen carrier was calculated as the molar amount (mmol) of carbon monoxide produced when carbon dioxide gas was flowing divided by the weight (g) of the filled oxygen carrier (mmol / g). The results of the amount of carbon monoxide produced are shown in Table 3. The amounts of carbon monoxide produced in each Example 3 are shown as relative values ​​when the amount produced in Comparative Example 3 is set as "1".

[0120] [Table 3]

[0121] From the above results, it is understood that the reaction efficiency during reduction and oxidation reactions is improved by introducing other elements such as sulfur into the oxygen carrier (reducing agent). [Explanation of symbols]

[0122] 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 4c: Reactor 4d: Reactor 41a: Reactor 41b: Reactor 42a: Reactor 42b: 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 20: Furnace 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: Gas line GL5b: Gas line GL5c: Gas Line GL5d: Gas Line J4: Gas junction

Claims

1. An oxygen carrier having a metal compound, The metal compound has a cation portion and an anion portion, The cation moiety contains at least a metal element, The anion portion contains at least an oxygen element, At least one of the cation moiety and the anion moiety contains an element different from the metal element and the oxygen element, The oxygen carrier, wherein the other element is an element belonging to Groups 14 to 17 and Periods 2 to 5.

2. 2. The oxygen carrier of claim 1, The oxygen carrier, wherein the metal element contained in the cation moiety is a transition metal element.

3. The oxygen carrier according to claim 1 or 2, An oxygen carrier, wherein the other element contains at least one element belonging to Groups 15 and 16.

4. The oxygen carrier according to any one of claims 1 to 3, An oxygen carrier that produces water upon contact with hydrogen and produces carbon values ​​upon contact of the reduced oxygen carrier with carbon dioxide.

5. The oxygen carrier according to any one of claims 1 to 4, An oxygen carrier, wherein the content of the other element contained in the metal compound is 0.001 mass % or more.

6. The oxygen carrier according to any one of claims 1 to 5, An oxygen carrier, wherein the content of the other element contained in the metal compound is 10 mass % or less.

7. A method for producing the oxygen carrier according to any one of claims 1 to 6, comprising the steps of: A method comprising the step of heating an elemental metal, alloy or metal oxide containing the metallic element while contacting it with a compound containing the other element.

8. The method for producing an oxygen carrier according to claim 7, The method, wherein the heating step is a step of heating the metal, the alloy, or the metal oxide while contacting it with a gas containing the compound containing the other element.

9. A method for producing a gas, comprising the steps of: A method comprising a step of contacting an oxygen carrier according to any one of claims 1 to 6 or an oxygen carrier obtained by the method for producing an oxygen carrier according to claim 7 or claim 8 with a raw material gas to obtain a product gas.

10. The method for producing a gas according to claim 9, The method comprises a step of contacting a gas having reducing properties with the oxygen carrier before or after the step of obtaining a product gas.

11. A method for producing a gas, comprising the steps of: A step of preparing an oxygen carrier precursor containing a metal element and a raw material gas containing a compound containing an element other than oxygen element that belongs to Groups 14 to 17 and Periods 2 to 5; The method includes a step of contacting the oxygen carrier precursor with the raw material gas to obtain a product gas while providing the element other than oxygen element belonging to Groups 14 to 17 and Periods 2 to 5 to the oxygen carrier precursor.

12. The method for producing a gas according to claim 11, The method comprises a step of contacting a gas having reducing properties with the oxygen carrier before or after the step of obtaining a product gas.

13. A gas production apparatus including a reactor, A gas production apparatus comprising the oxygen carrier according to claim 1 housed in the reactor.

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