WO2023120504A1 - Oxygen carrier, method for producing oxygen carrier, method for producing gas, and gas production device - Google Patents

Abstract

[Problem] To provide, inter alia, an oxygen carrier capable of efficiently producing a valuable carbon substance using a feedstock gas that contains carbon dioxide and a reducing gas that contains a reducing substance. [Solution] According to one embodiment of the present invention, an oxygen carrier having a metal compound is provided. The metal compound in this oxygen carrier has a cationic moiety and an anionic moiety. The cationic moiety contains at least a metal element. The anionic moiety contains at least an oxygen element. The cationic moiety and/or anionic moiety contain(s) another element different from the metal element and oxygen element. The other element belongs to groups 14-17 and periods 2-5.

Description

Oxygen carrier, method for producing oxygen carrier, method for producing gas, and gas production apparatus

The present invention relates to an oxygen carrier, an oxygen carrier manufacturing method, a gas manufacturing method, and a gas manufacturing apparatus.

In recent years, the atmospheric concentration of carbon dioxide (CO ₂ ), which is a kind of greenhouse gas, continues to rise. Rising concentrations of carbon dioxide in the atmosphere contribute to global warming. Therefore, it is important to recover the carbon dioxide released into the atmosphere, and if the recovered carbon dioxide can be converted into carbon valuables and reused, a carbon recycling society can be realized.
Also, as a global measure, as stated in the Kyoto Protocol of the United Nations Framework Convention on Climate Change, the reduction rate of carbon dioxide, which causes global warming, in developed countries based on 1990 as a standard It is stipulated that we will jointly achieve the reduction target value within the commitment period.

In order to achieve the reduction target, exhaust gas containing carbon dioxide generated from steel mills, smelters or thermal power plants is also targeted, and various technological improvements have been made regarding the reduction of carbon dioxide in these industries. ing. One example of such technology is _CO2 capture and storage (CCS). However, this technique has a physical limit of storage and is not a fundamental solution.
For example, Patent Literature 1 discloses a carbon dioxide reduction system comprising a chemical looping reactor. This chemical looping type reactor has two reactors filled with a metal oxide catalyst, one reactor for the first reaction of reducing carbon dioxide to carbon monoxide, and the other reactor for the reduction of carbon dioxide to carbon monoxide. A second reaction that oxidizes hydrogen to water takes place in the vessel.

International Publication No. 2019/163968 Pamphlet

However, there is still room for further improvement in industrially producing carbon monoxide (a carbon valuable product) from carbon dioxide more efficiently.
In view of the above circumstances, the present invention provides an oxygen carrier or the like that can efficiently produce carbon valuables by using a raw material gas containing carbon dioxide and a reducing gas containing a reducing substance.

According to one aspect of the present invention, an oxygen carrier having a metal compound is provided. The metal compound in this oxygen carrier has a cation portion and an anion portion. The cation part contains at least a metal element. The anion part contains at least an oxygen element. At least one of the cation portion and the anion portion contains an element different from the metal element and the oxygen element. Other elements are elements belonging to groups 14 to 17 and periods 2 to 5.

According to this aspect, it is possible to efficiently produce carbon valuables by using a raw material gas containing carbon dioxide and a reducing gas containing a reducing substance.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic which shows the whole structure of the gas manufacturing system using the gas manufacturing apparatus concerning this embodiment. It is a schematic diagram showing the configuration of the reaction section of the first embodiment. It is a schematic diagram showing the configuration of the reaction section of the second embodiment. FIG. 4 is a schematic diagram showing a method of switching gases to be passed through the reactor in the second embodiment;

Hereinafter, the present invention will be described in detail based on suitable embodiments shown in the accompanying drawings.

<Oxygen carrier>
First, the oxygen carrier of this embodiment will be described. The oxygen carrier of this embodiment is shown below.
An oxygen carrier comprising a metal compound,
The metal compound has a cation portion and an anion portion,
The cation portion contains at least a metal element,
The anion portion contains at least an oxygen element,
At least one of the cation part or the anion part contains another 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.

The oxygen carrier of the present embodiment contains a metal compound, and is typically reduced by a reduction reaction of a gas such as carbon dioxide (a carbon dioxide such as carbon monoxide is produced by contacting the reduced oxygen carrier with carbon dioxide). reaction to produce valuable substances) and oxidation reaction of gases such as hydrogen (reaction to produce water by contact with hydrogen). That is, since this metal compound functions as a carrier of oxygen, the above reduction reaction and oxidation reaction can proceed.

The metal compound described above has a cation part and an anion part, and the cation part has at least a metal element. This metal element can be selected as appropriate, but as an example, the metal element contained in the cation portion may be a transition metal element.
In addition, the metal element contained in the cation portion may contain at least one selected from metal elements belonging to Groups 3 to 12, and may be selected from metal elements belonging to Groups 4 to 12. may contain at least one of
In addition, the metal element contained in the cation portion contains at least one of indium, lanthanum, aluminum, titanium, vanadium, zirconium, iron, copper, zinc, nickel, manganese, chromium, cobalt, niobium and cerium. may

Moreover, this metal element may be appropriately selected according to the process in which the oxygen carrier is applied.
In particular, when an oxygen carrier is used in the process of converting carbon dioxide into carbon monoxide, the metal element preferably contains iron, cerium, or the like. If an oxygen carrier is used in the process of converting carbon dioxide to methane, this metallic element preferably contains at least one of nickel and ruthenium. When an oxygen carrier is used in the process of converting carbon dioxide to methanol, this metallic element preferably contains at least one of copper and zinc.

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 into carbon monoxide and hydrogen into water. It can be through emission or absorption.

In addition, the metal compound contained in the oxygen carrier of the present embodiment contains other elements different from the aforementioned metal element and oxygen element. Here, the other elements belong to Groups 14 to 17 and also belong to Periods 2 to 5.
Group 14 elements selected from carbon, silicon, germanium and tin; Group 15 elements selected from nitrogen, phosphorus, arsenic and antimony; Group 15 elements selected from sulfur, selenium and tellurium; Group 16 element; any Group 17 element selected from fluorine, chlorine, bromine and iodine.

Since the oxygen carrier of the present embodiment contains such other elements in the metal compound, the efficiency of various reactions is improved. The reason for this is not necessarily limited to the following, but the oxygen carrier subjected to the oxidation reaction or the reduction reaction has a non-stoichiometric compound composition (typically, relative to the metal element It can be a composition in which the oxygen element is deficient, or a composition in which the metal element is deficient with respect to the oxygen element). At that time, it is presumed that the presence of other elements in the oxygen carrier makes it easier to compensate for the deficiencies in the composition of the non-stoichiometric compound, thereby improving the efficiency of various reactions.

In addition, other elements may be selected according to the reaction to be performed. In the metal compound, the other elements may constitute part of the cation part, good too.

Among the above, the other element preferably contains at least one element belonging to Groups 15 and 16, and more preferably contains at least one element belonging to Group 16. .

The content of other elements can be appropriately selected depending on the purpose etc. As an example, the content of other elements is the content of other elements with respect to the metal compound (all constituent elements of the metal compound) 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 more preferably 0.01% by mass or more and 5% by mass or less . By setting the content of other elements within such a range, it becomes easier to contribute to the improvement of the intended reaction efficiency.

Moreover, such a metal compound can be obtained, for example, by heating a metal element, alloy, or metal oxide containing a metal element and a compound containing another element while bringing them into contact with each other. The compound containing other elements may be solid, liquid, or gas when brought into contact.
By heating the raw material containing the metal element and the compound containing the other element in contact with each other in this way, the other element is taken into the raw material, and the metal compound of the present 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 the oxygen element in the resulting metal compound.

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

The heating temperature for obtaining the metal compound can be appropriately set according to the metal compound to be produced. For example, the heating temperature is preferably 200° C. or higher and 1600° C. or lower, more preferably 350° C. or higher and 1400° C. or lower, and even more preferably 500° C. or higher and 1200° C. or lower. By setting such a temperature range, efficient compound conversion can be performed while controlling the energy to be used.

Note that the oxygen carrier of the present embodiment may be one in which a metal compound is supported on a carrier.
As _a constituent material of the carrier, a material that is difficult to be modified by contact with the exhaust gas (raw material gas), reaction conditions, etc. is preferable. Examples include oxides such as ZrO ₂ , TiO ₂ , V ₂ O ₅ , MgO, CeO ₂ , Al ₂ O ₃ and SiO ₂ and composite oxides containing these.

Among these, zeolite, montmorillonite, ZrO ₂ , TiO ₂ , V ₂ O ₅ , MgO, Al ₂ O ₃ , SiO ₂ and composite oxides containing these are preferable as the constituent material of the carrier. A carrier composed of such a material is preferable because it does not adversely affect the oxidation reaction or the reduction reaction and is excellent in supporting the metal compound.
In addition, in the oxygen carrier of the present embodiment, at least a part of the surface of the carrier may be coated with the aforementioned metal compound.

<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.

(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 this embodiment. FIG. 2 is a schematic diagram showing the configuration of the reaction section of the first embodiment.
A gas production system 100 shown in FIG. 1 includes a furnace 20 that generates an exhaust gas (raw material gas) containing carbon dioxide, and a gas production device 1 connected to the furnace 20 via a connector 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 simply referred to as the "downstream side". Moreover, each component provided in the present gas production system is not necessarily required to be installed, and may be appropriately omitted or replaced according to the process to be constructed.

The furnace 20 is not particularly limited, but is, for example, a furnace attached to an ironworks, a refinery, or a thermal power plant, preferably a combustion furnace, a blast furnace, a converter, or the like. In the furnace 20, exhaust gas is produced (generated) during combustion, melting, refining, and the like of the contents.
In the case of a combustion furnace (incinerator) in a garbage incineration plant, the contents (waste) include, for example, plastic waste, garbage, municipal waste (MSW), waste tires, biomass waste, household waste (bedding , paper), building materials, and the like. In addition, these wastes may contain 1 type independently, or may contain 2 or more types.

Exhaust gases typically contain, in addition to carbon dioxide, other gas components such as nitrogen, oxygen, carbon monoxide, water vapor, methane, and the like. 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% by volume or more, more preferably 5% by volume or more.
Exhaust gas from a combustion furnace in a garbage incineration plant contains 5-15% by volume of carbon dioxide, 60-70% by volume of nitrogen, 5-10% by volume of oxygen, and 15-25% by volume of water vapor.

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% by volume of carbon dioxide, 55 to 60% by volume of nitrogen, and 25 to 30% by volume of carbon monoxide. , containing 1 to 5% by volume of hydrogen.
In addition, the exhaust gas from the converter (converter gas) is a gas generated when steel is produced in the converter, and contains 15 to 20 volume% carbon dioxide, 50 to 60 volume% carbon monoxide, and nitrogen. It contains 15 to 25% by volume and 1 to 5% by volume of hydrogen.
The raw material gas is not limited to the exhaust gas, and a pure gas containing 100% by volume of carbon dioxide may be used.

However, if exhaust gas is used as the raw material gas, carbon dioxide, which has conventionally been discharged into the atmosphere, can be effectively used, and the burden on the environment can be reduced. Among these, from the viewpoint of carbon circulation, exhaust gas containing carbon dioxide generated in ironworks or smelters is preferable.
In addition, as the blast furnace gas and the converter gas, the untreated gas discharged from the furnace may be used as it is. good. The untreated blast furnace gas and the converter gas have gas compositions as described above, and the treated gas has a gas composition close to that shown for the exhaust gas from the combustion furnace. In this specification, all of the above gases (the gases before being supplied to the gas production apparatus 1) are called exhaust gas.

In the gas production apparatus 1, the exhaust gas (raw material gas containing carbon dioxide) discharged from the furnace 20 and supplied via the connection part 2 is brought into contact with a reducing agent 4R that reduces the carbon dioxide contained in the exhaust gas. , to produce a product gas (syngas) containing carbon monoxide.
In this specification, carbon monoxide will be described as a representative example of the carbon valuables. However, carbon valuables are not limited to carbon monoxide, and include, for example, methane, methanol and the like, and they may be used alone or in combination of two or more. Depending on the type of reducing agent, which will be described later, the type of carbon valuables produced will differ.

The gas production apparatus 1 mainly includes a connection section 2, a reducing gas supply section 3, and four reactors 41a, 42a, 41b, and 42b (hereinafter collectively referred to as "reactor 4ab"). a gas line GL1 connecting the connecting portion 2 and the reaction portion 4; a gas line GL2 connecting the reducing gas supply portion 3 and the reaction portion 4; and a gas line connected to the reaction portion 4. GL4.
In this embodiment, the connection part 2 constitutes an exhaust gas supply part (raw material gas supply part) that supplies the exhaust gas to the reaction part 4 .
In addition, if necessary, a pump for transferring gas may be arranged at a predetermined position in the middle of the gas line GL1, the gas line GL2, and the gas line GL4. For example, when the pressure of the exhaust gas is adjusted to be relatively low in the compression unit 6, which will be described later, the gas can be smoothly transferred within the gas production apparatus 1 by arranging a pump.

Gas line GL1 is connected to connecting portion 2 at one end thereof. On the other hand, the other end of the gas line GL1, as shown in FIG. It is connected.
With such a configuration, the exhaust gas supplied from the furnace 20 through the connecting portion 2 passes through the gas line GL1 and is supplied to the reactors 41a and 41b.
The gas switching unit 8 can be configured to include, for example, a branch gas line and a channel opening/closing mechanism such as a valve provided in the middle of the branch gas line.

As shown in FIG. 2, each reactor 4ab is a multi-tubular reaction device ( fixed bed type reactor). According to such a multi-tubular reactor, it is possible to ensure sufficient opportunities for contact between the reducing agent 4R and the exhaust gas and reducing gas. As a result, the production efficiency of the product gas can be enhanced.

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

The reducing agent 4R of the present embodiment is preferably in the form of particles (granules), scales, pellets, or the like, for example. With such a shape of the reducing agent 4R, the filling efficiency into the tubular body 41 can be enhanced, and the contact area with the gas supplied into the tubular body 41 can be further increased.

When the reducing agent 4R is particulate, its volume average particle diameter is not particularly limited, but is preferably 1 to 50 mm, 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, the 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 tumbling granulation because the sphericity is increased.

Here, in each reactor 4ab, the tubular body (cylindrical molded body) 41 may be produced from the reducing agent 4R itself. Furthermore, a block-like or lattice-like (for example, net-like or honeycomb-like) molded body may be produced from the reducing agent 4R and arranged in the housing 42 .

Among these, a configuration in which a net-like body is formed from the reducing agent 4R and arranged in the housing 42 is preferable. In the case of such a configuration, it is possible to prevent the passage resistance of the exhaust gas and the reducing gas from increasing in each reactor 4ab, and to ensure sufficient opportunities for contact between the reducing agent 4R and the exhaust gas and the reducing gas.
The volumes of the four reactors 41a, 42a, 41b, and 42b are set substantially 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 apparatus 1). Also, the volume of at least one of the four reactors 41a, 42a, 41b, 42b may be varied according to the types of exhaust gas and reducing gas.

A concentration adjusting section 5, a compressing section 6, a minor component removing section 7, and an exhaust gas heating section (source gas heating section) 10 are provided in this order from the connecting section 2 side in the middle of the gas line GL1.
The concentration adjustment unit 5 adjusts so as to increase the concentration of carbon dioxide contained in the exhaust gas (in other words, concentrate the 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 adjustment unit 5, the concentration of unnecessary gas components contained in the exhaust gas can be relatively reduced. Therefore, it is possible to prevent or suppress the adverse effect of the unnecessary gas component on the conversion efficiency of carbon dioxide to carbon monoxide by the reducing agent 4R.

It is preferable that the concentration adjustment unit 5 is configured by an oxygen removal device that removes oxygen contained in the exhaust gas. As a result, the amount of oxygen brought into the gas production apparatus 1 can be reduced (that is, the concentration of oxygen contained in the exhaust gas can be adjusted to be low). For this reason, the gas composition of the exhaust gas can be deviated from the explosion range, and ignition of the exhaust gas can be prevented. Among the gas producing apparatus 1, the oxygen removal apparatus consumes a large amount of electric energy, so it is effective to use electric power as renewable energy as described later.

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 less than 0.1% by volume with respect to the entire exhaust gas. Adjusting is even more preferable. Thereby, ignition of exhaust gas can be prevented more reliably.
Oxygen removal equipment for removing oxygen contained in flue gas includes cryogenic (cryogenic) separators, pressure swing adsorption (PSA) separators, membrane separation separators, and temperature swing adsorption (TSA) separators. It can be configured using one or more of a separator of the type, a separator of the chemical absorption type, a separator of the chemisorption type, and the like.
Note that the concentration adjustment unit 5 may adjust the concentration of carbon dioxide to a high level by adding carbon dioxide to the exhaust gas.

Compressor 6 increases the pressure of the exhaust gas before it is supplied to reactor 4ab. This makes it possible to increase the amount of exhaust gas that can be processed at one time in the reactor 4ab. Therefore, the conversion efficiency of carbon dioxide to carbon monoxide in the reactor 4ab can be further improved.
The compression unit 6 includes, for example, a centrifugal compressor, a turbo compressor such as an axial compressor, a reciprocating compressor (reciprocating compressor), a diaphragm compressor, a single screw compressor, a twin screw compressor, It can be composed of a volumetric compressor such as a scroll compressor, a rotary compressor, a rotary piston compressor, a slide vane compressor, a roots blower (two-leaf blower) capable of handling low pressure, a centrifugal blower, or the like.

Among these, the compression unit 6 is preferably configured with a centrifugal compressor from the viewpoint of easiness of increasing the scale of the gas production system 100, and from the viewpoint of reducing the production cost of the gas production system 100, A reciprocating compressor is preferred.
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 0.01 to 0.5 MPaG. More preferred. 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.

The minor component removing unit 7 removes minor components (a small amount of unnecessary gas components, etc.) contained in the exhaust gas.
The fine component removing section 7 can be composed of, for example, at least one processor selected from a gas-liquid separator, a protector (guard reactor) and a scrubber (absorption tower).
When using a plurality of processors, their arrangement order is arbitrary, but when using a combination of a gas-liquid separator and a protector, it is preferable to arrange the gas-liquid separator upstream of the protector. . In this case, it is possible to further improve the efficiency of removing minor components from the exhaust gas, and extend the period of use (life) of the protector.
Although such a configuration is provided in the gas production system 100 of FIG. 1, the minor component removing section 7 can be omitted depending on the composition of the material used as the raw material.

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 and removed in the condensed water.
The gas-liquid separator can be composed of, for example, a simple container, a swirling flow separator, a centrifugal separator, a surface tension separator, or the like. Among these, the gas-liquid separator is preferably configured with a simple container because of its simple configuration and low cost. In this case, a filter may be arranged at the gas-liquid interface in the container to allow passage of gas but block passage of liquid.

Also, in this case, a liquid line may be connected to the bottom of the container, and a valve may be provided in the middle of the line. According to such a 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.
Alternatively, the liquid line may be connected to the tank to reuse the condensed water discharged.

The exhaust gas from which the condensed water has been removed by the gas-liquid separator can be configured to be supplied to the protector, for example.
Such a protector is optionally provided with a substance capable of capturing a component (inactivating component), which is a minor component contained in the exhaust gas and which reduces the activity of the reducing agent 4R upon contact with the reducing agent 4R. can also
According to this configuration, when the exhaust gas passes through the protector, the substance in the protector reacts (captures) with the inactivating component, thereby preventing or suppressing the exhaust gas from reaching the reducing agent 4R in the reactor 4ab. and protect (ie, prevent loss of activity). Therefore, it is possible to prevent or suppress an extreme decrease in the conversion efficiency of carbon dioxide to carbon monoxide by the reducing agent 4R due to the adverse effects of the inactivating component.

Such a substance includes a substance that is contained in the reducing agent 4R and has a composition that reduces the activity of the reducing agent 4R by contact with an inactivating component, specifically, a metal element contained in the reducing agent 4R and Materials that are the same as or similar to at least one of the metal oxides can be used. Here, similar metal oxides refer to metal oxides that contain the same metal element but have different compositions, or metal oxides that contain different types of metal elements but belong to the same group in the periodic table. It refers to certain metal oxides.
The above substance may be any substance whose activity is lowered by the same component as the inactivating component of the reducing agent 4R. is preferred.

The protector has a structure in which a mesh material is arranged in a housing, and particles of the above substance are placed on the mesh material. A configuration in which a molded body is arranged can be employed.
In particular, when a protector is arranged between the compression unit 6 (gas-liquid separator) and the exhaust gas heating unit 10, it is necessary to improve the removal efficiency of the inactivated components while preventing the above substances from deteriorating due to heat. can be done.

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 unit 10, the conversion (reduction) reaction of carbon dioxide to carbon monoxide by the reducing agent 4R can be further promoted in the reactor 4ab. can.
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 pipes forming the gas line GL4 for discharging the gas (mixed gas) after passing through the reactor 4ab and bringing the pipes closer to the pipes forming the gas line GL1. According to 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 heat can be effectively used. can be planned.

Such heat exchangers include, for example, jacket heat exchangers, immersion coil heat exchangers, double tube heat exchangers, shell and tube heat exchangers, plate heat exchangers, spiral heat exchangers, and the like. Can be configured.
Further, in the exhaust gas heating section 10, either one of the electric heater and the heat exchanger may be omitted.
In the exhaust gas heating section 10, a combustion furnace or the like can be used instead of the electric heater. However, if an electric heater is used, electric power (electrical energy) as renewable energy can be used as the power source, so the load on the environment can be reduced.
As renewable energy, electric energy using at least one selected from solar power, wind power, hydraulic power, wave power, tidal power, biomass power, geothermal power, solar heat and geothermal heat is used. It is possible.

Further, on the upstream side of the exhaust gas heating unit 10 (for example, between the gas-liquid separator and the protector in the middle of the minor component removing unit 7), the exhaust gas line is branched from the gas line GL1, and the gas A vent portion provided outside the manufacturing apparatus 1 may be connected.
In this case, a valve is preferably provided in the middle of the exhaust gas line.
If the pressure in the gas production device 1 (gas line GL1) rises more than necessary, the valve is opened to discharge (release) part of the exhaust gas from the vent through the exhaust gas line. be able to. As a result, it is possible to prevent the gas production device 1 from being damaged due to an increase in pressure.

One end of the gas line GL2 is connected to the reducing gas supply section 3 . On the other hand, the gas line GL2 is connected to inlet ports of reactors 41a and 41b provided in the reaction section 4 via the gas switching section 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 of the present embodiment is composed of, for example, a hydrogen generator that generates hydrogen by electrolysis of water. ) 30 are connected. With this configuration, the reducing gas containing hydrogen (reducing substance) supplied from the hydrogen generator (reducing gas supply unit 3) passes through the gas line GL2 and is supplied to each reactor 4ab.

According to the hydrogen generator, a large amount of hydrogen can be generated relatively cheaply and easily. Moreover, there is also an advantage that the condensed water generated in the gas production apparatus 1 can be reused. Among the gas production apparatus 1, the hydrogen generator consumes a large amount of electric energy, so it is effective to use electric power as renewable energy as described above.

A device that generates by-product hydrogen can also be used as the hydrogen generator. In this case, a reducing gas containing by-product hydrogen is supplied to each reactor 4ab. As a device for generating by-product hydrogen, for example, a device for electrolyzing an aqueous solution of sodium chloride, a device for steam reforming petroleum, a device for producing ammonia, and the like can be mentioned.
Alternatively, the gas line GL2 may be connected to the coke oven outside the gas production apparatus 1 via a connecting portion, and the exhaust gas from the coke oven may be used as the reducing gas. In this case, the connecting portion constitutes the reducing gas supply portion. This is because the exhaust gas from the coke oven is mainly composed of hydrogen and methane, and contains 50 to 60% by volume of hydrogen.

A reducing gas heating unit 11 is provided in the middle of 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 pre-reaction (pre-oxidation) reducing gas 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.

The reducing gas heating section 11 can be configured in the same manner as the exhaust gas heating section 10 described above. The reducing gas heating unit 11 is preferably composed of only an electric heater, only a heat exchanger, or a combination of an electric heater and a heat exchanger, and may be composed of only a heat exchanger or a combination of an electric heater and a heat exchanger. is more preferred.
If the reducing gas heating unit 11 includes a heat exchanger, the heat of the high-temperature gas (for example, mixed gas) after passing through the reactor 4ab is used to heat the reducing gas before being supplied to the reactor 4ab. Since heat is generated by exchange, effective use of heat can be achieved.

According to the above configuration, by switching the gas line (flow path) in the gas switching unit 8, for example, exhaust gas can be transferred to the reactors 41a and 42a containing the oxygen carrier before oxidation via the gas line GL3a. By supplying (such as carbon dioxide) and bringing the oxygen carrier into contact with the exhaust gas, a reduction reaction can be performed on the exhaust gas. In addition, a reducing gas (reducing gas) is supplied through the gas line GL3b to the reactors 41b and 42b containing the oxidized carriers after the generation of the product gas (carbon monoxide, etc.). By bringing the oxygen carrier into contact with a reducing gas (reducing gas), the reducing gas can undergo an oxidation reaction. The step of contacting with a reducing gas (reducing gas) may be provided before generating a product gas (such as carbon monoxide).

Further, after that, by switching the gas lines in the opposite direction to the above in the gas switching unit 8, the oxidation reaction of the reducing gas is allowed to proceed in the reactors 41a and 42a, and the reduction of the exhaust gas is performed in the reactors 41b and 42b. Allow the reaction to proceed.

The gas production device 1 includes a reducing agent heating unit (see FIG. 1 inside, not shown).
By providing such a reducing agent heating unit, the temperature in the reaction between the exhaust gas or the reducing gas and the reducing agent 4R is maintained at a high temperature, thereby suitably preventing or suppressing a decrease in the conversion efficiency of carbon dioxide to carbon monoxide. , the regeneration of the reducing agent 4R by the reducing gas can be further promoted.

When the reaction to be performed is an exothermic reaction, the gas production device 1 preferably has a reducing agent cooling section for cooling the reducing agent 4R instead of the reducing agent heating section. By providing such a reducing agent cooling unit, deterioration of the reducing agent 4R during the reaction between the exhaust gas or the reducing gas and the reducing agent 4R can be suitably prevented, and the conversion efficiency of carbon dioxide to carbon monoxide can be improved. It is possible to suitably prevent or suppress the decrease and further promote the regeneration of the reducing agent 4R by the reducing gas.
In other words, it is preferable to provide the gas production device 1 with a reducing agent temperature control unit that adjusts the temperature of the reducing agent 4R depending on the type of the reducing agent 4R (exothermic reaction or endothermic reaction).

Gas lines GL4a and GL4b are connected to the outlet ports of the reactors 42a and 42b, respectively, and are merged at a gas junction J4 to form a gas line GL4. In addition, valves (not shown in FIG. 2) are provided in the middle of the gas lines GL4a and GL4b, respectively, as required.
For example, by adjusting the opening degree of the valve, the passage speed of the exhaust gas and the reducing gas passing through the reactor 4ab (that is, the processing speed of the exhaust gas with the reducing agent 4R and the processing speed of the reducing agent 4R with the reducing gas) are set. be able to.
In this embodiment, the reaction section 4 is mainly configured by the reactor 4ab and the gas switching section 8 .

A generated gas discharge section 40 for discharging the generated gas to the outside of the gas production apparatus 1 is connected to the opposite end of the gas line GL4 from the reactors 42a and 42b.
A gas refining section 9 is provided in the middle of the gas line GL4.
The gas purification unit 9 purifies carbon monoxide from the mixed gas and recovers a generated gas containing high-concentration carbon monoxide. Incidentally, if the carbon monoxide concentration in the mixed gas is sufficiently high, the gas refining section 9 may be omitted.

The gas purifying section 9 can be composed of, for example, at least one processor selected from coolers, gas-liquid separators, gas separators, separation membranes, and scrubbers (absorption towers).
When a plurality of processors are used, their arrangement order is arbitrary, but when a cooler, a gas-liquid separator and a gas separator are used in combination, they are preferably arranged in this order. In this case, the efficiency of purifying carbon monoxide from the mixed gas can be further enhanced.

A cooler cools the mixed gas. This produces condensed water (liquid).
Such a cooler has a structure similar to that of the reactor 4ab (see FIG. 2). A multi-pipe type cooling device, an air fin cooler, or the like, which allows coolant to pass through spaces 43 around 41 can be included.

The gas-liquid separator separates the condensed water generated when the mixed gas is cooled by the cooler from the mixed gas. At this time, the condensed water has the advantage of being able to dissolve and remove unnecessary gas components (particularly carbon dioxide) remaining in the mixed gas.

The gas-liquid separator can be configured in the same manner as the gas-liquid separator of the micro component removing section 7, and preferably can be configured as a simple container. In this case, a filter may be arranged at the gas-liquid interface in the container to allow passage of gas but block passage of liquid.
Also, in this case, a liquid line may be connected to the bottom of the container, and a valve may be provided in the middle of the line. According to such a configuration, the condensed water stored in the container can be discharged (released) out of the gas production apparatus 1 through the liquid line by opening the valve.

Furthermore, it is preferable to provide a drain trap downstream of the valve in the liquid line. As a result, even if the valve malfunctions and carbon monoxide or hydrogen flows out into the liquid line, it can be prevented from being stored in the drain trap and discharged outside the gas production apparatus 1 . . In place of this drain trap, or together with the drain trap, a malfunction detection function of the valve and a redundancy measure when the valve malfunctions may be provided.
Alternatively, the liquid line may be connected to the tank to reuse the condensed water discharged.

Gas separators include, for example, cryogenic (cryogenic) separators, pressure swing adsorption (PSA) separators, membrane separation separators, temperature swing adsorption (TSA) separators, metal ion (e.g., copper ions) and organic ligands (e.g., 5-azidoisophthalic acid) are combined into a separator using a porous coordination polymer (PCP), and separation using amine absorption. It can be configured using one or more of the vessels and the like.
A valve may be provided between the gas-liquid separator and the gas separator of the gas line GL4. In this case, the mixed gas processing speed (production gas production speed) can be adjusted by adjusting the opening of the valve.

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 produced gas containing carbon monoxide at a relatively low concentration (75 to 90% by volume) can be used, carbon monoxide can be directly supplied to the next step without purifying carbon monoxide from the mixed gas. That is, the gas separator can be omitted.
Such fields include, for example, the field of synthesizing carbon valuables (e.g., ethanol, etc.) from the generated gas by fermentation with microorganisms (e.g., Clostridium, etc.), and the field of manufacturing steel using the generated gas as fuel or reducing agent. , the field of manufacturing electric devices, and the field of synthesizing chemicals (phosgene, acetic acid, etc.) using carbon monoxide as a synthetic raw material.

On the other hand, in fields where it is necessary to utilize a product gas containing relatively high concentrations (greater than 90% by volume) of carbon monoxide, the carbon monoxide is purified from the mixed gas to produce a product gas containing high concentrations of carbon monoxide. get
Such fields include, for example, the field of using generated gas as a reducing agent (blast furnace), the field of thermal power generation using generated gas as fuel, the field of manufacturing chemicals using generated gas as a raw material, and the field of manufacturing chemicals using generated gas as fuel. and the field of fuel cells used as

Next, an example of how to use (action) of the gas production system 100 will be described. The method of using the gas production system 100 of the present embodiment is not limited to the following, and it is possible to add, replace, or omit steps as appropriate.
[1] First, by switching the gas line (flow path) in the gas switching section 8, the connection section 2 and the reactor 41a are communicated, and the reducing gas supply section 3 and the reactor 41b are communicated.
[2] Next, in this state, the supply of exhaust gas from the furnace 20 through the connecting portion 2 is started.
[3] Next, the exhaust gas passes through the oxygen removing device (concentration adjusting section 5). Oxygen is thereby removed from the exhaust gas, and the concentration of carbon dioxide contained in the exhaust gas increases.

[4] Next, the exhaust gas passes through the compression section 6 . This increases the pressure of the exhaust gas.
[5] Next, the exhaust gas is transferred and passed through the fine component removing section 7 as necessary. As a result, the condensed water generated when the exhaust gas is compressed in the compression unit 6 and the inactivating components that reduce the activity of the reducing agent 4R are removed from the exhaust gas.
[6] Next, the exhaust gas passes through the exhaust gas heating section 10 . This heats the exhaust gas.
[7] Next, the exhaust gas is supplied to the reactor 41a. In the reactor 41a, carbon dioxide in the exhaust gas is reduced to carbon monoxide by the reducing agent 4R. At this time, the reducing agent 4R is brought into an oxidized state by contact with carbon dioxide.

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 more preferably 700 to 1000°C. is more preferred. 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 during conversion of carbon dioxide to carbon monoxide can be prevented or suppressed. can proceed more smoothly.

[8] Exhaust gas is discharged from the reactor 41a to the gas line GL5a.
[9] Next, the exhaust gas is supplied to the reactor 42a. Also 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 brought into an oxidized state by contact with carbon dioxide.
The conditions of the reactor 42a can be the same as those of the reactor 41a.

[10] In parallel with the above steps [2] to [9], water (reducing gas raw material) is supplied to the hydrogen generator (reducing gas supply unit 3) to generate hydrogen from water.
[11] Next, the reducing gas containing hydrogen passes through the reducing gas heating section 11 . This heats the reducing gas.
[12] Next, the reducing gas is supplied to the reactor 41b. In the reactor 41b, the oxidized reducing agent 4R is reduced (regenerated) by contact with the reducing gas (hydrogen). At this time, water is produced.

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 more preferably 700 to 1000°C. It is even more preferable to have 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 during reduction (regeneration) of the reducing agent 4R in an oxidized state can be prevented or suppressed. The reduction reaction of the reducing agent 4R in can proceed more smoothly.

[13] The reducing gas is discharged from the reactor 41b to the gas line GL5b.
[14] The reducing gas is then supplied to the reactor 42b. Also in the reactor 42b, the oxidized reducing agent 4R is reduced (regenerated) by contact with the reducing gas (hydrogen). At this time, water is produced.
The conditions of reactor 42b can be the same as those of reactor 41b.

[15] Next, the gases that have passed through the reactors 42a and 42b join together to produce a mixed gas. At this point, the temperature of the mixed gas is typically 600-650°C. If the temperature of the mixed gas at this time is within the above range, it means that the temperature in the reactor 4ab is maintained at a sufficiently high temperature, and the conversion of carbon dioxide to carbon monoxide by the reducing agent 4R, It can be determined that the reduction of the reducing agent 4R by the reducing gas is progressing efficiently.
[16] Next, the mixed gas is cooled to 100 to 300° C. before reaching the gas refining section 9 .

[17] Next, the mixed gas passes through the gas refining section 9 . As a result, for example, the generated condensed water and carbon dioxide dissolved in the condensed water are removed. As a result, carbon monoxide is purified from the mixed gas to obtain a product gas containing a high concentration of carbon monoxide.
The temperature of the produced gas obtained is 20 to 50°C.
[18] Next, the generated gas is discharged from the generated gas discharge unit 40 to the outside of the gas production apparatus 1 and supplied to the next step.

(Second Embodiment of Gas Production System)
The reaction section 4 of the above-described gas production system can also have the following form (second embodiment).
FIG. 3 is a schematic diagram showing the configuration of the reaction section of the second embodiment. FIG. 4 is a schematic diagram showing a method of switching the gas to be passed through the reactor in the second embodiment.
Hereinafter, the reaction section 4 of the second embodiment will be described, but the description will focus on the differences from the reaction section 4 of the first embodiment, and the description of the same items will be omitted.

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 section 8a is connected to 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 join at the second gas switching section 8b to form a gas line GL4.
The first gas switching section 8a and the second gas switching section 8b are connected by four gas lines GL5a to GL5d.

With such a configuration, by switching the gas line (flow path) in the first gas switching unit 8a and the second gas switching unit 8b, for example, one reactor of the reactors 4a to 4d can supply exhaust gas (oxidation gas) can be fed through and through, while the remaining three reactors of reactors 4a-4d can be successively fed through with reducing gas, in that order.

That is, in the second embodiment, among the plurality of reactors 4a to 4d, one reactor to which the exhaust gas is supplied constitutes the first reactor, and when the exhaust gas is supplied to the first reactor, Three reactors fed with reducing gas in series may constitute the second reactor.

Specifically, in the first turn shown in FIG. 4(I), the exhaust gas (carbon dioxide) is supplied to the reactor (first reactor) 4a through the gas line GL3a, and the exhaust gas (one carbon oxides) can be discharged via gas line GL4a.

On the other hand, in the remaining reactors 4b to 4d, first, a reducing gas (hydrogen) is supplied to the reactor (first second reactor) 4b through the gas line GL3b, and then the reduction Gas (residual hydrogen) can be supplied to reactor (second reactor) 4c via gas line GL4b, gas line GL5c and gas line GL3c. Although not shown, a mechanism for removing water may be provided in the middle of the gas line GL5c, and the generated water may be discharged out of the system as appropriate.
After that, the reducing gas (residual hydrogen) that passed through the reactor 4c was supplied to the reactor (the third second reactor) 4d via the gas line GL4c, the gas line GL5d, and the gas line GL3d, and passed through it. A reducing gas (water) can be discharged via a gas line GL4d. Also at this time, the generated water may be discharged out of the system by a water removing mechanism provided in the middle of the gas line GL5d as appropriate.

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

In the second embodiment, a series of operations from the 1st turn to the 4th turn is regarded as one cycle, and by repeating a plurality of cycles, carbon dioxide can be continuously and stably converted into carbon monoxide.
For example, when using the reducing agent 4R, which has a lower efficiency of reducing the reducing agent 4R in the oxidized state by hydrogen (reducing substance) than the conversion efficiency of carbon dioxide to carbon monoxide, the reducing gas is supplied to one reactor only once. Passage causes the hydrogen (residual hydrogen) that has not been used to reduce the oxidized reducing agent 4R to be wasted. In contrast, in the present embodiment, the reducing gas can be passed through three reactors in succession, in other words, it can be passed through one reactor three times. Therefore, hydrogen (reducing gas) can be prevented from being wasted.

Also, by using three or more reactors, it is possible to provide reactors through which the exhaust gas and the reducing gas are not allowed to pass. Therefore, other operations can be performed on reactors not used for normal operation while continuing normal operation for producing product gas (carbon monoxide).
For example, when carbon dioxide is converted to carbon monoxide (carbon valuables), carbon may accumulate on the surface of the reducing agent 4R and the conversion efficiency may decrease. At this time, if oxygen is supplied to a reactor that is not used for normal operation, the carbon deposited on the surface of the reducing agent 4R can be removed by combustion to regenerate the reducing agent 4R.

In this case, before and after supplying oxygen to the reactor, the interior of the reactor may be purged with an inert gas (for example, nitrogen gas). As a result, it is possible to prevent the reducing gas and oxygen from unintentionally coming into contact with each other and reacting explosively.
According to the gas production apparatus 1 (gas production system 100) as described above, it is possible to efficiently produce carbon valuables using an oxidizing gas containing carbon dioxide and a reducing gas containing reducing substances.

(Third Embodiment of Gas Production System)
In the gas production systems of the first embodiment and the second embodiment, the oxygen carrier having the metal compound containing the above-described other element was used as the reducing agent 4R. can be adopted.
Hereinafter, the process for producing the generated gas in the third embodiment will be described, but the description will focus on the differences from the first and second embodiments, and the description of the same items will be omitted.

That is, as the reducing agent 4R accommodated in each reactor (reactor 4ab, etc.), an oxygen carrier precursor containing a metal element is selected, and this oxygen carrier precursor is added to Groups 14 to 17 and , a mode in which a source gas containing a compound containing an element (another element) other than the oxygen element belonging to the 2nd to 5th periods is brought into contact.
In this case, the generated gas can be obtained while adding an element (another element) other than the oxygen element belonging to Groups 14 to 17 and Periods 2 to 5 to the oxygen carrier precursor.

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 other elements are introduced. This is done within the system of the gas production system. With such a configuration as well, the reducing agent 4R with improved reaction efficiency can be realized.

Note that 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, the oxygen carrier precursor may be a metal simple substance or an alloy that does not substantially contain an oxygen element. As described above, even a metal simple substance or an alloy that does not substantially contain an oxygen element can be converted into the desired oxygen carrier because the raw material gas itself has an oxidizing function. be.

The raw material gas containing compounds containing other elements may be continuously used throughout the operating time of the gas production system, or may be used only at the beginning of the operation of the gas production system. In addition, it is also possible to employ a mode in which the source gas containing the compound containing the other element is intermittently used while the gas production system is in operation while monitoring the composition of the produced gas.
When a compound containing another element is contained in the source gas, the type and amount of the compound may be appropriately selected according to the type of source gas and process design.

After the generated gas is obtained in this way, the reducing gas is brought into contact with the oxygen carrier, and then the carbon valuables can be obtained by bringing it into contact with the raw material gas (oxidizing gas), The reducing gas can be brought into contact with the oxygen carrier before obtaining the product gas, as in the above-described embodiments.

Furthermore, it may be provided in each aspect described below.
The oxygen carrier, wherein the metal element contained in the cation portion is a transition metal element.
In the oxygen carrier, the other element contains at least one element belonging to Groups 15 and 16.
wherein said oxygen carrier is contacted with hydrogen to produce water and the reduced oxygen carrier is contacted with carbon dioxide to produce carbon values.
The oxygen carrier, wherein the content of the other element contained in the metal compound is 0.001% by mass or more.
In the oxygen carrier, the content of the other element contained in the metal compound is 10% by mass or less.
A method for producing the oxygen carrier, comprising the step of heating the elemental metal, alloy, or metal oxide containing the metal element and the compound containing the other element while bringing them into contact with each other.
In the method for producing an oxygen carrier, the step of heating is a step of heating while contacting the elemental metal, the alloy, or the metal oxide with a gas containing the compound containing the other element. .
A method for producing a gas, comprising the step of contacting the oxygen carrier or the oxygen carrier obtained by the method for producing the oxygen carrier with a raw material gas to obtain a product gas.
The method for producing the gas, comprising the step of contacting a reducing gas with the oxygen carrier before or after the step of obtaining the product gas.
A method for producing a gas, wherein the source gas contains an oxygen carrier precursor containing a metal element and a compound containing an element other than an oxygen element belonging to Groups 14 to 17 and belonging to Periods 2 to 5. and bringing the oxygen carrier precursor into contact with the raw material gas, thereby removing the elements other than oxygen elements belonging to Groups 14 to 17 and Periods 2 to 5. A method comprising obtaining a product gas while applying an oxygen carrier precursor.
The method for producing the gas, comprising the step of contacting a reducing gas with the oxygen carrier before or after the step of obtaining the product gas.
A gas production apparatus comprising a reactor, wherein the oxygen carrier is accommodated in the reactor.
Of course, this is not the only case.

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 embodiment can be embodied in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. The embodiment and its modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

For example, the gas production apparatus of the present invention may have any other additional configuration with respect to the above embodiments, and may be replaced with any configuration that exhibits similar functions. may be omitted.
In each of the above-described embodiments, an example in which the metal compound functions as a reducing agent that reduces carbon dioxide has been described, but this metal compound can also function as a catalyst that promotes the reaction between carbon dioxide and a reducing substance. . In this case, the reverse water gas shift reaction is carried out by housing a catalyst in a reactor and simultaneously supplying the exhaust gas and the reducing gas to the reactor.

Further, in each of the above-described embodiments, a gas containing hydrogen was described as a representative of the reducing gas. etc.) and ammonia.
Further, in the first embodiment, the number of reactors connected in series may be 3 or more, and in the second embodiment, the series reactor (reducing agent The number of reactors on the reduction side for reducing 4R may be two, or four or more.
Moreover, the number of reactors used for gas production may be one without being limited to each of the above embodiments.

The present invention will be described in more detail below with reference to examples and comparative examples. In addition, the present invention is not limited to the following examples.

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

(Example 1-1: CeO ₂ _La ₂ S ₃ -3 wt%)
First, as a precursor of a reducing agent, 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 and placed in a crucible. Mixed. 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 agglomerates were finely pulverized mechanically to obtain the desired reducing agent. The reducing agent was granular.

(Example 1-2: CeO ₂ _La ₂ S ₃ -5 wt%)
Example 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. A reducing agent was prepared in the same manner as in -1. The reducing agent was granular.

(Comparative Example 1: CeO ₂ )
First, as a precursor of a reducing agent, 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, and then heated to 950°C. The temperature was raised over 1 hour to 950° C., and sintered under the condition of being held at 950° C. for 8 hours. Finally, the fired agglomerates were finely pulverized mechanically to obtain the desired reducing agent. The reducing agent was granular.

₍ Example _{2 : Ce0.9Zr0.1O2_La2S3-5wt %} )
First, 0.32 g of zirconium (II) oxynitrate dihydrate (manufactured by Kishida Chemical Co., Ltd., purity: 99.0%) and 4.67 g of cerium (III) nitrate hexahydrate were used as precursors of the reducing agent. Wako (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., purity: 99.5%) was weighed respectively.
Next, 5.03 g of citric acid (manufactured by Fuji Film 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 above precursor (metal nitrate) was added to the aqueous citric acid solution at 65° C. while stirring.
After 30 minutes, 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.
A temperature of 80° C. was maintained with continuous stirring until a viscous gel was formed. After that, the gel was transferred to a drying oven. Drying of the gel was performed at 120° C. for 8 hours. The resulting swollen lumps of organic and inorganic compounds were pulverized, heated to 450°C over 1 hour, held at 450°C for 4 hours, then heated to 950°C over 1 hour, and heated to 950°C. and sintered for 8 hours. Finally, the fired agglomerates were mechanically finely pulverized 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 agglomerates were finely pulverized mechanically to obtain the desired reducing agent. The reducing agent was granular.

( _{Comparative Example} 2: _Ce0.9Zr0.1O2 )
A target metal oxide was obtained in the same manner as in Example 2, except that lanthanum sulfide was not added.

(Example ₃ : After _{Ce0.9Zr0.1O2_S} gas _reaction )
A fixed-bed flow reactor was filled with Ce _0.9 Zr _0.1 O ₂ as a precursor of the reducing agent. Thereafter, after heating the reactor to 850° C., H ₂ gas was flowed, and then CO ₂ gas mixed with 1% H ₂ S was flowed. This cycle was performed for 20 or more cycles. After cooling to room temperature, the desired reducing agent was obtained.

₍ Comparative _Example 3: _Ce0.9Zr0.1O2 )
A target metal oxide was obtained in the same manner as in Comparative Example 2.

For each oxygen carrier (reducing agent) obtained above, the amount of sulfur (elemental sulfur) contained is quantified by the following apparatus and method.
1: Apparatus ICP-AES: Agilent 5110 VDV type manufactured by Agilent Technologies Microwave thermal decomposition apparatus: MultiWave 3000 manufactured by Anton Paar
2: Method An acid and a sample were placed in a decomposition container, the container was sealed, and then microwaves were applied to thermally decompose. Subsequently, quantitative analysis (standard addition method) of S in the sample was performed by ICP-AES.

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

<Evaluation of oxygen carrier (reducing agent)>
The performance of the obtained oxygen carrier (reducing agent) was evaluated in terms of reactivity with hydrogen and reactivity with carbon dioxide.

(Reactivity with hydrogen (1))
Thermogravimetry (TG) was performed under a hydrogen atmosphere for each oxygen carrier (reducing agent). The specific procedure is as follows.
First, 50 to 100 mg of each oxygen carrier was filled on the sample table in the reactor. Subsequently, after flowing helium gas at a flow rate of 50 mL/min for 5 minutes, hydrogen gas was flowed at a flow rate of 50 mL/min, and the temperature was raised from room temperature to 900°C. At this time, the mass change rate is measured in the range of 400°C to 900°C. The temperature increase rate during thermogravimetric measurement was 10° C./min.
The evaluation is based on the amount of change when the mass at room temperature is taken as 100%. Shown as a relative value. In addition, Example 2 is shown as a relative value when the amount of change in Comparative Example 2 is set to "1".
The mass change rate results are shown in Table 2.

(Reactivity with carbon dioxide (1))
Measurements were performed 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 a columnar oxygen carrier formed to have a major diameter of 3 mm so that the layer height was 30 mm. Thereafter, while flowing helium gas at a flow rate of 20 mL/min, the temperature was raised to 850° C. at a temperature elevation rate of 40° C./min, and 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 discharge port contained water vapor. Thereafter, for gas exchange, helium gas is flowed at a flow rate of 20 mL/min for 5 minutes, and then carbon dioxide gas is flowed at a flow rate of 20 mL/min for 5 minutes to perform a carbon dioxide reduction reaction (second process). , the carbon dioxide gas (source gas) was reduced. At this time, carbon monoxide was contained in the generated gas discharged from the discharge port.
Next, the following process was performed 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 reducing reaction (first process) of the reducing agent, thereby reducing the reducing agent. At this time, the gas discharged from the discharge port contained water vapor. Thereafter, for gas exchange, helium gas is flowed at a flow rate of 3 mL/min for 5 minutes, and then carbon dioxide gas is flowed at a flow rate of 3 mL/min for 4 minutes to perform a carbon dioxide reduction reaction (second process). , the carbon dioxide gas (source gas) was reduced. At this time, carbon monoxide was contained in the generated gas discharged from the discharge port.
In the above process, the temperature of the oxygen carrier was maintained at 850° C. and atmospheric pressure conditions were applied when any gas was flowed.
The reaction rate of carbon dioxide by the oxygen carrier is the value (mmol/g) obtained by dividing the molar amount (mmol) of carbon monoxide generated when the carbon dioxide gas is flowing by the weight (g) of the filled oxygen carrier. Calculated.
Table 2 shows the results of the amount of carbon monoxide produced. In addition, each of Examples 1-1 and 1-2 is shown as a relative value when the production amount of Comparative Example 1 is set to "1". In addition, Example 2 is shown as a relative value when the production amount of Comparative Example 2 is set to "1".

(Reactivity with hydrogen (2))
The oxygen carriers (reducing agents) of Example 3 and Comparative Example 3 were subjected to thermogravimetry (TG) under a hydrogen atmosphere. The specific procedure is as follows.
First, 50 to 100 mg of each oxygen carrier was filled on the sample table in the reactor. Subsequently, after flowing helium gas at a flow rate of 50 mL/min for 5 minutes, hydrogen gas was flowed at a flow rate of 50 mL/min, and the temperature was raised from room temperature to 900°C. At this time, the mass change rate is measured in the range of 400°C to 700°C. The temperature increase rate during 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 Example 3 was shown as a relative value when the amount of change in Comparative Example 3 was set to "1".

(Reactivity with carbon dioxide (2))
Measurements were performed 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 a columnar oxygen carrier formed to have a major diameter of 3 mm so that the layer height was 30 mm. Thereafter, while flowing helium gas at a flow rate of 20 mL/min, the temperature was raised to 700° C. at a temperature elevation 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 discharge port contained water vapor. Thereafter, for gas exchange, helium gas is flowed at a flow rate of 20 mL/min for 5 minutes, and then carbon dioxide gas is flowed at a flow rate of 20 mL/min for 5 minutes to perform a carbon dioxide reduction reaction (second process). , the carbon dioxide gas (source gas) was reduced. At this time, carbon monoxide was contained in the generated gas discharged from the discharge port.
Next, the following process was performed 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 reducing reaction (first process) of the reducing agent, thereby reducing the reducing agent. At this time, the gas discharged from the discharge port contained water vapor. Thereafter, for gas exchange, helium gas is flowed at a flow rate of 3 mL/min for 5 minutes, and then carbon dioxide gas is flowed at a flow rate of 3 mL/min for 4 minutes to perform a carbon dioxide reduction reaction (second process). , the carbon dioxide gas (source gas) was reduced. At this time, carbon monoxide was contained in the generated gas discharged from the discharge port.
In the above process, the temperature of the oxygen carrier was maintained at 700° C. and atmospheric pressure conditions were maintained when any gas was flowed.
The reaction rate of carbon dioxide by the oxygen carrier is the value (mmol/g) obtained by dividing the molar amount (mmol) of carbon monoxide generated when the carbon dioxide gas is flowing by the weight (g) of the filled oxygen carrier. Calculated.
Table 3 shows the results of the amount of carbon monoxide produced. In addition, each Example 3 is shown as a relative value when the production amount of Comparative Example 3 is set to "1".

From the above results, it can be seen that the introduction of other elements such as sulfur into the oxygen carrier (reducing agent) improves the reaction efficiency during reduction and oxidation reactions.

Reference Signs List 1: Gas production device 2: Connection part 3: Reducing gas supply part 4: Reaction part 41: Tubular 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 : Concentration adjusting section 6 : Compressing section 7 : Minor component removing section 8 : Gas switching section 8a : First gas switching section 8b : Second gas switching section 9 : Gas purification unit 10 : Exhaust gas heating unit 11 : Reducing gas heating unit 20 : Furnace 40 : Generated gas discharge unit 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 (13)

1. An oxygen carrier comprising a metal compound,
   The metal compound has a cation portion and an anion portion,
   The cation portion contains at least a metal element,
   The anion portion contains at least an oxygen element,
   At least one of the cation part or the anion part contains another 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. The oxygen carrier of claim 1, wherein
   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 claim 2,
   The oxygen carrier, wherein the other element comprises 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 on contact with hydrogen and carbon values on contact of the reduced oxygen carrier with carbon dioxide.
5. The oxygen carrier according to any one of claims 1 to 4,
   The oxygen carrier, wherein the content of the other element contained in the metal compound is 0.001% by mass or more.
6. The oxygen carrier according to any one of claims 1 to 5,
   The oxygen carrier, wherein the content of the other element contained in the metal compound is 10% by mass or less.
7. A method for producing an oxygen carrier according to any one of claims 1 to 6,
   A method comprising the step of heating a metal simple substance, alloy or metal oxide containing the metal element and the compound containing the other element while contacting them.
8. In the method for producing an oxygen carrier according to claim 7,
   The heating step is a step of heating the elemental metal, the alloy, or the metal oxide and the gas containing the compound containing the other element while bringing them into contact with each other.
9. A method for producing gas,
   By bringing the oxygen carrier according to any one of claims 1 to 6 or the oxygen carrier obtained by the oxygen carrier production method according to claim 7 or 8 into contact with a raw material gas, A method comprising obtaining a product gas.
10. In the method for producing gas according to claim 9,
    A method comprising the step of contacting a reducing gas with said oxygen carrier before or after said step of obtaining a product gas.
11. A method for producing gas,
    preparing an oxygen carrier precursor containing a metal element and a raw material gas containing a compound containing an element other than an oxygen element belonging to groups 14 to 17 and belonging to periods 2 to 5;
    By bringing the oxygen carrier precursor into contact with the raw material gas, the element other than the oxygen element belonging to Groups 14 to 17 and Periods 2 to 5 is imparted to the oxygen carrier precursor. and obtaining a product gas.
12. In the method for producing gas according to claim 11,
    A method comprising the step of contacting a reducing gas with said oxygen carrier before or after said step of obtaining a product gas.
13. A gas production apparatus comprising a reactor,
    A gas production apparatus, wherein the oxygen carrier according to any one of claims 1 to 6 is accommodated in the reactor.

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