Gas production device

Abstract

To provide a gas production device in which separating a removal part from a reactor enables an increase in temperature of a reaction part and which is capable of efficiently producing a carbon valuable product.SOLUTION: According to one aspect of the present invention, a gas production device is provided. The gas production device includes: at least two reactors; and a removal part. Two reactors are configured to be connected in series with each other and be able to be supplied with an oxidizing gas containing carbon dioxide and a reducing gas containing a reduction substance. Each of the reactors accommodates at least one of metal and metal oxide. The at least one of metal and metal oxide promotes reduction of the carbon dioxide or reaction between the carbon dioxide and the reduction substance to thereby produce a carbon valuable product. The removal part has a phase separation mechanism which is connected between the two reactors and which performs phase separation of a separation component, the separation component including at least one of a liquid component and a solid component produced by cooling, and a gas component, thereby removing a product derived from gas supplied to the reactors.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, the concentration of carbon dioxide (CO2), a greenhouse gas, has been increasing in the atmosphere. This increase in the concentration of carbon dioxide in the atmosphere contributes to global warming. Therefore, it is important to capture carbon dioxide released into the atmosphere. If the captured carbon dioxide can be converted into valuable carbon resources and reused, a carbon recycling society can be realized. Furthermore, as a global measure, the Kyoto Protocol of the United Nations Framework Convention on Climate Change stipulates that developed countries must set their own reduction rates for carbon dioxide, the cause of global warming, using 1990 as the base year, and that they must jointly achieve reduction targets within the commitment period.

[0003] 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 emissions 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 production apparatus for producing carbon monoxide from carbon dioxide using cerium oxide containing zirconium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5858926 [Patent Document 2] Japanese Patent Publication No. 2020-23488 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to the studies of the present inventors, Patent Document 1 discloses an invention for identifying a metal oxide that efficiently converts carbon dioxide into carbon monoxide. However, Patent Document 1 only discloses conceptual or general information about the carbon monoxide production conditions and production equipment, as can be seen from the drawings, etc. Therefore, it was found that further technical improvements are necessary to industrially produce carbon valuables such as carbon monoxide.

[0006] Furthermore, from the viewpoint of industrial carbon monoxide production, it is also important to improve energy efficiency. In carbon monoxide production using the above-mentioned metal oxides, the gas produced contains unreacted carbon dioxide in addition to carbon monoxide. Furthermore, in order to regenerate the oxidized metal oxide, hydrogen is brought into contact with the metal oxide, and the gas produced in this process contains unreacted hydrogen as well as water vapor (water). When considering the reuse of unreacted carbon dioxide and unreacted hydrogen, it is effective to remove the reaction products, carbon monoxide and water, from the produced gas. For example, Patent Document 2 proposes a configuration in which a selectively permeable membrane (removal section) that separates reaction products from the reaction system is installed inside the reactor.

[0007] However, in a configuration in which a selectively permeable membrane is installed inside a reactor, there is a risk that the selectively permeable membrane may deteriorate or be damaged when the reaction system becomes hot, making it difficult to use. In view of the above circumstances, the present invention provides a gas production apparatus that can efficiently produce carbon valuables by separating the removal section from the reactor, thereby enabling the reaction section to be heated to a high temperature. [Means for solving the problem]

[0008] According to one aspect of the present invention, a gas production apparatus is provided. The gas production apparatus includes at least two reactors and a removal unit. The two reactors are connected in series and configured to be capable of supplying an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance. Each reactor contains at least one of a metal and a metal oxide. The at least one of the metal and the metal oxide reduces carbon dioxide or promotes a reaction between carbon dioxide and the reducing substance to produce carbon valuables. The removal unit is connected between the two reactors and has a phase separation mechanism that removes products derived from the gas supplied to the reactors by phase separation between a separated component containing at least one of a liquid component and a solid component generated by cooling and a gas component.

[0009] According to this aspect, carbon valuables can be efficiently produced using an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing the overall configuration of a gas production system using a gas production apparatus of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a reaction unit in the first embodiment. [Figure 3] FIG. 2 is a schematic diagram showing the configuration of a gas-liquid separation mechanism. [Figure 4] FIG. 10 is a schematic diagram showing another configuration of the gas-liquid separation mechanism. [Figure 5] FIG. 10 is a schematic diagram showing the configuration of a reaction unit of a second embodiment. [Figure 6] FIG. 10 is a schematic diagram showing a method for switching gases to be passed through a reactor in the second embodiment. [Figure 7] FIG. 10 is a schematic diagram showing another configuration of the gas-liquid separation mechanism. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas production apparatus according to the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings. First, the overall configuration of the gas production system will be described. First Embodiment Fig. 1 is a schematic diagram showing the overall configuration of a gas production system using a gas production apparatus of the present invention, Fig. 2 is a schematic diagram showing the configuration of a reaction section of a first embodiment. The gas production system 100 shown in FIG. 1 includes a furnace 20 that produces exhaust gas (oxidizing gas) containing carbon dioxide, and a gas production device 1 that is connected to the furnace 20 via a connection part 2. In this specification, the upstream side with respect to the gas flow direction will also be referred to simply as the "upstream side," and the downstream side will also be referred to simply as the "downstream side."

[0012] The furnace 20 is not particularly limited, but may be, for example, a furnace attached to a steel mill, 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 (emitted) when the contents are burned, melted, refined, etc. In the case of a combustion furnace (incinerator) at 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.

[0013] In addition to carbon dioxide, exhaust gas usually contains 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 (efficiency of conversion to carbon monoxide), it is preferably 1% by volume or more, and more preferably 5% by volume or more. The exhaust gas from the combustion furnace in a waste incineration plant contains 5 to 15 volume % carbon dioxide, 60 to 70 volume % nitrogen, 5 to 10 volume % oxygen, and 15 to 25 volume % water vapor.

[0014] 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 oxidizing gas is not limited to exhaust gas, and a pure gas containing 100% by volume of carbon dioxide may also be used.

[0015] However, if exhaust gas is used as the oxidizing gas, carbon dioxide that has conventionally been emitted into the atmosphere can be effectively utilized, thereby reducing the burden on the environment. Among these, from the viewpoint of carbon circulation, exhaust gas containing carbon dioxide generated in a steel mill or a smelter is preferred. Furthermore, the blast furnace gas and converter gas may be untreated gas discharged from the furnace and used 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 manufacturing apparatus 1) are referred to as exhaust gases.

[0016] The gas production device 1 produces a product gas (synthesis gas) containing carbon monoxide by contacting exhaust gas (oxidation gas containing carbon dioxide) discharged from the furnace 20 and supplied via the connection part 2 with a reducing agent 4R that reduces the carbon dioxide contained in the exhaust gas. In this specification, carbon monoxide will be used as a representative example of a carbon valuable material. However, the carbon valuable material is not limited to carbon monoxide, and examples thereof include methane, methanol, etc., which may be a single material or a mixture of two or more materials. The type of carbon valuable material produced will vary depending on the type of reducing agent described below.

[0017] 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, and 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 (oxidizing gas supply part) that supplies exhaust gas to the reaction part 4. If necessary, pumps for transferring gas may be provided at predetermined locations along the gas lines GL1, GL2, and GL4. For example, when the pressure of the exhaust gas is adjusted to a relatively low level in the compression section 6 described below, providing a pump allows the gas to be transferred smoothly within the gas production apparatus 1.

[0018] 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 provided 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 and 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.

[0019] As shown in Fig. 2, each reactor 4ab is configured as a multi-tubular reactor (fixed-bed reactor) including a plurality of tubular bodies 41 each filled with (accommodating) a reducing agent 4R and a housing 42 accommodating the plurality of tubular bodies 41. Such a multi-tubular reactor can ensure sufficient opportunities for the reducing agent 4R to come into contact with the exhaust gas and the reducing gas. As a result, the production efficiency of the generated gas can be improved. The reducing agent 4R of this embodiment is preferably in the form of, for example, particles (granules), scales, pellets, etc. The reducing agent 4R in such a shape can increase the filling efficiency into the tubular body 41 and can further increase the contact area with the gas supplied into the tubular body 41.

[0020] When the reducing agent 4R is in a particulate form, 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 efficiency of converting carbon dioxide to carbon monoxide can be further improved. Similarly, the regeneration (reduction) of the reducing agent 4R by a reducing gas containing a reducing substance can also be performed more efficiently. The particulate reducing agent 4R is preferably a compact produced by rolling granulation, since this increases the sphericity.

[0021] The reducing agent 4R may be supported on a carrier. The constituent material of the carrier may be any material that is not easily denatured by contact with exhaust gas (oxidizing gas) or by reaction conditions, and examples thereof include carbon materials (graphite, graphene, etc.), carbides such as MoC, zeolites, montmorillonite, oxides such as ZrO, TiO, V, MgO, CeO, AlO, and SiO, and composite oxides containing these.

[0022] Among these, zeolite, montmorillonite, ZrO2, TiO2, V2O5, MgO, Al2O3, SiO2, and composite oxides containing these are preferred as constituent materials of the carrier. Carriers made of such materials are preferred because they do not adversely affect the reaction of the reducing agent 4R and have excellent supporting ability for the reducing agent 4R. Here, the carrier does not participate in the reaction of the reducing agent 4R, but simply supports (holds) the reducing agent 4R. One example of such a configuration is one in which at least a portion of the surface of the support is coated with the reducing agent 4R.

[0023] The reducing agent 4R contains at least one of a metal and a metal oxide (oxygen carrier). The at least one of the metal and the metal oxide is not particularly limited as long as it can reduce carbon dioxide, but it preferably contains at least one metal element selected from Groups 3 to 12, more preferably at least one metal element selected from Groups 4 to 12, and even more preferably at least one element selected from titanium, vanadium, iron, copper, zinc, nickel, manganese, chromium, and cerium, with iron-containing metal oxides or composite metal oxides being particularly preferred. These metal oxides are useful because they have particularly good carbon dioxide conversion efficiency to carbon monoxide. Here, the metal includes a simple metal consisting of only one of the above metal elements, and an alloy consisting of two or more of the above metal elements.

[0024] In particular, iron oxide, cerium oxide, etc. are suitable as metal oxides that convert carbon dioxide to carbon monoxide. For example, zirconia, alumina, titania, silica, etc. that support or contain at least one of nickel and ruthenium are suitable as metal oxides that convert carbon dioxide to methane. For example, zirconia, alumina, silica, etc. that support or contain at least one of copper and zinc are suitable as metal oxides that convert carbon dioxide to methanol.

[0025] In each reactor 4ab, the reducing agent 4R (at least one of a metal and a metal oxide) itself may be used to form a tube (cylindrical molded body) 41. Furthermore, a block-shaped or lattice-shaped (e.g., mesh-shaped or honeycomb-shaped) molded body may be prepared using the reducing agent 4R and placed in the housing 42. In these cases, the reducing agent 4R may be omitted as a filler, or may be used in combination.

[0026] Among these, a preferred configuration is one in which a mesh body is made of the reducing agent 4R and placed inside the housing 42. In such a configuration, it is possible to prevent an increase in the resistance to passage of the exhaust gas and the reducing gas inside each reactor 4ab, while also ensuring sufficient opportunities 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 one another and are set appropriately depending on the amount of exhaust gas to be treated (the size of the furnace 20 and the size of the gas production apparatus 1). The volume of at least one of the four reactors 41a, 42a, 41b, and 42b may be made different depending on the types of exhaust gas and reducing gas, the performance of the reducing agent 4R, etc.

[0027] In the middle of the gas line GL1, a concentration adjusting section 5, a compressing section 6, a minor constituent removing section 7, and an exhaust gas heating section (oxidizing gas heating section) 10 are provided in this order from the connecting section 2 side. The concentration adjusting unit 5 adjusts the concentration of carbon dioxide contained in the exhaust gas to increase it (in other words, to concentrate 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 adjusting unit 5, the concentrations 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.

[0028] The concentration adjusting unit 5 is preferably configured with an oxygen remover 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 oxygen concentration in the exhaust gas to be lower). This makes it possible to keep the gas composition of the exhaust gas outside the explosive range and prevent the exhaust gas from igniting. Note that, since the oxygen remover consumes a large amount of electrical energy within the gas production apparatus 1, it is effective to use electricity as a renewable energy source, as described below.

[0029] 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 more reliably preventing 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. In addition, the concentration adjusting unit 5 may adjust the carbon dioxide concentration to a high level by adding carbon dioxide to the exhaust gas.

[0030] 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 to carbon monoxide in the reactor 4ab. The compression section 6 can be configured, for example, by 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 compressor, or a slide vane compressor, a roots blower (two-blade blower) that can handle low pressure, or a centrifugal blower.

[0031] Among these, it is preferable that the compression section 6 be configured with a centrifugal compressor from the viewpoint of facilitating the scale-up of the gas production system 100, and it is preferable that the compression section 6 be configured with a reciprocating compressor from the viewpoint of reducing the manufacturing costs of the gas production system 100. The pressure of the exhaust gas after passing through the compression section 6 is not particularly limited, but is preferably 0 to 1 MPaG, more preferably 0 to 0.5 MPaG, and even more preferably 0.01 to 0.5 MPaG. In this case, the efficiency of converting carbon dioxide to carbon monoxide in the reactor 4ab can be further improved without increasing the pressure resistance of the gas production apparatus 1 more than necessary.

[0032] The minor constituent removal section 7 removes minor constituents (trace amounts of unnecessary gas components, etc.) contained in the exhaust gas. The fine component removal section 7 can be configured with at least one type of treatment device from among, for example, a gas-liquid separator, a guard reactor, and a scrubber (absorption tower). When multiple treatment devices are used, they may be arranged in any order, but when a gas-liquid separator and a protector are used in combination, it is preferable to arrange the gas-liquid separator upstream of the protector, which can further increase the efficiency of removing trace components from the exhaust gas and extend the service life (lifespan) of the protector.

[0033] 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, a gas-liquid separator configured as a simple container is preferable because of its simple configuration and low cost. 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 inside the container.

[0034] In this case, a liquid line may be connected to the bottom of the container, and a valve may be provided along the line. With this configuration, condensed water stored in the container can be discharged to the outside of the gas production apparatus 1 via the liquid line by opening the valve. The liquid line may be connected to a tank 30, which will be described later, so that the discharged condensed water can be reused.

[0035] The exhaust gas from which condensed water has been removed in the gas-liquid separator may be configured to be supplied to, for example, a protector. Such a protector preferably includes a substance capable of capturing minor components contained in exhaust gas that reduce the activity of the reducing agent 4R by coming into contact with the reducing agent 4R (inactivating components). According to this configuration, when exhaust gas passes through the protector, the substance in the protector reacts with (captures) 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 effects of the inactivated components.

[0036] 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 upon contact with an inactivating component, specifically a substance that is the same as or similar to at least one of the 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.

[0037] The inactivating component is preferably at least one selected from sulfur, mercury, sulfur compounds, halogen compounds, organic silicones, organic phosphorus compounds, and organic metal compounds, and more preferably at least one selected from sulfur and sulfur compounds. By removing such inactivating components in advance, a rapid decrease in the activity of the reducing agent 4R can be effectively prevented. The 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 inactivating component.

[0038] The protector can be configured in such a way that a mesh material is placed inside a housing and particles of the above-mentioned substance 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 substance is placed inside the housing. In particular, when the protector is placed between the compression section 6 (gas-liquid separator) and the exhaust gas heating section 10, it is possible to improve the efficiency of removing inactivated components while preventing the above substances from being deteriorated by heat.

[0039] The exhaust gas heating unit 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. 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 portion of the piping constituting the gas line GL4, which 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 by heat exchange before being supplied to the reactor 4ab, thereby enabling effective use of heat.

[0040] Such a heat exchanger can be configured as, for example, a jacket-type heat exchanger, an immersed coil-type heat exchanger, a double-pipe-type heat exchanger, a shell-and-tube-type heat exchanger, a plate-type heat exchanger, a spiral-type heat exchanger, or the like. In addition, in the exhaust gas heating section 10, either the electric heater or the heat exchanger may be omitted. A combustion furnace or the like can be used instead of an electric heater in the exhaust gas heating section 10. However, if an electric heater is used, renewable energy (electrical energy) can be used as its power source, thereby reducing the burden on the environment. As renewable energy, electrical energy utilizing at least one selected from solar power generation, wind power generation, hydroelectric power generation, wave power generation, tidal power generation, biomass power generation, geothermal power generation, solar heat generation, and geothermal heat generation can be used.

[0041] 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 fine component 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 midway along 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 section via the exhaust gas line, thereby preventing damage to the gas production device 1 due to an increase in pressure.

[0042] 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 of this embodiment is configured as a hydrogen generation device that generates hydrogen by electrolysis of water, and a tank (reducing gas raw material storage unit) 30 that stores water and is outside the gas production apparatus 1 is connected to this hydrogen generation device. With this configuration, the reducing gas containing hydrogen (reducing substance) supplied from the hydrogen generation device (reducing gas supply unit 3) passes through the gas line GL2 and is supplied to each reactor 4ab.

[0043] The hydrogen generation device can generate a large amount of hydrogen relatively inexpensively and easily. Another advantage is that the condensed water generated within the gas production device 1 can be reused. Furthermore, since the hydrogen generation device consumes a large amount of electrical energy within the gas production device 1, it is effective to use electricity as a renewable energy source as described above.

[0044] The hydrogen generating device may be a device that generates by-product hydrogen. 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 aqueous sodium chloride solutions, devices that steam reform petroleum, and devices that produce ammonia. Alternatively, 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% by volume of hydrogen.

[0045] 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.

[0046] The reducing gas heating section 11 can be configured in the same manner as the above-described 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 used to heat the reducing gas by heat exchange before being supplied to the reactor 4ab, thereby enabling effective use of heat.

[0047] According to the above configuration, by switching the gas lines (flow paths) in the gas switching unit 8, for example, exhaust gas can be supplied via gas line GL3a to reactors 41a and 42a containing the reducing agent 4R before oxidation, and reducing gas can be supplied via gas line GL3b to reactors 41b and 42b containing the reducing agent 4R after oxidation. At this time, the reaction of formula 1 below proceeds in the reactors 41a and 42a, and the reaction of formula 2 below proceeds in the reactors 41b and 42b.

[0048] In the following formulas 1 and 2, the reducing agent 4R is iron oxide (FeO x-1 ) is shown as an example. Formula 1: CO2+ FeO x-1 → CO + FeO x Formula 2: H2+ FeO x → HO + FeO x-1 Thereafter, by switching the gas lines in the opposite direction in gas switching section 8, the reaction of formula 2 above can be allowed to proceed in reactors 41a and 42a, and the reaction of formula 1 above can be allowed to proceed in reactors 41b and 42b.

[0049] The reactions shown in the above formulas 1 and 2 are both endothermic reactions. Therefore, the gas production device 1 preferably further includes a reducing agent heating unit (not shown in FIG. 1) that heats the reducing agent 4R when the exhaust gas or reducing gas is brought into contact with the reducing agent 4R (i.e., when the exhaust gas or reducing gas reacts with the reducing agent 4R). By providing such a reducing agent heating section, the temperature in the reaction between the exhaust gas or reducing gas and the reducing agent 4R can be maintained at a high temperature, thereby suitably preventing or suppressing a decrease in the efficiency of converting carbon dioxide to carbon monoxide, and further promoting the regeneration of the reducing agent 4R by the reducing gas.

[0050] However, depending on the type of reducing agent 4R, the reactions shown in the above formulas 1 and 2 may be exothermic. In this case, the gas production apparatus 1 preferably has a reducing agent cooling unit that cools the reducing agent 4R, instead of a reducing agent heating unit. By providing such a reducing agent cooling unit, deterioration of the reducing agent 4R can be suitably prevented during the reaction between the exhaust gas or reducing gas and the reducing agent 4R, thereby suitably preventing or suppressing a decrease in the efficiency of conversion of carbon dioxide to carbon monoxide, and further promoting the regeneration of the reducing agent 4R by the reducing gas. That is, the gas production device 1 is preferably provided with a reducing agent temperature adjusting unit that adjusts the temperature of the reducing agent 4R depending on the type of reducing agent 4R (exothermic reaction or endothermic reaction).

[0051] Here, the conversion rate of carbon dioxide to carbon monoxide in reactor 4ab is preferably 80% or more, more preferably 82.5% or more, 85% or more, 87.5% or more, or 90% or more, even more preferably 92.5% or more, and particularly preferably 95% or more. The upper limit of the conversion rate of carbon dioxide to carbon monoxide is usually about 98%. Such a conversion rate can be set by adjusting the type of reducing agent 4R used, the concentration of carbon dioxide contained in the exhaust gas, the type of reducing substance, the concentration of the reducing substance contained in the reducing gas, the temperature of the reactor 4ab, the flow rates (flow speeds) of the exhaust gas and the reducing gas into the reactor 4ab, the timing of switching between the exhaust gas and the reducing gas, etc. The conversion rate (%) of carbon dioxide to carbon monoxide is calculated using the formula: CO out / CO 2in The value is calculated by multiplying CO by 100. 2in is the molar amount of carbon dioxide fed to reactor 4ab, and CO out is the molar amount of carbon monoxide discharged from reactor 4ab when carbon dioxide is converted into carbon monoxide through contact (reaction) with reducing agent 4R.

[0052] On the other hand, the conversion rate of hydrogen to water in reactor 4ab is preferably 40% or more, more preferably 45% or more, and even more preferably 50% or more. The upper limit of the conversion rate of hydrogen to water is usually about 85%. Such a conversion rate can be set by adjusting the type of reducing agent 4R used, the concentration of carbon dioxide contained in the exhaust gas, the type of reducing substance, the concentration of the reducing substance contained in the reducing gas, the temperatures of the reactors 4a and 4b, the flow rates (flow speeds) of the exhaust gas and reducing gas into the reactor 4ab, the timing of switching between the exhaust gas and the reducing gas, and the like. The conversion rate of hydrogen to water (%) is (H 2in -H 2out ) / H 2in This is the value calculated by multiplying H by 100. 2in is the molar amount of hydrogen fed to reactor 4ab, and H 2out is the molar amount of hydrogen that passes through reactor 4ab in an unreacted state and is discharged.

[0053] Gas lines GL4a and GL4b are connected to the outlet ports of the reactors 42a and 42b, respectively, and these join at a gas junction J4 to form the gas line GL4. In addition, valves (not shown) are provided midway along the gas lines GL4a and GL4b as necessary. For example, by adjusting the opening of the valve, it is possible to set the passing speed of the exhaust gas and reducing gas passing through the reactor 4ab (i.e., the treatment speed of the exhaust gas by the reducing agent 4R and the treatment speed of the reducing agent 4R by the reducing gas). In this embodiment, the reaction section 4 is mainly composed of the reactor 4ab and the gas switching section 8.

[0054] 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 and 42b. Further, a gas purification section 9 is provided midway along 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.

[0055] The gas purification section 9 can be configured with at least one type of treatment device selected from the group consisting of a cooler, a gas-liquid separator, a gas separator, a separation membrane, and a scrubber (absorption tower). When multiple treatment units are used, they may be arranged in any order, 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.

[0056] 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 the piping to allow a refrigerant to pass through, a multi-tube cooling device having a configuration similar to that of reactor 4ab (see Figure 2) and in which the mixed gas passes through a tubular body 41 and the refrigerant passes through a space 43 around the tubular body 41, an air fin cooler, or the like.

[0057] The gas-liquid separator separates the condensed water that is generated when the mixed gas is cooled in the cooler from the mixed gas. The condensed water has the advantage of being able to dissolve and remove unwanted gas components (especially carbon dioxide) remaining in the mixed gas.

[0058] The gas-liquid separator can be configured in the same manner as the gas-liquid separator of the fine component removal section 7, and preferably can 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 placed 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 along the line. With this configuration, the condensed water stored in the container can be discharged (released) to the outside of the gas production apparatus 1 via the liquid line by opening the valve.

[0059] Furthermore, it is preferable to provide a drain trap downstream of the valve in the liquid line. This will prevent carbon monoxide or hydrogen from being discharged outside the gas production apparatus 1, even if the valve malfunctions and the carbon monoxide or hydrogen leaks into the liquid line. Instead of or in addition to this drain trap, a valve malfunction detection function and redundancy measures in case of valve malfunction may be provided. The liquid line may be connected to the tank 30 described above so that the discharged condensed water can be reused.

[0060] The gas separator can be constructed using one or more of the following: a low-temperature separation (cryogenic) separator, a pressure swing adsorption (PSA) separator, a membrane separation separator, a temperature swing adsorption (TSA) separator, a separator using a porous coordination polymer (PCP) that combines metal ions (e.g., copper ions) with organic ligands (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 on 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.

[0061] 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) from generated gas by fermentation with microorganisms (e.g., Clostridium), the field of producing steel using generated gas as a 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.

[0062] On the other hand, in fields where it is necessary to use 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 chemical products, and a field in which the generated gas is used as fuel for fuel cells.

[0063] In this embodiment, the reactor 41a and the reactor 42a are connected in series by a gas line GL5a, and the reactor 41b and the reactor 42b are connected in series by a gas line GL5b. A removal unit 19 is provided midway along each of the gas lines GL5a and GL5b. The removal section 19 is configured to be capable of at least one of separating water (a product derived from the reducing gas) produced by contact (reaction) between the reducing agent 4R and hydrogen (reducing substance) from unreacted hydrogen (reducing substance), and separating carbon monoxide produced by contact between the reducing agent 4R and carbon dioxide from unreacted carbon dioxide.

[0064] That is, the removal section 19 is connected between the two reactors 4ab and has a gas-liquid separation mechanism (phase separation mechanism) 19' that removes products derived from the gas supplied to the reactor 4ab by performing gas-liquid separation of the liquid component (separated component) and the gas component generated by cooling. According to this configuration, products derived from the gas supplied to the reactors 41a and 41b can be removed, and therefore, it is possible to prevent a decrease in the reaction efficiency in the reactors 42a and 42b, i.e., the efficiency of converting carbon dioxide to carbon monoxide and the efficiency of reducing (regenerating) the oxidized reducing agent 4R. As a result, it is possible to efficiently generate carbon monoxide (carbon valuables) from carbon dioxide.

[0065] For example, the produced water and carbon monoxide are discharged to discharge lines 19a and 19b, while unreacted hydrogen and unreacted carbon dioxide are discharged to gas lines GL5a and GL5b. The gas discharged to the discharge lines 19a and 19b may contain gas components other than water or carbon monoxide, and the gas discharged to the gas lines GL5a and GL5b may contain gas components other than hydrogen or carbon dioxide.

[0066] The gas-liquid separation mechanism 19' that separates hydrogen, which is a reducing substance, from water, which is a product, into gas and liquid, will be described below. Fig. 3 is a schematic diagram showing the configuration of the gas-liquid separation mechanism, and Fig. 4 is a schematic diagram showing another configuration of the gas-liquid separation mechanism. The gas-liquid separation mechanism 19′ shown in FIG. 3 includes a cooler 191, a tank (storage unit) 192, and a check valve 193.

[0067] The cooler 191 is provided midway along the gas lines GL5a and GL5b. For this cooler 191, a cooler having the same configuration as that described for the gas purification unit 9 can be used. A tank 192 for storing water (liquid component) is connected to the cooler 191 via discharge lines 19a and 19b. The gas-liquid separation mechanism 19' is configured so that the liquid component (separated component) does not flow into the reactor 4ab, thereby further improving the conversion efficiency (conversion rate) of carbon dioxide to carbon monoxide and the conversion efficiency (conversion rate) of hydrogen to water.

[0068] 3, a gas-liquid separation mechanism (phase separation mechanism) 19' is disposed at a position vertically below the reactor 4ab, and a check valve 193 is provided between the gas-liquid separation mechanism 19' and the reactor 4ab. With such a relatively simple configuration, it is possible to prevent the liquid component from flowing into the reactor 4ab. Here, the "position vertically below the reactor 4ab" is not limited to a position directly below the reactor 4ab, but also includes a position diagonally below the reactor 4ab. It is also possible to adopt only one of the following configurations: a configuration in which the gas-liquid separation mechanism 19' is disposed vertically below the reactor 4ab; and a configuration in which the check valve 193 is provided between the gas-liquid separation mechanism 19' and the reactor 4ab. In this case, too, it is possible to sufficiently prevent the liquid component from flowing into the reactor 4ab. Discharge lines 19a and 19b are provided with check valves 193. Check valves 193 can be configured, for example, as duckbill valves, poppet check valves, lift check valves, swing check valves, ball check valves, wafer check valves, foot check valves, or the like.

[0069] When the boiling point of the liquid component stored in tank 192 (the temperature at which the separated component vaporizes) is X [°C], the cooling temperature in gas-liquid separation mechanism 19′ (cooler 191) is preferably about X-120°C or higher and X°C or lower, and above absolute zero, more preferably about X-100°C or higher and X-10°C or lower, and even more preferably about X-80°C or higher and X-20°C or lower. By cooling the gas that has passed through reactor 4ab at such a cooling temperature, the substance that should be converted into a liquid component by cooling can be condensed into a liquid state in a short time without freezing. When the substance to be made into the liquid component is water, the cooling temperature is preferably about -20°C or higher and 100°C or lower, more preferably about 0°C or higher and 90°C or lower, and even more preferably about 20°C or higher and 80°C or lower.

[0070] Furthermore, tank 192 is equipped with a pH meter (pH measurement unit) 194 that measures the pH of the stored water. The stored water may become acidic due to the dissolution of carbon dioxide, hydrogen sulfide, etc. For this reason, by providing pH meter 194, the pH of the water stored in tank 192 can be monitored. If the pH of the water becomes undesirably too low, a pH adjuster can be added to the water. In this case, in consideration of the decrease in the pH of the water, the tank 192 that stores the water can be made of an acid-resistant material. This can prevent or suppress corrosion of the tank 192 and extend the maintenance interval of the gas production apparatus 1. Examples of acid-resistant materials include various resin materials and metal materials such as stainless steel.

[0071] The gas-liquid separation mechanism 19' can also have the configuration shown in FIG. The following description of the configuration shown in FIG. 4 will focus on the differences from the configuration shown in FIG. 3, and a description of similar points will be omitted. 4, a switching valve (flow path blocking mechanism) 193' is provided in the discharge lines 19a and 19b. When the amount of water stored in the tank 192 exceeds a predetermined amount, the switching valve 193' can be switched to discharge the excess water into the switching lines 191a and 191b.

[0072] In addition, in the gas-liquid separation mechanism 19′ shown in FIG. 4, a liquid level sensor (liquid level detection unit) 195 that detects the liquid level of water (liquid component) is connected to the tank 192. By providing a liquid level sensor 195, the switching valve 193' can block the discharge lines 19a, 19b, which are flow paths that transport water (liquid components) to the tank (storage section) 192, and switch to the switching lines 191a, 191b to discharge the water, depending on the liquid level position detected by the liquid level sensor 195. In this case, the water may be returned to the tank 30. The gas-liquid separation mechanism 19' having such a configuration prevents the separated and removed water (liquid component) from flowing back into the gas production apparatus 1, thereby enabling the gas production apparatus 1 to operate stably.

[0073] Since the water stored in the tank 192 may foam, it is preferable to use a detection system that is not affected by foaming or is less affected by foaming when detecting the liquid level using the liquid level sensor 195. Such a liquid level sensor 195 makes it possible to accurately grasp the amount of water stored in the tank 192. The liquid level sensor 195 employing such a detection system can be configured as a differential pressure type liquid level gauge, an impedance type liquid level gauge, or an electrostatic capacitance type liquid level gauge. If foaming occurs in the water, a defoaming agent (for example, a surfactant) may be added to the water or gas may be blown onto the water.

[0074] The removal unit 19 may have a separation membrane instead of or in addition to the gas-liquid separation mechanism 19'. When the gas-liquid separation mechanism 19' and the separation membrane are used in combination, the separation membrane can be provided upstream, downstream, or both upstream and downstream of the gas-liquid separation mechanism 19'. The separation membrane either allows the product molecules to pass through and blocks other molecules from passing through, or blocks the product molecules from passing through and allows other molecules to pass through. Such a separation membrane can be made of a metal, an inorganic oxide, or a metal organic framework (MOF).

[0075] Examples of metals include titanium, aluminum, copper, nickel, chromium, cobalt, and alloys containing these. When a metal is used, the separation membrane is preferably a porous body with a porosity of 80% or more. Examples of inorganic oxides include silica and zeolite. Examples of the metal organic framework include a framework of zinc nitrate hydrate and terephthalic acid dianion, and a framework of copper nitrate hydrate and trimesic acid trianion.

[0076] The separation membrane is preferably made of a porous body having continuous pores (pores penetrating the cylindrical wall) in which adjacent pores are connected to each other. A separation membrane having such a configuration can increase the permeability of water or carbon monoxide, and can more smoothly and reliably separate water from hydrogen and / or carbon monoxide from carbon dioxide. The porosity of the separation membrane is not particularly limited, but is preferably 10 to 90%, and more preferably 20 to 60%, which prevents the mechanical strength of the separation membrane from decreasing significantly while maintaining a sufficiently high permeability to water or carbon monoxide. The shape of the separation membrane is not particularly limited, and examples thereof include cylindrical, rectangular, hexagonal and other rectangular tubular shapes.

[0077] From the viewpoint of further increasing the efficiency of converting carbon dioxide into carbon monoxide, it is effective to increase the reduction (regeneration) efficiency of the reducing agent 4R in an oxidized state. In this case, the average pore size of the separation membrane is preferably 600 pm or less, and more preferably 400 to 500 pm, which can further improve the efficiency of separation of water and hydrogen. The separation membrane is usually used in a state where it is housed in a housing. In this case, the space outside the separation membrane in the housing may be depressurized, or a carrier gas (sweep gas) may be passed through it. Examples of the carrier gas include inert gases such as helium and argon.

[0078] Furthermore, the separation membrane is preferably hydrophilic. If the separation membrane has hydrophilic properties, the affinity of water to the separation membrane increases, and water can more easily pass through the separation membrane. Methods for imparting hydrophilicity to a separation membrane include a method for improving the polarity of the separation membrane by changing the ratio of metal elements in the inorganic oxide (for example, by increasing the Al / Si ratio), a method for coating the separation membrane with a hydrophilic polymer, a method for treating the separation membrane with a coupling agent having a hydrophilic group (polar group), and a method for subjecting the separation membrane to plasma treatment, corona discharge treatment, etc. Furthermore, the affinity for water may be controlled by adjusting the surface potential of the separation membrane.

[0079] On the other hand, when separation of carbon monoxide and carbon dioxide is given priority in a separation membrane, or when separation of water and hydrogen and separation of carbon monoxide and carbon dioxide are simultaneously performed, the constituent material, porosity, average pore size, degree of hydrophilicity or hydrophobicity, surface potential, etc. of the separation membrane can be set in an appropriate combination. It is conceivable to configure the tubular body 41 of the reactor 4ab with such a separation membrane, but in this case, the temperature (reaction temperature) of the reactor 4ab cannot be set to a high temperature because the separation membrane is deteriorated by heat. In contrast to this, by disposing the separation membrane outside the reactor 4ab, the temperature of the reactor 4ab can be set to a relatively high temperature, and therefore the efficiency of converting carbon dioxide into carbon monoxide and the efficiency of regenerating (reducing) the reducing agent 4R by the reducing gas can be further increased.

[0080] Next, the method of use (operation) of the gas production system 100 will be described. [1] First, the gas line (flow path) is switched in the gas switching unit 8 to connect the connection unit 2 to the reactor 41a and connect the reducing gas supply unit 3 to 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.

[0081] [4] Next, the exhaust gas passes through compression section 6, which increases the pressure of the exhaust gas. [5] Next, the exhaust gas passes through the fine component removal section 7. This removes condensed water generated when the exhaust gas is compressed in the compression section 6 and inactive components that reduce the activity of the reducing agent 4R from the exhaust gas. [6] Next, the exhaust gas passes through the exhaust gas heating section 10. This heats the exhaust gas. [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.

[0082] The temperature (reaction temperature) of the reactor 41a (exhaust gas, reducing agent 4R) in the above step [7] is preferably 500°C or higher, more preferably 600°C or higher, even more preferably 650 to 1100°C, and particularly preferably 700 to 1000°C. If the reaction temperature is set within the above range, for example, a sudden decrease in the temperature of the reducing agent 4R due to an endothermic reaction when carbon dioxide is converted to carbon monoxide can be prevented or suppressed, and the reduction reaction of carbon dioxide in the reactor 41a can proceed more smoothly.

[0083] [9] The exhaust gas is discharged from the reactor 41a to the gas line GL5a. Then, when the exhaust gas passes through the removal unit 19, carbon monoxide may be removed from the exhaust gas, and the exhaust gas may be supplied to the gas line GL4 via the discharge line 19a.

[10] 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 of the reactor 42a can be the same as those of the reactor 41a.

[0084]

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

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

[12] Next, the reducing gas containing hydrogen passes through the reducing gas heating section 11. This heats the reducing gas.

[13] 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.

[0085] The temperature (reaction temperature) of the reactor 41b (reducing gas, reducing agent 4R) in the above step

[13] is preferably 500°C or higher, more preferably 600°C or higher, even more preferably 650 to 1100°C, and particularly preferably 700 to 1000°C. By setting the reaction temperature within the above range, for example, it is possible to prevent or suppress a sudden drop in the temperature of the reducing agent 4R due to an endothermic reaction when reducing (regenerating) the oxidized reducing agent 4R, and therefore the reduction reaction of the reducing agent 4R in the reactor 41b can proceed more smoothly.

[0086]

[14] The reducing gas is discharged from reactor 41b to gas line GL5b. Then, when the reducing gas passes through the removal section 19, water is removed from the reducing gas, and the gas is discharged from the discharge line 19b. This also reduces the amount of water contained in the mixed gas.

[15] Next, the reducing gas is supplied to the reactor 42b. 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 in reactor 42b can be the same as those in reactor 41b.

[0087]

[16] Next, the gases that have passed through the reactors 42a and 42b are combined to produce a mixed gas. At this point, the temperature of the mixed gas is typically 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.

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

[0088]

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

[19] Next, the produced gas is discharged from the produced gas discharge section 40 to the outside of the gas production apparatus 1 and is used for the next process.

[0089] Second Embodiment The reaction section 4 can also be configured as follows. Fig. 5 is a schematic diagram showing the configuration of a reaction section in the second embodiment, and Fig. 6 is a schematic diagram showing a method for switching the gas to be 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 same points will be omitted.

[0090] 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 join together at the second gas switching unit 8b to form the 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.

[0091] A removal section 19 is provided midway along each of the gas lines GL4a to GL4d. With this configuration, by switching the gas lines (flow paths) between the first gas switching unit 8a and the second gas switching unit 8b, it is possible to supply an exhaust gas (oxidizing gas) to one of the reactors 4a to 4d and pass it through, while continuously supplying a reducing gas to the remaining three reactors 4a to 4d in this order and passing it through.

[0092] That is, in this embodiment, three reactors are connected in series, and a removal section 19 capable of removing products derived from the gas supplied to the reactors is connected between two adjacent reactors. In this embodiment, among the multiple reactors 4a to 4d, one reactor to which exhaust gas is supplied constitutes the first reactor, and three reactors to which reducing gas is continuously supplied when exhaust gas is supplied to the first reactor constitute the second reactors.

[0093] Specifically, in the first turn shown in Figure 6(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 this can be discharged via the gas line GL4a.

[0094] On the other hand, for the remaining reactors 4b-4d, reducing gas (hydrogen) is first supplied to reactor (first second reactor) 4b via gas line GL3b, and then the reducing gas (residual hydrogen) that has passed through this can be supplied to reactor (second second reactor) 4c via gas line GL4b, gas line GL5c, and gas line GL3c. At this time, water is removed by removal unit 19 provided midway through gas line GL5c and discharged via discharge line 19c. Thereafter, the reducing gas (residual hydrogen) that has passed through reactor 4c is supplied to reactor (third second reactor) 4d via gas line GL4c, gas line GL5d, and gas line GL3d, and the reducing gas (water) that has passed through this can be discharged via gas line GL4d. At this time, water is removed by removal unit 19 provided midway through gas line GL5d and discharged via discharge line 19d.

[0095] Next, in the second turn shown in FIG. 6(II), exhaust gas is supplied to and passed through reactor (first reactor) 4b, while reducing gas is continuously supplied to and passed through reactors (second reactors) 4c, 4d, and 4a in this order. Next, in the third turn shown in FIG. 6(III), exhaust gas is supplied to and passed through reactor (first reactor) 4c, while reducing gas is continuously supplied to and passed through reactors (second reactors) 4d, 4a, and 4b in this order. Next, in the fourth turn shown in FIG. 6(IV), exhaust gas is supplied to and passed through reactor (first reactor) 4d, while reducing gas is continuously supplied to and passed through reactors (second reactors) 4a, 4b, and 4c in this order.

[0096] In this embodiment, a series of operations from the first turn to the fourth turn is considered as one cycle, and by repeating multiple cycles, carbon dioxide can be converted to carbon monoxide continuously and stably. 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 prevents the hydrogen (reducing gas) from being wasted.

[0097] Furthermore, 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, which allows other operations to be performed in the reactor that is not being used for normal operation while continuing normal operation to produce product gas (carbon monoxide). For example, when converting carbon dioxide to carbon monoxide (carbon valuables), carbon may accumulate on the surface of the reducing agent 4R, resulting in a decrease in 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.

[0098] 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 using an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance.

[0099] The gas-liquid separation mechanism 19' for separating carbon dioxide from the product carbon monoxide into gas and liquid can have the configuration shown in FIG. FIG. 7 is a schematic diagram showing another configuration of the gas-liquid separation mechanism. The following description of the configuration shown in FIG. 7 will focus on the differences from the configuration shown in FIG. 3, and a description of similar points will be omitted. 7, a cooler 191, a check valve 193, and a tank 192 are arranged in this order from the upstream side along gas lines GL5a and GL5b. The pH meter 194 is omitted. In this configuration example, a compressor is connected to the cooler 191 and the tank 192 to pressurize the interiors thereof in order to recover carbon dioxide as a liquid.

[0100] Carbon dioxide as a liquid component produced by cooling and pressurization in the cooler 191 is stored in a tank 192. On the other hand, carbon monoxide as a gas component is discharged from discharge lines 19a and 19b. Note that the discharge lines 19a and 19b may be connected to the gas line GL4. 7, the carbon dioxide stored in the tank 192 is vaporized again and then supplied to the reactors 42a and 42b. Therefore, a vaporizer may be provided in the gas line GL5a downstream of the tank 192. Furthermore, if the pressurizer is omitted, the carbon dioxide can be sublimated and recovered as a solid component (separated component). In this case, the phase separation mechanism constitutes a gas-solid separation mechanism that separates the solid component from the gas component. In this case, the temperature X [°C] at which the separated component vaporizes corresponds to the sublimation point of the solid component (solid carbon dioxide). The phase separation mechanism may be configured to separate a separation component that includes both a liquid component and a solid component from a gas component. However, a gas-liquid separation mechanism that separates a liquid component from a gas component is advantageous in that it does not complicate the device configuration and allows for a wider range of device configuration options. Furthermore, it may be provided in the following aspects.

[0101] (1) A gas production apparatus having at least two reactors and a removal unit, the two reactors being connected in series and configured to be able to supply an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance, each reactor containing at least one of a metal and a metal oxide, the at least one of the metal and the metal oxide generating carbon valuables by reducing the carbon dioxide or promoting a reaction between the carbon dioxide and the reducing substance, the removal unit being connected between the two reactors and having a phase separation mechanism that removes products derived from the gas supplied to the reactors by phase separation between a separated component containing at least one of a liquid component and a solid component generated by cooling and a gas component.

[0102] (2) The gas production apparatus according to (1) above, wherein the temperature of the reactor is 500°C or higher.

[0103] (3) The gas production apparatus according to (1) or (2) above, wherein the separated components are configured not to flow into the reactor.

[0104] (4) The gas manufacturing apparatus described in (3) above, having at least one of a configuration in which the phase separation mechanism is arranged at a position vertically below the reactor, and a configuration in which a check valve is provided between the phase separation mechanism and the reactor.

[0105] (5) In the gas manufacturing apparatus described in any one of (1) to (4) above, when the temperature at which the separated components vaporize is X [°C], the cooling temperature in the phase separation mechanism is not less than X-120°C and not more than X°C, and is not less than absolute zero.

[0106] (6) The gas manufacturing apparatus according to any one of (1) to (5) above, wherein the phase separation mechanism is a gas-liquid separation mechanism that separates the liquid component and the gas component into gas and liquid.

[0107] (7) The gas manufacturing apparatus described in (6) above further comprises a storage section, a liquid level detection section, and a flow path blocking mechanism, wherein the storage section stores the liquid component, the liquid level detection section detects the position of the liquid level of the liquid component, and the flow path blocking mechanism blocks the flow path that transports the liquid component to the storage section according to the position of the liquid level detected by the liquid level detection section.

[0108] (8) The gas manufacturing apparatus according to (7) above, wherein the liquid level detection unit is configured with a differential pressure type liquid level gauge, an impedance type liquid level gauge, or a capacitance type liquid level gauge.

[0109] (9) In the gas manufacturing apparatus described in any one of (1) to (8) above, at least one of the metal and the metal oxide functions as a reducing agent that reduces the carbon dioxide, and the reducing agent is oxidized by contact with the carbon dioxide and reduced by contact with the reducing substance.

[0110] (10) The gas production apparatus according to (9) above, wherein each of the reactors is configured to be able to switch between supplying the oxidizing gas and the reducing gas.

[0111] (11) The gas production apparatus according to (9) or (10) above, wherein the product is derived from the reducing gas.

[0112] (12) The gas production apparatus according to any one of (9) to (11) above, wherein the product is produced by a reaction between the reducing substance and at least one of the metal and metal oxide.

[0113] (13) The gas production apparatus according to any one of (1) to (12) above, wherein the reducing substance is hydrogen and the product is water.

[0114] (14) The gas production apparatus according to (13) above, further comprising a pH measurement unit that measures the pH of the water.

[0115] (15) The gas production apparatus according to (13) or (14) above, further comprising a storage section having a tank for storing the water, the tank being made of an acid-resistant material. Of course, this is not the case.

[0116] 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 spirit of the invention. Such embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as set forth in the claims.

[0117] For example, the gas manufacturing apparatus of the present invention may have any other additional configuration compared to the above embodiment, may be replaced with any configuration that performs a similar function, or may have some configurations omitted. In the first and second embodiments, at least one of a metal and a metal oxide functions as a reducing agent that reduces carbon dioxide. However, at least one of a metal and a metal oxide can also function as a catalyst that promotes the reaction between carbon dioxide and a reducing substance. In this case, the catalyst is housed 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.

[0118] Furthermore, in the above first and second 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. [Explanation of symbols]

[0119] 1: Gas production equipment 2: Connection part 3: Reducing gas supply unit 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 19:Removal section 19': Gas-liquid separation mechanism 191:Cooler 192: Tank 193: Check valve 193': Switching valve 194: pH meter 195: Liquid level sensor 20: Furnace 30: Tank 40: Produced gas discharge 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 19a: Discharge line 19b: Discharge line 19c: Discharge line 19d: Discharge line 191a: Switching line 191b: Switching line J4: Gas junction

Claims

1. A gas production method comprising: A first step of providing at least two reactors connected in series, each containing at least one of a metal and a metal oxide, an oxidizing gas containing carbon dioxide, and a reducing gas containing hydrogen; a second step of supplying the oxidizing gas and the reducing gas to each of the reactors, reducing the carbon dioxide through the action of at least one of the metal and metal oxide to generate carbon values, and reducing the at least one of the metal and metal oxide oxidized by the carbon dioxide through the action of the hydrogen to generate water, or promoting a reaction between the carbon dioxide and the hydrogen to generate carbon values ​​and water; the second step is configured to separate the water and the unreacted hydrogen while cooling them between the two reactors, generate hydrogen from the separated water, and return the hydrogen to the reducing gas in the first step.

2. In the gas production method according to claim 1, The gas production method, wherein the temperature of the reactor is 500°C or higher.

3. In the gas production method according to claim 1, a gas producing method, wherein the oxidizing gas and the reducing gas are alternately supplied to each of the reactors;

4. In the gas production method according to claim 1, The method for producing gas, wherein the carbon value is carbon monoxide.

5. In the gas production method according to claim 1, The separated unreacted hydrogen is supplied to another reactor.

6. In the gas production method according to claim 1, A gas production method, wherein at least a portion of the hydrogen contained in the reducing gas is produced by electrolysis of water.

7. In the gas production method according to claim 1, The gas production method, wherein the temperature during the cooling is 20°C or higher and 100°C or lower.

8. The gas production method according to claim 1, at least one of the metal and the metal oxide functions as a reducing agent that reduces the carbon dioxide; The gas production method, wherein the reducing agent is oxidized by contact with the carbon dioxide and reduced by contact with the hydrogen.

9. The gas production method according to claim 8, a gas producing method, wherein the oxidizing gas and the reducing gas are alternately supplied to each of the reactors;

10. The gas production method according to claim 8, The gas production method, wherein the water is produced by a reaction between the hydrogen and at least one of the metal and the metal oxide.

11. The gas production method according to claim 1, The method for producing a gas, wherein the water contains hydrogen sulfide or carbon dioxide.

12. A gas production apparatus, The system includes at least two reactors, a removal section, an oxidation gas supply section, and a reduction gas supply section including a hydrogen generation device; the two reactors are connected in series and configured to be able to supply an oxidizing gas containing carbon dioxide from the oxidizing gas supply unit and a reducing gas containing hydrogen from the reducing gas supply unit; each of the reactors contains at least one of a metal and a metal oxide; At least one of the metal and the metal oxide reduces the carbon dioxide to produce carbon values ​​and is oxidized, and is reduced by the action of the hydrogen to produce water, or promotes a reaction between the carbon dioxide and the hydrogen to produce carbon values ​​and water; the removal unit has a separation mechanism connected between the two reactors and configured to separate water generated from the hydrogen and unreacted hydrogen while cooling them, and then return the water to the hydrogen generation device.

13. In the gas production apparatus according to claim 12, The gas production apparatus is configured to prevent the water from flowing into the reactor.

14. In the gas production apparatus according to claim 12, The gas production apparatus has at least one of a configuration in which the separation mechanism is disposed at a position vertically below the reactor, and a configuration in which a check valve is provided between the separation mechanism and the reactor.

15. In the gas production apparatus according to claim 12, The gas production device further comprises a pH measuring unit that measures the pH of the water.

16. The gas production apparatus according to claim 12, Further, a storage unit having a tank for storing the water is provided, The gas production device, wherein the tank is made of an acid-resistant material.

17. The gas production apparatus according to claim 12, A gas production apparatus comprising a first gas switching section connected to each of the inlets of the at least two reactors and a second gas switching section connected to each of the outlets.

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