Gas production device

Abstract

[Problem] To provide a gas production device that makes it possible to raise the temperature of a reaction unit by separating a removal unit from a reactor and that can efficiently generate a valuable carbon substance. [Solution] Provided according to one aspect of the present invention is a gas production device. This gas production device has at least two reactors and a removal unit. The two reactors are connected in series and are configured to be capable of supplying an oxidizing gas that contains carbon dioxide and a reducing gas that contains a reducing substance. Each of the reactors accommodates a metal and / or a metal oxide. The metal and / or metal oxide promotes the reduction of the carbon dioxide or the reaction between the carbon dioxide and the reducing substance, thereby generating a valuable carbon substance. The removal unit is connected between the two reactors and has a phase separation mechanism that carries out phase separation of a gaseous component and a separated component including at least one of a liquid component and a solid component produced through cooling, thereby removing products derived from the gas supplied to the reactors.

Description

Gas production equipment

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

[0002] In recent years, carbon dioxide (CO ２ ) is continuing to increase in atmospheric concentration. Rising concentrations of carbon dioxide in the atmosphere contribute to global warming. Therefore, it is important to capture carbon dioxide released into the atmosphere, and if the captured carbon dioxide can be converted into carbon-valuable materials and reused, a carbon-circulating 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 each set their own reduction rates for carbon dioxide, a cause of global warming, using 1990 as a base year, and 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 have been made to reduce carbon dioxide in these industries. ２ Carbon capture and storage (CCS) is one example. However, this technology has physical limitations due to 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.

[0004] Patent No. 5858926 JP 2020-23488 A

[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 regarding the carbon monoxide production conditions and production apparatus, 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, improving energy efficiency is also important. In carbon monoxide production using the above-mentioned metal oxides, the generated gas 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 generated gas 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 generated gas. For example, Patent Document 2 proposes a configuration in which a selectively permeable membrane (removal unit) that separates reaction products from the reaction system is installed in a 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 will deteriorate or be damaged if the reaction system becomes hot, making it difficult to use. In view of the above circumstances, the present invention provides a gas production device 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.

[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.

[0010] Fig. 1 is a schematic diagram showing the overall configuration of a gas production system using the gas production apparatus of the present invention. Fig. 2 is a schematic diagram showing the configuration of a reaction section of a first embodiment. Fig. 3 is a schematic diagram showing the configuration of a gas-liquid separation mechanism. Fig. 4 is a schematic diagram showing another configuration of a gas-liquid separation mechanism. Fig. 5 is a schematic diagram showing the configuration of a reaction section of a second embodiment. Fig. 6 is a schematic diagram showing a method of switching gases to be passed through a reactor in the second embodiment. Fig. 7 is a schematic diagram showing another configuration of a gas-liquid separation mechanism.

[0011] The gas production apparatus of the present invention will be described in detail below based on 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 the gas production apparatus of the present invention. FIG. 2 is a schematic diagram showing the configuration of a reaction section of the first embodiment. The gas production system 100 shown in FIG. 1 includes a furnace 20 that generates exhaust gas (oxidizing gas) containing carbon dioxide, and a gas production apparatus 1 connected to the furnace 20 via a connection section 2. Note that, in this specification, the upstream side with respect to the gas flow direction will also be simply referred to as the "upstream side," and the downstream side will also be simply referred to as the "downstream side."

[0012] The furnace 20 is not particularly limited, but may be, for example, a furnace attached to a steelworks, a smelter, or a thermal power plant, and preferably includes a combustion furnace, a blast furnace, a converter, etc. In the furnace 20, exhaust gas is generated (or produced) during combustion, melting, refining, etc. of the contents. In the case of a combustion furnace (incinerator) at a waste incineration plant, examples of the contents (waste) include plastic waste, food waste, municipal solid waste (MSW), discarded tires, biomass waste, household waste (futons, paper), building materials, etc. Note that these wastes may be contained alone or in combination of two or more types.

[0013] Exhaust gas typically contains, in addition to carbon dioxide, other gas components such as nitrogen, oxygen, carbon monoxide, water vapor, and methane. 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, and more preferably 5% by volume or more. Exhaust gas from a combustion furnace in a waste incineration plant contains 5 to 15% by volume of carbon dioxide, 60 to 70% by volume of nitrogen, 5 to 10% by volume of oxygen, and 15 to 25% by volume of water vapor.

[0014] Exhaust gas from a blast furnace (blast furnace gas) is a gas generated when pig iron is produced in the 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. Exhaust gas from a 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, 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 volume % carbon dioxide may also be used.

[0015] However, if exhaust gas is used as the oxidizing gas, carbon dioxide, which 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 steelworks or smelter is preferred. Furthermore, as for blast furnace gas and converter gas, untreated gas discharged from the furnace may be used as is, or treated gas after treatment to remove carbon monoxide, etc., may be used. Untreated blast furnace gas and converter gas each have the gas composition described above, and treated gas has a gas composition close to the gas composition shown for the exhaust gas from the combustion furnace. In this specification, all of the above gases (gases before being supplied to the gas production apparatus 1) are referred to as exhaust gas.

[0016] The gas production apparatus 1 produces a product gas (synthesis gas) containing carbon monoxide by contacting exhaust gas (oxidizing 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 described as a representative example of a carbon valuable. However, carbon valuables are not limited to carbon monoxide, and examples include methane, methanol, etc., which may be a single substance or a mixture of two or more types. The type of carbon valuable produced will vary depending on the type of reducing agent described below.

[0017] The gas production apparatus 1 mainly includes a connection section 2, a reducing gas supply section 3, a reaction section 4 including four reactors 41a, 42a, 41b, and 42b (hereinafter collectively referred to as "reactors 4ab"); a gas line GL1 connecting the connection section 2 to the reaction section 4; a gas line GL2 connecting the reducing gas supply section 3 to the reaction section 4; and a gas line GL4 connected to the reaction section 4. In this embodiment, the connection section 2 constitutes an exhaust gas supply section (oxidizing gas supply section) that supplies exhaust gas to the reaction section 4. If necessary, pumps for transporting gas may be disposed 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, the provision of pumps allows for smooth gas transport within the gas production apparatus 1.

[0018] One end of the gas line GL1 is connected to the connection part 2. Meanwhile, 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. 2. 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 part 8 can be configured to include, for example, branch gas lines and flow path opening and closing mechanisms such as valves provided midway along the branch gas lines.

[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 containing the plurality of tubular bodies 41. Such a multi-tubular reactor ensures sufficient 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 improved. The reducing agent 4R of this embodiment is preferably in the form of particles (granules), flakes, pellets, or the like. Reducing agent 4R in such a shape can improve the filling efficiency of the tubular bodies 41 and further increase the contact area with the gas supplied into the tubular bodies 41.

[0020] When the reducing agent 4R is particulate, its volume average particle size is not particularly limited, but is preferably 1 to 50 mm, and more preferably 3 to 30 mm. In this case, the contact area between the reducing agent 4R and the exhaust gas (carbon dioxide) can be further increased, and the efficiency of converting carbon dioxide to carbon monoxide can be further improved. Similarly, regeneration (reduction) of the reducing agent 4R by a reducing gas containing a reducing substance can also be carried out more efficiently. The particulate reducing agent 4R is preferably a compact produced by tumbling granulation, as this increases the sphericity.

[0021] The reducing agent 4R may be supported on a carrier. The material of the carrier may be any material that is not easily denatured by contact with the exhaust gas (oxidizing gas) or by reaction conditions. For example, carbon materials (graphite, graphene, etc.), Mo ２ Carbides such as C, zeolites, montmorillonite, ZrO ２ , TiO ２ , V ２ O ５ , MgO, CeO ２ , Al ２ O ３ , SiO ２ and composite oxides containing these.

[0022] Among these, the constituent materials of the carrier include zeolite, montmorillonite, ZrO ２ , TiO ２ , V ２ O５ , MgO, Al ２ O ３ , SiO ２ and composite oxides containing these are preferred. A support made of such a material is preferred in that it does not adversely affect the reaction of the reducing agent 4R and has excellent supportability for the reducing agent 4R. Here, the support does not participate in the reaction of the reducing agent 4R, but simply supports (holds) the reducing agent 4R. One example of such a form is a configuration 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. However, 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. Iron-containing metal oxides or composite metal oxides are particularly preferred. These metal oxides are useful because they have particularly good efficiency in converting carbon dioxide 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, lattice-shaped (e.g., mesh-shaped, 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 configuration in which a mesh body is formed using the reducing agent 4R and placed in the housing 42 is preferred. In this configuration, it is possible to prevent an increase in the resistance to the passage of the exhaust gas and reducing gas within each reactor 4ab, while also ensuring sufficient opportunities for the reducing agent 4R to come into contact with the exhaust gas and reducing gas. The volumes of the four reactors 41a, 42a, 41b, and 42b are set to be approximately equal to each other and are appropriately set 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). Furthermore, 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] Along the gas line GL1, a concentration adjustment unit 5, a compression unit 6, a trace component removal unit 7, and an exhaust gas heating unit (oxidizing gas heating unit) 10 are provided in this order from the connection unit 2 side. The concentration adjustment 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 adjustment unit 5, the concentrations of the unnecessary gas components contained in the exhaust gas can be relatively reduced. This makes it possible to prevent or suppress the unnecessary gas components from adversely affecting the efficiency of carbon dioxide conversion 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. This more reliably prevents the exhaust gas from igniting. The oxygen removal device that removes oxygen contained in the exhaust gas can be configured using one or more of a low-temperature separation (cryogenic) separator, a pressure swing adsorption (PSA) separator, a membrane separation separator, a temperature swing adsorption (TSA) separator, a chemical absorption separator, a chemical adsorption separator, etc. Note that the concentration adjustment 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, with a positive displacement 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-lobe blower) that can handle low pressure, or a centrifugal blower.

[0031] Among these, the compression section 6 is preferably configured with a centrifugal compressor from the viewpoint of facilitating the scale-up of the gas production system 100, and is preferably configured with a reciprocating compressor from the viewpoint of reducing the manufacturing cost 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 fine component removal unit 7 removes fine components (such as trace amounts of unnecessary gas components) contained in the exhaust gas. The fine component removal unit 7 can be composed of at least one type of treatment device, for example, a gas-liquid separator, a protective device (guard reactor), and a scrubber (absorption tower). When multiple treatment devices are used, they can be arranged in any order, but when a gas-liquid separator and a protective device are used in combination, it is preferable to arrange the gas-liquid separator upstream of the protective device. In this case, the efficiency of removing fine components from the exhaust gas can be further improved, and the service life (lifespan) of the protective device can be extended.

[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 and removed in the condensed water. The gas-liquid separator can be configured, for example, as a simple container, a swirl-flow separator, a centrifugal separator, a surface tension separator, etc. Among these, it is preferable that the gas-liquid separator be configured as a simple container 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 placed at the gas-liquid interface inside the container.

[0034] In this case, a liquid line may be connected to the bottom of the container, with a valve provided along the line. With this configuration, the 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 can be configured to be supplied to a protector, for example. Such a protector preferably includes a substance capable of capturing trace components (inactivating components) contained in the exhaust gas that reduce the activity of the reducing agent 4R upon contact with the reducing agent 4R. According to this configuration, when the exhaust gas passes through the protector, the substance in the protector reacts with (captures) the inactivating components, thereby preventing or suppressing the reducing agent 4R from reaching the reducing agent 4R in the reactor 4ab, thereby protecting the reducing agent 4R (i.e., preventing a decrease in activity). Therefore, it is possible to prevent or suppress a drastic decrease in the efficiency of carbon dioxide conversion to carbon monoxide by the reducing agent 4R due to the adverse effects of the inactivating 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 sudden decrease in the activity of the reducing agent 4R can be effectively prevented. The above-mentioned substance may be any substance whose activity is decreased by the same components as the inactivating components 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 components.

[0038] The protector may be configured such that a mesh material is placed in a housing and particles of the substance are placed on the mesh material, or such that a honeycomb filter member or a cylindrical or particle-shaped molded body made of the substance is placed in 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 removal efficiency of the inactivated components while preventing deterioration of the substance due to heat.

[0039] The exhaust gas heating unit 10 heats the exhaust gas before it is supplied to the reactor 4ab. Preheating the pre-reaction (pre-reduction) exhaust gas in the exhaust gas heating unit 10 can further promote the conversion (reduction) reaction of carbon dioxide to carbon monoxide by the reducing agent 4R in the reactor 4ab. The exhaust gas heating unit 10 can be configured, for example, with 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 it is supplied to the reactor 4ab, thereby enabling effective use of heat.

[0040] The heat exchanger can be configured as, for example, a jacket-type heat exchanger, an immersion coil-type heat exchanger, a double-pipe heat exchanger, a shell-and-tube heat exchanger, a plate-type heat exchanger, a spiral-type heat exchanger, or the like. In the exhaust gas heating unit 10, either the electric heater or the heat exchanger may be omitted. In the exhaust gas heating unit 10, a combustion furnace or the like can be used instead of the electric heater. 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. The renewable energy that can be used can be at least one type of electrical energy 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, and geothermal heat.

[0041] Furthermore, an exhaust gas line may be branched 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 branched exhaust gas line. In this case, a valve is preferably provided midway through the exhaust gas line. If the pressure in the gas manufacturing apparatus 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. This makes it possible to prevent damage to the gas manufacturing apparatus 1 due to an increase in pressure.

[0042] One end of the gas line GL2 is connected to the reducing gas supply unit 3. Meanwhile, the gas line GL2 is connected to the inlet ports of the reactors 41a and 41b of the reaction unit 4 via the gas switching unit 8 and two gas lines GL3a and GL3b. 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 generator that generates hydrogen by electrolysis of water, and a tank (reducing gas raw material storage unit) 30 outside the gas production apparatus 1 that stores water is connected to this hydrogen generator. 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 of the reactors 4ab and 4b.

[0043] The hydrogen generation device can generate large amounts of hydrogen relatively inexpensively and easily. Another advantage is that 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 also 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 a device that electrolyzes a sodium chloride aqueous solution, a device that steam reforms petroleum, and a device that produces ammonia. Alternatively, the gas line GL2 may be connected to a coke oven outside the gas producing device 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 the 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 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 the gas line GL3a to the reactors 41a and 42a containing the reducing agent 4R before oxidation, and reducing gas can be supplied via the gas line GL3b to the reactors 41b and 42b containing the reducing agent 4R after oxidation. At this time, the reaction of the following formula 1 proceeds in the reactors 41a and 42a, and the reaction of the following formula 2 proceeds in the reactors 41b and 42b.

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

[0049] The reactions shown in the above formulas 1 and 2 are both endothermic reactions. For this reason, the gas production apparatus 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 unit, the temperature during 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 conversion of 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 reactions. 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 converting carbon dioxide to carbon monoxide, and further promoting the regeneration of the reducing agent 4R by the reducing gas. In other words, the gas production apparatus 1 preferably has a reducing agent temperature adjustment unit that adjusts the temperature of the reducing agent 4R depending on the type of reducing agent 4R (exothermic reaction or endothermic reaction).

[0051] Here, the conversion rate of carbon dioxide to carbon monoxide in the 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 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 (%) can be calculated using the formula: CO ｏｕｔ / CO ２ｉｎThis is the value calculated by multiplying CO by 100. ２ｉｎ is the molar amount of carbon dioxide supplied to reactor 4ab, and CO ｏｕｔ is the molar amount of carbon monoxide discharged from the reactor 4ab when carbon dioxide is converted into carbon monoxide through contact (reaction) with the reducing agent 4R.

[0052] On the other hand, the conversion rate of hydrogen to water in the 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 temperature 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, etc. The conversion rate of hydrogen to water (%) is calculated by (H ２ｉｎ -H ２ｏｕｔ ) / H ２ｉｎ This is the value calculated by multiplying the ２ｉｎ is the molar amount of hydrogen supplied to reactor 4ab, and H ２ｏｕｔ is the molar amount of hydrogen that passes through the 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 lines merge at a gas junction J4 to form the gas line GL4. Valves (not shown) are provided along the gas lines GL4a and GL4b as needed. For example, by adjusting the valve openings, it is possible to set the passage speeds 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 unit 8.

[0054] A produced gas discharge unit 40, which discharges the produced gas outside the gas production apparatus 1, is connected to the end of the gas line GL4 opposite the reactors 42a and 42b. A gas purification unit 9 is provided midway along the gas line GL4. The gas purification unit 9 purifies carbon monoxide from the mixed gas and recovers the produced gas containing a high concentration of carbon monoxide. Note that if the carbon monoxide concentration in the mixed gas is sufficiently high, the gas purification unit 9 may be omitted.

[0055] The gas purification section 9 can be composed of at least one type of treatment device, for example, a cooler, a gas-liquid separator, a gas separator, a separation membrane, and a scrubber (absorption tower). When multiple treatment devices are used, they may be arranged in any order. However, when a cooler, a gas-liquid separator, and a gas separator are used in combination, it is preferable to arrange them in this order. In this case, the purification efficiency of carbon monoxide from the mixed gas can be further improved.

[0056] The cooler cools the mixed gas, thereby generating condensed water (liquid). Such a cooler can be configured to include a jacket-type cooling device in which a jacket is arranged around a pipe for passing a refrigerant, a multi-tube cooling device having a configuration similar to that of the reactor 4ab (see FIG. 2 ) 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 condensed water, which 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 similarly to 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 gas to pass but prevents liquid from passing 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, condensed water accumulated 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 allows the carbon monoxide or hydrogen to be stored in the drain trap and prevented from being discharged outside the gas production apparatus 1, even if the valve malfunctions and 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 may be configured 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) composite of a metal ion (e.g., copper ion) and an organic ligand (e.g., 5-azidoisophthalic acid), and a separator using amine absorption. A valve may be provided between the gas-liquid separator and the gas separator in the gas line GL4. In this case, the processing rate of the mixed gas (the production rate of the product gas) can be adjusted by adjusting the valve opening.

[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 relative to the total mixed gas. Therefore, in fields where a product gas containing a relatively low concentration (75 to 90% by volume) of carbon monoxide can be used, the carbon monoxide can be directly supplied to the next process without being purified from the mixed gas. In other words, a gas separator can be omitted. Examples of such fields include the field of synthesizing carbon valuables (e.g., ethanol) from the product gas by fermentation with microorganisms (e.g., Clostridium), the field of steel production using the product gas as a fuel or reducing agent, the field of electrical device manufacturing, and the field of synthesizing chemicals (e.g., phosgene, acetic acid) 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 (more than 90% by volume), carbon monoxide is purified from a mixed gas to obtain a product gas containing carbon monoxide at a high concentration. Examples of such fields include fields where the product gas is used as a reducing agent (blast furnaces), fields where the product gas is used as a fuel to generate electricity by thermal power, fields where the product gas is used as a raw material to manufacture chemicals, and fields where the product gas is used as a 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 in each of the gas lines GL5a and GL5b. The removal unit 19 is configured to be capable of at least one of separating water (a product derived from the reducing gas) produced by the contact (reaction) of the reducing agent 4R with hydrogen (a reducing substance) from unreacted hydrogen (the reducing substance), and separating carbon monoxide produced by the contact of the reducing agent 4R with carbon dioxide from unreacted carbon dioxide.

[0064] That is, the removal unit 19 is connected between the two reactors 4ab and has a gas-liquid separation mechanism (phase separation mechanism) 19' that separates the liquid component (separated component) generated by cooling from the gas component, thereby removing products derived from the gas supplied to the reactor 4ab. This configuration makes it possible to remove products derived from the gas supplied to the reactors 41a and 41b, thereby preventing a decrease in the reaction efficiency in the reactors 42a and 42b, i.e., the conversion efficiency of carbon dioxide to carbon monoxide and the reduction (regeneration) efficiency of the oxidized reducing agent 4R. As a result, carbon monoxide (carbon valuables) can be efficiently produced from carbon dioxide.

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

[0066] The following describes a gas-liquid separation mechanism 19' that separates hydrogen, which is a reducing substance, from water, which is a product, into gas and liquid. FIG. 3 is a schematic diagram showing the configuration of the gas-liquid separation mechanism. 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 has 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. A cooler having the same configuration as that described for the gas purification unit 9 can be used as this cooler 191. 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 to prevent the liquid component (separated component) from flowing into the reactor 4ab. This makes it possible to further improve the conversion efficiency (conversion rate) of carbon dioxide to carbon monoxide and the conversion efficiency (conversion rate) of hydrogen to water.

[0068] Specifically, as shown in FIG. 3 , a gas-liquid separation mechanism (phase separation mechanism) 19′ is disposed 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, the inflow of liquid components into the reactor 4ab can be prevented. 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. Note that only one of the configurations of disposing the gas-liquid separation mechanism 19′ vertically below the reactor 4ab and providing a check valve 193 between the gas-liquid separation mechanism 19′ and the reactor 4ab may be employed. In this case, the inflow of liquid components into the reactor 4ab can also be sufficiently prevented. A check valve 193 is provided in the discharge lines 19a and 19b. This check valve 193 can be configured, for example, as a duckbill valve, a poppet check valve, a lift check valve, a swing check valve, a ball check valve, a wafer check valve, a foot check valve, or the like.

[0069] When the boiling point (the temperature at which the separated components vaporize) of the liquid component stored in tank 192 is X [°C], the cooling temperature in gas-liquid separation mechanism 19' (cooler 191) is preferably about X-120°C or higher and about X°C or lower, and above absolute zero, more preferably about X-100°C or higher and about X-10°C or lower, and even more preferably about X-80°C or higher and about X-20°C or lower. By cooling the gas that has passed through reactor 4ab at such a cooling temperature, the substance to be converted into a liquid component by cooling can be condensed and converted into a liquid state in a short time without freezing. When the substance to be converted into a 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, the 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. Therefore, by providing the pH meter 194, the pH of the water stored in the tank 192 can be monitored. If the pH of the water becomes undesirably low, a pH adjuster can be added to the water. In this case, in consideration of the decrease in the water pH, the tank 192 that stores the water can be made of an acid-resistant material. This prevents or suppresses corrosion of the tank 192, thereby extending 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' may also have the configuration shown in Figure 4. The following description of the configuration shown in Figure 4 will focus on the differences from the configuration shown in Figure 3, and similar aspects will not be described. In the gas-liquid separation mechanism 19' shown in Figure 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] 4, a liquid level sensor (liquid level detector) 195 that detects the liquid level of water (liquid component) is connected to the tank 192. By providing the liquid level sensor 195, the switching valve 193' can block the discharge lines 19a and 19b, which are flow paths that transfer the water (liquid component) to the tank (storage unit) 192, and switch to the switching lines 191a and 191b to discharge the water, depending on the liquid level 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 this configuration prevents the separated and removed water (liquid component) from flowing back into the gas production apparatus 1, thereby enabling stable operation of the gas production apparatus 1.

[0073] Since the water stored in the tank 192 may foam, it is preferable that the liquid level sensor 195 detects the liquid level using a detection system that is not or is not easily affected by foaming. Such a liquid level sensor 195 makes it possible to accurately determine the amount of water stored in the tank 192. The liquid level sensor 195 using such a detection system can be configured as a differential pressure level gauge, an impedance level gauge, or a capacitance level gauge. If foaming occurs in the water, an antifoaming agent (e.g., 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 a 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 product molecules to pass through and blocks other molecules from passing, or blocks product molecules from passing through and allows other molecules to pass. Such a separation membrane can be composed of a metal, an inorganic oxide, or a metal organic framework (MOF).

[0075] Examples of the metal include titanium, aluminum, copper, nickel, chromium, cobalt, and alloys containing these. When a metal is used, the separation membrane is preferably a porous body having a porosity of 80% or more. Examples of the inorganic oxide 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, allowing for smoother and more reliable separation of water and hydrogen and / or carbon monoxide and carbon dioxide. The porosity of the separation membrane is not particularly limited, but is preferably 10 to 90%, and more preferably 20 to 60%. This makes it possible to maintain a sufficiently high permeability of water or carbon monoxide while preventing an extreme decrease in the mechanical strength of the separation membrane. The shape of the separation membrane is not particularly limited, and examples include cylindrical, rectangular, hexagonal, and other rectangular tubular shapes.

[0077] From the viewpoint of further increasing the conversion efficiency of carbon dioxide to carbon monoxide, it is effective to increase the reduction (regeneration) efficiency of the oxidized reducing agent 4R. In this case, the average pore diameter of the separation membrane is preferably 600 pm or less, and more preferably 400 to 500 pm. This can further improve the separation efficiency of water and hydrogen. The separation membrane is usually used while housed in a housing. In this case, the space outside the separation membrane within the housing may be decompressed, 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 hydrophilic properties to the separation membrane include a method of 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 of coating the separation membrane with a hydrophilic polymer, a method of treating the separation membrane with a coupling agent having a hydrophilic group (polar group), and a method of subjecting the separation membrane to plasma treatment, corona discharge treatment, or the like. Furthermore, the affinity for water may be controlled by adjusting the surface potential of the separation membrane.

[0079] On the other hand, when the separation of carbon monoxide and carbon dioxide is prioritized in the separation membrane, or when both separation of water and hydrogen and separation of carbon monoxide and carbon dioxide are performed simultaneously, the constituent material, porosity, average pore size, degree of hydrophilicity or hydrophobicity, surface potential, etc. of the separation membrane can be appropriately combined and set. It is also conceivable to form the tubular body 41 of the reactor 4ab using such a separation membrane, but in this case, the separation membrane would deteriorate due to heat, and the temperature (reaction temperature) of the reactor 4ab cannot be set to a high temperature. In contrast, by disposing the separation membrane outside the reactor 4ab, the temperature of the reactor 4ab can be set to a relatively high temperature, thereby further improving the efficiency of conversion of carbon dioxide to carbon monoxide and the efficiency of regeneration (reduction) of the reducing agent 4R by the reducing gas.

[0080] Next, the usage (operation) of the gas production system 100 will be described. [1] First, by switching the gas line (flow path) in the gas switching unit 8, the connection unit 2 and the reactor 41a are connected, and the reducing gas supply unit 3 and the reactor 41b are connected. [2] Next, in this state, the supply of exhaust gas from the furnace 20 begins via the connection unit 2. [3] Next, the exhaust gas passes through the oxygen removal device (concentration adjustment unit 5). This removes oxygen from the exhaust gas, and the concentration of carbon dioxide contained in the exhaust gas increases.

[0081] [4] Next, the exhaust gas passes through the compression section 6. This 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 reducing agent 4R reduces carbon dioxide in the exhaust gas to carbon monoxide. 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, it is possible to prevent or suppress a sudden decrease in the temperature of the reducing agent 4R due to an endothermic reaction when converting carbon dioxide to carbon monoxide, and therefore 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 section 19, carbon monoxide is 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 tank 30 to the hydrogen generation device (reducing gas supply unit 3), and hydrogen is generated from the water.

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

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

[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. Setting the reaction temperature within the above range can prevent or suppress, for example, a sudden decrease in the temperature of the reducing agent 4R due to an endothermic reaction when reducing (regenerating) the oxidized reducing agent 4R, thereby allowing the reduction reaction of the reducing agent 4R in the reactor 41b to proceed more smoothly.

[0086]

[14] The reducing gas is discharged from the reactor 41b to the gas line GL5b. Then, as 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 of the reactor 42b can be the same as those of the 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 unit 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 product gas is discharged from the gas production apparatus 1 through the product gas discharge unit 40 and is used in the next process.

[0089] Second Embodiment The reaction section 4 may also be configured as follows. Fig. 5 is a schematic diagram showing the configuration of the reaction section of the second embodiment. Fig. 6 is a schematic diagram showing a method of switching the gas to be passed through the reactor in the second embodiment. The reaction section 4 of the second embodiment will be described below, focusing on differences from the reaction section 4 of the first embodiment, and a description of similar 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 section 8a is connected to the inlet ports of the reactors 4a to 4d via gas lines GL3a to GL3d. Gas lines GL4a to GL4d are connected to the outlet ports of the reactors 4a to 4d, respectively, and these gases merge at the second gas switching section 8b to form the 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.

[0091] Further, a removal unit 19 is provided midway along each of the gas lines GL4a to GL4d. With this configuration, by switching the gas lines (flow paths) at 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 have it pass through, while continuously supplying a reducing gas to the remaining three of the reactors 4a to 4d in this order and having it pass through.

[0092] That is, in this embodiment, three reactors are connected in series, and a removal unit 19 capable of removing products derived from the gas supplied to the reactors is connected between two adjacent reactors. In this embodiment, of 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 FIG. 6(I), exhaust gas (carbon dioxide) is supplied to the reactor (first reactor) 4a via a gas line GL3a, and the exhaust gas (carbon monoxide) that has passed through this can be discharged via a gas line GL4a.

[0094] Meanwhile, 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 (remaining 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 a removal unit 19 installed in the middle of gas line GL5c and discharged via discharge line 19c. Thereafter, the reducing gas (remaining hydrogen) that has passed through reactor 4c can be 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 a removal unit 19 installed in the middle of gas line GL5d and discharged via discharge line 19d.

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

[0096] In this embodiment, a series of operations from the first turn to the fourth turn constitutes 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, passing the reducing gas through one reactor only once will waste the hydrogen (residual hydrogen) that was not used in the reduction of the oxidized reducing agent 4R. In contrast, in this embodiment, the reducing gas can be passed through three reactors consecutively, in other words, it can be passed through one reactor three times. This prevents 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. Therefore, while continuing normal operation to produce product gas (carbon monoxide), other operations can be performed on the reactor that is not being used for normal operation. For example, when 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 an operation is performed to supply oxygen to the reactor that is not being used for normal operation, 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, an inert gas (e.g., nitrogen gas) may be purged into the reactor before and after supplying oxygen to the reactor. This prevents the reducing gas and oxygen from accidentally coming into contact with each other and causing an explosive reaction. According to the gas production device 1 (gas production system 100) described above, carbon valuables can be efficiently produced using an oxidizing gas containing carbon dioxide and a reducing gas containing a reducing substance.

[0099] Furthermore, a gas-liquid separation mechanism 19′ that separates carbon dioxide from the product carbon monoxide into gas and liquid may have the configuration shown in FIG. 7 . FIG. 7 is a schematic diagram showing another configuration of the gas-liquid separation mechanism. The configuration shown in FIG. 7 will be described below, focusing on differences from the configuration shown in FIG. 3 , and similar aspects will not be described again. In the gas-liquid separation mechanism 19′ shown in FIG. 7 , a cooler 191, a check valve 193, and a tank 192 are arranged in this order from the upstream side in the gas lines GL5a and GL5b. Note that a pH meter 194 is omitted. In this configuration example, a compressor that pressurizes the cooler 191 and the tank 192 is connected to recover carbon dioxide as a liquid.

[0100] Carbon dioxide as a liquid component generated by cooling and pressurization in the cooler 191 is stored in the tank 192. Meanwhile, carbon monoxide as a gas component is discharged through the discharge lines 19a and 19b. The discharge lines 19a and 19b may be connected to the gas line GL4. In the configuration shown in FIG. 7, the carbon dioxide stored in the tank 192 is re-vaporized 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, 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. Furthermore, 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 also be configured to separate the separated component, which includes both liquid and solid components, from the gas component. However, a gas-liquid separation mechanism that separates the liquid component from the gas component is advantageous in that it does not complicate the device configuration and allows for a wider range of device configuration options.

[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, which is configured so that the separated components do not 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 depending on 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 unit having a tank for storing the water, the tank being made of an acid-resistant material. Of course, this is not a limitation.

[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 production apparatus of the present invention may have any additional components compared to the above-described embodiments, may be replaced with any components that exhibit similar functions, or may omit some components. In the above-described first and second embodiments, examples have been described in which at least one of a metal and a metal oxide functions as a reducing agent that reduces carbon dioxide, but at least one of a metal and a metal oxide may 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 accommodating a catalyst in a reactor and simultaneously supplying exhaust gas and a reducing gas to the reactor.

[0118] In the first and second embodiments, a gas containing hydrogen is typically used as the reducing gas, but a gas containing at least one selected from hydrocarbons (e.g., methane, ethane, acetylene, etc.) and ammonia as a reducing substance can also be used as the reducing gas instead of or in addition to hydrogen. 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 connected in series to be used as the second reactor (reactors on the reduction side that reduce the reducing agent 4R) may be two or four or more.

[0119] REFERENCE SIGNS LIST 1: Gas production device 2: Connection section 3: Reducing gas supply section 4: Reaction section 41: Pipe 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 adjustment section 6: Compression section 7: Trace 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 apparatus comprising: 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 of the reactors contains at least one of a metal and a metal oxide; at least one of the metal and the metal oxide generates a carbonaceous product by reducing the carbon dioxide or promoting the reaction between the carbon dioxide and the reducing substance; the removal unit is connected between the two reactors and has a phase separation mechanism for removing a product derived from the gas supplied to the reactor by phase-separating a separation component containing at least one of a liquid component and a solid component generated by cooling and a gas component, the gas production apparatus.

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

3. The gas production apparatus according to claim 1, wherein the separation component is configured not to flow into the reactor, the gas production apparatus.

4. The gas production apparatus according to claim 3, wherein the gas production apparatus has at least one of a configuration in which the phase separation mechanism is disposed 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.

5. The gas production apparatus according to claim 1, wherein when the temperature at which the separation component vaporizes is X [°C], the cooling temperature in the phase separation mechanism is X - 120 °C or higher and X °C or lower and above absolute zero, the gas production apparatus.

6. The gas production apparatus according to claim 1, wherein the phase separation mechanism is a gas-liquid separation mechanism for gas-liquid separating the liquid component and the gas component, the gas production apparatus.

7. The gas production apparatus according to claim 6, further comprising a storage unit, a liquid level detection unit, and a flow path blocking mechanism, wherein the storage unit stores the liquid component, the liquid level detection unit detects the position of the liquid level of the liquid component, and the flow path blocking mechanism blocks a flow path for transferring the liquid component to the storage unit according to the position of the liquid level detected by the liquid level detection unit, the gas production apparatus.

8. The gas production apparatus according to claim 7, wherein the liquid level detection unit is composed of a differential pressure type liquid level gauge, an impedance type liquid level gauge, or a capacitance type liquid level gauge, the gas production apparatus.

9. The gas production apparatus according to claim 1, At least one of the metal and the metal oxide functions as a reducing agent for reducing the carbon dioxide, The reducing agent is a gas production device that is oxidized by contact with the carbon dioxide and reduced by contact with the reducing substance.

10. In the gas production device according to claim 9, Each of the reactors is configured to be able to switch and supply the oxidizing gas and the reducing gas, a gas production device.

11. In the gas production device according to claim 9, The product is derived from the reducing gas, a gas production device.

12. In the gas production device according to claim 9, The product is a gas production device produced by the reaction of the reducing substance with at least one of the metal and the metal oxide.

13. In the gas production device according to claim 1, The reducing substance is hydrogen, and the product is water, a gas production device.

14. In the gas production device according to claim 13, Furthermore, it includes a pH measurement unit for measuring the pH of the water, a gas production device.

15. In the gas production device according to claim 13, Furthermore, it includes a storage unit having a tank for storing the water, The tank is made of an acid-resistant material, a gas production device.