Chemical looping system and chemical looping method

Abstract

To provide a chemical looping system for making compatible both an improvement of the collection of carbon dioxide and an improvement of hydrogen yield, and a chemical looping method.SOLUTION: In order to solve a problem, a reduction reaction part and an oxidation reaction part are arranged in a circulation path. The reduction reaction part comprises a fuel reaction part for making oxygen carrier metal particles react with a fuel. The oxidation reaction part comprises a hydrogen creation part for creating hydrogen by making the after-reaction oxygen carrier metal particles generated in the fuel reaction part and aqueous vapor react with each other. Also, in the reduction reaction part, reduction states of the oxygen carrier metal particles exist in a plurality of stages. There are provided a chemical looping system for supplying only the oxidation carrier metal particles having high reduction degrees to the hydrogen creation part, and a chemical looping method using the system. According to this invention, it becomes possible to make compatible both an improvement of the collection of carbon dioxide and an improvement of hydrogen yield.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a chemical looping system and a chemical looping method, and more particularly to a chemical looping system and a chemical looping method that achieve both carbon dioxide capture and hydrogen production. [Background technology]

[0002] In recent years, a technology called chemical looping has been attracting attention in the combustion of fuels containing hydrocarbons. Chemical looping is an energy conversion system in which metal oxides known as oxygen carrier metal particles are circulated between multiple reaction towers as an oxygen source, and the combustion reaction is divided into a metal oxidation reaction and a metal oxide reduction reaction, producing thermal energy and useful gases.

[0003] For example, Patent Document 1 describes a chemical looping combustion apparatus equipped with a fuel reaction tower (reduction tower) and an oxidation tower, and a method for producing nitrogen and hydrogen using the same. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-164235 A Summary of the Invention [Problem to be solved by the invention]

[0005] Chemical Looping Combustion (CLC) is equipped with an oxidation tower that promotes the oxidation reaction of oxygen carrier metal particles by air, and a fuel reactor that promotes the combustion reaction of fuel and the reduction of oxygen carrier metal particles. In the oxidation tower, oxygen in the air is consumed by the reaction with oxygen carrier metal particles, and gas with a higher nitrogen concentration than normal air can be recovered. On the other hand, in the fuel reactor, air and fuel do not react directly, so nitrogen from the air does not get mixed in the exhaust gas generated by fuel combustion, making it possible to capture high-purity carbon dioxide. Therefore, chemical looping can be used in carbon dioxide capture and storage (CCS: Carbon dioxide Capture and Storage) and utilization (CCU: Carbon dioxide Capture and Utilization) technologies. In addition, it can also be used as a chemical looping hydrogen production system (CLH, or CLHG) system, which is equipped with a hydrogen production tower that supplies water vapor to the rear of the fuel reactor tower and generates and collects hydrogen by consuming the oxygen in the water vapor through an oxidation reaction with oxygen carrier metal particles.

[0006] Here, when considering CCS or CCU, complete combustion reaction is essential in the fuel reactor. To achieve complete combustion in the fuel reactor, it is necessary to add an excess of oxidized oxygen carrier metal particles to the fuel. However, when an excess of oxidized oxygen carrier metal particles is added to the fuel reactor, a large amount of unreacted oxygen carrier metal particles are present, making it difficult to increase the reduction rate of the entire oxygen carrier metal particles, resulting in a problem of reduced reaction efficiency in the hydrogen generation tower. On the other hand, in order to produce hydrogen at a high yield, it is necessary to increase the reduction rate of the oxygen carrier metal particles in order to increase the reaction efficiency in the hydrogen generation tower. However, in order to increase the reduction rate of the oxygen carrier metal particles in the fuel reaction tower, it is necessary to make the reaction an incomplete combustion reaction, which reduces the recovery rate of carbon dioxide. That is, in conventional chemical looping, there is a trade-off between improving the carbon dioxide recovery rate and improving the hydrogen yield.

[0007] Therefore, an object of the present invention is to provide a chemical looping system and a chemical looping method that achieve both improved carbon dioxide recovery and improved hydrogen yield. [Means for solving the problem]

[0008] As a result of intensive research into the above-mentioned problems, the inventors have discovered that in a chemical looping system and chemical looping method in which oxidation and reduction reactions of oxygen carrier metal particles are repeated, by dividing the reduction state of oxygen carrier metal particles into multiple stages during the reduction reaction in which oxygen carrier metal particles react with fuel, it is possible to improve carbon dioxide recovery and hydrogen yield, and have completed the present invention. That is, the present invention relates to the following chemical looping system and chemical looping method.

[0009] The chemical looping system of the present invention for solving the above problems is a chemical looping system in which oxygen carrier metal particles repeat oxidation and reduction reactions in a circulation flow path, style The passage is provided with a reduction reaction section and an oxidation reaction section. The reduction reaction section includes a fuel reaction section that reacts oxygen carrier metal particles with fuel. The oxidation reaction section includes a hydrogen generation section that reacts the oxygen carrier metal particles produced after the reaction in the fuel reaction section with water vapor to generate hydrogen. The reduction reaction section has the feature that the reduction state of the oxygen carrier metal particles exists in multiple stages, and only oxygen carrier metal particles with a high degree of reduction are supplied to the hydrogen generation section. The chemical looping system of the present invention allows the reduction state of the oxygen carrier metal particles to exist in multiple stages in the reduction reaction section, and supplies only oxygen carrier metal particles with a high degree of reduction to the hydrogen generation section, thereby making it possible to improve the hydrogen yield. Also, in the area where the reduction degree of the oxygen carrier metal particles is low, it is possible to suppress the generation of carbon monoxide and improve the carbon dioxide recovery efficiency. This makes it possible to achieve both improved carbon dioxide recovery and improved hydrogen yield in the chemical looping system.

[0010] In one embodiment of the chemical looping system of the present invention, the fuel reaction section comprises a complete combustion section where a complete combustion reaction takes place and an incomplete combustion section where an incomplete combustion reaction takes place, and is characterized in that the oxygen carrier metal particles after reaction produced in the incomplete combustion section are supplied to the hydrogen generation section, and the gas produced in the incomplete combustion section is supplied to the complete combustion section. According to this feature, by dividing the fuel reaction section into a complete combustion section and an incomplete combustion section, it becomes easy to form oxygen carrier metal particles with different reduction states. The oxygen carrier metal particles after the reaction generated in the incomplete combustion section have a high degree of reduction, and by supplying these oxygen carrier metal particles to the hydrogen generation section, it becomes possible to produce hydrogen at a high yield. In addition, by supplying the incomplete combustion gas generated in the incomplete combustion section to the complete combustion section and carrying out a complete combustion reaction, it becomes possible to recover high-purity carbon dioxide. This makes it possible to further increase the carbon dioxide recovery rate and hydrogen yield in the chemical looping system.

[0011] In one embodiment of the chemical looping system of the present invention, the oxygen carrier metal particles are characterized in that they contain iron, copper, manganese, cerium, molybdenum, tungsten, or atoms of these metals, even if only partially. According to this feature, by using oxygen carrier metal particles containing metal atoms mainly selected from the transition metal group, a plurality of reduced states can be stably formed. This makes it possible to provide oxygen carrier metal particles having a reduction degree suitable for each reaction (oxidation reaction or reduction reaction). This also makes it possible to increase the efficiency of each reaction in the chemical looping system.

[0012] In addition, the chemical looping method of the present invention for solving the above problems is a chemical looping method in which oxygen carrier metal particles repeat oxidation and reduction reactions in a circulation flow path, style Within the passage, a reduction reaction process and an oxidation reaction process proceed independently. The reduction reaction process includes a fuel reaction process in which oxygen carrier metal particles are reacted with fuel. The oxidation reaction process includes a hydrogen generation process in which the oxygen carrier metal particles after the reaction produced in the fuel reaction process are reacted with water vapor to generate hydrogen. The reduction reaction process is characterized in that there are multiple stages of reduction states of the oxygen carrier metal particles, and only oxygen carrier metal particles with a high degree of reduction are supplied to the hydrogen generation process. The chemical looping method of the present invention allows the reduction state of oxygen carrier metal particles to exist in multiple stages in the reduction reaction process, and supplies only oxygen carrier metal particles with a high degree of reduction to the hydrogen generation process, thereby making it possible to improve the hydrogen yield. In addition, it is possible to suppress the generation of carbon monoxide in areas where the reduction degree of the oxygen carrier metal particles is low, thereby making it possible to improve the carbon dioxide recovery efficiency. This makes it possible to achieve both improved carbon dioxide recovery and improved hydrogen yield in the chemical looping system. Effect of the Invention

[0013] According to the present invention, it is possible to provide a chemical looping system and a chemical looping method that achieve both improved carbon dioxide recovery and improved hydrogen yield. [Brief description of the drawings]

[0014] [Figure 1]FIG. 1 is a schematic explanatory diagram showing the configuration of a chemical looping system according to a first embodiment of the present invention. [Diagram 2] 1 is a graph showing the oxidation state of iron and the CO / CO2 partial pressure equilibrium curve. [Diagram 3] 1 is a graph showing the oxidation state of iron and the H2 / H2O partial pressure equilibrium curve. [Figure 4] FIG. 2 is a schematic diagram showing an example of a reaction in a fuel reaction section according to the first embodiment of the present invention. [Diagram 5] FIG. 2 is a schematic explanatory diagram showing the configuration of a chemical looping system according to a second embodiment of the present invention. [Figure 6] FIG. 1 is a schematic explanatory diagram showing the configuration of a conventional chemical looping system. [Figure 7] FIG. 1 is a schematic explanatory diagram showing another embodiment of the configuration of a conventional chemical looping system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the chemical looping system according to the present invention will be described in detail with reference to the drawings. Note that the chemical looping method of the present invention is replaced with the following description of the structure and operation of the chemical looping system. Furthermore, the structure of the chemical looping system described in the embodiment is merely an example for explaining the chemical looping system and chemical looping method according to the present invention, and is not limited thereto.

[0016] In the present invention, the oxygen carrier metal particles M are hereinafter represented as follows, particularly when indicating the redox state: M1 for the reduced state, MO for the partially oxidized state, and MO2 for the fully oxidized state. Note that these notations indicate the relative redox states of the metal compounds, and the reduced state M1 may include oxides.

[0017] Fig. 6 is a schematic explanatory diagram showing the configuration of a conventional chemical looping system, and Fig. 7 is a schematic explanatory diagram showing another embodiment of the configuration of the conventional chemical looping system.

[0018] As shown in FIGS. 6 and 7, the conventional chemical looping systems 100A and 100B include a circulation loop formed by lines L100 to L300 or lines L400 to L600. style The system includes fuel reaction towers 210 and 211 that react the fuel F containing hydrocarbon with oxygen carrier metal particles M to reduce the oxygen carrier metal particles M and collect carbon dioxide, hydrogen generation towers 310 and 311 that react the oxygen carrier metal particles M generated in the fuel reaction towers 210 and 211 with steam to partially oxidize the oxygen carrier metal particles M and generate hydrogen, and oxidation towers 410 and 411 that react the carrier metal particles M generated in the hydrogen generation towers 310 and 311 with air to completely oxidize the oxygen carrier metal particles M and generate nitrogen. In addition, a line L is connected to each part, and lines L40 to L45 indicate supply flow paths for fuel F, air, steam, etc., and lines L50 to L55 indicate recovery flow paths for generated gases such as hydrogen and carbon dioxide. The arrows of the line L in Figs. 6 and 7 indicate the flow directions of each substance.

[0019] When considering CCS or CCU, it is essential that the fuel reactor undergoes a complete combustion reaction. For example, in a conventional chemical looping system 100A shown in Fig. 6, when the oxygen carrier metal particles MO2 in a completely oxidized state are reacted with the fuel F in the fuel reactor 210 and completely combusted, the oxygen carrier metal particles MO2 produce oxygen carrier metal particles MO in a partially oxidized state. On the other hand, when the oxygen carrier metal particles MO produced in the fuel reactor 210 are supplied to the hydrogen generator 310 and reacted with steam, the reaction between the oxygen carrier metal particles MO and steam hardly progresses, so that the amount of hydrogen that can be recovered through the line L51 is small, and the hydrogen yield is greatly reduced.

[0020] On the other hand, when considering high-yield hydrogen production, it is necessary to increase the reduction rate of the oxygen carrier metal particles in order to increase the reaction efficiency in the hydrogen generation tower. For example, in the conventional chemical looping system 100B shown in Fig. 7, in order to increase the reduction rate of the oxygen carrier metal particles M in the fuel reaction tower 211 and obtain reduced oxygen carrier metal particles M1, an incomplete combustion reaction is required, and carbon monoxide and hydrogen are generated in addition to carbon dioxide in the fuel reaction tower 211 and discharged in the form of a mixed gas via line L53, making it difficult to recover carbon dioxide with high purity, resulting in a problem of a decrease in the recovery rate of carbon dioxide.

[0021] 6 and 7, it can be seen that there is a trade-off between carbon dioxide capture and hydrogen production in the conventional chemical looping systems 100A and 100B. On the other hand, the chemical looping system and chemical looping method of the present invention can improve both carbon dioxide capture and hydrogen yield by dividing the reduction state of oxygen carrier metal particles into multiple stages during the reduction reaction in which oxygen carrier metal particles react with fuel, and supplying only oxygen carrier metal particles with a high degree of reduction to the hydrogen generation section.

[0022] [First embodiment] FIG. 1 is a schematic explanatory diagram showing the configuration of a chemical looping system according to a first embodiment of the present invention. The chemical looping system 1A according to the first embodiment of the present invention is style In the passage, oxygen carrier metal particles M repeatedly undergo oxidation and reduction reactions, and an oxidation reaction section 10 and a reduction reaction section 11 are provided. Furthermore, the chemical looping system 1A in this embodiment includes a fuel reaction section 2 that reacts a fuel F containing a hydrocarbon with oxygen carrier metal particles M to recover carbon dioxide, and a hydrogen generation section 3 that reacts the oxygen carrier metal particles M produced after the reaction in the fuel reaction section 2 with water vapor to generate hydrogen, and includes a hydrogen production process that can obtain hydrogen in addition to recovering nitrogen and carbon dioxide.

[0023] As shown in Fig. 1, the chemical looping system 1A of this embodiment is a system equipped with a fuel reaction section 2 as a reduction reaction section 11, and a hydrogen generation section 3 and an oxidation treatment section 4 as an oxidation reaction section 10. Each section is connected to a line L, with lines L1 to L3 indicating circulation paths for oxygen carrier metal particles M, lines L20 to L22 indicating supply paths for fuel F, air, water vapor, etc., and lines L30 to L32 indicating recovery paths for generated gases such as hydrogen and carbon dioxide. The arrows on the line L in Fig. 1 indicate the flow directions of the respective substances.

[0024] (Fuel reaction section) The fuel reaction tower 21 as the fuel reaction section 2 is a place where the oxidized oxygen carrier metal particles MO2 react with the fuel F containing hydrocarbons (CmHn) and where the oxidized oxygen carrier metal particles MO2 are reduced. As shown in Fig. 1, fuel F is supplied to the fuel reactor 21 through a line L20, and oxygen carrier metal particles MO2 are supplied through a line L1. At this time, the inside of the fuel reactor 21 is set in a state where there are multiple reduction states of the oxygen carrier metal particles M (oxygen carrier metal particles MO2, MO, M1), and only the oxygen carrier metal particles M1 with a high degree of reduction are supplied to the hydrogen generator 3 through a line L2. In addition, carbon dioxide and water generated in the fuel reactor 21 are collected through a line L30. The fuel F may be not only a gaseous fuel such as methane gas or city gas, but also a solid fuel such as coal. In the fuel reaction section 2 of this embodiment, the means for providing a plurality of reduced states for the oxygen carrier metal particles M and for extracting only the oxygen carrier metal particles M1 with a high degree of reduction will be described later.

[0025] (Hydrogen generation section) The hydrogen generating tower 31 as the hydrogen generating unit 3 is a place where steam as an oxidizing agent is added to the oxygen carrier metal particles M1 to cause a reaction, where the oxygen carrier metal particles M1 are partially oxidized and H2 is generated from the steam. As shown in FIG. 1, water vapor is supplied to the hydrogen generation tower 3 through line L21. Also, only oxygen carrier metal particles M1 with a high degree of reduction are supplied through line L2. Therefore, in the hydrogen generation unit 3, the reaction between the oxygen carrier metal particles M1 with a high degree of reduction and water vapor proceeds efficiently, and partially oxidized oxygen carrier metal particles MO and hydrogen are generated with a high yield. The oxygen carrier metal particles MO reacted here are supplied to the oxidation treatment unit 4 through line L3. Also, H2 generated in the hydrogen generation tower 31 is recovered through line L31.

[0026] (Oxidation treatment section) The oxidation tower 41 as the oxidation treatment section 4 is a place where the partially oxidized oxygen carrier metal particles MO react with air, where the oxygen carrier metal particles M are completely oxidized, and where oxygen (O2) is removed from the air to obtain high-concentration nitrogen (N2). Note that since this reaction is an exothermic reaction, thermal energy may be recovered from the reaction and used in other systems, such as power generation. As shown in Fig. 1, air is supplied to the oxidation tower 41 through line L22, and oxygen carrier metal particles MO are supplied through line L2. After the reaction, the generated oxygen carrier metal particles MO2 are supplied to the fuel reaction section 2 through line L1. Nitrogen generated in the oxidation tower 41 is recovered through line L32. The air supplied through line L22 may be compressed air by a pressure pump such as a compressor, or air that has passed through an air preheater.

[0027] (Oxygen carrier metal particles) The oxygen carrier metal particles M can be any known metal material used in typical chemical looping systems. In the chemical looping system of the present invention, it is particularly preferable to use oxygen carrier metal particles M capable of forming a plurality of reduction states, such as iron (Fe), copper (Cu), manganese (Mn), cerium (Ce), molybdenum (Mo), and tungsten (W). This makes it possible to provide oxygen carrier metal particles M having a suitable reduction degree for the reaction (oxidation reaction or reduction reaction) in each section (fuel reaction section 2, hydrogen generation section 3, oxidation treatment section 4). This also makes it possible to increase the efficiency of each reaction in the chemical looping system 1A.

[0028] Hereinafter, when oxygen carrier metal particles M containing iron are used, the reduced state of oxygen carrier metal particles M suitable for recovering high-purity carbon dioxide and the reduced state of oxygen carrier metal particles M suitable for producing hydrogen with a high yield will be described.

[0029] Fig. 2 is a graph showing the reduction state of iron and the CO / CO2 partial pressure equilibrium curve, and Fig. 3 is a graph showing the reduction state of iron and the H2 / H2O partial pressure equilibrium curve. Note that Figs. 2 and 3 are graphs based on chemical equilibrium calculations using thermodynamic data. 2 and 3 show the reduced states of iron, namely, iron (Fe), wustite (ferrous oxide: FeO), magnetite (iron tetroxide: Fe3O4), and hematite (iron trioxide: Fe2O3). Note that iron and wustite correspond to oxygen carrier metal particle M1, magnetite corresponds to oxygen carrier metal particle MO, and hematite corresponds to oxygen carrier metal particle MO2.

[0030] In the fuel reaction section 2 (fuel reaction tower 21), when hematite (Fe2O3), which is a fully oxidized oxygen carrier metal particle MO2, is reacted with fuel F to recover high-purity carbon dioxide (CO2), it is possible to grasp to what degree the oxygen carrier metal particle MO2 is reduced by looking at the reduction state of iron when the CO2 partial pressure value is near 1 using Fig. 2. It can be seen from Fig. 2 that when the CO2 partial pressure value is near 1, over a wide temperature range, hematite (Fe2O3) is reduced only to magnetite (Fe3O4), which is a partially oxidized oxygen carrier metal particle MO.

[0031] On the other hand, when hydrogen is produced at a high yield by reacting oxygen carrier metal particles M containing iron with steam in the hydrogen generating unit 3 (hydrogen generating tower 31), the degree to which oxygen carrier metal particles M containing iron are oxidized by steam can be understood by looking at the reduction state of iron when the H2O partial pressure value is near 1 using FIG. 3. It can be seen from FIG. 3 that when the H2O partial pressure value is near 1, the oxygen carrier metal particles M containing iron are oxidized only to magnetite (Fe3O4) over a wide temperature range. In other words, it can be seen that in the hydrogen generating unit 3, unless the oxygen carrier metal particles M supplied are in a state more reduced than magnetite (Fe3O4), hydrogen generation itself is difficult.

[0032] From the above, in order to use oxygen carrier metal particles M containing iron to capture high-purity carbon dioxide and produce hydrogen with a high yield, it is necessary to stop the reduction reaction at magnetite (Fe3O4) in the fuel reaction section 2, while it is necessary to supply wustite (FeO) or iron (Fe), which is in a more reduced state than magnetite (Fe3O4), to the hydrogen generation section 3.

[0033] The chemical looping system 1A in this embodiment has a plurality of reduction states of the oxygen carrier metal particles M in the above-mentioned fuel reaction section 2, and extracts only the oxygen carrier metal particles M1 having a high degree of reduction and supplies them to the hydrogen generation section 3. That is, when the oxygen carrier metal particles M containing iron are used, for example, a reaction for producing magnetite (Fe3O4) and a reaction for producing wustite (FeO) are allowed to proceed in the fuel reaction section 2, so that only wustite (FeO) can be extracted.

[0034] Hereinafter, an example of a means for creating multiple reduction states of oxygen carrier metal particles M in the combustion reaction section 2 and extracting only oxygen carrier metal particles M1 with a high degree of reduction will be described, in which oxygen carrier metal particles M containing iron are used.

[0035] 4A to 4D are schematic diagrams showing an example of the reaction in the fuel reaction section 2 in this embodiment. Note that Fig. 4A to Fig. 4D sequentially show the progress of the reaction.

[0036] In the fuel reaction tower 21 as the fuel reaction section 2 in FIG. 4, a fixed bed is formed of hematite (Fe2O3) as oxygen carrier metal particles MO2 supplied via a line L1. First, as shown in Fig. 4A, when fuel F (CH4) is supplied to hematite (Fe2O3) through line L20, a reduction reaction proceeds in the fuel reaction tower 21, and carbon dioxide is generated. The carbon dioxide generated at this time is collected through line L30. Next, as shown in Fig. 4B, a reduction reaction proceeds near the line L20 that supplies fuel F, and part of the hematite (Fe2O3) that forms the fixed bed is reduced to magnetite (Fe3O4). At this time, carbon monoxide is generated by the reaction between magnetite (Fe3O4) and fuel F, but since the reaction continues while the generated carbon monoxide rises in the fixed bed, only carbon dioxide is discharged from the line L30. As shown in Fig. 4C, when the reduction reaction proceeds in the fixed bed in the fuel reactor 21, wustite (FeO), magnetite (Fe3O4), and hematite (Fe2O3) are present in a gradational manner in the fixed bed, and a state in which the oxygen carrier metal particles M have multiple reduction states in the fixed bed can be formed. Also, it becomes possible to extract only wustite (FeO), which is the oxygen carrier metal particle M1 with a high degree of reduction, from the fuel reactor 21 via line L2. At this time, carbon and carbon monoxide are generated in association with the reduction reaction of wustite (FeO) and magnetite (Fe3O4), but the reaction proceeds further in the fixed bed, and only carbon dioxide is discharged from line L30. As shown in FIG. 4D, when the reaction proceeds further, wustite (FeO) and magnetite (Fe3O4) are present in the fixed bed, and carbon monoxide is discharged from line L30 together with carbon dioxide, making it difficult to recover only carbon dioxide with high purity. That is, a fixed bed is formed in the fuel reaction tower 21 of the fuel reaction section 2, and a heterogeneous reaction between the oxygen carrier metal particles MO2 (hematite (Fe2O3)) and the fuel F is allowed to proceed, thereby forming the state shown in FIG. 4C. This makes it possible to recover high-purity carbon dioxide and to supply only the oxygen carrier metal particles M1 (wustite (FeO)) with a high degree of reduction to the hydrogen generation section 3.

[0037] By supplying wustite (FeO) to the hydrogen generator 3 via line L2, hydrogen is generated according to the following formula 1.

number

[0038] From equation 1, it can be seen that the equilibrium of equation 1 is inclined toward the generation of hydrogen (H2) because ΔG<0. Therefore, by supplying only highly reduced oxygen carrier metal particles M1 (wustite (FeO)) to the hydrogen generation unit 3, it is possible to produce hydrogen with a high yield.

[0039] As described above, in the chemical looping system 1A of this embodiment, the reduction reaction section allows the oxygen carrier metal particles to have multiple reduced states, and only oxygen carrier metal particles with a high degree of reduction are supplied to the hydrogen generation section, making it possible to produce hydrogen particularly efficiently. Furthermore, in the process of allowing the oxygen carrier metal particles to have multiple reduced states in the reduction reaction section, it is possible to recover high-purity carbon dioxide. Therefore, the chemical looping system 1A of this embodiment makes it possible to achieve both improved carbon dioxide recovery and improved hydrogen yield.

[0040] [Second embodiment] FIG. 5 is a schematic diagram showing the configuration of a chemical looping system according to the second embodiment of the present invention. 5, the chemical looping system 1B of the second embodiment includes a complete combustion section 22 and an incomplete combustion section 23 as the fuel reaction section 2. The complete combustion tower 22a as the complete combustion section 22 and the incomplete combustion tower 23a as the incomplete combustion section 23 are used for circulating the oxygen carrier metal particles M. style The incomplete combustion section 23 is connected to the complete combustion section 22 by a line L4 as a part of the path, and further includes a line L23 for supplying gas (incomplete combustion gas) generated in the incomplete combustion section 23 to the complete combustion section 22. Note that a description of the same configuration as in the first embodiment will be omitted.

[0041] In this embodiment, the chemical looping system 1B divides the fuel reaction section 2 into a complete combustion section 22 (complete combustion tower 22a) and an incomplete combustion section 23 (incomplete combustion tower 23a) and provides a means for providing a process related to the reduction reaction in multiple stages, making it easy to form oxygen carrier metal particles M with different reduction states.

[0042] An example of a means for making the oxygen carrier metal particles M have a plurality of reduced states in the combustion reaction section 2 of the chemical looping system 1B of this embodiment and for extracting only the oxygen carrier metal particles M1 having a high degree of reduction will be described. First, in the incomplete combustion section 23 (incomplete combustion tower 23a), fuel F is supplied via line L20 to increase the degree of reduction of oxygen carrier metal particles MO, thereby obtaining oxygen carrier metal particles M1 and generating incomplete combustion gases (carbon dioxide, carbon monoxide, hydrogen, etc.). Next, in the hydrogen generating section 3 (hydrogen generating tower 31), the oxygen carrier metal particles M1 reduced in the incomplete combustion section 23 are reacted with steam supplied through a line L21 to advance the oxidation reaction of the oxygen carrier metal particles M1 and efficiently generate hydrogen. The generated hydrogen is recovered through a line L31. Then, in the oxidation treatment unit 4 (oxidation tower 41), the oxygen carrier metal particles MO oxidized by the water vapor are converted into fully oxidized oxygen carrier metal particles MO2 by air supplied through line L22. The nitrogen generated at this time is recovered through line L32. Furthermore, in the complete combustion section 22 (complete combustion tower 22a), the oxygen carrier metal particles MO2 in a completely oxidized state are reacted with the incomplete combustion gas supplied via line L23, and completely combusted, thereby making it possible to recover high-purity carbon dioxide. The oxygen carrier metal particles MO2 in a completely oxidized state are reduced to oxygen carrier metal particles MO in a partially oxidized state by a complete combustion reaction. By supplying these oxygen carrier metal particles MO in a partially oxidized state to the incomplete combustion section 23 via line L4, a reaction of reducing the oxygen carrier metal particles MO to oxygen carrier metal particles M1 with a high degree of reduction proceeds in the incomplete combustion section 23. By repeating the above steps, the fuel reaction section 2 consisting of the complete combustion section 22 and the incomplete combustion section 23 can have a plurality of reduced states of the oxygen carrier metal particles M, and only the oxygen carrier metal particles M1 with a high degree of reduction can be taken out from the incomplete combustion section 23 via the line L2. This allows the hydrogen generation section 3 to produce hydrogen with a high yield. Also, the complete combustion section 22 can recover high-purity carbon dioxide.

[0043] In this embodiment, the complete combustion tower 22a as the complete combustion section 22 and the incomplete combustion tower 23a as the incomplete combustion section 23 may be either a fixed bed or a fluidized bed. For example, from the viewpoint of easily securing the gas flow rate and preventing blockage in the tower, it is more preferable to use a fluidized bed, but the present invention is not limited thereto.

[0044] As described above, in the chemical looping system 1B of this embodiment, by dividing the fuel reaction section into a complete combustion section and an incomplete combustion section, it becomes easy to form oxygen carrier metal particles with different reduction states. In addition, the oxygen carrier metal particles after the reaction generated in the incomplete combustion section have a high degree of reduction, and by supplying these oxygen carrier metal particles to the hydrogen generation section, it becomes possible to produce hydrogen at a high yield. In addition, by supplying the incomplete combustion gas generated in the incomplete combustion section to the complete combustion section and performing a complete combustion reaction, it becomes possible to recover high-purity carbon dioxide. As a result, the chemical looping system 1B of this embodiment can further increase the carbon dioxide recovery rate and hydrogen yield.

[0045] The above-described embodiment shows an example of a chemical looping system and a chemical looping method. The chemical looping system according to the present invention is not limited to the above-described embodiment, and the chemical looping system according to the above-described embodiment may be modified within the scope of the gist of the claims.

[0046] For example, in the chemical looping system of this embodiment, a solid-gas separator such as a cyclone or a heat exchanger may be provided in the recovery flow path to recover useful gases such as hydrogen and carbon dioxide. Also, a solid-gas separator and a valve may be provided in the circulation flow path of the oxygen carrier metal particles to control the supply amount of the oxygen carrier metal particles to each reaction tower. [Industrial Applicability]

[0047] The chemical looping system and chemical looping method of the present invention are used as a hydrogen production process and an environmentally friendly combustion process. The chemical looping system and chemical looping method of the present invention can also be used for generating and recovering carbon dioxide and nitrogen gas. Furthermore, the chemical looping system and chemical looping method of the present invention can also be used for thermal power generation using fossil fuels such as coal. [Explanation of symbols]

[0048] 1A, 1B chemical looping system, 10 oxidation reaction section, 11 reduction reaction section, 2 fuel reaction section, 21 fuel reaction tower, 22 complete combustion section, 22a complete combustion tower, 23 incomplete combustion section, 23a incomplete combustion tower, 3 hydrogen generation section, 31 hydrogen generation tower, 4 oxidation treatment section, 41 oxidation tower 100A, 100B Conventional chemical looping system, 210, 211 Fuel reactor, 310, 311 Hydrogen generator, 410, 411 Oxidizer F fuel, L line, L1~L4, L100~L600 circulation flow path of oxygen carrier metal particles, L20~L23, L40~L45 supply flow path, L30~32, L50~L55 recovery flow path, M oxygen carrier metal particles

Claims

1. A chemical looping system in which oxygen carrier metal particles repeat oxidation and reduction reactions in a circulation flow path, A reduction reaction section and an oxidation reaction section are provided in the circulation flow path, The reduction reaction section includes a fuel reaction section that reacts oxygen carrier metal particles with a fuel, the oxidation reaction section includes a hydrogen generation section that reacts the oxygen carrier metal particles after the reaction generated in the fuel reaction section with water vapor to partially oxidize the oxygen carrier metal particles and generate hydrogen, and an oxidation treatment section that completely oxidizes the partially oxidized oxygen carrier metal particles; The fuel reaction section has a complete combustion section where a complete combustion reaction proceeds and an incomplete combustion section where an incomplete combustion reaction proceeds, The fuel is supplied to the incomplete combustion section, The oxygen carrier metal particles after the reaction generated in the incomplete combustion section are supplied to the hydrogen generating section, and the gas generated in the incomplete combustion section is supplied to the complete combustion section, A chemical looping system, characterized in that in the reduction reaction section, the oxygen carrier metal particles have a plurality of stages of reduction state, and only oxygen carrier metal particles having a high degree of reduction are supplied to the hydrogen generation section.

2. 2. The chemical looping system according to claim 1, wherein the oxygen carrier metal particles contain at least one of iron, copper, manganese, cerium, molybdenum, and tungsten, and atoms of these metals.

3. A chemical looping method in which oxygen carrier metal particles repeat oxidation and reduction reactions in a circulation flow path, In the circulation flow path, a reduction reaction process and an oxidation reaction process proceed separately, The reduction reaction process includes a fuel reaction step of reacting oxygen carrier metal particles with a fuel, The oxidation reaction process includes a hydrogen generation step of reacting the oxygen carrier metal particles generated in the fuel reaction step with water vapor to partially oxidize the oxygen carrier metal particles and generate hydrogen, and an oxidation treatment step of completely oxidizing the partially oxidized oxygen carrier metal particles, The fuel reaction process has a complete combustion process in which a complete combustion reaction proceeds and an incomplete combustion process in which an incomplete combustion reaction proceeds, Supplying the fuel to the incomplete combustion step; The oxygen carrier metal particles after the reaction generated in the incomplete combustion step are supplied to the hydrogen generation step, and the gas generated in the incomplete combustion step is supplied to the complete combustion step; A chemical looping method, characterized in that in the reduction reaction process, the oxygen carrier metal particles have a plurality of stages of reduction state, and only oxygen carrier metal particles having a high degree of reduction are supplied to the hydrogen generation step.

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