Chemical loop reaction system

Abstract

[Problem] To improve operational efficiency by effectively utilizing generated carbon dioxide in a chemical loop reaction system. [Solution] A chemical loop reaction system 100 comprises an oxidation tower 10 that oxidizes metal particles M into oxidized metal particles MO, a reduction tower 20 that reacts the metal oxide particles MO with a reducing agent R to convert the metal oxide particles MO into metal particles M while generating carbon dioxide, and a circulation section 60 that circulates the metal particles M and the oxidized metal particles MO between the reduction tower 20 and the oxidation tower 10, wherein the reduction tower 20 and / or the oxidation tower 10 is provided with a carbon dioxide supply line 70 that supplies the carbon dioxide generated in the reduction tower 20.

Description

Chemical Looping Reaction System

[0001] The present invention relates to a chemical looping reaction system and a method for utilizing carbon dioxide.

[0002] Conventionally, a chemical looping reaction system has been known that includes an oxidation tower that oxidizes metal particles to form metal oxide particles, a reduction tower that reacts the metal oxide particles with a reducing agent to convert the metal oxide particles into metal particles while generating carbon dioxide, and a circulation unit that circulates the metal particles and metal oxide particles between the reduction tower and the oxidation tower (see, for example, Patent Document 1).

[0003] JP 2018-155437 A

[0004] In the system described in Patent Document 1, carbon dioxide is generated by reducing metal oxide particles with a reducing agent in a reduction tower. To prevent most of the generated carbon dioxide from being released into the atmosphere, it is necessary to treat the carbon dioxide, which increases the operating costs of the chemical looping reaction system. Therefore, to improve the efficiency of system operation, it is necessary to effectively utilize the generated carbon dioxide.

[0005] An object of the present invention is to provide a chemical looping reaction system and a method for utilizing carbon dioxide, which can improve operational efficiency by utilizing the produced carbon dioxide within the chemical looping reaction system.

[0006] A chemical looping reaction system according to one aspect of the present invention includes an oxidation tower in which metal particles are oxidized to form metal oxide particles, a reduction tower in which the metal oxide particles are reacted with a reducing agent to convert the metal oxide particles into metal particles while generating carbon dioxide, and a circulation unit that circulates the metal particles and the metal oxide particles between the reduction tower and the oxidation tower. At least one of the reduction tower and the oxidation tower is provided with a carbon dioxide supply line that supplies the carbon dioxide generated in the reduction tower.

[0007] A method for utilizing carbon dioxide according to an embodiment of the present invention is a chemical looping reaction system including an oxidation tower that oxidizes metal particles to form metal oxide particles, a reduction tower that reacts the metal oxide particles with a reducing agent to generate carbon dioxide while converting the metal oxide particles into metal particles, and a circulation unit that circulates the metal particles and metal oxide particles between the reduction tower and the oxidation tower. The method utilizes carbon dioxide produced in the reduction tower, and includes supplying carbon dioxide produced in the reduction tower to at least one of the reduction tower and the oxidation tower to cause the metal particles and metal oxide particles to flow.

[0008] According to the above-described embodiment, the generated carbon dioxide is supplied to at least one of the reduction tower and the oxidation tower, and part or all of the gas supplied to the reduction tower or the oxidation tower is replaced with carbon dioxide. This reduces the flow rate of the gas that should be supplied to the reduction tower or the oxidation tower, thereby improving the efficiency of the operation of the chemical looping reaction system. Furthermore, since the generated carbon dioxide is used in the chemical looping reaction system, carbon dioxide can be effectively utilized, and the amount of carbon dioxide released into the atmosphere can be reduced.

[0009] 1 is a diagram illustrating an example of a chemical looping reaction system according to a first embodiment; FIG. 2 is a diagram illustrating an example of an oxidation tower and a reduction tower; FIG. 3 is a diagram illustrating an example of a solid-gas separator connected to a reduction tower, with an enlarged view showing metal oxide particles entering the reduction tower; FIG. 4 is a flowchart illustrating an example of a carbon dioxide utilization method according to a first embodiment; FIG. 5 is a flowchart illustrating an example of a carbon dioxide utilization method according to a first embodiment, following FIG. 5; FIG. 6 is a flowchart illustrating a part of the flowchart of FIG. 7 in detail; FIG. 8 is a diagram illustrating an example of a chemical looping reaction system according to a second embodiment; FIG. 9 is a flowchart illustrating an example of a carbon dioxide utilization method according to a second embodiment; FIG. 10 is a diagram illustrating an example of a chemical looping reaction system according to a third embodiment; FIG. 11 is a flowchart illustrating an example of a carbon dioxide utilization method according to a third embodiment; FIG. 12 is a diagram illustrating an example of a chemical looping reaction system according to a fourth embodiment; FIG. 13 is a flowchart illustrating an example of a carbon dioxide utilization method according to the fourth embodiment; FIG. 14 is a diagram illustrating an example of a chemical looping reaction system according to a fifth embodiment; FIG. 15 is a diagram illustrating an example of a chemical looping reaction system according to a sixth embodiment.

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the contents described below. In addition, in order to explain the embodiments, the drawings are shown with appropriate scale changes, such as enlarging or emphasizing some parts, and the shape, dimensions, etc. of the actual product may differ.

[0011] First Embodiment [Chemical Looping Reaction System] Fig. 1 is a diagram illustrating an example of a chemical looping reaction system 100 according to a first embodiment. Fig. 2 is a diagram illustrating an example of an oxidation tower 10 and a reduction tower 20 in the chemical looping reaction system 100. Fig. 3 is an enlarged view showing metal oxide particles MO entering the reduction tower 20. Fig. 4 is a diagram illustrating an example of a solid-gas separator 50 connected to the reduction tower 20. The chemical looping reaction system 100 oxidizes the accommodated metal particles M to form metal oxide particles MO, and then reduces the metal oxide particles MO with a reducing agent to form metal particles M, thereby performing a reducing agent treatment. Details of the metal particles M will be described later.

[0012] As shown in Figures 1 and 2, the chemical looping reaction system 100 includes an oxidation tower 10, a reduction tower 20, an air supply line 19, a fuel supply line 21 (reducing agent supply line), a steam supply line 23, a fluidizing gas supply line 16, a nitrogen supply line 18, a circulation unit 60, a carbon dioxide supply line 70, and a control unit C. The oxidation tower 10 contains metal particles M. Details of the metal particles M will be described later. The oxidation tower 10 oxidizes the metal particles M to produce metal oxide particles MO. As shown in Figure 2, the oxidation tower 10 is a cylindrical outer tower made of a heat-resistant material such as a steel plate. The top end of the oxidation tower 10 is closed by a top plate 10A. The oxidation tower 10 includes an upper section 11, a central section 12, a lower section 13, and an exhaust section 14.

[0013] The upper portion 11 has a cylindrical upper portion 11A extending vertically and a reduced-diameter portion 11B whose diameter decreases downward from the lower end of the upper portion 11A. The central portion 12 is connected to the lower end of the reduced-diameter portion 11B and has a cylindrical shape extending downward. The lower portion 13 has an expanded-diameter portion 13A connected to the lower end of the central portion 12 and whose diameter increases downward, and a cylindrical lower portion 13B extending downward from the lower end of the expanded-diameter portion 13A. The lower end of the lower portion 13 is closed by a first bottom plate 13C. The diameter of the central portion 12 is smaller than the diameter of the lower portion 13B of the lower portion 13 and the diameter of the upper portion 11A of the upper portion 11. The diameter of the lower portion 13B of the lower portion 13 is also smaller than the diameter of the upper portion 11A of the upper portion 11.

[0014] The lower portion 13 includes an air nozzle 42, an air supply pipe 43, a fluidizing gas nozzle 44, and a fluidizing gas supply pipe 45. The air nozzle 42 sprays air upward to supply air to the oxidation tower 10. The air nozzle 42 is disposed above the lower end of the reduction tower 20. This configuration prevents air sprayed from the air nozzle 42 from entering the reduction tower 20. The air supply pipe 43 penetrates the first bottom plate 13C and holds the air nozzle 42 at its upper end. The air supply pipe 43 is set to a length that allows the air nozzle 42 to be disposed above the lower end of the reduction tower 20. The air supply pipe 43 connects the air chamber 31 (described later) and the air nozzle 42, and sends air from the air chamber 31 to the air nozzle 42. Note that, for example, a configuration may be provided in which a height adjustment mechanism is provided that can change the height of the air nozzle 42 by adjusting the length of the air supply pipe 43.

[0015] The fluidizing gas nozzle 44 ejects a fluidizing gas upward to supply the fluidizing gas to the oxidation tower 10. The fluidizing gas may be, for example, nitrogen. The fluidizing gas nozzle 44 is disposed below the lower end of the reduction tower 20. In this configuration, the fluidizing gas is ejected from the fluidizing gas nozzle 44 to supply the fluidizing gas to the oxidation tower 10, thereby fluidizing the metal particles M and metal oxide particles MO in the oxidation tower 10.

[0016] The fluidizing gas supply pipe 45 is provided to penetrate the first bottom plate 13C, and holds the fluidizing gas nozzle 44 at its upper end. The length of the fluidizing gas supply pipe 45 is set so that the fluidizing gas nozzle 44 is located below the lower end of the reduction tower 20. The fluidizing gas supply pipe 45 connects the fluidizing gas chamber 32 (described later) to the fluidizing gas nozzle 44, and sends the fluidizing gas from the fluidizing gas chamber 32 to the fluidizing gas nozzle 44. Note that the fluidizing gas supply pipe 45 may be configured to include a height adjustment mechanism that can change the height of the fluidizing gas nozzle 44 by adjusting the length of the fluidizing gas supply pipe 45, for example.

[0017] An air chamber 31 and a fluidizing gas chamber 32 are provided below the lower portion 13 of the oxidation tower 10. A cylindrical portion 30 is provided, the upper end of which is closed by a first bottom plate 13C and the lower end of which is closed by a second bottom plate 30A. The interior of this cylindrical portion 30 is partitioned by a partition plate 33 to form the air chamber 31 and the fluidizing gas chamber 32. The cylindrical portion 30 is provided with the same inner diameter as the lower portion 13. The air chamber 31 communicates with the lower portion 13 via an air supply pipe 43 and an air nozzle 42. The fluidizing gas chamber 32 communicates with the lower portion 13 via a fluidizing gas supply pipe 45 and a fluidizing gas nozzle 44.

[0018] The air chamber 31 includes an air inlet 46. The air inlet 46 penetrates the second bottom plate 30A and is connected to the air supply line 19. The air chamber 31 stores air sent via the air supply line 19 and the air inlet 46. The air chamber 31 is pressurized by the air sent from the air supply line 19. As the air chamber 31 is pressurized, the air in the air chamber 31 is ejected into the oxidation tower 10 from the air nozzle 42 via the air supply pipe 43. The air ejected into the oxidation tower 10 functions as an oxidizing agent in the oxidation tower 10.

[0019] The fluidizing gas chamber 32 includes a fluidizing gas inlet 47. The fluidizing gas inlet 47 penetrates the second bottom plate 30A and is connected to the fluidizing gas supply line 16. The fluidizing gas chamber 32 stores the fluidizing gas delivered via the fluidizing gas supply line 16 and the fluidizing gas inlet 47. The fluidizing gas chamber 32 is pressurized by the fluidizing gas delivered from the fluidizing gas supply line 16. As the fluidizing gas chamber 32 is pressurized, the fluidizing gas in the fluidizing gas chamber 32 is ejected from the fluidizing gas nozzle 44 into the oxidation tower 10 via the fluidizing gas supply pipe 45. The fluidizing gas ejected into the oxidation tower 10 fluidizes the metal oxide particles MO present in the oxidation tower 10. Furthermore, a portion of the fluidizing gas ejected into the oxidation tower 10 enters the reduction tower 20 and fluidizes the metal particles M or metal oxide particles MO in the reduction tower 20.

[0020] The exhaust section 14 is provided at the upper end of the oxidation tower 10, penetrating a fixed section 10B provided on the top plate 10A. The gas inside the oxidation tower 10 is discharged from the oxidation tower 10 through the exhaust section 14. A solid-gas separation section 15 is provided in the exhaust section 14. The solid-gas separation section 15 separates the gas from the solid components contained in the gas discharged from the exhaust section 14. The solid-gas separation section 15 may be, for example, a filter or a cyclone. As will be described later, the gas discharged from the exhaust section 14 is mainly composed of nitrogen and contains a small amount of oxygen. After the solid components are removed from the gas discharged from the exhaust section 14 in the solid-gas separation section 15, the gas is released into the atmosphere or reused as a fluidizing gas.

[0021] The reduction tower 20 is disposed inside the oxidation tower 10. The reduction tower 20 is a cylindrical inner tower made of a heat-resistant material such as steel plate and has an outer diameter smaller than the inner diameter of the oxidation tower 10. The reduction tower 20 reacts the metal oxide particles MO with a reducing agent to generate carbon dioxide and convert the metal oxide particles MO into metal particles M. The reduction tower 20 is disposed inside the oxidation tower 10 with its central axis aligned in the vertical direction. The reduction tower 20 is formed to have a length that extends in the vertical direction across the upper portion 11, central portion 12, and lower portion 13 of the oxidation tower 10. In this embodiment, one reduction tower 20 is disposed inside the oxidation tower 10, but this is not limited to this configuration, and multiple reduction towers 20 may be disposed inside the oxidation tower 10. Furthermore, the oxidation tower 10 and the reduction tower 20 may be disposed separately.

[0022] The reduction tower 20 includes a fuel nozzle 40, a fuel supply pipe 41, and a solid-gas separator 50. The fuel nozzle 40 is disposed in a state inserted into the reduction tower 20 at a position slightly above the lower end of the reduction tower 20. The fuel nozzle 40 ejects fuel (reducing agent), steam, and carrier gas upward. This configuration prevents the fuel and other gases ejected from the fuel nozzle 40 from being supplied to the outside of the reduction tower 20. The fuel (reducing agent), steam, and carrier gas will be described later. The outer diameter of the fuel nozzle 40 is smaller than the inner diameter of the reduction tower 20, and a gap is formed between the fuel nozzle 40 and the reduction tower 20 that allows the metal oxide particles MO to pass through.

[0023] The fuel supply pipe 41 holds the fuel nozzle 40 at its upper part. The fuel supply pipe 41 is provided to penetrate the first bottom plate 13C, the fluidizing gas chamber 32, and the second bottom plate 30A, and is connected to the fuel supply line 21 at its lower part. The length of the fuel supply pipe 41 is set to a value that allows the fuel nozzle 40 to be inserted into the reduction tower 20. Note that, for example, a height adjustment mechanism may be provided that can change the height of the fuel nozzle 40 by adjusting the length of the fuel supply pipe 41. Fuel, etc. is injected from the fuel supply line 21 through the fuel supply pipe 41 and into the reduction tower 20 from the fuel nozzle 40.

[0024] 3 , the fuel nozzle 40 sprays fuel and the like upward. As a result, as indicated by the outline arrow, an upward flow is formed within the reduction tower 20, and the metal oxide particles MO are taken in through the opening at the lower end of the reduction tower 20 and caused to rise. As described above, a gap is formed between the fuel nozzle 40 and the reduction tower 20, and the metal oxide particles MO rise within the reduction tower 20 through this gap. While rising within the reduction tower 20, they are reduced by the fuel sprayed from the fuel nozzle 40 to become metal particles M.

[0025] The solid-gas separator 50 is connected to the reduction tower 20 via a connecting pipe 53 provided at the top of the reduction tower 20. In this embodiment, the solid-gas separator 50 is connected to a protective tube 51 provided outside the reduction tower 20 and is provided in parallel to the reduction tower 20. The solid-gas separator 50 is, for example, a cyclone that separates the mixture into a solid component and a gas component by generating a swirling flow therein. The solid component is metal particles M and metal oxide particles MO that were not reduced in the reduction tower 20.

[0026] The solid-gas separator 50 returns the separated solid components to the oxidation tower 10. An exhaust pipe 54 is provided at the top of the solid-gas separator 50. The separated gas components are discharged from the exhaust pipe 54. The gas components are mainly carbon dioxide and may contain water vapor. The exhaust pipe 54 is connected to an exhaust unit 57. The exhaust unit 57 is provided by penetrating a fixing unit 10B provided on the top plate 10A. A gas-liquid separator 58 (see FIG. 1 ) is provided in the exhaust unit 57. The gas-liquid separator 58 separates liquid components (e.g., water vapor) contained in the gas components discharged from the exhaust unit 57.

[0027] As shown in Figure 4, solid-gas separation device 50 generates a swirling flow in cylindrical body 52 by guiding the flow discharged upward from connecting pipe 53 using introduction section 56. The swirling flow continues to swirl while moving downward in body 52. ​​In this swirling flow, solid components move downward while swirling near the inner wall of body 52 and are discharged into oxidation tower 10 from opening 55, which has a reduced diameter at the bottom of body 52. ​​Meanwhile, gas components flow upward in the center of the swirling flow and are discharged by exhaust section 57 via exhaust pipe 54. In other words, solid-gas separation device 50 returns metal particles M and the like from the solid-gas mixed flow discharged from reduction tower 20 to oxidation tower 10 and discharges carbon dioxide.

[0028] The circulation unit 60 circulates the metal particles M and the metal oxide particles MO between the reduction tower 20 and the oxidation tower 10. The metal particles M filled in the oxidation tower 10 are oxidized to become metal oxide particles MO, which are in a state of flowing in the lower part 13 of the oxidation tower 10. The flow of fuel ejected from the air nozzle 42 in the reduction tower 20 causes the metal oxide particles MO to enter the reduction tower 20, and after becoming metal particles M, the metal particles M are returned to the oxidation tower 10 by the solid-gas separator 50. The circulation unit 60 executes this circulation of the metal particles M and the metal oxide particles MO between the reduction tower 20 and the oxidation tower 10.

[0029] Returning to FIG. 1 , the air supply line 19 supplies air to the air chamber 31. One end of the air supply line 19 is connected to an air supply unit (not shown), and the other end is connected to an air introduction unit 46. The air supply unit may include, for example, a tank for storing air, a pump for supplying air, etc. The air supply line 19 supplies air from the air supply unit to the air introduction unit 46. The air supply line 19 may also include, for example, a flow meter, a pressure regulating valve, etc. By operating the flow meter, pressure regulating valve, etc., the air supply line 19 can supply air at a preset flow rate to the air introduction unit 46.

[0030] The fuel supply line 21 mixes an organic solvent, which is a fuel (reducing agent), with steam and supplies the mixture to the fuel nozzle 40. The organic solvent functions as a reducing agent in the reduction tower 20. The organic solvent includes a powdered or granular resin. The fuel supply line 21 is connected to a fuel supply unit (not shown). The fuel supply unit includes, for example, a tank for storing fuel, a liquid supply pump, and the like. The fuel supply line 21 has a mixing unit 22. A steam supply line 23 is connected to the mixing unit 22. The mixing unit 22 mixes the organic solvent sent through the fuel supply line 21 with the steam sent through the steam supply line 23 at a predetermined ratio.

[0031] The steam supply line 23 includes a steam generating unit 24, and supplies steam generated by the steam generating unit 24 to the mixing section 22. The steam generating unit 24 includes a heat source (not shown), and generates steam by heating water supplied from a water supply line 25. The water supply line 25 is connected to a water supply section (not shown), which includes, for example, a water storage tank, a water pump, etc.

[0032] A carrier gas supply line 26 is connected to the steam generating unit 24. The carrier gas supply line 26 supplies a carrier gas to the steam generating unit 24. The carrier gas is used to cause the steam generated in the steam generating unit 24 to flow into the steam supply line 23. The carrier gas supply line 26 is connected via a first switching valve 27 to a second nitrogen supply line 28 (described later) and a second connection line 79, which is part of a first line 74 of a carbon dioxide supply line 70 (described later).

[0033] The first switching valve 27 is controlled by the control unit C to switch the connection destination of the carrier gas supply line 26. The first switching valve 27 is connected to the carrier gas supply line 26, the second nitrogen supply line 28, and the second connection line 79. The first switching valve 27 switches the connection destination of the carrier gas supply line 26 between the second nitrogen supply line 28 and the second connection line 79. When the first switching valve 27 connects the carrier gas supply line 26 to the second nitrogen supply line 28, nitrogen is supplied as a carrier gas to the steam generation unit 24. When the first switching valve 27 connects the carrier gas supply line 26 to the second connection line 79, carbon dioxide is supplied as a carrier gas to the steam generation unit 24.

[0034] The fluidizing gas supply line 16 supplies the fluidizing gas to the fluidizing gas chamber 32. One end of the fluidizing gas supply line 16 is connected to a second switching valve 17, and the other end is connected to a fluidizing gas inlet 47. The second switching valve 17 is controlled by the control unit C to switch the connection destination of the fluidizing gas supply line 16. The second switching valve 17 is connected to a third connection line 80, which is a part of the first line 74, of the fluidizing gas supply line 16, the nitrogen supply line 18, and the carbon dioxide supply line 70.

[0035] The second switching valve 17 switches the connection destination of the fluidizing gas supply line 16 between the nitrogen supply line 18 and the third connection line 80. When the second switching valve 17 connects the fluidizing gas supply line 16 to the nitrogen supply line 18, nitrogen is supplied as a carrier gas to the fluidizing gas chamber 32. When the second switching valve 17 connects the fluidizing gas supply line 16 to the third connection line 80, carbon dioxide is supplied as a fluidizing gas to the fluidizing gas chamber 32.

[0036] The nitrogen supply line 18 is connected to a nitrogen supply unit (not shown). The nitrogen supply unit may include, for example, a tank for storing nitrogen, a pump, etc. The nitrogen supply line 18 may be connected to a nitrogen supply system installed in a building of a factory or the like, and may be configured to be connected to other devices. The nitrogen supply line 18 branches upstream of the second switching valve 17, forming a second nitrogen supply line 28. Therefore, the nitrogen flowing through the nitrogen supply line 18 is divided by the second nitrogen supply line 28 into a flow toward the second switching valve 17 and a flow toward the first switching valve 27.

[0037] The carbon dioxide supply line 70 supplies the carbon dioxide generated in the reduction tower 20 to at least one of the reduction tower 20 and the oxidation tower 10. The carbon dioxide supply line 70 is connected downstream of the gas-liquid separator 58 via an open / close valve 59. The open / close valve 59 is controlled by the control unit C and is capable of adjusting the flow rate of carbon dioxide flowing from the reduction tower 20 to the carbon dioxide supply line 70. The carbon dioxide supply line 70 includes a recovery line 71, a flow rate measuring device 72, an adjustment valve 73, a first line 74, a first tank 75, a second line 76, and a second tank 77.

[0038] The recovery line 71 connects the on-off valve 59 and a flow rate measuring device 72 (adjusting valve 73). The flow rate measuring device 72 measures the flow rate per unit time of carbon dioxide flowing through the recovery line 71. The adjusting valve 73 is provided in the recovery line 71 and is connected to the recovery line 71, a first line 74, and a second line 76. Note that, in the illustration, an example is given in which the flow rate measuring device 72 and the adjusting valve 73 are realized as a single device, but this is not limiting. For example, the adjusting valve 73 may be provided downstream of the flow rate measuring device 72 in the recovery line 71. The adjusting valve 73 is switchable between a first mode in which the recovery line 71 communicates with the first line 74, a second mode in which the recovery line 71 communicates with the second line 76, and a third mode in which the first line 74 communicates with the second line 76.

[0039] The regulating valve 73 may simultaneously execute the first mode and the second mode described above. That is, the regulating valve 73 may have a mode in which carbon dioxide in the recovery line 71 is sent to both the first line 74 and the second line 76. When the regulating valve 73 is set to the third mode, it becomes possible to flow carbon dioxide stored in the first tank 75 from the second line 76 through the regulating valve 73 to the first line 74.

[0040] The first line 74 is provided downstream of the regulating valve 73. The first line 74 includes a first connection line 78, a second connection line 79, and a third connection line 80. The first connection line 78 connects the regulating valve 73 and the first tank 75. The first tank 75 stores carbon dioxide delivered through the first connection line 78. The first tank 75 functions as a buffer that temporarily stores carbon dioxide flowing through the first line 74. The first tank 75 may or may not be provided, and the first tank 75 may be omitted. The second connection line 79 connects the first tank 75 and the first switching valve 27. The third connection line 80 branches off from the second connection line 79 and is connected to the second switching valve 17. In other words, the third connection line 80 connects the first tank 75 and the second switching valve 17.

[0041] The second line 76 is provided separately from the first line 74, and connects the regulating valve 73 and the second tank 77. The second tank 77 stores the carbon dioxide sent from the second line 76 when the regulating valve 73 is set to the second mode. When the flow rate of the carbon dioxide flowing through the recovery line 71 measured by the flow rate measuring instrument 72 does not reach the desired flow rate, the regulating valve 73 is set to the second mode, and the second tank 77 can send the carbon dioxide to the first line 74 via the second line 76. It is optional whether or not to provide the second line 76 and the second tank 77, and a configuration without the second line 76 and the second tank 77 is also possible.

[0042] As shown in Fig. 2, the oxidation tower 10 and the reduction tower 20 are installed on a floor surface F via a base 90. A load cell 91 is disposed between the base 90 and the floor surface F. The output of the load cell 91 is input to a control unit C. The load cell 91 outputs the loads of the metal particles M and the metal oxide particles MO in addition to the loads of the oxidation tower 10 and the reduction tower 20. The control unit C can measure the amount of the metal particles M and the metal oxide particles MO based on the output from the load cell 91.

[0043] The metal particles M and metal oxide particles MO may be broken when circulating between the oxidation tower 10 and the reduction tower 20 in the circulation section 60. These broken pieces may be discharged from the oxidation tower 10 together with gas components in the solid-gas separation device 50. As a result, the load of the metal particles M and metal oxide particles MO decreases by the amount of the broken pieces discharged from the oxidation tower 10. The control unit C may calculate, based on the output from the load cell 91, the amount of weight loss of the oxidation tower 10 and the reduction tower 20 (including the weight of the metal particles M and the metal oxide particles MO) from the start of operation when the metal particles M were stored, and determine whether or not the metal particles M should be replenished. That is, if the weight loss exceeds a predetermined threshold, it may be determined that the metal particles M and the metal oxide particles MO are insufficient, and a display device or the like may indicate a need to replenish the metal particles M. In this case, the control unit C may calculate the amount of metal particles M to be replenished from the amount of weight loss and display the replenishment amount on a display device or the like.

[0044] Next, the operation of the chemical looping reaction system 100 will be described. Prior to this operation, metal particles M are filled into the oxidation tower 10. Examples of the metal particles M include iron, iron oxide (FeO, Fe ２ O ３ , Fe ３ O ４ ), ilmenite (FeTiO ３ At the time of packing, not only the metal particles M but also metal oxide particles MO may be packed into the oxidation tower 10 .

[0045] The filling amount of the metal particles M is set within a range that allows the metal particles M (or metal oxide particles MO) to flow within the oxidation tower 10 by the fluidizing gas ejected into the oxidation tower 10 from the fluidizing gas nozzle 44, and that allows the metal particles M to be circulated by the circulation unit 60. Furthermore, if the amount of metal particles M is small, the amount of carbon dioxide generated in the reduction tower 20 will be small, which is undesirable. Therefore, the filling amount of the metal particles M is set within a range that allows sufficient carbon dioxide to be generated in the reduction tower 20.

[0046] After the metal particles M are loaded, the metal particles M are preheated to, for example, about 600°C by preheating means such as a preheating burner (not shown) disposed in the oxidation tower 10 (e.g., in the central portion 12 thereof) or an electric heater (not shown) attached to the peripheral wall of the oxidation tower 10 (e.g., in the central portion 12 thereof). After or during preheating, a predetermined amount of air is supplied from the air supply line 19 to the air chamber 31 via the air inlet 46. The air supplied to the air chamber 31 is sprayed into the oxidation tower 10 from the air nozzle 42. The air sprayed into the oxidation tower 10 functions as an oxidizing agent, oxidizing the metal particles M to form metal oxide particles MO.

[0047] Furthermore, a mixture of the organic solvent as fuel and steam is sprayed from the fuel supply line 21 to the fuel nozzle 40, and this mixture is supplied to the reduction reactor 20. The organic solvent used in this embodiment is not particularly limited, and examples thereof include organic agents used in organic synthesis of paints, plastics, etc., and chemicals in general, including various chemical solutions used in manufacturing semiconductor elements and liquid crystal display elements by techniques such as photolithography, DSA lithography, and imprint lithography. The organic solvent may also contain resins, etc.

[0048] Examples of chemical solutions include those containing polar solvents such as ketone-based solvents, ester-based solvents, alcohol-based solvents, ether-based solvents, and amide-based solvents; hydrocarbon-based solvents; etc. Examples of chemical solutions containing resins include resin solutions produced by separation and purification during organic resin synthesis, and examples of lithography chemical solutions containing resins include resin solutions in which resist resin components are dissolved in organic solvent components, resist compositions, insulating film compositions, antireflective film compositions, block copolymer compositions applied to directed self-assembly (DSA) technology, and imprint resin compositions. In addition, examples of lithography chemical solutions used in pattern formation, etc. include prewet solvents, resist solvents, and developers.

[0049] Examples of ketone solvents include 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, acetone, 2-heptanone (methyl amyl ketone), 4-heptanone, 1-hexanone, 2-hexanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, phenylacetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, acetonylacetone, ionone, diacetonyl alcohol, acetylcarbinol, acetophenone, methyl naphthyl ketone, isophorone, and propylene carbonate.

[0050] Examples of ester-based solvents include methyl acetate, butyl acetate, ethyl acetate, isopropyl acetate, pentyl acetate, isopentyl acetate, amyl acetate, propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl-3-ethoxypropionate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, methyl formate, ethyl formate, butyl formate, propyl formate, ethyl lactate, butyl lactate, and propyl lactate.

[0051] Examples of alcohol-based solvents include alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, n-hexyl alcohol, n-heptyl alcohol, n-octyl alcohol, and n-decanol; glycol-based solvents such as ethylene glycol, diethylene glycol, and triethylene glycol; and glycol ether-based solvents such as ethylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, diethylene glycol monomethyl ether, triethylene glycol monoethyl ether, and methoxymethylbutanol.

[0052] Examples of the ether solvent include the glycol ether solvents described above, as well as dioxane and tetrahydrofuran.

[0053] Examples of amide solvents include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, hexamethylphosphoric triamide, and 1,3-dimethyl-2-imidazolidinone.

[0054] Examples of hydrocarbon solvents include aromatic hydrocarbon solvents such as toluene and xylene, and aliphatic hydrocarbon solvents such as pentane, hexane, octane, decane, etc. Various solutions and solvents have been listed above, but the chemical solution may be a mixture of the above-mentioned various solutions and solvents with water.

[0055] Examples of resins include thermoplastic resins and thermosetting resins. Examples of thermosetting resins include polyethylene, polypropylene, polyvinyl chloride, polystyrene, acrylonitrile-butadiene-styrene, acrylonitrile-styrene, polymethyl methacrylic, polyvinyl alcohol, polyvinylidene chloride, polyethylene terephthalate, engineering plastics, and super engineering plastics. Examples of thermosetting resins include phenolic resin, urea resin, melamine resin, unsaturated polyester, epoxy resin, silicone resin, and polyurethane.

[0056] From the viewpoint of recycling waste materials as fuel, the organic solvent used in this embodiment is preferably a used or unnecessary organic solvent waste liquid, more preferably a resin solution produced by separation and purification during organic synthesis of a resin, an organic solvent waste liquid produced during the production of semiconductor elements or liquid crystal display elements, etc. Examples of this organic solvent waste liquid include the various chemical solutions described above and mixtures thereof.

[0057] The mixture of fuel and steam is sprayed into the reduction tower 20 from the fuel nozzle 40. The organic solvent sprayed into the reduction tower 20 functions as a reducing agent. At the beginning of operation, the first switching valve 27 is set so that the carrier gas supply line 26 is connected to the second nitrogen supply line 28. In this case, nitrogen is supplied as a carrier gas from the second nitrogen supply line 28 to the steam generation unit 24. The steam generated in the steam generation unit 24 is transported to the mixing section 22 by the nitrogen carrier gas, and mixed with the organic solvent fuel, and then supplied to the fuel nozzle 40.

[0058] Furthermore, a fluidizing gas is supplied from the fluidizing gas supply line 16 to the fluidizing gas chamber 32 via the fluidizing gas inlet 47. The fluidizing gas in the fluidizing gas chamber 32 is sprayed from the fluidizing gas nozzle 44 into the oxidation tower 10. The fluidizing gas fluidizes the metal particles M in the oxidation tower 10. At the start of operation, the second switching valve 17 is set so that the fluidizing gas supply line 16 is connected to the nitrogen supply line 18. Therefore, nitrogen is sprayed from the fluidizing gas nozzle 44 as the fluidizing gas.

[0059] In the oxidation tower 10, metal particles M preheated to a reaction temperature react with oxygen in the supplied air to produce metal oxide particles MO. At this time, heat is generated by the metal oxidation reaction, and the metal particles M, metal oxide particles MO, and air flowing through the oxidation tower 10 rise in temperature. In this case, the heat is generated by the metal oxidation reaction, and no high-temperature parts exceeding 1500°C are generated, so thermal NO ｘ However, the metal oxide particles MO may be further oxidized. For example, when the metal oxide particles MO are Fe ３ O ４ In this case, the metal oxide particles MO are further oxidized to Fe ２ O ３ etc. may occur.

[0060] The metal oxide particles MO and unoxidized metal particles M in the oxidation tower 10 flow into the reduction tower 20 and then rise within the reduction tower 20. During the process of rising within the reduction tower 20, the metal oxide particles MO are reduced by the organic solvent and become metal particles M. The solid and gas components rising within the reduction tower 20 are separated into the solid and gas components by the solid-gas separator 50. The gas components rise through the solid-gas separator 50 and are exhausted from an exhaust section 57 at the top of the reduction tower 20. The solid components, i.e., the metal particles M and remaining metal oxide particles MO, are returned to the oxidation tower 10 by the solid-gas separator 50.

[0061] Due to the oxidation reaction within oxidation tower 10, the air supplied to oxidation tower 10 becomes a high-temperature gas, which is discharged from exhaust section 14 at the top of oxidation tower 10. Metal pieces and the like in the gas discharged from oxidation tower 10 are separated by solid-gas separator 15 and returned to oxidation tower 10 as needed. Depending on the amount of air supplied to oxidation tower 10, the discharged gas will be either high-concentration nitrogen containing no oxygen or a mixed gas containing residual oxygen and nitrogen. Of the exhaust gas, for example, nitrogen may be sent to a nitrogen storage tank or the like via a recovery line (not shown) and stored therein.

[0062] The gas discharged from the reduction tower 20 contains carbon dioxide and water vapor produced by the reduction reaction described above. The gas discharged from the reduction tower 20 is condensed in a gas-liquid separator 58 through which cooling water circulates, and separated into water and high-concentration (90% or more, preferably 95% or more) carbon dioxide. The carbon dioxide obtained in the gas-liquid separator 58 is sent to a carbon dioxide supply line 70. In the carbon dioxide supply line 70, the carbon dioxide flows through a recovery line 71, and its flow rate is measured by a flow rate meter 72. The carbon dioxide that has passed through the flow rate meter 72 flows along the recovery line 71 to an adjustment valve 73.

[0063] The regulating valve 73 switches its mode depending on the measurement result by the flow rate measuring device 72. The regulating valve 73 is initially set to, for example, the first mode. That is, in the initial state, the recovery line 71 and the first line 74 are connected. Therefore, carbon dioxide flows from the recovery line 71 to the first line 74. The regulating valve 73 switches from the first mode to the second mode when the flow rate per unit time of carbon dioxide in the recovery line 71 exceeds a first threshold. In this case, the recovery line 71 and the second line 76 are connected. In the reduction tower 20, an increase in the amount of reduction reaction of the metal oxide particles MO increases, thereby increasing the amount of carbon dioxide generated. In such a case, in order to prevent excessive carbon dioxide from being sent via the first line 74, the regulating valve 73 switches from the first mode to the second mode. Therefore, the carbon dioxide is sent from the recovery line 71 to the second line 76 and stored in the second tank 77 via the second line 76.

[0064] Furthermore, the adjustment valve 73 switches from the first mode to the third mode when the flow rate per unit time of carbon dioxide in the recovery line 71 is less than a second threshold value. In this case, the first line 74 and the second line 76 are connected. In the reduction tower 20, when the amount of reduction reaction of the metal oxide particles MO decreases, the amount of carbon dioxide generated decreases. In such a case, in order to avoid a shortage of the amount of carbon dioxide supplied via the first line 74, the adjustment valve 73 switches from the first mode to the third mode. Therefore, the carbon dioxide stored in the second tank 77 is sent to the first line 74 via the second line 76 and the adjustment valve 73.

[0065] Note that the adjustment valve 73 maintains the first mode when the flow rate per unit time of carbon dioxide in the recovery line 71 is equal to or greater than the second threshold value and less than the first threshold value. The carbon dioxide sent from the recovery line 71 to the first line 74, or the carbon dioxide sent from the second line 76 to the first line 74, is sent to the first tank 75 via the first connection line 78 and stored in the first tank 75. By storing the carbon dioxide in the first tank 75, even if the amount of carbon dioxide required downstream of the first tank 75 fluctuates, this can be addressed by changing the amount of carbon dioxide sent from the first tank 75.

[0066] When the carrier gas supply line 26 and the second connection line 79 are connected by the first switching valve 27, the connection between the carrier gas supply line 26 and the second nitrogen supply line 28 is cut off, and the supply of nitrogen to the carrier gas supply line 26 is stopped. Meanwhile, the carbon dioxide stored in the first tank 75 flows from the second connection line 79 via the first switching valve 27 to the carrier gas supply line 26 and is supplied to the steam generating unit 24. Therefore, the carrier gas for transporting the steam is switched from nitrogen to carbon dioxide. The steam generated in the steam generating unit 24 is sent to the steam supply line 23 together with carbon dioxide. In this way, by supplying carbon dioxide instead of nitrogen as the carrier gas to the steam generating unit 24, nitrogen consumption can be suppressed.

[0067] When the fluidizing gas supply line 16 and the third connection line 80 are connected by the second switching valve 17, the connection between the fluidizing gas supply line 16 and the nitrogen supply line 18 is cut off, and the supply of nitrogen to the fluidizing gas supply line 16 is stopped. Meanwhile, the carbon dioxide stored in the first tank 75 flows through the third connection line 80 and then through the fluidizing gas supply line 16 via the second switching valve 17. Therefore, the fluidizing gas supplied to the fluidizing gas chamber 32 is switched from nitrogen to carbon dioxide. The carbon dioxide in the fluidizing gas chamber 32 is supplied to the oxidation tower 10 from the fluidizing gas nozzle 44 and used to fluidize the metal particles M and the metal oxide particles MO. In this way, by using carbon dioxide instead of nitrogen as the fluidizing gas, the amount of nitrogen used can be reduced.

[0068] [Method for Utilizing Carbon Dioxide] A method for utilizing carbon dioxide according to the first embodiment will now be described. The method for utilizing carbon dioxide according to the first embodiment can be performed by the chemical looping reaction system 100 according to the first embodiment. FIG. 5 is a flowchart showing an example of the method for utilizing carbon dioxide according to the first embodiment. FIG. 6 is a flowchart following FIG. 5, showing an example of the method for utilizing carbon dioxide according to the first embodiment. FIG. 7 is a flowchart showing a part of the flowchart in FIG. 6 in detail.

[0069] The operations shown in the flowcharts of Figures 5 to 7 may be controlled by the controller C or may be performed by an operator or the like. The controller C controls all of the operations in the chemical looping reaction system 100. As shown in Figure 5, first, metal particles M are loaded into the oxidation tower 10 (step S01). In step S01, the oxidation tower 10 is provided with a raw material inlet (not shown), and a predetermined amount of metal particles M is loaded through the raw material inlet to fill the oxidation tower 10. The metal particles M may be loaded by a supply device or the like, or by an operator. When the metal particles M are loaded by a supply device or the like, the loading amount may be set in advance and automatically controlled by the controller C.

[0070] Next, the temperatures of the oxidation tower 10 and the reduction tower 20 are increased (step S02). In step S02, the oxidation tower 10 and the reduction tower 20 are heated by an electric heater (not shown) or the like. Next, air is supplied to the oxidation tower 10 (step S03). In step S03, air is supplied to the oxidation tower 10 via the air nozzle 42. The amount of air supplied is set appropriately depending on the loading amount of metal particles M. Furthermore, nitrogen is supplied to the oxidation tower 10 and the reduction tower 20 (step S04). In step S04, nitrogen is supplied to the oxidation tower 10 via the fluidizing gas nozzle 44.

[0071] Furthermore, fuel and steam, which are reducing agents, are supplied to the reduction tower 20 (step S05). In step S05, the fuel and steam mixed in the mixer 22 are supplied to the reduction tower 20 from the fuel nozzle 40. Nitrogen is used as a carrier gas for the steam. Steps S03 to S05 may be performed sequentially or simultaneously. Subsequently, the solid-gas separator 50 is operated (step S06). Subsequently, the solid-gas separator 50 separates the carbon dioxide and the metal particles M (step S07). In step S07, the solid-gas separator 50 separates the carbon dioxide, which is a gas component, from the metal particles M, which are solid components.

[0072] Next, in the solid-gas separator 50, carbon dioxide is sent to the carbon dioxide supply line 70 (step S08). In step S08, the carbon dioxide is sent from the solid-gas separator 50 to the carbon dioxide supply line 70. In addition, in the solid-gas separator 50, the metal particles M are sent to the oxidation tower 10 (step S09). In step S09, the metal particles M are returned from the solid-gas separator 50 to the oxidation tower 10. Note that steps S08 and S09 may be performed sequentially or simultaneously.

[0073] 6 , carbon dioxide is supplied to the steam supply line 23 and the fluidizing gas supply line 16 (step S10). In step S10, the carbon dioxide is sent to the steam supply line 23 and the fluidizing gas supply line 16, respectively, via the recovery line 71 and the first line 74 of the carbon dioxide supply line 70. Then, the carbon dioxide is supplied to the reduction tower 20 together with water vapor and fuel (reducing agent) (step S11). In the above-mentioned step S10, water vapor is carried by the carbon dioxide in the steam supply line 23. In the mixing section 22, fuel is mixed with water vapor and carbon dioxide. Therefore, in step S11, carbon dioxide is supplied to the reduction tower 20 together with water vapor and fuel.

[0074] Carbon dioxide is also supplied to oxidation tower 10 (step S12). In step S12, carbon dioxide is supplied from carbon dioxide supply line 70 to oxidation tower 10 via fluidizing gas supply line 16. Note that by adjusting second selector valve 17, nitrogen sent via nitrogen supply line 18 and carbon dioxide sent via carbon dioxide supply line 70 may be mixed, and this mixed gas may be supplied to oxidation tower 10 via fluidizing gas supply line 16. Note that steps S11 and S12 may be performed simultaneously, or may be performed at different times by staggering the operation timing of first selector valve 27 and second selector valve 17.

[0075] Next, the operation state of the chemical looping reaction system 100 is continued for a predetermined time (step S13). In step S13, the flowchart shown in Fig. 7 is executed. Note that each step of the flowchart shown in Fig. 7 may be executed by the controller C or by an operator. As shown in Fig. 7, the operation time of the chemical looping reaction system 100 is measured (step S131). In step S131, the operation time is measured, for example, by a timer provided in the controller C.

[0076] Next, it is determined whether it is time to measure the weight (step S132). The control unit C determines whether the operation time measured in step S131 has elapsed, for example, a predetermined time. Note that the predetermined time may be set, for example, by obtaining in advance by a test operation or the like the amount (rate) of metal particles M decreasing over time, and setting it to a time when the metal particles M are expected to decrease. If it is not time to measure the weight (NO in step S132), step S132 is repeated.

[0077] If it is time to measure the weight (YES in step S132), the weights of the oxidation tower 10 and the reduction tower 20 are measured (step S133). In step S133, the control unit C measures the weights of the oxidation tower 10 and the reduction tower 20 based on the output of the load cell 91 (see FIG. 2). Next, it is determined whether the weights of the oxidation tower 10 and the reduction tower 20 are lighter than a threshold value (step S134). In step S134, the control unit C determines whether the weights of the oxidation tower 10 and the reduction tower 20 are lighter than a preset threshold value.

[0078] If the weights of the oxidation tower 10 and the reduction tower 20 are heavier than the threshold value (NO in step S134), the process returns to step S132. If the weights of the oxidation tower 10 and the reduction tower 20 are lighter than the threshold value (YES in step S134), metal particles M are replenished (step S135). As described above, when the amount of metal particles M decreases over time, the consumption of fuel used as a reducing agent decreases, and the amount of carbon dioxide generated from the reduction tower 20 also decreases. By replenishing metal particles M at the time when the amount of metal particles M decreases and the weights of the oxidation tower 10 and the reduction tower 20 become lighter than the threshold value, the amount of fuel consumed and the amount of carbon dioxide generated can be increased.

[0079] Next, it is determined whether the operation time of the chemical looping reaction system 100 has elapsed for a predetermined time (step S136). In step S136, the controller C determines whether the operation time of the chemical looping reaction system 100 has elapsed for a predetermined time using a timer or the like. If the operation time has not elapsed for a predetermined time (NO in step S136), the process returns to step S132. If the operation time has elapsed for a predetermined time (YES in step S136), step S14 shown in FIG. 6 is performed. As shown in FIG. 6, the controller C stops the supply of air, fuel (reducing agent), steam, and nitrogen (step S14). Next, the controller C stops the heating and solid-gas separation device 50 (step S15). In step S15, the operation of the chemical looping reaction system 100 is stopped, and the above-described series of processes is completed.

[0080] As described above, according to the chemical looping reaction system 100 and the method for utilizing carbon dioxide of the first embodiment, the carbon dioxide generated in the reduction tower 20 is supplied to the oxidation tower 10 and the reduction tower 20. Therefore, part or all of the nitrogen supplied to the oxidation tower 10 and the reduction tower 20 can be replaced with carbon dioxide, thereby reducing the amount of nitrogen used. As a result, the operation efficiency of the chemical looping reaction system can be improved. Furthermore, since the generated carbon dioxide is utilized in the chemical looping reaction system 100, the carbon dioxide can be utilized effectively, and the amount of carbon dioxide released into the atmosphere can be reduced.

[0081] Second Embodiment [Chemical Looping Reaction System] A chemical looping reaction system 100A according to the second embodiment will be described. Figure 8 is a diagram showing an example of the chemical looping reaction system 100A according to the second embodiment. Note that in Figure 8, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. As shown in Figure 8, the chemical looping reaction system 100A differs from the first embodiment in that the first line 74 of the carbon dioxide supply line 70 is directly connected to the oxidation tower 10 or the reduction tower 20. That is, carbon dioxide is sent to the oxidation tower 10 or the reduction tower 20 without passing through a line for supplying fuel or a fluidizing gas (nitrogen).

[0082] In the chemical looping reaction system 100A, the second connection line 79 of the carbon dioxide supply line 70 is connected to, for example, the fluidizing gas chamber 32. In this case, the carbon dioxide delivered through the carbon dioxide supply line 70 is supplied from the fluidizing gas chamber 32 (see FIG. 2) to the oxidation tower 10 via the fluidizing gas nozzle 44 (see FIG. 2) and is used to fluidize the metal particles M. In the fluidizing gas chamber 32, the carbon dioxide may be mixed with nitrogen delivered via the fluidizing gas supply line 16 and then supplied to the oxidation tower 10.

[0083] The carbon dioxide sent through the carbon dioxide supply line 70 may be supplied to the oxidation tower 10, for example, via a dedicated supply nozzle or supply pipe that is separately provided. Furthermore, the carbon dioxide sent through the carbon dioxide supply line 70 may be supplied to the reduction tower 20. When carbon dioxide is supplied to the reduction tower 20, for example, a dedicated supply nozzle, supply pipe, or the like may be provided in tandem with the fuel nozzle 40 and the fuel supply pipe 41, and the carbon dioxide may be supplied through these supply nozzles or supply pipes.

[0084] [Method for Utilizing Carbon Dioxide] A method for utilizing carbon dioxide according to a second embodiment will now be described. The method for utilizing carbon dioxide according to the second embodiment can be performed by the chemical looping reaction system 100A according to the second embodiment. FIG. 9 is a flowchart showing an example of the method for utilizing carbon dioxide according to the second embodiment. In FIG. 9, steps that are the same as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. The operations shown in the flowchart in FIG. 9 may be controlled by the controller C or may be performed by an operator or the like.

[0085] After steps S08 and S09 shown in Fig. 5, carbon dioxide is supplied alone to the oxidation tower 10 or the reduction tower 20 (step S21), as shown in Fig. 9. In step S21, carbon dioxide sent through the carbon dioxide supply line 70 is supplied to the oxidation tower 10 or the reduction tower 20 via a dedicated supply nozzle or the like. Note that steps S13 to S15 after step S21 are the same as those in the first embodiment, and therefore description thereof will be omitted.

[0086] As described above, according to the second embodiment, as in the first embodiment, the carbon dioxide generated in the reduction tower 20 is supplied to the reduction tower 20 or the oxidation tower 10, thereby reducing the amount of nitrogen used. Furthermore, the first switching valve 27, the second switching valve 17, and the third connecting line are not required in the chemical looping reaction system 100 of the first embodiment, thereby simplifying the system. Furthermore, since the generated carbon dioxide is utilized in the chemical looping reaction system 100A, the carbon dioxide can be utilized effectively.

[0087] Third Embodiment [Chemical Looping Reaction System] A chemical looping reaction system 100B according to the third embodiment will be described. Figure 10 is a diagram illustrating an example of the chemical looping reaction system 100B according to the third embodiment. In Figure 10, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. As shown in Figure 10, the chemical looping reaction system 100B differs from the first embodiment in that the first line 74 of the carbon dioxide supply line 70 is connected only to the carrier gas supply line 26 via a first switching valve 27. That is, carbon dioxide is used as a carrier gas for water vapor in the steam supply line 23 and is supplied to the reduction tower 20 together with the fuel and water vapor via the fuel supply line 21.

[0088] In the chemical looping reaction system 100B, as in the first embodiment, the second connection line 79 of the first line 74 is connected to the first selector valve 27. Therefore, by switching the first selector valve 27, the carrier gas for the water vapor generated in the steam generating unit 24 can be switched between nitrogen and carbon dioxide.

[0089] [Method for Utilizing Carbon Dioxide] A method for utilizing carbon dioxide according to a third embodiment will now be described. The method for utilizing carbon dioxide according to the third embodiment can be performed by the chemical looping reaction system 100B according to the third embodiment. FIG. 11 is a flowchart showing an example of the method for utilizing carbon dioxide according to the third embodiment. In FIG. 11, steps that are the same as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. The operations shown in the flowchart in FIG. 11 may be controlled by the controller C or may be performed by an operator or the like.

[0090] 5 , carbon dioxide is supplied to the steam supply line 23 (step S31), as shown in FIG. 11 . In step S31, the first switching valve 27 connects the second connection line 79 to the carrier gas supply line 26. As a result, the carbon dioxide sent through the carbon dioxide supply line 70 is supplied to the steam supply line 23 as a carrier gas for water vapor, and is supplied to the reduction tower 20 together with the fuel. Note that steps S11, S13, S14, and S15 subsequent to step S31 are the same as those in the first embodiment, and therefore will not be described.

[0091] As described above, according to the third embodiment, as in the first embodiment, the carbon dioxide generated in the reduction tower 20 is supplied to the reduction tower 20, thereby reducing the amount of nitrogen used as a carrier gas for water vapor. Furthermore, the second switching valve 17 and the third connection line are not required in the chemical looping reaction system 100 of the first embodiment, thereby simplifying the system. Furthermore, the generated carbon dioxide is utilized in the chemical looping reaction system 100B, allowing for effective utilization of the carbon dioxide.

[0092] Fourth Embodiment [Chemical Looping Reaction System] A chemical looping reaction system 100C according to the fourth embodiment will be described. Figure 12 is a diagram showing an example of the chemical looping reaction system 100C according to the fourth embodiment. In Figure 12, the same components as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. As shown in Figure 12, the chemical looping reaction system 100C differs from the first embodiment in that the first line 74 of the carbon dioxide supply line 70 is connected only to the fluidizing gas supply line 16 via the second switching valve 17. That is, carbon dioxide is supplied as a fluidizing gas to the oxidation tower 10 via the fluidizing gas supply line 16.

[0093] In the chemical looping reaction system 100C, as in the first embodiment, the third connection line 80 of the first line 74 is connected to the second selector valve 17. Therefore, by switching the second selector valve 17, the fluidizing gas can be switched between nitrogen and carbon dioxide.

[0094] [Method for Utilizing Carbon Dioxide] A method for utilizing carbon dioxide according to a fourth embodiment will now be described. The method for utilizing carbon dioxide according to the fourth embodiment can be performed by the chemical looping reaction system 100C according to the fourth embodiment. FIG. 13 is a flowchart showing an example of the method for utilizing carbon dioxide according to the fourth embodiment. In FIG. 13, steps that are the same as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified. The operations shown in the flowchart in FIG. 13 may be controlled by the controller C or may be performed by an operator or the like.

[0095] After steps S08 and S09 shown in Fig. 5, carbon dioxide is supplied to the fluidizing gas supply line 16 (step S41), as shown in Fig. 13. In step S41, the second switching valve 17 connects the third connection line 80 to the fluidizing gas supply line 16. As a result, the carbon dioxide sent through the carbon dioxide supply line 70 is supplied to the fluidizing gas supply line 16 and supplied as fluidizing gas to the oxidation tower 10. Note that steps S12 to S15 after step S41 are the same as those in the first embodiment, and therefore will not be described here.

[0096] As described above, according to the fourth embodiment, as in the first embodiment, the carbon dioxide produced in the reduction tower 20 is supplied to the oxidation tower 10, thereby reducing the amount of nitrogen used as a fluidizing gas. Furthermore, the first switching valve 27 and the second connection line 79 are not required in the chemical looping reaction system 100 of the first embodiment, thereby simplifying the system. Furthermore, the produced carbon dioxide is utilized in the chemical looping reaction system 100C, allowing for effective utilization of the carbon dioxide.

[0097] Fifth Embodiment [Chemical Looping Reaction System] A chemical looping reaction system 200 according to the fifth embodiment will be described. Fig. 14 is a diagram showing an example of a chemical looping reaction system 200 according to the fifth embodiment. Note that Fig. 14 mainly shows the oxidation tower 10 and the reduction tower 20 in the chemical looping reaction system 200, and other components are omitted because they are the same as those in the first to fourth embodiments. In Fig. 14, components similar to those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified.

[0098] As shown in FIG. 14 , the chemical looping reaction system 200 includes a heat recovery unit 171. The heat recovery unit 171 includes a pipe 172 spirally wound around the reduction tower 20 inside the oxidation tower 10. The pipe 172 is made of a material capable of transferring heat. A liquid serving as a heat transfer medium flows through the pipe 172 in the direction indicated by the arrows. This liquid may be, for example, water or a liquid with a boiling point higher than that of water. The liquid may be circulated through the pipe 172 in the direction indicated by the arrows.

[0099] Heat recovery can be achieved by heating the liquid flowing inside the pipe 172 in the spiral portion by receiving heat generated in the oxidation tower 10. The recovered heat may be used, for example, as a heat source for the steam generation unit 24 (see FIG. 1 ), or as a heat source for heating fuel supplied through the fuel supply line 21. It may also be used as a heat source for other devices. When water is used as the liquid, it can be heated in the spiral portion of the pipe 172 to become water vapor. Therefore, the heat recovery unit 171 can be used in place of the steam generation unit 24 described above.

[0100] As described above, according to the fifth embodiment, the heat generated during operation of the chemical looping reaction system 200 is recovered by the heat recovery unit 171. The recovered heat can be used as various heat sources, such as the heat source for the steam generation unit 24, thereby reducing system operating costs. Furthermore, in the case where steam is generated by the heat recovery unit 171, replacing the steam generation unit 24 with the heat recovery unit 171 reduces the installation space for the steam generation unit 24, thereby enabling the system to be downsized and simplified.

[0101] Sixth Embodiment [Chemical Looping Reaction System] A chemical looping reaction system 300 according to the sixth embodiment will be described. Fig. 15 is a diagram showing an example of a chemical looping reaction system 300 according to the sixth embodiment. Note that Fig. 15 mainly shows the oxidation tower 10 and the reduction tower 20 in the chemical looping reaction system 300, and other components are omitted because they are the same as those in the first to fourth embodiments. In Fig. 15, components that are the same as those in the first embodiment are denoted by the same reference numerals, and their description will be omitted or simplified.

[0102] As shown in Figure 15, the chemical looping reaction system 300 includes a heat recovery unit 271. The heat recovery unit 271 includes a pipe 272 spirally wound around the oxidation tower 10. The inside of the pipe 272 is made of a material capable of transferring heat. A liquid serving as a heat transfer medium flows through the pipe 272 in the direction indicated by the arrows. This liquid may be, for example, water or a liquid with a boiling point higher than that of water. The liquid may be circulated through the pipe 272 in the direction indicated by the arrows.

[0103] Heat recovery can be achieved by heating the liquid flowing inside the pipe 272 in the spiral portion by receiving heat generated in the oxidation tower 10. The recovered heat may be used, for example, as a heat source for the steam generation unit 24 (see FIG. 1 ), or as a heat source for heating fuel supplied via the fuel supply line 21. It may also be used as a heat source for other devices. Note that when water is used as the liquid, it can be heated in the spiral portion of the pipe 272 to become water vapor. Therefore, the heat recovery unit 271 can be used in place of the steam generation unit 24 described above.

[0104] As described above, according to the sixth embodiment, similar to the fifth embodiment, the heat generated during operation of the chemical looping reaction system 300 is recovered by the heat recovery unit 271, and the recovered heat can be used as a heat source for various purposes, thereby reducing system operation costs. Furthermore, in the case where steam is generated by the heat recovery unit 271, replacing the steam generation unit 24 with the heat recovery unit 271 reduces the installation space for the steam generation unit 24, thereby enabling the system to be more compact.

[0105] Although the embodiments have been described above, the technical scope of the present invention is not limited to the above-described embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above-described embodiments. Furthermore, forms incorporating such modifications or improvements are also included within the technical scope of the present invention. One or more of the requirements described in the above-described embodiments may be omitted. Furthermore, the requirements described in the above-described embodiments may be combined as appropriate. Furthermore, the order of execution of each operation shown in the embodiments can be realized in any order as long as the results of a previous operation are not used in a subsequent operation. Furthermore, even if the operations in the above-described embodiments are described using terms such as "first," "next," and "subsequently" for convenience, it is not necessary to perform them in this order.

[0106] Furthermore, in the above-described embodiment, an example has been described in which the reduction tower 20 is disposed inside the oxidation tower 10, but the present invention is not limited to this. For example, the oxidation tower 10 may be disposed inside the reduction tower 20. Alternatively, the oxidation tower 10 and the reduction tower 20 may be disposed separately, and a flow path for transferring the metal oxide particles MO from the oxidation tower 10 to the reduction tower 20 and a flow path for transferring the metal particles M from the reduction tower 20 to the oxidation tower 10 may be provided.

[0107] In addition, to the extent permitted by law, the contents of Japanese Patent Application No. 2022-090952 and all documents cited in the above-mentioned embodiments are incorporated by reference into the present text.

[0108] M...metal particles MO...metal oxide particles 10...oxidation tower 16...fluidizing gas supply line 17...second switching valve 18...nitrogen supply line 19...air supply line 20...reduction tower 21...fuel supply line (reducing agent supply line) 23...steam supply line 24...steam generation unit 25...water supply line 26...carrier gas supply line 27...first switching valve 28...nitrogen supply line 50...solid-gas separation device 60...circulation section 70...carbon dioxide supply line 71...recovery line 74...first line 75...first tank 76...second line 77...second tank 100, 100A, 100B, 100C, 200, 300...chemical looping reaction system

Claims

1. A chemical looping reaction system comprising: an oxidation tower that oxidizes metal particles to form metal oxide particles; a reduction tower that reacts the metal oxide particles with a reducing agent to convert the metal oxide particles into metal particles while generating carbon dioxide; and a circulation unit that circulates the metal particles and the metal oxide particles between the reduction tower and the oxidation tower, wherein the chemical looping reaction system comprises a carbon dioxide supply line that supplies the carbon dioxide generated in the reduction tower to at least one of the reduction tower and the oxidation tower.

2. The chemical looping reaction system according to claim 1, wherein the reducing agent is an organic solvent.

3. The chemical looping reaction system according to claim 2, wherein the organic solvent contains a powdered or granular resin.

4. The chemical looping reaction system according to any one of claims 1 to 3, wherein the carbon dioxide supply line supplies carbon dioxide from the lower part of at least one of the reduction tower and the oxidation tower.

5. The chemical looping reaction system according to any one of claims 1 to 3, wherein the carbon dioxide supply line includes a first tank capable of storing carbon dioxide, and carbon dioxide is supplied to at least one of the reduction tower and the oxidation tower via the first tank.

6. The chemical looping reaction system according to any one of claims 1 to 3, further comprising a reducing agent supply line that supplies the reducing agent to the reduction tower, and the carbon dioxide supply line is connected to the reducing agent supply line.

7. The chemical looping reaction system according to claim 6, comprising: a steam generating unit that generates steam; and a steam supply line that supplies the steam generated by the steam generating unit to the reducing agent supply line, wherein the carbon dioxide supply line is connected to the steam generating unit and supplies carbon dioxide together with the steam to the reducing agent supply line via the steam supply line.

8. The chemical looping reaction system according to any one of claims 1 to 3, further comprising a nitrogen supply line for supplying nitrogen to at least one of the reduction tower and the oxidation tower, and the carbon dioxide supply line is connected to the nitrogen supply line.

9. The chemical looping reaction system according to any one of claims 1 to 3, wherein the carbon dioxide supply line comprises: a flow meter that measures the flow rate of carbon dioxide; a recovery line connected to the reduction tower; a regulating valve provided in the recovery line; a first line downstream of the regulating valve for supplying carbon dioxide to at least one of the reduction tower and the oxidation tower; a second line provided separately from the first line downstream of the regulating valve; and a second tank connected to the second line and capable of storing carbon dioxide, wherein the regulating valve is switchable between a first mode in which the recovery line communicates with the first line, a second mode in which the recovery line communicates with the second line, and a third mode in which the first line communicates with the second line.

10. The chemical looping reaction system according to claim 9, wherein the regulating valve switches between the first mode, the second mode, and the third mode depending on the measurement result of the flow rate measuring device.

11. The chemical looping reaction system of claim 10, wherein the regulating valve switches from the first mode to the second mode when the flow rate per unit time of carbon dioxide in the recovery line exceeds a first threshold value.

12. The chemical looping reaction system of claim 10, wherein the regulating valve switches from the first mode to the third mode when the flow rate per unit time of carbon dioxide in the recovery line is less than a second threshold value.

13. A method for utilizing carbon dioxide produced in a chemical looping reaction system comprising an oxidation tower that oxidizes metal particles to produce metal oxide particles, a reduction tower that reacts the metal oxide particles with a reducing agent to convert the metal oxide particles into metal particles while generating carbon dioxide, and a circulation unit that circulates the metal particles and the metal oxide particles between the reduction tower and the oxidation tower, the method comprising supplying the carbon dioxide produced in the reduction tower to at least one of the reduction tower and the oxidation tower to cause the metal particles and the metal oxide particles to flow.

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