Chemical looping combustion system, chemical looping combustion method, and computer program

Abstract

This technology provides a solution for chemical looping combustion systems that achieves both improved thermal efficiency and enhanced operational stability. [Solution] The chemical looping combustion system comprises an oxidation tower that uses oxygen to oxidize metal particles, a reduction tower that uses hydrocarbon gas to reduce the metal particles oxidized in the oxidation tower, and a loop seal connected to the oxidation tower and the reduction tower respectively to suppress the movement of hydrocarbon gas from the reduction tower to the oxidation tower. The loop seal has an inlet that communicates with the oxidation tower and into which metal particles flow in from the oxidation tower, and an outlet that communicates with the inlet and the reduction tower respectively and allows the metal particles flowing into the inlet to flow out into the reduction tower. A retention section is formed on the outlet side of the inlet where metal particles are retained, and the outlet has a pressure reduction mechanism that makes the pressure on the inlet side less than the pressure on the reduction tower side.

Description

Technical Field

[0001] The present invention relates to a chemical looping combustion system, a chemical looping combustion method, and a computer program.

Background Art

[0002] Conventionally, a chemical looping combustion system that can separate and recover heat and carbon dioxide using metal particles as an oxygen carrier has been known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0008] In this configuration, the movement of hydrocarbon gas from the reduction tower to the oxidation tower is suppressed by a retention area of ​​metal particles in the loop seal. The pressure difference between the oxidation tower side and the reduction tower side in this retention area is kept relatively small by the pressure reduction mechanism. This allows the height of the retention area to be relatively small, and therefore the size of the loop seal to be relatively small. Consequently, the amount of heat dissipated from the loop seal can be reduced, improving the thermal efficiency of the system. Furthermore, even when the pressure in the reduction tower increases, the pressure reduction mechanism can reduce the pressure on the reduction tower side in the retention area, thus preventing the retention area from breaking down due to the pressure difference between the oxidation tower side and the reduction tower side. As a result, even if the pressure at the outlet fluctuates due to unstable operation in the reduction tower, the movement of hydrocarbon gas from the reduction tower to the oxidation tower by the retention area can be continuously suppressed. Therefore, the operational stability of the system can be improved. In this way, both improved thermal efficiency and improved operational stability of the system can be achieved.

[0009] (2) Another embodiment of the present invention provides a chemical looping combustion system. This chemical looping combustion system comprises an oxidation tower that uses oxygen to oxidize metal particles, a reduction tower that uses hydrocarbon gas to reduce the metal particles oxidized in the oxidation tower, and a loop seal connected to the oxidation tower and the reduction tower respectively, which suppresses the movement of oxygen from the oxidation tower to the reduction tower, wherein the loop seal has an inlet that communicates with the reduction tower and into which metal particles flow in from the reduction tower, and an outlet that communicates with the inlet and the oxidation tower respectively, which causes the metal particles flowing into the inlet to flow out into the oxidation tower, wherein a retention section is formed on the outlet side of the inlet section where metal particles are retained, and the outlet section has a pressure reduction mechanism that makes the pressure on the inlet side less than the pressure on the reduction tower side. With this configuration, in the loop seal, the movement of oxygen from the oxidation tower to the reduction tower is suppressed by the retention section of metal particles. In this stagnant section, the pressure difference between the reduction tower side and the oxidation tower side is kept relatively small by the pressure reduction mechanism. This allows for a relatively small height in the stagnant section, and therefore a relatively small loop seal size. Consequently, the amount of heat dissipated from the loop seal can be reduced, improving the system's thermal efficiency. Furthermore, even when the oxidation tower pressure increases, the pressure reduction mechanism can reduce the oxidation tower side pressure in the stagnant section, preventing the stagnant section from breaking due to the pressure difference between the reduction tower side and the oxidation tower side. This allows for continued suppression of oxygen movement from the oxidation tower to the reduction tower by the stagnant section, even if the outlet pressure fluctuates due to unstable operation in the oxidation tower. Therefore, the system's operational stability can be improved. In this way, both improved system thermal efficiency and improved system operational stability can be achieved.

[0010] (3) In the chemical looping combustion system of the above form, the pressure reduction mechanism may have a fluid injection nozzle that injects fluid on the inlet side of the flow direction of the metal particles in the outlet. With this configuration, the pressure reduction mechanism has a fluid injection nozzle that injects fluid on the inlet side of the flow direction of the metal particles in the outlet. This reduces the pressure near the fluid injection nozzle and suppresses the movement of gas from the opposite side of the outlet to the inlet side of the outlet. Therefore, it is possible to maintain a state in which the pressure on the inlet side of the outlet is lower than the pressure on the opposite side of the inlet, thereby further improving the operational stability of the system.

[0011] (4) In the chemical looping combustion system of the above form, the pressure reduction mechanism may have a throttling portion located between the inlet side and the side opposite to the inlet of the outlet. With this configuration, the pressure reduction mechanism has a throttling portion located between the inlet side and the side opposite to the inlet of the outlet. This makes it difficult for the gas on the side of the outlet opposite to the inlet to move to the inlet side of the outlet. Therefore, it is possible to maintain a state in which the pressure on the inlet side of the outlet is lower than the pressure on the side opposite to the inlet, thereby further improving the operational stability of the system.

[0012] (5) In the chemical looping combustion system of the above form, the oxidation tower comprises an oxidation furnace that uses air to oxidize metal particles and a first pressure detection unit that detects the pressure of the oxidation furnace exhaust gas containing nitrogen taken out from the oxidation furnace, the reduction tower comprises a reduction furnace that uses hydrocarbon gas to reduce metal particles and a second pressure detection unit that detects the pressure of the reduction furnace exhaust gas containing carbon dioxide and water vapor taken out from the reduction furnace, the loop seal comprises a flow rate adjustment unit that adjusts the flow rate of the fluid injected by the fluid injection nozzle, and the chemical looping combustion system may further comprise a control unit that controls the flow rate adjustment unit using the pressure of the oxidation furnace exhaust gas detected by the first pressure detection unit and the pressure of the reduction furnace exhaust gas detected by the second pressure detection unit. With this configuration, the control unit adjusts the flow rate of the fluid injected by the fluid injection nozzle using the pressure of the oxidation furnace exhaust gas containing nitrogen taken out from the oxidation furnace and the pressure of the reduction furnace exhaust gas containing carbon dioxide and water vapor taken out from the reduction furnace. This allows for adjustment of the pressure on the inlet side of the outlet based on the pressure changes associated with the oxidation process of metal particles in the oxidation furnace or the reduction process of metal particles in the reduction furnace, even if malfunctions occur during these processes. Therefore, the system's operational stability can be further improved while maintaining its thermal efficiency.

[0013] (6) In the chemical looping combustion system of the above form, the oxidation tower comprises an oxidation furnace that uses air to oxidize metal particles, a first particle collection unit that collects metal particles contained in the nitrogen-containing oxidation furnace exhaust gas taken out from the oxidation furnace, and a first pressure detection unit that detects the pressure of the oxidation furnace exhaust gas after the metal particles have been collected by the first particle collection unit, and the reduction tower comprises a reduction furnace that uses hydrocarbon gas to reduce the oxidized metal particles, and a reduction furnace exhaust gas containing carbon dioxide taken out from the reduction furnace. The chemical looping combustion system comprises a second particle collection unit for collecting metal particles contained in the gas, and a second pressure detection unit for detecting the pressure of the reduction furnace exhaust gas after the metal particles have been collected by the second particle collection unit, wherein the loop seal includes a flow rate adjustment unit for adjusting the flow rate of the fluid injected by the fluid injection nozzle, and the chemical looping combustion system may further include a control unit that controls the flow rate adjustment unit using the pressure of the oxidation furnace exhaust gas detected by the first pressure detection unit and the pressure of the reduction furnace exhaust gas detected by the second pressure detection unit. According to this configuration, the first pressure detection unit detects the pressure of the oxidation furnace exhaust gas after the metal particles contained in the oxidation furnace exhaust gas taken out of the oxidation furnace have been collected by the first particle collection unit, and the second pressure detection unit detects the pressure of the reduction furnace exhaust gas after the metal particles contained in the reduction furnace exhaust gas taken out of the reduction furnace have been collected by the second particle collection unit. The control unit controls the flow rate adjustment unit using the pressure of the oxidation furnace exhaust gas detected by the first pressure detection unit and the pressure of the reduction furnace exhaust gas detected by the second pressure detection unit. This allows the pressure on the inlet side of the outlet to be adjusted according to the state of the first and second particle collection units. Therefore, the thermal efficiency of the system can be improved while further enhancing the operational stability of the system.

[0014] (7) According to another embodiment of the present invention, a chemical looping combustion method using a chemical looping combustion system is provided. This chemical looping combustion method includes an oxidation step of oxidizing metal particles using oxygen in an oxidation tower, a reduction step of reducing the metal particles oxidized in the oxidation tower using hydrocarbon gas in a reduction tower, an inlet communicating with the oxidation tower into which metal particles flow in from the oxidation tower, and an outlet communicating with the inlet and the reduction tower respectively for discharging the metal particles flowing into the inlet to the reduction tower, wherein a retention section where metal particles are retained is formed on the outlet side of the inlet, and a negative pressure generation step is provided in a loop seal that suppresses the movement of hydrocarbon gas from the reduction tower to the oxidation tower, by reducing pressure mechanism, which makes the pressure on the inlet side of the outlet less than the pressure on the reduction tower side. According to this configuration, in the negative pressure generation step, in the loop seal, the difference between the pressure on the oxidation tower side and the pressure on the reduction tower side in the retention section that suppresses the movement of hydrocarbon gas from the reduction tower to the oxidation tower is kept relatively small by the reduction pressure mechanism. This allows for a relatively small height in the retention area, reducing heat dissipation from the loop seal and improving the system's thermal efficiency. Furthermore, even when the pressure in the reduction tower increases, the pressure difference between the oxidation tower and the reduction tower prevents the retention area from breaking down. Therefore, even if the pressure at the outlet fluctuates due to unstable operation in the reduction tower, the movement of hydrocarbon gas from the reduction tower to the oxidation tower via the retention area can be continuously suppressed. Consequently, the operational stability of the system can be improved. In this way, both improved system thermal efficiency and improved system operational stability can be achieved.

[0015] (8) According to yet another embodiment of the present invention, a computer program is provided which causes a computer to perform control of chemical looping combustion by a chemical looping combustion system. The computer program causes the computer to perform the following functions in a loop seal that suppresses the movement of hydrocarbon gas from the reduction tower: an oxidation function in an oxidation tower that uses oxygen to oxidize metal particles; a reduction function in a reduction tower that uses hydrocarbon gas to reduce the metal particles oxidized in the oxidation tower; an inlet that communicates with the oxidation tower and into which metal particles flow in from the oxidation tower; an outlet that communicates with the inlet and the reduction tower respectively and causes the metal particles flowing into the inlet to flow out into the reduction tower, wherein a retention section is formed on the outlet side of the inlet where metal particles are retained, and a negative pressure generation function is provided which uses a depressurization mechanism to make the pressure on the inlet side of the outlet less than the pressure on the reduction tower side. In this configuration, the negative pressure generation function maintains a relatively small pressure difference between the oxidation tower side and the reduction tower side in the stagnant section of the loop seal, which suppresses the movement of hydrocarbon gas from the reduction tower to the oxidation tower, through the pressure reduction mechanism. This allows the height of the stagnant section to be relatively small, thereby reducing the amount of heat dissipated from the loop seal and improving the thermal efficiency of the system. Furthermore, even when the pressure in the reduction tower increases, the pressure difference between the oxidation tower side and the reduction tower side prevents the stagnant section from breaking down. Therefore, even if the pressure at the outlet fluctuates due to unstable operation in the reduction tower, the movement of hydrocarbon gas from the reduction tower to the oxidation tower can be continuously suppressed by the stagnant section. Consequently, the operational stability of the system can be improved. In this way, both improved thermal efficiency and improved operational stability of the system can be achieved.

[0016] Incidentally, the present invention can be realized in various forms, for example, a loop seal provided with a decompression mechanism section, a method for manufacturing a loop seal, a method for manufacturing a chemical looping combustion system, a method for controlling a chemical looping combustion system, a computer program for causing chemical looping combustion to be executed in a chemical looping combustion system, a server device for distributing the computer program, a non-transitory storage medium storing the computer program, and the like.

Brief Description of Drawings

[0017] [Figure 1] It is a schematic diagram showing a schematic configuration of a chemical looping combustion system according to the first embodiment. [Figure 2] It is a schematic diagram explaining the principle of chemical looping combustion. [Figure 3] It is a schematic diagram showing a schematic configuration of a first loop seal. [Figure 4] It is a flowchart of a control method for a chemical looping combustion system according to the first embodiment. [Figure 5] It is a schematic diagram showing a schematic configuration of a loop seal of a comparative example. [Figure 6] It is a diagram explaining an operating region of a loop seal of a comparative example. [Figure 7] It is a diagram explaining an operating region of a first loop seal. [Figure 8] It is a schematic diagram showing a schematic configuration of a chemical looping combustion system according to the second embodiment. [Figure 9] It is a schematic diagram showing a schematic configuration of a chemical looping combustion system according to the third embodiment.

Modes for Carrying Out the Invention

[0018] <First Embodiment> Figure 1 is a schematic diagram showing the general configuration of the chemical looping combustion system 1 of the first embodiment. The chemical looping combustion system 1 of this embodiment generates heat and carbon dioxide separately by the repeated oxidation and reduction (chemical looping combustion) of metal particles Me circulating within the chemical looping combustion system 1. This allows the heat and carbon dioxide generated by the chemical looping combustion system 1 to be supplied to the end user. The chemical looping combustion system 1 of this embodiment comprises an oxidation tower 10, a first loop seal 20, a reduction tower 30, a second loop seal 40, and a control unit 50. The z-axis shown in Figure 1 indicates the vertical direction in the chemical looping combustion system 1, with the direction indicated by the arrow on the z-axis being vertically upward and the direction opposite to the direction indicated by the arrow on the z-axis being vertically downward.

[0019] Figure 2 is a schematic diagram illustrating the principle of chemical looping combustion in the chemical looping combustion system 1 of this embodiment. In chemical looping combustion, metal particles Me circulate between an oxidation tower 10 that oxidizes the metal particles Me and a reduction tower 30 that reduces the metal particles Me. In the chemical looping combustion system 1 of this embodiment, ilmenite (FeTiO3) with a particle size of 50 to 250 μm is used as the metal particles Me. However, the material and particle size used to form the metal particles Me in the chemical looping combustion system 1 of this embodiment are not limited to these. For example, when ilmenite is used as the metal particles Me and methane gas is used to reduce the oxidized ilmenite, the oxidation reaction of ilmenite shown in the following formula (1) proceeds in the oxidation tower 10, and the reduction reaction of ilmenite shown in the following formula (2) proceeds in the reduction tower 30. 8FeTiO3+ 2O2→ 4Fe2TiO5+ 4TiO2...(1) 4Fe2TiO5+ 4TiO2+CH4→ 8FeTiO3+ CO2+ 2H2O...(2)

[0020] In the oxidation tower 10, heat is generated by the oxidation of ilmenite using air. The heat generated in the oxidation tower 10 is supplied to the heat utilization site by the gas extracted from the oxidation tower 10 ("oxidation tower exhaust gas"). In the reduction tower 30, carbon dioxide is generated by reducing the oxidized ilmenite using methane gas. The carbon dioxide generated in the reduction tower 30 is extracted from the reduction tower 30 along with water vapor, a byproduct of the reduction reaction ("reduction tower exhaust gas"). The carbon dioxide extracted from the reduction tower 30 is separated from the water vapor by the dewaterer 51 and supplied to the carbon dioxide utilization site ("dried reduction tower exhaust gas").

[0021] The reduction reaction of ilmenite in reduction tower 30 is basically an endothermic reaction. The sum of equation (1) and equation (2) is given by equation (3) below. In other words, the total amount of heat obtained by chemical looping combustion in chemical looping combustion system 1, that is, the sum of the heat generated in the oxidation reaction in the oxidation tower and the heat absorbed in the reduction reaction in the reduction tower, is the same as the total amount of heat obtained by the combustion of methane gas. CH4+ 2O2→ CO2+ 2H2O ···(3)

[0022] The oxidation tower 10 comprises an oxidation furnace 11 and a cyclone 12. The oxidation tower 10 generates oxidation heat by oxidizing metal particles Me using an oxidation gas.

[0023] The oxidation furnace 11 is basically installed so that its longitudinal direction is approximately aligned with the vertical direction. A gas flow straightening plate 11a is placed inside the oxidation furnace 11. The oxidation furnace 11 is connected to an oxidation gas supply source 5 that can supply an oxidation gas containing oxygen (O2). As shown in Figure 1, when the oxidation gas supplied from the oxidation gas supply source 5 is supplied to the lower side of the gas flow straightening plate 11a, the metal particles Me accumulated on the vertically upper side of the gas flow straightening plate 11a are fluidized by the supplied oxidation gas, forming a fluidized bed FD1. In the fluidized bed FD1, the metal particles Me are oxidized by the oxidation gas, generating heat of oxidation. In this embodiment, air is used as the oxidation gas.

[0024] The heat of oxidation generated by the metal particles Me increases the temperature of the gas in the oxidation furnace 11. As a result, the relatively hot gas (mainly nitrogen) flows vertically upward in the oxidation furnace 11. When the gas flow velocity in the oxidation furnace 11 exceeds the terminal velocity of the metal particles Me, the oxidized metal particles Me in the oxidation furnace 11 move along with the gas in the oxidation furnace 11 from the vertical top of the oxidation furnace 11 to the cyclone 12 (see the dotted arrow Fm1 in Figure 1).

[0025] Cyclone 12 separates oxidized metal particles Me and a relatively high-temperature gas that have moved from the oxidation furnace 11. Specifically, the metal particles Me and the high-temperature gas that have moved from the oxidation furnace 11 to cyclone 12 rotate within cyclone 12, causing the metal particles Me to collide with the inner wall of cyclone 12 and fall vertically downward. A first loop seal 20 is connected to cyclone 12. The metal particles Me that fall vertically downward within cyclone 12 move into the first loop seal 20 (see dotted arrow Fm1 in Figure 1). The high-temperature gas inside cyclone 12 is sent to an external heat utilization site through an outlet 121 and gas pipe 122 located on the vertically upper side of cyclone 12. The gas pipe 122 is connected to a pressure detector 123 that detects the pressure of the gas flowing through the gas pipe 122, and a pressure control valve 124 that can control the pressure of the gas flowing through the gas pipe 122.

[0026] The first loop seal 20 is connected to the oxidation tower 10 and the reduction tower 30, respectively, and suppresses the movement of methane gas from the reduction tower 30 to the oxidation tower 10. The first loop seal 20 has an inlet 21 that communicates with the cyclone 12 of the oxidation tower 10 and into which oxidized metal particles Me flow in from the oxidation tower 10, and an outlet 22 that communicates with the inlet 21 and the reduction tower 30, respectively, and allows the metal particles Me flowing into the inlet 21 to flow out into the reduction tower 30.

[0027] Figure 3 is a schematic diagram showing the general configuration of the first loop seal 20 of this embodiment. The inlet 21 is positioned vertically below the cyclone 12 and is formed to extend vertically downward from the side connected to the cyclone 12. As a result, a retention section 211 is formed on the vertically downward side of the inlet 21 where metal particles Me are accumulated. In the first loop seal 20, the retention section 211 acts as a seal between the oxidation tower 10 and the reduction tower 30, suppressing the movement of methane gas from the reduction tower 30 to the oxidation tower 10.

[0028] The outflow section 22 is connected to the portion of the inflow section 21 where the retention section 211 is formed, and is designed to allow metal particles Me from the retention section 211 to flow into it. As shown in Figure 3, the outflow section 22 is designed to extend vertically upward from the portion connected to the inflow section 21, and then extend vertically downward while moving away from the inflow section 21.

[0029] The outlet section 22 has a pressure reduction mechanism 23 that makes the pressure on the inlet section 21 side lower than the pressure on the reduction tower 30 side. The pressure reduction mechanism 23 in this embodiment has a steam nozzle 231 and a throttling section 232.

[0030] The steam nozzle 231 is provided on the inlet 21 side of the outlet 22. As shown in Figure 3, the steam nozzle 231 is connected to the steam supply source 6 and injects steam Vp toward the throttling section 232. The steam nozzle 231 is formed such that its inner diameter decreases from the side connected to the steam supply source 6 toward its tip. As a result, the steam flowing through the steam nozzle 231 is compressed and then expands when ejected from the steam nozzle 231, generating negative pressure. Note that the direction in which the steam nozzle 231 injects steam is not limited to toward the throttling section 232. It is sufficient that negative pressure is generated on the inlet 21 side of the outlet 22 by the steam nozzle 231.

[0031] The throttling section 232 is located in the outlet section 22 between the side connected to the inlet section 21 and the side connected to the reduction tower 30. The throttling section 232 is the part of the outlet section 22 in which the cross-sectional area is relatively small in the flow direction of the metal particles Me in the outlet section 22. For convenience, if we consider the outlet section 22 as viewed from the throttling section 232, the part on the inlet section 21 side is called the negative pressure generation chamber 221 and the part on the reduction tower 30 side is called the connecting passage 222, then both the negative pressure generation chamber 221 and the connecting passage 222 are formed such that their cross-sectional area decreases as they approach the throttling section 232. As a result, in the negative pressure generation chamber 221, the water vapor injected from the water vapor nozzle 231 and expanded is compressed, and in the connecting passage 222, the flow of gas from the connecting passage 222 toward the negative pressure generation chamber 221 is restricted.

[0032] The steam supply source 6, which supplies steam to the steam nozzle 231, and the steam nozzle 231 are connected by a steam flow path 233. In the chemical looping combustion system 1 of this embodiment, the steam flow path 233 is connected to a flow control valve 234 that adjusts the flow rate of steam flowing through the steam flow path 233, and a flow detector 235 that detects the flow rate of steam flowing through the steam flow path 233.

[0033] Thus, in the first loop seal 20, the pressure in the negative pressure generation chamber 221 is kept lower than the pressure in the connecting passage 222 by the steam sprayed by the steam nozzle 231 and the throttling section 232 that restricts the flow of gas from the connecting passage 222 toward the negative pressure generation chamber 221.

[0034] The reduction tower 30 is equipped with a reduction furnace 31. The reduction tower 30 is in communication with both the first loop seal 20 and the second loop seal 40, which will be described later. The reduction furnace 31 uses methane gas supplied from the methane gas supply source 7 to reduce oxidized metal particles Me that are moving from the first loop seal 20.

[0035] The reduction furnace 31 of this embodiment has a methane gas supply port 311 and an outlet port 312. The methane gas supply port 311 is positioned in the reduction furnace 31 to supply gas to the vertically lower side of the gas rectifier plate 31a. The methane gas supply port 311 is connected to the methane gas supply source 7 via a gas pipe 311a. In the reduction furnace 31, when methane gas sent from the methane gas supply source 7 is supplied to the lower side of the gas rectifier plate 31a, the metal particles Me accumulated in the reduction furnace 31 are fluidized by the methane gas, forming a fluidized bed FD3. In this embodiment, the fluidized bed FD3 is formed between the gas rectifier plate 31a and the opening 31b of the connection part 31c in the direction in which the methane gas flows in the reduction furnace 31. The oxidized metal particles Me are reduced mainly by contact with methane gas inside the fluidized bed FD3. In the reduction furnace 31, the metal particles Me are reduced and move to the second loop seal 40 through the opening 31b (see dotted arrow Fm3 in Figure 1).

[0036] The outlet 312 is located vertically upward in the reduction furnace 31. The gas inside the reduction furnace 31 is removed to the outside of the reduction furnace 31 through the outlet 312. The gas inside the reduction furnace 31 removed through the outlet 312 contains carbon dioxide and water vapor generated by the reduction reaction of metal particles Me. The gas from the reduction furnace 31 removed through the outlet 312 flows through a gas pipe 313 connected to the outlet 312. A dewaterer 51 containing an adsorbent capable of adsorbing moisture is connected to the gas pipe 313, and the gas from the reduction furnace 31 removed through the outlet 312 is dewatered in the dewaterer 51. As a result, relatively high-purity carbon dioxide can be recovered from the reduction tower 30. The recovered carbon dioxide is supplied to an external carbon dioxide utilization site. A pressure detector 314 for detecting the pressure of the gas flowing through the gas pipe 313 and a pressure control valve 315 capable of controlling the pressure of the gas flowing through the gas pipe 313 are connected to the gas pipe 313.

[0037] The second loop seal 40 temporarily stores the metal particles Me reduced in the reduction tower 30. The second loop seal 40 has an inlet 41 communicating with the reduction furnace 31 and an outlet 42 communicating with the oxidation furnace 11. The inlet 41 and the outlet 42 are in communication with each other on their vertically downward side.

[0038] A gas rectifier plate 40a is positioned inside the second loop seal 40. Metal particles Me, reduced in the reduction furnace 31, accumulate on the upper side of the gas rectifier plate 40a. In the second loop seal 40, steam is supplied from the steam supply source 8 to the lower side of the gas rectifier plate 40a. When steam is supplied to the second loop seal 40, the metal particles Me accumulated inside the second loop seal 40 flow, forming a fluidized bed FD4. The flowing metal particles Me move from the vertically upper side of the second loop seal 40, along with the steam, to the oxidation furnace 11 (see dotted arrow Fm4 in Figure 1).

[0039] The control unit 50 is a computer comprising ROM, RAM, and a CPU. The control unit 50 is electrically connected to the pressure detectors 123 and 314, the pressure control valves 124 and 315, the flow control valve 234, and the flow detector 235. The control unit 50 controls the flow control valve 234 using the detection results from the pressure detectors 123 and 314 and the flow detector 235. Details of the control performed by the control unit 50 will be described later.

[0040] The oxidation tower 10 and the reduction tower 30 are connected internally, as shown by the dotted arrows Fm1, Fm2, Fm3, and Fm4 in Figure 1, allowing for the circulation of metal particles Me. This allows the metal particles Me, oxidized by air in the oxidation tower 10, to be reduced by methane gas in the reduction tower 30, and then oxidized again in the oxidation tower 10, generating a high-temperature gas. Furthermore, the reduction tower 30 recovers the carbon dioxide generated by the reduction of the oxidized metal particles Me, producing relatively high-purity carbon dioxide. Therefore, the chemical looping combustion system 1 can continuously generate both high-temperature gas and high-purity carbon dioxide.

[0041] Next, the control method for the chemical looping combustion system 1 of this embodiment will be described. Here, the control method for the seal in the first loop seal 20, which is a control method unique to the chemical looping combustion system 1 of this embodiment, will be described.

[0042] Figure 4 is a flowchart of the control method for the chemical looping combustion system 1 of this embodiment. The flowchart of the control method for the chemical looping combustion system 1 shown in Figure 4 is automatically started, for example, when the chemical looping combustion system 1 is activated.

[0043] In the control method for the chemical looping combustion system 1, the pressure of the gas discharged from the oxidation tower 10 ("oxidation tower exhaust gas") and the pressure of the gas discharged from the reduction tower 30 ("reduction tower exhaust gas") are first detected (step S11). In step S11, the control unit 50 acquires the pressure of the high-temperature gas detected by the pressure detector 123 and the pressure of the gas containing carbon dioxide and water vapor detected by the pressure detector 314. In the chemical looping combustion system 1 of this embodiment, a fluidized bed is formed in the oxidation furnace 11 and the reduction furnace 31, and the pressure detected by the pressure detector 123 and the pressure detected by the pressure detector 314 each have time variations. In step S11, the control unit 50 acquires the maximum and minimum values ​​of the pressure detected by the pressure detector 123 and the pressure detected by the pressure detector 314 at a preset time.

[0044] Next, the differential pressure between the exhaust gas pressure of the oxidation tower 10 and the exhaust gas pressure of the reduction tower 30 is calculated (step S12). In step S12, the control unit 50 uses the pressure detected by the pressure detector 123 and the pressure detected by the pressure detector 314 to calculate the maximum value of the differential pressure between the pressure of the oxidation furnace 11 and the pressure of the reduction furnace 31. Specifically, the control unit 50 calculates the differential pressure using the following equation (4), where the pressure detected by the pressure detector 123 is pressure P1 and the pressure detected by the pressure detector 314 is pressure P2.

number

[0045] Next, the amount of steam to be injected by the steam nozzle 231 is calculated, and the opening degree to be set for the steam nozzle 231 is calculated (step S13). In step S13, the control unit 50 calculates the differential pressure ΔP calculated in step S12. max Using the following equation (5), the theoretical amount of steam injected Q in the steam nozzle 231 of the first loop seal 20 is calculated. tar Calculate.

number

[0046] In step S13, the control unit 50 calculates the theoretical amount of water vapor injection Q. tar The control unit 50 uses the following equation (6) to calculate the opening degree of the flow control valve 234 that should be set. Specifically, the control unit 50 uses the current amount of water vapor injected, detected by the flow detector 235 as injection amount Q1, to calculate the opening degree V of the flow control valve 234 at the next time. tar Calculate

number

[0047] Next, the flow control valve 234 is controlled to open to the calculated opening (step S14). In step S14, the control unit 50 outputs a signal to the flow control valve 234 corresponding to the opening calculated in step S13. As a result, the steam nozzle 231 injects the amount of steam calculated in step S13, causing the pressure in the negative pressure generation chamber 221 to reach the desired pressure.

[0048] Figure 5 is a schematic diagram of the loop seal provided in the comparative example chemical looping combustion system. Here, the functions and effects of the chemical looping combustion system 1 of this embodiment will be explained in comparison with the comparative example chemical looping combustion system 9.

[0049] The comparative example chemical looping combustion system 9 comprises an oxidation tower that generates oxidation heat by oxidizing metal particles Me using an oxidizing gas, a reduction tower that reduces the metal particles Me oxidized in the oxidation tower using methane gas, and loop seals 90 communicating with the oxidation tower and the reduction tower, respectively. The loop seal 90 shown in Figure 5 is a loop seal that temporarily stores the metal particles Me oxidized in the oxidation tower, and corresponds to the first loop seal 20 of this embodiment. Note that the dashed lines Fm1 and Fm2 shown in Figure 5 are the same as the dashed lines showing the movement of metal particles Me in the chemical looping combustion system 1 shown in Figure 1.

[0050] The comparative example loop seal 90 has an inlet 91 that communicates with the oxidation furnace of the oxidation tower and an outlet 92 that communicates with the reduction furnace of the reduction tower. The inlet 91 and the outlet 92 are connected vertically downward. A packed bed 911 of metal particles Me, corresponding to the retention section 211 of the first loop seal 20 of this embodiment, is formed at the point where the inlet 91 and the outlet 92 are connected. In the comparative example loop seal 90, the inlet 91 and the outlet 92 are separated by the packed bed 911 of metal particles Me. In the comparative example loop seal 90, as shown in Figure 5, an inlet 93 for blowing water vapor into the packed bed 911 of metal particles Me is provided vertically downward on the outlet 92. In the comparative example loop seal 90, the water vapor contained in the packed bed 911 in the outlet 92 is blown out using the inlet 93, thereby moving the metal particles Me to the reduction furnace.

[0051] Figure 6 illustrates the operation of the loop seal in the comparative example chemical looping combustion system. In the comparative example's loop seal 90, it is necessary to maintain a constant circulation direction for the metal particles Me in order to ensure stable operation of the loop seal 90. However, in the loop seal 90, in order to prevent backflow of the metal particles Me, if the pressure difference between the pressure at the inlet 91 on one side of the packed bed 911 and the pressure at the outlet 92 on the other side of the packed bed 911 is large, the height of the packed bed 911 of the metal particles Me (length indicated by the symbol Hp in Figure 5) must be set to a certain level or higher.

[0052] Figure 6 shows the boundary line Th0, which indicates the boundary between the "region of stable operation" and the "region of unstable operation," in relation to the "differential pressure," which is the difference between the pressure at the outlet 92 and the pressure at the inlet 91, and the "packed bed height," which is the height of the packed bed 911. The "packed bed height" on the vertical axis in Figure 6 represents the height of the packed bed 911 within the loop seal 90. As shown in Figure 6, when the "differential pressure" becomes large, the "packed bed height" needs to be increased in order to operate the loop seal 90 stably. In addition, in the comparative example chemical looping combustion system 9, since both the oxidation tower and the reduction tower have a fluidized bed of metal particles, the pressure at the inlet 91 communicating with the oxidation tower and the pressure at the outlet 92 communicating with the reduction tower fluctuate over time. For this reason, if the "differential pressure" changes over time, there is a risk of instantaneously large "differential pressure" occurring, so the "packed bed height" also needs to be increased beyond safety limits. However, increasing the "packed bed height" requires increasing the size of the inlet 91, which not only increases the equipment cost of the chemical looping combustion system 9 but also increases the amount of heat radiated from the loop seal 90, thus reducing the thermal efficiency of the system.

[0053] Figure 7 illustrates the stable operating region of the loop seal in the chemical looping combustion system of this embodiment. Similar to the figure shown in Figure 6, Figure 7 shows two boundary lines indicating the boundary between the "region of stable operation" and the "region of unstable operation." The boundary line Th0, shown by the dashed line, is the boundary line in the loop seal 90 of the comparative example shown in Figure 6, and the boundary line Th1, shown by the solid line, is the boundary line in the first loop seal 20 of this embodiment. In the first loop seal 20 of the chemical looping combustion system 1 of this embodiment, a negative pressure generation chamber 221 with a pressure lower than that of the connecting channel 222 communicating with the reduction furnace 31 is arranged adjacent to the retention section 211 of metal particles Me. As a result, the differential pressure between the pressure of the inlet 21 on one side of the retention section 211 and the pressure of the negative pressure generation chamber 221 on the other side of the retention section 211 is smaller than the differential pressure between the pressure of the inlet 21 and the pressure of the connecting channel 222 that directly communicates with the reduction furnace 31. Therefore, the "packed bed height" required for the stable operation of the first loop seal 20 can be made smaller than that of the comparative example loop seal 90. In other words, the equipment costs of the chemical looping combustion system 1 can be reduced, and the amount of heat dissipated from the first loop seal 20 is reduced, thereby improving the operating stability of the system and improving the thermal efficiency of the system. Specifically comparing the first loop seal 20 of this embodiment with the comparative example loop seal 90, if the differential pressure between the pressure at the inlet and the pressure at the outlet (the pressure of the connecting flow path 222 in the first loop seal 20) is the same value, for example, 8.0 kPa, the packed bed height in the first loop seal 20 (height of the retention section 211) can be made 60.5 cm lower than the packed bed height in the comparative example loop seal 90.

[0054] As described above, in the chemical looping combustion system 1 of this embodiment, the movement of methane gas from the reduction tower 30 to the oxidation tower 10 is suppressed in the first loop seal 20 by the accumulation section 211 of metal particles Me. The pressure difference between the oxidation tower 10 side and the reduction tower 30 side in this accumulation section 211 is kept relatively small by the depressurization mechanism 23. As a result, the height of the accumulation section 211 can be made relatively small, and therefore the size of the first loop seal 20 can be made relatively small. Consequently, the amount of heat dissipated from the first loop seal 20 can be reduced, and the thermal efficiency of the system can be improved. Furthermore, even when the pressure in the reduction tower 30 increases, the depressurization mechanism 23 can reduce the pressure on the reduction tower 30 side in the accumulation section 211, thereby preventing the accumulation section 211 from breaking due to the pressure difference between the oxidation tower 10 side and the reduction tower 30 side. As a result, even if the pressure in the outlet section 22 fluctuates due to unstable operation in the reduction tower 30, the movement of methane gas from the reduction tower 30 to the oxidation tower 10 by the retention section 211 can be continuously suppressed. Therefore, the operational stability of the system can be improved. In this way, it is possible to achieve both improved thermal efficiency and improved operational stability of the system.

[0055] Furthermore, according to the chemical looping combustion system 1 of this embodiment, the pressure reduction mechanism 23 has a steam nozzle 231 that injects steam on the inlet 21 side in the flow direction of metal particles Me within the outlet 22. This reduces the pressure in the negative pressure generation chamber 221 while suppressing the movement of gas from the connecting channel 222 into the negative pressure generation chamber 221 at the outlet 22. Therefore, it is possible to maintain a state in which the pressure in the negative pressure generation chamber 221 is lower than the pressure in the connecting channel 222, thereby further improving the operational stability of the system.

[0056] Furthermore, according to the chemical looping combustion system 1 of this embodiment, the pressure reduction mechanism 23 has a throttling section 232 located between the negative pressure generation chamber 221 and the connecting passage 222 in the outlet section 22. This makes it difficult for the gas in the connecting passage 222 to move into the negative pressure generation chamber 221. Therefore, it is possible to maintain a state in which the pressure in the negative pressure generation chamber 221 is lower than the pressure in the connecting passage 222, thereby further improving the operational stability of the system.

[0057] Furthermore, according to the chemical looping combustion system 1 of this embodiment, the control unit 50 adjusts the amount of steam injected by the steam nozzle 231 using the pressure of the oxidation furnace exhaust gas containing nitrogen, which is taken out from the oxidation furnace 11, and the pressure of the reduction furnace exhaust gas containing carbon dioxide and steam, which is taken out from the reduction furnace 31. As a result, even if there are malfunctions such as instantaneous pressure fluctuations in the oxidation treatment of metal particles Me in the oxidation furnace 11 or the reduction treatment of metal particles Me in the reduction furnace 31, the pressure in the negative pressure generation chamber 221 can be adjusted based on the pressure changes linked to these treatments. Therefore, the operating stability of the system can be further improved while maintaining the thermal efficiency of the system.

[0058] Furthermore, according to the chemical looping combustion method using the chemical looping combustion system 1 of this embodiment, the first loop seal 20 maintains a relatively small pressure difference between the oxidation tower 10 side and the reduction tower 30 side in the retention section 211 by the pressure reduction mechanism 23. This allows the height of the retention section 211 to be relatively small, thereby reducing the amount of heat dissipated from the first loop seal 20 and improving the thermal efficiency of the system. In addition, even when the pressure in the reduction tower 30 increases, the difference between the pressure in the oxidation tower 10 side and the reduction tower 30 side prevents the retention section 211 from breaking down. Therefore, even if the operation of the reduction tower 30 becomes unstable and the pressure in the outlet section 22 fluctuates, the movement of methane gas from the reduction tower 30 to the oxidation tower 10 by the retention section 211 can be continuously suppressed. Thus, the operational stability of the system can be improved. In this way, both improved thermal efficiency and improved operational stability of the system can be achieved.

[0059] Furthermore, according to the computer program that controls the chemical looping combustion by the chemical looping combustion system 1 of this embodiment, the first loop seal 20 maintains a relatively small pressure difference between the oxidation tower 10 side and the reduction tower 30 side in the retention section 211 by the pressure reduction mechanism 23. This allows the height of the retention section 211 to be relatively small, thereby reducing the amount of heat dissipated from the first loop seal 20 and improving the thermal efficiency of the system. Also, even if the pressure in the reduction tower 30 increases, the difference between the pressure in the oxidation tower 10 side and the reduction tower 30 side prevents the retention section 211 from breaking down. Therefore, even if the operation of the reduction tower 30 becomes unstable and the pressure in the outlet section 22 fluctuates, the movement of methane gas from the reduction tower 30 to the oxidation tower 10 by the retention section 211 can be continuously suppressed. Thus, the operational stability of the system can be improved. In this way, both improved thermal efficiency and improved operational stability of the system can be achieved.

[0060] <Second Embodiment> Figure 8 is a schematic diagram showing the general configuration of the chemical looping combustion system of the second embodiment. The chemical looping combustion system of the second embodiment differs from the chemical looping combustion system of the first embodiment (Figure 1) in that a negative pressure generation chamber is formed in the loop seal through which metal particles moving from the reduction tower to the oxidation tower pass.

[0061] The chemical looping combustion system 2 of this embodiment comprises an oxidation tower 10, a first loop seal 60, a reduction tower 30, a second loop seal 70, and a control unit 50. The z-axis shown in Figure 8 indicates the vertical direction in the chemical looping combustion system 2, with the direction indicated by the arrow on the z-axis being vertically upward and the direction opposite to the direction indicated by the arrow on the z-axis being vertically downward.

[0062] The first loop seal 60 temporarily stores the metal particles Me oxidized in the oxidation tower 10. The first loop seal 60 has an inlet 61 communicating with the oxidation furnace 11 and an outlet 62 communicating with the reduction furnace 31. The inlet 61 and the outlet 62 are in communication with each other vertically downward. As shown in Figure 8, a packed bed 63 of metal particles Me is formed in the portion where the inlet 61 and the outlet 62 are connected.

[0063] In the first loop seal 60, steam supplied from the steam supply source 6 is blown in from vertically below the packed bed 63 located within the outlet section 62. This causes the metal particles Me deposited within the first loop seal 60 to flow. The flowing metal particles Me move together with the steam to the reduction furnace 31 from the vertically above the first loop seal 60 (see dotted arrow Fm2 in Figure 8).

[0064] The second loop seal 70 is connected to the reduction tower 30 and the oxidation tower 10 respectively, and suppresses the movement of oxidation gas from the oxidation tower 10 to the reduction tower 30. The second loop seal 70 has an inlet 71 that communicates with the reduction furnace 31 and into which metal particles Me reduced from the reduction furnace 31 flow, and an outlet 72 that communicates with the inlet 71 and the oxidation furnace 11 respectively and allows the metal particles Me flowing into the inlet 71 to flow out into the oxidation furnace 11.

[0065] The inlet 71 is positioned vertically below the reduction furnace 31 and is formed to extend vertically downward from the side connected to the reduction furnace 31. As a result, a retention section 711 is formed on the vertically downward side of the inlet 71 where metal particles Me are accumulated. In the second loop seal 70, the retention section 711 acts as a seal between the reduction furnace 31 and the oxidation furnace 11, suppressing the movement of oxidation gas from the oxidation furnace 11 to the reduction furnace 31.

[0066] The outflow section 72 is connected to the portion of the inflow section 71 where the retention section 711 is formed, and is designed to allow metal particles Me from the retention section 711 to flow into it. The outflow section 72 is designed to extend vertically upward from the portion connected to the inflow section 71, and then extend vertically downward while moving away from the inflow section 71.

[0067] The outlet section 72 has a pressure reduction mechanism 73 that makes the pressure on the inlet section 71 side lower than the pressure on the oxidation furnace 11 side. The pressure reduction mechanism 73 in this embodiment has a steam nozzle 731 and a throttling section 732.

[0068] The steam nozzle 731 is provided on the inlet 71 side of the outlet 72. The steam nozzle 731 is connected to the steam supply source 8 and injects steam Vp toward the throttling section 732. The steam nozzle 731 is formed such that its inner diameter decreases from the side connected to the steam supply source 8 toward its tip. As a result, the steam flowing through the steam nozzle 731 is compressed and then expands when ejected from the steam nozzle 731, generating negative pressure. Note that the direction in which the steam nozzle 731 injects steam is not limited to toward the throttling section 732. It is sufficient that negative pressure is generated on the inlet 71 side of the outlet 72 by the steam nozzle 731.

[0069] The throttling section 732 is located in the outlet section 72 between the side connected to the inlet section 71 and the side connected to the oxidation tower 10. The throttling section 732 is the part of the outlet section 72 in which the cross-sectional area is relatively small in the flow direction of the metal particles Me in the outlet section 72. For convenience, if we consider the outlet section 72 as viewed from the throttling section 732, the part on the inlet section 71 side is called the negative pressure generation chamber 721 and the part on the oxidation furnace 11 side is called the connecting passage 722, then both the negative pressure generation chamber 721 and the connecting passage 722 are formed such that their cross-sectional area decreases as they approach the throttling section 732. As a result, in the negative pressure generation chamber 721, the water vapor injected from the water vapor nozzle 731 and expanded is compressed, and in the connecting passage 722, the flow of gas from the connecting passage 722 toward the negative pressure generation chamber 721 is restricted.

[0070] The steam supply source 8, which supplies steam to the steam nozzle 731, and the steam nozzle 731 are connected by a steam flow path 733. In the chemical looping combustion system 2 of this embodiment, the steam flow path 733 is connected to a flow control valve 734 that adjusts the flow rate of steam flowing through the steam flow path 733, and a flow detector 735 that detects the flow rate of steam flowing through the steam flow path 733.

[0071] In this way, the second loop seal 70 maintains that the pressure in the negative pressure generation chamber 721 is lower than the pressure in the connecting passage 722 by the steam sprayed by the steam nozzle 731 and the throttling section 732 that restricts the flow of gas from the connecting passage 722 toward the negative pressure generation chamber 721.

[0072] The control unit 80 is a computer comprising ROM, RAM, and a CPU. The control unit 80 is electrically connected to the pressure detectors 123 and 314, the pressure control valves 124 and 315, the flow control valve 734, and the flow detector 735, respectively. Similar to the control unit 50 in the first embodiment, the control unit 80 controls the flow control valve 734 using the detection results of the pressure detectors 123 and 314 and the detection results of the flow detector 735.

[0073] As described above, in the chemical looping combustion system 2 of this embodiment, the movement of oxidizing gas from the oxidation tower 10 to the reduction tower 30 in the second loop seal 70 is suppressed by the accumulation section 711 of metal particles Me. The pressure difference between the oxidation tower 10 side and the reduction tower 30 side in this accumulation section 711 is kept relatively small by the pressure reduction mechanism 73. As a result, the height of the accumulation section 711 can be made relatively small, and therefore the size of the second loop seal 70 can be made relatively small. Consequently, the amount of heat dissipated from the second loop seal 70 can be reduced, and the thermal efficiency of the system can be improved. Furthermore, even when the pressure in the oxidation tower 10 increases, the pressure reduction mechanism 73 can reduce the pressure on the oxidation tower 10 side in the accumulation section 711, thereby preventing the accumulation section 711 from breaking due to the pressure difference between the oxidation tower 10 side and the reduction tower 30 side. As a result, even if the pressure in the outlet section 72 fluctuates due to unstable operation in the oxidation tower 10, the movement of methane gas from the oxidation tower 10 to the reduction tower 30 by the retention section 711 can be continuously suppressed. Therefore, the operational stability of the system can be improved. In this way, it is possible to achieve both improved thermal efficiency and improved operational stability of the system.

[0074] <Third Embodiment> Figure 9 is a schematic diagram showing the general configuration of the chemical looping combustion system of the third embodiment. The chemical looping combustion system of the third embodiment differs from the chemical looping combustion system of the first embodiment (Figure 1) in that it includes a particle collection unit that collects metal particles contained in the gas discharged from the oxidation tower and the reduction tower, respectively.

[0075] The chemical looping combustion system 3 of this embodiment comprises an oxidation tower 10, a first loop seal 20, a reduction tower 30, a second loop seal 40, and a control unit 50. The oxidation tower 10 comprises an oxidation furnace 11 and a cyclone 12, and the reduction tower 30 comprises a reduction furnace 31.

[0076] A pressure detector 123, a pressure control valve 124, and a particle collection unit 125 are connected to a gas pipe 122 that is connected to the outlet 121 of the cyclone 12. The particle collection unit 125 collects fragments of metal particles Me and other particles that are discharged mixed with the high-temperature gas taken out from the cyclone 12. In the chemical looping combustion system 3 of this embodiment, the pressure detector 123 is connected to the gas pipe 122 downstream of the particle collection unit 125 in the flow of high-temperature gas in the gas pipe 122.

[0077] A pressure detector 314, a pressure control valve 315, and a particle collection unit 316 are connected to a gas pipe 313 that is connected to an outlet 312 of the reduction furnace 31. The particle collection unit 316 collects fragments of metal particles Me and other particles that are discharged mixed with the gas containing carbon dioxide and water vapor extracted from the reduction furnace 31. In the chemical looping combustion system 3 of this embodiment, the pressure detector 314 is connected to the gas pipe 313 downstream of the particle collection unit 316 in the flow of the gas containing carbon dioxide and water vapor in the gas pipe 313.

[0078] In the chemical looping combustion system 3 of this embodiment, the control unit 50 controls the flow control valve 234 using the detection results of the pressure detectors 123 and 314 and the detection results of the flow detector 235. The pressure detector 123 detects the pressure when a pressure loss occurs due to the collection of metal particles Me in the particle collection unit 125, and the pressure detector 314 detects the pressure when a pressure loss occurs due to the collection of metal particles Me in the particle collection unit 316. In controlling the chemical looping combustion system 3, the control unit 50 calculates the amount of steam to be injected from the steam nozzle 231, taking into account the pressure loss in the particle collection units 125 and 316. As a result, even if the pressure in the oxidation furnace 11 or reduction furnace 31 changes due to the collection of metal particles Me, the movement of methane gas from the reduction furnace 31 to the oxidation furnace 11 in the first loop seal 20 can be reliably suppressed, thereby further improving the operational stability of the system.

[0079] As described above, according to the chemical looping combustion system 3 of this embodiment, the pressure detector 123 detects the pressure of the oxidation furnace exhaust gas after the metal particles Me contained in the oxidation furnace exhaust gas taken out from the oxidation furnace 11 have been collected by the particle collection unit 125, and the pressure detector 314 detects the pressure of the reduction furnace exhaust gas after the metal particles Me contained in the reduction furnace exhaust gas taken out from the reduction furnace 31 have been collected by the particle collection unit 316. The control unit 50 controls the flow rate control valve 234 using the pressure of the oxidation furnace exhaust gas detected by the pressure detector 123 and the pressure of the reduction furnace exhaust gas detected by the pressure detector 314. This makes it possible to adjust the pressure in the negative pressure generation chamber 221 of the outlet 22 according to the state of the particle collection unit 125 and the state of the particle collection unit 316. Therefore, the thermal efficiency of the system can be improved while further improving the operating stability of the system.

[0080] <Modified form of this embodiment> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit, for example, the following modifications are also possible.

[0081] [Example 1] In the embodiments described above, the metal particles in the chemical loop combustion apparatus were formed from ilmenite. However, the material used to form the metal particles is not limited to ilmenite. For example, copper, nickel, or the like may be used.

[0082] [Differentiation 2] In the embodiments described above, the oxidizing gas supplied to the oxidation tower was assumed to be air. However, the oxidizing gas for oxidizing metal particles is not limited to air. It may contain oxygen, or even be oxygen alone.

[0083] [Difference 3] In the above embodiment, the gas supplied to the reduction tower was assumed to be methane gas. However, the gas supplied to the reduction tower is not limited to methane gas. Other hydrocarbon gases, alcohol fuels, H2, and NH3 may also be used.

[0084] [Differentiation Example 4] In the above-described embodiment, the pressure reduction mechanism is provided with a steam injection nozzle and a throttle. However, the configuration of the pressure reduction mechanism is not limited to these. It is sufficient that a relatively low-pressure area is formed on the outlet side relative to the accumulation area of ​​metal particles formed within the loop seal; for example, it may consist of only a steam injection nozzle. By providing a pressure reduction mechanism, the differential pressure on both sides of the accumulation area becomes relatively small, making it less likely for the accumulation area to be damaged by fluctuations in differential pressure. Therefore, the loop seal can be made smaller, which allows for both improved thermal efficiency and improved operational stability of the system.

[0085] [Difference 5] In the above embodiment, the amount of water vapor injected into the loop seal by the water vapor nozzle was adjusted using the pressure of the high-temperature gas extracted from the oxidation tower and the pressure of the gas containing carbon dioxide and nitrogen extracted from the reduction tower. The amount of water vapor in the water vapor nozzle does not need to be adjusted. It is sufficient that the pressure in the negative pressure generation chamber becomes lower than the pressure in the connecting flow path when a certain amount of water vapor is injected.

[0086] [Modification 6] In the above embodiment, it was assumed that one stagnant area is formed within the loop seal. Multiple stagnant areas may be formed. In this case, it is sufficient that a relatively low-pressure portion is formed on the outlet side of one of the multiple stagnant areas.

[0087] [Difference 7] In the above-described embodiment, a negative pressure generation chamber is formed in either the first loop seal or the second loop seal. However, a negative pressure generation chamber may be formed in either the first loop seal or the second loop seal. Furthermore, in the second embodiment, a particle collection unit may be provided as in the third embodiment, and the control unit 80 may calculate the amount of steam to be injected from the steam nozzle 231, taking into account the pressure loss in the particle collection units 125,316.

[0088] [Differentiation 8] In the above embodiment, a dewatering device is provided to remove water vapor from the gas containing carbon dioxide and water vapor discharged from the reduction furnace. The dewatering device is not required. The configuration of the dewatering device and the method of dewatering are not limited thereto. Dewatering may also be performed by cooling the gas containing carbon dioxide and water vapor discharged from the reduction furnace.

[0089] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0090] <Application Example 1> A chemical looping combustion system, An oxidation tower that uses oxygen to oxidize metal particles, A reduction tower that uses hydrocarbon gas to reduce metal particles oxidized in the oxidation tower, The oxidation tower and the reduction tower are connected to each of the aforementioned, and each includes a loop seal that suppresses the movement of hydrocarbon gas from the reduction tower to the oxidation tower, The aforementioned loop seal is An inlet that communicates with the aforementioned oxidation tower and into which metal particles flow in from the aforementioned oxidation tower, The inlet and the reduction tower are each connected to an outlet, which is used to allow metal particles flowing into the inlet to flow out into the reduction tower. A retention area is formed on the outlet side of the inlet, where metal particles are accumulated. The outflow section has a pressure reduction mechanism that makes the pressure on the inflow section side less than the pressure on the reduction tower side. Chemical looping combustion system. <Application Example 2> A chemical looping combustion system, An oxidation tower that uses oxygen to oxidize metal particles, A reduction tower that uses hydrocarbon gas to reduce metal particles oxidized in the oxidation tower, The oxidation tower and the reduction tower are connected to each of the aforementioned, and each includes a loop seal that suppresses the movement of oxygen from the oxidation tower to the reduction tower, The aforementioned loop seal is An inlet that communicates with the reduction tower and into which metal particles flow in from the reduction tower, The inlet and the oxidation tower are each connected to an outlet, which is used to discharge metal particles flowing into the inlet into the oxidation tower. A retention area is formed on the outlet side of the inlet, where metal particles are accumulated. The outflow section has a pressure reduction mechanism that makes the pressure on the inflow section side lower than the pressure on the reduction tower side. Chemical looping combustion system. <Application Example 3> A chemical looping combustion system as described in Application Example 1 or Application Example 2, The pressure reduction mechanism has a fluid injection nozzle that injects fluid on the inlet side in the flow direction of the metal particles in the outlet section. Chemical looping combustion system. <Application Example 4> A chemical looping combustion system described in any one of Application Examples 1 to 3, The pressure reduction mechanism has a throttling portion located between the inlet side and the opposite side of the inlet in the outlet portion. Chemical looping combustion system. <Application Example 5> A chemical looping combustion system described in any one of Application Examples 1 to 4, The aforementioned oxidation tower is An oxidation furnace that uses air to oxidize metal particles, The system includes a first pressure detection unit for detecting the pressure of nitrogen-containing oxidation furnace exhaust gas taken out from the oxidation furnace, The reduction tower described above is A reduction furnace that uses hydrocarbon gas to reduce metal particles, The system includes a second pressure detection unit that detects the pressure of the exhaust gas from the reduction furnace, which contains carbon dioxide and water vapor, taken out from the reduction furnace. The loop seal includes a flow rate adjustment unit that adjusts the flow rate of the fluid injected by the fluid injection nozzle, The aforementioned chemical looping combustion system further includes: The system includes a control unit that controls the flow rate adjustment unit using the pressure of the oxidation furnace exhaust gas detected by the first pressure detection unit and the pressure of the reduction furnace exhaust gas detected by the second pressure detection unit. Chemical looping combustion system. <Application Example 6> A chemical looping combustion system described in any one of Application Examples 1 to 5, The aforementioned oxidation tower is An oxidation furnace that uses air to oxidize metal particles, A first particle collection unit for collecting metal particles contained in the nitrogen-containing exhaust gas from the oxidation furnace, which is removed from the oxidation furnace, The system includes a first pressure detection unit that detects the pressure of the exhaust gas from the oxidation furnace after metal particles have been collected by the first particle collection unit, The reduction tower described above is A reduction furnace that uses hydrocarbon gas to reduce oxidized metal particles, A second particle collection unit for collecting metal particles contained in the carbon dioxide-containing exhaust gas from the reduction furnace, which is taken out of the aforementioned reduction furnace, The system includes a second pressure detection unit that detects the pressure of the exhaust gas from the reduction furnace after metal particles have been collected by the second particle collection unit, The loop seal includes a flow rate adjustment unit that adjusts the flow rate of the fluid injected by the fluid injection nozzle, The aforementioned chemical looping combustion system further includes: The system includes a control unit that controls the flow rate adjustment unit using the pressure of the oxidation furnace exhaust gas detected by the first pressure detection unit and the pressure of the reduction furnace exhaust gas detected by the second pressure detection unit. Chemical looping combustion system. <Application Example 7> A chemical looping combustion method using a chemical looping combustion system, In an oxidation tower, an oxidation process is carried out in which metal particles are oxidized using oxygen, A reduction step in which a hydrocarbon gas is used to reduce metal particles oxidized in the oxidation tower in a reduction tower, A loop seal having an inlet that communicates with the oxidation tower and into which metal particles flow in from the oxidation tower, and an outlet that communicates with both the inlet and the reduction tower and allows the metal particles flowing into the inlet to flow out into the reduction tower, wherein a retention area where metal particles are retained is formed on the outlet side of the inlet, and the movement of hydrocarbon gas from the reduction tower to the oxidation tower is suppressed, and the loop seal comprises a negative pressure generation step in which a depressurization mechanism reduces the pressure on the inlet side of the outlet to be less than the pressure on the reduction tower side, Chemical looping combustion method. <Application Example 8> A computer program that causes a computer to control chemical looping combustion using a chemical looping combustion system, In an oxidation tower, the oxidation function uses oxygen to oxidize metal particles, In the reduction tower, a reduction function is provided that uses hydrocarbon gas to reduce metal particles oxidized in the oxidation tower, The loop seal has an inlet that communicates with the oxidation tower and into which metal particles flow in from the oxidation tower, and an outlet that communicates with both the inlet and the reduction tower and allows the metal particles flowing into the inlet to flow out into the reduction tower, wherein a retention area where metal particles are retained is formed on the outlet side of the inlet, and the computer is instructed to perform a negative pressure generation function by a depressurization mechanism that makes the pressure on the inlet side of the outlet less than the pressure on the reduction tower side. Computer program. [Explanation of Symbols]

[0091] 1, 2, 3… Chemical Looping Combustion System 10… Oxidation Tower 11… Oxidizing furnace 123,314… Pressure detectors 125,316... Particle collection section 20,60...First loop seal 21,61...Inflow part 211,711…Retention part 22,62…Outlet 221,721... Negative pressure generation chamber 222,722… Connection channel 23...Decompression mechanism 231,731... Steam nozzles 232,732... Aperture section 234,734… Flow control valve 30…Reduction Tower 31…Reduction furnace 40, 70... Second loop seal 41,71...Inflow part 42,72…Outlet 50, 80… Control Unit 73...Decompression mechanism Me…metal particles P1... Pressure P2... Pressure Q1…Injection amount

Claims

1. A chemical looping combustion system, An oxidation tower that uses oxygen to oxidize metal particles, A reduction tower that uses hydrocarbon gas to reduce metal particles oxidized in the oxidation tower, The oxidation tower and the reduction tower are connected to each of the aforementioned, and each includes a loop seal that suppresses the movement of hydrocarbon gas from the reduction tower to the oxidation tower, The aforementioned loop seal is An inlet that communicates with the aforementioned oxidation tower and into which metal particles flow in from the aforementioned oxidation tower, The inlet and the reduction tower are each connected to an outlet, which is used to allow metal particles flowing into the inlet to flow out into the reduction tower. A retention area is formed on the outlet side of the inlet, where metal particles are accumulated. The outflow section has a pressure reduction mechanism that makes the pressure on the inflow section side less than the pressure on the reduction tower side. Chemical looping combustion system.

2. A chemical looping combustion system, An oxidation tower that uses oxygen to oxidize metal particles, A reduction tower that uses hydrocarbon gas to reduce metal particles oxidized in the oxidation tower, The oxidation tower and the reduction tower are connected to each of the aforementioned, and each includes a loop seal that suppresses the movement of oxygen from the oxidation tower to the reduction tower, The aforementioned loop seal is An inlet that communicates with the reduction tower and into which metal particles flow in from the reduction tower, The inlet and the oxidation tower are each connected to an outlet, which is used to discharge metal particles flowing into the inlet into the oxidation tower. A retention area is formed on the outlet side of the inlet, where metal particles are accumulated. The outflow section has a pressure reduction mechanism that makes the pressure on the inflow section side less than the pressure on the reduction tower side. Chemical looping combustion system.

3. A chemical looping combustion system according to claim 1 or claim 2, The pressure reduction mechanism has a fluid injection nozzle that injects fluid on the inlet side in the flow direction of the metal particles in the outlet section. Chemical looping combustion system.

4. A chemical looping combustion system according to claim 1 or claim 2, The pressure reduction mechanism has a throttling portion located between the inlet side and the opposite side of the inlet in the outlet portion. Chemical looping combustion system.

5. A chemical looping combustion system according to claim 3, The aforementioned oxidation tower is An oxidation furnace that uses air to oxidize metal particles, The system includes a first pressure detection unit for detecting the pressure of nitrogen-containing oxidation furnace exhaust gas taken out from the oxidation furnace, The reduction tower described above is A reduction furnace that uses hydrocarbon gas to reduce metal particles, The system includes a second pressure detection unit that detects the pressure of the exhaust gas from the reduction furnace, which contains carbon dioxide and water vapor, taken out from the reduction furnace. The loop seal includes a flow rate adjustment unit that adjusts the flow rate of the fluid injected by the fluid injection nozzle, The aforementioned chemical looping combustion system further includes: The system includes a control unit that controls the flow rate adjustment unit using the pressure of the oxidation furnace exhaust gas detected by the first pressure detection unit and the pressure of the reduction furnace exhaust gas detected by the second pressure detection unit. Chemical looping combustion system.

6. A chemical looping combustion system according to claim 3, The aforementioned oxidation tower is An oxidation furnace that uses air to oxidize metal particles, A first particle collection unit for collecting metal particles contained in the nitrogen-containing exhaust gas from the oxidation furnace, which is removed from the oxidation furnace, The system includes a first pressure detection unit that detects the pressure of the exhaust gas from the oxidation furnace after metal particles have been collected by the first particle collection unit, The reduction tower described above is A reduction furnace that uses hydrocarbon gas to reduce oxidized metal particles, A second particle collection unit for collecting metal particles contained in the carbon dioxide-containing exhaust gas from the reduction furnace, which is taken out of the aforementioned reduction furnace, The system includes a second pressure detection unit that detects the pressure of the exhaust gas from the reduction furnace after metal particles have been collected by the second particle collection unit, The loop seal includes a flow rate adjustment unit that adjusts the flow rate of the fluid injected by the fluid injection nozzle, The aforementioned chemical looping combustion system further includes: The system includes a control unit that controls the flow rate adjustment unit using the pressure of the oxidation furnace exhaust gas detected by the first pressure detection unit and the pressure of the reduction furnace exhaust gas detected by the second pressure detection unit. Chemical looping combustion system.

7. A chemical looping combustion method using a chemical looping combustion system, In an oxidation tower, an oxidation process is carried out in which metal particles are oxidized using oxygen, A reduction step in which a hydrocarbon gas is used to reduce metal particles oxidized in the oxidation tower in a reduction tower, A loop seal having an inlet that communicates with the oxidation tower and into which metal particles flow in from the oxidation tower, and an outlet that communicates with both the inlet and the reduction tower and allows the metal particles flowing into the inlet to flow out into the reduction tower, wherein a retention area where metal particles are retained is formed on the outlet side of the inlet, and the movement of hydrocarbon gas from the reduction tower to the oxidation tower is suppressed, and the loop seal comprises a negative pressure generation step in which a depressurization mechanism reduces the pressure on the inlet side of the outlet to be less than the pressure on the reduction tower side, Chemical looping combustion method.

8. A computer program that causes a computer to control chemical looping combustion using a chemical looping combustion system, In an oxidation tower, the oxidation function uses oxygen to oxidize metal particles, In the reduction tower, a reduction function is provided that uses hydrocarbon gas to reduce metal particles oxidized in the oxidation tower, The loop seal has an inlet that communicates with the oxidation tower and into which metal particles flow in from the oxidation tower, and an outlet that communicates with both the inlet and the reduction tower and allows the metal particles flowing into the inlet to flow out into the reduction tower, wherein a retention area where metal particles are retained is formed on the outlet side of the inlet, and the computer is instructed to perform a negative pressure generation function by a depressurization mechanism that makes the pressure on the inlet side of the outlet less than the pressure on the reduction tower side. Computer program.

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