Chemical loop combustion system

Abstract

This chemical loop combustion system is provided with: an air tower that obtains heat generation while oxidizing metal particles by making oxygen react with the metal particles having a catalytic action that promotes decomposition reaction of a volatile organic compound; a fuel tower that reduces the metal particles by reacting the oxidized metal particles with hydrocarbon-based fuel, and discharges gas generated by the reduction of the metal particles; a loop seal part that restricts the movement of the gas between the air tower and the fuel tower; and a circulation pipe that circulates the metal particles between the air tower and the fuel tower. The air tower is provided with a supply port that supplies the volatile organic compound and air into the air tower.

Description

Chemical Looping Combustion System

[0001] The present invention relates to a chemical looping combustion system.

[0002] During paint drying and printing processes, exhaust gases containing trace amounts of volatile organic compounds (VOCs) that cause photochemical smog are generated. Because the VOCs contained in such exhaust gases emit an odor, they are decomposed by burning them with fuel such as city gas. Patent Document 1 discloses a deodorizing treatment device that decomposes VOCs by heating exhaust gases generated in paint drying ovens to high temperatures. Patent Document 2 also discloses an exhaust gas treatment system that includes a VOC removal device that removes VOCs contained in exhaust gases emitted from boilers or turbines, and a heating means that heats the exhaust gas before it is treated by the VOC removal device.

[0003] JP 2022-66638 A International Publication No. 2014 / 129402

[0004] However, in Patent Document 1, a large amount of energy is required to heat the exhaust gas to a high temperature. Furthermore, in Patent Documents 1 and 2, when capturing carbon dioxide generated during heating of the exhaust gas, the carbon dioxide is diluted with the surrounding exhaust gas to a low concentration, and the amount of energy required to capture the carbon dioxide also tends to increase. For this reason, there has been a demand for a technology that can achieve both efficient decomposition of volatile organic compounds and efficient capture of carbon dioxide.

[0005] The present invention has been made to solve at least part of the above-mentioned problems, and aims to provide a chemical looping combustion system that can efficiently decompose volatile organic compounds and efficiently capture carbon dioxide.

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) One aspect of the present invention provides a chemical looping combustion system comprising: an air tower that generates heat by oxidizing metal particles having a catalytic effect of accelerating the decomposition reaction of volatile organic compounds (VOCs) through a reaction between the metal particles and oxygen; a fuel tower that reduces the oxidized metal particles through a reaction between the oxidized metal particles and a hydrocarbon fuel and discharges gas generated by the reduction of the metal particles; a loop seal that restricts gas movement between the air tower and the fuel tower; and a circulation pipe that circulates the metal particles between the air tower and the fuel tower, wherein the air tower is provided with a supply port that supplies VOCs and air into the air tower.

[0008] This configuration allows the metal particles circulating within the chemical looping combustion system to have catalytic properties that accelerate the decomposition of volatile organic compounds, thereby reducing the amount of energy required for the decomposition of volatile organic compounds and thereby efficiently decomposing the volatile organic compounds. Furthermore, this configuration restricts the movement of gas between the air tower and the fuel tower using the loop seal, thereby preventing the carbon dioxide generated by the reaction between the metal particles and hydrocarbon fuel in the fuel tower from being diluted by the gas flowing inside the air tower. Furthermore, since the gas discharged from the fuel tower contains only carbon dioxide and water, high-purity carbon dioxide can be captured by simply removing water from the gas discharged from the fuel tower using a dehydrator, which generally consumes less energy than a carbon dioxide capture device. As a result, carbon dioxide can be efficiently captured. Therefore, this configuration allows for both efficient decomposition of volatile organic compounds and efficient carbon dioxide capture.

[0009] (2) In the chemical looping combustion system of the above embodiment, the supply ports may include a first supply port for supplying a gas to the interior of the system and a second supply port located downstream of the first supply port in the air tower and for supplying a gas to the interior of the system. This configuration allows one of the volatile organic compounds and air to be supplied through the first supply port while the other is supplied through the second supply port. This allows the decomposition reaction of the volatile organic compounds and the oxidation reaction of the metal particles to occur separately, and each reaction can be carried out at an appropriate temperature. That is, each reaction can be carried out at the minimum necessary temperature. As a result, unnecessary temperature rise can be avoided, and energy consumption can be reduced.

[0010] (3) In the chemical looping combustion system of the above embodiment, the cross-sectional area of ​​the flow path at each of the positions from the second position, where the second supply port is provided, to the third position, where the third supply port is located downstream of the second supply port, may be larger than the cross-sectional area at the first position, where the first supply port is located. With this configuration, the cross-sectional area of ​​the flow path at each of the positions from the second position to the third position is larger than the cross-sectional area at the first position. This suppresses an increase in the gas flow velocity between the second position and the third position, which would be caused by the gas supplied from the second supply port being added to the gas supplied from the first supply port. The increase in the gas flow velocity increases the amount of metal particles scattered and reduces the amount of metal particles remaining inside the air tower, which reduces the frequency of contact between the metal particles and volatile organic compounds, thereby reducing the decomposition efficiency of volatile organic compounds. Therefore, with this configuration, the suppression of the increase in the gas flow velocity inside the air tower suppresses a decrease in the decomposition efficiency of volatile organic compounds.

[0011] (4) The chemical looping combustion system of the above embodiment may further include a heat recovery unit that recovers heat from the exhaust gas discharged from the air tower. This configuration allows the thermal energy contained in the exhaust gas discharged from the air tower to be recovered. The recovered thermal energy can be used, for example, to preheat the volatile organic compounds and oxygen supplied to the air tower. This further reduces the amount of energy required for the decomposition reaction of volatile organic compounds in the chemical looping combustion system.

[0012] (5) The chemical looping combustion system of the above aspect may further include a controller that controls the chemical looping combustion system, and the controller may adjust the amount of air supplied to the air tower and the amount of fuel supplied to the fuel tower based on the difference between a temperature measured inside the system downstream of the supply port and a preset target temperature. With this configuration, the amount of air supplied to the air tower and the amount of fuel supplied to the fuel tower are adjusted based on the difference between the measured temperature and the target temperature, thereby adjusting the measured temperature to approach the target temperature. This stabilizes the temperature inside the air tower, thereby stabilizing the efficiency of the decomposition reaction of volatile organic compounds.

[0013] The present invention can be realized in various forms, such as a chemical looping combustion system, a chemical looping combustion plant, a chemical looping combustion apparatus, an apparatus and system including these, a method for producing carbon dioxide, a method for synthesizing carbon dioxide, a computer program for executing these apparatus and methods, a server device for distributing this computer program, and a non-transitory storage medium storing the computer program.

[0014] FIG. 1 is an explanatory diagram illustrating the configuration of a chemical looping combustion system according to a first embodiment; FIG. 2 is an explanatory diagram of a treatment device as a comparative example; FIG. 3 is an explanatory diagram illustrating the configuration of a chemical looping combustion system according to a second embodiment; FIG. 4 is an enlarged view of an air tower; FIG. 5 is a flowchart showing the procedure for the supply rate adjustment process; FIG. 6 is an explanatory diagram illustrating the configuration of a chemical looping combustion system according to a third embodiment; FIG. 7 is an explanatory diagram illustrating the configuration of a chemical looping combustion system according to a fourth embodiment; and FIG. 8 is an explanatory diagram illustrating the configuration of a chemical looping combustion system according to a fifth embodiment.

[0015] First Embodiment FIG. 1 is an explanatory diagram illustrating the configuration of a chemical looping combustion system 1 according to a first embodiment of the present invention. The chemical looping combustion system 1 generates heat through an oxidation reaction using metal particles MP circulating within the system, and generates carbon dioxide and the like through a reduction reaction using the metal particles MP circulating within the system. In the chemical looping combustion system 1, ilmenite (FeTiO ３ The compound used as the metal particles MP is ilmenite (FeTiO ３ ), as well as hematite (Fe ２ O ３ ), magnetite (Fe ３ O ４ ) and the like. Similar to ilmenite, these compounds have catalytic properties that promote the decomposition reaction of VOCs. These compounds may also be modified and used as metal particles MP. The chemical looping combustion system 1 includes an air tower 10, a cyclone 20, a first loop seal unit 30, a fuel tower 40, a dehydrator DH, a second loop seal unit 50, a circulation pipe 60, and a control unit 70.

[0016] The air tower 10 is a tower that generates heat while reacting metal particles MP with oxygen to oxidize the metal particles MP. The air tower 10 is provided with a supply port IG through which a treatment gas and air are supplied to the interior of the air tower 10. A piping (not shown) through which the treatment gas and air are circulated is connected to the supply port IG. The piping is also provided with an on-off valve (not shown) that adjusts the flow rate of VOCs and the flow rate of air. The opening of the on-off valve can be changed in accordance with a control signal from a control unit 70 (described later). The treatment gas is a gas that is the target of deodorization treatment and contains VOCs. Inside the air tower 10, the supply of treatment gas and air from the supply port IG causes the metal particles MP to scatter, and the metal particles MP are sent to the side of a cyclone 20 (described later) connected to the upper portion of the air tower 10 in the direction of gravity.

[0017] Inside the air tower 10, the metal particles MP are oxidized by reacting with oxygen (contained in the air supplied from the supply port IG). The oxidation of the metal particles MP at this time generates oxidation heat. In this embodiment, since the metal particles MP are ilmenite, the oxidation of the metal particles MP inside the air tower 10 is expressed by the following formula (1): 8FeTiO ３ +20 ２ →4Fe ２ TiO ５ +4TiO ２ ... (1) During the reaction represented by the above formula (1), heat is generated. Furthermore, oxygen is removed from the air during this reaction, resulting in the generation of high-concentration nitrogen gas as exhaust gas. In order for the reaction represented by the above formula (1) to proceed at a sufficient reaction rate, it is necessary to operate under temperature conditions of 800°C or higher.

[0018] Furthermore, inside the air tower 10, the metal particles MP promote the decomposition reaction of VOCs in the treatment gas supplied from the supply port IG. The VOC decomposition reaction can proceed by heating to a temperature range of 700-800°C without catalytic promotion. On the other hand, with catalytic promotion, the VOC decomposition reaction can proceed in a temperature range of 300-500°C. Furthermore, when catalytic promotion is present, heating to a temperature range of 700-800°C further accelerates the VOC decomposition reaction. In other words, the catalytic action of the metal particles MP increases the rate of the VOC decomposition reaction, allowing for the miniaturization of the air tower 10. Such miniaturization reduces heat loss, thereby reducing the amount of energy required for the VOC decomposition reaction. Thus, inside the air tower 10, oxidation of the metal particles MP and the decomposition reaction of VOCs promoted by the metal particles MP occur. The decomposition reaction of VOCs is an exothermic reaction, but since the VOC concentration in the treated gas is usually on the order of several hundred ppm, the amount of heat generated is extremely small.

[0019] The cyclone 20 is connected to the upper part of the air tower 10 in the direction of gravity, and separates the metal particles MP sent from the air tower 10 from the exhaust gas based on the difference in specific gravity. The exhaust gas, which is a high-concentration nitrogen gas, is sent out of the cyclone 20 from the upper part of the cyclone 20 in the direction of gravity.

[0020] The first loop seal unit 30 is connected to the lower portion of the cyclone 20 in the direction of gravity, and receives the metal particles MP separated from the exhaust gas by the cyclone 20. The first loop seal unit 30 restricts the movement of gas between the air tower 10 and the fuel tower 40 by appropriately supplying water vapor as a seal gas into the first loop seal unit 30. This seal gas also assists the flow of the metal particles MP within the first loop seal unit 30.

[0021] The fuel tower 40 is connected to the first loop seal part 30 via a first pipe 61, which will be described later, and is a tower that reduces the metal particles MP oxidized in the air tower 10 by reacting the metal particles MP with a hydrocarbon-based fuel and discharges the gas generated by the reduction of the metal particles MP. The hydrocarbon-based fuel is a fuel that generates carbon dioxide and water when burned, and is not limited to hydrocarbons composed only of carbon and hydrogen atoms, but may also be a compound containing atoms other than carbon and hydrogen atoms (for example, oxygen atoms). In this embodiment, methane (CH ４ ) is used. The hydrocarbon fuel may be an alcohol such as methanol or ethanol. The fuel tower 40 is provided with a supply port IF for supplying the hydrocarbon fuel into the fuel tower 40. A pipe (not shown) for circulating the hydrocarbon fuel is connected to the supply port IF. In addition, this pipe is provided with an on-off valve (not shown) for adjusting the amount of hydrocarbon fuel flowing. The opening of this on-off valve can be changed in accordance with a control signal from a control unit 70, which will be described later.

[0022] Inside the fuel tower 40, the metal particles MP are reduced by reacting with the hydrocarbon fuel. This reduction of the metal particles MP generates a gas containing only carbon dioxide and water. In this embodiment, since the metal particles MP are ilmenite, the reduction of the metal particles MP inside the fuel tower 40 is expressed by the following formula (2): 4Fe ２ TiO ５ +4TiO ２ +CH ４ →8FeTiO ３ +CO ２ +2H ２ O (2) In order to promote the reaction represented by the above formula (2), an electric heater may be provided to heat the inside of the fuel tower 40 .

[0023] The gas (containing only carbon dioxide and water) generated by the reaction expressed by the above formula (2) is discharged to the outside of the fuel tower 40 from the upper part of the fuel tower 40 in the direction of gravity. The dehydrator DH is provided above the fuel tower 40 in the direction of gravity and removes water from this gas. The gas that has passed through the dehydrator DH contains only carbon dioxide.

[0024] The second loop seal unit 50 is connected to the lower portion of the fuel tower 40 in the direction of gravity, and receives metal particles MP separated from the gas in the fuel tower 40. Similar to the first loop seal unit 30, the second loop seal unit 50 restricts the movement of gas between the air tower 10 and the fuel tower 40 by appropriately supplying water vapor as a seal gas therein. This seal gas also assists the flow of metal particles MP within the second loop seal unit 50.

[0025] The circulation pipe 60 circulates metal particles MP between the air tower 10 and the fuel tower 40. The circulation pipe 60 includes a first pipe 61 and a second pipe 62. The first pipe 61 connects the first loop seal unit 30 and the fuel tower 40 and defines a flow path for the metal particles MP to flow from the first loop seal unit 30 to the fuel tower 40. The metal particles MP used in the reduction reaction in the fuel tower 40 are sent from the first loop seal unit 30 to the fuel tower 40 via the first pipe 61. On the other hand, the second pipe 62 connects the second loop seal unit 50 and the air tower 10 and defines a flow path for the metal particles MP to flow from the second loop seal unit 50 to the air tower 10. The metal particles MP used in the oxidation reaction in the air tower 10 are sent from the second loop seal unit 50 to the air tower 10 via the second pipe 62.

[0026] The control unit 70 is configured as an ECU (Electronic Control Unit) and controls the chemical looping combustion system 1. The control unit 70 controls the aperture of the on-off valve that adjusts the flow rate of VOCs and air passing through the supply port IG, and the aperture of the on-off valve that adjusts the flow rate of hydrocarbon fuel through the supply port IF.

[0027] 2 is an explanatory diagram of a treatment device PS as a comparative example. The treatment device PS is a device for decomposing VOCs in a treatment gas by combustion. The treatment device PS has a burner BN and a CO ２The system is equipped with a recovery unit CL. The burner BN burns fuel such as city gas and air to generate combustion heat. The treatment gas is heated to a temperature range of 700 to 800°C by this combustion heat, and is decomposed. Because a large amount of energy is required to heat the treatment gas to a temperature range of 700 to 800°C, the treatment unit PS cannot efficiently decompose VOCs.

[0028] CO ２ The recovery unit CL contains an adsorbent that adsorbs carbon dioxide and recovers the carbon dioxide contained in the gas flowing downstream of the burner BN. Examples of adsorbents include zeolite and activated carbon. The carbon dioxide concentration in the treatment gas heated by the burner BN is approximately 10%. However, since the treatment gas heated by the burner BN is diluted by the surrounding treatment gas, the carbon dioxide concentration in the gas flowing downstream of the burner BN is ultimately approximately 0.3 to 2%. Generally, CO ２ The recovery of carbon dioxide by the recovery unit CL tends to require a larger amount of energy the lower the carbon dioxide concentration in the target gas, and particularly when the carbon dioxide concentration is 10% or less, the lower the carbon dioxide concentration, the less carbon dioxide can be recovered per unit of energy. Therefore, the treatment device PS cannot recover carbon dioxide efficiently.

[0029] In this regard, in the chemical looping combustion system 1 of the first embodiment, the metal particles MP circulating within the chemical looping combustion system 1 have a catalytic effect that promotes the decomposition reaction of VOCs, thereby reducing the amount of energy required for the VOC decomposition reaction and enabling efficient decomposition of VOCs. Furthermore, in the chemical looping combustion system 1 of the first embodiment, the first loop seal 30 and the second loop seal 50 restrict the movement of gas between the air tower 10 and the fuel tower 40, thereby preventing the carbon dioxide generated by the reaction between the metal particles MP and the hydrocarbon fuel in the fuel tower 40 from being diluted by the gas (air or process gas) flowing inside the air tower 10. Furthermore, since the gas discharged from the fuel tower 40 contains only carbon dioxide and water, the carbon dioxide generally produced by the reaction is not diluted by the gas (air or process gas) flowing inside the air tower 10. ２High-purity carbon dioxide can be recovered by simply removing water from the gas discharged from the fuel tower 40 using only the dehydrator DH, which is said to consume less energy than the recovery unit CL. As a result, carbon dioxide can be recovered efficiently. Therefore, the chemical looping combustion system 1 of the first embodiment can achieve both efficient VOC decomposition and efficient carbon dioxide recovery.

[0030] Next, the advantage of using water vapor as the seal gas fed into the first loop seal unit 30 in the chemical looping combustion system 1 of the first embodiment will be explained. Part of the seal gas fed into the first loop seal unit 30 flows into the fuel tower 40. The inflowing seal gas is mixed with the gas (containing only carbon dioxide and water) generated by the reaction expressed by the above formula (2) (the mixed gas here is referred to as a mixed gas). If the seal gas is air, the CO ２ In this regard, in the chemical looping combustion system 1 of the first embodiment, the seal gas sent into the first loop seal unit 30 is water vapor, so CO ２ Highly pure carbon dioxide can be recovered by simply removing water from the mixed gas discharged from the fuel tower 40 using only the dehydrator DH without using a recovery unit.

[0031] 3 is an explanatory diagram illustrating the configuration of a chemical looping combustion system 1a according to a second embodiment of the present invention. The chemical looping combustion system 1a of the second embodiment differs from the chemical looping combustion system 1 of the first embodiment mainly in that it includes an air tower 10a instead of the air tower 10.

[0032] The air tower 10a has a narrow diameter section 11 and a wide diameter section 12. The narrow diameter section 11 constitutes the upstream portion of the air tower 10a. Hereinafter, the upstream side refers to the upstream side in the circulation direction of the metal particles MP, and the downstream side refers to the downstream side in the circulation direction of the metal particles MP. The cross-sectional area of ​​the flow path in the narrow diameter section 11 is approximately constant. The cross-sectional area of ​​the flow path refers to the cross-sectional area of ​​the transverse section of the air tower 10a (a cross section taken along a plane perpendicular to the circulation direction) within the range in which the metal particles MP can move. The wide diameter section 12 constitutes the portion of the air tower 10a downstream of the narrow diameter section 11. The cross-sectional area of ​​the flow path in the wide diameter section 12 is approximately constant and is larger than the approximately constant cross-sectional area of ​​the flow path in the narrow diameter section 11.

[0033] The air tower 10a is provided with a first supply port IG1 and a second supply port IG2. Both the first supply port IG1 and the second supply port IG2 supply gas into the air tower 10a. The first supply port IG1 is provided upstream of the narrow diameter section 11. The second supply port IG2 is provided downstream of the first supply port IG1. The second supply port IG2 is provided upstream of the wide diameter section 12. As shown in FIG. 3 , in this embodiment, air is supplied from the first supply port IG1, and a process gas is supplied from the second supply port IG2.

[0034] As described above, in the chemical looping combustion system 1a, the VOC decomposition reaction utilizing the catalytic action of metal particles MP requires a temperature of 300–500°C, while the oxidation reaction of metal particles MP in formula (1) requires a temperature of 800°C or higher. That is, the two reactions occurring inside the air tower 10a—oxidation of metal particles MP and decomposition of VOCs utilizing the catalytic action of metal particles MP—have different optimal temperatures. However, in the chemical looping combustion system 1 of the first embodiment shown in FIG. 1 , a single inlet IG is used to supply both the process gas and air into the air tower 10, so both reactions occur in the same location. As a result, both the supplied air and the process gas must be heated to 800°C or higher inside the air tower 10 using the heat generated by formula (1) and maintained at 800°C or higher. Therefore, the process gas must be heated to 800°C or higher, which is higher than the 300–500°C required for the VOC decomposition reaction, resulting in extra energy consumption.

[0035] In this regard, the chemical looping combustion system 1a of the second embodiment is provided with two supply ports, a first supply port IG1 and a second supply port IG2, allowing the decomposition reaction of VOCs utilizing the catalytic action of metal particles MP and the oxidation reaction of metal particles MP of formula (1) to occur separately within the air tower 10. For example, as shown in FIG. 3 , when air is supplied through the first supply port IG1 and a process gas is supplied through the second supply port IG2, the oxidation reaction of metal particles MP occurs between the first supply port IG1 and the second supply port IG2, while the decomposition reaction of VOCs utilizing the catalytic action of metal particles MP occurs downstream of the second supply port IG2. This allows the temperature downstream of the second supply port IG2 to be set to 300 to 500 °C, which is the temperature required for the decomposition reaction of VOCs utilizing the catalytic action of metal particles MP. Unlike the first embodiment, the internal temperature of the process gas only needs to be raised to 300 to 500 °C, thereby reducing energy consumption.

[0036] FIG. 4 is an enlarged view of the air tower 10a. FIG. 4 shows a first position P1, where the first supply port IG1 is located; a second position P2, where the second supply port IG2 is located; and a third position P3, which is located downstream of the second position P2. As shown in FIG. 4, in the air tower 10a, the flow path cross-sectional area at each position from the second position P2 to the third position P3 is larger than the flow path cross-sectional area at the first position P1. The third position P3 may be any position in the air tower 10a, as long as it is located downstream of the second position P2. By designing the flow path cross-sectional areas at the first to third positions P1 to P3 in this manner, an increase in the gas flow rate caused by the gas supplied from the second supply port IG2 being further supplied to the gas supplied from the first supply port IG1 can be suppressed.

[0037] The air tower 10a is also provided with a thermocouple 13. The thermocouple 13 is provided inside the air tower 10a at a position downstream of the second position P2, and measures the temperature inside the air tower 10a. The thermocouple 13 may be provided at any position as long as the position is deemed to be a position where the oxidation reaction of the metal particles MP is sufficiently progressing. Information on the temperature measured by the thermocouple 13 is transmitted to the control unit 70.

[0038] 5 is a flowchart showing the steps of the supply rate adjustment process executed by the controller 70 in the chemical looping combustion system 1a. The supply rate adjustment process adjusts the amount of air supplied to the air tower 10a and the amount of fuel supplied to the fuel tower 40 based on the difference between the temperature measured by the thermocouple 13 and a preset target temperature. The supply rate adjustment process is executed periodically while the supply of air to the air tower 10a and the supply of fuel to the fuel tower 40 are ongoing.

[0039] When the supply amount adjustment process is started, the control unit 70 acquires the temperature measured by the thermocouple 13 at a position inside the air tower 10a downstream of the second position P2 (step S11). Next, the control unit 70 substitutes the acquired measured temperature into the following formula (3) and adjusts the amount of air supplied to the air tower 10a and the amount of fuel supplied to the fuel tower 40 using the following formula (4). Thereafter, the control unit 70 ends the supply amount adjustment process. Qｆｕｅｌ = k (T ｔａｒ -T １ )…(3) Q ａｉｒ = a Q ｆｕｅｌ / 0.21Φ…(4) Q ｆｕｅｌ : Amount of fuel supplied to the fuel tower 40 [slm] k: Proportionality constant T ｔａｒ : Target temperature inside the air tower 10a [°C] T １ : Measured temperature inside the air tower 10a [°C] Q ａｉｒ : Amount of air supplied to the air tower 10a [slm] a: Amount of oxygen required to completely combust 1 mol of fuel [mol-O ２ / mol-fuel] Φ: Equivalence ratio

[0040] The proportionality constant k is a constant set by the user. In the chemical looping combustion system 1a, a = 2. This is because adding the above equations (1) and (2) together gives the following equation (5): CH ４ +20 ２ →CO ２ +2H ２ O... (5) The 0.21 in the above formula (4) represents the proportion of oxygen contained in air. The equivalence ratio Φ represents how many times the stoichiometric ratio of fuel is supplied relative to oxygen. The equivalence ratio Φ is set by the user, just like the proportionality constant k.

[0041] The chemical looping combustion system 1a of the second embodiment described above can achieve both efficient VOC decomposition and efficient carbon dioxide capture, similar to the chemical looping combustion system 1 of the first embodiment. Furthermore, the chemical looping combustion system 1a of the second embodiment is provided with two supply ports: a first supply port IG1 and a second supply port IG2. Therefore, one of the process gas and air can be supplied through the first supply port IG1 while the other is supplied through the second supply port IG2. This allows the VOC decomposition reaction utilizing the catalytic action of the metal particles MP and the oxidation reaction of the metal particles MP of formula (1) to occur separately within the air tower 10, allowing each reaction to occur at an appropriate temperature. As a result, compared to the first embodiment shown in FIG. 1 , where a single supply port IG is used to supply both the process gas and air to the air tower 10, unnecessary temperature rise can be avoided, thereby reducing energy consumption.

[0042] Furthermore, in the chemical looping combustion system 1a of the second embodiment, the cross-sectional area of ​​the flow path at each position from the second position P2 to the third position P3 is larger than the cross-sectional area at the first position P1. Therefore, between the second position P2 and the third position P3, an increase in the gas flow velocity caused by the gas (process gas in the second embodiment) being supplied from the second supply port IG2 in addition to the gas (air in the second embodiment) supplied from the first supply port IG1 can be suppressed. The increase in the gas flow velocity increases the amount of metal particles MP scattered and reduces the amount of metal particles MP remaining inside the air tower, which reduces the frequency of contact between the metal particles MP and the process gas, thereby reducing the VOC decomposition efficiency. Therefore, in the chemical looping combustion system 1a of the second embodiment, the decrease in the VOC decomposition efficiency can be suppressed by suppressing the increase in the gas flow velocity inside the air tower 10a.

[0043] In the chemical looping combustion system 1a of the second embodiment, the measured temperature (T １ ) and target temperature (T ｔａｒ ) and the amount of air supplied to the air tower 10a and the amount of fuel supplied to the fuel tower 40 are adjusted according to the difference between the measured temperature (T １ ) is the target temperature (T ｔａｒ ) can be adjusted to approach the temperature inside the air tower 10a. Therefore, the temperature inside the air tower 10a is stabilized, and the efficiency of the VOC decomposition reaction can be stabilized.

[0044] 6 is an explanatory diagram illustrating the configuration of a chemical looping combustion system 1b according to a third embodiment of the present invention. The chemical looping combustion system 1b of the third embodiment differs from the chemical looping combustion system 1a of the second embodiment mainly in that it includes heat exchangers H1 and H2 and two dehydrators D1 and D2 instead of one dehydrator DH.

[0045] The heat exchanger H1 is provided above the cyclone 20 in the direction of gravity. The heat exchanger H1 exchanges heat between the treatment gas before being sent to the first supply port IG1 and the exhaust gas discharged from the upper part of the cyclone 20 in the direction of gravity to the outside of the cyclone 20. The exhaust gas discharged to the outside of the cyclone 20 has a relatively high temperature due to heat generated during oxidation of the metal particles MP represented by the above formula (1), and therefore the treatment gas before being sent to the first supply port IG1 is preheated via the heat exchanger H1.

[0046] The heat exchanger H2 is located above the heat exchanger H1 in the direction of gravity. The heat exchanger H2 exchanges heat between the heat medium and the exhaust gas that is discharged from the upper portion of the cyclone 20 in the direction of gravity to the outside of the cyclone 20 and then passes through the heat exchanger H1. The heat medium circulates through either a circulation flow path (not shown) that circulates inside the heat exchanger H2 and the dehydrator D1, or another circulation flow path (not shown) that circulates inside the heat exchanger H2 and the dehydrator D2. The circulation flow path through which the heat medium circulates can be switched in accordance with a control signal from the control unit 70. The heat exchangers H1 and H2 correspond to a heat recovery unit that recovers heat from the exhaust gas discharged from the air tower 10a.

[0047] The dehydrators D1 and D2 are arranged in parallel above the fuel tower 40 in the direction of gravity. Both the dehydrators D1 and D2 are temperature swing dehydrators that perform dehydration by swinging the temperature. An example of a temperature swing dehydrator is a dehydrator containing silica gel as an adsorbent that adsorbs water. Of the dehydrators D1 and D2, the one through which a heat transfer medium does not flow via the circulation flow path is in an unheated state. When the gas generated during the reduction of the metal particles MP (reduced gas) represented by the above formula (2) passes through the unheated dehydrator, the gas comes into contact with the adsorbent, thereby removing water from the reduced gas. Of the dehydrators D1 and D2, the one through which the reduced gas passes can be switched in accordance with a control signal from the control unit 70. Meanwhile, the one through which a heat transfer medium flows is in a heated state. In the heated dehydrator, water is desorbed from the adsorbent. That is, in response to a control signal from the control unit 70, water is removed from the gas generated during reduction in one of the dehydrators D1 and D2, and water is desorbed from the adsorbent in the other. Furthermore, if water cannot be sufficiently desorbed from the adsorbent by simply heating the dehydrator with the heat medium, desorption of water may be promoted by reducing the pressure using a vacuum pump or the like.

[0048] The chemical looping combustion system 1b of the third embodiment described above can achieve both efficient VOC decomposition and efficient carbon dioxide recovery, similar to the chemical looping combustion systems 1 and 1a of the first and second embodiments. Furthermore, the chemical looping combustion system 1b of the third embodiment includes heat exchangers H1 and H2 as heat recovery units that recover heat from the exhaust gas discharged from the air tower 10a. This allows the thermal energy contained in the exhaust gas discharged from the air tower 10a to be recovered. For example, as described with reference to FIG. 5 , the recovered thermal energy can be used to preheat the process gas supplied to the air tower 10a. It can also be used to preheat the air supplied to the air tower 10a. Therefore, the chemical looping combustion system 1b can further reduce the amount of energy required for the VOC decomposition reaction. Furthermore, the recovered thermal energy can also be used to heat the dehydrators D1 and D2, further reducing the amount of energy required for carbon dioxide recovery in the chemical looping combustion system 1b.

[0049] 7 is an explanatory diagram illustrating the configuration of a chemical looping combustion system 1c according to a fourth embodiment of the present invention. The chemical looping combustion system 1c of the fourth embodiment differs from the chemical looping combustion system 1b of the third embodiment mainly in that it includes heat storage units S1 and S2 instead of the heat exchanger H1.

[0050] The heat accumulators S1 and S2 are arranged in parallel above the air tower 10a in the direction of gravity and below the heat exchanger H2 in the direction of gravity. The heat accumulators S1 and S2 contain a heat storage material that can store and release heat by heat exchange with the gas flowing therethrough. The heat accumulators S1 and S2 contain ceramic balls as the heat storage material. The heat accumulators S1 and S2 are connected to flow paths F1 to F4.

[0051] Flow path F1 is a flow path that supplies process gas to each of heat accumulator S1 and heat accumulator S2. Flow path F1 is provided with on-off valves V1 and V2 for adjusting to which of heat accumulator S1 and heat accumulator S2 the process gas is supplied. Flow path F2 is a flow path that supplies process gas that has passed through each of heat accumulator S1 and heat accumulator S2 to the air tower 10a. Flow path F2 is provided with on-off valves V3 and V4 for adjusting to which of heat accumulator S1 and heat accumulator S2 the process gas is allowed to flow between and the air tower 10a.

[0052] Flow path F3 supplies the exhaust gas discharged from the air tower 10a to each of the heat accumulators S1 and S2. Flow path F3 is provided with on-off valves V5 and V6 to adjust which of the heat accumulators S1 and S2 the exhaust gas is supplied to. Flow path F4 sends the exhaust gas that has passed through each of the heat accumulators S1 and S2 to the outside of the chemical looping combustion system 1c. Flow path F4 is provided with on-off valves V7 and V8 to adjust which of the heat accumulators S1 and S2 the exhaust gas is allowed to flow between and the outside of the chemical looping combustion system 1c.

[0053] Of the heat accumulators S1 and S2, one preheats the process gas supplied to the inside of the air tower 10a, and the other recovers heat from the exhaust gas discharged from the air tower 10a. When functioning as the latter, the heat accumulators S1 and S2 correspond to a heat recovery unit that recovers heat from the exhaust gas discharged from the air tower 10a. For example, when the on-off valves V1, V3, V6, and V8 are open and the on-off valves V2, V4, V5, and V7 are closed, the heat accumulator S1 preheats the process gas supplied to the inside of the air tower 10a, and the heat accumulator S2 recovers heat from the exhaust gas discharged from the air tower 10a. On the other hand, when the on-off valves V1, V3, V6, and V8 are closed and the on-off valves V2, V4, V5, and V7 are open, the heat accumulator S1 recovers heat from the exhaust gas discharged from the air tower 10a, and the heat accumulator S2 preheats the treatment gas to be supplied into the air tower 10a. The exhaust gas from which heat has been recovered by the heat accumulator S1 or the heat accumulator S2 further has heat recovered by a heat medium when passing through the inside of the heat exchanger H2.

[0054] The chemical looping combustion system 1c of the fourth embodiment described above can achieve both efficient VOC decomposition and efficient carbon dioxide recovery, similar to the chemical looping combustion systems 1, 1a, and 1b of the first to third embodiments. Furthermore, the chemical looping combustion system 1b of the fourth embodiment includes a heat accumulator S1, a heat accumulator S2, and a heat exchanger H2 as a heat recovery unit that recovers heat from the exhaust gas discharged from the air tower 10a. Therefore, the chemical looping combustion system 1c can further reduce the amount of energy required for the VOC decomposition reaction and the amount of energy required for carbon dioxide recovery.

[0055] 8 is an explanatory diagram illustrating the configuration of a chemical looping combustion system 1d according to a fifth embodiment of the present invention. The chemical looping combustion system 1d of the fifth embodiment differs from the chemical looping combustion system 1 of the first embodiment mainly in that it includes an air tower 10d and a fuel tower 40d that are different from the air tower 10a and the fuel tower 40.

[0056] The air tower 10d is connected to the first pipe 61 and the second loop seal unit 50. The air tower 10d is also provided with a supply port IGd that supplies the treatment gas and air into the air tower 10d. Inside the air tower 10d, the metal particles MP sent through the first pipe 61 are sent by gravity to the second loop seal unit 50. During this time, the oxidation of the metal particles MP generates exhaust gas and promotes the decomposition reaction of VOCs in the treatment gas.

[0057] The fuel tower 40d is connected to the cyclone 20 and the second pipe 62. The fuel tower 40d is also provided with a supply port IFd that supplies hydrocarbon fuel to the interior of the fuel tower 40d. Inside the fuel tower 40d, the metal particles MP sent via the second pipe 62 are scattered by the supply of hydrocarbon fuel and sent to the cyclone 20. During this process, the metal particles MP are reduced to generate a gas containing only carbon dioxide and water. As in the first embodiment, the water contained in this gas is removed by a dehydrator DH that is provided above the fuel tower 40d in the direction of gravity.

[0058] The chemical looping combustion system 1d of the fifth embodiment described above can achieve both efficient VOC decomposition and efficient carbon dioxide recovery, similar to the chemical looping combustion systems 1, 1a, 1b, and 1c of the first to fourth embodiments.

[0059] <Modifications of this embodiment> The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the spirit of the present invention. For example, the following modifications are also possible.

[0060] In the first embodiment described above, the gases supplied from the supply port IG to the inside of the air tower 10 are the process gas and air. In this regard, the process gas itself contains air, but if the amount of air contained in the process gas itself is small, air is supplied separately together with the process gas. Note that if the amount of air contained in the process gas itself is large and sufficient to oxidize the metal particles MP, only the process gas may be supplied without separately supplying air.

[0061] In the second embodiment and the like described above, air is supplied from the first supply port IG1 and processing gas is supplied from the second supply port IG2, but this is not limited to this. For example, processing gas and air may be supplied from both the first supply port IG1 and the second supply port IG2. Note that, from the viewpoint of suppressing an increase in the gas flow rate, it is preferable that the total amount of processing gas and air supplied from the first supply port IG1 be adjusted to be less than the total amount of processing gas and air supplied from the second supply port IG2.

[0062] In the air tower 10a of the second embodiment described above, the flow path cross-sectional area at each position from the second position P2 to the third position P3 is approximately constant, but as long as the flow path cross-sectional area at each position from the second position P2 to the third position P3 is larger than the flow path cross-sectional area at the first position P1, the flow path cross-sectional area at each position from the second position P2 to the third position P3 does not have to be approximately constant.

[0063] In the second embodiment and the like described above, the thermocouple 13 is provided at a position downstream of the second position P2 inside the air tower 10a, but this is not limited thereto. For example, the thermocouple 13 may be provided at a position between the first position P1 and the second position P2 inside the air tower 10a. The thermocouple 13 may also be provided in the first embodiment and the fifth embodiment. In such a case, the thermocouple 13 is preferably provided at a position downstream of the positions where the supply ports IG and IGd are provided inside the air towers 10 and 10d. In such a case, the supply amount adjustment process described in FIG. 5 can also be performed.

[0064] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0065] The present invention can also be realized in the following aspects. [Application Example 1] A chemical looping combustion system comprising: an air tower that generates heat while oxidizing metal particles having a catalytic effect that accelerates the decomposition reaction of volatile organic compounds by reacting the metal particles with oxygen; a fuel tower that reduces the oxidized metal particles by reacting the oxidized metal particles with a hydrocarbon-based fuel and discharges gas generated by the reduction of the metal particles; a loop seal that restricts gas movement between the air tower and the fuel tower; and a circulation pipe that circulates the metal particles between the air tower and the fuel tower, wherein the air tower is provided with a supply port that supplies volatile organic compounds and air into the air tower. [Application Example 2] The chemical looping combustion system according to Application Example 1, wherein the supply port includes: a first supply port that supplies gas into the interior of the air tower; and a second supply port that is located in the air tower downstream of the first supply port and also supplies gas into the interior of the air tower. [Application Example 3] The chemical looping combustion system according to Application Example 1 or Application Example 2, wherein the flow path cross-sectional area at each position from the second position where the second supply port is provided to the third position downstream of the second position is larger than the flow path cross-sectional area at the first position where the first supply port is provided. [Application Example 4] The chemical looping combustion system according to any of Application Examples 1 to 3, further comprising: a heat recovery unit that recovers heat from the exhaust gas discharged from the air tower. [Application Example 5] The chemical looping combustion system according to any of Application Examples 1 to 4, further comprising: a controller that controls the chemical looping combustion system, wherein the controller adjusts the amount of air supplied to the air tower and the amount of fuel supplied to the fuel tower according to the difference between a temperature measured at a position downstream of the supply port within the chemical looping combustion system and a preset target temperature.

[0066] DESCRIPTION OF SYMBOLS 1, 1a to 1d... Chemical looping combustion system 10, 10a, 10d... Air tower 11... Narrow diameter section 12... Large diameter section 13... Thermocouple 20... Cyclone 30... First loop seal section 40, 40d... Fuel tower 50... Second loop seal section 60... Circulation piping 61... First piping 62... Second piping 70... Control unit D1, D2... Dehydrator DH... Dehydrator F1 to F4... Flow paths H1, H2... Heat exchanger IF, IFd... Supply port IG, IGd... Supply port IG1... First supply port IG2... Second supply port S1, S2... Heat accumulator V1 to V8... On-off valves

Claims

1. A chemical looping combustion system comprising: an air tower that generates heat by reacting metal particles having a catalytic effect that promotes the decomposition reaction of volatile organic compounds with oxygen to oxidize the metal particles; a fuel tower that reacts the oxidized metal particles with a hydrocarbon fuel to reduce the metal particles and discharges gas generated by the reduction of the metal particles; a loop seal that restricts the movement of gas between the air tower and the fuel tower; and a circulation pipe that circulates the metal particles between the air tower and the fuel tower, wherein the air tower is provided with a supply port that supplies volatile organic compounds and air into the air tower.

2. A chemical looping combustion system according to claim 1, wherein the supply ports include: a first supply port for supplying gas to the interior of the system; and a second supply port located in the air tower downstream of the first supply port and for supplying gas to the interior of the system.

3. A chemical looping combustion system according to claim 2, wherein the cross-sectional area of ​​the flow path at each position from the second position where the second supply port is provided to the third position downstream of the second position is larger than the cross-sectional area of ​​the flow path at the first position where the first supply port is provided.

4. The chemical looping combustion system according to any one of claims 1 to 3, further comprising a heat recovery section that recovers heat from the exhaust gas discharged from the air tower.

5. A chemical looping combustion system according to any one of claims 1 to 3, further comprising a control unit that controls the chemical looping combustion system, wherein the control unit adjusts the amount of air supplied to the air tower and the amount of fuel supplied to the fuel tower according to the difference between a temperature measured at a position downstream of the supply port within the chemical looping combustion system and a preset target temperature.

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