Particle circulative combustion system

Abstract

To provide a particle circulative combustion system capable of achieving both efficient decomposition of a volatile organic compound and efficient recovery of carbon dioxide.SOLUTION: A particle circulative combustion system comprises: metallic particles having a catalytic function for accelerating combustion of a hydrocarbon-based fuel and decomposition of a volatile organic compound; a combustion tower installed with a feeding port for allowing the hydrocarbon-based fuel and air to be fed to an inside, so as to burn the hydrocarbon-based fuel while using the metallic particles as a catalyst; a treatment tower for decomposing the volatile organic compound while using the metallic particles heated in the combustion tower as a catalyst; a loop seal part for restricting a movement of a gas between the combustion tower and the treatment tower; a circulation pipe for circulating the metallic particles between the combustion tower and the treatment tower; and a recovery vessel for recovering carbon dioxide contained in a gas after burning, emitted from the combustion tower due to burning of the hydrocarbon-based fuel.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a particle circulation combustion system. [Background technology]

[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 give off 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 the 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 gases before they are treated by the VOC removal device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-66638 [Patent Document 2] International Publication No. 2014 / 129402 Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Document 1 requires a large amount of energy 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, which tends to increase the amount of energy required to capture the carbon dioxide. 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 particle circulation combustion system that can efficiently decompose volatile organic compounds and efficiently capture carbon dioxide. [Means for solving the problem]

[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) According to one aspect of the present invention, there is provided a particle circulation combustion system comprising: catalytic metal particles that promote the combustion of a hydrocarbon-based fuel and the decomposition of volatile organic compounds; a combustion tower having a supply port for supplying the hydrocarbon-based fuel and air therein and combusting the hydrocarbon-based fuel using the metal particles as a catalyst; a treatment tower that decomposes the volatile organic compounds using the metal particles heated in the combustion tower as a catalyst; a loop seal that restricts the movement of gas between the combustion tower and the treatment tower; a circulation pipe that circulates the metal particles between the combustion tower and the treatment tower; and a recovery device that recovers carbon dioxide contained in the post-combustion gas discharged from the combustion tower by the combustion of the hydrocarbon-based fuel.

[0008] According to this configuration, the metal particles have a catalytic effect that promotes the combustion of the hydrocarbon fuel, thereby enabling efficient combustion of the hydrocarbon fuel. Furthermore, because the loop seal restricts the movement of gas between the treatment tower and the combustion tower, the post-combustion gas containing carbon dioxide and water generated by the combustion of the hydrocarbon fuel in the combustion tower is prevented from being diluted by the gas flowing inside the treatment tower. Therefore, the post-combustion gas is generated by efficient combustion and is not diluted by the gas flowing inside the treatment tower. Therefore, by recovering carbon dioxide from the post-combustion gas using a recovery device, the amount of energy required for carbon dioxide recovery can be reduced. In other words, efficient carbon dioxide recovery can be achieved. Furthermore, according to this configuration, the metal particles have a catalytic effect that promotes the decomposition reaction of volatile organic compounds and are heated by the combustion of the hydrocarbon fuel in the combustion tower before reaching the treatment tower, enabling efficient decomposition of the volatile organic compounds. Therefore, according to this configuration, efficient carbon dioxide recovery and efficient decomposition of volatile organic compounds can both be achieved.

[0009] (2) The particle circulation combustion system of the above embodiment may further include a heat recovery unit that recovers heat from the post-combustion gas. This configuration allows the recovery of thermal energy contained in the post-combustion gas discharged from the combustion tower. The recovered thermal energy can be used, for example, to preheat the volatile organic compounds supplied to the treatment tower. Therefore, the amount of energy required for the decomposition reaction of volatile organic compounds in the particle circulation combustion system can be further reduced.

[0010] (3) The particle circulation combustion system of the above embodiment may further include a control unit that controls the particle circulation combustion system, and the control unit may adjust the amount of the hydrocarbon fuel supplied to the combustion tower and the amount of air supplied to the combustion tower according to the difference between the measured temperature measured inside the treatment tower and a predetermined target temperature. According to this configuration, the amount of hydrocarbon fuel supplied to the combustion tower and the amount of air supplied to the combustion tower are adjusted according to the difference between the measured temperature inside the treatment tower and the target temperature, so that the measured temperature can be adjusted to approach the target temperature. As a result, the temperature inside the treatment tower is stabilized, and the efficiency of the decomposition reaction of volatile organic compounds can be stabilized.

[0011] The present invention can be realized in various forms, such as a particle circulation 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. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is an explanatory diagram illustrating the configuration of a particle circulation combustion system according to a first embodiment. [Figure 2] FIG. 10 is an explanatory diagram of a processing apparatus as a comparative example. [Figure 3] FIG. 10 is an explanatory diagram illustrating the configuration of a particle circulation combustion system according to a second embodiment. [Figure 4] 10 is a flowchart showing a procedure for supply amount adjustment processing. [Figure 5] FIG. 10 is an explanatory diagram illustrating the configuration of a particle circulation combustion system according to a third embodiment. [Figure 6] FIG. 10 is an explanatory diagram illustrating the configuration of a particle circulation combustion system according to a fourth embodiment. [Figure 7] FIG. 10 is an explanatory diagram illustrating the configuration of a particle circulation combustion system according to a fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] First Embodiment FIG. 1 is an explanatory diagram illustrating the configuration of a particle circulation combustion system 1 according to a first embodiment of the present invention. The particle circulation combustion system 1 is a system that uses metal particles MP circulating within the system as a catalyst to combust hydrocarbon fuels and perform deodorizing treatment to decompose volatile organic compounds (VOCs). In the particle circulation combustion system 1, ilmenite (FeTiO3) is used as the metal particles MP, which have a catalytic effect of promoting the combustion of hydrocarbon fuels and the decomposition of VOCs. In addition to ilmenite (FeTiO3), compounds that can be used as the metal particles MP include hematite (Fe2O3) and magnetite (Fe3O4). Like ilmenite, these compounds have a catalytic effect of promoting the combustion of hydrocarbon fuels and the decomposition reaction of VOCs. Furthermore, these compounds may be modified and used as the metal particles MP. The particle circulation combustion system 1 includes a combustion tower 10, a CO2 recovery unit CC, a first loop seal unit 20, a treatment tower 30, a cyclone 40, a second loop seal unit 50, a circulation pipe 60, and a control unit 70.

[0014] The combustion tower 10 is a tower that combusts hydrocarbon-based fuel using metal particles MP as a catalyst. A hydrocarbon-based fuel is a fuel that generates carbon dioxide and water upon combustion. It 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 (e.g., oxygen atoms). In this embodiment, methane (CH4) is used as the hydrocarbon-based fuel. Alcohols such as methanol and ethanol may also be used as the hydrocarbon-based fuel. When combusting a hydrocarbon-based fuel, catalytic combustion can maintain the reaction at a lower temperature than gas-phase combustion (when no catalytic combustion is performed). As a result, the temperature of the walls defining the combustion tower 10 does not increase too high, reducing heat loss to the atmosphere, thereby reducing the amount of energy required to combust the hydrocarbon-based fuel.

[0015] The combustion tower 10 is provided with a supply port IF for supplying hydrocarbon fuel and air into the interior. A pipe (not shown) for circulating the hydrocarbon fuel and air is connected to the supply port IF. The pipe is also provided with an on-off valve (not shown) for adjusting the flow rate of the hydrocarbon fuel and the flow rate of the air. The opening of the on-off valve can be changed in accordance with a control signal from a control unit 70, which will be described later.

[0016] The metal particles MP promote the combustion of the hydrocarbon fuel inside the combustion tower 10. In this embodiment, the hydrocarbon fuel is methane, and therefore the combustion of the hydrocarbon fuel is expressed by the following formula (1). CH4 + 2O2 → CO2 + 2H2O…(1) When a hydrocarbon fuel is combusted, post-combustion gas containing carbon dioxide and water is generated. This post-combustion gas is discharged from the upper part of the combustion tower 10 in the direction of gravity to the outside of the combustion tower 10. The CO2 capture unit CC, which is installed above the combustion tower 10 in the direction of gravity, captures the carbon dioxide contained in the post-combustion gas discharged from the combustion tower 10 by the combustion of the hydrocarbon fuel.

[0017] The first loop seal unit 20 is connected to the lower portion of the combustion tower 10 in the direction of gravity, and receives the metal particles MP separated from the combustion gas in the combustion tower 10. The first loop seal unit 20 restricts the movement of gas between the combustion tower 10 and the treatment tower 30 by appropriately supplying water vapor as a seal gas into the first loop seal unit 20. This seal gas also assists the flow of the metal particles MP within the first loop seal unit 20.

[0018] The treatment tower 30 is a tower that decomposes VOCs using metal particles MP heated in the combustion tower 10 as a catalyst. The metal particles MP are heated by the combustion of hydrocarbon fuel in the combustion tower 10 before reaching the treatment tower 30. The decomposition reaction of VOCs can proceed by heating to a temperature range of 700 to 800°C without catalytic promotion. On the other hand, with catalytic promotion, the decomposition reaction of VOCs can proceed in a temperature range of 300 to 500°C. Furthermore, when catalytic promotion is present, heating to a temperature range of 700 to 800°C further increases the rate of the VOC decomposition reaction.

[0019] The treatment tower 30 is provided with a supply port IG for supplying a treatment gas into the treatment tower 30. The treatment gas is a gas to be deodorized, and is a gas containing VOCs and air. A pipe (not shown) for circulating the treatment gas is connected to the supply port IG. The pipe is also provided with an on-off valve (not shown) for adjusting the flow rate of the treatment gas. 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. Inside the treatment tower 30, the metal particles MP are scattered by the supply of treatment gas from the supply port IG, and the metal particles MP are sent to the side of a cyclone 40 (described later) connected to the upper part of the treatment tower 30 in the direction of gravity.

[0020] The cyclone 40 is connected to the upper part of the treatment tower 30 in the direction of gravity, and separates the metal particles MP sent from the treatment tower 30 from the gas that has circulated within the treatment tower 30 based on the difference in specific gravity. The gas that has circulated within the treatment tower 30 is sent out of the cyclone 40 from the upper part of the cyclone 40 in the direction of gravity.

[0021] The second loop seal unit 50 is connected to the lower part of the cyclone 40 in the direction of gravity, and receives metal particles MP separated from the gas that has circulated through the treatment tower 30. Similar to the first loop seal unit 20, the second loop seal unit 50 restricts the movement of gas between the combustion tower 10 and the treatment tower 30 by appropriately supplying water vapor as a seal gas into the second loop seal unit 50. This seal gas also assists the flow of metal particles MP within the second loop seal unit 50.

[0022] The circulation pipe 60 circulates metal particles MP between the combustion tower 10 and the treatment tower 30. The circulation pipe 60 includes a first pipe 61 and a second pipe 62. The first pipe 61 connects the first loop seal unit 20 and the treatment tower 30 and defines a flow path for the metal particles MP to flow from the first loop seal unit 20 to the treatment tower 30. The metal particles MP used in the VOC decomposition reaction in the treatment tower 30 are sent from the first loop seal unit 20 to the treatment tower 30 via the first pipe 61. On the other hand, the second pipe 62 connects the second loop seal unit 50 and the combustion tower 10 and defines a flow path for the metal particles MP to flow from the second loop seal unit 50 to the combustion tower 10. The metal particles MP used in the hydrocarbon fuel combustion reaction in the combustion tower 10 are sent from the second loop seal unit 50 to the treatment tower 30 via the second pipe 62.

[0023] The control unit 70 is configured by an ECU (Electronic Control Unit) and controls the particle circulation combustion system 1. The control unit 70 controls the opening degree of an on-off valve that adjusts the flow rate of hydrocarbon fuel and air through the supply port IF and the opening degree of an on-off valve that adjusts the flow rate of processing gas through the supply port IG.

[0024] FIG. 2 is an explanatory diagram of a treatment device PS, a comparative example. The treatment device PS is a device for decomposing VOCs in a treatment gas by combustion. The treatment device PS is equipped with a burner BN and a CO2 recovery device CL. The burner BN burns fuel, such as city gas, and air to generate combustion heat. This combustion heat raises the temperature of the treatment gas to a temperature range of 700 to 800°C, thereby decomposing the VOCs in the treatment gas. Because a large amount of energy is required to raise the temperature of the treatment gas to a temperature range of 700 to 800°C, the treatment device PS cannot efficiently decompose VOCs.

[0025] The CO2 capture unit CL contains an adsorbent that adsorbs carbon dioxide and captures 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 treated gas heated by the burner BN is approximately 10%. However, because the treated gas heated by the burner BN is diluted by the surrounding treated gas, the final carbon dioxide concentration in the gas flowing downstream of the burner BN is approximately 1-2%. Generally, the capture of carbon dioxide by the CO2 capture unit CL tends to require more energy the lower the carbon dioxide concentration in the target gas. In particular, when the carbon dioxide concentration is 10% or less, the amount of carbon dioxide captured per unit energy decreases significantly as the carbon dioxide concentration decreases. Therefore, the treatment unit PS cannot capture carbon dioxide efficiently.

[0026] In this regard, the particle circulation combustion system 1 of the first embodiment can achieve both efficient carbon dioxide capture and efficient decomposition of volatile organic compounds. Details are described below. In the particle circulation combustion system 1 of the first embodiment, the metal particles MP have a catalytic effect that promotes the combustion of hydrocarbon-based fuel, thereby enabling efficient combustion of hydrocarbon-based fuel. Furthermore, the second loop seal 50 restricts the movement of gas between the treatment tower 30 and the combustion tower 10, thereby preventing the post-combustion gas containing carbon dioxide and water generated by the combustion of hydrocarbon-based fuel in the combustion tower 10 from being diluted by the gas flowing inside the treatment tower 30. Therefore, the post-combustion gas is generated by efficient combustion and is not diluted by the gas flowing inside the treatment tower 30. Therefore, by capturing carbon dioxide from the post-combustion gas using the CO2 capture unit CC, the amount of energy required for carbon dioxide capture can be reduced. In other words, the particle circulation combustion system 1 of the first embodiment can achieve efficient carbon dioxide capture. Furthermore, in the particle circulation combustion system 1 of the first embodiment, the metal particles MP have a catalytic effect that promotes the decomposition reaction of VOCs, and are heated by the combustion of hydrocarbon fuel in the combustion tower 10 before reaching the treatment tower 30, so that VOCs can be efficiently decomposed. Therefore, the particle circulation combustion system 1 of the first embodiment can achieve both efficient carbon dioxide recovery and efficient decomposition of volatile organic compounds.

[0027] Second Embodiment 3 is an explanatory diagram illustrating the configuration of a particle circulation combustion system 1a according to a second embodiment of the present invention. The particle circulation combustion system 1a of the second embodiment differs from the particle circulation combustion system 1 of the first embodiment mainly in that it includes a thermocouple 35, heat exchangers H1 and H2, and a dehydrator DH, and in that it includes a CO2 capturer Ca instead of a CO2 capturer CC.

[0028] The thermocouple 35 is provided inside the treatment tower 30 and measures the temperature inside the treatment tower 30. Information on the temperature measured by the thermocouple 35 is sent to the control unit 70.

[0029] The heat exchanger H1 is provided above the combustion tower 10 in the direction of gravity. The heat exchanger H1 exchanges heat between the process gas before it is sent to the supply port IG and the combustion gas that is discharged to the outside of the combustion tower 10 from the upper part of the combustion tower 10 in the direction of gravity. The combustion gas has a relatively high temperature due to the combustion reaction expressed by the above formula (1), and therefore preheats the process gas before it is sent to the supply port IG via the heat exchanger H1.

[0030] The heat exchanger H2 is located above the heat exchanger H1 in the direction of gravity. The heat exchanger H2 exchanges heat between a heat medium such as water and the combustion gas that is discharged from the upper part of the combustion tower 10 in the direction of gravity to the outside of the combustion tower 10 and then passes through the heat exchanger H1. The heat medium circulates in a circulation flow path (not shown) that circulates inside the heat exchanger H2 and the CO2 recovery unit Ca. The heat exchangers H1 and H2 correspond to a heat recovery unit that recovers heat from the combustion gas discharged from the combustion tower 10.

[0031] The dehydrator DH is provided above the heat exchanger H2 in the direction of gravity. The dehydrator DH removes water from the post-combustion gas that has passed through the heat exchanger H2.

[0032] The CO2 capture device Ca is located above the dehydrator DH in the direction of gravity. The CO2 capture device Ca is a temperature swing CO2 capture device that can switch between adsorption and desorption of carbon dioxide by changing the internal temperature. The CO2 capture device Ca contains zeolite as an adsorbent that adsorbs carbon dioxide at room temperature and desorbs carbon dioxide when heated. The adsorption and desorption of carbon dioxide by the CO2 capture device Ca can be switched in accordance with a control signal from the control unit 70. For example, the control unit 70 may stop the flow of the heat transfer medium in the circulation flow path when adsorbing carbon dioxide in the CO2 capture device Ca, and circulate the heat transfer medium in the circulation flow path when desorbing carbon dioxide from the CO2 capture device Ca. Alternatively, the control unit 70 may circulate the heat transfer medium through a flow path branched from the circulation flow path that does not pass through the interior of the CO2 capture device Ca when adsorbing carbon dioxide in the CO2 capture device Ca, and circulate the heat transfer medium in the circulation flow path when desorbing carbon dioxide from the CO2 capture device Ca.

[0033] 4 is a flowchart showing the procedure of the supply amount adjustment process executed by the control unit 70 in the particle circulation combustion system 1a. The supply amount adjustment process is a process for adjusting the supply amount of hydrocarbon fuel to the combustion tower 10 and the supply amount of air to the combustion tower 10 according to the difference between the temperature measured by the thermocouple 35 and a preset target temperature. The supply amount adjustment process is executed periodically while the supply of hydrocarbon fuel to the combustion tower 10 and the supply of air to the combustion tower 10 continue.

[0034] When the supply amount adjustment process is started, the control unit 70 acquires the measured temperature measured by the thermocouple 35 inside the treatment tower 30 (step S11). Next, the control unit 70 substitutes the acquired measured temperature into the following formula (2) and adjusts the supply amount of hydrocarbon fuel to the combustion tower 10 and the supply amount of air to the combustion tower 10 using the following formula (3). Thereafter, the control unit 70 ends the supply amount adjustment process. Q fuel =k(T tar -T1)…(2) Q air =a·Q fuel / 0.21Φ…(3) Q fuel : Amount of hydrocarbon fuel supplied to combustion tower 10 [slm] k: proportionality constant T tar : Target temperature inside the treatment tower 30 [°C] T1: Measured temperature inside the treatment tower 30 [°C] Q air : Amount of air supplied to combustion tower 10 [slm] a: The amount of oxygen required to completely combust 1 mol of hydrocarbon fuel [mol-O2 / mol-fuel] Φ: Equivalence ratio

[0035] The proportionality constant k is a constant set by the user. In the particle circulation combustion system 1a, a = 2. This is because the combustion of hydrocarbon fuel is expressed as in the above formula (1). 0.21 in the above formula (3) indicates the proportion of oxygen contained in the air. The equivalence ratio Φ is an amount that indicates how many times the stoichiometric ratio of hydrocarbon fuel is supplied to oxygen. The equivalence ratio Φ, like the proportionality constant k, is set by the user. When the equivalence ratio Φ is set to about 0.8 to 1.2, the carbon dioxide concentration in the post-combustion gas generated inside the combustion tower 10 is about 10%.

[0036] The particle circulation combustion system 1a of the second embodiment described above can achieve both efficient VOC decomposition and efficient carbon dioxide recovery, similar to the particle circulation combustion system 1 of the first embodiment. Furthermore, the particle circulation combustion system 1a of the second embodiment is equipped with heat exchangers H1 and H2 as heat recovery units. This allows for the recovery of thermal energy contained in the post-combustion gas discharged from the combustion tower 10. As described above, the recovered thermal energy can be used to preheat the treatment gas supplied to the treatment tower 30. Therefore, in the particle circulation combustion system 1a, the amount of energy required for the VOC decomposition reaction can be further reduced. Furthermore, the recovered thermal energy can also be used for carbon dioxide desorption in the CO2 recovery unit Ca. This reduces the amount of energy required for carbon dioxide recovery, thereby achieving efficient carbon dioxide recovery.

[0037] In the particle circulation combustion system 1a of the second embodiment, the measured temperature (T1) and the target temperature (T tar ) and the amount of hydrocarbon fuel supplied to the combustion tower 10 (Q fuel ) and the amount of air supplied to the combustion tower 10 (Q air ) is adjusted, so that the measured temperature (T1) is adjusted to the target temperature (T tar ) can be adjusted to approach the measured temperature (T1). tar ) is larger, the supply amount of hydrocarbon fuel to the combustion tower 10 (Q fuel ) and the amount of air supplied to the combustion tower 10 (Q air ) are both increased, and the temperature of the metal particles MP sent from the combustion tower 10 to the treatment tower 30 is raised, so that the measured temperature (T1) tar ) Therefore, the temperature inside the treatment tower 30 is stabilized by the above-described supply adjustment process, and the efficiency of the VOC decomposition reaction can be stabilized.

[0038] In the particle circulation combustion system 1a of the second embodiment, the seal gas sent into the second loop seal unit 50 is steam, as in the particle circulation combustion system 1 of the first embodiment. The advantages of this configuration are described below. Part of the seal gas sent into the second loop seal unit 50 flows into the combustion tower 10. The seal gas is mixed with post-combustion gas containing carbon dioxide and water produced by the combustion of hydrocarbon fuel in the combustion tower 10 (the resulting mixed gas). When the seal gas is air, the carbon dioxide concentration in the mixed gas decreases. Therefore, when attempting to capture carbon dioxide from such a mixed gas, the amount of carbon dioxide captured per unit energy is reduced. In this regard, in the particle circulation combustion system 1a of the second embodiment, the seal gas sent into the second loop seal unit 50 is steam, and the dehydrator DH is located below the CO2 capture unit Ca in the direction of gravity. Therefore, carbon dioxide is captured by the CO2 capture unit Ca from the mixed gas after water has been removed by the dehydrator DH. Therefore, in the mixed gas when carbon dioxide is captured by the CO2 capture unit Ca, the influence of dilution by the water vapor that is the seal gas is low, and carbon dioxide can be captured efficiently.

[0039] <Third embodiment> 5 is an explanatory diagram illustrating the configuration of a particle circulation combustion system 1b according to a third embodiment of the present invention. The particle circulation combustion system 1b according to the third embodiment is the same as the particle circulation combustion system 1a according to the second embodiment, except that it includes a dehydrator Db instead of the dehydrator DH and a CO2 capturer CC (the CO2 capturer CC according to the first embodiment) that is not a temperature swing type, instead of the CO2 capturer Ca.

[0040] In the particle circulation combustion system 1b, a circulation flow path (not shown) is arranged inside the heat exchanger H2 to circulate a heat medium between the inside of the heat exchanger H2 and the inside of the dehydrator Db.

[0041] The dehydrator Db is located above the heat exchanger H2 in the direction of gravity. The dehydrator Db is a temperature swing type dehydrator that can switch between water adsorption and desorption by changing the internal temperature. The dehydrator Db contains an adsorbent that can adsorb water. At room temperature, the adsorbent removes water from the post-combustion gas that has passed through the heat exchanger H2, and when heated, the adsorbent desorbs the adsorbed water. As with the CO2 recovery unit Ca described in the second embodiment, the adsorption or desorption of water by the dehydrator Db can be switched by changing the flow state of the heat medium using a control signal from the control unit 70.

[0042] The particle circulation combustion system 1b of the third embodiment described above can achieve both efficient decomposition of VOCs and efficient recovery of carbon dioxide, similar to the particle circulation combustion systems 1 and 1a of the first and second embodiments. Furthermore, in the particle circulation combustion system 1b of the third embodiment, the thermal energy recovered by the heat exchanger H2, which is the heat recovery unit, can also be used for desorption of water in the dehydrator Db. This reduces the amount of energy used to operate the dehydrator Db.

[0043] <Fourth embodiment> 6 is an explanatory diagram illustrating the configuration of a particle circulation combustion system 1c according to a fourth embodiment of the present invention. The particle circulation combustion system 1c of the fourth embodiment differs from the particle circulation combustion system 1a of the second embodiment mainly in that it includes heat accumulators S1 and S2 instead of the heat exchanger H1.

[0044] The heat accumulator S1 and the heat accumulator S2 are arranged in parallel above the combustion tower 10 in the direction of gravity and below the heat exchanger H2 in the direction of gravity. The heat accumulator S1 and the heat accumulator S2 contain a heat storage material that can store and release heat by heat exchange with the gas flowing inside. The heat accumulator S1 and the heat accumulator S2 contain ceramic balls as the heat storage material. The heat accumulator S1 and the heat accumulator S2 are connected to flow paths F1 to F4.

[0045] The flow path F1 is a flow path that supplies the process gas to each of the heat accumulator S1 and the heat accumulator S2. The flow path F1 is provided with on-off valves V1 and V2 for adjusting to which of the heat accumulators S1 and S2 the process gas is supplied. The flow path F2 is a flow path that supplies the process gas that has passed through each of the heat accumulators S1 and S2 to the treatment tower 30. The flow path F2 is provided with on-off valves V3 and V4 for adjusting to which of the heat accumulators S1 and S2 the process gas can flow between and the treatment tower 30.

[0046] Flow path F3 is a flow path that supplies the combustion gas discharged from the combustion tower 10 to each of the heat accumulator S1 and the heat accumulator S2. Flow path F3 is provided with on-off valves V5 and V6 for adjusting to which of the heat accumulators S1 and S2 the combustion gas is supplied. Flow path F4 is a flow path that sends the combustion gas that has passed through each of the heat accumulators S1 and S2 to the heat exchanger H2. Flow path F4 is provided with on-off valves V7 and V8 for adjusting to which of the heat accumulators S1 and S2 the combustion gas is allowed to flow between and the heat exchanger H2.

[0047] Of the heat accumulators S1 and S2, one heat accumulator preheats the treatment gas supplied into the treatment tower 30, and the other heat accumulator recovers the heat of the post-combustion gas discharged from the combustion tower 10. When functioning as the latter, the heat accumulators S1 and S2 correspond to a heat recovery section that recovers the heat of the post-combustion gas discharged from the combustion tower 10. 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 treatment gas supplied into the treatment tower 30, and the heat accumulator S2 recovers the heat of the post-combustion gas discharged from the combustion tower 10. 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 the heat of the post-combustion gas discharged from the combustion tower 10, and the heat accumulator S2 preheats the treatment gas to be supplied into the treatment tower 30. The post-combustion gas from which heat has been recovered by the heat accumulator S1 or the heat accumulator S2 further has heat recovered by the heat medium when passing through the inside of the heat exchanger H2.

[0048] The particle circulation combustion system 1c of the fourth embodiment described above can achieve both efficient VOC decomposition and efficient carbon dioxide recovery, similar to the particle circulation combustion systems 1, 1a, and 1b of the first to third embodiments. Furthermore, the particle circulation 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 post-combustion gas discharged from the combustion tower 10. Therefore, in the particle circulation combustion system 1c, the amount of energy required for the VOC decomposition reaction and the amount of energy used to operate the dehydrator Db can be reduced.

[0049] Fifth Embodiment 7 is an explanatory diagram illustrating the configuration of a particle circulation combustion system 1d according to a fifth embodiment of the present invention. The particle circulation combustion system 1d of the fifth embodiment differs from the particle circulation combustion system 1a of the second embodiment mainly in that it includes a combustion tower 10d and a processing tower 30d that are different from the combustion tower 10 and the processing tower 30.

[0050] The combustion tower 10d is connected to the cyclone 40 and a first pipe 61. The combustion tower 10d is also provided with a supply port IFd that supplies hydrocarbon fuel and air into the interior of the combustion tower 10d. Inside the combustion tower 10d, the metal particles MP sent through the first pipe 61 are scattered by the supply of hydrocarbon fuel and air and sent to the cyclone 40. During this time, the metal particles MP function as a catalyst that promotes the combustion of the hydrocarbon fuel. Similar to the second embodiment, heat exchangers H1 and H2, a dehydrator DH, and a CO2 recovery unit Ca are provided above the combustion tower 10d in the direction of gravity.

[0051] The treatment tower 30d is connected to the second pipe 62 and the first loop seal unit 20. The treatment tower 30d is also provided with a supply port IGd that supplies treatment gas into the treatment tower 30d. Inside the treatment tower 30d, the metal particles MP sent via the second pipe 62 are sent by gravity to the first loop seal unit 20. During this time, the metal particles MP function as a catalyst that promotes the decomposition reaction of VOCs.

[0052] The particle circulation combustion system 1d of the fifth embodiment described above can also achieve both efficient decomposition of VOCs and efficient recovery of carbon dioxide, similar to the particle circulation combustion systems 1, 1a, 1b, and 1c of the first to fourth embodiments.

[0053] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0054] In the above-described embodiment, water vapor is supplied as the seal gas into the inside of the first loop seal portion 20 and the inside of the second loop seal portion 50, but this is not limited to this. For example, in an environment where it is difficult to use water vapor, the seal gas may be air. As explained in the second embodiment, from the viewpoint of efficiently capturing carbon dioxide, it is preferable that the seal gas is water vapor. However, even if the seal gas is air, the amount of seal gas contained in the mixed gas is small, and therefore the amount of energy increased by mixing the seal gas (the amount of energy required to capture carbon dioxide) is also relatively small, so air may be used as the seal gas.

[0055] In the second to fifth embodiments described above, either the dehydrator or the CO2 recovery device is a temperature swing type, but this is not limited to this. Both the dehydrator and the CO2 recovery device may be temperature swing type. In such a case, it is preferable that both the dehydrator and the CO2 recovery device can be heated by a heat medium flowing inside the heat exchanger H2.

[0056] In the fifth embodiment described above, a treatment tower 30d is arranged at the position of the combustion tower 10 in the second embodiment, and a combustion tower 10d is arranged at the position of the treatment tower 30 in the second embodiment. Similarly, in the third and fourth embodiments described above, a treatment tower 30 may be arranged at the position of the combustion tower 10 shown in Figures 5 and 6, and a combustion tower 10 may be arranged at the position of the treatment tower 30 shown in Figures 5 and 6.

[0057] 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. [Explanation of symbols]

[0058] 1, 1a to 1d...Particle circulation combustion system 10, 10d...Combustion tower 20...First loop seal part 30, 30d... Treatment tower 35...Thermocouple 40...Cyclone 50...Second loop seal part 60...Circulation piping 61...First pipe 62...Second piping 70...Control unit CC, Ca...CO2 recovery unit DH,Db…Dehydrator F1~F4...flow path H1,H2…Heat exchanger IF, IFd…supply port IG, IGd…supply port MP…metal particles S1,S2…heat storage V1 to V8: On-off valves

Claims

1. 1. A particle circulation combustion system comprising: Metal particles having catalytic properties that promote the combustion of hydrocarbon fuels and the decomposition of volatile organic compounds; a combustion tower having a supply port for supplying the hydrocarbon fuel and air therein, the combustion tower combusting the hydrocarbon fuel while using the metal particles as a catalyst; a treatment tower for decomposing volatile organic compounds using the metal particles heated in the combustion tower as a catalyst; a loop seal portion that limits gas movement between the combustion tower and the treatment tower; a circulation pipe for circulating the metal particles between the combustion tower and the treatment tower; a recovery device that recovers carbon dioxide contained in post-combustion gas discharged from the combustion tower by combustion of the hydrocarbon fuel.

2. 10. The particle circulation combustion system of claim 1, further comprising: A particle circulation combustion system comprising a heat recovery section for recovering heat from the post-combustion gas.

3. The particle circulation combustion system according to claim 1 or claim 2, further comprising: a control unit for controlling the particle circulation combustion system; The control unit adjusts the amount of the hydrocarbon fuel supplied to the combustion tower and the amount of air supplied to the combustion tower according to the difference between the measured temperature inside the treatment tower and a preset target temperature.

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