Chemical looping combustion system and method for controlling a chemical looping combustion system

Abstract

To stably control output of a chemical looping combustion system.SOLUTION: A chemical looping combustion system comprises: an oxidation tower that oxidizes oxygen carrier particles; a cyclone that separates gas supplied from the oxidation tower from the oxidized oxygen carrier particles and discharges the separated gas; a fuel tower that reduces the oxidized oxygen carrier particles supplied from the cyclone with fuel containing carbon, separates the oxygen carrier particles from gas containing carbon dioxide, and discharges the separated gas; and a pressure adjustment unit that adjusts at least one of a pressure of the gas discharged from the cyclone and a pressure of the gas discharged from the fuel tower.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a chemical looping combustion system and a method for controlling the chemical looping combustion system.

Background Art

[0002] A chemical looping combustion (CLC) system capable of essentially separating carbon dioxide is known (see, for example, Patent Document 1 and Non-Patent Document 1). The chemical loop combustion apparatus described in Patent Document 1 includes a riser that moves oxidized oxygen carrier particles from vertically below to vertically above by a carrier gas. In this apparatus, the flow rate of the carrier gas is adjusted using the pressure loss of the carrier gas in the riser. Non-Patent Document 1 describes a CLC apparatus in which an oxidation tower that oxidizes oxygen carrier particles and a fuel tower that reduces oxygen carrier particles are integrally formed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0004]

Non-Patent Document 1

[0005] The amount of heat generated in a CLC system is determined by the circulation rate of oxygen carrier particles supplied to the oxidation tower and fuel tower per unit time. In other words, the operating output of the CLC system is controlled by the circulation rate of oxygen carrier particles. As described in Patent Document 1, the circulation rate of oxygen carrier particles changes by controlling the flow rate of the transport gas for oxygen carrier particles. However, when the flow rate of the transport gas changes, the motion state of the oxygen carrier particles changes, and the stoichiometric balance in the chemical reaction also changes. Therefore, controlling the output of the CLC system by controlling the flow rate of the transport gas for oxygen carrier particles has not been easy.

[0006] Patent Document 2 describes a particle circulation control device that circulates particles by blowing air into it, unlike a CLC system which has a two-tower configuration consisting of an oxidation tower that oxidizes oxygen carrier particles and a fuel tower that reduces oxygen carrier particles. In this device, particles separated from the gas by a separator are supplied to a fluidized gasifier. A gasifying agent is supplied to the bottom of the fluidized gasifier, and the particles in the fluidized gasifier are sent to an inclined pipe connected to a combustion furnace. In other words, the fluidized gasifier functions as a loop seal. In the technology described in Patent Document 2, the particle circulation flow rate is controlled by controlling the differential pressure before and after the fluidized gasifier. However, in the connection space with the inclined pipe where the pressure is measured downstream of the fluidized gasification flow path, a large amount of particles are suspended due to the supplied gasifying agent. Therefore, it is not easy to measure the pressure in the connection space.

[0007] The present invention has been made to solve at least some of the above-mentioned problems and aims to stabilize and control the output of a chemical looping combustion system. [Means for solving the problem]

[0008] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms.

[0009] (1) According to one embodiment of the present invention, a chemical looping combustion system is provided. This chemical looping combustion system comprises: an oxidation tower for oxidizing oxygen carrier particles; a cyclone for separating the gas supplied from the oxidation tower from the oxidized oxygen carrier particles and for discharging the separated gas; a fuel tower for reducing the oxidized oxygen carrier particles supplied from the cyclone with a carbon-containing fuel, separating the oxygen carrier particles from a carbon dioxide-containing gas, and for discharging the separated gas; and a pressure adjustment unit for adjusting at least one of the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower.

[0010] In this configuration, the pressure of the exhaust gas from the cyclone and the pressure of the exhaust gas from the fuel tower are adjusted. For example, setting a high pressure for the exhaust gas from the fuel tower increases the pressure inside the fuel tower. This increase in pressure inside the fuel tower increases the circulation rate of oxygen carrier particles circulating within the chemical looping combustion system. Conversely, setting a low pressure for the exhaust gas from the fuel tower reduces the circulation rate of oxygen carrier particles. In this configuration, since the gas flow rate supplied to the chemical looping combustion system does not change, changes in the flow state of oxygen carrier particles in response to changes in gas flow rate are suppressed. Furthermore, because the gas flow rate does not change, it is easy to set the circulation rate of oxygen carrier particles in the oxidation tower and fuel tower to match the amount of chemical substances contained in the gas. In other words, in this configuration, the output of the chemical looping combustion system is stably controlled by controlling the back pressure of the cyclone and fuel tower without changing the gas flow rate.

[0011] (2) In the chemical looping combustion system according to the above embodiment, the pressure adjustment unit may include a first pressure adjustment valve for adjusting the pressure of the gas discharged from the cyclone, a second pressure adjustment valve for adjusting the pressure of the gas discharged from the fuel tower, and an opening adjustment unit for adjusting at least one of the opening degree of the first pressure adjustment valve and the opening degree of the second pressure adjustment valve. In this configuration, the pressure of the exhaust gas from the cyclone is regulated by the opening of the first pressure regulating valve. Similarly, the pressure of the exhaust gas from the fuel tower is regulated by the opening of the second pressure regulating valve. In this configuration, the back pressure of the cyclone and the back pressure of the fuel tower are easily regulated using the opening of existing pressure regulating valves.

[0012] (3) In the chemical looping combustion system according to the above embodiment, the opening adjustment unit may adjust at least one of the opening of the first pressure regulating valve and the opening of the second pressure regulating valve using the difference between the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower. In this configuration, the opening degree of at least one of the first and second pressure regulating valves is adjusted according to the pressure difference between the exhaust gas pressure from the cyclone and the exhaust gas pressure from the fuel tower. In other words, the opening degrees of the first and second pressure regulating valves are easily adjusted by a single parameter, the pressure difference.

[0013] (4) In the chemical looping combustion system according to the above embodiment, the system further includes a temperature acquisition unit for acquiring the temperature of the cyclone, and the opening adjustment unit may adjust at least one of the opening of the first pressure regulating valve and the opening of the second pressure regulating valve using the temperature of the cyclone in addition to the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower. In this configuration, the opening degree of at least one of the first and second pressure regulating valves is adjusted using the pressure of the exhaust gas from the cyclone, the pressure of the exhaust gas from the fuel tower, and the temperature of the cyclone. In principle, the exhaust gas from the cyclone and the exhaust gas from the fuel tower do not contain oxygen carrier particles. However, some of the oxygen carrier particles that circulate within the chemical looping combustion system may be fragmented and included in the exhaust gas. In this case, the exhaust gas pressure obtained due to the fragmented oxygen carrier particles in the back pressure may contain errors. In this configuration, the cyclone temperature is used to adjust the opening degree of the pressure regulating valve, thereby suppressing the influence of errors occurring in the back pressure.

[0014] Furthermore, the present invention can be realized in various forms, for example, as a chemical looping combustion system, a chemical looping combustion apparatus, a chemical looping combustion method, a system comprising these apparatuses, a computer program for executing these apparatuses, a server device for distributing this computer program, a non-temporary storage medium storing the computer program, and so on. [Brief explanation of the drawing]

[0015] [Figure 1]It is a schematic block diagram of a chemical looping combustion system as an embodiment of the present invention. [Figure 2] It is an explanatory diagram of the principle of chemical looping combustion. [Figure 3] It is a flowchart of the pressure control of the first embodiment. [Figure 4] It is a schematic block diagram of a CLC system for confirming the particle circulation amount of metal particles. [Figure 5] It is an explanatory diagram of the particle circulation amount of metal particles that changes according to the back pressure difference. [Figure 6] It is a schematic block diagram of the CLC system of the second embodiment. [Figure 7] It is a flowchart of the pressure control of the second embodiment. [Figure 8] It is a schematic block diagram of a CLC system for confirming the temperature change in the cyclone. [Figure 9] It is an explanatory diagram of the temperature change in the cyclone and the air column when metal particles are circulating. [Figure 10] It is an explanatory diagram of the temperature change in the cyclone and the air column when metal particles are not circulating.

Mode for Carrying Out the Invention

[0016] <First Embodiment> Figure 1 is a schematic block diagram of a chemical looping combustion system (hereinafter also simply referred to as the "CLC system") 100 as one embodiment of the present invention. In the CLC system 100, the air tower (oxidation tower) 10 oxidizes metal particles (oxygen carrier particles) mg as oxygen carrier particles. The metal particles mg and gas discharged from the air tower 10 are supplied to the cyclone 30. The cyclone 30 separates the supplied metal particles mg from the gas and discharges the separated gas. The fuel tower 20 is supplied with oxidized metal particles mg from the cyclone 30. The fuel tower 20 reduces the metal particles mg with methane (CH4) as fuel. The fuel tower 20 separates the metal particles mg from the gas containing carbon dioxide (CO2) and discharges the gas. In this embodiment, the output of the CLC system 100 is stably controlled by adjusting the pressure of the gas discharged from the cyclone 30 and the pressure of the gas discharged from the fuel tower 20.

[0017] Within the CLC system 100, metal particles mg circulate, repeatedly undergoing oxidation in the air tower 10 and reduction in the fuel tower 20 to transport oxygen (O2) from the air from the air tower 10 to the fuel tower 20. In this embodiment, an example using the oxidation reaction of Fe3O4 as the metal particles mg will be described. The particle size of the metal particles mg is 50 μm to 250 μm. As shown in Figure 1, the CLC system 100 of the first embodiment includes an air tower 10, a fuel tower 20, a cyclone 30, an air tower side loop seal 40, a fuel tower side loop seal 50, filters F2, F3, a first control valve (first pressure control valve) V3, a second control valve (second pressure control valve) V2, pressure sensors SS1, SS2, a control unit 60, a dewaterer 70, and a heater 21 for heating the fuel tower 20.

[0018] Figure 2 is an explanatory diagram of the principle of chemical loop combustion. Figure 2 shows a schematic block diagram of the CLC system 100. In Figure 2, the metal atoms (or molecules) used as metal particles mg are represented as Me.

[0019] In the air tower 10, air is supplied as an oxidizing gas, and the reaction heat from the oxidation reaction of metal particles mg is supplied to the heat utilization site as high-temperature N2 that does not contain CO2. In the fuel tower 20, the oxidized metal particles mg are reduced by a fuel such as CH4 which contains carbon, and the mixed gas containing CO2 generated by the reduction reaction is supplied to the dewaterer 70. In the dewaterer 70, H2O is removed from the mixed gas, and the mixed gas containing high-purity CO2 is supplied to the CO2 utilization site.

[0020] In this embodiment, the air tower 10 uses air containing O2 to oxidize Fe3O4 as metal particles mg by causing the reaction shown in formula (1) below. The oxidation reaction in formula (1) is an exothermic reaction. Therefore, the reaction in formula (1) generates heat, warming the gas inside the air tower 10, and the inside of the air tower 10 is heated to approximately 1000 degrees Celsius (°C).

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[0021] As shown in Figure 1, the air tower 10 has a cylindrical shape extending vertically. A seal 10S is provided vertically downward inside the air tower 10. The seal 10S is a component with multiple small holes. The seal 10S allows air supplied from vertically downward into the air tower 10, carrying the metal particles mg vertically upward. On the other hand, since the size of the holes in the seal 10S is smaller than the metal particles mg, it prevents the metal particles mg from passing through the seal 10S and leaking out of the air tower 10. The gas flow velocity vertically upward inside the air tower 10 is set to the terminal velocity at which gravity and the drag force due to the gas flow balance, or to a velocity greater than or equal to the terminal velocity.

[0022] The metal particles mg oxidized in the air tower 10 flow into the cyclone 30, which is connected via piping. The cyclone 30 uses centrifugal force to separate the oxidized metal particles mg from the heated gas. As shown in Figure 1, the gas heated in the air tower 10 is discharged from vertically above the cyclone 30. The composition of the exhaust gas from the cyclone 30 is mostly N2 because the amount of O2 is reduced due to the oxidation of the metal particles mg in the air tower 10. After the crushed metal particles mg are removed from the exhaust gas from the cyclone 30 by the filter F3, it is sent to a heat utilization site. The first control valve V3, located downstream of the filter F3, is a pressure control valve whose opening degree is adjusted by the adjustment unit 60 (described later) to adjust the pressure of the exhaust gas from the cyclone 30. The pressure sensor SS1 detects the pressure P1 of the exhaust gas before it passes through the filter F3 and the first control valve V3.

[0023] The metal particles mg, separated from the gas within the cyclone 30, move through a vertically downward-extending pipe located in the central part of the cyclone 30 to the air tower-side loop seal 40, as shown in Figure 1.

[0024] As shown in Figure 1, the air tower side loop seal 40 is located downstream of the air tower 10 and upstream of the fuel tower 20. A seal 40S is provided vertically below the air tower side loop seal 40. The seal 40S is a component with multiple fine holes, similar to the seal 10S of the air tower 10. The fine holes formed in the seal 40S are smaller than the particle size of the metal particles mg. Therefore, as shown in Figure 1, a particle layer (hatched area) formed of multiple metal particles mg is formed on the upper surface of the seal 40S.

[0025] Steam is supplied from vertically below the seal 40S. The supplied steam passes through the seal 40S and flows into the fuel tower 20, which is connected to the downstream side of the air tower-side loop seal 40. Because steam is supplied into the air tower-side loop seal 40 from below the seal 40S, the flow of gas mainly composed of N2 through the particle layer from the cyclone 30 to the fuel tower 20 is suppressed. The steam is removed by the dewaterer 70 as the exhaust gas discharged from the fuel tower 20 passes through it.

[0026] A fluidized bed is provided in the piping connecting the air tower-side loop seal 40 and the fuel tower 20, allowing fluid to flow from the air tower-side loop seal 40 to the fuel tower 20. Due to the flow of the fluidized bed, metal particles mg discharged from the cylindrical air tower-side loop seal 40 are moved to the fuel tower 20.

[0027] In this embodiment, methane (CH4) or the like is supplied to the fuel tower 20, along with a gas containing oxidized metal particles mg from the air tower 10 and water vapor supplied to the air tower-side loop seal 40. The fuel tower 20 reduces the metal particles mg using fuel such as CH4. The mixed gas containing CO2 generated by the reduction reaction between the fuel and the metal particles mg is separated from the reduced metal particles mg and discharged. The exhaust gas from the fuel tower 20 is sent to a CO2 utilization site after the crushed metal particles mg are removed by the filter F2. The second control valve V2, located downstream of the filter F2, is a pressure control valve whose opening degree is adjusted by the adjustment unit 60, which will be described later. After the exhaust gas has passed through the second control valve V2, moisture is removed by the dewaterer 70 and then supplied to a CO2 utilization site. Examples of CO2 utilization sites include storage tanks that store CO2 after liquefaction or pressurization. The pressure sensor SS2 detects the pressure P2 of the exhaust gas before it passes through the filter F2 and the second control valve V2.

[0028] As shown in Figure 1, the fuel tower 20 has a cylindrical shape that extends vertically. A seal 20S is provided vertically downward inside the fuel tower 20. The seal 20S is a component with multiple small holes, similar to the seal 10S. In the fuel tower 20, gaseous fuel such as CH4 is supplied from below the seal 20S. The gas flow velocity inside the fuel tower 20 is set to a speed slower than the terminal velocity, and is controlled based on information from the fuel tower 20 to prevent metal particles mg from being ejected.

[0029] In the fuel tower 20, where CH4 is supplied as fuel, Fe2O3, which is metal particles mg oxidized in the air tower 10 as shown in equation (1) above, is reduced by CH4 to Fe3O4 as shown in equation (2) below, and changes to CO2. The reduction reaction shown in equation (2) below is an endothermic reaction. The inside of the fuel tower 20, where the temperature decreases due to the endothermic reaction, is heated by the heater 21.

[0030]

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[0031] When the oxidation reaction in the air tower 10 represented by formula (1) above and the reduction reaction of CH4 in the fuel tower 20 represented by formula (2) above are taken together, the reactions in the air tower 10 and fuel tower 20, including the reduction reaction by CH4 in the fuel tower 20, are the same as the combustion of CH4 shown in formula (3) below. That is, the total amount of heat obtained from the oxidation of metal particles mg and the reduction of metal particles mg by CH4 (the sum of the heat generated in the air tower 10 and the heat absorbed in the fuel tower 20) is the same as that of the combustion of CH4.

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[0032] As shown in Figure 1, the metal particles mg reduced by the reduction reaction within the fuel tower 20 move through a vertically downward-extending pipe located in the central part of the fuel tower 20 to the fuel tower-side loop seal 50.

[0033] The fuel tower-side loop seal 50, which is supplied with metal particles mg from within the fuel tower 20, is located downstream of the fuel tower 20 and upstream of the air tower 10. The fuel tower-side loop seal 50 has the same configuration as the air tower-side loop seal 40. A seal 50S is provided vertically below the fuel tower-side loop seal 50. The seal 50S is a component with multiple small holes, similar to the seal 10S. In the fuel tower-side loop seal 50, water vapor is supplied from vertically below the seal 50S. The supplied water vapor passes through the seal 50S and flows into the air tower 10, which is connected downstream of the fuel tower-side loop seal 50. A fluidized bed is provided in the piping connecting the fuel tower-side loop seal 50 and the air tower 10, which flows from the fuel tower-side loop seal 50 to the air tower 10. Due to the flow of the fluidized bed, the metal particles mg inside the cylindrical fuel tower-side loop seal 50 move to the air tower 10. As explained above, the metal particles mg are oxidized in the air tower 10, reduced in the fuel tower 20, and circulate between the air tower 10 and the fuel tower 20.

[0034] The adjustment unit 60 adjusts at least one of the exhaust gas pressure from the cyclone 30 and the exhaust gas pressure from the fuel tower 20. In this embodiment, the adjustment unit 60 adjusts the pressure of each exhaust gas by adjusting the opening degree of the first adjustment valve V3 and the opening degree of the second adjustment valve V2. The adjustment unit 60 acquires the exhaust gas pressure P1 from the cyclone 30 detected by the pressure sensor SS1 and the exhaust gas pressure P2 from the fuel tower 20 detected by the pressure sensor SS2. The adjustment unit 60 uses the back pressure difference ΔP between the acquired pressures P1 and P2 to adjust at least one of the opening degree of the first adjustment valve V3 and the opening degree of the second adjustment valve V2. Specifically, the adjustment unit 60 calculates the back pressure difference ΔP by subtracting pressure P1 from pressure P2, as shown in equation (4) below. The adjustment unit 60, the first adjustment valve V3, and the second adjustment valve V2 correspond to the pressure adjustment unit.

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[0035] The adjustment unit 60 sets the back pressure difference ΔP to a preset target back pressure difference ΔP tarThe opening degree of at least one of the first regulating valve V3 and the second regulating valve V2 is adjusted to achieve the desired result. Figure 3 is a flowchart of the pressure control according to the first embodiment. As shown in the pressure control flowchart of Figure 3, the adjustment unit 60 acquires the detected pressures P1 and P2 from the pressure sensors SS1 and SS2 (step S1). Step S1 corresponds to the first acquisition step and the second acquisition step.

[0036] The adjustment unit 60 calculates the back pressure difference ΔP using the acquired pressures P1 and P2 as shown in equation (4) above (step S2). The adjustment unit 60 determines that the calculated back pressure difference ΔP is equal to the target back pressure difference ΔP. tar To achieve this, the opening degree of at least one of the first control valve V3 and the second control valve V2 is adjusted (step S3). Steps S2 and S3 correspond to the pressure adjustment process.

[0037] The adjustment unit 60 determines whether or not to terminate the operation of the CLC system 100 (step S4). If it is determined that the operation will not be terminated because no termination signal has been received from the user (step S4: NO), the adjustment unit 60 repeats the processing from step S1 onwards. If it is determined that the operation of the CLC system 100 will be terminated (step S4: YES), the adjustment unit 60 terminates the pressure control flow.

[0038] Figures 4 and 5 are explanatory diagrams illustrating the effects of controlling the particle circulation rate. Figure 4 shows a schematic block diagram of the CLC system 100A for confirming the particle circulation rate of metal particles mg circulating within the CLC system. In the CLC system 100A shown in Figure 4, no fuel such as CH4 is supplied, so the oxidation-reduction reaction of metal particles mg does not occur. Therefore, compared to the CLC system 100 shown in Figure 1, the CLC system 100A does not have a heater 21, filters F2 and F3, and a dewaterer 70. In addition, the air tower 10, fuel tower 20, air tower side loop seal 40, and fuel tower side loop seal 50 are made of transparent acrylic. Therefore, the circulation behavior of metal particles mg inside the air tower 10, etc., can be visually confirmed.

[0039] Figure 5 shows the particle circulation rate of metal particles mg, which changes according to the back pressure difference ΔP. In Figure 5, the simulation result particle circulation rate Ms is shown by the solid line connecting the black circles, and the actual particle circulation rate Mr circulating within the CLC system 100A is shown by the dashed line connecting the white circles. Note that the particle circulation rate Mr for back pressure differences ΔP less than 1.1 kPa is not plotted because data has not been measured. As shown by the particle circulation rates Ms and Mr in Figure 5, it was confirmed that the amount of metal particles mg circulating within the CLC system 100A increases with increasing back pressure difference ΔP.

[0040] As described above, in the CLC system 100 of this embodiment, metal particles mg, which are oxygen carrier particles oxidized in the air tower 10, are supplied to the cyclone 30. The cyclone 30 separates the supplied metal particles mg from the gas and discharges the separated gas. The fuel tower 20 reduces the oxidized metal particles mg supplied from the cyclone 30 with CH4 or the like, which is a carbon-containing fuel. The fuel tower 20 separates the metal particles mg from the gas containing CO2 and discharges the separated gas. The adjustment unit 60 adjusts at least one of the exhaust gas pressure P1 from the cyclone 30 and the exhaust gas pressure P2 from the fuel tower 20. In this embodiment, for example, by setting the exhaust gas pressure P2 from the fuel tower 20 higher by the adjustment unit 60, the pressure inside the fuel tower 20 also increases. As the pressure inside the fuel tower 20 increases, the amount of metal particles mg circulating within the CLC system 100 increases. On the other hand, setting the exhaust gas pressure P2 from the fuel tower 20 low reduces the amount of metal particles mg circulated. When the gas flow velocity is low, the metal particles mg are fixed in the fluidized bed and do not move. As the gas flow velocity increases from this state, the metal particles mg change to a fluidized bed state in which they flow with complex gas bubbles. As the gas flow velocity increases further, the metal particles mg enter a turbulent flow state. Therefore, in order to generate particle circulation, it is necessary to maintain an appropriate flow state, and there is a limit to the range in which the gas flow velocity can be changed for this purpose. Also, since the amount of supplied chemical substances contained in the gas changes when the gas flow velocity changes, the reactions in the air tower 10 and the fuel tower 20 also change. In this embodiment, however, since the gas flow rate supplied into the CLC system 100 does not change, changes in the flow state of metal particles mg in response to changes in gas flow rate are suppressed. Also, because the gas flow rate does not change, the amount of metal particles mg circulated in the air tower 10 and the fuel tower 20 can be easily set to match the amount of chemical substances contained in the gas. In other words, in this embodiment, the output of the CLC system 100 is stably controlled by controlling the back pressure of the cyclone 30 and the fuel tower 20 without changing the gas flow rate.

[0041] In this embodiment, the first control valve V3 adjusts the exhaust gas pressure P1 from the cyclone 30. The second control valve V2 adjusts the exhaust gas pressure P2 from the fuel tower 20. The adjustment unit 60 adjusts at least one of pressure P1 and pressure P2 by adjusting the opening degree of the first control valve V3 and the opening degree of the second control valve V2. In this embodiment, the back pressure of the cyclone 30 and the back pressure of the fuel tower 20 are easily adjusted using the opening degree of existing pressure control valves.

[0042] Furthermore, the adjustment unit 60 of this embodiment adjusts at least one of the opening degree of the first adjustment valve V3 and the opening degree of the second adjustment valve V2 using the back pressure difference ΔP between the acquired pressures P1 and P2. In this embodiment, the opening degrees of the first adjustment valve V3 and the second adjustment valve V2 are easily adjusted by a single parameter, the back pressure difference ΔP.

[0043] <Modified form of the first embodiment> In the first embodiment, an example of pressure control using a back pressure difference ΔP was described, but pressure control using a back pressure difference ΔP is modifiable. For example, the adjustment unit 60 may control the opening degree of the first adjustment valve V3 so that the pressure P1(t+Δt) Δt seconds after time t detected by the pressure sensor SS1 is adjusted as shown in the following equation (5) using the pressure P1(t) at time t.

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[0044] Alternatively, the adjustment unit 60 may control the opening degree of the second adjustment valve V2 instead of the first adjustment valve V3, thereby adjusting the pressure P2(t+Δt) Δt seconds after time t detected by the pressure sensor SS2, as shown in the following equation (6) using the pressure P2(t) at time t.

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[0045] <Second Embodiment> Figure 6 is a schematic block diagram of the CLC system 100a of the second embodiment. The CLC system 100a of the second embodiment differs from the first embodiment in that, in addition to the exhaust gas pressure P1 from the cyclone 30 and the exhaust gas pressure P2 from the fuel tower 20, at least one of the pressures P1 and P2 is adjusted using the temperature T1 inside the cyclone 30.

[0046] As shown in Figure 6, the CLC system 100a of the second embodiment includes, in addition to the configuration of the CLC system 100 of the first embodiment, a temperature sensor (temperature acquisition unit) SS3 for detecting the temperature inside the cyclone 30. The temperature sensor SS3 is located vertically downward inside the cyclone 30.

[0047] The adjustment unit 60a of the second embodiment adjusts at least one of the pressures P1 and P2, in addition to the pressure P1 of the exhaust gas from the cyclone 30 and the pressure P2 of the exhaust gas from the fuel tower 20, using the temperature T1 inside the cyclone 30. The adjustment unit 60a adjusts the preset target temperature T tar Using the following equation (7), the pressure P1(t) at time t is used to adjust the pressure P1(t+Δt) Δt seconds after time t. Note that the target temperature T tar is the target temperature for control. In equation (7) below, k1 is a predetermined proportionality constant.

[0048]

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[0049] By adjusting the opening degree of the first control valve V3 that determines the pressure P1 using the above equation (7), the temperature T1 inside the cyclone 30 is brought to the target temperature T tar If the temperature is less than the target temperature, the pressure P1 decreases, the back pressure difference ΔP increases, and the circulation rate of metal particles mg increases. On the other hand, if the temperature T1 exceeds the target temperature, the pressure P1 increases, the back pressure difference ΔP decreases, and the circulation rate of metal particles mg decreases.

[0050] Figure 7 is a flowchart of the pressure control in the second embodiment. As shown in the pressure control flowchart in Figure 7, the adjustment unit 60a of the second embodiment acquires the detected pressures P1 and P2 from the pressure sensors SS1 and SS2 (step S11). The adjustment unit 60a further acquires the temperature T1 inside the cyclone 30 from the temperature sensor SS3 (step S12). Using the acquired pressures P1 and P2 and temperature T1, the adjustment unit 60a calculates the pressure P1(t+Δt) as shown in equation (7) above (step S13). The adjustment unit 60a adjusts the opening degree of the first adjustment valve V3 so that the calculated pressure P1(t+Δt) is achieved (step S14). The adjustment unit 60a determines whether or not to terminate the operation of the CLC system 100a (step S15). If it is determined not to terminate the operation (step S15: NO), the adjustment unit 60a repeats the process from step S11 onwards. If it is determined that the operation of the CLC system 100a is to be terminated (step S15: YES), the adjustment unit 60a terminates the pressure control flow.

[0051] Figures 8 to 10 are explanatory diagrams illustrating the temperature T1 inside the cyclone 30, which changes in accordance with particle circulation. Figure 8 shows a schematic block diagram of the CLC system 100B to confirm the change in temperature T1 inside the cyclone 30 depending on the presence or absence of particle circulation of metal particles mg circulating within the CLC system. As shown in Figure 8, the CLC system 100B does not have a dewaterer 70 compared to the CLC system 100a shown in Figure 7, and is equipped with a temperature sensor SS4 that detects the temperature T2 inside the air tower 10. The temperature sensor SS4 is located vertically downward inside the air tower 10. Therefore, the temperature sensor SS4 detects the temperature T2 of particles and gases that are accumulating above the seal 10S of the air tower 10. In the CLC system 100B, unlike the CLC system 100A shown in Figure 4, the air tower 10, fuel tower 20, air tower side loop seal 40, and fuel tower side loop seal 50 are formed of SUS310S. Therefore, even if oxidation and reduction of metal particles mg occur in the air tower 10 and fuel tower 20, the air tower 10 and fuel tower 20 will not be damaged.

[0052] Figure 9 shows the changes in temperature T1 and T2 when metal particles mg are circulating within the CLC system 100B. On the other hand, Figure 10 shows the changes in temperature T1 and T2 when metal particles mg are not circulating within the CLC system 100B. In Figures 9 and 10, the change in temperature T1 inside the cyclone 30 detected by temperature sensor SS3 is shown by a dashed line. Also, the change in temperature T2 inside the air tower 10 detected by temperature sensor SS4 is shown by a solid line. As shown in Figures 9 and 10, the temperature T2 inside the air tower 10 rises over time regardless of whether metal particles mg are circulating or not. On the other hand, the temperature T1 inside the cyclone 30 rises when metal particles mg are circulating, as shown in Figure 9, but does not change when metal particles mg are not circulating, as shown in Figure 10. When metal particles mg are circulating, the metal particles mg, which are generating heat due to oxidation, move instead of remaining in the air tower 10. Therefore, the temperature T1 inside the cyclone 30 rises over time. In other words, the results in Figures 9 and 10 show that the temperature T1 inside cyclone 30 increases as metal particles mg circulate within the CLC system B.

[0053] As described above, the adjustment unit 60a of the second embodiment adjusts at least one of pressures P1 and P2 using the temperature T1 inside the cyclone 30, in addition to the pressure P1 of the exhaust gas from the cyclone 30 and the pressure P2 of the exhaust gas from the fuel tower 20. In principle, in the CLC system 100a, the exhaust gas from the cyclone 30 and the exhaust gas from the fuel tower 20 do not contain metal particles mg. However, some of the metal particles mg that circulate within the CLC system 100a may be crushed and included in the exhaust gas. In this case, the crushed metal particles mg mixed in the exhaust gas may cause errors in the exhaust gas pressures P1 and P2. In this embodiment, by using the temperature T1 of the cyclone 30 to adjust the opening of the first adjustment valve V3 and the second adjustment valve V2, the influence of errors occurring in back pressure can be suppressed.

[0054] <Modified form of the second embodiment> In the second embodiment, an example of back pressure control using the temperature T1 inside the cyclone 30 was described, but back pressure control using temperature T1 is modifiable. For example, the adjustment unit 60a controls the opening degree of the second adjustment valve V2 using pressures P1, P2 and temperature T1. As a result, the pressure P2(t+Δt) Δt seconds after time t detected by the pressure sensor SS2 may be adjusted as shown in the following equation (8) using the pressure P2(t) at time t. In the following equation (8), k2 is a predetermined proportionality constant.

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[0055] <Modified examples of embodiments> The present invention is not limited to the embodiments described above, and can be implemented in various forms without departing from its spirit. For example, the following modifications are possible. Furthermore, in the above embodiments, some of the configurations implemented by hardware may be replaced with software, and conversely, some of the configurations implemented by software may be replaced with hardware.

[0056] <Example 1> The CLC systems 100 and 100a of the first and second embodiments described above are examples and can be modified to adjust at least one of the pressures of the gas separated and discharged in the cyclone 30 and the pressures of the gas separated and discharged in the fuel tower 20. For example, the CLC system 100 does not necessarily have to include the air tower side loop seal 40, the fuel tower side loop seal 50, and filters F2, F3, etc. The amount of metal particles mg circulating may be controlled by fixing the back pressure of one of the first control valve V3 and the second control valve V2, and adjusting the other control valve with the adjustment unit 60. Alternatively, at least one of the exhaust gas pressures from the cyclone 30 and the exhaust gas pressures from the fuel tower 20 may be adjusted by a method that does not use a pressure regulating valve, such as a vacuum pump. The back pressure difference ΔP was calculated as the difference between the detected values ​​of the two pressure sensors SS1 and SS2, but it may also be detected directly as a differential pressure.

[0057] The metal particles mg, which are oxygen carrier particles circulating in the CLC system 100, can be made of any known material other than FeTiO3. Similarly, the carbon-containing fuel supplied to the fuel tower 20 can be made of any known material other than CH4, such as C2H6 or C3H8. For example, nickel (Ni) or copper (Cu) may be used as the metal particles mg, and C2H6 may be used as the fuel. In this case, the reduction reaction occurring in the fuel tower 20 can be expressed as shown in equations (9) and (10) below.

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[0058] The gas supplied to the air tower 10 may be anything other than air, as long as it contains O2. The air tower 10 can also be described as an oxidation tower that is supplied with O2-containing gas to oxidize metal particles mg. Furthermore, the air tower 10 and the fuel tower 20 do not have to be formed as two separate towers, but may be formed as an integrated device including the air tower side loop seal 40 and the fuel tower side loop seal 50, as described in Non-Patent Literature 1.

[0059] <Modification 2> Furthermore, in the CLC system 100a of the second embodiment, the adjustment unit 60a used the pressures P1 and P2 detected by the pressure sensors SS1 and SS2. However, in the modified example, the adjustment unit may use only the temperature T1 inside the cyclone 30 detected by the temperature sensor SS3 to adjust at least one of the first adjustment valve V3 and the second adjustment valve V2. Since the temperature sensor SS3 is less expensive than the pressure sensors SS1 and SS2, in this modified example, the output of the CLC system is controlled inexpensively and stably. In this case, the temperature sensor SS3 and the adjustment unit 60a correspond to the pressure adjustment unit. As a result, the opening degree R of the first adjustment valve V3 after Δt seconds from time t is controlled. V3(t+Δt) may be adjusted as shown in equation (11) below, using the temperature T1(t) of the temperature sensor SS4 at time t. In equation (11) below, k3 is a predetermined proportionality constant.

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[0060] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0061] The present invention can also be realized in the following forms. [Application Example 1] A chemical looping combustion system, An oxidation tower for oxidizing oxygen carrier particles, A cyclone separates the gas supplied from the oxidation tower from the oxidized oxygen carrier particles and discharges the separated gas. A fuel tower that reduces the oxidized oxygen carrier particles supplied from the cyclone with a carbon-containing fuel, separates the oxygen carrier particles from a gas containing carbon dioxide, and discharges the separated gas, A pressure adjustment unit that adjusts at least one of the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower, A chemical looping combustion system equipped with [a specific feature]. [Application Example 2] The chemical looping combustion system described in Application Example 1, The aforementioned pressure adjustment unit is A first pressure regulating valve for adjusting the pressure of the gas discharged from the cyclone, A second pressure regulating valve for adjusting the pressure of the gas discharged from the fuel tower, An opening degree adjustment unit for adjusting at least one of the opening degree of the first pressure regulating valve and the opening degree of the second pressure regulating valve, A chemical looping combustion system having [a specific feature]. [Application Example 3] A chemical looping combustion system as described in Application Example 1 or Application Example 2, The opening degree adjustment unit adjusts at least one of the opening degree of the first pressure regulating valve and the opening degree of the second pressure regulating valve using the difference between the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower in a chemical looping combustion system. [Application Example 4] A chemical looping combustion system according to any one of Application Examples 1 to 3, further comprising: The system includes a temperature acquisition unit that acquires the temperature of the cyclone, A chemical looping combustion system in which the opening degree adjustment unit adjusts at least one of the opening degree of the first pressure regulating valve and the opening degree of the second pressure regulating valve using the pressure of the gas discharged from the cyclone, the pressure of the gas discharged from the fuel tower, and the temperature of the cyclone. [Application Example 5] A method for controlling a chemical looping combustion system, wherein a computer controls: A first acquisition step involves obtaining the pressure of the gas separated from the oxygen carrier particles and discharged by a cyclone supplied with gas and the oxidized oxygen carrier particles from an oxidation tower that oxidizes the oxygen carrier particles, A second acquisition step involves obtaining the pressure of a gas containing carbon dioxide that is separated from the oxygen carrier particles and discharged by a fuel tower that reduces the oxidized oxygen carrier particles supplied from the cyclone with a carbon-containing fuel, A pressure adjustment step that adjusts at least one of the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower, A control method for executing this. [Explanation of Symbols]

[0062] 10…Air tower (oxidation tower) 10S... Air tower seal 20…Fuel tower 20S…Fuel tower seal 21... Heater 30... Cyclone 40...Air tower side loop seal 40S...Air tower side loop seal 50…Fuel tower side loop seal 50S...Seal of the fuel tower side loop seal 60, 60a... Adjustment section (opening adjustment section) 70...Dehydrator 100, 100a, 100A, 100B…CLC system (Chemical Looping Combustion System) F2, F3... filters P1... Exhaust gas pressure from the cyclone P2… Exhaust gas pressure from the fuel tower SS1, SS2… Pressure sensors SS3…Temperature sensor (temperature acquisition unit) SS4…Temperature sensor T1... Temperature inside the cyclone T2... Temperature inside the air tower T tar …Target temperature V2…Second regulating valve (second pressure regulating valve) V3…First regulating valve (first pressure regulating valve) mg...metal particles (oxygen carrier particles) ΔP…back pressure difference ΔP tar ...Target back pressure difference

Claims

1. A chemical looping combustion system, An oxidation tower for oxidizing oxygen carrier particles, A cyclone separates the gas supplied from the oxidation tower from the oxidized oxygen carrier particles and discharges the separated gas. A fuel tower that reduces the oxidized oxygen carrier particles supplied from the cyclone with a carbon-containing fuel, separates the oxygen carrier particles from a gas containing carbon dioxide, and discharges the separated gas, A pressure adjustment unit that adjusts at least one of the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower, A chemical looping combustion system equipped with [a specific feature].

2. A chemical looping combustion system according to claim 1, The aforementioned pressure adjustment unit is A first pressure regulating valve for adjusting the pressure of the gas discharged from the cyclone, A second pressure regulating valve for adjusting the pressure of the gas discharged from the fuel tower, An opening degree adjustment unit for adjusting at least one of the opening degree of the first pressure regulating valve and the opening degree of the second pressure regulating valve, A chemical looping combustion system having [a specific feature].

3. A chemical looping combustion system according to claim 2, The opening degree adjustment unit adjusts at least one of the opening degree of the first pressure regulating valve and the opening degree of the second pressure regulating valve using the difference between the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower in a chemical looping combustion system.

4. A chemical looping combustion system according to claim 2 or claim 3, further comprising: The system includes a temperature acquisition unit that acquires the temperature of the cyclone, A chemical looping combustion system in which the opening degree adjustment unit adjusts at least one of the opening degree of the first pressure regulating valve and the opening degree of the second pressure regulating valve using the pressure of the gas discharged from the cyclone, the pressure of the gas discharged from the fuel tower, and the temperature of the cyclone.

5. A method for controlling a chemical looping combustion system, wherein a computer controls: A first acquisition step involves obtaining the pressure of the gas separated from the oxygen carrier particles and discharged by a cyclone supplied with gas and the oxidized oxygen carrier particles from an oxidation tower that oxidizes the oxygen carrier particles, A second acquisition step involves obtaining the pressure of a gas containing carbon dioxide that is separated from the oxygen carrier particles and discharged by a fuel tower that reduces the oxidized oxygen carrier particles supplied from the cyclone with a carbon-containing fuel, A pressure adjustment step that adjusts at least one of the pressure of the gas discharged from the cyclone and the pressure of the gas discharged from the fuel tower, A control method for executing this.

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