Carbon dioxide recovery system

Abstract

This carbon dioxide recovery system comprises: an adsorption unit that accommodates an adsorbent for adsorbing carbon dioxide from a target gas; a first heat medium that passes through the adsorption unit; and a first heat value changing unit that changes the temperature of the first heat medium. The first heat value changing unit comprises a heat exchanger through which a second heat medium passes, and a second heat value changing unit that changes the heat value of the second heat medium. Heat exchange between the first heat medium and the second heat medium exchange heat is carried out by the heat exchanger, or the first heat value changing unit includes a heat storage material and heat exchange between the first heat medium and the heat storage material is carried out by the first heat value changing unit.

Description

Carbon Dioxide Recovery System

[0001] This disclosure relates to a carbon dioxide recovery system. This application claims priority based on Japanese Patent Application No. 2025-026341 filed in Japan on February 21, 2025, and incorporates its content herein by reference.

[0002] In recent years, as a measure against global warming, efforts have been made to reduce and recover carbon dioxide. As one of them, DAC (Direct Air Capture) technology for recovering and concentrating carbon dioxide from the atmosphere has been developed. For recovering carbon dioxide, for example, in Patent Document 1, a target gas containing carbon dioxide is adsorbed on a part of an adsorbent honeycomb rotor, and the adsorbent honeycomb rotor is rotated to move the part on which the target gas is adsorbed to a regeneration zone, and the target gas adsorbed on the honeycomb is desorbed by a heated regeneration gas introduced into the regeneration zone to recover the target gas.

[0003] Japanese Patent Application Laid-Open No. 2021-133323

[0004] Thus, when recovering carbon dioxide, the temperature at the time of desorption is made higher than the temperature at the time of adsorption, and further, when regenerating the adsorbent, the adsorbent may be cooled again. Therefore, there is room for improvement in energy-saving of the electric power etc. required for heating and cooling the adsorbent.

[0005] In view of the above circumstances, an object of this disclosure is to provide a carbon dioxide recovery system capable of saving energy required for adsorption and desorption of carbon dioxide in an adsorbent.

[0006] The carbon dioxide recovery system in this disclosure includes an adsorption part that houses an adsorbent that adsorbs carbon dioxide from a target gas, a first heat medium that passes through the adsorption part, and a first heat quantity changing part that changes the temperature of the first heat medium. The first heat quantity changing part includes a heat exchanger through which a second heat medium passes and a second heat quantity changing part that changes the heat quantity of the second heat medium, and the first heat medium and the second heat medium exchange heat in the heat exchanger, or the first heat quantity changing part has a heat storage material, and the first heat medium and the heat storage material exchange heat in the first heat quantity changing part.

[0007] According to this disclosure, a carbon dioxide recovery system can be provided that reduces the energy required for the adsorption and desorption of carbon dioxide in the adsorbent.

[0008] This is a schematic diagram of the carbon dioxide capture system according to Embodiment 1, illustrating the cooling process of the adsorbent. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 1, illustrating the heating process of the adsorbent. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 1, illustrating the adsorption process of carbon dioxide onto the adsorbent. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 1, illustrating the process following Figure 2A. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 1, illustrating the process following Figure 2B. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 1, illustrating the process following Figure 2C. This is a schematic diagram of another carbon dioxide capture system according to Embodiment 1, illustrating the adsorption process of carbon dioxide onto the adsorbent. This is a schematic diagram of another carbon dioxide capture system according to Embodiment 1, illustrating the process following Figure 3A. This is a schematic diagram of another carbon dioxide capture system according to Embodiment 1, illustrating the process following Figure 3B. This is a schematic diagram of another carbon dioxide capture system according to Embodiment 1, illustrating the process following Figure 3C. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 2, illustrating the process of carbon dioxide adsorption onto the adsorbent. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 2, illustrating the process following Figure 4A. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 2, illustrating the process following Figure 4B. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 2, illustrating the process following Figure 4C. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 3, illustrating the process of carbon dioxide adsorption onto the adsorbent. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 3, illustrating the process following Figure 5A. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 3, illustrating the process following Figure 5B. This is a schematic diagram of the carbon dioxide capture system according to Embodiment 3, illustrating the process following Figure 5C. This is a schematic diagram of another carbon dioxide capture system according to Embodiment 3, illustrating the process following Figure 5C.This is a diagram illustrating the heat exchange in the auxiliary heat exchanger in the process shown in Figure 5E. This is a cross-sectional view taken along line G-G' in Figure 5F. This is a schematic diagram of the carbon dioxide recovery system according to Embodiment 4, illustrating the carbon dioxide desorption process. This is a schematic diagram of the carbon dioxide recovery system according to Embodiment 4, illustrating another example of the carbon dioxide desorption process. This is a schematic diagram of the carbon dioxide recovery system according to Embodiment 4. This is a schematic diagram of the carbon dioxide recovery system according to Embodiment 4.

[0009] Embodiments of this disclosure will be described below with reference to the drawings. However, the scope of this disclosure is not limited to the embodiments described below and can be modified at will within the scope of the technical idea of ​​this disclosure.

[0010] Embodiment 1. First, the basic configuration of the carbon dioxide recovery system 1 in Embodiment 1 will be described. Figures 1A to 1B are schematic diagrams of the carbon dioxide recovery system 1 according to Embodiment 1. As shown in Figures 1A to 1B, the carbon dioxide recovery system 1 includes an adsorption unit 10 that houses an adsorbent 11 capable of adsorbing carbon dioxide, a first heat transfer medium M1 that passes through the adsorption unit 10, and a first heat quantity change unit TC that changes the temperature of the first heat transfer medium M1. The first heat quantity change unit TC includes a heat exchanger 20 through which the second heat transfer medium M2 passes, and a second heat quantity change unit 30 that changes the heat quantity of the second heat transfer medium M2. The first heat transfer medium M1 and the second heat transfer medium M2 exchange heat in the heat exchanger 20.

[0011] - Adsorption section 10 The adsorption section 10 has a housing 12 and an adsorbent 11 placed inside the housing 12.

[0012] The adsorbent 11 contains a material capable of adsorbing carbon dioxide. The material of the adsorbent 11 may be a material that chemically and / or physically absorbs carbon dioxide, such as amines, zeolites, silica gel, diatomaceous earth, alumina, or activated carbon. Multiple materials may be selected from the above, or materials other than those listed above may be used. The adsorbent 11 may be granular (e.g., bead-shaped (spherical), pellet-shaped (cylindrical)). Alternatively, the adsorbent 11 may be in powder form. The adsorbent 11 may be supported on the surface of a substrate. The substrate may be, for example, a plate having a honeycomb structure with multiple approximately hexagonal pores smaller than the particle size. The adsorbent 11 may also be housed in a permeable case. For example, the adsorbent 11 may be housed in a case with multiple pores smaller than the particle size of the adsorbent 11. The case may be made entirely or partially of a mesh woven from wire. The materials of the substrate and case can be changed as appropriate, and may be metal or resin. Other structures besides those described above can also be used for the base material and case.

[0013] The housing 12 is a container capable of housing the adsorbent 11. For example, the housing 12 may be a box-shaped container composed of six sides, or it may be cylindrical in shape, etc. The housing 12 may have an opening (not shown) for inserting and removing the adsorbent 11 from the housing 12, and a door portion (not shown) for hermetically sealing the opening. The opening is an opening through which the adsorbent 11, or a base material and case containing the adsorbent 11, can pass, thereby allowing the adsorbent 11 to be inserted and removed by opening and closing the door portion.

[0014] The adsorption unit 10 may further include a heater 13 for heating the adsorbent 11. The heater 13 can be any known heater. In the examples of Figures 1A and 1B, the heater 13 is provided on the bottom surface of the housing 12, but it is not limited to this example and may be provided elsewhere, or in the internal space of the housing 12. In particular, the heater 13 may be a heater capable of directly heating the adsorbent 11, or it may be a heater capable of heating the adsorbent 11 by heating at least a part of the wall of the adsorption unit 10. As will be described in detail later, this allows the adsorbent 11 to be heated even when the inside of the adsorption unit 10 is depressurized.

[0015] The housing 12 is connected to a flow path F12 through which the first heat transfer medium M1 flows from the adsorbent 11 toward the heat exchanger 20, and to a flow path F21 through which the first heat transfer medium M1 flows from the heat exchanger 20 toward the adsorbent 11. Therefore, the first heat transfer medium M1 can circulate in this order through the adsorption unit 10, flow path F12, heat exchanger 20, and flow path F21. The circulation path of the first heat transfer medium M1 may or may not be a closed circuit. For example, flow path F21 may be connected to a flow path F2o for releasing the first heat transfer medium M1 that has flowed out of the heat exchanger 20, and a flow path Fo1 for introducing outside air into flow path F21, and the outflow of the first heat transfer medium M1 and the inflow of outside air may be adjusted as appropriate. In other words, the total amount of fluid supplied toward the adsorbent 11 may be adjusted so that a mixed gas of the first heat transfer medium M1 and outside air can be supplied to the adsorbent 11. In the example shown in Figure 1A, two flow paths, F2o and Fo1, are connected to flow path F21. However, flow path F21 may also be provided with only one flow path that allows for adjustment of the inflow of outside air and the outflow of the first heat transfer medium M1.

[0016] The first heat transfer medium M1 is a gas, such as air. Since the adsorbent 11 may preferentially adsorb liquids such as water rather than carbon dioxide, it is preferable that the first heat transfer medium M1 be a gas rather than a liquid. As will be described in detail later, the first heat transfer medium M1 may contain carbon dioxide that has been desorbed from the adsorbent 11.

[0017] In the following explanation, the passages through which the fluid containing the heat transfer medium, ambient air, and carbon dioxide desorbed from the adsorbent 11 passes will simply be referred to as "flow channels." A flow channel is, for example, a pipe through which fluid can pass. In the diagram, the direction of fluid movement is indicated by arrows. Note that in the flow channels connected to each component, the amount of heat possessed by the fluid flowing through the flow channel shown by a solid line is greater than the amount of heat possessed by the fluid flowing through the flow channel shown by a dashed line. In other words, heat is exchanged between the fluid and the component where the flow channels shown by solid lines and the flow channels shown by dashed lines are connected. Due to the exchange of heat, (1) the temperature of the fluid may change before and after passing through the component, and (2) the amount of heat exchanged may be within the range of the amount of heat (latent heat) required for the phase change of the fluid, and the temperature of the fluid may not change before and after passing through the component. Flow channels through which ambient air passes are indicated by double lines. For explanatory purposes, in the diagram, only flow channels through which fluid flows in each process are shown, and flow channels without fluid flow may be omitted from the illustration. The circulation of fluid in the flow path, and the inflow / outflow of fluid into the flow path, may be controlled by a circulation device such as a blower and a pump, and an on / off valve, controlled by a control unit (not shown).

[0018] ・Second heat quantity change section 30 In this embodiment, the second heat quantity change section 30 has a heat storage material 31 and a heat storage housing 32 that houses the heat storage material 31. The second heat quantity change section 30 is connected to a flow path F23 through which the second heat transfer medium M2 flows from the heat exchanger 20 toward the second heat quantity change section 30 and a flow path F32 through which the second heat transfer medium M2 flows from the second heat quantity change section 30 toward the heat exchanger 20. In the second heat quantity change section 30, it is possible to bring the second heat transfer medium M2 into thermal contact with the heat storage material 31, so that the heat quantity of the second heat transfer medium M2 can be changed. The heat storage housing 32 is a container that can house the heat storage material 31. For example, the heat storage housing 32 may be a box-shaped container composed of six surfaces, or it may be cylindrical in shape, etc. Note that the second heat quantity change section 30 does not necessarily have a heat storage housing 32. For example, if the heat storage material 31 is solid and there is no outflow of the heat storage material 31 and the second heat transfer medium M2 from the second heat quantity change section 30, the heat storage enclosure 32 may not be provided.

[0019] The heat storage material 31 may be a gas, liquid, or solid. The heat storage material 31 may be a material that does not undergo a phase change within the carbon dioxide capture system 1, or it may be a material that undergoes a phase change. The heat storage material 31 is preferably a material with a large heat capacity. Among the materials that do not undergo a phase change within the carbon dioxide capture system 1, gaseous heat storage material 31 may be air, liquid heat storage material 31 may be water, and solid heat storage material 31 may be metals such as iron, or inorganic materials such as rocks.

[0020] The material undergoing a phase change within the carbon dioxide recovery system 1 has a phase transition temperature lower than the desorption temperature of carbon dioxide from the adsorbent 11. For example, when carbon dioxide is desorbed with the adsorbent 11 at 120 to 150°C, the heat storage material 31 that undergoes a phase change from gas to liquid preferably has a boiling point of less than 120°C, and the heat storage material 31 that undergoes a phase change from liquid to solid preferably has a melting point of less than 120°C. Examples of heat storage materials 31 that undergo a phase change from gas to liquid include sugar alcohols (boiling point 100°C) and water (boiling point 100°C). Examples of heat storage materials 31 that undergo a phase change from liquid to solid include paraffin (melting point 5 to 42°C). When using a heat storage material 31 that can undergo a phase change to solid, a melting means may be provided in the flow path as appropriate.

[0021] If the heat storage material 31 is a fluid (i.e., a gas or liquid), the heat storage material 31 may function as a second heat transfer medium M2 that transports heat between the heat exchanger 20 and the second heat quantity change section 30. Furthermore, if the heat storage material 31 is a material that undergoes a phase change, the latent heat during the phase change can be utilized to more efficiently heat or cool the object to which heat is transferred. That is, when it condenses from gas to liquid and when it solidifies from liquid to solid, the heat generated during the phase change can increase the amount of heat in the object being heated in addition to the heat transported by the flow path. When it evaporates from liquid to gas and when it melts from solid to liquid, the heat absorbed during the phase change can decrease the amount of heat in the object.

[0022] The second heat transfer medium M2 circulates between the heat exchanger 20, the flow path F23, the second heat quantity change section 30, and the flow path F32 in this order, transporting heat. The second heat transfer medium M2 is a fluid (gas or liquid). Examples of a gaseous second heat transfer medium M2 include air, and examples of a liquid second heat transfer medium M2 include water. As described above, part or all of the heat storage material 31 may function as the second heat transfer medium M2.

[0023] • Heat exchanger 20 In the heat exchanger 20, heat exchange is performed by bringing the first heat transfer medium M1 and the second heat transfer medium M2 into thermal contact. It is preferable that the heat exchanger 20 is configured to ensure an area where the two heat transfer mediums can be in thermal contact and perform heat exchange. For example, a pipe having a fin and tube structure may be provided inside the housing of the heat exchanger 20 through which one of the two heat transfer mediums, a gaseous heat transfer medium, passes, and the other gaseous or liquid heat transfer medium may pass through the pipe. In addition, known heat exchangers such as double-tube heat exchangers and plate heat exchangers may be used.

[0024] <Carbon Dioxide Recovery Method> The operation of the carbon dioxide recovery system 1 of this embodiment will be explained with reference to Figures 1A and 1B. Generally, in the adsorbent 11, the equilibrium adsorption amount of carbon dioxide is larger at lower temperatures, and smaller at higher temperatures. For this reason, carbon dioxide can be desorbed by heating the adsorbent 11 that has adsorbed carbon dioxide. Adsorption and desorption of carbon dioxide due to temperature changes is called thermal swing adsorption (TSA). In order to make the adsorbent 11, after desorbing carbon dioxide, capable of adsorbing carbon dioxide again, it is necessary to cool the adsorbent 11. Conventionally, the heat removed from the adsorbent 11 was discarded as waste heat, but in this embodiment, this heat is transported to the heat storage material 31 and stored.

[0025] More specifically, Figure 1A shows the state after the adsorbent 11 has been heated and the carbon dioxide adsorbed on it has been desorbed. In this state, the adsorbent 11 is at a high temperature. To regenerate the adsorbent 11, it is cooled (cooling step). In the internal space of the adsorption unit 10, the high-temperature adsorbent 11 is in contact with the first heat transfer medium M1, and the high-temperature adsorbent 11 and the first heat transfer medium M1 are able to directly exchange heat. Therefore, the heat from the heated adsorbent 11 is transferred to the first heat transfer medium M1. The first heat transfer medium M1, having received heat from the adsorbent 11, passes through the flow path F12 and is transported to the heat exchanger 20. In the heat exchanger 20, the heat from the first heat transfer medium M1 is transferred to the second heat transfer medium M2, and the amount of heat in the second heat transfer medium M2 increases. After transferring heat to the second heat transfer medium M2, the first heat transfer medium M1 passes through the flow path F21 and is transported towards the adsorption unit 10. As a result, the temperature of the first heat transfer medium M1 passing through channel F21 is lower than the temperature of the first heat transfer medium M1 passing through channel F12.

[0026] In the heat exchanger 20, the second heat medium M2, having received heat from the first heat medium M1, passes through the flow path F23 and is transported to the second heat quantity change section 30. In the second heat quantity change section 30, the heat from the second heat medium M2 is transferred to the heat storage material 31, and the heat quantity of the heat storage material 31 increases. After transferring heat to the heat storage material 31, the second heat medium M2 passes through the flow path F32 and is transported towards the heat exchanger 20. As a result, the amount of heat in the second heat medium M2 passing through the flow path F32 is less than the amount of heat in the second heat medium M2 passing through the flow path F23. If the heat storage material 31 is a fluid, part or all of the heat storage material 31 circulates through the flow path together with the second heat medium M2.

[0027] In this way, the first heat transfer medium M1 and the second heat transfer medium M2 circulate through the flow path while transporting heat and transferring heat between the adsorption unit 10, the heat exchanger 20, and the second heat quantity change unit 30. As a result, for example, if the temperature of the second heat transfer medium M2 discharged from the second heat quantity change unit 30 is lower than the temperature of the first heat transfer medium M1 discharged from the adsorption unit 10, the excess heat from the adsorbent 11 after carbon dioxide desorption is transported to the second heat quantity change unit 30 by thermal contact between the first heat transfer medium M1 and the second heat transfer medium M2 in the heat exchanger 20, and heat is stored in the second heat quantity change unit 30. Furthermore, the adsorbent 11 is cooled and regenerated to a state where it can adsorb carbon dioxide again.

[0028] After the process shown in Figure 1A, carbon dioxide is adsorbed onto the adsorbent 11 again. When heating the adsorbent 11 to desorb the adsorbed carbon dioxide, the heat stored in the heat storage material 31 can be used. Specifically, as shown in Figure 1B, the heat stored in the heat storage material 31 is transported toward the adsorbent 11 to raise the temperature of the adsorbent 11 (adsorbent heating process). The heat from the heat storage material 31 is transported to the heat exchanger 20 via the second heat transfer medium M2 through the flow path F32. In the heat exchanger 20, the heat from the second heat transfer medium M2 is transferred to the first heat transfer medium M1, and the temperature of the first heat transfer medium M1 rises. After transferring heat to the first heat transfer medium M1, the second heat transfer medium M2 passes through the flow path F23 and is transported toward the second heat quantity change section 30. As a result, the amount of heat in the second heat transfer medium M2 passing through the flow path F23 is less than the amount of heat in the second heat transfer medium M2 passing through the flow path F32.

[0029] In the heat exchanger 20, the first heat medium M1, having received heat from the second heat medium M2, passes through the flow path F21 and is transported to the adsorption section 10. In the adsorption section 10, the heat from the first heat medium M1 causes the temperature of the adsorbent 11 to rise. After transferring heat to the adsorbent 11, the first heat medium M1 passes through the flow path F12 and is transported towards the heat exchanger 20. As a result, the temperature of the first heat medium M1 passing through the flow path F12 is lower than the temperature of the second heat medium M2 passing through the flow path F21.

[0030] Thus, even in the state shown in Figure 1B, the first heat transfer medium M1 and the second heat transfer medium M2 circulate through the flow path while transporting heat and transferring heat between the adsorption unit 10, the heat exchanger 20, and the second heat quantity change unit 30. As a result, for example, if the temperature of the first heat transfer medium M1 discharged from the adsorption unit 10 is lower than the temperature of the second heat transfer medium M2 discharged from the second heat quantity change unit 30, the heat from the second heat quantity change unit 30 is transported to the adsorbent 11 after carbon dioxide adsorption by the movement of the first heat transfer medium M1 and the second heat transfer medium M2, and carbon dioxide is desorbed from the heated adsorbent 11. The desorbed carbon dioxide is mixed with the first heat transfer medium M1 and circulates together with the first heat transfer medium M1 between the adsorption unit 10 and the heat exchanger 20, and then the carbon dioxide is recovered together with the first heat transfer medium M1. In this way, the first heat transfer medium M1 is both a medium for transporting heat and a medium for transporting carbon dioxide, which is the target of recovery.

[0031] Furthermore, during the heating process of the adsorbent 11, the adsorbent 11 may be further heated by the heater 13. In other words, if the heat transported from the second heat quantity change unit 30 is insufficient to raise the adsorbent 11 to the target temperature, the adsorbent 11 may be heated by the heater 13 as needed to compensate for the deficiency. For example, the system may include a thermometer (not shown) for measuring the temperatures of the adsorbent 11, the heat storage material 31, the first heat transfer medium M1, and the second heat transfer medium M2, and a control unit (not shown) for predicting the temperature change of the adsorbent 11 from the temperature measurement results and controlling the operation of the heater 13. If the target temperature of the adsorbent 11 is 120°C, and it is determined that the heat stored in the heat storage material 31 is insufficient to heat the adsorbent 11 to less than 120°C, the control unit may control the heater 13 to compensate for the heat deficiency of the adsorbent 11 with the heat generated by the heater 13.

[0032] Furthermore, as shown in Figures 2A to 2D, the carbon dioxide recovery system 1 may also include a vacuum pump P for sucking up the first heat transfer medium M1 containing carbon dioxide desorbed from the adsorbent 11, and a storage tank T for storing the carbon dioxide. Below, with reference to Figures 2A to 2D, the operation of the carbon dioxide recovery system 1 further comprising the vacuum pump P and the storage tank T, and the method of adsorbing and recovering carbon dioxide will be described. Note that in diagrams illustrating processes in which the vacuum pump P is not operating (for example, Figures 2A, 2B, and 2D of Figures 2A to 2D), the vacuum pump P is not shown.

[0033] As shown in Figure 2A of the carbon dioxide adsorption process, carbon dioxide-containing gas is introduced into the adsorption unit 10 from outside air or a storage tank T via the flow path F1in. At this time, the temperature of the adsorbent 11 is equivalent to the ambient temperature or the temperature of the gas in the storage tank T. The gas containing carbon dioxide, which is the target of recovery, such as outside air or the carbon dioxide-containing gas in the storage tank T, will henceforth be referred to as the target gas. The target gas is not limited to outside air or the carbon dioxide-containing gas in the storage tank T. For example, the target gas may be exhaust gas containing carbon dioxide emitted from various equipment. In the example in Figure 2A, carbon dioxide from the target gas is adsorbed onto the adsorbent 11 contained in the adsorption unit 10, but an adsorbent 11 that has already adsorbed carbon dioxide may be placed in the adsorption unit 10.

[0034] - Heating process for adsorbent 11 The heat stored in the second heat quantity change section 30 (heat storage material 31) is transported toward the adsorbent 11 to raise the temperature of the adsorbent 11. In the example in Figure 2B, outside air introduced into the adsorption section 10 from the flow path F1in is used as the first heat transfer medium M1. If a fluid other than air is used as the first heat transfer medium M1, the fluid may be purged into the adsorption section 10 before the heating process. Similar to the process described in Figure 1B, the heat from the heat storage material 31 is transported to the heat exchanger 20 via the second heat transfer medium M2 through the flow path F32. In the heat exchanger 20, the heat from the second heat transfer medium M2 is transferred to the first heat transfer medium M1, and the temperature of the first heat transfer medium M1 rises. After transferring heat to the first heat transfer medium M1, the second heat transfer medium M2 passes through the flow path F23 and is transported toward the second heat quantity change section 30.

[0035] In the heat exchanger 20, the first heat medium M1, having received heat from the second heat medium M2, passes through the flow path F21 and is transported to the adsorption section 10. In the adsorption section 10, the temperature of the adsorbent 11 rises due to the heat of the first heat medium M1. After transferring heat to the adsorbent 11, the first heat medium M1 passes through the flow path F12 and is transported towards the heat exchanger 20. If the heat transported from the second heat quantity change section 30 is insufficient to raise the adsorbent 11 to the desired temperature, the adsorbent 11 may be heated in the heater 13 as needed to compensate for the deficiency. As a result, the adsorbent 11 is heated to, for example, 120°C, and carbon dioxide is desorbed from the adsorbent 11 using the TSA method. As carbon dioxide is desorbed, the concentration of carbon dioxide contained in the first heat medium M1 increases.

[0036] - Desorption process of carbon dioxide from adsorbent 11 using the PTSA method PTSA (Pressure Thermal Swing adsorption) is the adsorption and desorption of carbon dioxide due to changes in temperature and pressure. As mentioned above, in adsorbent 11, the equilibrium adsorption amount of carbon dioxide is larger at lower temperatures and smaller at higher temperatures. In addition, generally, the equilibrium adsorption amount of carbon dioxide is larger at higher pressures and smaller at lower pressures. By utilizing these characteristics and changing the temperature and pressure, carbon dioxide is desorbed from adsorbent 11.

[0037] As shown in Figure 2C, the vacuum pump P is connected to the heat exchanger 20 by a flow path F2p and to the storage tank T by a flow path Fpt. By sucking the first heat transfer medium M1 containing carbon dioxide from the adsorption section 10 with the vacuum pump P, the pressure inside the adsorption section 10 becomes a low-pressure state, which is lower than atmospheric pressure. The pressure inside the adsorption section 10 may be, for example, -90 kPa or lower than -90 kPa relative to atmospheric pressure, or it may be a vacuum state. Since the equilibrium adsorption amount of carbon dioxide by the adsorbent 11 in the low-pressure state is smaller than the equilibrium adsorption amount at atmospheric pressure, further desorption of carbon dioxide from the adsorbent 11 occurs. Thus, desorption of carbon dioxide from the adsorbent 11 by the PTSA method occurs. The first heat transfer medium M1 containing carbon dioxide, sucked in by the vacuum pump P, transfers heat in the heat exchanger 20 and then heads towards the storage tank T.

[0038] The first heat transfer medium M1 containing carbon dioxide is transported to a storage tank T. In the storage tank T, the carbon dioxide may be concentrated and compressed for storage, or it may be liquefied for storage. Desorption of carbon dioxide is carried out, for example, until the desorption of carbon dioxide from the adsorbent 11 reaches equilibrium. After that, the process proceeds to a cooling step to regenerate the adsorbent 11.

[0039] - Cooling process of the adsorbent 11 The heat from the heated adsorbent 11 is transported toward the second heat quantity change section 30 (heat storage material 31) to cool the adsorbent 11. As shown in Figure 2D, the amount of the first heat transfer medium M1 in the adsorption section 10 is reduced by the suction of the fluid by the vacuum pump P, so air is taken in from the flow path Fo1 provided in the flow path F21 for taking in outside air. As a result, the taken-in outside air becomes the new first heat transfer medium M1 in addition to the fluid remaining in the adsorption section 10. After that, as in the process described in Figure 1B, the heat from the heated adsorbent 11 is transported by the first heat transfer medium M1 through the flow path F12 to the heat exchanger 20. In the heat exchanger 20, the heat from the first heat transfer medium M1 is transferred to the second heat transfer medium M2, and the amount of heat in the second heat transfer medium M2 increases. After transferring heat to the second heat transfer medium M2, the first heat transfer medium M1 passes through the flow path F21 and is transported toward the adsorption section 10.

[0040] In the heat exchanger 20, the second heat transfer medium M2, having received heat from the first heat transfer medium M1, passes through the flow path F23 and is transported to the second heat quantity change section 30. In the second heat quantity change section 30, the heat from the second heat transfer medium M2 is transferred to the heat storage material 31, and the heat quantity of the heat storage material 31 increases. After transferring heat to the heat storage material 31, the second heat transfer medium M2 passes through the flow path F32 and is transported back towards the heat exchanger 20.

[0041] In this way, the movement of the first heat transfer medium M1 and the second heat transfer medium M2 transports the excess heat from the adsorbent 11 after carbon dioxide desorption to the second heat quantity change section 30, where it is stored. Furthermore, the adsorbent 11 is cooled, regenerating it to a state where carbon dioxide can be adsorbed again. A flow path F1o for releasing the taken-in outside air may be provided in the flow path F12. The flow path F1o allows for the release of excess heat or rapid cooling of the adsorbent 11 by increasing the total amount of outside air released.

[0042] Furthermore, it is preferable to allow only the minimum necessary amount of outside air to flow in from the flow path Fo1. By reducing the total amount of air that comes into contact with the adsorbent 11 during the cooling process, the amount of carbon dioxide adsorbed by the adsorbent 11 in the next adsorption process can be increased. As a result, the regenerated adsorbent 11 can be suitably used for DAC (carbon dioxide adsorption by contacting it with air containing low concentrations of carbon dioxide).

[0043] The carbon dioxide adsorption process, the heating process of the adsorbent 11, the decarbonation process of the adsorbent 11, and the cooling process of the adsorbent 11 are repeated in this order, thereby repeatedly recovering carbon dioxide through adsorption and desorption onto the adsorbent 11. When a process moves to the next process, the flow of fluid into the channel and the inflow / outflow of fluid into the channel are switched, and these controls are managed by a control unit (not shown).

[0044] An example of the control of the process transition by the control unit will be described. When the control unit determines to proceed from the carbon dioxide adsorption process to the temperature increase process of the adsorbent 11, the control unit stops the inflow and outflow of the carbon dioxide-containing gas to the adsorption unit 10 from F1in and F1out, and starts the circulation of the first heat medium M1 between the adsorption unit 10 and the heat exchanger 20. Further, the heater 13 is controlled so that the adsorbent 11 is heated to the target temperature as necessary. The circulation of the second heat medium M2 between the second heat quantity change unit 30 and the heat exchanger 20 is started.

[0045] When the control unit determines to proceed from the temperature increase process of the adsorbent 11 to the carbon dioxide desorption process, the control unit closes the flow path F21 from the heat exchanger 20 to the adsorption unit 10 as necessary. Further, the control unit opens the flow paths F2p and Fpt and starts the operation of the vacuum pump P, and recovers the first heat medium M1 containing carbon dioxide from the adsorption unit 10 and the heat exchanger 20 toward the storage tank T.

[0046] When the control unit determines to proceed from the carbon dioxide desorption process to the cooling process of the adsorbent 11, the control unit closes the flow paths F2p and Fpt from the heat exchanger 20 to the vacuum pump P and the storage tank T, opens the flow path F21 from the heat exchanger 20 to the adsorption unit 10 as necessary, and controls so that the first heat medium M1 circulates through the heat exchanger 20 and the adsorption unit 10. Further, when the heater 13 is operating, the heating of the adsorbent 11 by the heater 13 is stopped. Further, the control unit controls the fluid flow in the flow paths Fo1 and F1o so that the intake and discharge of the outside air to the adsorption unit 10 are possible.

[0047] When the control unit determines to proceed from the cooling process of the adsorbent 11 to the carbon dioxide adsorption process, the control unit stops the circulation of the first heat medium M1 between the adsorption unit 10 and the heat exchanger 20, and allows the carbon dioxide-containing gas to flow into the adsorption unit 10.

[0048] Thus, when the control unit determines to proceed to the next step, the control unit controls the carbon dioxide recovery system 1 based on predetermined change conditions. In particular, the control unit controls at least the presence or absence of the circulation of the first heat medium M1 and the presence or absence of inflow into the flow path. Specifically, the control unit: (1) stops the circulation of the first heat medium M1 between the adsorption unit 10 and the heat exchanger 20 during the carbon dioxide adsorption step to the adsorbent 11; (2) causes the first heat medium M1 to circulate between the adsorption unit 10 and the heat exchanger 20 (between the flow path F12 and the flow path F21) during the temperature rise step of the adsorbent 11; (3) causes the first heat medium M1 to flow into the flow paths F2p and Fpt during the carbon dioxide desorption step from the adsorbent 11, and recovers the first heat medium M1 containing carbon dioxide from the adsorption unit 10 and the heat exchanger 20 toward the storage tank T; and (4) causes the first heat medium M1 to circulate between the heat exchanger 20 and the adsorption unit 10 (between the flow path F12 and the flow path F21) during the cooling step of the adsorbent 11. That is, the control unit switches the step by switching at least the flow path of the first heat medium M1. The timing of switching the step may be when each step is performed for a predetermined time, when the temperature of the adsorbent 11 reaches the target temperature, or when it is determined that the carbon dioxide adsorption amount of the adsorbent 11 in each step has reached equilibrium.

[0049] In the carbon dioxide recovery system 1, the heat exchanger 20 and the second heat medium M2 may be omitted. For example, as shown in FIGS. 3A to 3D, the first heat medium M1 passing through the adsorption unit 10 and the heat storage material 31 may be configured to exchange heat in the first heat quantity change unit TC. That is, in the examples of FIGS. 3A to 3D, the first heat quantity change unit TC has the heat storage material 31, and the first heat medium M1 and the heat storage material 31 exchange heat in the first heat quantity change unit TC. In this case, in the first heat quantity change unit TC, the heat storage material 31 and the first heat medium M1 directly exchange heat without passing through the second heat medium M2. The heat storage material 31 may exchange heat with the first heat medium M1隔着隔壁. This can prevent the heat storage material 31 from mixing with the first heat medium M1 even when the heat storage material 31 is a gas or a fluid.

[0050] The carbon dioxide adsorption step shown in FIG. 3A is the same as the step described in FIG. 2A.

[0051] In the heating step of the adsorbent 11 shown in Figure 3B, the first heat transfer medium M1 comes into thermal contact with the heat storage material 31 without passing through the second heat transfer medium M2. The heat from the heat storage material 31 is transported to the adsorption section 10 via the first heat transfer medium M1 through the flow path F31, and the heat from the first heat transfer medium M1 is transferred to the adsorbent 11, causing the temperature of the adsorbent 11 to rise. After transferring heat to the adsorbent 11, the first heat transfer medium M1 passes through the flow path F13 and is transported toward the first heat quantity change section TC. As a result, the temperature of the first heat transfer medium M1 passing through the flow path F13 is lower than the temperature of the first heat transfer medium M1 passing through the flow path F31.

[0052] In the carbon dioxide desorption process shown in Figure 3C, the first heat transfer medium M1 containing carbon dioxide is recovered from the adsorption unit 10 to the storage tank T via the first heat change unit TC. The first heat transfer medium M1 moves from the adsorption unit 10 to the first heat change unit TC via the flow path F13, and then moves from the first heat change unit TC to the vacuum pump P and storage tank T via the flow paths F3p and Fpt. At this time, the heat from the first heat transfer medium M1 is transported to the heat storage material 31 without passing through the second heat transfer medium M2, and the heat is stored in the heat storage material 31. After transferring heat to the heat storage material 31, the first heat transfer medium M1 is recovered to the storage tank T by the vacuum pump P.

[0053] In the cooling process of the adsorbent 11 shown in Figure 3D, the heat from the first heat transfer medium M1, which transports the heat from the heated adsorbent 11, is transported to the heat storage material 31 without passing through the second heat transfer medium M2, and the heat is stored in the heat storage material 31. Thus, in the carbon dioxide recovery system 1 shown in Figures 3A to 3D, which does not have a heat exchanger 20 and a second heat transfer medium M2, the configuration of the first heat quantity change section TC having a heat storage material 31 also functions as a heat exchanger that exchanges heat with the first heat transfer medium M1 passing through the adsorption section 10. The other configurations and operations of the carbon dioxide recovery system 1 shown in Figures 3A to 3D are basically the same as the configurations and operations described in Figures 2A to 2D.

[0054] As described above, the carbon dioxide recovery system 1 according to this embodiment includes an adsorption unit 10 containing an adsorbent 11 that adsorbs carbon dioxide from a target gas, a first heat transfer medium M1 that passes through the adsorption unit 10, and a first heat quantity change unit TC that changes the temperature of the first heat transfer medium M1. The first heat quantity change unit TC includes a heat exchanger 20 through which the second heat transfer medium M2 passes, and a second heat quantity change unit 30 that changes the heat quantity of the second heat transfer medium M2. The first heat transfer medium M1 and the second heat transfer medium M2 exchange heat in the heat exchanger 20, or the first heat quantity change unit TC has a heat storage material 31, and the first heat transfer medium M1 and the heat storage material 31 exchange heat in the first heat quantity change unit TC.

[0055] This makes it possible to reduce the energy required for the adsorption and desorption of carbon dioxide in the adsorbent 11. Furthermore, the second heat change section 30 has a heat storage material 31, or the first heat change section TC has a heat storage material 31. This makes it possible to store the heat removed when cooling the adsorbent 11 after the desorption of carbon dioxide in the heat storage material 31, and reuse it as heat to be used when desorbing carbon dioxide from the adsorbent 11 next time. This makes it possible to reduce the energy required for the adsorption and desorption of carbon dioxide and also reduces the cost of carbon dioxide recovery.

[0056] In the carbon dioxide recovery system 1 shown in Figures 1A to 2D, the first heat transfer medium M1 circulating within the adsorption unit 10 and the heat exchanger 20 serves as a transport medium for both heat and carbon dioxide. In the carbon dioxide recovery system 1 shown in Figures 3A to 3D, the first heat transfer medium M1 circulating within the adsorbent and the first heat change unit TC serves as a transport medium for both heat and carbon dioxide. During the heating step of the adsorbent 11 and the desorption step of carbon dioxide, the total amount of circulating first heat transfer medium M1 remains constant or does not increase excessively. Therefore, the first heat transfer medium M1 can function as a heat transport medium while simultaneously recovering carbon dioxide containing high concentrations of carbon dioxide. Furthermore, because the carbon dioxide contained in the first heat transfer medium M1 is highly concentrated, it is easy to concentrate the carbon dioxide from the recovered first heat transfer medium M1. For example, carbon dioxide can be concentrated in the storage tank T without a multi-stage configuration, thus enabling space-saving of the concentration equipment.

[0057] The system further includes a heater 13 for heating the adsorbent 11, a vacuum pump P for sucking up the first heat transfer medium M1 containing carbon dioxide detached from the adsorbent 11, and a storage tank T for storing carbon dioxide.

[0058] By using the heater 13, even if the heat stored in the heat storage material 31 is insufficient to raise the adsorbent 11 to the desired carbon dioxide desorption temperature, the adsorbent 11 can be raised to the desired temperature. By using the vacuum pump P, carbon dioxide can be desorbed from the adsorbent 11 using the PTSA method. The PTSA method allows for a larger amount of carbon dioxide to be desorbed from the adsorbent 11. By providing a storage tank T, the carbon dioxide desorbed from the adsorbent 11 can be stored.

[0059] Furthermore, the system includes a control unit that switches the flow path of the first heat transfer medium M1. By switching the flow path, carbon dioxide is adsorbed onto the adsorbent 11, the adsorbent 11 is heated, carbon dioxide is desorbed from the adsorbent 11, and the adsorbent 11 is cooled. In this way, in the carbon dioxide recovery system 1, by switching the flow path of the first heat transfer medium M1, the first heat transfer medium M1 can be used as both a heat transport medium and a carbon dioxide transport medium, thereby enabling energy savings in carbon dioxide adsorption and recovery.

[0060] Furthermore, the heat storage material 31 has a melting point lower than the carbon dioxide desorption temperature of the adsorbent 11. As a result, the heat storage material 31 undergoes a phase change when it receives and transfers heat from the object, and by utilizing the latent heat during the phase change, the object can be heated or cooled more efficiently. Moreover, compared to heat storage materials that do not undergo a phase change, the amount of heat stored per unit volume can be increased by utilizing latent heat, so the required volume of heat storage material 31 can be reduced compared to a heat storage material that does not undergo a phase change with the same heat capacity. Therefore, the configuration of the carbon dioxide capture system 1 can be miniaturized.

[0061] The carbon dioxide recovery system 1 according to this embodiment comprises an adsorption unit 10 that houses an adsorbent 11 for adsorbing carbon dioxide from a target gas, a first heat quantity change unit TC having a heat storage material 31 that exchanges heat with a first heat transfer medium M1 that passes through the adsorbent 11, a heater 13 for heating the adsorbent 11, a vacuum pump P for sucking up the first heat transfer medium M1 containing carbon dioxide desorbed from the adsorbent 11, and a storage tank T for storing carbon dioxide.

[0062] This allows the heat removed when cooling the adsorbent 11 after carbon dioxide has been removed to be stored in the heat storage material 31 and reused as heat when carbon dioxide is removed from the adsorbent 11 next time. Therefore, the energy required for carbon dioxide adsorption and desorption can be reduced, and the cost of carbon dioxide recovery can also be lowered.

[0063] Embodiment 2. Next, the carbon dioxide capture system 1 according to Embodiment 2 will be described with reference to Figures 4A to 4D. The carbon dioxide capture system 1 according to this embodiment has the same basic configuration as Embodiment 1, so the differences will be explained in detail.

[0064] As shown in Figures 4A to 4D, in this embodiment, a part of the heat pump H is used as the second heat quantity change section 30 and heat exchanger 20 of the first heat quantity change section TC. The heat pump H comprises a compressor Cm, a condenser C, an expansion valve Ev, and an evaporator E. The second heat transfer medium M2 circulates through the compressor Cm, condenser C, expansion valve Ev, and evaporator E in this order. At this time, the second heat transfer medium M2 circulates through a flow path Fce from condenser C to evaporator E, and a flow path Fec from evaporator E to condenser C. The second heat transfer medium M2 is the refrigerant of the heat pump H, and examples include hydrofluoroolefins, hydrocarbons, and refrigerants mainly composed of carbon dioxide, with a global warming potential (GWP) of 10 or less. The operating state of the compressor Cm and the expansion valve Ev is controlled by a control unit (not shown).

[0065] The carbon dioxide adsorption process shown in Figure 4A is the same as the adsorption process described in Figure 2A.

[0066] ・Heating process of adsorbent 11 In the heating process shown in Figure 4B, the first heat transfer medium M1 circulates through the flow path F1c from the adsorption unit 10 to the condenser C, and through the flow path Fc1 from the condenser C to the adsorption unit 10. In the heat pump H, the second heat transfer medium M2 is drawn into the compressor Cm in a gaseous state, compressed into a high-temperature, high-pressure gas, and discharged. Furthermore, the second heat transfer medium M2 condenses in the condenser C, changing from a gas to a liquid. The heat generated by the phase change of the second heat transfer medium M2 and the heat transported from the evaporator E are transported to the first heat transfer medium M1 passing through the condenser C. Subsequently, the liquid second heat transfer medium M2 is depressurized by the expansion valve Ev to become low temperature and low pressure, evaporates in the evaporator E to become a gas, and is drawn into the compressor Cm again. The evaporator E takes in outside air from the flow path Foe and absorbs heat from the outside air. This outside air is released from the flow path Feo. The heat transport by the first heat transfer medium M1 is the same as the heating process described in Figure 2B.

[0067] Thus, in the heating step of the adsorbent 11, the condenser C becomes a heat exchanger 20 that exchanges heat with the first heat transfer medium M1 passing through the adsorbent 11, and the evaporator E becomes a second heat quantity changing section 30 in which the heat quantity of the second heat transfer medium M2 changes.

[0068] ・Desorption process of carbon dioxide from adsorbent 11 using the PTSA method In the carbon dioxide desorption process shown in Figure 4C, the first heat transfer medium M1 containing carbon dioxide is sucked up by the vacuum pump P via the evaporator E and moved to the storage tank T. That is, the first heat transfer medium M1 containing carbon dioxide moves in the following order: through the flow path F1e from the adsorption unit 10 to the evaporator E, through the flow path Fep from the evaporator E to the vacuum pump P, and through the flow path Fpt from the vacuum pump P to the storage tank T. In the evaporator E of the heat pump H, the first heat transfer medium M1 containing carbon dioxide exchanges heat with the second heat transfer medium M2. At this time, in the evaporator E, heat can be efficiently transported from the first heat transfer medium M1 to the second heat transfer medium M2 and heat can be stored in the condenser C due to the endothermic effect of the phase change of the second heat transfer medium M2 from liquid to gas.

[0069] In the evaporator E, the second heat transfer medium M2, having received heat from the first heat transfer medium M1, is transported to the condenser C. After undergoing a heat transformation in the condenser C, the second heat transfer medium M2 is transported back towards the evaporator E.

[0070] Thus, in the carbon dioxide desorption process, the evaporator E becomes a heat exchanger 20 that exchanges heat with the first heat transfer medium M1 passing through the adsorbent 11, and the condenser C becomes a second heat quantity change section 30 where the heat quantity of the second heat transfer medium M2 changes. The principle of carbon dioxide desorption using the PTSA method is the same as the principle explained in Figure 2C.

[0071] - Cooling process of adsorbent 11 As shown in Figure 4D, the heat from the heated adsorbent 11 is transported to the condenser C via the evaporator E to cool the adsorbent 11. This is the same process as described in Figures 1B and 2D, but the heat from the heated adsorbent 11 moves through the flow path F1e via the first heat transfer medium M1 and is transported to the evaporator E. In the evaporator E, along with the endothermic reaction, the heat from the first heat transfer medium M1 is transferred to the second heat transfer medium M2. After transferring heat to the second heat transfer medium M2, the first heat transfer medium M1 moves through the flow path Fe1 and is transported toward the adsorption section 10. A flow path Fo1 into which outside air flows toward the adsorption section 10 may be connected to the flow path Fe1.

[0072] In the evaporator E, the second heat transfer medium M2, having received heat from the first heat transfer medium M1, is transported to the condenser C. After undergoing a heat transformation in the condenser C, the second heat transfer medium M2 is transported back towards the evaporator E.

[0073] Thus, in the cooling process of the adsorbent 11, the evaporator E becomes a heat exchanger 20 that exchanges heat with the first heat transfer medium M1 passing through the adsorbent 11, and the condenser C becomes a second heat quantity changing section 30 in which the heat quantity of the second heat transfer medium M2 changes.

[0074] As described above, the carbon dioxide recovery system 1 according to this embodiment includes a heat pump H having an evaporator E, a condenser C, a compressor Cm, and an expansion valve Ev, and the heat exchanger 20 and the second heat quantity change unit 30 are part of the heat pump H.

[0075] In this way, by using the heat pump H, the adsorbent 11 can be heated with less energy consumption. In addition, the energy consumption when heating the adsorbent 11 with the heater 13 can be reduced. Furthermore, in the cooling process of the adsorbent 11, the adsorbent 11 is cooled using the heat pump H, so the cooling time can be shortened and the amount recovered per unit time in cycle operation can be increased compared to when the adsorbent 11 is cooled with outside air.

[0076] Embodiment 3. Next, the carbon dioxide capture system 1 according to Embodiment 3 will be described with reference to Figures 5A to 5E. The carbon dioxide capture system 1 according to this embodiment has the same basic configuration as Embodiments 1 and 2, so the differences will be explained in detail.

[0077] As shown in Figures 5A to 5E, in this embodiment, a part of the heat pump H, an auxiliary heat exchanger 20a, and an auxiliary heat storage unit 30a are used as the second heat quantity change section 30 and heat exchanger 20 of the first heat quantity change section TC. The heat pump H has the same configuration as in Embodiment 2, but the manner in which the heat transfer medium passes through is different. The auxiliary heat exchanger 20a and the auxiliary heat storage unit 30a have the same configuration as the heat exchanger 20 and the second heat quantity change section 30 having a heat storage material 31 in Embodiment 1, respectively, but since the manner in which the heat transfer medium passes through is different, in this Embodiment 3 they are referred to as the auxiliary heat exchanger 20a and the auxiliary heat storage unit 30a. The heat transfer medium circulating in the auxiliary heat exchanger 20a and the auxiliary heat storage unit 30a is a medium that exchanges heat with the first heat transfer medium M1, and therefore constitutes a part of the second heat transfer medium M2. Hereafter, the heat transfer medium circulating in the auxiliary heat exchanger 20a and the auxiliary heat storage unit 30a will be specifically referred to as the second auxiliary heat transfer medium M2a. The second auxiliary heat transfer medium M2a circulates in the flow path F2a3a from the auxiliary heat exchanger 20a to the auxiliary heat storage unit 30a, and in the flow path F3a2a from the auxiliary heat storage unit 30a to the auxiliary heat exchanger 20a.

[0078] The carbon dioxide adsorption process shown in Figure 5A is the same as that shown in Figure 2A.

[0079] ・Heating process of adsorbent 11 In the heating process shown in Figure 5B, the heat pump H performs the operation described in the process shown in Figure 4B. The first heat transfer medium M1 circulates through the flow path F1c from the adsorption unit 10 to the condenser C, and through the flow path Fc1 from the condenser C to the adsorption unit 10. In the condenser C, the first heat transfer medium M1 exchanges heat with the second heat transfer medium M2 circulating inside the heat pump H and is heated. Furthermore, in the carbon dioxide recovery system 1 of this embodiment, outside air taken in by the auxiliary heat exchanger 20a is merged with the first heat transfer medium M1. The outside air is taken in from the auxiliary heat exchanger 20a through the flow path Fo2a, and this outside air is heated by the heat transported from the auxiliary heat storage unit 30a by the second auxiliary heat transfer medium M2a. The outside air heated in the auxiliary heat exchanger 20a passes through the flow path F2ac and is merged into the flow path F1c from the adsorption unit 10 to the condenser C. As a result, the heated outside air is mixed with the first heat transfer medium M1.

[0080] Furthermore, it is preferable to limit the intake of outside air from the auxiliary heat exchanger 20a to the minimum necessary amount. This is because if a large amount of outside air is taken in, the amount of the first heat transfer medium M1 (recovered gas) containing carbon dioxide obtained in the carbon dioxide desorption process will increase, which may lead to a decrease in the carbon dioxide concentration of the recovered gas.

[0081] Thus, in the heating step of the adsorbent 11, the condenser C becomes a heat exchanger 20 that exchanges heat with the first heat transfer medium M1 passing through the adsorbent 11, and the evaporator E becomes a second heat quantity change section 30 where the heat quantity of the second heat transfer medium M2 changes. Furthermore, the auxiliary heat exchanger 20a can be said to constitute a part of the heat exchanger 20 because it exchanges heat with the outside air which becomes the first heat transfer medium M1 passing through the adsorbent 11. In the auxiliary heat storage section 30a, the heat quantity of the second auxiliary heat transfer medium M2a, which constitutes a part of the second heat transfer medium M2, changes, so it can also be said to constitute a part of the second heat quantity change section 30.

[0082] ・Desorption process of carbon dioxide from adsorbent 11 using the PTSA method In the carbon dioxide desorption process shown in Figure 5C, the first heat transfer medium M1 containing carbon dioxide is sucked from the adsorption unit 10 through the auxiliary heat exchanger 20a by the vacuum pump P and moves to the storage tank T. That is, the first heat transfer medium M1 containing carbon dioxide moves in the following order: through the flow path F12a from the adsorption unit 10 to the auxiliary heat exchanger 20a, through the flow path F2ap from the auxiliary heat exchanger 20a to the vacuum pump P, and through the flow path Fpt from the vacuum pump P to the storage tank T. In the auxiliary heat exchanger 20a, the first heat transfer medium M1 containing carbon dioxide, which has been heated to a temperature that allows carbon dioxide to be desorbed from the adsorbent 11, and the second auxiliary heat transfer medium M2a exchange heat. That is, the heat from the first heat transfer medium M1 is transferred from the auxiliary heat exchanger 20a to the auxiliary heat storage unit 30a by the second auxiliary heat transfer medium M2a and stored.

[0083] Thus, in the carbon dioxide desorption process, the auxiliary heat exchanger 20a becomes a heat exchanger 20 that exchanges heat with the first heat transfer medium M1 passing through the adsorbent 11, and the auxiliary heat storage unit 30a becomes a second heat quantity changing unit 30 in which the heat quantity of the second auxiliary heat transfer medium M2a, which constitutes a part of the second heat transfer medium M2, changes. The principle of carbon dioxide desorption using the PTSA method is the same as the principle explained in Figure 2C.

[0084] - Cooling process of adsorbent 11 In the adsorption process shown in Figure 5D, the fluid remaining in the adsorption section 10 after the desorption process, and the outside air taken in from the flow path Fo1 become the first heat transfer medium M1, which transports the heat of the adsorbent 11. The first heat transfer medium M1 is cooled in the auxiliary heat exchanger 20a and returned to the adsorption section 10 again.

[0085] Specifically, the first heat transfer medium M1 released from the adsorption unit 10 moves through the flow path F12a and is transported to the auxiliary heat exchanger 20a. In the auxiliary heat exchanger 20a, the heat from the first heat transfer medium M1 is transferred to the second auxiliary heat transfer medium M2a and stored in the auxiliary heat storage unit 30a. The heat stored in the auxiliary heat storage unit 30a during the carbon dioxide desorption process and the cooling process of the adsorbent 11 is used to raise the temperature of the outside air during the next temperature-raising process of the adsorbent 11. After transferring heat to the second auxiliary heat transfer medium M2a, the first heat transfer medium M1 moves through the flow path F2a1 and is transported towards the adsorption unit 10.

[0086] Thus, in the cooling process of the adsorbent 11, the auxiliary heat exchanger 20a becomes a heat exchanger 20 that exchanges heat with the first heat transfer medium M1 passing through the adsorbent 11, and the auxiliary heat storage unit 30a becomes a second heat quantity changing unit 30 in which the heat quantity of the second auxiliary heat transfer medium M2a, which constitutes a part of the second heat transfer medium M2, changes.

[0087] Furthermore, during the cooling process of the adsorbent 11, the heat from the condenser C may be transported to the auxiliary heat exchanger 20a. For example, as shown in Figure 5E, the heat from the condenser C may be transported to the auxiliary heat exchanger 20a by a heat transfer medium Mc that moves the flow path Fc2a from the condenser C to the auxiliary heat exchanger 20a. In this case, as shown in Figure 5E, the first heat transfer medium M1 discharged from the adsorption unit 10 may be cooled in the auxiliary heat exchanger 20a and evaporator E before being returned to the adsorption unit 10.

[0088] Specifically, a portion of the first heat transfer medium M1 released from the adsorption unit 10 is transported to the auxiliary heat exchanger 20a in the same manner as described in Figure 5D.

[0089] The remaining first heat transfer medium M1 released from the adsorption unit 10 moves through the flow path F1e and is transported to the evaporator E. In the evaporator E, the heat from the first heat transfer medium M1 is transferred to the second heat transfer medium M2 and transported to the condenser C. Furthermore, the heat transported to the condenser C during the cooling process of the adsorbent 11 is transported to the auxiliary heat exchanger 20a in order to be used to raise the temperature of the first heat transfer medium M1 during the next temperature-raising process of the adsorbent 11. The heat from the condenser C to the auxiliary heat exchanger 20a may be transported by the heat transfer medium Mc moving through the flow path FC2a from the condenser C to the auxiliary heat exchanger 20a, or by other heat transfer means. The heat transported to the auxiliary heat exchanger 20a is stored in the auxiliary heat storage unit 30a.

[0090] Here, with reference to Figures 5F to 5G, an example of heat transfer between the auxiliary heat exchanger 20a and the auxiliary heat storage unit 30a from the heat transfer medium Mc moving through the flow path FC2a and the first heat transfer medium M1 moving through the flow path F12a will be described. The auxiliary heat exchanger 20a has a part of the flow path F12a and a plurality of fins F12a-f erected in the flow path F12a. In the example of Figure 5F, the flow path F12a is a pipe that has been branched into two, and has a first flow path F12a-1 and a second flow path F12a-2. The first flow path F12a-1 and the second flow path F12a-2 are U-shaped pipes. In Figures 5F and 5G, the forward path of the first flow path F12a-1 is denoted by the symbol F12a-1i, and the return path is denoted by the symbol F12a-1o. The forward path of the second flow path F12a-2 is denoted as F12a-2i, and the return path as F12a-2o. The fins F12a-f are provided spanning the first flow path F12a-1 and the second flow path F12a-2, respectively. The space between the fins F12a-f forms the flow path FC2a through which the heat transfer medium Mc passes.

[0091] The auxiliary heat storage unit 30a is positioned to cover the return paths F12a-1o and F12a-2o. This brings the auxiliary heat exchanger 20a and the auxiliary heat storage unit 30a into thermal contact. The forward paths F12a-1i and F12a-2i are not covered by the auxiliary heat storage unit 30a.

[0092] In the outbound paths F12a-1i and F12a-2i, heat is transferred from the heat transfer medium Mc to the first heat transfer medium M1. At this time, heat can be efficiently transported from the heat transfer medium Mc passing through the flow path Fc2a to the first heat transfer medium M1 via the fins F12a-f. In the return paths F12a-1o and F12a-2o, heat is transferred from the first heat transfer medium M1 to the auxiliary heat storage unit 30a. In the example shown in Figures 5F and 5G, the auxiliary heat exchanger 20a and the auxiliary heat storage unit 30a are integrated into a single structure. As a result, the heat from the first heat transfer medium M1 and the heat from the heat transfer medium Mc moving through the flow path FC2a from the condenser C to the auxiliary heat exchanger 20a are transported to the auxiliary heat storage unit 30a via the auxiliary heat exchanger 20a, and the heat can be stored in the auxiliary heat storage unit 30a. However, it is preferable that the relationship between the temperature of the heat transfer medium Mc > the temperature of the first heat transfer medium M1 > the temperature of the auxiliary heat storage unit 30a is satisfied when heat is being transported. Note that heat may be transported directly from the fins F12a-f to the auxiliary heat storage unit 30a without going through the piping of the flow path F12a of the auxiliary heat exchanger 20a.

[0093] In the configuration shown in Figure 5E, the capacity of the heat pump H can be used to cool the first heat transfer medium M1, thereby shortening the cooling time of the adsorbent 11 and increasing the amount recovered per unit time during cycle operation. In addition, since the amount of outside air that comes into contact with the adsorbent 11 during the cooling process can be reduced, the amount of carbon dioxide adsorbed onto the adsorbent 11 in the next adsorption process can be increased.

[0094] In the cooling process of the adsorbent 11 shown in Figure 5E, the evaporator E and auxiliary heat exchanger 20a become a heat exchanger 20 that exchanges heat with the first heat transfer medium M1 passing through the adsorbent 11, and the condenser C and auxiliary heat storage unit 30a become a second heat quantity changing unit 30 in which the heat quantity of the second heat transfer medium M2, which includes the second auxiliary heat transfer medium M2a, changes.

[0095] As described above, the carbon dioxide recovery system 1 according to this embodiment includes a heat pump H having an evaporator E, a condenser C, a compressor Cm, and an expansion valve Ev, an auxiliary heat exchanger 20a, and an auxiliary heat storage unit 30a, wherein the heat exchanger 20 and the second heat quantity change unit 30 are part of the heat pump H, the auxiliary heat exchanger 20a, or the auxiliary heat storage unit 30a.

[0096] This makes it possible to supply heat to the first heat transfer medium M1 and raise the temperature of the adsorbent 11 with less energy consumption by utilizing the heat pump H. It also makes it possible to reduce the energy consumption of the heater 13. Furthermore, since the capacity of the heat pump H can be used to cool the first heat transfer medium M1, the cooling time of the adsorbent 11 can be shortened compared to when the adsorbent 11 is cooled with outside air, and the amount recovered per unit time during cycle operation can be increased.

[0097] Embodiment 4. Next, the carbon dioxide capture system 1 according to Embodiment 4 will be described with reference to Figures 6A to 8. The carbon dioxide capture system 1 according to this embodiment has the same basic configuration as Embodiments 1 to 3, so the differences will be explained in detail.

[0098] As shown in Figures 6A to 8, this embodiment further includes a switching valve V1 located downstream of the adsorption unit 10. The switching valve V1 switches the flow path of the first heat transfer medium M1 that has flowed out of the adsorption unit 10 to either a flow path F11 that circulates the first heat transfer medium M1 back to the adsorption unit 10, or a flow path (F12, F1e, F12a) that transports it to the heat exchanger 20. Furthermore, an introduction switching valve V2 may be provided upstream of the adsorption unit 10. The introduction switching valve V2 switches whether or not outside air is introduced into the first heat transfer medium M1, and the direction in which the outside air is introduced. When outside air is introduced from the introduction switching valve V2, the flow path of the outside air is switched to either a flow path Fv21 that directs it towards the adsorption unit 10, or a flow path (Fv22, Fv2e, Fv22a) that transports it to the heat exchanger 20. The switching valve V1 and the introduction switching valve V2 are controlled by a control unit (not shown).

[0099] Figure 6A shows a carbon dioxide recovery system 1 according to Embodiment 1, in which a switching valve V1 and an introduction switching valve V2 are provided. In the carbon dioxide desorption process from the adsorbent 11, the switching valve V1 changes the flow path of the first heat transfer medium M1. When the switching valve V1 directs the first heat transfer medium M1 towards the flow path F11 and circulates the adsorption unit 10, the first heat transfer medium M1 can be repeatedly brought into contact with the adsorbent 11. This makes it possible to further increase the carbon dioxide concentration of the first heat transfer medium M1.

[0100] In this case, outside air may be introduced from the introduction switching valve V2 and mixed with the first heat transfer medium M1. The outside air is taken in from the introduction switching valve V2 and flows towards the adsorption unit 10 via the flow path Fv21. The outside air has a lower carbon dioxide concentration than the first heat transfer medium M1 which contains carbon dioxide desorbed from the adsorbent 11. Therefore, adding outside air to the first heat transfer medium M1 reduces the carbon dioxide concentration. As a result, the amount of carbon dioxide desorbed from the adsorbent 11 can be increased. Alternatively, as shown in Figure 6B, the switching valve V1 may direct the first heat transfer medium M1 discharged from the adsorption unit 10 only to the flow path F11, while the outside air taken in from the introduction switching valve V2 is introduced into the heat exchanger 20 via the flow path Fv22, the outside air is heated by the second heat transfer medium M2, and then the flow path F21 through which the heated outside air passes is merged with the flow path F11 to combine the heated outside air with the first heat transfer medium M1. Alternatively, to compensate for the temperature drop caused by the introduction of outside air, the adsorbent 11 may be heated by the heater 13, or an auxiliary heater (not shown) may be used to preheat the outside air introduced from the flow path Fo1.

[0101] Figure 7 shows a carbon dioxide recovery system 1 according to Embodiment 2, equipped with a switching valve V1 and an inlet switching valve V2. Figure 8 shows a carbon dioxide recovery system 1 according to Embodiment 3, equipped with a switching valve V1 and an inlet switching valve V2. The operation of the switching valve V1 and the inlet switching valve V2 in the carbon dioxide recovery system 1 shown in Figures 7-8 is the same as the operation described in Figures 6A-6B.

[0102] The fluid introduced from the flow path Fo1 is not limited to outside air. For example, exhaust gas with a higher temperature than the outside air may be taken in from the flow path Fo1 and supplied to the heat exchanger 20 through the flow paths (Fv22, Fv2e, Fv22a) leading from the introduction switching valve V2 to the heat exchanger 20. Since the heat from the exhaust gas is transported to the second heat quantity change section 30, for example, the excess heat from the exhaust gas stored in the heat storage material 31 of the second heat quantity change section 30 can be used in the subsequent heating and desorption steps. The exhaust gas after transferring heat may be released into the atmosphere or the like through an unillustrated discharge flow path. Alternatively, after transferring heat in the heat exchanger 20, the exhaust gas may pass through a flow path leading to the storage tank T (flow paths F2p and Fpt in Figure 6A) and be stored in the storage tank T, and then flow into the adsorption section 10 from flow path F1in as a target gas containing carbon dioxide, which is to be recovered in the next adsorption step. In this way, by using the switching valve V1 and the introduction switching valve V2, the degree of freedom in controlling the fluid flow is increased, and a system that can recover carbon dioxide more efficiently can be created.

[0103] As described above, the carbon dioxide recovery system 1 according to this embodiment further includes a switching valve V1 located downstream of the adsorbent 11 in the flow path through which the first heat transfer medium M1 passes. The switching valve V1 switches the flow path of the first heat transfer medium M1 to a flow path (F12, F1e, F12a) leading to the heat exchanger 20, or to a flow path F11 that reintroduces the fluid to the adsorption unit 10.

[0104] When the first heat transfer medium M1 is circulated multiple times through the flow path F11 into the adsorption unit 10, the carbon dioxide concentration in the first heat transfer medium M1 can be increased. As a result, for example, when the control unit determines that the carbon dioxide concentration in the circulating first heat transfer medium M1 has reached a target concentration, or when it determines that the desorption of carbon dioxide from the adsorbent 11 has reached equilibrium, the switching valve V1 can be used to switch the flow path of the first heat transfer medium M1 and recover the first heat transfer medium M1 containing a high concentration of carbon dioxide.

[0105] Other embodiments or modifications described above may be combined as appropriate.

[0106] Furthermore, the control unit described above has an internal computer system. The control unit may perform the processing described above by recording a program for realizing the functions of each component of the carbon dioxide capture system 1 onto a computer-readable recording medium, loading the program recorded on this recording medium into the computer system, and executing it. Alternatively, hardware other than the control unit may perform the processing described above.

[0107] Here, "loading a program recorded on a recording medium into a computer system and executing it" includes installing the program into the computer system. "Computer system" here includes the operating system and peripheral hardware.

[0108] Furthermore, "computer system" may include multiple computer devices connected via a network including the Internet or communication lines such as WANs, LANs, and dedicated lines. "Computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, as well as storage devices such as hard disks built into computer systems. Thus, the recording medium storing the program may also be a non-transient recording medium such as a CD-ROM.

[0109] Furthermore, the recording medium also includes internal or external recording media accessible from the distribution server for distributing the program. The program may be divided into multiple parts, each downloaded at a different time, and then combined in each configuration of the carbon dioxide capture system 1. The distribution servers distributing each of the divided programs may also be different. Moreover, "computer-readable recording media" includes volatile memory (RAM) within a computer system that acts as a server or client when the program is transmitted over a network, which retains the program for a certain period of time. The program itself may also be intended to implement some of the functions described above. Furthermore, the program may be a so-called differential file (differential program) that can implement the functions described above in combination with a program already recorded in the computer system.

[0110] 1...Carbon dioxide recovery system, 10...Adsorption unit, 11...Adsorbent, 12...Housing, 13...Heater, 20...Heat exchanger, 20a...Auxiliary heat exchanger, 30...Second heat quantity change unit, 30a...Auxiliary heat storage unit, 31...Heat storage material, P...Vacuum pump, T...Storage tank, TC...First heat quantity change unit, H...Heat pump, Cm...Compressor, C...Condenser, Ev...Expansion valve, E...Evaporator, V1...Switching valve

Claims

1. A carbon dioxide recovery system comprising: an adsorption section containing an adsorbent for adsorbing carbon dioxide from a target gas; a first heat transfer medium passing through the adsorption section; and a first heat quantity changing section for changing the temperature of the first heat transfer medium, wherein the first heat quantity changing section comprises a heat exchanger through which a second heat transfer medium passes and a second heat quantity changing section for changing the heat quantity of the second heat transfer medium, and the first heat transfer medium and the second heat transfer medium exchange heat in the heat exchanger, or the first heat quantity changing section has a heat storage material, and the first heat transfer medium and the heat storage material exchange heat in the first heat quantity changing section.

2. The carbon dioxide recovery system according to claim 1, further comprising: a heater for heating the adsorbent; a vacuum pump for sucking up the first heat transfer medium containing carbon dioxide desorbed from the adsorbent; and a storage tank for storing the carbon dioxide.

3. The carbon dioxide recovery system according to claim 1 or 2, wherein the second heat quantity change section has a heat storage material.

4. A carbon dioxide recovery system according to claim 1 or 2, comprising a heat pump having an evaporator, a condenser, a compressor, and an expansion valve, wherein the heat exchanger and the second heat quantity changing section are part of the heat pump.

5. A carbon dioxide recovery system according to claim 1 or 2, comprising a heat pump having an evaporator, a condenser, a compressor, and an expansion valve; an auxiliary heat exchanger; and an auxiliary heat storage unit, wherein the heat exchanger and the second heat quantity change unit are part of the heat pump, the auxiliary heat exchanger, or the auxiliary heat storage unit.

6. A carbon dioxide recovery system according to any one of claims 1 to 5, further comprising a control unit for switching the flow path of the first heat transfer medium, wherein the switching of the flow path performs the adsorption of carbon dioxide onto the adsorbent, the heating of the adsorbent, the desorption of carbon dioxide from the adsorbent, and the cooling of the adsorbent.

7. The carbon dioxide recovery system according to any one of claims 1 to 6, further comprising a switching valve provided downstream of the adsorption unit in the flow path through which the first heat transfer medium passes, wherein the switching valve switches the flow path of the first heat transfer medium to a flow path toward the heat exchanger or a flow path toward reintroduction to the adsorption unit.

8. A carbon dioxide recovery system comprising: an adsorption section containing an adsorbent for adsorbing carbon dioxide from a target gas; a first heat quantity change section having a heat storage material that exchanges heat with a first heat transfer medium through which the adsorbent passes; a heater for heating the adsorbent; a vacuum pump for sucking up the first heat transfer medium containing carbon dioxide desorbed from the adsorbent; and a storage tank for storing the carbon dioxide.

9. The carbon dioxide recovery system according to any one of claims 1 to 8, wherein the heat storage material has a melting point lower than the carbon dioxide desorption temperature of the adsorbent.

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