Carbon dioxide recovery apparatus and carbon dioxide recovery method

Abstract

This carbon dioxide recovery apparatus comprises: a separation unit that accommodates therein an adsorbent that has adsorbed carbon dioxide; an adjustment gas supply device that generates an adjustment gas of which the temperature has been controlled; a first flow path that supplies the adjustment gas to the separation unit; a second flow path that is connected from the separation unit to the adjustment gas supply device and causes a gas inside the separation unit to flow into the adjustment gas supply device; a first on-off valve that is provided in the first flow path; a second on-off valve that is provided in the second flow path; and a recovery flow path that is connected to the separation unit and is provided with a vacuum pump which sucks the gas inside the separation unit. The first on-off valve and the second on-off valve are opened when the adjustment gas is supplied to the separation unit, and the first on-off valve and the second on-off valve are closed when the gas inside the separation unit is sucked from the recovery flow path.

Description

Carbon Dioxide Recovery Device and Carbon Dioxide Recovery Method

[0001] The present disclosure relates to a carbon dioxide recovery device and a carbon dioxide recovery method. This application claims priority based on Japanese Patent Application No. 2024-160973 filed in Japan on September 18, 2024, and incorporates its content herein by reference.

[0002] Patent Document 1 discloses a separator for recovering carbon dioxide from gases discharged from a combustion furnace or the like. The separator includes an adsorbent for adsorbing carbon dioxide. The separator is connected to a source of carbon dioxide-containing gas such as a combustion furnace in a factory, and adsorbs carbon dioxide in the gas with the adsorbent (adsorption step). After the adsorption step, in order to desorb carbon dioxide from the adsorbent, the pressure and temperature inside the separator are changed to switch between the carbon dioxide adsorption step and the desorption step. Thus, in Patent Document 1, carbon dioxide in the exhaust gas is recovered by pressure-temperature swing adsorption (PTSA: Pressure Thermal Swing adsorption).

[0003] Japanese Patent Application Laid-Open No. 2022-188322

[0004] In the recovery of carbon dioxide by PTSA of Patent Document 1, when desorbing carbon dioxide from the adsorbent, a heat medium is introduced into the separator while reducing the pressure inside the separator. In this case, in the desorption step, since the heat medium is introduced into the separator, it becomes difficult to reduce the pressure inside the separator, and there is a possibility that the desorption of carbon dioxide from the adsorbent may not be sufficient.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a carbon dioxide recovery device and a carbon dioxide recovery method capable of increasing the amount of carbon dioxide desorbed from an adsorbent that has adsorbed carbon dioxide.

[0006] The carbon dioxide recovery apparatus in this disclosure comprises: a separation unit containing an adsorbent that has adsorbed carbon dioxide; a conditioning gas supply device that generates a temperature-controlled conditioning gas; a first flow path for supplying the conditioning gas to the separation unit; a second flow path connected from the separation unit to the conditioning gas supply device and allowing the gas in the separation unit to flow into the conditioning gas supply device; a first on-off valve provided in the first flow path; a second on-off valve provided in the second flow path; and a recovery flow path connected to the separation unit and equipped with a vacuum pump for sucking the gas in the separation unit, wherein the first on-off valve and the second on-off valve are opened when supplying the conditioning gas to the separation unit, and the first on-off valve and the second on-off valve are closed when sucking the gas in the separation unit from the recovery flow path.

[0007] The carbon dioxide recovery method in this disclosure involves housing an adsorbent containing carbon dioxide in a separation unit, supplying a temperature-controlled adjustment gas to the separation unit, and then depressurizing the separation unit after stopping the supply of the adjustment gas to the separation unit.

[0008] According to this disclosure, it is possible to provide a carbon dioxide recovery device and a carbon dioxide recovery method that can increase the amount of carbon dioxide released from an adsorbent that has adsorbed carbon dioxide.

[0009] This is a schematic diagram of a carbon dioxide recovery apparatus according to Embodiment 1, illustrating the TSA process. This is a schematic diagram of a carbon dioxide recovery apparatus according to Embodiment 1, illustrating the PSA process. This is a schematic diagram of a carbon dioxide recovery apparatus according to Embodiment 2. This is a schematic diagram of a carbon dioxide recovery apparatus according to Embodiment 3.

[0010] 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.

[0011] Embodiment 1. First, the basic configuration of the carbon dioxide recovery device 1 in Embodiment 1 will be described. Figures 1A to 1B are schematic diagrams of the carbon dioxide recovery device 1 according to Embodiment 1. As shown in Figures 1A to 1B, the carbon dioxide recovery device 1 includes a separation unit 10 that houses an adsorbent 11 that has adsorbed carbon dioxide, a regulating gas supply device 20 that generates a regulated gas at a controlled temperature, a first flow path 30 that supplies the regulated gas to the separation unit 10, a second flow path 40 connected from the separation unit 10 to the regulating gas supply device 20 and allowing the gas in the separation unit 10 to flow into the regulating gas supply device 20, a first on-off valve 31 provided in the first flow path 30, a second on-off valve 41 provided in the second flow path 40, and a recovery flow path 60 connected to the separation unit 10 and equipped with a vacuum pump 62 that sucks the gas in the separation unit 10.

[0012] The separation unit 10 includes a separation container 12. An adsorbent 11 is placed in the separation container 12. The adsorbent 11 contains a material capable of adsorbing carbon dioxide. Examples of materials for the adsorbent 11 include amines, zeolites, silica gel, diatomaceous earth, alumina, and 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. In the example shown in Figure 1A, spherical adsorbent 11 is placed in the separation container 12. The adsorbent 11 may also be supported on the surface of a substrate. The substrate may be, for example, a plate having a honeycomb structure with a plurality of substantially 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 a plurality of pores smaller than the particle size of the adsorbent 11. The case may be formed entirely or partially from a mesh structure in which wires are woven. The materials of the base material 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 separation container 12 is a container capable of containing the adsorbent 11 and can be airtightly sealed with the adsorbent 11 contained inside. For example, the separation container 12 in this embodiment is a box-shaped container composed of six surfaces. However, the separation container 12 is not limited to a box shape and may be cylindrical, for example. The separation container 12 has an opening 12a for inserting and removing the adsorbent 11 from the separation container 12 and a door portion 12b for airtightly sealing the opening 12a. The opening 12a is an opening through which the adsorbent 11, or a base material and case containing the adsorbent 11, can pass. In the example of Figure 1A, the opening 12a and the door portion 12b are provided on the upper surface of the separation container 12, but are not limited to the upper surface and may be provided on the side or bottom surface. The internal space of the separation container 12 is in communication with the first flow path 30, the second flow path 40, and the recovery flow path 60.

[0014] As will be described in detail later, the adsorbent 11 adsorbs carbon dioxide from a carbon dioxide-containing gas by coming into contact with the gas. After adsorbing carbon dioxide, it is possible to desorb the adsorbed carbon dioxide from the adsorbent 11 by changing the temperature and pressure. In this embodiment, the adsorbent 11, which has adsorbed carbon dioxide, is placed in the separation container 12. The adsorption of carbon dioxide by the adsorbent 11 is performed, for example, by bringing the adsorbent 11 into contact with a carbon dioxide-containing gas in an adsorption section (not shown). The adsorption of carbon dioxide by the adsorbent 11 is performed by bringing the adsorbent 11 into contact with a carbon dioxide-containing gas containing low concentrations of carbon dioxide (for example, about 410 ppm) present in the atmosphere in the adsorption section. This process of adsorbing low concentrations of carbon dioxide from the atmosphere onto the adsorbent 11 is specifically called DAC (Direct Air Capture). In DAC, airflow generated by fluid equipment capable of generating airflow, such as an outdoor unit, indoor unit, or ventilation fan of an air conditioner, may be used to bring the atmosphere onto the adsorbent 11. For example, the adsorbent 11 may be placed in the flow path of air flowing into or out of the fluid equipment. By placing the adsorbent 11 in a position where it is hit by the airflow, the air and the adsorbent 11 can be efficiently brought into contact. Furthermore, it is possible to efficiently bring the carbon dioxide-containing gas into contact with the adsorbent 11 using the power of existing equipment without requiring new power. The adsorption of carbon dioxide onto the adsorbent 11 is not limited to DAC, and may also be done by bringing the adsorbent 11 into contact with a carbon dioxide-containing gas containing a higher concentration of carbon dioxide than that present in the air emitted from various equipment. The carbon dioxide-containing gas may be, for example, gas emitted from fluid equipment, gas emission devices of refineries, and exhaust gas devices of power plants. Note that the carbon dioxide-containing gas is not limited to gas emitted from the above-mentioned equipment, but may be gas emitted from other equipment. In the separation unit 10 of this embodiment, the adsorbent 11 that has adsorbed carbon dioxide is placed in the separation unit 10, and the carbon dioxide adsorbed on the adsorbent 11 is desorbed by heating and / or reducing the pressure of the separation unit 10.

[0015] The regulated gas supply device 20 comprises a heater 21, a vaporizer 22, a fan 23, and a housing 24. The housing 24 houses the heater 21, the vaporizer 22, and the fan 23. The temperature of the air inside the housing 24 is regulated by the heater 21. Hereinafter, the temperature-regulated gas produced by the regulated gas supply device 20 will be referred to as "regulated gas." In this embodiment, the regulated gas includes high-temperature steam produced by the vaporizer 22. The housing 24 is a box-shaped container composed of six surfaces. Note that the housing 24 is not limited to a box shape and may be cylindrical, for example. The housing 24 is connected to the separation unit 10 by a first flow path 30 and a second flow path 40.

[0016] The heater 21 heats the air inside the housing 24. The vaporizer 22 supplies water vapor to the air inside the housing 24. The vaporizer 22 is, for example, a bubbling tank that vaporizes water to produce water vapor. The fan 23 is positioned near the connection between the first flow path 30 and the housing 24 and generates an airflow to send the conditioned gas to the separation unit 10 via the first flow path 30. The temperature and humidity of the conditioned gas are such that carbon dioxide is desorbed from the adsorbent 11. The temperature of the conditioned gas is higher than room temperature, for example, in the range of 50 to 120°C. The amount of water vapor contained in the conditioned gas is greater than the amount of moisture contained in the air surrounding the carbon dioxide recovery device 1.

[0017] The heater 21, vaporizer 22, and fan 23 are controlled by the control unit 70. This controls the temperature and humidity of the conditioned gas and whether or not airflow is generated by the fan 23. The conditioned gas supply device 20 may also be equipped with a thermometer / hygrometer (not shown) for measuring the temperature and humidity of the generated conditioned gas, and a sensor (not shown) for measuring the carbon dioxide in the conditioned gas. Based on these measurement results, the control unit 70 may control the heater 21, vaporizer 22, and fan 23. The temperature and humidity of the conditioned gas may be appropriately determined based on the type of adsorbent 11 or the target amount of carbon dioxide desorption. In this embodiment, the heater 21 and vaporizer 22 generate a conditioned gas containing high-temperature steam, but the vaporizer 22 may be omitted in the conditioned gas supply device 20.

[0018] The first flow path 30 is a pipe connecting the regulating gas supply device 20 and the separation unit 10. A first on-off valve 31 is provided in the first flow path 30. When the first on-off valve 31 is open, the regulating gas in the regulating gas supply device 20 is supplied to the separation unit 10. At this time, the regulating gas can be supplied to the separation unit 10 efficiently by the airflow generated by the fan 23. The first flow path 30 extends along the direction of airflow generated by the fan 23. In the example shown in Figure 1A, the fan 23 is provided on the lower surface of the regulating gas supply device 20, and the first flow path 30 extends along the lower surfaces of the separation unit 10 and the regulating gas supply device 20. Furthermore, since the adsorbent 11 is mounted on the lower surface inside the separation container 12, the regulating gas that has passed through the first flow path 30 is released from the regulating gas supply device 20 so as to hit the adsorbent 11.

[0019] The second flow path 40 is a pipe connecting the regulating gas supply device 20 and the separation unit 10. A second on-off valve 41 is provided in the second flow path 40. When the second on-off valve 41 is open, the gas in the separation unit 10 can flow into the regulating gas supply device 20. Here, when the first on-off valve 31 and the second on-off valve 41 are open, the airflow from the fan 23 introduces the regulating gas from the regulating gas supply device 20 to the separation unit 10 through the first flow path 30, and introduces the gas from the separation unit 10 to the regulating gas supply device 20 through the second flow path 40. This allows the regulating gas to be circulated within the carbon dioxide recovery device 1 (see arrow F1 in Figure 1A). In the example in Figure 1A, the second flow path 40 is located above the first flow path 30. This allows the regulating gas flowing into the separation unit 10 to come into contact with the adsorbent 11, and also allows the gas within the carbon dioxide recovery device 1 to be circulated effectively. The arrangement of the first flow path 30 and the second flow path 40 is not limited to the example in Figure 1A and can be changed as appropriate. For example, the first flow path 30 may be located above the second flow path 40, or the first flow path 30 and the second flow path 40 may be located at the same height. In addition, the arrangement of the fan 23 that generates airflow toward the first flow path 30 may be adjusted to match the position of the first flow path 30.

[0020] The open / closed states of the first on-off valve 31 and the second on-off valve 41 are controlled by the control unit 70. Since the first on-off valve 31 and the second on-off valve 41 are valves for controlling whether or not the regulating gas is introduced into the separation unit 10, both the first on-off valve 31 and the second on-off valve 41 are in an open state when the regulating gas is introduced into the separation unit 10, and both are in a closed state when the introduction is stopped. Therefore, the open / closed states of the first on-off valve 31 and the second on-off valve 41 are controlled simultaneously. Alternatively, the control unit 70 may control the opening and closing of the first on-off valve 31 and the second on-off valve 41 individually.

[0021] The recovery channel 60 is a pipe connected to the separation unit 10 for recovering gas from within the separation unit 10. The recovery channel 60 is equipped with a recovery valve 61 and a vacuum pump 62 located downstream of the recovery valve 61. The open / closed state of the recovery valve 61 and the operation of the vacuum pump 62 are controlled by the control unit 70. When the first on-off valve 31 and the second on-off valve 41 are open, the recovery valve 61 is closed and the vacuum pump 62 is stopped. By closing the first on-off valve 31 and the second on-off valve 41, opening the recovery valve 61, and operating the vacuum pump 62, the gas containing carbon dioxide desorbed from the adsorbent 11 is recovered from the separation unit 10 (see arrow F2 in Figure 1B). Note that the recovery valve 61 may be omitted. For example, the recovery of gas from the separation unit 10 by the recovery channel 60 may be controlled by the operation of the vacuum pump 62.

[0022] Downstream of the recovery channel 60, a storage section (not shown) is provided for storing carbon dioxide detached from the adsorbent 11. The storage section has, for example, a cylinder capable of storing carbon dioxide. In the storage section, carbon dioxide may be concentrated and compressed for storage, or it may be liquefied for storage.

[0023] <Desorption of Carbon Dioxide from Adsorbent> Generally, in the adsorbent 11, the equilibrium adsorption amount of carbon dioxide is greater at lower temperatures and smaller at higher temperatures. Also, the equilibrium adsorption amount of carbon dioxide is greater at higher pressures and smaller at lower pressures. By utilizing these characteristics and changing the temperature and / or pressure, carbon dioxide is adsorbed and desorbed by the adsorbent 11. Adsorption and desorption of carbon dioxide due to temperature changes is called thermal swing adsorption (TSA), and adsorption and desorption of carbon dioxide due to pressure changes is called pressure swing adsorption (PSA). This embodiment includes a TSA step in which carbon dioxide is desorbed from the adsorbent 11 by TSA, and a TSA step in which carbon dioxide is desorbed from the adsorbent 11 by PSA. The carbon dioxide recovery method including the TSA step and the PSA step will be described below.

[0024] <Carbon Dioxide Recovery Method> Referring to Figures 1A to 1B, the operation of the carbon dioxide recovery apparatus 1 of this embodiment and the carbon dioxide recovery method will be described. First, the door portion 12b of the separation unit 10 is opened, and the adsorbent 11, which has adsorbed carbon dioxide in the adsorption unit (not shown), is placed inside the separation container 12 of the separation unit 10. The movement of the adsorbent 11 from the adsorption unit, the opening and closing of the door portion 12b, and the placement of the adsorbent 11 inside the separation container 12 may be performed by an operator, or by a moving means such as a robotic arm or belt conveyor that operates according to a program. At this time, the first on-off valve 31, the second on-off valve 41, and the recovery valve 61 are in a closed state, and the inside of the separation container 12 is airtightly sealed by closing the door portion 12b after the adsorbent 11 has been placed inside the separation container 12. At this time, the initial temperature inside the separation unit 10 and the adsorbent 11 is, for example, the same as the temperature of the space in which the separation unit 10 is installed, and the pressure inside the separation unit 10 is the same as atmospheric pressure. For example, if the space in which the separation unit 10 is installed is indoors, the initial temperature of the separation unit 10 will be the room temperature, and if the separation unit 10 is installed outdoors, the initial temperature of the separation unit 10 will be the ambient temperature. As will be described in more detail later, the initial temperature of the separation unit 10 may be higher than the temperature of the space in which the separation unit 10 is installed and lower than the temperature of the regulating gas.

[0025] The conditioning gas supply device 20 generates conditioning gas having a target temperature in advance and prepares the conditioning gas inside the housing 24. The conditioning gas may contain high-temperature water vapor.

[0026] ・In the TSA process, as shown in Figure 1A, the first on-off valve 31 and the second on-off valve 41 are opened to circulate the regulating gas into the separation unit 10 and the regulating gas supply device 20. More specifically, the regulating gas is introduced into the separation unit 10 from the first flow path 30 by the airflow generated by the fan 23, exposing the adsorbent 11 to the high-temperature regulating gas. Since the equilibrium adsorption amount of carbon dioxide by the adsorbent 11 at the temperature of the regulating gas is smaller than the equilibrium adsorption amount at room temperature, carbon dioxide is desorbed from the adsorbent 11. As a result, the carbon dioxide concentration in the regulating gas increases. The regulating gas in the separation unit 10 is returned to the regulating gas supply device 20 from the second flow path 40 by the airflow of the regulating gas generated by the fan 23. In the regulating gas supply device 20, the heater 21 continuously adjusts the temperature of the regulating gas, making it possible to continuously introduce regulating gas at the desired temperature into the separation unit 10 through the first flow path 30 and the second flow path 40.

[0027] In this embodiment, the humidity of the conditioned gas is adjusted by the vaporizer 22 of the conditioned gas supply device 20. This further improves the amount of carbon dioxide separated from the adsorbent 11 in the TSA process.

[0028] In the regulating gas circulating within the separation unit 10 and the regulating gas supply device 20, the carbon dioxide concentration increases over time. After a certain period of time, the amount of carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium, and the carbon dioxide concentration of the regulating gas becomes constant. After the carbon dioxide concentration becomes constant, the first on-off valve 31 and the second on-off valve 41 are closed to terminate the separation of carbon dioxide from the adsorbent 11 by TSA. The control unit 70 may also include a determination unit that determines whether or not to change the open state of the first on-off valve 31 and the second on-off valve 41 from the open state. For example, the determination of whether or not to change the open state of the first on-off valve 31 and the second on-off valve 41 may be made based on whether or not a certain period of time has elapsed since the first on-off valve 31 and the second on-off valve 41 were opened, or whether or not the carbon dioxide concentration of the regulating gas exceeds a threshold. Here, the certain period of time may be the time until the amount of carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium under the regulating gas atmosphere. The threshold may be the carbon dioxide concentration at which the amount of carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium under the regulating gas atmosphere. Thus, it is preferable to carry out the TSA process until the amount of carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium at the temperature and humidity of the regulated gas. However, the termination of the TSA process is not limited to this embodiment; the TSA process may be terminated before the amount of adsorption by the adsorbent 11 reaches equilibrium, and the process may proceed to the PSA process.

[0029] ・PSA process After the TSA process, the recovery valve 61 is opened and the vacuum pump 62 is activated to recover the conditioned gas containing carbon dioxide from the separation unit 10. For example, the conditioned gas containing carbon dioxide is sent to a downstream storage unit (not shown), where the carbon dioxide is concentrated and then stored. The vacuum pump 62 brings the pressure inside the separation unit 10 to a low pressure state, which is lower than atmospheric pressure. The pressure inside the separation unit 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, carbon dioxide is desorbed from the adsorbent 11. Therefore, after the TSA process, carbon dioxide is further desorbed from the adsorbent 11 by the PSA process. Since this PSA process is performed after the TSA process, at least in the initial stage of the PSA process, the temperature of the adsorbent 11 is the same as that of the conditioned gas. Thus, in the PSA process of this embodiment, the adsorbent 11 is exposed to a high temperature and low pressure state, which allows for a larger amount of carbon dioxide to be desorbed.

[0030] After a certain period of time has elapsed under high temperature and low pressure conditions, the amount of carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium. In other words, the desorption of carbon dioxide from the adsorbent 11 by PSA is complete. After the desorption of carbon dioxide by PSA is complete, the recovery valve 61 is closed, the vacuum pump 62 is stopped, and the PSA process is terminated. The determination unit may determine whether or not to change the recovery valve 61 from the open state to the closed state and whether or not to stop the operation of the vacuum pump 62. For example, the determination may be made based on whether or not a certain period of time has elapsed since the recovery valve 61 was opened and the operation of the vacuum pump 62 was started, or whether or not the amount of carbon dioxide contained in the recovered regulated gas exceeds a threshold. Here, the certain period of time may be the time it takes for the amount of carbon dioxide adsorbed by the adsorbent 11 to reach equilibrium under high temperature and low pressure conditions. The threshold may be a target value for the amount of carbon dioxide desorbed from the adsorbent 11. Thus, it is preferable to perform the PSA process until the amount of carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium under high temperature and low pressure conditions. However, the time for performing the PSA process is not limited, and the PSA process may be terminated before the amount of adsorption reaches equilibrium.

[0031] In this embodiment, the adjustment gas is continuously generated in the adjustment gas supply device 20 during the PSA process, preparing the adjustment gas to be used in the next TSA process performed in the separation unit 10.

[0032] After the PSA process, the door 12b of the separation unit 10 is opened and the adsorbent 11 from which carbon dioxide has been desorbed is removed. Subsequently, by placing a new adsorbent 11 that has adsorbed carbon dioxide into the separation unit 10, the recovery of carbon dioxide from the new adsorbent 11 can be continued. For example, when M is a natural number, carbon dioxide can be separated sequentially by placing M adsorbent batches, each containing the adsorbent 11 that has adsorbed carbon dioxide, into the separation unit 10 one batch at a time. In this case, the initial temperature of the separation unit 10 when placing the second and subsequent adsorbent batches into the separation unit 10 may be equal to the temperature of the conditioned gas. In this case, the thermal energy required to heat the separation unit 10 to the target temperature can be reduced. The initial temperature of the separation unit 10 for the second and subsequent batches may be equal to the temperature of the space in which the separation unit 10 is installed. For example, if the inside of the separation unit 10 is in a vacuum state after the PSA process and ambient air flows into the inside of the separation unit 10 by opening the opening 12a, the initial temperature will be equal to the temperature of the air that has flowed into the separation unit 10. When performing the second TSA process after placing a new adsorbent 11, the regulated gas generated in the regulated gas supply device 20 during the first PSA process can be used. In other words, when n is a natural number, the regulated gas generated in the regulated gas supply device 20 during the nth PSA process, after closing the first on-off valve 31 and the second on-off valve 41 for the nth TSA process, can be used in the (n+1)th TSA process. This reduces the time required to prepare the regulated gas for the next TSA process, and thus reduces the time required to separate carbon dioxide from the adsorbent 11.

[0033] Conventionally, carbon dioxide was removed from an adsorbent using a pressure-temperature swing adsorption (PTSA) method, which involves simultaneously changing both the pressure and temperature inside the separator. In the PTSA method, it was difficult to sufficiently reduce the pressure inside the separator because a heat transfer medium was introduced into the separation section along with the pressure reduction of the separator. Furthermore, because the valve in the introduction passage for the heat transfer medium was in an open state, it was sometimes difficult to create a vacuum, for example, inside the separator. As a result, carbon dioxide was sometimes not sufficiently removed from the adsorbent in the PTSA method. In addition, when the adsorption and desorption of carbon dioxide to the adsorbent were performed in the same container, the apparatus could become complicated.

[0034] In contrast, in this embodiment, the adsorbent 11 is heated to a high temperature in the TSA process, and in the subsequent PSA process, the first on-off valve 31 and the second on-off valve 41 are closed without introducing a regulating gas into the separation unit 10, thereby keeping the adsorbent 11 in a high-temperature and low-pressure state. As a result, the pressure in the separation unit 10 can be made lower compared to the pressure in the separator in the conventional PTSA method. That is, carbon dioxide can be desorbed from the adsorbent 11 in a low-pressure state (for example, a vacuum state) where the equilibrium adsorption amount of carbon dioxide is smaller, thus increasing the amount of carbon dioxide recovered. In addition, the amount of carbon dioxide remaining in the adsorbent 11 after decarbonization can be reduced.

[0035] Furthermore, since the adjustment gas supply device 20 continues to generate adjustment gas even during the PSA process, the time required to raise the temperature in the separation unit 10 to the target temperature in the next TSA process after placing a new adsorbent 11 in the separation unit 10 can be shortened, thereby shortening the time required for carbon dioxide desorption. In this embodiment, the adsorption unit (not shown) for adsorbing carbon dioxide onto the adsorbent 11 and the separation unit 10 are provided separately. In other words, the equipment and processes required to set the temperature and pressure of the separation unit 10 to conditions suitable for adsorption of carbon dioxide onto the adsorbent 11 can be omitted. Therefore, the time required to optimize the temperature and pressure conditions of the separation unit 10 during carbon dioxide desorption, and the time required for desorption, can be shortened. In addition, the carbon dioxide recovery device 1 including the separation unit 10 can be made into a simpler configuration.

[0036] As described above, the carbon dioxide recovery device 1 according to this embodiment includes a separation unit 10 that houses an adsorbent 11 containing carbon dioxide, a regulated gas supply device 20 that generates a temperature-controlled regulated gas, a first flow path 30 that supplies the regulated gas to the separation unit 10, a second flow path 40 connected from the separation unit 10 to the regulated gas supply device 20 and allowing the gas in the separation unit 10 to flow into the regulated gas supply device 20, a first on-off valve 31 provided in the first flow path 30, a second on-off valve 41 provided in the second flow path 40, and a recovery flow path 60 connected to the separation unit 10 and equipped with a vacuum pump 62 that sucks the gas in the separation unit 10. The first on-off valve 31 and the second on-off valve 41 are opened when supplying the regulated gas to the separation unit 10, and the first on-off valve 31 and the second on-off valve 41 are closed when sucking the gas in the separation unit 10 from the recovery flow path 60.

[0037] This allows carbon dioxide to be desorbed from the adsorbent 11 at a lower pressure (e.g., a vacuum) where the equilibrium adsorption amount of carbon dioxide is smaller, thereby increasing the amount of carbon dioxide recovered. In addition, the amount of carbon dioxide remaining in the adsorbent 11 after desorption can be reduced.

[0038] Furthermore, when drawing gas from inside the separation unit 10 through the recovery channel 60, the adjustment gas supply device 20 continues to generate adjustment gas. This shortens the time required to raise the temperature in the separation unit 10 to the target temperature in the next TSA process, thereby reducing the time required for carbon dioxide desorption. The adjustment gas supply device 20 also adjusts the humidity of the adjustment gas. This further improves the separation of carbon dioxide from the adsorbent 11 in the TSA process.

[0039] In this embodiment of the carbon dioxide recovery method, an adsorbent 11 that has adsorbed carbon dioxide is placed in a separation unit 10, a temperature-controlled adjustment gas is supplied to the separation unit 10, and after stopping the supply of the adjustment gas to the separation unit 10, the separation unit 10 is depressurized. As a result, carbon dioxide can be desorbed from the adsorbent 11 at a lower pressure state (for example, a vacuum state) where the equilibrium adsorption amount of carbon dioxide is smaller, thereby increasing the amount of carbon dioxide recovered. In addition, the amount of carbon dioxide remaining in the adsorbent 11 after decarbonization can be reduced.

[0040] Embodiment 2. Next, with reference to Figure 2, the carbon dioxide recovery device 1 according to Embodiment 2 will be described. The carbon dioxide recovery device 1 according to this embodiment has the same basic configuration as Embodiment 1, so the differences will be explained in detail.

[0041] As shown in Figure 2, in this embodiment, a third channel 50 is provided that connects the first channel 30 and the second channel 40. The third channel 50 is provided so as to be able to thermally contact the separation container 12. In the example shown in Figure 2, the third channel 50 and the side wall 12s of the separation container 12 are in direct contact. As a result, when the regulating gas flows through the third channel 50, the heat of the regulating gas is transported to the outer surface of the side wall 12s of the separation container 12 by thermal conduction. Furthermore, this heat is transported from the outer surface of the side wall 12s to the adsorbent 11 via the wall portion of the separation container 12 and the inner surface of the separation container 12. Note that the thermal contact between the third channel 50 and the separation container 12 is not limited to the example where the two members are in direct contact with each other. For example, a member capable of heat transport may be provided between the two members.

[0042] The first on-off valve 31 and the second on-off valve 41 are provided on the separation unit 10 side rather than on the third flow path 50 side. In the example of FIG. 2, the first on-off valve 31 is provided at the connection portion between the first flow path 30 and the separation unit 10. The second on-off valve 41 is provided at the connection portion between the second flow path 40 and the separation unit 10. The first auxiliary valve 31a is provided at the connection portion between the first flow path 30 and the adjustment gas supply device 20. The second auxiliary valve 41a is provided at the connection portion between the second flow path 40 and the adjustment gas supply device 20. The opening and closing of the first auxiliary valve 31a and the second auxiliary valve 41a are controlled by the control unit 70. It should be noted that it is not essential to provide the first auxiliary valve 31a and the second auxiliary valve 41a, and they may be omitted. Also, an on-off valve (not shown) for changing the introduction or stop of the adjustment gas to the third flow path 50 may be provided in the third flow path 50 so as not to prevent the circulation of the adjustment gas between the separation unit 10 and the adjustment gas supply device 20 during the TSA process.

[0043] In the TSA process, the point that the first on-off valve 31 and the second on-off valve 41 are in the open state and the recovery valve 61 is in the closed state is the same as in the first embodiment. In the present embodiment, during the TSA process, the first auxiliary valve 31a and the second auxiliary valve 41a are also in the open state. Since the first on-off valve 31, the second on-off valve 41, the first auxiliary valve 31a, and the second auxiliary valve 41a are in the open state and the recovery valve 61 is in the closed state, the adjustment gas circulates through the adjustment gas supply device 20 and the separation unit 10, and carbon dioxide is desorbed from the adsorbent 11 by TSA.

[0044] In the carbon dioxide recovery device 1 in the PSA process shown in FIG. 2, the point that the adjustment gas supply device 20 continues to generate the adjustment gas, and the first on-off valve 31 and the second on-off valve 41 are in the closed state and the recovery valve 61 is in the open state is the same as in the first embodiment. In the present embodiment, during the PSA process, the first auxiliary valve 31a and the second auxiliary valve 41a are in the open state, and the adjustment gas circulates through the first flow path 30, the third flow path 50, and the second flow path 40 (see arrow F1a in FIG. 2). By passing the adjustment gas through the third flow path 50, the adsorbent 11 can be heated by the heat of the adjustment gas.

[0045] During the PSA process, the vacuum pump 62 brings the separation unit 10 into a low-pressure state. In this case, although convection occurs in the separation container 12 due to the gas recovery by the vacuum pump 62, as the gas becomes more dilute, the convection of the gas in the separation container 12 weakens, and the transfer of heat by convective heat transfer, where heat is transferred by the movement of gas molecules in the separation container 12, decreases. Therefore, in the PSA process, heat transfer by heat conduction between the piping of the third flow path 50 and the wall of the separation container 12 becomes dominant.

[0046] Therefore, it is preferable to increase the contact area between the third channel 50 and the separation container 12 so that heat transfer by heat conduction due to contact between the members occurs effectively. For the same reason, it is preferable to increase the contact area between the separation container 12 and the adsorbent 11. For example, the contact area with the side wall 12s of the separation container 12 may be increased by using a pipe with a rectangular cross-sectional shape for the third channel 50, or the contact area with the side wall 12s of the separation container 12 may be increased by making the third channel 50 meander along the side wall 12s. The adsorbent 11 may also be uniformly distributed across the entire bottom surface of the separation container 12. Furthermore, it is preferable that the third channel 50 and the separation container 12 be made of a material with high thermal conductivity. If the adsorbent 11 is provided on a substrate or inside a case, it is preferable to increase the contact area between the substrate or case and the separation container 12, and it is preferable that the substrate or case be made of a material with high thermal conductivity.

[0047] The desorption of carbon dioxide from the adsorbent 11 may be an endothermic reaction, and as carbon dioxide desorption progresses in the PSA process, the temperature of the adsorbent 11 may decrease. In this embodiment, in the PSA process, the heat absorbed by the endothermic reaction can be compensated for by the heat of the regulating gas passing through the third channel 50 while maintaining a low-pressure state. Therefore, a decrease in the temperature of the adsorbent 11 can be prevented, and the adsorbent 11 can be kept at a higher temperature more stably, thereby increasing the amount of carbon dioxide desorbed. Note that if heat supply to the adsorbent 11 is not required in the PSA process, the first auxiliary valve 31a and the second auxiliary valve 41a may be closed.

[0048] As described above, in the carbon dioxide recovery device 1 according to the present embodiment, a third flow path 50 connecting the first flow path 30 and the second flow path 40 is further provided, and when the first on-off valve 31 and the second on-off valve 41 are in the closed state, the adjustment gas passes through the third flow path 50. Thereby, in the PSA process, it is possible to prevent the temperature of the adsorbent 11 from decreasing, and to more stably maintain the adsorbent 11 in a high temperature state, so that the amount of carbon dioxide desorbed can be increased.

[0049] Embodiment 3. Next, referring to FIG. 3, the carbon dioxide recovery device 1 according to Embodiment 3 will be described. Since the basic configuration of the carbon dioxide recovery device 1 according to the present embodiment is the same as that of Embodiment 1, the description will focus on the differences.

[0050] As shown in FIG. 3, in the present embodiment, the carbon dioxide recovery device 1 further includes a separation unit fan 13 provided inside the separation unit 10 and a separation unit heater 14 that heats the separation unit 10. The operations of the separation unit fan 13 and the separation unit heater 14 are controlled by the control unit 70.

[0051] In the present embodiment, in the TSA process, the first on-off valve 31 and the second on-off valve 41 may be closed before the amount of carbon dioxide adsorbed by the adsorbent 11 in the high temperature state reaches an equilibrium state. For example, in the TSA process, after the first on-off valve 31 and the second on-off valve 41 are closed, the separation container 12 is heated by the separation unit heater 14, and the adjustment gas in the separation container 12 is circulated by the separation unit fan 13. Thereby, the adjustment gas can be made to flow convectionally in the separation unit 10, and the desorption efficiency of carbon dioxide from the adsorbent 11 can be increased. Further, as described above, the desorption of carbon dioxide from the adsorbent 11 is an endothermic reaction, so by using the separation unit heater 14, the heat absorbed by the endothermic reaction can be compensated. Therefore, even after the first on-off valve 31 and the second on-off valve 41 are closed, it is possible to circulate the adjustment gas in the separation unit 10 and maintain a high temperature state, and the TSA process can be continued until the amount of carbon dioxide desorbed from the adsorbent 11 in the high temperature state reaches an equilibrium state.

[0052] After closing the first on-off valve 31 and the second on-off valve 41, the adjustment gas supply device 20 continues to generate adjustment gas while the carbon dioxide is being desorbed from the adsorbent 11 by operating the separation heater 14 and the separation fan 13. This allows for a longer time to generate the adjustment gas to be used in the next TSA process.

[0053] In the regulating gas circulating within the separation container 12, once the amount of carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium and the carbon dioxide concentration becomes constant, the separation of carbon dioxide from the adsorbent 11 by TSA is terminated. At this time, the operation of the separation unit fan 13 may be stopped. The PSA process after the TSA process is the same as the embodiment described in Embodiment 1. However, since the separation container 12 can be heated by the separation unit heater 14, it is possible to compensate for the heat absorbed by the endothermic reaction of the adsorbent 11 in a low-pressure state, similar to the heating method using the regulating gas passing through the third flow path 50 in Embodiment 2.

[0054] In this embodiment, the first on-off valve 31 and the second on-off valve 41 can be closed before the amount of carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium at high temperatures, allowing the adjustment gas to be generated by the adjustment gas supply device 20 for use in the next TSA process. In other words, time can be secured for the adjustment gas to be generated by the adjustment gas supply device 20 for use in the (n+1)th TSA process from the time the first on-off valve 31 and the second on-off valve 41 are closed until the end of the nth PSA process. Therefore, the time required when performing multiple TSA and PSA processes consecutively can be shortened. The determination unit may determine whether or not to change the open / closed state of the first on-off valve 31 and the second on-off valve 41 from the open state to the closed state. For example, the determination of whether or not to change the open / closed state of the first on-off valve 31 and the second on-off valve 41 may be made based on whether or not a certain amount of time has elapsed since the first on-off valve 31 and the second on-off valve 41 were opened, or whether or not the carbon dioxide concentration of the adjustment gas has exceeded a threshold. Here, the specified time may be shorter than the time it takes for the carbon dioxide adsorbed by the adsorbent 11 to reach equilibrium under the controlled gas atmosphere. The threshold may be lower than the carbon dioxide concentration at which the carbon dioxide adsorbed by the adsorbent 11 reaches equilibrium under the controlled gas atmosphere.

[0055] In the example shown in Figure 3, the separation fan 13 is located near the connection point between the second flow path 40 and the separation container 12, but the position of the separation fan 13 can be changed as appropriate, and the model is not limited to this example. The separation fan 13 may not be stopped at the end of the TSA process, but may continue to operate during the PSA process. This allows, for example, the separation fan 13 to generate gas convection in the initial stage of depressurization during the PSA process.

[0056] In the example shown in Figure 3, the separation heater 14 is positioned opposite the top and bottom surfaces of the separation container 12, but the position and number of the separation heater 14 can be changed as appropriate, and the example is not limited to this example. In the TSA process, the pressure inside the separation container 12 is equivalent to atmospheric pressure, so by heating at least a portion of the wall of the separation section 10, the adsorbent 11 can be heated by heat conduction through the wall of the separation container 12 and by convection heat transfer of the gas inside the separation container 12. Also, as shown in the example in Figure 3, the adjustment gas supply device 20 does not have to be equipped with a vaporizer, but it may be equipped with a vaporizer 22.

[0057] As described above, the carbon dioxide recovery apparatus 1 according to this embodiment further includes a separation unit fan 13 provided inside the separation unit 10 and a separation unit heater 14 for heating the separation unit 10. This makes it possible to further shorten the time required when performing multiple TSA and PSA processes in succession.

[0058] Other embodiments or modifications described above may be combined as appropriate.

[0059] For example, in the above embodiment, after the nth TSA and PSA process, the adsorbent 11 in the separation unit 10 is replaced, and the (n+1)th TSA and PSA process is performed, but the invention is not limited to this example. The TSA and PSA processes may be performed multiple times with the same adsorbent 11 without replacing it. In this case, even if the temperature of the adsorbent 11 drops due to the endothermic reaction during carbon dioxide desorption in the nth PSA process, the adsorbent 11 can be reheated to the target temperature in the (n+1)th TSA process. In the subsequent (n+1)th PSA process, the adsorbent 11 is heated to the target temperature and under low pressure, allowing carbon dioxide to be desorbed from the adsorbent 11. In this way, by performing the TSA and PSA processes multiple times with the same adsorbent 11, the amount of carbon dioxide recovered can be increased. In addition, the amount of carbon dioxide remaining in the adsorbent 11 after desorption can be reduced.

[0060] Furthermore, the TSA process of Embodiment 3 and the PSA process of Embodiment 2 may be combined. In other words, in the TSA process, after closing the first on-off valve 31 and the second on-off valve 41, the adjustment gas in the separation section 10 is circulated by the separation section fan 13 and the separation section heater 14 to heat the adsorbent 11. Subsequently, in the PSA process, the adjustment gas may be flowed through the third flow path 50 to maintain a low-pressure state while heating the adsorbent 11.

[0061] Furthermore, the control unit 70 described above has an internal computer system. The control unit 70 may perform the processing by recording a program for realizing the functions of each component of the carbon dioxide capture device 1 described above on 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 70 may perform the processing described above.

[0062] 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.

[0063] 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.

[0064] 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 device 1. Also, different distribution servers may distribute each of the divided programs. Furthermore, "computer-readable recording medium" 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. Moreover, 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.

[0065] 1...Carbon dioxide recovery device, 10...Separation unit, 11...Adsorbent, 12...Separation container, 13...Separation unit fan, 14...Separation unit heater, 20...Adjusted gas supply device, 21...Heater, 22...Vaporizer, 23...Fan, 30...First flow path, 31...First on-off valve, 40...Second flow path, 41...Second on-off valve, 50...Third flow path, 60...Recovery flow path, 62...Vacuum pump

Claims

1. A carbon dioxide recovery device comprising: a separation unit containing an adsorbent that has adsorbed carbon dioxide; a conditioning gas supply device that generates a temperature-controlled conditioning gas; a first flow path for supplying the conditioning gas to the separation unit; a second flow path connected from the separation unit to the conditioning gas supply device, which allows the gas in the separation unit to flow into the conditioning gas supply device; a first on-off valve provided in the first flow path; a second on-off valve provided in the second flow path; and a recovery flow path connected to the separation unit, which is equipped with a vacuum pump for sucking the gas in the separation unit, wherein the first on-off valve and the second on-off valve are opened when supplying the conditioning gas to the separation unit, and the first on-off valve and the second on-off valve are closed when sucking the gas in the separation unit from the recovery flow path.

2. The carbon dioxide recovery apparatus according to claim 1, wherein when the gas in the separation section is drawn from the recovery channel, the adjustment gas supply device continues to generate the adjustment gas.

3. The carbon dioxide recovery apparatus according to claim 1 or 2, further comprising a third flow path connecting the first flow path and the second flow path, wherein the regulating gas passes through the third flow path when the first and second on-off valves are closed.

4. The carbon dioxide recovery apparatus according to any one of claims 1 to 3, further comprising a separation fan provided inside the separation section and a separation heater for heating the separation section.

5. The carbon dioxide recovery apparatus according to any one of claims 1 to 4, wherein the adjustment gas supply device adjusts the humidity of the adjustment gas.

6. A method for recovering carbon dioxide, comprising: placing an adsorbent containing carbon dioxide in a separation unit; supplying a temperature-controlled adjustment gas to the separation unit; and reducing the pressure in the separation unit after stopping the supply of the adjustment gas to the separation unit.

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