DAC device
Patent Information
- Application Number
- PCT/JP2025/012735
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2026-10-01
Smart Images
Figure JP2025012735_01102026_PF_FP_ABST
Abstract
Description
DAC apparatus
[0001] The present invention relates to a DAC (Direct Air Capture) apparatus that captures carbon dioxide (CO2) in the atmosphere.
[0002] For the purpose of mitigating climate change, research and development have been conducted on DAC technology that captures CO2, which is a major greenhouse gas. As such DAC technology, a DAC apparatus that captures CO2 in the atmosphere using an adsorbent that adsorbs or absorbs CO2 is known. For example, in the DAC apparatus disclosed in Patent Document 1, after atmospheric air is circulated through an adsorption chamber provided with an adsorbent to cause the adsorbent to adsorb CO2 in the atmosphere, the inside of the adsorption chamber is depressurized using a vacuum pump to desorb CO2 from the adsorbent, thereby recovering a desorbed gas with a high CO2 concentration.
[0003] Japanese Unexamined Patent Application Publication No. 2024-048937
[0004] However, when CO2 is captured using a vacuum pump as in the DAC apparatus described in Patent Document 1 mentioned above, as desorption progresses and the pressure inside the adsorption chamber approaches the ultimate pressure achievable by the vacuum pump, the pump efficiency decreases, desorption stagnates, and there is a risk that the CO2 capture efficiency of the entire apparatus will decrease.
[0005] One aspect of the present invention is a DAC device for recovering CO2 from the atmosphere. The DAC device includes a vacuum piping that includes a plurality of adsorption chambers provided with an adsorbent material for adsorbing or absorbing CO2 and water, a plurality of individual pipes connected to each of the plurality of adsorption chambers, and a junction pipe connecting the plurality of individual pipes to a vacuum pump, an atmospheric control valve for opening or closing each of the plurality of adsorption chambers to the atmosphere, a vacuum control valve provided on the vacuum piping, and a control unit that controls the atmospheric control valve and the vacuum control valve to alternately perform an adsorption stroke in which each of the plurality of adsorption chambers is opened to the atmosphere and flow to the vacuum piping is prohibited to adsorb CO2 from the atmosphere, and a desorption stroke in which each of the plurality of adsorption chambers is closed and flow to the vacuum piping is permitted to desorb CO2 from the adsorbent. The plurality of adsorption chambers include a first adsorption chamber and a second adsorption chamber in which the desorption stroke is started during the desorption stroke in the first adsorption chamber. The control unit controls the vacuum control valve to perform desorption assistance by flowing the desorbed gas, which has been detached from the adsorbent in the second adsorption chamber, into the first adsorption chamber after the start of the desorption process in the second adsorption chamber and before the end of the desorption process in the first adsorption chamber.
[0006] According to the present invention, CO2 recovery efficiency can be improved.
[0007] A schematic block diagram showing an example of the piping configuration of a DAC device according to an embodiment of the present invention. A time chart for explaining the overlap operation of the DAC device. A schematic block diagram showing an example of the control configuration of a DAC device according to an embodiment of the present invention. A diagram for explaining the gas flow in the vacuum piping when the degassing process is being performed in the trailing degassing reactor of Figure 2. A diagram for explaining the gas flow in the vacuum piping immediately after the degassing process has started in the trailing degassing reactor of Figure 2 (first half of the degassing process). A diagram for explaining the gas flow in the vacuum piping after the degassing assist in Figure 4B has finished.
[0008] Embodiments of the present invention will be described below with reference to Figures 1 to 4C. Figure 1 is a schematic block diagram showing an example of the piping configuration of a DAC device 100 according to an embodiment of the present invention. As shown in Figure 1, the DAC device 100 includes a plurality of reactors R (Ra, Rb, ...) provided with an adsorbent material for adsorbing or absorbing CO2.
[0009] The reactor R has a housing capable of forming a sealed space (adsorption chamber) inside, and an adsorbent is provided in the adsorption chamber of the reactor R. As the adsorbent, a solid material can be used that is configured to adsorb CO2 at room temperature and pressure and desorb CO2 as the temperature rises. For example, an amine-based solid absorbent, in which an amine-based compound is supported on a suitable carrier, can be used. Such an adsorbent also adsorbs or absorbs water in addition to CO2. The adsorbent is configured in a suitable granular form and is filled into, for example, a mesh-structured filter cartridge and housed in the adsorption chamber of the reactor R.
[0010] The reactor R is provided with atmospheric control valves 1 (1a, 1b, ...) and 2 (2a, 2b, ...) for opening or closing the reactor R to the atmosphere. The atmospheric control valves 1 and 2 may be provided in the piping connecting the adsorption chamber of the reactor R to the outside space, or they may be provided as part of the housing (wall) of the reactor R. When atmospheric control valves 1 and 2 are opened, the adsorption chamber of the reactor R is opened to the atmosphere, and when atmospheric control valves 1 and 2 are closed, the adsorption chamber of the reactor R is sealed. Atmospheric control valves 1 and 2 are provided facing each other with the adsorption chamber in between.
[0011] A fan 4 is connected to the reactor R via either of the atmospheric control valves 1 or 2 (atmospheric control valve 2 in the illustrated example) and appropriate piping (atmospheric piping) 3 to circulate air into the adsorption chamber of the reactor R. In the illustrated example, when atmospheric control valves 1 and 2 are opened and the fan 4 is driven, air is drawn into the reactor R via atmospheric control valve 1, and air is exhausted from the reactor R via atmospheric control valve 2, atmospheric piping 3, and fan 4. As air circulates through the reactor R, CO2 from the air is adsorbed onto the adsorbent material in the adsorption chamber (adsorption stroke). The atmospheric control valves 1 and 2 and the atmospheric piping 3 are configured to have a relatively large diameter so that a large amount of air can circulate through the reactor R. Multiple atmospheric control valves 1 and 2 may be provided.
[0012] Vacuum pipes 5 and 6 are further connected to the reactor R. Vacuum pipe 5 connects the adsorption chamber of the reactor R to the intake port of the vacuum pump 50 for CO2 recovery. More specifically, vacuum pipe 5 includes individual pipes 51 (51a, 51b, ...) that communicate with the adsorption chamber of each reactor R, and a merging pipe 52 that merges the individual pipes 51 and connects them to the vacuum pump 50 by communicating with the intake port of the vacuum pump 50.
[0013] Each individual pipe 51 is provided with a vacuum control valve 53 (53a, 53b, ...) that allows or prohibits the flow of gas in the individual pipe 51, i.e., the flow from the reactor R to the vacuum pipe 5. The vacuum control valve 53 may be composed of an on / off valve such as a ball valve, a control valve such as a butterfly valve, or a combination of these.
[0014] A storage tank 7 is connected to the exhaust port of the vacuum pump 50 via appropriate piping.
[0015] The vacuum piping 6 connects the adsorption chamber of the reactor R to the intake port of the vacuum pump 60. More specifically, the vacuum piping 6 includes individual pipes 61 (61a, 61b, ...) that communicate with the adsorption chambers of each reactor R, and a merging pipe 62 that merges the individual pipes 61 and connects them to the intake port of the vacuum pump 60, thereby connecting the individual pipes 61 to the vacuum pump 60 for degassing.
[0016] Each individual pipe 61 is provided with a vacuum control valve 63 (63a, 63b, ...) that allows or prohibits the flow of gas in the individual pipe 61, i.e., the flow from the reactor R to the vacuum pipe 6. The vacuum control valve 63, like the vacuum control valve 53, may be made up of an on / off valve such as a ball valve, or a control valve such as a butterfly valve, or a combination of these.
[0017] The junction pipe 62 is provided with a vacuum control valve 64 that allows or prohibits the flow of gas in the junction pipe 62, i.e., the flow from the vacuum pipe 6 to the vacuum pump 60. The vacuum control valve 64, like the vacuum control valves 53 and 63, may be made up of an on / off valve such as a ball valve, or a control valve such as a butterfly valve, or a combination of these.
[0018] The reactor R is also provided with a heating device for heating the adsorbent and a cooling device for cooling the adsorbent. For example, heat exchangers 8 (8a, 8b, ...) are provided for heating or cooling the adsorbent. The reactor R is also provided with pressure sensors 9 (9a, 9b, ...) for detecting the internal pressure P of the reactor R (pressure inside the adsorption chamber).
[0019] When the atmospheric control valves 1 and 2 and the vacuum control valve 63 are closed and the vacuum control valve 53 is opened, the vacuum pump 50 is driven, and the gas in the adsorption chamber of the reactor R is drawn out by the vacuum pump 50 via the vacuum piping 5. At this time, when the adsorbent in the adsorption chamber is heated by the heat exchanger 8, the CO2 adsorbed on the adsorbent is desorbed. As a result, the pressure in the adsorption chamber of the reactor R decreases compared to the time of adsorption, and the temperature of the adsorbent rises compared to the time of adsorption, causing the CO2 adsorbed on the adsorbent to desorb, and the desorbed gas, mainly containing the desorbed CO2, is drawn out of the reactor R and stored in the storage tank 7 for recovery (desorption process).
[0020] When the atmospheric control valves 1 and 2 and the vacuum control valve 53 are closed and the vacuum control valves 63 and 64 are opened, and the vacuum pump 60 is driven, the gas in the adsorption chamber of the reactor R is drawn out and exhausted by the vacuum pump 60 via the vacuum piping 6. As a result, the adsorption chamber of the reactor R is degassed (degassing process). Such a degassing process is performed after the end of the adsorption process and before the start of the desorption process. When the adsorbent is heated in the desorption process, if the adsorbent is heated while oxygen is present in the adsorption chamber, there is a risk that the adsorbent will oxidize and deteriorate. By performing a degassing process before the start of the desorption process, which involves heating the adsorbent, and removing the residual air in the adsorption chamber that contains oxygen, oxidative deterioration of the adsorbent can be prevented.
[0021] After the desorption process is completed and before the adsorption process begins, a cooling process is performed in which the adsorbent in the adsorption chamber of the reactor R is cooled by the heat exchanger 8. If oxygen-containing air flows through the adsorption chamber while the adsorbent is at a high temperature, the adsorbent may oxidize and deteriorate. By performing a cooling process before the start of the adsorption process in which air flows through the adsorption chamber, the adsorbent can be cooled, thus preventing oxidative deterioration of the adsorbent.
[0022] Figure 2 is a time chart illustrating the overlap operation of the DAC device 100. As shown in Figure 2, in overlap operation, the adsorption, degassing, desorption, and cooling processes in multiple reactors R (five reactors Ra to Re in Figure 2) are performed sequentially with time staggers. More specifically, each process in each reactor R is performed over a predetermined time and is started with a predetermined time stagger.
[0023] In this case, as the number of reactors R increases, the detachment process of the next reactor Rb begins after the detachment process of the previous reactor Ra has started, but before the detachment process is completed (i.e., during the detachment process). In other words, the detachment processes overlap between reactors R. In the example in Figure 2, during the detachment process of reactor Ra from time t2 to t11, the detachment process of reactor Rb begins at time t4, the detachment process of reactor Rc begins at time t6, the detachment process of reactor Rd begins at time t8, and the detachment process of reactor Re begins at time t10. In other words, the detachment processes overlap between the five reactors Ra to Re. In the following, the reactor Ra from which the desorption process begins first will be referred to as the preceding desorption reactor Ra, and the reactors Rb to Re from which the desorption process begins during the desorption process of the preceding desorption reactor Ra will be referred to as the succeeding desorption reactors Rb to Re.
[0024] Figure 2 also shows the reactor internal pressure (pressure inside the adsorption chamber) P (Pa to Pe) for each reactor R (Ra to Re). As shown in Figure 2, the reactor internal pressure P is normal pressure (atmospheric pressure) during the adsorption stroke, and decreases to the final pressure reached by the degassing vacuum pump 60 when the degassing stroke begins. Subsequently, when the desorption stroke begins, the pressure changes according to the amount of adsorbate desorbed from the adsorbent as the adsorbent heats up, and gradually decreases to near the final pressure reached by the CO2 recovery vacuum pump 50. When the cooling stroke begins and reactor R is repressurized, the pressure rises to atmospheric pressure. During the degassing and desorption strokes, the reactor internal pressure P is a negative pressure lower than atmospheric pressure, and the lower the reactor internal pressure P in Figure 2, the higher the vacuum level inside the adsorption chamber.
[0025] During the desorption process, as the adsorbent begins to heat up, the adsorbed substances such as CO2 and water adsorbed onto the adsorbent begin to desorb. More specifically, when the temperature of the adsorbent reaches the desorption temperature of water (for example, around 70°C), water begins to desorb, and then when it reaches the desorption temperature of CO2 (for example, around 100°C), which is higher than the desorption temperature of water, CO2 begins to desorb. In the first half of the desorption process, there is a large amount of adsorbent adsorbed onto the adsorbent, and the amount of desorption is large, so the reactor internal pressure P is relatively high. In the second half of the desorption process, the amount of adsorbent adsorbed onto the adsorbent decreases, and the amount of desorption decreases, so the reactor internal pressure P decreases.
[0026] In the latter half of the desorption process, as desorption progresses and the reactor internal pressure P approaches the final target pressure of the vacuum pump 50, the pumping efficiency of the vacuum pump 50 decreases, causing desorption to stall and potentially reducing the overall CO2 recovery efficiency of the device. The adsorption equilibrium, where the adsorption rate of adsorption of adsorbate onto the adsorbent and the desorption rate of desorption from the adsorbent are equal, is more skewed towards desorption as the CO2 partial pressure in the adsorption chamber decreases. Therefore, in this embodiment, the DAC device is configured as follows to improve CO2 recovery efficiency by introducing a water-rich desorption gas from the trailing desorption reactor Rd into the leading desorption reactor Ra and lowering the CO2 partial pressure.
[0027] Figure 3 is a schematic block diagram showing an example of the control configuration of the DAC device 100. As shown in Figure 3, the DAC device 100 includes a controller 10 that controls each part of the DAC device 100. The controller 10 is composed of a computer having a CPU, ROM, RAM, I / O interface, and other peripheral circuits.
[0028] The controller 10 is connected to the pressure sensor 9 shown in Figure 1, and a signal indicating the detected value of the pressure sensor 9 is input to the controller 10. In addition, various parts of the DAC device 100, such as the fan 4, heat exchanger 8, vacuum pumps 50 and 60, and control valves 1, 2, 53, 63, and 64 (atmospheric control valves 1 and 2 and vacuum control valves 53, 63, and 64), are connected to the controller 10, and control signals are transmitted from the controller 10 to each part of the DAC device 100.
[0029] After driving the fan 4 and vacuum pumps 50 and 60, the controller 10 controls each part of the DAC device 100 so that the adsorption process, degassing process, desorption process, and cooling process are performed sequentially in each reactor R according to a predetermined schedule. In the predetermined schedule, as shown in Figure 2, the time for each process to be performed in each reactor R and the time for staggering the start times of each process between reactors R are predetermined.
[0030] During the adsorption process, the controller 10 opens the atmospheric control valves 1 and 2 to allow atmospheric air to flow into the reactor R, closes the vacuum control valves 53 and 63 to prevent gas flow from the reactor R to the vacuum pipes 5 and 6, and controls the heat exchanger 8 to prevent heating and cooling. As a result, CO2 from the atmosphere is adsorbed onto the adsorbent material in the reactor R.
[0031] During the degassing process, the controller 10 closes the atmospheric control valves 1 and 2 to seal the reactor R, closes the vacuum control valve 53 to prevent the flow of gas from the reactor R to the vacuum piping 5, opens the vacuum control valves 63 and 64 to allow the flow of gas (residual atmosphere) from the reactor R to the degassing vacuum pump 60, and controls the heat exchanger 8 to prevent heating and cooling. As a result, the reactor R is degassed.
[0032] During the desorption process, the controller 10 closes the atmospheric control valves 1 and 2 to seal the reactor R, closes the vacuum control valve 63 to prevent the flow of gas from the reactor R to the vacuum piping 6, opens the vacuum control valve 53 to allow the flow of gas (desorbed gas) from the reactor R to the vacuum pump 50 for CO2 recovery, and controls the heat exchanger 8 to heat the adsorbent. As a result, CO2 is desorbed from the adsorbent in the reactor R.
[0033] During the cooling stroke, the controller 10 gradually opens the atmospheric control valves 1 and 2 to gradually open the reactor R to the atmosphere, closes the vacuum control valves 53 and 63 to prevent gas flow from the reactor R to the vacuum pipes 5 and 6, and controls the heat exchanger 8 to cool the adsorbent. Alternatively, a small-diameter pressure-recovering control valve may be provided in the reactor R, and during the cooling stroke, the pressure-recovering control valve may be gradually opened instead of the atmospheric control valves 1 and 2 to gradually open the reactor R to the atmosphere. This cools the adsorbent in the reactor R.
[0034] Figures 4A to 4C are diagrams illustrating the gas flow in the vacuum pipes 5 and 6 of Figure 1, and show the leading desorption reactor Ra, the trailing desorption reactor Rd, and the surrounding piping configuration of Figure 2.
[0035] Figure 4A shows the gas flow when the degassing process is being carried out in the trailing degassing reactor Rd (times t7 to t8 in Figure 2). As shown in Figure 2, when the degassing process is being carried out in the trailing degassing reactor Rd, the degassing process is being carried out in the leading degassing reactor Ra. At this time, as shown in Figure 4A, the vacuum control valve 53d is closed and the vacuum control valves 63d and 64d are opened, and the residual air from the trailing degassing reactor Rd is sucked out by the degassing vacuum pump 60 and exhausted. Also, the vacuum control valve 53a is opened and the vacuum control valve 63a is closed, and the degassed gas from the leading degassing reactor Ra is sucked out via the vacuum piping 5 by the CO2 recovery vacuum pump 50, stored in the storage tank 7 in Figure 1, and recovered.
[0036] Figure 4B shows the gas flow immediately after the desorption stroke begins in the trailing desorption reactor Rd (first half of the desorption stroke). More specifically, it shows the gas flow from the trailing desorption reactor Rd from the start of the desorption stroke in the trailing desorption reactor Rd until the start of the desorption stroke in the next trailing desorption reactor Re (times t8 to t9 in Figure 2).
[0037] As shown in Figure 2, immediately after the desorption process begins in the trailing desorption reactor Rd, the desorption process continues in the leading desorption reactor Ra, resulting in an overlap of desorption processes between reactors Ra and Rd. At this time, the desorbed gas from the trailing desorption reactor Rd contains a large amount of water, which desorbs at a lower temperature than CO2.
[0038] When the degassing process of the trailing degassing reactor Rd is completed and the degassing process begins, causing the adsorbent to start heating, the controller 10 closes the vacuum control valve 53d corresponding to the trailing degassing reactor Rd, leaves the vacuum control valve 63d open, and closes the vacuum control valve 64. As a result, the degassing gas containing a large amount of water from the trailing degassing reactor Rd flows into the vacuum piping 6 (individual piping 61d → merging piping 62).
[0039] Subsequently, after a predetermined waiting time (for example, about 10 seconds) has elapsed, the controller 10 opens the vacuum control valve 63a while keeping the vacuum control valve 53a corresponding to the leading desorption reactor Ra open. As a result, the desorption gas containing a large amount of water from the trailing desorption reactor Rd flows to the leading desorption reactor Ra via the vacuum piping 6 (combined piping 62 → individual piping 61a). In this case, the partial pressure of CO2 in the adsorption chamber of the leading desorption reactor Ra decreases, promoting CO2 desorption from the adsorbent, which shifts the adsorption equilibrium towards the desorption side and improves the CO2 recovery efficiency of the leading desorption reactor Ra in the latter half of the desorption process.
[0040] The desorbed gas from the leading desorption reactor Ra is drawn out by a vacuum pump 50 for CO2 recovery via vacuum piping 5 (individual piping 51a → confluence piping 52), stored in the storage tank 7 shown in Figure 1, and recovered. The CO2 contained in the desorbed gas from the trailing desorption reactor Rd is recovered together with the CO2 contained in the desorbed gas from the leading desorption reactor Ra. Even if the ambient temperature and the temperature of the adsorbent at the start of heating are relatively high, and CO2 begins to desorb at an early stage after the start of the desorption process, and even if the desorbed gas from the trailing desorption reactor Rd contains a large amount of CO2, it can be reliably recovered via the leading desorption reactor Ra.
[0041] In this way, by performing desorption assistance in which a water-rich desorption gas from the trailing desorption reactor Rd in the first half of the desorption stroke is introduced into the leading desorption reactor Ra, the CO2 partial pressure of the leading desorption reactor Ra in the second half of the desorption stroke can be reduced. That is, by increasing the relative water vapor partial pressure of the leading desorption reactor Ra with respect to the reactor internal pressure Pa (total pressure), which has decreased to near the final reach pressure of the vacuum pump 50, the CO2 partial pressure can be reduced. This improves the CO2 recovery efficiency of the leading desorption reactor Ra in the second half of the desorption stroke.
[0042] Figure 4C shows the gas flow after the desorption assist has finished. When a predetermined assist time has elapsed from the start of the desorption assist, the controller 10 keeps the vacuum control valve 53a corresponding to the leading desorption reactor Ra open, closes the vacuum control valve 63a, and closes the vacuum control valve 63d corresponding to the trailing desorption reactor Rd. As a result, communication between the trailing desorption reactor Rd and the leading desorption reactor Ra via the vacuum piping 6 is severed, the desorption assist ends, and the leading desorption reactor Ra returns to the normal desorption process.
[0043] Subsequently, after a predetermined waiting time (for example, about 10 seconds) has elapsed, the controller 10 opens the vacuum control valve 53d corresponding to the trailing desorption reactor Rd. This allows the trailing desorption reactor Rd to return to the normal desorption process. That is, the desorbed gas from reactors Ra and Rd is sucked out by the CO2 recovery vacuum pump 50 via the vacuum piping 5 (individual piping 51a, 51d → merging piping 52), stored in the storage tank 7 shown in Figure 1, and recovered.
[0044] Desorption assist may be performed only for a predetermined period of time (assist time), or may be performed until the internal pressure Pa of the preceding desorption reactor Ra reaches a predetermined pressure. In this case, the controller 10 determines the timing to end the desorption assist based on the internal pressure Pa of the preceding desorption reactor Ra detected by the pressure sensor 9a. A CO2 sensor for measuring CO2 concentration may be provided in addition to the pressure sensor 9 in FIG. 1, the CO2 partial pressure may be calculated from the detection values of the pressure sensor 9 and the CO2 sensor, and the desorption assist may be performed until the calculated CO2 partial pressure reaches a predetermined pressure.
[0045] According to the embodiment of the present invention, the following operational effects can be obtained. (1) The DAC device 100 includes: a plurality of reactors R provided with an adsorbent that adsorbs or absorbs CO2 and water; a plurality of individual pipes 51, 61 connected to each reactor R; merging pipes 52, 62 connecting the plurality of individual pipes 51, 61 to vacuum pumps 50, 60; vacuum pipes 5, 6 including the foregoing; atmosphere control valves 1, 2 that open each reactor R to the atmosphere or seal the reactor; vacuum control valves 53, 63, 64 provided on the vacuum pipes 5, 6; and a controller 10 that controls the atmosphere control valves 1, 2 and the vacuum control valves 53, 63, 64 so as to alternately perform: an adsorption step in which each reactor R is opened to the atmosphere, flow to the vacuum pipes 5, 6 is blocked, and the adsorbent is caused to adsorb CO2 in the atmosphere, and a desorption step in which each reactor R is sealed, flow to the vacuum pipe 5 is permitted, and CO2 is desorbed from the adsorbent (FIG. 1, FIG. 3).
[0046] The plurality of reactors R include a preceding desorption reactor Ra and a subsequent desorption reactor Rd for which a desorption step is started during the desorption step of the preceding desorption reactor Ra (FIG. 2, FIGS. 4A to 4C). The controller 10 controls the vacuum control valves 53, 63, 64 to perform desorption assist, in which desorption gas desorbed from the adsorbent of the subsequent desorption reactor Rd is caused to flow into the preceding desorption reactor Ra, after the start of the desorption step of the subsequent desorption reactor Rd (time t8) and before the end of the desorption step of the preceding desorption reactor Ra (time t11) (FIG. 2, FIG. 4B).
[0047] As described above, by performing desorption assist in which desorption gas containing a large amount of water from the subsequent desorption reactor Rd in the first half of the desorption step is introduced into the preceding desorption reactor Ra, the CO₂ partial pressure of the preceding desorption reactor Ra in the second half of the desorption step can be reduced. This improves the CO₂ recovery efficiency of the preceding desorption reactor Ra in the second half of the desorption step.
[0048] (2) The DAC device 100 further includes a heat exchanger 8 that heats the adsorbent (Fig. 1). The controller 10 further controls the heat exchanger 8 to heat the adsorbent in each reactor R during the desorption step. In the desorption step, water desorbs when the temperature of the adsorbent reaches the desorption temperature of water, and CO₂ desorbs when the temperature of the adsorbent reaches the desorption temperature of CO₂, which is higher than the desorption temperature of water. In this case, the desorption gas from the subsequent desorption reactor Rd in the first half of the desorption step contains a large amount of water that desorbs at a temperature lower than that of CO₂.
[0049] (3) The merging pipe 52 connects the individual pipes 51 and the vacuum pump 50 for CO₂ recovery. The merging pipe 62 connects the individual pipes 61 and the vacuum pump 60 for degassing. The vacuum control valve 53 is provided on the individual pipe 51, and permits or prohibits the flow from each reactor R to the vacuum pipe 5. The vacuum control valve 63 is provided on the individual pipe 61, and permits or prohibits the flow from each reactor R to the vacuum pipe 6. The vacuum control valve 64 is provided on the merging pipe 62, and permits or prohibits the flow from the vacuum pipe 6 to the vacuum pump 60.
[0050] The controller 10 controls the atmosphere control valves 1, 2 and the vacuum control valves 53, 63, 64 to perform a degassing step after the end of the adsorption step and before the start of the desorption step, in which each reactor R is sealed, the flow to the vacuum pipe 5 is prohibited, and the flow to the vacuum pump 60 is permitted to degas each reactor R (Figs. 2, 4A). In the desorption assist, the vacuum control valves 53, 63, 64 are controlled such that desorption gas flows from the subsequent desorption reactor Rd to the preceding desorption reactor Ra via the vacuum pipe 6, and desorption gas flows from the preceding desorption reactor Ra to the vacuum pipe 5 (Fig. 4B).
[0051] In this way, by reusing the vacuum piping 6 for degassing, desorption assistance can be performed with a simple configuration. Furthermore, during desorption assistance, the CO2 contained in the desorbed gas introduced from the trailing desorption reactor Rd to the leading desorption reactor Ra is recovered as desorbed gas from the leading desorption reactor Ra. Even if the ambient temperature and the temperature of the adsorbent at the start of heating are relatively high, and CO2 begins to desorb at an early stage after the start of the desorption process, and even if the desorbed gas from the trailing desorption reactor Rd contains a large amount of CO2, it can be reliably recovered via the leading desorption reactor Ra.
[0052] (4) Desorption assistance is performed for a predetermined assistance time, or until the reactor internal pressure P (partial pressure of CO2) of the leading desorption reactor Ra reaches a predetermined pressure. When assistance is performed for a predetermined assistance time, the controller 10 can easily control each part of the DAC device 100 according to a predetermined schedule. When assistance is performed in accordance with the reactor internal pressure P (partial pressure of CO2) of the leading desorption reactor Ra, the controller 10 can control the reactor internal pressure Pa (partial pressure of CO2) of the leading desorption reactor Ra in the latter half of the desorption process with greater precision, and manage the desorption rate and recovery efficiency of CO2.
[0053] The above description is merely an example, and the present invention is not limited by the embodiments and modifications described above, as long as the features of the present invention are not impaired. It is also possible to arbitrarily combine one or more of the above embodiments and modifications, and to combine modifications with each other.
[0054] 1,2 Atmospheric control valve (control valve), 3 Atmospheric piping, 4 Fan, 5,6 Vacuum piping, 7 Storage tank, 8 Heat exchanger, 9 Pressure sensor, 10 Controller, 50,60 Vacuum pump, 51,61 Individual piping, 52,62 Combined piping, 53,63,64 Vacuum control valve (control valve), 100 DAC device, R Reactor
Claims
1. A DAC device for recovering CO2 from the atmosphere, comprising: a plurality of adsorption chambers provided with an adsorbent material for adsorbing or absorbing CO2 and water; a plurality of individual pipes connected to each of the plurality of adsorption chambers; a combined pipe connecting the plurality of individual pipes to a vacuum pump; an atmospheric control valve for opening or closing each of the plurality of adsorption chambers to the atmosphere; a vacuum control valve provided on the vacuum pipe; and a control unit for controlling the atmospheric control valve and the vacuum control valve to alternately perform an adsorption stroke in which each of the plurality of adsorption chambers is opened to the atmosphere and flow to the vacuum pipe is prohibited to adsorb CO2 from the atmosphere, and a desorption stroke in which each of the plurality of adsorption chambers is closed and flow to the vacuum pipe is permitted to desorb CO2 from the adsorbent, wherein the plurality of adsorption chambers include a first adsorption chamber and a second adsorption chamber in which the desorption stroke is started during the desorption stroke in the first adsorption chamber. The DAC device is characterized in that the control unit controls the vacuum control valve to perform desorption assistance, which involves flowing the desorbed gas desorbed from the adsorbent in the second adsorption chamber into the first adsorption chamber after the start of the desorption process in the second adsorption chamber and before the end of the desorption process in the first adsorption chamber.
2. The DAC apparatus according to claim 1, further comprising a heating device for heating the adsorbent, wherein the control unit further controls the heating device to heat the adsorbent in each of the plurality of adsorption chambers during the desorption process, and in the desorption process, water is desorbed when the temperature of the adsorbent reaches a first temperature, and CO2 is desorbed when the temperature of the adsorbent reaches a second temperature higher than the first temperature.
3. In the DAC device according to claim 1 or 2, each of the plurality of individual pipes includes a first individual pipe and a second individual pipe; the merging pipe includes a first merging pipe connecting the first individual pipe and a first vacuum pump for CO2 recovery, and a second merging pipe connecting the second individual pipe and a second vacuum pump for vacuum exhaust; the vacuum pipe includes a first vacuum pipe including the first individual pipe and the first merging pipe, and a second vacuum pipe including the second individual pipe and the second merging pipe; the vacuum control valve includes a first vacuum control valve provided in the first individual pipe for allowing or prohibiting flow from each of the plurality of adsorption chambers to the first vacuum pipe; a second vacuum control valve provided in the second individual pipe for allowing or prohibiting flow from each of the plurality of adsorption chambers to the second vacuum pipe; and a third vacuum control valve provided in the second merging pipe for allowing or prohibiting flow from the second vacuum pipe to the second vacuum pump. The control unit controls the atmospheric control valve and the vacuum control valve to perform a degassing process in which, after the completion of the adsorption process and before the start of the degassing process, the control unit seals each of the plurality of adsorption chambers and prohibits flow to the first vacuum piping, and allows flow to the second vacuum pump to degas each of the plurality of adsorption chambers; and in the degassing assist, the vacuum control valve is controlled so that the degassed gas flows from the second adsorption chamber to the first adsorption chamber via the second vacuum piping, and the degassed gas flows from the first adsorption chamber to the first vacuum piping.
4. A DAC apparatus according to claim 1 or 2, characterized in that the desorption assist is performed for a predetermined time, or until the pressure in the first adsorption chamber reaches a predetermined pressure.