DAC device

Abstract

A DAC device (100) for recovering CO2 in the atmosphere comprises: a plurality of adsorption chambers (R) provided with an adsorbent material for adsorbing or absorbing CO2; a plurality of opening / closing valves (1, 2) for opening to the atmosphere or sealing each of the plurality of adsorption chambers; vacuum piping (5) for connecting the plurality of adsorption chambers and a vacuum pump; a plurality of regulating valves (9) for regulating flow rates of gas flowing from each of the plurality of adsorption chambers to the vacuum piping; and a control unit for controlling the plurality of opening / closing valves and the plurality of regulating valves so as to alternately perform an adsorption process of opening each of the plurality of adsorption chambers to the atmosphere, prohibiting the flow of gas to the vacuum piping, and adsorbing CO2 present in the atmosphere onto the adsorbent material, and a desorption process of sealing each of the plurality of adsorption chambers, permitting the flow of gas to the vacuum piping, and desorbing CO2 from the adsorbent material. The plurality of adsorption chambers include a first adsorption chamber, and a second adsorption chamber in which the desorption process is started during the desorption process in the first adsorption chamber. The control unit controls the plurality of regulating valves so that a pressure change pattern during the desorption process of each of the plurality of adsorption chambers becomes a prescribed pattern.

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 on DAC technology for capturing CO2, which is a major greenhouse gas, has been conducted. As such DAC technology, a DAC apparatus configured to capture 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 CO2 is adsorbed onto the adsorbent by passing air through an adsorption chamber provided with the adsorbent, CO2 is desorbed from the adsorbent by depressurizing the inside of the adsorption chamber using a vacuum pump, thereby collecting desorbed gas with a high CO2 concentration. Further, in the DAC apparatus disclosed in Patent Document 2, a plurality of adsorption chambers each provided with an adsorbent are provided, and adsorption and desorption are performed simultaneously at staggered timings.

[0003] Japanese Unexamined Patent Application Publication No. 2024-048937European Patent Application Publication No. 3806981 Specification

[0004] However, when a plurality of adsorption chambers are provided as in the DAC apparatus described in Patent Document 2 mentioned above, desorbed gas from each adsorption chamber delays CO2 desorption in other adsorption chambers, which may cause a decrease in CO2 capture efficiency of the entire apparatus.

[0005] One aspect of the present invention is a DAC device for recovering CO2 from the atmosphere. The DAC device comprises a plurality of adsorption chambers provided with an adsorbent for adsorbing or absorbing CO2, a plurality of on-off valves for opening or sealing each of the plurality of adsorption chambers to the atmosphere, vacuum piping connecting the plurality of adsorption chambers to a vacuum pump, a plurality of control valves for adjusting the flow rate of gas from each of the plurality of adsorption chambers to the vacuum piping, and a control unit that controls the plurality of on-off valves and a plurality of control valves to alternately perform an adsorption process in which each of the plurality of adsorption chambers is opened to the atmosphere and the flow of gas to the vacuum piping is prohibited to adsorb CO2 from the atmosphere onto the adsorbent, and a desorption process in which each of the plurality of adsorption chambers is sealed and the flow of gas 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 process is started during the desorption process in the first adsorption chamber. The control unit controls the plurality of control valves so that the pressure change pattern during the desorption process in each of the plurality of adsorption chambers follows a predetermined pattern.

[0006] According to the present invention, the CO2 recovery efficiency of a DAC device including multiple adsorption chambers can be improved.

[0007] A schematic block diagram showing an example of the piping configuration of a DAC device including multiple reactors. A time chart for explaining the overlap operation of the DAC device. A time chart for explaining the pattern of change in reactor internal pressure during the decompression stroke when the decompression strokes do not overlap between reactors. A time chart for explaining the pattern of change in reactor internal pressure of a leading decompressed reactor during the decompression stroke when the decompression strokes overlap between reactors. A schematic block diagram showing an example of the piping configuration of a DAC device according to an embodiment of the present invention. A schematic block diagram showing another example of the piping configuration of a DAC device according to an embodiment of the present invention. A schematic block diagram showing an example of the control configuration of a DAC device according to an embodiment of the present invention. A time chart for explaining the target opening of the control valves in Figures 5 to 7 corresponding to the reactors during the decompression stroke. A diagram for explaining the amount of opening change when controlling the control valve corresponding to the reactor according to the reactor internal pressure of the reactor itself. A diagram for explaining the amount of opening change when controlling the control valve corresponding to the reactor according to the reactor internal pressure of other reactors.

[0008] Embodiments of the present invention will be described below with reference to Figures 1 to 10. Figure 1 is a schematic block diagram showing an example of the piping configuration of a DAC device 100A including a plurality of reactors R (Ra, Rb, ...). Each reactor R has a housing capable of forming a sealed space (adsorption chamber) inside, and an adsorbent for adsorbing or absorbing CO2 is provided in the adsorption chamber of the reactor R. As the adsorbent, for example, a solid material configured to adsorb CO2 at room temperature and pressure and desorb CO2 as the temperature rises can be used, for example, an amine-based solid absorbent in which an amine-based compound is supported on a suitable carrier can be used. The adsorbent is configured in a suitable granular form and is filled into a filter cartridge with a mesh structure, for example, and housed in the adsorption chamber of the reactor R. The reactor R is also provided with a heating device for heating the adsorbent and a cooling device for cooling the adsorbent. For example, a heat exchanger for heating or cooling the adsorbent is provided.

[0009] As shown in Figure 1, the reactor R is provided with on-off valves 1 (1a, 1b, ...) and 2 (2a, 2b, ...) for opening or closing the reactor R to the atmosphere. The on-off 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 the on-off valves 1 and 2 are opened, the adsorption chamber of the reactor R is opened to the atmosphere, and when the on-off valves 1 and 2 are closed, the adsorption chamber of the reactor R is sealed. The on-off valves 1 and 2 are provided facing each other with the adsorption chamber in between.

[0010] A fan 4 is connected to the reactor R via either of the on-off valves 1 and 2 (on-off 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 the on-off valves 1 and 2 are opened and the fan 4 is driven, air is drawn into the reactor R via on-off valve 1, and air is exhausted from the reactor R via on-off valve 2, atmospheric piping 3, and fan 4. Hereinafter, on-off valve 1 will be referred to as intake valve 1, and on-off valve 2 as exhaust valve 2. When air circulates through the reactor R in this way, CO2 from the air is adsorbed onto the adsorbent material in the adsorption chamber (adsorption stroke). The intake valve 1, exhaust valve 2, and 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 intake valves 1 and exhaust valves 2 may be provided.

[0011] Vacuum piping 5 is further connected to the reactor R. Vacuum piping 5 connects the adsorption chamber of the reactor R to the intake port of the vacuum pump 6. More specifically, vacuum piping 5 includes individual pipes 51 (51a, 51b, ...) that communicate with the adsorption chambers of each reactor R, and a combined pipe 52 that merges the individual pipes 51 and communicates with the intake port of the vacuum pump 6. Each individual pipe 51 is provided with an on-off valve 7 (7a, 7b, ...) that allows or prohibits the flow of gas in the individual pipe 51. The on-off valve 7 is configured, for example, as a ball valve. A storage tank 8 is connected to the exhaust port of the vacuum pump 6 via appropriate piping.

[0012] When the intake valve 1 and exhaust valve 2 are closed and the on / off valve 7 is opened, the vacuum pump 6 is driven, and the gas in the adsorption chamber of the reactor R is drawn out by the vacuum pump 6 via the vacuum piping 5. At this time, depending on the type of adsorbent, the adsorbent in the adsorption chamber is heated by a heat exchanger provided in the reactor R as needed, thereby desorbing the CO2 adsorbed on the adsorbent. 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 increases 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 8 for recovery (desorption process).

[0013] After the adsorption process is completed and before the desorption process begins, a degassing process may be performed to remove air from the adsorption chamber of the reactor R. When the adsorbent is heated during the desorption process, if the adsorbent is heated while oxygen is present in the adsorption chamber, there is a risk of oxidative degradation of the adsorbent. By performing a degassing process before the start of the desorption process, which involves heating the adsorbent, and removing the residual air containing oxygen from the adsorption chamber, oxidative degradation of the adsorbent can be prevented. The degassing process may be performed using vacuum piping 5 and vacuum pump 6, but it may also be performed using a separate vacuum pump (degassing vacuum pump) connected to the adsorption chamber of the reactor R via a separate vacuum piping (degassing vacuum piping) from vacuum piping 5. In this case, the residual air removed from the adsorption chamber of the reactor R can be exhausted via the degassing vacuum pump without being guided to the storage tank 8, thereby further increasing the concentration of CO2 recovered in the storage tank 8.

[0014] After the desorption process is completed and before the adsorption process begins, a cooling process may be performed to cool the adsorbent in the adsorption chamber of the reactor R. 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, thereby preventing oxidative deterioration of the adsorbent. During the cooling process, the system may wait until the temperature of the adsorbent drops to a temperature range where oxidation reactions do not proceed, or the adsorbent in the adsorption chamber may be cooled by a heat exchanger provided in the reactor R. In this case, the time required for the cooling process can be shortened, and the DAC device 100A can be operated efficiently.

[0015] The DAC device 100A is equipped with a controller 10 that controls each part of the DAC device 100A, including an intake valve 1, an exhaust valve 2, a fan 4, a vacuum pump 6, and an on / off valve 7. The controller 10 is composed of a computer having a CPU, ROM, RAM, I / O interface, and other peripheral circuits. The controller 10 controls each part of the DAC device 100A so that the adsorption stroke and the desorption stroke are performed alternately in each reactor R.

[0016] More specifically, with the fan 4 and vacuum pump 6 running, the DAC device 100A is controlled to open the intake valve 1 and exhaust valve 2 and close the on-off valve 7 during the adsorption stroke, and to close the intake valve 1 and exhaust valve 2 and open the on-off valve 7 during the desorption stroke. As a result, during the adsorption stroke, the reactor R is opened to the atmosphere and the flow of gas into the vacuum piping 5 is prohibited, allowing CO2 from the atmosphere to be adsorbed onto the adsorbent, and during the desorption stroke, the reactor R is sealed and the flow of gas into the vacuum piping 5 is permitted, allowing CO2 to be desorbed from the adsorbent.

[0017] Figure 2 is a time chart illustrating the overlap operation of the DAC device 100A. As shown in Figure 2, in overlap operation, the adsorption and desorption processes in multiple reactors R (four reactors Ra, Rb, Rc, and Rd 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.

[0018] In this case, as the number of reactors R increases, the detachment process of the next reactor Rb may begin after the detachment process of the previous reactor Ra has started, but before it has finished (i.e., while the detachment process is still in progress). In other words, the detachment processes of reactors R may overlap. In the example in Figure 2, during the detachment process of reactor Ra from time t1 to t5, the detachment process of reactor Rb begins at time t2, the detachment process of reactor Rc begins at time t3, and the detachment process of reactor Rd begins at time t4. In other words, the detachment processes of the four reactors Ra, Rb, Rc, and Rd overlap. In the following, the reactor Ra from which the desorption process begins first will be referred to as the "first desorption reactor Ra," and the reactors Rb, Rc, and Rd from which the desorption process begins during the desorption process of the first desorption reactor Ra will be referred to as the "second desorption reactors Rb, Rc, and Rd."

[0019] Figures 3 and 4 are time charts illustrating the pattern of change in the reactor internal pressure (pressure inside the adsorption chamber) P of reactor R during the desorption stroke. Figure 3 shows an example of the pattern of change in reactor internal pressure P when the desorption strokes do not overlap between reactors R, and Figure 4 shows an example of the pattern of change in reactor internal pressure Pa of the leading desorption reactor Ra when the desorption strokes overlap between reactors R. The reactor internal pressure P during the desorption stroke is a negative pressure lower than atmospheric pressure, and the lower the reactor internal pressure P in Figures 3 and 4, the higher the vacuum level inside the adsorption chamber.

[0020] As shown in Figure 3, if the desorption processes do not overlap between reactors R, after the residual air in the adsorption chamber is drawn out during the degassing process, the desorption process begins at time t1 and the adsorbent starts to heat up, causing the adsorbates such as CO2 and water adsorbed on the adsorbent to begin to desorb. In the first half of the desorption process, there is a large amount of adsorbent adsorbed on the adsorbent and a large amount of desorption, so the reactor internal pressure P is relatively high. In the second half of the desorption process, the amount of adsorbent adsorbed on the adsorbent decreases and the amount of desorption decreases, so the reactor internal pressure P decreases.

[0021] The adsorption equilibrium, where the adsorption rate of adsorbate to the adsorbent is equal to the desorption rate of adsorbate detached from the adsorbent, shifts towards desorption as the partial pressure of CO2 in the adsorption chamber decreases. Since water, which desorbs at a lower temperature than CO2, is mostly desorbed in the first half of the desorption process, the partial pressure of CO2 in the adsorption chamber in the second half of the desorption process is approximately equal to the total pressure in the adsorption chamber (reactor internal pressure P).

[0022] As shown in Figures 2 and 4, when the desorption strokes overlap between reactors R, when the desorption strokes of the later desorption reactors Rb, Rc, and Rd begin at times t2, t3, and t4, the reactor internal pressure Pa of the preceding desorption reactor Ra increases, and the CO2 partial pressure in the adsorption chamber increases. That is, a large amount of desorbed gas in the first half of the desorption stroke, drawn out from the later desorption reactors Rb, Rc, and Rd, flows into the preceding desorption reactor Ra via the confluence pipe 52 in Figure 1, causing the reactor internal pressure Pa of the preceding desorption reactor Ra to increase and the CO2 partial pressure in the adsorption chamber to increase. In this case, the adsorption equilibrium of the preceding desorption reactor Ra shifts towards the adsorption side, hindering CO2 desorption and reducing the overall CO2 recovery efficiency of the system.

[0023] Therefore, in this embodiment, the DAC device is configured as follows to reduce the influence of desorbed gas from the adsorption chambers of other reactors R, thereby facilitating CO2 desorption in the adsorption chambers of each reactor R and improving the overall CO2 recovery efficiency of the device.

[0024] Figures 5 and 6 are schematic block diagrams showing an example of the piping configuration of a DAC device 100 according to an embodiment of the present invention. In the DAC device 100 of Figure 5, instead of the on-off valves 7, individual piping 51 is provided with adjustment valves 9 (9a, 9b, ...) that adjust the flow rate of gas flowing from each reactor R to the vacuum piping 5. The adjustment valves 9 are, for example, butterfly valves. In the DAC device 100 of Figure 6, in addition to the on-off valves 7, adjustment valves 9 are provided in the individual piping 51 downstream of the on-off valves 7. As shown in Figures 5 and 6, by providing adjustment valves 9 in the individual piping 51, the flow rate of desorbed gas flowing from each reactor R to the vacuum piping 5 can be adjusted.

[0025] The control valve 9, such as a butterfly valve, can prevent the flow of desorbed gas in the individual piping 51 by adjusting the flow rate to "0". Therefore, even if only the control valve 9 is installed in the individual piping 51 as shown in Figure 5, it is possible to adjust the flow rate and ensure the airtightness of the vacuum piping 5. In this case, the overall configuration of the device can be simplified. If both the on / off valve 7 and the control valve 9 are installed as shown in Figure 6, it is possible to adjust the flow rate and further ensure the airtightness of the vacuum piping 5.

[0026] As shown in Figures 5 and 6, the reactor R is equipped with pressure sensors 11 (11a, 11b, ...) for detecting the reactor internal pressure P. The DAC device 100 is also equipped with sensors for detecting environmental conditions, such as a temperature sensor 12 and a humidity sensor 13. The temperature sensor 12 and humidity sensor 13 may detect the temperature (outside air temperature) and humidity (outside air humidity) of the air drawn into the reactor R, respectively, or they may be provided in each reactor R to detect the temperature and humidity inside the adsorption chamber. Alternatively, a combination of these may be used. The temperature sensor 12 may also detect the temperature of the adsorbent. As an example, the temperature sensor 12 is configured to detect the outside air temperature as a temperature representative of the adsorbent temperature.

[0027] Figure 7 is a schematic block diagram showing an example of the control configuration of the DAC device 100. As shown in Figure 7, the controller 10 is connected to a pressure sensor 11, a temperature sensor 12, and a humidity sensor 13, and signals indicating the detected values ​​of each sensor are input to the controller 10. In addition, various parts of the DAC device 100, such as a fan 4, a vacuum pump 6, on-off valves 1, 2, and 7 (intake valve 1, exhaust valve 2, on-off valve 7), a control valve 9, and a heat exchanger, are connected to the controller 10, and control signals are transmitted from the controller 10 to each part of the DAC device 100.

[0028] The controller 10 drives the fan 4 and the vacuum pump 6, starts the heat exchanger as needed, and then controls each part of the DAC device 100 so that the adsorption and desorption processes are performed alternately in each reactor R in accordance with 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 as overlapping operation.

[0029] During the adsorption stroke, the controller 10 opens the intake valve 1 and exhaust valve 2 to allow air to flow into the reactor R, and closes the on-off valve 7 and / or adjusts the opening degree A of the control valve 9 to "0" to prohibit the flow of gas from the reactor R to the vacuum piping 5. During the desorption stroke, the controller 10 closes the intake valve 1 and exhaust valve 2 to seal the reactor R, and if there is an on-off valve 7, opens the on-off valve 7, and adjusts the opening degree A of the control valve 9 to allow the flow of desorbed gas from the reactor R to the vacuum piping 5 and adjusts the flow rate.

[0030] Figure 8 is a time chart illustrating the target opening degree A0 of the control valve 9a corresponding to the reactor Ra during the decompression stroke. The controller 10 controls the control valve 9 so that the change pattern of the reactor internal pressure P during the decompression stroke, as detected by the pressure sensor 11, follows a predetermined pattern. The predetermined pattern is the change pattern of the reactor internal pressure P when there is no subsequent decompression reactor R, that is, when the decompression strokes do not overlap between reactors R, as shown in Figure 3.

[0031] For example, the characteristics of the target opening degree A0 of the control valve 9 are predetermined according to the elapsed time since the start of the decompression process, so that the pattern of change of the reactor internal pressure P during the decompression process follows a predetermined pattern, and are stored in the controller 10 (ROM). Based on the elapsed time since the start of the decompression process and the predetermined and stored characteristics of the target opening degree A0, the controller 10 (CPU) performs feedforward control of the control valve 9 so that the opening degree A becomes the target opening degree A0.

[0032] In the characteristics of the target opening degree A0 of the control valve 9, for example, as shown in Figure 8, the target opening degree A0 is determined in stages according to the elapsed time. More specifically, the target opening degree A0a is set to increase in stages from an intermediate opening to fully open in each of four stages: from the start of the departure stroke of the leading departure reactor Ra to the start of the departure stroke of the trailing departure reactor Rb (times t1 to t2), from the start of the departure stroke of the trailing departure reactor Rb to the start of the departure stroke of the trailing departure reactor Rc (times t2 to t3), from the start of the departure stroke of the trailing departure reactor Rc to the start of the departure stroke of the trailing departure reactor Rd (times t3 to t4), and from the start of the departure stroke of the trailing departure reactor Rd to the end of the departure stroke of the leading departure reactor Ra (times t4 to t5). In other words, the target opening degree A0a of the control valve 9a corresponding to the preceding decompression reactor Ra during the decompression stroke is determined in stages according to the number of subsequent decompression reactors Rb, Rc, and Rd that are performing the decompression stroke.

[0033] The target opening degree A0 of the control valve 9 may be further corrected by environmental conditions detected by the temperature sensor 12 and the humidity sensor 13. That is, when the ambient temperature is high and the temperature of the adsorbent is high at the start of the desorption process, the adsorbent heats up faster than when the ambient temperature is low and the temperature of the adsorbent is low at the start of the desorption process, and a large amount of desorbed gas is generated. Also, when the ambient humidity is high, more water is adsorbed on the adsorbent than when the ambient humidity is low, and a large amount of water-containing desorbed gas is generated during the heating of the adsorbent. The conditions that result in a large amount of desorbed gas, that is, the higher the ambient temperature detected by the temperature sensor 12 and the higher the ambient humidity detected by the humidity sensor 13, the smaller the target opening degree A0 of the control valve 9 is set to.

[0034] Figures 9 and 10 illustrate the amount of opening change ΔA when the control valve 9 is controlled according to the reactor internal pressure P of the reactor R during the detachment stroke detected by the pressure sensor 11. Hereinafter, among the reactors R during the detachment stroke, the specific reactor R that is of interest for controlling the control valve 9 will be referred to as the self-reactor Rs, and the reactors R other than the self-reactor Rs will be referred to as other reactors Ro.

[0035] Figure 9 is a diagram illustrating the amount of opening change ΔA when controlling the control valve 9 corresponding to the self-reactor Rs in accordance with the reactor internal pressure Ps of the self-reactor Rs. The controller 10 controls the control valve 9 corresponding to the self-reactor Rs so that the change pattern of the reactor internal pressure Ps of the self-reactor Rs follows a predetermined pattern. The predetermined pattern is set in advance as the characteristics of the target reactor internal pressure P0 according to the elapsed time since the start of the detachment stroke and is stored in the controller 10 (ROM).

[0036] As shown in Figure 9, when the current reactor internal pressure Ps detected by the pressure sensor 11 is lower than the target reactor internal pressure P0 (Ps - P0 < 0), the controller 10 reduces the opening A of the control valve 9, i.e., changes it to the closed position. By adjusting the opening A of the control valve 9 to the closed position and reducing the flow rate of desorbed gas flowing from the reactor Rs to the vacuum piping 5, the reactor internal pressure Ps of the reactor Rs can be increased and brought closer to the target reactor internal pressure P0. At this time, the opening change amount ΔA is a negative value (ΔA < 0), and the absolute value of the opening change amount ΔA |ΔA| becomes larger as the difference |Ps - P0| between the current reactor internal pressure Ps and the target reactor internal pressure P0 increases.

[0037] When the current reactor internal pressure Ps is higher than the target reactor internal pressure P0 (Ps - P0 > 0), the controller 10 increases the opening degree A of the control valve 9, i.e., changes it to the open side. By adjusting the opening degree A of the control valve 9 to the open side and increasing the flow rate of desorbed gas flowing from the reactor Rs to the vacuum piping 5, the reactor internal pressure Ps of the reactor Rs can be lowered and brought closer to the target reactor internal pressure P0. At this time, the opening degree change amount ΔA is a positive value (ΔA > 0), and the absolute value of the opening degree change amount ΔA |ΔA| becomes larger as the difference between the current reactor internal pressure Ps and the target reactor internal pressure P0 |Ps - P0| is larger.

[0038] As shown in Figure 9, the characteristics of the opening degree change amount ΔA of the control valve 9 corresponding to the value obtained by subtracting the target reactor internal pressure P0 from the current reactor internal pressure Ps (Ps - P0) are predetermined and stored in the controller 10 (ROM). The characteristics of the opening degree change amount ΔA may be defined as a straight line, as shown by the solid line in Figure 9, or as a curve, as shown by the dashed line. The controller 10 (CPU) provides feedback control to the control valve 9 to change the opening degree A by the opening degree change amount ΔA based on the value obtained by subtracting the target reactor internal pressure P0 from the current reactor internal pressure Ps (Ps - P0) and the predetermined and stored characteristics of the opening degree change amount ΔA.

[0039] The controller 10 can perform a combination of feedforward control of the control valve 9 based on the target opening A0 and feedback control of the control valve 9 based on the difference between the current reactor internal pressure Ps of the self-reactor Rs and the target reactor internal pressure P0. When feedback control is performed, the control valve 9 can be controlled with high precision so that the change pattern of the reactor internal pressure P during the disengagement stroke follows a predetermined pattern. When feedforward control and feedback control are performed in combination, it is possible to prevent the opening change amount |ΔA| from becoming excessive and to control the control valve 9 stably.

[0040] Figure 10 is a diagram illustrating the amount of opening change ΔA when controlling the control valve 9 corresponding to the self-reactor Rs in accordance with the reactor internal pressure Po of another reactor Ro. The controller 10 controls the control valve 9 corresponding to the self-reactor Rs so that the change pattern of the reactor internal pressure Po of the other reactor Ro becomes a predetermined pattern.

[0041] As shown in Figure 10, when the current reactor internal pressure Po of the other reactor Ro detected by the pressure sensor 11 is lower than the target reactor internal pressure P0 (Po - P0 < 0), the controller 10 increases the opening degree A of the control valve 9 corresponding to its own reactor Rs, i.e., changes it to the open side. By adjusting the opening degree A of the control valve 9 to the open side and increasing the flow rate of desorbed gas flowing out of its own reactor Rs into the vacuum piping 5, the reactor internal pressure Po of the other reactor Ro can be increased and brought closer to the target reactor internal pressure P0. At this time, the opening degree change amount ΔA is a positive value (ΔA > 0), and the absolute value of the opening degree change amount ΔA |ΔA| becomes larger as the difference |Po - P0| between the current reactor internal pressure Po of the other reactor Ro and the target reactor internal pressure P0 increases.

[0042] When the current reactor pressure Po of the other reactor Ro is higher than the target reactor pressure P0 (Po - P0 > 0), the controller 10 reduces the opening A of the control valve 9 corresponding to its own reactor Rs, i.e., changes it to the closed position. By adjusting the opening A of the control valve 9 to the closed position and reducing the flow rate of desorbed gas flowing from its own reactor Rs into the vacuum piping 5, the reactor pressure Po of the other reactor Ro can be lowered and brought closer to the target reactor pressure P0. The amount of opening change ΔA at this time is a negative value (ΔA < 0), and the absolute value of the opening change ΔA |ΔA| becomes larger as the difference |Po - P0| between the current reactor pressure Po of the other reactor Ro and the target reactor pressure P0 increases.

[0043] As shown in Fig. 10, the characteristic of the opening change amount ΔA of the regulating valve 9 corresponding to the own reactor Rs, which is determined in accordance with the value obtained by subtracting the target reactor internal pressure P0 from the current reactor internal pressure Po of the other reactor Ro (Po-P0), is predetermined and stored in the controller 10 (ROM). The characteristic of the opening change amount ΔA may be defined as a straight line as shown by the solid line in Fig. 10, or may be defined as a curve as shown by the broken line in Fig. 10. The controller 10 (CPU) performs feedback control on the regulating valve 9 to change the opening A by the opening change amount ΔA, based on the value (Po-P0) obtained by subtracting the target reactor internal pressure P0 from the current reactor internal pressure Po of the other reactor Ro and the predetermined and stored characteristic of the opening change amount ΔA.

[0044] It should be noted that feedback control is similarly performed in the following cases: when the own reactor Rs is the preceding desorption reactor Ra and the other reactor Ro is the succeeding desorption reactor Rb; when the own reactor Rs is the succeeding desorption reactor Rb and the other reactor Ro is the preceding desorption reactor Ra; and when the own reactor Rs is the reactor Rb and the other reactor Ro are the preceding desorption reactor Ra and the succeeding desorption reactor Rc relative to the reactor Rb.

[0045] When there are a plurality of succeeding desorption reactors Rb, Rc, Rd, after performing weighting processing for each of the preceding desorption reactors Ra, Rb, Rc relative to the succeeding desorption reactor Rd serving as the own reactor Rs on the opening change amount ΔAd calculated based on the current reactor internal pressure Pd of the succeeding desorption reactor Rd serving as the other reactor Ro, the final opening change amounts ΔAa, ΔAb, ΔAc of the regulating valves 9 respectively corresponding to the preceding desorption reactors Ra, Rb, Rc may be determined. For example, the sum of values kaΔAd, kbΔAd, kcΔAd obtained by multiplying the opening change amount ΔAd by weighting coefficients ka, kb, kc respectively (kaΔAd + kbΔAd + kcΔAd) may be used as the final opening change amounts ΔAa, ΔAb, ΔAc to perform feedback control, where ka + kb + kc = 1.

[0046] Similarly, the opening change amount ΔAa calculated based on the current reactor internal pressure Pa of the preceding desorption reactor Ra as the other reactor Ro may be weighted for each of the succeeding desorption reactors Rb, Rc, and Rd as the own reactor Rs, and then the final opening change amounts ΔAb, ΔAc, and ΔAd of the regulating valves 9 respectively corresponding to the succeeding desorption reactors Rb, Rc, and Rd may be determined. For example, feedback control may be performed with the total value (kbΔAa + kcΔAa + kdΔAa) of values kbΔAa, kcΔAa, kdΔAa obtained by multiplying the opening change amount ΔAa by weighting coefficients kb, kc, kd respectively as the final opening change amounts ΔAb, ΔAc, ΔAd (kb + kc + kd = 1).

[0047] The controller 10 can perform a combination of feedforward control of the regulating valve 9 based on a target opening A0 and feedback control of the regulating valve 9 based on a difference between the current reactor internal pressure Po of the other reactor Ro and a target reactor internal pressure P0. When feedback control is performed, the regulating valve 9 can be accurately controlled such that the change pattern of the reactor internal pressure P during the desorption step matches a predetermined pattern. When feedforward control and feedback control are performed in combination, the opening change amount |ΔA| can be prevented from becoming excessively large, and the regulating valve 9 can be stably controlled.

[0048] According to the embodiment of the present invention, the following operational effects can be obtained. (1) The DAC device 100 comprises: a plurality of reactors R provided with an adsorbent that adsorbs or absorbs CO2; an intake valve 1 and an exhaust valve 2 that open each reactor R to the atmosphere or seal each reactor R; a vacuum pipe 5 that connects the plurality of reactors R to a vacuum pump 6; a regulating valve 9 that regulates the flow rate of gas flowing from each reactor R to the vacuum pipe 5; and a controller 10 that controls the intake valve 1, the exhaust valve 2, and the regulating valve 9 so as to alternately perform: an adsorption step in which each reactor R is opened to the atmosphere, the flow of gas to the vacuum pipe 5 is blocked, and the adsorbent is caused to adsorb CO2 in the atmosphere; and a desorption step in which each reactor R is sealed, the flow of gas to the vacuum pipe 5 is allowed, and CO2 is desorbed from the adsorbent (Figs. 5 and 7).

[0049] The multiple reactors R include a leading decompression reactor Ra and subsequent decompression reactors Rb, Rc, and Rd, whose decompression process begins during the decompression process of the leading decompression reactor Ra (Figures 2 and 8). The controller 10 controls the control valve 9 so that the pattern of change in the internal pressure P of each reactor R during its decompression process follows a predetermined pattern (Figure 8).

[0050] When the desorption strokes overlap between reactors R, when the desorption stroke of the later desorption reactors Rb, Rc, and Rd begins, a large amount of desorbed gas from the later desorption reactors Rb, Rc, and Rd in the first half of the desorption stroke flows into the earlier desorption reactor Ra via the confluence pipe 52. In this case, the reactor internal pressure Pa of the earlier desorption reactor Ra increases, the partial pressure of CO2 in the adsorption chamber increases, and the adsorption equilibrium of the earlier desorption reactor Ra shifts towards the adsorption side, causing CO2 desorption to stagnate and reducing the overall CO2 recovery efficiency of the system. By controlling the control valve 9 so that the pattern of change in the reactor internal pressure P during the desorption stroke of each reactor R follows a predetermined pattern, the influence of desorbed gas from the adsorption chambers of other reactors R via the confluence pipe 52 can be reduced, and the CO2 recovery efficiency can be improved.

[0051] (2) The predetermined pattern is the pattern of change in the reactor internal pressure P when there is no subsequent desorption reactor R, that is, when the desorption strokes do not overlap between reactors R (Figures 3, 4, and 8). In this case, the predetermined pattern and the target reactor internal pressure P0 can be set to a necessary and sufficient pressure value, so that the CO2 recovery efficiency is not reduced by excessive flow rate restriction.

[0052] (3) The controller 10 feedforward controls the control valve 9 based on the characteristics of the target opening A0 according to the elapsed time since the start of the detachment stroke, which are predetermined so that the change pattern of the reactor internal pressure P becomes a predetermined pattern (Figure 8). In this case, since the control valve 9 can be controlled according to a predetermined schedule, the control valve 9 can be controlled simply and accurately so that the change pattern of the reactor internal pressure P during the detachment stroke becomes a predetermined pattern.

[0053] (4) In the characteristics of the target opening degree A0, the target opening degree A0 is determined in stages according to the elapsed time (Figure 8). In this case, the control valve 9 can be controlled more easily.

[0054] (5) The DAC device 100 further includes a pressure sensor 11 for detecting the reactor internal pressure P (Figures 5 to 7). Based on the reactor internal pressure P detected by the pressure sensor 11, the controller 10 provides feedback control to the adjustment valve 9 so that the change pattern of the reactor internal pressure P follows a predetermined pattern. In this case, the adjustment valve 9 can be controlled with even greater precision.

[0055] (6) The DAC device 100 is further equipped with a pressure sensor 11 for detecting the reactor internal pressure P (Figures 5 to 7). Based on the reactor internal pressure Ps of its own reactor Rs detected by the pressure sensor 11, the controller 10 provides feedback control to the adjustment valve 9 corresponding to its own reactor Rs so that the change pattern of the reactor internal pressure Ps becomes a predetermined pattern (Figure 9).

[0056] (7) The DAC device 100 further includes a pressure sensor 11 for detecting the reactor internal pressure P (Figure 7). Based on the reactor internal pressure Po of another reactor Ro detected by the pressure sensor 11, the controller 10 feedback-controls the adjustment valve 9 corresponding to its own reactor Rs so that the change pattern of the reactor internal pressure Po becomes a predetermined pattern (Figure 10).

[0057] (8) Each control valve 9 is composed of a butterfly valve that adjusts the flow rate of the gas. The DAC device 100 is further provided with a ball valve located between each reactor R and the butterfly valve, which allows or prohibits the flow of gas (Figure 6). In this case, the flow rate of the desorbed gas flowing from each reactor R to the vacuum piping 5 can be adjusted, and the airtightness of the vacuum piping 5 can be further ensured.

[0058] 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.

[0059] 1. Intake valve (on / off valve), 2. Exhaust valve (on / off valve), 3. Atmospheric piping, 4. Fan, 5. Vacuum piping, 6. Vacuum pump, 7. On / off valve, 8. Storage tank, 9. Control valve, 10. Controller, 11. Pressure sensor, 12. Temperature sensor, 13. Humidity sensor, 51. Individual piping, 52. Combined piping, 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; a plurality of on-off valves for opening or sealing each of the plurality of adsorption chambers to the atmosphere; vacuum piping connecting the plurality of adsorption chambers to a vacuum pump; a plurality of control valves for adjusting the flow rate of gas from each of the plurality of adsorption chambers to the vacuum piping; and a control unit for controlling the plurality of on-off valves and the plurality of control valves to alternately perform an adsorption stroke in which each of the plurality of adsorption chambers is opened to the atmosphere and the flow of gas to the vacuum piping is prohibited to adsorb CO2 from the atmosphere onto the adsorbent material, and a desorption stroke in which each of the plurality of adsorption chambers is sealed and the flow of gas to the vacuum piping is permitted to desorb CO2 from the adsorbent material, 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 plurality of regulating valves so that the pressure change pattern during the desorption stroke of each of the plurality of adsorption chambers becomes a predetermined pattern.

2. The DAC apparatus according to claim 1, characterized in that the predetermined pattern is the change pattern when the second adsorption chamber is absent.

3. A DAC device according to claim 1 or 2, wherein the control unit controls the plurality of control valves based on the characteristics of a target opening degree corresponding to the elapsed time since the start of the disengagement stroke, which are predetermined so that the change pattern becomes the predetermined pattern.

4. A DAC device according to claim 3, characterized in that, in the characteristics, the target opening degree is determined in steps according to the elapsed time.

5. A DAC device according to claim 1 or 2, further comprising a pressure detection unit for detecting the pressure, wherein the control unit controls the plurality of control valves based on the pressure detected by the pressure detection unit so that the change pattern becomes the predetermined pattern.

6. A DAC device according to claim 1 or 2, further comprising a pressure detection unit for detecting the pressure, wherein the control unit controls a control valve corresponding to one of the first adsorption chambers and the second adsorption chamber, based on the pressure detected by the pressure detection unit, so that the change pattern becomes the predetermined pattern.

7. A DAC device according to claim 1 or 2, further comprising a pressure detection unit for detecting the pressure, wherein the control unit controls a control valve corresponding to the other of the first and second adsorption chambers based on the pressure in one of the first and second adsorption chambers detected by the pressure detection unit, such that the change pattern becomes the predetermined pattern.

8. A DAC device according to claim 1 or 2, wherein each of the plurality of control valves is composed of a butterfly valve for adjusting the flow rate of the gas, and further comprises a ball valve provided between each of the plurality of adsorption chambers and the butterfly valve for allowing or prohibiting the flow of the gas.

Images