DAC device
Patent Information
- Application Number
- PCT/JP2025/012738
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2026-10-01
Smart Images
Figure JP2025012738_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 for capturing CO₂, which is a major greenhouse gas. 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 outside air is introduced into an adsorption chamber provided with an adsorbent to allow the adsorbent to adsorb CO₂, the adsorbent is heated with a regeneration fluid heated by a heat pump unit, and the adsorption chamber is depressurized by a vacuum pump to desorb CO₂, and then the regeneration exhaust fluid containing the desorbed CO₂ is cooled with a regeneration fluid cooled by the heat pump unit, thereby liquefying and separating CO₂.
[0003] International Publication No. 2024 / 013957
[0004] However, when a plurality of cooperatively operating devices such as a heat pump and a vacuum pump are used as in the DAC apparatus described in the above-mentioned Patent Document 1, it is difficult to start each device at appropriate timing to efficiently start the entire apparatus.
[0005] One aspect of the present invention is a DAC device for recovering CO2 from the atmosphere. The DAC device comprises an adsorption chamber provided with an adsorbent for adsorbing or absorbing CO2, an atmospheric valve for opening or closing the adsorption chamber to the atmosphere, a vacuum pump connected to the adsorption chamber via vacuum piping, a vacuum valve for allowing or prohibiting the flow of gas from the adsorption chamber to the vacuum piping, a heat exchanger provided to exchange heat with the adsorbent, a heat pump that cools the vacuum pump and transfers heat from a low-temperature heat medium that cools the adsorbent via the heat exchanger to a high-temperature heat medium that heats the adsorbent via the heat exchanger, a low-temperature heat medium temperature detection unit for detecting the temperature of the low-temperature heat medium, a heat medium control valve for controlling the supply of the low-temperature heat medium and the high-temperature heat medium to the heat exchanger, and a control unit that controls the atmospheric valve, vacuum valve, and heat medium control valve to alternately perform an adsorption process in which the adsorption chamber 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 the adsorption chamber is closed, the flow of gas to the vacuum piping is permitted, and the adsorbent is heated to desorb CO2 from the adsorbent. When the control unit starts the DAC device, it starts the heat pump and vacuum pump on the condition that the temperature of the low-temperature heat medium detected by the low-temperature heat medium temperature detection unit is above the lower limit temperature.
[0006] According to the present invention, the entire device can be started efficiently.
[0007] A schematic block diagram showing an example of the gas piping configuration of a DAC device according to an embodiment of the present invention. A schematic block diagram showing an example of the heat transfer medium piping configuration of a DAC device according to an embodiment of the present invention. A schematic block diagram showing an example of the piping configuration between the heat pump in Figure 2 and the high-temperature water tank and low-temperature water tank. A schematic block diagram showing an example of the control configuration of a DAC device according to an embodiment of the present invention. A flowchart showing an example of the heat pump startup process performed by the controller in Figure 4. A diagram for explaining the low-temperature water temperature management process performed by the controller in Figure 4. A flowchart showing an example of the vacuum pump startup process performed by the controller in Figure 4. A diagram for explaining the flow of high-temperature water when the bypass valve is opened in step S12 of Figure 7. A flowchart showing an example of the schedule adjustment process performed by the controller in Figure 4.
[0008] Embodiments of the present invention will be described below with reference to Figures 1 to 9. Figure 1 is a schematic block diagram showing an example of the configuration of gas piping in a DAC device 100 according to an embodiment of the present invention. As shown in Figure 1, the DAC device 100 mainly comprises 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 valves (control valves) 1 (1a, 1b, ...), 2 (2a, 2b, ...) for opening or closing the reactor R to the atmosphere. Atmospheric 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 valves 1 and 2 are opened, the adsorption chamber of the reactor R is opened to the atmosphere, and when atmospheric valves 1 and 2 are closed, the adsorption chamber of the reactor R is sealed. Atmospheric valves 1 and 2 are provided facing each other with the adsorption chamber in between.
[0011] A fan 3 is connected to the reactor R via either atmospheric valve 1 or 2 (atmospheric valve 2 in the illustrated example) and appropriate piping (atmospheric piping) 30 to circulate air into the adsorption chamber of the reactor R. In the illustrated example, when atmospheric valves 1 and 2 are opened and the fan 3 is driven, air is drawn into the reactor R via atmospheric valve 1, and air is exhausted from the reactor R via atmospheric valve 2, atmospheric piping 30, and fan 3. 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 valves 1 and 2 and the atmospheric piping 30 are configured to have a relatively large diameter so that a large amount of air can circulate through the reactor R. Multiple atmospheric valves 1 and 2 may be provided.
[0012] Vacuum piping 40 is further connected to the reactor R. The vacuum piping 40 connects the adsorption chamber of the reactor R to the intake port of the vacuum pump 4. More specifically, the vacuum piping 40 includes individual pipes 41 (41a, 41b, ...) that communicate with the adsorption chamber of each reactor R, and a merging pipe 42 that merges the individual pipes 41 and connects the individual pipes 41 to the vacuum pump 4 by communicating with the intake port of the vacuum pump 4.
[0013] Each individual pipe 41 is provided with a vacuum valve (control valve) 43 (43a, 43b, ...) that allows or prohibits the flow of gas in the individual pipe 41, i.e., the flow of gas from the reactor R to the vacuum pipe 40. The vacuum valve 43 may be composed of an on / off valve such as a ball valve, or a control valve such as a butterfly valve, or a combination of these. A storage tank 5 is connected to the exhaust port of the vacuum pump 4 via appropriate piping (storage piping) 50. The control valve 43 is closed during the adsorption stroke.
[0014] A gas-liquid separator 52 is connected to the storage piping 50 between the vacuum pump 4 and the storage tank 5 via a branch pipe 51. As the gas-liquid separator 52, for example, a condenser that cools the gas and condenses the water by heat exchange can be used. The gas-liquid separator 52 is equipped with an exhaust valve 53 and a drain valve 54. Furthermore, a storage valve (control valve) 55 is provided in the storage piping 50 downstream of the branching point where the branch pipe 51 branches off, which allows or prohibits the flow of gas to the storage tank 5.
[0015] During operation of the DAC device 100, the exhaust valve 53 and drain valve 54 are closed, and the storage valve 55 is open. In this case, the gas flowing from the vacuum pump 4 to the storage tank 5 flows into the gas-liquid separator 52 via the storage piping 50 and branch piping 51, where moisture is removed before the gas is stored in the storage tank 5. The water separated in the gas-liquid separator 52 is stored in the water storage space within the gas-liquid separator 52.
[0016] The reactor R is provided with heat exchangers 6 (6a, 6b, ...) for heating or cooling the adsorbent. The heat exchangers 6 are supplied with a high-temperature heat transfer medium (e.g., high-temperature water) and a low-temperature heat transfer medium (e.g., low-temperature water) at room temperature, corresponding to the CO2 desorption temperature. When high-temperature water is supplied, the heat exchangers 6 heat the adsorbent, and when low-temperature water is supplied, they cool the adsorbent.
[0017] The reactor R is also provided with a group of sensors 7 (7a, 7b, ...) which includes a pressure sensor for detecting the pressure P inside the adsorption chamber, a CO2 concentration sensor for detecting the CO2 concentration inside the adsorption chamber, and an adsorbent temperature sensor for detecting the temperature (adsorbent temperature) Ta of the adsorbent.
[0018] When atmospheric valves 1 and 2 are closed and vacuum valve 43 is opened, and vacuum pump 4 is driven, the gas in the adsorption chamber of reactor R is drawn out by vacuum pump 4 via vacuum piping 40. Furthermore, when the adsorbent material in the adsorption chamber is heated by heat exchanger 6, the CO2 adsorbed on the adsorbent material of reactor R is desorbed, and the desorbed gas, mainly containing the desorbed CO2, is drawn out of reactor R and stored in storage tank 5 for recovery (desorption process).
[0019] After the adsorption process is completed and before the desorption process begins, a degassing process may be performed to degas the adsorption chamber of the reactor R. The degassing process may be performed using vacuum piping 40 and vacuum pump 4, or a separate vacuum pump (degassing vacuum pump) may be connected to the adsorption chamber of the reactor R via separate vacuum piping (degassing vacuum piping) from vacuum pump 4, and the degassing process may be performed using the degassing vacuum pump.
[0020] The reactor R is further provided with pressure-restoring valves (control valves) 8 (8a, 8b, ...) for restoring pressure to the adsorption chamber of the reactor R. The pressure-restoring valves 8 may be installed in the piping connecting the adsorption chamber of the reactor R to the outside space, or they may be installed directly on the housing (wall) of the reactor R. The pressure-restoring valves 8 are closed during the adsorption and desorption strokes.
[0021] After the desorption process is completed and before the adsorption process begins, control valves 1, 2, 8, and 43 are closed, and the adsorbent is cooled by the heat exchanger 6. Once the adsorbent has cooled to room temperature, the pressure restoration valve 8 is opened, and air is introduced from the outside to restore the adsorption chamber to atmospheric pressure (cooling and pressure restoration process). If oxygen-containing air flows through the adsorption chamber while the adsorbent is at a high temperature, the adsorbent may oxidize and deteriorate. By cooling the adsorbent to a temperature range where oxidation reactions do not proceed before introducing air into the adsorption chamber and restoring pressure, oxidative deterioration of the adsorbent can be prevented.
[0022] In the DAC device 100, the adsorption process, desorption process, and cooling / repressurization process are performed sequentially in multiple reactors R with staggered timings. More specifically, the order in which the multiple reactors R perform each process, the duration of each process, and the time intervals for staggering the start times of each process between the reactors R are predetermined.
[0023] Figure 2 is a schematic block diagram showing an example of the configuration of the heat transfer fluid piping in the DAC device 100. As shown in Figure 2, the DAC device 100 is equipped with a heat pump 60 for supplying high-temperature water and low-temperature water to the heat exchangers 6 provided in each reactor R.
[0024] The heat pump 60 has an evaporator (heat exchanger) that evaporates the working fluid, a compressor that compresses the evaporated working fluid, a condenser (heat exchanger) that condenses the compressed working fluid, and an expansion valve that expands the condensed working fluid, thereby transferring heat from low-temperature water to high-temperature water. In the evaporator, the heat from the low-temperature water is absorbed by the working fluid, causing the working fluid to evaporate (vaporize) (evaporation stroke). In the compressor, the gaseous working fluid becomes high temperature and high pressure through adiabatic compression (compression stroke). In the condenser, the heat from the gaseous working fluid is released to the high-temperature water, causing the working fluid to condense (liquefy) (condensation stroke). In the expansion valve, the liquid working fluid becomes low temperature and low pressure through adiabatic expansion (expansion stroke). The heat pump 60 circulates the working fluid between low-temperature water and high-temperature water, repeating the evaporation stroke, compression stroke, condensation stroke, and expansion stroke, thereby transferring heat from the low-temperature water to the high-temperature water.
[0025] In the heat pump 60, the compressor speed is adjusted to raise the temperature of the high-temperature water to a preset target temperature according to the CO2 desorption temperature (for example, around 100°C). In other words, the compressor speed is adjusted so that the temperature of the high-temperature water coming out of the heat pump 60 reaches the target temperature, depending on the temperature of the high-temperature water entering the heat pump 60. In the heat pump 60, the heat absorbed from the low-temperature water in the evaporator is released to the high-temperature water in the condenser, causing the temperature of the high-temperature water to rise. Therefore, the greater the rise in the temperature of the high-temperature water, the greater the drop in the temperature of the low-temperature water. The higher the compressor speed and the greater the load (power consumption) of the heat pump 60, the greater the rise in the temperature of the high-temperature water and the greater the drop in the temperature of the low-temperature water.
[0026] The heat pump 60 is connected via appropriate piping to a high-temperature water tank 61 for storing high-temperature water circulated to the condenser of the heat pump 60, and a low-temperature water tank 62 for storing low-temperature water circulated to the evaporator of the heat pump 60. The high-temperature water tank 61 is equipped with a high-temperature water temperature sensor 61S for detecting the temperature of the high-temperature water (high-temperature water temperature) TwH. The low-temperature water tank 62 is equipped with a low-temperature water temperature sensor 62S for detecting the temperature of the low-temperature water (low-temperature water temperature) TwL.
[0027] The high-temperature water tank 61 and the low-temperature water tank 62 are further connected to the heat exchangers 6 of each reactor R via appropriate piping, and the high-temperature water stored in the high-temperature water tank 61 and the low-temperature water stored in the low-temperature water tank 62 are circulated to the heat exchangers 6 of each reactor R via the piping.
[0028] More specifically, the high-temperature water stored in the high-temperature water tank 61 flows through a channel 611 equipped with a water supply pump 610 at a flow rate corresponding to the rotation speed of the water supply pump 610, and is supplied to the heat exchangers 6 of each reactor R. After heating the adsorbent in each reactor R, the high-temperature water discharged from the heat exchangers 6 flows through a channel 612 and returns to the high-temperature water tank 61.
[0029] Similarly, the cold water stored in the cold water tank 62 flows through the flow path 621, which is equipped with a water supply pump 620, at a flow rate corresponding to the rotation speed of the water supply pump 620, and is supplied to the heat exchangers 6 of each reactor R. After cooling the adsorbent in each reactor R, the cold water discharged from the heat exchangers 6 flows through the flow path 622 and returns to the cold water tank 62.
[0030] At the inlet of the heat exchanger 6 of each reactor R, there is a heat transfer medium valve (three-way proportional control valve) 63 (63a, 63b, ...) that switches whether to supply high-temperature water from the flow path 611 or low-temperature water from the flow path 621 as the heat transfer medium flowing through the heat exchanger 6. At the outlet of the heat exchanger 6 of each reactor R, there is a heat transfer medium valve (three-way proportional control valve) 64 (64a, 64b, ...) that switches whether to return the heat transfer medium discharged from the heat exchanger 6 back to the flow path 612 or back to the flow path 622. The heat transfer medium valves 63 and 64 can adjust the flow rate of the heat transfer medium (high-temperature water or low-temperature water) flowing through the heat exchanger 6 and can switch whether or not to flow the heat transfer medium into the heat exchanger 6. The heat transfer valves 63 and 64 are controlled so that high-temperature water is circulated through the flow paths 611 and 612 in the heat exchanger 6 of reactor R during the desorption stroke, and low-temperature water is circulated through the flow paths 621 and 622 in the heat exchanger 6 of reactor R during the cooling and repressurization stroke.
[0031] A bypass channel 65 is provided between the heat transfer fluid valves 63 and 64 of each reactor R and the inlet of the heat exchanger 6. The bypass channel 65 connects the inlet of the heat exchanger 6 of one reactor R to the outlet of the heat exchanger 6 of another reactor R, and returns the heat transfer fluid (high-temperature water or low-temperature water) from channel 611 or channel 621 to channel 612 or channel 622, bypassing the heat exchanger 6. In the example in Figure 2, the bypass channel 65 connects the inlet of the heat exchanger 6b of reactor Rb to the outlet of the heat exchanger 6a of reactor Ra, and returns the heat transfer fluid from channel 611 or channel 621 to channel 612 or channel 622, bypassing the heat exchanger 6b. The bypass channel 65 is provided with a bypass valve (control valve) 66 that allows or prohibits the flow of heat transfer fluid in the bypass channel 65. The bypass valve 66 is closed when the DAC device 100 is in operation.
[0032] Figure 3 is a schematic block diagram showing an example of the piping configuration between the heat pump 60 shown in Figure 2 and the high-temperature water tank 61 and low-temperature water tank 62. As shown in Figure 3, the high-temperature water stored in the high-temperature water tank 61 flows through a flow path 614 equipped with a water supply pump 613 at a flow rate corresponding to the rotation speed of the water supply pump 613, enters the condenser of the heat pump 60, and is heated to the target temperature by heat dissipation from the working fluid. The high-temperature water heated to the target temperature by the heat pump 60 flows through a flow path 615 and returns to the high-temperature water tank 61. Flow paths 614 and 615 are provided with on-off valves (control valves) 616 that allow or prohibit the circulation of high-temperature water between the heat pump 60 and the high-temperature water tank 61.
[0033] Similarly, the cold water stored in the cold water tank 62 flows through a channel 624 equipped with a water supply pump 623 at a flow rate corresponding to the rotation speed of the water supply pump 623, enters the evaporator of the heat pump 60, and is cooled by heat absorption by the working fluid. The cold water cooled by the heat pump 60 flows through a channel 625 and returns to the cold water tank 62. Channels 624 and 625 are provided with on-off valves (control valves) 626 that allow or prohibit the circulation of cold water between the heat pump 60 and the cold water tank 62. A portion of the channel 625 from the heat pump 60 to the cold water tank 62 is provided in close contact with the vacuum pump 4 shown in Figure 1, thereby allowing the vacuum pump 4 to be cooled by the cold water cooled by the heat pump 60.
[0034] A heater 67 is provided in the flow path 624 from the low-temperature water tank 62 to the heat pump 60 to heat the low-temperature water flowing through the flow path 624. A flow path 627 that bypasses the heater 67 is connected to the flow path 624. A heat dissipation section 68 is provided in the flow path 627 to dissipate the heat from the low-temperature water flowing through the flow path 627. The heat dissipation section 68 has a heat exchanger through which the low-temperature water flows and a fan that air-cools such a heat exchanger, and cools the low-temperature water by promoting heat exchange between the low-temperature water and the outside air. In the heat dissipation section 68, the low-temperature water is cooled before it is cooled by the heat pump 60. In the flow path 624 from the branching point to the confluence point of the flow path 627, an on-off valve (control valve) 628 is provided to allow or prohibit the flow of low-temperature water through the heater 67, and in the flow path 627, an on-off valve (control valve) 629 is provided to allow or prohibit the flow of low-temperature water through the heat dissipation section 68.
[0035] The heat pump 60 transfers heat from the low-temperature water to the high-temperature water, raising the temperature of the high-temperature water to the target temperature. Therefore, during the operation of the heat pump 60, it is necessary to manage the temperature of the low-temperature water entering the heat pump 60 so that it remains within an appropriate temperature range. During the operation of the heat pump 60, the heater 67, the heat dissipation unit 68 (fan), and the on-off valves 628 and 629 are controlled so that the low-temperature water temperature TwL detected by the low-temperature water temperature sensor 62S remains within an appropriate temperature range.
[0036] In the DAC device 100, the fan 3, vacuum pump 4, and control valves 1, 2, 8, and 43 provided in the gas piping shown in Figure 1, and the heat pump 60, heater 67, heat dissipation unit 68, water pumps 610, 613, 620, 623, and control valves 63, 64, 66, 616, 626, 628, and 629 provided in the heat medium piping shown in Figures 2 and 3, all work in coordination. In this embodiment, the DAC device 100 is configured as follows to enable efficient startup of the entire device by starting the heat pump 60 and vacuum pump 4, which take time to start up, at an appropriate timing when the DAC device 100 is started up.
[0037] Figure 4 is a schematic block diagram showing an example of the control configuration of the DAC device 100. As shown in Figure 4, the DAC device 100 is provided with a controller 10 that controls each part of the DAC device 100, including the fan 3, vacuum pump 4, heat pump 60, heater 67, heat dissipation unit 68 (fan), water supply pumps 610, 613, 620, 623, and control valves 1, 2, 8, 43, 63, 64, 66, 616, 626, 628, 629 shown in Figures 1 to 3. The controller 10 is composed of a computer having a CPU, ROM, RAM, I / O interface, and other peripheral circuits.
[0038] The DAC device 100 is also equipped with a high-temperature water pressure sensor 11, which is located in the flow path 611 shown in Figure 2 through which high-temperature water flows, and which detects the pressure (water pressure) of the high-temperature water. The controller 10 is connected to the sensor group 7 shown in Figures 1 to 3, the high-temperature water temperature sensor 61S, the low-temperature water temperature sensor 62S, and the high-temperature water pressure sensor 11, and signals indicating the detected values of each sensor are input to the controller 10.
[0039] When the controller 10 receives a request to start the DAC device 100, it executes the startup process for each part of the DAC device 100. More specifically, it controls the atmospheric valves 1 and 2 of each reactor R to open, and the vacuum valve 43, pressure recovery valve 8, heat transfer fluid valves 63 and 64, and bypass valve 66 to close, and then executes the heat pump startup process shown in Figure 5, the vacuum pump startup process shown in Figure 7, and the schedule adjustment process shown in Figure 9.
[0040] Figure 5 is a flowchart showing an example of the heat pump startup process performed by the controller 10. The heat pump startup process in Figure 5 is initiated when the DAC device 100 is requested to be started.
[0041] As shown in Figure 5, the controller 10 first controls the drain valve 54 in Figure 1 to open in step S1. Then, in step S2, it controls the on-off valves 616, 626, and 628 in Figure 3 to open and the on-off valve 629 to close, driving the water supply pumps 613 and 623 between the high-temperature water tank 61 and the low-temperature water tank 62 and the heat pump 60. This starts the circulation of high-temperature water between the heat pump 60 and the high-temperature water tank 61, and the circulation of low-temperature water between the heat pump 60 and the low-temperature water tank 62.
[0042] In step S2, the sensors shown in Figure 4 (sensor group 7, high-temperature water temperature sensor 61S, low-temperature water temperature sensor 62S, and high-temperature water pressure sensor 11) are activated. Next, in step S3, it is determined whether a predetermined time (for example, about 15 seconds) has elapsed since the circulation of high-temperature and low-temperature water started in step S2. Step S3 is repeated until the result is positive. The processes in steps S1 to S3 are commonly performed in the heat pump startup process in Figure 5, the vacuum pump startup process in Figure 7, and the schedule adjustment process in Figure 9.
[0043] In the heat pump startup process, if an affirmative determination is made in step S3, the process proceeds to step S4, and it is determined whether or not the low-temperature water temperature TwL detected by the low-temperature water temperature sensor 62S is equal to or higher than a first predetermined temperature TwL1 (for example, about 25° C.) preset as an appropriate temperature for the low-temperature water entering the heat pump 60. If a negative determination is made in step S4, the process proceeds to step S5 to start the heater 67 in FIG. 3 to heat the low-temperature water, and then proceeds to step S6 to determine whether or not the low-temperature water temperature TwL is equal to or higher than a lower-limit temperature TwLmin (for example, about 10° C.). Step S6 is repeated until an affirmative determination is made. If an affirmative determination is made in step S4 or step S6, the process proceeds to step S7 to start the heat pump 60.
[0044] As described above, by referring to the actual low-temperature water temperature TwL and starting the heater 67 to heat the low-temperature water as necessary, the heat pump 60 can be started after the temperature of the low-temperature water entering the heat pump 60 is adjusted to within an appropriate temperature range. Further, when the low-temperature water temperature TwL is extremely low, the heat pump 60 is started after waiting until the low-temperature water temperature TwL reaches the lower-limit temperature TwLmin. Accordingly, in the heat pump 60, the heat of the low-temperature water can be appropriately transferred to the high-temperature water to raise the temperature of the high-temperature water, and warm-up can be appropriately performed. When the heat pump 60 is started, a low-temperature water temperature control process for controlling the low-temperature water temperature TwL is started.
[0045] FIG. 6 is a diagram for explaining the low-temperature water temperature control process executed by the controller 10. As shown in FIG. 6, in the low-temperature water temperature control process, after starting the heat pump 60, when the low-temperature water temperature TwL is in a normal water temperature state equal to or higher than the first predetermined temperature TwL1, the controller 10 continues the operation of the heat pump 60 without performing heating or cooling on the low-temperature water (normal water temperature operation). In the normal water temperature operation, the controller controls the opening / closing valve 628 in FIG. 3 to open and the opening / closing valve 629 to close, and stops the heater 67 and the heat radiating unit 68 (fan).
[0046] On the other hand, after the heat pump 60 is started, when the low-temperature water temperature TwL is in a low water temperature state lower than the first predetermined temperature TwL1, the low-temperature water is heated by the heater 67, and then the operation of the heat pump 60 is continued (low water temperature operation). In the low water temperature operation, control is performed to open the on-off valve 628 and close the on-off valve 629 in Fig. 3, the heater 67 is started, and the heat radiating portion 68 (fan) is stopped.
[0047] During normal water temperature operation, when the low-temperature water temperature TwL falls below a preset second predetermined temperature TwL2 (for example, about 22°C) that is slightly lower than the first predetermined temperature TwL1, the operation shifts from the normal water temperature operation to the low water temperature operation. During the low water temperature operation, when the low-temperature water temperature TwL becomes equal to or higher than the first predetermined temperature TwL1, the operation shifts from the low water temperature operation to the normal water temperature operation.
[0048] During normal water temperature operation, when the low-temperature water temperature TwL exceeds a preset third predetermined temperature TwL3 (for example, about 27°C) that is slightly higher than the first predetermined temperature TwL1 and enters a high water temperature state, the operation shifts from the normal water temperature operation to the high water temperature operation. In the high water temperature operation, control is performed to close the on-off valve 628 and open the on-off valve 629 in Fig. 3, the heater 67 is stopped, the heat radiating portion 68 (fan) is driven, the low-temperature water is cooled by the heat radiating portion 68 (fan), and then the operation of the heat pump 60 is continued.
[0049] During the high water temperature operation, when the low-temperature water temperature TwL becomes equal to or lower than the first predetermined temperature TwL1, the operation shifts from the high water temperature operation to the normal water temperature operation.
[0050] During the low water temperature operation, when the low-temperature water temperature TwL falls below the lower limit temperature TwLmin and enters an extremely low water temperature state, the operation of the heat pump 60 is stopped. In this case, when the low-temperature water temperature TwL becomes equal to or higher than the first predetermined temperature TwL1, the operation returns to the low water temperature operation, and shifts to the normal water temperature operation after a predetermined standby time.
[0051] As described above, when the heat pump 60 is started, the low-temperature water temperature TwL is controlled so as to be within an appropriate temperature range.
[0052] In the heat pump startup process shown in Figure 5, after starting the heat pump 60 in step S7, the process proceeds to step S8. In step S8, it is determined whether a predetermined time required for the heat pump 60 to warm up has elapsed while the high-temperature water temperature TwH detected by the high-temperature water temperature sensor 61S is at or above the lower limit temperature TwHmin (for example, about 80°C). Step S8 is repeated until the result is positive. If the result is positive in step S8, the process proceeds to step S9, where the fan 3 shown in Figure 1 is driven, and the water supply pumps 610 and 620 between the high-temperature water tank 61 and the low-temperature water tank 62 shown in Figure 2 and the heat exchangers 6 of each reactor R are driven. This makes it possible to supply the high-temperature water heated by the heat pump 60 and the cooled low-temperature water to the heat exchangers 6 of each reactor R.
[0053] Figure 7 is a flowchart showing an example of the vacuum pump startup process executed by the controller 10. The vacuum pump startup process in Figure 7 also starts when the DAC device 100 is requested to start. As shown in Figure 7, in the vacuum pump startup process, if the result in step S3 is positive, the process proceeds to step S10 to determine whether the low-temperature water temperature TwL is greater than or equal to the lower limit temperature TwLmin. If the result in step S10 is negative, the process proceeds to step S11 to determine whether the difference between the low-temperature water temperature TwL and the high-temperature water temperature TwH (TwH - TwL) is greater than or equal to a predetermined temperature greater than 0°C. If the result in step S11 is negative, the process returns to step S10. Even if the process returns to step S10 after being negative in step S11, the low-temperature water temperature TwL will rise when the low-temperature water is heated in step S5 of Figure 5, which is executed in parallel.
[0054] On the other hand, if step S11 is affirmed, the process proceeds to step S12. In step S12, the bypass valve 66 in Figure 2 is controlled to open, and the heat transfer valves 63 and 64 are controlled to mix the high-temperature water from the flow path 611 with the low-temperature water flowing through the flow path 622 via the bypass flow path 65, and the process returns to step S10. As a result, the low-temperature water temperature TwL rises.
[0055] Figure 8 is a diagram illustrating the flow of high-temperature water when the bypass valve 66 is opened in step S12 of Figure 7. As shown in Figure 8, when the bypass valve 66 is opened, the high-temperature water supplied from the high-temperature water tank 61 to the inlet of the heat exchanger 6 of one reactor R via the flow path 611 is mixed with the low-temperature water flowing through the flow path 622 via the bypass flow path 65 and returns to the low-temperature water tank 62. As a result, the temperature of the low-temperature water flowing through the flow paths 621 and 622 rises.
[0056] In the vacuum pump startup process shown in Figure 7, if the result in step S10 is positive, the process proceeds to step S13, where the bypass valve 66 in Figure 2 is controlled to close. Next, in step S14, the storage valve 55 in Figure 1 is controlled to close, the exhaust valve 53 is opened, and the vacuum pump 4 is driven. If a degassing vacuum pump is provided, the degassing vacuum pump is also driven. As a result, exhaust gas from the vacuum pump 4 is discharged through the branch pipe 51 and the gas-liquid separator 52.
[0057] In this way, by referring to the actual low-temperature water temperature TwL and, if necessary, opening the bypass valve 66 to heat the low-temperature water with high-temperature water, the temperature of the low-temperature water that cools the vacuum pump 4 can be brought within an appropriate temperature range before starting the vacuum pump 4. If the heat from the high-temperature water cannot be used, the vacuum pump 4 is started only after waiting for the low-temperature water to be heated to the lower limit temperature TwLmin in the heat pump startup process shown in Figure 5. This prevents the vacuum pump 4 from being overcooled by the low-temperature water and allows for proper warm-up.
[0058] Next, in step S15, it is determined whether a predetermined time required for warming up the vacuum pump 4 has elapsed. Warming up for the predetermined time allows the operating oil temperature of the vacuum pump 4 to rise sufficiently, enabling rated operation. If this is not the case in step S15, the process proceeds to step S16, where it is determined whether the rotational speed of the vacuum pump 4 has reached a predetermined rotational speed after warming up is complete. If this is also not the case in step S16, the process returns to step S15. If the result in step S15 or step S16 is positive, the process proceeds to step S17, where the storage valve 55 in Figure 1 is opened, and the exhaust valve 53 and drain valve 54 are closed. This allows the exhaust from the vacuum pump 4 to be introduced into the storage tank 5 via the storage piping 50.
[0059] As described above, in the heat pump startup process shown in Figure 5 and the vacuum pump startup process shown in Figure 7, the heat pump 60 and the vacuum pump 4 are started on the condition that the low-temperature water temperature TwL is equal to or greater than the lower limit temperature TwLmin. This allows the heat pump 60 and the vacuum pump 4 to be warmed up in an appropriate state, and by completing the warm-up within a predetermined warm-up time, the entire DAC device 100 can be started efficiently.
[0060] Figure 9 is a flowchart showing an example of a schedule adjustment process performed by the controller 10. The schedule adjustment process in Figure 9 also starts when the DAC device 100 is requested to be started. As shown in Figure 9, in the schedule adjustment process, if the result in step S3 is affirmed, the process proceeds to step S20, where it is determined whether or not there is a previously unused reactor R that was not used due to a malfunction or the like during the previous operation of the DAC device 100, or more specifically, when it was shut down.
[0061] If the result in step S20 is positive, the process proceeds to step S21; if the result in step S20 is negative, the process proceeds to step S25. In step S21, the water supply pumps 610 and 620 between the high-temperature water tank 61 and the low-temperature water tank 62 in Figure 2 and the heat exchangers 6 of each reactor R are stopped. Next, in step S22, it is confirmed that the pressure of the high-temperature water flowing through the flow path 611 detected by the high-temperature water pressure sensor 11 becomes "0", and that the flow of high-temperature water in the flow path 611 has completely stopped. Next, in step S23, the heat medium valves 63 and 64 corresponding to the previously unused reactor R identified in step S20 are controlled to close, and it is confirmed that no heat medium (high-temperature water or low-temperature water) flows to the heat exchanger 6 of the previously unused reactor R. Next, in step S24, the operation of the water supply pumps 610 and 620 is restarted.
[0062] Next, in step S25, it is determined whether a predetermined amount of time has elapsed since the fan 3 in Figure 1 was driven in step S9 in Figure 5, allowing air to be introduced into each reactor R. Step S25 is repeated until it is confirmed. If it is confirmed in step S25, the process proceeds to step S26, where the reactor R with the largest adsorption amount of CO2 to be adsorbed onto the adsorbent material is identified.
[0063] When the DAC device 100 is stopped and then restarted, the controller 10 controls the atmospheric valves 1 and 2, the vacuum valve 43, and the heat transfer valves 63 and 64 so that the desorption process is carried out sequentially from the reactor R with the largest adsorption capacity, in a predetermined order. By starting the desorption process from the reactor R with the largest adsorption capacity when the DAC device 100 is restarted, CO2 can be recovered efficiently.
[0064] The controller 10 can determine the reactor R that was performing the adsorption process when the DAC device 100 was shut down as the reactor R with the highest adsorption amount, which is the one that started the adsorption process first, had the longest adsorption time, and is considered to have the highest adsorption amount. In this case, the reactor R with the highest adsorption amount can be easily determined based on the previous operating history.
[0065] In step S26, the controller 10 may determine the reactor R with the highest CO2 concentration detected by the sensor group 7 (CO2 concentration sensor) as the reactor R with the maximum adsorption amount. In this case, the reactor R with the largest CO2 adsorption capacity and the highest CO2 concentration in the adsorption chamber because almost no CO2 from the atmosphere in the adsorption chamber is adsorbed can be identified, and the reactor R with the maximum adsorption amount can be determined with even greater accuracy.
[0066] In step S27, it is determined whether the reactor R with the highest adsorption capacity determined in step S26 based on the CO2 concentration differs from the reactor R with the highest adsorption capacity determined based on the previous operating history, and whether the current operating schedule needs to be changed. If affirmed in step S27, the process proceeds to step S28, and the operating schedule is changed so that the desorption process is carried out sequentially in a predetermined order, starting with the reactor R with the highest adsorption capacity determined based on the CO2 concentration. If denied in step S27, the operating schedule is not changed, and the desorption process is carried out sequentially in a predetermined order, starting with the reactor R with the highest adsorption capacity determined based on the previous operating history.
[0067] According to embodiments of the present invention, the following effects can be achieved. (1) The DAC device 100 includes a reactor R provided with an adsorbent that adsorbs or absorbs CO2, atmospheric valves 1 and 2 for opening or closing the reactor R to the atmosphere, a vacuum pump 4 connected to the reactor R via a vacuum pipe 40, a vacuum valve 43 for allowing or prohibiting the flow of gas from the reactor R to the vacuum pipe 40, a heat exchanger 6 provided to exchange heat with the adsorbent, a heat pump 60 that cools the vacuum pump 4 and transfers heat from low-temperature water that cools the adsorbent via the heat exchanger 6 to high-temperature water that heats the adsorbent via the heat exchanger 6, and the low-temperature water temperature Tw The system includes a low-temperature water sensor 62S for detecting L, control valves 63, 64, and 66 for controlling the supply of low-temperature and high-temperature water to the heat exchanger 6, and a controller 10 for controlling atmospheric valves 1 and 2, vacuum valve 43, and control valves 63, 64, and 66 to alternately perform an adsorption process in which the reactor R is opened to the atmosphere and the flow of gas to the vacuum piping 40 is prohibited, allowing CO2 from the atmosphere to be adsorbed onto the adsorbent, and a desorption process in which the reactor R is sealed, the flow of gas to the vacuum piping 40 is permitted, and the adsorbent is heated to desorb CO2 from the adsorbent (Figures 1, 2, and 4).
[0068] When the controller 10 starts the DAC device 100, it starts the heat pump 60 and the vacuum pump 4 on the condition that the low-temperature water temperature TwL detected by the low-temperature water temperature sensor 62S is equal to or greater than the lower limit temperature TwLmin (steps S6 to S7 in Figure 5, and steps S10 and S14 in Figure 7). This allows the heat pump 60 and the vacuum pump 4 to warm up in an appropriate state and complete the warm-up within a predetermined warm-up time, thereby enabling the entire DAC device 100 to start up efficiently.
[0069] (2) The DAC device 100 further includes a flow path 611 through which high-temperature water flows from the heat pump 60 to the heat exchanger 6, a flow path 622 through which low-temperature water flows from the heat exchanger 6 to the heat pump 60, a bypass flow path 65 connecting the flow paths 611 and 622, and a bypass valve 66 provided in the bypass flow path 65 (Figure 2). When the vacuum pump 4 is started, the controller 10 controls the bypass valve 66 to open so that high-temperature water from the heat pump 60 flows to the heat pump 60 via the bypass flow path 65 if the low-temperature water temperature TwL detected by the low-temperature water temperature sensor 62S is less than the lower limit temperature TwLmin (steps S10 and S12 in Figure 7). This allows the high-temperature water to be mixed with the low-temperature water via the bypass flow path 65, thereby raising the low-temperature water temperature TwL.
[0070] (3) The order in which the multiple reactors R perform the adsorption and desorption processes is predetermined. When the DAC device 100 is stopped and then restarted, the controller 10 controls the atmospheric valves 1 and 2, the vacuum valve 43, and the control valves 63, 64, and 66 so that the desorption process is performed sequentially in the predetermined order, starting with the reactor R with the largest adsorption amount of CO2 adsorbed onto the adsorbent material. By starting the desorption process with the reactor R with the largest adsorption amount when the DAC device 100 is restarted, CO2 can be recovered efficiently.
[0071] (4) The controller 10 determines the reactor R that was performing the adsorption process first among the reactors R that were performing the adsorption process when the DAC device 100 was stopped as the reactor R with the maximum adsorption amount. In this case, the reactor R with the maximum adsorption amount can be easily determined based on the previous operating history.
[0072] (5) The DAC device 100 further includes a sensor group 7, which includes a CO2 concentration sensor for detecting the CO2 concentration in the adsorption chamber of the reactor R (Figures 1 and 4). When the controller 10 starts up the DAC device 100, it determines the reactor R with the highest CO2 concentration detected by the sensor group 7 (CO2 concentration sensor) as the reactor with the maximum adsorption amount (step S26 in Figure 9). In this case, it is possible to identify the reactor R that has the largest CO2 adsorption amount and where almost no CO2 from the atmosphere in the adsorption chamber is adsorbed, resulting in the highest CO2 concentration in the adsorption chamber, and thus determine the reactor with the maximum adsorption amount R with even greater accuracy.
[0073] In the above embodiment, steps S6 and S7 in Figure 5, and steps S10 and S14 in Figure 7, etc., describe an example in which both the heat pump 60 and the vacuum pump 4 are started on the condition that the low-temperature water temperature TwL is equal to or greater than the lower limit temperature TwLmin. However, the lower limit temperature of the low-temperature heat medium when starting the heat pump and the lower limit temperature of the low-temperature heat medium when starting the vacuum pump are not limited to the same temperature. The temperature threshold as the starting condition for the heat pump 60, which is compared with the low-temperature water temperature TwL in step S6 of Figure 5, and the temperature threshold as the starting condition for the vacuum pump 4, which is compared with the low-temperature water temperature TwL in step S10 of Figure 7, may be set to different temperatures. In this case, the one of the heat pump 60 and the vacuum pump 4 with the lower temperature threshold as the starting condition will be started when the low-temperature water temperature TwL reaches that temperature threshold. By setting the temperature threshold as the starting condition according to the specifications of the heat pump 60 and the vacuum pump 4, it is possible to start them under more appropriate conditions.
[0074] 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.
[0075] 1,2 Atmospheric valve (control valve), 3 Fan, 4 Vacuum pump, 5 Storage tank, 6 Heat exchanger, 7 Sensor group, 8 Pressure restoration valve (control valve), 10 Controller, 11 High-temperature water pressure sensor, 30 Atmospheric piping, 40 Vacuum piping, 41 Individual piping, 42 Combined piping, 43 Vacuum valve (control valve), 50 Storage piping, 51 Branch piping, 52 Gas-liquid separator, 53 Exhaust valve, 54 Drain valve, 55 Storage valve (control valve), 60 Heat pump, 61 High-temperature water tank, 61S High-temperature water temperature sensor, 62 Low-temperature water tank, 62S Low-temperature water temperature sensor, 63,64 Heat transfer valve (control valve), 65 Bypass channel, 66 Bypass valve (control valve), 67 Heater, 68 Heat dissipation section, 100 DAC device, 610,613,620,623 Water supply pumps, 611, 612, 614, 615, 621, 622, 624, 625; Flow channels, 616, 626, 628, 629; On / off valves (control valves), R; Reactor
Claims
1. A DAC device for recovering CO2 from the atmosphere, comprising: an adsorption chamber provided with an adsorbent for adsorbing or absorbing CO2; an atmospheric valve for opening or sealing the adsorption chamber to the atmosphere; a vacuum pump connected to the adsorption chamber via vacuum piping; a vacuum valve for allowing or prohibiting the flow of gas from the adsorption chamber to the vacuum piping; a heat exchanger provided to exchange heat with the adsorbent; a heat pump that cools the vacuum pump and transfers heat from a low-temperature heat medium that cools the adsorbent via the heat exchanger to a high-temperature heat medium that heats the adsorbent via the heat exchanger; a low-temperature heat medium temperature detection unit for detecting the temperature of the low-temperature heat medium; and a heat medium control valve for controlling the supply of the low-temperature heat medium and the high-temperature heat medium to the heat exchanger. A DAC device comprising: an adsorption step in which the adsorption chamber 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 step in which the adsorption chamber is sealed, the flow of gas to the vacuum piping is permitted, and the adsorbent material is heated to desorb CO2 from the adsorbent material, and a control unit controls the atmospheric valve, the vacuum valve, and the heat medium control valve to alternately perform these steps, wherein when the DAC device is started, the control unit starts at least one of the heat pump and the vacuum pump on the condition that the temperature of the low-temperature heat medium detected by the low-temperature heat medium temperature detection unit is above the lower limit temperature.
2. The DAC device according to claim 1, further comprising: a high-temperature forward path through which the high-temperature heat medium flows from the heat pump to the heat exchanger; a low-temperature return path through which the low-temperature heat medium flows from the heat exchanger to the heat pump; a connecting path connecting the high-temperature forward path and the low-temperature return path; and an on-off valve provided in the connecting path, wherein the control unit controls the on-off valve to open so that the high-temperature heat medium from the heat pump flows to the heat pump via the connecting path when the vacuum pump is started and the temperature of the low-temperature heat medium detected by the low-temperature heat medium temperature detection unit is below the lower limit temperature.
3. A DAC apparatus according to claim 1 or 2, wherein the order in which the multiple adsorption chambers perform the adsorption process and the desorption process is predetermined, and the control unit controls the atmospheric valve, the vacuum valve, and the heat medium control valve so that when the operation of the DAC apparatus is stopped and then restarted, the desorption process is performed sequentially from the adsorption chamber with the largest amount of CO2 adsorbed onto the adsorbent material, in accordance with the predetermined order.
4. The DAC apparatus according to claim 3, wherein the control unit determines the adsorption chamber in which the adsorption process was first started among the adsorption chambers in which the adsorption process was performed when the DAC apparatus was stopped as the adsorption chamber in which the amount of CO2 adsorbed onto the adsorbent material is the largest.
5. A DAC device according to claim 3, further comprising a CO2 detection unit for detecting the CO2 concentration in the adsorption chamber, wherein the control unit, when starting the DAC device, determines the adsorption chamber with the highest CO2 concentration detected by the CO2 detection unit as the adsorption chamber with the largest amount of CO2 adsorbed onto the adsorbent material.