DAC device

Abstract

A direct air capture (DAC) device (100) recovers CO2 in the atmosphere, and comprises: an adsorption chamber (R) in which is provided an adsorbent that adsorbs or absorbs CO2 and water; a vacuum pump (4) that is connected to the adsorption chamber (R) via vacuum piping (40) and that draws in desorbed gas from the adsorbent; a heat pump (60) that moves heat from a low-temperature heat transfer medium that cools the adsorbent and the vacuum pump (4) to a high-temperature heat transfer medium that heats the adsorbent; a gas-liquid separator (7) that is provided to the vacuum piping (40) and separates water from the desorbed gas; a water tank (8) that stores the water separated by the gas-liquid separator (7); and a heat exchanger (81) that cools the low-temperature heat transfer medium using the water stored in the water tank (8).

Description

DAC apparatus

[0001] The present invention relates to a DAC (Direct Air Capture) apparatus for recovering carbon dioxide (CO₂) from the atmosphere.

[0002] Research and development on DAC technology for recovering CO₂, which is a major greenhouse gas, has been conducted for the purpose of mitigating climate change. As such DAC technology, a DAC apparatus that recovers CO₂ from the atmosphere using an adsorbent that adsorbs or absorbs CO₂ is known. For example, in the DAC apparatus disclosed in Patent Document 1, CO₂ in the atmosphere is adsorbed onto an adsorbent, a gas containing CO₂ is desorbed from the adsorbent using high-temperature steam, the desorbed gas is recovered by a vacuum pump, then the desorbed gas is cooled by an air cooler to condense water, and the condensed water is reused for steam generation.

[0003] Japanese National Publication of International Patent Application No. 2024-505621

[0004] However, when CO₂ is recovered using a vacuum pump as in the DAC apparatus described in the above Patent Document 1, pump efficiency decreases due to water desorbed together with CO₂, and there is a risk that the CO₂ recovery efficiency of the entire apparatus may decrease.

[0005] One aspect of the present invention is a DAC apparatus for recovering CO₂ from the atmosphere. The DAC apparatus comprises: an adsorption chamber provided with an adsorbent that adsorbs or absorbs CO₂ and water; a vacuum pump connected to the adsorption chamber via a vacuum pipe and configured to suck desorbed gas desorbed from the adsorbent; a heat pump that transfers heat from a low-temperature heat medium that cools the adsorbent and the vacuum pump to a high-temperature heat medium that heats the adsorbent; a gas-liquid separator provided in the vacuum pipe and configured to separate water from the desorbed gas; a water tank that stores the water separated by the gas-liquid separator; and a heat exchanger that cools the low-temperature heat medium with the water stored in the water tank.

[0006] According to the present invention, the CO₂ recovery efficiency of the DAC apparatus can be improved.

[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 around the gas-liquid separator provided in the vacuum piping of Figure 1. A schematic block diagram showing an example of the control configuration of a DAC device according to an embodiment of the present invention. A diagram for explaining the rotation speed of the water supply pump for condensate in Figure 3. A diagram for explaining the switching between the flow path and the bypass flow path through the heat exchanger in Figure 3.

[0008] Embodiments of the present invention will be described below with reference to Figures 1 to 6. Figure 1 is a schematic block diagram showing an example of the gas piping configuration of 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 control valves 1 (1a, 1b, ...) and 2 (2a, 2b, ...) for opening or closing the reactor R to the atmosphere. The control valves 1 and 2 may be provided in the piping connecting the adsorption chamber of the reactor R to the outside space, or they may be provided as part of the housing (wall) of the reactor R. When the control valves 1 and 2 are opened, the adsorption chamber of the reactor R is opened to the atmosphere, and when the control valves 1 and 2 are closed, the adsorption chamber of the reactor R is sealed. The control 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 control valve 1 or 2 (control 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 control valves 1 and 2 are opened and the fan 3 is driven, air is drawn into the reactor R via control valve 1, and air is exhausted from the reactor R via control 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 control valves 1 and 2 and 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 control 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 control valve 43 (43a, 43b, ...) that allows or prohibits the flow of gas in the individual pipe 41, i.e., the flow from the reactor R to the vacuum pipe 40. The control valve 43 may be composed of an on / off valve such as a ball valve, or a regulating 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. The control valve 43 is closed during the adsorption stroke.

[0014] 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.

[0015] When control valves 1 and 2 are closed and control valve 43 is opened, and the vacuum pump 4 is driven, the gas in the adsorption chamber of reactor R is drawn out by the vacuum pump 4 via the vacuum piping 40. Furthermore, when the adsorbent material in the adsorption chamber is heated by the 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 the storage tank 5 for recovery (desorption process).

[0016] After the desorption process is completed and before the adsorption process begins, control valves 1, 2 and control valve 43 are closed, and the adsorbent in the adsorption chamber is cooled by the heat exchanger 6 (cooling process).

[0017] In the DAC device 100, the adsorption process, desorption process, and cooling process are performed sequentially in multiple reactors R with staggered timings.

[0018] 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.

[0019] 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.

[0020] The heat pump 60 is connected via appropriate piping to a high-temperature water tank 61 that stores the high-temperature water circulated to the condenser of the heat pump 60, and a low-temperature water tank 62 that stores the low-temperature water circulated to the evaporator of the heat pump 60. The low-temperature water tank 62 is equipped with a water temperature sensor 62S that detects the temperature T of the low-temperature water.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] At the inlet of the heat exchanger 6 of each reactor R, control valves (three-way valves) 63 (63a, 63b, ...) are provided to switch between supplying 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, control valves (three-way valves) 64 (64a, 64b, ...) are provided to switch between returning the heat transfer medium discharged from the heat exchanger 6 to the flow path 612 or to the flow path 622. The control valves 63 and 64 are controlled so that high-temperature water circulates through the flow paths 611 and 612 in the heat exchanger 6 of the reactor R during the desorption stroke, and low-temperature water circulates through the flow paths 621 and 622 in the heat exchanger 6 of the reactor R during the cooling stroke.

[0025] During the desorption process, the reactor R is heated by the heat exchanger 6, causing the adsorbent to rise in temperature and the CO2 and water adsorbed on the adsorbent to desorb. More specifically, when the temperature of the adsorbent reaches the desorption temperature of water (for example, about 70°C), water is desorbed, and then when it reaches the desorption temperature of CO2, which is higher than the desorption temperature of water (for example, about 100°C), CO2 is desorbed. In this embodiment, a gas-liquid separator is provided in the vacuum piping 40 to remove water from the desorbed gas, and the pump efficiency of the vacuum pump 4 is improved, thereby improving the overall CO2 recovery efficiency of the apparatus. The DAC apparatus 100 is configured as follows.

[0026] Figure 3 is a schematic block diagram showing an example of the piping configuration around a gas-liquid separator 7 installed in the vacuum piping 40. The gas-liquid separator 7 may be installed in the confluence pipe 42 immediately before the vacuum pump 4 in the vacuum piping 40 of Figure 1, or it may be installed in the individual pipes 41 of each reactor R. If multiple reactors R are grouped together as a reactor group, and a group confluence pipe is provided that connects the individual pipes 41 of each reactor group to the confluence pipe 42, the gas-liquid separator 7 may be installed in the group confluence pipe.

[0027] As shown in Figures 1 and 3, the gas-liquid separator 7 is installed in the vacuum piping 40 between the reactor R and the vacuum pump 4, and separates water from the desorbed gas. The gas-liquid separator 7 is a condenser such as a plate heat exchanger that cools and condenses the water vapor in the desorbed gas with a refrigerant such as water, and a flow path is formed inside through which the refrigerant from a cooler (not shown) and the desorbed gas from the vacuum piping 40 flow alternately.

[0028] A condensate tank 8 is connected to the vacuum piping 40 immediately downstream of the gas-liquid separator 7, and the condensate separated by the gas-liquid separator 7 is stored in the condensate tank 8. The condensate tank 8 is equipped with a water level sensor 8S that detects the water level L of the condensate stored in the condensate tank 8.

[0029] By installing a gas-liquid separator 7 in the vacuum piping 40 between the reactor R and the vacuum pump 4, water (water vapor) can be separated and removed from the desorbed gas. This allows the pressure of the desorbed gas in the vacuum piping 40 to be reduced in proportion to the partial pressure of the water vapor removed by the gas-liquid separator 7. This improves the pumping efficiency of the vacuum pump 4 and the CO2 recovery efficiency, especially in the first half of the desorbing process when the amount of water desorbed is large, thereby improving the overall CO2 recovery efficiency of the system. Furthermore, by removing moisture from the desorbed gas before recovery, the concentration of CO2 recovered in the storage tank 5 can be further increased. Additionally, by using a heat exchanger as the gas-liquid separator 7, water can be separated from the desorbed gas with a simple configuration.

[0030] The gas-liquid separator 7 and the condensate tank 8 are insulated from the outside. When condensate vaporizes (re-evaporates) in the gas-liquid separator 7 and the condensate tank 8, the heat of vaporization lowers the temperature of the gas-liquid separator 7 and the condensate tank 8, causing the water vapor to condense immediately, thus suppressing the overall re-evaporation of the condensate. In addition, the gas-liquid separator 7 and the condensate tank 8 are maintained at extremely low temperatures, and extremely low-temperature condensate is stored.

[0031] The temperature of the condensate stored in the condensate tank 8 is extremely low (around 0°C) regardless of the ambient temperature. By using this extremely low-temperature condensate to cool various parts of the DAC device 100, the thermal energy of the entire device can be utilized efficiently. In particular, by sufficiently cooling the vacuum pump 4, which is used under high load conditions, the power consumption required to drive the vacuum pump 4 can be suppressed, and the pumping efficiency and CO2 recovery efficiency of the vacuum pump 4 can be improved. Furthermore, when supplying water vapor to the reactor R to regenerate the adsorbent or adjust the humidity of the adsorbent, the condensate can be used as water vapor.

[0032] Specifically, the condensate tank 8 is connected to a steam generation unit 9, which generates steam, via appropriate piping. The flow path 80 from the condensate tank 8 to the steam generation unit 9 is equipped with heat exchangers 81 and 82 that perform heat exchange between the condensate flowing through the flow path 80 and the low-temperature water from the heat pump 60. The flow path 80 is further equipped with a check valve 83 to prevent backflow of condensate from the flow path 80 to the condensate tank 8, and a water supply pump 84 that pressurizes and sends condensate from the condensate tank 8 to the steam generation unit 9. The condensate stored in the condensate tank 8 flows through the flow path 80 at a flow rate corresponding to the rotation speed of the water supply pump 84 and is supplied to the steam generation unit 9.

[0033] Bypass channels 810 and 820, which bypass the heat exchangers 81 and 82, are connected to the flow path 80.

[0034] A control valve (on-off valve) 811 is provided in the channel 80 downstream of the branching point where the bypass channel 810 branches off from the main channel 80 and upstream of the heat exchanger 81 to allow or prohibit the flow of condensate to the heat exchanger 81. A control valve (on-off valve) 812 is also provided in the bypass channel 810 to allow or prohibit the flow of condensate in the bypass channel 810. The control valves 811 and 812 allow switching between the flow through the heat exchanger 81 and a bypass. That is, when control valve 811 is open and control valve 812 is closed, the condensate from the condensate tank 8 flows to the heat exchanger 81; when control valve 811 is closed and control valve 812 is open, the condensate bypasses the heat exchanger 81. Instead of control valves 811 and 812, a control valve (three-way valve) may be provided at the branching point where the bypass channel 810 branches off from the main channel 80.

[0035] A control valve (on-off valve) 821 is provided in the channel 80 downstream of the branching point where the bypass channel 820 branches off from the main channel 80 and upstream of the heat exchanger 82 to allow or prohibit the flow of condensate to the heat exchanger 82. A control valve (on-off valve) 822 is also provided in the bypass channel 820 to allow or prohibit the flow of condensate in the bypass channel 820. The control valves 821 and 822 allow switching between the flow through the heat exchanger 82 and a bypass. That is, when control valve 821 is open and control valve 822 is closed, the condensate from the condensate tank 8 flows to the heat exchanger 82; when control valve 821 is closed and control valve 822 is open, the condensate bypasses the heat exchanger 82. Instead of control valves 821 and 822, a control valve (three-way valve) may be provided at the branching point where the bypass channel 820 branches off from the main channel 80.

[0036] The chilled water stored in the chilled water tank 62 flows through a flow path 624, which is equipped with a water supply pump 623 and a heat exchanger 82, at a flow rate corresponding to the rotation speed of the water supply pump 623, into the evaporator of the heat pump 60, and is cooled by heat absorption by the working fluid. The chilled water cooled by the heat pump 60 flows through a flow path 625 and returns to the chilled water tank 62. Flow paths 624 and 625 are connected by a flow path 626, which is equipped with a heat exchanger 81. More specifically, flow path 626 connects flow path 625 and flow path 624 between the chilled water tank 62 and the water supply pump 623.

[0037] In the flow path 626, a water supply pump 627 is provided upstream of the heat exchanger 81, and a portion of the low-temperature water flowing in the flow path 625 flows through the flow path 626 at a flow rate corresponding to the rotation speed of the water supply pump 627. The flow path 626 downstream of the heat exchanger 81 is provided in close proximity to the vacuum pump 4, and the vacuum pump 4 is cooled by the low-temperature water flowing through the flow path 626 downstream of the heat exchanger 81. As a result, the vacuum pump 4 can be sufficiently cooled (for example, to about 30°C) by the low-temperature water that has been cooled by the heat pump 60 and then further cooled by heat exchange with the cryogenic condensate water from the condensate water tank 8 in the heat exchanger 81.

[0038] The cold water, whose temperature has risen after cooling the vacuum pump 4, is drawn into the water supply pump 623 and enters the flow path 624 from the flow path 626. There, it merges with the cold water flowing from the cold water tank 62 to the heat pump 60, flows through the heat exchanger 82, and enters the heat pump 60. In the heat exchanger 82, the condensed water whose temperature has risen after being cooled in the heat exchanger 81, or the extremely cold condensed water from the condensed water tank 8 that bypassed the heat exchanger 81, is heated by heat exchange with the cold water flowing in the flow path 624 downstream of the connection point of the flow path 626. That is, after the adsorbent material of each reactor R and the vacuum pump 4 have been cooled and their temperatures have risen, they are heated by the cold water before it is cooled in the heat pump 60. By supplying the condensed water heated in the heat exchanger 82 to the steam generation unit 9, the energy consumption required for steam generation can be suppressed.

[0039] 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, water supply pumps 84, 610, 620, 623, 627, and control valves 1, 2, 43, 63, 64, 811, 812, 821, 822 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. The water level sensor 8S and water temperature sensor 62S shown in Figure 3 are connected to the controller 10, and signals indicating the detected values ​​of each sensor are input to the controller 10.

[0040] When the DAC device 100 is started, the controller 10 drives the fan 3, vacuum pump 4, heat pump 60, and water supply pumps 84, 610, 620, 623, 627, and controls the control valves 1, 2, 43, 63, 64, 811, 812, 821, and 822. More specifically, the controller 10 controls the control valves 1, 2, 43, 63, and 64 so that the adsorption, desorption, and cooling processes are carried out sequentially in multiple reactors R with staggered timings. The controller 10 also controls the water supply pump 84 for condensate based on the water level L of the condensate detected by the water level sensor 8S. Furthermore, the controller 10 controls the control valves 811, 812, 821, and 822 to switch whether the water passes through or bypasses the heat exchangers 81 and 82 based on the low-temperature water temperature T detected by the water temperature sensor 62S.

[0041] Figure 5 is a diagram illustrating the rotational speed (target rotational speed) of the condensate supply pump 84. As shown in Figure 5, the controller 10 controls the condensate supply pump 84 according to predetermined characteristics, such that the rotational speed increases as the condensate water level L detected by the water level sensor 8S increases, and decreases as the water level L decreases. When the water level L is below the first water level L1 and the amount of water stored in the condensate tank 8 is very small, the target rotational speed of the supply pump 84 is set to "0", and the supply of condensate water from the condensate tank 8 to the steam generation unit 9 is stopped.

[0042] When the water level L rises above the first water level L1, the target rotation speed is set to increase in stages according to the range of water levels L, such as a low water level below the second water level L2, a medium water level between the second water level L2 and the third water level L3, and a high water level above the third water level L3. Alternatively, the target rotation speed may be set to increase continuously according to the water level L. This ensures that condensed water at an appropriate flow rate, corresponding to the amount of water stored in the condensed water tank 8, is supplied from the condensed water tank 8 to the steam generation unit 9.

[0043] Figure 6 is a diagram illustrating the switching between the flow path 80 through the heat exchangers 81 and 82 shown in Figure 3 and the bypass flow paths 810 and 820. As shown in Figure 6, the controller 10 controls the control valves 811, 812, 821, and 822 based on the low-temperature water temperature T detected by the water temperature sensor 62S, switching between the flow path 80 through the heat exchangers 81 and 82 and the bypass flow paths 810 and 820.

[0044] More specifically, in a low temperature range where the low-temperature water temperature T is lower than a first temperature T1 (for example, about 25°C), the control valves 811 and 821 are controlled to be closed and the control valves 812 and 822 are controlled to be opened, so that the flow paths are switched to bypass flow paths 810 and 820 that bypass the heat exchangers 81 and 82. In a normal temperature range where the low-temperature water temperature T is equal to or higher than the first temperature T1 and lower than a second temperature T2 (for example, about 35°C), the control valve 811 is controlled to be opened and the control valve 812 is controlled to be closed, so that the flow path is switched to the flow path 80 passing through the heat exchanger 81; meanwhile, the control valve 821 is controlled to be closed and the control valve 822 is controlled to be opened, so that the flow path is switched to the bypass flow path 820 that bypasses the heat exchanger 82. In a high temperature range where the low-temperature water temperature T is equal to or higher than the second temperature T2, the control valves 811 and 821 are controlled to be opened and the control valves 812 and 822 are controlled to be closed, so that the flow path is switched to the flow path 80 passing through the heat exchangers 81 and 82.

[0045] That is, as the temperature difference between high-temperature water and low-temperature water increases, the load on the heat pump 60 (compressor), which transfers heat from the low-temperature water to the high-temperature water, increases, leading to an increase in power consumption. In the low temperature range, by switching to the bypass flow paths 810 and 820 that bypass the heat exchangers 81 and 82 and prohibiting cooling of the low-temperature water by condensed water, the power consumption of the heat pump 60 can be suppressed. In this case, the vacuum pump 4 can be sufficiently cooled by the low-temperature water in the low temperature range without requiring heat exchange with the condensed water in the heat exchanger 81.

[0046] In the normal temperature range and the high temperature range, by switching to the flow path 80 passing through the heat exchanger 81, and cooling the low-temperature water that has been cooled by the heat pump 60 and before cooling the vacuum pump 4 using condensed water, the vacuum pump 4 can be sufficiently cooled by the low-temperature water whose temperature has been sufficiently lowered. In this case, since the low-temperature water temperature T rises again after cooling the vacuum pump 4, the low-temperature water temperature T when entering the heat pump 60 does not become excessively high.

[0047] In the high temperature range, the flow path is switched to the flow path 80 passing through the heat exchanger 82, and the low-temperature water before entering the heat pump 60 is cooled by condensed water. In this case, by transferring the surplus heat of the low-temperature water in the high temperature range to the condensed water before being supplied to the steam generation unit 9 to heat the condensed water, the energy required for steam generation in the steam generation unit 9 can be reduced.

[0048] According to an embodiment of the present invention, the following operational effects can be obtained. (1) The DAC device 100 includes: a reactor R provided with an adsorbent that adsorbs or absorbs CO₂ and water; a vacuum pump 4 connected to the reactor R via a vacuum pipe 40 and configured to suck desorbed gas from the adsorbent; a heat pump 60 that transfers heat from low-temperature water that cools the adsorbent and the vacuum pump 4 to high-temperature water that heats the adsorbent; a gas-liquid separator 7 provided in the vacuum pipe 40 and configured to separate water from the desorbed gas; a condensed water tank 8 that stores condensed water separated by the gas-liquid separator 7; and a heat exchanger 81 that cools a low-temperature heat medium with the condensed water stored in the condensed water tank 8 (Figures 1 to 3).

[0049] As described above, by providing the gas-liquid separator 7 in the vacuum pipe 40 and separating and removing water from the desorbed gas, the pressure of the desorbed gas in the vacuum pipe 40 can be reduced, and in particular, the pumping efficiency of the vacuum pump 4 and the CO₂ recovery efficiency can be improved in the first half of the desorption process where a large amount of water is desorbed. Thereby, the CO₂ recovery efficiency of the entire device can be improved. In addition, by cooling the low-temperature water for cooling the vacuum pump 4 with the cryogenic condensed water from the condensed water tank 8, the vacuum pump 4 can be sufficiently cooled by the low-temperature water whose temperature has been sufficiently lowered. Thereby, the power consumption required for driving the vacuum pump 4 can be suppressed to reduce the power consumption of the entire device, and the pumping efficiency of the vacuum pump 4 and the CO₂ recovery efficiency can be improved.

[0050] (2) The DAC device 100 further includes: a low-temperature water tank 62 that stores low-temperature water; flow paths 621 and 622 through which the low-temperature water flows between the low-temperature water tank 62 and the reactor R; a flow path 624 through which the low-temperature water flows from the low-temperature water tank 62 to the heat pump 60; a flow path 625 through which the low-temperature water flows from the heat pump 60 back to the low-temperature water tank 62; and a flow path 626 that connects the flow path 624 and the flow path 625 (Figures 1 to 3). The adsorbent is cooled by the low-temperature water flowing through the flow paths 621 and 622 (Figures 1 and 2). The vacuum pump 4 is cooled by the low-temperature water flowing through the flow path 626 (Figure 3). The heat exchanger 81 is provided in the flow path 626 upstream of the vacuum pump 4 (Figure 3).

[0051] In this way, by cooling the low-temperature water with condensate after it has been cooled by the heat pump 60 and before it cools the vacuum pump 4, the vacuum pump 4 can be sufficiently cooled by the low-temperature water whose temperature has been sufficiently reduced. In this case, the low-temperature water temperature T rises again as the vacuum pump 4 is cooled, so it is possible to suppress the excessive decrease in the low-temperature water temperature T when it enters the heat pump 60, which would increase the power consumption of the heat pump 60.

[0052] (3) The DAC device 100 further includes a heat exchanger 82 that heats the condensate after the low-temperature water has been cooled in the heat exchanger 81 by low-temperature water flowing in the flow path 624 downstream of the connection point of the flow path 626, and a steam generation unit 9 that generates steam supplied to the reactor R from the condensate heated in the heat exchanger 82 (Figure 3). In this way, by using condensate heated by low-temperature water whose temperature has risen after cooling the adsorbent and vacuum pump 4 for steam generation, the condensate can be effectively utilized and the energy consumption required for steam generation can be suppressed.

[0053] (4) The DAC device 100 further includes control valves 811, 812, 821, and 822 installed in the flow path 80 from the condensate tank 8 to the steam generation unit 9, which switch whether to pass through or bypass the heat exchangers 81 and 82, and a controller 10 that controls the control valves 811, 812, 821, and 822 based on the low temperature water temperature T (Figures 3 and 4). The controller 10 controls the control valves 811, 812, 821, and 822 so that when the low temperature water temperature T is less than the first temperature T1, the water bypasses the heat exchangers 81 and 82; when the low temperature water temperature T is greater than or equal to the first temperature T1 and less than the second temperature T2, the water passes through the heat exchanger 81 and bypasses the heat exchanger 82; and when the low temperature water temperature T is greater than or equal to the second temperature T2, the water passes through the heat exchangers 81 and 82 (Figure 6). This makes it possible to maintain the low-temperature water temperature T and the temperature difference between the high-temperature water and the low-temperature water within an appropriate range, thereby suppressing the load and power consumption of the heat pump 60 that transfers heat from the low-temperature water to the high-temperature water.

[0054] In the above embodiment, an example was described in which a water level sensor 8S is provided in the condensate tank 8 to detect the water level L, as shown in Figures 3 and 4. However, the water level in the water tank is not limited to what is detected by the water level sensor. For example, the controller 10 may estimate the water level L in the condensate tank 8 based on environmental conditions such as humidity and temperature, the operating conditions of the DAC device, etc. In this case, the configuration of the condensate tank 8 can be simplified, and it is possible to easily maintain the adiabatic state.

[0055] 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.

[0056] 1, 2, 43, 63, 64, 811, 812, 821, 822 Control valve, 3 Fan, 4 Vacuum pump, 5 Storage tank, 6 Heat exchanger, 7 Gas-liquid separator, 8 Condensate tank, 8S Water level sensor, 9 Steam generation unit, 10 Controller, 30 Atmospheric piping, 40 Vacuum piping, 41 Individual piping, 42 Combined piping, 60 Heat pump, 61 High-temperature water tank, 62 Low-temperature water tank, 62S Water temperature sensor, 80, 611, 612, 621, 622, 624, 625, 626 Flow path, 81, 82 Heat exchanger, 83 Check valve, 84, 610, 620, 623, 627 Water supply pump, 810, 820 Bypass flow path, 100 DAC device, 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 and water; a vacuum pump connected to the adsorption chamber via vacuum piping for sucking desorbed gas from the adsorbent; a heat pump for transferring heat from a low-temperature heat medium for cooling the adsorbent and the vacuum pump to a high-temperature heat medium for heating the adsorbent; a gas-liquid separator provided in the vacuum piping for separating water from the desorbed gas; a water tank for storing the water separated by the gas-liquid separator; and a heat exchanger for cooling the low-temperature heat medium with the water stored in the water tank.

2. A DAC apparatus according to claim 1, further comprising: a low-temperature heat medium tank for storing the low-temperature heat medium; a first flow path through which the low-temperature heat medium flows between the low-temperature heat medium tank and the adsorption chamber; a second flow path through which the low-temperature heat medium flows from the low-temperature heat medium tank to the heat pump; a third flow path through which the low-temperature heat medium flows from the heat pump to the low-temperature heat medium tank; and a fourth flow path connecting the second flow path and the third flow path, wherein the adsorbent is cooled by the low-temperature heat medium flowing through the first flow path; the vacuum pump is cooled by the low-temperature heat medium flowing through the fourth flow path; and the heat exchanger is provided in the fourth flow path upstream of the vacuum pump.

3. The DAC apparatus according to claim 2, wherein the heat exchanger is a first heat exchanger, and further comprises a second heat exchanger that heats the water after the low-temperature heat medium has been cooled in the first heat exchanger by the low-temperature heat medium flowing in the second flow path downstream of the connection part of the fourth flow path, and a steam generation unit that generates steam supplied to the adsorption chamber from the water heated in the second heat exchanger.

4. A DAC device according to claim 3, further comprising: a first control valve provided in a fifth flow path from the water tank to the steam generation unit for switching whether to pass through or bypass the first heat exchanger; a second control valve provided in the fifth flow path for switching whether to pass through or bypass the second heat exchanger; and a control unit that controls the first control valve and the second control valve based on the temperature of the low-temperature heat medium, wherein the control unit controls the first control valve and the second control valve so that when the temperature is less than a first temperature, the flow bypasses the first heat exchanger and the second heat exchanger; when the temperature is equal to or greater than the first temperature and less than the second temperature, the flow passes through the first heat exchanger and bypasses the second heat exchanger; and when the temperature is equal to or greater than the second temperature, the flow passes through the first heat exchanger and the second heat exchanger.

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