CO2 recovery device

Abstract

To provide a CO2 capture device that can efficiently store CO2 without increasing the size of the CO2 storage section. [Solution] In a CO2 recovery device, the CO2 recovery unit introduces exhaust gas in the adsorption process and adsorbs CO2 from the exhaust gas, and in the regeneration process, it desorbs the CO2 adsorbed in the adsorption process and discharges the CO2-containing gas. The CO2 storage unit introduces the CO2-containing gas from the CO2 recovery unit, adsorbs CO2, and discharges the residual gas remaining after the CO2 adsorption. A check valve is provided in the discharge passage for the residual gas, allowing the residual gas to flow out in the discharge direction through the discharge passage, while preventing or suppressing the inflow of air in the opposite direction to the discharge direction through the discharge passage.

Description

Technical Field

[0001] The present disclosure relates to a CO2 recovery device.

Background Art

[0002] A CO2 separation device for an internal combustion engine has been proposed, which is provided in the exhaust system of an internal combustion engine and separates CO2 from exhaust gas (see, for example, Patent Document 1). The technique described in Patent Document 1 is configured to store the CO2 separated from the exhaust gas in a storage tank.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when desorbing CO2 from the CO2 adsorber, the gas discharged from the CO2 adsorber contains gas components other than CO2. Therefore, in the case of the technique described in Patent Document 1, in addition to the CO2 gas, gas components other than the CO2 gas are also stored in the storage tank.

[0005] When it is assumed that a predetermined amount of CO2 gas is to be stored, if gas components other than the CO2 gas are also stored in the storage tank, the capacity of the storage tank increases by the amount of the gas components other than the CO2 gas stored compared to the case where the gas components other than the CO2 gas are not stored. Therefore, in this case, it leads to an increase in the size of the storage tank, and consequently to an increase in the size of the CO2 recovery device, which becomes a factor increasing the weight of the CO2 recovery device.

[0006] If a storage tank of a predetermined capacity is to be used, the amount of CO2 gas that can be stored in the tank will decrease if gas components other than CO2 gas are stored in the tank, compared to when other gas components are not stored. Therefore, when recovering gas from the storage tank, the frequency of recovery will increase. Alternatively, when replacing the storage tank, the frequency of replacement will increase.

[0007] Furthermore, when pumping gas to a storage tank, if the premise is to store a predetermined amount of CO2 in a storage tank of a predetermined capacity, then if gas components other than CO2 are also stored in the storage tank, the internal pressure of the storage tank will increase compared to when no other gas components are stored. Consequently, the pump will have to pump the gas at a higher pressure, resulting in the consumption of extra energy in the pump.

[0008] In one aspect of this disclosure, it is desirable to provide a CO2 recovery device that can efficiently store CO2 without increasing the size of the CO2 storage section. [Means for solving the problem]

[0009] (A) One aspect of the present disclosure is a CO2 recovery device for recovering CO2 from the exhaust gas of an internal combustion engine. The CO2 recovery device comprises at least one CO2 recovery unit, a CO2 storage unit, and a check valve. The CO2 recovery unit is configured to be switched between at least an adsorption step and a regeneration step. When switched to the adsorption step, it is configured to introduce exhaust gas and adsorb CO2 in the exhaust gas. When switched to the regeneration step, it is configured to desorb the CO2 adsorbed in the adsorption step and discharge the CO2-containing gas containing the desorbed CO2. The CO2 storage unit is configured to introduce the CO2-containing gas discharged from the CO2 recovery unit, adsorb CO2 in the CO2-containing gas, and discharge the residual gas remaining after the adsorption of CO2. The check valve is provided in the discharge passage for the residual gas discharged from the CO2 storage unit and is configured to allow the residual gas to flow out in the discharge direction through the discharge passage, while preventing or suppressing the inflow of air in the opposite direction to the discharge direction through the discharge passage.

[0010] In a CO2 recovery device configured in this way, CO2 and residual gases other than CO2 are separated in the CO2 storage section, and a check valve causes the residual gas to flow out in the discharge direction. Therefore, unlike technologies that do not have a configuration to discharge residual gas to the outside of the CO2 storage section, it is possible to prevent or suppress the accumulation of gas components other than CO2 gas in the CO2 storage section.

[0011] Therefore, if the premise is to store a predetermined amount of CO2 gas, the capacity of the CO2 storage unit can be reduced compared to a system where residual gas (i.e., gas components other than CO2 gas) is also stored, because the residual gas does not need to be stored. Thus, the CO2 storage unit can be made smaller, which in turn allows for the CO2 recovery device to be made smaller and lighter.

[0012] Assuming the use of a CO2 storage unit of a predetermined capacity, the amount of CO2 gas that can be stored can be increased compared to a system where residual gas is also stored, because residual gas does not need to be stored. Therefore, when recovering gas from the CO2 storage unit, the frequency of recovery can be reduced. Alternatively, when replacing the CO2 storage unit, the frequency of replacement can be reduced.

[0013] Furthermore, the check valve prevents or suppresses the inflow of air in the opposite direction to the discharge direction, thus preventing or suppressing the wasteful consumption of the CO2 storage capacity due to the inflow of air.

[0014] (B) In one aspect of the present disclosure, the system may include a pump provided in the flow path from the CO2 recovery unit to the CO2 storage unit, which, when in operation, pumps CO2-containing gas from the CO2 recovery unit to the CO2 storage unit.

[0015] In this case, when the gas is pumped to the CO2 storage section, if residual gas is discharged from the CO2 storage section, the rise in internal pressure of the CO2 storage section can be suppressed accordingly. Therefore, compared to the case where residual gas is not discharged from the CO2 storage section, the pump can pump the CO2 gas to the CO2 storage section at a lower pressure, thus reducing the amount of energy the pump consumes.

[0016] (C) In one aspect of this disclosure, at least one CO2 recovery unit may be a plurality of CO2 recovery units. In this case, CO2 can be recovered by utilizing multiple CO2 recovery units.

[0017] (D) In ​​one aspect of the present disclosure, the exhaust gas flow path may be switched such that exhaust gas is introduced into the CO2 recovery unit that is switched to the adsorption process, and exhaust gas is not introduced into the CO2 recovery unit that is switched to the regeneration process.

[0018] In this case, exhaust gas is introduced into the CO2 recovery unit that is switched to the adsorption process, while exhaust gas is not introduced into the CO2 recovery unit that is switched to the regeneration process. Therefore, the CO2 recovery unit that performs the adsorption process and the CO2 recovery unit that performs the regeneration process can be operated in parallel. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a schematic diagram showing the general configuration of the CO2 capture device. [Figure 2] Figure 2A is an explanatory diagram showing a state where the first channel system is in the adsorption process and the second channel system is in the regeneration process. Figure 2B is an explanatory diagram showing a state where the first channel system is in the regeneration process and the second channel system is in the adsorption process. [Figure 3] Figure 3A is a diagram showing a modified configuration for switching flow paths. Figure 3B is a diagram showing a modified configuration for a single flow path system. [Figure 4] Figure 4 is a diagram showing a modified configuration without a water recovery unit.

Best Mode for Carrying Out the Invention

[0020] Next, the above-described CO2 recovery device will be described with exemplary embodiments. [Configuration of CO2 Recovery Device] The CO2 recovery device 1 shown in FIG. 1 is a device that recovers CO2 from the exhaust gas of an internal combustion engine. The CO2 recovery device 1 includes a heat exchanger 11, a plurality of water recovery units 13A and 13B, a plurality of CO2 recovery units 15A and 15B, pumps 17 and 19, a CO2 storage unit 21, and a check valve 23.

[0021] The heat exchanger 11, the water recovery units 13A and 13B, and the CO2 recovery units 15A and 15B are connected to flow paths 31A, 31B, 31C, and 31D. More specifically, the flow path 31A is connected to the upstream side of the heat exchanger 11. The flow path 31B is connected to the downstream side of the heat exchanger 11 and the upstream side of the water recovery units 13A and 13B. The flow path 31C is connected to the downstream side of the water recovery units 13A and 13B and the upstream side of the CO2 recovery units 15A and 15B. The flow path 31D is connected to the downstream side of the CO2 recovery units 15A and 15B.

[0022] The water recovery units 13A and 13B and the pump 17 are connected to flow paths 31E and 31F. More specifically, the flow path 31E is connected to the upstream side of the water recovery units 13A and 13B and the pump 17. The flow path 31F is connected to the downstream side of the pump 17.

[0023] The CO2 recovery units 15A and 15B, the pump 19, the CO2 storage unit 21, and the check valve 23 are connected to flow paths 31G, 31H, 31I, and 31J. More specifically, the flow path 31G is connected to the upstream side of the CO2 recovery units 15A and 15B and the pump 19. The flow path 31H is connected to the downstream side of the pump 19 and the upstream side of the CO2 storage unit 21. The flow path 31I is connected to the downstream side of the CO2 storage unit 21 and the upstream side of the check valve 23. The flow path 31J is connected to the downstream side of the check valve 23.

[0024] Flow path 31B is provided with flow path switching valve 37A. Flow path 31C is provided with flow path switching valves 37B and 37C. Flow path 31D is provided with flow path switching valve 37D. Flow path 31E is provided with flow path switching valve 37E. Flow path 31G is provided with flow path switching valve 37F.

[0025] The heat exchanger 11 lowers the temperature of the exhaust gas by exchanging heat between the high-temperature exhaust gas and a medium that is colder than the exhaust gas. The medium that is colder than the exhaust gas is not particularly limited, but for example, it could be ambient air or the cooling water of an onboard cooling system. The heat exchanger 11 lowers the temperature of the exhaust gas to a temperature at which CO2 can be easily adsorbed.

[0026] In this embodiment, the multiple water recovery units 13A, 13B are two water recovery units 13A, 13B. The water recovery units 13A, 13B are configured to introduce exhaust gas from the upstream flow path 31A and pass it through the downstream flow path 31B. More specifically, the water recovery units 13A, 13B have a structure in which an adsorbent having the ability to adsorb water and CO2 is filled inside a container having an inlet and an outlet, and are configured to introduce exhaust gas from the inlet and pass it through to the outlet.

[0027] The adsorbent used in the water recovery sections 13A and 13B is not particularly limited as long as it is an adsorbent that has the ability to adsorb water. For example, silica gel, zeolite, and activated alumina are preferred.

[0028] Furthermore, in this embodiment, the multiple CO2 recovery units 15A, 15B are actually two CO2 recovery units 15A, 15B. The CO2 recovery units 15A, 15B are configured to introduce exhaust gas that has passed through the water recovery units 13A, 13B from the upstream flow path 31C and pass it through to the downstream flow path 31D. More specifically, the CO2 recovery units 15A, 15B are constructed by filling the inside of a container having an inlet and an outlet with an adsorbent material that has the ability to adsorb CO2, and are configured to introduce exhaust gas that has passed through the water recovery units 13A, 13B from the inlet and pass it through to the outlet.

[0029] The adsorbent used in the CO2 recovery units 15A and 15B is not particularly limited as long as it is an adsorbent that has the ability to adsorb CO2. For example, zeolite, MOF (Metal Organic Frameworks), activated carbon, magnesium oxide, solid amine, and calcium oxide are suitable. The CO2 recovery units 15A and 15B adsorb CO2 from the exhaust gas as it passes through.

[0030] Pump 17 is a vacuum pump used to evacuate the inside of water recovery sections 13A and 13B when restoring their adsorption capacity. The gas sucked out from inside the water recovery sections 13A and 13B by pump 17 when it is operating contains water but almost no CO2, and is therefore released from pump 17 to the outside (i.e., outside the CO2 recovery device 1 system). When evacuating the inside of the water recovery sections 13A and 13B, the inside of the water recovery sections 13A and 13B may be heated. As a heat source for this heating, for example, heat obtained from the high-temperature exhaust gas in the heat exchanger 11 can be used.

[0031] Pump 19 is a vacuum pump used to evacuate the inside of CO2 recovery sections 15A and 15B when restoring their adsorption capacity. The gas sucked out from inside the CO2 recovery sections 15A and 15B by pump 19 when it is operating contains CO2, which is the target of recovery by the CO2 recovery device 1, and is therefore stored in the CO2 storage section 21. When evacuating the inside of the CO2 recovery sections 15A and 15B, the inside of the CO2 recovery sections 15A and 15B may be heated. As a heat source for this heating, for example, heat obtained from high-temperature exhaust gas in the heat exchanger 11 can be used.

[0032] As described above, the CO2 storage unit 21 stores the gas sucked from inside the CO2 recovery units 15A and 15B by the pump 19. The CO2 storage unit 21 is filled with gas by the pump 19. In the CO2 storage unit 21, CO2 and gas components other than CO2 (corresponding to residual gas in this disclosure) are separated. As a method for separating CO2 and gas components other than CO2, for example, the inside of the CO2 storage unit 21 can be filled with an adsorbent similar to that in the CO2 recovery units 15A and 15B to adsorb CO2.

[0033] The check valve 23 allows the non-CO2 gas components to flow out in the discharge direction when CO2 and other gas components are separated in the CO2 storage section 21. The check valve 23 also prevents or suppresses the inflow of air in the opposite direction to the discharge direction. The non-CO2 gas components are mainly nitrogen gas (N2). Specifically, the CO2 concentration in the exhaust gas is about 10%, and the remaining 90% is N2.

[0034] When adsorbent material is filled inside the CO2 recovery sections 15A and 15B, the adsorbent material occupies approximately 70% of the total volume of the CO2 recovery sections 15A and 15B, and CO2 is adsorbed onto this adsorbent material. On the other hand, approximately 30% of the total volume of the CO2 recovery sections 15A and 15B is the volume of voids (gaps) that occur between the adsorbent material particles, and such spaces contain N2.

[0035] Therefore, when the pump 19 draws gas from inside the CO2 recovery sections 15A and 15B, in addition to the CO2 released from the adsorbent, N2 present between the adsorbent particles is also drawn in and flows into the CO2 storage section 21. There, the CO2 storage section 21 separates the CO2 from other gas components, and the other gas components are released to the outside through the check valve 23. This makes it possible to increase the CO2 concentration of the gas stored in the CO2 storage section 21.

[0036] Furthermore, if the CO2 storage unit 21 becomes full, if the CO2 storage unit 21 is replaceable, it can be replaced with a new CO2 storage unit 21; if the CO2 storage unit 21 is not replaceable, the CO2 in the CO2 storage unit 21 can be recovered by another device.

[0037] In this embodiment, the flow path switching valves 37A to 37F are each composed of a three-way valve. The flow path switching valves 37A to 37F are operated under the control of an ECU (electronic control unit) (not shown).

[0038] [Switching between adsorption and regeneration processes] Figure 2A shows the state in the CO2 recovery device 1 where the flow path system (hereinafter also referred to as the first flow path system) comprising the water recovery unit 13A and the CO2 recovery unit 15A is in the adsorption process. At this time, the flow path system (hereinafter also referred to as the second flow path system) comprising the water recovery unit 13B and the CO2 recovery unit 15B is in the regeneration process. Figure 2B shows the state in the CO2 recovery device 1 where the second flow path system (comprising the water recovery unit 13B and the CO2 recovery unit 15B) is in the adsorption process. At this time, the first flow path system (comprising the water recovery unit 13A and the CO2 recovery unit 15A) is in the regeneration process.

[0039] In this embodiment, the state shown in Figure 2A and the state shown in Figure 2B are alternately switched by the ECU. In this embodiment, as described above, two systems, the first flow path system and the second flow path system, are switched alternately, but it is also possible to configure the system to switch between three or more flow path systems in sequence.

[0040] For example, if the service life of one channel system in the adsorption process is only half the time required for the regeneration process, it is advisable to operate by sequentially switching between three channel systems. In this case, by operating one channel system in the adsorption process while overlapping and operating the other two channel systems in the regeneration process, continuous operation is possible with at least one system always in the adsorption process.

[0041] Furthermore, even if, for example, the service life of one channel system in the adsorption process is twice the time required for the regeneration process, it is advisable to operate by sequentially switching between the three channel systems. In this case, by operating two channel systems in the adsorption process with overlapping configurations while operating one channel system in the regeneration process, continuous operation is possible with two systems always in the adsorption process.

[0042] [effect] According to the CO2 recovery device 1 described above, CO2 and other gas components are separated in the CO2 storage section 21, and at that time, the check valve 23 causes the gas components other than CO2 to flow out in the discharge direction. Therefore, unlike technologies that do not have a configuration to discharge gas components other than CO2 to the outside of the CO2 storage section 21, it is possible to prevent or suppress the accumulation of gas components other than CO2 in the CO2 storage section 21.

[0043] Therefore, if the premise is to store a predetermined amount of CO2 gas, the capacity of the CO2 storage unit 21 can be reduced compared to the case where gas components other than CO2 gas are also stored, because it is not necessary to store gas components other than CO2 gas. Thus, the CO2 storage unit 21 can be made smaller, and consequently the CO2 recovery device 1 can be made smaller and lighter.

[0044] Assuming the use of a CO2 storage unit 21 of a predetermined capacity, the amount of CO2 gas that can be stored can be increased compared to cases where gas components other than CO2 gas are also stored, because other gas components do not need to be stored. Therefore, when recovering gas from the CO2 storage unit 21, the recovery frequency can be reduced. Alternatively, when replacing the CO2 storage unit 21, the replacement frequency can be reduced.

[0045] Furthermore, when pump 19 pumps gas to the CO2 storage section 21, if gas components other than CO2 gas are discharged from the CO2 storage section 21, the rise in internal pressure of the CO2 storage section 21 can be suppressed accordingly. Therefore, compared to the case where gas components other than CO2 gas are not discharged from the CO2 storage section 21, pump 19 can pump CO2 gas to the CO2 storage section 21 at a lower pressure, thus reducing the need for pump 19 to consume extra energy.

[0046] Furthermore, the check valve 23 prevents or suppresses the inflow of air in the opposite direction to the discharge direction, thereby preventing or suppressing the wasteful consumption of the CO2 storage unit 21 by air.

[0047] [Other embodiments] Although the CO2 capture device has been described above with reference to exemplary embodiments, the above-described embodiments are merely illustrative examples of one aspect of the present disclosure. In other words, the present disclosure is not limited to the above-described exemplary embodiments and can be implemented in various forms without departing from the technical idea of ​​the present disclosure.

[0048] For example, in the above embodiment, the flow path switching valves 37A to 37F are each shown to be composed of three-way valves. However, as shown in the CO2 recovery device 2 in Figure 3A, the flow path switching valves 41A, 41B, 41C, 41D, 41E, 41F, 41G, 41H, 41I, 41J, 41K, and 41L may each be composed of two-way valves.

[0049] Furthermore, in the above embodiment, an example is shown in which a first flow path system and a second flow path system are configured with two water recovery units 13A, 13B and two CO2 recovery units 15A, 15B, and it is mentioned that three or more flow path systems may be configured, but a single flow path system may also be configured. Specifically, as shown in the CO2 recovery device 3 illustrated in Figure 3B, one water recovery unit 13 and one CO2 recovery unit 15 may be provided.

[0050] In this case, during the adsorption process, the three-way valve, flow path switching valve 43A, closes the flow path 31K side, connecting the heat exchanger 11 side and the water recovery unit 13 side. Also, the two-way valves, flow path switching valves 43B and 43C, are opened, and the two-way valve, flow path switching valve 43D, is closed. As a result, water is recovered from the exhaust gas in the water recovery unit 13, and CO2 is recovered in the CO2 recovery unit 15.

[0051] In the regeneration process, the flow path switching valve 43A closes the water recovery section 13 side, connecting the heat exchanger 11 side and the flow path 31K side. As a result, the exhaust gas is discharged outside the system through the flow path 31K. In addition, flow path switching valves 43B and 43C are closed and flow path switching valve 43D is opened. In this state, vacuuming is performed by pumps 17 and 19. As a result, water is desorbed from the water recovery section 13 and discharged outside the system. In addition, CO2 is desorbed from the CO2 recovery section 15 and stored in the CO2 storage section 21.

[0052] Even with such a CO2 recovery device 3, the CO2 storage section 21 and the check valve 23 are configured in the same way as in CO2 recovery devices 1 and 2, so CO2 can be stored efficiently without increasing the size of the CO2 storage section 21.

[0053] Furthermore, although the CO2 recovery device 3 described above was equipped with a water recovery unit 13, if a hydrophobic adsorbent is used as the adsorbent in the CO2 recovery unit 15, the CO2 recovery device 4 shown in Figure 4 may be configured without a water recovery unit. In other words, the heat exchanger 11 and the CO2 recovery unit 15 may be directly connected via the flow path 31L.

[0054] In this case, during the adsorption process, the three-way valve, flow path switching valve 45A, closes the flow path 31M side, connecting the heat exchanger 11 side and the CO2 recovery unit 15 side. At the same time, the two-way valve, flow path switching valve 45B, is opened, and the two-way valve, flow path switching valve 45C, is closed. As a result, CO2 is recovered in the CO2 recovery unit 15.

[0055] In the regeneration process, the flow path switching valve 45A closes the CO2 recovery unit 15 side, connecting the heat exchanger 11 side and the flow path 31M side. As a result, the exhaust gas is discharged outside the system through the flow path 31M. At the same time, the flow path switching valve 45B is closed and the flow path switching valve 45C is opened. In this state, vacuuming is performed by the pump 19. As a result, CO2 is released from the CO2 recovery unit 15 and stored in the CO2 storage unit 21.

[0056] Even with such a CO2 recovery device 4, the CO2 storage section 21 and the check valve 23 are configured in the same way as in CO2 recovery devices 1, 2, and 3, so CO2 can be stored efficiently without increasing the size of the CO2 storage section 21.

[0057] In addition, in the CO2 recovery devices 1 and 2 described above, if a hydrophobic adsorbent is used as the adsorbent in the CO2 recovery section 15, the water recovery sections 13A and 13B can be omitted.

[0058] Furthermore, multiple functions realized by one component as exemplified in the above embodiment may be realized by multiple components. One function realized by one component as exemplified in the above embodiment may be realized by multiple components. Multiple functions realized by multiple components as exemplified in the above embodiment may be realized by one component. One function realized by multiple components as exemplified in the above embodiment may be realized by one component. Some of the configurations exemplified in the above embodiment may be omitted. At least a part of the configuration exemplified in one of the above embodiments may be added to or replaced with the configuration exemplified in the other embodiments. [Explanation of symbols]

[0059] 1,2,3,4…CO2 recovery unit, 11…heat exchanger, 13,13A,13B…water recovery unit, 15,15A,15B…CO2 recovery unit, 17,19…pump, 21…CO2 storage unit, 23…check valve, 31A,31B,31C,31D,31E,31F,31G,31H,31I,31J,31K,31L,31M…flow path, 37A,37B,37C,37D,37E,37F,41A,41B,41C,41D,41E,41F,41G,41H,41I,41J,41L,43A,43B,43C,43D,45A,45B,45C…flow path switching valve.

Claims

1. A CO2 recovery device that recovers CO2 from the exhaust gas of an internal combustion engine, At least one CO2 recovery unit is configured to switch between an adsorption step and a regeneration step, and when switched to the adsorption step, it is configured to introduce the exhaust gas and adsorb CO2 in the exhaust gas, and when switched to the regeneration step, it is configured to desorb the CO2 adsorbed in the adsorption step and discharge the CO2-containing gas containing the desorbed CO2, A CO2 storage unit is configured to introduce the CO2-containing gas discharged from the CO2 recovery unit, adsorb the CO2 in the CO2-containing gas, and discharge the residual gas remaining after the adsorption of the CO2, A check valve is provided in the discharge channel for the residual gas discharged from the CO2 storage unit, and is configured to allow the residual gas to flow out in the discharge direction through the discharge channel, while preventing or suppressing the inflow of air in the opposite direction to the discharge direction through the discharge channel. A CO2 recovery device equipped with the following features.

2. A CO2 recovery device according to claim 1, A pump is provided in the flow path from the CO2 recovery section to the CO2 storage section, and when in operation, it pumps the CO2-containing gas from the CO2 recovery section to the CO2 storage section. A CO2 recovery device equipped with the following features.

3. A CO2 recovery device according to claim 1 or claim 2, The aforementioned at least one CO2 recovery unit is a plurality of CO2 recovery units. CO2 recovery device.

4. A CO2 recovery device according to claim 3, Of the plurality of CO2 recovery units, the exhaust gas is introduced into the CO2 recovery unit that is switched to the adsorption process, and the exhaust gas is not introduced into the CO2 recovery unit that is switched to the regeneration process, as the exhaust gas flow path is configured to be switched. CO2 recovery device.

Images