Co2 recovery system for on-vehicle engine

Abstract

To improve adsorption efficiency of a CO2 adsorbent without increasing the size of a heat exchanger.SOLUTION: A CO2 recovery system S includes: a first heat exchanger 24 disposed downstream of an exhaust catalyst 23; a first gas-water separator 25 disposed downstream of the first heat exchanger 24; a CO2 adsorbent 271 disposed downstream of the first gas-water separator 25 to adsorb CO2 in exhaust gas at least one of at high pressure and low temperature and desorb the adsorbed CO2 at least one of at low pressure and high temperature; a gas storage tank 51 disposed downstream of the CO2 adsorbent 271 to cause the CO2 containing gas desorbed from the CO2 adsorbent 271 and containing CO2 to flow in; a first flow pipe 61 to which condensation water separated by the first gas-water separator 25 flows in; and a water injector 63 connected to the first flow pipe 61 to inject the condensation water to an outer surface 2f of an exhaust pipe 2 located upstream of the first heat exchanger 24.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a CO2 capture system for an on-board engine. [Background technology]

[0002] For example, Patent Document 1 discloses a CO2 separation device for an internal combustion engine. This device includes a CO2 adsorbent, an injector arranged upstream of the CO2 adsorbent, and a control means for performing various controls. The CO2 adsorbent adsorbs CO2 in exhaust gas at low temperatures and desorbs the adsorbed CO2 at high temperatures. The injector adds water for the adsorption reaction.

[0003] According to Patent Document 1, the control means executes water addition control to add water from the water adding means to the CO2 adsorbent when desorbing CO2 from the CO2 adsorbent. According to Patent Document 1, by adsorbing water into the CO2 adsorbent, the temperature of the CO2 adsorbent is increased by the heat of reaction, thereby improving desorption of CO2 from the CO2 adsorbent. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-152077 Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, when using a CO2 adsorbent such as that described in Patent Document 1, in order to improve the CO2 adsorption efficiency, it is advantageous to remove as much moisture as possible from the exhaust gas that reaches the CO2 adsorbent.

[0006] One possible solution to this problem would be to make the heat exchanger located upstream of the CO2 adsorbent larger than before. However, in the case of a typical vehicle engine, it is not easy to provide space large enough to accommodate a larger heat exchanger. Furthermore, making the heat exchanger larger would be inconvenient from the perspective of the degree of freedom in the heat exchanger layout.

[0007] The present disclosure has been made in view of the above points, and an object thereof is to improve the adsorption efficiency of a CO2 adsorbent without increasing the size of the heat exchanger. [Means for solving the problem]

[0008] A first aspect of the present disclosure relates to a CO2 capture system for an automotive engine, which is disposed between a cylinder of the automotive engine and the downstream end of an exhaust pipe, and which circulates exhaust gas discharged from the cylinder and captures CO2 in the exhaust gas.

[0009] According to the first aspect, the CO2 recovery system includes: a first heat exchanger, which is arranged downstream of an exhaust catalyst and performs heat exchange between the exhaust gas and a heat exchange medium so as to receive heat from the exhaust gas after passing through the exhaust catalyst; a first steam-water separator, which is arranged downstream of the first heat exchanger and separates condensed water generated in the exhaust gas from the exhaust gas; a CO2 adsorbent, which is arranged downstream of the first steam-water separator and adsorbs CO2 in the exhaust gas under at least one of high pressure and low temperature conditions and desorbs the adsorbed CO2 under at least one of low pressure and high temperature conditions; a gas storage tank, which is arranged downstream of the CO2 adsorbent and receives an inlet of CO2-containing gas containing CO2 desorbed from the CO2 adsorbent; a first circulation pipe into which the condensed water separated by the first steam-water separator flows; and a water injector, which is connected to the first circulation pipe and injects condensed water onto an outer surface of the exhaust pipe located upstream of the first heat exchanger.

[0010] According to the first aspect, the controller injects condensed water from the water injector. The condensed water is injected onto the outer surface of the exhaust pipe located upstream of the first heat exchanger. This allows the condensed water to pre-cool the exhaust gas immediately before it passes through the first heat exchanger. By pre-cooling the exhaust gas, the moisture contained in the exhaust gas can be removed by condensation. As a result, the adsorption of CO2 by the CO2 adsorbent can be promoted. This allows the adsorption efficiency of the CO2 adsorbent to be improved without increasing the size of the heat exchanger.

[0011] Furthermore, according to a second aspect of the present disclosure, the CO2 recovery system may include: a second heat exchanger that is arranged midway from the CO2 adsorbent to the gas storage tank and performs heat exchange between the CO2-containing gas and a heat exchange medium so as to receive heat from the gas; a second steam-water separator that is arranged downstream of the second heat exchanger and upstream of the gas storage tank and separates condensed water generated in the CO2-containing gas from the CO2-containing gas; and a second circulation pipe into which the condensed water separated by the second steam-water separator flows, and the second circulation pipe may be connected to the water injector so as to send the condensed water to the water injector.

[0012] According to the second aspect, the second heat exchanger can be used to remove heat from the CO2-containing gas. This can promote the adsorption of CO2 by the CO2 adsorbent in the gas storage tank. This can improve the adsorption efficiency of the CO2 adsorbent when viewed from the perspective of the entire CO2 capture system. Furthermore, by injecting condensed water generated in the second heat exchanger from the water injector, the cooling efficiency of the exhaust gas can be improved.

[0013] According to a third aspect of the present disclosure, the exhaust pipe may include a specific portion located upstream of the first heat exchanger and having an outer surface arranged to face the nozzle of the water injector, the outer surface of the specific portion having a plurality of fins protruding outward in the flow direction of the exhaust gas so as to increase the surface area of ​​the outer surface, and the nozzle of the water injector may be arranged to face the plurality of fins.

[0014] According to the third aspect, by increasing the surface area of ​​the outer surface of the exhaust pipe onto which the water injected from the water injector is sprayed, it is possible to increase the contact area between the injected condensed water and the exhaust pipe, thereby further improving the efficiency of cooling the exhaust gas by the injection of condensed water.

[0015] Furthermore, according to a fourth aspect of the present disclosure, the specific portion may be branched into a plurality of exhaust pipe sections that allow exhaust gas to flow in parallel, and each of the plurality of exhaust pipe sections may have the plurality of fins.

[0016] According to the fourth aspect, the surface area of ​​the outer surface onto which the condensed water is sprayed can be further increased, thereby further increasing the contact area between the sprayed condensed water and the exhaust pipe, thereby further improving the cooling efficiency of the exhaust gas by the sprayed condensed water. [Effects of the Invention]

[0017] As described above, according to the present disclosure, the adsorption efficiency of the CO2 adsorbent can be improved without increasing the size of the heat exchanger. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram illustrating the overall configuration of a CO2 recovery system for an in-vehicle engine. [Figure 2] FIG. 2 is a system diagram illustrating the configuration of the collection system. [Figure 3]FIG. 3 is a diagram illustrating the configuration of a gas storage tank. [Figure 4] FIG. 4 is a block diagram illustrating the configuration of the controller. [Figure 5A] FIG. 5A is a diagram illustrating the functions performed by the flow path switching device. [Figure 5B] FIG. 5B is a diagram illustrating the functions performed by the flow path switching device. [Figure 6] FIG. 6 is a flowchart showing a specific example of adsorption control. [Figure 7] FIG. 7 is a flowchart showing a specific example of desorption control. [Figure 8] FIG. 8 is a flowchart showing a specific example of water injection control. [Figure 9] FIG. 9 is a diagram illustrating the structure of a specific portion of the exhaust pipe. [Figure 10] FIG. 10 is a view corresponding to FIG. 2 showing a recovery system according to the second embodiment. [Figure 11] FIG. 11 is a diagram illustrating the pressure and temperature dependence of the CO2 adsorption amount in the CO2 adsorbent. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. Note that the following description is for illustrative purposes only.

[0020] <1. Overall structure> 1 is a schematic diagram illustrating the overall configuration of a CO2 capture system S for an on-vehicle engine 1. Hereinafter, the "CO2 capture system S" may also be simply referred to as the "capture system S." This capture system S is connected between a cylinder 11 of the on-vehicle engine 1 and the downstream end of the exhaust pipe 2 (tail pipe 20).

[0021] The vehicle engine 1 is an internal combustion engine mounted on an automobile. The vehicle engine 1 has a cylinder 11 that forms a combustion chamber 12. The cylinder 11 is connected to an intake pipe 13 that supplies air from the outside to the combustion chamber 12, and an exhaust pipe 2 that discharges exhaust gas from the combustion chamber 12.

[0022] A tail pipe 20 is disposed at the downstream end of the exhaust pipe 2. The recovery system S according to this embodiment is disposed in the exhaust pipe 2 midway from the cylinder 11 to the tail pipe 20.

[0023] <2. Collection system> FIG. 2 is a system diagram illustrating the configuration of the recovery system S. In FIG. 2, the passage through which the exhaust gas flows, i.e., the exhaust pipe 2, is indicated by a thick solid line. In the same figure, a passage dedicated to the gas (gas that may contain CO2, hereinafter referred to as "CO2-containing gas") desorbed from the first and second adsorption devices 27A, 27B is indicated by a thin solid line. The exhaust pipe 2 also serves as a passage for the CO2-containing gas. In addition, in FIG. 2, the passage through which the heat exchange medium for cooling the exhaust gas flows is indicated by a dotted line. As shown in FIG. 2, the exhaust pipe 2 connects the cylinder 11 and the tailpipe 20.

[0024] A branching section 2a and a merging section 2b are arranged midway along the exhaust pipe 2. At the branching section 2a, the single exhaust pipe 2 branches into two exhaust pipes 2, each consisting of a first branching pipe 21 and a second branching pipe 22. At the merging section 2b, the first branching pipe 21 and the second branching pipe 22 merge again into a single pipe. A tail pipe 20 is connected to the combined exhaust pipe 2.

[0025] Hereinafter, "upstream" refers to "upstream" based on the flow direction of the exhaust gas or CO2-containing gas in the exhaust pipe 2. Similarly, "downstream" refers to "downstream" based on the flow direction of the exhaust gas or CO2-containing gas in the exhaust pipe 2. For example, the branching section 2a described above is disposed upstream of the junction section 2b, as shown in FIG. 2.

[0026] In the exhaust pipe 2, in a section from the cylinder 11 to the branching portion 2a, an exhaust catalyst 23, a first heat exchanger 24, and a first steam-water separator 25 are arranged in this order from the upstream side.

[0027] The exhaust catalyst 23 purifies the exhaust gas. The exhaust catalyst 23 purifies harmful components contained in the exhaust gas and emits harmless gas. The harmful components include NOx, CO, and HC. The harmless gas is a gas composed of nitrogen (N2), CO2, and H2O. The exhaust catalyst 23 is, for example, a three-way catalyst.

[0028] The first heat exchanger 24 is disposed downstream of the exhaust catalyst 23. The first heat exchanger 24 exchanges heat between the exhaust gas and a heat exchange medium so as to receive heat from the exhaust gas after passing through the exhaust catalyst 23. The heat exchange medium is, for example, a cooling liquid. The heat exchange medium is, for example, water. The first heat exchanger 24 is configured to pass the exhaust gas and to receive heat from the exhaust gas that has passed through it. The heat exchange medium circulates through a flow path system (heat exchange system 4) that is independent of the exhaust pipe 2.

[0029] The heat exchange system 4 is a system for circulating a heat exchange medium. The heat exchange medium circulating through the heat exchange system 4 receives heat in the first heat exchanger 24, passes through a second heat exchanger 38 (described later), and receives further heat in the second heat exchanger 38. The heat exchange medium that received heat in the second heat exchanger 38 is cooled by a third heat exchanger 41, and then passes through the first heat exchanger 24 again.

[0030] In this way, the heat exchange medium circulates through the heat exchange system 4 in the order of the first heat exchanger 24, the second heat exchanger 38, and the third heat exchanger 41. The third heat exchanger 41 is an electrically driven cooling device that is configured to cool the heat exchange medium passing through the third heat exchanger 41 and then send the cooled heat exchange medium to the first heat exchanger 24. The third heat exchanger 41 may be configured as a "chiller" that uses electric power to drive a pump and cools the heat exchange medium (cooled medium) with a circulating liquid circulated by the drive of the pump.

[0031] The first water-steam separator 25 is disposed downstream of the first heat exchanger 24. The first water-steam separator 25 separates condensed water generated in the exhaust gas from the exhaust gas. That is, the temperature of the exhaust gas that has passed through the first heat exchanger 24 drops by the amount of heat removed by the first heat exchanger 24. Due to this temperature drop, the water contained in the exhaust gas liquefies and becomes condensed water. The first water-steam separator 25 is configured to allow the exhaust gas to pass through and to collect condensed water from the exhaust gas that has passed through it.

[0032] In addition, in the exhaust pipe 2, in the section from the branching section 2a through the first branching pipe 21 to the confluence section 2b, there are arranged, in order from the upstream side, a first upstream control valve 26A, a first adsorption device 27A, and a first downstream control valve 28A.

[0033] The first upstream control valve 26A opens and closes the first branch pipe 21 upstream of the first adsorption device 27A. The first upstream control valve 26A is electrically connected to a controller 100 (described later), and opens and closes in response to a control signal received from the controller 100.

[0034] The first adsorption device 27A is disposed downstream of the exhaust catalyst 23, the first heat exchanger 24, the first steam-water separator 25, the branching section 2a, and the first upstream control valve 26A. The first adsorption device 27A is configured to include a CO2 adsorbent 271. The CO2 adsorbent 271 adsorbs CO2 in the exhaust gas at high pressure and / or low temperature, and desorbs the adsorbed CO2 at low pressure and / or high temperature.

[0035] Specifically, the CO2 adsorbent 271 according to this embodiment adsorbs more CO2 as the pressure decreases under the same temperature condition (equal temperature condition), and adsorbs more CO2 as the pressure approaches atmospheric pressure under the same pressure condition (equal pressure condition), as illustrated in Fig. 11. At a given temperature, the CO2 adsorbent 271 has a maximum CO2 adsorption amount near atmospheric pressure.

[0036] More specifically, the CO2 adsorbent 271 adsorbs CO2 in the exhaust gas when exhaust pressure (exhaust pressure) equal to or higher than atmospheric pressure is applied, that is, when the CO2 adsorption amount is at its maximum. Furthermore, the CO2 adsorbent 271 desorbs the adsorbed CO2 when negative pressure (lower than atmospheric pressure) is applied (specifically, when the vacuum pump 36, described later, is operating). The CO2 adsorbent 271 is, for example, an adsorbent made of zeolite.

[0037] The CO2 adsorbent 271 of this embodiment is configured to desorb CO2 mainly by the pressure swing method using the vacuum pump 36. The first heat exchanger 24 of this embodiment is configured to separate condensed water from the exhaust gas and to promote adsorption of CO2 by the CO2 adsorbent 271. That is, in this embodiment, while the pressure swing method is mainly used, the temperature dependency of the amount of CO2 adsorption in the CO2 adsorbent 271 is also partially used in combination.

[0038] The first downstream control valve 28A opens and closes the first branch pipe 21 downstream of the first adsorption device 27A. The first downstream control valve 28A is electrically connected to a controller 100 (described later), and opens and closes in response to a control signal received from the controller 100.

[0039] In addition, in the exhaust pipe 2, in the section from the branching section 2a through the second branching pipe 22 to the confluence section 2b, there are arranged, in order from the upstream side, a second upstream control valve 26B, a second adsorption device 27B, and a second downstream control valve 28B.

[0040] The second upstream control valve 26B opens and closes the second branch pipe 22 upstream of the second adsorption device 27B. The second upstream control valve 26B is electrically connected to a controller 100 (described later) and opens and closes in response to a control signal from the controller 100.

[0041] The second adsorption device 27B is disposed downstream of the exhaust catalyst 23, the first heat exchanger 24, the first steam-water separator 25, the branching section 2a, and the second upstream control valve 26B. The second adsorption device 27B is configured to include a CO2 adsorbent 271. The CO2 adsorbent 271 adsorbs CO2 in the exhaust gas at high pressure and / or low temperature, and desorbs the adsorbed CO2 at low pressure and / or high temperature.

[0042] Specifically, the CO2 adsorbent 271 according to this embodiment adsorbs more CO2 as the pressure decreases under the same temperature condition (equal temperature condition), and adsorbs more CO2 as the pressure approaches atmospheric pressure under the same pressure condition (equal pressure condition), as shown in Fig. 11. At a given temperature, the CO2 adsorbent 271 maximizes the amount of CO2 adsorbed near atmospheric pressure.

[0043] More specifically, the CO2 adsorbent 271 adsorbs CO2 in the exhaust gas when exhaust pressure (exhaust pressure) equal to or higher than atmospheric pressure is applied, that is, when the CO2 adsorption amount is at its maximum. Furthermore, the CO2 adsorbent 271 desorbs the adsorbed CO2 when negative pressure (lower than atmospheric pressure) is applied (specifically, when the vacuum pump 36, described later, is operating). The CO2 adsorbent 271 is, for example, an adsorbent made of zeolite.

[0044] As shown in FIG. 2, the second adsorption device 27B can be considered to be connected in parallel with the first adsorption device 27A in the flow direction of the exhaust gas.

[0045] The second downstream control valve 28B opens and closes the second branch pipe 22 downstream of the second adsorption device 27B. The second downstream control valve 28B is electrically connected to a controller 100 (described later), and opens and closes in response to a control signal received from the controller 100.

[0046] A desorbed gas circulation system that circulates the CO2-containing gas desorbed from the first and second adsorption devices 27A and 27B is connected to the first and second branch pipes 21 and 22. The desorbed gas circulation system according to this embodiment is configured as one element of the recovery system S.

[0047] Specifically, a first desorption branch 2c is provided in a portion of the first branch pipe 21 between the first upstream control valve 26A and the first adsorption device 27A. A third branch pipe 31, through which the CO2-containing gas desorbed from the first adsorption device 27A flows, is connected to the first desorption branch 2c.

[0048] Similarly, a second desorption branch 2d is provided in a portion of the second branch pipe 22 between the second upstream control valve 26B and the second adsorption device 27B. A fourth branch pipe 32, through which the CO2-containing gas desorbed from the second adsorption device 27B flows, is connected to the second desorption branch 2d.

[0049] A first desorption control valve 33 is disposed in the third branch pipe 31 to open and close the third branch pipe 31. A second desorption control valve 34 is disposed in the fourth branch pipe 32 to open and close the fourth branch pipe 32. The first and second desorption control valves 33 and 34 are each electrically connected to the controller 100, and open and close in response to a control signal from the controller 100.

[0050] The third branch pipe 31 and the fourth branch pipe 32 join at a desorbed gas junction 2e to form an integrated desorbed gas pipe 35. In the desorbed gas pipe 35, a vacuum pump 36, a compressor 37, a second heat exchanger 38, a second steam-water separator 39, and a gas storage tank 51 are arranged in this order from the upstream side in the flow direction of the desorbed gas (CO2-containing gas).

[0051] The vacuum pump 36 generates an air pressure (negative pressure) that is lower than atmospheric pressure. The vacuum pump 36 is electrically connected to the controller 100 and operates in response to a control signal from the controller 100. The negative pressure generated by the vacuum pump 36 can promote desorption of CO2 from the first and second adsorption devices 27A, 27B. Heaters that heat the first and second adsorption devices 27A, 27B, respectively, may be used instead of the vacuum pump 36.

[0052] The compressor 37 compresses the CO2-containing gas that is sucked into the vacuum pump 36 and passes through the vacuum pump 36. The compressor 37 is electrically connected to the controller 100, and operates upon receiving a control signal from the controller 100.

[0053] The second heat exchanger 38 is disposed downstream of the compressor 37. More generally, the second heat exchanger 38 according to this embodiment is disposed midway from the CO2 adsorbents 271 of the first and second adsorption devices 27A and 27B to the gas storage tank 51. The second heat exchanger 38 exchanges heat between the exhaust gas and a heat exchange medium so as to receive heat from the CO2-containing gas after passing through the compressor 37.

[0054] The second steam-water separator 39 is disposed downstream of the second heat exchanger 38 and upstream of the gas storage tank 51, and separates condensed water generated in the CO2-containing gas from the CO2-containing gas. That is, the temperature of the CO2-containing gas that has passed through the second heat exchanger 38 drops by the amount of heat removed by the second heat exchanger 38. Due to this temperature drop, the water contained in the CO2-containing gas liquefies to become condensed water. The second steam-water separator 39 is configured to allow the CO2-containing gas to pass through and to collect condensed water from the CO2-containing gas that has passed through it.

[0055] 3 is a diagram illustrating the configuration of the gas storage tank 51. The gas storage tank 51 is disposed downstream of the second steam-water separator 39. More generally, the gas storage tank 51 according to this embodiment is disposed downstream of the first and second adsorption devices 27A and 27B and the CO2 adsorbents 271 provided therein. The gas storage tank 51 receives the CO2-containing gas from one of the first and second adsorption devices 27A and 27B.

[0056] 3, the gas storage tank 51 contains a CO2 adsorbent 272. The CO2 adsorbent 272 contained in the gas storage tank 51 may be the same as the zeolite CO2 adsorbent 271 contained in the first and second adsorption devices, or may be a different material.

[0057] The gas storage tank 51 has an inlet 51a and an outlet 51b. The outlet 51b is open so that the gas that has flowed into the gas storage tank 51 can flow out of the gas storage tank 51.

[0058] 2, a first circulation pipe 61 is connected to the first steam-water separator 25. Condensed water separated by the first steam-water separator 25 flows into the first circulation pipe 61.

[0059] The first circulation pipe 61 is connected to a water injector 63. Specifically, the upstream end of the first circulation pipe 61 is connected to the first steam-water separator 25, and the downstream end of the first circulation pipe 61 is connected to the water injector 63. The first circulation pipe 61 supplies the condensed water separated in the first steam-water separator 25 to the water injector 63.

[0060] A water tank 64 is disposed in the first flow pipe 61 midway between the first steam-water separator 25 and the water injector 63. The water tank 64 stores condensed water. The water tank 64 is provided with a water volume sensor Sw11 that detects the remaining amount of condensed water in the water tank 64. A detection signal from the water volume sensor Sw11 is input to the controller 100.

[0061] 2, a second circulation pipe 62 is connected to the second steam-water separator 39. Condensed water separated by the second steam-water separator 39 flows into the second circulation pipe 62.

[0062] The second circulation pipe 62 is connected to the water injector 63 so as to send condensed water to the water injector 63. Specifically, the upstream end of the first circulation pipe 61 is connected to the second steam-water separator 39, and the downstream end of the second circulation pipe 62 is connected to a portion of the first circulation pipe 61. More specifically, the downstream end of the second circulation pipe 62 is connected to the first circulation pipe 61 midway from the first steam-water separator 25 to the water tank 64. The second circulation pipe 62 supplies the condensed water separated in the first steam-water separator 25 to the water injector 63.

[0063] The water injector 63 injects condensed water onto the outer surface 2f of the exhaust pipe 2 located upstream of the first heat exchanger 24. In detail, the water injector 63 injects condensed water onto the outer surface 2f of the exhaust pipe 2 located downstream of the exhaust catalyst 23 and upstream of the first heat exchanger 24.

[0064] Here, among the multiple parts that make up the exhaust pipe 2, the part located upstream of the first heat exchanger 24 (more specifically, downstream of the exhaust catalyst 23 and upstream of the first heat exchanger 24) is referred to as a "specific part 29."

[0065] In this embodiment, the specific portion 29 has an outer surface 2f that is arranged to face the injection port of the water injector 63. That is, the water injector 63 according to this embodiment is constructed and arranged to inject condensed water toward the outer surface 2f of the specific portion 29.

[0066] Fig. 9 is a diagram illustrating the structure of the specific portion 29 of the exhaust pipe 2. As shown in Fig. 9, the outer surface 2f of the specific portion 29 has a plurality of fins 291 that protrude outward in the flow direction of the exhaust gas to increase its surface area. The injection port of the water injector 63 is disposed so as to face the plurality of fins 291.

[0067] Furthermore, the specific portion 29 of the exhaust pipe 2 branches into a plurality of exhaust pipe sections 292 through which exhaust gas flows in parallel. Each of the plurality of exhaust pipe sections 292 has a plurality of fins 291.

[0068] <3. Controller> 4 is a block diagram illustrating the configuration of the controller 100. The controller 100 includes hardware such as a processor 100a, a memory 100b, and an input / output bus 100c, and software such as a database and a control program. The controller 100 according to this embodiment is configured by a so-called ECU (Engine Control Unit).

[0069] Various sensors are connected to the controller 100. Specifically, an accelerator pedal sensor Sw1, an engine rotation speed sensor Sw2, an exhaust temperature sensor Sw3, an exhaust pressure sensor Sw4, an adsorption layer temperature sensor Sw5, a tank pressure sensor Sw6, and a water volume sensor Sw11 are connected to the controller 100 so as to be able to receive electrical signals. The electrical signals generated by these sensors are input to the controller 100.

[0070] The accelerator pedal sensor Sw1 detects the depression of the vehicle's accelerator pedal and generates an electrical signal indicating the detected depression. The engine speed sensor Sw2 detects the rotation speed of the vehicle engine 1 and generates an electrical signal indicating the detected rotation speed. The exhaust temperature sensor Sw3 detects the temperature of the exhaust gas flowing through the exhaust pipe 2 and generates an electrical signal indicating the detected temperature. The exhaust pressure sensor Sw4 detects the pressure of the exhaust gas flowing through the exhaust pipe 2 and generates an electrical signal indicating the detected pressure. The adsorption bed temperature sensor Sw5 detects the temperature of the CO2 adsorbent 271 of each of the first adsorption device 27A and the second adsorption device 27B and generates an electrical signal indicating each detected temperature. The tank pressure sensor Sw6 detects the pressure of the air in the gas storage tank 51 and generates an electrical signal indicating the detected pressure. The water volume sensor Sw11 is as described above.

[0071] Various actuators are connected to the controller 100. Specifically, the first upstream control valve 26A, the first downstream control valve 28A, the second upstream control valve 26B, the second downstream control valve 28B, the first and second desorption control valves 33, 34, the vacuum pump 36, the compressor 37, and the water injector 63 are connected to the controller 100 so as to be able to transmit electrical signals.

[0072] Hereinafter, among these actuators, the first upstream control valve 26A, the first downstream control valve 28A, the second upstream control valve 26B, the second downstream control valve 28B, and the first and second desorption control valves 33, 34 will be collectively referred to as the flow path switching device 5. The function performed by the flow path switching device 5 will be described later.

[0073] The controller 100 generates control signals based on the electrical signals input from the sensors described above, and inputs the signals to various actuators electrically connected to the controller 100 .

[0074] For example, the controller 100 can calculate a target load for the vehicle engine 1 based on the opening degree detected by the accelerator pedal sensor Sw1. This target load can be used for operating the vehicle engine, such as adjusting the fuel injection amount, or for controlling the gas amount adjusting unit 53, which will be described later.

[0075] 5A and 5B are diagrams for explaining the functions performed by the flow path switching device 5. In these figures, the heat exchange system 4 is shown with most of it omitted for clarity of the drawings.

[0076] Among the circuit symbols showing control valves in Figures 5A and 5B, the open circuit symbols indicate that the valve is in an open state. Similarly, among the circuit symbols showing control valves in Figures 5A and 5B, the filled circuit symbols indicate that the valve is in a closed state. The meanings of solid lines, dashed lines, etc. in Figures 5A and 5B are as shown in the legends of each figure.

[0077] The flow path switching device 5 according to this embodiment can alternately switch the first and second adsorption devices 27A, 27B between a state in which they are connected between the exhaust catalyst 23 and the tail pipe 20 and a state in which they are disconnected from the exhaust catalyst 23 and connected to the gas storage tank 51. This switching can be performed based on an electrical signal input from the controller 100 to the flow path switching device 5.

[0078] The former state (adsorption state) contributes to the adsorption of CO2 from the exhaust gas and the discharge of the exhaust gas with adsorbed CO2. The latter state (desorption state) contributes to the desorption of CO2 adsorbed in the adsorption device and the supply of CO2-containing gas to the gas storage tank 51. Hereinafter, for each of the first and second adsorption devices 27A and 27B, the process for setting the flow path structure to the adsorption state will be referred to as "adsorption control." Similarly, for each of the first and second adsorption devices 27A and 27B, the process for operating the vacuum pump 36 after setting the flow path structure to the desorption state will be referred to as "desorption control."

[0079] 5A, the first upstream control valve 26A and the first downstream control valve 28A are opened, and the second upstream control valve 26B and the second downstream control valve 28B are closed. At the same time, the first desorption control valve 33 is closed, and the second desorption control valve 34 is opened. In this case, the first adsorption device 27A is in an adsorption state, and the second adsorption device 27B is in a desorption state.

[0080] 5B, the first upstream control valve 26A and the first downstream control valve 28A are closed, and the second upstream control valve 26B and the second downstream control valve 28B are opened. At the same time, the first desorption control valve 33 is opened, and the second desorption control valve 34 is closed. In this case, the first adsorption device 27A is in a desorption state, and the second adsorption device 27B is in an adsorption state.

[0081] The controller 100 alternately switches the first and second adsorption devices 27A, 27B between an "adsorption state" and a "desorption state." This allows the two adsorption devices to perform well-balanced adsorption and desorption of CO2. When one of the first and second adsorption devices 27A, 27B is in the "adsorption state," the other is in the "desorption state." When the first adsorption device 27A transitions in the order of the "adsorption state," "desorption state," and "adsorption state," the second adsorption device 27B transitions in the order of the "desorption state," "adsorption state," and "desorption state."

[0082] In addition to the adsorption control and desorption control described above, the controller 100 is configured to execute a process (water injection control) for appropriately injecting condensed water from the water injector 63. Specific examples of processes including the water injection control will be described below with reference to flowcharts.

[0083] <4. Specific examples of processing by the controller> (4-1. Adsorption control) 6 is a flowchart showing a specific example of suction control. Here, suction control for the first suction device 27A will be described, but suction control for the second suction device 27B is also performed in the same manner.

[0084] First, in step S101 of Fig. 6, the controller 100 reads the detection signals from the sensors exemplified in Fig. 4. The subsequent processing is performed when the first suction device 27A is in the suction state.

[0085] In the following step S102, the controller 100 estimates the CO2 adsorption amount at that time for the CO2 adsorbent 271 in the first adsorption device 27A based on the target load of the engine 1 calculated based on the accelerator pedal sensor Sw1, the engine speed, the detected temperature of the exhaust, and the detected temperature of the CO2 adsorbent 271.

[0086] In the following step S103, the controller 100 determines whether the estimated value of the CO2 adsorption amount (estimated adsorption amount) obtained in step S102 has reached or exceeded a value (predetermined value) near the adsorption limit of the CO2 adsorbent 271 in the first adsorption device 27A. If this determination is NO, the controller 100 skips the following step S104 and returns. In this case, the first adsorption device 27A is maintained in an adsorption state, and the second adsorption device 27B is maintained in a desorption state. Note that the predetermined value here is the maximum value that can be adsorbed at atmospheric pressure or exhaust pressure during idling. It is advantageous for the CO2 adsorbent 271 in the present disclosure to have a characteristic (see FIG. 11) that maximizes its CO2 adsorption amount at atmospheric pressure or during idling.

[0087] On the other hand, if the determination in step S103 is YES, the controller 100 advances the control process to step S104. In step S103, the controller 100 controls the flow path switching device 5 to change the first adsorption device 27A from the adsorption state to the desorption state and change the second adsorption device 27B from the desorption state to the adsorption state. When the first adsorption device 27A is changed to the desorption state, the controller 100 executes desorption control, which will be described later, on the first adsorption device 27A instead of adsorption control.

[0088] (4-2. Desorption control) 7 is a flowchart showing a specific example of desorption control. Here, desorption control for the first adsorption device 27A will be described, but desorption control for the second adsorption device 27B is also performed in the same manner.

[0089] First, in step S201 of Fig. 6, the controller 100 reads the detection signals from the sensors exemplified in Fig. 4. The subsequent processing is performed when the first suction and absorption device 27A is in the detaching state.

[0090] In the following step S202, the controller 100 predicts the period (desorption period) required for CO2 to be desorbed from the CO2 adsorbent 271 in the first adsorption device 27A based on the target load of the engine 1 calculated based on the accelerator pedal sensor Sw1, the engine speed, the detected temperature of the exhaust, and the detected temperature of the CO2 adsorbent 271.

[0091] In the next step S203, the controller 100 determines the flow rate (introduction flow rate) of the CO2-containing gas flowing out from the first adsorption device 27A per unit time according to the desorption period predicted in step S202. The longer the desorption period, the smaller the flow rate of the CO2-containing gas. The estimated adsorption amount calculated in the adsorption control may be used to determine the desorption period or the introduction flow rate.

[0092] In the following step S204, the controller 100 controls the vacuum pump 36 based on the introduction flow rate determined in step S203 and the detected pressure in the gas storage tank 51.

[0093] In the following step S205, the controller 100 estimates the amount of CO2 desorption at that time from the CO2 adsorbent 271 of the first adsorption device 27A based on the introduction flow rate determined in step S203 and the elapsed time since the first adsorption device 27A was placed in a desorption state.

[0094] In the following step S206, the controller 100 determines whether the estimated value of the CO2 desorption amount (estimated desorption amount) obtained in step S205 has reached or exceeded a value (predetermined value) near the desorption limit of the CO2 adsorbent 271 in the first adsorption device 27A. If the determination is NO, the controller 100 returns to step S204. In this case, the first adsorption device 27A is maintained in a desorption state, and the second adsorption device 27B is maintained in an adsorption state.

[0095] On the other hand, if the determination in step S206 is YES, the controller 100 advances the control process to step S207. In step S207, the controller 100 controls the flow path switching device 5 to change the first adsorption device 27A from the desorption state to the adsorption state, and change the second adsorption device 27B from the adsorption state to the desorption state. When the first adsorption device 27A is changed to the adsorption state, the controller 100 executes the above-described adsorption control instead of the desorption control for the first adsorption device 27A.

[0096] As described above, the first and second adsorption devices 27A, 27B are alternately switched between an "adsorption state" and a "desorption state." That is, when one of the first and second adsorption devices 27A, 27B is in the "adsorption state," the other of the first and second adsorption devices 27A, 27B is in the "desorption state." The adsorption control illustrated in FIG. 6 is executed for one of the devices in the adsorption state, and the desorption control illustrated in FIG. 7 is executed for the other device in the desorption state.

[0097] In this case, adsorption control of one of the first and second adsorption devices 27A, 27B in the "adsorption state" and desorption control of the other in the "desorption state" are simultaneously executed. If the determination in step S103 in the adsorption control or the determination in step S206 in the desorption control is YES first, the controller 100 forcibly switches between the "adsorption state" and the "desorption state" without waiting for the other determination to be YES.

[0098] Specifically, when the determination in step S103 in the adsorption control or the determination in step S206 in the desorption control becomes YES first, the controller 100 executes the process of step S104 without waiting for the determination in step S206 to become YES. One of the first and second adsorption devices 27A, 27B that has been executing the adsorption control transitions from the "adsorption state" to the "desorption state" and then starts the desorption control of Fig. 7. The other of the first and second adsorption devices 27A, 27B that has been executing the desorption control forcibly stops the desorption control, transitions forcibly from the "desorption state" to the "adsorption state", and then starts the adsorption control of Fig. 6.

[0099] Similarly, if the determination in step S103 in the adsorption control or the determination in step S206 in the desorption control becomes YES first, the controller 100 executes the process of step S207 without waiting for the determination in the former to become YES. One of the first and second adsorption devices 27A, 27B that was executing the desorption control transitions from the "desorption state" to the "adsorption state" and then starts the adsorption control of Fig. 6. The other of the first and second adsorption devices 27A, 27B that was executing the adsorption control forcibly stops the adsorption control, transitions from the "adsorption state" to the "desorption state", and then starts the desorption control of Fig. 7.

[0100] (4-3. Water injection control) 8 is a flowchart showing a specific example of water injection control. The water injection control is performed in parallel with the adsorption control, particularly the adsorption control, of the adsorption control and desorption control described above.

[0101] First, in step S301 of Fig. 8, the controller 100 reads detection signals from the sensors exemplified in Fig. 4. In the following step S302, the controller 100 determines whether the exhaust temperature exceeds a predetermined temperature. If the determination is YES, the controller 100 advances the control process to step S303.

[0102] In step S303, the controller 100 sets the amount of water to be injected based on the exhaust temperature so that the amount of water to be injected corresponds to the exhaust temperature. The higher the exhaust temperature, the greater the amount of water to be injected.

[0103] In the following step S304, the controller 100 injects water from the water injector 63 so as to achieve the injection amount set in step S304 or step S306, which will be described later.

[0104] Meanwhile, in step S305 branched from step S302, the controller 100 determines whether the remaining amount of condensed water in the water tank 64 is equal to or greater than a predetermined allowable upper limit based on the detection signal of the water volume sensor Sw11. The allowable upper limit is an index for determining whether the water tank 64 is close to being full, and is set in advance.

[0105] If the determination in step S305 is YES, the controller 100 proceeds to step S306. In this case, the controller 100 sets the amount of water to be injected from the water injector 63 to the minimum injection amount, regardless of the exhaust temperature. The minimum injection amount may be, for example, the minimum amount of water that can be injected from the water injector 63. This causes water to be injected to an extent that prevents the water tank 64 from becoming full.

[0106] If the determination in step S305 is NO, the controller 100 advances the control process to step S307. In step S307, the controller 100 waits without starting water injection. Thereafter, the controller 100 returns the control process to step S301, and repeats each process from step S301.

[0107] <5. Significance of water injection control> As described above, in the embodiment, the controller 100 injects condensed water from the water injector 63. As illustrated in FIG. 9, the condensed water is injected onto the outer surface 2f of the exhaust pipe 2 located upstream of the first heat exchanger 24. This allows the exhaust gas to be pre-cooled by the condensed water just before passing through the first heat exchanger 24. Pre-cooling the exhaust gas can promote the adsorption of CO2 by the CO2 adsorbent 271. This allows the adsorption efficiency of the CO2 adsorbent 271 to be improved without increasing the size of the heat exchanger.

[0108] 9, the fins 291 are used to increase the surface area of ​​the outer surface 2f of the specific portion 29 onto which the condensed water injected from the water injector 63 is sprayed. This increases the contact area between the condensed water injected from the water injector 63 and the exhaust pipe 2. This further improves the efficiency of cooling the exhaust gas by the injection of the condensed water.

[0109] 9, by branching the specific portion 29 into multiple exhaust pipe sections 292, it is possible to further increase the surface area of ​​the outer surface 2f onto which the condensed water is sprayed. This further increases the contact area between the sprayed condensed water and the exhaust pipe 2. This further improves the cooling efficiency of the exhaust gas by spraying the condensed water.

[0110] Furthermore, when the first adsorption device 27A and the second adsorption device 27B alternately enter the "adsorption state" as in the above embodiment, the first steam-water separator 25 and the second steam-water separator 39 capture more moisture than in a configuration that includes only the first adsorption device 27A. Providing the water tank 64 as in this embodiment and performing processes such as steps S305 and S306 are particularly effective in a configuration in which a large amount of moisture is captured.

[0111] <Other embodiments> In the above embodiment, the compressor 37 is disposed downstream of the vacuum pump 36, but the compressor 37 is not essential. Also, instead of or in addition to the vacuum pump 36, heaters capable of individually heating the first and second adsorption devices 27A, 27B may be used.

[0112] In this case, in this embodiment, the adsorption and desorption of CO2 is dominated by the pressure swing method using exhaust pressure and the vacuum pump 36, but if both the vacuum pump 36 and a heater are used, the pressure swing method using exhaust pressure and the vacuum pump 36 and the temperature swing method using the heat exchanger and heater are used together during both adsorption and desorption. Furthermore, if a heater is used instead of the vacuum pump 36 without using the vacuum pump 36, the temperature swing method using the heat exchanger and heater becomes dominant.

[0113] In addition, in the above embodiment, the configuration is provided with two suction devices, namely, the first and second suction devices 27A and 27B, but such a configuration is not essential to the present disclosure. Only one of the first and second suction devices 27A and 27B may be provided.

[0114] Figure 10 is a diagram corresponding to Figure 2, showing a collection system S' according to a second embodiment. With some exceptions, elements having the same configurations and functions as those in the embodiment (first embodiment) described with reference to Figures 1 to 9 and 11 are denoted by the same reference numerals in Figures 10 and 2.

[0115] The recovery system S' according to the second embodiment includes only one adsorption device (first adsorption device 27A). In this case, the second branch pipe 22 functions as a bypass pipe that bypasses the first adsorption device 27A, and a bypass valve 28C that opens and closes the second branch pipe 22 as a bypass pipe may be provided instead of the second upstream control valve 26B and the second downstream control valve 28B. The second branch pipe 22 extends from the branch point 2a to the junction point 2b, and there is no need to connect it to the fourth branch pipe 32 via the second desorption branch point 2d.

[0116] The bypass valve 28C of the second embodiment is closed when the first intake device 27A is in the adsorption state, and is open when the first intake device 27A is in the desorption state. In this case, it is advantageous to perform the water injection control described above when the first intake device 27A is in the adsorption state. [Explanation of symbols]

[0117] S CO2 capture system 1. Vehicle engine 11 cylinders 2 exhaust pipes 20 Tail pipe (downstream end) 23 Exhaust catalyst 24 1st heat exchanger 25 1st steam separator 271 CO2 absorbent 29 Specific parts 291 Finn 202 Exhaust pipe section 38 Second heat exchanger 39 Second steam / water separator 51 Gas storage tank 61 1st flow pipe 62 2nd flow pipe 63 Water Injector Sw11 water level sensor

Claims

1. The exhaust gas purifier is disposed between a cylinder of an on-vehicle engine and the downstream end of an exhaust pipe, and allows the exhaust gas discharged from the cylinder to flow through the exhaust gas purifier. ２ CO2 from vehicle engines ２ 1. A recovery system comprising: a first heat exchanger disposed downstream of the exhaust catalyst and configured to exchange heat between the exhaust gas and a heat exchange medium so as to receive heat from the exhaust gas after passing through the exhaust catalyst; a first steam-water separator disposed downstream of the first heat exchanger and configured to separate condensed water generated in the exhaust gas from the exhaust gas; a second steam-water separator disposed downstream of the first steam-water separator, the second steam-water separator configured to separate CO2 from the exhaust gas when the CO2 is in the exhaust gas at least one of a high pressure and a low temperature; ２ At least one of low pressure and high temperature is adsorbed CO ２ CO desorbed ２ an adsorbent; The CO ２ A CO2 absorber is disposed downstream of the adsorbent, and the CO2 absorber is desorbed from the CO2 absorbent. ２ containing CO ２ a gas storage tank into which the contained gas flows; a first flow pipe into which condensed water separated by the first steam-water separator flows; a water injector connected to the first flow pipe and configured to inject condensed water onto an outer surface of the exhaust pipe located upstream of the first heat exchanger. CO2 of an on-vehicle engine ２ Collection system.

2. The CO2 of the vehicle engine according to claim 1. ２ In the collection system, The CO ２ The CO ２ a second heat exchanger for exchanging heat between the gas and a heat exchange medium so as to receive heat from the gas; a CO ２ The condensed water generated in the CO-containing gas is ２ a second steam separator for separating the water from the contained gas; a second flow pipe into which the condensed water separated by the second steam-water separator flows, The second flow pipe is connected to the water injector to deliver condensed water to the water injector. CO2 of an on-vehicle engine ２ Collection system.

3. The CO2 of the vehicle engine according to claim 1. ２ In the collection system, the exhaust pipe is located upstream of the first heat exchanger and includes a specific portion having an outer surface arranged to face an injection port of the water injector; the outer surface of the specific portion has a plurality of fins that protrude outward in the flow direction of exhaust gas so as to increase the surface area of ​​the outer surface, The nozzle of the water injector is disposed to face the plurality of fins. CO2 of an on-vehicle engine ２ Collection system.

4. The CO2 of the vehicle engine according to claim 3. ２ In the collection system, The specific portion branches into a plurality of exhaust pipe sections through which exhaust gas flows in parallel, Each of the plurality of exhaust pipe sections has the plurality of fins. CO2 of an on-vehicle engine ２ Collection system.

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