JP2022152472A - Co2 separation device of internal combustion engine - Google Patents

Abstract

To provide a CO2 separation device of an internal combustion engine capable of maintaining a CO2 adsorbent to an appropriate temperature to perform excellent adsorption/desorption of CO2, preventing overheating of the CO2 adsorbent, and further discharging exhaust gas to the outside safely when an abnormality occurs in the CO2 separation device.SOLUTION: A CO2 separation device of an internal combustion engine comprises: an exhaust passage through which exhaust gas flows; a CO2 adsorbent that is provided in the exhaust passage, adsorbs CO2 at low temperature and desorbs CO2 at high temperature; control means of selectively executing CO2 adsorption control to adsorb CO2 in the exhaust gas to the CO2 adsorbent, and CO2 desorption control to desorb the adsorbed CO2; a bypass passage that branches off from the exhaust passage, bypasses the CO2 adsorbent and is open to the atmosphere; and flow rate control means of controlling a flow rate of the exhaust gas flowing into the exhaust passage by releasing the exhaust gas to the bypass passage side in order to adjust the temperature of the CO2 adsorbent during the CO2 desorption control.SELECTED DRAWING: Figure 1

Description

The present invention relates to a CO2 separation device for an internal combustion engine, which is provided in an exhaust system of an internal combustion engine and separates CO2 from exhaust gas.

CO2 (carbon dioxide) contained in the exhaust gas of internal combustion engines installed in automobiles is said to be one of the causes of global warming. A reduction in the amount is required.

2. Description of the Related Art Conventionally, a CO2 separation device for separating CO2 from exhaust gas is known, and is disclosed in Patent Document 1, for example. This CO2 separation device includes an exhaust gas supply source, two adsorption units (adsorption units) each containing a CO2 adsorbent for adsorbing CO2 in the exhaust gas, a hydrogen supply source, and a supply of hydrogen to the two adsorption units. A switching means for switching the supply of exhaust gas and hydrogen is provided. The CO2 adsorbent is composed of zeolite, silica gel, or the like, which has CO2 absorption performance.

In this CO2 separation device, the switching means allows hydrogen to be supplied from the hydrogen supply source to the other adsorption section while the exhaust gas is being supplied from the exhaust gas supply source to the other adsorption section. In one adsorption part, the CO2 in the inflowing exhaust gas is adsorbed by the CO2 adsorbent, and in the other adsorption part, the CO2 already adsorbed by the CO2 adsorbent is desorbed by the inflowing hydrogen and mixed with the hydrogen. be. By alternately repeating such adsorption/desorption operations between the two adsorption units, CO2 is separated from the exhaust gas.

JP 2020-164424 A

The adsorption performance of the CO2 adsorbent made of zeolite or the like as described above changes according to the temperature, and exhibits temperature characteristics such that the lower the adsorbent temperature, the higher the adsorption performance, and the higher the adsorbent temperature, the lower the adsorption performance. Therefore, in a CO2 separation device that switches CO2 adsorption/desorption by changing the temperature of the CO2 adsorbent and thereby separates and recovers CO2 in the exhaust gas, the CO2 adsorption performance of the CO2 adsorbent is maximized. In order to utilize it, it is necessary to appropriately control the temperature state of the CO2 adsorbent so that it becomes a low temperature suitable for adsorption during CO2 adsorption and a high temperature suitable for desorption during CO2 desorption.

In particular, in the case of a system that uses the waste heat of the internal combustion engine (exhaust gas heat) to raise the temperature of the CO2 adsorbent during desorption, the exhaust gas temperature can fluctuate greatly depending on factors such as the operating state of the internal combustion engine. It is desirable to appropriately control the temperature of the CO2 adsorbent so as to maintain the temperature of the CO2 adsorbent supplied with the exhaust gas at a temperature suitable for adsorption/desorption of CO2 regardless of such fluctuations in the exhaust gas temperature. .

Further, in general, CO2 adsorbents are irreversibly deteriorated or damaged by being continuously exposed to high temperatures that greatly exceed the appropriate temperature for CO2 desorption. Therefore, when the exhaust gas temperature is such a high temperature, it is desirable to protect the CO2 adsorbent by, for example, restricting the supply of the exhaust gas to the CO2 adsorbent.

Furthermore, in the event of an abnormality in the temperature or pressure of the CO2 separator, which includes the CO2 adsorbent, the supply of exhaust gas to the CO2 separator will be stopped and measures will be taken to safely discharge the exhaust gas to the outside. It is desirable to be prepared.

The present invention has been made to solve such problems, and maintains the CO2 adsorbent at an appropriate temperature even when the temperature of the exhaust gas supplied to the CO2 adsorbent rises, It is an object of the present invention to provide a CO2 separation device for an internal combustion engine that can effectively adsorb/desorb CO2 by a CO2 adsorbent and prevent overheating of the CO2 adsorbent. Another object of the present invention is to provide a CO2 separation device for an internal combustion engine that can safely discharge exhaust gas to the outside when an abnormality occurs in the CO2 separation device.

In order to achieve this object, a CO2 separation device for an internal combustion engine according to claim 1 of the present invention is a CO2 separation device for an internal combustion engine that is provided in an exhaust system of an internal combustion engine and separates CO2 from exhaust gas, provided in an exhaust passage (exhaust passage 4, first exhaust passage 4a, second exhaust passage 4b in the embodiment (hereinafter the same applies in this section)) connected to an internal combustion engine and through which exhaust gas flows; , CO2 adsorbents (first and second CO2 adsorbers 7A and 7B) that adsorb CO2 in the exhaust gas and desorb the adsorbed CO2 at high temperatures, and the CO2 in the exhaust gas is adsorbed by the CO2 adsorbent Control means (ECU 2, FIG. 4) for selectively executing CO2 adsorption control and CO2 desorption control for desorbing CO2 adsorbed on the CO2 adsorbent; A bypass passage 19 that bypasses the adsorbent and is open to the atmosphere, and an exhaust gas that flows into the exhaust passage by releasing the exhaust gas to the bypass passage 19 side in order to adjust the temperature of the CO2 adsorbent during CO2 desorption control. and flow control means (ECU 2, step 7 in FIG. 4, FIG. 5) for controlling the flow rate of the gas.

This CO2 separation device for an internal combustion engine is provided with a bypass passage branching from the exhaust passage on the upstream side of the CO2 adsorbent. to control the flow rate of By controlling the flow rate of the exhaust gas in this way, the flow rate of the high-temperature exhaust gas flowing into the CO2 adsorbent is reduced, so that the temperature rise of the CO2 adsorbent provided in the exhaust passage can be suppressed. As a result, even when the temperature of the exhaust gas rises, the CO2 adsorbent is maintained at a temperature suitable for desorption during the CO2 desorption control, and the CO2 adsorption/desorption by the CO2 adsorbent is performed satisfactorily. In addition, overheating of the CO2 adsorbent can be prevented.

The invention according to claim 2 of the present invention provides the CO2 separation device for an internal combustion engine according to claim 1, wherein the temperature of the exhaust gas flowing into the CO2 adsorbent is set to the exhaust temperature (first exhaust temperature TgasIN1, second exhaust temperature TgasIN2). ) and a target temperature setting means (ECU 2) for setting a target value of the exhaust temperature as a target temperature TgasIN_CMD, The flow rate control means is characterized by controlling the flow rate of the exhaust gas based on the exhaust gas temperature and the target temperature (steps 22 to 28 in FIG. 5).

According to this configuration, during CO2 desorption control, the exhaust gas flow rate is controlled based on the detected exhaust temperature and the target temperature. As a result, the adsorption/desorption of CO2 by the CO2 adsorbent can be performed more satisfactorily, and overheating of the CO2 adsorbent can be more appropriately prevented.

The invention according to claim 3 of the present invention is the CO2 separation device for an internal combustion engine according to claim 1, wherein the CO2 adsorbent comprises a first CO2 adsorbent (first CO2 adsorber 7A) and a second CO2 adsorbent. A first heat exchanger (first heat and a second heat exchanger (second heat exchanger 6B) that is provided adjacent to the second CO2 adsorbent and absorbs the heat of the exhaust gas through heat exchange with the exhaust gas. Further, the exhaust passages are branched from the downstream side of the branched portion with the bypass passage 19, and sequentially from the upstream side, a first exhaust passage (first an exhaust passage 4a) and a second exhaust passage (second exhaust passage 4b) passing through a first heat exchanger and a second CO2 adsorbent in order from the upstream side, through which exhaust gas flows, Exhaust switched to the second exhaust passage during CO2 desorption control targeting the first CO2 adsorbent, and switched to the first exhaust passage during the CO2 desorption control targeting the second CO2 adsorbent. It is characterized by further comprising passage switching means (ECU 2, FIG. 4).

According to this configuration, the second heat exchanger and the first CO2 adsorbent are provided in order from the upstream side in the first exhaust passage, and the first heat exchanger and the second CO2 adsorbent are provided in the second exhaust passage. The adsorbents are provided in order from the upstream side, and the exhaust passage through which the exhaust gas flows is switched to the second exhaust passage during CO2 desorption control for the first CO2 adsorbent, and the second CO2 adsorbent is switched to the second exhaust passage. Switching to the first exhaust passage during the CO2 desorption control targeting the adsorbent. As a result, when CO2 desorption control is performed for one of the CO2 adsorbents, the CO2 adsorbent that desorbs CO2 is warmed by the heat absorbed from the exhaust gas by the heat exchanger provided adjacently. Therefore, the temperature can be efficiently raised to a temperature suitable for desorption. In addition, since the exhaust gas that has been cooled by passing through the heat exchanger flows into the CO2 adsorbent for which CO2 desorption control is not performed, the cooled CO2 adsorbent efficiently adsorbs CO2. will be

In addition, by switching the exhaust passage, the CO2 adsorbent that adsorbs CO2 and the CO2 adsorbent that desorbs CO2 can be alternately switched to continuously adsorb/desorb CO2. Adsorption/desorption of CO2 can be performed well

Furthermore, during the CO2 desorption control, the flow rate of the exhaust gas flowing into the exhaust passage is controlled by letting the exhaust gas escape to the bypass passage side. It is possible to prevent overheating of the CO2 adsorbent that performs CO2 adsorption and maintain it at an appropriate temperature, and to appropriately cool the exhaust gas flowing into the CO2 adsorbent that adsorbs CO2 with the heat exchanger. Therefore, adsorption/desorption of CO2 by the CO2 adsorbent can be performed satisfactorily.

The invention according to claim 4 of the present invention provides the CO2 separation device for an internal combustion engine according to claim 3, wherein the temperature of the exhaust gas flowing into the first or second CO2 adsorbent is set to the first or second exhaust gas temperature. Exhaust temperature detection means (first exhaust temperature sensor 15, second exhaust temperature sensor 16) that detects as (first exhaust temperature TgasIN1, second exhaust temperature TgasIN2), and a target value of the first or second exhaust temperature target temperature setting means (ECU2) for setting the temperature TgasIN_CMD, and the flow rate control means, during CO2 desorption control for the first CO2 adsorbent, based on the second exhaust gas temperature and the target temperature, The exhaust gas flow rate is controlled based on the first exhaust gas temperature and the target temperature during the CO2 desorption control for the second CO2 adsorbent.

In this configuration, when the first CO2 adsorbent desorbs CO2, the first CO2 adsorbent transfers the heat of the exhaust gas flowing into the second CO2 adsorbent through the first heat exchanger. receiving, and when the second CO2 adsorbent performs CO2 desorption, the second CO2 adsorbent receives the heat of the exhaust gas flowing into the first CO2 adsorbent through the second heat exchanger; become. Therefore, during CO2 desorption control targeting the first CO2 adsorbent, the second CO2 adsorbent is controlled based on the second exhaust gas temperature, which is the temperature of the exhaust gas flowing into the second CO2 adsorbent, and the target temperature. During CO2 desorption control for It is possible to maintain the CO2 adsorbent at the optimum temperature for desorption at the time, so that the CO2 adsorption/desorption by the CO2 adsorbent can be performed well, and overheating of the CO2 adsorbent can be prevented more appropriately.

A CO2 separation device for an internal combustion engine according to claim 5 of the present invention is a CO2 separation device for an internal combustion engine that is provided in an exhaust system of an internal combustion engine and separates CO2 from an exhaust gas, is connected to the internal combustion engine, and is connected to the exhaust gas. is provided in the exhaust passage (exhaust passage 4, first exhaust passage 4a, second exhaust passage 4b) through which the gas flows, and in the exhaust passage, adsorbs CO2 in the exhaust gas when the temperature is low, and desorbs the adsorbed CO2 when the temperature is high. a CO2 adsorbent (first and second CO2 adsorbers 7A and 7B) separated from each other; a bypass passage 19 branched from the upstream side of the CO2 adsorbent of the exhaust passage and bypassing the CO2 adsorbent and open to the atmosphere; Abnormality detection means (ECU 2) for detecting an abnormality in the separation device, and exhaust gas flowing into the exhaust passage by releasing the exhaust gas to the side of the bypass passage 19 when an abnormality in the CO2 separation device is detected by the abnormality detection means. and a flow rate control means (ECU 2, steps 21 and 29 in FIG. 5) for controlling the flow rate to decrease.

This CO2 separation device for an internal combustion engine is provided with a bypass passage branching from the exhaust passage on the upstream side of the CO2 adsorbent. Since the flow rate of the exhaust gas flowing through the exhaust passage is reduced, the exhaust gas can be safely discharged to the outside when an abnormality occurs in the CO2 separation device.

1 is a diagram schematically showing a CO2 separation device to which the present invention is applied together with an internal combustion engine; FIG. It is a block diagram showing the configuration of the control system of the CO2 separation device. FIG. 3 is a diagram showing temperature characteristics of adsorption performance of a CO2 adsorbent; 4 is a flowchart showing a CO2 adsorption/desorption control process; It is a flow chart which shows flow control processing in a CO2 separation device. It is a map for setting the degree of opening of the exhaust valve. FIG. 4 is a diagram illustrating the operation of the CO2 separation device and the flow of exhaust gas during normal operating conditions of the internal combustion engine; FIG. 4 is a diagram showing the operation of the CO2 separation device and the flow of exhaust gas when an abnormality is detected;

Preferred embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a CO2 separation device 1 according to this embodiment together with an internal combustion engine 3 .

An internal combustion engine (hereinafter referred to as "engine") 3 is, for example, a gasoline engine mounted on a vehicle (not shown) as a power source. An intake passage (not shown) and an exhaust passage 4 are connected to the engine 3 . In the engine 3, in each cylinder (not shown), a mixture of fuel injected from a fuel injection valve (not shown) and air taken in from an intake passage is ignited by a spark plug (not shown). High-temperature combustion gas generated by combustion is discharged to the exhaust passage 4 as exhaust gas. The exhaust passage 4 branches into a first exhaust passage 4a and a second exhaust passage 4b downstream of the engine 3, and each downstream end is open to the atmosphere via a one-way valve 5. As shown in FIG.

The CO2 separation device 1 separates and recovers CO2 (carbon dioxide) from the exhaust gas flowing through the exhaust passage 4, and includes a first heat exchanger 6A, a second heat exchanger 6B, and a first CO2 adsorber 7A. , a second CO2 adsorber 7B, a compressor 9, and a storage tank 10.

The first heat exchanger 6A is provided adjacent to the first CO2 adsorber 7A, and the second heat exchanger 6B is provided adjacent to the second CO2 adsorber 7B. In addition, the first exhaust passage 4a is provided so as to pass through the second heat exchanger 6B and the first CO2 adsorber 7A in order from the upstream side, and the second exhaust passage 4b passes through the first heat exchanger in order from the upstream side. 6A and the second CO2 adsorber 7B. A first branch passage 11a and a second branch passage 11b are branched from the downstream side of the first CO2 adsorber 7A in the first exhaust passage 4a and the downstream side of the second CO2 adsorber 7B in the second exhaust passage 4b, respectively. The first branch passage 11a and the second branch passage 11b join on the downstream side to form a branch passage 11, and the branch passage 11 is provided with a compressor 9 and a storage tank 10 in order from upstream. there is

The first and second heat exchangers 6A, 6B cool the exhaust gas by exchanging heat with the high-temperature exhaust gas flowing through the first and second exhaust passages 4a, 4b, and heat absorbed from the exhaust gas. functions to heat up the adjacent CO2 adsorber. Note that "adjacent" is not limited to direct contact, and may be a structure in which, for example, a substance with high thermal conductivity is interposed therebetween. The first and second heat exchangers 6A and 6B may have any structure as long as they are capable of exchanging heat with the exhaust gas. radiating fin structure).

The first and second CO2 adsorbers 7A and 7B are for adsorbing/desorbing CO2 in the exhaust gas, and contain CO2 adsorbents (not shown) for that purpose. The CO2 adsorbent is provided so as to be exposed to the exhaust gas flowing through the CO2 adsorbers 7A, 7B. Also, the CO2 adsorbent is composed of, for example, lithium composite oxide or zeolite, and has adsorption performance depending on temperature as shown in FIG.

Specifically, as shown in FIG. 3, the amount of CO2 that can be adsorbed by the CO2 adsorbent changes according to the temperature of the CO2 adsorbent. The lower the temperature, the larger the adsorption amount, and the higher the temperature. decreases as Further, if the temperature of the CO2 adsorbent exceeds the temperature suitable for desorption of CO2, the CO2 adsorbent may be deteriorated or damaged. In the CO2 separation device 1 of the present embodiment, the temperature characteristic of the CO2 adsorbent is used to lower the temperature of the CO2 adsorber during CO2 adsorption control, and to adjust the temperature to a temperature suitable for CO2 adsorption (for example, 50° C.), as will be described later. ) to adsorb CO2 in the exhaust gas, and during CO2 desorption control, raise the temperature of the CO2 adsorber to a temperature suitable for CO2 desorption (for example, 250 ° C.) to desorb the adsorbed CO2. By separating, the adsorption/desorption of CO2 is controlled.

The compressor 9 is composed of, for example, an electric pump, and compresses the CO2 that has been desorbed from the CO2 adsorbent and stored in the storage tank 10 . Driving/stopping of the compressor 9 is controlled by the ECU 2 .

A first switching valve 12 is provided at a branching portion of the exhaust passage 4 between the first exhaust passage 4a and the second exhaust passage 4b. The first switching valve 12 switches the flow of exhaust gas from the engine 3 to either the first exhaust passage 4a or the second exhaust passage 4b. The operation of the first switching valve 12 is controlled by the ECU2. That is, the ECU 2 functions as exhaust passage switching means.

A second switching valve 13 is provided at the junction of the first branch passage 11a and the second branch passage 11b. The second switching valve 13 selectively opens either the first branch passage 11a or the second branch passage 11b to the compressor 9 side, so that the first CO2 adsorber can The CO2 desorbed from either 7A or the second CO2 adsorber 7B is made to flow into the compressor 9 and the storage tank 10. The operation of the second switching valve 13 is controlled by the ECU2.

A first exhaust temperature sensor 15 is provided upstream of the second heat exchanger 6B in the first exhaust passage 4a, and a second exhaust temperature sensor 15 is provided upstream of the first heat exchanger 6A in the second exhaust passage 4b. An exhaust temperature sensor 16 is provided. The first and second exhaust temperature sensors 15 and 16 detect the temperature of the exhaust gas at their installation positions as a first exhaust temperature TgasIN1 and a second exhaust temperature TgasIN2, respectively. Those detection signals are output to the ECU 2 .

A first CO2 concentration sensor 17 is provided downstream of the first CO2 adsorber 7A in the first exhaust passage 4a, and a second CO2 concentration sensor 18 is provided downstream of the second CO2 adsorber 7B in the second exhaust passage 4b. is provided. The first and second CO2 concentration sensors 17, 18 detect the CO2 concentration of the exhaust gas at their installation positions as a first CO2 concentration CCO2A and a second CO2 concentration CCO2B, respectively. Those detection signals are output to the ECU 2 .

A bypass passage 19 branches off from the exhaust passage 4 upstream of the first switching valve 12 . The bypass passage 19 is a passage provided to bypass the above-described first and second heat exchangers 6A, 6B, first and second CO2 adsorbers 7A, 7B, compressor 9, storage tank 10, and the like. , is open to the atmosphere via a one-way valve 5 at its downstream end. An exhaust valve 20 is provided in the bypass passage 19, and the exhaust valve 20 adjusts the flow rate of the exhaust gas flowing through the bypass passage 19 by changing its opening (hereinafter referred to as exhaust valve opening VEX). and thereby adjust the flow rate of the exhaust gas flowing through the exhaust passage 4 . That is, as the exhaust valve opening VEX increases, the amount of exhaust gas flowing toward the bypass passage 19 increases, and the amount of exhaust gas flowing toward the exhaust passage 4 decreases accordingly.

In this specification, to fully close the exhaust valve opening VEX (VEX=0%) means to completely close the exhaust valve 20. In this case, the exhaust gas does not flow to the bypass passage 19 side. . Further, fully opening the exhaust valve opening VEX (VEX=100%) means that the exhaust valve 20 is completely opened. The exhaust gas flows into the 19 side, and the amount of exhaust gas flowing into the exhaust passage 4 side becomes very small. A change in the exhaust valve opening VEX is controlled by the ECU 2 . That is, the ECU 2 functions as flow control means.

FIG. 2 shows the configuration of the control system of the CO2 separation device. The ECU 2 is composed of a microcomputer including a CPU, RAM, ROM, and I/O interface (none of which are shown). The ECU 2 executes CO2 adsorption/desorption control and flow rate control for controlling the adsorption and desorption of CO2 by the CO2 separation device 1 according to the detection signals of the exhaust temperature sensors 15, 16 and the CO2 concentration sensors 17, 18. do. In this embodiment, the ECU constitutes the control means. The ECU 2 also detects an abnormality in the CO2 separation device 1 based on detection signals from various sensors (none of which are shown) such as a temperature sensor, a flow rate sensor, and a pressure sensor installed at various locations in the CO2 separation device 1. It also functions as an anomaly detection means.

The basic operation of the CO2 separation device 1 of this embodiment will be described based on the above configuration. In the CO2 separation device 1 of this embodiment, the high-temperature exhaust gas discharged from the engine 3 flows through either the first and second exhaust passages 4a and 4b, and then flows through the first and second heat exchangers. Pass either 6A or 6B. The low-temperature exhaust gas cooled by heat exchange with the heat exchanger is then adsorbed with CO2 when passing through either the first or second CO2 adsorber 7A, 7B, and then de-CO2 exhaust gas (N2 , water, etc.) into the atmosphere. Meanwhile, the heat absorbed by the heat exchanger from the hot exhaust gas is transferred to the adjacent CO2 adsorber to which the exhaust gas is not introduced. As a result, the previously adsorbed CO2 is desorbed from the warmed CO2 adsorber. The desorbed CO 2 is stored in the storage tank 10 after being compressed by the compressor 9 through the branch passage 11 .

In the CO2 separation device 1 of the present embodiment, as described above, when the CO2 adsorber to which the exhaust gas is introduced adsorbs CO2, the CO2 adsorber to which the exhaust gas is not introduced adsorbs CO2 by then. It operates to desorb CO2. Further, under predetermined conditions, the first switching valve 12 is controlled to switch between the first exhaust passage 4a and the second exhaust passage 4b, thereby switching the heat exchanger and the CO2 adsorber through which the exhaust gas passes. As a result, the CO2 adsorber that has been adsorbing CO2 starts desorbing the adsorbed CO2, and the CO2 adsorber that has been desorbing CO2 is released from the newly introduced exhaust gas. Start adsorption.

Furthermore, in the CO2 separation device 1 of the present embodiment, flow rate control is performed to control the flow rate of the exhaust gas flowing through the exhaust passage 4 by changing the exhaust valve opening degree VEX for the following three purposes. The first purpose is to appropriately release part of the exhaust gas to the bypass passage 19 side so that the CO2 adsorber is maintained at a temperature suitable for CO2 adsorption/desorption, so that it flows to the exhaust passage 4 side. It is to adjust the flow rate of the exhaust gas. The second purpose is to prevent the overheating of the CO2 adsorber by limiting the flow rate of the exhaust gas flowing toward the exhaust passage 4 in order to protect the CO2 adsorber when the temperature of the exhaust gas becomes too high. It is to prevent. A third object is to bypass the CO2 separation device 1 and safely discharge the exhaust gas to the outside when an abnormality occurs in the CO2 separation device 1 including the CO2 adsorber and the exhaust passage 4. Specific flows of CO2 adsorption/desorption control and flow rate control for controlling adsorption and desorption of CO2 by the CO2 separation device 1 will be described below with reference to FIGS. 4 and 5. FIG.

FIG. 4 is a flow chart showing control processing of the above-described CO2 adsorption/desorption control. This process is executed at predetermined time intervals while the engine 3 is in a normal operating state. In this process, first, in step 1 (illustrated as "S1"; the same shall apply hereinafter), it is determined whether or not the adsorption control flag F_CO2REC is "1". The adsorption control flag F_CO2REC is a flag for determining which of the first CO2 adsorber 7A and the second CO2 adsorber 7B is currently adsorbing CO2. It is set to "1" when it is the first CO2 adsorber 7A.

When the determination result of step 1 is YES, the process proceeds to step 2 to acquire the first CO2 concentration CCO2A from the first CO2 concentration sensor 17 provided downstream of the first CO2 adsorber 7A. Next, in step 3, it is determined whether or not the obtained first CO2 concentration CCO2A exceeds a predetermined value CCO2REF.

When the CO2 adsorption by the CO2 adsorber is performed normally, most of the CO2 in the exhaust gas is adsorbed when passing through the CO2 adsorber. is low, and the output of the CO2 concentration sensor shows a small value. On the other hand, there is a limit to the amount of CO2 that the CO2 adsorbent can adsorb. flow out to the downstream side of the vessel, and the sensor output rises sharply. In this embodiment, it is determined whether or not the CO2 adsorbent has reached saturation depending on whether or not the value of the sensor output exceeds a predetermined value CCO2REF.

If the determination result in step 3 is NO and the first CO2 concentration CCO2A does not exceed the predetermined value CCO2REF, it is determined that CO2 adsorption by the first CO2 adsorber 7A is normally performed, and the process proceeds to step 7 to After executing the control, the process ends. Details of the flow rate control will be described later.

On the other hand, if the determination result in step 3 is YES and the first CO2 concentration CCO2A exceeds the predetermined value CCO2REF, it is determined that the first CO2 adsorber 7A has reached a saturated state. Control is performed to switch the operation of the first CO2 adsorber 7A from CO2 adsorption to CO2 desorption, and to switch the operation of the second CO2 adsorber 7B from CO2 desorption to CO2 adsorption.

First, in step 4, the value of the adsorption control flag F_CO2REC is set to "0". As a result, it is stored that the second CO2 adsorber 7B is to adsorb CO2 thereafter.

Next, in step 5, the first switching valve 12 is switched to the B side. Here, "switching the first switching valve 12 to the B side" means switching the flow of the exhaust gas from the engine 3 to the second exhaust passage 4b side. As a result, the exhaust gas is introduced into the second CO2 adsorber 7B instead of the first CO2 adsorber 7A, and CO2 adsorption by the second CO2 adsorber 7B is started.

Subsequently, in step 6, the second switching valve 13 is switched to the A side. Here, "switching the second switching valve 13 to the A side" means opening the first branch passage 11a to the downstream side of the compressor 9 (at the same time, closing the second branch passage 11b). there is In step 5 described above, the exhaust gas flow is switched to the second exhaust passage 4b side, so that the high-temperature exhaust gas passes through the first heat exchanger 6A. The heat absorbed from the exhaust gas by the first heat exchanger 6A is transferred to the adjacent first CO2 adsorber 7A. As a result, in the first CO2 adsorber 7A, the temperature of the CO2 adsorbent rises, and the adsorbed CO2 is desorbed. The desorbed CO2 is sucked by the compressor 9 downstream of the branch passage 11 and stored in the storage tank 10 in a compressed state. After that, the process proceeds to step 7, and after the flow rate control is executed, the process ends. Details of the flow rate control will be described later.

On the other hand, when the determination result of step 1 is NO, the process proceeds to step 8 to acquire the second CO2 concentration CCO2B from the second CO2 concentration sensor 18 provided downstream of the second CO2 adsorber 7B. Next, in step 9, it is determined whether or not the obtained second CO2 concentration CCO2B exceeds a predetermined value CCO2REF. If the determination result in step 9 is NO and the second CO2 concentration CCO2B does not exceed the predetermined value CCO2REF, it is determined that CO2 adsorption by the second CO2 adsorber 7B is normally performed, and the process proceeds to step 7 to After executing the control, the process ends. Details of the flow rate control will be described later.

On the other hand, if the determination result in step 9 is YES, and the second CO2 concentration CCO2B exceeds the predetermined value CCO2REF, it is determined that the second CO2 adsorber 7B has reached a saturated state, and steps 10 to 12 are performed. Control is performed to switch the operation of the second CO2 adsorber 7B from CO2 adsorption to CO2 desorption, and to switch the operation of the first CO2 adsorber 7A from CO2 desorption to CO2 adsorption.

Steps 10-12 are the reverse processing of steps 4-6 described above. First, in step 10, the value of the adsorption control flag F_CO2REC is set to "1". As a result, it is stored that the first CO2 adsorber 7A is the one that adsorbs CO2 thereafter. Next, in step 11, the first switching valve 12 is switched to the A side. Here, "switching the first switching valve 12 to the A side" means switching the flow of the exhaust gas from the engine 3 to the first exhaust passage 4a side. It is introduced into the first CO2 adsorber 7A instead of 7B, and CO2 adsorption by the first CO2 adsorber 7A is started.

Subsequently, in step 12, the second switching valve 13 is switched to the B side. Here, "switching the second switching valve 13 to the B side" means opening the second branch passage 11b to the downstream side of the compressor 9 (at the same time, closing the first branch passage 11a). there is In step 11 described above, the flow of the exhaust gas is switched to the side of the first exhaust passage 4a, so that the high-temperature exhaust gas passes through the second heat exchanger 6B. The heat absorbed from the exhaust gas by the second heat exchanger 6B is transferred to the adjacent second CO2 adsorber 7B. As a result, the temperature of the CO2 adsorbent increases in the second CO2 adsorber 7B, and the adsorbed CO2 is desorbed. The desorbed CO2 is sucked by the compressor 9 downstream of the branch passage 11 and stored in the storage tank 10 in a compressed state.

As described above, by the processing of steps 2 to 6 or steps 8 to 12, the adsorption/desorption operation of the CO2 adsorber is switched according to the state of the CO2 adsorber that is adsorbing CO2. At 7, flow rate control for controlling the flow rate of the exhaust gas flowing through the exhaust passage 4 is executed. Flow rate control is performed by the process of FIG.

First, in step 21, the detection values of various sensors installed in the CO2 separation device 1 are acquired, and it is determined whether or not an abnormal value is detected, thereby determining whether or not the CO2 separation device 1 is abnormal. judge. Sensors used for this abnormality determination include, for example, a temperature sensor (not shown) for detecting abnormal temperatures in the exhaust passage 4 and the CO2 adsorber, and a sensor for detecting blockage of the exhaust passage due to freezing. A flow rate sensor (not shown), a pressure sensor (not shown) for detecting abnormal pressure due to detachment or breakage of the exhaust passage, and the like can be used, but are not limited to these. When abnormal values are detected from these various sensors, it is determined that an abnormality has occurred in the CO2 separation device 1, and the process proceeds to step 29.

In step 29, the exhaust valve opening degree VEX is controlled to fully open. As a result, almost all of the exhaust gas from the engine 3 flows into the bypass passage 19 side, which has a small flow resistance and a small pressure loss. Therefore, the exhaust gas can be safely discharged to the outside by bypassing the CO2 separation device 1 in which an abnormality has been detected.

On the other hand, if no abnormality is detected in step 21 , the process proceeds to step 22 . At step 22, it is determined whether or not the adsorption control flag F_CO2REC is "1".

If the determination result in step 22 is YES, that is, if the first CO2 adsorber 7A is currently adsorbing CO2, in step 23, the The first exhaust temperature sensor 15 detects the first exhaust temperature TgasIN1. Next, in step 24, the difference (=TgasIN1-TgasIN_CMD) between the detected first exhaust gas temperature TgasIN1 and the predetermined target value TgasIN_CMD is calculated as the temperature deviation ΔTgasIN, and the process proceeds to step 27.

On the other hand, if the determination result in step 22 is NO, that is, if it is the second CO2 adsorber 7B that is currently adsorbing CO2, in step 25, the upstream side of the second CO2 adsorber 7B and the first heat exchanger 6A A second exhaust gas temperature TgasIN2 is detected by a second exhaust gas temperature sensor 16 provided in the . Next, in step 26, the difference (=TgasIN2-TgasIN_CMD) between the detected second exhaust gas temperature TgasIN2 and the predetermined target value TgasIN_CMD is calculated as the temperature deviation ΔTgasIN, and the process proceeds to step 27.

In step 27, the exhaust valve opening VEX is set by searching the map of FIG. 6 based on the calculated temperature deviation ΔTgasIN. Subsequently, in step 28, the exhaust valve opening degree VEX is changed so as to become the set exhaust valve opening degree VEX, and this processing is terminated.

In the map of FIG. 6, when the temperature deviation ΔTgasIN is 0 or less, that is, when the first exhaust temperature TgasIN1 or the second exhaust temperature TgasIN2 is less than the target value TgasIN_CMD, the exhaust valve opening VEX is set to 0%. there is That is, when the detected exhaust temperature is equal to or lower than the target value TgasIN_CMD, the temperature of the exhaust gas is suitable for the CO2 adsorber to adsorb/desorb CO2, and the flow rate of the exhaust gas flowing to the CO2 adsorber side is It is judged that it is not necessary to lower the temperature of the CO2 adsorber by lowering, and the exhaust valve opening degree VEX is controlled to be fully closed.

On the other hand, when the temperature deviation ΔTgasIN is greater than 0, that is, when the first exhaust temperature TgasIN1 or the second exhaust temperature TgasIN2 is higher than the target value TgasIN_CMD, the exhaust valve opening VEX increases as the temperature deviation ΔTgasIN increases. set to a value. As a result, the higher the detected exhaust temperature, the larger the exhaust valve opening degree VEX, and the more the flow rate of the exhaust gas flowing to the CO2 adsorber side is decreased, so that the temperature of the CO2 adsorber is controlled near the target value TgasIN_CMD. .

FIG. 7 is a diagram illustrating the operation of the CO2 separation device 1 and the flow of exhaust gas in the normal operating state of the engine 3. FIG. According to the flow rate control of the present embodiment, when the temperature of the exhaust gas flowing into the CO2 adsorber becomes higher than the target value TgasIN_CMD in the normal operating state of the engine 3, the exhaust valve is adjusted according to the temperature of the exhaust gas. Since the opening degree VEX is appropriately adjusted, the CO2 adsorber is controlled to an appropriate temperature by adjusting the flow rate of the exhaust gas flowing to the CO2 adsorber side. In addition, even if the temperature of the exhaust gas becomes too high due to high-load driving, etc., the exhaust valve opening degree VEX is controlled to be larger according to the temperature, thereby limiting the flow rate of the exhaust gas flowing to the CO2 adsorber side. and prevent overheating of the CO2 adsorber.

FIG. 8 is a diagram showing the operation of the CO2 separation device and the flow of exhaust gas when an abnormality is detected. According to the flow rate control of the present embodiment, when an abnormality occurs in the CO2 separation device 1, the exhaust valve opening degree VEX is controlled to be fully open. can be safely discharged to the outside.

It should be noted that the present invention is not limited to the described embodiments and can be implemented in various ways. For example, in the embodiment, two heat exchangers and two CO2 adsorbers are provided, and the operation of CO2 adsorption/desorption is alternately performed, but one heat exchanger and one CO2 adsorber are provided. It is also possible to set it as the structure provided only, or to set it as the structure provided with each 3 or more.

Further, in the embodiment, the difference in flow path resistance between the exhaust passage and the bypass passage is utilized to allow the exhaust gas to flow into the bypass passage according to the degree of opening of the exhaust valve provided in the bypass passage. Alternatively, a switching valve may be provided at the branch of the exhaust passage and the bypass passage, and the flow rate may be controlled by adjusting the opening of the switching valve.

Further, the embodiments are examples in which the present invention is applied to a gasoline engine mounted on a vehicle, but the present invention is not limited to this, and may be applied to other types of engines such as diesel engines. , and can also be applied to engines other than those for vehicles. In addition, it is possible to change the detailed configuration as appropriate within the scope of the present invention.

1 CO2 separation device 2 ECU (electronic control unit) (control means, flow rate control means, target temperature setting means, abnormality detection means)
3 Engine (internal combustion engine)
4 exhaust passage 4a first exhaust passage (first exhaust passage)
4b second exhaust passage (second exhaust passage)
6a first heat exchanger (first heat exchanger)
6b second heat exchanger (second heat exchanger)
7a First CO2 adsorber (first CO2 adsorbent)
7b Second CO2 adsorber (second CO2 adsorbent)
15 first exhaust temperature sensor (exhaust temperature detection means)
16 second exhaust temperature sensor (exhaust temperature detection means)
19 Bypass passage 20 Exhaust valve (flow control means)
TgasIN1 First exhaust temperature (exhaust temperature, first exhaust temperature)
TgasIN2 Second exhaust temperature (exhaust temperature, second exhaust temperature)
TgasIN_CMD Target temperature

Claims (5)

A CO2 separation device for an internal combustion engine that is provided in an exhaust system of an internal combustion engine and separates CO2 from exhaust gas,
an exhaust passage connected to the internal combustion engine through which exhaust gas flows;
a CO2 adsorbent provided in the exhaust passage that adsorbs CO2 in the exhaust gas at low temperatures and desorbs the adsorbed CO2 at high temperatures;
control means for selectively executing CO2 adsorption control for causing the CO2 in the exhaust gas to be adsorbed by the CO2 adsorbent and CO2 desorption control for desorbing the CO2 adsorbed by the CO2 adsorbent;
a bypass passage that branches from the upstream side of the CO2 adsorbent of the exhaust passage, bypasses the CO2 adsorbent and is open to the atmosphere;
flow rate control means for controlling the flow rate of the exhaust gas flowing into the exhaust passage by releasing the exhaust gas to the bypass passage side in order to adjust the temperature of the CO2 adsorbent during the CO2 desorption control;
A CO2 separation device for an internal combustion engine, comprising: exhaust temperature detection means for detecting the temperature of the exhaust gas flowing into the CO2 adsorbent as the exhaust temperature;
and target temperature setting means for setting the target value of the exhaust gas temperature as the target temperature,
2. The CO2 separation device for an internal combustion engine according to claim 1, wherein said flow rate control means controls the flow rate of exhaust gas based on said exhaust gas temperature and said target temperature. The CO2 adsorbent is composed of a first CO2 adsorbent and a second CO2 adsorbent,
a first heat exchanger provided adjacent to the first CO2 adsorbent and absorbing heat of the exhaust gas by heat exchange with the exhaust gas;
a second heat exchanger that is provided adjacent to the second CO adsorbent and absorbs the heat of the exhaust gas by heat exchange with the exhaust gas;
The exhaust passage branches from a downstream side of a branching portion with the bypass passage, and sequentially from the upstream side, a first exhaust passage passing through the second heat exchanger and the first CO2 adsorbent; A second exhaust passage passing through the first heat exchanger and the second CO adsorbent in order from the side,
The exhaust passage through which the exhaust gas flows is switched to the second exhaust passage during the CO2 desorption control for the first CO2 adsorbent, and the CO2 desorption for the second CO2 adsorbent is performed. 2. The CO2 separation device for an internal combustion engine according to claim 1, further comprising exhaust passage switching means for switching to said first exhaust passage during release control. exhaust temperature detection means for detecting the temperature of the exhaust gas flowing into the first or second CO2 adsorbent as a first or second exhaust temperature;
a target temperature setting means for setting a target value of the first or second exhaust gas temperature as a target temperature;
During the CO2 desorption control for the first CO2 adsorbent, the flow rate control means controls the CO2 desorption control for the second CO2 adsorbent based on the second exhaust gas temperature and the target temperature. 4. The CO2 separation device for an internal combustion engine according to claim 3, wherein during desorption control, the flow rate of exhaust gas is controlled based on said first exhaust gas temperature and said target temperature. A CO2 separation device for an internal combustion engine that is provided in an exhaust system of an internal combustion engine and separates CO2 from exhaust gas,
an exhaust passage connected to the internal combustion engine through which exhaust gas flows;
a CO2 adsorbent provided in the exhaust passage that adsorbs CO2 in the exhaust gas at low temperatures and desorbs the adsorbed CO2 at high temperatures;
a bypass passage that branches from the upstream side of the CO2 adsorbent of the exhaust passage, bypasses the CO2 adsorbent and is open to the atmosphere;
Abnormality detection means for detecting an abnormality in the CO2 separation device;
flow control means for controlling the flow rate of the exhaust gas flowing through the exhaust passage to decrease by releasing the exhaust gas to the bypass passage side when the abnormality detection means detects an abnormality in the CO2 separation device; ,
A CO2 separation device for an internal combustion engine, comprising:

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