CN213253755U

CN213253755U - Carbon dioxide separation membrane structure

Info

Publication number: CN213253755U
Application number: CN202020433610.1U
Authority: CN
Inventors: 小沢英隆; 牧美里; 菅文康
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2020-03-30
Filing date: 2020-03-30
Publication date: 2021-05-25
Anticipated expiration: 2030-03-30

Abstract

The utility model aims to solve the problem that a carbon dioxide separation membrane structure is provided, it is small and exquisite light, and the mountable is on the vehicle to can effectively utilize the used heat of internal-combustion engine. In order to solve the above problem, a carbon dioxide separation membrane structure 30 that is mounted on a vehicle and separates carbon dioxide contained in exhaust gas of an internal combustion engine is proposed, the carbon dioxide separation membrane structure including: a filter substrate 34 having a honeycomb structure and including a porous material; and a carbon dioxide adsorption/desorption layer 39 formed on the surface of the filter substrate 34 and containing a lithium composite oxide.

Description

Carbon dioxide separation membrane structure

Technical Field

The utility model relates to a carbon dioxide separation membrane structure.

Background

Conventionally, as a technique for separating carbon dioxide from combustion gas, a chemical absorption method, a solid absorption method, and the like are known and have been put to practical use. For example, a carbon dioxide separation membrane has been proposed which separates carbon dioxide from flue gas of a coal-fired power plant, exhaust gas of a hydrogen plant using a hydrocarbon steam reforming process, or a heat source of any industrial process which generates a large amount of carbon dioxide (for example, refer to patent document 1). The carbon dioxide separation membrane is tubular and comprises, in order from the inside: a substrate layer comprising ZrO₂Or Al₂O₃Etc.; barrier layer comprising high density Li₂ZrO₃(ii) a A two-phase layer comprising porous Li₂ZrO₃An adsorbent; and, a covering layer comprising ZrO₂Or Al₂O₃And the like. By sucking the outside fuel gas from the inside of the pipe, carbon dioxide in the fuel gas is separated and recovered in the pipe.

Documents of the prior art

(patent document)

Patent document 1: specification of U.S. Pat. No. 8454732

SUMMERY OF THE UTILITY MODEL

(problem to be solved by the utility model)

However, in the conventional carbon dioxide separation technology, since a device for temporarily storing the exhaust gas, a device for bringing the exhaust gas to a high temperature and a high pressure, and the like are required, there are problems that energy consumption is large and the device is large in size.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a carbon dioxide separation membrane structure which is small and light, can be mounted on a vehicle, and can effectively use waste heat of an internal combustion engine.

(means for solving the problems)

(1) The present invention provides a carbon dioxide separation membrane structure (for example, a carbon dioxide

separation membrane structure

30,30A described later) that is mounted on a vehicle (for example, a vehicle V described later) and separates carbon dioxide contained in exhaust gas of an internal combustion engine (for example, an engine 1 described later), the carbon dioxide separation membrane structure including: a filter substrate (for example,

filter substrates

34 and 34A described later) having a honeycomb structure and containing a porous material; and a carbon dioxide adsorption/desorption layer (for example, carbon dioxide adsorption/desorption layers 39 and 39A described later) formed on the surface of the filter substrate and containing a lithium composite oxide.

In the carbon dioxide separation membrane structure of (1), since the carbon dioxide adsorption/desorption layer is formed of the lithium composite oxide, the lithium composite oxide has a chemical property that the carbon dioxide adsorption/desorption capacity per unit area is high and carbon dioxide is adsorbed and desorbed depending on the temperature and the carbon dioxide partial pressure, and therefore, carbon dioxide in the exhaust gas can be efficiently separated by utilizing such a property. Therefore, the carbon dioxide separation membrane structure according to the above (1) is small and light, can be mounted on a vehicle, and can effectively use waste heat of an internal combustion engine, and thus, can remarkably reduce energy consumption.

(2) The carbon dioxide separation membrane structure according to the above (1), wherein the carbon dioxide adsorption/desorption layer may contain one or more compounds selected from the group consisting of Li₂ZrO₃、Li₄SiO₄、Li₄TiO₄And Li₂CuO₂At least one member of the group consisting of.

(3) The carbon dioxide separation membrane structure according to the above (1) or (2), wherein the carbon dioxide adsorption/desorption layer may contain Li₂ZrO₃。

In the carbon dioxide separation membrane structure of the above (2) or (3), the carbon dioxide separation membrane is composed of Li₂ZrO₃、Li₄SiO₄、 Li₄TiO₄、Li₂CuO₂Forming a carbon dioxide adsorption and desorption layer. In particular, since these lithium composite oxides have high carbon dioxide adsorption/desorption capacity per unit area, the effect (1) is more reliably achieved.

(4) The carbon dioxide separation membrane structure according to any one of the above (1) to (3), wherein the filter substrate may have: a plurality of exhaust-side units (for example, an exhaust-side unit 35 described later) that are open on the upstream side in the flow direction of the exhaust gas and are provided with a back pressure valve on the downstream side; and a plurality of permeate-side cells (e.g., permeate-side cells 37 described later) that close the upstream side in the flow direction of the exhaust gas and are provided with openings on the downstream side; the plurality of exhaust-side cells and the plurality of permeate-side cells are alternately arranged in a direction orthogonal to the flow direction of the exhaust gas, and the carbon dioxide adsorption-desorption layer is formed on the surface of the inner wall of the exhaust-side cell.

In the carbon dioxide separation membrane structure of the above (4), the carbon dioxide in the exhaust gas is selectively adsorbed by the carbon dioxide adsorption-desorption layer, moves toward the permeate-side cell in the carbon dioxide adsorption-desorption layer, passes through the partition wall, flows into the permeate-side cell, and is recovered. Therefore, according to the carbon dioxide separation membrane structure of the above (4), carbon dioxide in the exhaust gas can be separated and recovered more reliably.

(5) The carbon dioxide separation membrane structure according to any one of the above (1) to (3), wherein the filter substrate may have: a plurality of exhaust-side cell groups (for example, an exhaust-side cell group 36 described later) in which a plurality of exhaust-side cells (for example, an exhaust-side cell 35A described later) that are open on the upstream side in the exhaust gas flow direction and are provided with a back pressure valve (for example, a back pressure valve 30c described later) on the downstream side are arranged in a row in the direction orthogonal to the exhaust gas flow direction; and a plurality of permeate-side cell groups (e.g., permeate-side cell group 38 described later) in which a plurality of permeate-side cells (e.g., permeate-side cell group 37A described later) that close the upstream side in the flow direction of the exhaust gas and have openings at the middle or downstream side are arranged in a direction orthogonal to the flow direction of the exhaust gas and parallel to the arrangement direction of the exhaust-side cells; the plurality of exhaust-side cell groups and the plurality of permeate-side cell groups are alternately arranged in a direction orthogonal to the flow direction of the exhaust gas and orthogonal to the arrangement direction of the exhaust-side cells and the permeate-side cells, and the carbon dioxide adsorption-desorption layer is formed on the surface of the inner wall of the exhaust-side cell.

In the carbon dioxide separation membrane structure according to the above (5), the carbon dioxide in the exhaust gas is selectively adsorbed by the carbon dioxide adsorption-desorption layer, moves toward the permeate-side cell in the carbon dioxide adsorption-desorption layer, passes through the partition wall, flows into the permeate-side cell, and is recovered. Therefore, according to the carbon dioxide separation membrane structure of (5), carbon dioxide in the exhaust gas can be separated and recovered more reliably.

(6) The carbon dioxide separation membrane structure according to the above (5), wherein the permeate-side cell group may have communication channels (for example, communication channels 38b described later) in which carbon dioxide flows, the communication channels being formed by openings (for example, openings 38a described later) formed in the wall surfaces in the arrangement direction of the adjacent permeate-side cells communicating with each other.

In the carbon dioxide separation membrane structure of the above (6), the carbon dioxide separated by the action of the carbon dioxide adsorption/separation layer is discharged through the communication passage formed by the openings formed in the wall surfaces in the arrangement direction of the adjacent permeate-side cells communicating with each other. Therefore, according to the carbon dioxide separation membrane structure of (6), carbon dioxide in the exhaust gas can be separated and recovered more reliably.

(effects of the utility model)

According to the utility model discloses, can provide a carbon dioxide separation membrane structure, it is small and exquisite light, the mountable is on the vehicle to can effectively utilize the used heat of internal-combustion engine.

Drawings

Fig. 1 is a diagram showing a structure of a vehicle equipped with a carbon recycling system according to an embodiment of the present invention.

Fig. 2 is a perspective view showing the structure of the carbon dioxide separation membrane structure of the first embodiment.

Fig. 3 is an enlarged view of the region R in fig. 2.

Fig. 4 is a view showing a permeate-side unit of the carbon dioxide separation membrane structure of the first embodiment.

Fig. 5 is a diagram showing a mechanism of separating carbon dioxide in the carbon dioxide separation membrane structure according to the first embodiment.

Fig. 6 is a partially sectional perspective view showing the structure of a carbon dioxide separation membrane structure according to a second embodiment.

Fig. 7 is a schematic view of the structure of a carbon dioxide separation membrane of the second embodiment.

Detailed Description

An embodiment of the present invention will be described in detail below with reference to the drawings.

The carbon dioxide separation membrane structure of the present embodiment is small and lightweight, and therefore can be mounted on a vehicle to separate carbon dioxide contained in exhaust gas of an internal combustion engine. Therefore, the carbon dioxide separation membrane structure of the present embodiment will be described below by taking an example of application to a vehicle equipped with a carbon recovery system (carbon recovery system) for separating, recovering and reusing carbon dioxide.

Fig. 1 is a diagram showing the structure of a vehicle V to which a carbon recovery system S of the present embodiment is mounted. The vehicle V includes an internal combustion engine 1 (hereinafter, referred to as an "engine") in which the internal combustion engine 1 converts thermal energy generated by combustion of liquid hydrocarbon fuel into mechanical energy, and drives driving wheels (not shown) to move forward by using the mechanical energy obtained by the engine 1.

The vehicle V includes: an engine 1; a fuel supply device 2 that supplies fuel to the engine 1; CO 2₂A recovery device 3 for recovering carbon dioxide (CO) from exhaust gas flowing through an exhaust pipe 16 of the engine 1₂) (ii) a An exhaust gas purification device 4 that purifies exhaust gas flowing through the exhaust pipe 16; reactor 5 from CO₂The carbon dioxide recovered by the recovery device 3 is converted into methanol (CH)₃OH) synthesis gas; a hydrogen supply device 6 for supplying hydrogen (H) to the reactor 5₂) (ii) a And a condenser 7 for recovering methanol from the synthesis gas discharged from the reactor 5. In addition, from CO₂The recovery device 3, the reactor 5, the hydrogen supply device 6, and the condenser 7 constitute a carbon recovery system S.

The engine 1 is, for example, a multi-cylinder reciprocating engine, and includes: a plurality of cylinders; a piston disposed in each cylinder so as to be freely reciprocated; an ignition plug provided in each cylinder in a combustion chamber partitioned by a piston; and a crankshaft rotated by the reciprocation of the piston. These ignition plugs ignite in response to a command from a control device, not shown, and burn a mixture of fuel and air supplied to each cylinder.

The intake pipe 15 is a pipe that connects an intake port communicating with each cylinder of the engine 1 and the outside of the vehicle and introduces air from the outside of the vehicle into each cylinder. The exhaust pipe 16 is a pipe connecting an exhaust port communicating with each cylinder of the engine 1 and the outside of the vehicle. The exhaust pipe 16 is provided with an exhaust gas purification device 4 and CO in this order from the exhaust upstream side to the downstream side₂And a recovery device 3. In each cylinder of the engine 1, exhaust gas generated by burning a mixture gas passes through the exhaust gas purification apparatus 4 and CO₂The recovery device 3 and discharged to the outside of the vehicle.

The fuel supply device 2 includes: a fuel tank 20 that stores fuel; a fuel injection valve 21 provided in an intake port communicating with each cylinder of the engine 1; and a fuel supply pipe 24 connecting the fuel tank 20 and the fuel injection valve 21.

The fuel tank 20 stores liquid hydrocarbon fuel such as gasoline, methanol, or a mixed fuel obtained by mixing such gasoline and methanol. The fuel supply pipe 24 compresses the fuel stored in the fuel tank 20 by a high-pressure pump, not shown, and supplies the compressed fuel to the fuel injection valve 21. The fuel injection valve 21 is opened in response to a command from a control device, not shown, to inject fuel supplied from the fuel supply pipe 24. A mixture gas obtained by mixing the fuel injected from the fuel injection valve 21 and the air supplied from the intake pipe 15 is supplied to each cylinder of the engine 1.

The exhaust gas purification device 4 includes an exhaust gas purification catalyst (e.g., a three-way catalyst), and purifies unburned Hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and the like contained in the exhaust gas of the engine 1 by the action of the exhaust gas purification catalyst.

CO₂Recovery unit 3 utilizes CO₂The pipe 31 is connected to the reactor 5. CO 2₂RecoveringThe device 3 recovers carbon dioxide from the exhaust gas flowing through the exhaust pipe 16 and passes the CO₂The pipe 31 is supplied to the reactor 5. More specifically, CO₂The recovery device 3 separates the exhaust gas flowing through the exhaust pipe 16 into a recovery gas containing carbon dioxide as a main component and nitrogen (N) gas₂) CO removal as a main component₂Exhausting and converting the recovered gas to CO₂Discharging from the pipe 31 to remove CO₂The exhaust gas is discharged to the outside of the vehicle through a tail pipe not shown.

CO₂The recovery device 3 includes a carbon dioxide separation membrane structure that selectively permeates carbon dioxide in the exhaust gas flowing through the exhaust pipe 16. CO 2₂The recovery device 3 separates the exhaust gas of the engine 1 into a recovered gas and a CO-removed gas by using the carbon dioxide separation membrane structure₂And (5) exhausting. In addition, details of the structure of the carbon dioxide separation membrane will be described in the following paragraphs.

The hydrogen gas supply device 6 includes: high pressure H₂A tank 61 that stores high-pressure hydrogen gas; h₂A pipe 63 connected to the high pressure H₂Tank 61 and reactor 5; and, a regulator 64 disposed at H₂On the piping 63. The regulator 64 will store at a high pressure H₂The hydrogen gas in the tank 61 is reduced in pressure to a predetermined pressure and passed through the hydrogen passage H₂The pipe 63 supplies the reaction mixture to the reactor 5.

The hydrogen gas supply device 6 of the present embodiment is not limited to the one that stores the hydrogen gas at the high pressure H₂The case where hydrogen gas in the tank 61 is supplied to the reactor 5. The hydrogen gas supply device 6 may be configured to supply hydrogen gas generated from water by an electrolysis device to the reactor 5, or may be configured to supply hydrogen gas generated from ammonia gas to the reactor 5.

A reactor 5, by passing CO₂Carbon dioxide and H contained in the recovered gas supplied from the pipe 31₂The hydrogen gas supplied from the pipe 63 is subjected to hydrogenation reaction at a predetermined ratio in the reaction cylinder to reduce carbon dioxide and synthesize methanol.

More specifically, the reactor 5 includes: a reaction cylinder into which CO is introduced₂A recovery gas supplied through the pipe 31; h₂An injector injecting fuel H into the reaction cylinder₂Hydrogen gas supplied from the piping 63; a carbon dioxide reduction catalyst disposed within the reaction cylinder; a heating device for heating the gas in the reaction cylinder; a compression device for compressing the gas in the reaction cylinder; and a synthesis gas pipe 51 connecting the reaction cylinder and the condenser 7.

And a carbon dioxide reduction catalyst for promoting a hydrogenation reaction of carbon dioxide, wherein the hydrogenation reaction of carbon dioxide is to reduce carbon dioxide and generate methanol in the presence of carbon dioxide and hydrogen. As the carbon dioxide reduction catalyst, for example, a known reduction catalyst such as a copper zinc oxide-based catalyst is used.

The heating device heats the gas in the reaction cylinder to a temperature necessary for the hydrogenation reaction of carbon dioxide by using a part of the waste heat of the engine 1, that is, the heat energy generated by burning the fuel in the engine 1. The compression device compresses the gas in the reaction cylinder to a pressure required for the methanol synthesis reaction by using a part of mechanical energy obtained by burning the fuel in the engine 1, more specifically, by using the power of the crankshaft of the engine 1.

In the reactor 5 as described above, from CO₂A pipe 31 introduces a predetermined amount of recovery gas into the reaction cylinder and also introduces the recovery gas from H₂The injector injects hydrogen gas into the reaction cylinder in such a quantity that the ratio of carbon dioxide to hydrogen gas in the reaction cylinder is a predetermined ratio, and the gas in the reaction cylinder is heated and compressed by a heating device and a compression device. Thus, in the reaction cylinder, the hydrogenation reaction of carbon dioxide is carried out by the action of the carbon dioxide reduction catalyst (see the following formula (1)), and methanol is produced. At the same time, the action of the carbon dioxide reduction catalyst is utilized to perform a reverse water gas shift reaction (see the following formula (2)) and a hydrogenation reaction of carbon monoxide (see the following formula (3)) to produce a synthesis gas containing methanol.

CO₂+3H₂→CH₃OH+H₂O (1)

CO₂+H₂→CO+H₂O (2)

CO+2H₂→CH₃OH (3)

Through the above-described steps, the synthesis gas generated in the reaction cylinder is supplied to the condenser 7 through the synthesis gas pipe 51. The synthesis gas discharged from the synthesis gas pipe 51 contains unreacted carbon dioxide and CO in addition to methanol produced by the methanol synthesis reaction₂The nitrogen gas and the like mixed in the recovery gas without being completely separated in the recovery device 3.

The condenser 7 recovers methanol from the synthesis gas supplied from the reactor 5 and supplies it to the fuel tank 20. More specifically, the condenser 7 condenses the synthesis gas discharged from the reactor 5 by heat exchange, thereby separating the synthesis gas into a liquid phase containing methanol as a main component and a gas phase containing unreacted carbon dioxide and nitrogen as main components, and discharges the liquid phase from a liquid phase port and the gas phase from a gas phase port.

The liquid phase port of the condenser 7 and the fuel tank 20 are connected by a liquid phase pipe 71. Therefore, the liquid phase discharged from the liquid phase port of the condenser 7 is introduced into the fuel tank 20 through the liquid phase pipe 71. Further, among the gas phase port of the condenser 7 and the exhaust pipe 16, the exhaust gas purifying device 4 and CO₂The recovery devices 3 are connected to each other by a gas-phase pipe 72. Therefore, the gas phase discharged from the gas phase port of the condenser 7 is guided to the CO through the gas phase pipe 72₂And a recovery device 3.

The carbon flow in the vehicle V equipped with the carbon recycling system S as described above will be explained. When a mixture gas of the hydrocarbon fuel initially stored in the fuel tank 20 and the air introduced from the intake pipe 15 is combusted in the engine 1, exhaust gas containing nitrogen, carbon dioxide, and water as main components is discharged from the engine 1. In addition, carbon dioxide in the exhaust gas is CO₂The recovering device 3 recovers and supplies to the reactor 5. In the reactor 5, a synthesis gas containing methanol is generated by reacting carbon dioxide with hydrogen. Methanol in this synthesis gas is recovered by the condenser 7 and stored as fuel in the fuel tank 20. In addition, unreacted carbon dioxide contained in the synthesis gas is again CO-converted₂The recovery device 3 recovers, andis supplied to the reactor 5. In this way, the vehicle V equipped with the carbon recovery system S introduces carbon dioxide from the outside air into the fuel tank 20, the engine 1, and the CO₂The recovery device 3, the reactor 5, and the condenser 7 are circulated to reduce the amount of carbon dioxide discharged from the tail pipe to the outside of the vehicle.

Next, the structure of the carbon dioxide separation membrane will be described in detail.

First, the carbon dioxide separation membrane structure 30 of the first embodiment will be explained. Fig. 2 is a perspective view showing the configuration of the carbon dioxide separation membrane structure 30 of the first embodiment. As shown in fig. 2, the carbon dioxide separation membrane structure 30 of the first embodiment includes: a housing 32; and a carbon dioxide separation membrane main body 33 housed in the case 32.

Fig. 3 is an enlarged view of the region R in fig. 2. Fig. 4 is a view showing the permeate-side unit 37 of the carbon dioxide separation membrane structure 30 according to the first embodiment. As shown in fig. 3, the carbon dioxide separation membrane main body 33 includes a filter substrate 34 and a carbon dioxide adsorption/separation layer 39.

The filter substrate 34 has a honeycomb structure. The filter substrate 34 contains a porous material such as ceramic. The filter substrate 34 includes a plurality of units having a quadrangular cross section. The cross-sectional shape of the cell is not limited, and the cell may have a cross-sectional shape such as a pentagon or a hexagon.

The filter base 34 includes a plurality of exhaust-side cells 35, and the exhaust-side cells 35 are opened on the upstream side in the flow direction of the exhaust gas and are provided with a back pressure valve (not shown) on the downstream side. In the plurality of exhaust-side cells 35, exhaust gas flows in from the opening on the upstream side. The filter substrate 34 includes a plurality of permeate-side cells 37, and the plurality of permeate-side cells 37 close the upstream side in the flow direction of the exhaust gas and have openings on the downstream side (see fig. 4). The plurality of exhaust-side cells 35 and the plurality of permeate-side cells 37 are alternately arranged in a direction orthogonal to the flow direction of the exhaust gas. That is, as shown in fig. 3, the exhaust-side cells 35 and the permeate-side cells 37 are arranged in a checkered pattern shape. Therefore, the carbon dioxide permeated from the exhaust-side cell 35 through the partition wall flows into the plurality of permeation-side cells 37. The mechanism of carbon dioxide separation is described in detail in the following paragraphs.

As shown in fig. 4, the plurality of permeate-side units 37 communicate on the downstream side. Carbon dioxide separated by the action of the carbon dioxide adsorption/separation layer 39 by the mechanism of separating carbon dioxide described in detail in the following paragraphs flows through the permeate-side unit 37 and is recovered from the discharge port 37a provided on the downstream side of the communication. The downstream side of the permeate-side unit 37 is set to a negative pressure by a pump, not shown, whereby carbon dioxide can be recovered.

And a carbon dioxide adsorption and desorption layer 39 formed on the surface of the filter substrate 34 having the honeycomb structure. This ensures a sufficient area of the carbon dioxide adsorption/desorption layer 39, and can cope with a variation in the flow rate of the exhaust gas containing carbon dioxide. Preferably, as shown in fig. 3, the carbon dioxide adsorption-desorption layer 39 is formed on the surface of the inner wall of the exhaust-side cell 35.

The carbon dioxide adsorption-desorption layer 39 contains a lithium composite oxide. Preferably, the carbon dioxide adsorption-desorption layer 39 contains a material selected from the group consisting of Li₂ZrO₃、Li₄SiO₄、Li₄TiO₄And Li₂CuO₂At least one member of the group consisting of. Among these, the carbon dioxide adsorption-desorption layer 39 more preferably contains Li₂ZrO₃. For example, by impregnating the filter substrate 34 with a slurry containing a lithium composite oxide in a state where the discharge port 37a is closed, the carbon dioxide adsorbing-releasing layer 39 can be formed on the surface of the inner wall of the exhaust-side cell 35.

Fig. 5 is a diagram showing a mechanism of separating carbon dioxide in the carbon dioxide separation membrane structure 30 of the first embodiment. In FIG. 5, as an example, the inclusion of Li is shown₂ZrO₃The carbon dioxide adsorption separation layer 39. As shown in fig. 5, the exhaust gas flowing into the exhaust-side cell 35 from the opening on the upstream side of the exhaust-side cell 35, and Li formed on the inner wall surface of the exhaust-side cell 35 and containing Li₂ZrO₃The carbon dioxide adsorbing and separating layer 39 is contacted with and flows downstream.

In this case, the adsorption and desorption of carbon dioxide are formedLi of layer 39₂ZrO₃The lithium composite oxide has a high ability to adsorb and desorb carbon dioxide per unit area, and has a characteristic of selectively absorbing carbon dioxide by a chemical reaction. Therefore, components (nitrogen, water vapor, etc.) in the exhaust gas other than carbon dioxide are not adsorbed by the carbon dioxide adsorption-desorption layer 39, but are released into the atmosphere from the downstream side of the exhaust-side unit 35 by the back pressure valve, and only carbon dioxide is adsorbed on the carbon dioxide adsorption-desorption layer 39. In particular, in the use of Li₂ZrO₃When the lithium composite oxide is used, carbon dioxide in the exhaust gas is adsorbed on the carbon dioxide adsorption/desorption layer 39 by the following reaction formula (4). Since the exhaust gas from the engine 1 flows into the exhaust-side cell 35, the carbon dioxide concentration is generally high, that is, the carbon dioxide partial pressure is generally high, and the equilibrium of the following reaction formula (4) shifts to the right side, so that the adsorption of carbon dioxide proceeds better.

Li₂ZrO₃+CO₂→Li₂CO₃+ZrO₂ (4)

Next, as shown in FIG. 5, the molten carbonate Li produced by adsorbing carbon dioxide on the carbon dioxide adsorbing/releasing layer 39 is expressed by the reaction formula (4)₂CO₃Carbonate ions are formed and move in the form of a gradient in carbon dioxide concentration (partial pressure) within the carbon dioxide adsorption and separation layer 39 toward the permeate-side unit 37. Then, the adsorbed carbon dioxide is desorbed from the carbon dioxide adsorption/desorption layer 39 by the following reaction formula (5). In the permeate-side unit 37, since the negative pressure is generally set by a pump, not shown, as described above, the carbon dioxide concentration is generally low, that is, the partial pressure of carbon dioxide is generally low, and the equilibrium of the following reaction formula (5) shifts to the right side, so that the removal of carbon dioxide is more preferably performed.

Li₂CO₃+ZrO₂→Li₂ZrO₃+CO₂ (5)

As described above, the change Δ G in the free energy of reaction of the chemical reactions of the above reaction formulae (4) and (5) depends on the partial pressure of carbon dioxide, but in addition, depends on the temperature. When below a certain temperature, reaction formula (4) is performed to advance the adsorption of carbon dioxide; on the other hand, when the temperature is higher than the specific temperature, the reaction formula (5) is performed to advance the desorption of carbon dioxide. When the temperature is constant, the driving force of the separation mechanism performed by the adsorption and desorption of carbon dioxide described above depends on the differential pressure between the partial pressure of carbon dioxide on the exhaust-side cell 35 side and the partial pressure of carbon dioxide on the permeate-side cell 37 side into which the exhaust gas flows. Therefore, since the temperature and the carbon dioxide partial pressure are appropriately set and the carbon dioxide passage rate can be adjusted, low power consumption operation due to a low driving differential pressure can be expected.

Next, a carbon dioxide separation membrane structure 30A of a second embodiment will be described. Fig. 6 is a partially sectional perspective view showing the structure of a carbon dioxide separation membrane structure 30A of the second embodiment. Fig. 7 is a schematic view of a carbon dioxide separation membrane structure 30A of the second embodiment. The carbon dioxide separation membrane structure 30A of the second embodiment includes a carbon dioxide separation membrane main body 33A housed in a case, not shown, as in the first embodiment. The carbon dioxide separation membrane main body 33A includes a filter substrate 34A and a carbon dioxide adsorption/separation layer 39A.

The filter substrate 34A has a honeycomb structure and is made of a porous material such as ceramic. The filter substrate 34 includes a plurality of units having a quadrangular cross section. The cross-sectional shape of the cell is not limited, and may be a cell having a cross-sectional shape such as a pentagon or a hexagon.

As shown in fig. 6, the filter substrate 34A includes a plurality of exhaust-side cells 35A, and the exhaust-side cells 35A are opened on the upstream side in the flow direction of the exhaust gas and are provided with a back pressure valve 30c on the downstream side (see fig. 7). The filter base 34A includes a plurality of exhaust-side cell groups 36, and the plurality of exhaust-side cell groups 36 are arranged in a direction orthogonal to the flow direction of the exhaust gas.

As also shown in fig. 6, the filter substrate 34A includes a plurality of permeate-side cells 37A, and the plurality of permeate-side cells 37A close the upstream side in the flow direction of the exhaust gas and have openings in the middle or downstream side. The filter substrate 34A further includes a plurality of permeate-side cell groups 38, and the plurality of permeate-side cell groups 38 are arranged in a direction perpendicular to the flow direction of the exhaust gas and parallel to the arrangement direction of the exhaust-side cells 35A.

As shown in fig. 6, the plurality of exhaust-side cell groups 36 and the plurality of permeate-side cell groups 38 are alternately arranged in a direction orthogonal to the flow direction of the exhaust gas and orthogonal to the arrangement direction of the exhaust-side cells 35A and the permeate-side cells 37A. In fig. 6, the plurality of exhaust-side cell groups 36 and the plurality of permeate-side cell groups 38 are arranged alternately in the vertical direction.

The permeate-side cell group 38 has communication passages 38b, and the communication passages 38b are formed by communicating openings 38a formed in the wall surfaces in the arrangement direction of the adjacent permeate-side cells 37A with each other. In the example shown in fig. 6, two openings 38a formed at a predetermined interval are communicated with each other on both sides in the longitudinal direction of the permeate-side cell 37A to form a communication passage 38 b. Carbon dioxide flows through this communication passage 38 b.

The carbon dioxide adsorption-desorption layer 39A is preferably formed on the surface of the inner wall of the exhaust-side cell 35A, as in the first embodiment. The carbon dioxide adsorption-release layer 39A may be formed of the same material as that used in the first embodiment. The carbon dioxide adsorbing and releasing layer 39A is manufactured by the same manufacturing method as that of the first embodiment.

The mechanism of separating carbon dioxide in the carbon dioxide separation membrane structure 30A of the second embodiment is the same as that of the first embodiment, and therefore, is appropriately simplified and will be described below. First, as shown in fig. 6 and 7, the exhaust gas to which an appropriate boost pressure is applied by the pump 30A is supplied to the carbon dioxide separation membrane structure 30A and flows into the exhaust-side cell 35A. Carbon dioxide in the exhaust gas flowing into the exhaust-side cell 35A is selectively adsorbed by the carbon dioxide adsorption-desorption layer 39A formed on the inner wall surface of the exhaust-side cell 35A. The adsorbed carbon dioxide moves toward the permeate-side cell 37A in the carbon dioxide adsorption/desorption layer 39A, and flows into the permeate-side cell 37A through the partition wall. The carbon dioxide flowing into the permeate-side cell 37A is recovered by a weak negative pressure applied by the pump 30 b. On the other hand, since the back pressure valve 30c is not provided in the downstream side of the exhaust side unit 35A in a bottomless cylindrical structure, an appropriate back pressure is applied, and nitrogen gas and the like other than carbon dioxide in the exhaust gas are discharged from the back pressure valve 30 c. As described above, carbon dioxide is separated and recovered from the exhaust gas.

According to the above embodiment, the following effects are achieved.

In the above embodiment, the

filter substrates

34,34A having a honeycomb structure and containing a porous material, and the carbon dioxide adsorption and desorption layers 39,39A formed on the surfaces of the

filter substrates

34,34A and containing a lithium composite oxide are provided. The lithium composite oxide has chemical characteristics that carbon dioxide is highly adsorbed and desorbed per unit area, and carbon dioxide is adsorbed and desorbed depending on the temperature and the carbon dioxide partial pressure, and therefore, carbon dioxide in exhaust gas can be efficiently separated by utilizing such characteristics. Therefore, according to the above embodiment, it is small and light, can be mounted on the vehicle V, can effectively use the waste heat of the engine 1 of the vehicle V, and thus can significantly reduce energy consumption.

In the above embodiment, the carbon dioxide adsorption/desorption layers 39,39A are made of Li₂ZrO₃、 Li₄SiO₄、Li₄TiO₄、Li₂CuO₂And (4) forming. In particular, since these lithium composite oxides have high carbon dioxide adsorption/desorption capacity per unit area, the above-described effects can be more reliably achieved.

In the above embodiment, a plurality of exhaust-side cells 35 and a plurality of permeate-side cells 37 are provided, the plurality of exhaust-side cells 35 being open on the upstream side and provided with a backpressure valve on the downstream side, the plurality of permeate-side cells 37 being closed on the upstream side and provided with an opening on the downstream side, and the plurality of exhaust-side cells 35 and the plurality of permeate-side cells 37 being arranged alternately in a direction orthogonal to the flow direction of the exhaust gas. Further, a carbon dioxide adsorption and desorption layer 39 is formed on the surface of the inner wall of the exhaust-side cell 35. Thus, the carbon dioxide in the exhaust gas is selectively adsorbed by the carbon dioxide adsorption-desorption layer 39, moves toward the permeate-side cell 37 in the carbon dioxide adsorption-desorption layer 39, and flows into the permeate-side cell 37 through the partition wall, whereby the carbon dioxide can be separated and recovered more reliably.

In the above embodiment, the exhaust-side cell groups 36 each including the exhaust-side cells 35A arranged in a direction orthogonal to the flow direction of the exhaust gas and the permeate-side cell groups 38 each including the permeate-side cells 37A arranged in a direction orthogonal to the flow direction of the exhaust gas and parallel to the arrangement direction of the exhaust-side cells 35A are provided, the exhaust-side cells 35A are open on the upstream side and the permeate-side valves 30c are provided on the downstream side, the permeate-side cells 37A close the upstream side and have openings on the middle or downstream side, and the exhaust-side cell groups 36 and the permeate-side cell groups 38 are alternately arranged in a direction orthogonal to the flow direction of the exhaust gas and orthogonal to the arrangement direction of the exhaust-side cells 35A and the permeate-side cells 37A. Further, a carbon dioxide adsorption and desorption layer 39A is formed on the surface of the inner wall of the exhaust-side cell 35A. Thus, the carbon dioxide in the exhaust gas is selectively adsorbed by the carbon dioxide adsorption-desorption layer 39A, moves toward the permeate-side cell 37A in the carbon dioxide adsorption-desorption layer 39A, and flows into the permeate-side cell 37A through the partition wall, whereby the carbon dioxide can be separated and recovered more reliably.

In addition, in the above embodiment, the communication passages 38b are provided, and the communication passages 38b are formed by the openings 38a formed in the wall surfaces in the arrangement direction of the adjacent permeate-side cells 37A communicating with each other. Thus, the carbon dioxide separated by the action of the carbon dioxide adsorption/separation layer 39A is discharged through the communication passage 38b, and therefore, the carbon dioxide in the exhaust gas can be separated and recovered more reliably.

In addition, the present invention is not limited to the above embodiments, and all modifications and improvements within the scope of the object of the present invention can be achieved are included in the present invention.

List of reference numerals

30. 30A: carbon dioxide separation membrane structure

32: shell body

33. 33A: carbon dioxide separation membrane body

34. 34A: filter substrate

35. 35A: exhaust side unit

36: exhaust side unit group

37. 37A: permeate side unit

38: permeate side unit group

39. 39A: a carbon dioxide adsorption and desorption layer.

Claims

1. A carbon dioxide separation membrane structure that is mounted on a vehicle and separates carbon dioxide contained in exhaust gas of an internal combustion engine, comprising:

a filter substrate having a honeycomb structure and comprising a porous material; and a process for the preparation of a coating,

and a carbon dioxide adsorption/desorption layer formed on the surface of the filter substrate.

2. The carbon dioxide separation membrane structure according to claim 1, wherein the filter substrate has:

a plurality of exhaust-side units that are open on an upstream side in a flow direction of exhaust gas and are provided with a back pressure valve on a downstream side; and a process for the preparation of a coating,

a plurality of permeate-side cells that close an upstream side in a flow direction of the exhaust gas and are provided with openings on a downstream side; and the number of the first and second electrodes,

the plurality of exhaust-side cells and the plurality of permeate-side cells are alternately arranged in a direction orthogonal to the flow direction of the exhaust gas,

the carbon dioxide adsorption and desorption layer is formed on the surface of the inner wall of the exhaust-side cell.

3. The carbon dioxide separation membrane structure according to claim 1, wherein the filter substrate has:

a plurality of exhaust-side cell groups in which a plurality of exhaust-side cells that are open on the upstream side in the flow direction of the exhaust gas and are provided with a back pressure valve on the downstream side are arranged in a direction orthogonal to the flow direction of the exhaust gas; and a process for the preparation of a coating,

a plurality of permeate-side cell groups in which a plurality of permeate-side cells, which close the upstream side in the flow direction of the exhaust gas and have openings in the middle or downstream side, are arranged in a direction orthogonal to the flow direction of the exhaust gas and parallel to the arrangement direction of the exhaust-side cells; and the number of the first and second electrodes,

the plurality of exhaust-side cell groups and the plurality of permeate-side cell groups are alternately arranged in a direction orthogonal to the flow direction of the exhaust gas and orthogonal to the arrangement direction of the exhaust-side cells and the permeate-side cells,

4. The carbon dioxide separation membrane structure according to claim 3, wherein the permeate-side cell group has a communication passage in which openings formed in the wall surfaces in the arrangement direction of the adjacent permeate-side cells communicate with each other, and carbon dioxide flows through the communication passage.