CN113494337A - Exhaust gas purification system - Google Patents
Exhaust gas purification system Download PDFInfo
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- CN113494337A CN113494337A CN202110289338.3A CN202110289338A CN113494337A CN 113494337 A CN113494337 A CN 113494337A CN 202110289338 A CN202110289338 A CN 202110289338A CN 113494337 A CN113494337 A CN 113494337A
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- exhaust gas
- carbon dioxide
- gas purification
- carbon monoxide
- internal combustion
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/101—Three-way catalysts
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N13/00—Exhaust or silencing apparatus characterised by constructional features ; Exhaust or silencing apparatus, or parts thereof, having pertinent characteristics not provided for in, or of interest apart from, groups F01N1/00 - F01N5/00, F01N9/00, F01N11/00
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Abstract
The present invention provides the following techniques: when carbon dioxide in the exhaust gas of an internal combustion engine is subjected to a hydrogenation reaction and reused as fuel, carbon monoxide produced as a by-product can be effectively utilized. An exhaust gas purification system 10 of an engine 1 purifies exhaust gas discharged from the engine 1, and includes: an exhaust gas purification device 4 provided in an exhaust pipe 16 of the engine 1 and including an exhaust gas purification catalyst having a NOx reduction function of reducing NOx contained in the exhaust gas; a carbon dioxide reduction device 11 having a carbon dioxide reduction catalyst that causes a hydrogenation reaction of carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device 4, reduces the carbon dioxide, and generates methanol; and a carbon monoxide supply device 12 that supplies carbon monoxide, which is a by-product of the hydrogenation reaction, to the exhaust gas purification device 4.
Description
Technical Field
The present invention relates to an exhaust gas purification system.
Background
The present applicant is advancing the development of the following technologies: on-board vehicles (automobiles) hydrogenate carbon dioxide contained in the exhaust gas of internal combustion engines to methanol, and use the methanol as a fuel for internal combustion engines. Here, for example, a technique of synthesizing methanol from a mixed gas of carbon dioxide and hydrogen has been proposed (for example, see patent document 1).
[ Prior art documents ]
(patent document)
Patent document 1: japanese examined patent publication No. 45-16682
Disclosure of Invention
[ problems to be solved by the invention ]
However, the present applicant has found, according to the research of the present applicant, that carbon monoxide is produced in a large amount as a by-product when methanol is produced in the conventional art. Therefore, it is desired to develop a technique capable of effectively utilizing carbon monoxide as a by-product.
The present invention has been made in view of the above circumstances, and an object thereof is to provide the following technology: when carbon dioxide in the exhaust gas of an internal combustion engine is subjected to a hydrogenation reaction and reused as fuel, carbon monoxide produced as a by-product can be effectively utilized.
[ means for solving problems ]
(1) The present invention provides an exhaust gas purification system (for example, an exhaust gas purification system 10 described later) for an internal combustion engine, which purifies exhaust gas discharged from the internal combustion engine (for example, an engine 1 described later), the exhaust gas purification system including: an exhaust gas purification device (for example, an exhaust gas purification device 4 described later) provided in an exhaust passage (for example, an exhaust pipe 16 described later) of the internal combustion engine and including an exhaust gas purification catalyst having a NOx reduction function of reducing NOx contained in the exhaust gas; a carbon dioxide reduction device (for example, a carbon dioxide reduction device 11 described later) having a carbon dioxide reduction catalyst that reduces carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device to produce methanol by performing a hydrogenation reaction on the carbon dioxide; and a carbon monoxide supply device (for example, a carbon monoxide supply device 12 described later) that supplies carbon monoxide, which is a by-product of the hydrogenation reaction, to the exhaust gas purification device.
(1) The invention of (1) has a configuration including a carbon monoxide supply device that supplies carbon monoxide, which is generated as a by-product when carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device is reduced by a hydrogenation reaction to produce methanol, to the exhaust gas purification device. This makes it possible to make the exhaust gas purification catalyst more in the reducing atmosphere, and to improve the NOx reduction purification rate. Therefore, according to the invention (1), it is possible to provide a technique that, when carbon dioxide in the exhaust gas of an internal combustion engine is subjected to a hydrogenation reaction and reused as fuel, carbon monoxide generated as a by-product can be effectively used for reduction purification of NOx without being discharged from the tail pipe.
(2) In the exhaust gas purification system of an internal combustion engine according to (1), the carbon monoxide supply device may include a pressurizer (for example, pressurizer 8 described later) that pressurizes and supplies carbon monoxide, which is a by-product of the hydrogenation reaction, to the exhaust gas purification device.
(2) The invention of (1) has a configuration including a pressurizer for pressurizing and supplying carbon monoxide, which is a by-product of the hydrogenation reaction, to the exhaust gas purification apparatus. This makes it possible to efficiently and reliably supply the by-produced carbon monoxide to the exhaust gas purification device into which the high-pressure exhaust gas is introduced.
(3) In the exhaust gas purification system of an internal combustion engine of (1) or (2), the aforementioned exhaust gas purification catalyst may be a three-way catalyst.
(3) In the invention of (1), carbon monoxide is supplied to the three-way catalyst. Thus, since the exhaust gas flowing into the three-way catalyst usually has a stoichiometric composition, carbon monoxide (CO) and Hydrocarbons (HC) can be completely oxidized and purified, but the NOx reduction purification rate is low, and according to the invention (3), the three-way catalyst can be made more on the reducing atmosphere side by supplying carbon monoxide, and the NOx reduction purification rate can be improved.
(4) The exhaust gas purification system for an internal combustion engine according to any one of (1) to (3) may further include a carbon dioxide separation and recovery device (for example, CO described later)2A recovery device 3) for separating and recovering carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device, and supplying the carbon dioxide to the carbon dioxide reduction device.
(4) In the invention according to (1), the exhaust gas purification device further includes a carbon dioxide separation and recovery device for separating and recovering carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device and supplying the carbon dioxide to the carbon dioxide reduction device. Thus, carbon dioxide in the exhaust gas passing through the exhaust gas purification device can be efficiently separated, recovered, and supplied to the carbon dioxide reduction device. Further, if carbon monoxide, which is a by-product generated by the hydrogenation reaction of carbon dioxide in the carbon dioxide reduction apparatus, is supplied directly to the carbon dioxide separation and recovery apparatus, for example, the carbon monoxide is discharged from the carbon dioxide separation and recovery apparatus to the tail pipe, and as a result, the CO emission is deteriorated, and this can be avoided according to the invention (4).
(5) In the exhaust gas purification system for an internal combustion engine according to any one of (1) to (4), the carbon monoxide supply device may supply the carbon monoxide to the exhaust gas purification device at the time of starting the internal combustion engine.
(5) In the invention of (1), the carbon monoxide is supplied to the exhaust gas purification device at the time of starting the internal combustion engine. This makes it possible to increase the NOx reduction purification rate at the time of startup of the internal combustion engine in which the exhaust purification catalyst is low in temperature and therefore the NOx purification rate is low.
[ Effect of the invention ]
According to the present invention, the following technique can be provided: when carbon dioxide in the exhaust gas of an internal combustion engine is subjected to a hydrogenation reaction and reused as fuel, carbon monoxide produced as a by-product can be effectively utilized.
Drawings
Fig. 1 is a diagram showing a configuration of a vehicle in which an exhaust gas purification system according to an embodiment of the present invention is mounted.
Fig. 2 is a graph showing a relationship between λ and CO purification rate.
Fig. 3 is a graph showing a relationship between λ and the HC purification rate.
Fig. 4 is a graph showing a relationship between λ and the NOx purification rate.
Detailed Description
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
The exhaust gas purification system of the present embodiment effectively uses carbon monoxide generated as a by-product for purification of exhaust gas when carbon dioxide in exhaust gas of an internal combustion engine is reused as fuel. Therefore, the exhaust gas purification system of the present embodiment will be described below by taking an example of application to a vehicle equipped with a carbon cycle system that separates and recovers carbon dioxide and reuses the carbon dioxide as fuel.
Fig. 1 is a diagram showing a configuration of a vehicle V on which a carbon cycle system S of the present embodiment is mounted. The vehicle V includes an internal combustion engine 1 (hereinafter, referred to as "engine") that converts thermal energy generated by burning liquid hydrocarbon fuel into mechanical energy, and travels by driving wheels (not shown) 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 an 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 in the exhaust pipe 16; a reactor 5 consisting of CO2The carbon dioxide recovered by the recovery device 3 is used to generate methanol (CH)3OH) synthesis gas; a hydrogen supply device 6 for supplying hydrogen (H) to the reactor 52) (ii) a A condenser 7 for separating and recovering methanol and carbon monoxide from the synthesis gas discharged from the reactor 5; a pressurizer 8 for pressurizing the gas phase gas mainly composed of carbon monoxide discharged from the condenser 7; and a supply valve 9 for controlling the pressure of the pressurized liquid by the pressurizer 8Supply of carbon monoxide and the like to the exhaust gas purification apparatus 4.
The carbon cycle system S is constituted by the above-mentioned respective structures. The exhaust gas purification system 10 of the present embodiment is composed of the exhaust gas purification device 4 and CO2A recovery device 3, a carbon dioxide reduction device 11 and a carbon monoxide supply device 12, wherein the carbon dioxide reduction device 11 is composed of a reactor 5 and a hydrogen supply device 6, and the carbon monoxide supply device 12 is composed of a condenser 7, a pressurizer 8 and a supply valve 9. The exhaust gas purification system 10 of the present embodiment will be described in detail below.
The engine 1 is, for example, a multi-cylinder reciprocating engine, and includes: a plurality of gas cylinders; a piston provided to be movable in a reciprocating manner in each cylinder; an ignition plug provided in a combustion chamber partitioned by a piston in each cylinder; and a crankshaft rotated according to the reciprocating motion of the piston. These ignition plugs are ignited in response to a command from a control device, not shown, and burn a mixture of fuel and air supplied into each air cylinder.
The intake pipe 15 is a pipe for connecting an intake port communicating with each cylinder of the engine 1 to the outside of the vehicle and guiding air outside the vehicle to each cylinder. The exhaust pipe 16 is a pipe connecting an exhaust port communicating with each cylinder of the engine 1 to the outside of the vehicle. An exhaust gas purification device 4 and CO are provided in the exhaust pipe 16 in this order from the exhaust upstream side to the downstream side2And a recovery device 3. Exhaust gas generated by combustion of a gas mixture in each cylinder of the engine 1 passes through the exhaust gas purifying device 4 and CO2The recovery device 3 is discharged to the outside of the vehicle.
The fuel supply device 2 includes: a fuel tank 20 that accumulates 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 accumulated 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, and injects fuel supplied from the fuel supply pipe 24. An air-fuel mixture in which the fuel injected from the fuel injection valve 21 is mixed with the air supplied from the intake pipe 15 is supplied to each cylinder of the engine 1.
The exhaust gas purification apparatus 4 includes an exhaust gas purification 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. The exhaust gas purification catalyst may have a NOx reduction function of reducing NOx, and examples thereof include a three-way catalyst (TWC) and a NOx selective reduction catalyst (SCR). The more preferable exhaust gas purification catalyst is generally a three-way catalyst into which exhaust gas of stoichiometric environment flows.
CO2Recovery unit 3 passing CO2The pipe 31 is connected to the reactor 5. CO 22The recovery device 3 separates and recovers carbon dioxide from the exhaust gas flowing through the exhaust pipe 16, and passes the carbon dioxide through 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)2) CO removal as a main component2Waste 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 apparatus 3 is based on the use of CO, for example2The adsorbent separates the exhaust gas of the engine 1 into a recovered gas and CO removal2Exhaust gas of the aforesaid CO2The adsorbent selectively adsorbs carbon dioxide in the exhaust gas flowing through the exhaust pipe 16 under a predetermined adsorption condition, and desorbs the adsorbed carbon dioxide under a predetermined desorption condition. With respect to CO2For the adsorbent, for example, a lithium composite oxide can be used.
CO of the present embodiment2The recovery unit 3 is not limited to the use of CO2The adsorption/desorption characteristics of the carbon dioxide by the adsorbent separate the exhaust gas of the engine 1 into a recovered gas and a desorbed CO2The case of exhaust gas. CO 22The recovery device 3 may have the following configuration: by making use ofCO through which carbon dioxide in exhaust gas flowing through the exhaust pipe 16 selectively permeates2A separation membrane, thereby separating the exhaust gas of the engine 1 into a recovered gas and CO removal2And (4) exhaust gas.
The hydrogen supply device 6 includes: high pressure H2A tank 61 that stores high-pressure hydrogen; h2A pipe 63 for introducing high pressure H2Tank 61 is connected to reactor 5; and, an adjuster 64 provided at H2And a pipe 63. The regulator 64 will deliver a high pressure H2The hydrogen stored in the tank 61 is depressurized to a predetermined pressure and then passed through the hydrogen tank via the hydrogen gas2The pipe 63 is supplied to the reactor 5.
The hydrogen supply device 6 of the present embodiment is not limited to the high pressure H2The hydrogen stored in the tank 61 is supplied to the reactor 5. The hydrogen supply device 6 may be configured to supply hydrogen generated from water by the electrolysis device to the reactor 5, or may be configured to supply hydrogen generated from ammonia to the reactor 5.
Reactor 5 for the removal of CO from the reaction mixture2Carbon dioxide contained in the recovered gas supplied from the pipe 31 and the secondary gas H2The hydrogen supplied from the pipe 63 is hydrogenated at a predetermined ratio in the reaction cylinder, thereby reducing carbon dioxide and synthesizing methanol.
More specifically, the reactor 5 includes: a reaction cylinder introduced from CO2A recovery gas supplied from the pipe 31; h2An injector for injecting the secondary stream H into the reaction cylinder2Hydrogen supplied from the pipe 63; a carbon dioxide reduction catalyst provided in 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 tube and the condenser 7.
The carbon dioxide reduction catalyst promotes a hydrogenation reaction of carbon dioxide in which carbon dioxide is reduced in the presence of carbon dioxide and hydrogen and methanol is produced. As the carbon dioxide reduction catalyst, for example, there can be used: is made of Alumina (AI)2O3) Or silicon dioxide (SiO)2) A carrier composed of an oxide such as copper (Cu) or zinc (Zn), a catalyst metal composed of a transition metal such as zinc (Zn), or the like, and a known catalyst such as a copper-zinc oxide catalystAn oxidizing agent.
The heating device heats the gas in the reaction tube to a temperature required for the hydrogenation reaction of carbon dioxide by using waste heat of the engine 1, that is, a part of heat energy generated by burning 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 fuel in the engine 1, more specifically, power of a crankshaft of the engine 1.
In the reactor 5 as described above, CO is introduced2The piping 31 introduces a predetermined amount of the recovered gas into the reaction cylinder, and hydrogen is measured from H so that the ratio of carbon dioxide to hydrogen in the reaction cylinder becomes a predetermined ratio2The injector is injected into the reaction cylinder, and then the gas in the reaction cylinder is heated and compressed by the heating device and the compression device. Thus, the hydrogenation reaction of carbon dioxide is carried out in the reaction tube by the action of the carbon dioxide reduction catalyst (see the following formula (1)), and methanol is produced. At the same time, the reverse water gas shift reaction (see the following formula (2)) and the hydrogenation reaction of carbon monoxide (see the following formula (3)) are also carried out by the action of the carbon dioxide reduction catalyst, and a methanol-containing synthesis gas is produced.
CO2+3H2→CH3OH+H2O (1)
CO2+H2→CO+H2O (2)
CO+2H2→CH3OH (3)
The synthesis gas generated in the reaction tube in the above-described procedure is supplied to the condenser 7 through the synthesis gas pipe 51. The synthesis gas discharged from the synthesis gas pipe 51 contains methanol produced by the methanol synthesis reaction, and also contains carbon monoxide, unreacted carbon dioxide, and CO as by-products2Nitrogen and the like in the recovery gas are mixed into the recovery apparatus 3 without being completely separated. In particular, the present applicant has found that, in the case of a carbon dioxide reduction catalyst comprising a copper-zinc oxide-based catalyst which has been known in the past, the catalyst comprisesA catalyst metal made of a transition metal such as copper (Cu) or zinc (Zn) as a metal is oxidized to change into copper oxide (CuO) or zinc oxide (ZnO), and as a result, carbon monoxide is generated in a large amount as a by-product. Therefore, carbon monoxide that is the by-product can be effectively used by the exhaust gas purification system 10 according to the present embodiment, as will be described in detail below.
The condenser 7 recovers methanol from the synthesis gas supplied from the reactor 5 and supplies the recovered methanol to the fuel tank 20. More specifically, the condenser 7 condenses the synthesis gas discharged from the reactor 5 by heat exchange, separates the synthesis gas into a liquid phase containing methanol as a main component and a gas phase containing by-products, carbon monoxide, unreacted carbon dioxide, and nitrogen, discharges the liquid phase from a liquid phase port, and discharges the gas phase from a gas phase port.
The liquid port of the condenser 7 is connected to the fuel tank 20 by a liquid pipe 71. Therefore, the liquid phase discharged from the liquid phase port of the condenser 7 is guided into the fuel tank 20 by the liquid phase pipe 71. The gas phase port of the condenser 7 and the space between the engine 1 and the exhaust gas purification apparatus 4 in the exhaust pipe 16 are connected by a gas phase pipe 72. Therefore, the gas phase discharged from the gas phase port of the condenser 7 is guided to the exhaust gas purification apparatus 4 through the gas phase pipe 72.
A pressurizer 8 and a supply valve 9 are provided in the middle of the gas phase pipe 72. The pressurizer 8 pressurizes the gas phase gas containing carbon monoxide discharged from the condenser 7. The pressurizer 8 is constituted by a compressor or the like, for example. The supply valve 9 is opened and closed in response to a command from a control device, not shown, to control the supply of carbon monoxide or the like pressurized by the pressurizer 8 to the exhaust gas purification device 4. The supply of carbon monoxide can be restricted by the supply valve 9 so as not to become excessively rich during rich driving, for example, during rich control after recovery from a Fuel Cut (Fuel Cut).
The flow of carbon in the vehicle V having the carbon cycle system S as described above will be described. First, when a mixture of the hydrocarbon fuel 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. The carbon dioxide in the exhaust gas is composed of CO2The recovery device 3 separates and recoversAnd then supplied to the reactor 5. In the reactor 5, a synthesis gas containing methanol is produced by reacting carbon dioxide with hydrogen. Methanol in the synthesis gas is recovered by the condenser 7 and supplied as fuel to the engine 1 by the fuel supply device 2. On the other hand, carbon monoxide in the synthesis gas is recovered by the condenser 7 and supplied to the exhaust gas purification apparatus 4 in a pressurized state by the pressurizer 8 and the supply valve 9. In this way, the vehicle V having the carbon cycle S mounted thereon circulates carbon in the carbon cycle S while introducing carbon dioxide from the outside air, thereby reducing the amount of carbon dioxide discharged from the tail pipe to the outside of the vehicle.
Next, the exhaust gas purification system 10 of the present embodiment will be described in detail.
As described above, the exhaust gas purification system 10 of the present embodiment is composed of the exhaust gas purification device 4 and CO2 A recovery device 3, a carbon dioxide reduction device 11 and a carbon monoxide supply device 12, wherein the carbon dioxide reduction device 11 is composed of a reactor 5 and a hydrogen supply device 6, and the carbon monoxide supply device 12 is composed of a condenser 7, a pressurizer 8 and a supply valve 9. The following experiment was performed using the exhaust gas purification system 10 of the present embodiment.
First, a conventionally known carbon cycle system is applied to a conventional gasoline engine vehicle, and methanol generated by a carbon dioxide reduction device is supplied to the engine. As a result, carbon dioxide (CO)2) 14% of water (H)2O) is 21%, oxygen (O)2) 2%, carbon monoxide (CO) 1900ppm, Hydrocarbon (HC) 5700ppmc, nitrogen monoxide (NO) 1350ppm, hydrogen (H)2) 1700ppm, the remainder being nitrogen (N)2)。
In contrast, as an example, in the reactor 5 constituting the carbon dioxide reduction device 11 of the present embodiment, CO is controlled2The recovery unit 3 and the hydrogen supply unit 6, whereby the mixing ratio of carbon monoxide and hydrogen is set to 25: 75, hydrogenation reaction is carried out under the conditions of 250 ℃ and 8 MPa. Thus, the amount of carbon monoxide produced as a by-product was 3600 ppm.
Therefore, in this embodiment, 3600ppm of carbon monoxide (CO) is supplied to the exhaust gas purifying device 4. That is, carbon monoxide (CO) in the exhaust gas introduced into the exhaust gas purification device 4 is shifted to the reducing atmosphere side from 1900ppm +3600ppm to 5500ppm, and the air-fuel ratio λ with respect to the stoichiometric air-fuel ratio is 0.994.
As a comparative example, the following structure was employed: supplying carbon monoxide (CO) produced as a by-product by the carbon dioxide reduction device to CO on the downstream side of the exhaust gas purification device 42And (5) a recovery device. Therefore, in this comparative example, the exhaust gas introduced into the exhaust gas purification apparatus 4 is kept stoichiometric, and the air-fuel ratio λ relative to the stoichiometric air-fuel ratio is kept at 1.
Here, fig. 2 is a graph showing a relationship between λ and CO purification rate. As shown in fig. 2, in the comparative example in which the air-fuel ratio λ is 1 with respect to the stoichiometric air-fuel ratio, the CO purification rate is almost 100%. On the other hand, it was confirmed that in the present example in which the air-fuel ratio λ relative to the stoichiometric air-fuel ratio was 0.994, a CO purification rate close to 100% was obtained, although it was slightly inferior to the comparative example.
Fig. 3 is a graph showing a relationship between λ and the HC purification rate. As can be seen from fig. 3, the HC purification rate is about 90% in the comparative example in which the air-fuel ratio λ is 1 with respect to the stoichiometric air-fuel ratio. On the other hand, it was confirmed that in the present example in which the air-fuel ratio λ relative to the stoichiometric air-fuel ratio was 0.994, the HC purification rate was higher than that in the comparative example, and an HC purification rate almost close to 100% was obtained.
Fig. 4 is a graph showing a relationship between λ and the NOx purification rate. As shown in fig. 4, in the comparative example in which the air-fuel ratio λ is 1 with respect to the stoichiometric air-fuel ratio, the NOx purification rate is low at about 60%. On the other hand, it was confirmed that in the present example in which the air-fuel ratio λ relative to the stoichiometric air-fuel ratio was 0.994, the NOx purification rate was particularly high as compared with the comparative example, and a NOx purification rate close to 100% was obtained.
According to the exhaust gas purification system 10 of the present embodiment, the following effects are exhibited.
In the present embodiment, the carbon monoxide supply device 12 is provided, and the carbon monoxide supply device 12 supplies carbon monoxide, which is generated as a by-product when carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device 4 is reduced by a hydrogenation reaction to produce methanol, to the exhaust gas purification device 4. This makes it possible to make the exhaust gas purification catalyst more in the reducing atmosphere, and to improve the NOx reduction purification rate. Therefore, according to the present embodiment, the following technique can be provided: carbon monoxide generated as a by-product when carbon dioxide in the exhaust gas of the engine 1 is reused as fuel by hydrogenation reaction can be effectively used for reduction purification of NOx without being discharged from a tail pipe.
In the present embodiment, a pressurizer 8 is provided, and the pressurizer 8 pressurizes and supplies carbon monoxide, which is a by-product of the hydrogenation reaction, to the exhaust gas purification apparatus 4. This makes it possible to efficiently and reliably supply the by-produced carbon monoxide to the exhaust gas purification device 4 into which the high-pressure exhaust gas is introduced.
In the present embodiment, it is preferable that carbon monoxide be supplied to the three-way catalyst. Thus, since the exhaust gas flowing into the three-way catalyst is generally stoichiometric in composition, although carbon monoxide (CO) and Hydrocarbons (HC) can be completely oxidized and purified, the NOx reduction purification rate is low, and here, according to the present embodiment, the three-way catalyst can be made more on the reducing atmosphere side in response to the supply of carbon monoxide, and the NOx reduction purification rate can be improved.
In the present embodiment, the present invention is further provided with CO2The structure of the recovery apparatus 3, the above-mentioned CO2The recovery device 3 separates and recovers carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device 4, and supplies the carbon dioxide to the carbon dioxide reduction device 11. This enables carbon dioxide in the exhaust gas passing through the exhaust gas purification device 4 to be efficiently separated and recovered and supplied to the carbon dioxide reduction device 11. Then, carbon monoxide, which is a by-product generated by the hydrogenation reaction of carbon dioxide in the carbon dioxide reduction device 11, is supplied directly to CO, for example2 A recovery unit 3 for recovering CO2The recovery device 3 discharges to the tail pipe, and as a result, the CO emission deteriorates, and this can be avoided according to the present embodiment.
In the present embodiment, carbon monoxide is supplied to the exhaust gas purification device 4 at the time of starting the engine 1. This makes it possible to increase the NOx reduction purification rate at the time of starting the engine 1 in which the NOx purification rate is low because the exhaust purification catalyst is low in temperature.
The present invention is not limited to the above-described embodiments, and variations and modifications within a range that can achieve the object of the present invention are included in the present invention.
Reference numerals
1: engine (internal combustion engine)
3：CO2Recovery device (carbon dioxide separation and recovery device)
4: exhaust gas purification device
5: reactor (carbon dioxide reduction device)
6: hydrogen supply device (carbon dioxide reduction device)
7: condenser (carbon monoxide supply device)
8: pressurizer (carbon monoxide supply device)
9: supply valve (carbon monoxide supply device)
10: exhaust gas purification system
11: carbon dioxide reduction device
12: carbon monoxide supply device
16: exhaust pipes (exhaust passage)
Claims (5)
1. An exhaust gas purification system for an internal combustion engine, which purifies exhaust gas discharged from the internal combustion engine, comprising:
an exhaust gas purification device provided in an exhaust passage of the internal combustion engine and including an exhaust gas purification catalyst having an NOx reduction function of reducing NOx contained in the exhaust gas;
a carbon dioxide reduction device having a carbon dioxide reduction catalyst that reduces carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device to produce methanol by performing a hydrogenation reaction on the carbon dioxide; and a process for the preparation of a coating,
and a carbon monoxide supply device for supplying carbon monoxide, which is a by-product of the hydrogenation reaction, to the exhaust gas purification device.
2. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the carbon monoxide supply device includes a pressurizer that pressurizes and supplies carbon monoxide, which is a by-product of the hydrogenation reaction, to the exhaust gas purification device.
3. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein the exhaust gas purification catalyst is a three-way catalyst.
4. The exhaust gas purification system for an internal combustion engine according to claim 1, further comprising a carbon dioxide separation and recovery device for separating and recovering carbon dioxide contained in the exhaust gas passing through the exhaust gas purification device and supplying the carbon dioxide to the carbon dioxide reduction device.
5. The exhaust gas purification system for an internal combustion engine according to claim 1, wherein said carbon monoxide supply device supplies said carbon monoxide to said exhaust gas purification device at the time of starting said internal combustion engine.
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| CN114852305B (en) * | 2022-05-31 | 2023-05-16 | 江南造船(集团)有限责任公司 | Ship carbon emission reduction system and fuel gas transport ship |
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