CN113847123A

CN113847123A - Vehicle and tail gas aftertreatment system thereof

Info

Publication number: CN113847123A
Application number: CN202010600459.0A
Authority: CN
Inventors: 赵振兴; 石伟; 田园
Original assignee: Great Wall Motor Co Ltd
Current assignee: Great Wall Motor Co Ltd
Priority date: 2020-06-28
Filing date: 2020-06-28
Publication date: 2021-12-28
Anticipated expiration: 2040-06-28
Also published as: CN113847123B

Abstract

The invention relates to the field of vehicle tail gas aftertreatment systems, and provides a vehicle and a tail gas aftertreatment system thereof, wherein the vehicle comprises lean burn NO_XA trapping device, the vehicle exhaust aftertreatment system further comprising a nitrous oxide trapping device located at the lean NO_XDownstream of the trap device, the nitrous oxide trap device includes a carrier and a catalyst coating coated on the carrier, the catalyst coating includes a noble metal, the noble metal includes rhodium, and the weight percentage of the rhodium in the noble metal is not less than 90%. In the vehicle exhaust aftertreatment system of the invention, lean NO is first passed_XA trapping device for generating a certain amount of N₂O; and when the tail gas flows to the nitrous oxide trapping device, N is trapped by the catalyst coating layer taking rhodium as a main component₂O is adsorbed "competitively" so that N is present in the gas exiting the exhaust gas aftertreatment system₂The content of O is greatly reducedLow.

Description

Vehicle and tail gas aftertreatment system thereof

Technical Field

The invention relates to the technical field of vehicle tail gas aftertreatment, in particular to a vehicle and a tail gas aftertreatment system thereof.

Background

In both diesel-engine-equipped vehicles and gasoline-engine vehicles, nitrous oxide (N) is generated to a greater or lesser extent in the engine and exhaust system₂O). This phenomenon is more obvious especially for the light-duty diesel vehicle after-treatment system matched with LNT, and the existing light-duty diesel vehicle after-treatment system roughly comprises lean-burn NO in sequence along the direction of exhaust emission as shown in FIG. 1_XTrapping device (lean NO)_Xtrap, LNT)1, a Diesel Particulate Filter (DPF) 5, and a Selective Catalytic Reduction device (SCR) 6.

And in the gas entering the tail gas aftertreatment system from the exhaust inlet after the supercharger, the NO accounts for more than 90 percent. When the engine is in rich combustion (such as the working condition of an oil filling valve), CO and NO discharged to an after-treatment system generate a certain amount of N under the action of noble metals Pt, Pd and Rh inside an LNT₂0, the reaction formula is as follows: 2NO + CO → N₂O+CO₂。

N₂The greenhouse effect produced by O is CO₂Multiple 310. N is a radical of₂O has been valued by the automotive industry, e.g. N in national VI regulations for light-duty diesel vehicles₂The emission limit of O is 30mg/km, and future European VII is presumed to be directed to N₂O emission limits will be more stringent, but N₂O emission reduction is a difficult problem in the whole automobile industry, and an effective method for effectively reducing the emission of the automobile N is not available yet₂The design of O is already pressing.

Disclosure of Invention

In view of the above, the present invention is directed to a vehicle and an exhaust gas after-treatment system thereof, which can effectively reduce the content of nitrous oxide in the exhaust gas.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

an exhaust gas after-treatment system for a vehicle, the exhaust gas after-treatment system for a vehicle comprising lean NO_XA trapping device, the exhaust gas after-treatment system of the vehicle further comprising a nitrous oxide trapping device located at the lean NO_XDownstream of the trap device, the oxygenThe nitrous oxide trapping device comprises a carrier and a catalyst coating coated on the carrier, wherein the catalyst coating comprises a precious metal, the precious metal comprises rhodium, and the weight percentage of the rhodium in the precious metal is not less than 90%.

Further, the nitrous oxide trapping device further comprises a shell and a gasket, the carrier is located in the shell, the shell is provided with openings at two ends, two ends of the carrier along the longitudinal direction respectively face the openings of the shell at the corresponding side, and the gasket is clamped between the outer peripheral wall of the carrier and the inner peripheral wall of the shell; the carrier is provided with a plurality of pore channels extending along the longitudinal direction, and the inner walls of the pore channels are coated with the catalyst coating.

Further, the support comprises alumina and one of ceramic, metal, silicon carbide and aluminum titanate; and/or the housing comprises a first connecting pipe section, a first expanding section, a main body section, a second expanding section and a second connecting pipe section in sequence from one end to the other end along the longitudinal direction, the carrier is positioned in the main body section, the inner diameters of the first expanding section and the second expanding section are gradually increased from one end to the other end, and the ends with larger inner diameters of the first expanding section and the second expanding section face the main body section.

Further, the ratio of the rhodium content in the catalyst coating layer to the volume of the carrier is more than 100 mg/L.

Further, the exhaust gas after-treatment system further comprises a carbon monoxide injection device, wherein the carbon monoxide injection device is positioned upstream of the nitrous oxide capture device and is used for injecting carbon monoxide into the exhaust gas after-treatment system.

Further, carbon monoxide injection apparatus includes carbon monoxide storage portion, carbon monoxide pipeline, flow control portion and nozzle, flow control portion is located on the carbon monoxide pipeline, carbon monoxide injection apparatus sets up to the orientation spray high pressure carbon monoxide among the tail gas aftertreatment system.

Further, the vehicle comprises a control system, the exhaust gas aftertreatment system further comprises a temperature sensor, a signal output end of the temperature sensor is electrically connected to a signal input end of the control system, and a signal output end of the control system is electrically connected to a signal input end of the flow control portion, so that the flow control portion is controlled to work according to a measurement result of the temperature sensor.

Further, the temperature sensor includes a sensor proximate the lean NO_XA first temperature sensor disposed in the trap device and a second temperature sensor disposed adjacent to the nitrous oxide trap device.

Further, the exhaust gas aftertreatment system further comprises a diesel particulate trap and a selective catalytic reduction device, wherein the lean NO is in the direction of gas flow in the exhaust gas aftertreatment system_XThe trapping device, the diesel particulate trap, the selective catalytic reduction device, the carbon monoxide injection device and the nitrous oxide trapping device are sequentially arranged.

Another aspect of the present invention provides a vehicle provided with the exhaust gas after-treatment system of the vehicle.

In the exhaust gas after-treatment system of a vehicle of the present invention, in the lean NO_XThe nitrous oxide trapping device 2 arranged at the downstream of the trapping device comprises a carrier and a catalyst coating coated on the carrier 21 and used for specifically trapping nitrous oxide, wherein the catalyst coating on which the nitrous oxide trapping device acts mainly contains rhodium elements, and the rhodium elements can well trap nitrous oxide. When tail gas (main component is NO)_XAnd CO) into the exhaust aftertreatment system, first by lean NO_XTrapping arrangements in lean-burn NO_XIn the trapping device, under the action of noble metals of Pt, Pd and Rh, NO and CO are mainly trapped to generate a certain amount of N₂O; when the tail gas continues to flow downstream to the nitrous oxide trapping device, the nitrogen oxide mainly contained in the tail gas is N₂O, N trapped by a catalyst coating containing rhodium as the main component₂O is adsorbed on the surface of the nitrous oxide trap catalyst coating layer in a competition-free manner, so that N in the gas discharged into the exhaust gas aftertreatment system₂O containsThe amount is greatly reduced.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic diagram of a prior art exhaust aftertreatment system;

FIG. 2 is a schematic view of an exhaust aftertreatment system for a vehicle according to an embodiment of the invention;

fig. 3 is a schematic view of the internal structure of the nitrous oxide trapping device in fig. 2.

Description of the reference numerals

1 lean NO_XA trapping device; a nitrous oxide capture device; 21 a carrier; 22 a housing; 23, a liner; 3 a carbon monoxide injection device; 31 a carbon monoxide storage part; 32 carbon monoxide delivery lines; 33 a flow rate control unit; 34 a nozzle; 41 a first temperature sensor; 42 a second temperature sensor; 5 a diesel particulate trap; 6 selective catalytic reduction device

Detailed Description

In addition, the embodiments of the present invention and the features of the embodiments may be combined with each other without conflict.

In the present invention, it is to be understood that the terms "away", "toward", and the like indicate an orientation or positional relationship corresponding to an orientation or positional relationship in actual use; "inner and outer" refer to the inner and outer relative to the profile of the components themselves. These are merely for convenience in describing the invention and to simplify the description, and are not intended to indicate that the device or component in question must have a particular orientation, be constructed and operated in a particular orientation, and are not to be construed as limiting the invention.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; may be mechanically coupled, may be electrically coupled or may be in communication with each other; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations. The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

The invention provides an exhaust gas after-treatment system for a vehicle, comprising lean-burn NO_X A trap device 1, the exhaust gas after-treatment system of the vehicle further comprises a nitrous oxide trap device 2, the nitrous oxide trap device 2 being located at the lean NO_XDownstream of the trap device 1, the nitrous oxide trap device 2 includes a support 21 and a catalyst coating applied on the support 21, the catalyst coating including a noble metal, the noble metal including rhodium, and the weight percentage of rhodium in the noble metal being not less than 90%.

In the exhaust gas after-treatment system of a vehicle of the present invention, in the lean NO_XThe nitrous oxide trapping device 2 arranged at the downstream of the trapping device 1 comprises a carrier 21 and a catalyst coating coated on the carrier 21 and used for specifically trapping nitrous oxide, wherein the catalyst coating on which the nitrous oxide trapping device 2 acts mainly contains rhodium element which can trap nitrous oxide well. When tail gas (main component is NO)_XAnd CO) into the exhaust aftertreatment system, first by lean NO_XTrapping device 1 in lean NO_XIn the trap device 1, mainly NO and CO are trapped by the action of the noble metals Pt, Pd, Rh to generate a certain amount of N₂O, the reaction formula is as follows: 2NO + CO → N₂O+CO₂(ii) a When the tail gas continues to flow downstream to the nitrous oxide capture device 2, the nitrogen oxide mainly contained in the tail gas is N₂O, N trapped by a catalyst coating containing rhodium as the main component₂O is adsorbed on nitrous oxide trap device without competition2 catalyst coating surface so that N is contained in gas discharged to exhaust gas after-treatment system₂The content of O is greatly reduced; wherein, for example, the weight percentage of rhodium in the noble metal may be 93%, 95% or 97%.

Wherein the noble metal can selectively comprise noble metals Pt, Pd, Rh and the like besides rhodium, but metal rhodium is a main component, and can trap N well₂O, capturing N more rapidly and efficiently than other noble metals₂O and metal rhodium as a main component can effectively prevent other noble metals from reacting with CO to consume CO, thereby inhibiting N₂Trapping and absorbing of O; it will be appreciated that in a preferred case the noble metal consists of rhodium, i.e. the noble metal comprises rhodium only.

And, preferably, the ratio of the rhodium content in the catalyst coating layer to the volume of the carrier 21 is more than 100mg/L, so that the carrier 21 contains a sufficient amount of rhodium for reacting with N₂O reaction, further preferably, the ratio of the rhodium content in the catalyst coating layer to the volume of the support 21 may be in the range of 180-220mg/L, such as 190mg/L, 200mg/L or 210 mg/L.

In some embodiments, the nitrous oxide capture device 2 further comprises a housing 22 and a gasket 23, the carrier 21 is located in the housing 22, the housing 22 has openings at two ends, two ends of the carrier 21 in the longitudinal direction are respectively directed to the openings of the housing 22 at the corresponding sides, and the gasket 23 is sandwiched between the outer peripheral wall of the carrier 21 and the inner peripheral wall of the housing 22; the carrier 21 is formed with a plurality of cells extending in the longitudinal direction, and the inner walls of the cells are coated with the catalyst coating layer. The gas flow enters the housing 22 from one end of the housing 22, flows through the carrier 21 arranged therein, and is discharged from the other end, and when passing through the carrier 21, the gas flow flows through a plurality of pore channels on the carrier 21, so that the contact area is increased, and the gas flow is effectively adsorbed on the catalyst coating layers on the pore channels.

Alternatively, the support 21 is composed of an inert substance, such as one of ceramics, metals, silicon carbide and aluminum titanate, and the support 21 contains alumina, aluminaProviding higher specific surface area and enhancing N₂O attachment ability; the gasket 23 plays a role in ensuring sealability and shock absorption protection; the catalyst coating component mainly comprises an auxiliary agent besides the noble metal, wherein the auxiliary agent is effective in improving the activity of the catalyst, the high-temperature stability and the sulfur resistance, and the auxiliary agent can comprise one or the combination of zirconium oxide and cerium oxide.

And, structurally, as an option, the housing 22 includes, in order from one end to the other end in the longitudinal direction (extending direction), a first connecting pipe section, a first expanding section, a main body section, a second expanding section, and a second connecting pipe section, the carrier 21 being located in the main body section, the first expanding section and the second expanding section being formed such that the inner diameters thereof gradually increase from one end to the other end, and the ends of the first expanding section and the second expanding section, which have the larger inner diameters, are both directed toward the main body section, so that the main body section has the respective large inner diameters, i.e., the larger inner spaces, to accommodate the carrier 21, enabling the gas flow flowing through the main body section to be more sufficiently attached, trapped, and reacted therein.

Preferably, the exhaust gas aftertreatment system further comprises a carbon monoxide injection device 3, wherein the carbon monoxide injection device 3 is positioned upstream of the nitrous oxide capture device 2 and is used for injecting carbon monoxide into the exhaust gas aftertreatment system. The catalyst coating in the nitrous oxide trap device 2 can effectively adsorb N₂O, cracking it to N₂And O_XHowever, the reaction rate is slower, so that when N is used₂When the amount of O is large, N is trapped and reacted for more efficiency₂O, the inventors of the present application designed to inject carbon monoxide gas before the nitrous oxide trapping device 2, which is advantageous to accelerate N₂O cracking to N₂And O_XAnd rapidly generate N₂And CO₂。

Specifically, in some embodiments, the carbon monoxide injection device 3 includes a carbon monoxide storage part 31, a carbon monoxide delivery pipe 32, a flow control part 33, and a nozzle 34, the flow control part 33 is located on the carbon monoxide delivery pipe 32, and the carbon monoxide injection device 3 is configured to inject high-pressure carbon monoxide into the exhaust gas aftertreatment system. Wherein, the flow control part 33 is configured to measure, collect and feed back the information of the gas flow passing through the carbon monoxide conveying pipeline 32, and control the flow of the gas flow passing through the carbon monoxide conveying pipeline 32; the carbon monoxide storage part 31 may include a carbon monoxide storage tank and a high-pressure decompression device (e.g., a high-pressure pump).

In addition, the vehicle comprises a control system (which can be an ECU of the vehicle), the exhaust aftertreatment system further comprises a temperature sensor, the signal output end of the temperature sensor is electrically connected with the signal input end of the control system, the signal output end of the control system is electrically connected with the signal input end of the flow control part 33, to control the operation of the flow rate control portion 33 based on the measurement result of the temperature sensor, the inventors of the present application have found that, for a required amount of carbon monoxide, which is related to the amount of nitrogen oxides produced upstream and the rate of nitrogen oxides reaction downstream, the amount of carbon monoxide injected into the system can be controlled by the temperature signal of a temperature sensor within the system, thereby providing as much carbon monoxide as possible to the nitrogen oxides so that the nitrogen oxides can react sufficiently to cause the carbon monoxide not to be ejected too much to cause the carbon monoxide to escape in large quantities to pollute the air.

Preferably, the temperature sensor comprises a sensor adjacent to the lean NO_XA first temperature sensor 41 arranged in the trap device 1 and a second temperature sensor 42 arranged adjacent to said nitrous oxide trap device 2, wherein the first temperature sensor 41 is adjacent to said lean NO_XThe trapping device 1 is provided with a first temperature sensor 41 arranged in said lean NO_XConditions at the trapping device 1 and the proximity of the first temperature sensor 41 to the lean NO_XTrap device 1 but with said lean-burn NO_XThe trapping device 1 still has a certain distance, and similarly, the arrangement of the second temperature sensor 42 adjacent to the nitrous oxide trapping device 2 includes the case where the second temperature sensor 42 is arranged at the nitrous oxide trapping device 2 and the case where the second temperature sensor 42 is arranged close to the nitrous oxide trapping device 2 but still has a same position as the nitrous oxide trapping device 2In the case of fixed distance. The inventors of the present application found that for the amount of carbon monoxide required, which is related to the amount of nitrogen oxides produced upstream and the rate of reaction of the nitrogen oxides downstream, when the upstream is lean-burning NO_XWhen the temperature of the trapping device 1 is 200-400 ℃ and is kept in the temperature range for a period of time, a large amount of nitrous oxide can be generated in the upstream nitrous oxide trapping device 2, and carbon monoxide is required to be sprayed to enable the nitrous oxide to fully react; when the temperature in the downstream nitrous oxide capturing device 2 does not reach a certain temperature, for example, 370 °, the reaction of carbon monoxide with nitrous oxide is slow in the nitrous oxide capturing device 2, and if a large amount of carbon monoxide is injected upstream, the carbon monoxide will escape to the outside after having NO time to react with nitrous oxide, causing environmental pollution_XThe temperature of the trapping device 1 is 200-400 ℃ and is kept in the temperature range for the first time (the first time can be determined according to different vehicle models, for example, 70 seconds) and the carbon monoxide is injected when the temperature of the downstream nitrous oxide trapping device 2 reaches a certain temperature (the certain temperature can be determined according to different vehicle models, for example, 370 ℃), so that the excessive carbon monoxide is effectively prevented from being directly discharged to the outside to cause environmental pollution.

In addition, in the present embodiment, the exhaust gas aftertreatment system further includes a diesel particulate trap 5 and a selective catalytic reduction device 6, and the lean NO is combusted in the direction of the gas flow in the exhaust gas aftertreatment system_XThe trap device 1, the diesel particulate trap 5, the selective catalytic reduction device 6, the carbon monoxide injection device 3, and the nitrous oxide trap device 2 are provided in this order.

A second aspect of the invention provides a vehicle provided with an exhaust gas aftertreatment system of said vehicle; the vehicle can be a light-duty diesel vehicle, and N is contained in tail gas after the tail gas after-treatment system of the vehicle is arranged₂The content of O is greatly reduced, and N can be reduced₂The O emission is reduced to the level of 5-17 mg/km.

In the description herein, reference to the terms "one embodiment," "some embodiments," "for example," or "example," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the various embodiments or examples and features of the various embodiments or examples described in this specification can be combined and combined by those skilled in the art without contradiction.

The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention. Including each of the specific features, are combined in any suitable manner. The invention is not described in detail in order to avoid unnecessary repetition. Such simple modifications and combinations should be considered within the scope of the present disclosure as well.

Claims

1. An exhaust gas after-treatment system for a vehicle, the exhaust gas after-treatment system for a vehicle comprising lean NO_XTrap device (1), characterized in that the exhaust gas after-treatment system of the vehicle further comprises a nitrous oxide trap device (2), the nitrous oxide trap device (2) being located at the lean NO_XDownstream of the trap device (1), the nitrous oxide trap device (2) includes a carrier (21) and a catalyst coating coated on the carrier (21), the catalyst coating including a noble metal, the noble metal including rhodium, and the weight percentage of rhodium in the noble metal being not less than 90%.

2. The exhaust aftertreatment system according to claim 1, wherein the nitrous oxide trap device (2) further includes a housing (22) and a gasket (23), the carrier (21) is located in the housing (22), the housing (22) has openings at both ends, both ends of the carrier (21) in the longitudinal direction are respectively directed toward the openings of the housing (22) at the corresponding sides, and the gasket (23) is interposed between an outer peripheral wall of the carrier (21) and an inner peripheral wall of the housing (22); the carrier (21) is formed with a plurality of cells extending in the longitudinal direction, and the inner walls of the cells are coated with the catalyst coating.

3. The vehicle exhaust aftertreatment system of claim 2, wherein the carrier (21) comprises alumina and one of ceramic, metal, silicon carbide, and aluminum titanate; and/or the housing (22) comprises a first connecting pipe section, a first expanding section, a main body section, a second expanding section and a second connecting pipe section in sequence from one end to the other end along the longitudinal direction, the carrier (21) is positioned in the main body section, the inner diameters of the first expanding section and the second expanding section are gradually increased from one end to the other end, and the ends with larger inner diameters of the first expanding section and the second expanding section face the main body section.

4. The vehicle exhaust aftertreatment system according to claim 1, wherein the ratio of the rhodium content in the catalyst coating to the volume of the support (21) is greater than 100 mg/L.

5. The exhaust gas after-treatment system of a vehicle according to any one of claims 1-4, characterized in that the exhaust gas after-treatment system further comprises a carbon monoxide injection device (3), the carbon monoxide injection device (3) being located upstream of the nitrous oxide capture device (2) for injecting carbon monoxide into the exhaust gas after-treatment system.

6. The exhaust gas aftertreatment system of a vehicle according to claim 5, characterized in that the carbon monoxide injection device (3) comprises a carbon monoxide storage section (31), a carbon monoxide delivery line (32), a flow control section (33) and a nozzle (34), the flow control section (33) being located on the carbon monoxide delivery line (32), the carbon monoxide injection device (3) being arranged to inject high pressure carbon monoxide into the exhaust gas aftertreatment system.

7. The exhaust gas aftertreatment system according to claim 6, wherein the vehicle comprises a control system, the exhaust gas aftertreatment system further comprising a temperature sensor, a signal output of the temperature sensor being electrically connected to a signal input of the control system, a signal output of the control system being electrically connected to a signal input of the flow control portion (33) for controlling the operation of the flow control portion (33) according to a measurement result of the temperature sensor.

8. The vehicle exhaust aftertreatment system of claim 7, wherein the temperature sensor comprises proximate the lean NO_XA first temperature sensor (41) disposed in the trap device (1) and a second temperature sensor (42) disposed adjacent to the nitrous oxide trap device (2).

9. The exhaust aftertreatment system of a vehicle according to claim 5, characterized in that the exhaust aftertreatment system further comprises a diesel particulate trap (5) and a selective catalytic reduction device (6), the lean NO being in the direction of flow in the exhaust aftertreatment system_XThe trapping device (1), the diesel particulate trap (5), the selective catalytic reduction device (6), the carbon monoxide injection device (3), and the nitrous oxide trapping device (2) are arranged in sequence.

10. A vehicle characterized by being provided with an exhaust gas after-treatment system of a vehicle according to any one of claims 1-9.