KR20200114380A - After treatment system for lean-burn engine - Google Patents

Abstract

An objective of the present invention is to provide a post-treatment apparatus for a lean-burn engine which can increase an ammonia production amount at a rich air-fuel ratio. According to an embodiment of the present invention, the post-treatment apparatus for a lean-burn engine comprises: an exhaust pipe connected to a lean-burn engine to allow discharge gas produced by the lean-burn engine to flow therein; an ammonia production catalyst module which is mounted on the exhaust pipe, purifies discharge matters included in discharge gas, and produces ammonia by using nitrogen oxide included in discharge gas or nitrogen oxide stored therein when the air-fuel ratio is rich; an integrated catalyst unit which is mounted on the exhaust pipe downstream of the ammonia production catalyst module (35), reduces nitrogen oxide included in discharge gas, and purifies carbon monoxide included in discharge gas; and a controller to detect information on the temperature and air-fuel ratio of the discharge gas, and control the air-fuel ratio of the discharge gas based on the temperature and the air-fuel ratio information of the discharge gas.

Description

After treatment device for lean-burn engine {AFTER TREATMENT SYSTEM FOR LEAN-BURN ENGINE}

The present invention relates to a lean-burn engine post-treatment device, and more particularly, to a lean-burn engine post-treatment device including a selective reduction catalyst and a carbon monoxide removal catalyst.

Vehicles are equipped with catalytic converters to reduce emissions contained in exhaust gases. The exhaust gas discharged from the engine through the exhaust manifold is guided and purified by a catalytic converter installed in the exhaust pipe, and noise is attenuated while passing through the muffler, and then discharged into the atmosphere through the tail pipe. The catalytic converter described above purifies the emission contained in the exhaust gas. In addition, a soot filter for collecting particulate matter (PM) included in the exhaust gas may be mounted on the exhaust pipe.

The three-way catalyst is a kind of catalytic converter and removes these compounds by simultaneously reacting with hydrocarbon compounds, carbon monoxide, and nitrogen oxides (NOx), which are harmful components of exhaust gas. The three-way catalyst is mainly installed in gasoline vehicles, and Pt/Rh, Pd/Rh or Pt/Pd/Rh systems are used.

Among gasoline engines, the lean burn engine improves fuel economy by burning a soft mixer. The lean burn engine burns a soft mixer, so the air-fuel ratio of the exhaust gas is also soft. However, when the air-fuel ratio is soft, the three-way catalyst does not sufficiently reduce nitrogen oxides contained in the exhaust gas and slips. Therefore, a vehicle equipped with a lean-burn engine is further equipped with a selective catalytic reduction (SCR) catalyst for purifying nitrogen oxides slipping from the three-way catalyst. The selective reduction catalyst used in a vehicle equipped with a lean burn engine may be a passive type selective reduction catalyst.

When the air-fuel ratio is rich, the three-way catalyst reduces nitrogen oxides to produce ammonia, and the ammonia produced in the three-way catalyst is stored in a passive type selective reduction catalyst. When the air-fuel ratio is low, the passive type selective reduction catalyst purifies nitrogen oxides contained in the exhaust gas using the stored ammonia.

A lean-burn engine including a three-way catalyst and a passive type selective reduction catalyst needs to adjust the air-fuel ratio richly by increasing the amount of fuel for a set period in order to store sufficient ammonia in the passive type selective reduction catalyst. If the amount of nitrogen oxides emitted from the lean-burn engine increases, the period and number of times the lean-burn engine operates at a rich air-fuel ratio increases. Therefore, fuel economy may deteriorate.

In addition, when the air-fuel ratio is rich, the three-way catalyst can slip carbon monoxide and hydrocarbons. Carbon monoxide and hydrocarbons slipped in the three-way catalyst cannot be purified and may be discharged to the outside of the vehicle. Accordingly, an additional catalytic converter or control is required to reduce slipping carbon monoxide and hydrocarbons when the air-fuel ratio is thickly adjusted to produce ammonia.

The matters described in this background are prepared to enhance an understanding of the background of the invention, and may include matters not known in the prior art to those of ordinary skill in the field to which this technology belongs.

An embodiment of the present invention is to provide a post-treatment device for a lean burn engine capable of increasing the amount of ammonia produced at a rich air-fuel ratio.

Another embodiment of the present invention is to provide a post-treatment device for a lean burn engine capable of reducing the amount of carbon monoxide and hydrocarbons discharged to the outside at a rich air-fuel ratio.

Another embodiment of the present invention is to provide a catalyst chamber heat exchange structure capable of improving catalyst purification efficiency by maintaining a high temperature.

A post-treatment apparatus for a lean-burn engine according to an embodiment of the present invention includes an exhaust pipe connected to the lean-burn engine through which exhaust gas generated from the lean-burn engine flows, and is mounted on the exhaust pipe, and purifies the emission contained in the exhaust gas , When the air-fuel ratio is rich, an ammonia generation catalyst module that generates ammonia using nitrogen oxides contained in the exhaust gas or nitrogen oxides stored therein, and the ammonia generation catalyst module 35 are mounted on an exhaust pipe downstream of the exhaust gas. An integrated catalyst unit that reduces contained nitrogen oxides and purifies carbon monoxide contained in the exhaust gas, and detects information on the air-fuel ratio and temperature of the exhaust gas, and determines the exhaust gas based on the information on the air-fuel ratio and temperature of the exhaust gas. It includes a controller configured to control the air-fuel ratio.

The integrated catalyst unit is mounted in an exhaust pipe downstream of the ammonia generation catalyst module, stores ammonia generated in the ammonia generation catalyst module, and uses the stored ammonia to reduce nitrogen oxides contained in the exhaust gas. Catalytic Reduction (SCR), and a carbon monoxide removal catalyst (CO Clean-up Catalyst; CUC) mounted on an exhaust pipe downstream of the selective reduction catalyst and purifying carbon monoxide contained in the exhaust gas may be included.

The selective reduction catalyst and the carbon monoxide removal catalyst are provided inside the integrated catalytic unit case, and the integrated catalytic unit is provided inside the integrated catalytic unit case and connected to the exhaust pipe, and the high-temperature exhaust gas introduced from the exhaust pipe is the It may include a carbon monoxide removal catalyst heating chamber formed in a form surrounding the carbon monoxide removal catalyst so as to pass through the periphery of the carbon monoxide removal catalyst.

The carbon monoxide removal catalyst is contained in the carbon monoxide removal catalyst can, and a cross section in a direction parallel to the flow direction of the exhaust gas of the carbon monoxide removal catalyst can has a rear end of the carbon monoxide removal catalyst can than the front end based on the exhaust gas flow direction. It may have a streamlined shape formed to have a smaller radius.

The outer surface of the carbon monoxide removal catalyst can may have a plurality of fin-shaped patterns formed along the flow direction of the exhaust gas.

The carrier of the carbon monoxide removal catalyst may be a metal carrier.

The integrated catalyst case may be disposed under the vehicle.

A baffle for partitioning locations of the carbon monoxide removal catalyst heating chamber and the selective reduction catalyst may be provided inside the integrated catalyst case.

The integrated catalytic unit case includes a front hall and a rear hall so that the interior and exterior of the integrated catalytic unit case are communicated to the front and rear ends of the region where the selective reduction catalyst is located divided by the baffle. ) Can be formed respectively.

The ammonia generation catalyst module is mounted on a three-way catalyst (TWC) that purifies hydrocarbons, carbon monoxide, and nitrogen oxides contained in exhaust gas, and an exhaust pipe downstream of the three-way catalyst, and when the air-fuel ratio is soft, nitrogen oxides When the air-fuel ratio is rich, hydrogen is generated to desorb the stored nitrogen oxide, and an ammonia production catalyst (APC) that generates ammonia using the desorbed nitrogen oxide and the generated hydrogen may be included.

According to the present invention, it is possible to improve the exhaust gas purification performance of a next-generation gasoline lean burn engine by applying a carbon monoxide removal catalyst (CUC) and a selective reduction catalyst (SCR).

In addition, by improving the ammonia (NH3) storage capacity of the selective reduction catalyst, it is possible to improve the driving fuel efficiency of a gasoline lean burn engine vehicle by reducing the rich combustion conditions for artificial generation of ammonia.

In addition, by placing the position of the selective reduction catalyst at the rear end of the exhaust system layout, durability of the catalyst from high temperature heat fatigue can be increased.

In addition, by maintaining a high temperature condition for activating the carbon monoxide removal catalyst through the carbon monoxide removal catalyst heating chamber, it is possible to reduce the amount of precious metal loading of the carbon monoxide removal catalyst and reduce the cost.

1 is a schematic diagram of an aftertreatment apparatus for a lean burn engine according to an embodiment of the present invention.
2 is a perspective view schematically showing an integrated catalyst unit of an aftertreatment apparatus for a lean burn engine according to an embodiment of the present invention.
3 is a plan view schematically showing an integrated catalyst unit of an aftertreatment apparatus for a lean burn engine according to an embodiment of the present invention.
4 is a view showing an exhaust gas flow of a lean-burn engine post-treatment apparatus according to an embodiment of the present invention.
5 is a view schematically showing a carbon monoxide removal catalyst heating chamber of the aftertreatment apparatus for a lean burn engine according to an embodiment of the present invention.
6 is a view schematically showing an integrated catalyst unit after partially cutting a carbon monoxide removal catalyst heating chamber of the aftertreatment apparatus for a lean burn engine according to an embodiment of the present invention.
7 is a view schematically showing a carbon monoxide removal catalyst heating chamber after a partial cut-out of the post-treatment apparatus for a lean burn engine according to an embodiment of the present invention.
8 is a plan view schematically showing an integrated catalyst unit after removing a carbon monoxide removal catalyst heating chamber of a lean burn engine post-treatment apparatus according to an embodiment of the present invention.
9 is a perspective view schematically showing an integrated catalyst unit after removing the carbon monoxide removal catalyst heating chamber of the post-treatment apparatus for a lean burn engine according to an embodiment of the present invention.
10 is a cross-sectional view of a carbon monoxide removal catalyst can taken along line AA of FIG. 8.
FIG. 11 is an enlarged view of the surface of a carbon monoxide removal catalyst can in a portion'B' of FIG. 9.
12 is a perspective view schematically showing an integrated catalyst unit having a rear hole formed in the aftertreatment apparatus for a lean burn engine according to an embodiment of the present invention.
13 is a perspective view schematically showing an integrated catalyst unit having a front hole formed in the aftertreatment apparatus for a lean burn engine according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

In addition, in various embodiments, components having the same configuration will be representatively described in one embodiment by using the same reference numerals, and in other embodiments, only configurations different from the one embodiment will be described.

Note that the drawings are schematic and have not been drawn to scale. Relative dimensions and ratios of parts in the drawings are exaggerated or reduced in size for clarity and convenience in the drawings, and arbitrary dimensions are merely exemplary and not limiting. In addition, the same reference numerals are used to indicate similar features to the same structure, element, or part appearing in two or more drawings. When a part is referred to as being "on" or "on" another part, it may be directly on top of another part, or other parts may be involved in between.

Examples of the present invention specifically represent one embodiment of the present invention. As a result, various variations of the illustration are expected. Accordingly, the embodiment is not limited to a specific shape in the illustrated area, and includes, for example, a modification of the shape by manufacturing.

Hereinafter, a description will be given of a lean burn engine post-treatment apparatus according to an embodiment of the present invention with reference to FIG. 1.

1 is a schematic diagram of an aftertreatment apparatus for a lean burn engine according to an embodiment of the present invention.

As shown in FIG. 1, the post-treatment apparatus for a lean-burn engine according to an embodiment of the present invention includes an engine 10, an exhaust pipe 20, an ammonia generation catalyst module 35, and an integrated catalyst unit 55. ), and a controller 90.

The engine 10 converts chemical energy into mechanical energy by burning a mixture of fuel and air. The engine 10 is connected to the intake manifold 16 to receive air into the combustion chamber 12, and exhaust gas generated in the combustion process is collected in the exhaust manifold 18 and then discharged out of the engine 10. . The combustion chamber 12 is equipped with an ignition plug 14 to ignite the mixer in the combustion chamber 12. The engine 10 may be a gasoline engine. Depending on the type of gasoline engine, fuel may be injected directly into the combustion chamber 12 or a mixer may be supplied to the combustion chamber 12 through the intake manifold 16. Also, the engine 10 may be a lean-burn engine. Therefore, the engine 10 is operated at a soft air-fuel ratio except for special driving conditions.

The exhaust pipe 20 is connected to the exhaust manifold 18 to discharge exhaust gas to the outside of the vehicle. The exhaust pipe 20 is equipped with an ammonia generation catalyst module 35 and an integrated catalyst unit 55 to purify or remove the emission contained in the exhaust gas.

The ammonia production catalyst module 35 includes a three-way catalyst (TWC) 30 and an ammonia production catalyst (APC) 40. The three-way catalyst 30 and the ammonia generation catalyst 40 are not limited thereto. It can be placed in one housing. The ammonia generation catalyst module 35 may generate ammonia using nitrogen oxide contained in the exhaust gas or nitrogen oxide stored in the ammonia generation catalyst module 35 at a rich air-fuel ratio. The ammonia generation catalyst module 35 includes an oxygen storage material having an oxygen storage capacity (OSC).

The three-way catalyst 30 is disposed in the exhaust pipe 20 through which the exhaust gas discharged from the engine 10 passes, and harmful substances including carbon monoxide, hydrocarbons, and nitrogen oxides contained in the exhaust gas are removed by an oxidation-reduction reaction. Changes to harmless ingredients. In particular, the three-way catalyst 30 may reduce nitrogen oxides contained in the exhaust gas to ammonia when the air-fuel ratio (AFR) is rich. At this time, the three-way catalyst 30 may slip without sufficiently purifying carbon monoxide and hydrocarbons in the exhaust gas. In addition, the three-way catalyst 30 oxidizes carbon monoxide and hydrocarbons contained in the exhaust gas when the air-fuel ratio is soft. Since the three-way catalyst 30 is well known to those skilled in the art, a detailed description thereof will be omitted.

The ammonia generation catalyst 40 is disposed in the exhaust pipe 20 downstream of the three-way catalyst 30. The ammonia generation catalyst 40 stores nitrogen oxides included in the exhaust gas when the air-fuel ratio is low, and generates hydrogen when the air-fuel ratio is rich to desorb the stored nitrogen oxides, and generates ammonia using the desorbed nitrogen oxides and the generated hydrogen. do.

In one aspect, the ammonia generation catalyst 40 is based on the total weight, 0.4 to 0.9% by weight of platinum (Pt), 0.057 to 0.3% by weight of palladium (Pd), 0.03 to 0.1% by weight of rhodium (Rh) , 5.0 to 15.0 wt% of barium (Ba), 10 to 30 wt% of ceria (CeO ₂ ), 48.7 to 84.513 wt% of magnesium oxide (MgO) and alumina (Al ₂ O ₃ ) composite, 0 to 5 wt% % Additives may be included.

In another aspect, the ammonia generation catalyst 40 is based on the total weight of the catalyst, based on the total weight of the catalyst, 0.4 to 0.9% by weight of platinum (Pt), 0.057 to 0.3% by weight of palladium (Pd), 0.03 to 0.1 Wt% of rhodium (Rh), 5.0 to 15.0 wt% of barium (Ba), 10 to 25 wt% of ceria (CeO ₂ ), 48.7 to 79.513 wt% of magnesium oxide (MgO) and alumina (Al ₂ O ₃ ) Of the complex, may contain 0 to 10% by weight of additives.

The additive is added to improve the performance of ceria and alumina, and includes at least one of lanthanum (La), zirconium (Zr), magnesium (Mg), and praseodymium (Pr).

Platinum included in the ammonia generation catalyst 40 oxidizes nitrogen oxides so that the ammonia generation catalyst 40 can store nitrogen oxides. In addition, platinum increases the amount of hydrogen (H ₂ ) generated by the ammonia generation catalyst 40.

Palladium contained in the ammonia generation catalyst 40 improves the heat resistance of the ammonia generation catalyst 40. Since the ammonia-generating catalyst 40 is disposed close to the engine 10, its temperature can rise to 950°C. Therefore, palladium is included in the ammonia generation catalyst 40 to improve its heat resistance.

In order to increase the amount of ammonia and hydrogen produced, the weight ratio of platinum and palladium included in the ammonia generation catalyst 40 may be 3:1 to 7:1. Preferably, the weight ratio of platinum and palladium contained in the ammonia generation catalyst 40 may be 3:1 to 5:1.

Rhodium contained in the ammonia generation catalyst 40 purifies nitrogen oxides contained in the exhaust gas when the air-fuel ratio is stoichiometric AFR.

Barium and ceria contained in the ammonia generation catalyst 40 have a function of storing nitrogen oxides in the form of nitrates. Ceria contains oxygen storage materials.

In addition, ceria increases the production of hydrogen. However, if the ammonia generation catalyst 40 contains a large amount of ceria, the generated ammonia may be oxidized again. Therefore, the ammonia generation catalyst 40 preferably contains 10 to 30% by weight of ceria based on the total weight.

The complex of magnesium oxide and alumina contained in the ammonia generation catalyst 40 functions as a carrier. The magnesium oxide and alumina composite may contain 15 to 25% of magnesium oxide based on the total weight of the magnesium oxide and alumina composite. Magnesium oxide increases the thermal stability of barium.

The integrated catalyst unit 55 may include a selective reduction catalyst (SCR) 50 and a carbon monoxide removal catalyst (CUC) 60.

The selective reduction catalyst 50 is mounted in the exhaust pipe 20 downstream of the ammonia generating catalyst 40. The selective reduction catalyst 50 stores ammonia generated in the ammonia generation catalyst module 35 (i.e., the three-way catalyst 30 and the ammonia generation catalyst 40) when the air-fuel ratio is rich, and the stored ammonia when the air-fuel ratio is soft The nitrogen oxide contained in the exhaust gas is reduced by using. This type of selective reduction catalyst 50 is also referred to as a passive type selective reduction catalyst 50.

The selective reduction catalyst 50 may be composed of one of a zeolite catalyst and a metal catalyst supported on porous alumina, or a combination thereof. The zeolite catalyst is one or more of copper (Cu), platinum (Pt), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), cesium (Cs), and gallium (Ga). The element may be ion-exchanged. Metal catalysts supported on porous alumina include platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), tungsten (W), chromium (Cr), manganese (Mn), iron ( At least one metal among Fe), cobalt (Co), copper (Cu), zinc (Zn), and silver (Ag) may be supported on porous alumina.

The carbon monoxide removal catalyst 60 is mounted in the exhaust pipe 20 downstream of the selective reduction catalyst 50. The carbon monoxide removal catalyst 60 purifies carbon monoxide contained in the exhaust gas. In particular, when the air-fuel ratio is rich, carbon monoxide may slip from the ammonia generation catalyst module 35 (ie, the three-way catalyst 30 and the ammonia generation catalyst 40). Accordingly, the carbon monoxide removal catalyst 60 is mounted at the most downstream of the post-treatment device to prevent carbon monoxide from being discharged to the outside of the vehicle. The carbon monoxide removal catalyst 60 may be one in which platinum (Pt), palladium (Pd), rhodium (Rh), barium (Ba), and the like are supported on ceria (CeO ₂ ) and alumina (Al ₂ O ₃ ).

In one aspect, the carbon monoxide removal catalyst 60 comprises 0.2 to 1.5% by weight of platinum (Pt), 0 to 0.4% by weight of palladium (Pd), and 0 to 0.4% by weight of rhodium (Rh) based on the total weight. , 0 to 5.0% by weight of barium (Ba), 40 to 90% by weight of ceria (CeO ₂ ), 9.8 to 59.8% by weight of alumina (Al ₂ O ₃ ), 0 to 10% by weight of additives may be included. .

In another aspect, the carbon monoxide removal catalyst 60 comprises 0.2 to 1.5% by weight of platinum (Pt), 0 to 0.4% by weight of palladium (Pd), and 0 to 0.4% by weight of rhodium (Rh) based on the total weight. ), 0 to 5.0 wt% of barium (Ba), 40 to 90 wt% of ceria (CeO ₂ ), 9.8 to 59.8 wt% of alumina (Al ₂ O ₃ ), 0 to 20 wt% of additives have.

The additive is added to improve the performance of ceria and alumina, and includes at least one of lanthanum (La), zirconium (Zr), magnesium (Mg), and praseodymium (Pr).

The carbon monoxide removal catalyst 60 has platinum/ceria as its main component. Here, platinum plays a role of oxidizing carbon monoxide, and ceria contains an oxygen storage material, helping to oxidize carbon monoxide at low temperatures where the air-fuel ratio is rich. Although palladium/alumina plays a similar role to platinum/ceria, it is preferable that the amount of platinum/ceria is higher than that of palladium/alumina in order to improve the low-temperature oxidation ability.

Barium contained in the carbon monoxide removal catalyst 60 serves to remove a trace amount of nitrogen oxides that cannot be removed by the selective reduction catalyst 50 when the air-fuel ratio is soft.

Rhodium contained in the carbon monoxide removal catalyst 60 is for promoting reduction of nitrogen oxides when the air-fuel ratio is rich.

The exhaust pipe 20 may be equipped with a plurality of sensors 32, 34, 36, 62, 64 for detecting the air-fuel ratio of the exhaust gas and the operation of the catalysts 30, 40, 50, 60.

The first oxygen sensor 32 is mounted on the exhaust pipe 20 at the front end of the three-way catalyst 30, detects the concentration of oxygen contained in the exhaust gas at the front end of the three-way catalyst 30, and transmits a signal to the controller 90 ). The air-fuel ratio (hereinafter referred to as'λ') of the exhaust gas described here may mean the measured value of the first oxygen sensor 32. In addition, the air-fuel ratio control described herein may mean controlling the air-fuel ratio of the exhaust gas to become a target air-fuel ratio.

The second oxygen sensor 34 is mounted on the exhaust pipe 20 at the rear end of the three-way catalyst 30, and detects the concentration of oxygen contained in the exhaust gas at the rear end of the three-way catalyst 30 and transmits a signal to the controller 90 To pass on.

The third oxygen sensor 36 is mounted on the exhaust pipe 20 at the rear end of the ammonia generating catalyst 40, and oxygen contained in the exhaust gas at the rear end of the ammonia generating catalyst 40 (that is, the ammonia generating catalyst module 35). It detects the concentration of and transmits a signal for this to the controller 90. The measured value of the third oxygen sensor 36 may be used to determine whether the oxygen storage capacity of the ammonia generation catalyst module 35 is exhausted.

The first temperature sensor 62 is mounted on the exhaust pipe 20 at the front end of the selective reduction catalyst 50, detects the temperature of the exhaust gas at the front end of the selective reduction catalyst 50, and transmits a signal to the controller 90. Deliver.

The second temperature sensor 64 is mounted on the exhaust pipe 20 at the rear end of the selective reduction catalyst 50, detects the temperature of the exhaust gas at the rear end of the selective reduction catalyst 50, and sends a signal to the controller 90. Deliver.

In addition to the sensors 32, 34, 36, 62, and 64 described herein, the post-processing apparatus may further include various sensors. For example, an additional temperature sensor may be installed in the exhaust pipe 20 at the front and rear ends of the three-way catalyst 30 to detect the temperature of the exhaust gas at the front and rear ends of the three-way catalyst 30. Further, the post-treatment apparatus further includes a nitrogen oxide sensor, a hydrocarbon sensor, a carbon monoxide sensor, etc. mounted on the exhaust pipe 20, and may detect the concentration of the emission contained in the exhaust gas through these sensors.

The controller 90 is electrically connected to the sensors 32, 34, 36, 62, 64, 66 to receive signals corresponding to values detected by the sensors 32, 34, 36, 62, 64, 66. After receiving, the driving conditions of the vehicle, the air-fuel ratio, the temperature of the catalysts 30, 40, 50, 60, etc. may be determined based on the signals. The controller 90 may control the engine 10 based on the determination to control the ignition timing, fuel injection timing, fuel quantity, and the like. The controller 90 may be implemented by one or more processors operated by a set program, and the set program may be programmed to perform each step of the post-processing method for a lean-burn engine according to an embodiment of the present invention.

2 is a perspective view schematically showing an integrated catalyst unit of a lean-burn engine post-treatment device according to an embodiment of the present invention, and FIG. 3 is It is a plan view shown.

2 and 3, the integrated catalyst unit 55 includes a selective reduction catalyst 50 and a carbon monoxide removal catalyst 60 provided in the integrated catalyst unit case 52. The exhaust pipe 20 is connected to one end of the integrated catalytic unit case 52 and is provided to sequentially connect the selective reduction catalyst 50 and the carbon monoxide removal catalyst 60 inside the integrated catalytic unit case 52.

On the other hand, the integrated catalyst unit 55 is formed in a form surrounding the carbon monoxide removal catalyst 60 so that the high-temperature exhaust gas flowing from the exhaust pipe 20 passes through the surroundings of the carbon monoxide removal catalyst 60 is heated. It includes a chamber 65.

The exhaust pipe 20 is connected to one end and the other end of the carbon monoxide removal catalyst heating chamber 65 inside the integrated catalyst part case 52, and the other end of the carbon monoxide removal catalyst heating chamber 65 is selectively selected by the exhaust pipe 20. It is connected to one end of the reduction catalyst 50. In addition, the other end of the selective reduction catalyst 50 is connected to another end of the carbon monoxide removal catalyst heating chamber 65, the other end is connected to the exhaust pipe 20, the exhaust pipe 20 is an integrated catalyst part case It extends to the outside through the other end of (52).

4 is a view showing an exhaust gas flow of a lean-burn engine post-treatment apparatus according to an embodiment of the present invention.

As shown in FIG. 4, the high-temperature exhaust gas passes through the carbon monoxide removal catalyst heating chamber 65 through the exhaust pipe 20, and then the low-temperature exhaust gas passes through the selective reduction catalyst 50. The low-temperature exhaust gas that has passed through the selective reduction catalyst 50 passes through the carbon monoxide removal catalyst heating chamber 65 and becomes high temperature while absorbing the heat of the high-temperature exhaust gas, and passes through the carbon monoxide removal catalyst 60 provided therein. Is done. High temperature conditions for activation of the carbon monoxide removal catalyst 60 may be maintained by such heat exchange.

5 is a view schematically showing a carbon monoxide removal catalyst heating chamber of a lean burn engine post-treatment apparatus according to an embodiment of the present invention, and FIG. 6 is a carbon monoxide removal of a lean burn engine post-treatment apparatus according to an embodiment of the present invention. It is a diagram schematically showing the integrated catalyst unit after partially cutting the catalyst heating chamber, and FIG. 7 is a view schematically showing the carbon monoxide removal catalyst heating chamber after partial cutting of the post-treatment apparatus for a lean burn engine according to an embodiment of the present invention.

5 to 7, the carbon monoxide removal catalyst 60 may be contained in the carbon monoxide removal catalyst can 63, and the carbon monoxide removal catalyst heating chamber 65 is high temperature flowing from the exhaust pipe 20. The exhaust gas of may be formed to surround the carbon monoxide removal catalyst can 63 so that the exhaust gas passes through the outer surface of the carbon monoxide removal catalyst can 63.

FIG. 8 is a plan view schematically showing an integrated catalyst unit after removing a carbon monoxide removal catalyst heating chamber of a post-treatment apparatus for a lean-burn engine according to an embodiment of the present invention, and FIG. 9 is A perspective view schematically showing the integrated catalyst unit after removing the carbon monoxide removal catalyst heating chamber of the treatment device, FIG. 10 is a cross-sectional view of the carbon monoxide removal catalyst can taken along line AA of FIG. 8, and FIG. 11 is It is a view showing an enlarged surface of a carbon monoxide removal catalyst can.

As shown in FIGS. 8 to 11, the carbon monoxide removal catalyst can 63 may be formed in a streamlined shape. The cross-sectional shape of the carbon monoxide removal catalyst can 63 cut along the line AA of FIG. 8 is as shown in FIG. 10, wherein the rear end of the carbon monoxide removal catalyst can 63 has a smaller radius than the front end based on the exhaust gas flow direction. It can be formed to have. When the cross-sectional shape of the conventional carbon monoxide removal catalyst can is in the shape of a circle, there is a problem in that a vortex is generated at the rear end of the can and the exhaust gas back pressure increases, but the shape of the can 63 according to an embodiment of the present invention is By applying a streamlined shape formed so that the rear end of the can 63 has a smaller radius than the front end, the generation of eddy current at the rear end of the can 63 can be reduced, thereby reducing the exhaust gas back pressure.

Meanwhile, referring to FIG. 11, which is an enlarged view of the surface of the carbon monoxide removal catalyst can 63 in the portion'B' of FIG. 9, the outer surface of the carbon monoxide removal catalyst can 63 is fin along the flow direction of the exhaust gas. ) A plurality of patterns may be formed. That is, by applying a fine fin-shaped pattern to the outer surface of the carbon monoxide removal catalyst can 63, the exhaust gas flow can be smoothly guided, and the exhaust gas back pressure at the rear end of the can 63 can be reduced.

Meanwhile, the carrier of the carbon monoxide removal catalyst 60 may be made of a metal carrier. Accordingly, the heat transfer efficiency of the carbon monoxide removal catalyst 60 may be increased.

In addition, the integrated catalyst part case 52 may be disposed under the vehicle. The integrated catalytic unit case 52 includes a selective reduction catalyst 50 and a carbon monoxide removal catalyst 60 inside to keep the carbon monoxide removal catalyst 60 warm, and the selective reduction catalyst 50 and the carbon monoxide removal catalyst 60 Protection, and the aesthetics of the lower part of the vehicle can be improved.

12 is a perspective view schematically showing an integrated catalyst unit having a rear hole of a lean-burn engine post-treatment apparatus according to an embodiment of the present invention, and FIG. 13 is a diagram illustrating a lean-burn engine post-treatment apparatus according to an embodiment of the present invention. It is a perspective view schematically showing an integrated catalyst unit having a front hole.

12 and 13, a baffle 58 for partitioning the positions of the carbon monoxide removal catalyst heating chamber 65 and the selective reduction catalyst 50 is provided inside the integrated catalyst part case 52 Can be. By separating the internal structure of the integrated catalyst part case 52 with the baffle 58, it is possible to maintain the heating and thermal insulation effect of the carbon monoxide removal catalyst 60.

Meanwhile, the front hall 57 and the rear are connected to the inside and outside of the integrated catalytic unit case 52 at the front and rear ends of the region where the selective reduction catalyst 50 partitioned by the baffle 58 is located. Each of the holes 59 may be formed. When the exhaust gas temperature at the front end of the selective reduction catalyst 50 is high, a front hole 57 and a rear hole 59 are formed at the front and rear ends of the integrated catalyst case 52 to lower the temperature of the peripheral portion of the selective reduction catalyst 50. Through the inflow of running wind is induced, the cooling effect of the selective reduction catalyst 50 can be maximized.

As described above, according to the present invention, by applying a carbon monoxide removal catalyst (CUC) and a selective reduction catalyst (SCR), it is possible to improve the exhaust gas purification performance of the next generation gasoline lean burn engine.

In addition, by improving the ammonia (NH3) storage capacity of the selective reduction catalyst, it is possible to improve the driving fuel efficiency of a gasoline lean burn engine vehicle by reducing the rich combustion conditions for artificial generation of ammonia.

In addition, by placing the position of the selective reduction catalyst at the rear end of the exhaust system layout, durability of the catalyst from high temperature heat fatigue can be increased.

In addition, by maintaining a high temperature condition for activating the carbon monoxide removal catalyst through the carbon monoxide removal catalyst heating chamber, it is possible to reduce the amount of precious metal loading of the carbon monoxide removal catalyst and reduce the cost.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the embodiments of the present invention are easily changed by those of ordinary skill in the art to which the present invention pertains. It includes all changes to the extent deemed acceptable.

10: engine 12: combustion chamber
14: spark plug 16: intake manifold
18: exhaust manifold 20: exhaust pipe
30: three-way catalyst 32: first oxygen sensor
34: second oxygen sensor 35: ammonia generation catalyst module
36: third oxygen sensor 40: ammonia generation catalyst
50: selective reduction catalyst 52: integrated catalyst part case
55: integrated catalyst part 57: front hole
58: baffle 59: rear hall
60: carbon monoxide removal catalyst 62: first temperature sensor
63: carbon monoxide removal catalyst can 64: second temperature sensor
65: carbon monoxide removal catalyst heating chamber
90: controller

Claims (10)

An exhaust pipe connected to the lean burn engine through which exhaust gas generated from the lean burn engine flows;
An ammonia generation catalytic module mounted on the exhaust pipe and purifying the emission contained in the exhaust gas, and generating ammonia using nitrogen oxide contained in the exhaust gas or nitrogen oxide stored therein when the air-fuel ratio is high;
An integrated catalyst unit mounted on an exhaust pipe downstream of the ammonia generation catalyst module, reducing nitrogen oxides contained in the exhaust gas and purifying carbon monoxide contained in the exhaust gas; And
And a controller configured to detect information on the air-fuel ratio and temperature of the exhaust gas, and to control the air-fuel ratio of the exhaust gas based on the information on the air-fuel ratio and temperature of the exhaust gas. In claim 1,
The integrated catalyst unit,
A selective reduction catalyst (Selective Catalytic Reduction (SCR)) which is mounted on an exhaust pipe downstream of the ammonia generation catalyst module, stores ammonia generated in the ammonia generation catalyst module, and reduces nitrogen oxides contained in the exhaust gas using the stored ammonia. ; And
A post-treatment device for a lean-burn engine, which is mounted on an exhaust pipe downstream of the selective reduction catalyst and includes a carbon monoxide removal catalyst (CO Clean-up Catalyst; CUC) that purifies carbon monoxide contained in exhaust gas. In claim 2,
The selective reduction catalyst and the carbon monoxide removal catalyst are provided inside the case of the integrated catalyst unit,
The integrated catalyst unit is provided in the case of the integrated catalyst unit, is connected to the exhaust pipe, and surrounds the carbon monoxide removal catalyst so that the high-temperature exhaust gas introduced from the exhaust pipe passes past the circumference of the carbon monoxide removal catalyst. A post-treatment device for a lean burn engine comprising a formed carbon monoxide removal catalyst heating chamber. In claim 3,
The carbon monoxide removal catalyst is contained in the carbon monoxide removal catalyst can,
The cross section in a direction parallel to the flow direction of the exhaust gas of the carbon monoxide removal catalyst can is a streamlined shape formed such that the rear end of the carbon monoxide removal catalyst can has a smaller radius than the front end based on the exhaust gas flow direction. Device. In claim 4,
A post-treatment device for a lean-burn engine in which a plurality of fin-shaped patterns are formed on the outer surface of the carbon monoxide removal catalyst can along the flow direction of the exhaust gas. In claim 3,
The carrier of the carbon monoxide removal catalyst is a metal carrier, a post-treatment device for a lean burn engine. In claim 3,
The integrated catalyst part case is a post-treatment device for a lean burn engine disposed under a vehicle. In claim 3,
Inside the integrated catalyst part case,
A post-treatment device for a lean-burn engine provided with a baffle for partitioning the carbon monoxide removal catalyst heating chamber and the selective reduction catalyst. In claim 8,
The integrated catalyst part case,
For a lean-burn engine in which a front hall and a rear hall are respectively formed so that the inside and outside of the integrated catalytic unit case communicate with each other at the front and rear ends of the region in which the selective reduction catalyst is located divided by the baffle Post-treatment device. In claim 1,
The ammonia generation catalyst module,
Three-Way Catalyst (TWC) for purifying hydrocarbons, carbon monoxide, and nitrogen oxides contained in exhaust gas; And
It is installed in the exhaust pipe downstream of the three-way catalyst, and when the air-fuel ratio is low, it stores nitrogen oxide, and when the air-fuel ratio is high, it generates hydrogen to desorb the stored nitrogen oxide and generate ammonia using the desorbed nitrogen oxide and the generated hydrogen. A lean-burn engine post-treatment device comprising an ammonia production catalyst (APC).

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