WO2016171366A1

WO2016171366A1 - Exhaust gas post-processing device and method therefor

Info

Publication number: WO2016171366A1
Application number: PCT/KR2015/013472
Authority: WO
Inventors: 이대훈; 송영훈; 김관태; 변성현; 조성권
Original assignee: 한국기계연구원
Priority date: 2015-04-24
Filing date: 2015-12-09
Publication date: 2016-10-27

Abstract

The objective of the present invention is to provide an exhaust gas post-processing device, which simplifies an exhaust gas post-processing system so as to lower manufacturing costs and reduce installation space. The exhaust gas post-processing device according to one embodiment of the present invention comprises: an exhaust pipe allowing the exhaust gas of an engine to flow therethrough; a hydrocarbon selective catalytic reduction (HC SCR) provided in the exhaust pipe so as to remove nitrogen oxides contained in the exhaust gas; and a plasma reactor connected to the exhaust pipe between the engine and the HC SCR so as to modify fuel, thereby generating a reducing agent of hydrogen and an HC species or combusting the fuel.

Description

Exhaust gas aftertreatment device and method

The present invention relates to an exhaust gas aftertreatment apparatus and a method for simplifying the exhaust gas aftertreatment system.

As environmental regulations tighten, various exhaust gas aftertreatment devices have been proposed. These exhaust aftertreatment units have a combination of devices for treating particulate matter (PM) and nitrogen oxides (NOx), respectively.

In this case, the configuration of the exhaust gas aftertreatment device is complicated and bulky. For example, the exhaust gas aftertreatment device may include a urea water selective catalytic reduction (SCR) for supplying ammonia to remove NOx. In this case, the urea water storage device, the urea water decomposition device and An additional urea water injection device is needed.

That is, diesel exhaust catalyst (DOC), diesel particulate filter (DPF), selective catalytic reduction (SCR) and ammonia oxidation catalyst (AOC) Are sequentially installed, and the urea water storage device, the urea water decomposition device and the urea water injection device are sequentially installed and connected to the urea water SCR.

Therefore, the exhaust gas aftertreatment device increases the manufacturing cost by additional devices connected to the urea water SCR to remove NOx, and requires a large installation space.

On the other hand, small and medium-sized vehicles remove nitrogen oxides (NOx) contained in the exhaust gas of the engine, adopt a nitrogen oxide occlusion catalyst (LNT, lean NOx trap), or urea water selective catalytic catalyst (Urea SCR, selective catalytic) reduction is adopted.

However, in order to respond to more stringent regulations such as EURO VI or later emissions control, especially real driving emissions (RDE), a system can be added that removes NOx from existing technology. Needs to be.

For example, even in medium and large vehicles, it is necessary to construct a system with a lower cost and simple structure while having a NOx removal rate equivalent to that of a urea water selective reduction catalyst (Urea SCR).

The nitrogen oxide storage catalyst (LNT) occupies NOx due to the characteristics of the engine during lean burn conditions of the engine, and periodically forms a rich burn condition in the engine to reduce NOx that is desorbed.

In the case of over-combustion conditions, the fuel may be additionally injected after combustion of the equivalence ratio in the engine to form a reducing agent in the LNT, or by installing a separate fuel injector in the exhaust pipe and injecting the fuel in front of the LNT as the reducing agent. When the nitrogen oxide storage catalyst (LNT) is applied, fuel consumption may be lowered and engine burden may be generated due to frequent excessive combustion conditions of the engine.

In addition, urea water selective reduction catalyst (Urea SCR) has high de-NOx performance but denitrification performance in high temperature condition of 220 ~ 230 ° C and lower NOx treatment efficiency in low temperature condition.

A separate urea tank and a urea injector are required, and in some cases, a hydrolysis reactor for separating ammonia (NH ₃ ) from urea water may be required. In the case of applying the urea selective reduction catalyst (Urea SCR), due to the complexity of the system, the price of the device may be increased and the installation space of the device may be increased in a vehicle.

One aspect of the present invention is to provide an exhaust gas after-treatment apparatus that simplifies the exhaust gas after-treatment system to reduce manufacturing costs and reduce installation space.

In addition, it is to provide an exhaust gas after-treatment apparatus that reduces the fuel economy of the engine and the burden on the engine, secures a high denitrification rate, and has a denitrification performance even at low temperature conditions.

In addition, another aspect of the present invention to provide an exhaust gas after-treatment method for the post-treatment of the exhaust gas of the engine using the exhaust gas after-treatment device.

Exhaust gas after-treatment apparatus according to an embodiment of the present invention, an exhaust pipe for circulating the exhaust gas of the engine, a hydrocarbon selective reduction catalyst (HC SCR) provided in the exhaust pipe to remove nitrogen oxides contained in the exhaust gas, and the And a plasma reactor connected to the exhaust pipe between the engine and the hydrocarbon selective reduction catalyst to reform fuel to produce a reductant of hydrogen and hydrocarbon (HC) species or to combust the fuel.

The exhaust pipe further includes a particulate particulate filter (DPF, diesel particulate filter) for trapping and burning particulate matter (PM, particulate matter) contained in the exhaust gas, the particulate filter is the hydrocarbon selective reduction catalyst It is built.

The hydrocarbon may have a carbon number of C1 to C11.

The soot filtration filter includes a case connected to the exhaust pipe, a ceramic carrier embedded in the case and forming an exhaust gas passage, and a plug alternately closing both ends of the ceramic carrier, and the hydrocarbon selective reduction catalyst (HC). SCR) may be formed as a coating on the exhaust gas passage wall of the ceramic carrier.

Exhaust gas after-treatment apparatus according to an embodiment of the present invention may further include a selective reduction catalyst (SCR) provided in the exhaust pipe at the rear of the smoke filter.

Exhaust gas after-treatment apparatus according to another embodiment of the present invention is provided in the exhaust pipe behind the hydrocarbon selective reduction catalyst, the nitrogen oxide storage catalyst for removing the nitrogen oxide remaining in the exhaust gas via the hydrocarbon selective reduction catalyst It may further include (LNT).

The hydrocarbon may have a carbon number of C1 to C5.

Exhaust gas after-treatment method according to an embodiment of the present invention, by supplying fuel and air to the plasma reactor in the normal operation mode to reform the fuel to the first calorific value (partial oxidation conditions) selectively hydrocarbon (HC) species (species) ) And a first step of producing a large amount of hydrogen, a second step of supplying the produced hydrogen and hydrocarbon species on a hydrocarbon selective reduction catalyst (HC SCR) provided in the soot filtration filter (DPF), the normal operation When the differential pressure in the exhaust pipe due to the elapsed time set in the mode or the particulate matter accumulated on the particulate filter exceeds a predetermined pressure, the particulate matter (PM) removal mode is switched to the particulate matter (PM) removal mode. A third step of producing a second calorific value higher than the first calorific value, and repeatedly the normal operation mode and the particulate matter (PM) removal mode And a fourth step of switching to.

The first step may produce hydrocarbon (HC) species having a carbon number of C 1 to C 11 and hydrogen to partially oxidize or decompose light oil to function as a reducing agent.

In the second step, the produced hydrogen and hydrocarbon species may act as a reducing agent on the hydrocarbon selective reduction catalyst (HC SCR) to reduce nitrogen oxide (NOx) included in exhaust gas to nitrogen (N ₂ ).

In the third step, the particulate matter accumulated on the hydrocarbon selective reduction catalyst (HC SCR) of the particulate filter (DPF) by a combustion reaction by increasing the ratio of fuel to air in the plasma reactor compared to the normal operation mode ( PM) can be removed by burning.

Exhaust gas after-treatment method according to another embodiment of the present invention, the first step of producing a large amount of hydrocarbon (HC) species and hydrogen by reforming the fuel by supplying fuel and air to the reformer in lean combustion conditions, The second step of supplying the produced hydrogen and hydrocarbon species to the selective catalytic reduction (HC SCR) for circulating the exhaust gas, the nitrogen oxide storage catalyst disposed behind the hydrocarbon selective reduction catalyst (HC SCR) ( LNT) circulating the exhaust gas via the hydrocarbon selective reduction catalyst in step 3 ′, and the fourth step of switching to lean combustion conditions after the engine operation is switched to rich combustion conditions after a predetermined time in lean combustion conditions. It includes.

In the first step, the hydrogen and the hydrocarbon (HC) species having a carbon number of C1 to C5 and hydrogen acting as a reducing agent may be produced by partially oxidizing or cracking the diesel oil.

In the second step, after the hydrocarbon selective reduction catalyst (HC SCR) is activated, the produced hydrogen and hydrocarbon species act as a reducing agent on the hydrocarbon selective reduction catalyst (HC SCR), so that the nitrogen oxide contained in the exhaust gas ( NOx) can be reduced to nitrogen (N ₂ ).

In the third step, before the hydrocarbon selective reduction catalyst HC SCR is activated, the nitrogen oxide contained in the exhaust gas may be occluded in the nitrogen oxide storage catalyst LNT.

As such, one embodiment of the present invention includes a hydrocarbon selective reduction catalyst in a soot filtration filter, and reforms the fuel in a plasma reactor to selectively produce hydrogen and hydrocarbon species (repeating agents) or produce a high temperature. It is possible to remove nitrogen oxides (NOx) from the hydrocarbon selective reduction catalyst with a reforming agent modified at, and to oxidatively remove particulate matter of the soot filtration filter at high temperature in the particulate matter removal mode.

Thus, one embodiment of the present invention can remove additional devices of the prior art for removing NOx contained in exhaust gas. That is, the manufacturing cost of the exhaust gas aftertreatment device is lowered and the installation space may be reduced when applied to a vehicle.

In addition, an embodiment of the present invention, the exhaust pipe is equipped with a hydrocarbon selective reduction catalyst (HC SCR) and nitrogen oxide storage catalyst (LNT) in sequence, and the reducing agent of the hydrogen and hydrocarbon species modified in the reformer is a hydrocarbon selective reduction catalyst ( HC SCR) to remove nitrogen oxides, thereby reducing the fuel economy and engine burden.

That is, in one embodiment, the hydrocarbon selective reduction catalyst (HC SCR) is activated during daily operation to reduce nitrogen oxide discharged from the engine, and only nitrogen oxide that is not reduced in the hydrocarbon selective reduction catalyst (HC SCR) is occluded. It is possible to significantly increase the reduction operation cycle of the nitrogen oxide storage catalyst by occluding in the catalyst (LNT), and also through nitrogen oxide storage catalyst in low temperature conditions where the hydrocarbon selective reduction catalyst (HC SCR) is not activated, such as cold startup. By occluding the oxide, it is possible to secure a means for removing nitrogen oxides in the exhaust gas under any conditions. That is, the denitrification performance can be ensured even at low temperature conditions.

Through this process, the fuel efficiency of the engine can be improved and the burden on the engine can be reduced compared to the existing oxide removing device.

1 is a block diagram of an exhaust gas aftertreatment apparatus according to a first embodiment of the present invention.

2 is a cross-sectional view of the plasma reactor applied to FIG.

3 is a cross-sectional view of a diesel particulate filter (DPF) applied to FIG. 1.

4 is a block diagram of an exhaust gas aftertreatment apparatus according to a second embodiment of the present invention.

5 is a configuration diagram of an exhaust gas aftertreatment apparatus according to a third exemplary embodiment of the present invention.

6 is a flowchart illustrating an exhaust gas post-treatment method according to an embodiment of the present invention.

7 is a flow chart of the exhaust gas after-treatment method according to another embodiment of the present invention.

8 is a graph comparing the lean and excessive combustion conditions according to another embodiment of the present invention and the prior art.

Figure 9 is a graph comparing the denitrification performance according to another embodiment of the present invention and the prior art.

Description of the sign

1, 2, 3: exhaust gas aftertreatment device 10: engine

20: exhaust pipe 30: soot filtration filter (DPF)

31: case 32: ceramic carrier

33: Plug 37: Hydrocarbon selective reduction catalyst (HC SCR)

40: plasma reactor 41: housing

42: electrode 43: insulating member

44: oxidant supply port 45: surge chamber

46: fuel supply port 50: nitrogen oxide storage catalyst (LNT)

60: selective reduction catalyst (SCR)

G: discharge gap P: exhaust gas passage

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like elements throughout the specification.

1 is a block diagram of an exhaust gas aftertreatment apparatus according to a first embodiment of the present invention. Referring to FIG. 1, the exhaust gas aftertreatment apparatus 1 according to the first embodiment includes an exhaust pipe 20 through which exhaust gas from the engine 10 flows, and a soot filtration filter (DPF, diesel) provided in the exhaust pipe 20. particulate filter 30 and plasma reactor 40.

The soot filtration filter 30 is installed in the exhaust pipe 20 to collect particulate matter (PM) contained in the exhaust gas while circulating the exhaust gas. In addition, the soot filtration filter 30 removes nitrogen oxides with a reducing agent of hydrogen and hydrocarbon (HC) species supplied from the plasma reactor 40, and burns particulate matter at a high temperature supplied from the plasma reactor 40. It is configured to be removable.

The plasma reactor 40 is connected to the exhaust pipe 20 between the engine 10 and the soot filtration filter 30 to reform the fuel to produce a reducing agent of hydrogen and hydrocarbon species, or to burn the fuel. It is configured to produce high temperatures. For example, the hydrocarbon species may have a carbon number of C1 to C11. The plasma reactor 40 produces a reducing agent under the first calorific value corresponding to the partial oxidation condition by supplying an air amount smaller than the combustion condition, or generates combustion heat generated by supplying excess air than the reducing agent producing condition as the second calorific value condition. It is supplied to the soot filtration filter 30 to burn particulate matter.

2 is a cross-sectional view of the plasma reactor applied to FIG. Referring to FIG. 2, the plasma reactor 40 generates a plasma to produce a reducing agent from the fuel and supplies it to the soot filtration filter 30, thereby removing the NOx contained in the exhaust gas from the soot filtration filter 30. .

The plasma reactor 40 may be configured to generate plasma with a rotating flow arc. For example, the plasma reactor 40 includes a housing 41 connected to the exhaust pipe 20, and an electrode 42 embedded in the housing 41 and forming a discharge gap G between the inner surface of the housing 41. ).

When the housing 41 is electrically grounded and a voltage HV is applied to the electrode 42, a rotating flow arc is generated in the discharge gap G using an oxidant (gas or gas containing oxygen) as the discharge gas. By supplying fuel to this rotating flow arc, the fuel is reformed with a reducing agent of hydrogen and hydrocarbon (HC) species or burned to a high temperature and ejected out of the housing 41.

One side of the housing 41 is sealed through the insulating member 43, and the electrode 42 is installed in the insulating member 43. Therefore, the insulating member 43 electrically insulates the housing 41 and the electrode 42, thereby enabling the generation of an arc in the discharge gap G.

The housing 41 includes an oxidant supply port 44 for supplying an oxidant between the insulating member 43 and the discharge gap G, and supplies a surge chamber 45 connected to the oxidant supply port 44 to the oxidant supply port. It is provided in the outskirts of (44).

The oxidant supply port 44 is formed in a tangential direction from the housing 41 toward the electrode 42 (not shown) to induce a rotational flow of the oxidant supplied into the housing 41. The surge chamber 45 temporarily stores the supplied oxidant to make the amount of the oxidant rotated and supplied to the plurality of oxidant supply ports 44 uniform.

The housing 41 also includes a fuel supply port 46 in a cylinder corresponding to the end of the electrode 42. The fuel supply port 46 may supply a part of the fuel supplied to the engine 10.

The plasma reactor 40 produces a reducing agent of hydrogen and hydrocarbon (HC) species in a plasma reaction by a rotary flow arc of the fuel supplied to the fuel supply port 46 and the oxidant supplied to the oxidant supply port 44, or the fuel By burning it to produce high temperature. Since the housing 41 of the plasma reactor 40 is connected to the exhaust pipe 20, the generated reducing agent or high temperature is supplied to the soot filtration filter 30 through the exhaust pipe 20.

3 is a cross-sectional view of a diesel particulate filter (DPF) applied to FIG. 1. Referring to FIG. 3, a soot filtration filter (DPF) 30 incorporates a hydrocarbon selective reduction catalyst (HC SCR) 37 for circulating exhaust gas.

The soot filtration filter 30 includes a case 31 connected to the exhaust pipe 20, a ceramic carrier 32 embedded in the case 31 and forming an exhaust gas passage P, and both ends of the ceramic carrier 32. And a plug 33 which alternately closes.

The hydrocarbon selective reduction catalyst (HC SCR) 37 may be formed as a coating layer on the exhaust gas passage P wall of the ceramic carrier 32. Therefore, the hydrocarbon selective reduction catalyst 37 does not occupy a separate installation space and does not increase the volume of the soot filtration filter 30. For example, the hydrocarbon selective reduction catalyst (HC SCR) 37 may be formed of Ag / Al ₂ O ₃ or Cu / Zeolite.

In the normal operation mode, a reducing agent of hydrogen and hydrocarbon (HC) species generated in the first calorific value in the plasma reactor 40 is supplied to the soot filtration filter 30 so that the hydrocarbon selective reduction catalyst (HC SCR) 37 is exhaust gas. the NOx contained in the denitration acts to convert N _2. The plasma reactor 40 and the hydrocarbon selective reduction catalyst 37 can reduce manufacturing costs and installation space by eliminating additional components for removing nitrogen oxides.

In the particulate matter removing mode, the high temperature generated by the second calorific value in the plasma reactor 40 is supplied to the soot filtration filter 30 to burn off particulate matter deposited in the exhaust gas passage P.

Hereinafter, a second embodiment of the present invention will be described. The same configuration as that of the first embodiment will be omitted, and different configurations will be described.

4 is a block diagram of an exhaust gas aftertreatment apparatus according to a second embodiment of the present invention. Referring to FIG. 4, the exhaust gas aftertreatment apparatus 2 according to the second embodiment further includes a selective reduction catalyst (SCR) 60 in the exhaust gas aftertreatment apparatus 1 of the first embodiment.

The selective reduction catalyst (SCR) 60 is installed in the exhaust pipe 20 at the rear of the soot filtration filter 30, and the denitrification action of the hydrocarbon selective reduction catalyst (HC SCR) 37 provided in the soot filtration filter 30 is provided. In addition, it is possible to give a denitrification ability to further remove residual nitrogen oxides.

Hereinafter, a third embodiment of the present invention will be described. The same configuration as that of the first embodiment will be omitted, and different configurations will be described.

5 is a configuration diagram of an exhaust gas aftertreatment apparatus according to a third exemplary embodiment of the present invention. Referring to FIG. 5, the exhaust gas aftertreatment apparatus 3 according to the third embodiment includes a hydrocarbon selective reduction catalyst (HC SCR) provided in the exhaust pipe 20 through which the exhaust gas of the engine 10 flows, and the exhaust pipe 20. ) 37, nitrogen oxide storage catalyst (LNT) 50, and plasma reactor 40.

Hydrocarbon selective reduction catalyst (HC SCR) 37 is installed in the exhaust pipe 20 and is configured to remove nitrogen oxides contained in the exhaust gas. The exhaust gas aftertreatment apparatus 1 according to the first embodiment is a type in which a hydrocarbon selective reduction catalyst (HC SCR) 37 is embedded in a soot filtration filter (DPF). The aftertreatment device 3 does not include a soot filtration filter (DPF), and may be separately provided with a hydrocarbon selective reduction catalyst (HC SCR) 37.

The nitrogen oxide storage catalyst (LNT) 50 is installed in the exhaust pipe 20 behind the hydrocarbon selective reduction catalyst (HC SCR) 37, and the nitrogen oxide remaining in the exhaust gas via the hydrocarbon selective reduction catalyst 37 is provided. Remove it.

The nitrogen oxide storage catalyst (LNT) 50 further increases the denitrification rate of the hydrocarbon selective reduction catalyst (HC SCR) 37 and expands the denitrification temperature range throughout the exhaust aftertreatment apparatus.

The plasma reactor 40 is configured to reform the fuel to produce a reducing agent of hydrogen and hydrocarbon (HC) species, and is connected to the exhaust pipe 20 in front of the hydrocarbon selective reduction catalyst 37. Therefore, the reducing agent of hydrogen and hydrocarbon (HC) species produced in the plasma reactor 40 is supplied to the hydrocarbon selective reduction catalyst (HC SCR) 37 together with the exhaust gas. For example, the hydrocarbon produced in the plasma reactor 40 may have a carbon number of C1 to C5.

6 is a flowchart illustrating an exhaust gas post-treatment method according to an embodiment of the present invention. 6 and the first embodiment, the exhaust gas post-treatment method of the embodiment includes the first step (ST1) to the fourth step (ST4).

In the first step ST1, fuel and air are supplied to the plasma reactor 40 in the normal operation mode to reform the fuel at a first calorific value to produce a large amount of hydrocarbon (HC) species and hydrogen.

For example, the first step ST1 may partially hydrogenate or decompose light oil to produce hydrocarbon (HC) species and hydrogen having a carbon number of C1 to C11 that functions as a reducing agent.

In the second step ST2, the produced hydrogen and hydrocarbon species are supplied onto a hydrocarbon selective reduction catalyst (HC SCR) 37 provided in the soot filtration filter (DPF) 30.

For example, in the second step (ST2), the produced hydrogen and hydrocarbon species act as a reducing agent on a hydrocarbon selective reduction catalyst (HC SCR) 37 to convert nitrogen oxide (NOx) contained in exhaust gas to nitrogen (N _2). Reduction).

In the third step ST3, when the differential pressure in the exhaust pipe 20 caused by the particulate matter accumulated on the smoke filtration filter 30 or the time set in the normal operation mode is higher than the set pressure, the particulate matter removing mode is switched. The plasma reactor 40 produces a second calorific value at a temperature higher than the first calorific value of the normal operation mode.

For example, the third step ST3 is a hydrocarbon selective reduction catalyst (HC SCR) of the particulate filter (DPF) 30 as a combustion reaction by increasing the ratio of fuel to air in the plasma reactor 40 compared to the normal operation mode. The particulate matter (PM) accumulated on the (37) is burned and removed. The combustion reaction may include a reaction close to the combustion reaction as a reaction capable of burning particulate matter.

The fourth step ST4 repeatedly switches between the normal operation mode and the particulate matter removal mode. Although a separate control unit is not illustrated in the exhaust gas post-treatment method, an engine control unit (not shown) controlling the engine 10 may switch the operation mode of the plasma reactor 40.

7 is a flow chart of the exhaust gas after-treatment method according to another embodiment of the present invention. Referring to FIG. 7, the exhaust gas post-treatment method according to another embodiment includes first step ST1 ′ to fourth step ST4 ′.

In the first stage ST1, fuel and air are reformed by supplying fuel and air to the reformer 50 in lean combustion conditions to produce a large amount of hydrocarbon (HC) species and hydrogen. The first stage ST1 may partially produce hydrogen (HC) species and hydrogen having a carbon number of C1 to C5 which functions as a reducing agent by partially oxidizing or cracking the diesel oil.

The second stage (ST2 ') feeds the produced hydrogen and hydrocarbon species onto a hydrocarbon selective reduction catalyst (HC SCR) which distributes the exhaust gas.

The modified hydrocarbon (HC) species and hydrogen are supplied to the hydrocarbon selective reduction catalyst 37 through the exhaust pipe 20 to denitrify the hydrocarbon selective reduction catalyst 37.

That is, in the second step ST2, after the hydrocarbon selective reduction catalyst (HC SCR) 37 is activated, the produced hydrogen and hydrocarbon species act as a reducing agent on the hydrocarbon selective reduction catalyst 37 to be included in the exhaust gas. Reduced nitrogen oxides (NOx) to nitrogen (N ₂ ).

The third step ST3 is circulating exhaust gas via the hydrocarbon selective reduction catalyst 37 in a nitrogen oxide storage catalyst (LNT) 50 disposed behind the hydrocarbon selective reduction catalyst (HC SCR) 37. Let's do it.

That is, in the third step ST3 ', the nitrogen oxide storage catalyst (LNT) 50 occludes the nitrogen oxide contained in the exhaust gas before the hydrocarbon selective reduction catalyst (HC SCR) 37 is activated. The nitrogen oxide storage catalyst 50 absorbs NOx while the hydrocarbon selective reduction catalyst (HC SCR) 37 does not denitrify, or the residual nitrogen oxide which has not been reduced by the hydrocarbon selective reduction catalyst (HC SCR) 37. It is occluded and reduced to compensate for the denitrification performance of the hydrocarbon selective reduction catalyst (HC SCR) 37.

Therefore, in order to remove nitrogen oxides stored in the nitrogen oxide storage catalyst 50 at a high temperature, the period of the rich combustion conditions for the nitrogen oxide storage catalyst 50 which implements the rich combustion conditions may be significantly longer. That is, the time for driving in the rich combustion condition in the engine is shortened, and the time for driving in the lean burn condition becomes long.

The fourth step ST4 'is switched to the rich combustion condition after the time set in the lean combustion condition, and then to the lean combustion condition after the engine operation.

8 is a graph comparing the lean and excessive combustion conditions according to another embodiment of the present invention and the prior art. Referring to FIG. 8, during the same operation time of the engine 10, the prior art on the left shows a short period of rich combustion that removes nitrogen oxides from the nitrogen oxide storage catalyst.

In contrast, in the embodiment on the right, the rich combustion cycle for removing nitrogen oxide from the nitrogen oxide storage catalyst 50 is very long. Therefore, in one embodiment, the fuel economy of the engine 10 may be improved, and the burden on the engine 10 may be reduced.

Figure 9 is a graph comparing the denitrification performance according to another embodiment of the present invention and the prior art. Referring to FIG. 9, the prior art hydrocarbon selective reduction catalyst (HC SCR) and urea water selective reduction catalyst (Urea SCR) have excellent denitrification performance at relatively high temperature and low denitrification performance at low temperature.

In contrast, another embodiment of the present invention has excellent denitrification performance corresponding to the prior art at high temperature, and at the same time has excellent denitrification performance at low temperature (L1). That is, under the same operating temperature conditions, it will remove more nitrogen oxides than in the prior art.

That is, another embodiment of the present invention may have a high denitrification performance since it occludes the nitrogen oxide in the nitrogen oxide storage catalyst (LNT) 50 before the hydrocarbon selective reduction catalyst (HC SCR) 37 is activated.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

According to an embodiment of the present invention, the manufacturing cost of the exhaust gas aftertreatment device is lowered, and the installation space may be reduced when applied to a vehicle.

Claims

An exhaust pipe for circulating the exhaust gas of the engine;

A hydrocarbon selective reduction catalyst (HC SCR) provided in the exhaust pipe to remove nitrogen oxides contained in the exhaust gas; And

A plasma reactor connected to the exhaust pipe between the engine and the hydrocarbon selective reduction catalyst to reform fuel to produce a reductant of hydrogen and hydrocarbon (HC) species or to combust the fuel

Exhaust gas after-treatment device comprising a.
The method of claim 1,

Diesel particulate filter (DPF), which is provided in the exhaust pipe and collects, burns and removes particulate matter (PM) contained in exhaust gas.

More,

The soot filtration filter is

Exhaust gas after-treatment device containing the hydrocarbon selective reduction catalyst.
The method of claim 2,

The hydrocarbon is

Exhaust gas aftertreatment device having a carbon number of C1 to C11.
The method of claim 2,

The soot filtration filter is

A case connected to the exhaust pipe,

A ceramic carrier embedded in the case and forming an exhaust gas passage;

Plugs for alternately closing both ends of the ceramic carrier

Including,

The hydrocarbon selective reduction catalyst (HC SCR) is

Exhaust gas after-treatment apparatus is formed as a coating layer on the exhaust gas passage wall of the ceramic carrier.
The method of claim 4, wherein

Exhaust gas after-treatment apparatus further comprises a selective reduction catalyst (SCR) provided in the exhaust pipe at the rear of the soot filtration filter.
The method of claim 1,

A nitrogen oxide storage catalyst (LNT) provided in the exhaust pipe behind the hydrocarbon selective reduction catalyst to remove nitrogen oxide remaining in the exhaust gas via the hydrocarbon selective reduction catalyst (LNT).

Exhaust gas after-treatment device further comprising.
The method of claim 6,

The hydrocarbon is

Exhaust gas aftertreatment device having a carbon number of C1 to C5.
Supplying fuel and air to the plasma reactor in the normal operation mode to reform the fuel at a first calorific value to selectively produce a large amount of hydrocarbon (HC) species and hydrogen;

Supplying the produced hydrogen and hydrocarbon species on a hydrocarbon selective reduction catalyst (HC SCR) provided in a soot filtration filter (DPF);

When the differential pressure in the exhaust pipe due to the elapsed time set in the normal operation mode or the particulate matter accumulated on the particulate filter exceeds a predetermined pressure, the particulate matter (PM) removal mode is switched to the normal state in the plasma reactor. A third step of producing a second calorific value higher than the first calorific value in an operation mode; And

A fourth step of repeatedly switching between the normal operation mode and the PM removal mode;

Exhaust gas after-treatment method comprising a.
The method of claim 8,

The first step is

Exhaust gas after-treatment method of producing hydrogen and hydrocarbon (HC) species having a carbon number of C1 to C11 that acts as a reducing agent by partially oxidizing or decomposing light oil.
The method of claim 9,

The second step is

The produced hydrogen and hydrocarbon species act as a reducing agent on the hydrocarbon selective reduction catalyst (HC SCR) to reduce nitrogen oxides (NOx) contained in the exhaust gas to nitrogen (N 2 ).
The method of claim 8,

The third step,

Compared to the normal operation mode, the plasma reactor increases the ratio of fuel to air to burn and remove particulate matter (PM) accumulated on the hydrocarbon selective reduction catalyst (HC SCR) of the particulate filter (DPF) by a combustion reaction. Exhaust gas post-treatment method.
Supplying fuel and air to the reformer under lean combustion conditions to reform the fuel to produce a large amount of hydrocarbon (HC) species and hydrogen;

Supplying the produced hydrogen and hydrocarbon species to a hydrocarbon selective reduction catalyst (HC SCR) for circulating exhaust gas;

A third step of circulating the exhaust gas via the hydrocarbon selective reduction catalyst in a nitrogen oxide storage catalyst (LNT) disposed behind a hydrocarbon selective reduction catalyst (HC SCR); And

A fourth step of switching to the lean combustion condition after the engine operation is switched to the rich combustion condition when the time set in the lean combustion condition has elapsed.

Exhaust gas after-treatment method comprising a.
The method of claim 12,

The first step is

A method for exhaust gas aftertreatment that produces hydrogen and C1 to C5 hydrocarbon species and hydrogen that act as a reducing agent by partially oxidizing or cracking light oil.
The method of claim 13,

The second step is

After the hydrocarbon selective reduction catalyst (HC SCR) is activated,

The produced hydrogen and hydrocarbon species act as a reducing agent on the hydrocarbon selective reduction catalyst (HC SCR) to reduce nitrogen oxides (NOx) included in the exhaust gas to nitrogen (N 2 ).
The method of claim 12,

In the third step,

Before the hydrocarbon selective reduction catalyst (HC SCR) is activated,

Exhaust gas after-treatment method for storing the nitrogen oxide contained in the exhaust gas in the nitrogen oxide storage catalyst (LNT).