KR20220094297A - Reductant injection system for after-treatment of exhaust gas of old diesel vehicle - Google Patents

Abstract

In an after-treatment system of exhaust gas comprising: a diesel oxidation catalyst (DOC) mounted on an exhaust pipe of an internal combustion engine to oxidize hydrocarbon (HC) or carbon monoxide (CO) contained in exhaust gas or to oxidize a soluble organic fraction (SOF) contained in particulate matter, and a selective catalyst reduction (SCR) for purifying nitrogen oxides (NO_x), the present invention provides a reductant injection system for the after-treatment of exhaust gas, comprising: a urea introducing part located at the fore-end of the DOC to introduce an aqueous solution of urea; a urea flow pipe arranged to penetrate the DOC and through which the aqueous solution of urea introduced through the urea introducing part passes; and a urea mixer arranged on an end at a downstream side of the urea flow pipe and mixing the aqueous solution of urea and the exhaust gas. Therefore, provided is a reductant injection system for the after-treatment of exhaust gas, wherein an after-treatment system of exhaust gas can be downsized and the hydrolysis of the aqueous solution of urea can be facilitated.

Description

{REDUCTANT INJECTION SYSTEM FOR AFTER-TREATMENT OF EXHAUST GAS OF OLD DIESEL VEHICLE}

The present invention relates to a reducing agent injection system of an exhaust gas after-treatment system, and more particularly, to a reducing agent injection system of an exhaust gas after-treatment system for purifying exhaust gas emitted from internal combustion engines mounted on ships, generators, etc. as well as vehicles. will be.

In general, the demand for diesel engines capable of high efficiency and high output operation in vehicles, ships, generators, etc. continues to increase. This is because diesel oil is inexpensive and has advantages in terms of fuel efficiency and output.

When driving such a diesel engine, nitrogen oxides (NOx) and particulate matter (PM), which cause air pollution, are included in exhaust gas and are emitted.

As an example, as shown in FIG. 1, the conventional exhaust gas after-treatment system is a Diesel Particulate matter Filter (DPF) for collecting particulates (PM) in order to purify the exhaust gas discharged from the internal combustion engine ( 23), and a Selective Catalyst Reduction (SCR) 22 for purifying nitrogen oxides (NO _x ), and hydrocarbons ( It may include a Diesel Oxidation Catalyst (DOC) 21 that oxidizes HC) or carbon monoxide (CO) or oxidizes soluble organic fraction (SOF) contained in particulate matter.

Since the selective catalytic reduction device 22 uses urea as a reducing agent to reduce or remove nitrogen oxides, the front end of the selective catalytic reduction device 22 is provided with a urea injector 31 for injecting urea into the intermediate pipe. At this time, in order to optimize the urea injection in order to improve the nitrogen oxide reduction ability, between the urea injector 31 and the selective catalytic reduction device 22, water is hydrolyzed by the urea aqueous solution introduced through the urea injector 31 A urea mixer 32 may be included so that the decomposed ammonia is mixed with the exhaust gas and uniformly mixed in a wide range to be introduced into the selective catalytic reduction device 22 (refer to Korean Patent Registration No. 1195799, etc.).

In such a system, as shown in FIG. 1 , catalysts performing each function must exist independently, and thus, there is a problem in that the size or length of the exhaust gas after-treatment system is increased.

Therefore, recently, SDPF (SCR on Diesel Particulate Filter) technology, which provides both DPF and SCR functions, has been applied to the exhaust gas after-treatment system of diesel vehicles to compensate for the disadvantages of this technology. As shown in FIG. 3 , this system is a technology to which the DOC-SDPF-SCR-AOC technology is applied, and is a technology in which the PM capture technology of DPF and the nitrogen oxide reduction technology of SCR are grafted to SDPF. In this case, the SCR catalyst may not be installed depending on the performance of the catalyst and the amount of reduction.

This system also uses urea or ammonia as a reducing agent to remove nitrogen oxides, and the mixer mentioned in Korean Patent Registration No. 1195799, etc. is installed in the exhaust pipe between DOC and SDPF.

As described above, when the selective catalytic reduction device 22 is used to reduce nitrogen oxides in the prior art, the urea injector 31 is required, as well as the selective catalytic reduction device to uniformly mix the hydrolyzed ammonia with the exhaust gas. Since an intermediate pipe is required at the front end of (22), there is a problem in that it cannot be miniaturized by reducing the length or size of the entire exhaust gas after-treatment system.

Accordingly, there is a need for a technology to solve the problem that the exhaust gas post-treatment system having a selective catalytic reduction device cannot be downsized.

KR 10-1195799 B1 KR 10-1369651 B1 KR 10-2122849 B1 KR 10-2028423 B1

An object of the present invention is to provide a reducing agent injection system for an exhaust gas after-treatment system that can downsize the exhaust gas after-treatment system and smoothly cause a hydrolysis reaction of an aqueous urea solution.

In order to solve the above problems, the present invention is mounted on the exhaust pipe of an internal combustion engine to oxidize hydrocarbon (HC) or carbon monoxide (CO) contained in exhaust gas, or soluble organic fraction (SOF) contained in particulate matter. ) In the exhaust gas post-treatment system comprising a diesel oxidation catalyst (Diesel Oxidation Catalyst) for oxidizing and a Selective Catalyst Reduction (SCR) for purifying nitrogen oxides (NO _x ), the diesel Located in front of the oxidation catalyst device, the urea introduction part into which the aqueous urea solution is introduced, a urea flow pipe through which the urea solution introduced through the urea introduction part passes through the diesel oxidation catalyst device, and the urea flow pipe line It is provided at the downstream end, and provides a reducing agent injection system of the exhaust gas post-treatment system including a urea mixer for mixing the urea solution and the exhaust gas.

According to an embodiment, the selective catalytic reduction device may be a Selective Catalyst Reduction-on-Diesel Particulate Filter (SDPF) integrally formed with a particulate collection device for collecting particulate matter and purifying exhaust gas.

According to one embodiment, located at the rear end of the selective catalytic reduction device, an ammonia slip catalyst device (AOC; Ammonia Oxidation Catalyst) for oxidizing and purifying ammonia leaked from the selective catalytic reduction device may be further included.

According to one embodiment, it is located at the rear end of the diesel oxidation catalyst device, further comprising a Diesel Particulate Filter (DPF) for collecting particulates (PM) to purify the exhaust gas, the urea flow pipe may be provided through the diesel oxidation catalyst device and the particulate collection device.

According to an embodiment, the urea introduction unit may be introduced together with high-pressure air so that the urea aqueous solution can pass through the urea flow pipe.

According to an embodiment, the urea flow pipe may be provided along the longitudinal direction at the center of the diesel oxidation catalyst device.

According to an embodiment, the urea flow pipe may be a heat conductor so that heat can be transferred to the urea aqueous solution flowing in the urea flow pipe when the diesel oxidation catalyst device generates heat by a catalytic reaction.

According to an embodiment, the urea mixer includes a tubular body for mixing the urea aqueous solution and the exhaust gas, an inner side along the inner circumferential surface of the body, and a plurality of blades extending toward the selective catalytic reduction device. Doedoe blade mixer, the plurality of blades may have a twisted shape.

According to an embodiment, the urea mixer includes an introduction tube into which the urea aqueous solution is introduced, a head provided at the distal end of the introduction tube and formed to be expanded, and a distal end of the head so that the urea aqueous solution can be sprayed in a radial direction. It may be a radial injection mixer including a hemispherical head cover having a plurality of injection ports.

According to an embodiment, a urea injector for injecting the urea aqueous solution may not be provided between the diesel oxidation catalyst device and the selective catalytic reduction device.

When the urea aqueous solution causes a hydrolysis reaction so that vaporized ammonia reacts with nitrogen oxides of the exhaust gas to be purified into nitrogen and water vapor, the reducing agent injection system of the exhaust gas after-treatment system according to the present invention, urea is diesel Since it is heated by the heat generated during the reaction of the diesel oxidation catalyst device when passing through the oxidation catalyst device, there is an effect that can facilitate hydrolysis.

In addition, since the reducing agent injection system of the exhaust gas post-treatment system according to the present invention does not require a separate urea injection space between the diesel oxidation catalyst device and the selective catalytic reduction device, the exhaust gas post-treatment system can be compact. have.

In addition, when the urea mixer uses a radial injection mixer instead of a blade mixer, there is an effect that can further reduce the space between the diesel oxidation catalyst device and the selective catalytic reduction device.

1 is a block diagram of a conventional exhaust gas after-treatment system.
2 to 5 are block diagrams of a reducing agent injection system of an exhaust gas after-treatment system according to an embodiment of the present invention.
6 is a view showing the overall appearance of the diesel oxidation catalyst device according to an embodiment of the present invention.
7 is a view showing the overall appearance of the blade mixer according to an embodiment of the present invention.
8 is a view showing the overall appearance of the radial injection mixer according to an embodiment of the present invention.
9 is a view showing an embodiment of a urea flow pipe according to an embodiment of the present invention.

Hereinafter, the embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings, but the same or similar components are assigned the same reference numbers regardless of reference numerals, and redundant description thereof will be omitted. The suffixes "module" and "part" for the components used in the following description are given or mixed in consideration of only the ease of writing the specification, and do not have distinct meanings or roles by themselves. In addition, in describing the embodiments disclosed in the present specification, if it is determined that detailed descriptions of related known technologies may obscure the gist of the embodiments disclosed in the present specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are only for easy understanding of the embodiments disclosed in the present specification, and the technical spirit disclosed herein is not limited by the accompanying drawings, and all changes included in the spirit and scope of the present invention , should be understood to include equivalents or substitutes.

When a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but it is understood that other components may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that the other element does not exist in the middle.

The singular expression includes the plural expression unless the context clearly dictates otherwise.

In this specification, terms such as "comprises" or "have" are intended to designate that the features, numbers, steps, operations, components, parts, or combinations thereof described in the specification exist, but one or more other features It should be understood that this does not preclude the existence or addition of numbers, steps, operations, components, parts, or combinations thereof.

2 to 5 are block diagrams of an exhaust gas post-treatment system according to an embodiment of the present invention.

2 to 5, the exhaust gas aftertreatment system according to an embodiment of the present invention is mounted on an exhaust pipe of an internal combustion engine to oxidize hydrocarbon (HC) or carbon monoxide (CO) contained in exhaust gas. Diesel Oxidation Catalyst ( _DOC ) that oxidizes soluble organic components (SOF; Soluble Organic Fraction) contained in or Reduction), but located at the front end of the diesel oxidation catalyst device 21 and provided through the urea introduction part 110 into which the urea aqueous solution is introduced, the diesel oxidation catalyst device 21, and the urea introduction part 110 introduced through A urea flow pipe line 120 through which the urea solution passes, and a urea mixer 130 provided at the downstream end of the urea flow pipe line 120 to mix ammonia hydrolyzed by the urea solution with the exhaust gas. have.

According to an embodiment of the present invention, since a space for urea injection is not separately required between the diesel oxidation catalyst device 21 and the selective catalytic reduction device 22, as in the prior art, the entire exhaust gas after-treatment system is downsized. can do.

However, since the components shown in FIGS. 2 to 5 are not essential, it goes without saying that an exhaust gas aftertreatment system having more or fewer components may be implemented.

Hereinafter, each component will be described.

The particle collecting device 23 is mounted on an exhaust pipe through which the exhaust gas discharged from the engine 10 passes, and the particle collecting device 23 collects most of particulate matter (PM) included in the exhaust gas, and the exhaust pipe It is possible to purify the exhaust gas discharged to the outside.

The particle collecting device 23 may be a filter, that is, a Wall Flow Monoliths type, in which the inlet and outlet of the porous ceramic honeycomb cell are alternately plugged in order to collect particulate matter included in the exhaust gas. The exhaust gas flows into the inlet of the unplugged cell, passes through the particulate matter (PM) collection cell wall formed at the boundary with the unplugged adjacent cell, and flows out to the outlet of the unplugged cell, The cell wall collects particulate matter (PM), and soot particles of the particulate matter are collected in the form of a cake on the wall.

Although the particulate matter collection device 23 physically collects particulate matter in the exhaust gas of the engine 10 using a filter, there is a limit to the amount of collection that can be collected. Through forced regeneration, which burns and removes the captured particulate matter through the

Since the temperature of the exhaust gas differs depending on the operation pattern of the internal combustion engine, the oxidation reaction of particulate matter using the temperature of the exhaust gas has irregular cycles and cannot be reproduced when the exhaust gas temperature is low such as low speed/low load conditions. It is necessary to regenerate soot through an auxiliary heat source.

To this end, a burner (not shown) is positioned on the upstream side of the particle collection device 23 to heat the exhaust gas flowing into the particle collection device 23 to increase the temperature. Electricity or microwaves may be used to heat the exhaust gas, but the type is not particularly limited.

Meanwhile, according to an embodiment of the present invention, a diesel oxidation catalyst (DOC) 21 may be located upstream of the particulate collecting device 23 .

The diesel oxidation catalyst device 21 uses, as a catalyst, a noble metal such as platinum (Pt), palladium (Pd), or rhodium (Rh) on a support of a honeycomb structure made of ceramics using cordierite or the like as a raw material, and oxygen in exhaust gas. (O ₂ ) is used to oxidize hydrocarbons (HC) or carbon monoxide (CO) contained in exhaust gas or oxidize soluble organic fractions (SOF; Souluble Organic Fraction) contained in particulate matter to form water (H ₂ O) and It is a catalyst device that converts carbon dioxide (CO ₂ ) into carbon dioxide (CO 2 ).

In addition, the diesel oxidation catalyst device 21 oxidizes nitrogen monoxide (NO) to produce nitrogen dioxide (NO ₂ ), and the oxidized nitrogen dioxide (NO ₂ ) is oxidized with the carbon captured in the particle collecting device 23 . to cause

The particulate collection device 23 reduces gaseous substances that have not reacted in the diesel oxidation catalyst device 21, and at the same time performs an oxidation reaction with soot (carbon) collected in the filter to convert carbon dioxide and water into soot ( soot) is regenerated (oxidized).

The chemical reaction formula occurring in the diesel oxidation catalyst device 21 is the same as the following Chemical Formula 1, and then the chemical reaction formula occurring in the particulate collecting device 23 located at the rear end of the diesel oxidation catalyst device 21 is the same as the following Chemical formula 2.

[Formula 1]

HC(SOF) + O ₂ → CO ₂ + H ₂ O

HC, CO + O ₂ → CO ₂ + H ₂ O(CO from Engine)

NO + O ₂ → NO ₂

[Formula 2]

C(Soot) + O ₂ → CO/CO ₂

C(Soot) + NO ₂ → CO/CO ₂ + NO

NO + O ₂ → NO ₂

Cㅒ + O ₂ → CO ₂ (CO from Soot)

HC, CO + O ₂ → CO ₂ + H ₂ O (residual gas phase HC, CO)

As described above, when the exhaust gas is low temperature, the combustion rate of particulate matter (PM) by the catalyst is slower than the production rate of particulate matter (PM) generated in the engine 10, so the particulate collecting device 23 located at the rear end Particulate matter (PM) accumulates in the back pressure and increases. After all, there is a limit to only the natural regeneration method using a catalyst, and by increasing the exhaust temperature using a fuel burner, the particulate matter (PM) accumulated in the particulate collection device 23 is burned forcibly to be regenerated, thereby reducing the soot. can

A hydrocarbon injector (not shown) may be located on the upstream side of the diesel oxidation catalyst device 21, and the hydrocarbon injector injects hydrocarbons (HC) into the exhaust pipe, due to the increased carbon monoxide and hydrogen components, the diesel oxidation catalyst device 21 ), heat is generated due to the oxidation of the exhaust gas introduced into the exhaust gas, and the temperature of the exhaust gas flowing into the selective catalytic reduction device 22 is increased. Accordingly, it is possible to reduce ammonia slip and improve the selective reduction catalyst purification performance by maintaining the temperature of the exhaust gas flowing into the selective catalytic reduction device 22 above the active temperature even under low-temperature and low-load rough load conditions.

On the other hand, the selective catalytic reduction device 22 may be positioned at the front or rear end of the particle collecting device 23 .

In the selective catalytic reduction device 22, a zeolite catalyst such as aluminosilicate doped with iron or copper or a vanadium-based catalyst doped with vanadium titania is supported on a carrier such as ceramic honeycomb, and a reducing agent urea (or Urea water) is converted to ammonia _by the heat of exhaust gas, and nitrogen oxides are converted to nitrogen gas (N ₂ ) and water (N ₂ ) and water ( H ₂ O) to reduce it.

To this end, conventionally, urea is injected by the urea injector 31 located in the upstream side exhaust pipe, but according to an embodiment of the present invention, the urea introduction part 110 in which the urea aqueous solution is introduced into the front end of the diesel oxidation catalyst device 21 . The urea solution introduced through the urea introduction unit 110 passes through the urea flow pipe 120 provided through the diesel oxidation catalyst device 21, and ammonia hydrolyzed by the urea solution is selectively catalytic reduction device It can be sprayed on one side of (22).

The urea aqueous solution introduced through the urea introduction unit 110 passes through the urea flow pipe 120 formed through the longitudinal direction of the diesel oxidation catalyst device 21 so that ammonia can be injected into the selective catalytic reduction device 22, An air compressor 111 may be connected to one side of the branch pipe 113 provided between the urea storage tank 112 and the urea introduction unit 110 . That is, the urea aqueous solution discharged from the urea storage tank 112 through the high-pressure air provided by the air compressor 111 is pressurized to the urea flow pipe line 120 and can pass through the urea flow pipe line 120 .

6 is a view showing the overall appearance of the diesel oxidation catalyst device according to an embodiment of the present invention.

6, the diesel oxidation catalyst device 21 according to an embodiment of the present invention may include a through hole 211 formed so that the urea flow pipe 120 can be inserted and installed in the longitudinal direction. . According to a preferred embodiment, the through hole 211 into which the urea flow pipe 120 is inserted is formed along the longitudinal direction in the center of the diesel oxidation catalyst device 21, so that the diesel oxidation catalyst device 21 is exhausted. When heat is generated due to oxidation of the gas, it is preferable to effectively transfer the heat to the urea aqueous solution passing through the urea flow pipe 120 .

Of course, the urea flow pipe 120 inserted and installed in the through hole 211 of the diesel oxidation catalyst device 21 is a heat conductor, for example, a metal material ( Ag, Cu, Al, Au, etc.) is preferable.

As a result, the urea aqueous solution passing through the urea flow pipe line 120 is heated by the reaction heat of the diesel oxidation catalyst device 21 without using a separate temperature increasing device (or heating device) to smoothly cause the hydrolysis reaction. there is

The urea flow pipe line 120 is not particularly limited, but since a flow path through which the high-pressure urea solution passes is provided, the urea flow pipe line 120 has first and second protruding protrusion members 121 to 124 provided on the outer circumferential surface. can be

6 shows the diesel oxidation catalyst device 210 as an example, but as shown in FIG. 2 , when the particle collecting device 23 is located at the rear end of the diesel oxidation catalyst device 210, the urea flow pipe line 120 ) can be provided through both the diesel oxidation catalyst device 210 and the particle collecting device 23, of course.

9 is a view showing an embodiment of a urea flow pipe according to an embodiment of the present invention.

As shown in FIG. 9, the diesel oxidation catalyst device 210 is interposed and fixed between the first and second protrusion members 121 to 124 formed on the outer circumferential surface of the urea flow pipe 120, so that the high-pressure urea aqueous solution is It is desirable not to move even if inflow/outflow.

According to an embodiment, the first and second protruding members 121 to 122 are, as shown in FIG. 9 (a), a ring ( ring) shape, the distance between the first and second protruding members 121 to 122 corresponds to the length of the diesel oxidation catalyst device 21, and urea fitted into the through hole 211 of the diesel oxidation catalyst device 210 The flow pipe 120 does not move and the position may be fixed.

The first and second protruding members 121 to 122 have heat resistance, and the inner circumferential surface is made of a silicone material having frictional force, and the first and second protruding members 121 to 122 are attachable and detachable to the urea flow pipe 120 . It is implemented so that the first and second protrusion members 121 to 122 can be inserted and mounted in a state in which the urea flow pipe 120 is inserted into the through hole 211 .

Alternatively, as shown in FIG. 9(b), the first and second protrusion members 123 to 124 may be protrusions having an elastic force, such as a pogo pin, and the first and second protrusions Each of the protruding members 123 to 124 is provided along the outer circumferential surface of the urea flow pipe 120, and at least one is provided between the first and second protruding members 123 to 124 by the length of the diesel oxidation catalyst device 210. may be spaced apart.

The first and second protrusion members 123 to 124 press any one of the first and second protrusion members 123 to 124 with an external force when the urea flow pipe line 120 is inserted into the through hole 211 . It can be inserted in a press-fitted state, and when the urea flow pipe line 120 is inserted into the through hole 211, any one of the protrusion members 123 to 124 pressed by the elastic force protrudes by the elastic force, so that the diesel oxidation catalyst The installation of the urea flow pipe 120 to the device 210 may be completed.

As a result, the diesel oxidation catalyst device 210 interposed therebetween is fixed by the first and second protruding members 123 to 124 protruding from the outer circumferential surface of the urea flow pipe 120, and the high-pressure urea aqueous solution is transferred to the urea flow pipe. Even if it flows in/outs along the furnace 120 , it does not move on the diesel oxidation catalyst device 21 and may be fixed at its position.

On the other hand, according to an embodiment of the present invention, at the downstream end of the urea flow pipe line 120, ammonia hydrolyzed by the urea aqueous solution that has passed through the urea flow pipe line 120 and the diesel oxidation catalyst device 21 are passed. It may include a urea mixer 130 for mixing one exhaust gas.

The urea mixer 130 according to an embodiment may be a blade mixer 131 as shown in FIG. 7 to mix ammonia hydrolyzed by an aqueous urea solution and exhaust gas.

The blade mixer 131 has a tubular body 1311 provided to fit into the inner circumferential surface of the front end exhaust pipe of the selective catalytic reduction device 22, and a plurality of blades 1312 extending inward along the inner circumferential surface of the body 1311. may include

At this time, the blade 1312 is for inducing the flow of ammonia and exhaust gas so that ammonia and exhaust gas can be uniformly mixed with each other when flowing, and the blade 1312 is downstream along the flow direction, that is, the selective catalytic reduction device (22) is formed extending in the direction, it may have a twisted shape to induce a screw-like airflow.

That is, the ammonia and the exhaust gas are effectively mixed by flowing along the outer surface of the blade, and the mixed ammonia and the exhaust gas are sprayed on one surface of the selective catalytic reduction device 22, so that the nitrogen of the selective catalytic reduction device 22 It is possible to improve the oxide removal ability.

According to another embodiment, the urea mixer 130, as shown in FIG. 8, a plurality of ammonia hydrolyzed by the urea aqueous solution passing through the urea flow pipe 120 can be sprayed into fine particles. It may be a radial jet mixer 132 having a hemispherical head cover 1323 having a fine jet port.

That is, ammonia is finely split through the injection holes o perforated in a number of fine sizes in the head cover 1323 of the radial injection mixer 132, and the ammonia of the fine particles is released in the radial direction by the hemispherical head cover 1323. By being injected toward the selective catalytic reduction device 22, it is possible to mix well with the exhaust gas that has passed through the diesel oxidation catalyst device 21. In this way, the uniformly mixed exhaust gas and ammonia are sprayed on one surface of the selective catalytic reduction device 22 , thereby improving the nitrogen oxide removal ability of the selective catalytic reduction device 22 .

As shown in FIG. 8 , the radial injection mixer 132 includes an introduction tube 1321 through which ammonia is introduced, and an introduction tube 1321 so that ammonia can be injected into the head cover 132 having a large area. It is provided at the distal end and may include a head 1322 formed of an expansion tube to induce ammonia to the head cover 132 .

In this way, since the radial injection mixer 132 according to an embodiment of the present invention can further reduce the space in the exhaust pipe for installing the blade mixer 131 at the front end of the selective catalytic reduction device 22, after the entire exhaust gas There is an effect that the processing system can be further downsized.

Meanwhile, according to an embodiment of the present invention, the selective catalytic reduction device 22 may be a Selective Catalyst Reduction-on-Diesel Particulate Filter (SDPF) 22a combined with the particle collecting device 23 . have.

The SDPF 22a coats the DPF with an SCR catalyst (eg, Cu-zeolite, Fe-zeolite, etc.) to react ammonia supplied from the front end of the SDPF and NOx in the exhaust gas on the SCR catalyst to purify NOx with water and nitrogen can do it In addition, since the SDPF 22a functions as a filter, particulate matter (PM) in the exhaust gas, which is a function of the DPF, can be collected.

The SDPF (22a) can be divided into a passive type and an active type depending on the type, but this is outside the scope of the present invention, and a detailed description thereof will be omitted.

As shown in FIGS. 4 and 5, when the selective catalytic reduction device 22 is replaced with the SDPF 22a, the length or size of the entire exhaust gas after-treatment system can be further reduced and miniaturized, and the As described above, in order to improve the NOx reduction capability, the SDPF 22a and the selective catalytic reduction device 22 may be arranged in combination in series and parallel.

In addition, the rear end of the selective catalytic reduction device 22 further includes an ammonia slip catalyst (AOC; Ammonia Oxidation Catalyst) 24 to oxidize ammonia (NH ₃ ) in the exhaust gas to nitrogen (N ₂ ) and water. By changing to (H ₂ O), ammonia leaked from the selective reduction catalyst device 22 can be purified to prevent ammonia from leaking into the atmosphere.

Here, in the ammonia slip catalyst device, similar to the diesel oxidation catalyst device 21, platinum (Pt), palladium (Pd), rhodium (Rh), etc. Noble metals, such as, may be comprised as a catalyst.

Of course, as shown in FIG. 6 , when the selective catalytic reduction device 22 is replaced with the SDPF 22a and the AOC 24 is omitted, the length or size of the entire exhaust gas aftertreatment system can be minimized.

As above, preferred embodiments of the present invention have been described in detail with reference to the drawings. The description of the present invention is for illustrative purposes, and those skilled in the art to which the present invention pertains will understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention.

Accordingly, the scope of the present invention is indicated by the claims described later rather than the detailed description, and all changes or modifications derived from the meaning, scope, and equivalent concept of the claims are included in the scope of the present invention. should be interpreted

10: engine 21: diesel oxidation catalyst device
22: selective catalytic reduction device 22a: SDPF
23: particle collecting device 24: ammonia slip catalyst device
31: urea injector 32: mixer
110: urea introduction part 111: air compressor
112: urea storage tank 113: branch pipe
120: urea flow pipe 121, 123: first protruding member
122, 124: second protrusion member 130: urea mixer
131: blade mixer 1311: body
1312: blade 132: radial jet mixer
1321: introduction tube 1322: head
1323: head cover 210: diesel oxidation catalyst device
211: through hole

Claims (10)

Diesel oxidation catalyst device (DOC) installed in the exhaust pipe of an internal combustion engine to oxidize hydrocarbon (HC) or carbon monoxide (CO) contained in exhaust gas or oxidize soluble organic fraction (SOF) contained in particulate matter Diesel Oxidation Catalyst) and nitrogen oxides (NO _x ) In the exhaust gas post-treatment system comprising a selective catalytic reduction (SCR; Selective Catalyst Reduction) for purifying,
a urea introduction unit located in front of the diesel oxidation catalyst device, into which an aqueous urea solution is introduced;
a urea flow pipe provided through the diesel oxidation catalyst device, through which the aqueous urea solution introduced through the urea introduction part passes; and
a urea mixer provided at the downstream end of the urea flow pipe to mix ammonia hydrolyzed by the urea aqueous solution and the exhaust gas;
Reductant injection system of the exhaust gas after-treatment system comprising a. The method of claim 1,
The selective catalytic reduction device is an exhaust gas post-treatment system, characterized in that it is a Selective Catalyst Reduction-on-Diesel Particulate Filter (SDPF) integrally formed with a particle collection device that collects particulate matter and purifies the exhaust gas. of reducing agent injection system. 3. The method of claim 2,
Exhaust gas post-treatment system, which is located at the rear end of the selective catalytic reduction device, further comprising an ammonia slip catalyst device (AOC; Ammonia Oxidation Catalyst) for oxidizing and purifying ammonia leaked from the selective catalytic reduction device of reducing agent injection system. The method of claim 1,
It is located at the rear end of the diesel oxidation catalyst device, further comprising a Diesel Particulate Filter (DPF) for collecting particulates (PM) to purify the exhaust gas,
The reducing agent injection system of the exhaust gas post-treatment system, characterized in that the urea flow pipe is provided through the diesel oxidation catalyst device and the particulate collection device. The method of claim 1,
The urea introduction unit, the reducing agent injection system of the exhaust gas post-treatment system, characterized in that the urea aqueous solution is introduced together with high-pressure air to pass through the urea flow pipe. The method of claim 1,
The urea flow pipe path, the reducing agent injection system of the exhaust gas post-treatment system, characterized in that provided along the longitudinal direction in the center of the diesel oxidation catalyst device. The method of claim 1,
The urea flow pipe path is a reducing agent injection system of an exhaust gas post-treatment system, characterized in that it is a heat conductor to transfer heat to the urea aqueous solution flowing in the urea flow pipe path when the diesel oxidation catalyst device generates heat due to a catalytic reaction. The method of claim 1,
The urea mixer,
A blade mixer comprising a tubular body to mix the ammonia and the exhaust gas, and a plurality of blades extending inside along the inner circumferential surface of the body and toward the selective catalytic reduction device, wherein the plurality of blades are twisted The reducing agent injection system of the exhaust gas after-treatment system, characterized in that the shape. The method of claim 1,
The urea mixer,
A radial type comprising an introduction tube into which the ammonia is introduced, a head provided at the distal end of the introduction tube and formed to be expanded, and a hemispherical head cover provided at the distal end of the head and having a plurality of injection holes so that the ammonia can be sprayed in a radial direction. The reducing agent injection system of the exhaust gas after-treatment system, characterized in that it is an injection mixer. The method of claim 1,
Between the diesel oxidation catalyst device and the selective catalytic reduction device, a urea injector for injecting the urea aqueous solution is not provided.

Images