KR102441028B1 - System for after-treatment of exhaust gas for diesel engine including the filter coated with denitrification catalyst - Google Patents

Abstract

The present invention provides an exhaust gas post-treatment system including a denitrification catalyst-coated filter. The exhaust gas post-treatment system including a diesel oxidation catalyst (DOC) and mounted on an exhaust pipe of a combustion engine to oxidize hydrocarbon (HC) or carbon monoxide (CO) included in exhaust gas or to oxidize a soluble organic fraction (SOF) included in a particulate matter, further comprises a selective catalyst reduction on diesel particulate filter (SCR on DPF) coated with a denitrification catalyst for purifying nitrogen oxide (NO_x) on a diesel particulate matter filter (DPF) for purifying exhaust gas by collecting the particulate matter, wherein the diesel particulate matter filter is coated with the denitrification catalyst in a slurry state having a particle size of 2-4 ㎛, a pH of 5-7, and a viscosity of 150-300 cp. Therefore, provided is an exhaust gas post-treatment system for a diesel engine including a denitrification catalyst-coated filter, wherein back pressure increase and total nitrogen oxide emission can be minimized.

Description

Exhaust gas aftertreatment system for diesel engine including filter coated with denitrification catalyst {SYSTEM FOR AFTER-TREATMENT OF EXHAUST GAS FOR DIESEL ENGINE INCLUDING THE FILTER COATED WITH DENITRIFICATION CATALYST}

The present invention relates to an exhaust gas post-treatment system for a diesel engine including a filter coated with a denitration catalyst, and more particularly, including a filter coated with a denitration catalyst for purifying exhaust gas discharged from a diesel engine of a medium-to-large operating vehicle It relates to an exhaust gas aftertreatment system.

Diesel engines emit harmful exhaust gas substances such as carbon monoxide (CO), unburned hydrocarbons (HC), particulate matter (PM), and nitrogen oxides (NO _X ) by combustion reaction. In order to reduce the emission of harmful gas emitted from the diesel engine, environmental regulations are being strengthened, and as the regulation is strengthened, an exhaust gas after-treatment system capable of reducing exhaust gas emitted from the diesel engine is being installed.

For example, in the case of a vehicle currently equipped with a diesel engine, diesel that oxidizes hydrocarbon (HC) or carbon monoxide (CO) contained in exhaust gas or oxidizes soluble organic fraction (SOF) contained in particulate matter Diesel Oxidation Catalyst (DOC), Diesel Particulate Matter Filter (DPF) to collect particulates (PM), Selective Catalyst (SCR) to purify nitrogen oxides (NO _x ) Reduction), and / or an ammonia slip catalyst device (Ammonia Oxidation Catalyst) for purifying ammonia is additionally equipped with an exhaust gas after-treatment system including.

Recently, environmental regulations have been tightening regulations on nitrogen oxide reduction, and for this reason, a particulate collection device coated with a selective reduction catalyst is being applied to vehicles. The particulate collection device coated with this selective reduction catalyst is applied with a small engine of 3,000cc or less along with new engine technology when newly manufacturing a vehicle. is in non-existent state.

When a particulate collection device coated with a selective reduction catalyst is applied to a diesel engine vehicle, a selective reduction catalyst capable of reducing nitrogen oxides is adjacent to the engine, and the selective reduction catalyst adjacent to the engine reacts with engine heat generated from the engine. Since the temperature is reached faster, there is an advantage in that the reduction rate of nitrogen oxides is increased.

In addition, compared to the exhaust gas post-treatment system in which the particulate collection device and the selective catalytic reduction device are separately provided in the prior art, there is an effect of reducing the volume of the catalyst device, and thus the cost of the exhaust gas post-treatment system has the advantage of reducing However, in the case of mid- to large-sized vehicles equipped with diesel engines prior to EURO-6, back pressure due to differences in exhaust gas characteristics, such as the generation of a large amount of particulate matter (PM) and the ratio of emitted particulates and nitrogen oxides (PM/NO _X ratio) There are disadvantages in that it is difficult to rise and naturally regenerate particulates (PM).

Therefore, in order to apply the particulate collection device coated with the selective reduction catalyst to the exhaust gas post-treatment system, it is necessary to minimize the increase in back pressure due to the coating of the selective reduction catalyst, and to apply the exhaust gas after treatment to various types of vehicles. It is necessary to develop a processing system.

US 10-1195799 B1 US 10-1369651 B1 US 10-2122849 B1 US 10-2028423 B1

An object of the present invention is to provide an exhaust gas post-treatment system for a diesel engine including a filter coated with a denitration catalyst capable of minimizing an increase in back pressure and a total amount of nitrogen oxide emission.

In order to solve the above problems, the present invention is mounted on the exhaust pipe of an internal combustion engine to oxidize hydrocarbons (HC) or carbon monoxide (CO) contained in exhaust gas or soluble organic components (SOF) contained in particulate matter; ), in the exhaust gas post-treatment system including a Diesel Oxidation Catalyst (DOC) that oxidizes nitrogen oxides in a Diesel Particulate Matter Filter (DPF) that collects particulate matter and purifies the exhaust gas (NO _x ) A denitration catalyst coated SDPF (SCR on DPF; Selective Catalyst Reduction - on - Diesel Particulate Filter) for purifying further comprises, wherein the denitration catalyst has a particle size of 2 to 4 μm, pH 5 to 7, and It provides an exhaust gas post-treatment system including a filter coated with a denitration catalyst, characterized in that it is coated on the particle collecting device in a slurry state of a viscosity of 150 to 300 cp.

According to an embodiment, the particle collecting device may be a symmetrical filter made of cordierite or silicon carbide, in which the size of the cells on the upstream side through which the exhaust gas flows and on the downstream side through which the exhaust gas flows out are the same. have.

According to an embodiment, the particle collecting device is an asymmetric filter made of cordierite or silicon carbide, wherein the size of the cells on the upstream side through which the exhaust gas flows and on the downstream side through which the exhaust gas flows out are different from each other. can

According to an embodiment, a selective catalytic reduction device (SCR; Selective Catalyst Reduction) for purifying nitrogen oxides (NO _x ) may be further included.

According to an embodiment, it may further include an ammonia slip catalyst device (AOC; Ammonia Oxidation Catalyst) disposed at the rear end of the SDPF to oxidize and purify ammonia leaked from the SDPF.

According to an embodiment, it is located between the diesel oxidation catalyst device and the SDPF, further comprising a urea mixer for mixing the urea aqueous solution and the exhaust gas, wherein the urea mixer, a ring-shaped body and an inner circumferential surface of the body a plurality of blades provided to be spaced apart from each other along have.

According to an embodiment, a burner for heating and raising the temperature of the exhaust gas, and a urea injector positioned in front of the SDPF to inject urea may be further included.

According to an embodiment, a first vessel including the diesel oxidation catalyst device, a second vessel including the SDPF, and an exhaust gas flow pipe through which the exhaust gas flows between the first and second vessels are parallel to each other Doedoe, the urea mixer, doedoe provided in the exhaust gas flow pipe, the urea injector, may inject urea to the front end of the urea mixer.

According to an embodiment, it is located in front of the diesel oxidation catalyst device, is provided through the urea introduction part into which the aqueous urea solution is introduced, and the diesel oxidation catalyst device, the urea solution introduced through the urea introduction part passes through the urea. Further comprising a flow pipe, the urea mixer may be provided at a downstream end of the urea flow pipe.

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.

The exhaust gas post-treatment system including the filter coated with the denitration catalyst according to the present invention can minimize the back pressure increase and the total amount of nitrogen oxide emission of the exhaust gas post-treatment system by using the particulate collecting device coated with the denitration catalyst.

In addition, since the aqueous urea solution is heated by the heat generated during the reaction of the diesel oxidation catalyst device as the urea flow pipe through which the urea solution is introduced and flows from the outside passes through the diesel oxidation catalyst device, the effect of smoothing the hydrolysis there is

1 is a block diagram of an exhaust gas post-treatment system according to an embodiment of the present invention.
2 is a view showing the appearance of an SDPF according to an embodiment of the present invention.
3A is a block diagram of an exhaust gas post-treatment system according to another embodiment of the present invention.
3B is a block diagram of an exhaust gas post-treatment system according to another embodiment of the present invention.
4 is a view showing the appearance of an exhaust gas post-treatment system according to another embodiment of the present invention.
FIG. 5 is a diagram illustrating a state of the exhaust gas flowing in the exhaust gas post-treatment system of FIG. 4 .
6 is a view showing a urea mixer according to an embodiment of the present invention and a urea mixer according to a comparative example.
7 is a view showing the urea mixer according to an embodiment of the present invention viewed from multiple angles.
8 is a view showing any one blade of the urea mixer of FIG.

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 numerals 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 this specification, the detailed description thereof will be omitted. In addition, the accompanying drawings are only for easy understanding of the embodiments disclosed in this specification, and the technical idea 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 the present 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 is to be understood that this does not preclude the possibility of the presence or addition of numbers, steps, operations, components, parts, or combinations thereof.

1 is a block diagram of an exhaust gas post-treatment system according to an embodiment of the present invention.

As shown in FIG. 1 , the exhaust gas after-treatment system for a diesel engine according to an embodiment of the present invention is mounted on an exhaust pipe of an internal combustion engine, and hydrocarbon (HC) contained in exhaust gas generated from the engine 1 . Diesel Oxidation Catalyst (DOC) 21 that oxidizes carbon monoxide (CO) or oxidizes soluble organic fraction (SOF) contained in particulate matter, and exhaust gas by collecting particulate matter SDPF (SCR on DPF; Selective Catalyst Reduction - on - Diesel Particulate Filter) (41) coated with a denitration catalyst to purify nitrogen oxides (NO _x ) was installed in the Diesel Particulate Matter Filter (DPF) that purifies the may include

However, since the components shown in FIG. 1 are not essential, an exhaust gas aftertreatment system having more or fewer components may be implemented.

Hereinafter, each component will be described.

In the first container 20 mounted on the exhaust pipe through which the exhaust gas discharged from the engine 1 passes, hydrocarbon (HC) or carbon monoxide (CO) contained in the exhaust gas is oxidized or particulate matter (PM). It may include a diesel oxidation catalyst (DOC; Diesel Oxidation Catalyst) 21 to oxidize the soluble organic component (SOF; Souluble Organic Fraction) contained in the.

The diesel oxidation catalyst device 21 is a catalyst coated with 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. Oxygen (O ₂ ) in the gas is used to oxidize hydrocarbons (HC) or carbon monoxide (CO) contained in exhaust gas or to oxidize soluble organic fractions (SOF) contained in particulate matter, so that water (H ₂ It is a catalyst device that converts O) and carbon dioxide (CO ₂ ).

In addition, the diesel oxidation catalyst device 21 oxidizes nitrogen monoxide (NO) to generate nitrogen dioxide (NO ₂ ), and the oxidized nitrogen dioxide (NO ₂ ) causes an oxidation reaction with the carbon captured in the particle collecting device. do.

The chemical reaction formula occurring in the diesel oxidation catalyst device 21 is as shown in the following formula (1).

[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

In addition, the exhaust gas post-treatment system according to an embodiment of the present invention can collect most of the particulate matter included in the exhaust gas discharged from the engine 1 and purify the exhaust gas discharged to the outside through the exhaust pipe. have.

At this time, the particulate collection device (DPF) may be located at the rear end of the diesel oxidation catalyst device 21, specifically, it may be provided in the second container 40 connected to communicate with the first container 20. .

In order to collect particulate matter contained in exhaust gas, the DPF is a porous ceramic honeycomb structure, for example, or a filter plugged by alternating the inlet and outlet of the porous ceramic honeycomb cell, that is, the Wall Flow. It can be Monoliths Type. 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 on the wall in the form of a cake.

In addition, the particle collection device (DPF) causes an oxidation reaction with soot (carbon) collected in the filter to convert carbon dioxide and water to regenerate (oxidize) soot.

The chemical reaction formula occurring in the particle collecting device (DPF) is as shown in the following formula (2).

[Formula 2]

C(Soot) + O ₂ → CO/CO ₂

C(Soot) + NO ₂ → CO/CO ₂ + NO

The particle collection device (DPF) physically collects particulate matter in the exhaust gas of the engine 1 using a filter, but 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

However, since the temperature of the exhaust gas varies depending on the operation pattern of the internal combustion engine, the oxidation reaction of particulate matter using the temperature of the exhaust gas is irregular in cycle, and regeneration is not possible when the exhaust gas temperature is low such as under low speed/low load conditions. Since it is impossible, soot regeneration through an auxiliary heat source is required.

To this end, a burner 23 is positioned on the upstream side of the particle collection device (DPF), and the exhaust gas flowing into the particle collection device (DPF) can be heated to increase the temperature.

As a specific example, the burner 23 is provided in the first container 20 , and the flame or heat generated by the burner 23 may increase the temperature of the exhaust gas flowing from the engine 1 . Here, the burner 23 for heating the exhaust gas may use not only fuel such as light oil, but also electricity, microwave, etc., but the type is not particularly limited.

As described above, when the exhaust gas is low temperature, the combustion rate of particulate matter (PM) by the catalyst is slower than the rate of generation of particulate matter (PM) generated in the engine 1, so that the particulate matter is eventually stored in the particulate collecting device located at the rear end. (PM) accumulates and the back pressure rises. After all, there is a limit to only the natural regeneration method using a catalyst, and by increasing the exhaust temperature using a fuel-using burner 23, the particulate matter (PM) accumulated in the particulate collection device is burned for forced regeneration, thereby reducing soot. can

On the other hand, it is preferable that the particle collecting device (DPF) according to the embodiment of the present invention described above is the SDPF 41 coated with a denitration catalyst.

Specifically, the particle collection device (DPF) is a filter ( 2), and the denitration catalyst coated therein uses a V ₂ O ₅ -WO ₃ /TiO ₂ denitration catalyst to ensure high sulfur resistance and denitrification performance, and the composition is V ₂ O ₅ 1 to 10 wt. %, WO ₃ 1-15 wt%, SiO ₂ 1-10 wt%, TiO ₂ 65-97 wt%. In addition, one or more transition metal oxides such as Mo, Ce, Fe, Cu, etc. may be used as the co-catalyst, and 0.5 to 5% may be included in the composition.

According to another embodiment, the denitration catalyst coated on the particle collection device (DPF) may use a zeolite-based denitration catalyst, and the ion-exchanged transition metal to the zeolite may use one of Cu and Fe, The content of the ion-exchanged transition metal may be 1 to 5% of the total content of the zeolite.

At this time, in order to coat the denitration catalyst on the particle collection device (DPF), the slurry characteristics of the denitration catalyst are very important. This is because even if the same catalyst and the same catalyst loading amount are applied, if the coating is not uniform due to the characteristics of the catalyst slurry, an increase in back pressure and a decrease in performance occur. Therefore, the denitration catalyst according to an embodiment of the present invention is preferably coated on the particle collecting device in a slurry state having a particle size of 2 to 4 μm, a pH of 5 to 7, and a viscosity of 150 to 300 cp (hereinafter, Example 1). is abbreviated).

The particle collection device coated with the denitration catalyst according to Example 1 of the present invention, the particle collection device not coated with the denitration catalyst (Comparative Example 1), and other physical properties (particle size 4-8 μm, pH 3-5, And the results of testing the back pressure in comparison with the particle collecting device (Comparative Example 2) coated with a slurry having a viscosity of 500 to 800 cp) are shown in Table 1 below. Here, as the particle collecting device, a honeycomb filter having a porosity of 48 to 50% and a pore size of 12 to 15 μm made of cordierite was used.

in the particle collection device
Whether or not a denitrification catalyst is applied Physical properties of denitrification catalyst Back Pressure Test Results (CFM) Particle size (㎛) pH Viscosity (cp) Comparative Example 1 Particle collection device - - - 11.5 Comparative Example 2 Particle collecting device coated with denitrification catalyst 4-8 3-5 500-800 16.8 Example 1 Particle collecting device coated with denitrification catalyst 2-4 5-7 150-300 13.8

The denitration catalyst according to Example 1 of the present invention was prepared to have a particle size of 2 to 4 μm, and the pH was adjusted to 5 to 7, but the pH was adjusted using nitric acid, acetic acid or aqueous ammonia. In addition, the viscosity of the denitration catalyst in the slurry state before coating on the particle collecting device was adjusted to 150-300 cp.

As a result of the back pressure test, the back pressure of the particle collecting device coated with the denitration catalyst according to Example 1 of the present invention was 13.8 CFM, which is 2.3 CFM higher than the back pressure of 11.5 CFM of the particle collecting device without the denitration catalyst coated, but Comparative Example 2 It was confirmed that the back pressure was 3 CFM lower than the particle collecting device coated with the denitration catalyst with a particle size of 4-8 μm, pH 3-5, and viscosity of 500-800 cp.

In addition, a medium-to-large post-processing device to which the particle collecting device coated with the denitration catalyst according to Example 1 of the present invention is applied was manufactured and mounted on an actual engine to perform a dynamometer performance test. As the test engine, the D6DB engine, which is widely applied to current vehicles, was used, and the ND-13 Mode test was performed by installing it on a 6600cc D6DB engine.

The results of the ND-13 Mode test are shown in Table 2 below.

in the particle collection device
Whether or not a denitrification catalyst is applied Physical properties of denitrification catalyst ND-13 Mode Test Result Particle size (㎛) pH Viscosity (cp) Maximum output back pressure (mbar) Total NO _X emissions (g/kwh) Comparative Example 2 Particle collecting device coated with denitrification catalyst 4-8 3-5 500-800 280.3 1.287 Example 1 Particle collecting device coated with denitrification catalyst 2-4 5-7 150-300 269 0.45

As a result of the experiment, when the particle collecting device coated with the denitration catalyst having the physical properties of Comparative Example 2 was applied, the maximum output back pressure was 280.3 mbar and the total NO _X emission was 1.287 g/kwh, and the physical properties of Example 1 of the present invention When the particle collecting device coated with the _denitration catalyst having It was confirmed that the reduction effect and the nitrogen oxide removal efficiency were large.

On the other hand, the same denitration catalyst as in Example 1 of the present invention was coated on various types of particulate collection devices, and engine dynamometer performance tests were performed, and the results are shown in Table 3 below.

Specifically, with respect to the particle collecting device having a honeycomb cell structure made of cordierite, a symmetrical filter in which the cell size of the upstream side through which exhaust gas is introduced and the cell size of the downstream side through which exhaust gas is discharged are identical to each other (Example 2) was tested with the same symmetric filter as in Example 2, but was tested with a filter (Example 3) to which a SiC material, not cordierite, was applied, and a honeycomb cell structure made of the same cordierite material as in Example 1 An asymmetrical filter, in which the cell size of the upstream side through which exhaust gas is introduced and the cell size of the downstream side through which exhaust gas is discharged, is different, for example, an upstream cell size is 1.2 times larger than that of the downstream side. A larger filter (Example 4) was tested.

Particle collection device
type Physical properties of denitrification catalyst ND-13 Mode Test Result Particle size (㎛) pH Viscosity (cp) Maximum output back pressure (mbar) Total NO _X emissions (g/kwh) Example 2 Particle collecting device coated with denitrification catalyst
(Cordierite Symmetric Filter) 2-4 5-7 150-300 269 0.45 Example 3 Particle collecting device coated with denitrification catalyst
(SiC filter) 2-4 5-7 150-300 273 0.613 Example 4 Particle collecting device coated with denitrification catalyst
(cordierite asymmetric filter) 2-4 5-7 150-300 277 0.447

As a result of the experiment, the symmetrical particle collecting device made of cordierite (Example 2) has the most excellent effect in terms of back pressure and NO _x emission, but the SDPF of Examples 2 to 4 uses SiC as the material of the particle collecting device ( In Example 3), even if the particle collecting device made of cordierite was asymmetric rather than symmetrical (Example 4), it was confirmed that there was an excellent effect in terms of back pressure and NO _x emission compared to Comparative Examples 1 and 2.

On the other hand, in the SDPF 41 according to an embodiment of the present invention, urea (or urea water) as a reducing agent is converted into ammonia by the heat of exhaust gas by the coated denitration catalyst, and the denitration catalyst (or selective reduction catalyst) ) as a catalytic reaction of nitrogen oxides (NO _x ) and ammonia (NH ₃ ) in the exhaust gas to reduce nitrogen oxides into nitrogen gas (N ₂ ) and water (H ₂ O).

In order to remove nitrogen oxides in this way, reactivity with a reducing agent capable of reacting with nitrogen oxides is very important. Therefore, it is important to design a urea mixer for vaporization of urea water and uniform mixing with exhaust gas.

The urea mixer 32 according to an embodiment of the present invention is for communication between the first container 20 including the diesel oxidation catalyst device 21 and the second container 40 including the SDPF 41. It is provided in the exhaust gas flow pipe 30, it is possible to mix the exhaust gas that has passed through the diesel oxidation catalyst device 21 and the urea solution introduced into the urea solution through the urea inductor 31. Here, the urea injector 31 is provided on one side of the pipe of the exhaust gas flow pipe 30 so as to inject urea into the exhaust gas flow pipe 30, and may be provided at the front end of the urea mixer 32. (see Fig. 3a).

The urea mixer 32 may have various shapes, but the urea mixer 32 according to an embodiment of the present invention is of a ring-shaped ring type, as shown in FIGS. 7( b ) and 8 . A body 321 and a plurality of blade blades 323 provided to be spaced apart from each other along the inner circumferential surface of the body 321, wherein the blade 323 is an extension formed extending inward from the inner circumferential surface of the body 321 ( 3231) and a wing piece 3232 bent clockwise or counterclockwise at the inner distal end of the extension piece.

That is, the blade piece 3232 is formed to extend to be bent toward the SDPF 41 direction, and the blade 323 has a twisted screw shape to induce a screw airflow.

Figure 7 (a) is a perspective view of the urea mixer 32 according to an embodiment of the present invention, Figure 7 (b) is a bottom view, Figure 7 (c) is a side view.

That is, as shown in FIG. 7 , the urea mixer 32 according to an embodiment of the present invention extends from at least one of the ring-shaped body 321 and the inner circumferential surface of the body 321 toward the center. It may include a rib 322 having at least one crossbar crossing the inner circumferential surface of the body 321 , and a blade 323 extending inwardly from the inner circumferential surface of the body 321 .

At this time, the blade 323 is, as shown in FIG. 8 , a flat, substantially trapezoidal extension 3231 and a free end of the extension 3231 , that is, the inner side of the body 321 of the extension 3231 . It may include a wing piece 3232 bent in either direction at the end extending toward the . One end 3231b of the extension piece 3231 is fixed to the inner circumferential surface of the body 321 , and another end 3231a of the extension piece 3231 is fixed to the rib 322 , and the other end The wing piece 3232 may be provided.

In addition, the wing piece 3232 bent in either direction at the inner end of the extension piece 3231 may have an approximately flag shape or a trapezoidal shape on a plate, and at this time, a portion of the wing piece 3232 is shown in FIG. 7 . As shown in (c), it may be formed to extend to protrude out of the body 321 of the urea mixer 32, but is not particularly limited at this time, but the corner portion of the free end of the wing piece 3232 is chamfered to form a round shape. can be

The urea mixer 32 (see Fig. 6(b)) according to an embodiment of the present invention was compared with a urea mixer 320 (see Fig. 6(a)) of a different shape known in the art and the back pressure change, and the like, and the result is shown in Table 4 below.

For reference, the urea mixer 320 as a comparison object shown in Fig. 6(a) has a ring-shaped body 3201 and a ring-shaped body 3201 extending inward from any one end of the body 3201, in any one direction It may include several inclined plate-shaped blades 3202.

Particle collection device type Mixer shape Selective reduction catalyst properties ND-13 Mode Test Result Particle size (㎛) pH Viscosity (cp) Maximum output back pressure (mbar) Total NO _X emissions (g/kwh) Comparative Example 3 Particle collecting device coated with denitrification catalyst (Cordealite asymmetric filter) Fig. 6(a) 2-4 5-7 150-300 277 0.447 Example 5 Particle collecting device coated with denitrification catalyst (Cordealite asymmetric filter) Figure 6(b) 2-4 5-7 150-300 262 0.379

As a result of performing the ND-13 mode test on the engine dynamometer after changing only the shape of the urea mixer 32, the urea mixer 32 having the shape of FIG. 6(b) according to an embodiment of the present invention compared to Comparative Example 3 ), the back pressure at the maximum output decreased by about 15 mbar, and the total amount of NO _X emission was also reduced by 0.068 g/kwh.

Meanwhile, in the exhaust gas post-treatment system according to an embodiment of the present invention, as shown in FIG. 3A , in addition to the diesel oxidation catalyst device 21 and the SDPF 41, a selective catalytic reduction device is provided at the rear end of the SDPF 41. (42) may be additionally provided.

The selective catalytic reduction device 42, like the denitration catalyst of the SDPF 41, supports a zeolite catalyst such as aluminosilicate doped with iron or copper or a vanadium-based catalyst doped with vanadium titania on a carrier such as a ceramic honeycomb. As a result, urea, a reducing agent, is converted to ammonia by the heat of exhaust gas, and nitrogen oxide is converted into nitrogen gas as a catalytic reaction of nitrogen oxide (NO _x ) and ammonia (NH ₃ ) in exhaust gas by a denitration catalyst (or selective reduction catalyst) (N ₂ ) and water (H ₂ O) to reduce.

Meanwhile, in the exhaust gas post-treatment system according to an embodiment of the present invention, as shown in FIG. 3A , in addition to the diesel oxidation catalyst device 21 and the SDPF 41 , an ammonia slip catalyst device is installed at the rear end of the SDPF 41 . (AOC; Ammonia Oxidation Catalyst) (43) by oxidizing ammonia (NH ₃ ) in the exhaust gas and changing it into nitrogen (N ₂ ) and water (H ₂ O), ammonia leaked from the SDPF (41) It can also be purified to prevent ammonia from escaping into the atmosphere.

Here, the ammonia slip catalyst device 43 is also similar to the diesel oxidation catalyst device 21, platinum (Pt), palladium (Pd), rhodium on a honeycomb-structured support made of ceramic using cordierite or the like as a raw material. A noble metal such as (Rh) may be constituted as the catalyst.

On the other hand, in the exhaust gas post-treatment system according to another embodiment of the present invention, as shown in FIG. 3A , urea is not injected through the urea injector 31 located on one side of the exhaust gas flow pipe 30 . , as shown in FIG. 3b, the urea introduction part 11 to which the urea aqueous solution is introduced is located at the front end of the diesel oxidation catalyst device 21, and the urea aqueous solution introduced through the urea introduction part 11 is transferred to the diesel oxidation catalyst device ( Through the urea flow pipe 12 provided through the passage 21), ammonia obtained by hydrolyzing the urea aqueous solution and/or urea as a reducing agent by the heat of the exhaust gas may be injected onto one surface of the SDPF 41 .

The urea aqueous solution introduced through the urea introduction unit 11 passes through the urea flow pipe 12 formed through the longitudinal direction of the diesel oxidation catalyst device 21, and the urea aqueous solution and/or ammonia can be sprayed to the SDPF 41. So, the 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 aqueous urea 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 12 and can pass through the urea flow pipe 12 .

Accordingly, the diesel oxidation catalyst device 21 according to another embodiment of the present invention may include a through-hole formed through the longitudinal direction so that the urea flow pipe 12 can be inserted and installed in the longitudinal direction. That is, the through hole into which the urea flow pipe 12 is inserted is formed in the longitudinal direction at the center of the diesel oxidation catalyst device 21, and when the diesel oxidation catalyst device 21 generates heat due to the oxidation of the exhaust gas It is desirable to ensure that the heat can be effectively transferred to the urea aqueous solution passing through the urea flow pipe (12).

The urea flow pipe 12 inserted and installed in the through hole of the diesel oxidation catalyst device 21 is a heat conductor, for example, a metal material (Ag, Cu. Al) so that the heat emitted from the diesel oxidation catalyst device 21 can be transmitted well. , Au, etc.) is preferred.

As a result, the urea aqueous solution passing through the urea flow pipe 12 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

At this time, the urea mixer 32 may be provided to be located at the downstream end of the urea flow pipe (12).

Meanwhile, FIG. 4 is a view showing the appearance of an exhaust gas post-treatment system according to another embodiment of the present invention.

According to an embodiment of the present invention, as shown in FIG. 1 and the like, the first container 20 including the diesel oxidation catalyst device 21, the second container 40 including the SDPF 41, and the second container The exhaust gas flow pipe 30 through which the exhaust gas flows between the first and second containers may be connected in series with each other, but the present invention is not limited thereto, and according to another embodiment, as shown in FIG. , the first vessel 20, the exhaust gas flow pipe 30 and the second vessel 40 may be connected to each other in parallel.

At this time, in order to connect the first container 20 , the exhaust gas flow pipe 30 and the second container 40 in parallel to each other, the other end of the first container 20 (a burner provided in the first container 20 ) A first connecting duct 25 may be provided to connect the opposite end of the one end to which fuel is supplied to 23) and one end of the exhaust gas flow pipe 30 so as to be able to communicate with each other, and similarly, the second container A second connecting duct 35 may be provided to connect the other end of the 40 (the opposite end of the one end from which the purified exhaust gas is discharged) and the other end of the exhaust gas flow pipe 30 to communicate with each other. have.

Here, the unexplained reference numeral 30a of FIG. 4 denotes a urea injection hole 30a formed through the first connection duct 25 through which urea may be injected and injected into the exhaust gas flow pipe 30 .

In addition, the unexplained reference numeral 20a of FIG. 4 indicates a fuel inlet to which the fuel used by the burner 23 is supplied, and the reference numeral 22a is an exhaust gas inlet and a connection hole through which the exhaust gas generated from the engine 1 is introduced. Reference numeral 40a denotes an exhaust gas outlet through which exhaust gas purified by the exhaust gas post-treatment system is discharged, and reference numeral 32a denotes a mixer housing 32a having a urea mixer 32 therein, the The mixer housing 32a may be interposed in the middle of the exhaust gas flow pipe 30, but the present invention is not limited thereto, and the mixer housing 32a may be provided at the front end of the exhaust gas flow pipe 30. .

In this way, according to another embodiment of the present invention, the first vessel 20, the exhaust gas flow pipe 30 and the second vessel 40 are not connected in series, but are connected in parallel, as shown in FIG. As described above, there is an advantage in that the flow of exhaust gas is not inhibited, and the length of the entire exhaust gas after-treatment system can be reduced to make it compact.

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 of ordinary skill 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 below rather than the above 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

1: Engine 10: Exhaust gas inlet pipe
11: Urea introduction part 12: Urea flow pipe
111: air compressor 112: urea storage tank
113: branch pipe 20: first vessel
20a: fuel inlet 21: diesel oxidation catalyst device
22: exhaust gas inlet 22a: exhaust gas inlet
23: burner 25: first connecting duct
30: exhaust gas flow pipe line 30a: urea injection port
31: urea injector 32: urea mixer
32a: mixer housing 321: body
322: rib 323: blade
3231: extension 3232: wings
35: second connection duct 40: second container
40a: exhaust gas outlet 41: SDPF
42: selective reduction catalyst device 43: ammonia slip catalyst device
320: urea mixer 3201: body
3202: Blade

Claims (10)

Diesel oxidation catalyst device (DOC) that is installed in the exhaust pipe of an internal combustion engine to oxidize hydrocarbons (HC) or carbon monoxide (CO) contained in exhaust gas or oxidize soluble organic fractions (SOF) contained in particulate matter. In the exhaust gas after-treatment system comprising: Diesel Oxidation Catalyst),
Selective Catalyst Reduction (SCR on DPF; Selective Catalyst Reduction - on - Diesel Particulate) coated with a denitration catalyst to purify nitrogen oxides (NOx) on Diesel Particulate Matter Filter (DPF) that collects particulate matter and purifies exhaust gas Filter); and
a urea mixer positioned between the diesel oxidation catalyst device and the SDPF to mix the urea aqueous solution and the exhaust gas;
further comprising,
The denitration catalyst is coated on the particle collecting device in the form of a slurry having a particle size of 2 to 4 μm, a pH of 5 to 7, and a viscosity of 150 to 300 cp,
The urea mixer includes a ring-shaped body, a rib having at least one crossbar provided to cross the body, and a plurality of blades provided to be spaced apart from each other along the inner circumferential surface of the body,
The blade is a trapezoidal extension extending along the crossbar from the inner circumferential surface of the body inwardly, the trapezoidal extension being fixed to the body and the crosspiece, and extending from the hypotenuse, which is the distal end of the trapezoidal extension. It includes a wing piece that is formed to extend so that a part protrudes beyond the height of the body,
The wing piece is formed to extend from the hypotenuse by a predetermined angle in a clockwise or counterclockwise direction, and the distal end is formed to extend to the crossbar to which the adjacent blade is fixed. Including a filter coated with a denitration catalyst Exhaust gas aftertreatment system. The method of claim 1,
The particle collecting device,
Exhaust including a filter coated with a denitration catalyst, characterized in that it is a symmetrical filter made of cordierite or silicon carbide, wherein the cells on the upstream side through which the exhaust gas flows and on the downstream side through which the exhaust gas flows are the same size. gas aftertreatment system. The method of claim 1,
The particle collecting device,
Including a filter coated with a denitration catalyst, characterized in that it is an asymmetric filter made of cordierite or silicon carbide, wherein the size of the cells on the upstream side through which the exhaust gas flows and on the downstream side through which the exhaust gas flows out are different from each other Exhaust gas aftertreatment system. The method of claim 1,
Selective Catalyst Reduction (SCR) for purifying nitrogen oxides (NO _x );
Exhaust gas post-treatment system including a filter coated with a denitration catalyst, characterized in that it further comprises. The method of claim 1,
After exhaust gas including a filter coated with a denitration catalyst, it is located at the rear end of the SDPF, and further comprises an ammonia slip catalyst (AOC) for oxidizing and purifying ammonia leaked from the SDPF. processing system. delete The method of claim 1,
a burner for heating the exhaust gas to increase the temperature; and
Located in front of the SDPF, a urea injector for injecting urea;
Exhaust gas post-treatment system including a filter coated with a denitration catalyst, characterized in that it further comprises. 8. The method of claim 7,
A first container including the diesel oxidation catalyst device, a second container including the SDPF, and an exhaust gas flow pipe through which the exhaust gas flows between the first and second containers are connected in parallel to each other,
The urea mixer, doedoe provided inside the exhaust gas flow pipe, the urea injector, Exhaust gas post-treatment system including a filter coated with a denitration catalyst, characterized in that for injecting urea to the front end of the urea mixer. The method of claim 1,
a urea introduction unit located in front of the diesel oxidation catalyst device, into which an aqueous urea solution is introduced; and
a urea flow pipe provided through the diesel oxidation catalyst device, through which the aqueous urea solution introduced through the urea introduction part passes;
further comprising,
The urea mixer, exhaust gas post-treatment system including a filter coated with a denitration catalyst, characterized in that provided at the downstream end of the urea flow pipe. 10. The method of claim 9,
The urea introduction unit, Exhaust gas post-treatment system including a filter coated with a denitration catalyst, characterized in that the urea aqueous solution is introduced together with high-pressure air to pass through the urea flow pipe.

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