KR20120042778A - Unification catalytic converter apparatus - Google Patents

Abstract

PURPOSE: An integrated type catalyst purifying apparatus is provided to simultaneously reduce particulate materials and nitrogen oxide materials from the exhaust gas of diesel engines and to minimize the volume of a catalytic apparatus. CONSTITUTION: Exhaust gas is introduced through an introducing pipe(110). A filter(101) for eliminating particulate materials eliminates particulate materials from the exhaust gas. An exhausting pipe(150) discharges the purified exhaust gas through the filter to outside. A lean NOx catalyst(LNT) coating part oxidizes hydrogen carbide, carbon monoxide, volatile materials, and nitrogen monoxide. During the oxidization, the hydrogen carbide and nitrogen oxides are reacted to generate ammonia as an intermediate product. A selective catalytic reduction catalyst coating part uses the ammonia from the LNT coating part to eliminate non-purified nitrogen oxide materials.

Description

Integrated catalytic purifier {UNIFICATION CATALYTIC CONVERTER APPARATUS}

The present invention relates to a catalyst purifying apparatus for purifying exhaust gas of an automobile, and more particularly, to construct a two-stage coating of a particulate NOx trap (LNT) catalyst and a selective catalytic reduction (SCR) catalyst on a filter for removing particulate matter. The present invention relates to an integrated catalytic purifier for removing particulate matter and nitrogen oxides.

Conventionally, in order to reduce particulate matter (PM) in diesel engine exhaust gas, a breathable carrier DPF (Diesel Particulate Filter) and nitrogen oxides (NOx, nitrogen oxides) to reduce LNO (Lean NOx Trap), SCR ( Selective Catalytic Reduction Catalytic Purifiers were used individually.

In general, the particulate matter and nitrogen oxide purification device of a diesel engine has been practically separated and practically used as a separate device for filtering particulate matter and a catalytic device for purifying gaseous nitrogen oxides.

Therefore, the space occupied by these purifiers is heavy and heavy, which is very disadvantageous to apply when space is limited and fuel consumption is important.

The present invention has been made to solve the problems of the prior art as described above, the object of the present invention, in particular, the nitrogen oxide reduction catalyst in the DPF to reduce the particulate matter and nitrogen oxides in the exhaust gas of the diesel engine at the same time The LNT catalyst and the SCR catalyst are composed of two stages, and the volume of the catalyst device can be minimized to minimize the mounting space, and the mass of the system can be minimized to achieve fuel efficiency, ease of mass production, and exhaust treatment. An integrated catalyst purifier is provided.

According to the present invention, the catalyst purifying apparatus for purifying exhaust gas of a diesel vehicle, the induction pipe into which the exhaust gas flows; A particulate matter removal filter for removing particulate matter from an exhaust gas introduced through the induction pipe; It includes a discharge pipe for discharging the exhaust gas purified from the filter for removing particulate matter to the outside; The particulate matter removal filter oxidizes hydrocarbons, carbon monoxide, volatile substances, and nitrogen monoxide (NO) of the exhaust gas. At this time, the nitrogen and the intermediate product ammonia (NH ₃ ) are reacted with the nitrogen oxide stored in the hydrocarbon as a reducing agent. In the catalyst coating for LNT and the catalyst coating for LNT, Generated It is achieved by an integrated catalyst purifier, characterized in that it has a catalyst coating for the SCR to remove nitrogen oxides not purified using the ammonia.

Here, it is preferable to further include an injector for injecting the reducing agent required for the LNT catalyst to the filter for removing particulate matter on the catalyst coating side for the LNT.

At this time, the reducing agent is more effective to include ammonia, urea, hydrocarbons.

In addition, the SCR catalyst coating part is an SCR catalyst due to heat generated by oxidation reaction of nitrogen oxide (NO ₂ ), hydrocarbon, carbon monoxide, or volatile material having high oxidizing power, which is not removed from the catalyst coating part for LNT (Lean NOx Trap). More preferably, oxidation proceeds in the phase.

According to the present invention, in the case of exhaust post-treatment in which the LNT catalyst and the SCR catalyst are coated on the particulate matter removing filter in two stages, the particulate matter can be reduced as well as the nitrogen oxides in the exhaust gas of the diesel engine. .

In addition, according to the present invention by coating the LNT catalyst and the SCR catalyst on the particulate material removal filter in two stages, the structure of the exhaust aftertreatment device can be simplified to reduce the number of parts of the vehicle, so that it is easy to install and improve the productivity. It also has the effect of reducing weight and contributing to improved fuel economy.

1 is a block diagram showing an integrated catalytic purifier according to an embodiment of the present invention.
FIG. 2 shows the ammonia concentration generated from the shear LNT catalyst in the integrated catalytic purifier 100 of FIG. 1. It is a graph showing.
FIG. 3 is a graph showing nitrogen oxide purification performance when an LNT and an SCR (for example, Fe-ZSM-5) catalyst are disposed at the front end of the catalyst in the experiment of FIG. 2.

Hereinafter, an integrated catalyst purifying apparatus according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The basic principle of the present invention is a gamma (or alpha, which is a wash coat) on a SiC (silica carbide), TiO ₂ , cordierite (cordierite) carrier, which is used as a carrier for a particulate particulate filter (DPF). Beta phase) Alumina is coated with the main catalyst noble metals Pt, Pd, Rh, and rare earth metals such as Ba, Zr, Ce, La, etc., to reduce nitrogen oxides of LNT (Lean NOx Trap) function. A catalyst capable of simultaneously reducing particulate matter and particulate matter was applied to the front end, followed by a Cu, Fe-ZSM-5 catalyst such as NH ₃ (or urea) -SCR (Selective Catalytic Reduction (SCR)) catalyst, etc. Coating to place it inside the casing with the outlet and the inlet at the rear end.

In the present invention, the catalyst coating for LNT is disposed at the front end, and the catalyst coating for SCR is disposed at the rear end.

In describing the present invention, when it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a block diagram showing an integrated catalytic purification apparatus for removing particulate matter and nitrogen oxides according to an embodiment of the present invention.

Referring to FIG. 1, the integrated catalyst purifying apparatus 100 for removing particulate matter and nitrogen oxide according to the present invention includes a particulate material having an induction pipe 110, a catalyst coating part 120 for an LNT, and an SCR catalyst coating part. It is comprised including the filter 101, the injector 130, and the discharge pipe 150.

The operation of the integrated catalyst purification apparatus 100 for removing particulate matter and nitrogen oxide according to the present invention configured as shown in FIG. 1 is as follows.

First, although the basic structure of the particulate matter removal filter 101 is not shown in detail, it is composed of a cell through which exhausts of various shapes such as triangular, square, hexagonal, and circular can pass, similar to the three-way catalyst of the ceramic carrier. The wall of this cell is characterized by the development of pores to allow exhaust gas to pass through. If the inlet side of the cell is open, the outlet of the cell is blocked, and particulate matter, which is a solid substance in the exhaust, is filtered through the cell. The gas passes through the cell wall and exits into the adjacent cell. The inlet of the adjacent cell of the cell in which the cell inlet side is open is blocked and the outlet is open so that the filtered gas enters and flows through the cell wall.

When the exhaust gas of the diesel engine enters through the purification apparatus induction pipe 110, hydrocarbon, carbon monoxide and volatile substances, which are oxides in the exhaust gas, are oxidized in the catalyst coating unit 120 for LNT in the front end, and nitrogen monoxide (NO) is It is oxidized to form nitrogen dioxide (NO ₂ ). At this time, nitrogen (N 2) and ammonia (NH ₃ ) are generated by the reaction of the nitrogen oxide stored with the hydrocarbon supplied as a reducing agent.

In addition, particulate matter accumulates in the catalyst coating part 120 for the LNT, and when the temperature of the catalyst coating part 120 for the LNT rises more than 250 degrees, the coated precious metal and the rare earth cocatalyst are continuously regenerated. Reduction is performed by the function of the LNT catalyst, in which the reducing agent (ammonia, urea, hydrocarbon, etc.) required for the LNT catalyst is supplied from the outside through the injector 130.

Then, the material to be oxidized in the catalyst coating unit 120 for LNT is oxidized, and the generated NH ₃ and NO ₂ or NO are introduced into the catalyst coating unit 140 for SCR at the rear end to completely remove nitrogen oxides (NOx). .

On the other hand, the material of the SCR catalyst coating 140 may be silica carbide, cordierite, or titanium dioxide, but titanium dioxide may be more efficient in purifying nitrogen oxides in this carrier coating the SCR catalyst.

The particulate matter is almost removed at the front end, but the particulate matter that has not yet been removed is accumulated at the rear end and oxidized on the SCR catalyst due to the heat generated by the oxidation reaction of NO ₂ , hydrocarbon, carbon monoxide, and volatile substances, which are strongly oxidized. It has an ongoing feature.

In this case, the volume ratio of the LNT catalyst coating part 120 and the SCR catalyst coating part 140 at the front end may have any one value of 100% by adding two ratios in the range of 30 to 90:10 to 70. However, it is preferable that the volume of the shear is large.

2 is a graph showing the ammonia production concentration according to the catalyst temperature of the integrated catalyst purification apparatus 100 of FIG.

Referring to FIG. 2, (a) shows an example of ammonia production concentration according to catalyst temperature when using only LNT catalyst, and (b) shows an example of ammonia production concentration according to catalyst temperature when using both LNT catalyst and SCR catalyst. Shows.

For example, the catalyst is coated on cordierite square cells (cell density: 600 cells / in ² ) at a noble metal Pt / Pd / Rh = 6/6/1 ratio, and contains barium (Ba) as a nitrogen adsorption material.

In addition, the simulated combustion gas used for performance evaluation was in a lean state (excess air ratio, λ = 1.6), 450 ppm C1 of propane (C ₃ H ₈ ), 500 ppm of carbon monoxide (CO), 250 ppm of nitrogen monoxide (NO), and nitrogen dioxide (NO _2). ) 250ppm, oxygen 12%, H ₂ O 1.5%.

The ammonia production evaluation result (a) shows that 90 ppm is produced and discharged at 200 ° C., and lower concentration is generated and discharged at a higher temperature.

On the other hand, ammonia production evaluation result (b) is characterized in that the ammonia generated and discharged from the LNT can be supplied as a reducing agent of the SCR catalyst without an auxiliary device (for example, urea water injection system) for the production of ammonia. . After all, the ammonia produced in the front LNT is useful as a reducing agent for the removal of nitrogen oxides in the back SCR .

Therefore, in (b), emission of ammonia hardly occurs.

FIG. 3 is a graph showing nitrogen oxide purification performance when LNT and SCR (for example, Fe-ZSM-5) catalyst are disposed at the front end of the catalyst in the experiment of FIG. 2.

For reference, the results of FIG. 3 are the same reaction conditions as those of FIG. 2.

Referring to FIG. 3, (c) shows the purification rate of nitrogen oxide according to catalyst temperature when using only LNT catalyst, and (d) shows the purification rate of nitrogen oxide when using both LNT catalyst and SCR catalyst.

According to the performance evaluation, the nitrogen oxide purification rate was maintained about 60% when only LNT was used. When the LCR catalyst was placed at the front and the SCR catalyst was disposed at the front, the nitrogen oxide purification rate was lower than the LNT only. Up to about 30%.

In this way, the LNT and the SCR catalyst were composed of two stages, and examples of effectively purifying nitrogen oxides in the exhaust gas of the diesel engine were shown. As proposed herein, the conventional particulate filter for removing particulate matter The exhaust post-treatment consisting of two stages coated with the LNT catalyst and the SCR catalyst has the advantage of reducing not only the nitrogen oxides in the exhaust gas of the diesel engine but also the particulate matter at the same time.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

100: integral catalytic purification device 101: filter for removing particulate matter
110: induction pipe 120: catalyst coating for LNT
140: SCR catalyst coating 150: discharge pipe

Claims (4)

In the catalytic purifier for purifying exhaust gas of a diesel vehicle,
An induction pipe into which the exhaust gas flows;
A particulate matter removal filter for removing particulate matter from an exhaust gas introduced through the induction pipe;
It includes a discharge pipe for discharging the exhaust gas purified from the filter for removing particulate matter to the outside;
The particulate matter removal filter
Catalyst coating for LNT, which oxidizes hydrocarbons, carbon monoxide, volatiles and nitrogen monoxide (NO) of the exhaust gas, and reacts with hydrocarbons, which are reducing agents, and nitrogen oxides stored therein, to generate nitrogen and intermediate product ammonia (NH ₃ ). Wealth,
In the catalyst coating for LNT Generated Integrated catalyst purification apparatus having a catalyst coating for the SCR to remove the nitrogen oxides not purified using the ammonia. The method of claim 1,
And an injector for injecting a reducing agent required for the LNT catalyst to flow into the particulate matter removing filter on the catalyst coating side of the LNT. The method of claim 2,
The reducing agent is an integral catalytic purifier, characterized in that it comprises ammonia, urea, hydrocarbons. The method of claim 2,
Catalyst coating for SCR
Particles that are not removed from the catalyst coating part for LNT (Lean NOx Trap) are oxidized on the SCR catalyst due to heat generated by the oxidation reaction of nitrogen oxide (NO ₂ ) with strong oxidizing power, hydrocarbon, carbon monoxide, or volatile material. An integrated catalyst purifying apparatus.

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