JP2003510175A - Apparatus for supplying reactants to flowing gas - Google Patents

Abstract

(57) Abstract: A device for supplying a reactant, particularly a reducing agent, to a flowing gas, particularly an exhaust gas, wherein a supply pipe formed with an opening (2) is provided in a wall of the device. A feed pipe (1) upstream of said opening (2), wherein the reactant introduced into the feed pipe via said opening can be introduced into the flowing gas. The diaphragm is arranged at the center.

Description

Detailed Description of the Invention

The invention relates to a device of the type described in the preamble of claim 1 for supplying a reactant, in particular a reducing agent, to a flowing gas, in particular exhaust gas.

In order to reduce the value of harmful substances in automobiles, extensive development has been carried out, especially in catalytic technology for reducing nitrogen oxides in exhaust gas. In this case, reduced catalysts have proved to be particularly promising.

An apparatus for post-treating exhaust gas is, for example, European Patent Application Publication No. 0.
A system is known from JP 381236 A, in which ammonia or urea as a reducing agent is metered into the exhaust gas. In this known system, a reducing agent is injected into the premixing chamber via an injection valve, which premixing chamber opens into an exhaust pipe leading to the reducing catalyst. In such a device for introducing a reducing agent into the exhaust pipe section of an internal combustion engine leading to a reducing catalyst, the premixing chamber forms a reducing agent conduit which opens into the exhaust pipe.

A wall film is formed even if part of the reducing agent is atomized in the mixing chamber or mixing section. The use of the spray tube described in EP-A-0 381 236, cited above, leads to non-uniform wall film collapse, especially in the case of small amounts of reducing agent, in the deflection zone. This wall membrane collapse is based on the formation of different flow velocities of air, exhaust gas or another carrier substance used for carrying the reducing agent in the inner or outer zone of the tube bend. This does not guarantee a good even distribution of the reducing agent throughout the operating range of the system. As a result, the conversion rate in the catalyst is relatively poor.

In a known exhaust gas aftertreatment device for an internal combustion engine based on German patent application DE 196 25 447 A1, the fuel serves as a reducing agent in order to assist the action of a reducing catalyst connected downstream. It is metered via a metering valve and brought to the exhaust valve via a vaporizer. The vaporizer is a metal sleeve equipped with a glow plug and having a flow opening on the end face side, and the vaporized reducing agent is introduced into the exhaust gas flow through the flow opening. Although vaporization of the reducing agent is thermally assisted in this system, this solution is technically laborious and requires high energy demand to heat and vaporize the reducing agent.

It is therefore an object of the present invention to produce a good aerosol formation in the largest possible characteristic field range, to increase the overall efficiency of the reaction system, in particular of the catalytic system, and to obtain, for example, lower NOx emissions. In particular, it is an object to provide a device for supplying a reactant, especially a reducing agent, to exhaust gas.

This problem is solved by a device having the features of claim 1.

With the device of the present invention, it is possible to supply the reactant or reducing agent to the fluidized gas, especially the exhaust gas, more uniformly than the conventional solution to the fluidized gas, especially the exhaust gas. The more homogeneous reactant or reducing agent distribution guaranteed according to the invention is already obtained in conventional systems, for example when a relatively small amount of reducing agent is provided in the exhaust gas to be catalytically worked up in the catalytic system. Allows for significantly better conversion rates compared to.

[0009]   Advantageous configurations of the device according to the invention are described in the subclaims.

In a particularly advantageous configuration of the device according to the invention, the means for the uniform distribution of the reactants are formed as throttles contained in the tube. Such a restriction can be provided very inexpensively and can easily be accommodated in a desired position of the reactant supply pipe or the metering pipe.

In a further advantageous configuration of the device according to the invention, the supply pipe extends substantially parallel to the flow direction of the flowing gas and a first region extending substantially perpendicular to the flow direction of the flowing gas. A second region, in which case an opening through which the reactant can be introduced from the supply pipe into the flowing gas is formed in the tube wall section of said second region, Means for even distribution are provided immediately upstream of the tube wall section. It has been found that the thus-formed supply pipe can be easily attached to an exhaust conduit through which exhaust gas flows. For example, the supply of the reducing agent in the exhaust system is performed with the aid of pressure air in the case of a commercial vehicle, for example. That is, the reducing agent to be supplied is conveyed through the supply pipe via the pressurized air. In particular, in the case of small amounts of reducing agent, due to the different flow velocities at the turning points of the feed pipe (transition between the first and second regions of the feed pipe), the uneven wall of reducing agent Membrane collapse occurs. In the conventional manner, the reducing agent flows out only through a part of the opening provided at the end of the supply pipe, which no longer guarantees a good even distribution over the operating range of the system. In the present invention, said non-uniform wall film collapse is compensated by re-focusing the reducing agent in the center of the spray tube, for example using a throttle, and then by said compressed air through an outlet opening into the exhaust gas stream as an aerosol. Can be brought evenly.

Advantageously, a plurality of openings are provided evenly on the peripheral surface of the tube. Due to the cooperation of such evenly arranged openings and the means for the uniform distribution of the reactants, it is possible to supply the reactants to the flowing gas particularly uniformly.

[0013]   Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows an exhaust pipe section 10 in which exhaust gas is guided from an internal combustion engine to a reducing catalyst.
Walls are shown. The flow direction of the exhaust gas is indicated by the arrow p. A supply pipe 1 is open in the exhaust pipe section 10 via which a reducing agent can be brought from a reducing agent store (not shown) to the exhaust pipe section. In addition to hydrocarbons, reducing agents include, for example, diesel fuels, in particular urea-water-solutions, which are supplied via injection nozzles, vaporizers or other metering devices, for example. Brought to the conduit.

In a manner which is conventional per se, the supply conduit 1 has, inside the exhaust pipe, a first region 1a extending substantially perpendicularly to the flow direction of the exhaust gas and a first region 1a substantially parallel to the flow direction of the gas. It has a second region 1b extending in parallel and a bending region 1c connecting these regions 1a and 1b. The second region 1b of the supply pipe is preferably arranged centrally with respect to the exhaust pipe and extends at least in substantially the same direction as the exhaust gas flow in the exhaust pipe.

At the end portion on the downstream side of the supply pipe 1, there is formed a section indicated by reference numeral X, which is enlarged and shown in FIG. In this range X, the supply pipe 1 has a plurality of openings 2 formed in the peripheral surface of the wall of the pipe section 1b, from which openings the reducing agent is fed.
Can enter the exhaust pipe. A diaphragm 3 is arranged in front of the opening 2 toward the downstream side, and the diaphragm 3 has a central diaphragm opening 3a. The function of the diaphragm 3 in its operative coupling with the aperture 2 will be explained below.

The supply pipe 1 is fixed to the wall 10 of the exhaust pipe by, for example, a screw fastening portion 11.

The use of the spray tube shown leads to a non-uniform wall film collapse in the deflection zone, especially with small amounts of reducing agent. This wall-membrane collapse is based on the formation of different flow velocities of air, exhaust gas or another carrier material used to carry the reducing agent in the inner or outer zone of the tube bend. This does not guarantee a good even distribution of the reducing agent throughout the operating range of the system. As a result, the conversion rate in the catalyst is relatively poor.

The squeeze 3 serves to concentrate the wall film in the center of the spray tube, and thereby
The effects of a severed wall membrane can be compensated. The reducing agent concentrated in the center of the feed pipe 1 by the throttle 3 is forced through the central opening 3a of the throttle 3 by said pressurized air, which leads to a uniform supply of the reducing agent to the opening 2.

As can be seen from the above, the use of the diaphragm 3 significantly improves the quality of the aerosol production compared to the conventional configuration, so that the overall efficiency of the system, that is, the NOx reduction, is lower than the conventional one. It can be improved compared to the configuration. The system can be adapted to different requirements or internal combustion engines, with parameters relating to the arrangement, size and number of the openings 2 and the size of the central opening 3a of the diaphragm 3.

[Brief description of drawings]

[Figure 1]   1 shows a cross-sectional side view of an advantageous embodiment of the device according to the invention.

[Fig. 2]   It is an enlarged view of the range X of FIG.

[Explanation of symbols]

1 supply pipe, 1a 1st area | region, 1b 2nd area | region, 2 opening, 3
Throttle, 10 exhaust pipe section, 11 screw fastening part, p flow direction

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F01N 3/08 F term (reference) 3G091 AA02 AB04 BA14 BA39 CA13 CA16 CA17 DA01 DA02 4D002 AA12 AC10 BA06 CA11 CA20 DA07 DA57 4D048 AA06 AB02 AC03 CC61 4G068 AA03 AB11 AC13 AD18 AF40

Claims (4)

[Claims] 1. A device for supplying a reactant, in particular a reducing agent, to a flowing gas, in particular exhaust gas, the wall of which is provided with a supply pipe formed with an opening (2). In the type in which the reactant introduced into the supply pipe through the opening can be introduced into the flowing gas, the supply pipe (1) is provided upstream of the opening (2). Device for supplying a reactant to a flowing gas, characterized in that a throttle is arranged. 2. A supply pipe (1) has a first region (1a) extending substantially perpendicular to the flowing direction of the flowing gas and a second region extending substantially parallel to the flowing direction of the flowing gas. (1b) and an opening is formed in one section (X) of this second region (1b). 3. A device according to claim 1, wherein the supply pipe (1) is provided with a plurality of openings (2) evenly distributed on the peripheral surface thereof. 4. The diaphragm (3) has a central diaphragm opening (3a) with respect to the supply pipe (1).
) The device according to any one of claims 1 to 3, characterized in that