WO1999005401A1

WO1999005401A1 - Exhaust cleaning arrangement for a diesel motor

Info

Publication number: WO1999005401A1
Application number: PCT/DE1998/002039
Authority: WO
Inventors: Frank Witzel; Wieland Mathes; Steffen Schnapp
Original assignee: Siemens Aktiengesellschaft
Priority date: 1997-07-24
Filing date: 1998-07-20
Publication date: 1999-02-04
Also published as: DE19731926C1

Abstract

The invention relates to an arrangement containing an injection device (6) for means of reduction (r), a mixing device (8) and a catalytic converter device (14), said devices being located inside of, for instance, a vertically placed exhaust pipe (4). According to the invention, a fine-meshed protection screen (12) is placed inside the exhaust pipe (4). Said screen prevents the broken-up particles, especially the catalytic converter chunks or blades of the mixing device (8), from falling in the direction of the diesel engine. This protects the turbo-supercharger (2) which is generally located down from the diesel motor. The protection screen (12) preferably forms a structural unit with the mixing device (8) which can be handled as a single unit.

Description

description

7Λ gas cleaning system for a diesel engine

The invention relates to an ignition system for cleaning exhaust gas for a diesel engine, in which an injection device for a reducing agent, a mixing device and a catalyst device are arranged in an exhaust pipe. The 7Λnlage can be used in particular for a marine diesel engine.

A system of the type mentioned at the outset is marketed under the name SiNOx exhaust gas purification system by Siemens AG, Berlin and Munich, Germany (company brochure "SINOx nitrogen oxide reduction for stationary diesel engines", order number A96001-U91-A232).

With such a system, the nitrogen oxide emission of a diesel engine can be drastically reduced. The mode of operation of the SiNOx exhaust gas cleaning system is based on the SCR process (Selective Catalytic Reduction). The nitrogen oxides of the exhaust gas are mixed with a reducing agent, such as ammonia or urea, in the exhaust pipe, passed into a reactor space and converted to the environmentally friendly substances hydrogen and nitrogen at the catalyst device. A static mixer is used to mix the reducing agent with the exhaust gas.

Such a static mixer is known for example from EP 0 594 657. It can be used in particular in an exhaust gas purification system for the exhaust gas from power plants, but also from diesel engines. It has a number of deflection elements or wings, which serve to swirl the flowing exhaust gas.

The exhaust pipe can in particular between the turbocharger (compressor) of a diesel engine and between the exhaust gas supply system for nitrogen oxide cleaning. It has now been found in practice that parts can fall into the exhaust pipe during assembly work or service work on the system. This can be broken off parts from the catalyst device, but also wings from the mixing device. This can result in damage to the turbocharger and thus to a standstill of the diesel engine, especially with a vertically or diagonally laid pipeline for the exhaust gas - the exhaust gas is routed from bottom to top. The exhaust gas cleaning systems described in the prior art and known here do not contain any protective devices against such falling parts.

The object of the present invention is accordingly to design a plant of the type mentioned at the outset in such a way that it ensures protection from parts, in particular from falling parts. If the exhaust pipe originates from a turbocharger of the diesel engine, this turbocharger in particular should also be protected.

To achieve this object, a system of the type mentioned is characterized according to the invention by a fine-meshed protective grille in the exhaust pipe.

This screen or protective grille is preferably combined with the mixing device. The protective grille and the mixing device, which generally consist of metal, can be welded to one another so that they result in a relatively thin structural unit. The above-mentioned static mixer is preferably used as the mixing device.

The protective grille should be installed on the upstream side of the mixer if possible. It then prevents not only broken chunks of the catalytic converter from falling, but also broken blades of the mixer in the direction of the turbocharger and the diesel engine which may be present. The protective grille can be installed directly on or especially directly below the catalyst device. If a mixer is integrated in front of the injection device, it makes sense to attach the protective grille here.

The advantage of the invention is in particular that the turbocharger, if present, is also protected from particles present in the exhaust pipe. The fine-meshed protective grille generally does not represent an additional pressure loss.

Exemplary embodiments of the invention are explained in more detail below with reference to three figures. Various variants for the arrangement of the protective grille in the exhaust pipe of an exhaust gas cleaning system for a diesel engine (stationary or movable) are shown therein. Combinations are also possible. The same reference numerals are used in the figures for the same components. The individual shows:

1 shows an exhaust gas cleaning system with a protective grille directly on the upstream side of the catalyst device,

2 shows an exhaust gas cleaning system with a combination of mixing device and protective grille between

Injection device and catalyst device, as well

3 shows an exhaust gas cleaning system with a combination of mixing device and protective grille in the flow direction in front of a injection device.

According to FIG. 1, a diesel engine (not shown), in particular a marine diesel engine, emits exhaust gas A into an exhaust pipe 4 via a compressor or turbocharger 2. The exhaust pipe 4 is here in particular laid vertically or at a slight angle to the vertical. The introduced exhaust gas A meets an injection nozzle direction 6 for a reducing agent r, for example for ammonia (NH ₃ ) or in particular for urea in aqueous solution. The mixture of exhaust gas A and reducing agent r then meets a mixing device 8, which is made in particular of a corrosion-resistant metal. This mixing device is a so-called "static mixer" and can preferably be constructed according to EP 0 594 657. A good mixing or swirling takes place here. The mixture of exhaust gas A and reducing agent r is then passed into an enlarged reaction space 10. In this there is a sieve or protective grid 12. This protective grid 12 consists of a woven fabric of metal threads; its thickness d is, for example, between 2 mm and 4 mm. Immediately afterwards, a catalytic converter device 14 is installed, which in the present case consists of three modules of a DeNOx-CATalyser one above the other in levels I, II and III. The exhaust gas A 'cleaned here is passed on via an outlet opening 18, for example discharged outdoors.

It is clear from FIG. 1 that the protective grid 12 protects the mixing device 8, the injection device 6 and also the turbocharger 12 from falling off broken catalyst particles or lumps.

FIG. 2 largely corresponds to FIG. 1. However, here the metallic protective grille 12 is arranged between the injection device 6 and the mixing device 8, namely directly in front of its inflow surface. It is also clear from FIG. 2 that the protective grid 12 and the mixing device 8 are integrated into one another and form a structural unit. In other words, they can be welded together. In this variant, the protective grille 12 protects both the injection device 6 and the turbocharger 2 against broken catalyst particles and against mixing blades that have broken away from the mixing device 6. Protection of the turbocharger 2 is thus also ensured here and thus prevents the diesel engine from being stopped. 3, an integration or combination of metallic protective grille 12 and metallic mixing device 8 is also provided. These two components 8, 12 can also be welded together again here. The combination 8, 12 is here - as seen in the flow direction of the exhaust gas A - arranged in front of the injection device 6 for the reducing agent r, the protective grille 12 facing the turbocharger 2. The protective grid 12 is therefore arranged on the side of the turbocharger 2. The arrangement is such that the injection device 6 lies in the turbulence area of the combination 8, 12. Here, too, the protective grille 12 and the mixing device 8 preferably form a unit that can be handled in a uniform manner.

Finally, it should also be mentioned that in all embodiments, an access opening (not shown), for example also a manhole, can expediently be arranged in the exhaust pipe 4 in the vicinity of the protective grille 12, this access opening in the vicinity of the protective grille 12 is useful in order to prevent falling particles , for example Quickly remove catalyst pieces, mixer pieces or nozzle parts.

Claims

claims

1. Plant for purifying exhaust gas (A) for a diesel engine, in which an injection device (6) for a reducing agent (r), a mixing device (8) and a catalyst device (14 ) are arranged, characterized by a fine-meshed protective grille (12) in the exhaust pipe (4).

2. System according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the protective grille (12) with the mixing device (8) is combined.

3. Plant according to claim 2, d a d u r c h g e k e n n z e i c h n e t that the protective grille (12) on the upstream side of the mixing device (8) is fixedly arranged.

4. System according to one of claims 1 to 3, d a d u r c h g e k e n n e e c h n e t that the protective grille (12) - seen in the flow direction of the exhaust gas (A) - is arranged behind or in front of the injection device (6) (Fig. 2 or 3).

5. Plant according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the protective grille (12) is fixedly arranged directly on the upstream side of the catalyst device (14) (Fig. 1).

6. System according to one of claims 1 to 5, that the exhaust pipe (4) is laid vertically or at an angle to the vertical.

7. Plant according to one of claims 1 to 6, characterized in that the exhaust pipe (4) is connected to a turbocharger (2).

8. Installation according to one of claims 1 to 7, d a d u r c h g e k e n n e e c h n e t that the protective grid (12) consists of a fabric of metal threads.

9. Plant according to one of claims 1 to 8, that the thickness (d) of the protective grille (12) is between 2 mm and 4 mm.

10. Plant according to one of claims 1 to 9, d a d u r c h g e k e n n e e c h n e t that the catalyst device (14) comprises several levels (I, II, III).

11. System according to one of claims 1 to 10, g e k e n n z e i c h n e t d u r c h their application in a marine diesel engine.

12. System according to one of claims 1 to 11, d a d u r c h g e k e n n e e c h n e t that an access opening is provided in the exhaust pipe (4) near the protective grille (12).