DE102016110319A1 - Method and device for generating ammonia in an exhaust gas stream of an internal combustion engine - Google Patents

Abstract

The invention relates to a method for producing ammonia in an exhaust gas stream (5) of an internal combustion engine, in particular a diesel engine, from an aqueous urea solution injected by an injector (1). In the method, a first partial flow (18) and a second partial flow (19) of the exhaust gas flow are separated, a first partial flow (18) of the exhaust gas flow (5) being conducted separately from a second partial flow (19) in an inner housing (10) , which is surrounded by an outer housing (2), so that the second partial flow (19) of the exhaust gas stream (5) between the inner housing (10) and outer housing (2) can flow. In addition, an injection of aqueous urea solution substantially into the first partial flow (18) and heating and mixing of the injected aqueous urea solution and the first partial flow in the inner housing (10). In addition, a delay of the first partial flow of the exhaust gas flow in the inner housing, so that a residence time of the exhaust gas flow is increased in the inner housing and passing the resulting mixture by a hydrolysis catalyst (3) in an end portion of the inner housing (20), and the merging of the Partial streams (18, 19) downstream of the hydrolysis catalyst takes place.

Description

The present invention relates to the production of ammonia in an exhaust gas stream of an internal combustion engine, in particular a diesel engine. In modern motor vehicles, the exhaust gases are cleaned by internal combustion engines in order to release as little pollutant into the ambient air. In particular, nitrogen oxides are purified by the so-called SCR process (Selective Catalytic Reduction), for which purpose certain amounts of reducing agent, in particular ammonia, have to be fed into the exhaust gas before this purification.

Many different methods of providing ammonia are known in the art, and the present invention is concerned with the production of ammonia from an aqueous urea solution. Urea in aqueous solution is typically carried in a separate tank in a motor vehicle and supplied to the exhaust gas purification system as needed.

Also for the type of feeder very different systems are known. Thus, the aqueous solution can be injected directly into an exhaust gas stream. However, it is also the production of ammonia from the aqueous urea solution by means of a so-called ammonia generator outside of the exhaust stream known, in which case only the generated ammonia is supplied to the exhaust gas. The present invention is concerned with the production of ammonia from an aqueous urea solution by means of an ammonia generator which generates the ammonia in a partial flow of the exhaust gas. Such systems are for example from the EP 1 052 009 B1 known. This document also describes the possibility of dividing an exhaust gas stream into two concentric partial streams and to carry out the production of ammonia in the internal partial stream.

Starting from the known systems, it is an object of the present invention to provide an improved method for generating ammonia in an exhaust gas stream, and to provide a compact component which can be arranged in an exhaust system upstream of an SCR catalyst and which ensures the trouble-free provision of suitable quantities of ammonia for the exhaust gas purification.

To achieve this object, a method according to claim 1 and an exhaust treatment component according to claim 5. Advantageous embodiments, which can be realized individually and combined in a technically meaningful manner, are described in the respective dependent claims.

• a) ein erster Teilstrom und ein zweiter Teilstrom des Abgasstroms werden voneinander getrennt,
• b) ein erster Teilstrom des Abgasstroms wird getrennt von einem zweiten Teilstrom in einem Innengehäuse geführt, welches von einem Außengehäuse umgeben ist, so dass der zweite Teilstrom des Abgasstroms zwischen Innengehäuse und Außengehäuse strömen kann,
• c) die Injektion von wässriger Harnstofflösung erfolgt im Wesentlichen in den ersten Teilstrom, wobei dieser in dem Innengehäuse beheizbar ist und mit der eingedüsten wässrigen Harnstofflösung gemischt wird,
• d) in dem Innengehäuse erfolgt eine Verzögerung des ersten Teilstroms des Abgasstroms, so dass eine Verweilzeit des Abgasstroms in dem Innengehäuse erhöht wird.
• e) in einem Endbereich des Innengehäuses wird das entstehende Gemisch durch einen Hydrolysekatalysator geleitet und
• f) stromabwärts von dem Hydrolysekatalysator werden die Teilströme wieder zusammengeführt.

The method according to the invention for producing ammonia in an exhaust gas stream of an internal combustion engine, in particular a diesel engine, from an aqueous urea solution injected by an injector comprises the following steps:

• a) a first partial flow and a second partial flow of the exhaust gas flow are separated from one another,
• b) a first partial flow of the exhaust gas flow is conducted separately from a second partial flow in an inner casing, which is surrounded by an outer casing, so that the second partial flow of the exhaust gas flow can flow between inner casing and outer casing,
• c) the injection of aqueous urea solution takes place essentially in the first partial flow, wherein this is heatable in the inner housing and mixed with the injected urea aqueous solution,
• d) in the inner housing there is a delay of the first partial flow of the exhaust gas flow, so that a residence time of the exhaust gas flow in the inner housing is increased.
• e) in an end region of the inner housing, the resulting mixture is passed through a hydrolysis catalyst and
• f) downstream of the hydrolysis catalyst, the partial streams are brought together again.

The first partial flow can also be referred to as inner partial flow. The second partial flow can also be referred to as an external partial flow. Due to the possibility of heating the first partial flow, the ammonia production can be maintained independently of the respective temperature of the exhaust gas flow. In addition, undesirable deposits on an injector for adding aqueous urea solution into the exhaust stream and around the injector can be avoided. Also, the ammonia production can be easily adapted to different exhaust gas volumes per unit time.

• – Betriebssituation direkt nach dem ersten Start einer Verbrennungskraftmaschine bei niedrigen Umgebungstemperaturen;
• – Hochlastbetrieb mit einem Lastanteil von mehr als 50 %, bevorzugt mehr als 80 %, insbesondere Vollastbetrieb unmittelbar nachfolgendend zu Betriebsphasen mit Niedriglastbetrieb mit einem Lastanteil unter 20 %, bevorzugt unter 10 % oder sogar unter 5 %, insbesondere Leerlaufbetrieb oder Schubbetrieb.

According to step c), the first partial flow in the inner housing can be heated. Preferably, the heating of the first partial flow is effected by a heating element, in particular a centrally and coaxially arranged electrically operated heating element. Heating rods are known in the prior art in various designs and electrical energy for their operation is available in every motor vehicle. Heating is preferably carried out when carrying out the described method only if very rare special situations of operation of an internal combustion engine occur. Such special situations include, for example, the following operating situations:

• - Operating situation directly after the first start of an internal combustion engine at low ambient temperatures;
• - High load operation with a load share of more than 50%, preferably more than 80%, in particular full load immediately after operating phases with low load operation with a load rate less than 20%, preferably less than 10% or even less than 5%, in particular idling or coasting.

Immediately after the cold start, an exhaust gas treatment device in a motor vehicle is usually still very cold. A low temperature can be compensated here with the heating.

In a high-load operation in direct succession after a low-load operation, low temperatures can also occur in an exhaust gas treatment device, which can be compensated with the heating.

Full load operation is a case of high load operation here. The idling operation and the overrun operation are here a case of the low load operation.

The term "overrun operation" here includes operating phases in which the internal combustion engine is towed, that is kept in rotational motion by the movement of the motor vehicle. In a coasting operation usually no combustion takes place in the internal combustion engine. There is no fuel supplied to the internal combustion engine. Such operation takes place, for example, when a motor vehicle with a coupled internal combustion engine rolls downhill. Then high speeds of the internal combustion engine can stop. Optionally, the internal combustion engine functions as an air pump that conveys air into the exhaust treatment device. This air can lead to a strong cooling in an exhaust system.

With the delay of the first partial flow taking place in step d), it is achieved in particular here that the first partial flow flows much slower than the second partial flow. This can be explained on the basis of two (mental) volume sections of the exhaust gas flow. These two (mental) volume sections of the exhaust gas flow are in an (intellectual) inlet cross-sectional plane through the exhaust gas flow at the level of a housing inlet of the inner housing immediately adjacent to each other. These (intellectual) volume sections of the exhaust gas flow are then divided by the separation of the two partial flows (first partial flow and second partial flow) such that a first volume section is supplied to the first partial flow and a second volume section to the second partial flow. Then, the volume portion supplied to the first partial flow reaches an (intellectual) outlet cross-sectional plane at the level of a housing outlet of the inner housing substantially later than the volume portion supplied to the second partial flow. A first period of time, which a first volume section in the first partial flow requires in order to reach an intellectual outlet cross-sectional plane, is preferably at least twice as large as a second time span which a second volume section in the second partial flow requires to reach the outlet cross-sectional plane , Most preferably, this first period of time but even at least five times as large or even at least ten times as large. Preferably, the first partial flow of the exhaust gas is guided helically in the interior of the inner housing. As a result, on the one hand, the mixture is favored with aqueous urea solution and on the other hand increases the residence time of the first partial flow in the inner housing. In this way, an effective Enthalpiezufuhr, (mixing, evaporation, thermolysis and hydrolysis) can be effected.

The time required for a first volume section of the exhaust gas flow associated with the first partial flow to pass from the inlet cross-sectional plane to the outlet cross-sectional plane corresponds to the above-mentioned residence time of the exhaust gas flow in the inner housing. Accordingly, the residence time is preferably at least twice as long, preferably at least five times as long and particularly preferably at least ten times as long as the second time span.

It has been found that for complete conversion of urea into ammonia by hydrolysis, a chemical / physical process time of at least about 0.2 seconds is required. The described method and an exhaust gas treatment component provided for the described method are therefore preferably designed such that the residence time of the first partial flow in the inner housing reaches or, if possible, exceeds this process time under all relevant operating conditions and is thus preferably greater than 0.2 seconds. The residence time of the first partial flow preferably exceeds 0.4 seconds under all relevant operating conditions. This can be achieved by a suitable structure and a suitable design of the exhaust gas treatment component provided for the described method, specific features of the exhaust gas treatment component for achieving this goal being described in detail below. Due to the delay of the first partial flow can be achieved that the residence time of the first partial flow in the inner housing is always maintained, if necessary. This applies in particular to idling operation and partial load operation up to a full load fraction of 30%, preferably 40% and particularly preferably 50%. At a Part load operation with a higher proportion of load, it is regularly no longer necessary that the residence time is greater than the process time described, because an operation with a higher load share is regularly associated with such high exhaust gas temperatures that even below the process time is acceptable. Mixing, evaporation, thermolysis and hydrolysis can then take place partly after the merger of the first partial flow and the second partial flow. The said full load shares of up to 30%, preferably up to 40% and particularly preferably up to 50% are referred to herein as the "relevant operating conditions".

The fact that the first time span or residence time is greater than 0.2 seconds under all relevant operating conditions allows the complete conversion of aqueous urea solution to ammonia to be substantially independent of the total volume flow of the exhaust gas and to be of consistent quality , The reduction of the residence time could in fact lead to an insufficient conversion of the urea solution to ammonia. By observing the residence time in all of the operating conditions referred to herein as "relevant", heating is preferably required only in the above-mentioned very rare special situations of operation of an internal combustion engine.

The division between the first and second partial flow, in which preferably a proportion of 5-10% for the first partial flow should be achieved, on the one hand from the flow resistance of the two flow paths and on the other hand, this distribution is also by flow influencing means, in particular at least one inlet panel and / or at least one transversely to the first partial flow arranged in the inner housing Staumittel, in particular a perforated disc causes. By suitable dimensioning of these flow influencing means, the first partial flow for different exhaust gas systems can be brought into the desired order of magnitude. By suitable tests, it is also possible in particular to design flow influencing means on a housing inlet and a housing outlet on an exhaust gas treatment component in such a way that the percentage distribution of the first partial flow and the second partial flow is largely decoupled from the size of the exhaust gas flow as a whole (consisting of the first partial flow and the second partial flow) are set. Almost all components of the inner housing and its internals are structurally suitable for influencing the flow and for influencing the flow resistance as a function of the pressure and / or volume flow of the exhaust gas. Thus, in particular the design of the hydrolysis catalytic converter, inlet diaphragm, accumulation means and flow guiding structure can be coordinated and selected so that a substantial decoupling of the first partial flow from the total volume flow of the exhaust gas is achieved.

• – ein, in einem Außengehäuse gehaltertes, Innengehäuse, wobei das Außengehäuse eine Einlassöffnung, einen Zentralbereich mit gegenüber der Einlassöffnung erweitertem Querschnitt und eine Auslassöffnung aufweist,
• – einen Injektor für wässrige Harnstofflösung, wobei der Injektor so angeordnet ist, dass er im Wesentlichen wässrige Harnstofflösung in eine Einlassstrecke des Innengehäuses eindüsen kann,
• – Strömungsleitmittel zur Führung eines ersten Teilstroms eines, in die Abgasbehandlungskomponente strömenden, Abgasstroms durch das Innengehäuse und
• – eine Verzögerungsstrecke im Innengehäuse sowie einen Hydrolysekatalysator in einem Endbereich des Innengehäuses.

An exhaust gas treatment component is also to be described here, in particular for carrying out the method described above, which has the following parts:

• An inner housing supported in an outer housing, the outer housing having an inlet opening, a central area with a cross-section widened in relation to the inlet opening and an outlet opening,
• An aqueous urea solution injector, wherein the injector is arranged to inject substantially aqueous urea solution into an inlet passage of the inner case,
• - Flow guiding means for guiding a first partial flow of, flowing into the exhaust treatment component, exhaust gas flow through the inner housing and
• - A delay path in the inner housing and a hydrolysis in an end region of the inner housing.

The particular advantages and design features described in connection with the exhaust treatment component are applicable to the described method and transferable. The same applies to the particular advantages and design features described in connection with the method, which are applicable to the described exhaust gas treatment component and transferable.

The exhaust treatment component may be installed upstream of an SCR catalyst in a typical exhaust pipe, in particular downstream of a turbocharger and / or a particulate filter. The delay line in the inner housing leads to known systems to a better mixing of aqueous urea solution and first partial flow of the exhaust stream and allows in this area an adjustment of the temperature of the resulting mixture either by contact with the walls of the inner housing, which in turn with the second partial flow of the exhaust stream be in contact or by an additional heating. In addition, the delay section improves the conversion of urea solution to ammonia, because with the delay path a defined extended residence time of a first partial flow in the inner housing can be achieved. This extended residence time significantly improves the quality of the conversion of the urea solution to ammonia.

Preferably, the outer housing has a narrowing in the region of the outlet opening Outlet cone. The outlet opening preferably adjoins the narrowing outlet cone (in the flow direction). In addition, the outer housing preferably has an inlet cone widening in the direction of flow in the region of the inlet opening. The inlet cone preferably adjoins the inlet opening (in the flow direction).

Preferably, the outer housing in the region of the inlet cone to a recess, in particular to about the inlet section of the inner housing, the injector can be arranged to save space in this recess. An injector outlet of the injector is preferably connected directly to the inner housing or such injector outlet of the injector terminates in the inner housing. While known systems do not deal with the space-saving arrangement of an injector directly to an exhaust gas component, this preferred embodiment of the invention offers the possibility to accommodate an injector very space-saving on an exhaust gas treatment component according to the invention. Due to the depression, there is also the synergy effect here that direct supply of the urea solution into the inner housing is made possible. Additional pipe elements for introducing the urea solution in the inner housing can be omitted. The depression, which can be adapted in its dimension and shape to the shape of the injector, affects the second partial flow of the exhaust gas flow in the exhaust gas treatment component only slightly, but allows very short ways of aqueous urea solution when injected into the first partial flow. The recess may also be referred to as a dent, which reduces the volume of the outer housing and extends to the inner housing. The outer housing is preferably designed to be cylindrical in the central area arranged between inlet cone and outlet cone. It preferably has a circular cross section in the central area.

The inner housing preferably has a housing inlet and a housing outlet. The housing inlet is located in an (intellectual) inlet cross-sectional plane through the exhaust treatment component. The housing outlet is located in an (intellectual) outlet cross-sectional plane.

A decisive influence on the operation of the exhaust treatment component and in particular on the degree of distribution of the exhaust gas in the first partial flow and the second partial flow has the relative arrangement of the housing inlet and the housing outlet within the outer housing.

Preferably, the housing inlet is disposed within an inlet cone of the outer housing or even in the exhaust gas flow direction in front of the inlet cone. The (mental) inlet cross-sectional plane thus intersects the inlet cone or even lies in the exhaust gas flow direction in front of the inlet cone.

The housing outlet is preferably arranged inside the outlet cone of the outer housing or even in the exhaust gas flow direction in front of the outlet cone of the outer housing. The (mental) outlet cross-section plane thus intersects the outlet cone or even lies in the exhaust gas flow direction in front of the outlet cone.

The inner housing is preferably also at least partially cylindrical and at least in a central region preferably also has a circular cross-section. Preferably, a wall portion of the inner housing and a wall portion of the outer housing in the region of the recess to each other. In the region of this wall section, in each case an opening (or bore) is provided in the inner housing and in the outer housing, which openings are arranged congruently to one another. The injector, a spray nozzle of the injector or an extension element for conveying a spray cone from the injector into the exhaust gas preferably extends through these openings. These openings are preferably sealed off in an airtight manner by the components (in particular the injector) arranged therein, so that no exhaust gas can escape from the exhaust gas treatment component at these openings.

Particularly preferred in the present invention, a heating element is arranged in the inner housing, in particular an electric heating element. Typically, such a heating element has a round cross-section and is arranged centrally and coaxially in the inner housing, so that forms an annular space for the first partial flow. This annular space is arranged concentrically around the heating element.

In a further preferred embodiment, the heating element has at least two independently controllable heating areas or even heating zones. This allows, for example, a first heating region or a first heating zone, to which the injected aqueous urea solution initially strikes, particularly strongly heated and / or a second heating zone or a second heating zone upstream of the hydrolysis catalytic converter in dependence on a measured temperature of the first partial flow regulate.

It is advantageous if the heating element is angled or bent and guided through the outer housing to the outside, in particular through the inlet cone. In this way, it is not necessary to separate electrical leads separately through the To lay inside the exhaust treatment component. Electrical connections may in this embodiment be provided outside the exhaust treatment component at the angled end of the heating element.

There are preferably openings in the inner housing and in the outer housing through which the heating element extends. Preferably, these openings are sealed off in an airtight manner by the components arranged therein, so that no exhaust gas can escape from the exhaust gas treatment component at these openings. Electrical contacts are preferably arranged on the heating elements such that they are accessible from outside the exhaust gas treatment component, in particular at the angled end of the heating element. These openings are preferably sealed off in an airtight manner by the components (in particular the heating element) arranged therein, so that no exhaust gas can escape from the exhaust gas treatment component at these openings.

It is particularly favorable if the heating element in the angled region, which in practice is a bend with a certain radius of curvature, has an impact surface for the evaporation of aqueous urea solution, in particular a first heating region which is arranged separately with respect to its temperature. Typically, the injector and feedthrough of the heating element may be disposed opposite to the inlet cone, whereby the injected solution meets the bending of the heating element.

In a particularly preferred embodiment of the invention, the heating element is a heating element arranged concentrically in the interior of the inner housing, which is surrounded on the outside by a substantially helical flow-guiding structure. This embodiment considerably lengthens the path of the first partial flow in the inner housing, which at the same time leads to good mixing and uniform heating of the resulting mixture. At the same time, this embodiment improves the transfer of heat from the heating element to the first partial flow of the exhaust gas.

Outer and / or inner housing of the exhaust gas treatment component according to the invention preferably consist of half-shells, wherein preferably the inner housing is supported by at least one bearing on the outer housing. In order to be able to absorb thermal expansions and mechanical loads, it is advantageous to provide elastic bearings, in particular two bearings, between the outer housing and the inner housing.

Particularly preferably, the elastic bearings are designed such that a twist is induced in the second partial flow. More preferably, the elastic bearings between the half-shells of the outer housing and the inner housing are braced.

• – einen Aufweitungsbereich zum Abbremsen des ersten Teilstroms,
• – eine beheizte Auftrefffläche für wässrige Harnstofflösung,
• – eine Verzögerungsstrecke zum Erhöhen der Verweildauer des ersten Teilstroms im Innengehäuse mit einer Strömungsleitstruktur zur Verlängerung des Strömungswegs,
• – ein Stauelement, insbesondere eine perforierte Scheibe und einen Temperaturfühler, und
• – einen Hydrolysekatalysator zur Umsetzung von wässriger Harnstofflösung in Ammoniak.

In a specific embodiment of the present exhaust gas treatment component, the inner housing has the following sections in succession in the flow direction:

• A widening area for braking the first partial flow,
• A heated impingement surface for aqueous urea solution,
• A delay line for increasing the residence time of the first partial flow in the inner housing with a flow guide structure for extending the flow path,
• - A baffle element, in particular a perforated disc and a temperature sensor, and
• - A hydrolysis catalyst for the reaction of aqueous urea solution in ammonia.

The features of the inner housing mentioned here are arranged one behind the other along the inner housing from the housing inlet to the housing inlet in the flow direction of the exhaust gas. Preferably, the (central) region of the inner housing adjoining the widening region is cylindrical. The shape of the inner housing predetermined by the widening area and the adjoining (central) cylindrical area can be described in particular as a cigar-shaped inner housing.

In the automotive industry, standardized components are often used, but they should be adaptable to different applications. For this purpose, the exhaust gas treatment component according to the invention preferably has a widening area with an inlet panel that can be adapted to different exhaust gas conditions and exhaust gas systems, preferably by making the widening area replaceable.

The inlet aperture here preferably is a conical, funnel-shaped component which has a housing inlet of the inner housing with a smaller cross section and a connecting flange with a larger cross section. In between, the aforementioned widening area is formed. The connection flange can be connected to the following part of the cylindrical inner housing, in which the delay line, the hydrolysis catalyst and the other components are located.

In the flow direction downstream of the hydrolysis catalytic converter, a conical constriction region reducing the flow cross section is preferably still arranged on the inner housing, in which the inner housing constricts again. This constriction area has the effect that the first partial flow is accelerated again before a merger with the second partial flow takes place. As a result, there is also a pressure equalization between the first partial flow and the second partial flow before the merger. In addition, the formation of further turbulence is positively influenced at this point.

The preferably designed as a perforated disc baffle preferably spans the cross section of the inner housing or in particular the space between the inner housing and the heating element completely. Due to the configuration of the perforation of the perforated disc, as by the amount and size of the openings of the perforation, the volume flow of exhaust gas through the perforated disc can be fixed. The perforated disc is therefore preferred, as well as the inlet orifice, adaptable to various exhaust conditions and exhaust systems. Depending on which exhaust system the exhaust treatment component treated here is used, an adapted perforated disc can be used. The baffle element also causes the dissolution and / or the reduction of a possibly generated by the delay line twist of the flow and thereby also improves the uniformity of the flow of the hydrolysis.

An exhaust gas treatment component of the type described preferably has an overall length of the component of 330 mm to 400 mm, wherein the outer diameter of the outer housing 75 mm to 100 mm, and preferably the injector by installation in a recess only a maximum of 40 mm to 80 mm on the outer housing protrudes radially. This implements a particularly compact arrangement of an injector on an exhaust gas treatment component.

An embodiment of the described exhaust gas treatment component, to which the invention is not limited, is shown below in the drawing. The components shown simultaneously in this embodiment need not necessarily be used together in an application of the invention. It is also possible to realize the invention with only a part of the features illustrated in the embodiment.

1 shows a schematic longitudinal section of an exhaust gas treatment component according to the invention for generating and introducing ammonia into an exhaust gas stream.

An embodiment of the invention according to 1 shows an exhaust treatment component, as it can be installed in a typical exhaust pipe of an internal combustion engine, in particular in a motor vehicle. An exhaust gas flow 5 enters through an inlet opening 21 into the exhaust treatment component and passes through an inlet cone 22 in a central area 23 that has a larger diameter than the inlet opening 21 Has. In an outlet cone 24 becomes the exhaust gas flow 5 again to an outlet opening 25 merged. The whole exhaust treatment component is of an outer casing 2 enclosed, which the inlet cone described here 22 , the central area 23 and the outlet cone 24 forms. In the outer casing 2 and supported by two bearings 15 there is an approximately cigar-shaped inner casing 10 with a housing inlet 29 and a housing outlet 30 , The typical features of the cigar shape of the inner casing 10 are described above in detail. This inner case 10 has one, from an inlet panel 4 formed, expansion area 28 and goes into a delay line 27 above. The inlet panel 4 also forms the housing inlet 29 out. The inlet panel 4 is with a connection flange 31 to the other inner housing 10 connected. In one end area 20 of the inner casing 10 is a hydrolysis catalyst 3 arranged. In the end area 20 , behind the hydrolysis catalyst 3 , is optionally still a narrowing area 32 in which the cross section of the inner housing tapers again. A perforated disc 11 upstream of the hydrolysis catalyst 3 serves as a baffle element and allows to specify the flow resistance in the inner housing. Coaxial inside the inner casing 10 is a heating element 6 arranged in the form of a heating element, said heating element 6 angled, or bent and in the area of the inlet cone 22 led to the outside, so that an electrical connection 7 can be provided outside of the entire exhaust treatment component. The inlet cone 22 has a recess 16 on, in which an injector 1 is arranged for aqueous urea solution. An injector outlet 17 of the injector 1 ends near an inlet route 9 in the inner housing 10 , being in this inlet section 9 also the angled or bent part of the heating element 6 is arranged. Preferably, this bent or bent part of the heating element is a first heating region 8th formed, separated from other areas of the heating element 6 heat and, if necessary, regulate. The heating rod 6 still has at least a second heating area 13 downstream of the first heating area 8th on. In or on the heating rod 6 is also preferably a temperature sensor 12 arranged, the exact setting of a final temperature in the first partial flow 18 before the hydrolysis catalyst 3 allows. The heating rod 6 forms together with the inner housing 10 an annular space in which a helical Strömungsleitstruktur 14 is arranged. Occurs an exhaust gas flow 5 in the inventive Exhaust treatment component, so this is in a first partial flow 18 and a second partial flow 19 split, the first partial flow 18 through the inner housing 10 flows and the second partial flow 19 , between the outer casing 2 and the inner housing 10 flows. Typically, the system is dimensioned so that the first partial flow 18 about 5-10% of the second partial flow 19 is. This is due to the size of the inlet panel 4 , the expansion area 28 , the sizing of the annulus between heating element 6 and inner housing 10 , as well as the dimensioning and the number of holes (the perforation) in the perforated disc 11 to adjust. The first partial flow 18 flows through the expansion area 28 to the inlet route 9 , in which aqueous urea solution from the Injektorauslass 17 is injected. The urea solution meets an impact surface 26 of the heating element 6 in the area of the first heating area 8th , A sufficiently high temperature of the first heating area 8th makes sure that in the area of the injector outlet 17 and the inlet route 9 do not form deposits in the long term, especially no isocyanate deposits. For this purpose, temperatures above 500 ° C are advantageous. The first partial flow 18 continues to flow through a delay line 27 , which in the present embodiment by a helical Strömungsleitstruktur 14 is formed. The first partial flow flowing helically there 18 remains through this delay line 27 much longer in the inner housing 10 , as without Strömungsleitstruktur. This allows effective heating and thorough mixing of the first partial flow 18 with the supplied aqueous urea solution. The final temperature of the first partial flow 18 , approximately in the area of the perforated disc 11 can by means of the temperature sensor 12 measured and by appropriate control of the heating areas 8th . 13 of the heating rod 6 be managed. Finally, the first partial stream passes to the hydrolysis catalyst 3 , in which ammonia, water and carbon dioxide are generated, which then together with the first partial flow 18 to the outlet cone 24 in which she returns with the second partial flow 19 be merged, and to the outlet opening 25 reach. In a subsequent SCR catalytic converter, an effective conversion of the nitrogen oxides possibly contained in the exhaust gas can take place. The entire exhaust treatment component preferably has an axial length of 330 to 400 mm and an outer diameter of the outer casing 2 from 75 to 100 mm, taking in the recess 16 built-in injector extends only about 40 to 80 mm radially beyond the outer housing. A typical heating element 6 has a diameter of 15 to 25 mm, wherein for heating a power of preferably up to 1000 W can be introduced.

Warehousing 15 of the inner casing 10 in the outer housing 2 can preferably be constructed by radial lamellae, for example with an S-blow to compensate for expansions and vibrations, etc., with an axial angle of attack of the fins to an additional swirl generation in the second partial flow 19 , Such a spin can be mixed later with the first partial flow 18 improve. It should be noted that when a necessary heating of the first partial flow 18 (For example, in cold start phases or if only too cool exhaust gas is available), a heat flow to the second partial flow 19 generally undesirable, which is why the inner casing 10 should be designed and / or insulated so that no large heat flow into the second partial flow 19 or to the outer casing 2 through storage 15 he follows. In any case, the partial flow represents 19 An effective insulation against the loss of over the heating element 6 Consequently, the introduced heating energy can also be effectively passed through an optionally downstream SCR catalyst and the temperature level of the same efficiently improved. The injector 1 and the hydrolysis catalyst 3 are known elements, as they are already used by default.

The present invention provides a compact component, easily integrated into a typical exhaust line, for generating ammonia from an aqueous urea solution and allowing the reliable supply of suitable amounts of ammonia in the exhaust gas for removal of nitrogen oxides under various operating conditions.

LIST OF REFERENCE NUMBERS

1

injector

2

outer casing

3

hydrolysis catalyst

4

inlet aperture

5

exhaust gas flow

6

Heater / heating rod

7

Electrical connection

8th

First heating area

9

intake path

10

inner housing

11

Damp element / perforated disc

12

temperature sensor

13

Second heating area

14

Spiral flow guide structure

15

Storage of the inner housing

16

deepening

17

injector outlet

18

First partial flow

19

Second partial flow

20

End region of the inner housing

21

inlet port

22

intake cone

23

Central area

24

outlet cone

25

outlet

26

incident

27

delay path

28

widening range

29

housing inlet

30

housing outlet

31

flange

32

throat area

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1052009 B1 [0003]

Claims (15)

Process for the production of ammonia in an exhaust gas stream ( 5 ) of an internal combustion engine from a through an injector ( 1 ) urea aqueous solution, - separating a first partial flow ( 18 ) and a second partial flow ( 19 ) of the exhaust gas flow, wherein a first partial flow ( 18 ) of the exhaust gas stream ( 5 ) separated from a second substream ( 19 ) in an inner housing ( 10 ) guided by an outer housing ( 2 ), so that the second partial flow ( 19 ) of the exhaust gas stream ( 5 ) between inner housing ( 10 ) and outer housing ( 2 ), injection of aqueous urea solution essentially into the first partial flow ( 18 ) and heating and mixing the injected aqueous urea solution and the first partial flow in the inner housing ( 10 ), - delaying the first partial flow of the exhaust gas flow in the inner housing, so that a residence time of the exhaust gas flow in the inner housing is increased, - passing the resulting mixture through a hydrolysis catalyst ( 3 ) in an end region ( 20 ) of the inner housing ( 10 ) and - merging the partial streams ( 18 . 19 ) downstream of the hydrolysis catalyst. Method according to claim 1, wherein the heating of the first substream ( 18 ) by a heating element ( 6 ), in particular a coaxially arranged, electrically operated heating element takes place. Process according to claim 1 or 2, wherein the mixing and heating of the first substream ( 18 ) by a substantially helical Strömungsleitstruktur ( 14 ) inside the inner housing ( 10 ) he follows. Method according to one of the preceding claims, wherein the division of the exhaust gas flow ( 5 ) into a first substream ( 18 ) and a second partial flow ( 19 ) by flow influencing means ( 4 . 11 ), in particular at least one inlet panel ( 4 ) and / or at least one transversely to the first partial flow arranged in the inner housing stowage element, in particular a perforated disc ( 11 ), preferably with a proportion of 5% to 10% for the first partial flow ( 18 ). Exhaust gas treatment component, in particular for carrying out the method according to one of claims 1 to 4, with - one in an outer housing ( 2 ) supported inner housing ( 10 ), wherein the outer housing ( 2 ) an inlet opening ( 21 ), a central area ( 23 ) with respect to the inlet opening ( 21 ) extended cross section and an outlet opening ( 25 ), - an injector ( 1 ) for aqueous urea solution, wherein the injector ( 1 ) is arranged so that it is substantially aqueous urea solution in an inlet section ( 9 ) of the inner housing ( 10 ), - flow guiding means ( 4 . 28 . 11 ) for guiding a first partial flow ( 18 ) of an exhaust gas stream flowing into the exhaust gas treatment component ( 5 ) through the inner housing ( 10 ), and a delay line ( 27 ) in the inner housing ( 10 ), and - a hydrolysis catalyst ( 3 ) in an end region of the inner housing ( 20 ). Exhaust treatment component according to claim 5, wherein the outer housing ( 2 ) in the region of the inlet cone ( 22 ) a recess ( 16 ), preferably up to about the inlet section ( 9 ) of the inner housing ( 10 ), in which the injector ( 1 ) is arranged. Exhaust treatment component according to claim 5 or 6, wherein the inner housing ( 10 ) a heating element ( 6 ), in particular an electric heating element having. Exhaust treatment component according to claim 7, wherein the heating element ( 6 ) at least two independently controllable heating areas ( 8th . 13 ) having. Exhaust treatment component according to claim 7 or 8, wherein the heating element ( 6 ) angled or bent and by the outer housing ( 2 ) is guided to the outside, in particular through the inlet cone ( 22 ). Exhaust treatment component according to claim 9, wherein the heating element ( 6 ) in an angled or bent area an impact surface ( 26 ), in particular with respect to its temperature separately controllable first heating area ( 8th ), for evaporation of aqueous urea solution. Exhaust treatment component according to one of claims 7 to 10, wherein the heating element ( 6 ) coaxially inside the inner housing ( 10 ) is arranged outside of a helical Strömungsleitstruktur ( 14 ) is surrounded. Exhaust treatment component according to one of claims 5 to 9, wherein the inner housing ( 10 ) and / or the outer housing ( 2 ) are constructed from half-shells, wherein preferably the inner housing ( 10 ) by at least one elastic support ( 15 ) on the outer housing ( 2 ) is supported. Exhaust treatment component according to one of claims 5 to 12, wherein the inner housing ( 10 ) resembles the shape of a cigar and contains one after the other in the direction of flow: - a widening area ( 28 ) for braking the first partial flow ( 18 ) - a heated impact surface ( 26 ) for aqueous urea solution, - a delay line ( 27 ) for increasing the residence time of the first substream ( 18 ) in the inner housing ( 10 ) with a flow guiding structure ( 14 ) for extending the flow path, - a baffle element ( 11 ), in particular a perforated disc and a temperature sensor ( 12 ), - a hydrolysis catalyst ( 3 ) for the conversion of aqueous urea solution into ammonia. Exhaust treatment component according to claim 13, wherein the expansion region ( 28 ) with an inlet panel ( 4 ) is adaptable to different exhaust conditions and exhaust systems, preferably by the expansion area ( 28 ) is designed interchangeable. Exhaust treatment component according to one of claims 5 to 14, wherein the total length of the component is 330 mm to 400 mm, the outer diameter of the outer housing ( 2 ) Is 75 mm to 100 mm, preferably the injector ( 1 ) by installation in a depression ( 16 ) only 20 mm to 40 mm over the outer housing ( 2 ) protrudes radially.

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