WO1999056858A2 - Method and device for catalytic reduction of nitrogen oxide - Google Patents

Method and device for catalytic reduction of nitrogen oxide Download PDF

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Publication number
WO1999056858A2
WO1999056858A2 PCT/DE1999/001223 DE9901223W WO9956858A2 WO 1999056858 A2 WO1999056858 A2 WO 1999056858A2 DE 9901223 W DE9901223 W DE 9901223W WO 9956858 A2 WO9956858 A2 WO 9956858A2
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WO
WIPO (PCT)
Prior art keywords
substance
urea
exhaust gas
reservoir
ammonia
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PCT/DE1999/001223
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German (de)
French (fr)
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WO1999056858A3 (en
Inventor
Günther PAJONK
Lothar Hofmann
Manfred Weigl
Gerhard Wissler
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Siemens Aktiengesellschaft
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Publication of WO1999056858A2 publication Critical patent/WO1999056858A2/en
Publication of WO1999056858A3 publication Critical patent/WO1999056858A3/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8631—Processes characterised by a specific device
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2067—Urea
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/02—Adding substances to exhaust gases the substance being ammonia or urea
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/12—Adding substances to exhaust gases the substance being in solid form, e.g. pellets or powder
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/12—Improving ICE efficiencies

Definitions

  • the invention relates to a method and a device for the catalytic reduction of nitrogen oxide in an exhaust gas stream by means of a reaction with ammonia.
  • a device for the denitrification of exhaust gases from an internal combustion engine is known.
  • Devices and methods are known for denitrifying the exhaust gas of an internal combustion engine, in particular a diesel engine, which reduce the nitrogen oxides to nitrogen even in the presence of oxygen with ammonia as a reducing agent on so-called DeNO x catalysts.
  • a suitable substance from which ammonia can be obtained safely and without odor is urea.
  • the aqueous ammonia required for selective catalytic reduction (SCR) is formed from an aqueous urea solution by hydrolysis and pyrolysis.
  • SCR selective catalytic reduction
  • the object of the invention is to provide a simple method by which an effective nitrogen oxide reduction at temperatures below 200 ° C is made possible.
  • Another object of the invention is to provide a device with which an effective nitrogen oxide reduction at temperatures below 200 ° C is possible.
  • the object aimed at specifying a method is achieved by a method for the catalytic reduction of nitrogen oxide in an exhaust gas by means of a reaction with ammonia, in which a substance is admixed to the exhaust gas at an exhaust gas temperature below 200 ° C. which is released Ammonia decomposes at a lower temperature than urea.
  • a substance is admixed to the exhaust gas at an exhaust gas temperature below 200 ° C. which is released Ammonia decomposes at a lower temperature than urea.
  • a compound from the NH3-CO2-H2O system in particular ammonium carbonate or ammonium hydrogen carbonate or ammonium carbamate, is preferably used as the substance. Such compounds begin to decompose at temperatures around 60 ° C and thereby release ammonia. When these compounds are used in aqueous solution, ammonia is available from 100 ° C.
  • the object directed to a process is further achieved according to the invention by a process for the catalytic reduction of nitrogen oxides in an exhaust gas with an exhaust gas temperature below 200 ° C. by means of a reaction with ammonia, the ammonia being obtained at least partially from a decomposition of urea from a urea reservoir, and whereby the urea reacts with a substance from a substance reservoir, which releases ammonia from urea.
  • Such a process makes ammonia available at temperatures below 200 ° C for nitrogen oxide reduction by releasing the ammonia present in the urea by the reaction with the substance at temperatures which are below the temperature at which urea usually decomposes.
  • the ammonia required to reduce nitrogen oxide can come exclusively from the urea or can also be obtained from the substance.
  • These substances can either be released with the urea to release ammo- react niak or catalyze the conversion of urea into NH 3 . They can also release ammonia if they decompose.
  • a mixture is preferably first prepared from the substance and the urea and the mixture is then fed to the exhaust gas.
  • the decomposition of the urea by the substance thus takes place before the urea is admitted to the exhaust gas. This leads to a particularly large release of ammonia from the urea.
  • the substance is more preferably mixed with the urea at a temperature between 20 ° C. and 90 ° C. At such a temperature, ammonia is released particularly efficiently from urea.
  • the substance is preferably mixed with the urea in the exhaust gas.
  • the urea is mixed and reacted with the substance during or after the urea and the substance have been introduced into the exhaust gas.
  • An aqueous urea solution is preferably passed through the substance reservoir, in which the substance is in a solid state, in particular in the form of granules.
  • This configuration has the advantage, among other things, that the substance is stored in a particularly simple manner.
  • the urea reacts with the substance by passing it over the surface of the substance.
  • the decomposing urea and the released ammonia are then introduced into the exhaust gas stream.
  • a substance which is sparingly soluble or insoluble in the aqueous phase and has acidic or basic properties, in particular a metal oxide or a metal mixed oxide, is preferably used as the substance.
  • a substance or a silica is more preferred.
  • gear metal mixed oxide in particular based on titanium or silicon, or an active alumina. Of course, several of these connections can also be used at the same time.
  • a hydrolysis-active enzyme in particular urease, is preferably used as the substance, which is fixed on a support insoluble in water.
  • the urea is preferably conducted through the flow path filled with the substance at a temperature between 20 ° C. and 90 ° C.
  • the method is preferably used in a combustion system operated with diesel, in particular in a diesel motor vehicle.
  • a motor vehicle in particular, idle times result in a significant proportion of a partial load of the total operating time, in which the exhaust gas has temperatures below 200 ° C.
  • This proportion of part load time can e.g. Amount to 20%. It is therefore particularly advantageous here to reduce the nitrogen oxide emissions by improving the nitrogen oxide reduction at comparatively cool exhaust gas temperatures.
  • the object directed to a device is achieved by a device for catalytic nitrogen oxide reduction in an exhaust gas stream by means of a reaction with ammonia, which comprises: a) an exhaust gas line for guiding the exhaust gas stream, b) a substance reservoir with a substance, through which a release occurs ammonia can be produced from urea, the reservoir being fluidly connectable to the exhaust pipe, c) a urea reservoir which is fluidically connectable to the exhaust pipe.
  • a mixing section is preferably provided, which is connected in terms of flow between the exhaust pipe on the one hand and between the urea reservoir and the substance reservoir on the other hand.
  • the mixing section is more preferably heatable, in particular to a temperature between 20 ° C. and 90 ° C.
  • the substance reservoir is preferably connected between the urea reservoir and the exhaust gas line in terms of flow technology, the substance being in a solid state, in particular in the form of granules.
  • the substance is further preferably a silica or a transition metal mixed oxide, in particular based on titanium and silicon, or an active alumina.
  • the substance is preferably a hydrolysis-active enzyme, in particular urease, which is water-insoluble in a carrier.
  • the substance reservoir can preferably be heated, in particular to a temperature between 20 ° C. and 90 ° C.
  • the device is preferably used in a combustion system operated with diesel.
  • FIG. 1 shows a device in which urea and a substance are miscible in an exhaust gas stream
  • FIG. 2 shows a device in which urea and a substance are miscible and then can be conducted into an exhaust gas stream
  • FIG. 3 shows a device in which an aqueous urea solution is passed through a Substance and then passed into the exhaust gas stream.
  • the same reference numerals have the same meaning in the individual figures.
  • FIG. 1 shows an exhaust gas line 2 for an exhaust gas stream 4.
  • the exhaust gas line 2 is connected in terms of flow technology to a substance reservoir 6 for a substance 7.
  • a line 12 opens into the exhaust line 2, through which line 12 a urea reservoir 10 for urea 11 is connected in terms of flow to the exhaust line 2.
  • an exhaust gas stream 4 is passed through the exhaust gas line 2.
  • the exhaust gas stream 4 contains nitrogen oxides as pollutants.
  • the exhaust gas stream 4 is fed urea 11 from the urea reservoir 10 via the line 12 as required.
  • the urea 11 decomposes and releases ammonia. This ammonia reacts with the nitrogen oxides and thus reduces the nitrogen oxide emissions.
  • the decomposition of urea 11 is insufficient.
  • line 7 from which the substance 7, preferably a connection from the substance reservoir 6 system NH 3 -C0 2 -H 2 0, is added to the exhaust gas stream 4 as required.
  • Substance 7 decomposes at temperatures below the decomposition temperature of urea 11. Ammonia is released from substance 7. This ammonia reduces nitrogen oxide emissions.
  • the urea reservoir 10 and the substance reservoir 6 can be switched on or off by means not shown, for example valves in the lines 12 and 8, respectively. For example, only substance 7 or only urea 11 or both can be introduced into exhaust gas stream 4 at the same time.
  • FIG. 2 also shows an exhaust gas line 2 for a b-gas stream 4.
  • a line opens into this exhaust pipe 2 device 15.
  • the line 15 is connected to a mixing room 14.
  • the mixing room 14 is surrounded by a heater 16.
  • a line 8 also opens into the mixing chamber 14 and is connected to a substance reservoir 6 for a substance 7.
  • urea 11 is introduced via line 12 from urea reservoir 10 into mixing chamber 14.
  • the urea 11 is in the form of an aqueous urea solution ILA in the
  • Urea reservoir 10 can also e.g. are in solid form and the introduction into the substance reservoir is transferred to an aqueous solution.
  • the substance 7 is introduced via the line 8 from the substance reservoir 6 into the mixing chamber 14.
  • the introduction of the substance can be dispensed with as required.
  • the substance 7 and the urea 11 mix in the mixing chamber 14. At least some of the urea 11 reacts with the substance 7, so that the urea 11 decomposes at least partially and / releases ammonia.
  • the substance 7, which brings about or contributes to the decomposition of the urea 11, can in turn release 7 mmoniak in turn by decomposition.
  • the mixing chamber 14 is heated by the heater 16, preferably to a temperature between 20 ° C. and 90 ° C. From the mixing chamber 14, the mixture of urea 11 and substance 7 and / or the released ammonia passes via line 15 into the exhaust gas line 2. There ammonia reacts with the nitrogen oxides in the exhaust gas stream 4, so that nitrogen oxide is reduced.
  • FIG. 3 also shows an exhaust gas line 2 for an exhaust gas stream 4.
  • a line 15 opens into this exhaust line 2.
  • the line 15 is connected to a substance reservoir 6.
  • the substance reservoir 6 is surrounded by a heater 16.
  • In the sub- Punch reservoir 6 is a substance 7 stored in the solid state as granules.
  • urea 11 is fed from the urea reservoir 10 via the line 12 to the substance reservoir 6.
  • urea can be added separately to the exhaust gas via a feed line, not shown here.
  • the urea 11 passes through the substance reservoir 6 and comes into contact with the surface of the granules consisting of the substance 7.
  • the substance 7 at least partially decomposes the urea 11.
  • the substance reservoir 6 is kept at a temperature between 20 ° C. and 90 ° C. with the heater 16.
  • Urea 11 or ammonia pass through line 15 in the exhaust line 2 and mix there with the exhaust gas stream 4. As explained above, a nitrogen oxide reduction is brought about in this way, even effectively at temperatures below 200 ° C.

Abstract

The invention relates to a method for catalytic reduction of nitrogen oxide in a waste gas flow (4) by reaction with ammonium. Ammonia is released from urea (11) starting at temperatures below 200 DEG C by reacting a substance (7).

Description

Beschreibungdescription
Verfahren und Vorrichtung zur katalytischen StickoxidminderungProcess and device for catalytic nitrogen oxide reduction
Die Erfindung betrifft ein Verfahren und eine Vorrichtung zur katalytischen Stickoxidminderung in einem Abgasstrom mittels einer Reaktion mit Ammoniak.The invention relates to a method and a device for the catalytic reduction of nitrogen oxide in an exhaust gas stream by means of a reaction with ammonia.
Aus der EP 0 577 853 Bl ist eine Einrichtung zur Entstickung von Abgasen eines Verbrennungsmotors bekannt. Zur Entstickung des Abgases eines Verbrennungsmotors, insbesondere eines Dieselmotors, sind Einrichtungen und Verfahren bekannt, die die Stickoxide auch in Anwesenheit von Sauerstoff mit Ammoniak als Reduktionsmittel an sogenannten DeNOx-Katalysatoren zu Stickstoff reduzieren. Eine geeignete Substanz, aus der gefahrlos und geruchsfrei Ammoniak gewonnen werden kann, ist Harnstoff. Aus einer wäßrigen Harnstofflösung entsteht durch Hydrolyse und Pyrolyse der für eine selektive katalytische Reduktion (SCR) benötigte Ammoniak. Diese Umsetzung ist jedoch temperaturabhängig.From EP 0 577 853 B1 a device for the denitrification of exhaust gases from an internal combustion engine is known. Devices and methods are known for denitrifying the exhaust gas of an internal combustion engine, in particular a diesel engine, which reduce the nitrogen oxides to nitrogen even in the presence of oxygen with ammonia as a reducing agent on so-called DeNO x catalysts. A suitable substance from which ammonia can be obtained safely and without odor is urea. The aqueous ammonia required for selective catalytic reduction (SCR) is formed from an aqueous urea solution by hydrolysis and pyrolysis. However, this implementation is temperature-dependent.
Aufgabe der Erfindung ist es, ein einfaches Verfahren anzugeben, durch welches eine effektive Stickoxidminderung bei Tem- peraturen unterhalb von 200 °C ermöglicht wird. Weitere Aufgabe der Erfindung ist die Angabe einer Vorrichtung, mit der eine effektive Stickoxidminderung bei Temperaturen unterhalb von 200 °C möglich ist.The object of the invention is to provide a simple method by which an effective nitrogen oxide reduction at temperatures below 200 ° C is made possible. Another object of the invention is to provide a device with which an effective nitrogen oxide reduction at temperatures below 200 ° C is possible.
Erfindungsgemäß wird die auf die Angabe eines Verfahrens gerichtete Aufgabe gelöst durch ein Verfahren zur katalytischen Stickoxidminderung in einem Abgas mittels einer Reaktion mit Ammoniak, bei dem dem Abgas bei einer Abgastemperatur unterhalb von 200 °C eine Substanz beigemischt wird, die sich un- ter Freisetzung von Ammoniak bei einer niedrigeren Temperatur zersetzt als Harnstoff. Damit wird auch schon bei niedrigen Temperaturen Ammoniak verfügbar, welcher mit Stickoxiden im Abgas reagiert. Dadurch lassen sich auch Stickoxidemissionen in einem vergleichsweise kühlen Abgas reduzieren.According to the invention, the object aimed at specifying a method is achieved by a method for the catalytic reduction of nitrogen oxide in an exhaust gas by means of a reaction with ammonia, in which a substance is admixed to the exhaust gas at an exhaust gas temperature below 200 ° C. which is released Ammonia decomposes at a lower temperature than urea. This makes ammonia available even at low temperatures, which reacts with nitrogen oxides in the exhaust gas. This also reduces nitrogen oxide emissions in a comparatively cool exhaust gas.
Bevorzugt wird als Substanz eine Verbindung aus dem System NH3-CO2-H2O, insbesondere Ammoniumcarbonat oder Ammoniumhydro- gencarbonat oder Ammoniumcarbamat verwendet. Solche Verbindungen beginnen sich bereits bei Temperaturen um 60 °C zu zersetzen und setzen dabei Ammoniak frei. Beim Einsatz dieser Verbindungen in wäßriger Lösung wird Ammoniak ab 100 °C verfügbar.A compound from the NH3-CO2-H2O system, in particular ammonium carbonate or ammonium hydrogen carbonate or ammonium carbamate, is preferably used as the substance. Such compounds begin to decompose at temperatures around 60 ° C and thereby release ammonia. When these compounds are used in aqueous solution, ammonia is available from 100 ° C.
Die auf ein Verfahren gerichtete Aufgabe wird erfindungsgemäß weiterhin gelöst durch ein Verfahren zur katalytischen Stickoxidminderung in einem Abgas mit einer Abgastemperatur unterhalb von 200 °C mittels einer Reaktion mit Ammoniak, wobei der Ammoniak zumindest teilweise aus einer Zersetzung von Harnstoff aus einem Harnstoffreservoir erhalten wird, und wo- bei der Harnstoff mit einer Substanz aus einem Substanzreservoir reagiert, die eine Freisetzung von Ammoniak aus Harnstoff bewirkt.The object directed to a process is further achieved according to the invention by a process for the catalytic reduction of nitrogen oxides in an exhaust gas with an exhaust gas temperature below 200 ° C. by means of a reaction with ammonia, the ammonia being obtained at least partially from a decomposition of urea from a urea reservoir, and whereby the urea reacts with a substance from a substance reservoir, which releases ammonia from urea.
Durch ein solches Verfahren wird Ammoniak bei Temperaturen unterhalb von 200 °C dadurch für eine Stickoxidminderung verfügbar, daß der im Harnstoff vorhandene Ammoniak durch die Reaktion mit der Substanz bei Temperaturen freigesetzt wird, die unterhalb der Temperatur liegen, bei der sich Harnstoff üblicherweise zersetzt. Der zur Stickoxidminderung erforder- liehe Ammoniak kann dabei ausschließlich aus dem Harnstoff stammen oder aber auch aus der Substanz erhalten werden.Such a process makes ammonia available at temperatures below 200 ° C for nitrogen oxide reduction by releasing the ammonia present in the urea by the reaction with the substance at temperatures which are below the temperature at which urea usually decomposes. The ammonia required to reduce nitrogen oxide can come exclusively from the urea or can also be obtained from the substance.
Bevorzugt wird als Substanz eine Verbindung aus dem System NH3-C02-H20, insbesondere Ammoniumcarbonat oder Ammoniumhydro- gencarbonat oder Ammoniumcarbamat oder wässrige Ammoniakoder Wasserstoffperoxidlösung verwendet. Diese Substanzen können entweder mit dem Harnstoff unter Freisetzung von Ammo- niak reagieren oder die Umsetzung von Harnstoff in NH3 katalysieren. Auch können sie ihrerseits Ammoniak bei einer Zersetzung freisetzen.A compound from the system NH 3 -C0 2 -H 2 0, in particular ammonium carbonate or ammonium hydrogen carbonate or ammonium carbamate or aqueous ammonia or hydrogen peroxide solution, is preferably used as the substance. These substances can either be released with the urea to release ammo- react niak or catalyze the conversion of urea into NH 3 . They can also release ammonia if they decompose.
Vorzugsweise wird aus der Substanz und dem Harnstoff zuerst ein Gemisch hergestellt und das Gemisch anschließend dem Abgas zugeführt. Die Zersetzung des Harnstoffs durch die Substanz erfolgt somit bereits vor einem Einlaß des Harnstoffs in das Abgas. Dies führt zu einer besonders großen Freiset- zung von Ammoniak aus dem Harnstoff. Weiter bevorzugt erfolgt die Mischung der Substanz mit dem Harnstoff bei einer Temperatur zwischen 20 °C und 90 °C. Bei einer solchen Temperatur ergibt sich eine besonders effiziente Freisetzung von Ammoniak aus Harnstoff.A mixture is preferably first prepared from the substance and the urea and the mixture is then fed to the exhaust gas. The decomposition of the urea by the substance thus takes place before the urea is admitted to the exhaust gas. This leads to a particularly large release of ammonia from the urea. The substance is more preferably mixed with the urea at a temperature between 20 ° C. and 90 ° C. At such a temperature, ammonia is released particularly efficiently from urea.
Vorzugsweise wird die Substanz mit dem Harnstoff im Abgas gemischt. In diesem besonders einfachen Verfahren erfolgt also eine Mischung und Reaktion des Harnstoffs mit der Substanz bei oder nach einer Einleitung des Harnstoffs und der Sub- stanz in das Abgas.The substance is preferably mixed with the urea in the exhaust gas. In this particularly simple process, the urea is mixed and reacted with the substance during or after the urea and the substance have been introduced into the exhaust gas.
Vorzugsweise wird eine wässrige Harnstofflösung durch das Substanzreservoir geleitet, in welchem sich die Substanz in einem festen Aggregatzustand, insbesondere als Granulat, be- findet. Diese Ausgestaltung hat u.a. den Vorteil, daß die Substanz in einer besonders einfach handhabbaren Weise gespeichert ist. Zudem wird dadurch das Einbringen eines weiteren Stoffes in den Abgasstrom und damit möglicherweise über den Katalysator in die Umwelt sicher vermieden. Der Harnstoff reagiert mit der Substanz dadurch, daß er über die Substanzoberfläche geleitet wird. Der sich dadurch zersetzende Harnstoff und der frei werdende Ammoniak werden anschließend in den Abgasstrom eingeleitet. Vorzugsweise wird dabei als Substanz ein in wäßriger Phase schwer löslicher oder unlöslicher Festkörper mit sauren oder basischen Eigenschaften verwendet, insbesondere ein Metalloxid oder ein Metallmischoxid. Weiter bevorzugt wird als Substanz eine Kieselsäure oder ein Über- gangsmetall-Mischoxid, insbesondere auf Titan- oder Silizium- basis, oder eine Aktivtonerde verwendet. Natürlich können auch gleichzeitig mehrere dieser Verbindungen verwendet werden.An aqueous urea solution is preferably passed through the substance reservoir, in which the substance is in a solid state, in particular in the form of granules. This configuration has the advantage, among other things, that the substance is stored in a particularly simple manner. In addition, the introduction of another substance into the exhaust gas flow and thus possibly via the catalytic converter into the environment is reliably avoided. The urea reacts with the substance by passing it over the surface of the substance. The decomposing urea and the released ammonia are then introduced into the exhaust gas stream. A substance which is sparingly soluble or insoluble in the aqueous phase and has acidic or basic properties, in particular a metal oxide or a metal mixed oxide, is preferably used as the substance. A substance or a silica is more preferred. gear metal mixed oxide, in particular based on titanium or silicon, or an active alumina. Of course, several of these connections can also be used at the same time.
Vorzugsweise wird als Substanz ein hydrolyseaktives Enzym, insbesondere Urease, verwendet, welches auf einem Träger wasserunlöslich fixiert ist.A hydrolysis-active enzyme, in particular urease, is preferably used as the substance, which is fixed on a support insoluble in water.
Die Leitung des Harnstoffs durch den mit der Substanz gefüllten Strömungsweg geschieht vorzugsweise bei einer Temperatur zwischen 20 °C und 90 °C.The urea is preferably conducted through the flow path filled with the substance at a temperature between 20 ° C. and 90 ° C.
Bevorzugt wird das Verfahren in einer mit Diesel betriebenen Verbrennungsanlage angewendet, insbesondere in einem Diesel- Kraftfahrzeug. Gerade in einem Kraftfahrzeug kommt es durch Standzeiten zu einem erheblichen Anteil einer Teillastzeit von der Gesamtbetriebszeit, bei der das Abgas Temperaturen unterhalb von 200 °C aufweist. Dieser Anteil an Teillastzeit kann z.B. 20% betragen. Mithin ist es hier besonders vorteilhaft, durch eine Verbesserung der Stickoxidminderung bei vergleichsweise kühlen Abgastemperaturen die Stickoxidemissionen zu reduzieren.The method is preferably used in a combustion system operated with diesel, in particular in a diesel motor vehicle. In a motor vehicle in particular, idle times result in a significant proportion of a partial load of the total operating time, in which the exhaust gas has temperatures below 200 ° C. This proportion of part load time can e.g. Amount to 20%. It is therefore particularly advantageous here to reduce the nitrogen oxide emissions by improving the nitrogen oxide reduction at comparatively cool exhaust gas temperatures.
Erfindungsgemäß wird die auf eine Vorrichtung gerichtete Aufgabe gelöst durch eine Vorrichtung zur katalytischen Stick- oxidminderung in einem Abgasstrom mittels einer Reaktion mit Ammoniak, die aufweist: a) eine Abgasleitung zur Führung des Abgasstroms, b) ein Substanzreservoir mit einer Substanz, durch welche eine Freisetzung von Ammoniak aus Harnstoff bewirkbar ist, wobei das Reservoir strömungstechnisch mit der Abgasleitung verbindbar ist, c) ein Harnstoffreservoir, welches mit der Abgasleitung strö- mungstechnisch verbindbar ist. Die Vorteile einer solchen Vorrichtung ergeben sich entsprechend den obigen Ausführungen zu den Vorteilen des Verfahrens zur katalytischen Stickoxidminderung.According to the invention, the object directed to a device is achieved by a device for catalytic nitrogen oxide reduction in an exhaust gas stream by means of a reaction with ammonia, which comprises: a) an exhaust gas line for guiding the exhaust gas stream, b) a substance reservoir with a substance, through which a release occurs ammonia can be produced from urea, the reservoir being fluidly connectable to the exhaust pipe, c) a urea reservoir which is fluidically connectable to the exhaust pipe. The advantages of such a device result in accordance with the above explanations regarding the advantages of the method for catalytic nitrogen oxide reduction.
Bevorzugt ist eine Mischstrecke vorgesehen, welche strömungstechnisch zwischen einerseits der Abgasleitung und andererseits zwischen dem Harnstoffreservoir und dem Substanzreservoir geschaltet ist. Weiter bevorzugt ist die Mischstrecke beheizbar, insbesondere auf eine Temperatur zwischen 20 °C und 90 °C.A mixing section is preferably provided, which is connected in terms of flow between the exhaust pipe on the one hand and between the urea reservoir and the substance reservoir on the other hand. The mixing section is more preferably heatable, in particular to a temperature between 20 ° C. and 90 ° C.
Bevorzugtermaßen ist das Substanzreservoir strömungstechnisch zwischen das Harnstoffreservoir und die Abgasleitung geschaltet, wobei die Substanz in einem festen Aggregatzustand, ins- besondere als Granulat, vorliegt. Weiter bevorzugt ist die Substanz eine Kieselsäure oder ein Übergangsmetallmischoxid, insbesondere auf Titan- und Siliziumbasis, oder eine Aktivtonerde. Bevorzugtermaßen ist die Substanz ein hydrolyseaktives Enzym, insbesondere Urease, welches mit einem Träger was- serunlöslich verbunden ist. Bevorzugt ist das Substanzreservoir beheizbar, insbesondere auf eine Temperatur zwischen 20 °C und 90 °C.The substance reservoir is preferably connected between the urea reservoir and the exhaust gas line in terms of flow technology, the substance being in a solid state, in particular in the form of granules. The substance is further preferably a silica or a transition metal mixed oxide, in particular based on titanium and silicon, or an active alumina. The substance is preferably a hydrolysis-active enzyme, in particular urease, which is water-insoluble in a carrier. The substance reservoir can preferably be heated, in particular to a temperature between 20 ° C. and 90 ° C.
Bevorzugt wird die Vorrichtung in einer mit Diesel betriebe- nen Verbrennungsanlage verwendet.The device is preferably used in a combustion system operated with diesel.
Die Erfindung wird anhand der Zeichnung schematisch und nicht maßstäblich beispielhaft näher erläutert. Es zeigen:The invention will be explained in more detail by way of example and schematically with reference to the drawing. Show it:
FIG 1 eine Vorrichtung, bei der Harnstoff und eine Substanz in einem Abgasstrom mischbar sind, FIG 2 eine Vorrichtung, bei der Harnstoff und eine Substanz mischbar und anschließend in einen Abgasstrom leitbar sind, und FIG 3 eine Vorrichtung, bei der eine wässrige Harnstofflösung über eine Substanz und anschließend in den Abgasstrom geleitet wird. Gleiche Bezugszeichen haben in den einzelnen Figuren die gleiche Bedeutung.1 shows a device in which urea and a substance are miscible in an exhaust gas stream, FIG. 2 shows a device in which urea and a substance are miscible and then can be conducted into an exhaust gas stream, and FIG. 3 shows a device in which an aqueous urea solution is passed through a Substance and then passed into the exhaust gas stream. The same reference numerals have the same meaning in the individual figures.
Figur 1 zeigt eine Abgasleitung 2 für einen Abgasstrom 4. Die Abgasleitung 2 ist durch eine Leitung 8 strömungstechnisch mit einem Substanzreservoir 6 für eine Substanz 7 verbunden. Der Leitung 8 gegenüberliegend mündet eine Leitung 12 in die Abgasleitung 2, durch welche Leitung 12 ein Harnstoffreservoir 10 für Harnstoff 11 mit der Abgasleitung 2 strömungs- technisch verbunden ist.FIG. 1 shows an exhaust gas line 2 for an exhaust gas stream 4. The exhaust gas line 2 is connected in terms of flow technology to a substance reservoir 6 for a substance 7. Opposite the line 8, a line 12 opens into the exhaust line 2, through which line 12 a urea reservoir 10 for urea 11 is connected in terms of flow to the exhaust line 2.
Im Betrieb einer solchen Vorrichtung wird ein Abgasstrom 4 durch die Abgasleitung 2 geleitet. Der Abgasstrom 4 enthält als Schadstoffe Stickoxide. Bei Temperaturen oberhalb von 200 °C wird dem Abgasstrom 4 bedarfsabhängig Harnstoff 11 aus dem Harnstoffreservoir 10 über die Leitung 12 zugeführt. Der Harnstoff 11 zersetzt sich und setzt dabei Ammoniak frei. Dieser Ammoniak reagiert mit den Stickoxiden und reduziert so die Stickoxidemission. Bei Temperaturen unterhalb von 200 °C ist die Zersetzung von Harnstoff 11 unzureichend. Um trotzdem genügend Ammoniak für eine Reduzierung der Stickoxidemissionen bereitstellen zu können, wird über die Leitung 8 aus dem die Substanz 7, vorzugsweise eine Verbindung aus dem Substanzreservoir 6 System NH3-C02-H20 dem Abgasstrom 4 bedarfs- abhängig beigemischt. Die Substanz 7 zersetzt sich bereits bei Temperaturen unterhalb der Zersetzungstemperatur von Harnstoff 11. Dabei wird aus der Substanz 7 Ammoniak freigesetzt. Durch diesen Ammoniak wird die Stickoxidemission gemindert. Das Harnstoffreservoir 10 und das Substanzreservoir 6 können durch nicht näher dargestellte Mittel, z.B. Ventile in den Leitungen 12 bzw. 8, zugeschaltet oder abgeschaltet werden. Es kann also z.B. nur die Substanz 7 oder nur der Harnstoff 11 oder beides gleichzeitig in den Abgasstrom 4 eingeleitet werden.In the operation of such a device, an exhaust gas stream 4 is passed through the exhaust gas line 2. The exhaust gas stream 4 contains nitrogen oxides as pollutants. At temperatures above 200 ° C., the exhaust gas stream 4 is fed urea 11 from the urea reservoir 10 via the line 12 as required. The urea 11 decomposes and releases ammonia. This ammonia reacts with the nitrogen oxides and thus reduces the nitrogen oxide emissions. At temperatures below 200 ° C, the decomposition of urea 11 is insufficient. In order nevertheless to be able to provide sufficient ammonia for a reduction of the nitrogen oxide emissions, line 7 from which the substance 7, preferably a connection from the substance reservoir 6 system NH 3 -C0 2 -H 2 0, is added to the exhaust gas stream 4 as required. Substance 7 decomposes at temperatures below the decomposition temperature of urea 11. Ammonia is released from substance 7. This ammonia reduces nitrogen oxide emissions. The urea reservoir 10 and the substance reservoir 6 can be switched on or off by means not shown, for example valves in the lines 12 and 8, respectively. For example, only substance 7 or only urea 11 or both can be introduced into exhaust gas stream 4 at the same time.
In Figur 2 ist ebenfalls eine Abgasleitung 2 für einen b- gasstrom 4 gezeigt. In diese Abgasleitung 2 mündet eine Lei- tung 15. Die Leitung 15 ist mit einem Mischraum 14 verbunden. Der Mischraum 14 ist von einer Heizung 16 umgeben. In den Mischraum 14 mündet eine Leitung 12, die mit einem Harnstoffreservoir 10 für Harnstoff 11 verbunden ist. In den Mischraum 14 mündet außerdem eine Leitung 8, die mit einem Substanzreservoir 6 für eine Substanz 7 verbunden ist.FIG. 2 also shows an exhaust gas line 2 for a b-gas stream 4. A line opens into this exhaust pipe 2 device 15. The line 15 is connected to a mixing room 14. The mixing room 14 is surrounded by a heater 16. A line 12, which is connected to a urea reservoir 10 for urea 11, opens into the mixing chamber 14. A line 8 also opens into the mixing chamber 14 and is connected to a substance reservoir 6 for a substance 7.
Beim Betrieb wird Harnstoff 11 über die Leitung 12 aus dem Harnstoffreservoir 10 in den Mischraum 14 eingeleitet. Dabei liegt der Harnstoff 11 als wässrige Harnstofflösung ILA imDuring operation, urea 11 is introduced via line 12 from urea reservoir 10 into mixing chamber 14. The urea 11 is in the form of an aqueous urea solution ILA in the
Harnstoffreservoir 10 vor, kann aber auch z.B. in fester Form vorliegen und der Einleitung in das Substanzreservoir in eine wässrige Lösung überführt werden. Gleichzeitig wird die Substanz 7 über die Leitung 8 aus dem Substanzreservoir 6 in den Mischraum 14 eingeleitet. Bei Abgastemperaturen oberhalb von 200°C kann bedarfsabhängig auf die Einleitung der Substanz verzichtet werden. Im Mischraum 14 vermischen sich die Substanz 7 und der Harnstoff 11. Dabei erfolgt zumindest teilweise eine Reaktion des Harnstoffs 11 mit der Substanz 7, so daß sich der Harnstoff 11 zumindest teilweise zersetzt und /Ammoniak freisetzt. Die Substanz 7, die die Zersetzung des Harnstoffs 11 bewirkt oder zu dieser beiträgt, kann dabei gleichzeitig ihrerseits durch Zersetzung 7Λmmoniak freisetzen. Durch die Heizung 16 wird der Mischraum 14 beheizt, vorzugs- weise auf eine Temperatur zwischen 20 °C und 90 °C. Aus dem Mischraum 14 gelangt das Gemisch aus Harnstoff 11 und Substanz 7 und/oder der freigesetzte Ammoniak über die Leitung 15 in die Abgasleitung 2. Dort reagiert Ammoniak mit den Stickoxiden im Abgasstrom 4, so daß eine Stickoxidminderung erfolgt.Urea reservoir 10, but can also e.g. are in solid form and the introduction into the substance reservoir is transferred to an aqueous solution. At the same time, the substance 7 is introduced via the line 8 from the substance reservoir 6 into the mixing chamber 14. At exhaust gas temperatures above 200 ° C, the introduction of the substance can be dispensed with as required. The substance 7 and the urea 11 mix in the mixing chamber 14. At least some of the urea 11 reacts with the substance 7, so that the urea 11 decomposes at least partially and / releases ammonia. The substance 7, which brings about or contributes to the decomposition of the urea 11, can in turn release 7 mmoniak in turn by decomposition. The mixing chamber 14 is heated by the heater 16, preferably to a temperature between 20 ° C. and 90 ° C. From the mixing chamber 14, the mixture of urea 11 and substance 7 and / or the released ammonia passes via line 15 into the exhaust gas line 2. There ammonia reacts with the nitrogen oxides in the exhaust gas stream 4, so that nitrogen oxide is reduced.
In Figur 3 ist ebenfalls eine Abgasleitung 2 für einen Abgasstrom 4 gezeigt. In dieser Abgasleitung 2 mündet eine Leitung 15. Die Leitung 15 ist mit einem Substanzreservoir 6 verbunden. Das Substanzreservoir 6 ist von einer Heizung 16 umgeben. In das Substanzreservoir 6 mündet eine Leitung 12, welche mit einem Harnstoffreservoir 10 verbunden ist. Im Sub- Stanzreservoir 6 ist eine Substanz 7 im festen Aggregatzustand als Granulat gespeichert.FIG. 3 also shows an exhaust gas line 2 for an exhaust gas stream 4. A line 15 opens into this exhaust line 2. The line 15 is connected to a substance reservoir 6. The substance reservoir 6 is surrounded by a heater 16. A line 12, which is connected to a urea reservoir 10, opens into the substance reservoir 6. In the sub- Punch reservoir 6 is a substance 7 stored in the solid state as granules.
Bei Abgastemperaturen des Abgasstroms 4 unterhalb von 200 °C wird Harnstoff 11 aus dem Harnstoffreservoir 10 über die Leitung 12 dem Substanzreservoir 6 zugeführt. Bei Abgastemperaturen oberhalb von 200°C kann Harnstoff über eine hier nicht dargestellte Zuleitung separat dem Abgasstro zugesetzt werden. Der Harnstoff 11 durchläuft den Substanzreservoir 6 und kommt dabei mit der Oberfläche des aus der Substanz 7 bestehenden Granulates in Berührung. Die Substanz 7 bewirkt dabei zumindest teilweise eine Zersetzung des Harnstoffs 11. Dabei wird der Substanzreservoir 6 mit der Heizung 16 auf eine Temperatur zwischen 20 °C und 90 °C gehalten. Bei der Zersetzung des Harnstoffs 11 wird Ammoniak frei. Harnstoff 11 bzw. Ammoniak gelangen über die Leitung 15 in der Abgasleitung 2 und vermischen sich dort mit dem Abgasstrom 4. Wie oben ausgeführt, wird so eine Stickoxidminderung bewirkt, und zwar schon in effektiver Weise auch bei Temperaturen unterhalb von 200 °C. At exhaust gas temperatures of the exhaust gas stream 4 below 200 ° C., urea 11 is fed from the urea reservoir 10 via the line 12 to the substance reservoir 6. At exhaust gas temperatures above 200 ° C, urea can be added separately to the exhaust gas via a feed line, not shown here. The urea 11 passes through the substance reservoir 6 and comes into contact with the surface of the granules consisting of the substance 7. The substance 7 at least partially decomposes the urea 11. The substance reservoir 6 is kept at a temperature between 20 ° C. and 90 ° C. with the heater 16. When the urea 11 decomposes, ammonia is released. Urea 11 or ammonia pass through line 15 in the exhaust line 2 and mix there with the exhaust gas stream 4. As explained above, a nitrogen oxide reduction is brought about in this way, even effectively at temperatures below 200 ° C.

Claims

Patentansprüche claims
1. Verfahren zur katalytischen Stickoxidminderung in einem Abgas mittels einer Reaktion mit Ammoniak, bei dem dem Abgas bei einer Abgastemperatur unterhalb von 200 °C eine Substanz (7) beigemischt wird, die sich unter Freisetzung von Ammoniak bei einer niedrigeren Temperatur zersetzt als Harnstoff (11).1.A process for the catalytic reduction of nitrogen oxides in an exhaust gas by means of a reaction with ammonia, in which a substance (7) is admixed to the exhaust gas at an exhaust gas temperature below 200 ° C, which decomposes with release of ammonia at a lower temperature than urea (11 ).
2. Verfahren nach Anspruch 1, bei dem als Substanz (7) eine Verbindung aus dem System NH3- C02-H20, insbesondere Ammoniumcarbonat oder Ammoniumhydrogen- carbonat oder Ammoniumcarbamat, verwendet wird.2. The method of claim 1, in which a compound from the system NH 3 - C0 2 -H 2 0, in particular ammonium carbonate or ammonium bicarbonate or ammonium carbamate, is used as the substance (7).
3. Verfahren zur katalytischen Stickoxidminderung in einem Abgas mit einer Abgastemperatur unterhalb von 200 °C mittels einer Reaktion mit Ammoniak, wobei der Ammoniak zumindest teilweise aus einer Zersetzung von Harnstoff (11) aus einem Harnstoffreservoir (10) erhalten wird, und wobei der Harnstoff (11) mit einer Substanz (7) reagiert, die eine Freiset- zung von Ammoniak aus dem Harnstoff (11) bewirkt.3. A process for the catalytic reduction of nitrogen oxides in an exhaust gas with an exhaust gas temperature below 200 ° C. by means of a reaction with ammonia, the ammonia being obtained at least partially from a decomposition of urea (11) from a urea reservoir (10), and wherein the urea ( 11) reacts with a substance (7) which releases ammonia from the urea (11).
4. Verfahren nach Anspruch 3, bei dem als Substanz (7) eine Verbindung aus dem System NH3-CO2-H2O, insbesondere Ammoniumcarbonat oder Ammoniumhydrogencarbonat oder Ammoniumcarbamat verwendet wird.4. The method according to claim 3, in which a compound from the system NH3-CO 2 -H 2 O, in particular ammonium carbonate or ammonium hydrogen carbonate or ammonium carbamate, is used as substance (7).
5. Verfahren nach Anspruch 3, bei dem als Substanz (7) eine verdünnte Ammoniak- oder Was- serstoffperoxidlösung verwendet wird.5. The method according to claim 3, in which a dilute ammonia or hydrogen peroxide solution is used as the substance (7).
6. Verfahren nach einem der Ansprüche 3 bis 5, bei dem aus der Substanz (7) und dem Harnstoff (11) zuerst ein Gemisch hergestellt wird und das Gemisch anschließend dem Abgas zugeführt wird. 6. The method according to any one of claims 3 to 5, in which a mixture is first produced from the substance (7) and the urea (11) and the mixture is then fed to the exhaust gas.
7. Verfahren nach Anspruch 6, bei dem die Herstellung der Mischung der Substanz (7) mit dem Harnstoff (11) bei einer Temperatur zwischen 20 °C und 90 °C erfolgt.7. The method according to claim 6, wherein the preparation of the mixture of the substance (7) with the urea (11) at a temperature between 20 ° C and 90 ° C.
8. Verfahren nach einem der Ansprüche 3 bis 5, bei dem die Substanz (7) mit dem Harnstoff (11) im Abgas gemischt wird.8. The method according to any one of claims 3 to 5, wherein the substance (7) with the urea (11) is mixed in the exhaust gas.
9. Verfahren nach Anspruch 3 oder 4, bei dem der Harnstoff (11) als eine wässrige Harnstofflösung (11A) durch das Substanzreservoir (6) geleitet wird, in welchem sich die Substanz (7) in einem festen Aggregatzustand, insbesondere als Granulat, befindet.9. The method according to claim 3 or 4, wherein the urea (11) as an aqueous urea solution (11A) is passed through the substance reservoir (6), in which the substance (7) is in a solid state, in particular as granules .
10. Verfahren nach Anspruch 9, bei dem als Substanz (7) ein in wässriger Phase schwerlöslicher oder unlöslicher Festkörper mit sauren oder basischen Eigenschaften verwendet wird, insbesondere ein Metalloxid oder ein Metall-Mischoxid.10. The method according to claim 9, in which a substance which is sparingly soluble or insoluble in the aqueous phase and has acidic or basic properties, in particular a metal oxide or a metal mixed oxide, is used as the substance (7).
11. Verfahren nach Anspruch 10, bei dem als Substanz (7) eine Kieselsäure oder ein Übergangsmetall-Mischoxid, insbesondere auf Titan- und Silizium-Basis, oder eine Aktivtonerde verwendet wird.11. The method according to claim 10, in which the substance (7) is a silica or a transition metal mixed oxide, in particular based on titanium and silicon, or an active alumina.
12. Verfahren nach Anspruch 9, bei dem als Substanz (7) ein hydrolyseaktives Enzym, insbesondere Urease, verwendet wird, welches an einem Träger wasserunlöslich fixiert ist.12. The method according to claim 9, in which a hydrolysis-active enzyme, in particular urease, is used as the substance (7), which enzyme is fixed to a support insoluble in water.
13. Verfahren nach einem der Ansprüche 9 bis 12, bei dem der Harnstoff (11) bei einer Temperatur zwischen 20 °C und 90 °C durch das Substanzreservoir (6) geleitet wird.13. The method according to any one of claims 9 to 12, wherein the urea (11) at a temperature between 20 ° C and 90 ° C is passed through the substance reservoir (6).
14. Anwendung des Verfahrens nach einem der vorhergehenden14. Application of the method according to one of the preceding
Ansprüche in einer mit Diesel betriebenen Verbrennungsanlage. Claims in a diesel-powered incinerator.
15. Vorrichtung zur katalytischen Stickoxidminderung in einem Abgasstrom (4) mittels einer Reaktion mit Ammoniak, die aufweist: a) eine Abgasleitung (12) zur Führung des Abgasstromes (4), b) ein Substanzreservoir (6) mit einer Substanz (7), durch welche eine Freisetzung von Ammoniak aus Harnstoff (11) bewirkbar ist, wobei das Substanzreservoir (6) strömungstechnisch mit der Abgasleitung (12) verbindbar ist, c) ein Harnstoffreservoir (10) , welches mit der Abgasleitung (12) strömungstechnisch verbindbar ist.15. Device for the catalytic reduction of nitrogen oxide in an exhaust gas stream (4) by means of a reaction with ammonia, which comprises: a) an exhaust gas line (12) for guiding the exhaust gas stream (4), b) a substance reservoir (6) with a substance (7), by means of which ammonia can be released from urea (11), the substance reservoir (6) being fluidically connectable to the exhaust gas line (12), c) a urea reservoir (10) which is fluidically connectable to the exhaust gas line (12).
16. Vorrichtung nach Anspruch 15, welche eine Mischstrecke (14) aufweist, welche strömungstech- nisch zwischen einerseits der Abgasleitung (12) und anderer- seits dem Harnstoffreservoir (10) und dem Substanzreservoir (6) geschaltet ist.16. The apparatus of claim 15, which has a mixing section (14) which is connected in terms of flow between the exhaust pipe (12) on the one hand and the urea reservoir (10) and the substance reservoir (6) on the other.
17. Vorrichtung nach Anspruch 16, bei der die Mischstrecke (14) beheizbar ist, insbesondere auf eine Temperatur zwischen 20 °C und 90 °C.17. The apparatus of claim 16, wherein the mixing section (14) is heatable, in particular to a temperature between 20 ° C and 90 ° C.
18. Vorrichtung nach Anspruch 15, bei dem das Substanzreservoir (6) strömungstechnisch zwischen das Harnstoffreservoir (10) und die Abgasleitung (12) ge- schaltet ist, wobei die Substanz (7) in einem festen Aggregatzustand, insbesondere als Granulat, vorliegt.18. Device according to claim 15, in which the substance reservoir (6) is connected between the urea reservoir (10) and the exhaust gas line (12) in terms of flow technology, the substance (7) being in a solid state, in particular in the form of granules.
19. Vorrichtung nach Anspruch 18, bei der die Substanz (7) eine Kieselsäure oder ein Übergangs- metall-Mischoxid, insbesondere auf Titan- und Silizium-Basis, oder eine Aktivtonerde ist.19. The apparatus of claim 18, wherein the substance (7) is a silica or a transition metal mixed oxide, in particular based on titanium and silicon, or an active alumina.
20. Vorrichtung nach Anspruch 18, bei der die Substanz (7) ein hydrolyseaktives Enzym, insbesondere Urease, ist, welches mit einem Träger wasserunlöslich verbunden ist. 20. The apparatus of claim 18, wherein the substance (7) is a hydrolysis-active enzyme, in particular urease, which is water-insoluble connected to a carrier.
21. Vorrichtung nach Anspruch 18, 19 oder 20, bei der das Substanzreservoir (6) beheizbar ist, insbesondere auf eine Temperatur zwischen 20 °C und 90 °C.21. The apparatus of claim 18, 19 or 20, wherein the substance reservoir (6) is heatable, in particular to a temperature between 20 ° C and 90 ° C.
22. Verwendung einer Vorrichtung nach einem der Ansprüche 15 bis 21 in einer mit Diesel betriebenen Verbrennungsanlage . 22. Use of a device according to one of claims 15 to 21 in a diesel-operated incinerator.
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