EP0703417B1 - Water-heater with catalytic burner - Google Patents

Water-heater with catalytic burner Download PDF

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Publication number
EP0703417B1
EP0703417B1 EP95113285A EP95113285A EP0703417B1 EP 0703417 B1 EP0703417 B1 EP 0703417B1 EP 95113285 A EP95113285 A EP 95113285A EP 95113285 A EP95113285 A EP 95113285A EP 0703417 B1 EP0703417 B1 EP 0703417B1
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EP
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Prior art keywords
catalyst body
water
water chamber
contact
area
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EP95113285A
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German (de)
French (fr)
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EP0703417A1 (en
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Walter Dipl.-Ing. Daniel (Fh)
Walter Dr. Lehr
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Robert Bosch GmbH
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Robert Bosch GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN  A CARRIER GAS OR AIR 
    • F23C13/00—Apparatus in which combustion takes place in the presence of catalytic material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
    • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
    • F24H1/0027—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters using fluid fuel
    • F24H1/0045—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters using fluid fuel with catalytic combustion

Definitions

  • the invention relates to a water heater with a catalytic burner according to the preamble of the main claim.
  • the monolytic catalyst is assigned to a second combustion stage and the first combustion stage is provided with a split burner in which a fuel gas / air mixture flows through annular combustion gaps between a catalytically coated and a ceramic-coated wall of a water chamber .
  • the reaction should take place in the central area of the support structure as far as possible, so that the high temperatures in this area can be used even at low concentrations of the fuel gas and a large part of the heat of reaction reaches the exhaust gas heat exchanger via the exhaust gas.
  • the support structure consists of ceramic, the outer ceramic layer bordering the wall of the water chamber being shielded from the inflowing reaction mixture by an annular diaphragm.
  • the wall of the water chamber delimiting the combustion gap is covered with the ceramic layer and removed from the catalyst layer by the burner gap.
  • catalytic Burner in which between a burner gap and a water chamber a gap for feeding Combustion air is arranged, the excessive heat radiation to the water chamber prevented (DE 43 06 722 C1).
  • a single-stage catalytic burner is also known (Magazine Sanitary and Heating Technology 1992, Issue 12, Pp. 878 - 880) in which a porous, cylindrical Fiber body an axial input channel for a fuel-air mixture has and on the circumference of the coat with a catalytic coated mesh is covered. That in the fiber body axially blown and radially deflected in this mixture reacts with the catalyst layer on the network, after which the combustion gases through an annular gap between the network and a water chamber to a downstream exhaust gas heat exchanger stream. This version also becomes one strong cooling of the catalyst body through the annular gap avoided between this and the water chamber.
  • EP A 256 322 describes a generic water heater proposed, however, as a carrier material for the Catalyst body non-metallic materials, such as Example proposed aluminum oxide or silicon oxide become. Due to the low thermal conductivity of this Carrier substances can be those remaining in the catalyst body excess heat only to a small extent water to be heated can be removed.
  • the support structure of the catalyst body can, for example made of sintered metal parts (preferably spherical) or consist of a wire mesh. When using a wire mesh is expedient by sintering or solidified by another method. Furthermore, the Support structure also from one with through holes or Bores provided metallic body exist. On the The catalytic layer is known in the carrier structure Way, applied by means of wash coat. As a catalytic Layers come from platinum group metals or oxides, e.g. Chromium oxides and mixed oxides in question.
  • the heat dissipation from the catalyst body to the water chamber can be advantageously influenced by this and the operating behavior of the catalyst can be adjusted if the in the flow direction length of the fuel-air mixture the contact area of the catalyst body and water chamber shortened compared to the total length of the catalyst body is executed. This creates a large temperature gradient in the area of the heat-dissipating zone of the catalyst body achieved without excessive catalyst temperatures in the areas of the Adjust the catalyst body.
  • the support structure can advantageously be designed so that the thermal conductivity of the catalyst body continuously over the Radius changes.
  • the different conductivity can, for example due to different grain sizes or wire diameters, by influencing the sintering process or by different hole or hole spacing or diameter can be realized.
  • the catalyst body When the burner is started, the catalyst body can be heated to operating temperature by igniting the from the Fuel-air mixture emerging catalyst body take place. The resulting flame sits on the catalyst body and heats its surface until after a certain time the catalyst body has heated up so far that the catalytic combustion gets going and the reaction only takes place in the catalyst body.
  • This method of Heating to operating temperature is more energy efficient than the known measure, the fuel-air mixture supplied to the burner preheat electrically.
  • the specific surface load must not exceed a value of approx. 30 W / cm 2 .
  • the water heater is compact, if a first penetrates centrally through the catalyst body Water chamber and a second water chamber surrounding it on the outside is provided.
  • Figures 1 to 7 show simplified one of the exemplary embodiments in longitudinal section.
  • the water heater according to Figure 1 has one with an insulating jacket provided housing 10, in which a as a cylindrical Block of trained monolytic catalyst bodies 12 is inserted. This encloses a water chamber 14, which lies in the course of a hot water pipe 16, 18.
  • the housing 10 has an inlet 20 below for a fuel-air mixture, which after the reaction in the catalyst body 12 as exhaust gas through an exhaust gas heat exchanger 22 flows.
  • the catalyst body 12 has a continuously metallic support structure 24, the through openings of which with a catalytic layer covered walls are limited.
  • the Support structure 24 lies directly on a metallic one bare metal section 26 of the water chamber 14, so that there is good thermal contact between the parts.
  • a barrier 30 in the form of a wall section 26 surrounding washer provided an incomplete Reaction in that adjacent to the water chamber 14 prevents the inner region of the catalyst body 12.
  • the Barrier 30 is dimensioned so that at least on its edge the reaction temperature of the catalyst is reached.
  • the water heater according to Figure 2 differs from the one described above Embodiment only in that a monolytic catalyst body 34 by a truncated cone executed end wall 36 is limited to the same Outside diameter a larger area than the plane End wall 28 according to Figure 1 has. This ensures that the at the start of the burner flame framing the front wall 36 less thermal stress or more heat on the Catalyst body 34 can transfer than it does when running according to Figure 1 is the case.
  • the water heater according to FIG. 3 differs from the exemplary embodiment according to FIG. 2 only in that a catalyst body 38 is in heat-conducting connection with the water chamber 14 only via a bare metallic wall section 40, the axial length L 1 of which is essentially the result of a central recess 42 in the catalyst body 38 is shorter than its total axial length L 2 .
  • a large temperature gradient is achieved in the area of the heat-dissipating zone 44 without the catalyst temperatures in the areas 46 further away being set too high.
  • the water heater according to Figure 4 differs from that according to Figure 1 only in that except for an inner Water chamber 14 a parallel to the water flow arranged outer water chamber 48 in the course of the hot water pipe 16, 18 is provided.
  • the catalyst body 12 is with the outer water chamber 48 via a metallic bare wall section 50 in good thermal contact, wherein to prevent an incomplete reaction in the adjacent Area of the catalyst body 12 through this an annular barrier 52 is covered.
  • the water heater according to Figure 5 is also with two water chambers 14 and 48 and with a monolytic catalyst body 54 provided, as in the embodiment according to Figures 2 and 3 a frustoconical end wall 36 has. Due to this design of the end wall 36 and a central one starting from the lower end The recess 56 of the catalyst body 44 is only short Wall sections 58, 60 with the water chambers 14, 48 in metallic heat-conducting contact, whereby the desired large temperature gradients in the range of heat-dissipating zones.
  • the water heater of Figure 6 differs from that Design according to Figure 1 in that a monolytic catalyst body 62 has a support structure 64, the through openings formed as fine bores or holes 66 are, whose walls with a catalytically effective Layer are coated.
  • a similar support structure has one Catalyst body 68 of a water heater shown in Figure 7, which, like the explanations according to FIGS. 4 and 5 has two water chambers 14 and 48 and these by appropriate Shaping only on shortened wall sections 70, 72 touched.

Description

Stand der TechnikState of the art

Die Erfindung geht aus von einem Wassererhitzer mit einem katalytischen Brenner nach der Gattung des Hauptanspruchs. Bei bekannten Wassererhitzern dieser Gattung (DE 42 04 320 C1) ist der monolytische Katalysator einer zweiten Verbrennungsstufe zugeordnet und die erste Verbrennungsstufe mit einem Spaltbrenner versehen, in welchem ein Brenngas-Luftgemisch durch ringförmige Verbrennungsspalte zwischen einer katalytisch beschichteten und einer keramisch beschichteten Wand einer Wasserkammer strömt. Im monolytischen Katalysatorkörper der zweiten Verbrennungsstufe soll die Reaktion möglichst im zentralen Bereich der Trägerstruktur stattfinden, damit die hohen Temperaturen in diesem Bereich auch bei geringen Konzentrationen des Brenngases ausgenutzt werden und ein großer Teil der Reaktionswärme über das Abgas in einen Abgaswärmetauscher gelangt. Zu diesem Zweck besteht die Trägerstruktur aus Keramik, wobei die äußere, an die Wand der Wasserkammer grenzende Keramikschicht durch eine Ringblende gegenüber dem anströmenden Reaktionsgemisch abgeschirmt ist. Demgegenüber soll im Spaltbrenner der ersten Verbrennungsstufe an die Wasserkammer soviel Wärme übertragen werden, daß die Reaktionstemperatur gehalten, jedoch nicht in einen Bereich ansteigen kann, in dem eine nennenswerte NOx-Bildung eintritt. Zu diesem Zweck ist die den Verbrennungsspalt begrenzende Wand der Wasserkammer mit der Keramikschicht überzogen und durch den Verbrennerspalt von der Katalysatorschicht entfernt.The invention relates to a water heater with a catalytic burner according to the preamble of the main claim. In known water heaters of this type (DE 42 04 320 C1), the monolytic catalyst is assigned to a second combustion stage and the first combustion stage is provided with a split burner in which a fuel gas / air mixture flows through annular combustion gaps between a catalytically coated and a ceramic-coated wall of a water chamber . In the monolytic catalyst body of the second combustion stage, the reaction should take place in the central area of the support structure as far as possible, so that the high temperatures in this area can be used even at low concentrations of the fuel gas and a large part of the heat of reaction reaches the exhaust gas heat exchanger via the exhaust gas. For this purpose, the support structure consists of ceramic, the outer ceramic layer bordering the wall of the water chamber being shielded from the inflowing reaction mixture by an annular diaphragm. In contrast, so much heat should be transferred to the water chamber in the cracking burner of the first combustion stage that the reaction temperature is maintained but cannot rise to a range in which a significant formation of NO x occurs. For this purpose, the wall of the water chamber delimiting the combustion gap is covered with the ceramic layer and removed from the catalyst layer by the burner gap.

Der gleiche Gedanke einer Wärmedämmung liegt einem katalytischen Brenner zugrunde, bei welchem zwischen einem Verbrennerspalt und einer Wasserkammer ein Spalt zum Zuführen von Verbrennungsluft angeordnet ist, der eine zu starke Wärmeabstrahlung an die Wasserkammer verhindert (DE 43 06 722 C1). Ferner ist ein einstufiger katalytischer Brenner bekannt (Zeitschrift Sanitär - und Heizungstechnik 1992, Heft 12, S. 878 - 880) bei welchem ein poröser, zylindrischer Faserkörper einen axialen Eingangskanal für ein Brennstoff-Luftgemisch hat und am Mantelumfang mit einem katalytisch beschichteten Netz umhüllt ist. Das in den Faserkörper axial eingeblasene und in diesem radial umgelenkte Gemisch reagiert mit der Katalysatorschicht am Netz, wonach die Verbrennungsgase durch einen Ringspalt zwischen dem Netz und einer Wasserkammer zu einem nachgeschalteten Abgaswärmetauscher strömen. Auch bei dieser Ausführung wird eine zu starke Kühlung des Katalysatorkörpers durch den Ringspalt zwischen diesem und der Wasserkammer vermieden.The same idea of thermal insulation is catalytic Burner, in which between a burner gap and a water chamber a gap for feeding Combustion air is arranged, the excessive heat radiation to the water chamber prevented (DE 43 06 722 C1). A single-stage catalytic burner is also known (Magazine Sanitary and Heating Technology 1992, Issue 12, Pp. 878 - 880) in which a porous, cylindrical Fiber body an axial input channel for a fuel-air mixture has and on the circumference of the coat with a catalytic coated mesh is covered. That in the fiber body axially blown and radially deflected in this mixture reacts with the catalyst layer on the network, after which the combustion gases through an annular gap between the network and a water chamber to a downstream exhaust gas heat exchanger stream. This version also becomes one strong cooling of the catalyst body through the annular gap avoided between this and the water chamber.

In der EP A 256 322 wird ein gattungsgemäßer Wassererhitzer vorgeschlagen, bei dem jedoch als Trägermaterial für den Katalysatorkörper nichtmetallische Werkstoffe, wie zum Beispiel Aluminiumoxid oder Siliziumoxid vorgeschlagen werden. Aufgrund der geringen Wärmeleitfähigkeit dieser Trägersubstanzen kann die im Katalysatorkörper verbleibende überschüssige Wärme nur in geringen Maßen an das aufzuheizende Wasser abgeführt werden. EP A 256 322 describes a generic water heater proposed, however, as a carrier material for the Catalyst body non-metallic materials, such as Example proposed aluminum oxide or silicon oxide become. Due to the low thermal conductivity of this Carrier substances can be those remaining in the catalyst body excess heat only to a small extent water to be heated can be removed.

Vorteile der ErfindungAdvantages of the invention

Bei der erfindungsgemäßen Anordnung mit den kennzeichnenden Merkmalen des Hauptanspruchs wird die überschüssige Wärme im Katalysatorkörper über dessen Trägerstruktur unmittelbar an die Wasserkammer abgeführt, wobei durch entsprechende Bemessung bzw. Gestaltung des Katalysatorkörpers und Abstimmung mit anderen Parametern die Abkühlung in den gewünschten Grenzen gehalten wird. Der Brenner kommt mit wenigen Einzelteilen aus, wobei in vielen Fällen auf eine zweistufige Ausführung verzichtet werden kann.In the arrangement according to the invention with the characteristic Characteristics of the main claim is the excess heat in the Catalyst body directly over its support structure the water chamber discharged, with appropriate Dimensioning or design of the catalyst body and coordination with other parameters the cooling in the desired Limits are kept. The burner comes with a few individual parts from, in many cases to a two-stage version can be dispensed with.

Die Trägerstruktur des Katalysatorkörpers kann beispielsweise aus gesinterten Metallteilen (vorzugsweise kugelförmig) oder aus einem Drahtgeflecht bestehen. Bei der Verwendung eines Drahtgeflechts ist dieses zweckmäßig durch Sintern oder durch ein anderes Verfahren verfestigt. Ferner kann die Trägerstruktur auch aus einem mit durchgehenden Löchern bzw. Bohrungen versehenen metallischen Körper bestehen. Auf die Trägerstruktur ist die katalytische Schicht in bekannter Weise, mittels Wash-Coat aufgebracht. Als katalytische Schichten kommen Metalle der Platingruppe oder Oxide, z.B. Chromoxide und Mischoxide in Frage.The support structure of the catalyst body can, for example made of sintered metal parts (preferably spherical) or consist of a wire mesh. When using a wire mesh is expedient by sintering or solidified by another method. Furthermore, the Support structure also from one with through holes or Bores provided metallic body exist. On the The catalytic layer is known in the carrier structure Way, applied by means of wash coat. As a catalytic Layers come from platinum group metals or oxides, e.g. Chromium oxides and mixed oxides in question.

Durch die in den Unteransprüchen aufgeführten Merkmale sind vorteilhafte Ausgestaltungen und Weiterbildungen der Anordnung nach dem Hauptanspruch möglich.By the features listed in the subclaims advantageous refinements and developments of the arrangement possible after the main claim.

Die Wärmeabfuhr vom Katalysatorkörper auf die Wasserkammer kann vorteilhaft dadurch beeinflußt und an das Betriebsverhalten des Katalysators angepaßt werden, wenn die in Strömungsrichtung des Brennstoff-Luftgemisches gemessene Länge der Berührungsfläche von Katalysatorkörper und Wasserkammer gegenüber der Gesamtlänge des Katalysatorkörpers verkürzt ausgeführt ist. Dadurch wird ein großer Temperaturgradient im Bereich der wärmeabführenden Zone des Katalysatorkörpers erreicht, ohne daß sich zu hohe Katalysatortemperaturen in den weiter von der Wasserkammer entfernten Bereichen des Katalysatorkörpers einstellen. The heat dissipation from the catalyst body to the water chamber can be advantageously influenced by this and the operating behavior of the catalyst can be adjusted if the in the flow direction length of the fuel-air mixture the contact area of the catalyst body and water chamber shortened compared to the total length of the catalyst body is executed. This creates a large temperature gradient in the area of the heat-dissipating zone of the catalyst body achieved without excessive catalyst temperatures in the areas of the Adjust the catalyst body.

Dem gleichen Zweck dient es, wenn der Katalysatorkörper durch entsprechende Ausbildungen der Trägerstruktur in dem an der Berührungsfläche mit der Wasserkammer liegenden Bereich eine kleinere Wärmeleitfähigkeit hat als in den weiter davon entfernten Bereichen. Die Trägerstruktur kann vorteilhaft so ausgebildet sein, daß sich die Wärmeleitfähigkeit des Katalysatorkörpers kontinuierlich über dessen Radius ändert. Die unterschiedliche Leitfähigkeit kann beispielsweise durch unterschiedliche Korngrößen bzw. Drahtdurchmesser, durch Beeinflußung des Sintervorgangs oder durch unterschiedliche Loch- bzw. Bohrungsabstände oder -durchmesser realisiert werden.It serves the same purpose if the catalyst body through appropriate training of the support structure in the lying on the interface with the water chamber Area has a lower thermal conductivity than in the areas further away. The support structure can advantageously be designed so that the thermal conductivity of the catalyst body continuously over the Radius changes. The different conductivity can, for example due to different grain sizes or wire diameters, by influencing the sintering process or by different hole or hole spacing or diameter can be realized.

Eine zu starke Abkühlung des an die Berührungsfläche mit der Wasserkammer angrenzenden Bereichs des Katalysatorkörpers und eine dadurch verursachte unvollständige Reaktion der Verbrennungskomponenten kann verhindert werden, wenn der Katalysatorkörper am ausgangsseitigen Ende der Berührungsfläche mit einer die Gemischströmung in diesem Bereich behindernden Barriere versehen ist.Excessive cooling of the contact surface with the Water chamber adjacent area of the catalyst body and an incomplete reaction caused by the Combustion components can be prevented if the Catalyst body at the outlet end of the contact surface with an obstacle to the mixture flow in this area Barrier is provided.

Beim Start des Brenners kann die Aufheizung des Katalysatorkörpers auf Betriebstemperatur durch Entflammen des aus dem Katalysatorkörper austretenden Brennstoff-Luftgemisches erfolgen. Die entstehende Flamme sitzt auf dem Katalysatorkörper auf und erwärmt dessen Oberfläche, bis sich nach einer gewissen Zeit der Katalysatorkörper soweit erwärmt hat, daß die katalytische Verbrennung in Gang kommt und die Reaktion nur noch im Katalysatorkörper stattfindet. Diese Methode der Aufheizung auf Betriebstemperatur ist energiesparender als die bekannte Maßnahme, das dem Brenner zugeführte Brennstoff-Luftgemisch elektrisch vorzuheizen. When the burner is started, the catalyst body can be heated to operating temperature by igniting the from the Fuel-air mixture emerging catalyst body take place. The resulting flame sits on the catalyst body and heats its surface until after a certain time the catalyst body has heated up so far that the catalytic combustion gets going and the reaction only takes place in the catalyst body. This method of Heating to operating temperature is more energy efficient than the known measure, the fuel-air mixture supplied to the burner preheat electrically.

Damit der beim Start des Brenners bestehende Flammensaum genügend Wärme an den Katalysatorkörper übertragen kann, darf die spezifische Flächenbelastung einen Wert von ca. 30 W/cm2 nicht überschreiten. Um diesen Wert einzuhalten, ohne den Durchmesser des Katalysatorkörpers aus diesem Grunde vergrößern zu müssen, wird vorgeschlagen, die ausgangsseitige Stirnwand des Katalysatorkörpers kegelstumpfförmig auszubilden und dadurch die Fläche bei gleichem Außendurchmesser gegenüber einer ebenen Ausführung zu vergrößern.So that the flame seam existing at the start of the burner can transfer enough heat to the catalyst body, the specific surface load must not exceed a value of approx. 30 W / cm 2 . In order to maintain this value without having to enlarge the diameter of the catalyst body for this reason, it is proposed to design the outlet-side end wall of the catalyst body in the shape of a truncated cone and thereby to enlarge the area with the same outer diameter compared to a flat design.

Eine kompakte Ausführung des Wassererhitzers ergibt sich, wenn eine den Katalysatorkörper zentral durchsetzende erste Wasserkammer und eine ihn außen umschließende zweite Wasserkammer vorgesehen wird.The water heater is compact, if a first penetrates centrally through the catalyst body Water chamber and a second water chamber surrounding it on the outside is provided.

Zeichnungdrawing

Sieben Ausführungsbeispiele des Erfindungsgegenstandes sind in der Zeichnung dargestellt und in der nachfolgenden Beschreibung näher erläutert. Die Figuren 1 bis 7 zeigen vereinfacht je eines der Ausführungsbeispiele im Längsschnitt.Seven exemplary embodiments of the subject matter of the invention are shown in the drawing and in the description below explained in more detail. Figures 1 to 7 show simplified one of the exemplary embodiments in longitudinal section.

Beschreibung der AusführungsbeispieleDescription of the embodiments

Der Wassererhitzer nach Figur 1 hat ein mit einem Isoliermantel versehenes Gehäuse 10, in welches ein als zylinderförmiger Block ausgebildeter monolytischer Katalysatorkörper 12 eingesetzt ist. Dieser umschließt eine Wasserkammer 14, die im Zuge einer Warmwasserleitung 16, 18 liegt. Das Gehäuse 10 hat unten einen Einlaß 20 für ein Brennstoff-Luftgemisch, welches nach der Reaktion im Katalysatorkörper 12 als Abgas durch einen Abgaswärmetauscher 22 strömt. The water heater according to Figure 1 has one with an insulating jacket provided housing 10, in which a as a cylindrical Block of trained monolytic catalyst bodies 12 is inserted. This encloses a water chamber 14, which lies in the course of a hot water pipe 16, 18. The housing 10 has an inlet 20 below for a fuel-air mixture, which after the reaction in the catalyst body 12 as exhaust gas through an exhaust gas heat exchanger 22 flows.

Der Katalysatorkörper 12 hat eine durchgehend metallene Trägerstruktur 24, deren Durchgangsöffnungen von mit einer katalytischen Schicht überzogenen Wänden begrenzt sind. Die Trägerstruktur 24 liegt unmittelbar an einem metallisch blanken Metallabschnitt 26 der Wasserkammer 14 an, so daß zwischen den Teilen ein guter Wärmekontakt besteht. An der ausgangsseitigen Stirnwand 28 des Katalysatorkörpers 12 ist eine Barriere 30 in Form einer den Wandabschnitt 26 umschließenden Ringscheibe vorgesehen, die eine unvollständige Reaktion in dem der Wasserkammer 14 benachbarten inneren Bereich des Katalysatorkörpers 12 verhindert. Die Barriere 30 ist so bemessen, daß an ihrem Rand mindestens die Reaktionstemperatur des Katalysators erreicht wird.The catalyst body 12 has a continuously metallic support structure 24, the through openings of which with a catalytic layer covered walls are limited. The Support structure 24 lies directly on a metallic one bare metal section 26 of the water chamber 14, so that there is good thermal contact between the parts. At the is the output end wall 28 of the catalyst body 12 a barrier 30 in the form of a wall section 26 surrounding washer provided an incomplete Reaction in that adjacent to the water chamber 14 prevents the inner region of the catalyst body 12. The Barrier 30 is dimensioned so that at least on its edge the reaction temperature of the catalyst is reached.

Über der Stirnwand 28 des Katalysatorkörpers 12 ist ein Elektrodenpaar 32 angeordnet, über welches beim Start des Brenners das zugeführte Brennstoff-Luftgemisch entzündet wird. Die entstehende Flamme sitzt auf der Stirnwand 28 auf, wodurch sich der Katalysatorkörper 12 soweit erwärmt, daß die katalytische Verbrennung in Gang kommt und die Reaktion nur noch im Katalysatorkörper 12 stattfindet. Dieser gibt nun einen Teil der Reaktionswärme an das durchfließende Wasser ab, das im Abgaswärmetauscher 22 durch die Restwärme weiter aufgeheizt wird. Durch entsprechende Abstimmungen von Größe und Gestalt des Katalysatorkörpers 12 mit der Größe des Wandabschnittes 26 der Wasserkammer 14, der Durchströmgeschwindigkeit des Wassers und weiterer Parameter ist der Wärmeübergang vom Katalysatorkörper 12 auf die Wasserkammer 14 so bestimmt bzw. begrenzt, daß der Katalysatorkörper 12 nicht unter die zur vollständigen Reaktion notwendige Temperatur abkühlt. Above the end wall 28 of the catalyst body 12 is a Arranged pair of electrodes 32, via which at the start of Brenners ignites the supplied fuel-air mixture becomes. The resulting flame sits on the end wall 28, whereby the catalyst body 12 heats up so far that the catalytic combustion gets going and the reaction only takes place in the catalyst body 12. This gives now a part of the heat of reaction to the flowing Water from that in the exhaust gas heat exchanger 22 by the residual heat is further heated. By appropriate votes from Size and shape of the catalyst body 12 with the size of the wall section 26 of the water chamber 14, the flow rate of water and other parameters is the Heat transfer from the catalyst body 12 to the water chamber 14 determined or limited so that the catalyst body 12th not below the temperature necessary for complete reaction cools down.

Der Wassererhitzer nach Figur 2 unterscheidet sich vom vorbeschriebenen Ausführungsbeispiel lediglich dadurch, daß ein monolytischer Katalysatorkörper 34 durch eine kegelstumpfförmig ausgeführte Stirnwand 36 begrenzt ist, die bei gleichem Außendurchmesser eine größere Fläche als die ebene Stirnwand 28 nach Figur 1 hat. Dadurch ist erreicht, daß der beim Start des Brenners entstehende Flammensaum die Stirnwand 36 weniger thermisch belastet bzw. mehr Wärme an den Katalysatorkörper 34 übertragen kann, als es bei der Ausführung nach Figur 1 der Fall ist.The water heater according to Figure 2 differs from the one described above Embodiment only in that a monolytic catalyst body 34 by a truncated cone executed end wall 36 is limited to the same Outside diameter a larger area than the plane End wall 28 according to Figure 1 has. This ensures that the at the start of the burner flame framing the front wall 36 less thermal stress or more heat on the Catalyst body 34 can transfer than it does when running according to Figure 1 is the case.

Der Wassererhitzer nach Figur 3 unterscheidet sich vom Ausführungsbeispiel nach Figur 2 lediglich dadurch, daß ein Katalysatorkörper 38 mit der Wasserkammer 14 nur über einen metallisch blanken Wandabschnitt 40 in wärmeleitender Verbindung steht, dessen axiale Länge L1 in Folge einer zentralen Aussparung 42 im Katalysatorkörper 38 wesentlich kürzer als dessen axiale Gesamtlänge L2 ist. Bei dieser Ausführung wird ein großer Temperaturgradient im Bereich der wärmeabführenden Zone 44 erreicht, ohne daß sich zu hohe Katalysatortemperaturen in den weiter entfernten Bereichen 46 einstellen.The water heater according to FIG. 3 differs from the exemplary embodiment according to FIG. 2 only in that a catalyst body 38 is in heat-conducting connection with the water chamber 14 only via a bare metallic wall section 40, the axial length L 1 of which is essentially the result of a central recess 42 in the catalyst body 38 is shorter than its total axial length L 2 . In this embodiment, a large temperature gradient is achieved in the area of the heat-dissipating zone 44 without the catalyst temperatures in the areas 46 further away being set too high.

Der Wassererhitzer nach Figur 4 unterscheidet sich von jenem nach Figur 1 lediglich dadurch, daß außer einer inneren Wasserkammer 14 eine bezüglich der Wasserströmung parallel dazu angeordnete äußere Wasserkammer 48 im Zuge der Warmwasserleitung 16, 18 vorgesehen ist. Der Katalysatorkörper 12 steht mit der äußeren Wasserkammer 48 über einen metallisch blanken Wandabschnitt 50 in gutem Wärmekontakt, wobei zur Verhinderung einer unvollständigen Reaktion in dem angrenzenden Bereich des Katalysatorkörpers 12 dieser durch eine ringförmige Barriere 52 abgedeckt ist. The water heater according to Figure 4 differs from that according to Figure 1 only in that except for an inner Water chamber 14 a parallel to the water flow arranged outer water chamber 48 in the course of the hot water pipe 16, 18 is provided. The catalyst body 12 is with the outer water chamber 48 via a metallic bare wall section 50 in good thermal contact, wherein to prevent an incomplete reaction in the adjacent Area of the catalyst body 12 through this an annular barrier 52 is covered.

Der Wassererhitzer nach Figur 5 ist ebenfalls mit zwei Wasserkammern 14 und 48 und mit einem monolytischen Katalysatorkörper 54 versehen, der wie bei dem Ausführungsbeispiel nach den Figuren 2 und 3 eine kegelstumpfförmige Stirnwand 36 hat. Aufgrund dieser Ausbildung der Stirnwand 36 und einer von der unteren Stirnseite ausgehenden zentralen Ausnehmung 56 steht der Katalysatorkörper 44 nur über kurze Wandabschnitte 58, 60 mit den Wasserkammern 14, 48 in metallischer wärmeleitender Berührung, wodurch sich die gewünschten großen Temperaturgradienten im Bereich der wärmeabführenden Zonen ergeben.The water heater according to Figure 5 is also with two water chambers 14 and 48 and with a monolytic catalyst body 54 provided, as in the embodiment according to Figures 2 and 3 a frustoconical end wall 36 has. Due to this design of the end wall 36 and a central one starting from the lower end The recess 56 of the catalyst body 44 is only short Wall sections 58, 60 with the water chambers 14, 48 in metallic heat-conducting contact, whereby the desired large temperature gradients in the range of heat-dissipating zones.

Der Wassererhitzer nach Figur 6 unterscheidet sich von der Ausführung nach Figur 1 dadurch, daß ein monolytischer Katalysatorkörper 62 eine Trägerstruktur 64 hat, deren Durchgangsöffnungen als feine Bohrungen bzw. Löcher 66 ausgebildet sind, deren Wände mit einer katalytisch wirksamen Schicht überzogen sind. Eine ähnliche Trägerstruktur hat ein Katalysatorkörper 68 eines in Figur 7 dargestellten Wassererhitzers, der wie die Ausführungen nach den Figuren 4 und 5 zwei Wasserkammern 14 und 48 hat und diese durch entsprechende Formgebung nur an verkürzten Wandabschnitten 70, 72 berührt.The water heater of Figure 6 differs from that Design according to Figure 1 in that a monolytic catalyst body 62 has a support structure 64, the through openings formed as fine bores or holes 66 are, whose walls with a catalytically effective Layer are coated. A similar support structure has one Catalyst body 68 of a water heater shown in Figure 7, which, like the explanations according to FIGS. 4 and 5 has two water chambers 14 and 48 and these by appropriate Shaping only on shortened wall sections 70, 72 touched.

Claims (7)

  1. Water heater having a catalytic burner, which has a catalyst body (12, 34, 38, 54, 62, 68), whose through-openings, which are formed in a support structure (24, 64) and are intended for a fuel/air mixture, are defined by walls (26, 40, 50, 58, 60, 70, 72) covered with a catalytically effective layer, and also having at least one chamber (14, 48), through which the water to be heated flows and which has an active wall section to which the catalytic reaction heat is applied, characterized in that the catalyst body (12, 34, 38, 54, 62, 68) has a continuously metallic support structure (24, 64), which is in direct heat contact with a wall (26, 40, 50, 58, 60, 70, 72) of the water chamber (14, 48).
  2. Water heater according to Claim 1, characterized in that the length of the area of contact of catalyst body (38, 54, 68) and water chamber (14, 48), which length is measured in the direction of flow of the fuel/air mixture, is designed to be shorter than the total length of the catalyst body (38, 54, 68).
  3. Water heater according to Claim 1 or 2, characterized in that the catalyst body, by appropriate design of the support structure, has lower thermal conductivity in the region lying at the area of contact with the water chamber than in the regions further away from it.
  4. Water heater according to one of the preceding claims, characterized in that the catalyst body (12, 34, 38, 54), at the outlet-side end of the area of contact with the water chamber (14, 48), is provided with a barrier (30, 52) hindering the mixture flow in the region adjoining the area of contact.
  5. Burner according to one of the preceding claims, characterized in that the catalyst body (12, 34, 38, 54, 62, 68) is heated to operating temperature by ignition of the fuel/air mixture being discharged from the catalyst body.
  6. Burner according to Claim 5, characterized in that the outlet-side end wall (36) of the catalyst body (34, 38, 54) is of frustoconical design.
  7. Burner according to one of the preceding claims, characterized by a water chamber (14) passing centrally through the catalyst body (12, 54, 68) and by a second water chamber (48) enclosing the catalyst body on the outside.
EP95113285A 1994-09-24 1995-08-24 Water-heater with catalytic burner Expired - Lifetime EP0703417B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4434249 1994-09-24
DE4434249A DE4434249A1 (en) 1994-09-24 1994-09-24 Water heater with a catalytic burner

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EP0703417A1 EP0703417A1 (en) 1996-03-27
EP0703417B1 true EP0703417B1 (en) 1999-12-08

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DE (2) DE4434249A1 (en)
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Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH690282A5 (en) * 1994-07-25 2000-06-30 Vaillant Gmbh Heater with a catalytic burner.
DE19904921C2 (en) * 1999-02-06 2000-12-07 Bosch Gmbh Robert Liquid heater
DE19937152B4 (en) * 1999-08-06 2006-09-21 Nucellsys Gmbh Combined component for the afterburning of anode exhaust gases of a fuel cell system and for evaporating educts to be supplied to the fuel cell system

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4168946A (en) * 1975-03-24 1979-09-25 Comstock & Wescott, Inc. Catalytic fuel combustion apparatus and method
IT1197078B (en) * 1986-08-07 1988-11-25 Umberto Viani BOILERS WITH METHANE CATALYTIC COMBUSTION FOR WATER HEATING FOR DOMESTIC USE
DE4204320C1 (en) 1992-02-13 1993-08-12 Fraunhofer-Gesellschaft Zur Foerderung Der Angewandten Forschung Ev, 8000 Muenchen, De
DE4306722C1 (en) 1993-03-04 1994-03-03 Buderus Heiztechnik Gmbh Catalytic gas and air mixture burner - has catalyst-coated combustion gap heat sealed from water space by air gap

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DE59507375D1 (en) 2000-01-13
DE4434249A1 (en) 1996-03-28
EP0703417A1 (en) 1996-03-27
ES2141285T3 (en) 2000-03-16

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