EP0655583B1 - Method for controlling and monitoring combustion - Google Patents

Method for controlling and monitoring combustion Download PDF

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Publication number
EP0655583B1
EP0655583B1 EP94118375A EP94118375A EP0655583B1 EP 0655583 B1 EP0655583 B1 EP 0655583B1 EP 94118375 A EP94118375 A EP 94118375A EP 94118375 A EP94118375 A EP 94118375A EP 0655583 B1 EP0655583 B1 EP 0655583B1
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EP
European Patent Office
Prior art keywords
oxygen
exhaust gas
sensor
hydrogen sensor
combustion
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EP94118375A
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German (de)
French (fr)
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EP0655583A1 (en
Inventor
Albrecht Dr. Vogel
Gunar Dr. Baier
Harald Weber
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Lamtec Mess- und Regeltechnik fur Feuerungen GmbH
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Lamtec Mess- und Regeltechnik fur Feuerungen & Co KG GmbH
LAMTEC MESS und REGELTECHNIK F
Lamtec Mess- und Regeltechnik fur Feuerungen & Co KG GmbH
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/24—Preventing development of abnormal or undesired conditions, i.e. safety arrangements
    • F23N5/242—Preventing development of abnormal or undesired conditions, i.e. safety arrangements using electronic means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/003—Systems for controlling combustion using detectors sensitive to combustion gas properties
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2223/00—Signal processing; Details thereof
    • F23N2223/08—Microprocessor; Microcomputer
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N2227/00—Ignition or checking
    • F23N2227/12—Burner simulation or checking
    • F23N2227/16—Checking components, e.g. electronic

Definitions

  • the invention relates to a method for controlling and monitoring the combustion according to the preamble of claim 1.
  • a circuit for regulating the air flow required for a combustion process for the burner of a steam generator is known.
  • the circuit is designed so that flue gas is continuously removed from the flue gas duct and fed to a flue gas analysis device for determining the oxygen content in the exhaust gas. Based on this analysis, the specified fuel-air ratio is corrected and the desired value set.
  • the output signal of the flue gas analysis device is processed in a transducer and compared in a first controller with a fixed setpoint. Depending on the current setpoint deviation, a signal appears at the output of the controller, which is connected to a control loop via the signal path. Since the burner does not allow driving with a constant excess of air, the setpoint is corrected accordingly using a setpoint generator. In addition, the proportion of unburned substances in the form of Co, H in the exhaust gas is measured.
  • DE-A-3 517 471 describes a regulation for the fuel-air ratio of a gas-heated circulating water heater.
  • the control is provided with a sensor for the composition of the exhaust gases, a setpoint generator and a controller as well as a sensor for determining the oxygen content and a sensor for determining the carbon monoxide content in the exhaust gas.
  • the controller outputs a manipulated variable as long as one of the measured variables deviates from the setpoint. If a heat request signal is present, a signal corresponding to this is given to the burner, which can be varied in terms of its output, via an actuator in order to generate a specific burner output. A further signal is derived from this signal, with which the air throughput of the burner is changed. If a setpoint for the maximum carbon monoxide or carbon dioxide content is exceeded, the gas throughput is throttled while the air throughput remains constant.
  • DE-A-25 10 717 describes a method in which the exhaust gas is checked with the aid of two oxygen sensors. The amount of unburned constituents is determined directly after the flame from the voltage signals from these sensors.
  • the disadvantage here is that the sensors in the case of burns with excess air only indicate the content of unburned constituents with very small signals which cannot be easily evaluated, so that only serious defects of the incineration plant can be detected with this arrangement.
  • a device which can directly determine the pollutant emissions, in particular the content of carbon monoxide.
  • the fuel / air ratio is regulated by setting an oxygen setpoint in the exhaust gas via an oxygen sensor.
  • the oxygen setpoint is predetermined by the signal from a sensor for combustible components, in which the minimum excess air is determined, at which unburned components, preferably in the range from 200 to 400 ppm, occur.
  • a semiconducting metal oxide sensor is used as a sensor for the unburned components, the performance of which depends on the content of combustible components.
  • DE-A-38 07 752 describes a device with two ceramic sensors, one of which is provided for the determination of combustible components in the exhaust gas and the second for the determination of gaseous oxygen.
  • the first sensor is formed by a solid electrolyte made of zirconium dioxide. This is provided with an electrode exposed to a reference gas and an electrode made of molybdenum disilicate which is exposed to the measuring gas.
  • the second sensor also has a solid electrolyte made of zirconium dioxide.
  • the first sensor is heated to an operating temperature that differs from the operating temperature of the second sensor. In this way, a broad concentration range of the combustible components in an exhaust gas to be measured can be determined by calculation based on the output power of the two sensors for the gaseous oxygen.
  • the object of the invention is to demonstrate a method with which it is possible to keep the exhaust gas of an incineration plant of the type mentioned at the outset continuously free of pollutants.
  • FIG. 1 shows a control and monitoring device 1 which has an oxygen sensor 2, a hydrogen sensor 3, a processing unit 4 and a control device 5.
  • the oxygen sensor 2 and the hydrogen sensor 3 are installed in the exhaust duct 21 of an incinerator 20.
  • the structure and the mode of operation of the oxygen sensor 2 are disclosed in DE-C-29 45 698.
  • a hydrogen sensor 3, as used in the device 1, is described in DE-A-40 21 929.
  • the hydrogen sensor 3 has the property that it can also be operated as an oxygen sensor in the event that the exhaust gas has no combustible components.
  • the signal inputs and outputs of the two sensors 2 and 3 are connected to the signal inputs and outputs of the processing unit 4, from which, among other things, all fault messages are output.
  • the output signal of the processing unit 4 is fed to the control device 5. This can control the air supply for the combustion system 20 with the aid of an air flap 7 with an output signal which is fed to an actuator 6.
  • the fuel that is supplied via the line 9 is mixed with just enough air that the fuel / air mixture that the combustion system 20 is fed via line 8, just allows complete combustion. If the burner characteristic changes, which can be caused by changes in the fuel's calorific value, fluctuations in air pressure and temperature, blockages in the nozzles or changes in the load of the combustion system, incomplete combustion begins. To avoid this, periodic reviews are carried out the operating point of the incinerator. If there is a deviation from complete combustion, the operating point is reset immediately. If no new operating point can be found, the processing unit 4 issues a corresponding fault message.
  • FIG 2 the cyclic control of the operating point and its readjustment is shown in a diagram.
  • the control is based on the actual state, ie on the current operating point of the incineration plant 20.
  • the air supply via the line 8 to the incineration plant 20 is reduced so that the rest of the oxygen in the exhaust gas is reduced by an amount of X% is reduced by 0.1%.
  • the decrease in the residual oxygen in the exhaust gas 22 can be detected with the help of the oxygen probe 2.
  • the voltage signal of the hydrogen probe 3 is checked. By reducing the oxygen supply, the incinerator 20 will transition from complete combustion to incomplete combustion. This means that the voltage signal U of the hydrogen sensor 3 rises.
  • the difference U d U n ⁇ U v between the voltage signal U v before the reduction in the oxygen supply and the voltage signal U n after the reduction in the oxygen supply is formed in the processing unit 4.
  • the proportion of hydrogen in the exhaust gas 22 increases suddenly during the transition from a complete combustion to an incomplete combustion.
  • FIG. 4 shows, this also applies to the voltage signal that is formed between the two electrodes of the hydrogen sensor 3.
  • the difference U d formed between the two voltage signals U n and U v is compared with a threshold value or limit value. This limit value is stored in the processing unit 4 and has a value of 100 mV in the example described here.
  • Figure 5 shows another way of operating point control and setting.
  • the oxygen supply is reduced in such a way that the remaining proportion of oxygen in the exhaust gas 22 is reduced by X%, equal to 0.1%.
  • the processing unit 4 in turn forms the difference U d between the voltage signals U v and U n , which are tapped at the hydrogen probe 3 before and after the reduction in oxygen in the exhaust gas.
  • the processing unit 4 then forms the quotient U d / X% from the voltage difference U d and the percentage X% of the reduction in the residual oxygen in the exhaust gas.
  • the processing unit 4 now checks whether this quotient is greater or less than a limit value that is stored in the processing unit 4. In the example described here, the limit is set at 2000 mV /%.
  • the oxygen supply to the combustion system 20 is reduced again, in such a way that the proportion of the remaining oxygen in the exhaust gas is reduced by another 0.1%. Then the quotient U d / X% is again formed and compared with the limit value. These process steps are carried out until the quotient U d / X% is greater than the limit value. Then the air supply to the incinerator 20 is increased by D%, equal to 0.3%, so that just a complete one Combustion takes place. The incinerator is then operated with this excess oxygen until the next check.
  • the periodic monitoring of the sensors 2 or 3 and the O 2 is also necessary -Regulation at regular intervals e.g. B. required daily. This can also be carried out with the aid of the control and monitoring device according to the invention.
  • the operating point of the combustion system 20 is first reset, specifically as described above. If the hydrogen sensor 3 for flammable components shows an increased signal rise, the operating point is reset again. If a new operating point is found, a message is output that a check of the operating parameters is required.
  • the air supply to the combustion system 20 is increased with the aid of the control device 5 to such an extent that the combustion takes place with excess air.
  • the voltage signal U of the hydrogen sensor becomes smaller, which is equivalent to a shift in the operating point in the direction of complete combustion.
  • information is output that the hydrogen sensor is OK, but the oxygen control is defective.
  • a message is also output that the incinerator continues to operate with mechanically adjusted excess air. If the size of the voltage signal U at the hydrogen sensor 3 is not reduced by the mechanical increase in the air supply to the combustion system 20, the sensor 3 is defective. There is a message that the hydrogen sensor 3 is defective and the combustion system 20 continues to be operated with a mechanically adjusted excess air.
  • the two sensors 2 and 3 are checked as in FIG. 7, such that the air supply to the incinerator 20 is increased to such an extent that the oxygen content in the exhaust gas 22 has an excess of V%, which can be, for example, between 6.5% and 9%. It is now checked whether the voltage signal U of the hydrogen sensor 3 is within a permissible bandwidth of, for example, 5 to 60 mV. If this is not the case, a fault message is output that the H 2 sensor is defective and the oxygen content of the exhaust gas after a permanently programmed one Map is set in the processing unit 4.
  • the air supply to the incineration plant is changed three times so that the oxygen content in the exhaust gas 22 at three different O 2 values R%, S%, T%, for example at 7% , 5% and 3%.
  • the oxygen fraction is calculated according to the voltage characteristic of the hydrogen sensor 3 with the help of the processing unit 4. If these values do not match the oxygen values determined by the oxygen sensor 2, a fault message is issued that the H 2 sensor or the O 2 sensor is defective and the combustion system 20 is operated at a fixed operating point with a large excess of air.
  • the air supply to the combustion system 20 is throttled for a short time so that the oxygen content in the exhaust gas is only U%, for example only 0.8%. If the voltage signal of the hydrogen sensor 3 then rises, the processing unit issues a message that the O 2 sensor is defective, and that the hydrogen probe is OK. If the voltage signal does not rise, a message is output that the air supply to the incinerator according to a permanently programmed characteristic curve.

Description

Die Erfindung bezieht sich auf ein Verfahren zur Regelung und Überwachung der Verbrennung gemäß dem Oberbegriff des Patentanspruches 1.The invention relates to a method for controlling and monitoring the combustion according to the preamble of claim 1.

Zur Energieeinsparung und Vermeidung von Umweltschäden ist die Überwachung bzw. Regelung von Verbrennungsprozessen in Verbrennungsanlagen unbedingt notwendig. Die Messung des Sauerstoffgehalts in Abgasen allein kann keinen Hinweis auf eine unvollständige Verbrennung liefern. Deshalb ist es besonders wichtig, die Anteile der im Abgas enthaltenen nicht verbrannten Bestandteile zu erfassen und zu minimieren. Zu diesen unverbrannten Bestandteilen gehören Kohlenmonoxid und Wasserstoff. Tritt eine unvollständige Verbrennung ein, so treten im Abgas Wasserstoff- und Kohlenmonoxidemissionen immer gemeinsam auf. Das genaue Verhältnis von Wasserstoff zu Kohlenmonoxid kann dagegen je nach Brennereinstellung, Lastfaktor, Brennstoffbeschaffenheit sowie Lufttemperatur und Luftdruck schwanken. Als Leitgröße, an der sich erkennen läßt, ob eine unvollständige Verbrennung einsetzt, kann das Auftreten von Wasserstoff ebenso wie das Auftreten von Kohlenmonoxid im Abgas herangezogen werden.To save energy and avoid environmental damage, the monitoring and control of combustion processes in incineration plants is absolutely necessary. The measurement of the oxygen content in exhaust gases alone cannot provide an indication of incomplete combustion. It is therefore particularly important to record and minimize the proportions of the unburned components contained in the exhaust gas. These unburned components include carbon monoxide and hydrogen. If incomplete combustion occurs, hydrogen and carbon monoxide emissions always occur together in the exhaust gas. The exact ratio of hydrogen to carbon monoxide, on the other hand, can vary depending on the burner setting, load factor, fuel quality, air temperature and air pressure. The occurrence of hydrogen as well as the occurrence of carbon monoxide in the exhaust gas can be used as a guide variable by which it can be recognized whether incomplete combustion is starting.

Aus der DE-A-2 035 016 ist eine Schaltung zum Regeln des für einen Verbrennungsvorgang benötigten Luftstroms für den Brenner eines Dampferzeugers bekannt. Mit ihr soll die Leistung des Dampferzeugers durch eine Verbrennungsvorgang mit gutem dynamischen Verhalten und hoher statischer Genauigkeit im vorgeschriebenen optimalen Bereich auch bei Störungen wie Heizwertänderungen des Brennstoffes aufrechterhalten werden, so daß schädliche Auswirkungen der Hoch- und Niedertemperaturkorrosion sowie Wirkungsgradabsenkungen vermieden werden. Die Schaltung ist so ausgebildet, daß dem Rauchgaskanal kontinuierlich Rauchgas entnommen und einer Rauchgasanalyseeinrichtung zur Bestimmung des Sauerstoffgehalts im Abgas zugeführt. Auf Grund dieser Analyse wird das vorgegebene Brennstoff-Luftverhältnis korrigiert und der gewünschte Wert eingestellt. Zu diesem Zweck wird das Ausgangssignal der Rauchgasanalyseeinrichtung in einem Meßwertumformer verarbeitet und in einem ersten Regler mit einem fest eingestellten Sollwert verglichen. Je nach der momentan anstehenden Sollwertabweichung erscheint am Ausgang des Reglers ein Signal, das über den Signalpfad mit einem Stellregelkreis verbunden ist. Da der Brenner ein Fahren mit einem konstanten Luftüberschuß nicht gestattet, wird der Sollwert über einen Sollwertgeber entsprechend korrigiert. Zusätzlich wird der Anteil an unverbrannten Stoffen in Form von Co, H im Abgas gemessen.From DE-A-2 035 016 a circuit for regulating the air flow required for a combustion process for the burner of a steam generator is known. With it, the performance of the steam generator is to be maintained by a combustion process with good dynamic behavior and high static accuracy in the prescribed optimal range even in the event of faults such as changes in the heating value of the fuel, so that harmful effects of high and low temperature corrosion and efficiency reductions are avoided. The circuit is designed so that flue gas is continuously removed from the flue gas duct and fed to a flue gas analysis device for determining the oxygen content in the exhaust gas. Based on this analysis, the specified fuel-air ratio is corrected and the desired value set. For this purpose, the output signal of the flue gas analysis device is processed in a transducer and compared in a first controller with a fixed setpoint. Depending on the current setpoint deviation, a signal appears at the output of the controller, which is connected to a control loop via the signal path. Since the burner does not allow driving with a constant excess of air, the setpoint is corrected accordingly using a setpoint generator. In addition, the proportion of unburned substances in the form of Co, H in the exhaust gas is measured.

In der DE-A-3 517 471 ist eine Regelung für das Brennstoff-Luftverhältnis eines gasbeheizten Umlaufwasserheizers beschrieben. Die Regelung ist mit einem Meßfühler für die Zusammensetzung der Abgase, einem Sollwertgeber und einem Regler sowie einem Meßfühler zum Ermitteln des Sauerstoffgehalt und einem Meßfühler zur Bestimmung des Kohlenmonoxydgehalt im Abgas vorgesehen. Der Regler gibt solange eine Stellgröße ab, wie eine der Meßgrößen vom Sollwert abweicht. Beim Vorliegen eines Wärmeanforderungssignals wird ein diesem entsprechendes Signal zum in seiner Leistung variierbaren Brenner über ein Stellglied gegeben, um eine bestimmte Brennerleistung zu erzeugen. Von diesem Signal wird ein weiteres Signal abgeleitet, mit welchem der Luftdurchsatz des Brenner verändert wird. Beim Überschreiten eines Sollwert für den maximalen Kohlenmonoxid- oder Kohlendioxidgehalt wird der Gasdurchsatz bei konstant bleibendem Luftdurchsatz gedrosselt.DE-A-3 517 471 describes a regulation for the fuel-air ratio of a gas-heated circulating water heater. The control is provided with a sensor for the composition of the exhaust gases, a setpoint generator and a controller as well as a sensor for determining the oxygen content and a sensor for determining the carbon monoxide content in the exhaust gas. The controller outputs a manipulated variable as long as one of the measured variables deviates from the setpoint. If a heat request signal is present, a signal corresponding to this is given to the burner, which can be varied in terms of its output, via an actuator in order to generate a specific burner output. A further signal is derived from this signal, with which the air throughput of the burner is changed. If a setpoint for the maximum carbon monoxide or carbon dioxide content is exceeded, the gas throughput is throttled while the air throughput remains constant.

In der DE-A-25 10 717 ist ein Verfahren beschrieben, bei dem mit Hilfe von zwei Sauerstoffsensoren das Abgas geprüft wird. Die Menge an unverbrannten Bestandteilen wird direkt nach der Flamme aus den Spannungssignalen dieser Sensoren ermittelt. Nachteilig hierbei ist, daß die Sensoren bei Verbrennungen mit Luftüberschuß den Gehalt an unverbrannten Bestandteilen nur mit sehr kleinen Signalen anzeigen, die nicht leicht auswertbar sind, so daß mit dieser Anordnung nur schwerwiegende Defekte der Verbrennungsanlage nachgewiesen werden können.DE-A-25 10 717 describes a method in which the exhaust gas is checked with the aid of two oxygen sensors. The amount of unburned constituents is determined directly after the flame from the voltage signals from these sensors. The disadvantage here is that the sensors in the case of burns with excess air only indicate the content of unburned constituents with very small signals which cannot be easily evaluated, so that only serious defects of the incineration plant can be detected with this arrangement.

Aus der DE-B-34 35 902 ist eine Vorrichtung bekannt, welche die Schadstoffemissionen, insbesondere den Gehalt an Kohlenmonoxid, direkt bestimmen kann. Das Brennstoff-/Luftverhältnis wird dadurch geregelt, daß über einen Sauerstoffsensor ein Sauerstoffsollwert im Abgas eingestellt wird. Der Sauerstoffsollwert wird durch das Signal eines Sensors für brennbare Bestandteile vorgegeben, in dem der minimale Luftüberschuß bestimmt wird, bei dem unverbrannte Bestandteile, vorzugsweise im Bereich von 200 bis 400 ppm auftreten. Als Sensor für die unverbrannten Bestandteile wird ein halbleitender Metalloxidsensor verwendet, dessen Leistungsfähigkeit vom Gehalt an brennbaren Bestandteilen abhängt. Da eine Konzentration an Kohlenmonoxid von mehr als 100 ppm heute bereits als Fehlfunktion einer Verbrennungsanlage gilt, der verwendete Halbleitersensor jedoch nur zur einer Regelung der unverbrannten Bestandteile in einem Bereich von 200 bis 400 ppm geeignet ist, entspricht diese Vorrichtung den heutigen Anforderungen nicht mehr.From DE-B-34 35 902 a device is known which can directly determine the pollutant emissions, in particular the content of carbon monoxide. The fuel / air ratio is regulated by setting an oxygen setpoint in the exhaust gas via an oxygen sensor. The oxygen setpoint is predetermined by the signal from a sensor for combustible components, in which the minimum excess air is determined, at which unburned components, preferably in the range from 200 to 400 ppm, occur. A semiconducting metal oxide sensor is used as a sensor for the unburned components, the performance of which depends on the content of combustible components. Since a concentration of carbon monoxide of more than 100 ppm is already considered a malfunction of an incinerator today, but the semiconductor sensor used is only suitable for controlling the unburned components in a range of 200 to 400 ppm, this device no longer meets today's requirements.

In der DE-A-38 07 752 ist eine Vorrichtung mit zwei keramischen Sensoren beschrieben, wobei der ein erster Sensor für die Bestimmung von brennbaren Bestandteilen im Abgas und der zweite für die Ermittlung von gasförmigem Sauerstoff vorgesehen ist. Der erste Sensor wird durch einen Festelektrolyten aus Zirkoniumdioxid gebildet. Dieser ist mit einer einem Referenzgas ausgesetzten Elektrode und einer vom Meßgas beaufschlagten Elektrode aus Molybdändisilikat versehen. Der zweite Sensor weist ebenfalls einen Festelektrolyten aus Zirkondioxid auf. Der erste Sensor wird auf eine Betriebstemperatur erwärmt, die sich von der Betriebstemperatur des zweiten Sensors unterscheidet. Auf diese Weise läßt sich ein breiter Konzentrationsbereich der brennbaren Bestandteile in einem zu messenden Abgas durch Berechnung auf der Basis der Abgabeleistung der beiden Sensoren für den gasförmigen Sauerstoff bestimmen.DE-A-38 07 752 describes a device with two ceramic sensors, one of which is provided for the determination of combustible components in the exhaust gas and the second for the determination of gaseous oxygen. The first sensor is formed by a solid electrolyte made of zirconium dioxide. This is provided with an electrode exposed to a reference gas and an electrode made of molybdenum disilicate which is exposed to the measuring gas. The second sensor also has a solid electrolyte made of zirconium dioxide. The first sensor is heated to an operating temperature that differs from the operating temperature of the second sensor. In this way, a broad concentration range of the combustible components in an exhaust gas to be measured can be determined by calculation based on the output power of the two sensors for the gaseous oxygen.

Aufgabe der Erfindung ist es, ein Verfahren aufzuzeigen, mit dem es möglich ist, das Abgas einer Verbrennungsanlage der eingangs genannten Art ständig schadstoffrei zu halten.The object of the invention is to demonstrate a method with which it is possible to keep the exhaust gas of an incineration plant of the type mentioned at the outset continuously free of pollutants.

Diese Aufgabe wird erfindungsgmäß durch die Merkmale des Patentanspruches 1 oder 2 gelöst.This object is achieved according to the invention by the features of claim 1 or 2.

Weitere erfindungswesentliche Merkmale sind in den Unteransprüchen gekennzeichnet.Further features essential to the invention are characterized in the subclaims.

Die Erfindung wird nachfolgend anhand von Zeichnungen näher erläutert.The invention is explained in more detail below with reference to drawings.

Es zeigen:

Fig. 1
eine erfindungsgemäße Regel- und Überwachungsvorrichtung,
Fig. 2
die zyklische Kontrolle des Arbeitspunktes im Diagramm,
Fig. 3
den sprunghaften Anstieg des Wasserstoffanteils im Abgas bei Änderung der Verbrennung,
Fig. 4
den Verlauf des Meßsignals eines Wasserstoffsensors,
Fig. 5
eine Variante des in Fig. 2 dargestellten Diagramms,
Fig. 6
die Überprüfung der O2-Regelung im Diagramm,
Fig. 7
die Überprüfung der O2- und H2-Sensoren im Diagramm.
Show it:
Fig. 1
a control and monitoring device according to the invention,
Fig. 2
cyclical control of the working point in the diagram,
Fig. 3
the sudden increase in the proportion of hydrogen in the exhaust gas when the combustion changes,
Fig. 4
the course of the measurement signal of a hydrogen sensor,
Fig. 5
a variant of the diagram shown in Fig. 2,
Fig. 6
checking the O 2 control in the diagram,
Fig. 7
checking the O 2 and H 2 sensors in the diagram.

Figur 1 zeigt eine Regel- und Überwachungsvorrichtung 1, die einen Sauerstoffsensor 2, einen Wasserstoffsensor 3, eine Verarbeitungseinheit 4 sowie eine Regeleinrichtung 5 aufweist. Der Sauerstoffsensor 2 und der Wasserstoffsensor 3 sind in den Abgaskanal 21 einer Verbrennungsanlage 20 eingebaut. Der Aufbau und die Funktionsweise des Sauerstoffsensors 2 sind in der DE-C-29 45 698 offenbart. Ein Wasserstoffsensor 3, wie er in der Vorrichtung 1 verwendet wird, ist in der DE-A-40 21 929 beschrieben. Der Wasserstoffsensor 3 weist die Eigenschaft auf, daß er für den Fall, daß das Abgas keine brennbaren Bestandteile aufweist, ebenfalls als Sauerstoffsensor betrieben werden kann. Die Signalein- und Ausgänge der beiden Sensor 2 und 3 sind mit den Signalein-und -ausgängen der Verarbeitungseinheit 4 verbunden, von der unter anderem alle Störmeldungen ausgegeben werden. Das Ausgangssignal der Verarbeitungseinheit 4 wird der Regeleinrichtung 5 zugeführt. Diese kann mit einem Ausgangssignal, das einem Stellglied 6 zugeleitet wird, die Luftzufuhr für die Verbrennungsanlage 20 mit Hilfe einer Luftklappe 7 steuern.FIG. 1 shows a control and monitoring device 1 which has an oxygen sensor 2, a hydrogen sensor 3, a processing unit 4 and a control device 5. The oxygen sensor 2 and the hydrogen sensor 3 are installed in the exhaust duct 21 of an incinerator 20. The structure and the mode of operation of the oxygen sensor 2 are disclosed in DE-C-29 45 698. A hydrogen sensor 3, as used in the device 1, is described in DE-A-40 21 929. The hydrogen sensor 3 has the property that it can also be operated as an oxygen sensor in the event that the exhaust gas has no combustible components. The signal inputs and outputs of the two sensors 2 and 3 are connected to the signal inputs and outputs of the processing unit 4, from which, among other things, all fault messages are output. The output signal of the processing unit 4 is fed to the control device 5. This can control the air supply for the combustion system 20 with the aid of an air flap 7 with an output signal which is fed to an actuator 6.

Damit das aus der Verbrennungsanlage 20 kommende Abgas 22 keinen, oder nur einen sehr geringen Anteil an brennbaren Bestandteilen aufweist, wird dem Brennstoff, der über die Leitung 9 zugeführt wird, gerade so viel Luft beigemischt, daß das Brennstoff-/Luftgemisch, das der Verbrennungsanlage 20 über die Leitung 8 zugeführt wird, gerade noch eine vollständige Verbrennung ermöglicht. Ändert sich die Brennerkennlinie, was auf Grund von Heizwertänderungen des Brennstoffs, von Luftdruck- und Temperaturschwankungen, Düsenverstopfungen oder auch Laständerungen der Verbrennungsanlage hervorgerufen werden kann, so setzt eine unvollständige Verbrennung ein. Um diese zu vermeiden, werden zyklische Überprüfungen des Arbeitspunktes der Verbrennungsanlage durchgeführt. Bei Abweichung von einer vollständigen Verbrennung wird sofort eine Neueinstellung des Arbeitspunktes durchgeführt. Kann kein neuer Arbeitspunkt gefunden werden, so gibt die Verarbeitungseinheit 4 eine entsprechende Störmeldung aus.So that the exhaust gas 22 coming from the combustion system 20 has no or only a very small proportion of combustible constituents, the fuel that is supplied via the line 9 is mixed with just enough air that the fuel / air mixture that the combustion system 20 is fed via line 8, just allows complete combustion. If the burner characteristic changes, which can be caused by changes in the fuel's calorific value, fluctuations in air pressure and temperature, blockages in the nozzles or changes in the load of the combustion system, incomplete combustion begins. To avoid this, periodic reviews are carried out the operating point of the incinerator. If there is a deviation from complete combustion, the operating point is reset immediately. If no new operating point can be found, the processing unit 4 issues a corresponding fault message.

In Figur 2 ist in einem Diagramm die zyklische Kontrolle des Arbeitspunktes und dessen Neueinstellung dargestellt. Bei der Kontrolle wird von dem Istzustand ausgegangen, d. h. von dem augenblicklichen Arbeitspunkt der Verbrennungsanlage 20. Mit Hilfe der Regeleinrichtung 5 wird die Luftzufuhr über die Leitung 8 zur Verbrennungsanlage 20 so reduziert, daß der Rest des Sauerstoffs im Abgas um einen Betrag von X%, gleich 0,1% reduziert wird. Die Abnahme des Restsauerstoffs im Abgas 22 kann mit Hilfe der Sauerstoffsonde 2 erfaßt werden. Gleichzeitig wird das Spannungssignal der Wasserstoffsonde 3 überprüft. Durch die Reduzierung der Sauerstoffzufuhr wird die Verbrennungsanlage 20 von einer vollständigen Verbrennung zu einer unvollständigen Verbrennung übergehen. Dies bedeutet, daß das Spannungssignal U des Wasserstoffsensors 3 ansteigt. In der Verarbeitungseinheit 4 wird die Differenz Ud = Un - Uv zwischen dem Spannungssignal Uv vor der Reduzierung der Sauerstoffzufuhr und dem Spannungssignal Un nach der Reduzierung der Sauerstoffzufuhr gebildet. Wie anhand der Figuren 3 und 4 zu sehen ist, steigt der Anteil des Wasserstoffs im Abgas 22 beim Übergang von einer vollständigen Verbrennung zu einer unvollständigen Verbrennung sprunghaft an. Wie Figur 4 zeigt, gilt das auch für das Spannungssignal, das sich zwischen den beiden Elektroden des Wasserstoffsensors 3 ausbildet. Die zwischen den beiden Spannungssignalen Un und Uv gebildete Differenz Ud wird mit einem Schwellwert bzw. Grenzwert verglichen. Dieser Grenzwert ist in der Verarbeitungseinheit 4 gespeichert und hat bei dem hier beschriebenen Beispiel einen Wert von 100 mV. Ist die Differenz Ud kleiner, so wird die Sauerstoffzufuhr für die Verbrennungsanlage 20 nochmals reduziert, derart, daß sich der Sauerstoffanteil im Abgas 22 nochmals um 0,1% reduziert. Dieser Vorgang wird solange durchgeführt, bis die Differenz Ud größer als der Grenzwert ist. Ist das der Fall, so wird die Arbeitspunkteinstellung fortgesetzt. Die Luftzufuhr für die Verbrennungsanlage 20 wird jetzt um einen Betrag von D% erhöht, so daß gerade wieder eine vollständige Verbrennung erfolgt. Dieser Werts liegt bei 0,3%. Damit ist der neue Arbeitspunkt eingestellt. Die Verbrennungsanlage wird nun mit dieser Arbeitspunkteinstellung bis zur nächsten Prüfung betrieben.In Figure 2, the cyclic control of the operating point and its readjustment is shown in a diagram. The control is based on the actual state, ie on the current operating point of the incineration plant 20. With the help of the control device 5, the air supply via the line 8 to the incineration plant 20 is reduced so that the rest of the oxygen in the exhaust gas is reduced by an amount of X% is reduced by 0.1%. The decrease in the residual oxygen in the exhaust gas 22 can be detected with the help of the oxygen probe 2. At the same time, the voltage signal of the hydrogen probe 3 is checked. By reducing the oxygen supply, the incinerator 20 will transition from complete combustion to incomplete combustion. This means that the voltage signal U of the hydrogen sensor 3 rises. The difference U d = U n −U v between the voltage signal U v before the reduction in the oxygen supply and the voltage signal U n after the reduction in the oxygen supply is formed in the processing unit 4. As can be seen on the basis of FIGS. 3 and 4, the proportion of hydrogen in the exhaust gas 22 increases suddenly during the transition from a complete combustion to an incomplete combustion. As FIG. 4 shows, this also applies to the voltage signal that is formed between the two electrodes of the hydrogen sensor 3. The difference U d formed between the two voltage signals U n and U v is compared with a threshold value or limit value. This limit value is stored in the processing unit 4 and has a value of 100 mV in the example described here. If the difference U d is smaller, the oxygen supply becomes for the incinerator 20 again reduced in such a way that the oxygen content in the exhaust gas 22 is reduced again by 0.1%. This process is carried out until the difference U d is greater than the limit. If this is the case, the operating point setting is continued. The air supply for the incinerator 20 is now increased by an amount of D%, so that a complete combustion is taking place again. This value is 0.3%. The new working point is now set. The incinerator is now operated with this operating point setting until the next test.

Figur 5 zeigt eine andere Möglichkeit, der Arbeitspunktkontrolle und -einstellung. Hierfür wird die Sauerstoffzufuhr gemindert, und zwar so, daß der restliche Anteile des Sauerstoffs im Abgas 22 um X%, gleich 0,1% reduziert wird. In der Verareitungseinheit 4 wird wiederum die Differenz Ud zwischen den Spannungssignalen Uv und Un gebildet, die vor und nach der Reduzierung des Sauerstoffs im Abgas an der Wasserstoffsonde 3 abgegriffen werden. Anschließend bildet die Verarbeitungseinheit 4 den Quotienten Ud/X% aus der Spannungsdifferenz Ud und dem prozentualen Anteil X% der Reduzierung des Restsauerstoffes im Abgas. Nun wird von der Verarbeitungseinheit 4 geprüft, ob dieser Quotient größer oder kleiner als ein Grenzwert ist, der in der Verarbeitungseinheit 4 gespeichert ist. Bei dem hier beschriebenen Beispiel ist der Grenzwert auf 2000 mV/% festgelegt. Ist der Quotient Ud/X% kleiner, so wird die Sauerstoffzufuhr zur Verbrennungsanlage 20 nochmals reduziert, und zwar derart, daß sich der Anteil des restlichen Sauerstoffs im Abgas um nochmal 0,1% reduziert. Anschließend wird wieder der Quotienten Ud/X% gebildet und mit dem Grenzwert verglichen. Diese Verfahrensschritte werden solange durchgeführt, bis der Quotient Ud/X% größer ist als der Grenzwert. Anschließend wird die Luftzufuhr zur Verbrennungsanlage 20 um D%, gleich 0,3% erhöht, so daß gerade wieder eine vollständige Verbrennung erfolgt. Die Verbrennungsanlage wird dann bis zur nächsten Überprüfung mit diesem Überschuß an Sauerstoff betrieben. Die besonderen Vorteile dieser hier beschriebenen Quotientenbildung als Kriterium zur Erkennung des Einsetzens einer unvollständigen Verbrennung liegen darin, daß kleine Änderungen der Spannung U des Wasserstoffsensors keinen Einfluß auf die Funktionen haben, da ja nur relative Signaländerungen betrachtet werden. Die Verringerung der absoluten Sensorempfindlichkeit durch Elektrodenalterung hat zudem keinen Einfluß auf die Funktion, da die Steigung der Sensorkennlinie, die in Figur 4 dargestellt ist, auch noch deutlich zwischen vollständiger und unvollständiger Verbrennung unterscheidet, wenn der absolute Signalwert im steilen Ast der Kennlinie auf Grund von Elektrodenalterung abnimmt. Vorteilhaft ist weiterhin, daß die Steigung der Sensorkennlinie nach Figur 4 bereits ansteigt, sobald der Übergang zu einem Zustand unvollständiger Verbrennung erfolgt. Mit dieser Art der Regelung wird also die Wasserstoffemission auf Werte unterhalb von 100 ppm begrenzt. Die Regel- und Überwachungsvorrichtung 1 erlaubt eine stündliche Überwachung und Neueinstellung des Arbeitspunktes.Figure 5 shows another way of operating point control and setting. For this purpose, the oxygen supply is reduced in such a way that the remaining proportion of oxygen in the exhaust gas 22 is reduced by X%, equal to 0.1%. The processing unit 4 in turn forms the difference U d between the voltage signals U v and U n , which are tapped at the hydrogen probe 3 before and after the reduction in oxygen in the exhaust gas. The processing unit 4 then forms the quotient U d / X% from the voltage difference U d and the percentage X% of the reduction in the residual oxygen in the exhaust gas. The processing unit 4 now checks whether this quotient is greater or less than a limit value that is stored in the processing unit 4. In the example described here, the limit is set at 2000 mV /%. If the quotient U d / X% is smaller, the oxygen supply to the combustion system 20 is reduced again, in such a way that the proportion of the remaining oxygen in the exhaust gas is reduced by another 0.1%. Then the quotient U d / X% is again formed and compared with the limit value. These process steps are carried out until the quotient U d / X% is greater than the limit value. Then the air supply to the incinerator 20 is increased by D%, equal to 0.3%, so that just a complete one Combustion takes place. The incinerator is then operated with this excess oxygen until the next check. The particular advantages of this quotient formation described here as a criterion for recognizing the onset of incomplete combustion are that small changes in the voltage U of the hydrogen sensor have no influence on the functions, since only relative signal changes are considered. The reduction in the absolute sensor sensitivity due to electrode aging also has no influence on the function, since the slope of the sensor characteristic curve, which is shown in FIG. 4, also clearly differentiates between complete and incomplete combustion if the absolute signal value in the steep branch of the characteristic curve is due to Electrode aging decreases. It is also advantageous that the slope of the sensor characteristic according to FIG. 4 already increases as soon as the transition to a state of incomplete combustion takes place. With this type of control, the hydrogen emission is limited to values below 100 ppm. The control and monitoring device 1 permits hourly monitoring and readjustment of the working point.

Da sich der Arbeitspunkt nicht nur durch eine Änderung der Kennlinie der Verbrennungsanlage 20 verschieben kann, sondern auch auf Grund eines Fehlverhaltens einer der Sensors 2 oder 3 oder der O2-Regelung, ist auch die periodische Überwachung der Sensoren 2 oder 3 und der O2-Regelung in regelmäßigen Intervallen z. B. täglich erforderlich. Das kann ebenfalls mit Hilfe der erfindungsgemäßen Regel- und Überwachungseinrichtung durchgeführt werden. Bei der Überwachung der O2-Regelung, wie sie in Figur 6 dargestellt ist, wird zunächst der Arbeitspunkt der Verbrennungsanlage 20 neu eingestellt, und zwar wie oben beschrieben. Zeigt der Wasserstoffsensor 3 für brennbare Bestandteile einen erhöhten Signalanstieg, so wird der Arbeitspunkt nochmals neu eingestellt. Ist ein neuer Arbeitspunkt gefunden, so wird eine Meldung ausgegeben, daß eine Überprüfung der Betriebsparameter erforderlich ist. Wird kein neuer Arbeitspunkt gefunden, so wird mit Hilfe der Regeleinrichtung 5 die Luftzufuhr zur Verbrennunganlage 20 soweit erhöht, daß die Verbrennung mit Luftüberschuß erfolgt. Dies hat zur Folge, daß das Spannungssignal U des Wasserstoffsensors kleiner wird, was gleichbedeutend ist mit einer Verschiebung des Arbeitspunktes in Richtung einer vollständigen Verbrennung. In diesem Fall wird eine Information ausgegeben, daß der Wasserstoffsensor in Ordnung ist, jedoch die Sauerstoffregelung defekt. Ferner wird eine Meldung ausgegeben, daß die Verbrennungsanlage weiter mit mechanisch eingestelltem Luftüberschuß arbeitet. Wird durch die mechanische Erhöhung der Luftzufuhr zur Verbrennungsanlage 20, die Größe des Spannungssignals U am Wasserstoffsensor 3 nicht reduziert, so ist der Sensor 3 defekt. Es erfolgt eine Meldung, daß der Wasserstoffsensor 3 defekt und die Verbrennungsanlage 20 weiter mit mechanisch eingestelltem Luftüberschuß betrieben wird.Since the operating point can not only shift due to a change in the characteristic curve of the combustion system 20, but also due to a malfunction of one of the sensors 2 or 3 or the O 2 control , the periodic monitoring of the sensors 2 or 3 and the O 2 is also necessary -Regulation at regular intervals e.g. B. required daily. This can also be carried out with the aid of the control and monitoring device according to the invention. When monitoring the O 2 control , as shown in FIG. 6, the operating point of the combustion system 20 is first reset, specifically as described above. If the hydrogen sensor 3 for flammable components shows an increased signal rise, the operating point is reset again. If a new operating point is found, a message is output that a check of the operating parameters is required. If no new working point is found, the air supply to the combustion system 20 is increased with the aid of the control device 5 to such an extent that the combustion takes place with excess air. As a result, the voltage signal U of the hydrogen sensor becomes smaller, which is equivalent to a shift in the operating point in the direction of complete combustion. In this case, information is output that the hydrogen sensor is OK, but the oxygen control is defective. A message is also output that the incinerator continues to operate with mechanically adjusted excess air. If the size of the voltage signal U at the hydrogen sensor 3 is not reduced by the mechanical increase in the air supply to the combustion system 20, the sensor 3 is defective. There is a message that the hydrogen sensor 3 is defective and the combustion system 20 continues to be operated with a mechanically adjusted excess air.

Wird der Arbeitspunkt der Verbrennunganlage 20 zyklisch eingestellt, und weist das Spannungssignals U des Wasserstoffsensors 3 trotzdem einen erhöhten Anstieg auf, so ist dies ein Hinweis darauf, daß sich die Kennlinie der Verbrennungsanlage drastisch verändert hat, oder der Sauerstoff- bzw. der Wasserstoffsensor defekt ist.If the operating point of the combustion system 20 is set cyclically and the voltage signal U of the hydrogen sensor 3 nevertheless has an increased rise, this is an indication that the characteristic curve of the combustion system has changed drastically or that the oxygen or hydrogen sensor is defective .

Die Überprüfung der beiden Sensoren 2 und 3 erfolgt, wie in Figur. 7 dargestellt, derart, daß die Luftzufuhr zur Verbrennungsanlage 20 soweit erhöht wird, daß der Sauerstoffanteil im Abgas 22 einen Überschuß von V% aufweist, der beispielsweise zwischen 6,5% und 9% liegen kann. Nun wird geprüft, ob das Spannungssignal U des Wasserstoffsensors 3 innerhalb einer zulässigen Bandbreite von beispielsweise 5 bis 60 mV liegt. Ist das nicht der Fall, so wird eine Störmeldung ausgegeben, daß der H2-Sensor defekt ist, und der Sauerstoffanteil des Abgases nach einem fest einprogrammierten Kennfeld in der Verarbeitungseinheit 4 eingestellt wird. Weist das Spannungssignal der Wasserstoffsonde 3 einen Wert zwischen 5 und 60 mV auf, so wird die Luftzufuhr zur Verbrennungsanlage dreimal so verändert, daß der Sauerstoffanteil im Abgas 22 bei drei verschiedenen O2-Werten R%, S%, T% beispielsweise bei 7%, 5% und 3% liegt. Aus den hieraus resultierenden Spannungssignalen UR, US und UT des Wasserstoffsensors 3 wird der Sauerstoffanteil gemäß der Spannungskennlinie des Wasserstoffsensors 3 mit Hilfe der Verarbeitungseinheit 4 berechnet. Stimmen diese Werte nicht mit den Sauerstoffwerten überein, die von dem Sauerstoffsensor 2 ermittelt werden, wird eine Störmeldung ausgegeben, daß der H2-Sensor oder der O2-Sensor defekt ist, und die Verbrennungsanlage 20 auf festem Arbeitspunkt mit hohem Luftüberschuß gefahren wird. Stimmen die ermittelten Sauerstoffwerte mit den gemessenen Sauerstoffwerten des Sauerstoffsensors 2 überein, so wird die Luftzufuhr zur Verbrennungsanlage 20 kurzfristig so gedrosselt, daß der Sauerstoffanteil im Abgas nur noch U%, beispielsweise nur noch 0,8% beträgt. Steigt daraufhin das Spannungssignal der Wasserstoffsensor 3 an, so wird von der Verarbeitungseinheit eine Meldung ausgegeben, daß der O2-Sensor defekt ist, und daß der Wasserstoffsonde in Ordnung ist Steigt das Spannungssignal nicht an, wird eine Meldung ausgegeben, daß die Luftzufuhr zur Verbrennungsanlage gemäß einer fest einprogrammierten Kennlinie erfolgt.The two sensors 2 and 3 are checked as in FIG. 7, such that the air supply to the incinerator 20 is increased to such an extent that the oxygen content in the exhaust gas 22 has an excess of V%, which can be, for example, between 6.5% and 9%. It is now checked whether the voltage signal U of the hydrogen sensor 3 is within a permissible bandwidth of, for example, 5 to 60 mV. If this is not the case, a fault message is output that the H 2 sensor is defective and the oxygen content of the exhaust gas after a permanently programmed one Map is set in the processing unit 4. If the voltage signal of the hydrogen probe 3 has a value between 5 and 60 mV, the air supply to the incineration plant is changed three times so that the oxygen content in the exhaust gas 22 at three different O 2 values R%, S%, T%, for example at 7% , 5% and 3%. From the resulting voltage signals U R , U S and U T of the hydrogen sensor 3, the oxygen fraction is calculated according to the voltage characteristic of the hydrogen sensor 3 with the help of the processing unit 4. If these values do not match the oxygen values determined by the oxygen sensor 2, a fault message is issued that the H 2 sensor or the O 2 sensor is defective and the combustion system 20 is operated at a fixed operating point with a large excess of air. If the determined oxygen values correspond to the measured oxygen values of the oxygen sensor 2, the air supply to the combustion system 20 is throttled for a short time so that the oxygen content in the exhaust gas is only U%, for example only 0.8%. If the voltage signal of the hydrogen sensor 3 then rises, the processing unit issues a message that the O 2 sensor is defective, and that the hydrogen probe is OK. If the voltage signal does not rise, a message is output that the air supply to the incinerator according to a permanently programmed characteristic curve.

Claims (5)

  1. Method for controlling and monitoring combustion of a combustion plant (20) for flowing gaseous or liquid fuels, downstream of which a hydrogen sensor (2) and an oxygen sensor (3) are connected, characterized in that, in order to check the working point of the combustion plant to ensure that complete combustion just takes place, the air supply to the combustion plant (20) is reduced to such an extent that the residual proportion of oxygen in the exhaust gas is reduced by X%, in that the difference Ud = Un - Uv is formed from the voltage signals Uv, Un of the hydrogen sensor (3) which are measured before and after the reduction in the proportion of oxygen in the exhaust gas (22) and the said difference is compared with a limit value, in that the proportion of oxygen in the exhaust gas (22) is reduced incrementally by X% until the difference voltage Ud which is formed is greater than the prescribed limit value, in that, after this, the supply of oxygen to the combustion plant (20) is increased to such an extent that the residual proportion of the oxygen in the exhaust gas is increased by D% and thus complete combustion just takes place, the values X% = 0.1% and D% = 0.3% being selected, and in that this setting is used as a new working point for the next test, and the monitoring of this setting, the monitoring of the O2 control system and that of the hydrogen sensor and of the oxygen sensor takes place cyclically.
  2. Method for controlling and monitoring the combustion of a combustion plant (20) for flowing gaseous or liquid fuels, downstream of which a hydrogen sensor (2) and oxygen sensor (3) are connected, characterized in that the supply of air to the combustion plant (20) is reduced in such a way that the residual proportion of the oxygen in the exhaust gas is reduced by X%, in that the difference Ud = Un - Uv is formed from the voltage signals Uv, Un of the hydrogen sensor (3) which are determined before and after the reduction, and the quotient Ud/X% is formed from the said difference with the percentile proportion of X% of the reduced quantity of oxygen, in that this quotient is compared with a prescribed limit value and the reduction of the residual oxygen in the exhaust gas is carried out incrementally by X% until the quotient is greater than the prescribed limit value, and in that, subsequently, the supply of air to the combustion plant (20) is increased to such an extent that the residual proportion of the oxygen in the exhaust gas is increased by D% and thus complete combustion just takes place, the values X% = 0.1% and D% = 0.3% being selected, and in that this setting is used as the new working point until the next test, and the monitoring of this setting, the monitoring of the O2 control system as well as that of the hydrogen sensor and of the oxygen sensor take place cyclically.
  3. Method according to one of Claims 1 or 2, characterized in that, in order to check the O2 control system with increased voltage signal (U) of the hydrogen sensor (3), resetting of the working point is performed, in that, when a new working point is not reached, the supply of air to the combustion plant (20) is increased mechanically to such an extent that the combustion takes place with excess air, in that, when this results in a reduction in the voltage signal (U) of the hydrogen sensor, a message is output that the oxygen control system is defective, and in that, when a reduction in the voltage signal (U) is not achieved in this way, a message is output that the hydrogen sensor (3) is defective, and in that, when the oxygen sensor (2) is defective or the hydrogen sensor (3) is defective, a message is additionally output that the combustion plant should continue to operate a mechanically set excess-air setting.
  4. Method according to one of Claims 1 or 2, characterized in that, in order that the sensors (2 and 3) check one another, the air supply to the combustion plant (20) is increased to such an extent that the residual proportion of oxygen in the exhaust gas (22) rises to V%, V% lying between 6.5% and 9%, in that, when this results in a voltage signal (U) of the hydrogen sensor (3) outside the permissible interval, a fault signal H2 sensor defective is output, in that the combustion plant is operated according to a permanently programmed characteristic diagram with a smallest possible oxygen excess in the exhaust gas.
  5. Method according to Claim 4, characterized in that, given a voltage signal of the hydrogen sensor (3) in the permissible range after the proportion of oxygen in the exhaust gas (20) has been increased to V%, the air supply to the combustion plant (20) is set in three stages to R%, S% and T% of the residual proportion of oxygen in the exhaust gas (20), in that the associated oxygen value is determined from the respectively measured voltage signals (UR, US and UT) of the hydrogen sensor (3) at R%, S% and T% proportion of oxygen in the exhaust gas, from the characteristic curve of the oxygen sensor (3), in that the calculated oxygen values are compared with the measured oxygen values in the exhaust gas, and when they do not correspond a fault message: oxygen sensor (2) or hydrogen sensor (3) defective and the combustion plant (20) is operating with an excessive air excess, is output, in that, when they do correspond the quantity of air supplied to the combustion plant (20) is briefly reduced to such an extent that the proportion of oxygen in the exhaust gas is reduced to U%, in that, when the voltage signal of the hydrogen sensor (3) rises, a message: hydrogen sensor (3) satisfactory, is output, and in that, otherwise, a fault report: hydrogen sensor (3) defective, is output and the combustion plant is operated according to a permanently programmed characteristic curve in such a way that the exhaust gas (22) has the smallest possible oxygen excess, the values R% = 7%, S% = 5%, T% = 3%, U% = 0.8% and V% between 6.5% and 9% being selected.
EP94118375A 1993-11-29 1994-11-23 Method for controlling and monitoring combustion Expired - Lifetime EP0655583B1 (en)

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AT500257A2 (en) * 2003-04-28 2005-11-15 Vaillant Gmbh PROCEDURE FOR ERROR MONITORING OF AN EVALUATION CIRCUIT
DK1522790T3 (en) 2003-10-08 2012-03-19 Vaillant Gmbh Procedure for regulating a gas burner, especially for fan heaters
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DE3517471A1 (en) * 1984-05-19 1985-11-28 Joh. Vaillant Gmbh U. Co, 5630 Remscheid Control for the fuel/air ratio of a fuel-heated heat source
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