AT521855B1 - Method for detecting ignition and / or combustion in a burner of a fuel cell system - Google Patents

Abstract

The present invention relates to a method for detecting ignition and / or combustion in a burner (1) of a fuel cell system (2), having the following steps: supplying fuel and air into the burner (1) for combustion of a fuel / air Mixture in the burner (1), determining a temperature increase at a gas inlet area (3) of the burner (1), comparing the determined temperature increase at the gas inlet area (3) with a reference temperature increase, and detecting ignition and / or combustion of the fuel / air mixture in the burner (1) based on the comparison of the determined temperature increase with the reference temperature increase, an additional amount of fuel being fed into the burner (1) from a predeterminable temperature at the gas inlet area (3) of the burner (1). The invention also relates to a computer program (7), a storage means, a controller (8) and the use of the controller (8) in a fuel cell system 2, in particular in a stationary fuel cell system, for detecting ignition and / or combustion in a burner ( 1).

Description

description

METHOD OF DETECTING IGNITION AND / OR BURNING IN A BURNER OF A FUEL CELL SYSTEM

The present invention relates to a method for detecting ignition and / or combustion in a burner of a fuel cell system. The invention also relates to a computer program, a storage means, a controller and the use of a controller in a fuel cell system, in particular in an SOFC system, for detecting ignition and / or combustion in a burner.

In order to bring SOFC systems, especially stationary SOFC systems, to operating temperature, burners in the form of so-called starting burners / afterburners, or electrical heating means are usually used. Two-stage afterburners with a catalyst chamber and a downstream, catalyst-free combustion chamber are often used as burners. If such an afterburner is used, ignition and / or combustion of fuel can be detected by various systems available in the prior art. According to German patent application DE 10 2011 089 530 A1, this can be implemented, for example, with a temperature sensor for determining a temperature prevailing in the burner.

Generic systems for temperature detection have, for example, flame monitors for visible and / or invisible radiation, acoustic flame monitoring and / or the measurement of the electrical conductivity of gases in a combustion chamber. The systems usually provide that the measurement takes place in the afterburner or downstream of the afterburner.

[0004] Further systems for monitoring combustion are known from WO 2007091160 A1 and JP 2003002605 A, for example.

Due to the mass of an afterburner, it is not possible in the combustion chamber after the catalyst chamber to determine the ignition promptly via a temperature change, since the mass and the heat capacity of the catalyst or the catalyst chamber, the heat generated at the beginning of the combustion is relatively strong record, tape.

[0006] The object of the present invention is to at least partially take account of the problems described above.

In particular, it is the object of the present invention to create an improved method for detecting ignition and / or combustion in a burner of a fuel cell system.

Furthermore, it is an aim to provide a computer program, a storage means, a controller and a use of a controller in a fuel cell system for the improved detection of an ignition and / or a combustion in a burner of the fuel cell system.

[0009] The above object is achieved by the patent claims. In particular, the above object is achieved by the method according to claim 1, the computer program according to claim 6, the storage means according to claim 7, the controller according to claim 8 and the use according to claim 9. Further advantages of the invention emerge from the dependent claims, the description and the drawings. Features and details that are described in connection with the method naturally also apply in connection with the computer program according to the invention, the memory means according to the invention, the controller according to the invention, the use according to the invention and vice versa, so that with regard to the disclosure to the individual aspects of the invention, there is always mutual reference is or can be taken.

According to a first aspect of the present invention, a method for recognizing

nen an ignition and / or a combustion in a burner of a fuel cell system is made available. The procedure consists of the following steps:

- Feeding fuel and air into the burner for combustion of a fuel / air mixture in the burner,

- Determination of a temperature increase in a gas inlet area of the burner,

- Compare the determined temperature increase at the gas inlet area with a reference temperature increase, and

- Detection of an ignition and / or combustion of the fuel / air mixture in the burner based on the comparison of the determined temperature increase with the reference temperature increase, with an additional amount of fuel being fed into the burner from a predeterminable temperature at the gas inlet area of the burner.

The combustion of the fuel generates heat in the burner, which greatly heats the fuel / air mixture in the gas inlet area or in the fuel / air inlet area of the burner. This results in a clearly recognizable temperature increase in or at the gas inlet area of the burner, which can be easily measured with conventional measuring systems. This was recognized within the scope of the present invention and led to the method according to the invention. More precisely, it was surprisingly found that a temperature measurement at the gas inlet area permits a faster and more accurate detection of a temperature change within the burner than the previously usual temperature measurement inside the burner or downstream of the burner. Accordingly, an ignition and / or a sought-after combustion in the burner can be recognized particularly quickly and reliably by the present method.

The gas inlet area is to be understood as meaning an area, for example in the form of an antechamber or a line volume, upstream of the burner or a catalyst chamber on the burner, preferably directly on the burner. That is, the gas inlet area can be part of the burner or be designed separately directly on the burner. The determination of the temperature increase can be understood to mean a measurement of the temperature increase. The temperature increase is preferably determined by a continuous or at least regular temperature measurement in or at the gas inlet area.

With the determination of the temperature increase, it is possible to detect the occurrence of the ignition in the catalytic converter and / or a desired combustion, in particular a complete combustion, or at least derive it with simple means. In extensive measurements that were carried out within the scope of the present invention, it was also found that it is possible with a suitable catalyst material in the burner in combination with the now possible rapid reaction to temperature changes in the burner and a correspondingly rapid adaptation of the operating mode of the fuel cell system Influencing the ignition temperature in the burner so that complete combustion of the fuel in the burner can be ensured.

Accordingly, the method according to the invention can also reliably diagnose complete combustion in suitable catalytic converters and any post-combustion in a possible second stage of the burner in a simple manner. Such a two-stage burner can have a dedicated catalyst chamber and a dedicated catalyst-free combustion chamber. In the present case, however, the burner can be designed in either one or two stages.

In the present method, the temperature or the temperature increase at the gas inlet area is preferably measured with a temperature sensor. By determining the temperature increase upstream or at the gas inlet of the burner, a method for indirect detection of ignition and / or complete combustion of the fuel / air mixture in the burner is made available, so to speak. With the proposed method

Ren it is possible to recognize the heat development corresponding to the ignition and / or complete combustion in the burner in a time of less than 10 seconds. In this way it can be avoided, for example, that larger amounts of unburned fuel flow through the fuel cell system.

The method according to the invention is carried out in particular during a starting process or a heating process of the fuel cell system. A gaseous fuel, preferably a natural gas mixture which mainly consists of methane, is preferably used as the fuel. Natural gas is to be understood in particular as a natural gas mixture, which can also consist exclusively or almost exclusively of methane. The air is used in particular in the form of ambient air, it being understood that the fuel can also be burned with the addition or admixture of another oxygen-containing fluid. In principle, a liquid fuel can also be used as fuel, which, however, has to be vaporized before being fed to the burner or to the fuel cell stack arranged upstream. It is therefore particularly advantageous if the process is carried out with operating fluids that are already gaseous.

With the aid of the method, the ignition and / or the combustion in the burner can be automatically recognized on the basis of the comparison of the determined temperature increase with the reference temperature increase. That is, a reading out and / or an interpretation of the comparison for recognizing or determining the ignition and / or the combustion can for example be carried out automatically by a computer.

The burner is preferably designed for burning cathode exhaust gas from a cathode section and / or anode exhaust gas from an anode section of a fuel cell stack during normal operation, ie after the starting process for heating up the fuel cell system.

The method is preferably carried out in a stationary fuel cell system, in particular in a stationary SOFC system. The burner can be designed both as a starting burner and as an afterburner or as an integral component for a starting burner and / or afterburner.

According to a further aspect of the present invention, it is possible that a combustion air ratio A is set to a value between 1 and 2 in the burner in a method when feeding fuel and air into the burner. The combustion of the fuel / air mixture generates heat in the burner, which greatly heats the fuel / air mixture in the inlet area of the burner. By choosing a suitable combustion air ratio, the gradient of a temperature increase in the gas inlet area can be influenced. Extensive tests within the scope of the present invention have shown that a combustion air ratio between 1 and 2 is particularly advantageous during ignition. That is, according to the invention, at least the necessary oxygen for complete combustion is made available, but a maximum of twice the necessary amount.

It is also possible that in a method according to the invention, the burner, when feeding fuel and air, is preheated by an electrical heating device at least for a predeterminable period of time and / or to a predeterminable temperature, in particular to a predetermined operating temperature. In the context of the invention, the operating temperature can be understood to be a temperature from which complete combustion of the fuel / air mixture is possible. The heating device can be arranged directly on the burner for heating the burner. However, the heating device is preferably arranged at a distance from the burner and accordingly heats it indirectly by an operating fluid, in particular air, which is heated by the heating device upstream of the burner and then fed to the burner. The heating device is preferably arranged outside a so-called hot box of the fuel cell system in which the burner is located. Accordingly, the operating fluid for heating the burner is preferably heated outside the hotbox and also fed to the burner from there. In experiments within the scope of the present invention it has surprisingly been found that laying the heating device from a

Position directly on the burner inside the hotbox at a position outside the hotbox hardly leads to an impairment of the heating function of the heating device for the burner. That is, although the heating device was arranged outside the hotbox, the burner could still be heated as desired or supplied with the required heating air. The heating device outside the hotbox is exposed to significantly lower temperatures than inside the hotbox. As a result, it is no longer necessary to undertake complex heat protection measures for the heating device. Costs for this can be saved accordingly. With the aid of the heating device, when fuel and air are supplied, the burner can be preheated by a temperature control fluid at least for a predeterminable period of time and / or to a predeterminable temperature, in particular to a predetermined operating temperature.

In the present invention, a method is further provided that from a predeterminable temperature at the gas inlet area of the burner, an additional amount of fuel are fed into the burner. If the gas temperature reaches a certain temperature at the entry into a catalyst chamber of the burner, for example in a range between 600 ° C and 900 ° C, in particular between 700 ° C and 800 ° C, an additional amount of fuel, i.e. in addition to an already The amount of fuel fed into the burner, with which the selected combustion air ratio can be achieved or set to the desired value. This procedure can be implemented particularly effectively due to the fact that it is possible to react quickly to changing temperatures in the burner.

Furthermore, it is possible that in a method according to the present invention from a predeterminable temperature at the gas inlet area of the burner, an additional amount of air is conveyed into the burner. Due to the increased supply of air or of another oxygen-containing fluid, the temperature can reliably be kept at a value below a permissible maximum operating temperature of the burner, in particular of a catalyst chamber or a catalyst in the catalyst chamber of the burner. In this way, the ignition and / or the combustion in the burner can be recognized for the fuel cell system in a particularly gentle and safe manner. Alternatively, it is possible to set the combustion air ratio accordingly so that a calculated flame temperature in the burner cannot exceed a maximum operating temperature of the burner.

It is particularly advantageous if, in a method, the burner has a catalyst chamber and a catalyst-free combustion chamber downstream of the catalyst chamber, an additional amount of air at least partially from a predeterminable temperature at the gas inlet area of the burner to increase a gas flow rate in the burner Relocation of a combustion, in particular the complete combustion, of the fuel / air mixture from the catalyst chamber into the combustion chamber is conveyed into the burner. Due to the two-stage design of the burner and the use of the process steps described, a gradual and appropriately controlled combustion is possible, whereby an exit temperature of the burned fuel / air mixture from the burner is reached which is higher than a temperature otherwise permissible for the catalyst chamber. By dividing the burner according to the invention, it is possible to keep a temperature in the catalyst chamber lower, as a result of which a catalytic coating of the same is spared. In addition, the method according to the invention makes it possible to use the burner which is already necessary in the system as a starting burner. An afterburner and / or a starting burner can be understood by the burner.

To implement an afterburner and a starter burner, only one burner is necessary, which is used as a starter burner or afterburner depending on an operating mode of the fuel cell system. The flow rate can be increased with the increase in the air so that the complete combustion does not take place in the catalytic converter or a corresponding catalytic converter chamber, but only in the downstream, catalytic converter-free combustion chamber. It is of further advantage if the flow speed of the fuel / air mixture is increased to such an extent that it exceeds a flame speed. This can prevent backfire in the gas inlet area of the

Burner or in a corresponding mixing space upstream of the burner can be prevented.

According to a further aspect of the present invention, a computer program is provided, comprising instructions which, when the computer program is executed by a computer, cause the computer to execute the method described in detail above. A computer program according to the invention thus brings the same advantages as have been described in detail with reference to the method according to the invention.

The computer program can be implemented as computer-readable instruction code in any suitable programming language such as, for example, JAVA, C ++ and / or C #. The computer program can be stored on a computer-readable storage medium, such as a data disc, a removable drive, a volatile or non-volatile memory or a built-in memory / processor. The instruction code can program a computer or other programmable device, such as a controller, to perform the desired functions. Furthermore, the computer program can be provided or be in a network, such as for example the Internet, from which it can be downloaded by a user if necessary. The computer program can be implemented both by means of software and by means of one or more special electronic circuits, i.e. in hardware, or in any hybrid form, i.e. by means of software components and hardware components.

Furthermore, a storage means is provided with a computer program stored thereon which is configured and designed to carry out a method as described above. The storage medium is to be understood as meaning, in particular, a computer-readable storage medium, such as a data disk, a removable drive, a volatile or a non-volatile storage medium. In addition, a controller with a computer program installed therein for recognizing ignition and / or combustion in a burner of a fuel cell system can be provided, having a determination device for determining a temperature increase at a gas inlet area of the burner, a comparison device for comparing the determined temperature increase at the gas inlet area with a Reference temperature increase and a detection device for detecting ignition and / or combustion of the fuel / air mixture in the burner based on the comparison of the determined temperature increase with the reference temperature increase. The determination device, the comparison device and / or the detection device can each be provided in the form of software and / or hardware components. In the present case, the controller can be understood as a storage means, whereas the storage means generally does not include a controller. In addition, the use of such a controller in a fuel cell system for detecting ignition and / or combustion in a burner of the fuel cell system is proposed within the scope of the invention. The advantages described above can thus also be achieved by the storage means, the controller and the use of the controller according to the invention.

Further measures improving the invention emerge from the following description of various exemplary embodiments of the invention, which are shown schematically in the figures. They each show schematically:

FIG. 1 shows a block diagram to explain an embodiment of the present invention, and FIG

FIG. 2 shows a curve diagram to explain an embodiment of the present invention.

In Fig. 1, a fuel cell system 2 is shown schematically in the form of a stationary SOFC system. The fuel cell system 2 has a fuel cell stack 14 with an anode section 12 and a cathode section 13. The fuel cell stack 14 can generate electrical power in the context of an electrochemical reaction. The

Fuel cell system 2 furthermore has a reformer 17 for reforming a fuel mixture into an anode feed gas to the anode section 12. In addition, the fuel cell system 2 has a burner 1, which in the present case can be operated both for burning anode exhaust gas from the anode section 12 and cathode exhaust gas from the cathode section 13 and as a starting burner for heating the fuel cell system 2 during a starting process or heating process of the fuel cell system 2. The burner 1 comprises a first chamber in the form of a catalyst chamber 5 and a second chamber in the form of a combustion chamber 6. The catalyst chamber 5 comprises a catalytic material, which is designed, for example, as a fabric, whereas the combustion chamber 6 comprises a flame burner not shown in FIG. 1 . The catalyst chamber 5 and the combustion chamber 6 directly adjoin one another in the direction of flow, a fuel / air mixture flowing through the first catalyst chamber 5 and then through the combustion chamber 6 during operation of the fuel cell system 2. According to FIG. 1, the direction of flow is indicated from right to left. In the present case, the catalyst chamber 5 can also be understood as a combustion chamber for burning, in particular for catalytic burning, of the fuel / air mixture.

As shown in FIG. 1, the fuel cell system 2 also has an electrical heating device 4 for preheating the burner 1 during the starting process of the fuel cell system 2. The fuel cell stack 14, the reformer 17 and the burner 1 are arranged within a hot box 15 of the fuel cell system 2. The heating device 4, however, is arranged outside the hotbox 15 on the latter. A heat exchanger 16 is also arranged inside the hot box 15, the cold side of which is arranged upstream of the cathode section 13 and with its hot side is arranged downstream of the burner 1. A blower 18 is arranged upstream of the heating device 4 for charging the heating device 4 with the air to be supplied to the burner 1.

A controller 8 is provided for recognizing an ignition and / or a combustion in the burner 1. The controller 8 can be understood to mean a control and / or regulating system. The controller 8 has a determination device 9 for determining a temperature increase at a gas inlet area 3 of the burner 1, a comparison device 10 for comparing the determined temperature increase at the gas inlet area 3 with a reference temperature increase, and a detection device 11 for detecting ignition and / or combustion of the fuel / air Mixture in burner 1 based on the comparison of the determined temperature increase with the reference temperature increase. That is, if it is recognized, for example, that the temperature increase is greater than the reference temperature increase, it can be concluded that an ignition and / or combustion in the burner has occurred. If, on the other hand, it is recognized that the temperature increase is weaker than the reference temperature increase, it can be assumed that there is still no ignition and / or the combustion sought.

In the controller 8, a computer program 7 is installed, which comprises commands that cause the computer program 7 to be executed by a computer or the controller 8, a method described below with reference to FIGS. 1 and 2 for Detecting ignition and / or combustion in the burner. In Fig. 2, S1 stands for the temperature of the air supplied by the heating device 4, S2 for the temperature of the fuel / air mixture in the gas inlet area 3 and S3 for the temperature of the burned fuel / air mixture downstream of the burner 1. Z1 stands for a first point in time at which fuel is fed to burner 1 in the form of methane. Z2 stands for a second point in time at which the ignition is recognized. When the ignition is detected, the heating device 4 is deactivated and the air supply to the burner 1 can be increased to further regulate the temperature in the catalytic converter. Z3 stands for a third point in time at which the fuel supply to burner 1 is increased. This point in time can be influenced by the desired regulation. The point in time Z3 basically marks a point in the process sequence from which it is possible to increase the amount of fuel further so that more thermal power can be provided. According to the desired operating temperature

the amount of fuel and the amount of air are subsequently set. However, the linear courses are only intended to represent a basic possibility and not exclude other heating strategies. For example, the amount of fuel gas can also be reduced in order to achieve a slower heating process. The amount of air required is always set as a function of the amount of fuel gas and the operating temperature of the catalyst desired at the operating point.

V1 stands for the air volume flow led to the burner 1 and V2 stands for the fuel volume flow led to the burner 1.

In the following, a possible heating scenario is described in more detail using the example shown in FIG. In this case, 16,000 NI / h of air are fed to burner 1 before time Z1, this amount or this volume flow being increased to 35,000 NI / h from time Z2. From the point in time Z1, as soon as the burner 1 is preheated to the desired self-ignition temperature of the natural gas of approx. 670 ° C., the burner 1 1000 NI / h fuel is fed. From time Z3, this amount or the volume flow is increased to 1,500 NI / h.

According to the method, in a first step, air preheated by the heating device 4 is thus first fed into the burner 1 in order to preheat the burner 1 to a desired temperature. As soon as the desired temperature is reached at time Z1, fuel is added to burner 1. The ignition is recognized at time Z2 and the air flow to burner 1 is increased. That is, from the detection of the ignition of the fuel in the burner 1, an additional amount of air is conveyed to increase the gas flow rate in the burner 1. This prevents reignition in the mixing chamber in front of the catalytic converter. If the flow velocity is increased sufficiently, a combustion, in particular complete combustion, of the fuel / air mixture can be at least partially shifted from the catalyst chamber 5 into the combustion chamber 6 into the burner 1.

As soon as the ignition and the combustion of the fuel / air mixture in the burner 1 have been recognized based on the temperature jump with respect to the temperature of the fuel / air mixture in the gas inlet area 3, the heating device 4 is deactivated. The sought temperature increase or temperature jump is recognized by comparing the continuously determined temperature at the gas inlet area with a reference temperature. In other words, the ignition and the sought-after combustion of the fuel / air mixture in the burner 1 are recognized on the basis of a comparison of a temperature increase determined at the gas inlet area 3 with a reference temperature increase.

In addition to the illustrated embodiments, the invention allows further design principles. That is to say, the invention should not be viewed as restricted to the exemplary embodiments explained with reference to the figures.

Austrian AT 521 855 B1 2020-10-15

REFERENCE LIST

10 11 12 13 14 15 16 17 18

Ss1 S2 sS3

Z1 Z2 Z3

V1 V2

Burner Fuel cell system Gas inlet area Electrical heating device Catalyst chamber Combustion chamber Computer program controller Determination device Comparison device Recognition device Anode section Cathode section Fuel cell stack Hotbox Heat exchanger Reformer

fan

Temperature profile of the air supplied by the heating device Temperature profile in the gas inlet area

Temperature profile downstream of the burner, first time, second time

third point in time

Air volume flow

Volume flow of fuel

Claims (9)

Claims 1. A method for detecting ignition and / or combustion in a burner (1) of a fuel cell system (2), comprising the steps: - Feeding fuel and air into the burner (1) for combustion of a fuel / air mixture in the burner (1), - Determination of a temperature increase in a gas inlet area (3) of the burner (1), - Comparing the determined temperature increase at the gas inlet area (3) with a reference temperature increase, and - Detection of ignition and / or combustion of the fuel / air mixture in the burner (1) on the basis of the comparison of the determined temperature increase with the reference temperature increase, characterized in that from a predeterminable temperature at the gas inlet area (3) of the burner (1) an additional amount of fuel is conveyed into the burner (1). 2, method according to claim 1, characterized in that When fuel and air are fed into the burner (1), a combustion air ratio A is set in the burner (1) to a value between 1 and 2. 3. The method according to any one of the preceding claims, characterized in that the burner (1), when fuel and air are supplied, is preheated by an electrical heating device (4) at least for a predeterminable period of time and / or to a predeterminable temperature. 4. The method according to any one of the preceding claims, characterized in that From a predeterminable temperature at the gas inlet area (3) of the burner (1), an additional amount of air is conveyed into the burner (1). 5. The method according to any one of the preceding claims, characterized in that the burner (1) has a catalyst chamber (5) and a catalyst-free combustion chamber (6) downstream of the catalyst chamber (5), with an additional amount of air from a predeterminable temperature at the gas inlet area (3) of the burner (1) to increase a gas flow rate in the burner (1) for at least partial relocation of combustion, in particular complete combustion, of the fuel / air mixture from the catalyst chamber (5) into the combustion chamber (6) into the burner (1). 6. Computer program (7), comprising instructions which, when the computer program (7) is executed by a computer, cause the computer to carry out the method according to one of the preceding claims. 7. Storage means with a computer program (7) stored thereon which is configured and designed for performing a method according to one of claims 1 to 5. 8. Controller (8) with a computer program (7) according to claim 6 installed therein for detecting ignition and / or combustion in a burner (1) of a fuel cell system (2), having a detection device (9) for detecting a temperature increase at a Gas inlet area (3) of the burner (1), a comparison device (10) for comparing the determined temperature increase at the gas inlet area (3) with a reference temperature increase, and a detection device (11) for detecting a ner ignition and / or combustion of the fuel / air mixture in the burner (1) based on the comparison of the determined temperature increase with the reference temperature increase. 9. Use of a controller (8) according to claim 8 in a fuel cell system (2) for detecting ignition and / or combustion in a burner (1) of the fuel cell system (2). 1 sheet of drawings