Method for operating a burner device

Abstract

The invention relates to a method for operating a burner device. Air is conveyed into a combustion chamber (1); ignition sparks are generated using an ignition device (2) arranged in the combustion chamber (1), which is flooded with air; a combustible gas is added to the air while the ignition sparks are continuously generated; and in the period of time which starts before the ignition sparks are generated and ends after the combustible gas is added, electric voltage values are measured on the ignition device (2). According to the invention, the voltage values which are measured in the aforementioned period of time and which form a voltage curve are analyzed in order to detect a formation of flames, beginning when the combustible gas-air mixture which contains at least 20 vol.% of hydrogen is combusted.

Description

[0001] Method for operating a burner device

[0002] The invention relates to a method for operating a burner device according to the preamble of patent claim 1.

[0003] A method of the type mentioned at the outset is known from document DE 10 2020 107 735 A1. In this method, air is pumped into a combustion chamber. Furthermore, ignition sparks are generated by an ignition device arranged in the combustion chamber flooded with air. Moreover, a fuel gas is added to the air while the ignition sparks are being generated. Finally, electrical voltage values ​​present at the ignition device are measured in the period from before the ignition sparks are generated until after the fuel gas is added. With this solution, however, the voltage is measured not only while the ignition spark is present, but also beforehand, in order to be able to determine from the voltage change resulting during the measurement that this value is at a minimum, and therefore that the ignition spark has a minimum quality. Or again in other words: This method is used to assess the quality of the ignition spark.

[0004] The invention is based on the object of improving a process of the type mentioned at the outset. In particular, a process is to be created with which (if necessary in addition to the aforementioned process) the simplest possible adjustment of the fuel gas-air mixture can be achieved, even when using a fuel gas containing hydrogen. This object is achieved with a process of the type mentioned at the outset by the features listed in the characterizing part of patent claim 1.

[0005] According to the invention, it is therefore provided that the voltage values ​​measured in the said 5 period, which form a voltage curve, are evaluated to detect a flame formation beginning with the combustion of the fuel gas-air mixture containing at least 20 vol . — % hydrogen.

[0006] 10

[0007] In other words, the method according to the invention is characterized in that the phase of admixing the fuel gas during start-up of the burner device is precisely monitored with regard to the resulting electrical voltage. This method serves, in particular, to detect the quality of the fuel gas and to regulate the burner device based on or derived from it.

[0008] Other advantageous developments of the method according to the invention emerge from the dependent patent claims. 20

[0009] The method according to the invention, including its advantageous developments according to the dependent claims, is explained in more detail below with reference to the drawing of a preferred embodiment. 25

[0010] It shows

[0011] Figure 1 shows schematically the burner device for carrying out the method according to the invention; Figure 2 shows a voltage curve during flame formation with a small hydrogen content in the fuel gas; and

[0012] Figure 3 shows a voltage curve during flame formation with a large hydrogen content in the fuel gas. 5

[0013] Figure 1 schematically shows a burner device with which the method according to the invention can be carried out. In this method, air is first conveyed into a combustion chamber 1 in a known manner, in particular, as shown, via line 1.1 and burner 1.2. Furthermore, ignition sparks are generated by an ignition device 2 (in particular an electrical one) arranged in the air-flooded combustion chamber 1, preferably having two ignition electrodes 2.2. Furthermore, while the ignition sparks 15 are being generated, a fuel gas is mixed with the air, again via line 1.1 and burner 1.2. In the period from before the ignition sparks are generated until after the fuel gas is added, electrical voltage values ​​(in the physical unit "volts") present at the ignition device 2 are also measured. Looking at this in somewhat more detail, the electrical voltage between the aforementioned ignition electrodes 2.2 is measured in particular.The voltmeter 2.3 shown schematically in Figure 1 is used for this purpose.

[0014] 25 It is now essential for the method according to the invention that the voltage values ​​measured in the said period, which form a voltage curve, are evaluated to detect flame formation beginning with combustion of the fuel gas-air mixture containing at least 20 vol.% hydrogen. 30 It is particularly preferred that the fuel gas contains at least 90 vol.% hydrogen. It is further particularly preferred that, in order to detect flame formation, the voltage curve is measured at a capacitor 2.1 arranged between the two electrodes 2.2 of the ignition device 2. Preferably, the voltage curve is recorded in analogue form but digitized (in a corresponding electronic unit) for evaluation.

[0015] Looking at it in more detail, it is particularly preferred that a change in the voltage curve at the capacitor 2.1 during the said period be interpreted as a sign of flame formation. Depending on the ignition transformer used, the said change can be either a drop (as shown in Figures 2 and 3) or an increase 15 (not shown separately) in the voltage curve.

[0016] It is furthermore particularly preferred that a comparatively large gradient in the voltage curve of the capacitor 2 . 1 be interpreted as a sign of a comparatively large hydrogen content in the fuel gas, and a comparatively small gradient in the voltage curve of the capacitor 2 . 1 be interpreted as a sign of a comparatively small hydrogen content in the fuel gas. As can be seen, Figure 2 shows the small gradient and Figure 3 the large gradient. 25

[0017] Again with reference to the two figures, it is further preferably provided that a comparatively large difference (see figure 2) between the voltage value at the capacitor 2.1 before and after the flame formation is interpreted as a sign of a comparatively small and a comparatively small difference (see figure 3) between the voltage value at the capacitor 2.1 before and after the flame formation is interpreted as a sign of a comparatively large hydrogen content in the fuel gas.

[0018] To put it in other words: Using the detection according to the invention, it is ultimately even possible to determine how much hydrogen is contained in the fuel gas, since this proportion influences - as shown - on the one hand the steepness and on the other hand the final level of the curve.

[0019] 10

[0020] With regard to the aforementioned adjustment of the fuel gas-air mixture, it is furthermore preferably provided, as is known per se, that during the said period, a volume flow of supplied fuel gas is continuously increased, starting from zero. However, it is also particularly preferably provided according to the invention 15 that the volume flow of supplied fuel gas is kept constant from the moment a flame is detected, i.e., the ratio of fuel gas to air is ideally fixed at exactly the ratio at which the flame was formed (optimal combustion). 20

[0021] Expressed in other words, the method according to the invention is characterized in particular as follows:

[0022] The burner is started by supplying the combustion system with a constant air volume flow. The ignition is then switched on, causing high-voltage discharges between the ignition electrodes 2.1. Within a few milliseconds, the resulting plasma of the ionized air reaches the maximum breakdown voltage. The ignition spark creates a voltage on the capacitor 2.1, which serves as a measurement signal and is digitized in the burner control unit (not shown separately). When the ignition is switched on, the capacitor 2.1 has a charging behavior typical of a capacitor. To suppress electromagnetic effects, the digitized signal is filtered by software. If "safe" ignition has been determined (again compare document DE 10 2020 107 735 A1), the gas safety valve is opened and the gas control valve is moved according to the characteristic curve (gas ramp).After the fuel gas-air mixture has reached the combustion chamber or the electrodes, thermochemical, predominantly exothermic reactions begin immediately, leading to self-sustaining flame propagation. The exothermicity of the flame itself leads to a change in the conductivity at the ignition electrodes 2, 1, which reduces the breakdown voltage. This causes the capacitor to discharge, even though the ignition is switched on. The digitized signal also changes depending on the selected filter settings. By means of threshold (level-based) or gradient-based evaluation of the signal, various processes in the start-up sequence, such as flame detection or stopping the gas ramp, can be controlled, as described in more detail above. Conclusions about the composition of the fuel gas-air mixture can be drawn, for example, by evaluating the ignition time and the gradient of the signal.

[0023] List of reference symbols

[0024] 1 combustion chamber

[0025] 1 . 1 line

[0026] 1 . 2 burners

[0027] 2 ignition device

[0028] 2 . 1 capacitor

[0029] 2 .2 Ignition electrode

[0030] 2 .3 Voltmeter

Claims

Patent claims 1. A method for operating a burner device in which air is supplied to a combustion chamber (1), in which ignition sparks are generated by an ignition device (2) arranged in the combustion chamber (1) flooded with air, in which a fuel gas is mixed with the air while the ignition sparks are being generated, and in which electrical voltage values ​​applied to the ignition device (2) are measured during the period from before the generation of the ignition sparks until after the fuel gas has been mixed, characterized in that the voltage values ​​measured during the said period, which form a voltage curve, are evaluated to detect a flame formation beginning with the combustion of the fuel gas-air mixture containing at least 20 vol% hydrogen.

2. Method according to claim 1, characterized in that the voltage profile is measured at a capacitor (2.1) arranged between two electrodes of the ignition device (2) to detect the formation of the flame.

3. Method according to claim 2, characterized in that a change in the voltage profile at the capacitor (2.1) during the said period is considered a sign of flame formation. A method according to claim 2 or 3, characterized in that a comparatively large gradient in the voltage profile of the capacitor (2.1) is considered an indicator of a comparatively large hydrogen content in the fuel gas, and a comparatively small gradient in the voltage profile of the capacitor (2.1) is considered an indicator of a comparatively small hydrogen content. A method according to any one of claims 2 to 4, characterized in that a comparatively large difference between the voltage value at the capacitor (2.1) before and after flame formation is considered an indicator of a comparatively small hydrogen content in the fuel gas, and a comparatively small difference between the voltage value at the capacitor (2.1) before and after flame formation is considered an indicator of a comparatively large hydrogen content in the fuel gas.A method according to any one of claims 1 to 5, characterized in that, during the aforementioned period, the volume flow rate of supplied fuel gas is continuously increased from zero. A method according to claim 6, characterized in that the volume flow rate of supplied fuel gas is kept constant from the moment a flame is detected. A method according to any one of claims 1 to 7, characterized in that the fuel gas contains at least 90% hydrogen by volume. A method according to any one of claims 1 to 8, characterized in that the voltage curve is recorded analogously but digitized for evaluation.

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