EP4143486A1

EP4143486A1 - Device and method for combustion control for a fuel gas with a proportion of additive gas

Info

Publication number: EP4143486A1
Application number: EP21722786.7A
Authority: EP
Inventors: Sebastian Hack
Original assignee: Viessmann Climate Solutions SE
Current assignee: Viessmann Climate Solutions SE
Priority date: 2020-04-29
Filing date: 2021-04-27
Publication date: 2023-03-08
Anticipated expiration: 2041-04-27
Also published as: WO2021219582A1; DE102020205449A1; EP4143486B1; ES2981251T3; PL4143486T3

Abstract

The invention relates to a method for controlling the combustion of fuel gas by means of a gas burner, wherein the gas burner comprises a measuring device and a control circuit, and wherein the fuel gas contains natural gas and an additive gas. Using the method, the type and proportion of the additive gas in the fuel gas can be detected, a control variable for controlling the combustion can be derived and the combustion can be correspondingly adjusted. The invention also relates to a corresponding gas burner.

Description

COMBUSTION CONTROL DEVICE AND METHOD FOR A

FUEL GAS WITH PARTICULAR ADDITIONAL GAS

TECHNICAL FIELD

The invention relates to an apparatus and a method for

Combustion control, whereby an additional gas is detected in the combustion gas and control variables for the combustion can be adjusted accordingly.

TECHNICAL BACKGROUND

It is an object of the invention to provide a device and a method for combustion control which makes it possible to detect the type of an additional gas, in particular hydrogen, in a fuel gas. In particular, it should also be possible to determine a proportion of the additional gas in the fuel gas.

Natural gas is generally used as the fuel gas. Natural gas is a gas mixture containing hydrocarbons, the chemical composition of which fluctuates considerably depending on where it was found. The main component, however, is usually methane, whereby the proportion can vary between 75 and 99 mol%.

In addition to methane, burner test gases can contain an admixture of additional gas such as nitrogen or propane. Burner test gases can also consist of 100% methane or even 100% of an additional gas such as propene. Examples are the burner test gases G271 and G21 or G20 and G32.

Motivated by long-term savings in _{CO 2} emissions, it is planned to feed in climate-neutral hydrogen as an additional gas into the existing natural gas network with a volume share of up to 40% by volume.

However, adding hydrogen to the base gas creates numerous technical challenges, especially for operation and combustion control in gas burners. First of all, compared to natural gas, hydrogen has a lower calorific value in terms of volume. This means that in order to achieve a comparable performance, the volume flow of fuel gas must be increased in the case of adding hydrogen. In addition, the reaction kinetics is the Combustion changes compared to pure natural gas, which strongly influences the flame speed, length and geometry, as well as the flame temperature, the ignition properties and the heat radiation.

For example, it was found that with a linear increase in the hydrogen concentration, the flame speed increases exponentially. In addition, the maximum of the laminar flame speed shifts to the more fuel-rich area of the combustion, i.e. to lower lambda values. With about 3.5 m / s, hydrogen reaches the highest maximum flame speed if the combustion mixture is not preheated. The higher the flame speed, the more likely a transition from deflagration, i.e. the spread of the reaction front through diffusion, to detonation, i.e. the spread of the reaction front due to a pressure wave. In addition, the ignition delay time of hydrogen is 1000 times less than that of natural gas, with a significantly lower ignition energy and a higher upper ignition limit.

The knowledge of which additional gas, in particular hydrogen, is present in the fuel gas and in what proportion, is therefore essential for the operation and combustion control in gas burners, both under combustion and safety aspects.

DE 10 2013 224 246 A1 describes, for example, a device for determining the Fh content of Fh / natural gas mixtures, with an input interface for reading in a calorific value of the Fh / natural gas mixture, which was determined at a transfer station of a gas network; an input interface for the Fh / natural gas mixture, for introducing the Fh / natural gas mixture into the device; a proton-conducting layer, which enables a current-voltage characteristic to be determined, the proton-conducting layer being fluidically connected to the input interface for the Fh / natural gas mixture, and a control device which is connected to the proton-conducting layer and the input interface for the Fh / natural gas mixture and is set up for this purpose is to carry out the following steps: a) Determine, with the aid of the current-voltage characteristic of the proton-conducting layer, whether there is a hydrogen depletion of the proton-conducting layer when a volume flow of the Fh / natural gas mixture flows through the proton-conducting layer, and measuring the volume flow with a sensor for measuring the volume flow of the H2 / natural gas mixture in the proton-conducting layer, which is connected to the control unit; b) If there is no hydrogen depletion of the proton-conducting layer, then changing the volume flow of the Ph / natural gas mixture by means of a control device and repeating the previous step; c) If the proton-conducting layer is depleted of hydrogen, then determining the critical current density of the proton-conducting layer at which the hydrogen depletion is present on the proton-conducting layer with the associated measured volume flow of the Ph / natural gas mixture; d) Establishing, by means of a map, the Ph content of the Ph / natural gas mixture based on the determined critical current density; e) determining the current calorific value of the Ph / natural gas mixture based on the determined Ph content of the Ph / natural gas mixture and the calorific value of the Ph / natural gas mixture from the transfer station of the gas network; f) Output of the current calorific value of the Ph / natural gas mixture.

THE SOLUTION OF THE PROBLEM

The above-mentioned object is achieved with the features of independent claim 1 and the independent claim 11. The dependent claims are directed to particular embodiments of the invention.

A method according to the invention for regulating the combustion of fuel gas by means of a gas burner, wherein the gas burner has a measuring device and a control circuit, and wherein the fuel gas contains natural gas and an additional gas, comprises the step a) of setting a burner load to a first predetermined load value LI at a Actual air ratio / is _t .

The term fuel gas describes mixtures of natural gas as the base gas with admixtures of an additional gas of different types, such as nitrogen, hydrogen, propane or propene, in variable proportions. The air ratio or the lambda value A describes an air to fuel gas ratio of an air / fuel gas mixture.

According to the invention, the first predetermined load value LI is not restricted. In a preferred embodiment, however, the load value LI can be in a range from 5 to 10 kW.

The method according to the invention further comprises the step b) of approaching a predetermined target air ratio Asoii in a predetermined time period Ati_i.

According to the invention, the target air ratio Asoii is not restricted as long as it is different from the actual air ratio. In a preferred embodiment, Aist> Asoii can apply. Particularly preferably, however, the target air ratio Asoii = 1 can be. In this case, the actual air ratio Ai _st can thus be lowered into the range of the stoichiometric combustion at l = 1.

The predetermined time period Ati_i is also not restricted according to the invention and can be selected such that the profile of the flame temperature TF _, LI determined in this time period in step c) contains the information necessary to determine the fuel gas parameter in step d). For example, the predetermined period of time Atu _. between 10s and 60s, preferably between 20s and 40s, particularly preferably 30s.

In general, different variants of the temporal air-fuel gas mixture management (enrichment) in the gas burner are conceivable. Preferably, however, the predetermined target air ratio Asoii can be approached linearly via the time constant change in the gas flow rate in the gas burner. Alternatively, the predetermined target air ratio Asoii can also be approached in a parabolic or exponential manner over time. The method according to the invention further comprises the step c) of determining a profile of a flame temperature TF _, LI in the time period AtLi.

The term flame temperature, as used herein, more precisely describes a temperature reading of the flame from the combustion chamber of the gas burner. For the sake of simplicity, however, the term flame temperature is used in the following. The flame temperature can generally be determined in different ways, for example using one or more thermocouples. Preferably, however, the flame temperature can be determined using the glowing electrical effect on the ignition electrode (temperature of the flame on the ignition electrode), as described, for example, in EP 2 549 187 B1.

The glowing electrical effect mentioned above (also Richardson effect, Edison effect or Edison-Richardson effect, see for example Neil W. Ashcroft, N. David Mermin: Solid State Physics. Saunders College Publishing, New York 1976, pp. 362-364) refers to the fact that electrons from a heated metal electrode overcome the work function above a material-dependent minimum temperature and can escape from the electrode. The current generated in this way allows conclusions to be drawn about the temperature of the electrode. The flame temperature can thus be determined in a simple manner by means of a voltage tapped at the ignition electrode of the burner. Such an ignition electrode is mandatory in the burner space of every burner and, once the air-fuel gas mixture has been ignited, is no longer required for the operation of the gas burner.

The inventors have found that the profile of the flame temperature TF as a function of time at a given load value has characteristic features, the evaluation of which allows conclusions to be drawn as to the type of additional gas and the proportion of it in the fuel gas.

The method according to the invention comprises the step d) of determining a fuel gas parameter from the profile of the flame temperature TF _, LI and deriving a control variable for regulating the combustion in the gas burner as a function of the fuel gas parameter.

The term fuel gas parameter is to be interpreted broadly here and relates to the type and proportion of the additional gas in the fuel gas. In a preferred embodiment, the fuel gas parameter can therefore correspond to a volume fraction of the additional gas in the fuel gas.

As already described in detail, different additional gases can be added to the fuel gas. In a further preferred embodiment, however, the additional gas can be hydrogen. In this way, with the inventive Process of a planned injection of hydrogen into the natural gas network can be flexibly countered.

The fuel gas parameter can therefore indicate, for example, which additional gas is present in the fuel gas and how high the proportion of additional gas is. A corresponding control variable for regulating the combustion in the gas burner can then be derived as a function of the determined fuel gas parameter.

To determine the proportion of the additional gas, calibration coefficients can be stored in the form of a characteristic curve. Depending on the determined share, the controlled variable for the combustion can then be derived independently by a control circuit in the gas burner and the combustion can be adjusted.

In a preferred embodiment, the method according to the invention between steps c) and d) can further include step i) of moving back to the air ratio st and setting the burner load to a second predetermined load value L2> LI, as well as step ii) of restarting the predetermined target air ratio lbo _ΐ i in a predetermined period of time Äti_2, and the step iii) of determining the course of the flame temperature TF _, L2 in the period of time Äti_2, then in step d) the fuel gas parameter from the course of the flame temperature TF _, LI and TF _, L2 can be determined.

In this way, the fuel gas parameter can advantageously be determined even more precisely in step d) and the regulation of the combustion can be derived even more precisely.

The load value L2 is also not restricted according to the invention as long as the flame kinetics differ significantly from the load value LI. According to a preferred embodiment, however, the load value L2 can be in a range from 10 to 20 kW.

In a further preferred embodiment, the fuel gas parameter can be determined by comparing the respective determined flame temperature profile TF with a corresponding reference profile of the flame temperature TF _, Ret for natural gas as the fuel gas. For this purpose, for example, the flame temperature profile for a given load value for natural gas as fuel gas can be stored in the control circuit of the gas burner. From a comparison of a currently determined flame temperature curve with the same load value, it can then be determined which additional gas is present in the currently available fuel gas and how high the proportion is.

In a further preferred embodiment, the fuel gas parameter can in each case be determined on the basis of a minimum flame temperature TF _, min and / or on the basis of one or more flame temperature differences ATF determined from the respective profile of the flame temperature TF. For example, the type and proportion of an additional gas can be determined on the basis of the measurement of a minimum and / or maximum based on an initial state. For hydrogen, for example, the difference between the fleas and a characteristically occurring maximum in the flame temperature curve is specific. The extent of the fleas difference also shows the proportion of hydrogen.

In a further preferred embodiment, the gas burner can additionally have an ignition electrode, means for generating an ignition voltage and a switch arrangement for connecting the ignition electrode to and for disconnecting the ignition electrode from the means for generating the ignition voltage and the profile of the flame temperature TF can be determined using the ignition electrode be determined. As already mentioned above, the course of the flame temperature can advantageously be determined in particular on the basis of the use of the glowing electrical effect on the ignition electrode.

A gas burner according to the invention comprises a control circuit and a measuring device which are configured to carry out a method which includes the step a) of setting a burner load to a first predetermined load value LI at an actual air ratio Ais _t ; the step b) of approaching a predetermined target air ratio Asoii in a predetermined time period Atu _. ; the step c) of determining a profile of a flame temperature TF _, LI in the period Ati_i; and the step d) of determining a fuel gas parameter from the profile of the flame temperature TF _, LI and deriving a control variable for regulating the combustion in the gas burner as a function of the fuel gas parameter.

In a preferred embodiment, the control circuit and the measuring device can also be configured to carry out a method which, between steps c) and d), additionally includes step i) of returning to the air ratio Ais _t and setting the burner load to a second predetermined one Load value L2>LI; step ii) of restarting the predetermined target air ratio lbo _ΐ i in a predetermined period of time Äti_2 _; ; and the step iii) of determining the course of the flame temperature TF _, L2 in the period of time Äti_2, wherein in step d) the fuel gas parameter can be determined _{from the course of the flame temperature TF,} LI and TF _{, L2.}

In a further preferred embodiment, the gas burner can additionally have an ignition electrode, means for generating an ignition voltage and a switch arrangement for connecting the ignition electrode to and for separating the ignition electrode from the means for generating the ignition voltage.

The method according to the invention and the gas burner according to the invention have numerous advantages. For example, while calibration by means of ionization when starting lambda 1 is sufficient to differentiate whether a burner test gas such as G21 or G271 is present, the method described above can be used to determine whether there is generally an additional gas in the fuel gas, and what type it is and how high the proportion is. Hydrogen proportions cannot be determined with the calibration described above by means of ionization due to other causalities of the target values.

With the method according to the invention and the gas burner according to the invention, moreover, the nominal air ratios and thus also the device output for fuel gases proportionate to hydrogen can be achieved, as well as low NO _x values. This can avoid the risk of thermal acoustics and overheating of the gas burner.

In addition, no upstream system with corresponding data exchange is necessary, since the detection of the additional gas and its proportion takes place in the gas burner. A simple sensor system can be used for this, lambda sensors are not necessary.

BRIEF DESCRIPTION OF THE FIGURES

Figures 1 to 5 schematically show embodiments of the method for regulating the combustion of fuel gas by means of a gas burner, as well as embodiments of the gas burner. In particular, FIG. 1 shows a flow chart to illustrate an embodiment of a method for regulating the combustion of fuel gas by means of a gas burner, the gas burner having a measuring device and a control circuit, and the fuel gas containing natural gas and an additional gas.

FIG. 2 shows a flow chart of a further embodiment of a method for regulating the combustion of fuel gas by means of a gas burner, the gas burner having a measuring device and a control circuit, and the fuel gas containing natural gas and an additional gas.

FIG. 3 shows two flame temperature profiles at a first predetermined load value LI for methane as the fuel gas and for a mixture of methane and hydrogen as the fuel gas.

FIG. 4 shows the two flame temperature curves at the first predetermined load value LI from FIG. 3 and additionally the flame temperature curves at a second predetermined load value L2, also for methane as the fuel gas and for a mixture of methane and hydrogen as the fuel gas.

FIG. 5 shows a block diagram of a gas burner according to an embodiment.

DETAILED DESCRIPTION OF THE FIGURES AND PREFERRED EMBODIMENTS

In the following, examples and exemplary embodiments of the present invention are described in detail with reference to the accompanying figures. Identical or similar elements in the figures can be designated with the same reference symbols, but sometimes also with different reference symbols.

It should be emphasized that the present invention, however, is in no way limited or restricted to the exemplary embodiments described below and their design features, but rather further comprises modifications of the exemplary embodiments, in particular those that are achieved by modifying the features of the examples described or by combining individual ones or several features of the examples described are included within the scope of protection of the claims. FIG. 1 shows a flow chart to illustrate an embodiment of a method for regulating the combustion of fuel gas by means of a gas burner, the gas burner having a measuring device and a control circuit, and the fuel gas containing natural gas and an additional gas.

In step S101, a burner load is set to a first predetermined load value LI at an actual air ratio Aist. According to the invention, the load value is not restricted. In a preferred embodiment, the load value LI can be in a range from 5 to 10 kW. The load value LI can advantageously be stored in the control circuit of the gas burner and automatically approached in step S101 when the method is carried out.

The actual air ratio Aist is likewise not restricted according to the invention and can result, for example, from a current mixture control during the regular operation of the gas burner. In this way, the method can be carried out while the gas burner is in operation, and the mixture control can be flexibly and optimally adapted to varying fuel gases, for example by adding an additional gas, in particular hydrogen.

As can be seen from FIG. 1, in a next step S102 a predetermined target air ratio Asoii is approached in a predetermined time period Ati_i. The desired air ratio Asoii is not restricted according to the invention either, but it is different from the actual air ratio Aist. In a preferred embodiment, Aist> Asoii can apply. This advantageously takes into account the fact that in normal operation of a gas burner with natural gas as the fuel gas, the mixture flow is in the lean range, so that the air ratio Asoii can be achieved by enriching the mixture. Particularly preferably, stoichiometric combustion can be started at Asoii = 1. In general, different variants of the temporal mixture control (enrichment) in the gas burner are conceivable. Preferably, however, the predetermined target air ratio Asoii can be approached linearly via the time constant change in the gas flow rate in the gas burner. Alternatively, the predetermined target air ratio Asoii can also be approached in a parabolic or exponential manner over time.

The length of the time period Ati_i is also not restricted according to the invention insofar as the profile of a flame temperature TF _, UL determined in this time period in step S103 is used to determine the fuel gas parameter in step S104 includes necessary information. For example, the predetermined period of time Atu _. between 10s and 60s, preferably between 20s and 40s, particularly preferably 30s.

As already mentioned, the course of the flame temperature TF, LI in the time period Ati_i is determined in step S103. The flame temperature TF, LI can be measured in different ways, for example using one or more thermocouples. Preferably, however, the flame temperature TF, LI can be determined using the glowing electrical effect by means of an ignition electrode. For this purpose, according to a preferred embodiment, the gas burner can additionally have an ignition electrode, means for generating an ignition voltage and a switch arrangement for connecting the ignition electrode to and for separating the ignition electrode from the means for generating the ignition voltage. To determine the flame temperature profile TF, LI in the period AtuL, the flame temperature TF, LI can be measured continuously, but individual measured values can also be recorded at a certain time interval within the period At_i, as long as a sufficiently accurate flame temperature profile TF, LI is recorded can be. For this purpose, for example, the number of recorded measured values can be increased in the areas in which characteristic features in the flame temperature profile TF, LI ZU are expected, for example minima and / or maxima, whereas fewer measured values are recorded in uncharacteristic areas, for example with a constant flame temperature profile TF, LI can be.

As shown in FIG. 1, in step S104 a fuel gas parameter is then determined from the profile of the flame temperature TF, LI and a control variable for regulating the combustion in the gas burner is derived as a function of the fuel gas parameter. The determination of the fuel gas parameter and the derivation of the controlled variable is described in more detail below with reference to FIGS. 3 to 5.

The method steps S201 to S204 shown in FIG. 2 can follow the method steps S101 to S103 shown in FIG Step S104 can replace. As shown in FIG. 2, the air ratio st can be reduced in step S201 and the burner load can be set to a second predetermined load value L2> LI. The air ratio can the original air ratio shown in Figure 1 correspond. In this way, when the predetermined setpoint air ratio lbo _ΐ i is approached again in a predetermined period of time Äti_2 in step S202, the same air ratio range can be traversed at a different load value L2.

According to the invention, the load value L2 is not restricted as long as the flame kinetics differ significantly from the load value LI. According to a preferred embodiment, however, the load value L2 can be in a range from 10 to 20 kW.

Step S203 in FIG. 2 can then provide for the determination of the course of the flame temperature TF _, L2 in the period of time Äti_2. Analogous to FIG. 1, the measurement of the flame temperature TF _, L2 and the length of the time period Äti_2 are not restricted according to the invention. However, here too the flame temperature is advantageously measured using the ignition electrode and the length of the period Dΐi_ ₂ advantageously corresponds to the length of the period Dΐi_i.

In step S204, as shown in FIG. 2, the fuel gas parameter can then be determined from the profiles of the flame temperature TF _, LI and TF _, L2 and a control variable for regulating the combustion in the gas burner can be derived.

In the following, the determination of the fuel gas parameter from the profile of the flame temperature TF _, LI or TF _, L2 will now be explained in more detail with reference to FIGS. 3 and 4. The inventors have advantageously found that the profile of the flame temperature TF for natural gas as fuel gas has specific features in comparison to mixtures of natural gas and an additional gas at the respective predetermined first and second load values LI and L2. Based on the evaluation of these specific features, the type of additional gas and its proportion in the fuel gas can then be determined as fuel gas parameters.

First, Figure 3 shows flame temperature curves TF _, LI at a first predetermined load value LI for pure methane (G20) as fuel gas 1 and for 70% methane and 30% hydrogen as fuel gas 2. Since the main component of natural gas is methane, pure methane is used in the present example Used as a substitute for natural gas. on In this way, a uniform reference point can advantageously be created, regardless of fluctuations caused by the sites.

In the example in FIG. 3, the load value LI is set to 10 kW. The actual air ratio was in the lean range and the respective air-fuel gas mixture was enriched in the period Dΐi_i = 30s from lΐ _Xΐ > 1 to the target air ratio lboΐi = 1 by means of linear mixture control. The flame temperature profile TF _, LI was also determined during this period. _{Normalized values for the flame temperature TF,} LI determined by means of an ignition electrode are plotted on the y-axis. At this point it is pointed out that the flame temperature values plotted in FIGS. 3 and 4 are given in an artificial unit [I] which is inversely related to the actual temperature. The values shown in FIGS. 3 and 4 are digitized measured values that an AD converter in the automatic furnace of the gas burner can determine from a corresponding input channel. The time t is plotted in [s] on the x-axis.

As can be seen from FIG. 3, the respective curves show courses for pure methane as fuel gas 1 and for 70% methane and 30% hydrogen as fuel gas 2, differently pronounced characteristic features as a function of time t. Both curves 1, 2 show a minimum la, 2a (indicated by the arrow 3) that is differently pronounced. The minimum 2a for 70% methane and 30% hydrogen as fuel gas also precedes the minimum la for pure methane as fuel gas.

Figure 4 shows the flame temperature curves at the first predetermined load value LI = 10kW from Figure 3 and additionally the flame temperature curves at a second predetermined load value L2 = 20kW also for pure methane as fuel gas and for the mixture of 70% methane and 30% hydrogen as fuel gas.

Before determining the flame temperature _{profiles TF,} L2 at the load value L2 = 20kW, the air ratio was set to the original actual air ratio pulled back (evident from the step-like jumps in curves 1 and 2). In the flame temperature curves shown in FIG. 4, the gas burner runs in the areas in which the flame temperature signals are constant, in each case at a constant load with the same air ratio, for example l = 1.34. Basically, the different load values (load levels) are accompanied by different basic levels of the flame temperature. At the load value L2 = 20kW it was then also the corresponding air-fuel gas mixture in the time period Äti_2 = 60s from Ais _t <1 again enriched to the target air ratio Asoii = 1 by means of linear mixture control. The flame temperature profile TF _, L2 was then also determined during this period.

As can be seen from FIG. 4, the respective curves show courses for pure methane as fuel gas 1 and for 70% methane and 30% hydrogen as fuel gas 2, even with the load value L2 = 20 kW, differently pronounced characteristic features as a function of time t. Both curves 1, 2 again show a minimum lb, 2b (indicated by the arrow 4) of different strengths, with curve 2 additionally having a maximum 2c downstream of the minimum 2b for 70% methane and 30% hydrogen as fuel gas. Even with the load value L2 = 20kW, the minimum 2b for 70% methane and 30% hydrogen as fuel gas precedes the minimum lb for pure methane as fuel gas.

According to a preferred embodiment, the fuel gas parameter can be determined by comparing the respective determined flame temperature profile TF with a corresponding reference profile of the flame temperature TF _, Ret for natural gas as the fuel gas.

With reference to FIGS. 3 and 4, for example, the flame temperature profile TF for pure methane can serve as a reference profile for the load values LI = 10 kW and L2 = 20 kW. From the comparison with the flame temperature profile TF determined for 70% methane and 30% hydrogen as fuel gas at the same load values LI and L2, the fuel gas parameter can then be determined on the basis of the different characteristic features, as described above.

According to a further preferred embodiment, the fuel gas parameter can in each case be determined on the basis of a minimum flame temperature TF _, min and / or on the basis of one or more flame temperature differences ATF determined from the respective profile of the flame temperature TF.

As described with reference to FIGS. 3 and 4, for example, a mixture of 70% methane and 30% hydrogen compared to pure methane shows a temporally preceding minimum in the course of the flame temperature TF _, LI at the first predetermined load value LI. The difference in relation to the initial value (indicated by arrow 3 in FIGS. 3 and 4) is also lower for the mixture of 70% methane and 30% hydrogen. At the load value L2 = 20kW, the mixture of 70% methane and 30% hydrogen compared to pure methane also shows a temporally preceding minimum in the course of the flame temperature TF _, L2, as well as a maximum following the minimum. In the case of the load value L2, too, the difference in the minimum with respect to the initial value (indicated by the arrow 4 in FIG. 4) is smaller for the mixture of 70% methane and 30% hydrogen. From the height difference of the maximum in relation to the initial value (indicated by the arrow 5 in FIG. 4), the proportion of hydrogen in the fuel gas can also be determined, since this is specific for hydrogen.

Such characteristic features also have other additional gases, for example. For example, nitrogen as an additional gas, in contrast to hydrogen, also shows a maximum following the minimum in time at the load value LI. Propane as an additional gas, on the other hand, does not show any maximum in the course of the flame temperature. However, here, too, the two minima are shifted to shorter times compared to pure methane, the difference to the initial value being greater in each case than with methane.

FIG. 5 shows a block diagram of a gas burner according to an embodiment. The gas burner 100 has a combustion chamber 101 in which a combustion process can take place with the supply of an air-fuel gas mixture. An ignition electrode 102 protrudes into the combustion chamber 101. Optionally, an ionization electrode can also be provided in the gas burner 100, which additionally protrudes into the combustion chamber. An ionization electrode is generally used for flame monitoring.

The ignition electrode 102 is connected to a device for generating an ignition voltage 104 in such a way that the ignition electrode 102 can be separated from the device for generating the ignition voltage 104. This can be done by a switch arrangement 103 connected between the ignition electrode 102 and the device for generating the ignition voltage 104. The switch arrangement 103 can in particular be set up in such a way that after the ignition electrode 102 has been separated from the device for generating the ignition voltage 104, the ignition electrode 102 is connected as a passive electrode. The gas burner 100 also has a measuring device 105. The measuring device 105 can be used to draw conclusions about the temperature of the flame at the electrode using the glowing electrical effect mentioned, and thus the flame temperature profile can be measured with a correspondingly set load value. For this purpose, the switch arrangement 103 is connected to the measuring device 105 and can receive signals from the measuring device 105. The measuring device 105 can also have a time measuring device by means of which the predetermined time periods can be set.

The measuring device 105 is also connected to a control circuit 106. The combustion in the gas burner 100 can be regulated via the regulating circuit 106 by means of a burner control 109. For this purpose, the burner control 109 has a valve control 110 for changing the proportion of fuel gas in the air-fuel gas mixture, as well as a fan control 111 for varying the proportion of air.

The control circuit 106 has, in particular, a device for determining a fuel gas parameter 107. The facility for determining the

Fuel gas parameter 107 is connected to the measuring device 105 and receives the measured values determined in the respective time periods to determine the

Flame temperature, which was determined by means of the ignition electrode 102 in the combustion chamber 101. In the device for determining the fuel gas parameter 107, the flame temperature profiles are evaluated and, as described above, the fuel gas parameter is determined on the basis of the respective characteristic features. The fuel gas parameter indicates a type of additional gas determined and its proportion in the fuel gas, for example hydrogen, proportion 30%.

The device for determining the fuel gas parameter 107 is connected to a device for deriving a controlled variable 108 for regulating the combustion in the gas burner 100. The controlled variable can be, for example, an air ratio l changed taking into account the fuel gas parameter and / or a changed volume flow. By adding hydrogen, for example, the maximum of the laminar flame speed is shifted to lower lambda values, and a higher volume flow is required for an output comparable to that of pure natural gas. The controlled variable is then transmitted by the device for deriving the controlled variable 108 to the burner control 109, which can then regulate the combustion in the gas burner 100 accordingly or adapt it to the changed fuel gas via the valve control 110 and / or the fan control 111.

REFERENCE MARK

1 Flame temperature profile TF _, LI TF _, L2 for pure methane

2 Flame temperature profile TF _, LI TF _, L2 for 70% methane and 30% hydrogen la minimum in the flame temperature profile TF _, LI for pure methane 2a minimum in the flame temperature profile TF _, LI for 70% methane and 30%

Hydrogen lb minimum in the flame temperature curve TF _, L2 for pure methane

2b Minimum in the flame temperature profile TF _, L2 for 70% methane and 30%

Hydrogen 2c maximum in the flame temperature profile TF _, LI for 70% methane and 30% hydrogen

3 Difference between the minimum and the initial value in the flame temperature curve TF _, LI for 70% methane and 30% hydrogen

4 Difference between the minimum and the initial value in the flame temperature profile TF _, L2 for 70% methane and 30% hydrogen

5 Difference between the maximum and the initial value in the flame temperature profile TF _, L2 for 70% methane and 30% hydrogen

100 gas burners

101 combustion chamber 102 ignition electrode

103 Switch arrangement

104 Device for generating an ignition voltage

105 measuring device

106 Control circuit 107 Device for determining a fuel gas parameter

108 Device for deriving a controlled variable Burner control, valve control, fan control

Claims

EXPECTATIONS

1. A method for regulating the combustion of fuel gas by means of a gas burner (100), wherein the gas burner (100) has a measuring device (105) and a control circuit (106), and wherein the fuel gas contains natural gas and an additional gas, characterized in that the The method comprises: a) setting (S101) a burner load to a first predetermined load value LI at an actual air ratio Ais _t ; b) starting (S102) a predetermined target air ratio Asoii in a predetermined period of time Äti_i _; c) determining (S103) a profile of a flame temperature TF _, LI (1, 2) in the time period Atu _. ; and d) determining (S104) a fuel gas parameter from the profile of the flame temperature TF _, LI (1, 2) and deriving (S104) a control variable for regulating the combustion in the gas burner (100) as a function of the fuel gas parameter.

2. The method according to claim 1, characterized in that the method between steps c) and d) additionally comprises the steps: i) moving back (S201) to the air ratio Ais _t and setting the burner load to a second predetermined load value L2>LI; ii) restarting (S202) the predetermined target air ratio Asoii in a predetermined period of time Äti_2; iii) determining (S203) the course of the flame temperature TF _, L2 (1, 2) in the period Dΐi_2, wherein in step d) the fuel gas parameters from the course of the flame temperature

T _, LI and T _, L2 (1, 2) is determined (S204).

3. The method according to claim 1 or 2, characterized in that the fuel gas parameter is determined by comparing the respective determined flame temperature curve (1, 2) with a corresponding reference curve (1) of the flame temperature TF _, Ret for natural gas as the fuel gas.

4. The method according to any one of claims 1 to 3, characterized in that the fuel gas parameter in each case based on a minimum flame temperature TF _, min (la, 2a, lb, 2b) and / or based on one or more flame temperatures determined from the respective course of the flame temperature TF -Differences ATF (3, 4, 5) is determined.

5. The method according to any one of claims 1 to 4, characterized in that the load value LI is in a range from 5 to 10 kW.

6. The method according to claim 2 or one of claims 3 to 5 in their

Dependency on claim 2, characterized in that the load value L2 is in a range from 10 to 20 kW.

7. The method according to any one of claims 1 to 6, characterized in that the gas burner (100) additionally has an ignition electrode (102), means for generating an ignition voltage (104) and a switch arrangement (103) for connecting the ignition electrode (102) to and for separating the ignition electrode (102) from the means for generating the ignition voltage (104) and the profile of the flame temperature TF (1, 2) is determined in each case using the ignition electrode (102).

8. The method according to any one of claims 1 to 7, characterized in that applies

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9. The method according to any one of claims 1 to 8, characterized in that the fuel gas parameter corresponds to a volume fraction of the additional gas in the fuel gas.

10. The method according to any one of claims 1 to 9, characterized in that the additional gas is hydrogen.

11. Gas burner (100), characterized by a measuring device (105) and a control circuit (106) which are configured to carry out a method comprising the following steps: a) setting (S101) a burner load to a first predetermined one

Load value LI with an actual air ratio Ais _t ; b) Starting (S102) a predetermined target air ratio Asoii in a predetermined time period Atu _. ; c) determining (S103) a profile of a flame temperature TF _, LI (1, 2) in the time period Atu _. ; and d) determining (S104) a fuel gas parameter from the profile of the flame temperature TF _, LI (1, 2) and deriving (S104) a control variable for regulating the combustion in the gas burner (100) as a function of the fuel gas parameter.

12. Gas burner (100) according to claim 11, characterized in that the measuring device (105) and the control circuit (106) are additionally configured to carry out a method which additionally comprises the following steps between steps c) and d): i) Returning (S201) to the air ratio Ais _t and setting the burner load to a second predetermined load value L2>LI; ii) restarting (S202) the predetermined target air ratio Asoii in a predetermined time period At_2; iii) Determining (S203) the course of the flame temperature T _{F, L} 2 (1, 2) in the period Dΐi_2, wherein in step d) the fuel gas parameter is determined from the course of the flame temperature T _, LI and T _, L2 (1, 2) will.

13. Gas burner (100) according to claim 11 or 12, wherein the gas burner (100) additionally has an ignition electrode (102), means for generating an ignition voltage (104) and a switch arrangement (103) for connecting the ignition electrode (102) to and for disconnection of the ignition electrode (102) from the means for generating the ignition voltage (104).