DE102023105827A1 - Method for operating a variable burner, burner and computer program - Google Patents

Abstract

Method for operating a burner (1) of a gas heater (2), wherein the burner (1) has a variably adjustable burner surface (3), and the gas heater (2) can be operated with each of the burner surfaces (3) with a minimum power (Pmin) and a maximum power (Pmax), characterized in that each of the burner surfaces (3) can be operated with a power range of at least 2 kW, wherein at least one of the following parameters is used to activate and/or deactivate a burner surface (3): mass flow and/or volume flow of fuel gas and/or combustion air, pressure parameters of a fuel gas supply and/or a combustion air supply, combustion parameters, setting of flow adjustment devices (5, 4) for the fuel gas and/or the combustion air and/or an air-fuel gas mixture. A burner (1) and a computer program are also disclosed.

Description

The invention particularly relates to methods for operating a variable burner with a hydrogen-containing fuel gas, a burner suitable therefor and a computer program.

The combustion of hydrogen in heating devices for the general public is in its early stages of development. When designing a hydrogen heating module, particular consideration must be given to the speed of the hydrogen flame, which is approximately seven times faster than that of natural gas (NG). This property leads to significant differences in burner design and operation compared to natural gas-powered heating devices.

To take this physical property into account, the typical operation of a hydrogen-fuelled heater is carried out mainly at partial load, which requires increasing the air-gas ratio, i.e. the "lambda", which may result in a control curve that has a higher lambda at partial load than at nominal load. This mode of operation is carried out with a fixed geometry burner and a single gas-air mixture channel, i.e. there are no structurally different configurations of the burner at partial load and nominal load during combustion, except for the gas-air mixture flow rate. The use of such a burner and such operational management can entail several disadvantages.

One possibility to manage the lambda of a hydrogen-powered heater in a similar way to the well-known natural gas-powered heaters could be the use of a variable burner geometry, ie a more complex burner. Such a concept is derived, for example, from the DE 197 28 965 A1 This proposes a premixing blower burner whose burner plate is designed with a mixture feed chamber that can be partially closed off, so that the burner plate is only partially active. This allows the areas of the burner that remain in operation to operate at the area output corresponding to full output, thus ensuring that burner operation remains stable.

However, studies have shown that this concept is practically impossible to implement in hydrogen combustion at partial load with the lambda that is usual at nominal load. Even with improved burner cooling, the burner becomes too hot at partial load to maintain combustion at a constant lambda. This is due to the above-mentioned property of the flame speed as well as additional properties of the hydrogen flame (in most cases shorter and closer to the burner compared to natural gas application).

There is therefore a desire for an efficient, robust combustion process in a heater that runs on hydrogen, especially at partial load.

It is therefore the object of the invention to alleviate the problems described with reference to the prior art and/or to offer a suitable solution to the above-mentioned request. In particular, a method for operating a burner of a gas heater with hydrogen-containing fuel gas is to be specified that can be modulated over a wide range. A stable combustion process should be adjustable, which is also gentler on the burner of the gas heater.

A method for operating a burner of a gas heater contributes to this, wherein the burner has a variably adjustable burner surface, and the gas heater can be operated with each of the burner surfaces with a minimum output (Pmin) and a maximum output (Pmax). Each of the burner surfaces can be operated with a power range of at least 2 kW [kilowatts]. At least one of the following parameters is used to activate and/or deactivate a burner surface: mass flow and/or volume flow of fuel gas and/or combustion air, combustion parameters, pressure parameters of a fuel gas supply and/or a combustion air supply, setting of flow adjustment devices for the fuel gas and/or the combustion air and/or an air-fuel gas mixture.

• - wandhängende Heizkessel, insbesondere Brennwertheizkessel,
• - Kombikessel mit einfachem oder doppeltem Anschluss für Zentralheizung und/oder Warmwasserbereitung,
• - Heizgeräte mit einer einzelnen Abgasanlage oder einer Mehrfachbelegung.

The gas heater is in particular one that is designed for the combustion of a hydrogen-containing fuel gas, in particular with a hydrogen content of over 95%. With regard to the structure of the gas heater, various configurations can be used, such as:

• - wall-mounted boilers, in particular condensing boilers,
• - Combined boiler with single or double connection for central heating and/or hot water preparation,
• - Heaters with a single exhaust system or multiple occupancy.

The heater is usually assigned an air line (also called combustion air supply) and a fuel gas line (also called fuel gas supply), whereby a mass or volume The air and/or fuel gas flow is adjustable. Air and fuel gas are at least partially (specifically) mixed upstream of the burner. A fan can be used to convey (in particular to suck in) the air. An (adjustable) fuel gas valve can be used to add the fuel gas to the air flow. It is possible for the air and fuel gas to be brought together downstream or (preferably) upstream of a fan. In the latter case, the fan feeds an air-fuel gas mixture to the burner, preferably on the pressure side. However, designs are also possible in which the fan is positioned in the exhaust system of the heater and thus sucks in the air-fuel gas mixture through the burner.

Different burner geometries can be implemented for the burner, such as a flat/level burner, a cylindrical burner, a hemispherical burner or similar. At least one flame arrester can be assigned to the burner. The burner can be integrated into a so-called heat module (with a heat exchanger) or a heat exchanger can be assigned to it. It is possible to supply the burner with a fully or partially premixed air-fuel gas mixture.

The burner has a variably adjustable burner surface. This means in particular that the burner surface can be completely or partially exposed to an air-fuel gas mixture and then a flame forms (only) in the areas of the burner surface that are exposed to the flow. Where an air-fuel gas mixture flows through the burner surface or where a flame forms, the burner surface is active. Where no air-fuel gas mixture flows through the burner surface or where no flame forms, the burner surface is inactive.

It is possible for the burner surface to be divided into partial burner surfaces of equal size (in terms of area), but this is not mandatory; at least some of the partial burner surfaces can form larger and/or smaller partial burner surfaces. A (maximum) burner surface is divided or can be divided into several, preferably at least three, four, five or six, partial burner surfaces. It is possible for one partial burner surface not to be deactivated and all others to be deactivated and activated. It is possible for all partial burner surfaces to be deactivated and activated.

It is possible for local flow barriers to be assigned to the burner surface, in particular one for each partial burner surface to be activated or deactivated. The flow barriers can in particular be transferred in a controlled manner into two (end) positions, e.g. an OPEN position and a CLOSED position, whereby in an OPEN position the air-fuel gas mixture can flow through the flow barrier (and thus the assigned partial burner surface) and in a CLOSED position the air-fuel gas mixture can block the flow barrier (and thus the assigned partial burner surface), in particular completely block it. The flow barrier can be provided in or next to the fuel gas mixture line, in the vicinity of the burner surface, in the combustion chamber of the burner and/or the exhaust gas line. The positions of the flow barrier can be adjustable by moving and/or pivoting the flow barrier. It is possible for the flow barrier to cover part of the burner surface (impenetrably) and/or to divert the air-combustion gas mixture from a (deactivated) part of the burner surface, e.g. towards another (activated) part of the burner surface. The flow barriers can in particular be pneumatically, mechanically and/or electrically actuated or adjustable.

The heater or burner can in particular be designed as shown in the DE 197 28 965 A1 so that full reference can be made to the design variants therein, in particular with regard to the design and/or arrangement of the flow barriers (flaps, partitions, injectors/gas nozzles, slide valves, orifices, etc.).

Each of the (partial) burner surfaces can be operated with a power range of (at least) 2.0 kW. A modulation range describes the relationship between the partial load (Pmin) and the nominal load (Pmax) and means that with a modulation range of 1:5 there is a nominal load that is five times higher than its partial load (= 20%). In particular, the heater is set up to operate a heat module or associated heat exchanger with at least a modulation range of 1:5 (efficiently). The nominal load describes the maximum useful heat output from the boiler in continuous operation. The burner is designed for this under nominal conditions. The unit kilowatts is usually specified. This power is therefore actually available. Losses due to the conversion from one form of energy to another are already taken into account. To adjust the partial load, the mass or volume flow of fuel gas in particular can be reduced.

• - Ein Massenstrom Brenngas und/oder Verbrennungsluft bzw. eines Gemisches aus Brenngas und Verbrennungsluft; dieser kann gemessen und/oder berechnet werden.
• - Ein Volumenstrom von Brenngas und/oder Verbrennungsluft bzw. eines Gemisches aus Brenngas und Verbrennungsluft, dieser kann gemessen und/oder berechnet werden.
• - Ein Verbrennungsparameter, wie insbesondere zumindest einer ausgewählt aus der folgenden Gruppe: eine Flammentemperatur, eine Brennertemperatur, eine Strömungsgeschwindigkeit des Brenngas-Luft-Gemisches im Bereich der Brennerfläche, eine Flammengeschwindigkeit, eine Flammengüte, eine Flammenabstand zur Brennerfläche, ein Wärmestrom im Bereich des Wärmemoduls bzw. des Wärmetauschers.
• - Ein Druckparameter, insbesondere im Bereich einer Venturi-Anordnung an/in der Brenngaszufuhr und/oder an/in der Verbrennungsluftzufuhr.
• - Eine Einstellung von Strömungseinstellgeräten für das Brenngas und/oder die Verbrennungsluft und/oder ein Luft-Brenngas-Gemisches, also z.B. eine Drehzahl eines Gebläses und/oder eine Ventilstellung eines Brenngasventils; diese können beispielsweise sensorisch oder elektronisch abgefragt werden.

For the (automatic) activation and/or deactivation of a (partial) burner area, at least one of the parameters described in more detail below is used.

• - A mass flow of fuel gas and/or combustion air or a mixture of fuel gas and combustion air; this can be measured and/or calculated.
• - A volume flow of fuel gas and/or combustion air or a mixture of fuel gas and combustion air, which can be measured and/or calculated.
• - A combustion parameter, such as in particular at least one selected from the following group: a flame temperature, a burner temperature, a flow velocity of the fuel gas-air mixture in the region of the burner surface, a flame speed, a flame quality, a flame distance to the burner surface, a heat flow in the region of the heat module or the heat exchanger.
• - A pressure parameter, in particular in the area of a Venturi arrangement at/in the fuel gas supply and/or at/in the combustion air supply.
• - A setting of flow adjustment devices for the fuel gas and/or the combustion air and/or an air-fuel gas mixture, e.g. a speed of a fan and/or a valve position of a fuel gas valve; these can be queried, for example, by sensors or electronically.

At least one of the parameters is therefore monitored/queried (permanently) during operation of the burner or gas heater. The current value of at least one parameter can be compared with stored reference values and/or other parameter values. The result of the comparison can be evaluated so that a decision can be made (automatically) as to whether the burner area should be increased or reduced or maintained.

The activation or deactivation signal can come from a sensor and/or an actuator. It can be, for example: a mass flow sensor (MFS) that measures either the air flow, the gas flow or the mixture flow; a temperature sensor, such as a thermocouple or a so-called hot surface ignitor (HSI), which measures the flame temperature; a fan; a gas volume flow meter; a gas valve.

If only one signal/parameter is evaluated, a threshold value can be stored in the memory board of a control unit and trigger the activation/deactivation of the (partial) burner area. When using an MFS, for example, an air mass flow value could be used. By using two or more signals/parameters, the tolerances of the system can be reduced and more precise results achieved. For example, the use of an MFS and a temperature sensor would each provide information on the heat supply and the lambda of an operating point, whereby various threshold values, particularly in table form, can preferably be provided for comparison. can be used advantageously.

When using two or more signals/parameters, there is also a far-reaching possibility of setting up a more intelligent system that, for example, determines or derives the difference between the mixture inflow velocity and the flame velocity. The difference between these velocities could then be compared with a (predetermined or stored) minimum threshold that must not be exceeded and would trigger the activation/deactivation of the (partial) burner area.

The lambda value for each of the adjustable burner surfaces is preferably controlled within a range limited by a lower lambda limit at minimum power (Lu(min)), a lower lambda limit at maximum power (Lu(max)), as well as a lower lambda limit at minimum power (Lo(min)) and an upper lambda limit at maximum power (Lo(max)). In particular, the following should always apply: Lu(min) < Lu(max) < Lo(max) < Lo(min), or in particular Lu(min) < Lu(max) < Lnominal < Lo(max) < Lo(min). In order to achieve optimum performance during hydrogen combustion, the lambda should remain fairly stable over the entire modulation or power range. For this reason, a type of lambda envelope curve is specified here, which describes a (permissible) upper lambda limit at maximum output and a (permissible) lower lambda limit at maximum output, and analogously a (permissible) upper lambda limit at minimum output and a corresponding (permissible) lower lambda limit at minimum output. The definition of the lambda range in which operation is possible is determined taking into account the gas heater or the burner. In particular, it can depend on or be selected based on the nominal heat supply, the partial load heat supply, a number of adjustable partial burner surfaces, and a specified nominal lambda (at nominal heat supply).

Here, it is proposed to consider the power range for each (partial) burner area, with a lambda range of Lu(min) and Lo(min) at partial load (Pmin) and a lambda range of Lu(max) and Lo(max) at nominal load (Pmax). In particular, Lu(min) is the smallest lambda value of a lower lambda curve over the power range and Lo(max) is the smallest lambda value of an upper lambda curve over the power range. The lower lambda curve and the upper lambda curve envelop, in particular, permissible lambda values around a predetermined nominal lambda. It is possible that the lower lambda value (Lu) increases from P(min) to P(max), in particular increases linearly. It is possible that the upper lambda value (Lo) decreases from P(min) to P(max), in particular decreases linearly. It is possible that the distance from the upper lambda value (Lo) to the lower lambda value (Lu) decreases from P(min) to P(max) over the power range. The lower lambda curve and the upper lambda curve can be mirror-symmetrical to one another over the power range (or modulation range) to a straight line through the nominal lambda.

The same lower lambda limit (Lu) and upper lambda limit (Lo) can be specified for each of the adjustable burner surfaces. In other words, this means in particular that regardless of the extent of the activated or deactivated (partial) burner surface(s), the same values of lower lambda limits (Lu(min) and Lu(max)) and upper lambda limits (Lo(min) and Lo(max)) are maintained across the power range.

Let us first consider the setup at maximum power: The upper lambda limit Lo(max) corresponds in particular to the following specification: nominal lambda x (1.0 + SK), where SK is in the range from 0.05 to 0.01, preferably in the range from 0.07 to 0.08. SK (referred to here as the stability coefficient) is in particular 7.5%. The lower lambda limit Lu(max) corresponds in particular to the following specification: nominal lambda x (1.0 - SK). When the fan is running fast, i.e. the situation P(max) applies, the stability coefficient should be applied to take into account the system-related speed control tolerances, which are usually smaller in this situation than at low speeds. The value for SK can therefore be kept relatively small, so that in the case of P(max) a relatively small lambda window can be specified.

The system is now considered at minimum power (partial load): The lower lambda limit Lu(min) corresponds in particular to the following specification: nominal lambda x (1.0 - VK), where VK is in the range from 0.1 to 0.2, preferably in the range from 0.12 to 0.17. VK (referred to here as the variability coefficient) is in particular 15%. The upper lambda limit Lo(min) corresponds in particular to the following specification: nominal lambda x (1.0 + VK). If the fan is running slowly, i.e. the situation P(min) applies, the variability coefficient should be applied in order to take into account the system-related speed control tolerances, which are larger in this situation than at higher speeds. Therefore, the value for VK can be selected to be at least 1.2 times, in particular 2 times, and a maximum of 2.7 times larger than the value for SK. Thus, in the case of P(min), a larger lambda window is specified than for P(max).

Most preferably, the lambda upper limit over the entire modulation range is not more than 1.80, in particular not more than 1.65, in particular not more than 1.50 and particularly preferably not more than 1.45. Most preferably, the lambda lower limit over the entire modulation or power range is not less than 1.00.

Preferably, at least three different burner surfaces can be set, with the output range for each of the burner surfaces being at least 7 kW [kilowatts]. This means, for example, that when one (partial) burner surface is activated, a maximum/nominal heat output of approx. 7 kW can be achieved, when two (partial) burner surfaces are activated, approx. 14 kW heat output, and when the entire burner surface is activated, approx. 21 kW heat output. It is possible that the heat output of a (partial) burner surface (each) is greater than 7 kW by a factor of 1, e.g. by a factor of 2, or even 2.5, or even 3.0.

It can be provided that at least one limit value and/or tolerance range is provided, which is compared with one of the determined parameters for activating and/or deactivating a burner surface, and that when the limit value is reached or the tolerance range is left, one of the burner surfaces is automatically activated or deactivated. The limit values and/or tolerance ranges for one or more parameters can be stored electronically and can be retrieved. The limit value and/or tolerance range can be rigidly specified (e.g. device-dependent). It is possible for the limit value and/or tolerance range to be variable, for example, adjustable during operation of the gas heater (independently or manually).

According to a further aspect, a burner of a gas heating device is proposed, wherein the burner has a variably adjustable burner surface and means which are adapted to carry out the steps of the method disclosed here. For further characterization of the burner, gas heating device and/or the means, the explanations of the method can be used in full, and vice versa. In particular, it is possible to have a gas heating device with a burner which comprises a regulating and control unit which is set up to carry out the operation of the burner according to the method disclosed here. The regulating and control unit can comprise a computing unit, a storage unit, a signal or data comparator, etc. which are set up accordingly. Sensors, switches, etc. can be provided which are activated or read out as part of the process.

Furthermore, a computer program is proposed, comprising instructions that cause the burner specified here to carry out the steps of the method disclosed here. A computer-readable medium can be provided on which the computer program is stored.

A number of advantages can be achieved with the devices and methods proposed here.

The variable geometry burner offers the possibility of adjusting the pressure drops. By increasing the modulation set point (MSP), the pressure drop of the burner is reduced, so the fan can be less powerful or smaller to reach the nominal load than with a fixed geometry burner. Using a less powerful fan (or other device that sets the flow in motion) also offers the possibility of reducing the noise level of the device, especially when operating at nominal load.

It is possible to use a pneumatic gas valve with the thermal module. First, a throttle setting can be made to set the gas flow at nominal load. Next, a reference pressure point is read from the component and used to set the gas flow. This setting should not be changed in the field. Finally, a pressure offset, which is also included in the gas flow setting, is used to accurately set the lambda value at partial load. This setting should not be changed in the field. Operating a hydrogen boiler with a pneumatic gas valve and with a fixed geometry burner is possible, but entails the need to set the pressure offset (factory setting) to a very low value, such as -30 Pascal. This has disadvantages in certain situations that can be avoided if the lambda control curve remains flat over the modulation range of the device.

This method of operating the burner and the heat module moves the distance to the flashback limit away, thereby increasing safety during operation.

In a fixed geometry burner, the lambda control curve must rise sharply at part load to avoid flashback, i.e. the fuel gas-air mixture must be leaner at part load. However, emissions of unburned hydrogen gas can become high at lambda values above 2.5 and higher as the mixture becomes leaner. These emissions should be avoided. In addition, flame stability is compromised when a hydrogen burner is operated with lean mixtures; this can lead to combustion noise or flame loss. Using a variable geometry burner makes it possible to remain at a lower lambda level and thus avoid the two problems mentioned above.

• 1: eine Ausführungsform eines Heizgerätes mit variablem Brenner;
• 2: Beispiele für Regelkurven bei Brennern mit fester und variabler Brennerfläche;
• 3: Wirkungsgradkurven für Wasserstoff in Abhängigkeit von der Abgastemperatur und für verschiedene Lambda-Werte;
• 4: Drehzahlkurven für Brenner mit fester und variabler Brennerfläche
• 5: ein Beispiel für eine Lambda-Hüllkurve.

The invention and the technical environment are explained in more detail below using figures. It should be noted that the figures are schematic and exemplary and are not intended to limit the invention. They show:

• 1 : an embodiment of a heater with a variable burner;
• 2 : Examples of control curves for burners with fixed and variable burner area;
• 3 : Efficiency curves for hydrogen as a function of exhaust gas temperature and for different lambda values;
• 4 : Speed curves for burners with fixed and variable burner area
• 5 : an example of a lambda envelope.

1 shows a burner 1 of a gas heater 2, wherein the burner 1 has a variably adjustable burner surface 3. The gas heater 2 can be operated with each of the burner surfaces 3 with a minimum power (Pmin) and a maximum power (Pmax), wherein each of the burner surfaces 3 can be operated with a power range of at least 2.0 kW [kilowatts].

Starting from the top, an air line 11 is shown schematically, which can be designed with an air mass flow sensor 6 and can be used to suck in air from the surroundings of the gas heater 2 and feed it to the burner 1. A fuel gas line 12 opens into the air line 11, via which hydrogen or a hydrogen-containing fuel gas in particular can be introduced into the air. A controllable fuel gas valve 5 and, if necessary, a fuel gas mass flow sensor 7 are provided in the fuel gas line 12. The fuel gas-air mixture is conveyed through a fuel gas mixture line 10 to the burner 1. A fan 4 in the fuel gas mixture line 10 contributes to this.

Downstream of the fan 4, in particular in the burner 1, an inflow area 16 is provided towards the burner surface 3. This is divided into several partial inflow areas (16a, 16b, 16c, 16d, 16e) under divided, for example by partitions that separate the partial inflow areas (16a, 16b, 16c, 16d, 16e) from one another. In the partial inflow areas (16a, 16b, 16c, 16d, 16e) identical or similar flow barriers can be provided, here as a pivotable actuator 17 with a flap. The actuators 17 can be used to open and/or close the partial inflow areas (16a, 16b, 16c, 16d, 16e).

Depending on the position of the actuators 17, a premixed fuel gas-air mixture is fed to the burner surface 3 (which is flat here) through the blower 4 and via the (open) partial inflow areas (16a, 16b, 16c, 16d, 16e). Each partial inflow area (16a, 16b, 16c, 16d, 16e) is assigned a section of the burner surface 3, so that a plurality of partial burner surfaces (3a, 3b, 3c, 3d, 3e) are formed. The partial burner surfaces in which the associated partial inflow areas are open are active, i.e. combustion or flame formation takes place there. The partial burner surfaces in which the associated partial inflow areas are closed are inactive/deactivated, i.e. no combustion or flame formation takes place there. The five partial burner surfaces (3a, 3b, 3c, 3d, 3e) can be set so that the power range for each of the partial burner surfaces (3a, 3b, 3c, 3d, 3e) is approximately 7 kW. The flame or the surrounding parameters around it can be observed with a flame sensor 9.

The fuel gas-air mixture burning under the burner surface 3 with one or more flames develops heat that can be released to a downstream heat exchanger 14. The resulting exhaust gas can flow out via an exhaust line 15.

Furthermore, a control unit 13 is schematically provided, which is connected in particular to a selection or all of the following components, wherein the control unit 13 can in particular receive, send and/or process signals, measured values and/or control signals: air mass flow sensor 6, fuel gas valve 5, blower 4, fuel gas mass flow sensor 7, volume flow sensor air-fuel gas mixture 8, actuator(s) 17, flame sensor 9.

The device is set up in such a way that at least one of the following parameters is used to activate and/or deactivate a (partial) burner surface 3: mass flow and/or volume flow of fuel gas and/or combustion air (by means of the sensors 6, 7, 8), a pressure signal at the fuel gas supply and/or at the combustion air supply (e.g. with the aid of a Venturi arrangement on/in the air line 12 and/or fuel gas line 11), combustion parameters (by means of the flame sensor 9), setting of flow adjustment devices (fuel gas valve 5, fan 4) for the fuel gas and/or the combustion air and/or an air-fuel gas mixture. In particular, at least one limit value and/or a tolerance range can be provided via the control unit 13, which is compared with one of the determined parameters for activating and/or deactivating a (partial) burner surface 3. If the limit value is reached or the tolerance range is exceeded, one of the (partial) burner surfaces 3 can be automatically activated or deactivated.

2 shows an example of possible control curves for a burner 1 with a fixed, i.e. non-variable geometry or burner surface (curve marked with "3") and a burner 1 with variable geometry or three partial burner surfaces 3a, 3b, 3c. The diagram shows the air-fuel gas ratio, ie "lambda", over the heat supply Qc [kW]. For burner 1 with a fixed geometry, the significant increase in lambda at partial load is determined by the constraints mentioned above. This can be set more independently with a burner 1 with a variably adjustable burner surface 3. In addition, 3 It is clear that the efficiency η or the net efficiency E decreases with increasing lambda (compared at a predetermined exhaust gas temperature and here, for example, up to a maximum of 68°C). Consequently, an increase in efficiency can be achieved when using a burner 1 with a variable burner surface 3. The activation and/or deactivation of a burner surface 3 can take place in particular based on a determined and/or expected efficiency.

4 illustrates the speeds of the fuel gas-air mixture and the flame at a constant lambda of 1.3. In this example, the burner surface 3 is provided with a large number of holes through which flow can take place. The flame speed in the case of hydrogen depends mainly on two influencing factors, namely the temperature of the fuel gas-air mixture in front of the flame and the lambda value. The flame speed, which is defined by the (horizontal) line c in 4 was derived at constant lambda (1.3) and constant temperature (here approx. 560°C). The rising line a represents the speed of the fuel gas-air mixture in a burner 1 with a fixed or non-variably adjustable burner surface 3. At partial load (small Qc, sections below line c), the speed of the fuel gas-air mixture can drop to such an extent that it is lower than the (very high for hydrogen) flame speed (line c), and a flashback occurs. The (jagged) curve b represents the speed of the fuel gas-air mixture at Use of a component with three partial burner surfaces 3a, 3b, 3c. In this example, the burner 1 offers a first cross-section of 250 mm ² up to 12 kW (partial burner surface 3a), a cross-section of 600 mm ² up to 24 kW (with additional partial burner surface 3b), a cross-section of 1200 mm ² cross-section over 24 kW (with additional partial burner surface 3c). With such a burner 1, the speed of the fuel gas-air mixture can be kept above the flame speed (line c) over the entire modulation range, in particular including a (at least) 10% safety threshold (line d). The activation and/or deactivation of a burner surface 3 can take place in particular based on a determined or expected speed of the fuel gas-air mixture and/or the flame.

5 illustrates a so-called lambda envelope curve for a burner 1 with three partial burner surfaces 3a, 3b, 3c. In order to achieve the best possible performance in hydrogen combustion, the lambda should remain largely stable over the entire modulation range. For this reason, a lambda envelope curve should be included, which is described in more detail below.

The definition of the lambda range in which operation is to take place must be agreed for each heating device. It depends on the following parameters: nominal heat supply; partial load heat supply; number of partial burners; nominal lambda (at nominal heat supply). In addition to these parameters, two constant coefficients, which were determined or adapted as part of the work underlying the invention, are introduced for the "minimum" and "maximum" operation of the (partial) burner surfaces: a stability coefficient (SK) of preferably approx. 7.5% and a variability coefficient (VK) of preferably approx. 15%. If the fan is running fast, the stability coefficient SK must be applied to take into account the system-related tolerances. At this value, in particular, the relative speed deviations are smaller than at low speeds. If the fan is running at low speed, the variability coefficient VK should be applied for larger tolerances.

An example of this requirement is in 5 which illustrates an upper lambda curve (line x) and a lower lambda curve (line z) over the power range (Qc). For this gas heater 2, the lambda at 30 kW (nominal load) has the (nominal) value 1.25 (line y). At each maximum partial burner load, the maximum/minimum lambda deviation from the nominal lambda is the stability coefficient. In 5 For example, at 13 kW (partial burner area 3a), 21.5 kW (partial burner area 3a + 3b) and 30 kW (partial burner area 3a + 3b + 3c) the maximum permissible lambda value is 1.25 x (1.00 + 0.075) = 1.34 (= upper lambda limit at maximum power (Lo(max)). At each minimum partial burner load, the maximum/minimum lambda deviation from the nominal lambda is the variability coefficient. In 5 For example, at 5 kW (partial burner area 3a), 13 kW (partial burner area 3a + 3b) and 21.5 kW (partial burner area 3a + 3b + 3c), the minimum permissible lambda value is 1.25 x (1.00 - 0.15) = 1.06 (lower lambda limit at minimum power (Lu(min)).

List of reference symbols

1

burner

2

Gas heater

3

Burner surface

4

fan

5

Fuel gas valve

6

Mass flow sensor air

7

Mass flow sensor fuel gas

8

Volume flow sensor air-fuel gas mixture

9

Flame sensor

10

Fuel gas mixture line

11

Air line

12

Fuel gas line

13

Control and regulation unit

14

Heat exchanger

15

Exhaust pipe

16

Inflow chamber

17

Actuator

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 19728965 A1 [0004, 0015]

Claims (11)

Method for operating a burner (1) of a gas heater (2), wherein the burner (1) has a variably adjustable burner surface (3), and the gas heater (2) can be operated with each of the burner surfaces (3) with a minimum power (Pmin) and a maximum power (Pmax), characterized in that each of the burner surfaces (3) can be operated with a power range of at least 2.0 kW, wherein at least one of the following parameters is used to activate and/or deactivate a burner surface (3): mass flow and/or volume flow of fuel gas and/or combustion air, pressure parameters of a fuel gas supply and/or a combustion air supply, combustion parameters, setting of flow adjustment devices (5, 4) for the fuel gas and/or the combustion air and/or an air-fuel gas mixture. Procedure according to Claim 1 , characterized in that a control of the lambda value for each of the adjustable burner surfaces (3) takes place in a range which is limited by a lambda lower limit (Lu) and a lambda upper limit (Lo). Procedure according to Claim 2 , characterized in that for each of the adjustable burner surfaces (3) the same lambda lower limits (Lu) and lambda upper limits (Lo) are specified. Procedure according to Claim 2 or 3 , characterized in that the lambda upper limit at maximum power (Lo(max)) corresponds to the following specification: nominal lambda x (1.0 + SK), where SK is in the range from 0.05 to 0.01. Procedure according to Claim 4 , characterized in that SK is in the range of 0.07 to 0.08. Method according to one of the preceding Claims 2 until 5 , characterized in that the lambda lower limit at minimum power (Lu(min)) corresponds to the following specification: nominal lambda x (1.0 - VK), where VK is in the range from 0.1 to 0.2. Procedure according to Claim 6 , characterized in that VK is in the range of 0.12 to 0.17. Method according to one of the preceding claims, characterized in that at least three different burner surfaces (3) are set, the power range for each of the burner surfaces (3) being at least 7 kW. Method according to one of the preceding claims, characterized in that at least one limit value and/or one tolerance range is provided, which is compared with one of the determined parameters for activating and/or deactivating a burner surface (3), and is automatically activated or deactivated when the limit value is reached or the tolerance range of one of the burner surfaces (3) is left. Burner (1) of a gas heating device (2), wherein the burner (1) has a variably adjustable burner surface (3) and means adapted to carry out the steps of the method according to one of the Claims 1 until 10 carry out. Computer program comprising instructions which cause the burner (1) of the Claim 9 the steps of the procedure according to any of the Claims 1 until 9 executes.

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