METHOD FOR OPERATING A GAS HEATER, GAS HEATER WITH CONTROL AND REGULATION DEVICE FOR EXECUTING THE METHOD AND USE OF A TEMPERATURE OF A FLAME OF A HEATER FOR FLAME DETECTION

Description

[0001] The invention relates to a method for operating a gas heating appliance, a computer program, a storage medium, a gas heating appliance and the use of a detected temperature and a detected ionization current.

[0002] Gas-fired heating appliances typically have a flame detection device, often required by law, which prevents unburned fuel gas-air mixture from escaping the combustion chamber. The flame detection system automatically shuts off the gas supply to the heating appliance as soon as it detects no flame, thus ensuring particularly safe operation.

[0003] Heating appliances designed for the combustion of hydrocarbons often employ flame detection based on the measured ionization current of the flame. By detecting the charge carriers released during combustion, this solution enables safe and reliable flame detection.

[0004] Such a flame detection system is shown in FR 2 061 441 A5. The ionization measurement is wired such that an ignition device is activated when there is no ionization current. When an ionization current is present, the ignition device is deactivated by a thyristor. A PTC thermistor, acting as a thermocouple, is connected in parallel and operates a gas safety valve via a relay. Thus, if a flame loss and the associated temperature drop are detected, the gas supply can be detected. In this device, a failure of the ionization measurement would result in a permanently activated ignition device, and a failure of the thermocouple could potentially lead to the escape of unburned fuel gas. Therefore, the device shown poses significant operational risks.

[0005] Flame detection based on the detection of an ionization current of the flame is not possible in hydrogen-powered heating appliances, especially at low power output of the heating appliance, because a hydrogen flame releases significantly fewer charge carriers than a flame during the combustion of hydrocarbons (for example, natural gas).

[0006] Therefore, hydrogen-powered heating appliances often use flame detection based on UV light, where an ultraviolet light sensor can be directed at the flame. If the UV sensor fails or becomes contaminated, for example due to combustion product deposits, reliable flame detection cannot be guaranteed, and the operating range must be reduced or the operation of the heating appliance even interrupted.

[0007] Based on this, the object of the invention is to propose a method for flame detection (flame monitoring) of a gas heating appliance that at least partially overcomes the problems of the prior art described above. In particular, the method should enable safe operation of the heating appliance even after a failure of a first flame detection device.

[0008] Furthermore, the installation of a heating device for carrying out a procedure proposed here should not increase its complexity or only increase it insignificantly, and the procedure should be feasible with simple means.

[0009] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the independent claims. It should be noted that the features listed in the dependent claims can be combined with one another in any technologically meaningful way and define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, which also presents further preferred embodiments of the invention.

[0010] This includes a method for operating a gas heating appliance, comprising a burner, a conveying device which conveys a mixture of a gaseous fuel and combustion air through a mixture channel of the gas heating appliance to the burner, and a first flame detection device, comprising at least the following steps: a) Detecting a failure of the first flame detection device, b) Detecting at least one temperature of the flame of the gas heater, c) Operating the gas heater by means of flame detection taking into account the at least one temperature detected in step b).

[0011] Steps a), b), and c) are typically performed at least once in the specified order during a regular procedure. It is also possible to perform step b) continuously or at intervals, for example, at a set sampling rate.

[0012] The method serves to operate a gas heating appliance, in particular to provide flame detection for emergency operation of the heating appliance in the event of a failure of a primary flame detection device (a primary flame detection system). The method can also be used to control the combustion process during emergency operation, in particular to control the proportions of fuel gas and combustion air in the mass flow of the combustion mixture supplied to the burner of the gas heating appliance.

[0013] The solution described here is, in particular, a very simple and safe way to ensure (emergency) operation of a heating device in the event of a failure of the first flame detection system.

[0014] The heating appliance is a gas-fired boiler designed to burn a gaseous fuel, such as natural gas or, in particular, hydrogen, using ambient air. The resulting heat can be transferred to a heating circuit or used to provide hot water. The heating appliance has at least one burner and a delivery system that conveys a mixture of fuel (gas) and combustion air through a mixing channel to the burner. The combustion products can then be vented through an exhaust duct to a flue system.

[0015] The heating appliance can be operated in particular with pure hydrogen or a fuel gas with more than 90% hydrogen content, preferably more than 97%.

[0016] A first flame detection device can be based, in particular, on the detection and evaluation of the UV (ultraviolet) radiation emitted by the flame. For this purpose, the flame detection device can include a UV radiation sensor that can be directed towards the burner of the heating appliance or a flame generated there. The use of a flame detection system based on UV radiation can be particularly advantageous for hydrogen-powered heating appliances. This is because the combustion of hydrogen produces very few free charge carriers, which would complicate the use of a flame detection system based on the detection of an ionization current.

[0017] A first flame detection device can be implemented alternatively or cumulatively using at least one infrared flicker detector, acoustic flame detection, and / or high-voltage ionization. According to step a), a failure of the first flame detection device is detected. This detection can be achieved, for example, by comparing the flame detection readings with stored reference values ​​during operation of the heating appliance at defined operating points, in order to verify the first flame detection device.

[0018] Alternatively or cumulatively, a failure of the first flame detection device can also be detected during device startup, in which no signal or only an implausible signal is detected by the first flame detection device after the ignition process of the heating appliance. Here are two examples: 1) If a flame is detected even though the fuel gas valve is closed, the first flame detection device is implausible. 2) An electrical detection of a short circuit or broken wire at the sensor of the first flame detection device can also lead to the first flame detection device being classified as implausible.

[0019] If the first flame detection device includes a UV sensor for detecting UV radiation from a heating appliance's flame, a failure of the first flame detection device can be caused by a failure of the UV sensor or by contamination of the sensor. Contamination of the UV sensor would result in sensor drift, which can render the UV sensor signal unusable for controlling the heating appliance. Sensor drift can be detected by evaluating the sensor signal, in particular by including and comparing it with other operating parameters of the heating appliance that allow conclusions to be drawn about the expected sensor signal.

[0020] Detecting a failure of the first flame detection device according to step a) can be performed before the heating appliance is put into operation or even during operation. In particular, a detected ionization current of the heating appliance's flame can be used to detect a failure of the first flame detection device. Therefore, it may be advantageous to perform step b) of the procedure presented here continuously or at regular intervals.

[0021] According to an advantageous embodiment, at least one operating parameter of the heating appliance can be used to detect a failure of the first flame detection device according to step a). Advantageously, various operating parameters of the heating appliance are already available on a control unit of the heating appliance when implementing the method proposed here. The operating parameters can be, for example, a flow and / or return temperature of the heating system and / or operating parameters that allow conclusions to be drawn about the mass flow of combustion gas and combustion air supplied to the burner. Comparing the operating parameters with a detected signal from the first flame detection device can, particularly when considering a longer period, enable the detection of sensor drift and thus also allow the detection of a failure of the first flame detection device according to step a).

[0022] According to step b), at least one temperature of the flame of the heating device is measured. For this purpose, a signal from at least one temperature sensor located in the immediate vicinity of the flame of the heating device can be measured.

[0023] In principle, any temperature sensor can be used to measure at least one temperature. In particular, a resistance-based temperature sensor, such as a thermistor (PTC or NTC), a platinum or silicon resistance thermometer, and / or a semiconductor temperature sensor can be used.

[0024] According to a preferred embodiment, the temperature sensor can be an ignition device, in particular a hot-surface igniter of the heating device. A hot-surface igniter is an ignition device for a heating device that has a temperature-dependent resistance and thus enables temperature detection. Advantageously, this does not increase the complexity of the heating device, and no additional components are necessary to carry out the method proposed here.

[0025] It is understood that, in order to detect at least one temperature, the signals from several (different) temperature sensors can be included.

[0026] According to step c), the heating appliance is operated by means of flame detection based on at least one temperature recorded in step b). Advantageously, this ensures (emergency) operation of the heating appliance even if the first flame detection device has failed.

[0027] If a failure of the first flame detection device, as described in step a), is detected during a start-up of the heating appliance due to a missing and / or implausible signal from the first flame detection device, step c) can now be used to determine whether the missing or implausible signal from the first flame detection device is actually due to a fault in the flame detection or to another problem with the heating appliance that may be preventing the ignition of a flame. For this purpose, the flame temperature or ionization current of the heating appliance, as determined in step b), can be used. This can be done during a further start-up attempt of the heating appliance or during the first start-up attempt by performing steps a) and b) in parallel.

[0028] According to an advantageous embodiment, the temperature of the flame (and an ionization current) are continuously recorded in order to have as much information as possible about the flame state at any given time.

[0029] In an advantageous embodiment, when the heating device is operated in step c) according to step e), the heating device's power rate can be set such that a change in the heating device's power (for example, due to a lower heat demand) is detectable by the flame going out based on the temperature measured in step b). Advantageously, this compensates for the thermal mass of a temperature sensor used to detect the flame temperature according to step b), which can lead to a delayed response of the sensor's temperature signal. For this purpose, a suitable power rate can, for example, be stored in a memory of a control unit implementing the method presented here.A reduced rate of power change means that a new operating point of the heating appliance, for example based on a lower heat demand, is approached at a lower speed, and thus operating the heating appliance at reduced power is clearly distinguishable from a loss of flame.

[0030] According to a further advantageous embodiment, the heating device can be operated by means of flame detection based on the at least one temperature detected in step b) within a limited power range (modulation range) of the heating device. The power range can be limited, in particular, to ensure reliable flame detection based on a detected flame temperature. The limited power range can also be stored, for example, on a control unit that performs a method presented here.

[0031] According to a further advantageous embodiment, an ionization current of the heating device's flame can additionally be detected during step b). Measuring an ionization current is a proven method for flame detection, but it is not used with hydrogen-powered heating devices because a hydrogen flame at low power and / or high lambda releases too few charge carriers to enable reliable flame detection. However, at higher power or a sufficiently low lambda, reliable flame detection of a hydrogen flame is possible. Advantageously, flame detection using an ionization current also has a high reaction rate, so that the reduction in the rate of power change described above for flame detection using a measured temperature is unnecessary.

[0032] It is proposed as a particularly advantageous embodiment to operate the heating device according to step c) at a heating device output Below a threshold power for flame detection, a detected ionization current of the flame is used, and above the threshold power for flame detection, a temperature of the flame of the heating device is used.

[0033] The threshold power of the heating device can be determined in particular by ensuring that above the threshold power the (hydrogen) flame of the heating device releases sufficient free charge carriers so that flame detection based on the ionization current is reliably possible.

[0034] The threshold power of a heating appliance can be determined by various operating parameters that allow conclusions to be drawn about the heating appliance's output. Suitable operating parameters include, for example, the power input or rotational speed of the conveying system that supplies a fuel-air mixture to the burner, or the volumetric flow rate of the fuel-air mixture. A value for the threshold power of the heating appliance can be stored in a storage device, particularly in the appliance's control unit.

[0035] According to an advantageous embodiment, an (additional) detection of the ionization current of the heating device's flame can be achieved by means of an ignition device (ignition electrode) of the heating device. Advantageously, this does not increase the complexity of the heating device.

[0036] According to an advantageous embodiment, in step d), the heating appliance can provide or transmit information about the failure of the first flame detection device. In particular, providing or transmitting this information can be done via a network, especially the internet. For example, after detecting a failure of the first flame detection device according to step a), the heating appliance could automatically send information about this to a selected specialist company, which could then schedule and carry out a maintenance appointment for the heating appliance to repair the first flame detection device. Until then, the heating appliance can advantageously be operated in (emergency) mode according to step c), so that no comfort restrictions arise for the user.

[0037] Another aspect is the proposal of a computer program designed to (at least partially) execute the procedure presented here. In other words, this specifically concerns a computer program (product) comprising instructions that, when executed by a computer, cause it to carry out the procedure proposed here.

[0038] Another aspect that is proposed is a machine-readable storage medium on which the computer program is stored. This machine-readable storage medium is typically a computer-readable data carrier.

[0039] In addition, a control unit for a heating appliance is proposed, designed to carry out a procedure proposed here. This control unit may, for example, include a processor. In this context, the processor can, for instance, execute the procedure stored in the control unit's memory. Furthermore, operating data and a power change rate, to be set according to step e), may be stored in the control unit's memory for the purpose of carrying out the procedure presented here.

[0040] Another aspect being considered is the proposal for a gas heating appliance, incorporating a control and regulation device as suggested here. This gas heating appliance is specifically a hydrogen-powered gas heating appliance. The gas heating appliance can include a burner and a delivery system for supplying a mixture of combustion gas (hydrogen) and combustion air to the burner.

[0041] Another aspect proposes the use of at least one detected temperature of a flame in a heating appliance for operating the appliance, particularly for flame detection to operate the heating appliance after a failure of a primary flame detection device. Specifically, the at least one temperature can be detected by a temperature sensor located in or in the immediate vicinity of the flame.

[0042] In this process, a measured ionization current of the heating device's flame is used for flame detection above a certain heating device power threshold. Below this threshold, the measured temperature can be used for flame detection, as reliable flame detection using a measured ionization current is not possible in this power range.

[0043] The details, features, and advantageous configurations discussed in connection with the process may also occur in the computer program, storage medium, gas heating appliance, and / or its use presented here, and vice versa. In this respect, full reference is made to the explanations provided therein for a more detailed characterization of the features.

[0044] This document describes a method for operating a gas heating appliance, a computer program, a machine-readable storage medium, a gas heating appliance, and the use of at least one temperature signal and a measured ionization current, which at least partially solve the problems described with reference to the prior art. In particular, the method, the gas heating appliance, and the use of at least one temperature signal and a measured ionization current contribute to enabling the safe operation of a heating appliance after the failure of a primary flame detection device. Specifically, when optional step d) is performed, no action is required to operate the heating appliance, as the appliance automatically switches to (emergency) operation and transmits information about the failure of the primary flame detection device, for example, to a service center.

[0045] Furthermore, the invention can be implemented very simply and, in particular, without or with only very minor structural modifications to a heating device. Specifically, when the ionization current of the heating device is detected according to step b) via a device on the heating device, no structural modifications to the heating device are necessary to carry out the method proposed here.

[0046] It should be noted as a precaution that the numerical terms used here ("first", "second", etc.) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and thus do not necessarily dictate any dependency and / or sequence between these objects, quantities, or processes. Should a dependency and / or sequence be required, this is explicitly stated here, or it will be obvious to a person skilled in the art upon studying the specific configuration described. Where a component can occur multiple times ("at least one"), the description of one of these components may apply equally to all or some of the multiple components, but this is not mandatory.

[0047] The invention and its technical context are explained in more detail below with reference to the accompanying figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the situations described in the figures and combine them with other components and findings from the present description. It should be emphasized that the figures, and especially the depicted dimensions, are only schematic. They show: Fig. 1 : a sequence of a procedure proposed here, Fig. 2 : a burner of a heating appliance proposed here, Fig. 3 : a parameter profile that can occur when carrying out a procedure proposed here, and Fig. 4 : another parameter profile that may occur when carrying out a procedure proposed here.

[0048] Fig. 1 Figure 1 shows an exemplary and schematic representation of the sequence of a procedure proposed here. The procedure serves to ensure (emergency) operation of a heating device 1 after the failure of a first flame detection device 4. The sequence of steps a), b), and c), represented by blocks 110, 120, and 130, can occur during normal operation.

[0049] In block 110, according to step a), a failure of the first flame detection device 4 is detected. The first flame detection device 4 can include a UV sensor that detects UV radiation emitted by the flame 3 and can thus detect a flame 3 of the heating appliance. The detection of a failure of the first flame detection device 4 can be carried out, for example, based on the signal of the flame detection device 4 itself or by comparing the signal of the flame detection device 4 with reference values ​​for defined operating states of the heating appliance 1.

[0050] In block 120, according to step b), at least one temperature of a flame 3 of the heating device 1 is detected. This temperature can be detected by a temperature sensor 5. According to an advantageous embodiment, the temperature sensor 5 can be an ignition device, in particular a hot-surface igniter of the heating device 1. According to a further advantageous embodiment, several temperature sensors 5 can also be provided, which, for example, can be arranged at different positions in or in the immediate vicinity of the flame 3 of the heating device 1.

[0051] In block 130, according to step c), the heating device 1 is operated by means of flame detection based on the at least one temperature recorded in step b).

[0052] The first flame detection device 4 and the at least one temperature sensor 5 can advantageously be electrically connected to a control and regulating unit 8 on which a method presented here is carried out.

[0053] Fig. 2 Figure 1 shows an exemplary and schematic representation of a heating device 1 proposed here. The heating device 1 has a control and regulating unit 8, which is configured to carry out a method presented here. The heating device 1 has a burner 2, which can generate a flame 3 that can be detected by means of a first flame detection device 4. The heating device 1 also has a temperature sensor 5, which can be arranged such that the temperature of the flame 3 can be detected.

[0054] Fig. 3 Figure 3 shows an exemplary and schematic parameter profile that can occur when carrying out a procedure presented here. The abscissa of the diagram shown in Figure 3 represents the time course t, whereby at time t A a first flame detection device 4 fails, which is detected according to step a) (Block 110). By means of the first flame detection device 4 (here, for example, implemented as a UV sensor), the heating device 1 can be operated in a power range (modulation range) 6, since flame detection by means of the first flame detection device 4 is ensured in this power range 6.After the failure of the first flame detection device 4 at time t A, the heating device 1 can only be operated in a power range 7 in which control of the heating device 1 based on a detected temperature of the flame 3 is safely possible when operating the heating device 1 by means of flame detection based on the at least one temperature detected in step b) (block 120) according to step c) (block 130).

[0055] According to an advantageous embodiment, the power change rate of the temperature-based flame detection 10 can be reduced for operation of the heating device according to step b) (Block 120) in order to distinguish a reduction in the heating device's power output caused by the control unit 8 (for example, due to a lower heat demand) from a flame loss. In the present example, the power change rate of the temperature-based flame detection 10 can be set noticeably lower than the power change rate of the first flame detection device 9. It is understood that the power change rate for the temperature-based flame detection 10 should only be changed for a power reduction, since there is no risk of confusion with a flame loss when the power output increases.

[0056] Fig. 4Figure 1 shows an exemplary and schematic parameter profile that can occur when carrying out a method presented here, wherein, after the failure of a first flame detection device 4 at time t A, flame detection below a threshold power 13 is carried out by means of a temperature measured by the temperature sensor 5, and above the threshold power 13 by means of an ionization current measured by an ionization electrode 14. In a power range of the flame detection using ionization current 12, a power change rate of the ionization-based flame detection 11 is advantageously possible that is considerably higher than the power change rate for the temperature-based flame detection 10. Reference symbol list

[0057] 1 Heater 2 Burner 3 Flame 4 First flame detection device 5 Temperature sensor 6 Power range of first flame detection device 7 Power range of flame detection temperature sensor 8 Control unit 9 Power change rate of first flame detection device 10 Power change rate of temperature-based flame detection 11 Power change rate of ionization-based flame detection 12 Power range of flame detection ionization current 13 Threshold power 14 Ionization electrode

Claims

1. Method for operating a gas heater (1) comprising a burner (2), a conveyor device which conveys a mixture of a gaseous fuel and combustion air through a mixture channel of the gas heater (1) to the burner (2), and a first flame detection device (4), comprising at least the following steps: a) detecting a failure of the first flame detection device (4), b) detecting a temperature of a flame (3) of the gas heater (1), c) Operating the gas heating appliance (1) by means of flame detection based on the temperature detected in step b).

2. Method according to claim 1, wherein the gas heater (1) is operated with hydrogen as fuel.

3. Method according to one of the preceding claims, wherein the first flame detection device (4) detects UV radiation emitted by the flame (3) of the gas heater (1).

4. Method according to one of the preceding claims, wherein in step e) a rate of change in power of the gas heater (1) is set such that, in the event of a change in the temperature detected in step b), an extinction of the flame (3) can be distinguished from a reduction in power of the gas heater (1).

5. Method according to one of the preceding claims, wherein in step b) several temperatures of the flame (3) are detected at different positions of the flame (3).

6. Method according to one of the preceding claims, wherein in step b) an ionisation current of the flame (3) is additionally detected and operation of the gas heater (1) according to step c) is performed with flame detection based on - a detected ionisation current of the flame (3) at a power of the gas heating appliance (1) below a threshold power (13), and - a detected temperature of the flame (3) at an output of the gas heating appliance (1) above the threshold output (13).

7. Method according to one of the preceding claims, wherein in step d) the gas heating appliance (1) provides or sends information about the failure of the first flame detection device (4).

8. Gas heating appliance (1), comprising a burner (2), a conveyor device which is designed to convey a mixture of a gaseous fuel and combustion air through a mixture channel of the gas heater (1) to the burner (2) n, a first flame detection device (4) and a control and regulating device (8) designed to carry out a method according to one of the preceding claims.

9. Computer program product comprising instructions that cause a gas heater (1) according to claim 8 to carry out a method according to one of claims 1 to 7.

10. A machine-readable storage medium on which the computer program product according to claim 9 is stored.

11. Use of at least one detected temperature of a flame (3) of a heating appliance (1) for flame detection of the heating appliance (1) after failure of a first flame detection device (4), wherein a detected ionisation current of the flame (3) is additionally used for flame detection above a threshold power (13) of the heating appliance (1).