METHOD FOR COMMISSIONING A HEATING APPLIANCE, COMPUTER PROGRAM, CONTROL AND REGULATION DEVICE AND HEATING APPLIANCE

Description

[0001] The invention relates to a method for starting a heating device, a computer program, a control and regulation device and a heating device.

[0002] During the operation of a gas burner, the start-up process in particular can trigger critical conditions. Examples of such critical conditions include a hard ignition, a deflagration, or a flame flashback—that is, flame propagation from the burner into the fuel gas / combustion air supply during the start-up or ignition process, which can lead to damage to the heating appliance. When using hydrogen as the fuel gas, such critical conditions are more likely because hydrogen's volatility and low density result in significantly less reliable start-up behavior. A cold start of a cold heating appliance can be particularly difficult, as a gas flow must first be re-established at the gas control valve, which diffuses out during periods of inactivity.

[0003] To avoid such critical conditions, EP 3 992 529 A1 proposes using a pilot flame with its own fuel supply to ignite a main burner, the function of which can be monitored by a sensor and which is also arranged in such a way that the pilot flame cannot be extinguished by air escaping from the main burner. However, such a design is associated with considerable effort.

[0004] However, it was observed that, particularly after prolonged interruptions in burner operation, there can be time delays between the opening of the gas valve and the commencement and stabilization of the fuel gas flow. This can lead to a situation where, after the safety time of an ignition process has elapsed, no flame is detected and a new ignition process must be initiated. The resulting delay in the commissioning of the heating appliance leads to a loss of comfort for users, which can be particularly noticeable when hot water is required.

[0005] US 2014 / 0199640 A1 describes a locally powered intermittent combustion controller that cannot contribute to solving these problems.

[0006] DE 197 44 008 A1 discloses a method for starting a gas burner in which the composition of the gas-air mixture exiting the burner is monitored, and the ignition device is only activated after an ignitable mixture has been reached. A disadvantage of this solution is its complexity and the need for monitoring equipment.

[0007] Based on this, the object of the invention is to propose a method for starting a heating device, a computer program, a control and regulation device, and a heating device that at least partially overcome the problems of the prior art described above. In particular, the invention is intended to enable a successful initial ignition process of a heating device, especially a hydrogen-powered heating device.

[0008] Furthermore, the process should be suitable for at least partial automation and require as few structural changes as possible compared to a state-of-the-art heating device.

[0009] These problems are solved by the features of the independent claims. Further advantageous embodiments of the solution proposed here are specified in the dependent claims. In addition, the features specified in the claims are further detailed and explained in the description, which also presents further preferred embodiments of the invention.

[0010] This is achieved by a method for starting a heating appliance, wherein the heating appliance comprises at least a conveying device for supplying a combustion mixture of fuel gas and combustion air to a burner, an ignition device for the combustion mixture, and a gas valve, wherein the gas valve is briefly opened before the conveying device is started, thereby filling the gas valve with fuel gas. The period of this brief opening does not exceed a safety period for an ignition process.

[0011] This procedure can be carried out during every start-up process, and possibly also during commissioning, of the heating appliance. The procedure is particularly useful for ensuring a safe and successful initial ignition of a heating appliance, especially one powered by hydrogen or a hydrogen-containing mixture. Specifically, it can reduce or eliminate time delays that occur after a prolonged interruption of burner operation, from the opening of the gas valve until the fuel gas flow begins and stabilizes.

[0012] The heating appliance comprises at least one heat generator, in particular a gas condensing boiler, which releases thermal energy through the combustion of a fuel and can transfer it to a heating circuit via at least one heat exchanger. Consumers in the heating circuit can be connected to the heating appliance via a flow and a return line. The exhaust gases produced during combustion can be routed to an exhaust system via an exhaust duct in the heating appliance. A circulation pump can be installed in the heating circuit within the heating appliance to circulate a heat transfer medium (heating water). Heated heat transfer medium is supplied to consumers, such as convectors or underfloor heating systems, via a heating flow line and returned to the heat generator or the at least one heat exchanger via a heating return line.

[0013] For this purpose, the heating appliance has a conveying device, in particular a blower, which can supply a mixture of combustion air and fuel (hydrogen) to a burner of the heating appliance. The conveying device may include a power control, in particular a speed controller.

[0014] The gas valve can include a gas safety valve that opens only under defined safety-relevant conditions, such as an activated ignition device of the heating appliance. The gas valve also includes a gas control valve designed to regulate the mass flow of fuel gas and thus the combustion air ratio.

[0015] The gas valve may also have a pressure regulator that can set a constant pressure of the fuel gas at the gas control valve, thus compensating for pressure fluctuations in the gas supply.

[0016] The heating device can, in particular, form a pneumatic gas-air mixture (pneumatic mixture formation) in which a mass flow of fuel gas, supplied via a gas supply, is added to a mass flow of combustion air according to a negative pressure (control pressure) at a throttling point, such as a Venturi nozzle, in the combustion air supply. This allows a predefined (specified) air-fuel ratio (air ratio, lambda) to be established. The control pressure, as a measure of the incoming mass flow of combustion air, can draw a mass flow of fuel gas from the gas control valve. By setting an offset value on the gas valve, the zero point of the incoming mass flow of fuel gas can be shifted, thus influencing the outgoing mass flow of fuel gas. Such a gas valve is also referred to as a pneumatic gas valve.

[0017] Alternatively, the heating appliance can feature an electronic gas-air mixture control system. This system uses a signal from a flame or exhaust gas monitoring system (for example, a lambda sensor) to determine the flame and the combustion air-fuel ratio (also known as lambda or air-fuel ratio), thus enabling its regulation. Based on the flame monitoring signal, the control system can determine and adjust the opening width of the gas valve to approximate a desired combustion air-fuel ratio derived from the signal. The gas valve can adjust its opening width according to the required mass flow of fuel gas, often by means of an electronically controlled stepper motor.

[0018] The heating appliance can be specifically designed for burning hydrogen as fuel or a mixture containing hydrogen. The fuel mixture can have a hydrogen content of at least 80% or at least 90%.

[0019] Furthermore, the heating appliance may feature flame monitoring. This often involves the use of an ionization electrode, which utilizes the flame's ionization current to detect its presence. However, this principle is not reliably applicable to hydrogen flames, as the combustion of hydrogen produces significantly fewer free charge carriers. Therefore, hydrogen-powered heating appliances frequently employ other methods, such as detecting the electromagnetic radiation emitted by the flame, particularly infrared (IR) and / or ultraviolet (UV) radiation, or measuring the flame temperature. A signal from flame monitoring can indicate the presence of a flame and also provide information about the flame's air-fuel ratio.

[0020] The starting process for the heater can proceed as follows. First, a control unit, such as the heater's regulator, can start a fuel delivery system, usually a blower, at a predetermined starting power or speed. Once the starting power or speed is reached, a fuel flow rate specified for that speed is supplied, and the ignition system is activated. If, after a safety period, the flame sensor detects no flame, the start-up attempt is terminated, and the gas valve is closed. The fuel delivery system can then purge any remaining fuel gas from the mixture channel or combustion chamber for a (regular) purging period before another start-up attempt can be made.A necessary duration for a (regular) purging cycle is often 5 to 10 seconds and can be determined empirically, for example, depending on the starting speed and the volumes to be purged. The safety time can be designed to limit the amount of energy supplied by the fuel gas to such an extent that damage to the heating device can be prevented in the event of a misfire.

[0021] The mass flow of fuel gas specified for the starting speed can be set using the control pressure of the throttle point in a pneumatic gas-air system and electronically controlled in an electronic gas-air system.

[0022] The heating appliance also has an ignition device that can ignite the combustion mixture exiting the burner. The ignition device can, for example, include a spark or glow igniter, or even a pilot flame.

[0023] It is proposed that, during the (re)commissioning or start-up process of the heating appliance, the gas valve be briefly opened (immediately) before the delivery system is activated, allowing the gas valve to fill with fuel gas. This involves briefly opening and then closing the gas valve, and only then activating a blower. Specifically, it is possible to prevent the activation of the delivery system by sending a start command to the heating appliance until the gas valve is securely closed again after the brief opening. It has been found that this significantly reduces the problematic time delay between opening the gas valve and the onset and stabilization of the fuel gas flow. Filling the gas valve, particularly its control chambers, also allows the gas control valve to operate more quickly and precisely.

[0024] A brief opening refers to a period of opening sufficient for the gas valve to fill with fuel gas. During this time, no or only a very small amount of fuel gas should escape into the flow path or mixture channel of the heating appliance. The appropriate opening time can be determined, for example, using a reference heating appliance and can range from 0.5 seconds to 3 seconds. In any case, the brief opening time must not exceed the safety time of an ignition cycle of the heating appliance and, in particular, must be less than half the safety time.

[0025] According to one embodiment, if the gas valve includes a pressure regulator, the period of brief opening can be dimensioned so that the gas valve and pressure regulator can fill with fuel gas.

[0026] According to one embodiment, a negative offset value can be set on the gas valve of a heating appliance with pneumatic mixture formation during the brief opening of the gas valve. The offset value here refers to a shift in the zero point of the gas valve's opening width. By setting a negative offset value, the amount of gas exiting the valve is reduced, so that essentially only the control chambers of the gas valve are filled with fuel gas.

[0027] According to one embodiment, the mass flow of combustion air in the combustion air supply can be detected (immediately) before the gas valve is briefly opened. This can be done, in particular, using a flow sensor, with the detected values ​​being stored in a memory, for example, in the control unit. The detected mass flow of combustion air can be compared with a limit value. The brief opening of the gas valve can be enabled if the detected mass flow is below the limit value. Particularly in a heating appliance with pneumatic mixture formation, this ensures that no control pressure builds up in the throttle point (due to the mass flow of combustion air through it), which could cause the gas valve to open (further). Furthermore, any combustion gas that might escape during the brief opening would not spread into the mixture channel and the combustion chamber.A mass flow of combustion air can form, for example, due to gusts of wind at the intake of the combustion air or in the area of ​​an outlet of the exhaust system of the heating device.

[0028] According to one embodiment, if a combustion air mass flow rate above a certain threshold is detected (immediately) before the gas valve is briefly opened, the brief opening of the gas valve can be delayed or omitted. The delay could continue until a combustion air mass flow rate below the threshold is detected. In the event of a pause, the heating appliance could start up without briefly opening the gas valve before the pumping system is activated. The same could occur if a combustion air mass flow rate exceeding a certain threshold period is detected. This threshold period can be selected accordingly; for example, 2, 5, or 10 seconds might be appropriate.

[0029] According to one embodiment, following the brief opening of the gas valve, the conveying device can be started up, and any remaining fuel in the heating appliance's flow path can be removed during a shortened purge period. Advantageously, the purge period following the brief opening of the gas valve can be significantly shortened because only very small amounts of fuel gas can escape into the heating appliance's flow path during this brief opening, which then need to be removed during the purge period. In particular, the shortened purge time can be less than half or less than a third of the regular purge time and, for example, range from 2 to 5 seconds. The heating appliance can then undergo a regular start-up attempt.

[0030] According to one embodiment, the ignition device of the heating appliance can be activated during the brief opening of the gas valve. This can increase safety, as ignitable combustion mixture escaping from the burner due to the brief opening might be ignited. This undesirable occurrence would be safety-relevant and could be detected by flame monitoring in the heating appliance. Upon detecting a flame during the brief opening, the heating appliance could enter a fault state or suspend the execution of the proposed procedure and provide information about this, for example, via a display device or a network.

[0031] According to one embodiment, the duration of the (last) interruption of burner operation can be recorded, and the duration of the brief interruption can be adjusted to this recorded duration. For example, if the interruption lasts less than 5 to 10 minutes, the brief opening of the gas valve could be omitted, as only small amounts of fuel gas would escape from the gas valve during this period.

[0032] In this context, it should be noted that a mass flow rate (combustion air, fuel, or a mixture of both) can also characterize a volume flow rate, and vice versa. Thus, a mass flow rate can easily be converted into a volume flow rate, and vice versa, if the density and temperature of the medium are known.

[0033] In addition, a computer program is proposed which is designed to (at least partially) carry out a method presented here. In other words, this relates in particular to a computer program (product) comprising commands which, when executed by the control unit of a heating device, cause it to execute the method according to the invention proposed here.

[0034] In addition, a control unit for a heating appliance is proposed, configured to carry out the method proposed here according to the invention. For this purpose, the control unit can, for example, include and / or have a processor. In this context, the processor can, for example, execute the method stored in a memory (of the control unit). The control unit is electrically connected to the conveying device, the gas valve, and the flame monitoring system. Data relevant for carrying out the method proposed here can be stored in a memory of the control unit, for example, the duration of the brief opening of the gas valve and / or a limit value for the detected mass flow of combustion air.

[0035] Another aspect is the proposal for a heating appliance, including a control and regulation device as proposed here. The heating appliance is a gas-fired appliance, specifically a hydrogen-powered gas-fired appliance. The gas-fired appliance comprises a burner, a delivery system, and a gas valve, the delivery system of which supplies a combustion mixture of fuel gas (hydrogen) and combustion air to the burner.

[0036] The details, features, and advantageous configurations discussed in connection with the process can also occur in the computer program, control unit, and heating device 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.

[0037] This document presents a method for operating a heating appliance, a computer program, a control unit, and a heating appliance itself, which at least partially solve the problems described with reference to the state of the art. In particular, the method for operating the heating appliance, the computer program, the control unit, and the heating appliance contribute to enabling successful and safe initial commissioning or restarting of the burner after a prolonged interruption of operation. Furthermore, the method proposed here is advantageously fully computer-implemented and therefore requires no structural modifications to the heating appliance.

[0038] 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 limited by the exemplary embodiments shown. In particular, it should be noted that the figures, and especially the depicted dimensions, are only schematic. They show: Fig. 1: a heating device proposed here, Fig. 2 and 3: parameter curves during the commissioning of the heating device, and Fig. 4 a) to d): parameter curves that can occur when carrying out a procedure proposed here.

[0039] Fig. 1Figure 1 shows an exemplary and schematic representation of a heating device 1 proposed here. This device can include a burner 3 arranged in a combustion chamber 8. Combustion air can be drawn in via a combustion air supply 4, in which a flow sensor 16 may be arranged, by a conveying device 2, which may be designed as a blower. The conveying device 2 can be connected to a speed controller 6, which can regulate the speed n of the conveying device 2 by means of a pulse-width modulated (PWM) signal. A gas valve 5 can add fuel gas from a gas supply 14 to the drawn-in mass flow of combustion air and may include a safety valve and a gas control valve for controlling the mass flow of fuel gas to be added. The resulting mixture of fuel gas and combustion air can flow to the burner 3 via a mixture channel 11 and be ignited there by an ignition device 12.The burner 3 can have a cylindrical shape, which can be attached to a burner door 15 at its base in such a way that the combustion mixture can flow from the mixture channel into the burner 3. After combustion, the combustion products can be discharged to the outside via an exhaust pipe 9 of the heating appliance and an exhaust system 10.

[0040] The heating device 1 proposed here can be configured specifically for the combustion of hydrogen. Furthermore, the heating device 1 can have a flame monitoring device 13 on or in the burner door 15, which can, for example, be designed as a sensor for UV (ultraviolet) radiation emitted by the flame.

[0041] A control unit 7 can be configured to control the heating appliance 1. For this purpose, it can be electrically connected, for example, to the speed controller 6, the conveying device 2, the gas valve 5, the flame monitoring device 13, the ignition device 12, and the flow sensor. The control unit 7 can be configured to carry out a procedure proposed here.

[0042] The Fig. 2 The diagram illustrates, by way of example and schematically, the opening process of a gas valve 5. The diagram shows the curve 17 of a voltage U applied to the gas valve 5, given in volts [V], which can cause the gas safety valve of the gas valve 5 to open. In addition, a time-dependent curve 18 of a pressure P, given in millibars [mbar], is shown, which is a measure of the outflowing mass flow rate. GasAt a first time point 22, a voltage U, controlled by the control unit 7, can be applied to the gas valve 5, causing the gas control valve to open and allowing fuel gas to flow into the gas valve 5. After a dead time 19, during which no increase in the pressure curve 18 of the pressure P can be detected, the pressure curve 18 of the pressure P begins to rise at a second time point 23. After a rise period 21, the pressure curve 18 of the pressure P reaches a value corresponding to the desired mass flow rate at a third time point 24. Gas This corresponds to the entire period from the first point in time 22 to the third point in time 24, which is referred to as the opening period 20.

[0043] Fig. 3The bar chart shows the opening times tO, given in seconds [s], after different periods of interruption of the burner operation of the heating appliance 1 for two start cycles N, where the second start cycle 37 occurs after a purge time 34 following the first start cycle 36. A first bar 25 shows the opening time after an interruption of burner operation of 5 minutes, a second bar 26 shows the opening time after an interruption of burner operation of 15 minutes, a third bar 27 shows the opening time after an interruption of burner operation of 30 minutes, a fourth bar 28 shows the opening time after an interruption of burner operation of one hour, a fifth bar 29 shows the opening time after an interruption of burner operation of six hours, and a sixth bar 30 shows the opening time after an interruption of burner operation of 64 hours.The opening time t O clearly increases with increasing duration of the burner interruption. For example, the opening time of the first bar 25 (after a 5-minute interruption) is 0.55 seconds, and that of the sixth bar 30 (after a 64-hour interruption) is 1 second, thus increasing almost by a factor of two. During the second commissioning 37, the aforementioned differences in the opening times t O for the different durations of the burner interruption are negligible.

[0044] Fig. 4 a) to d) This shows exemplary and schematic parameter profiles over time t that can occur when carrying out a procedure proposed here, namely in: Fig. 4a ) the course of the rotational speed n of the conveying device 2, Fig. 4 b) the course of an open position Pos Gas of the gas safety valve of the gas valve 5, Fig. 4 c) the course of a mass flow of fuel gas Gas , and Fig. 4 d)the course of an ignition power PZ .

[0045] When carrying out the procedure proposed here during the starting of the heating appliance 1, the gas valve 5 is briefly opened 32 for a duration of 32 at a start time 31. During this brief opening 32, the conveying device 2 is out of operation, and the rotational speed n is reduced. Fig. 4 a) is 0. Gas valve 5 is open ( Fig. 4 b) ) and a very low mass flow of fuel gas occurs Gas out of ( Fig. 4 c) ). The ignition device 12 can be in operation during the brief opening 32 ( Fig. 4 d) ), however, this is optional. Immediately following the brief opening 32, the conveying device 2 can be put into operation and brought up to a starting power / starting speed 38 (see Fig. 4 a)For a shortened purge period 33, the conveying device 2 remains at starting speed 38, with the gas valve 5 closed and accordingly no mass flow of fuel gas occurs. Gas on ( Fig. 4 a) bis c) The ignition device 12 is also out of service ( Fig. 4 d) ).

[0046] Following the shortened purge period 33, regular commissioning of the heating unit 1 can take place. For this purpose, the gas valve 5 is opened for an (initial) safety period 35, while the conveying unit 2 is operated at starting speed 38, so that a mass flow of fuel gas is established. Gas The combustion air flow rate is adjusted according to the mass flow rate. The ignition device 12 is in operation throughout the entire safety period 35. Due to the implementation of the procedure proposed here, there is a high probability that commissioning will be successful during the first safety period 35.

[0047] If necessary, further regular commissioning or start-up procedures can be carried out. For this purpose, after the first safety period 35 has ended, a regular purging period 34 can follow to remove any remaining fuel gas from the flow path of the heating device 1. The gas valve 5 can then be opened and the ignition device 12 put into operation again during another safety period 35. This can be repeated for further start-up attempts until a maximum number of start-up attempts has been reached. Reference symbol list

[0048] 1 Heating unit 2 Conveyor 3 Burner 4 Combustion air supply 5 Gas valve 6 Speed ​​controller 7 Control unit 8 Combustion chamber 9 Exhaust pipe 10 Exhaust system 11 Mixture channel 12 Ignition device 13 Flame monitoring 14 Gas supply 15 Burner door 16 Flow sensor 17 Voltage curve 18 Pressure curve 19 Dead time 20 Rise period 21 Opening period 22 First time point 23 Second time point 24 Third time point 25 First bar 26 Second bar 27 Third bar 28 Fourth bar 29 Fifth bar 30 Sixth bar 31 Start time 32 Brief opening 33 Reduced purge period 34 Regular purge period 35 Safety period / Safety time 36 First start-up 37 Second start-up 38 Starting speed / Starting power

Claims

1. Method for starting a heating device (1), comprising a conveyor device (2) for conveying a combustion mixture of fuel gas and combustion air to a burner (3), an ignition device (12) for the combustion mixture and a gas valve (5), wherein, before starting the conveyor device (2), the gas valve (5) is opened briefly (32), causing the gas valve (5) to fill with fuel gas, wherein the duration of the brief opening (32) does not exceed a regular safety period (35) of an ignition process.

2. Method according to claim 1, wherein the gas valve (5) has an integrated pressure regulator which fills with combustible gas due to the brief opening (32) of the gas valve (5).

3. Method according to claim 1, wherein the heating device (1) has a pneumatic mixture formation and an offset setting is set to a negative range during the brief opening (32) of the gas valve (5).

4. Method according to claim 1, wherein before the brief opening of the gas valve (5), a mass flow of combustion air is detected in a combustion air supply (4) and, if a limit value of the mass flow of combustion air is exceeded by the detected mass flow of combustion air, the brief opening (32) of the gas valve (5) is suspended until a mass flow of combustion air below the limit value is detected.

5. Method according to one of the preceding claims, wherein the ignition device (12) is in operation during the brief opening (32) of the gas valve (5).

6. Method according to one of the preceding claims, wherein the duration of the brief opening (32) of the gas valve (5) is at most half of the regular safety period (35) for starting the heating device (1).

7. Method according to one of the preceding claims, wherein a period of time since the last interruption of burner operation of the heating device (1) is recorded and the brief opening of the gas valve (5) is not carried out if the period of time since the last interruption of burner operation is below a predetermined limit value.

8. Control and regulating device (7) for a heating appliance (1) comprising a gas valve (5), a delivery device (2), an ignition device (12) and a burner (3), wherein the control and regulating device (7) is designed to carry out a method according to one of claims 1 to 7.

9. Heating appliance (1) comprising a conveyor device (2), a gas valve (5), an ignition device (12) and a burner (3) as well as a control and regulation device (7) according to claim 8.

10. Computer programme comprising commands which cause a heating device (1) according to claim 9 to execute the method steps of a method according to one of claims 1 to 7.