EP4357671B1 - Method for starting up a heating device, computer program, regulating and control device and heating device - Google Patents

Description

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

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.

To avoid such critical situations, in the EP 3 992 529 A1 It has been proposed to use 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.

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.

The US 2014/0199640 A1 describes a locally energy-powered intermittent combustion controller that cannot contribute to solving these problems.

The DE 197 44 008 A1 This shows 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. The disadvantage of this solution is its complexity and the need for monitoring equipment.

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.

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.

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.

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.

This procedure can be performed 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 a... Heating appliances powered by hydrogen, or a hydrogen-containing mixture, as fuel. In particular, time delays between opening the gas valve and the onset and stabilization of the fuel gas flow, which can occur due to a prolonged interruption of burner operation, can be reduced or avoided.

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.

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.

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

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.

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.

Alternatively, the heating appliance can have 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, to a target combustion air-fuel ratio. 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.

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%.

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.

The starting process for the heater can proceed as follows. First, a control unit, for example, can start a delivery system, usually a blower, up to a predetermined starting power or speed. Then, once the starting power or speed has been reached, a fuel flow rate predetermined for that speed can be supplied, and the ignition system can be activated. If, after a safety period, no flame is detected by the flame monitoring system, the start-up attempt is terminated and the gas valve is closed. Subsequently, the feed system may purge any remaining fuel gas from the mixture channel or combustion chamber for a (regular) purge period before another start-up attempt can be made. A necessary duration for a (regular) purge period 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 period can be designed to limit the amount of energy supplied by the fuel gas to such an extent that damage to the heating appliance can be prevented in the event of a misfire.

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.

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.

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. In particular, it is possible that with Upon receiving a start command to the heating unit, the activation of the delivery system is initially prevented until the gas valve is securely closed again after its brief opening. It was found that this significantly reduces the problematic time delay between the opening of the gas valve and the commencement and stabilization of the fuel gas mass flow. Thus, by filling the gas valve, and especially its control chambers, the gas regulating valve can also operate more quickly and precisely.

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.

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.

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 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.

According to one embodiment, a 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 be generated, for example, by gusts of wind at the combustion air intake or in the area of an outlet of the heating appliance's exhaust system.

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 occur 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 is detected. A cutoff period is determined. The cutoff period can be selected accordingly; for example, 2, 5, or 10 seconds might be appropriate.

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.

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.

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.

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.

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.

In another respect, a control and regulating device for a heating appliance is also proposed, designed to carry out the method proposed here according to the invention. For this purpose, the control and regulating device can, for example, include a processor, and/or The processor can, for example, execute the procedure stored in a memory (of the control unit). For this purpose, the control unit is electrically connected to the conveying system, the gas valve, and the flame monitoring system. Data relevant for carrying out a procedure proposed here can be stored in the control unit's memory, such as the duration of the brief opening of the gas valve and/or a limit value for the detected mass flow of combustion air.

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.

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.

This document describes a method for operating a heating appliance, a computer program, a control and monitoring device, and a heating appliance, which at least partially solve the problems described with reference to the state of the art. In particular, the method for operating a heating appliance, the computer program, the control and monitoring device contribute to the solution of the problems described with reference to the state of the art. The control unit and the heating appliance contribute at least to enabling a successful and safe initial start-up or a restart 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.

Fig. 1:

ein hier vorgeschlagenes Heizgerät,

Fig. 2 und 3:

Parameterverläufe während der Inbetriebnahme des Heizgerätes, und

Fig. 4 a) bis d):

Parameterverläufe die sich bei Durchführung eines hier vorgeschlagenen Verfahrens einstellen können.

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 suggested here,

Figs. 2 and 3:

Parameter profiles during the commissioning of the heating unit, and

Fig. 4 a) to d):

Parameter profiles that can occur when carrying out a procedure proposed here.

Fig. 1 Figure 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, in particular 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 intake mass flow of combustion air and includes a safety valve and a gas control valve for controlling the mass flow of fuel gas to be added. The generated 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, the base of which can be attached to a burner door 15 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.

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.

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.

The Fig. 2 The diagram illustrates, by way of example and schematically, the opening process of a gas valve 5. The diagram shows the course 17 of a voltage U applied to the gas valve 5, given in volts [V], which opens the gas safety valve of the gas valve 5. This can cause. Furthermore, a pressure profile 18, given in millibars [mbar], is defined, which is a measure of the outflowing mass flow rate ṁ of _gas . At a first time 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 profile 18 can be observed, the pressure profile 18 begins to increase at a second time 23. After an increase period 21, the pressure profile 18 reaches a value corresponding to the desired mass flow rate ṁ of _gas at a third time 24. The entire period from the first time 22 to the third time 24 is referred to as the opening period 20.

Fig. 3 The bar chart shows the opening times t _{_O} , 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 a 5-minute interruption of burner operation, a second bar 26 shows the opening time after a 15-minute interruption, a third bar 27 shows the opening time after a 30-minute interruption, a fourth bar 28 shows the opening time after a one-hour interruption, a fifth bar 29 shows the opening time after a six-hour interruption, and a sixth bar 30 shows the opening time after a 64-hour interruption. The opening time t_{_O} clearly increases with increasing duration of the burner operation interruption; thus, the opening time of the first bar 25 (after an interruption) is... (of 5 minutes) 0.55 seconds and of the sixth bar 30 (after an interruption of 64 hours) 1 second, thus increasing by almost a factor of two. During the second commissioning 37, the aforementioned differences in the opening times t _O for the different periods of interruption of burner operation are negligible.

• Fig. 4a) den Verlauf der Drehzahl n der Fördereinrichtung 2,
• Fig. 4 b) den Verlauf einer Öffnungsstellung Pos_Gas des Gassicherheitsventils des Gasventils 5,
• Fig. 4 c) den Verlauf eines Massestromes Brenngas ṁ_Gas , und
• Fig. 4 d) den Verlauf einer Zündleistung P_Z.

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 ṁ _gas , and
• Fig. 4 d) the course of an ignition power P _Z .

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 small mass flow of fuel _gas ṁ escapes ( 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 purging period 33, the conveying device 2 remains at starting speed 38, with the gas valve 5 closed. and consequently no mass flow of fuel _gas ṁ occurs ( Fig. 4 a) to c) The ignition device 12 is also out of service ( Fig. 4 d) ).

Following the shortened purge period 33, the heating appliance 1 can be commissioned normally. 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 ṁ _gas is established corresponding to the conveyed mass flow of combustion air. The ignition device 12 is in operation for 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 initial safety period 35.

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

1

heater

2

Funding institution

3

burner

4

Combustion air supply

5

Gas valve

6

Speed controller

7

Control and monitoring unit

8

combustion chamber

9

exhaust pipe

10

Exhaust system

11

Mixture channel

12

Ignition system

13

Flame monitoring

14

Gas supply

15

burner door

16

Flow sensor

17

Course of tension

18

Print history

19

Dead time

20

Increase period

21

Opening period

22

first point in time

23

second point in time

24

third point in time

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

shortened flushing period

34

regular flushing period

35

Security period / Security time

36

first commissioning

37

second commissioning

38

Starting speed/starting power

Claims (10)

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.