A surface-stabilized, fully premixed gas premix burner for burning hydrogen gas, and a method for starting such a burner.

Abstract

A method for starting a burner supplied with a premixed gas comprising a combustible gas and air, the combustible gas comprising at least 50% by volume of hydrogen. The method comprises the following steps: during a start-up phase, supplying a premixed gas having a first lambda value to a burner surface, the first lambda value being at least 1.85, and igniting the supplied premixed gas having the first lambda value using an ignition source. During an operating phase after the premixed gas has been ignited, supplying a premixed gas having a second lambda value to the burner surface, the first lambda value being greater than the second lambda value. Independent claims relating to burners and heating appliances are included.

Description

Technical Field

[0001] The present invention relates to the field of premix burners for surface-stabilized fully premixed gases for combusting combustible gases containing hydrogen gas, methods for starting such burners, and appliances including such burners.

Background Art

[0002] Surface-stabilized premix burners are well-known for the combustion of hydrocarbon gases such as natural gas, methane gas, and propane gas in heating appliances, particularly gas-fired heating appliances. These have advantages in terms of size, emissions, and the ability to adjust to different loads, also known as modulation.

[0003] The most common method of controlling the mixing of combustible gas and air in a gas-fired heating appliance equipped with a surface-stabilized premix burner is to use a pneumatic gas valve. In this system, the ratio of combustible gas to air is determined by the gas valve. For example, the gas valve is biased to a closed position and can be opened by the force of pneumatic pressure. Said force depends on the air flow, and the opening degree of the gas valve in a certain air flow is determined by the design of the gas valve. This is a master (air) - slave (combustible gas) solution. Other systems such as control valves can also be utilized. There are also systems that use a feedback loop to control the ratio of gas to air.

[0004] Most systems apply the following sequence to ignite the combustible gas. The fan is started, and in most cases, it is established that air is flowing. Next, the ignition sequence is started by creating a spark or other ignition source on the burner surface of the burner. The next step is the opening of the gas valve. Ignition occurs if the ratio of combustible gas to air is within a certain range.

[0005] In recent years, the use of natural gas and propane gas has been criticized due to carbon dioxide emissions. Therefore, hydrogen has been proposed as an alternative fuel, particularly for heating appliances in homes and industrial settings. However, hydrogen, or gaseous fuels rich in hydrogen, exhibit different combustion behavior than conventional hydrocarbon gases, such as a faster flame velocity. This different combustion behavior can lead to several problems, such as flame flashback. Flame flashback is a phenomenon that occurs when flames propagated upstream return and propagate back into the burner, and this can be caused by a high flame velocity.

[0006] International Patent Application (Publication No. 2020 / 182902), which claims priority from the European Patent Application No. EP19162278 of the present applicant, discloses a method for adjusting the ratio of air to flammable gas based on the burner load to mitigate risks such as flashback. EP19162278 and International Patent Application (Publication No. 2020 / 182902) are incorporated herein by reference.

[0007] If a hydrogen-fueled system is started according to the sequence described above, and ignition is delayed for any reason, a hydrogen-containing mixture will fill the combustion chamber. Tests have shown that ignition with at least a portion of the combustion chamber filled with this hydrogen-air mixture can cause explosive combustion and damage components of the heating device.

[0008] Furthermore, standards have been created to ensure the safe operation of burners. These standards include several tests as acceptance criteria. For example, the European standard EN15502-1, Gas Combustion Heating Boilers Part 1, General Requirements and Tests, for Natural Gas and LPG, includes several tests. Currently, there are no standards for hydrogen as a fuel, but it is expected that safety tests similar to those described in EN15502-1 will be applicable to future gas combustion heating boilers using gases other than those mentioned in, for example, EN437. Similar standards for hydrogen as a fuel are expected to exist and / or be developed outside of Europe as well.

[0009] One of the tests in the current standards is the "delayed ignition test." In the delayed ignition test, a flammable gas and air are first briefly introduced into the combustion chamber, and then ignited by an ignition source. This should not cause damage or other undesirable side effects. However, tests have shown that when using hydrogen as fuel in a conventional burner, flame flashback may occur during this test. [Overview of the project] [Problems that the invention aims to solve]

[0010] The object of the present invention is to mitigate one or more of the drawbacks described above, or to provide at least an alternative to existing methods and burners. [Means for solving the problem]

[0011] This objective is achieved in each of the methods, burners, and hydrogen gas combustion heating devices according to the present invention as described herein.

[0012] The present invention relates to a method for starting a burner in which a premixed gas containing a flammable gas and air is supplied to the burner surface of the burner, The flammable gas contains at least 50 volume percent hydrogen, The lambda value is defined as the ratio between the amount of air actually supplied and the amount of air required for the stoichiometric combustion of the premixed gas. The burner is preferably a surface-stabilized, fully premixed gas premix burner. The burner is preferably configured to be modulated between minimum load and full load. The method is, During the starting phase, a premixed gas having a first lambda value of preferably at least 1.85 is supplied to the burner surface, and the supplied premixed gas having the first lambda value is ignited using an ignition source. Preferably, the step of supplying a premixed gas having a second lambda value to the burner surface during the operating phase after the premixed gas has been ignited, wherein the first lambda value is greater than the second lambda value, Regarding methods including

[0013] The present invention relates to a method for starting a burner. The burner is preferably a surface-stabilized, fully premixed gas premix burner, which can be used, for example, in heating appliances for household and / or industrial applications. In such applications, it may be desirable for the burner to be able to operate at various loads. For example, in a household application, the required load when an inhabitant is taking a hot shower may be much greater than the required load to maintain the temperature of the house. Therefore, the burner is preferably configured to be modulated between a minimum load and a full load. The modulation ratio, defined as the ratio of the full load to the minimum load, can be, for example, at least 3, preferably greater than 4, more preferably greater than 5, more preferably greater than 7, and more preferably greater than 10. For example, the full load of the burner may be 24 kW, for example, when the burner is used in a household heating appliance such as a boiler.

[0014] According to the present invention, a premixed gas containing a combustible gas is supplied to the burner surface of a burner. The combustible gas contains at least one gaseous fuel that can be burned to provide heating energy, which in this invention is hydrogen. It should be noted that while some gases used in conventional heating appliances contain small amounts of hydrogen, in these mixtures the combustion behavior is still substantially entirely determined by the predominantly present hydrocarbon. It has been found that when the combustible gas contains a significant amount of hydrogen, the combustion behavior changes significantly compared to conventional hydrocarbon gases. In particular, in the context of this invention, the combustible gas contains at least 50 volume percent hydrogen. In addition to hydrogen, the combustible gas may contain additives such as colorants and odorants, or nitrogen. It may also contain carbon monoxide or carbon dioxide produced during the hydrogen production process. The combustible gas may also contain small amounts of hydrocarbons such as methane or propane. These hydrocarbons may be intentionally added to lower the price of the combustible gas, or they may be residual gases present in pipes used for hydrogen distribution, in which case the pipes have been previously used for the distribution of the hydrocarbons. Flammable gases may contain small amounts of oxygen, which can affect the amount of oxygen or air needed for combustion. The type and concentration of chemicals to add may depend on the required purity of the hydrogen.

[0015] Premixed gases also contain air. Air contains oxygen, which is necessary to ignite flammable gases. Typically, air is drawn from the environment where the burner is installed, for example, from outdoors. A specific amount of air is required for the stoichiometric combustion of the premixed gas, depending on the composition of the flammable gas and the composition of the air. However, in practice, the actual amount of air contained in the premixed gas is different. Traditionally, in the case of hydrocarbon gases, a small excess of air is supplied to avoid incomplete combustion, which can cause carbon monoxide. The lambda value is defined as the ratio of the amount of air actually supplied to the amount of air required for the stoichiometric combustion of the premixed gas. Therefore, the lambda value represents an excess of air.

[0016] According to the present invention, the method includes a first step of supplying a premixed gas having a first lambda value to the burner surface during the startup phase. During the startup phase, the supplied premixed gas having the first lambda value is ignited using an ignition source.

[0017] It should be noted that in some embodiments, the ignition source may be pre-activated, for example, by generating a spark, before the premixed gas having a first lambda value is supplied. Furthermore, in some embodiments, air may first be supplied to the burner surface, then the ignition source may be activated, then the combustible gas may be supplied to the premixed gas, and then the premixed gas having a first lambda value may be supplied to the burner surface.

[0018] This method preferably further includes the step of supplying a premixed gas having a second lambda value to the burner surface during the operating phase after the premixed gas has been ignited. According to the present invention, the first lambda value is greater than the second lambda value.

[0019] A difference is established between the startup phase and the operating phase. The startup phase includes supplying a premixed gas having a first lambda value and igniting the supplied premixed gas. Note that the burner can be modulated to a different load in the startup phase than in the operating phase. It is also possible to modulate the burner to a different load in the startup phase and / or even in the operating phase itself. In such cases, the first and / or second lambda values ​​may not be constant.

[0020] The present invention initially requires that the premixed gas supplied to the burner surface during the startup phase contains a relatively large amount of excess air. The inventors have found that when the premixed gas contains more air, the flame velocity decreases, and as a result, the risk of flame flashback also decreases. Furthermore, it has been found that after the premixed gas with the initial lambda value that was present is ignited, a premixed gas with a lower lambda value can be supplied during the operating phase. Since the accumulated premixed gas is no longer present or at least reduced, the risk of flame flashback is reduced.

[0021] A further advantage of the present invention is the reduced likelihood of flashback due to recirculation. Recirculation occurs when outlet gas is drawn into the burner inlet, for example, the fan inlet. In practice, recirculation can occur when the outlet and inlet of a boiler system are located close to each other, for example, on the roof of a building. Certain weather conditions, such as strong winds, can increase recirculation. When recirculation occurs, the air supplied by the fan becomes less oxygenated. Furthermore, unburned combustible gas may also be recirculated during the startup phase before the combustible gas is ignited. As a result, the ratio of oxygen to combustible gas in the premixed gas supplied to the burner surface decreases, i.e., the actual lambda value decreases. By controlling the lambda value to be high during startup, the likelihood of flashback can be reduced.

[0022] Advantageously, the excess air can be arbitrarily reduced, and as a result, a second lambda value during the operating phase can be selected to improve other characteristics, such as efficiency. The first lambda value is preferably at least 1.85. This has been found to be a practical lower limit that yields satisfactory results. It should be noted that conventional hydrocarbons such as methane will not burn or will burn very poorly at lambda values ​​above 1.85.

[0023] The lambda value can be controlled during the startup phase and optionally during the operating phase. The lambda value can be controlled, for example, by controlling the amount of air supplied by the air passage and / or the amount of combustible gas supplied by the combustible gas passage, for example, using a controller. Several practical methods for controlling the lambda value are described in detail herein.

[0024] In one embodiment, the burner comprises a premixed gas supply circuit, the premixed gas supply circuit comprising an air flow path for supplying air, a combustible gas flow path for supplying combustible gas, a mixing flow path for mixing the air supplied by the air flow path and the combustible gas supplied by the combustible gas flow path to form a premixed gas supplied to the burner surface, and at least one flow path blocking element for partially blocking the combustible gas flow path and / or the air flow path. In this embodiment, the method further comprises the following steps. During the start-up phase, partially blocking the combustible gas flow path with at least one flow path blocking element such that less combustible gas is supplied to the mixing flow path during the start-up phase than during the operating phase, and / or during the operating phase, partially blocking the air flow path with at least one flow path blocking element such that more air is supplied to the mixing flow path during the operating phase than during the start-up phase.

[0025] In this embodiment, the flow path blocking element is used to block the combustible gas flow path and / or the air flow path, so that less combustible gas and / or air is supplied to the premixed gas, respectively. Thus, the lambda value can be adapted, for example, from a first lambda value to a second lambda value. The flow path blocking element can be realized in a number of ways, some of which are described in more detail below in this specification.

[0026] In one embodiment, at least one flow path blocking element is arranged in a rest position during the start-up phase. In this embodiment, the method further comprises the step of actuating the flow path blocking element to arrange the flow path blocking element in an operating position during the operating phase.

[0027] Therefore, the resting position of the flow path occlusion element corresponds to the startup phase. To lower the second lambda value, a step of actively activating the flow path occlusion element is required. In the event of a failure that prevents the activation step from being completed, the premixed gas during the operation phase still has the first lambda value, which can lead to unsatisfactory efficiency. However, the failure does not affect the first lambda value during the startup phase. The flow path occlusion element is thus fail-safe.

[0028] In one embodiment, the first lambda value is greater than 1.9, preferably greater than 2, for example between 2 and 5, preferably greater than 3, for example between 3 and 5, and more preferably greater than 4, for example between 4 and 5. The larger the first lambda value, the less likely the flame is to flash back when the premixed gas having the first lambda value is ignited. However, if the first lambda value is too large, the premixed gas may not burn because there is too little flammable gas. Also, a large first lambda value may reduce the efficiency of the burner. Tests have shown that a suitable upper limit is 7, preferably 6, and more preferably 5. For example, the first lambda value may be between 2 and 7, 2 and 6, 3 and 7, 3 and 6, 4 and 7, or 4 and 6.

[0029] In one embodiment, the second lambda value is between 1 and 2, preferably between 1.05 and 1.5, and more preferably between 1.05 and 1.3. Optionally, the second lambda value is the lambda value at full load. These have been shown to be lambda values ​​suitable for safe and efficient operation. Theoretically, the required amount of air corresponds to a lambda value of 1, but it may be preferable to supply a slightly excessive amount of air during the operating phase. This means a slightly lower flame velocity and also provides a buffer to avoid incomplete combustion in situations where the air contains less oxygen than usual, for example due to weather or the burner being in the same location as idle air, or when the combustible gas has a different composition than expected. Incomplete combustion is inefficient because it reduces the use of energy in the combustible gas. In addition, incomplete combustion can cause safety problems if the concentration of combustible gas in the exhaust gas is too high, as this can cause explosions or fires in undesirable locations further downstream. Furthermore, reducing the lambda value may increase NOx in the exhaust gas.

[0030] In one embodiment, the first lambda value is at least 1.5 times, preferably at least 2 times, for example, at least 3 times, the second lambda value. These have been found to be practical first lambda values ​​that can yield satisfactory results.

[0031] In one embodiment, the flammable gas contains at least 75 volume% hydrogen, preferably at least 80 volume% hydrogen, more preferably at least 95 volume% or at least 98 volume% hydrogen. The more hydrogen the flammable gas contains, the greater the advantages associated with using hydrogen as fuel. However, at the same time, the flame velocity and the risk of flame flashback increase, which in turn makes the present invention far more advantageous.

[0032] In one embodiment, the starting phase lasts for at least 1 second, preferably at least 2 seconds, more preferably at least 3 seconds, for example, 3 to 6 seconds. Preferably, the starting phase is long enough to ensure that the supplied premixed gas is ignited. Thus, the starting phase may last for at least a short time, for example, 1 to 2 seconds, after the ignition source has been activated. The starting phase may also last for at least a short time, for example, 1 to 2 seconds, after a flame has been detected by a flame detector. This ensures that the premixed gas having a first lambda value is ignited before the operation phase begins. If a flame detector is used, some time, for example, 1 to 2 seconds, may be required after the ignition source has been activated for the flame to be detected. If the burner is started for a delayed ignition test, standard EN15502-1 specifies that the starting phase may last for 10 seconds. If the premixed gas having a first lambda value is not ignited, for example, if no flame is detected, the burner start may be terminated, for example, after a predetermined time corresponding to a safety time in accordance with EN15502. Optionally, the method according to the present invention may be restarted after the aforementioned discontinuation.

[0033] In one embodiment, the method includes the step of setting the fan to a high load during startup, for example, more than 80% of the rotations per minute (RPM) at full load, for example more than 90% of the RPM at full load, for example more than 95% of the RPM at full load, for example full load.

[0034] The advantages of this embodiment can be understood from the example of a resident wanting to take a hot shower while the boiler, including the burner, is stopped. To sufficiently heat the water for the shower, it is desirable for the burner to be at full load. However, with conventional burners, the burner must be started at a lower load, for example, 25-40%. After combustion has started, the burner can be slowly increased to full load by adjusting the fan speed. However, this can take several seconds, for example, because safety and proper mixing of the premixed gas must be ensured while increasing the fan flow. On the other hand, in this invention, more air is supplied during the startup phase. Therefore, the fan can be set to a high load before the flammable gas is added to the premixed gas, and this can be done more quickly. Once combustion has started, the amount of flammable gas can be adjusted during the operating phase, and the burner can reach the desired high load or full load more quickly. Therefore, when the method according to this embodiment is applied, residents can get hot water for their shower more quickly.

[0035] In one embodiment, the second lambda value is adapted to the load. This is described in detail in the applicant's international patent application, International Publication No. 2020 / 182902, which claims priority from the applicant's European patent application, specification No. EP19162278. EP19162278 and International Publication No. 2020 / 182902 are incorporated herein by reference. As described in EP19162278 and International Publication No. 2020 / 182902, the lambda value at minimum load may be at least 20% higher than at full load, and optionally, the lambda value at average load may be less than 10% higher than at full load. Generally, the burner is started at a load within the modulation range. According to the present invention, when the burner is started at any given load, the first lambda value at the load is higher than the second lambda value at the load. However, in some embodiments, the burner can be started at a load below the minimum load, but this is limited by the reduced minimum load. Below the reduced minimum load, it may not be possible to determine that ignition has occurred, or that stable combustion cannot be maintained. On the other hand, above the full load, the increased velocity of the premixed gas passing over the burner surface may cause the flame to move further away from the burner surface than the flame detection sensor, similarly making it impossible to determine that ignition has occurred.

[0036] In one embodiment, the second lambda value is defined as the operating lambda value at the same load under which the burner is started.

[0037] In one embodiment, the second lambda value is defined as the lambda value during operation at full load of the burner.

[0038] In one embodiment, the burner is started with a starting load in the starting phase that is different from the desired load in the operating phase, and the method further includes a transition phase in which the starting phase transitions to the operating phase after the premixed gas has been ignited, the transition phase including the step of changing the load to the desired load.

[0039] For example, in practical use, a predetermined second lambda value may be stored in memory for each load during the operating phase. The second lambda value may vary depending on the load. If the burner is started at a starting load, according to the present invention, if the load in the operating phase is equal to the starting load, the first lambda value will be greater than the second lambda value corresponding to the starting load. However, the burner may normally be started at a starting load, which may be a relatively low load, regardless of the desired load actually desired in the operating phase. If the desired load in the operating phase is different from the starting load at which the burner is started in the starting phase, there may be a transition phase after the premixed gas is ignited, transitioning from the starting phase to the operating phase.

[0040] In the first embodiment, the transition step includes the steps of changing the lambda value of the supplied premixed gas to a second lambda value associated with the starting load when the load in the operating step is equal to the starting load, and then changing the load to a desired load and changing the lambda value to a second lambda value associated with the desired load.

[0041] In a second embodiment, the transition step includes changing the load to a desired load while maintaining the lambda value of the supplied premixed gas at a first lambda value, and then changing the lambda value to a second lambda value associated with the desired load.

[0042] In a third embodiment, the transition step simultaneously includes the steps of changing the load to a desired load and changing the lambda value of the supplied premixed gas to a second lambda value associated with the desired load.

[0043] If the desired load is greater than the starting load, the first and third embodiments in the transitional phase are preferable because, in the second embodiment, the fan may not be able to supply the first lambda value at higher desired loads.

[0044] It should be noted that if the desired load is smaller than the starting load, the second lambda value associated with the desired load may actually be larger than the first lambda value at which the burner starts at the starting load. However, according to a preferred embodiment of the present invention, if the load during the operating phase is equal to the starting load, the first lambda value at which the burner starts is larger than the second lambda value associated with the starting load.

[0045] In one embodiment, the first lambda value is less than the extinction value. The extinction value is the lambda value at which there is very little flammable gas in the premixed gas relative to the air, and there is not enough flammable gas to keep the flame burning, so all flames on the burner surface are extinct by the premixed gas.

[0046] In one embodiment, the first lambda value is such that the concentration of the flammable gas in the premixed gas is below the upper limit of flammability, also known as UFL, and / or above the lower limit of flammability, also known as LFL. It should be noted that the lower and upper limits of flammability are determined by the composition of the flammable gas, but also depend on factors such as temperature and pressure. If the concentration exceeds UFL, the premixed gas may be too concentrated to burn, and if it falls below LFL, it may be too dilute to burn.

[0047] In one embodiment, the first lambda value corresponds to an amount of air lower than the amount of air supplied by the fan when the fan is at full load.

[0048] In one embodiment, the first lambda value is such that the concentration of the flammable gas in the premixed gas is below the lower explosive limit, also known as the LEL, meaning that the first lambda value should exceed the lambda value corresponding to the LEL. It may also be preferable to control the first lambda value to differ from the lower explosive limit by a predetermined safety margin, for example, 1.2 or 1.5 times. This ensures safe starting even if the actual composition of the air or flammable gas differs from expectations. It should be noted that while the LEL and LFL coincide for many gases, they differ for gases containing hydrogen. For gases containing hydrogen, there exists a concentration range in which the premixed gas is flammable but not explosive, and this is a preferred range during the starting phase. This range depends on temperature, pressure, other components that may be present in the flammable gas, and the mixture. For pure hydrogen, when the premixed gas contains 4–17 volume% hydrogen, its concentration is between the LFL and the LEL.

[0049] In one embodiment, the method further includes the step of maintaining an ignition source in an ignition period ignition state after it has been detected that a supplied premixed gas having a first lambda value has been ignited. The ignition state corresponds to the operation performed by the ignition source to ignite the premixed gas. For example, the ignition source may continue to emit a spark during the ignition state. For example, if the ignition source is a glow plug or a hot surface igniter, the current supplied to it may be maintained at a level that generates heat in the ignition source at a temperature that ignites the premixed gas. The ignition period may be a predetermined period, for example, 1 second, 2 seconds, or 5 seconds. The ignition period may overlap, for example, with the end of the starting phase and / or the start of the operating phase and / or the transition phase between the starting phase and the operating phase, where the lambda value is adapted toward a second lambda value and / or the load is adapted from a starting load to a desired load. In one embodiment, the burner is started in the starting phase with a starting load different from the desired load in the operating phase, and the ignition source is maintained in the ignition state until the burner is modulated to the desired load and / or a second lambda value associated with the desired load.

[0050] This embodiment allows, for example, the accumulation of premixed gas inside the burner or combustion chamber to be ignited by the ignition source. Accumulation of premixed gas can occur, for example, when the flame rapidly moves further away from the burner surface without burning all of the present gas. The accumulated gas can cause unexpected and / or undesirable flame behavior after changes in flame velocity, which can occur, for example, when the burner is adjusted to a different load. By igniting and burning the accumulated gas, this embodiment avoids the aforementioned unexpected and / or undesirable behavior and thus further reduces the risk of, for example, flame flashback. It should be noted that this embodiment may be advantageous when the ignition source is a glow plug or a hot surface igniter, particularly when a flame detector is used in which the spark from a spark igniter may adversely affect flame detection. It is also possible to stop the spark-ignited ignition source, for example, to detect the flame, and then start the ignition period after flame detection.

[0051] The present invention further relates to a burner configured to carry out a method according to the present invention. Preferably, the burner is a premixed burner for a surface-stabilized, fully premixed gas. Optionally, the burner also conforms to a burner described later.

[0052] The present invention further relates to a burner, as described below. The method according to the present invention can be carried out using the burner, but neither the method nor the burner is limited thereto. Nevertheless, the features and definitions described in reference to the method according to the present invention shall be similarly interpreted when referred to in reference to a burner, and vice versa. Furthermore, the features and / or embodiments described in reference to the method according to the present invention may be added to a burner according to the present invention to achieve similar advantages, and vice versa.

[0053] The present invention relates to a burner for burning a combustible gas containing at least 50 volume% hydrogen, wherein the burner is preferably a surface-stabilized premixed gas premix burner, and the burner is preferably configured to be modulated between a minimum load and a full load. The aforementioned burner, - Burner surface and, - A premixed gas supply circuit, i. Air passages for supplying air, ii. A combustible gas flow path for supplying combustible gas, iii. A mixing channel for mixing air supplied by an air channel and combustible gas supplied by a combustible gas channel to produce a premixed gas supplied to the burner surface, wherein the lambda value of the mixing channel is defined as the ratio of the amount of air actually supplied to the amount of air required for stoichiometric combustion of the premixed gas, A premixed gas supply circuit equipped with, - An ignition source for igniting the premixed gas supplied to the burner surface, - A controller configured to control the lambda value of a supplied premixed gas by controlling the amount of air supplied by an air passage and / or the amount of combustible gas supplied by a combustible gas passage, i. During the burner startup phase, the ignition source is configured to supply a premixed gas having a first lambda value, and the ignition source is configured to ignite the supplied premixed gas having a first lambda value, the first lambda value being preferably at least 1.85. ii. During the burner's operating phase after the ignition source is configured to ignite a supplied premixed gas having a first lambda value, a premixed gas having a second lambda value is preferably supplied, wherein the first lambda value is greater than the second lambda value. Controller and It is equipped with.

[0054] The burner according to the present invention is preferably a surface-stabilized, fully premixed gas premix burner. In this context, surface stabilization should be interpreted as the flame being intended to be on or near the burner surface during normal operation. In this context, fully premixed gas should be interpreted as the premixed gas having (substantially) all the air added before it reaches the burner surface. This is different from, for example, a nozzle mix system where the flammable gas and air merge at the burner surface, or a partially premixed system where some of the air is added before the gas reaches the burner surface and some of the air is supplied directly to the burner surface.

[0055] The burner is adapted for the combustion of a flammable gas containing at least 50 volume percent hydrogen and can be modulated between minimum and full load. The full load depends on the intended use, e.g., a single household, multiple households such as an apartment building, or industrial use. Examples of full loads may be, for example, 20 kW, 24 kW, 30-40 kW, 90-150 kW, 200-300 kW, or 2200-3000 kW.

[0056] The burner according to the present invention comprises a premixed gas supply circuit, a burner surface, and an ignition source. The premixed gas is supplied to the burner surface by the premixed gas supply circuit. The burner surface may include, for example, circular or elongated openings or perforations through which the premixed gas can flow, for example, into a combustion chamber. The ignition source is positioned, for example, near the burner in the combustion chamber. The ignition source is configured to ignite the premixed gas so that it burns and / or begins to burn. The ignition source may be, for example, a spark igniter, a glow plug, or a hot surface igniter. Once the premixed gas is ignited, a flame is present. As long as a flame is present, the premixed gas supplied to the burner surface is usually ignited as soon as it reaches the flame. Ideally, the flame is present on the burner surface throughout the operating phase. The burner surface may have any suitable shape, for example, circular, curved, or flat.

[0057] The premixed gas supply circuit comprises an air passage, a combustible gas passage, and a mixing passage. In the mixing passage, the air supplied by the air passage and the combustible gas supplied by the combustible gas passage are mixed to form a premixed gas. Mixing may be achieved naturally by the flow, or optionally with the help of a mixing element such as a fan. The air passage may be connected to ambient air, for example by a suction inlet, to supply air, and the air may be supplied to the mixing passage by, for example, a fan. The fan can be positioned upstream or downstream of the mixing passage. Typically, the volume of air required is greater than the volume of combustible gas required. Therefore, the air passage may be larger than the combustible gas passage. Preferably, the combustible gas is supplied to the mixing passage at least partially by the use of the Venturi effect. This can be achieved, for example, by providing a narrow or constricted section in the air passage at the point where the combustible gas passage is connected to the air passage. This narrow or constricted section locally increases the air velocity, thereby reducing the pressure and creating an attractive force on the combustible gas.

[0058] According to the present invention, the burner further comprises a controller. The controller is configured to control the lambda value of the supplied premixed gas. The controller can be configured to do this in a number of ways, some of which embodiments are described in more detail below. Generally, the controller is configured to control the lambda value by controlling the amount of air supplied by the air passage and / or the amount of combustible gas supplied by the combustible gas passage.

[0059] According to the present invention, the controller is configured such that, during the startup phase, a premixed gas having a first lambda value is supplied to the burner surface and the supplied premixed gas is ignited by an ignition source. Only after the supplied premixed gas having the first lambda value has been ignited, the controller controls the lambda value so that a premixed gas having a second lambda value is supplied during the operating phase. According to the present invention, the first lambda value is greater than the second lambda value, preferably the first lambda value is at least 1.85. Thus, the same advantages associated with the method according to the present invention are achieved.

[0060] In one embodiment, the burner further comprises at least one flow path occlusion element for partially blocking the combustible gas flow path and / or the air flow path. The controller is further configured to control at least one flow path occlusion element to partially block the combustible gas flow path during the startup phase and / or partially block the air flow path during the operating phase.

[0061] Flow path occlusion elements can be implemented in various ways, some of which are described in more detail below. By partially occluding the flammable gas flow path or the air flow path, less flammable gas or air enters the mixed flow path, respectively. By occluding the gas flow path during the startup phase and / or the air flow path during the operating phase, it is possible to achieve a first lambda value greater than a second lambda value.

[0062] Generally, the flow path occlusion element preferably has at least a first position where it is positioned in each flow path to partially occlude a combustible gas flow path or an air flow path. It further has a second position where it is not positioned in each flow path, or where it occludes at least each flow path less. Optionally, in the second position or an additional third position, the flow path occludes each of the other flow paths.

[0063] In one embodiment, at least one flow path blocking element has an operating position and a resting position, and at least one flow path blocking element is configured to be in the operating position during the operation phase and in the resting position during the start-up phase.

[0064] Therefore, the resting position of the flow blockage element corresponds to the startup phase. To achieve a lower second lambda value, a step is required to actively activate the flow blockage element. In the event of a failure that prevents this activation step from being completed, the premixed gas during the operation phase still has the first lambda value, which can lead to unsatisfactory efficiency. However, the failure does not affect the first lambda value during the startup phase. Thus, the flow blockage element is fail-safe.

[0065] Whether the pause position corresponds to the first position or the second position depends on whether the flow path blocking element is located in the flammable gas flow path or the air flow path.

[0066] In one embodiment, at least one flow path blocking element is actuated by pneumatic, hydraulic, magnetic, or mechanical force and is configured to block a flammable gas flow path and / or an air flow path.

[0067] In one embodiment, the burner comprises a gas valve in addition to at least one flow path occlusion element, the gas valve being located in the flammable gas flow path, and the gas valve having a closed position that prevents the flammable gas from flowing through the flammable gas flow path, and an open position that allows the flammable gas to flow through the flammable gas flow path. Note that in this embodiment, both the gas valve and the flow path occlusion element are present, i.e., exist as separate components. The gas valve is located in the flammable gas flow path, and the flow path occlusion element can be located in either the flammable gas flow path or the air flow path. Optionally, a controller is configured to control the gas valve.

[0068] This embodiment has the advantage that the flammable gas flow path can be opened and closed using a gas valve, independently of the flow path blocking element. Thus, the functions are separated. Furthermore, the gas valve can be implemented with a simpler or less expensive structure, such as a pneumatic gas valve.

[0069] In some embodiments, the gas valve may be a control valve, such as an electronically actuated control valve, a pneumatically actuated control valve, or a hydraulically actuated control valve. In other embodiments, the gas valve is a pneumatic gas valve, preferably a master-slave component in which the airflow in the air passage is the master. For example, the pneumatic gas valve may be biased to the closed position and opened by air pressure, the force of which depends on the airflow. The degree of opening of the pneumatic gas valve at a particular airflow rate can be determined by the design of the pneumatic gas valve. In this system, the ratio of flammable gas to air is determined by the design of the pneumatic gas valve.

[0070] Optionally, pneumatic gas valves are designed with a negative offset, meaning they can only open when a predetermined threshold airflow or low pressure is present. This avoids unwanted flow of flammable gas when there is no airflow, which could occur when the pneumatic gas valve opens due to other reasons, such as a suction force further downstream, causing low pressure. Such unwanted flow of flammable gas could result in flammable exhaust gases, which is undesirable for safety reasons.

[0071] In one embodiment, at least one flow path occlusion element is a valve, such as an electronically operated control valve, a pneumatically operated control valve, or a hydraulically operated control valve. This allows for precise control of the volume of flammable gas and / or air supplied to the mixing flow path, and therefore the lambda value of the premixed gas.

[0072] In a further embodiment, at least one of the at least one occluding element corresponds to a gas valve located in a combustible gas flow path, the gas valve having a closed position that prevents combustible gas from flowing through the combustible gas flow path and an open position that allows combustible gas to flow through the combustible gas flow path.

[0073] In one embodiment, the burner further comprises at least one oxygen sensor configured to measure a value representative of the oxygen content of the flue gas produced by the burner, or a value representative of the oxygen content of the premixed gas supplied to the burner surface. The measured value may represent the lambda value of the supplied premixed gas. The controller may be configured to control the lambda value based on the measured value.

[0074] In one embodiment, the burner further comprises at least one flame detector configured to detect when the supplied premixed gas has been ignited and / or is burning and to generate a corresponding flame signal, preferably the controller further configured to control the premixed gas to have a second lambda value after receiving a flame signal from the detector. If the supplied premixed gas having a second lambda value is supplied when the supplied premixed gas having a first lambda value has not yet been ignited, the premixed gas having the first lambda value and the premixed gas having the second lambda value will be mixed. As a result, a gas with a lambda value that carries a risk of flame flashback may be produced. This risk is mitigated in this embodiment. In a further embodiment, the controller may be configured to stop supplying the premixed gas if the flame detector does not detect ignition or combustion of the premixed gas after a predetermined time, for example, 2, 5, or 10 seconds.

[0075] In one embodiment, the burner includes a porous metal plate for stabilizing the flame while the supplied premixed gas is burning. The porous metal plate may correspond to the burner surface, or it may be positioned inside the burner surface, in which case the porous metal plate may also be referred to as a distributor or pressure distributor. In one embodiment, the porous metal plate is realized according to one or more embodiments shown in the following applications of the applicant, which are incorporated herein by reference: International Publication 2011 / 069839, International Publication 2009 / 077505, or International Publication 02 / 44618.

[0076] In one embodiment, the burner includes a second air passage having an air valve. The air valve has a first position in which it can supply air to the premixed gas through the second air passage at a first flow rate, and a second position in which it can supply air to the premixed gas through the second air passage at a second flow rate. The second flow rate may be less than or greater than the first flow rate, and optionally the second flow rate may be approximately zero. The controller is further configured to control the air valve so that it is in the first position during the startup phase and in the second position during the operation phase. The air valve is preferably biased to the first position.

[0077] In one embodiment, the burner includes a second combustible gas flow path having a second combustible gas valve. The second combustible gas valve has a first position in which combustible gas can be supplied to the premixed gas through the second combustible gas flow path at a first flow rate, and a second position in which combustible gas can be supplied to the premixed gas through the second combustible gas flow path at a second flow rate. The second flow rate may be less than or greater than the first flow rate, and optionally the second flow rate may be zero. The controller is further configured to control the second combustible gas valve to be in the second position during the startup phase and in the first position during the operation phase. The second combustible gas valve is preferably biased to the second position.

[0078] In one embodiment, the controller may be further configured to modulate the burner between minimum load and full load. To do this, the controller may control, for example, a fan, and / or a gas valve, and / or one or more flow path blocking elements.

[0079] In one embodiment, the burner may further include a combustion chamber in which, for example, an ignition source and / or an oxygen sensor and / or a flame detector is located.

[0080] In one embodiment, the burner may further include a fan, and optionally the controller is configured to control the fan.

[0081] The present invention further relates to a hydrogen gas combustion heating appliance including a burner according to the present invention. This heating appliance can be used, for example, in household or industrial applications, such as boilers.

[0082] The present invention is described below with reference to the figures. The same reference numeral in different figures indicates the same feature. However, it should be noted that the figures are merely examples of combinations of some arbitrary features. The present invention is not limited to what is shown in the figures. [Brief explanation of the drawing]

[0083] [Figure 1] A burner according to the first embodiment of the present invention is shown. [Figure 2] Here is an example of a lambda value as a function of time. [Figure 3] In any embodiment, several factors that may be considered when determining the first and / or second lambda values ​​are shown. [Figure 4] A second embodiment of the burner according to the present invention is shown. [Figure 5] A third embodiment of the burner according to the present invention is shown. [Figure 6] The steps of a method for starting a burner according to a possible embodiment of the present invention are schematically shown. [Modes for carrying out the invention]

[0084] Figure 1 schematically shows a burner 100 according to a first embodiment of the present invention. The burner 100 is preferably a surface-stabilized, fully premixed gas premix burner modulated between minimum load and full load. The burner 100 comprises a burner surface 123 to which the premixed gas is supplied by a premixed gas supply circuit. In the illustrated example, the burner surface 123 comprises a perforation through which the premixed gas flows into a combustion chamber 130. The combustion chamber 130 may be, for example, part of a heating appliance in which water is heated. An ignition source 124 is further provided for igniting the supplied premixed gas. In the illustrated embodiment, the burner surface 123 is schematically depicted as circular. However, in practice, the burner surface 123 can have any suitable shape, for example, circular, curved, or flat. The shape of the burner surface 123 may depend on the shape of the combustion chamber 130, and / or vice versa.

[0085] The premixed gas contains a flammable gas and air. Therefore, the premixed gas supply circuit comprises a flammable gas flow path 111 connected to a flammable gas supply source 114. In the illustrated example, the flammable gas supply source 114 is a tank; however, other options include distribution networks similar to those known for the distribution of conventional hydrocarbon gases such as methane in local or industrial areas. In the context of the present invention, the flammable gas contains at least 50 vol%, and in some embodiments at least 80 vol%, at least 95 vol%, or at least 98 vol% hydrogen.

[0086] A gas valve 112 is provided in the flammable gas passage 111, and this gas valve 112 can regulate the amount of flammable gas flowing through the flammable gas passage 111. In the illustrated example, the gas valve 112 is an electronically operated control valve controlled by an electronic actuator 113. However, it is also known to design the gas valve 112 to open based on air pressure. For example, the gas valve 112 may be biased to the closed position by spring force, but when the pressure downstream of the gas valve 112 decreases due to airflow, it may automatically open, allowing a desired amount of flammable gas to pass through.

[0087] Oxygen is required to ignite a flammable gas. In this invention, air is used to supply the oxygen. Therefore, the premixed gas supply circuit includes an air passage 101 for supplying air. Preferably, a fan 102 is provided to supply and circulate the air. In the illustrated example, the fan 102 is located upstream of the point where the air passage 101 and the flammable gas passage 111 merge, but in some embodiments, the fan 102 may be located downstream of the aforementioned point. It is also possible to arrange multiple fans at arbitrary locations. The air passage 101 is further connected upstream to an air supply source (not shown). Typically, the air supply source is simply ambient air. For example, the air passage 101 may be connected to the outside air, for example, through a hole in a wall, and the fan 102 provides suction to draw air into the air passage 101.

[0088] Figure 1 further shows that the air passage 101 may optionally include a constriction 121, that is, a portion that is narrower than the upstream portion of the air passage 101. As can be derived from Bernoulli's principle, the air velocity increases in the constriction, and therefore the pressure decreases. The flammable gas passage 111 is connected to this constriction 121. Because the air pressure decreases, an attractive force is obtained for the flammable gas, resulting in a Venturi effect, and consequently, the mixing of the flammable gas and air is improved.

[0089] The premixed gas supply circuit further includes a mixing channel 122. In the mixing channel 122, the air supplied from the air channel 101 and the combustible gas supplied from the combustible gas channel 111 are premixed to form a gas that is supplied to the burner surface 123. Based on the composition of the combustible gas, a certain amount of oxygen is required for the combustible gas to burn completely. Based on the composition of the air, the amount of air required can be derived from the amount of oxygen required. In reality, the amount of air is different from this, so the lambda value is defined as the ratio of the amount of air actually supplied to the amount of air required for the stoichiometric combustion of the premixed gas.

[0090] Normally, the burner 100 is started in the following procedure. First, the fan 102 is started to supply air to the air passage 101. Next, the ignition source 124 is started, but since there is no flammable gas yet, combustion does not occur. After that, the gas valve 112 is opened to supply flammable gas to the flammable gas passage 111. The flammable gas and air are mixed in the mixing passage 122, and the premixed gas enters the combustion chamber 130 through the holes in the burner surface 123. The operating ignition source 124 ignites the supplied premixed gas, and combustion and a flame are present in the combustion chamber 130.

[0091] However, if, for example, the ignition source 124 malfunctions or fails, the supplied premixed gas may not ignite immediately. As a result, the premixed gas containing flammable gas will accumulate in the combustion chamber 130. The same thing can happen during delayed ignition tests. Tests have shown that if the flammable gas contains a significant amount of hydrogen, igniting the accumulated premixed gas after a certain period of time can cause several problems. These problems can lead to undesirable damage and / or hazards. For example, flame flashback may occur, meaning the flame may propagate backward through the burner surface 123. An explosion may also occur in the combustion chamber 130.

[0092] This invention provides a solution by supplying additional excess air during the startup phase compared to the operating phase. An example of the lambda value as a function of time is shown in Figure 2. As can be seen, the lambda value is 4 between 1 second and 6 seconds. Note that initially only the fan is started to supply air, and the flammable gas is added after 1 second. After 8 seconds, the lambda value in the illustrated example is approximately 1.3, although the exact lambda value may depend on the load. Tests have shown that increasing the lambda value during the startup phase reduces the above problem. Furthermore, note that the load during the startup phase may differ from the load during the operating phase. During the transition from the startup phase to the operating phase, which corresponds to the time interval of 6 to 8 seconds in Figure 2, the fan can also be adapted to provide a different flow.

[0093] Embodiments of the present invention will be described in more detail with reference to Figure 1. The burner 100 comprises a controller 150. The controller 150 is configured to control the lambda value of the supplied premixed gas. In the illustrated example, the controller 150 does this by controlling a gas valve 112. In particular, the controller 150 has an output terminal 150.1 for transmitting a control signal 151 to an input terminal 113.1 of the actuator 113 of the gas valve 112. By controlling the position of the gas valve 112, the amount of flammable gas entering the mixing channel 122 is controlled, and as a result, the air-to-flammable gas ratio and the lambda value are controlled. However, it should be noted that several other possibilities can be applied as alternatives or combinations to the electronically operated controlled gas valve 112, some of which are described in detail herein.

[0094] According to the present invention, the controller 150 is configured to supply a premixed gas having a first lambda value during the starting phase of the burner 100. The period before the ignition source 124 ignites the supplied premixed gas having the first lambda value is part of the starting phase. Ignition itself also occurs during the starting phase. The control device 150 is further configured to supply a premixed gas having a second lambda value during the operating phase of the burner. The operating phase begins after the ignition source 124 ignites the supplied premixed gas having the first lambda value. According to the present invention, the first lambda value is greater than the second lambda value.

[0095] In the event of a malfunction or during a delayed ignition test, the premixed gas with a first lambda value may accumulate in the combustion chamber 130 until ignition. The premixed gas that is ignited first has a lower first lambda value, thus reducing the flame velocity. This reduces the risk of flame flashback and explosion.

[0096] Preferably, the first lambda value is at least 1.85. This has been found to be a practical lower limit for obtaining satisfactory results.

[0097] The burner 100 preferably includes at least one flow path occlusion element 112, which in the example shown in Figure 1 is implemented as a gas valve 112. In this embodiment, the flow path occlusion element 112 is arranged to partially occlude the flammable gas flow path 111. The controller 150 can control the flow path occlusion element 112 by outputting a control signal 151 to the input terminal 113.1 of the actuator 113 via the output terminal 150.1. During the startup phase, the controller 150 controls the flow path occlusion element 112 so that the flammable gas flow path 111 is partially occluded. In this way, less flammable gas is supplied to the premixed gas, resulting in a larger first lambda value.

[0098] Preferably, the flow path blocking element 112 is in a resting position during the startup phase. The gas valve 112 may then be biased to partially close by, for example, one or more springs. By applying force with the actuator 113, the gas valve 112 can be further opened to the operating position during the operating phase, allowing more combustible gas to be supplied to the premixed gas. However, if, for example, the controller 150 or the actuator 113 fails, the gas valve 112 remains in the resting position even during the operating phase, and the premixed gas during the operating phase will have a first lambda value. While this may result in inefficient combustion, safety is ensured because, in the event of such a failure, the lambda value during the startup phase is avoided as being too low.

[0099] There are several possible ways to determine when to transition from the startup phase to the operation phase. Preferably, the startup phase lasts for at least 1 second, preferably at least 2 seconds, and more preferably at least 3 seconds, for example, 3 to 6 seconds. In some embodiments, the controller 150 can be configured to automatically switch to the operation phase after a predetermined time.

[0100] Figure 1 shows that an optional flame detector 131 is provided in the combustion chamber 130. The flame detector 131 is configured to generate a flame signal 153 when it detects a flame in the combustion chamber 130, which indicates that the supplied premixed gas is igniting and / or burning. The flame detector 131 can be implemented according to any known preferred principle for flame detection. The flame signal 153 is output to the controller 150 via output terminal 131.1 and input terminal 150.3. The controller 150 can use the information provided by the flame signal 153 in several ways. For example, the controller 150 can be configured to operate the gas valve 112 to the operating position only after a flame has been detected, thereby preventing a premixed gas with a second lambda value from reaching the combustion chamber 130 before the already present premixed gas is ignited. This can be done instead of, or in addition to, waiting for a predetermined time as described above. Furthermore, as shown in Figure 1, for example, the controller 150 can control the ignition source 124 so that a control signal 152 can be transmitted via the output terminal 150.2 and the input terminal 124.1. In this case, the controller 150 can be configured to stop the ignition source 124 from igniting the premixed gas if the flame detector 131 does not detect a flame after a certain period of time. This avoids a dangerous situation where a considerable amount of premixed gas accumulates in the combustion chamber 130 without being ignited. Some standards require this as a mandatory measure. On the other hand, by controlling the ignition source 124, it is also possible to ensure that the premixed gas supplied into the combustion chamber 130 is ignited only if the premixed gas has a satisfactory lambda value. It is also possible for the controller 150 to control the ignition source 124 to maintain the ignition state during the ignition period after detecting the initial ignition of the premixed gas. In this way, the accumulated premixed gas can be burned even when the flame moves away from the accumulated premixed gas.

[0101] Figure 3 shows several factors that may be considered when determining the first and / or second lambda values ​​in any embodiment. These factors may be considered separately or in combination with each other. The horizontal axis of Figure 3 represents the burner load, and the vertical axis represents the lambda value. Each line in the graph represents a different factor, which is described below. Each line is accompanied by an arrow indicating which side of the line the lambda value is preferable to be on.

[0102] The burner is configured to be modulated between the minimum load and the full load. For example, in the case of a household heating appliance, the full load may be 24 kW. Conventionally, the modulation ratio, i.e., the ratio of the full load to the minimum load, was around 4:1 to 5:1, but recently, modulation ratios of up to 10:1 have been proposed. In Figure 3, line 3.6 shows the lower limit of 20% when the modulation ratio is 5:1, and line 3.7 shows the lower limit of 10% when the modulation ratio is 10:1.

[0103] The second lambda value is typically in the range of 1.05 to 1.3, especially at high load or full load. A small amount of excess air is supplied to avoid incomplete combustion if the air and flammable gas are not sufficiently mixed, or if the composition of the air and / or flammable gas is deviant. Line 3.8 in Figure 3 shows an example of a second lambda value depending on the load. When the flammable gas contains a significant amount of hydrogen, it has been found that it may be optimal to adapt the lambda value, and therefore, for example, the second lambda value, based on the load at the operating stage. As described in the European Patent Application No. 19162278, the lambda value at minimum load may be at least 20% higher than at full load, and optionally the lambda value at average load may be less than 10% higher than at full load. Generally, the burner is started at a load within the modulation range. According to the present invention, when the burner is started at any given load, the first lambda value at this given load is higher than the second lambda value at the said load. This is shown by line 3.10 in Figure 3, which corresponds to line 3.8 multiplied by 1.5. However, in some embodiments, the burner can be started at a load that is below the minimum load, but this is limited by the reduced minimum load, because below that minimum load, it may not be possible to determine whether the flame or burner is on or off within the allowable time.

[0104] Preferably, the first lambda value is less than the extinction value. The extinction value is the lambda value at which the flame on the burner surface is extinct due to the premixed gas, as there is very little flammable gas in the premixed gas relative to the air, and there is not enough flammable gas to keep the flame burning.

[0105] Preferably, the first lambda value is such that the concentration of flammable gas in the premixed gas is below the upper limit of flammability, also known as UFL, shown by line 3.2 in Figure 3. Preferably, the first lambda value is such that the concentration of flammable gas in the premixed gas exceeds the lower limit of flammability, also known as LFL, shown by line 3.1 in Figure 3. Otherwise, the premixed gas may be too rich or too lean, making ignition impossible. Note that a concentration of flammable gas in the premixed gas exceeding a certain threshold corresponds to the lambda value being less than the lambda value corresponding to that threshold. Furthermore, note that while the upper and lower limits of flammability are determined by the composition of the flammable gas, they also depend on factors such as temperature and pressure.

[0106] In practice, the first lambda value can be limited by a fan, particularly in embodiments where the lambda value is adjusted by partially blocking the air passage. The maximum capacity or power of the fan determines the maximum amount of air that can flow through the air passage, which in turn, along with a given amount of flammable gas supplied, determines the lambda value of the premixed gas. While theoretically it is possible to install a larger fan, this may be undesirable in practice from a cost perspective. Therefore, the first lambda value preferably corresponds to an amount of air lower than the amount of air supplied by the fan when the fan is at full load. This is shown by line 3.3 in Figure 3. It should be noted that the amount of flammable gas can be determined by the fan, particularly if the fan is located downstream of where the flammable gas passage and the air passage merge.

[0107] Preferably, the first lambda value is such that the concentration of the flammable gas in the premixed gas is below the lower explosive limit, also known as the LEL, meaning that the first lambda value should exceed the lambda value corresponding to the LEL, shown by line 3.4 in Figure 3. It may also be preferable to control the first lambda value to differ from the lower explosive limit by a predetermined safety margin, for example, the safety margin being 1.2 or 1.5 times, shown by line 3.5 in Figure 3. This ensures safe starting even if the actual composition of the air or flammable gas differs from what is expected.

[0108] Preferably, the first lambda value is below the lower temperature limit shown by line 3.9 in Figure 3. In this context, the lower temperature limit is defined as the temperature at which the flame of the ignited premixed gas is extinguished. If the combustible gas contains only hydrogen, the temperature is approximately 571°C.

[0109] As can be seen from Figure 3, following all of the above arbitrary restrictions reveals an ideal range for the first lambda value, which is indicated by the reference digit 3.50 in Figure 3. This can be used to determine the optimal first lambda value based on the composition of the flammable gas and air, as well as environmental conditions such as temperature and pressure. This range can be determined more precisely by considering how many of the above factors are considered. However, in some cases, estimates or standard values ​​may be used for one or more factors.

[0110] However, in practice, determining all the lines shown in Figure 3 to determine the first and second lambda values ​​may be cumbersome. The applicant has found through testing and simulation that, in general, the following rules of thumb give satisfactory results: The first lambda value is at least 1.85, preferably at least 1.9, preferably greater than 2, for example between 2 and 5, preferably greater than 3, for example between 3 and 5, and more preferably greater than 4, for example between 4 and 5. The second lambda value can be between 1 and 2, preferably between 1.05 and 1.5, and more preferably between 1.05 and 1.3. In general, it is preferable that the first lambda value is at least 1.5 times, preferably at least 2 times, for example at least 3 times, the magnitude of the second lambda value.

[0111] Figure 4 shows a second embodiment of the burner 300 according to the present invention. The burner 300 shown in Figure 4 differs from the burner 100 shown in Figure 1 in its flow path occlusion element and gas valve. In Figure 4, the flow path occlusion element 312 is not the same element as the gas valve 212; on the contrary, the flow path occlusion element 312 exists in addition to the gas valve 212. Furthermore, in the illustrated embodiment, the gas valve 212 is not an electronically operated control valve, but rather a mechanism that opens based on the balance of air pressure upstream and downstream of the valve 212. However, this is not a requirement specification for the embodiment of the flow path occlusion element 312 shown in Figure 4.

[0112] The flow path occlusion element 312 is configured to be positioned in the flammable gas flow path 111 in the rest position, as shown in Figure 4. In the operating position (not shown), the flow path occlusion element 312 is not in the flammable gas flow path 111, or at least the amount of obstruction the flammable gas flow path 111 by the flow path occlusion element 312 is less compared to the rest position. An actuator 313 is provided to move the flow path occlusion element 312 from the rest position to the operating position. The flow path occlusion element 312 is preferably biased towards the rest position so that it can be moved back to the rest position using an attached force, including, for example, a spring force or gravity. The actuator 313 may be configured to move the flow path occlusion element 312 based on air pressure, hydraulic pressure, mechanical force, and / or magnetic force. The controller 150 is configured to control the actuator 313 with a control signal 351 via output terminal 150.1 and input terminal 313.1. The controller 150 is configured to position the flow path blocking element 312 in a resting position during the startup phase and in an operating position during the operation phase. The flow path blocking element 312 itself can take any suitable shape and form.

[0113] Figure 5 shows a third embodiment of the burner 400 according to the present invention. The burner 400 shown in Figure 5 differs from the burner 100 shown in Figure 1 in its flow path occlusion element and valve. In Figure 5, the flow path occlusion element 412 is not the same element as the valve 212. Also, in the illustrated embodiment, the valve 212 is not an electronically operated control valve, but rather a mechanism that opens based on the balance of air pressure upstream and downstream of the valve 212, although this is not a required specification for the embodiment of the flow path occlusion element 412 shown in Figure 5.

[0114] The flow path occlusion element 412 is configured to be located within the air flow path 101 in the operating position, as shown in Figure 5. In the resting position (not shown), the flow path occlusion element 412 is not in the air flow path 101, or at least the amount of obstruction of the air flow path 101 by the flow path occlusion element 412 is less compared to the operating position. An actuator 413 is provided to move the flow path occlusion element 412 from the resting position to the operating position. The flow path occlusion element 412 is preferably biased to the resting position so that it can be moved back to the resting position using an attached force, such as a spring force or gravity. The actuator 413 may be configured to move the flow path occlusion element 412 based on air pressure, hydraulic pressure, mechanical force, and / or magnetic force. The controller 150 is configured to control the actuator 413 with a control signal 451 via output terminal 150.1 and input terminal 413.1. The controller 150 is configured to position the flow path occlusion element 412 in the resting position during the startup phase and in the operating position during the operation phase. The flow path blocking element 412 itself can take on any appropriate shape and form.

[0115] In this embodiment, unlike the embodiments shown in Figures 1 and 3, the amount of air is reduced during the operating phase, rather than during the startup phase.

[0116] In embodiments not shown, the flow path blocking element 412 is configured to be positioned in the constricted section 121. In this case, the constricted section 212 is further narrowed, which increases the velocity and decreases the pressure, and the reduced pressure draws in more flammable gas.

[0117] Figure 6 schematically shows the steps of a burner starting method according to a possible embodiment of the present invention. In step 1001, there is a heat demand. The heat demand may arise, for example, from turning on the heating in a building or from a request for hot water from a faucet or shower. The heat demand may optionally initiate pre-purging in step 1002. Pre-purging involves blowing air through the burner to ensure that no flammable gases are present. After pre-purging, in step 1003, a premixed gas having a first lambda value is supplied, and in step 1004, the ignition source is controlled to be in an ignition state. In the ignition state, the ignition source is adapted to ignite the premixed gas having the first lambda value. Step 1004 can be performed before or concurrently with step 1003. Preferably, the first lambda value is at least 1.85. Optionally, in step 1005, the ignition source is controlled to no longer be in an ignition state before flame detection is performed using the flame detector in step 1006. Step 1005 may be particularly useful if, for example, the ignition source is a spark igniter and this measure is not taken, it may cause poor flame detection, although this also depends on the type of sensor used as the flame detector. Steps 1001-1006 are part of the starting phase 1100.

[0118] If no flame is detected in step 1006 after the safety time, step 1007 provides a restart, in which case the pre-purging in step 1002 ensures that no unburned premixed gas is present in the burner. Optionally, step 1007 may be performed a predetermined number of times to completely shut off the burner, for example, if it cannot be started after five attempts. The safety time may conform to EN15502.

[0119] If a flame is detected in step 1006, the method may optionally include a transition step 1200 after the starting step 1100. The transition step 1200 may be particularly useful if the burner is started with a starting load different from the desired load in the starting step 1100. In the illustrated embodiment, the transition step 1200 includes step 1009, which changes the lambda value of the supplied premixed gas to a second lambda value associated with the starting load, assuming that the load in the operating step will be equal to the starting load. The transition step 1200 then includes step 1010, which changes the load to the desired load and changes the lambda value to a second lambda value associated with the desired load. Other embodiments of the transition step 1200 are also possible, as described herein.

[0120] Following the transition phase, the method may include an operating phase 1400. The operating phase 1400 includes step 1012 of supplying a premixed gas having a second lambda value to the burner surface. The first lambda value is greater than the second lambda value.

[0121] Figure 6 further shows an arbitrary ignition period 1300. The ignition period 1300 begins in step 1008, when the ignition source is controlled to be in an ignition state, and ends in step 1011, when the ignition source is controlled not to be in an ignition state. In the illustrated example, the ignition period 1300 coincides with the end of the start-up phase 1100, the transition phase 1200, and the start of the operation phase 1400.

[0122] It should be noted that, although shown as separate embodiments in this specification, one or more of the embodiments of Figure 1, i.e., the gas valve 112 functioning as a flow path occlusion element 112, the embodiment of Figure 4, i.e., the flow path occlusion element 312 positioned in the combustible gas flow path 111, and the embodiment of Figure 5, i.e., the flow path occlusion element 412 positioned in the air flow path 101, can be combined.

[0123] Where necessary, this document describes detailed embodiments of the present invention. However, it should be understood that the disclosed embodiments serve solely as examples, and the present invention can be implemented in other forms. Accordingly, the specific structural aspects disclosed herein should not be considered limiting to the present invention, but merely as the basis for the claims and for enabling the invention to be implemented by an average person skilled in the art.

[0124] Furthermore, the various terms used herein should not be interpreted as restrictive, but rather as comprehensively describing the present invention.

[0125] As used herein, the word “a” means one or more unless otherwise specified. The phrase “a plurality of” means two or more. Also, the words “comprising” and “having” constitute an open language and do not exclude the existence of more elements.

[0126] The reference numerals in the claims should not be construed as limiting the invention. No particular embodiment is required to achieve all of the objectives described.

[0127] The mere fact that specific technical means are defined in different dependent claims still allows for the possibility that combinations of these technical means can be applied advantageously.

Claims

1. A method for starting a burner, wherein a premixed gas containing a flammable gas and air is supplied to the burner surface of the burner, The aforementioned flammable gas contains at least 50% by volume of hydrogen, The lambda value is defined as the ratio between the amount of air actually supplied and the amount of air required for the stoichiometric combustion of the premixed gas. The burner is a surface-stabilized, fully premixed gas premix burner, The premixed burner includes a porous metal plate for stabilizing the flame when the supplied premixed gas is burning. The porous metal plate corresponds to the burner surface, The burner is configured to be modulated between minimum load and full load, The aforementioned method, During the startup phase, a premixed gas having a first lambda value of at least 1.85 is supplied to the burner surface, and the supplied premixed gas having the first lambda value is ignited using an ignition source. During the operating phase after the premixed gas has been ignited, a step is to supply a premixed gas having a second lambda value to the burner surface, wherein the first lambda value is greater than the second lambda value. Includes, The second lambda value is between 1.05 and 1.

5. method.

2. The method according to claim 1, wherein the lambda value is controlled during the startup phase by controlling the amount of air supplied by the air passage and / or the amount of combustible gas supplied by the combustible gas passage.

3. The burner is equipped with a premixed gas supply circuit, and the premixed gas supply circuit is An air passage for supplying air, A combustible gas flow path for supplying combustible gas, A mixing channel for mixing the air supplied by the air channel and the combustible gas supplied by the combustible gas channel to form a premixed gas supplied to the burner surface, The system comprises at least one flow path blocking element that partially blocks the combustible gas flow path and / or the air flow path, The aforementioned method, During the startup phase, the step of partially blocking the combustible gas flow path with at least one flow path blocking element so that less combustible gas is supplied to the mixing flow path during the startup phase compared to the operation phase, and / or During the operation phase, the step of partially blocking the air passage with at least one passage blocking element so that more air is supplied to the mixing passage during the operation phase than during the startup phase, Further including, The method according to claim 1 or 2.

4. The at least one flow path blocking element is positioned in a resting position during the startup phase. The method according to claim 3, further comprising the step of operating the flow path blocking element to position the flow path blocking element in an operating position during the operation stage.

5. The method according to any one of claims 1 to 4, wherein the first lambda value is greater than 2, for example between 2 and 6, preferably greater than 3, for example between 3 and 5, and more preferably greater than 4, for example between 4 and 5.

6. The method according to any one of claims 1 to 5, wherein the second lambda value is between 1.05 and 1.

3.

7. The method according to any one of claims 1 to 6, wherein the first lambda value is at least 1.5 times, preferably at least 2 times, for example at least 3 times, the second lambda value.

8. The method according to any one of claims 1 to 7, wherein the flammable gas comprises at least 75 volume% hydrogen, preferably at least 80 volume% hydrogen, more preferably at least 95 volume% or at least 98 volume% hydrogen.

9. The method according to any one of claims 1 to 8, wherein the startup step lasts for at least 1 second, preferably at least 2 seconds, more preferably at least 3 seconds, for example, 3 to 6 seconds.

10. The burner is started with a starting load in the starting stage that is different from the desired load in the operating stage. The method further includes a transition step of moving from the starting step to the operating step after the premixed gas has been ignited. The method according to any one of claims 1 to 9, wherein the transition step includes changing the load to the desired load.

11. The method according to any one of claims 1 to 10, further comprising the step of maintaining the ignition source in an ignition period state after it is detected that the supplied premixed gas having the first lambda value has been ignited.

12. A burner configured to perform the method according to any one of claims 1 to 11, which is a surface-stabilized, fully premixed gas premixing burner.

13. A burner for burning a combustible gas containing at least 50 volume percent hydrogen, wherein the burner is a surface-stabilized, fully premixed gas premix burner, and the burner is configured to be modulated between minimum load and full load. The aforementioned burner, Burner surface and The flame is stabilized when the supplied premixed gas is burning, and a porous metal plate corresponding to the burner surface is provided. A premixed gas supply circuit, i. Air passages for supplying air, ii. A combustible gas flow path for supplying combustible gas, iii. A mixing channel for mixing the air supplied by the air channel and the combustible gas supplied by the combustible gas channel to produce a premixed gas supplied to the burner surface, wherein the lambda value of the mixing channel is defined as the ratio of the amount of air actually supplied to the amount of air required for stoichiometric combustion of the premixed gas, A premixed gas supply circuit equipped with, An ignition source for igniting the premixed gas supplied to the burner surface, A controller configured to control the lambda value of the supplied premixed gas by controlling the amount of air supplied by the air passage and / or the amount of combustible gas supplied by the combustible gas passage, i. During the starting phase of the burner, the ignition source is configured to supply a premixed gas having a first lambda value, and the ignition source is configured to ignite the supplied premixed gas having the first lambda value, wherein the first lambda value is at least 1.

85. ii. During the operating phase of the burner after the ignition source is configured to ignite the supplied premixed gas having the first lambda value, the burner is configured to supply a premixed gas having a second lambda value between 1.05 and 1.5, wherein the first lambda value is greater than the second lambda value. Controller and A burner equipped with a burner.

14. The system further comprises at least one flow path blocking element for partially blocking the combustible gas flow path and / or the air flow path, The burner according to claim 13, wherein the controller is further configured to control the at least one flow path blocking element to partially block the combustible gas flow path during the startup phase and / or to partially block the air flow path during the operation phase.

15. The at least one flow path blocking element has an operating position and a resting position, The burner according to claim 14, wherein the at least one flow path blocking element is configured to be in the operating position during the operation phase and in the resting position during the start-up phase.

16. The burner is equipped with a gas valve in addition to the at least one flow path blocking element, The burner according to claim 14 or 15, wherein the gas valve is positioned in the combustible gas flow path, and the gas valve has a closed position that prevents the combustible gas from flowing through the combustible gas flow path, and an open position that allows the combustible gas to flow through the combustible gas flow path.

17. The burner according to claim 14 or 15, wherein the flow path blocking element is a valve, for example, an electronically operated control valve.

18. The burner according to any one of claims 13 to 17, further comprising at least one oxygen sensor configured to measure a value representative of the oxygen content of the flue gas generated by the burner, or a value representative of the oxygen content of the premixed gas supplied to the burner surface.

19. The system further comprises at least one flame detector configured to detect when the supplied premixed gas is igniting and / or burning and to generate a corresponding flame signal. Preferably, the controller is further configured to control the premixed gas to have the second lambda value after receiving the flame signal from the detector, according to any one of claims 13 to 18.

20. A hydrogen gas combustion heating appliance comprising a burner according to any one of claims 13 to 19.