Premixed combustion processes and premixed burners

Abstract

In order to enable safe combustion with ultra-low NOx production, the invention provides a combustion process for burning a fuel-air mixture (except in gas turbines), comprising: a) complete premixing of 100% of an air flow (10) provided for combustion with (gaseous) fuel (12), where step a) comprises: b) adding a first portion (A.1) of the fuel (12) to the air flow (10) in a first premixing zone (14.1), so that a lean fuel-air mixture (16) which is not yet ignitable is formed; and c) admixing one or more remaining portions (An) of the fuel (12) to the lean fuel-air mixture (16) in at least one further premixing zone (14.n) which is spaced apart from the first premixing zone (14.1) in the flow direction in order to produce an ignitable fuel-air mixture (18) with excess air, where step c) comprises: d) swirling the fuel-air mixture (18) produced in the at least one further premixing zone (14.n). Furthermore, a premix burner (40) configured to carry out such premixing and combustion is proposed.

Description

This invention relates to a combustion method for burning a fuel-air mixture with premix. The invention further relates to a premixing burner.The invention is in the field of combustion processes for burning, in particular, gaseous fuel for buildings, ships, industrial vessels and industry, and in the field of burners for carrying out such combustion processes, as are described in particular in [6] to

[10] .For technological background, reference is made to the following references:[1] DE 43 29 971 A1[2] DE 36 06 625 A1[3] DE 1 264 668 B[4] US 2007 / 0207426 A1[5] US 2004 / 0018461 A1[6] WO 2018 / 141647 A1[7] "Technical information monoblock burner - weisdom burner monarch® - WM30 350 to 6.200 kW", company brochure of the Max Weisdom GmbH, download on 30.11.2023 at https: / / www.weisdom.de / uploads / tx_weisdom_documments / documents / 8 3211601.pdf[8] Web page of the Max Weisdom GmbH, product information Weisdom Brank Bauz WM monarch® download on 30.11.2023 at https: / / www.weisdom.de / produkt / bran / weisdom Baurenktypese- wm-monarchr-55-12000-kw[9] Weisdom Brank WKmono, company brochure of the Max-Weisdom GmbH, download on 30.11.2023 at https: / / www.weisdom.de / uploads / tx_weisdom_documments / documents / 8 3216401.pdf

[10] Weisdom Industrial Burner WK, Company brochure of the Max-Weisdom GmbH, download on 30.11.2023 at https: / / www.weisdom De / uploads / tx_weisdom Formulations / documents / 8:3159801.pdf

[11] Information sheet no. 66 of the Federal Association of the Deutsche Kerndustrie (BDH), download on 30.11.2023 at https: / / www.bdh-industrie.de / fileadmin / user_upload / publications / infoblaetter / infosheet_add_ 66_NOx-Emission_Feuerungsanlagen_022020.pdf

[12] Wikipedia: Nitric oxides; download on 30.11.2023 at https: / / de.wikipedia.org / wiki / Nitric oxidesHitherto, as described in [6], premix burners in which a fuel-air mixture is premixed before being added to a flame chamber have already been used in order to achieve low NOx emissions. In all known premix burners, a rich mixture is first produced which is leaned by adding air. However, with the burners known hitherto for the above-mentioned purposes of use, NOx emissions can only be achieved up to a certain limit.It is an object of the invention to provide methods and apparatuses with which stable combustion of gaseous fuel with ultra-low NOx generation is made possible.To achieve this object, the invention provides the combustion method according to claim 1.Advantageous embodiments are the subject matter of the dependent claims.According to a first aspect thereof, the invention provides a combustion method for burning a fuel-air mixture (mixture of gaseous fuel and air) comprising: a) fully premixing 100% of an air flow provided for the combustion with (gaseous) fuel, wherein step a) comprises:b) adding a first portion of the fuel to the air stream in a first premixing zone to form a lean fuel-air mixture that is not yet ignitable; andc) mixing one or more remaining portions of the fuel into the lean fuel-air mixture in at least one further premixing zone that is spaced apart from the first premixing zone in the direction of flow in order to produce an ignitable fuel-air mixture with excess air, wherein step c) comprises:d) Swirling of the fuel-air mixture.In embodiments of the invention, all the air provided for combustion is completely premixed; in particular, homogeneous mixing takes place. In some embodiments, a homogeneous ignitable fuel-air mixture is produced in which fuel and air are distributed homogeneously or uniformly throughout. In other words, there are no zones with a lower fuel concentration or a higher fuel concentration in the fuel-air mixture thus produced, in particular no zones of pure air without fuel. In order to achieve complete premixing, good mixing is initially carried out in at least one first premixing zone, with sufficient fuel being supplied to form an as yet non-ignitable but preferably already completely or largely homogeneous lean fuel-air mixture. In a second or more than two premixing zones, in particular in the last premixing zone, fuel is supplied in such a way that a preferably still lean, but ignitable homogeneous fuel-air mixture is formed. After the last premixing zone and the swirling, the homogeneous fuel-air mixture is present in particular with excess air.In some embodiments, the combustion method comprises the step of: generating the air flow by means of a blower.In some embodiments, the combustion method comprises the step of: preheating the air flow, in particular by means of a heat exchanger using exhaust gas heat.In some embodiments, the combustion method includes the step of: adjusting the velocity of the airflow.In some embodiments, the combustion method includes the step of: adjusting fuel sharing among the premixing zones.In some embodiments, the combustion method comprises the step of: creating a main flame from the fuel-air mixture after leaving a flame head in a combustion chamber.In some embodiments, the combustion method includes the step of: stabilizing a main flame generated with the ignitable fuel-air mixture by means of a primary flame.In some embodiments, the combustion method includes the step of: providing a larger exit area for the ignitable fuel-air mixture to a combustion chamber in a full load operation and a smaller exit area for the ignitable fuel-air mixture in a partial load operation.In some embodiments, the combustion method comprises the step of: dividing the fuel-air mixture via an outlet region with a defined outlet cross section and an outlet region with a controllable outlet cross section, and controlling the controllable outlet cross section depending on the combustion power to be generated.In some embodiments, the combustion method and in particular step a) comprises the step of: producing a homogeneous ignitable fuel-air mixture in which there is an identical distribution of fuel and air over the entire flow cross section at least at the end of the last premixing zone.In some embodiments, step b) comprises the step of:feeding from 10% to 80% of the fuel in the first premixing zone.In some embodiments, step b) comprises the step of:30% to 70% feeding of the fuel in the first premixing zone.In some embodiments, step b) comprises the step of:supplying 40% to 60% of the fuel in the first premixing zone.Particularly preferably, approximately equal proportions of the fuel are distributed over the premixing zones. The fuel is added successively and mixed well until a homogeneous ignitable fuel-air mixture with excess air is formed.In some embodiments, step b) comprises the step of:supplying fuel via at least one or more hollow bodies. According to some embodiments, the hollow bodies used are, in particular, a hollow body having nozzles distributed over the surface thereof, a hollow body having a perforated surface, a perforated gas tube, a gas tube having lateral bores, a gas tube having bores extending transversely with respect to the flow direction, a gas tube having bores extending longitudinally with respect to the flow direction, a partially annularly extending perforated hollow body, an annular perforated hollow body, a hollow annular body, which preferably extends with its central axis in the flow direction and has bores on at least one inwardly directed cylinder jacket surface and / or at least one outwardly directed cylinder jacket surface, a hollow swirl vane having bores, and a hollow body which combines a plurality of properties of the aforementioned hollow bodies.In some embodiments, step b) comprises the step of:creating a swirl in the air flow and supplying the first portion of the swirling air flow.In some embodiments, step b) comprises the step of:generating opposing swirls in the air flow in different ring regions of the first premixing zone.In some embodiments, step c) comprises the step of:Mixing the remaining portion in a second premixing zone.In some embodiments, step c) comprises the step of:Mixing the remaining portion in a second and a third premixing zone.In some embodiments, step c) comprises the step of:Mixing in a proportion of 1% to 15% of the fuel in a primary flame generating device for generating a primary flame. Preferably, the fuel content for the primary flame is between about 5% and about 15%. In particular, a proportion of less than 10% of the fuel is mixed in the primary flame-generating device, i.e. for example about 4, 5, 6 or 7%. By about values is meant in particular all values which are enclosed by a number rounded to an integer. For example, "about 5%" thus comprises in particular values between 4.50% and 5.49%.In some embodiments, step c) comprises the step of:Admixing fuel via at least one or more hollow bodies. According to some embodiments, the hollow body for mixing in the at least one further premixing zone is likewise in particular a hollow body having nozzles distributed over the surface thereof, a hollow body having a perforated surface, a perforated gas tube, a gas tube having lateral bores, a gas tube having bores extending transversely with respect to the flow direction, a gas tube having bores extending longitudinally with respect to the flow direction, a perforated hollow body extending partially annularly, an annular perforated hollow body, a hollow annular body, which preferably extends with its central axis in the flow direction and has bores on at least one inwardly directed cylinder jacket surface and / or at least one outwardly directed cylinder jacket surface, a hollow swirl vane having bores, and a hollow body which combines a plurality of properties of the abovementioned hollow bodies.In some embodiments, step c) comprises the step of:Admixing fuel via at least one opening in a baffle plate.In some embodiments, step d) comprises the step of:generating opposing swirls in the fuel-air mixture in different ring regions of the at least one further premixing zone.In some embodiments, step d) comprises the step of:generating a swirl in the fuel-air mixture when passing into the at least one further premixing zone.In some embodiments, step d) comprises the step of:creating a swirl prior to mixing.In some embodiments, step d) comprises the step of:creating a spin during mixing.In some embodiments, step d) comprises the step of:generating a swirl by means of gas-conducting and perforated swirl vanes.Particularly preferred embodiments optionally provide for a possible combustion of liquid fuel. In particular, an option is provided between a mode for burning gaseous fuel according to one of the preceding configurations and a mode for burning liquid fuel. In two-fuel operation, liquid fuel can also be burned in addition to the combustion of the gaseous fuel according to one of the aforementioned configurations.According to a further aspect, the invention provides a premixing burner comprising a flame tube, an air supply device for providing the entire air flow for combustion to the flame tube, a premixing device which is configured to receive 100% of the air flow from the air supply device and to premix it with fuel before it leaves the flame tube, and a swirl device, wherein the premixing device comprises a first fuel supply device having control means which are configured to add a first proportion of the fuel to the air flow in a first premixing zone, such that an as yet non-ignitable lean fuel-air mixture is formed, and at least one further fuel supply device having control means which is configured to add the remaining proportion or proportions of the fuel to the lean fuel-air mixture in at least one further premixing zone, which is spaced apart from the first premixing zone in the flow direction, in order to produce an ignitable fuel-air mixture with excess air, wherein the swirl device is designed at least for swirling the mixture formed in the at least one second premixing zone.In some embodiments, the control means are mechatronic control means in which an electronic, in particular computer-implemented control unit, for example, embodied as part of an overall control (e.g., firing manager) with processor and memory with software loaded accordingly therein, is combined with mechanical control elements, such as flaps, actuators, slides or permanently or variably set flow cross sections.In some embodiments, the combustor can includes a cylindrical shell. In some embodiments, the combustor can includes an inlet opening that is 100% arranged and configured to receive the airflow.In some embodiments, the combustor can includes an exit orifice region configured to discharge the fuel-air mixture into a combustion chamber for combustion. In some embodiments, the combustor liner has a taper near a downstream end. In some embodiments, the fire tube includes exit area adjustment means for adjusting the exit area of a portion of an exit opening area. In some embodiments, the combustor liner includes at least one gate for variably adjusting an outlet cross-section of the combustor liner.In some embodiments, the air supply device comprises a blower for generating the air flow. In some embodiments, the air supply device has a preheating device for preheating the air flow. In some embodiments, the air supply device comprises an exhaust gas heat exchanger for preheating the air flow with exhaust gas heat. In some embodiments, the air supply means comprises an exhaust gas supply means for supplying exhaust gas to the air flow. In some embodiments, the air supply device comprises control means for controlling the air flow. The control means of the air supply device in some embodiments are also mechatronic control means as explained above. As control means, for example, in a computer-implemented control of the premix burner, a control routine is provided as part of the control software, with which a blower of the air supply device and / or air flaps or the like are controlled. In some embodiments, the air supply device has a control interface which can be connected to a controller of the premix burner or to a superordinate controller.In some embodiments, the premixing device includes the first premixing zone and a second premixing zone spaced therefrom in the flow direction. In some embodiments, the premixing device includes first, second and third premixing zones arranged in series in the direction of flow. In some embodiments, the premixing device has fixed or variable adjusted fuel flow areas for dividing the proportions of fuel to the first and each further fuel supply device. In some embodiments, the premixing device includes an adjuster for adjusting fuel split. In some embodiments, the premixing device includes a fuel distribution ring for distributing fuel to the plurality of premixing zones. In some embodiments, the premixing device comprises control means (in particular mechatronic control means as explained above) for controlling the fuel supply. In some embodiments, the premixing device has a control interface connectable to a controller.In some embodiments, the first fuel supply device has an inflow cross section which is dimensioned relative to an inflow cross section of the at least one further fuel supply device such that the predetermined first portion of the fuel flows through the first fuel supply device. In some embodiments, the first fuel supply means comprises adjusting means for adjusting the inflow cross section. In some embodiments, the first fuel supply device comprises at least one or more hollow bodies for supplying the fuel. According to some embodiments, the hollow bodies used of the first fuel feed device are, in particular, a hollow body having nozzles distributed over the surface thereof, a hollow body having a perforated surface, a perforated gas tube, a gas tube having lateral bores, a gas tube having bores extending transversely with respect to the flow direction, a gas tube having bores extending longitudinally with respect to the flow direction, a perforated hollow body extending partially annularly, an annular perforated hollow body, a hollow annular body, which preferably extends with its central axis in the flow direction and has bores on at least one inwardly directed cylinder jacket surface and / or at least one outwardly directed cylinder jacket surface, a hollow swirl vane having bores, and a hollow body which combines a plurality of properties of the aforementioned hollow bodies. In some embodiments, the first fuel supply device includes computer implemented control means for controlling fuel supply.For example, these are provided as part of control software in a controller of the premixing burner.In some embodiments, the one or more further fuel supply devices have an inflow cross section which is dimensioned relative to the inflow cross section of the first fuel supply such that the predetermined further portion of the fuel flows through the respective further fuel supply device. In some embodiments, the one or more further fuel feeders include a second fuel feeder in a second premixing zone. In some embodiments, the one or more further fuel feeders include a third fuel feeder in a third premixing zone. In some embodiments, the one or more further fuel supply devices comprise a pilot flame fuel supply device for supplying a proportion of the fuel smaller than the proportions of the first fuel supply and a second fuel supply by at least a factor of 3 to a pilot flame. In some embodiments, the one or more further fuel feed devices comprise an adjustment device for adjusting an inflow cross section of the further fuel feed. In some embodiments, the one or more further fuel supply devices each have at least one or more hollow bodies for the admixture of the further fuel components. According to some embodiments, the hollow bodies of the respective further fuel feed device used are, in particular, a hollow body having nozzles distributed over the surface thereof, a hollow body having a perforated surface, a perforated gas tube, a gas tube having lateral bores, a gas tube having bores extending transversely with respect to the flow direction, a gas tube having bores extending longitudinally with respect to the flow direction, a perforated hollow body extending partially annularly, an annular perforated hollow body, a hollow annular body, which preferably extends with its central axis in the flow direction and has bores on at least one inwardly directed cylinder jacket surface and / or at least one outwardly directed cylinder jacket surface, a hollow swirl vane having bores, and a hollow body which combines a plurality of properties of the aforementioned hollow bodies. In some embodiments, the one or more further fuel feeders comprise computer implemented control means for controlling the fuel supply. These too are provided, for example, as part of the control software in the control of the premix burner.In some embodiments, the swirl device comprises a swirl unit for swirling the air flow entering the first premixing zone. In some embodiments, the swirl device has a counter-swirl device for generating swirl with opposite swirl directions in different annular zones of the flame tube. In some embodiments, the swirl device has a first swirl unit in or upstream of the first premixing zone and at least one further swirl unit in the transition to or in a further premixing zone. In some embodiments, the swirl device includes an inner array of swirl vanes and an outer array of swirl vanes. In some embodiments, the swirl device has swirl vanes designed as hollow bodies with nozzles for supplying fuel. In some embodiments, the swirl device comprises a primary flame swirl unit on a baffle plate.In some embodiments, the premix burner further includes a baffle for stabilizing a primary flame. In some embodiments, the premix burner further includes liquid fuel nozzles for delivering liquid fuel into a combustion chamber downstream of the combustor liner. In some embodiments, the premix burner further includes a controller with processor and memory. In some embodiments, the premix burner further comprises control means for controlling the ratio of fuel to air flow. As explained above, the control means are preferably mechatronic control means. In some embodiments, the premix burner further includes a controller configured to cause the premix burner to perform any of the embodiments of the combustion method discussed above.According to a further aspect, the invention provides a controller for a premix burner according to one of the preceding configurations, which controller is configured to cause the premix burner to automatically carry out one of the embodiments of the combustion method explained above.According to a further aspect, the invention provides a computer program comprising instructions which cause a premix burner according to one of the preceding configurations to carry out the combustion method according to one of the embodiments explained above.In the following, particular effects of advantageous embodiments of the invention are explained in more detail. In prior combustion processes in which fuel is premixed with air, an excessively rich fuel-air mixture is intentionally produced, to which a further air stream is then added in order to achieve a cooler flame temperature. Thus, the generation of thermal NOx can be reduced. The reduction of thermal NOx has up to now been solely in focus in the prior art, as is explained in more detail in

[11] .However, as explained in

[12] , nitrogen oxides in the furnace are usually divided into three types according to their sources and the formation mechanism, namely, thermal NOx, fuel NOx and prompt NOx. Thermal NOx is formed due to oxidation of the nitrogen contained in the air at relatively high temperatures. Only here are previous combustion concepts starting for NOx reduction, see

[11] . Sources of fuel NOxare the proportions of nitrogen bound in the fuel. This proportion is dependent on the fuel used and cannot be reduced if a predetermined fuel, such as ammonia or biogas, is to be burned. However, the proportion of fuel NOx is subordinate to some gaseous fuels, such as natural gas, and is only very small.With the combustion method according to the invention and its advantageous configurations and the premix burners according to the invention and its advantageous configurations configured to carry out the combustion, it is also possible to reduce the formation of prompt NOx, so that now it is also possible to achieve a NOx reduction over the previously possible extent. In order to achieve a clearly below 50 mg NOx per standard cubic meter during the combustion of gaseous fuels such as natural gas, the prompt nox is also taken into account according to the invention.In some embodiments of the invention, the 100 percent combustion air flow is passed through a pre-mix region of a burner in which at least a first pre-mix zone and a second pre-mix zone are spaced apart in the direction of flow. In the first premixing zone located upstream, fuel (gas) is fed in such a way that the mixture formed is not ignitable. For example, the combustion air ratio λ is greater than 2. in the downstream second (or a third or further) premixing zone, which is still located in the premixing region through which the combustion air is conducted, a further part of the fuel is admixed in such a way that an ignitable mixture is now produced. Advantageously, excess air is still used to cool the flame and reduce the generation of thermal NOx. For example, the ignitable mixture is still lean with a combustion air ratio λ greater than 1. swirl generation exists in order to achieve good mixing. The ignitable mixture is directed to the combustion chamber through a flow cross-sectional area which, in some embodiments, can be reduced for part-load operation.By producing a completely premixed gas-air mixture, the formation of prompt NOxis avoided or at least significantly reduced. Nevertheless, the load is well controllable and there is no back ignition.The combustion method according to advantageous embodiments of the invention makes do without metal grids or other measures for avoiding a flame breakdown. Ignitable fuel mixture is formed only in the last premixing zone in the direction of flow. There, the flow velocity can be kept so high that back-blows of the flame are avoided. If, however, the flame flash back occurs, the volume of ignitable mixture is very small. A high flow velocity can thus be achieved, so that high combustion capacities can be achieved, wherein a stable combustion method can nevertheless be achieved despite extremely low NOx generation.Accordingly, in the invention, a complete premixing is carried out in such a way that fuel is initially supplied to the air stream in a first premixing zone, with the result that the mixture formed is not yet ignitable, and further fuel is supplied up to the flammability in at least one second premixing zone which is still located in the premixing region within the air stream.Preferred embodiments relate to a combustion method which is skied as above and which can be carried out, for example, with a corresponding design and control of a premix burner. In particular, advantageous embodiments include a corresponding control of a premixing burner. Further embodiments relate to a control means which is correspondingly configured for carrying out the combustion method with corresponding premixing zones, fuel feeds and control means, in particular at least partially computer-implemented control means (that is to say not only suitable but actually configured therefor).Preferred embodiments of the premixing burner proceed from the prior art according to one of the literature references [6] to

[10] and have embodiments known from these literature references-provided they are not replaced by the special features according to embodiments of the invention which are explained in more detail below. Reference is therefore made for more detailed possible embodiments to references [6] to

[10] , which are incorporated by reference.Exemplary embodiments of the invention are explained in more detail below with reference to the attached drawings. The following shows: FIG. 1 is a block diagram illustrating an ultra-low NOx generation premixed combustion process and some components of a premixed burner configured to perform the combustion process, according to advantageous embodiments; FIG. 2 shows an axial longitudinal section through a burner head of a first embodiment of a premix burner for carrying out the combustion process; FIG. 3 shows an axial longitudinal section through a burner head of a second embodiment of a premix burner for carrying out the combustion process; FIG. 4 is a block diagram illustrating a configuration of the combustion method at full load that can be carried out with the premixing burner with the burner head according to FIG. 2 ; FIG. 5 is a block diagram illustrating a partial load configuration of the combustion method that can be carried out with the premix burner with the burner head according to FIG. 2 ; FIG. 6 shows a perspective illustration of a premixing device for a burner head of a premixing burner according to a further configuration for carrying out the combustion process; FIG. 7 shows an axial longitudinal section through the burner head with the premixing device from FIG. 6 in an adjustment for full load operation, wherein an air flow and also curves of fuel and fuel-air mixtures are shown; FIG. 8 shows an axial longitudinal section through the burner head similar to FIG. 6 in an adjustment for partial load operation, wherein fuel profiles are shown, wherein a variant of the premixing device is shown; FIG. 9 shows a perspective illustration of the premixing device of the burner head from FIG. 8 ; FIG. 10 shows a perspective illustration of a mixing device in two-component embodiment gas / liquid fuel with fuel division for a burner head with the premixing device according to FIGS. 8 and 9 ; and FIG. 11 shows a section through a burner head with a mixing device of two-substance design, which has the premixing device according to FIG. 8 or FIG. 9 and a central atomizing nozzle for liquid fuel.Referring now to FIGS. 1, 4 and 5, there are shown block diagrams of a combustion method for burning a fuel-air mixture in which gaseous fuel is premixed with air.In the combustion method, 100% of an air flow 10 provided for the combustion is completely premixed with gaseous fuel 12. The step of fully premixing includes the steps of:• adding a first portion A.1 of the fuel 12 to the air flow 10 in a first premixing zone 14.1, so that an as yet non-flammable lean fuel-air mixture 16 is produced; and• Admixing the remaining portion or portions A.n of the fuel 12 to the lean fuel-air mixture 16 in at least one further premixing zone 14.n, which is spaced apart from the first premixing zone 14.1 in the direction of flow, in order to produce an ignitable fuel-air mixture 18 with excess air (n here denotes a natural number greater than 1).At least the admixing step further comprises the step of: swirling the fuel-air mixture 18.For example, at least a first premixing zone 14.1 and a second premixing zone 14.2 are provided. Further premixing zones 14.n, such as a third premixing zone 14.3, for example, can also be provided.In some embodiments, a completely homogeneous ignitable fuel-air mixture 18 with excess air is produced by admixing fuel in a plurality of premixing zones and swirling. Therein, at least in the region of an inflow cross section 70 for the inflow of the fuel-air mixture 18 into a combustion chamber 60, the fuel is distributed over the entire flow cross section with the same concentration in the air. In some embodiments, the formation of prompt NOxis prevented or at least significantly reduced, in particular by such a "homogeneous premixing" in the second / last premixing zone.Preferred embodiments of the method are further characterized in that a possibility for the combustion of liquid fuels can be integrated.The first premixing zone 14.1 is assigned a first fuel supply device 20.1, which is controlled by suitable control means, which comprise actuators 22 and an electronic control unit 24, in such a way that the first fraction A.1 of fuel 12 is supplied to the air stream 10 in such a way that the still non-ignitable lean fuel-air mixture 16 is produced in the first premixing zone 14.1. Each further premixing zone 14.n is assigned a further fuel supply device 20.n, which is likewise controlled by means of the control means in such a way that the remaining fraction or fractions A.n of fuel 12 are supplied to the lean fuel-air mixture 16 in such a way that the ignitable fuel-air mixture 18 with excess air is formed at least in the last further premixing zone 14.n in the direction of flow.At least in or on the last premixing zone 14.n in the direction of flow, a swirl unit 26 of a swirl device 28 is provided for swirling the fuel-air mixture 16, 18. As is shown in FIG. 1 with dashed lines, the other premixing zones 14.1 can also be provided with a swirl unit 26.The respective fuel supply device 20.1, 20.n has at least one hollow body 30 for discharging the fuel 12. The hollow body 30 is provided in particular with nozzles or bores in such a way that the fuel 12 is added as well as possible distributed to the premixing zone 14.1, 14.2. This contributes to homogeneous premixing. Gas pipes 32 are provided as hollow bodies 30, for example, which can extend in the flow direction or transversely to the flow direction, for example, and preferably have bores distributed over their surface. Furthermore, ring elements 34 with a cylindrical inner side and outer side, which have gas outlet openings distributed over them, can be provided as hollow bodies 30. In some embodiments, swirl vanes 36 of the swirl device 28 are provided as hollow bodies 30, which have gas outlet openings distributed on their surface in order to feed or mix the gaseous fuel 12.FIG. 1 also shows a block diagram of a premixing burner 40, which is configured to carry out the combustion method. The premixing burner 40 has a burner head 42 (also referred to as a flame head) with a flame tube 44 which is omitted for clarity in FIG. 1, but is illustrated in FIGS. 2, 6, 7 and 10, and a premixing device 46. The premixing zones 14.1, 14.n are formed in the flame tube 44. The premixing device 46 has the fuel feed devices 20.1, 20.n. An air supply device 48 for providing the air flow 10 is formed, for example, by a blower 50. The premix burner 40 further includes an electronic controller 52 with processor 54 and memory 56. The memory 56 stores a control routine as software (computer program). The controller 52 controls the blower 50 and actuators of the premixed burner 40 to perform the above-mentioned combustion process. The controller 52 thus also provides at least a portion of the fuel supply control means as part of the control routine.FIG. 1 also shows a combustion chamber 60 with the flame 62 generated during the combustion downstream of the flame head, as well as an optional exhaust gas recirculation 64 for adding exhaust gas to the inlet of the air supply device 48, as well as a likewise optional air heating device 66 for heating the combustion air. For example, the air is preheated with heat from the exhaust gas by means of an exhaust gas heat exchanger 68 upstream of the blower 50.As is also shown schematically in FIG. 1 by dashed lines, an outlet cross section 70 for the ignitable fuel-air mixture 18 can optionally be changed with excess air by means of suitable control elements that can be controlled by the controller 52. The outlet cross section 70 has, for example, a fixed outlet cross section area 70.1 and a variable outlet cross section area 70.2 that can be changed by means of an actuator, such as a movable air slide 72. Thus, in a full load operation, a larger outlet cross section for the ignitable fuel-air mixture 18 can be provided to the combustion chamber 60, and 18 in a partial load operation, a smaller outlet cross section for the ignitable fuel-air mixture can be provided.For example, the fuel 12 is divided-in particular by providing or setting flow cross sections of the corresponding gas feed lines 58.1, 58.n-at the same or optionally at different proportions A1, A.n-into the different premixing zones 14.1, 14.n. The total amount of fuel 12 is controlled via the controller 52 in accordance with the desired load and the air flow 12 set for this purpose by the blower 50. The combustion air flow--air flow 10--is conducted at 100 percent through a premixing region of the premixing burner 40, in which at least the first premixing zone 14.1 and a second premixing zone 14.2 are spaced apart from one another in the direction of flow. In the first premixing zone 14.1 located upstream, fuel 12 (gas) is fed in such a way that the mixture 16 formed is not ignitable. For example, the combustion air ratio λ is greater than 2. in the downstream second (or a third or further) premixing zone 14.2, 14.n, which is still located in the premixing region through which the combustion air is conducted, a further part A.n of the fuel 12 is admixed in such a way that an ignitable mixture 18 is now produced. Advantageously, excess air is still used to cool the flame 62 and reduce the generation of thermal NOx. For example, the ignitable mixture 18 is still lean with a combustion air ratio λ greater than 1. swirl generation at least at the last premixing zone in the flow direction optionally also at at least one or all of the other premixing zones 14.1, 14.2, 14.n, in order to achieve good mixing. The ignitable mixture 18 is conducted through a flow cross-sectional area 70.1, 70.2 to the combustion chamber 62, which in some embodiments can be reduced for part load operation.FIG. 2 shows a first specific exemplary embodiment of the burner head 42 of the premixing burner 40, this embodiment starting from the burners shown in the documents [9] and

[10] , which are provided with the premixing device 46 in the burner head 42 shown in FIG. 2, the software being set up in the controller 52, which is designated as firing manager in the documents [9] and

[10] , in accordance with the execution of the combustion method shown here.The premixing device 46 shown in FIG. 2 has the first premixing zone 14.1, the second premixing zone 14.2, a third premixing zone 14.3 and also a pilot flame-generating zone 76. The pilot flame generating region 76 has a conical slotted baffle plate 78, over which a portion of the lean fuel-air mixture 16 is conducted for providing primary air for a pilot flame and which generates a primary swirl at this portion. The first and second premixing zones 14.1, 14.2 each have perforated gas pipes 32 running in the flow direction and transversely to the flow direction. The third premixing zone 14.3 has the gas-conducting swirl vanes 36.Optionally, the premix burner 46 shown in FIG. 2 can be provided for two-component operation with secondary nozzles 80 for heating oil. Natural gas N is fed as fuel 12 to the premixing device 46. An adjustment device 82 is also provided for adjusting the division of the fuel 46 between the premixing zones 14.1, 14.2, 14.3.FIG. 2 shows in particular an ultra-low NOx WK burner, for example in the form of a gas and two-component burner, for very high powers, for example of 200 to 18 000 kW.The premix burner 46 has the following NOx mitigation technique for operating with natural gas N. Premixing fuel 12 and air 10 reduces the formation of prompt NOx, in contrast to the classic diffusion flame. The flame temperature is lowered by means of a high excess of air. This reduces the formation of thermal NOx. The premix flame is characterized by its compactness or short flame length.Fuel 12 is supplied via the first premixing zone 14.1 and the second premixing zone 14.2 via the gas pipes 32 (along and transversely with respect to the burner axis) with bores of the combustion air 10 or the lean fuel-air mixture 16. In the third premixing zone 14.3, fuel 12 is fed directly to the swirling flow of the fuel-air mixture 16 via fuel-conveying swirl vanes 36. The fuel / air mixture 18 which is then ignitable leaves the flame head 42 into the combustion chamber 60, in which the main flame generated by the fuel-air mixture 18 is stabilized by a primary flame and burned off. The primary flame stabilizes by means of a conical slot baffle 78 and a primary swirl.A small part (for example, smaller by an order of magnitude, at least by a factor of 3 to 10, than the other parts) of the total fuel quantity is fed onto the pilot flame generation region provided with the baffle 78. The primary flame (this may be a diffusion flame or a premix flame) stabilizes the main flame.Advantages of stabilization with the pilot flame (also called primary flame) are, for example, defined, constant ignition conditions for the premixed air / fuel volume 18; reliable ignition and process monitoring. For example, a probe 84 indicated in FIG. 1 is used to measure a parameter for the combustion process, for example an ionization current of the primary flame.In the embodiment shown in FIG. 2, adjustment possibilities for the supplied fuel quantity into the three premixing zones 14.1, 14.2, 14.3 are located on a fuel distributor ring 86. In a simplified embodiment, the quantity of fuel can be adjusted by means of variable, adjustable locking means by means of screw threads in all inflow cross sections of the feed pipes.By means of the air slide 72, outlet cross sections 70, 70.2 at the flame head 42 are reduced in size towards the partial load. This causes a pressure build-up and thus a flow velocity build-up and prevents the back ignition of the flame 62 into the premixing zones 14.1, 14.n even in the partial load range.The fuel injection into the premix is effected by arranging perforated tube cross sections and / or any desired hollow geometric bodies 30 with nozzles. In the embodiment of FIG. 2, gas pipes 32 with bores and hollow swirl vanes 36 with likewise bores are used as gas outlet.A possibly additional atomizing unit can be provided with a spray unit, for example in burners of the Germany. Max Weisdoat GmbH, sold under the trademark multiflam® can be operated using a conventional diffusion flame.To increase the plant efficiency, preheated combustion air can be supplied to the flame head 42 via the optional exhaust gas heat exchanger 68.To reduce the excess air ratio, for comparable pollutant emissions, exhaust gas recirculated via the combustion air fan can alternatively be mixed from the boiler end of the combustion air. This allows pollutant emissions to be reduced.FIG. 3 shows a second embodiment for the burner head 42 of the premixing burner 40, which is substantially the same as the first embodiment, but in an embodiment with only a first and a second premixing zone 14.1, 14.2. The gas tubes 32 arranged more centrally in the direction of flow, which in the first embodiment form a middle premixing zone arranged between the first and last premixing zones, are omitted in the second embodiment. Otherwise, the second embodiment corresponds to the first embodiment, so that for further details reference is made to the above description of the first embodiment.FIG. 4 shows a block diagram for a purely exemplary full-load operation of the premixing burner 40, in particular of the type illustrated in FIG. 2 : FIG. 4 shows more specifically simplified gas streams (fuel streams) G and air streams L for the premixing device 46 for an ultralow NOx burner of the series WK, derived from the known burners according to [9] and

[10] at full load VL. FIG. 5 shows a block diagram for an exemplary part load operation of the same premix burner 40. The block diagrams are self-explanatory taking into account the following label:B gas streams L air streams and mixture streams VL full load TL partial load 100 within first premixing zone 14.1 102 close to the flame head outlet (further premixing zone(s)) 62 flame 104 "λ"=1.45 (example of combustion air ratio ignitable fuel-air mixture 18) 106 full load: 10,000 kW / λ=1.45 / O 2,tr.= 7% 108 air damper 72 opened 110 gas concentration 2.3 vol %<<EEG !!! (λ=1.45) (When λ=1 is driven, the gas concentration is 3.3 vol %<<EEG). 112 fictive λ=4.48 114 combustion air (100%) 116 13,800 m N3 / h (example for 100% combustion air flow 10) 118 312 m N3 / h (example value for fuel supply) 120 first gas introduction via perforated tubes (A.1=32%-example) 122 tertiary mixture via air slide valves (example: 50%) 124 6,900 m N3 / h 126 second gas introduction via perforated gas tubes (A.2=32%-example) 128 secondary mixture via secondary swirl (example: 38%) 130 5,200 m N3 / h 132 third gas introduction via hollow swirl vanes (A.3=32%-example) Example) 134 Primary mixture via primary swirl (12%) 136 1.700 m N3 / h 138 29 m N3 / h ≈ 3% (A.4 fraction of the fuel for pilot flame) 140 Minimum amount of primary gas via baffle plate 142 Gas concentration 6.8% by volume 144 Gas concentration 8.2% by volume 146 Secondary flame (= Haupt flame) 148 Gas concentration 4 by volume 150 Primary flame (=Pilot flame) 152 Partial load: 3.500 kW / λ=1.45 / O 2,tr.= 7% 154 Air damper 72 closed 156 4.800 m N3 / h 158 109 m N3 / h 160 Tertiary mixture via Air damper (0%) 162 secondary mixture via secondary swirl (75%) 164 3,600 m N3 / h 166 primary mixture via primary swirl (25%) 168 1,200 m N3 / h 170 10 m N3 / h ≈3% 172 gas concentration 8.2 vol% 174 gas concentration 3.1 vol%The values indicated in FIGS. 4 and 5 are merely exemplary of a design of a specific burner, depending on the design, the values can deviate upward or downward-in particular with identical ratios to one another, for example by a factor which is in the range of 0.3-4, in particular 0.5-2. In particular, the partial load can vary. The values are calculated on standard volumes, assuming an immediate ideal mixture. The values are to be regarded as a rough estimate. The illustrations in FIGS. 4 and 5 represent the processes in the premixing device 46 in a greatly simplified manner. UEG denotes the lower ignition limit; this is E=4.9 vol % for natural gas in the example. OEG denotes the upper ignition limit; in the example for natural gas E=14.7% by volume.In the following, further embodiments for premix burners 40 are explained with reference to FIGS. 6 to 11, which-because of the design of the fuel distribution and the computer-implemented controller 52-are configured to carry out combustion methods with ultra-low NOx reduction explained above with reference to FIG. 1 by way of example, taking the prompt NOx into account.The exemplary embodiments shown in FIGS. 6 to 11 are designed in particular for a medium power range and proceed in particular from known burners, as are explained in the literature references [7] and [8], wherein instead of the burner heads or flame heads shown there, the embodiments of burner heads 42 with the premixing devices 46 explained below with reference to FIGS. 6 to 11 are provided, and wherein the software is modified in the control system referred to as firing manager in the literature references [7] and [8], so that 100% of the total air flow 10 is supplied in the first premixing zone 14.1 in such a way that the still non-ignitable lean fuel-air mixture 16 is formed, to which fuel-air mixture in at least one further premixing zone 14.n, and optionally in a pilot flame generation region 76, the remaining portion or portions A.n of the fuel are supplied in such a way that the ignitable fuel-air mixture 18 is formed with excess air under the action of swirl. As mentioned above, the complete, i.e. homogeneous, premixing avoids or at least greatly reduces prompt-NOx.FIG. 6 shows the premixing device 46 in a variant without the flame tube 44, FIG. 7 shows premixing device 46 in the burner head 42 with flame tube 44 and air or mixture flows L and fuel flows B in a setting for full-load operation. FIG. 8 shows the burner head 42 with flame tube 44 and premixing device 46 in a slightly modified variant in an adjustment for part-load operation, wherein fuel streams B are indicated. FIG. 9 shows a further variant of the premixing device 46, and FIGS. 10 and 11 show optional embodiments of the burner head 42 with the premixing device 46 for two-component operation (gas / liquid fuel such as oil).In the embodiments of FIGS. 6 to 11, in addition to the first premixing zone 14.1 with the first fuel feed 20.1, only a second premixing zone 14.2 with the second fuel feed 20.2 is provided.As hollow body 30, the fuel feeds 20.1, 20.2 also each have, in addition to a central perforated gas tube 32, an annular body 34 with a cylinder-jacket-shaped inner wall and a cylinder-jacket-shaped outer wall, both of which have gas outlet openings distributed over their surface. In a variant not shown, only one of the fuel feed lines, for example the second fuel feed line 20.2, is provided with the annular body 34, the first fuel feed line, on the other hand, has gas tubes which extend, for example, radially transversely to the flow direction.The swirl device 28 has at least one, preferably a plurality of counter-swirl devices 88, for generating swirl with opposite swirl directions in different annular zones of the flame tube 44.In particular, a first swirl unit 26.1 is provided in or preferably upstream of the first premixing zone 14.1 and at least one second swirl unit 26.2, 26.n is provided in the transition to or in the further second premixing zone 20.2, 20.n. In the variant shown in FIGS. 6 and 7, a third swirl unit 26.3 is provided (e.g. at an inlet opening 98 of a sheathing 96 of a bluff body), which is omitted in the other variants shown in FIGS. 8 to 11. In the embodiments shown, each swirl unit 26.1, 26.2, which is designed as a counter-swirl device 88, has an inner arrangement 90 of swirl vanes 92.1 (here designed as simple metal sheets without an inner gas duct) and an outer arrangement 92 of swirl vanes 92.2. The inner swirl vanes 92.1 are provided with an opposite pitch / inclination to the outer swirl vanes 92.2.FIG. 7 shows the extension of the first premixing zone 14.1, in which non-flammable lean fuel-air mixture 16 is formed, and of the second premixing zone 14.2, in which flammable fuel-air mixture 18 is formed homogeneously with excess air.The burner head 42 is further provided, as explained above with reference to the embodiment of FIG. 2, with the pilot flame generating region 76 with the swirl-generating baffle 78.Furthermore, a conical jacket 96 is provided near the outlet of the flame tube 44. Between the conical jacket 96 and the mouth of the flame tube 44, the outlet cross section 70 is formed. The casing 96 is displaceable and thus forms the air slide 72 for adapting the outlet cross section 70, 70.1, 70.2.At the upstream end, the shroud 96 has a mixture inlet port 98 for supplying the pilot flame. The cross section of the inlet port 98 is smaller than the cross section between the upstream end of the shroud and the combustor can.Due to the tapering of the flow cross section between jacket 96 and flame tube and due to the outlet cross section 70, a high velocity is formed near the end of the flame head, so that no back ignition can occur in the second premixing zone 14.2. If, contrary to expectation, a re-ignition nevertheless occurs, then only the second pre-mixing zone 14.2 contains ignitable mixture 18, so that only a very small critical mass is present.As a comparison of FIGS. 7 and 8 shows, by displacement of the casing 96, the outlet cross section 70 can be reduced for partial load operation, so that even in partial load operation, the high speed can be maintained despite a lower mixture 18 flowing per unit time, in order to further avoid back ignition.FIG. 8 further illustrates a self-centering 180 for the premixing device 46, which simplifies the assembly. In addition, a gas guide 181 for uniform pressure distribution is shown, which is improved compared to burners known hitherto. In a pivoting flange region 182 that is not tight due to its function (not shown in detail, since it is already known from [8] and [9]), there is no gas / air mixture.FIG. 10 shows an optional two-component embodiment of gas / liquid fuel (e.g. oil), wherein, in addition to the premixing device 46 with the different premixing zones 14.1, 14.2 for gas operation, a fuel distribution 184 for liquid fuel, such as oil, is also shown, as is already fundamentally known in multiflam® burners. Instead of or in addition to the fuel division 184, a central atomizing nozzle 186, for example, centrally in the baffle plate 78, can also be provided, as shown in FIG. 11.In order to enable safe combustion with ultra-low NOx generation, a combustion method for burning a fuel-air mixture (except in gas turbines) has been proposed, comprising: a) completely premixing 100% of an air flow (10) provided for the combustion with (gaseous) fuel (12), wherein step a) comprises:b) adding a first portion (A.1) of the fuel (12) to the air flow (10) in a first premixing zone (14.1) to form an as yet non-flammable lean fuel-air mixture (16); andc) Admixing one or more remaining portions (A.n) of the fuel (12) to the lean fuel-air mixture (16) in at least one further premixing zone (14.n) which is spaced apart from the first premixing zone (14.1) in the direction of flow in order to produce an ignitable fuel-air mixture (18) with excess air, wherein step c) comprises:d) Swirling of the fuel-air mixture (18) formed in the at least one further premixing zone (14.n).Furthermore, a premixing burner ( 40) correspondingly designed for carrying out such premixing and combustion has been proposed.List of reference numbers:10 Air flow 12 Fuel (gaseous) 14.1 First premixing zone 14.n Further premixing zone (nth premixing zone, where n>1) 16 non-ignitable lean fuel-air mixture 18 ignitable fuel-air mixture with excess air 20.1 first fuel supply device 20.n further fuel supply device (nth fuel supply device) 22 actuator 24 electronic control unit 26 swirl unit 26.1 first swirl unit 26.2 second swirl unit 26.3 third swirl unit 28 swirl device 30 hollow body for supplying or admixing fuel 32 gas pipe 34 annular body 36 swirl vanes 40 premix burner 42 burner head (flame head) 44 flame pipe 46 premix device 48 air supply device 50 blower 52 controller (for example for electronic part of the control means) 54 processor 56 store 58.1 gas supply line of the first fuel supply device 58.n gas supply line of the further (nth) fuel supply device 60 combustion chamber 62 flame 64 EGR 66 Air heating device 68 Exhaust gas heat exchanger 70 Outlet cross section 70.1 Fixed outlet cross section region 70.2 Variable outlet cross section region 72 Air slide 76 Pilot flame generation region 78 Baffle plate 80 Secondary nozzle 82 Adjusting device 84 Probe 86 Fuel distribution ring 88 Counter-swirl device 90 Inner arrangement 92 Swirl vane 94 Outer arrangement 96 Casing 98 Inlet opening 100 within first premixing zone 14.1 102 Near Flamehead outlet (further premixing zone(s)) 104 "X"=1.45 (example of combustion air ratio of ignitable fuel-air mixture 18) 106 Full load: 10,000 kW / λ=1.45 / O 2,tr.= 7% ( example of parameters at full load) 108 Air slide 72 Opened 110 Gas concentration 2.3 vol %<<EUG !! (λ=1.45) (If λ=1 is driven, the gas concentration is 3.3 vol %<<EEG). 112 fictive λ=4.48 114 combustion air (100%) 116 13,800 m N3 / h (example for 100% combustion air flow 10) 118 312 m N3 / h (example value for fuel supply) 120 first gas introduction via perforated tubes (A.1=32%-example) 122 tertiary mixture via air slide valves (example: 50%) 124 6,900 m N3 / h 126 second gas introduction via perforated gas tubes (A.2=32%-example) 128 secondary mixture via secondary swirl (example: 38%) 130 5,200 m N3 / h 132 third gas introduction via hollow swirl vanes (A.3=32%-example) Example) 134 Primary mixture via primary swirl (12%) 136 1.700 m N3 / h 138 29 m N3 / h ≈ 3% (A.4 fraction of the fuel for pilot flame) 140 Minimum amount of primary gas via baffle plate 142 Gas concentration 6.8% by volume 144 Gas concentration 8.2% by volume 146 Secondary flame (= Haupt flame) 148 Gas concentration 4 by volume 150 Primary flame (=Pilot flame) 152 Partial load: 3.500 kW / λ=1.45 / O 2,tr.= 7% 154 Air damper 72 closed 156 4.800 m N3 / h 158 109 m N3 / h 160 Tertiary mixture via Air damper (0%) 162 secondary mixture via secondary swirl (75%) 164 3,600 m N3 / h 166 primary mixture via primary swirl (25%) 168 1,200 m N3 / h 170 10 m N3 / h ≈3% 172 gas concentration 8.2 vol % 174 gas concentration 3.1 vol % 180 self-centering 181 gas guide 182 swivel flange region 184 fuel division (liquid fuel / oil) 186 central atomizer nozzle A.1 first fraction A.n n-th fraction B gas streams L air streams and mixture streams VL full load TL partial loadReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 43 29 971 A1

[0003] DE 36 06 625 A1

[0003] DE 1 264 668 B

[0003] US 2007 / 0207426 A1

[0003] US 2004 / 0018461 A1

[0003] WO 2018 / 141647 A1

[0003] Cited Non-Patent LiteratureTechnical information Monoblock Burner - Weisdom Burner monarch® - WM30 350 to 6.200 kW", company brochure of the Max Weisdom GmbH, download on 30.11.2023 at https: / / www.weisdom.de / uploads / tx_weisdom_documules / documents / 8 3211601.pdf

[0003] Web page of the Max Weisdom GmbH, Product information Weisdom Brank Bauz WM monarch® download on 30.11.2023 at https: / / www.weisdom.de / produkt / bran / weisdom Branktypeseit-wm-monarchr-55-12000-kw

[0003] Weisdom Industrial Burner WK, Company brochure of the Max-Weisdom GmbH, download on 30.11.2023 at https: / / www.weisdom De / uploads / tx_weisdom _documments / documents / 8:3159801.pdf

[0003] Information sheet no. 66 of the Federal Association of the Deutsche Kernustrie (BDH), download on 30.11.2023 at https: / / www.bdh-industrie.de / fileadmin / user_upload / publications / infoblaetter / infosheet_add_ 66_NOx-Emission_Feuerungsanlagen_022020.pdf

[0003] https: / / de.wikipedia.org / wiki / Noxide

[0003]

Claims

A combustion method for burning a fuel-air mixture, comprising: a) fully premixing 100% of an air flow (10) provided for combustion with fuel (12), wherein step a) comprises: b) adding a first portion (A.1) of the fuel (12) to the air flow (10) in a first premixing zone (14.1) to form an as yet non-flammable lean fuel-air mixture (16); and c) mixing one or more remaining portions (A.n) of the fuel (12) into the lean fuel-air mixture (16) in at least one further premixing zone (14.n) which is spaced apart from the first premixing zone (14.1) in the direction of flow in order to produce an ignitable fuel-air mixture (18) with excess air, wherein step c) comprises: d) swirling the fuel-air mixture (18) formed in the at least one further premixing zone (14.n).Combustion method according to claim 1, further comprising at least one or more of the following steps: 2.1 generating the air flow (10) by means of a blower (50); 2.2 preheating the air flow (10), in particular by means of a heat exchanger (68), using exhaust gas heat; 2.3 adjusting the speed of the air flow (10); 2.4 adjusting a fuel distribution to the premixing zones (14.1, 14.n); 2.5 generating a main flame from the ignitable fuel-air mixture (18) after it has left a flame head (42) in a combustion chamber (60); 2.6 stabilizing a main flame generated with the ignitable fuel-air mixture (18) by means of a primary flame; 2.7 Providing a larger outlet cross section (70, 70.1, 70.2) for the ignitable fuel-air mixture (18) to a combustion chamber (60) in a full load operation and a smaller outlet cross section (70, 70.1) for the ignitable fuel-air mixture (18) in a part load operation; 2.8 Dividing the ignitable fuel-air mixture (18) over an outlet region with a fixed outlet cross section (70, 1) and an outlet region with a controllable outlet cross section (70.2) and controlling the controllable outlet cross section (70.2) as a function of the combustion power to be generated; 2.9 Generating a homogeneous ignitable fuel-air mixture (18) in which, at least at the end of the last premixing zone (14.n), there is an identical distribution of fuel and air over the entire outlet flow cross section (70).The combustion method according to any one of the preceding claims, wherein step b) includes at least one, more or all of the steps: b1) supplying from 10% to 80% of the fuel (12) in the first premixing zone (14.1); b2) supplying from 30% to 70% of the fuel (12) in the first premixing zone (14.1); b3) supplying from 40% to 60% of the fuel (12) in the first premixing zone (14.1); b4) supplying fuel (12) via at least one or more hollow bodies (30) selected from the group comprising a hollow body (30) with nozzles distributed over its surface, a hollow body (30) with perforated surface, a perforated gas tube (32), a gas tube (32) with lateral bores, a gas tube (32) with bores extending transversely to the flow direction, a gas tube (32) with bores extending longitudinally to the flow direction, a partially annularly extending perforated hollow body (30, 34, 36), an annular perforated hollow body (30, 34), a hollow annular body (34) extending with its central axis in the flow direction with bores on at least one inwardly or outwardly directed cylinder jacket surface, a hollow swirl vane (36) with bores and combinations of the aforementioned hollow bodies (30); b5) generating a swirl in the air flow (10) and supplying the first fraction of the swirling air flow (10); b6) generating opposing swirl in the air flow (10) in different annular regions of the first premixing zone (14.1); b7) generating a homogeneous lean fuel-air mixture (16) in which a uniform distribution of fuel and air is present over the entire flow cross section at least at the end of the first premixing zone (14.1).Combustion method according to any one of the preceding claims, wherein step c) comprises at least one, several or all of the steps: c1) admixing a remaining portion (A.n) in a second premixing zone (14.2); c2) admixing a remaining portion (A.n) in a second and a third premixing zone (14.2, 14.3); c3) feeding a remaining portion of 1% to 15% of the fuel (12) into a primary flame generating region (76) for generating a primary flame; c4) Admixing fuel (12) via at least one or more hollow bodies (30) selected from the group comprising a hollow body (30) with nozzles distributed over its surface, a hollow body (30) with perforated surface, a perforated gas pipe (32), a gas pipe (32) with lateral bores, a gas pipe (32) with bores extending transversely to the flow direction, a gas pipe (32) with bores extending longitudinally to the flow direction, a partially annularly extending perforated hollow body (30, 34, 36), an annular perforated hollow body (30, 34), a hollow annular body (34) extending with its central axis in the flow direction with bores on at least one inwardly or outwardly directed cylinder jacket surface, a hollow swirl vane (36) with bores and combinations of the aforementioned hollow bodies (30); c5) Supplying fuel (12) via at least one opening in a baffle (78).Combustion method according to one of the preceding claims, wherein step d) contains at least one, several or all of the steps: d1) swirling the fuel-air mixture (16, 18) located in the further premixing zone (14.n); d2) generating opposing swirl on the fuel-air mixture (16, 18) in different annular regions of the at least one further premixing zone (14.n); d3) generating swirl on the fuel-air mixture (16) on passing into the at least one further premixing zone (14.n); d4) generating swirl on the lean fuel-air mixture (16) before admixing; d5) generating swirl on the fuel-air mixture (16, 18) to be enriched for flammability during admixing; d6) Generating a swirl by means of gas-conducting and perforated swirl vanes (36); d7) Generating a swirl for a pilot flame by means of a baffle plate (78) designed as a swirl unit (26).Premix burner (40) comprising a flame tube (44), an air supply device (48) for providing the entire air flow (10) for combustion to the flame tube (44); a premix device (46) which is designed to receive 100% of the air flow (10) from the air supply device (46) and premix it with fuel (12) before it exits the flame tube (44), and a swirl device (28), wherein the premix device (46) comprises a first fuel supply device (20.1) with control means, wherein the first fuel supply device (20.1) is designed to add a first proportion (A.1) of the fuel (12) to the air flow (10) in a first premix zone (14.1), such that an as yet non-ignitable lean fuel-air mixture (16) is produced, and at least one further fuel supply device (20.n) with control means, wherein the at least one further fuel supply device (20.n) is configured to mix one or more remaining fractions (A.n) of the fuel (16) to the lean fuel-air mixture (16) in at least one further premixing zone (14.n), which is spaced apart from the first premixing zone (14.1) in the flow direction, in order to produce an ignitable fuel-air mixture (18) with excess air, wherein the swirl device (28) is configured at least for swirling the fuel-air mixture (16, 18) which is formed or located in the at least one further premixing zone (14.n).Premix burner (40) according to Claim 6, wherein the flame tube (44) has at least one or more of the following features: 7.1 a cylindrical jacket; 7.2 an inlet opening which is designed to take up 100% of the air flow; 7.3 an outlet opening region (70) which is designed to discharge the ignitable fuel-air mixture (18) into a combustion chamber (60) for combustion; 7.4 a taper close to a downstream end; 7.5 an outlet cross-section setting device (72) for setting the outlet cross-section (70.2) of part of an outlet opening region (70); 7.6 at least one slide (72) for variably setting an outlet cross-section of the flame tube (44).Premix burner (40) according to one of Claims 6 or 7, wherein the air supply device (46) has at least one or more of the following features: 8.1 a fan (50) for generating the air flow (10); 8.2 a preheating device (66) for preheating the air flow (10); 8.3 an exhaust gas heat exchanger (68) for preheating the air flow (10) with exhaust gas heat; 8.4 an exhaust gas supply device (64) for supplying exhaust gas to the air flow (10); 8.5 control means for controlling the air flow (10); 8.6 a control interface which can be connected to a controller (52).Premix burner (40) according to one of Claims 6 to 8, wherein the premix device (46) further has at least one or more of the following features: 9.1 the first premix zone (14.1) and a second premix zone (14.2) spaced apart therefrom in the flow direction; 9.2 a first, second and third premix zone (14.1, 14.2, 14.3) which follow one another in the flow direction; 9.3 permanently or variably set fuel flow cross sections for dividing the fractions (A.1, A.n) of fuel (12) to the first and each further fuel feed device (20.1, 20.n); 9.4 a setting device (82) for setting a fuel distribution; 9.5 a fuel distributor ring (84) for distributing fuel (12) to the plurality of premix zones (14.1, 14.n); 9.6 Control means for controlling the fuel supply; 9.7 A control interface connectable to a controller (52).Premix burner (40) according to one of Claims 6 to 9, wherein the first fuel feed device (20.1) has at least one or more of the following features: 10.1 an inflow cross section which is dimensioned relative to the inflow cross section of the at least one further fuel feed (20.n) such that the predetermined first proportion (A.1) of the fuel (12) flows through the first fuel feed device (20.1); 10.2 an adjustment device (82) for adjusting an inflow cross section of the first fuel feed (20.1); 10.3 at least one or more hollow bodies (30) for supplying the fuel, which at least one hollow body is selected from the group comprising a hollow body (30) with nozzles distributed over its surface, a hollow body (30) with perforated surface, a perforated gas tube (32), a gas tube (32) with lateral bores, a gas tube (32) with bores extending transversely to the flow direction, a gas tube (32) with bores extending longitudinally to the flow direction, a partially annularly extending perforated hollow body (30, 34, 36), an annular perforated hollow body (30, 34), a hollow annular body (34) with bores extending with its central axis in the flow direction on at least one inwardly or outwardly directed cylinder jacket surface, a hollow swirl vane (36) with bores and combinations of the aforementioned hollow bodies (30); 10.4 computer implemented control means for controlling fuel delivery.Premix burner (40) according to one of Claims 6 to 10, wherein the further fuel feed device(s) (20.n) has / have at least one or more of the following features: 11.1 an inflow cross section which is dimensioned relative to the inflow cross section of the first fuel feed (20.1) such that the predetermined further proportion (A.n) of the fuel (12) flows through the further fuel feed device (20.n); 11.2 a second fuel feed device (20.2) in a second premix zone (14.2); 11.3 a third fuel feed device (20.3) in a third premix zone (14.3); 11.4 a pilot flame fuel supply device for supplying a proportion of the fuel (12), which is smaller than the proportions (A.1, A2, A3) of the first fuel supply and a second fuel supply (20.1, 20.2, 20.3), by at least a factor of 3, to a pilot flame; 11.5 an adjusting device (82) for adjusting an inflow cross section of the further fuel supply (20.n); 11.6 at least one or more hollow bodies (30) for admixing the fuel, which at least one hollow body is selected from the group comprising a hollow body (30) with nozzles distributed over its surface, a hollow body (30) with perforated surface, a perforated gas tube (32), a gas tube (32) with lateral bores, a gas tube (32) with bores extending transversely to the flow direction, a gas tube (32) with bores extending longitudinally to the flow direction, a partially annularly extending perforated hollow body (30, 34, 36), an annular perforated hollow body (30, 34), a hollow annular body (34) with bores extending with its central axis in the flow direction on at least one inwardly or outwardly directed cylinder jacket surface, a hollow swirl vane (36) with bores and combinations of the aforementioned hollow bodies (30); 11.7 computer implemented control means for controlling fuel delivery.Premix burner (40) according to one of Claims 6 to 11, wherein the swirl device (28) has at least one or more of the following features: 12.1 a swirl unit (26) for swirling the air flow (10) entering the first premix zone (14.1); 12.2 a counter-swirl device (88) for generating swirl with opposite directions of swirl in different annular zones of the flame tube (44); 12.3 a first swirl unit (26.1) in or upstream of the first premix zone (14.1) and at least one further swirl unit (26.2) passing to or in a further premix zone (14.n); 12.4 an inner arrangement (90) of swirl vanes (92) and an outer arrangement (94) of swirl vanes (92); 12.5 swirl vanes (36) designed as hollow bodies (30) with nozzles for supplying fuel; 12.6 a primary flame swirl unit (26) on a baffle plate (78).Premix burner (40) according to one of Claims 6 to 12, comprising at least one or more of the following further features: 13.1 a baffle plate (78) for stabilizing a primary flame; 13.2 liquid fuel nozzles (80) for discharging liquid fuel into a combustion chamber (60) downstream of the flame tube (44); 13.3 a controller (52) with processor (54) and memory (56); 13.4 control means for controlling the ratio of fuel (12) to the air flow (10); 13.5 a controller (52) which is configured to cause the premix burner (40) to carry out the combustion method according to one of Claims 1 to 5.The controller (52) for a premix burner (40) of any one of claims 6 to 13, configured to cause the premix burner (40) to automatically perform the combustion process of any one of claims 1 to 5.A computer program comprising instructions that cause a premix burner (40) according to any one of claims 6 to 13 to perform the combustion method according to any one of claims 1 to 5.

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