Premix combustion method, premixing burner, control system, and computer program

Abstract

In order to enable stable combustion with ultra-low NOx generation, the invention relates to a combustion method for combusting a fuel-air mixture (excluding in gas turbines), the method comprising: a) completely premixing 100% of an air flow (10), provided for combustion, with (gaseous) fuel (12), wherein step a) comprises: b) adding a first portion (A.1) of the fuel (12) to the airflow (10) in a first premixing zone (14.1) so as to form a lean fuel-air mixture (16) that is not yet ignitable; and c) mixing in one or more remaining portions (A.n) of the fuel (12) with the lean fuel-air mixture (16) in at least one additional premixing zone (14. n), which is positioned at a distance 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 additional premixing zone (14.n). The invention also relates to a premixing burner (40) designed to carry out such premixing and combustion.

Description

[0001] Premixed combustion process and premixed burner as well as control and computer program

[0002] The invention relates to a combustion method for burning a premixed fuel-air mixture. Furthermore, the invention relates to a premix burner. Finally, the invention relates to a control system and a computer program for such a premix burner.

[0003] The invention is in the field of combustion processes for burning, in particular, gaseous fuel for buildings, ships, trade and industry as well as in the field of burners for carrying out such

[0004] Combustion processes as described in particular in [6] to

[0010] .

[0005] For the technological background, please refer to the following literature:

[0006] [1] DE 4329 971 A1

[0007] [2] DE 36 06 625 A1

[0008] [3] DE 1 264 668 B

[0009] [4] US 2007 / 0207426 A1

[0010] [5] US 2004 / 0018461 A1

[0011] [6] WO 2018 / 141647 A1

[0012] [7] "Technical information Monoblock burners - Weishaupt burners monarch® - WM30 350 to 6,200 kW", company brochure of Max Weishaupt GmbH, download on 30.11.2023 at https: / / www.weishaupt.de / uploads / tx_weishaupt_documents / documents / 8 3211601.pdf

[0013] [8] Website of Max Weishaupt GmbH, product information Weishaupt burner series WM monarch®, download on 30.11.2023 at https: / / www.weishaupt.de / produkte / brenner / weishaupt-brenner- typenreihe-wm-monarchr-55-12000-kw [9] Weishaupt burner WKmono, company brochure of Max Weishaupt GmbH, download on 30.11.2023 at https: / / www.weishaupt.de / uploads / tx_weishaupt_documents / documents / 8 3216401.pdf

[0014]

[0010] Weishaupt Industrial Burner WK, company brochure of Max-Weishaupt GmbH, download on 30.11.2023 at https: / / www.weishaupt.de / uploads / tx_weishaupt_documents / documents / 8 3159801.pdf

[0015]

[0011] Information Sheet No. 66 of the Federal Association of the German Heating Industry (BDH), download on 30 November 2023 at https: / / www.bdh-industrie.de / fileadmin / user_upload / Publikationen / lnfoblaetter / lnfoblatt_Nr_ 66_NOx-Emission_Feuerungsanlagen_022020.pdf

[0016]

[0012] Wikipedia: Nitrogen oxides; downloaded on 30.11.2023 from https: / / de.wikipedia.org / wiki / Stickoxide

[0017]

[0013] DE 43 30 160 A1

[0018]

[0014] WO 2021 / 250517 A1

[0019] According to

[0014] , a distinction is made between premix burners, which completely premix a fuel-air mixture before it is discharged into a combustion chamber where a flame develops, and diffusion burners, in which air and fuel are introduced separately into the combustion chamber, where they are then mixed for combustion.

[0014] describes a burner for a very specific purpose, namely the pretreatment of various steel components prior to a hot-dip galvanizing process. The burner can be operated either in a diffusion burner mode, in which fuel and air are fed separately to the combustion chamber, or in a premix mode, in which air and fuel are premixed to form a fuel-air mixture with excess air and then introduced into the combustion chamber.

[0020]

[0013] describes a burner for gas turbines with a premixing device in which a non-ignitable fuel-air mixture is generated, and with a fuel lance that extends into the combustion chamber and adds further fuel there to immediately generate a flame. This is intended to combine the advantages of premixing burners and orifice burners (i.e., diffusion burners).

[0021] According to [6], premix burners, in which a fuel-air mixture is premixed before being added to a combustion chamber, have already been used to achieve low NOx emissions. All known premix burners initially produce a rich mixture, which is then leaned out by adding air. However, with the burners known to date for the above-mentioned applications, NOx emissions can only be achieved up to a certain limit.

[0022] The object of the invention is to provide methods and devices that enable stable combustion of gaseous fuel with ultra-low NOx production.

[0023] To achieve this object, the invention provides the combustion method according to claim 1. A premix burner as well as a control system and a computer program therefor are the subject of the further independent claims.

[0024] Advantageous embodiments are the subject of the subclaims.

[0025] 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) complete premixing of 100% of an air flow provided for combustion with (gaseous) fuel, wherein step a) comprises: b) adding a first portion of the fuel to the air flow in a first premixing zone, so that a not yet ignitable lean fuel-air mixture is formed; and c) admixing one or more remaining portions 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 step c) comprises: d) swirling the fuel-air mixture.

[0026] The completely premixed fuel-air mixture flows through an outlet opening into a combustion chamber and is burned there with a flame.

[0027] In embodiments of the invention, all of the air provided for combustion is completely premixed; in particular, homogeneous mixing occurs. In some embodiments, a homogeneous, ignitable fuel-air mixture is produced in which fuel and air are homogeneously or evenly distributed throughout. In other words, there are no zones with a lower or higher fuel concentration in the fuel-air mixture thus produced, in particular no zones of pure air without fuel. To achieve complete premixing, thorough mixing is first carried out in at least one first premixing zone, with sufficient fuel being supplied to create a lean fuel-air mixture that is not yet ignitable, but preferably already completely or largely homogeneous.In a second premixing zone, or in the case of more than two premixing zones, especially in the last premixing zone, fuel is supplied in such a way that a homogeneous fuel-air mixture is created, preferably still lean but ignitable. After the last premixing zone and the rotation, the homogeneous fuel-air mixture with excess air is present. This then flows from the premixing device through the outlet opening area into the combustion chamber.

[0028] In some embodiments, the combustion method comprises the step of generating the air flow by means of a fan.

[0029] 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 comprises the step of adjusting the speed of the air flow.

[0030] In some embodiments, the combustion method comprises the step of adjusting the fuel distribution to the premixing zones.

[0031] In some embodiments, the combustion method comprises the step of generating a main flame from the fuel-air mixture after it has left a combustion head in the combustion chamber.

[0032] In some embodiments, the combustion method comprises the step of stabilizing the main flame generated with the ignitable fuel-air mixture by means of a primary flame.

[0033] In some embodiments, the combustion method comprises the step of providing a larger exit cross-section for the ignitable fuel-air mixture to a combustion chamber in full-load operation and a smaller exit cross-section for the ignitable fuel-air mixture in part-load operation.

[0034] In some embodiments, the combustion method comprises the step of dividing the fuel-air mixture over an outlet region with a fixed 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.

[0035] In some embodiments, the combustion process, and in particular step a), comprises the step of generating a homogeneous, ignitable fuel-air mixture in which, at least at the end of the last premixing zone, there is an equal distribution of fuel and air across the entire flow cross-section. In some embodiments, step b) comprises the step of supplying 10% to 80% of the fuel in the first premixing zone.

[0036] In some embodiments, step b) comprises the step of: supplying 30% to 70% of the fuel in the first premixing zone.

[0037] In some embodiments, step b) comprises the step of supplying 40% to 60% of the fuel in the first premixing zone.

[0038] Particularly preferred is approximately equal proportions of fuel distributed among the premixing zones. The fuel is added successively and thoroughly mixed until a homogeneous, ignitable fuel-air mixture with excess air is formed.

[0039] 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 with nozzles distributed over its surface, a hollow body with a perforated surface, a perforated gas pipe, a gas pipe with lateral bores, a gas pipe extending transversely to the flow direction with bores, a gas pipe extending longitudinally to the flow direction with bores, a perforated hollow body extending partially in a ring shape, an annular perforated hollow body, a hollow annular body - preferably extending with its central axis in the flow direction - with bores on at least one inwardly directed cylinder surface and / or at least one outwardly directed cylinder surface, a hollow swirl vane with bores, and a hollow body that combines several properties of the aforementioned hollow bodies.

[0040] In some embodiments, step b) comprises the step:

[0041] Creating a swirl in the air flow and supplying the first portion to the wired air flow. In some embodiments, step b) comprises the step:

[0042] Generate opposing swirls in the air flow in different ring areas of the first premixing zone.

[0043] In some embodiments, step c) comprises the step of admixing the remaining portion in a second premixing zone.

[0044] In some embodiments, step c) comprises the step of admixing the remaining portion in a second and a third premixing zone.

[0045] In some embodiments, step c) comprises the step of admixing a proportion of 1% to 15% of the fuel in a primary flame generation device to generate a primary flame. Preferably, the fuel proportion for the primary flame is between approximately 5% and approximately 15%. In particular, a proportion of less than 10% of the fuel is admixed in the primary flame generation device, for example approximately 4, 5, 6, or 7%. Approximately values ​​refer in particular to all values ​​enclosed by a number rounded to a whole number. For example, “approximately 5%” therefore includes in particular values ​​between 4.50% and 5.49%.

[0046] In some embodiments, step c) comprises the step of:

[0047] Mixing of 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 also, in particular, a hollow body with nozzles distributed over its surface, a hollow body with a perforated surface, a perforated gas tube, a gas tube with lateral bores, a gas tube extending transversely to the flow direction with bores, a gas tube extending longitudinally to the flow direction with bores, a partially annular perforated hollow body, an annular perforated hollow body, a hollow annular body - preferably extending with its central axis in the flow direction - with bores on at least one inwardly directed cylindrical surface and / or at least one outwardly directed cylindrical surface, a hollow swirl vane with bores, and a hollow body that combines several properties of the aforementioned hollow bodies.

[0048] In some embodiments, step c) comprises the step of admixing fuel via at least one opening in a baffle plate.

[0049] In some embodiments, step d) comprises the step of generating opposing swirls on the fuel-air mixture in different annular regions of the at least one further premixing zone.

[0050] In some embodiments, step d) comprises the step:

[0051] Generating a swirl in the fuel-air mixture as it passes into the at least one further premixing zone.

[0052] In some embodiments, step d) comprises the step of creating a swirl prior to admixing.

[0053] In some embodiments, step d) comprises the step of generating a swirl during the mixing.

[0054] In some embodiments, step d) comprises the step of generating a swirl by means of gas-conducting and perforated swirl vanes.

[0055] Particularly preferred embodiments optionally provide for the possible combustion of liquid fuel. In particular, a choice is provided between a mode for burning gaseous fuel according to one of the above embodiments and a mode for burning liquid fuel. In dual-fuel operation, liquid fuel can also be burned in addition to the combustion of the gaseous fuel according to one of the aforementioned embodiments.

[0056] According to a further aspect, the invention provides a premix 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 designed to receive 100% of the air flow from the air supply device and to premix it with fuel before exiting the flame tube, and a swirl device, wherein the premixing device comprises a first fuel supply device with control means which is designed to add a first portion of the fuel to the air flow in a first premixing zone so that a lean fuel-air mixture which is not yet ignitable is produced, and at least one further fuel supply device with control means which is designed to add the remaining portion(s) 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, to produce an ignitable fuel-air mixture with excess air, wherein the swirl device is designed at least to swirl the mixture produced in the at least one second premixing zone. The flame tube has an outlet opening region configured to discharge the fully premixed fuel-air mixture into a combustion chamber for combustion.

[0057] In some embodiments, the control means are mechatronic control means in which an electronic, in particular computer-implemented, control unit, for example designed as part of an overall control system (e.g. combustion manager) with processor and memory with correspondingly loaded software, is combined with mechanical control elements, such as flaps, actuators, slides or fixed or variable flow cross sections.

[0058] In some embodiments, the flame tube has a cylindrical shell. In some embodiments, the flame tube has an inlet opening arranged and configured to receive 100% of the air flow. In some embodiments, the flame tube has a taper near a downstream end. In some embodiments, the flame tube has an outlet cross-section adjustment device for adjusting the outlet cross-section of a portion of an outlet opening region. In some embodiments, the flame tube has at least one slide for variably adjusting an outlet cross-section of the flame tube.

[0059] In some embodiments, the air supply device comprises a fan for generating the air flow. In some embodiments, the air supply device comprises 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 device comprises an exhaust gas supply device for supplying exhaust gas to the air flow. In some embodiments, the air supply device comprises control means for controlling the air flow. In some embodiments, the control means of the air supply device are also mechatronic control means as explained above.As a control means, for example, in a computer-implemented control system of the premix burner, a control routine is provided as part of the control software, with which a fan of the air supply device and / or air dampers or the like are controlled. In some embodiments, the air supply device has a control interface connectable to a control system of the premix burner or a higher-level control system.

[0060] In some embodiments, the premixing device comprises the first premixing zone and a second premixing zone spaced therefrom in the flow direction. In some embodiments, the premixing device comprises first, second, and third premixing zones that follow one another in the flow direction. In some embodiments, the premixing device comprises fixed or variable fuel flow cross-sections for distributing the portions of fuel to the first and each additional fuel supply device. In some embodiments, the premixing device comprises an adjustment device for adjusting a fuel distribution. In some embodiments, the premixing device comprises 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 described above) for controlling the fuel supply. In some embodiments, the premixing device comprises a control interface connectable to a controller.

[0061] In some embodiments, the first fuel supply device has an inflow cross-section that is dimensioned relative to an inflow cross-section of the at least one further fuel supply such that the predetermined first portion of the fuel flows through the first fuel supply device. In some embodiments, the first fuel supply device has an adjustment device for adjusting the inflow cross-section. In some embodiments, the first fuel supply device has at least one or more hollow bodies for supplying the fuel.According to some embodiments, the hollow bodies used for the first fuel supply device are in particular a hollow body with nozzles distributed over its surface, a hollow body with a perforated surface, a perforated gas pipe, a gas pipe with lateral bores, a gas pipe extending transversely to the flow direction with bores, a gas pipe extending longitudinally to the flow direction with bores, a perforated hollow body extending partially in a ring shape, an annular perforated hollow body, a hollow annular body - preferably extending with its central axis in the flow direction - with bores on at least one inwardly directed cylinder surface and / or at least one outwardly directed cylinder surface, a hollow swirl vane with bores, and a hollow body that combines several properties of the aforementioned hollow bodies.In some embodiments, the first fuel supply device has computer-implemented control means for controlling the fuel supply. For example, these are provided as part of control software in a controller of the premix burner. In some embodiments, the one further fuel supply device or the plurality of further fuel supply devices have an inflow cross-section that 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 further fuel supply device or the plurality of further fuel supply devices have a second fuel supply device in a second premixing zone.In some embodiments, the one further fuel supply device or the plurality of further fuel supply devices comprise a third fuel supply device in a third premixing zone. In some embodiments, the one further fuel supply device or the plurality of further fuel supply devices comprise a pilot flame fuel supply device for supplying a portion of the fuel to a pilot flame that is at least a factor of 3 smaller than the portions of the first fuel supply and a second fuel supply. In some embodiments, the one further fuel supply device or the plurality of further fuel supply devices comprise an adjustment device for adjusting an inflow cross-section of the further fuel supply.In some embodiments, the one further fuel supply device or the several further fuel supply devices each have at least one or more hollow bodies for admixing the further fuel components.According to some embodiments, the hollow bodies used for the respective further fuel supply device are in particular a hollow body with nozzles distributed over its surface, a hollow body with a perforated surface, a perforated gas pipe, a gas pipe with lateral bores, a gas pipe extending transversely to the flow direction with bores, a gas pipe extending longitudinally to the flow direction with bores, a perforated hollow body extending partially in a ring shape, an annular perforated hollow body, a hollow annular body - preferably extending with its central axis in the flow direction - with bores on at least one inwardly directed cylinder surface and / or at least one outwardly directed cylinder surface, a hollow swirl vane with bores, and a hollow body that combines several properties of the aforementioned hollow bodies.In some embodiments, the one or more additional fuel supply devices comprise computer-implemented control means for controlling the fuel supply. These are also provided, for example, as part of the control software in the control system of the premix burner.

[0062] In some embodiments, the swirl device has 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 has an inner arrangement of swirl vanes and an outer arrangement 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 has a primary flame swirl unit on a baffle plate.

[0063] In some embodiments, the premix burner further comprises a baffle plate for stabilizing a primary flame. In some embodiments, the premix burner further comprises liquid fuel nozzles for discharging liquid fuel into a combustion chamber downstream of the flame tube. In some embodiments, the premix burner further comprises a controller with a 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 comprises a controller configured to cause the premix burner to perform one of the embodiments of the combustion method explained above.According to a further aspect, the invention provides a control system for a premix burner according to one of the preceding embodiments, which is designed to cause the premix burner to automatically carry out one of the embodiments of the combustion method explained above.

[0064] According to a further aspect, the invention provides a computer program comprising instructions which cause a premix burner according to one of the preceding embodiments to carry out the combustion method according to one of the embodiments explained above.

[0065] Special effects of advantageous embodiments of the invention are explained in more detail below. In previously known combustion processes in which fuel is premixed with air, an excessively rich fuel-air mixture is intentionally created, to which an additional air stream is then added to achieve a cooler flame temperature. This reduces the generation of thermal NOx. The reduction of thermal NOx has so far been the sole focus of the prior art, as explained in more detail in

[0011] .

[0066] As explained in

[0012] , nitrogen oxides in combustion are generally divided into three types depending on their sources and formation mechanism: thermal NOx, fuel NOx, and prompt NOx. Thermal NOx is formed at relatively high temperatures through the oxidation of the nitrogen contained in the air. This is the only area where previous combustion concepts for NOx reduction have been applied (see

[0011] ). The source of fuel NOx is the nitrogen bound in the fuel. This proportion depends 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 and very small for some gaseous fuels, such as natural gas.

[0067] With the combustion process according to the invention and its advantageous embodiments, as well as the premix burners configured for combustion according to the invention and their advantageous embodiments, the formation of prompt NOx can also be reduced, so that NOx reduction beyond what was previously possible is now achievable. In order to achieve significantly below 50 mg NOx per standard cubic meter when burning gaseous fuels such as natural gas, prompt NOx is also taken into account according to the invention.

[0068] In some embodiments of the invention, 100 percent of the combustion air flow is passed through a premixing region of a burner, in which at least a first premixing zone and a second premixing zone are spaced apart from one another in the flow direction. In the upstream first premixing zone, fuel (gas) is supplied in such a way that the resulting mixture is non-ignitable. For example, the combustion air ratio A 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 passed, a further portion of the fuel is mixed in such a way that an ignitable mixture is now formed. Advantageously, excess air is still used in this case to cool the flame and reduce the generation of thermal NOx.For example, the ignitable mixture is still lean with a combustion air ratio A greater than 1. Swirl is generated to achieve good mixing. The ignitable mixture is directed through a flow cross-sectional area—the outlet opening area—which can be reduced in some embodiments for part-load operation, to the combustion chamber (also called the combustion chamber). This is where the flame is generated.

[0069] By creating a fully premixed gas-air mixture, the formation of prompt NOx is avoided or at least significantly reduced. Nevertheless, the load is easily controllable, and there is no backfire.

[0070] The combustion process according to advantageous embodiments of the invention does not require metal grids or other measures to prevent flame penetration. An ignitable fuel mixture is only formed in the last premixing zone in the flow direction. There, the flow velocity can be kept high enough to prevent flashback. Should flashback occur, the volume of ignitable mixture is very small. This allows a high flow velocity to be achieved, allowing high combustion performance while still maintaining a stable combustion process despite extremely low NOx generation.

[0071] Accordingly, in the invention, a complete premixing is carried out in such a way that fuel is first supplied to the air stream in a first premixing zone, so that the resulting mixture is not yet ignitable, and in at least one second premixing zone, which is still located in the premixing area within the air stream, further fuel is supplied until it is ignitable.

[0072] Preferred embodiments relate to a combustion process as outlined above, 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 premix burner. Further embodiments relate to a premix burner that is configured (i.e., not only suitable, but actually configured) for carrying out the combustion process with corresponding premixing zones, fuel feeds, and control means, in particular at least partially computer-implemented control means.

[0073] Preferred embodiments of the premix burner are based on the prior art according to one of the references [6] to

[0010] and have known configurations from these references - unless they are replaced by the special features explained in more detail below according to embodiments of the invention. Therefore, for more detailed possible embodiments, reference is made to the references [6] to

[0010] , which are incorporated by reference. Embodiments of the invention are explained in more detail below with reference to the accompanying drawings. In the drawings:

[0074] Fig. 1 is a block diagram showing a premixed combustion process with ultra-low NOx production and some components of a premixed burner configured to carry out the combustion process according to advantageous embodiments;

[0075] Fig. 2 is an axial longitudinal section through a burner head of a first embodiment of a premix burner for carrying out the combustion process;

[0076] Fig. 3 is an axial longitudinal section through a burner head of a second embodiment of a premix burner for carrying out the combustion process;

[0077] Fig. 4 is a block diagram illustrating an embodiment of the combustion process at full load that can be carried out with the premix burner having the burner head according to Fig. 2;

[0078] Fig. 5 is a block diagram illustrating an embodiment of the combustion process at partial load that can be carried out with the premix burner having the burner head according to Fig. 2;

[0079] Fig. 6 is a perspective view of a premixing device for a burner head of a premixing burner according to a further embodiment for carrying out the combustion method;

[0080] Fig. 7 is an axial longitudinal section through the burner head with the premixing device of Fig. 6 in a setting for full-load operation, illustrating an air flow and fuel and fuel-air mixture profiles; Fig. 8 is an axial longitudinal section through the burner head similar to Fig. 6 in a setting for partial-load operation, illustrating fuel profiles, and showing a variant of the premixing device;

[0081] Fig. 9 is a perspective view of the premixing device of the burner head of Fig. 8;

[0082] Fig. 10 is a perspective view of a dual-fuel gas / liquid fuel mixing device with fuel distribution for a burner head with the premixing device according to Figs. 8 and 9; and

[0083] Fig. 11 shows a section through a burner head with a mixing device in dual-component design, which has the premixing device according to Fig. 8 or Fig. 9 and a central atomizing nozzle for liquid fuel.

[0084] Figures 1, 4 and 5 show block diagrams of a combustion process for burning a fuel-air mixture in which gaseous fuel is premixed with air.

[0085] In the combustion process, 100% of an air flow 10 provided for combustion is fully premixed with gaseous fuel 12. The complete premixing step comprises the following steps:

[0086] • 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

[0087] • Mixing the remaining portion(s) 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 (n here denotes a natural number greater than 1). At least the mixing step further comprises the step:

[0088] Swirling of the fuel-air mixture 18.

[0089] For example, at least a first premixing zone 14.1 and a second premixing zone 14.2 are provided. Additional premixing zones 14.n, such as a third premixing zone 14.3, may also be provided.

[0090] In some embodiments, a completely homogeneous, ignitable fuel-air mixture 18 with excess air is created by admixing fuel in several premixing zones and rotating them. In this mixture, at least in the area of ​​an outlet opening 70 for the fuel-air mixture 18 to flow into a combustion chamber 60, the fuel is distributed across the entire flow cross-section with a uniform concentration in the air. In some embodiments, such "homogeneous premixing" in the second / final premixing zone, in particular, prevents or at least significantly reduces the formation of prompt NOx.

[0091] Preferred embodiments of the process are further characterized by the fact that a possibility for the combustion of liquid fuels can be integrated.

[0092] 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, such that the first portion A.1 of fuel 12 is supplied to the air stream 10 in such a way that the not yet ignitable lean fuel-air mixture 16 is formed in the first premixing zone 14.1. Each further premixing zone 14.n is assigned a further fuel supply device 20.n, which is also controlled by the control means such that the remaining portion(s) An of fuel 12 is / 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 flow direction. At least in or at the last premixing zone 14.n in the flow direction.n, a swirl unit 26 of a swirl device 28 is provided for swirling the fuel-air mixture 16, 18. As shown in Fig. 1 with dashed lines, the other premixing zones 14.1 can also be provided with a swirl unit 26.

[0093] The respective fuel supply device 20.1, 20.n has at least one hollow body 30 for dispensing the fuel 12. The hollow body 30 is in particular provided with nozzles or bores so that the fuel 12 is added to the premixing zone 14.1, 14.2 with the best possible distribution. This contributes to homogeneous premixing. Gas pipes 32, for example, are provided as hollow bodies 30, which can extend, for example, in the direction of flow or transversely to the direction of flow and preferably have bores distributed over their surfaces. Furthermore, ring elements 34 with a cylindrical inner and outer side, which have gas outlet openings distributed thereover, 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 over their surfaces in order to supply or mix the gaseous fuel 12.

[0094] Fig. 1 also shows a block diagram of a premix burner 40 that is designed to carry out the combustion process. The premix burner 40 has a burner head 42 (also called a combustion head) with a flame tube 44 (omitted in Fig. 1 for clarity but shown 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 supply devices 20.1, 20.n. An air supply device 48 for providing the air flow 10 is formed, for example, by a fan 50. The premix burner 40 further has an electronic control system 52 with a processor 54 and memory 56. A control routine is stored in the memory 56 as software (computer program). The controller 52 controls the fan 50 and actuators of the premix burner 40 to perform the above-mentioned combustion process.The controller 52 thus also provides at least part of the control means for the fuel supply as part of the control routine.

[0095] Fig. 1 also shows a combustion chamber 60 with the flame 62 generated during combustion downstream of the combustion head, as well as an optional exhaust gas recirculation system 64 for admixing exhaust gas to the inlet of the air supply device 48, and a likewise optional air heating device 66 for heating the combustion air. For example, the air upstream of the fan 50 is preheated with heat from the exhaust gas by means of an exhaust gas heat exchanger 68.

[0096] As further shown schematically in dashed lines in Fig. 1, an outlet cross-section of the outlet opening region 70 for the ignitable fuel-air mixture 18 with excess air can optionally be changed by means of suitable actuators controllable by the controller 52. The outlet opening region 70 has, for example, a fixed outlet cross-section region 70.1 and a variable outlet cross-section region 70.2 that can be changed by means of an actuator such as a movable air slide 72. This allows a larger outlet cross-section for the ignitable fuel-air mixture 18 to the combustion chamber 60 to be provided during full-load operation, and a smaller outlet cross-section for the ignitable fuel-air mixture to be provided during partial-load operation.

[0097] For example, the fuel 12 is distributed—in particular by providing or adjusting flow cross-sections of the corresponding gas supply lines 58.1, 58.n—in equal or optionally different proportions A1, An between the various premixing zones 14.1, 14.n. The total amount of fuel 12 is controlled by the controller 52 according to the desired load and the air flow 12 adjusted for this purpose using the blower 50. The combustion air flow—air flow 10—is 100 percent passed through a premixing region of the premix 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 flow direction. In the upstream first premixing zone 14.1, fuel 12 (gas) is supplied in such a way that the resulting mixture 16 is not ignitable. For example, the combustion air ratio A 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 passed, a further portion An of the fuel 12 is added in such a way that an ignitable mixture 18 is now formed. Advantageously, excess air is still used in order 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 A greater than 1. Swirl is generated 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 an outlet opening region 70 to the combustion chamber 60, wherein the outlet cross-section of the outlet opening region 70 can be reduced for partial load operation in some embodiments.

[0098] Fig. 2 shows a first concrete embodiment of the burner head 42 of the premix burner 40. This embodiment is based on the burners shown in the literature references [9] and

[0010] , which are provided with the burner head 42 shown in Fig. 2 with the premixing device 46, wherein the software in the control 52 referred to as the combustion manager in the literature references [9] and

[0010] is set up accordingly to carry out the combustion process shown here.

[0099] 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 a pilot flame generation zone 76. The pilot flame generation region 76 has a conical slotted baffle plate 78, over which a portion of the lean fuel-air mixture 16 is passed to provide primary air for a pilot flame and which generates a primary swirl in 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 dual-fuel operation with secondary nozzles 80 for heating oil. Natural gas N is supplied to the premixing device 46 as fuel 12.Furthermore, an adjusting device 82 is provided for adjusting the distribution of the fuel 46 to the premixing zones 14.1, 14.2, 14.3.

[0100] Fig. 2 shows in particular an ultra-low NOx WK burner, for example designed as a gas and dual-fuel burner, for very high outputs, e.g. from 200 to 18,000 kW.

[0101] The premix burner 46 features the following NOx reduction technology for operation with natural gas N. By premixing fuel 12 and air 10, the formation of prompt NOx is reduced, in contrast to the classic diffusion flame. A high excess air lowers the flame temperature. This reduces the formation of thermal NOx. The premixed flame is characterized by its compactness and short flame length.

[0102] Via the first premixing zone 14.1 and the second premixing zone 14.2, fuel 12 is fed to the combustion air 10 and the lean fuel-air mixture 16 via gas pipes 32 (longitudinal and transverse to the burner axis) with bores. In the third premixing zone 14.3, fuel 12 is fed directly to the swirl flow of the fuel-air mixture 16 via fuel-carrying swirl vanes 36. The then ignitable fuel-air mixture 18 leaves the combustion head 42 into the combustion chamber 60, where the main flame generated by the fuel-air mixture 18 is stabilized and burned by a primary flame. The primary flame is stabilized by means of a conical slotted baffle plate 78 and a primary swirl.

[0103] A small portion of the total fuel quantity (e.g., by an order of magnitude, at least by a factor of 3 to 10 smaller than the other portions) is directed to the pilot flame generation area equipped with the baffle plate 78. The primary flame (this can be a diffusion flame or a premixed flame) stabilizes the main flame. Advantages of stabilization with the pilot flame (also called the primary flame) include defined, constant ignition conditions for the premixed air / fuel volume 18; reliable ignition; and process monitoring.

[0104] For example, a parameter for the combustion process, e.g. an ionization current of the primary flame, is measured by means of a probe 84 indicated in Fig. 1.

[0105] In the embodiment shown in Fig. 2, a fuel distribution ring 86 provides adjustment options for the fuel quantity supplied to the three premixing zones 14.1, 14.2, 14.3. In a simplified version, the fuel quantity can be adjusted via variable, adjustable screw threads in all inflow cross-sections of the supply pipes.

[0106] By means of the air slide 72, the outlet cross sections 70.1, 70.2 at the combustion head 42 are reduced towards partial load. This causes a pressure buildup and thus a flow velocity buildup and prevents the flame 62 from reigniting into the premixing zones 14.1, 14.n even in the partial load range.

[0107] The fuel is injected into the premixture via an arrangement of perforated pipe cross-sections and / or any hollow geometric bodies 30 with nozzles. In the embodiment shown in Fig. 2, gas pipes 32 with holes and hollow swirl vanes 36, also with holes, are used as gas outlets.

[0108] Any additional atomisation unit can be operated with a NOx reduction technology known, for example, from burners from Max Weishaupt GmbH, which are sold under the multiflam® brand, and which involves a conventional diffusion flame.

[0109] To increase system efficiency, preheated combustion air can be supplied to the combustion head 42 via the optional exhaust gas heat exchanger 68. To reduce the excess air ratio while maintaining comparable pollutant emissions, recirculated exhaust gas from the boiler end can alternatively be mixed with the combustion air via the combustion air fan. This can reduce pollutant emissions.

[0110] Fig. 3 shows a second embodiment for the burner head 42 of the premix burner 40, which essentially corresponds to the first embodiment, but in a design with only a first and a second premixing zone 14.1, 14.2. The gas pipes 32, which are arranged more centrally in the flow direction and which, in the first embodiment, form a central 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.

[0111] Fig. 4 shows a block diagram for a purely exemplary full-load operation of the premix burner 40, in particular of the type shown in Fig. 2. More specifically, Fig. 4 shows simplified gas flows (fuel flows) G and air flows L for the premixing device 46 for an ultra-low NOx burner of the WK series, derived from the known burners according to [9] and

[0010] at full load VL. Fig. 5 shows a block diagram for an exemplary partial-load operation of the same premix burner 40. More specifically, Fig. 5 shows simplified gas flows (fuel flows) B and air flows L for the premixing device 46 for an ultra-low NOx burner of the WK series, derived from the known burners according to [9] and

[0010] at partial load TL. The block diagrams are self-explanatory considering the following labeling: B Gas flows

[0112] L Air flows and mixture flows

[0113] VL full load

[0114] TL partial load

[0115] 100 within first premixing zone 14.1

[0116] 102 near combustion head outlet (further premixing zone(s))

[0117] 62 Flame “A” = 1 .45 (example of combustion air ratio ignitable fuel

[0118] Air mixture 18)

[0119] Full load: 10,000 kW / A = 1.45 / O2,tr. = 7%

[0120] Air slide 72 open

[0121] Gas concentration 2.3 vol% «LEL!!! (A = 1.45)

[0122] (When A=1 is used, the gas concentration is 3.3 vol% « LEL). Fictitious Ä = 4.48

[0123] Combustion air (100%)

[0124] 13,800 rriN 3 / h (Example for 100% combustion air flow 10)

[0125] 312 rriN 3 / h (example value for fuel supply) first gas introduction via perforated pipes (A.1 = 32% - example)

[0126] Tertiary mixture via air valve (example: 50%)

[0127] 6,900 m N3 / h second gas injection via perforated gas pipes (A.2 = 32% - example)

[0128] Secondary mixture via secondary swirl (example: 38%)

[0129] 5,200 m N 3 / h third gas injection via hollow swirl vanes (A.3 = 32% - example)

[0130] Primary mixture via primary swirl (12%)

[0131] 1,700 m N 3 / h

[0132] 29 m N 3 / h « 3% (A.4 - Proportion of fuel for pilot flame)

[0133] Minimum amount of primary gas via baffle plate

[0134] Gas concentration 6.8 vol%

[0135] Gas concentration 8.2 vol%

[0136] Secondary flame (= main flame)

[0137] Gas concentration 4 vol%

[0138] Primary flame (=pilot flame)

[0139] Partial load: 3,500 kW / A = 1.45 / O2, tr. = 7%

[0140] Air slide 72 closed

[0141] 4,800 mN 3 / h

[0142] 109 m N 3 / h

[0143] Tertiary mixture via air valve (0%)

[0144] Secondary mixture via secondary swirl (75%)

[0145] 3,600 m N 3 / h

[0146] Primary mixture over primary swirl (25%) 168 1,200 m N 3 / h

[0147] 170 10 m N 3 / h « 3%

[0148] 172 gas concentration 8.2 vol% 174 gas concentration 3.1 vol%

[0149] The values ​​given in Figs. 4 and 5 are merely examples for the design of a specific burner. Depending on the design, the values ​​- especially with the same ratios to one another - can deviate upwards or downwards, for example by a factor in the range 0.3 - 4, in particular 0.5 - 2. In particular, the part load can vary. The values ​​are calculated using standard volumes, assuming immediate ideal mixing. The values ​​given are to be regarded as a rough estimate. The illustrations in Figs. 4 and 5 provide a highly simplified representation of the processes in the premixing device 46. LEL denotes the lower ignition limit; in the example for natural gas this is E = 4.9 vol%. UEL denotes the upper ignition limit; in the example for natural gas this is E = 14.7 vol%.

[0150] In the following, further embodiments of premix burners 40 are explained with reference to Figures 6 to 11, which - due to the design of the fuel distribution and the computer-implemented control 52 - are set up to carry out combustion processes with ultra-low NOx reduction, taking prompt NOx into account, as explained above by way of example with reference to Figure 1.

[0151] The embodiments shown in Figs. 6 to 11 are designed in particular for a medium power range and are based in particular on known burners as explained in the literature references [7] and [8], wherein instead of the burner heads or combustion heads shown there, the embodiments of burner heads 42 with the premixing devices 46 as explained below with reference to Figs. 6 to 11 are provided and wherein the software in the control referred to in the literature references [7] and [8] as the combustion manager is modified so that in the first premixing zone 14.1 fuel 12 100% of the total air flow 10 is supplied in such a way that the not yet ignitable lean fuel-air mixture 16 is produced, to which in at least one further premixing zone 14.n, and optionally in a pilot flame generation area 76 the remaining portion(s) A.n of the fuel are supplied in such a way that the ignitable fuel-air mixture 18 with excess air is formed under the influence of swirl. As mentioned above, the complete, ie homogeneous, premixing avoids or at least significantly reduces prompt NOx.

[0152] Fig. 6 shows the premixing device 46 in a variant without the flame tube 44, Fig. 7 shows the premixing device 46 in the burner head 42 with flame tube 44 and air or mixture flows L as well as 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 a setting for partial load operation, with fuel flows B indicated. Fig. 9 shows a further variant of the premixing device 46 and Figs. 10 and 11 show optional designs of the burner head 42 with the premixing device 46 for dual-fuel operation (gas / liquid fuel such as oil).

[0153] In the embodiments of Figs. 6 to 11, in addition to the first premixing zone 14.1 with the first fuel supply 20.1, only a second premixing zone 14.2 with the second fuel supply 20.2 is provided.

[0154] The fuel feeds 20.1, 20.2 each comprise, as hollow bodies 30, a central perforated gas tube 32, and an annular body 34 with a cylindrical inner wall and a cylindrical outer wall, both of which have gas outlet openings distributed over their surfaces. In a variant not shown, only one of the fuel feeds, for example, the second fuel feed 20.2, is provided with the annular body 34, while the first fuel feed has gas tubes that extend, for example, radially transversely to the flow direction.

[0155] The swirl device 28 has at least one, preferably several

[0156] Counter-swirl devices 88 for generating swirl with oppositely directed

[0157] 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 casing 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 designed as a counter-swirl device 88 has an inner arrangement 90 of swirl vanes 92.1 (here designed as simple sheets without internal gas guidance) and an outer arrangement 92 of swirl vanes 92.2. The inner swirl vanes 92.1 are equipped with opposite pitch / inclination as the outer swirl vanes 92.2.

[0158] Fig. 7 shows the extension of the first premixing zone 14.1, in which non-ignitable lean fuel-air mixture 16 is formed, and the second premixing zone 14.2, in which ignitable fuel-air mixture 18 with excess air is formed homogeneously.

[0159] The burner head 42 is further provided, as explained above with respect to the embodiment of Fig. 2, with the pilot flame generation region 76 with the swirl-generating baffle plate 78.

[0160] Furthermore, a conical shroud 96 is provided near the outlet of the flame tube 44. The outlet opening region 70 is formed between the conical shroud 96 and the mouth of the flame tube 44. The shroud 96 is movable and thus forms the air slide 72 for adjusting the outlet cross-section 70.1, 70.2 of the outlet opening region 70.

[0161] At the upstream end, the shroud 96 has an inlet opening 98 for the mixture to supply the pilot flame. The cross-section of the inlet opening 98 is smaller than the cross-section between the upstream end of the shroud and the flame tube. Due to the tapered flow cross-section between the shroud 96 and the flame tube, as well as due to the outlet cross-section of the outlet opening region 70, a high velocity develops near the end of the flame head, so that no backfire can occur in the second premixing zone 14.2. Should backfire occur, contrary to expectations, the ignitable mixture 18 is only present in the second premixing zone 14.2, so that only a very small critical mass is present.

[0162] As a comparison of Figures 7 and 8 shows, by shifting the casing 96, the outlet cross-section of the outlet opening region 70 can be reduced for partial load operation, so that even in partial load operation, despite a lower mixture 18 flowing per unit of time, the high speed can be maintained in order to continue to avoid backfiring.

[0163] Fig. 8 further illustrates a self-centering mechanism 180 for the premixing device 46, which simplifies assembly. Furthermore, a gas guide 181, which is improved compared to previously known burners, is shown for uniform pressure distribution. There is no gas / air mixture in a swivel flange area 182, which is leaky due to its function (not shown in detail, as this is already known in principle from [8] and [9]).

[0164] Fig. 10 shows an optional dual-fuel gas / liquid fuel (e.g., oil) design. In addition to the premixing device 46 with the different premixing zones 14.1, 14.2 for gas operation, a fuel divider 184 for liquid fuel such as oil is also shown, as is already generally known in multiflam® burners. Instead of or in addition to the fuel divider 184, a central atomizing nozzle 186, for example, in the center of the baffle plate 78, can also be provided, as shown in Fig. 11.

[0165] In order to enable safe combustion with ultra-low NOx production, a combustion process for burning a fuel-air mixture (except in gas turbines) has been proposed, comprising: a) complete premixing of 100% of an air flow (10) provided for 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) so that a lean fuel-air mixture (16) which is not yet ignitable is produced; 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 adjacent to the first premixing zone (14.1 ) is spaced apart in the flow direction in order to produce an ignitable fuel-air mixture (18) with excess air, wherein step c) comprises: d) swirling the fuel-air mixture (18) produced in the at least one further premixing zone (14.n).

[0166] Furthermore, a premix burner (40) configured to carry out such premixing and combustion has been proposed.

[0167] List of reference symbols:

[0168] 10 Air flow

[0169] 12 Fuel (gaseous)

[0170] 14.1 first pre-mixing zone

[0171] 14.n further premixing zone (n-th premixing zone, with n>1 )

[0172] 16 non-ignitable lean fuel-air mixture

[0173] 18 ignitable fuel-air mixture with excess air

[0174] 20.1 first fuel supply device

[0175] 20. n additional fuel supply device (n-th fuel supply device)

[0176] 22 Actuator

[0177] 24 electronic control unit

[0178] 26 Drill unit

[0179] 26.1 first drilling unit

[0180] 26.2 second drill unit

[0181] 26.3 third drill unit

[0182] 28 Twisting device hollow body for feeding or mixing fuel

[0183] gas pipe

[0184] Ring body

[0185] Swirl wing

[0186] Premix burner

[0187] Burner head (combustion head)

[0188] Flame tube

[0189] Premixing device

[0190] Air supply device

[0191] fan

[0192] Control (example of electronic part of the control means)

[0193] processor

[0194] memory

[0195] Gas supply line of the first fuel supply device

[0196] Gas supply line of the further (n-th) fuel supply device

[0197] Firebox

[0198] flame

[0199] Exhaust gas recirculation

[0200] Air heating device

[0201] exhaust gas heat exchanger

[0202] Outlet opening area fixed outlet cross-section area variable outlet cross-section area

[0203] air damper

[0204] Pilot flame generation area

[0205] baffle plate

[0206] secondary nozzle

[0207] Adjustment device

[0208] probe

[0209] Fuel distribution ring

[0210] Counter-swirl device internal arrangement

[0211] Swirl vane outer arrangement casing

[0212] Inlet opening within the first premixing zone 14.1 near the combustion head outlet (further premixing zone(s))

[0213] “Ä” = 1 ,45 (example of combustion air ratio ignitable fuel

[0214] Air mixture 18)

[0215] Full load: 10,000 kW / A = 1.45 / O2.tr. = 7% (Example for parameters at

[0216] full load)

[0217] Air slide 72 open

[0218] Gas concentration 2.3 vol% «LEL!!! (A = 1.45)

[0219] (When A=1 is used, the gas concentration is 3.3 vol% « LEL). Fictitious Ä = 4.48

[0220] Combustion air (100%)

[0221] 13,800 rriN 3 / h (Example for 100% combustion air flow 10)

[0222] 312 rriN 3 / h (example value for fuel supply) first gas introduction via perforated pipes (A.1 = 32% - example)

[0223] Tertiary mixture via air valve (example: 50%)

[0224] 6,900 m N 3 / h second gas injection via perforated gas pipes (A.2 = 32% - example)

[0225] Secondary mixture via secondary swirl (example: 38%)

[0226] 5,200 m N 3 / h third gas injection via hollow swirl vanes (A.3 = 32% - example)

[0227] Primary mixture via primary swirl (12%)

[0228] 1,700 m N 3 / h

[0229] 29 m N 3 / h « 3% (A.4 - Proportion of fuel for pilot flame)

[0230] Minimum amount of primary gas via baffle plate

[0231] Gas concentration 6.8 vol%

[0232] Gas concentration 8.2 vol%

[0233] Secondary flame (= main flame)

[0234] Gas concentration 4 vol%

[0235] Primary flame (=pilot flame)

[0236] Partial load: 3,500 kW / A = 1.45 / O2.tr. = 7%

[0237] Air slide 72 closed

[0238] 4,800 m N 3 / h 158 109 m N 3 / h

[0239] 160 Tertiary mixture via air valve (0%)

[0240] 162 Secondary mixture via secondary swirl (75%)

[0241] 164 3,600 m N 3 / h

[0242] 166 Primary mixture via primary swirl (25%)

[0243] 168 1,200 m N 3 / h

[0244] 170 10 m N 3 / h « 3%

[0245] 172 Gas concentration 8.2 vol%

[0246] 174 Gas concentration 3.1 vol%

[0247] 180 Self-centering

[0248] 181 Gas routing

[0249] 182 Swivel flange range

[0250] 184 Fuel distribution (liquid fuel / oil)

[0251] 186 central atomizing nozzle

[0252] A.1 first share

[0253] An n-th share

[0254] B Gas flows

[0255] L Air flows and mixture flows

[0256] VL full load

[0257] TL partial load

Claims

Claims:

1. Combustion method for burning a fuel-air mixture, comprising: a) complete premixing of 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), so that a lean fuel-air mixture (16) which is not yet ignitable is produced; 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 an excess of air, wherein step c) comprises: d) swirling the fuel (12) present in the at least one further premixing zone (14.n) resulting fuel-air mixture (18), the combustion process further comprising: e) flowing the fuel-air mixture (18) produced in step c) through an outlet opening region (70) into a combustion chamber (60) and f) burning the fuel-air mixture (18) with a flame (62, 146) in the combustion chamber (60).

2. 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 fan (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 air flow speed (10); 2.4 Setting a fuel distribution to the premixing zones (14.1, 14.n); 2.5 generating a main flame (146) from the ignitable fuel-air mixture (18) after it has left a combustion head (42) in the combustion chamber (60); 2.6 Stabilising the main flame (146) generated with the ignitable fuel-air mixture (18) by means of a primary flame (150); 2.7 Providing a larger outlet cross-section (70, 70.1, 70.2) for the ignitable fuel-air mixture (18) to the combustion chamber (60) in full-load operation and a smaller outlet cross-section (70, 70.1) for the ignitable fuel-air mixture (18) in partial-load operation; 2.8 dividing the ignitable fuel-air mixture (18) over an outlet area with a fixed outlet cross-section (70.1) and an outlet area with a controllable outlet cross-section (70.2) and controlling the controllable outlet cross-section (70.2) depending on the combustion power to be generated; 2.9 Generating a homogeneous ignitable fuel-air mixture (18) in which there is an equal distribution of fuel and air over the entire outlet flow cross-section (70) at least at the end of the last premixing zone (14.n).

3. Combustion method according to one of the preceding claims, wherein step b) contains at least one, several or all of the steps: b1) feeding 10% to 80% of the fuel (12) in the first premixing zone (14.1); b2) feeding 30% to 70% of the fuel (12) in the first premixing zone (14.1); b3) feeding 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 a perforated surface, a perforated gas pipe (32), a gas pipe (32) with lateral bores, a gas pipe (32) extending transversely to the flow direction with bores, a gas pipe (32) extending longitudinally to the flow direction with Bores, a partially annularly extending perforated hollow body (30, 34, 36), an annularly perforated hollow body (30, 34), a hollow annular body (34) extending with its central axis in the flow direction and having bores on at least one inwardly or outwardly directed cylinder 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 portion to the wired air flow (10); b6) generating opposing swirls 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 there is an equal distribution of fuel and air over the entire flow cross-section at least at the end of the first premixing zone (14.1).

4. Combustion process according to one of the preceding claims, wherein step c) comprises at least one, several or all of the steps: c1) admixing a remaining portion (An) in a second premixing zone (14.2); c2) admixing a remaining portion (An) 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 generation region (76) to generate 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 a perforated surface, a perforated gas pipe (32), a gas pipe (32) with lateral bores, a gas pipe (32) extending transversely to the flow direction with bores, a gas pipe (32) extending longitudinally to the flow direction with bores, a perforated hollow body (30, 34, 36 extending partially in a ring shape, 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 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 plate (78).

5. 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 swirls in the fuel-air mixture (16, 18) in different annular regions of the at least one further premixing zone (14.n); d3) generating a swirl in the fuel-air mixture (16) as it passes into the at least one further premixing zone (14.n); d4) generating a swirl in the lean fuel-air mixture (16) before admixing; d5) generating a swirl in the fuel-air mixture (16, 18) to be enriched for ignitability during admixing; d6) generating a swirl by means of gas-conducting and perforated swirl vanes (36); d7) generating a twist for a pilot flame (150) by means of a baffle plate (78) formed by the twist unit (26).

6. Premix burner (40), comprising a flame tube (44) with an outlet opening region (70) which is designed to deliver ignitable fuel-air mixture (18) for combustion into a combustion chamber (60); an air supply device (48) for providing the entire air flow (10) for combustion to the flame tube (44); a premixing device (46) which is designed to deliver 100% of the air flow (10) from the air supply device (46) and supplied with fuel (12) before outlet from the flame tube (44), and a twisting device (28), wherein the premixing device (46) a first fuel supply device (20.1) with control means, wherein the first fuel supply device (20.1) is designed to add 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) that is not yet ignitable 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 designed to add one or more remaining portions (An) of the fuel (16) to the lean fuel-air mixture (16) in at least one further premixing zone (14.n) that belongs to the first premixing zone (14.1 ) in the direction of flow, in order to produce the ignitable fuel-air mixture (18) with excess air for discharge through the outlet opening region (70) of the flame tube (44) into the combustion chamber (60), wherein the swirl device (28) is designed at least for swirling the fuel-air mixture (16, 18) arising or located in the at least one further premixing zone (14.n).

7. 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 shell; 7.2 an inlet opening designed to accommodate 100% of the air flow; 7.3 a taper near a downstream end; 7.4 an outlet cross-section adjustment device (72) for adjusting the outlet cross-section (70.2) of a part of the outlet opening area (70); 7.5 at least one slide (72) for variably adjusting an outlet cross-section of the flame tube (44).

8. 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 connectable to a controller (52).

9. Premix burner (40) according to one of claims 6 to 8, wherein the premixing device (46) further comprises at least one or more of the following features: 9.1 the first premixing zone (14.1) and a second premixing zone (14.2) spaced apart therefrom in the direction of flow; 9.2 a first, second and third premixing zone (14.1, 14.2, 14.3) which follow one another in the direction of flow; 9.3 fixed or variably adjusted fuel flow cross-sections for distributing the portions (A.1, An) of fuel (12) to the first and each further fuel supply device (20.1, 20.n); 9.4 an adjusting device (82) for adjusting a fuel distribution; 9.5 a fuel distribution ring (84) for distributing fuel (12) to the plurality of premixing zones (14.1, 14.n); 9.6 Control means for controlling the fuel supply; 9.7 a control interface connectable to a controller (52).

10. Premix burner (40) according to one of claims 6 to 9, wherein the first fuel supply 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 supply (20.n) such that the predetermined first portion (A.1) of the fuel (12) flows through the first fuel supply device (20.1); 10.2 an adjusting device (82) for adjusting an inflow cross-section of the first fuel supply (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, which comprises a hollow body (30) with nozzles distributed over its surface, a hollow body (30) with a perforated surface, a perforated gas pipe (32), a gas pipe (32) with lateral bores, a gas pipe (32) extending transversely to the flow direction and having bores, a gas pipe (32) extending longitudinally to the flow direction and having bores, a perforated hollow body (30, 34, 36) extending partially in a ring shape, an annular perforated hollow body (30, 34), a hollow annular body (34) extending with its central axis in the flow direction and having bores on at least one inwardly or outwardly directed cylindrical surface, a hollow swirl vane (36) with bores, and combinations of the aforementioned hollow bodies (30); 10.4 computer-implemented control means for controlling the fuel supply.

11. Premix burner (40) according to one of claims 6 to 10, wherein the further fuel supply 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 supply (20.1) such that the predetermined further portion (An) of the fuel (12) flows through the further fuel supply device (20.n); 11 .2 a second fuel supply device (20.2) in a second premixing zone (14.2); 11 .3 a third fuel supply device (20.3) in a third premixing zone (14.3); 11 .4 a pilot flame fuel supply device for supplying a portion of the fuel (12) to a pilot flame (150) which is at least a factor of 3 smaller than the portions (A.1, A.2, A.3) of the first fuel supply and a second fuel supply (20.1, 20.2, 20.3); 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 a perforated surface, a perforated gas pipe (32), a gas pipe (32) with lateral bores, a gas pipe (32) extending transversely to the flow direction and having bores, a gas pipe (32) extending longitudinally to the flow direction and having bores, a perforated hollow body (30, 34, 36) extending partially in a ring shape, an annular perforated hollow body (30, 34), a hollow annular body (34) extending with its central axis in the flow direction and having bores on at least one inwardly or outwardly directed cylinder surface, a hollow swirl vane (36) with bores, and combinations of the aforementioned hollow bodies (30); 11 .7 computer-implemented control means for controlling the fuel supply.

12. 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 premixing zone (14.1); 12.2 a counter-twisting device (88) for generating twist with opposite twist directions in different annular zones of the flame tube (44); 12.3 a first twist unit (26.1) in or before the first premixing zone (14.1) and at least one further twist unit (26.2) in the transition to or in a further premixing zone (14.n); 12.4 an inner arrangement (90) of twist blades (92) and an outer arrangement (94) of twist blades (92); 12.5 twist vanes (36) designed as hollow bodies (30) with nozzles for fuel supply; 12.6 a primary flame swirl unit (26) on a baffle plate (78).

13. 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 stabilising a primary flame (146); 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 air flow (10); 13.5 a controller (52) configured to cause the premix burner (40) to carry out the combustion method according to one of claims 1 to 5.

14. A control (52) for a premix burner (40) according to any one of claims 6 to 13, which is configured to cause the premix burner (40) to automatically carry out the combustion method according to any one of claims 1 to 5.

15. A computer program comprising instructions for causing a premix burner (40) according to any one of claims 6 to 13 to carry out the combustion method according to any one of claims 1 to 5.

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