Fuel nozzle having expansion slits for a pulverized-coal burner

Abstract

The invention relates to a fuel nozzle (100) for a burner for burning particulate fuel, in particular powdered, carbon-containing fuel such as coal or biomass, the fuel nozzle comprising a fuel pipe portion (110), which is to be associated with a fuel pipe or primary-air pipe (200) of the burner, and comprising an opening portion (120), which is integrally connected to the fuel pipe portion (110) and is provided for forming an opening region (210) of the fuel pipe or primary-air pipe (200), the fuel pipe portion (110) having a fuel-pipe-side end (111) for connecting to the fuel pipe or primary-air pipe (200) and the opening portion (120) having an opening-side end (121). The aim of the invention is to provide a solution which allows the service life of burners for burning particulate fuel to be optimized by reducing thermal stresses in the material, in particular in the opening region of the fuel pipe or primary-air pipe (200) or in the fuel nozzle (100). This is achieved because the fuel nozzle (100) has expansion slits (160) for compensating a thermal alternating load on the fuel nozzle (100), which expansion slits are arranged along the circumference of the fuel nozzle, extend axially along the longitudinal extent of the fuel nozzle toward the opening-side end (121), end in an opening-side end face (122) of the fuel nozzle (100) and are in the form of notches that extend through and sever the material wall of the fuel nozzle (100) in the radial direction.

Description

[0001] The invention relates to a fuel nozzle for a burner for the combustion of particulate fuel, in particular dust-like, carbon-containing fuel such as coal or biomass, wherein the fuel nozzle is designed as a cast part with a fuel tube section to be assigned to a fuel or primary air tube of the burner and a mouth section connected in one piece with the fuel tube section and provided for forming an opening region of the fuel or primary air tube, wherein the fuel tube section has a fuel tube-side end for connection to the fuel or primary air tube and the mouth section has a mouth-side end and,wherein the orifice section of the fuel nozzle is designed radially outwardly as a flow element in the form of an air deflection groove which widens conically radially outwards in the direction of the orifice-side end of the fuel nozzle and has a radially inwardly pointing stabilising ring provided with teeth at its orifice-side end,

[0002] Furthermore, the invention is directed to a method for producing a fuel nozzle for a burner for the combustion of particulate fuel, in particular dust-like, carbon-containing fuel such as coal or biomass, wherein the fuel nozzle is designed as a cast part with a fuel tube section to be assigned to a fuel or primary air tube of the burner and a mouth section connected in one piece with the fuel tube section and provided for forming an opening region of the fuel or primary air tube.

[0003] Finally, the invention is directed to a burner for the combustion of particulate fuel, in particular dust-like, carbon-containing fuel such as coal or biomass, with a fuel or primary air pipe and a jacket or secondary air pipe coaxially surrounding the fuel or primary air pipe, wherein the fuel or primary air pipe opens into a fuel nozzle and the fuel nozzle is designed as a cast part with a fuel pipe section assigned to the fuel or primary air pipe and a mouth section connected in one piece with the fuel pipe section and forming a mouth region of the fuel or primary air pipe, with a mouth-side end,wherein the orifice section of the fuel nozzle is designed radially outwardly as a flow element in the form of an air deflection groove which widens conically radially outwards in the direction of the orifice-side end of the fuel nozzle and has a radially inwardly pointing stabilising ring provided with teeth at its orifice-side end.

[0004] When developing burners for the combustion of particulate fuels, especially pulverized, carbonaceous fuels such as coal or biomass, and especially pulverized coal, particular emphasis is still placed on a low rate of nitrogen oxide (NOx) released during combustion. For example, dividing the combustion air into several partial streams and adjusting the individual air streams in terms of air volume, air distribution, and swirl intensity enables a reduction in nitrogen oxide emissions during the combustion of pulverized, carbonaceous fuels.

[0005] For example, DE 10 2005 032 109 B4 discloses a pulverized coal burner with a fuel or primary air tube that conveys the fuel, in particular pulverized coal. To enable a staged air supply, the fuel or primary air tube is coaxially surrounded by a jacket air or secondary air tube, which in turn is surrounded by a tertiary air tube. A core air tube equipped with an ignition lance is arranged centrally within the fuel or primary air tube. The ignition of the pulverized fuel occurs in the outlet area of the fuel tube and is achieved by igniting the volatile components escaping from the solid fuel during initial pyrolysis by means of the ignition lance.

[0006] By clearly defining the ignition conditions in terms of time and location in the outlet region of the fuel or primary air pipe, the NO x emissions released during combustion can be further reduced. For this purpose, various flow elements can be provided in the outlet region of the fuel or primary air pipe. For example, according to EP 1 741 977 B1, a section that widens conically radially outwards, a so-called air guide groove, on the outside of the outlet end of the fuel pipe can ensure an ignition process that takes place without influencing the secondary air and is not disrupted by air fluctuations or turbulence. An internally arranged stabilizing ring with a radially inwardly projecting toothed ring serves to capture, delay and deflect the fuel in order to ignite the fuel particles, preferably in the region of the toothed ring of the stabilizing ring.Typically, the fuel or primary air tube and the stabilizing ring, on the one hand, and the fuel or primary air tube and the air deflector groove, on the other, are connected to each other in the outlet area by welds, clamps, or bolts. However, such welds or joints can lead to increased susceptibility to repair and failure in the outlet area of the fuel or primary air tube, which is subject to high stress and aggressive media flowing through it, and consequently to a reduced service life.

[0007] To avoid such a reduction in service life, EP 1 741 977 B1 further proposes producing the outlet region of the fuel or primary air pipe as a separate component or fuel nozzle in one piece, and embodying it on the outside in the form of a conically extending radially outwardly directed jacket air or secondary air deflection cone, and on the inside in the form of a stabilizing ring with a radially inwardly directed toothed ring. This preferably cast component can then be welded, for example, to the end face of a fuel or primary air pipe using a circumferential weld seam in order to reduce the total number of welds in the outlet region of the fuel or primary air pipe. EP 1 741 977 A1 discloses a fuel nozzle having the features of the preamble of claim 1 and a method for producing a fuel nozzle having the features of the preamble of claim 7.

[0008] Such a burner with primary, secondary and tertiary tubes arranged concentrically to one another and a fuel nozzle forming the mouth area of the fuel or primary air tube and provided in one piece with an outwardly facing air deflection cone and an inwardly facing stabilizing ring is also known from WO 2017 / 008937 A1.

[0009] However, even with the previously described fuel nozzles, which are formed as a single piece in the orifice area of the fuel or primary air pipe, cracking due to temperature fluctuations can occur after several years of operation and frequent load changes.

[0010] In other fields of expertise, it is known from the state of the art to provide elongated recesses in the form of slots to compensate for thermally induced stresses.

[0011] In the field of exhaust gas turbochargers for internal combustion engines, for example, EP 1 724 443 A1 discloses a nozzle ring designed to direct the working medium to the guide vanes of the exhaust gas turbocharger's turbine. The nozzle ring essentially comprises an outer ring and an inner ring, as well as a plurality of flow guide vanes arranged therebetween. The flow guide vanes are connected to the outer ring in such a way that they can deform elastically in the radial direction. Between each two guide vanes of the nozzle ring, a slot is formed in the outer ring along the guide vane contour to enable the guide vanes, under high thermal loads, to deform elastically in the radial direction independently of one another and of the nozzle ring.

[0012] EP 1 512 489 A1 also concerns a similar problem, namely creating a turbine blade exposed to particularly low thermal stresses. In gas turbines, in addition to the mechanical stress caused by high speeds, high temperatures also cause thermal stress on the blade material. To relieve thermal stresses caused by the high temperatures, relief slots are provided in the trailing edge of the gas turbine blade. These slots extend transversely through the trailing edge.

[0013] While the turbine blades described above are exposed to high but essentially constant temperatures, low-NOx burners of the type described above are subject to thermal cycling, particularly in conventional power plants with fossil-fired steam generators. Due to the recent increase in the use of electrical energy from renewable energy sources, whose feed-in to the power grid is not uniform but depends on the availability of solar or wind power, even fossil-fired power plants are subject to greater demands on load flexibility. The steam generation capacity currently required for feed-in to the power grid is varied by changing the mill or burner capacity and by switching individual grinding plants and their associated burners on or off.This means that with frequent load changes, the burner must be started up and shut down accordingly and consequently an increased number of ignition processes with associated temperature changes must take place.

[0014] From CN 206 191 575 U a fuel nozzle is known which has evenly distributed expansion joints or expansion slots.

[0015] A generic fuel nozzle and a generic burner are known from EP 1 741 977 A1. This document also discloses a method for producing a generic burner nozzle using a casting process.

[0016] In conventional low-NOx burners, the ignition firing system typically consists of ignition lances or similar burners, which generate the ignition flame required for combustion by burning gaseous or liquid auxiliary fuel, such as natural gas or heating oil. During the ignition process, the burner, which is initially not in operation ("out of operation"), is exposed to different temperatures determined by the sequential stages of the ignition process. Thus, the ignition of the auxiliary burner for combustion of the gaseous or liquid auxiliary fuel is followed by the ignition of the main burner for combustion of the particulate, particularly dust-like, carbonaceous fuel. To reduce the steam generator output, combustion is stopped, and the burner returns to the "out of operation" state.Frequent burner operating cycles therefore often result in significant temperature fluctuations in the range between 300°C and 1100°C, the respective maximum values of which are reached at the combustion chamber end, i.e., in the orifice area of the fuel or primary air tube, also known as the dust tube, formed by the fuel nozzle. Due to these thermal cycling loads, the material of the fuel nozzle, particularly in one-piece fuel nozzles, is subject to an increased risk of cracking, which can ultimately lead to a loss of shape of the flow-defining components and, consequently, to a reduction in functionality or even loss of functionality.

[0017] The invention is therefore based on the object of creating a solution that makes it possible to optimize the service life of burners for the combustion of particulate fuel.

[0018] This object is achieved according to the invention by a burner nozzle according to claim 1, a method according to claim 7 and a burner according to claim 8.

[0019] Advantageous embodiments and expedient further developments of the invention are the subject of the respective subclaims.

[0020] In a fuel nozzle of the type described in more detail at the outset, the above object is achieved according to the invention in that the fuel nozzle has expansion slots arranged along its circumference and extending axially in its longitudinal extent in the direction of the orifice-side end and terminating in an orifice-side end face of the fuel nozzle and designed in the form of incisions penetrating and severing the material wall of the fuel nozzle in the radial direction to compensate for thermally induced alternating loading of the fuel nozzle, wherein the orifice section of the fuel nozzle is divided into separate individual segments by means of the expansion slots in such a way that the air deflection groove is divided into individual air deflection segments due to the expansion slots and the stabilization ring is divided into individual stabilization segments due to the expansion slots,wherein a stabilizing segment is delimited on the inside by a toothed ring arch connected in one piece with the respective stabilizing segment, and wherein the individual segments each form an air deflection segment on the outside and a stabilizing segment on the inside, and wherein the fuel tube section and the mouth section divided into the individual segments are connected to one another and formed in one piece by means of an unslotted, cylindrical-tubular section of the fuel tube section formed on the side of the fuel tube section facing the fuel or primary air tube.

[0021] According to the invention, it is thus provided to compensate for thermal stress caused by temperature changes, in particular thermally induced volume changes in the material of the fuel nozzle, particularly in the orifice region of the fuel or primary air tube, by designing the fuel nozzle with expansion slots. These expansion slots are designed as material recesses in the form of narrow, elongated incisions or openings that run axially in the direction of the orifice-side end of the fuel nozzle and, along their longitudinal extent, completely penetrate and sever the material wall of the fuel nozzle radially from the outside to the inside of the fuel nozzle. They are arranged along the circumference of the fuel nozzle in such a way that a compensation space is created for thermal expansion of the material of the fuel nozzle, for example, caused by the ignition process of the burner.The fuel tube section and the orifice section remain connected to one another lengthwise and by means of a circular, cylindrical tube-shaped section of the fuel tube section which is formed on the side of the fuel or primary air tube and has no expansion slots, or via such a section of the fuel tube section, so that the fuel nozzle as a whole, but also the fuel tube section together with the orifice section cut into individual segments, are formed in one piece.

[0022] According to the invention, the expansion slots are used to divide the orifice section of the fuel nozzle, and consequently the orifice region of the respective associated fuel or primary air tube, into separate individual segments that are movable independently of one another in the event of temperature-related volume changes in the fuel nozzle material. In this way, the transfer of thermally induced stresses that occur locally in one area or on an individual segment of the fuel nozzle to other areas and / or adjacent individual segments of the fuel nozzle can be prevented.

[0023] In summary, the expansion slots provided according to the invention and the division of the fuel nozzle orifice into individual segments allow thermally induced alternating loads, such as those that occur particularly during the operation of burners in steam generators, and the associated volume changes in the fuel nozzle material to be compensated, thus reducing material stresses. This reduces the formation of cracks or even completely prevents them, which in turn increases the durability of the fuel nozzle and thus the service life of the associated burner.

[0024] A particularly suitable location for the initial ignition of the burner is the nozzle end or the nozzle section of the fuel nozzle. As described, therefore, external (i.e., radially outwardly directed) and / or internal (i.e., radially inwardly directed) flow elements in the form of an air deflection groove and / or a stabilizing ring are preferably arranged at the nozzle end or in the region of the nozzle section to define the ignition conditions. However, particularly high temperatures or temperature fluctuations occur precisely at the initial ignition location, which exposes the fuel nozzle material to particularly severe stresses.

[0025] For this reason, the invention also provides that the orifice section of the fuel nozzle is designed as an air deflection groove which widens conically radially outwards in the direction of the orifice-side end and is divided into individual air deflection segments due to the expansion slots.

[0026] Accordingly, according to the invention, the orifice section of the fuel nozzle comprises, at its orifice-side end, a radially inwardly facing stabilizing ring, in particular provided with teeth, which is divided into individual stabilizing segments by means of the expansion slots. The orifice section and the stabilizing segments, in particular provided with teeth, are formed as a single-piece component. The single-piece construction is achieved by / via the connection of the stabilizing segments to the unslotted, cylindrical-tubular section of the fuel tube section on the side of the fuel tube section facing the fuel or primary tube.

[0027] By designing flow elements arranged on the outside and / or inside of the fuel nozzle orifice section, such as an air deflection groove as separate, independent, and radially outward-facing air deflection segments and / or a stabilization ring as separate, independent, and radially inward-facing stabilization segments, stresses that occur particularly in the area of the fuel nozzle orifice section due to alternating thermal loading can also be reduced in the flow elements arranged there. In this way, crack formation can be reduced, particularly within the flow elements that are crucial for defining the ignition location and ignition conditions—the air deflection segments and / or the stabilization segments—and their service life can be increased.In their entirety, the individual air deflection segments then fulfil the function of the known air deflection groove and the individual stabilization segments fulfil the function of the known stabilization ring, thereby ensuring a clear temporal and spatial definition of the ignition conditions in the muzzle area.

[0028] A radially inwardly pointing stabilization segment terminates in a plurality of teeth formed in the form of a toothed rim arch, i.e. the stabilization segment is delimited on the inside by a toothed rim arch connected in one piece with the respective stabilization segment.

[0029] The entire fuel nozzle is designed as a single-piece component, with the air deflection segments and the stabilizing segments, which terminate in a respective gear ring arc, separated from each other in the nozzle opening section by the expansion slots provided there. These features result in a fuel nozzle optimized for thermal cycling, such as those encountered at fuel nozzles in the opening area of a fuel or primary air pipe, particularly during the operation of steam generators in fossil-fueled power plants, and suitable for defining specific ignition conditions.

[0030] In an advantageous embodiment of the invention, the axial length of the expansion slots corresponds approximately to 1 / 3 to 2 / 3 of the total axial length of the fuel nozzle.

[0031] As far as the number of expansion slots is concerned, according to an equally preferred embodiment of the invention it is advantageous that the number, depending on the circumference of the fuel nozzle, is in a range between 4 and 8.

[0032] A ratio between the axial length of the expansion slots and the total axial length of the fuel nozzle, which lies in a range between 1 / 3 and 2 / 3, especially in combination with a number of expansion slots which lies in a range between 4 and 8, represents an optimized compromise between the flexibility required to compensate for the alternating thermal load and the overall necessary stability of the fuel nozzle. The exact number of expansion slots depends on the size of the burner or the circumference of the fuel nozzle.

[0033] A further advantage of the invention consists in a configuration according to which the expansion slots extend into the region of the fuel tube section of the fuel nozzle and each open into a circular recess.

[0034] Due to the continuous radial curvature of the circular recess, stresses occurring locally in the area of the fuel tube section at the respective end of the expansion slots can be reduced.

[0035] It may be expedient for the respective recesses to be designed as circular bores and for the expansion slots to be designed as incisions extending from the respective recess to the orifice-side end of the fuel nozzle. A fuel nozzle designed in this way offers advantages above all from the point of view of the manufacture or production of fuel nozzles. During production of a fuel nozzle according to the invention, the radial and / or axial position of the end of an expansion slot arranged in the fuel tube section of the fuel nozzle can be precisely determined by introducing a circular bore into the fuel tube section at the desired position, extending radially in the direction of the longitudinal axis of the fuel nozzle through the material wall of the fuel nozzle.Starting from the circular bore, the corresponding expansion slot can then be designed as an incision directed axially towards the orifice end of the fuel nozzle and cutting through the material wall of the fuel nozzle.

[0036] To further simplify production and reduce manufacturing costs, a preferred embodiment of the invention provides that the expansion slots are arranged to extend in their longitudinal extent parallel to a longitudinal axis of the fuel nozzle, in particular parallel to one another, and to coaxially surround the longitudinal axis of the fuel nozzle.

[0037] Particularly advantageous in this fuel nozzle variant is that all expansion slots can be cut into the material wall of the fuel nozzle in a single or the same manufacturing step.

[0038] Finally, according to one embodiment of the invention, it is also advantageous for a fuel nozzle to be designed as a centrifugally cast component.

[0039] A design of the fuel nozzle as a cast part, in particular as a centrifugally cast part, is particularly suitable for producing a one-piece component which has the shape of radially outwardly and / or radially inwardly directed flow elements, such as radially outwardly pointing air deflection segments and / or radially inwardly pointing stabilization segments, in particular comprising teeth.

[0040] To achieve the object of the invention mentioned at the outset, a method for producing a fuel nozzle, in particular a fuel nozzle according to the invention according to one of the previously described embodiments, for a burner for the combustion of particulate fuel, in particular dust-like, carbon-containing fuel such as coal or biomass, is also suitable, wherein the fuel nozzle is designed as a cast part with a fuel tube section to be assigned to a fuel or primary air tube of the burner and a mouth section connected in one piece with the fuel tube section and provided for forming an opening region of the fuel or primary air tube,wherein in a first manufacturing step, the fuel nozzle is cast as a one-piece component with a mouth section designed as an air deflection groove that widens conically in the direction of the mouth-side end radially outwards and a stabilizing ring that points radially inwards at the mouth-side end of the mouth section and is provided with teeth, and in a second manufacturing step following the first manufacturing step, circular recesses are drilled along the circumference of the fuel nozzle into the fuel tube section through the material wall of the fuel nozzle, in particular at a distance from one another, and in a third manufacturing step following the second manufacturing step, starting from the circular recesses drilled into the fuel tube section, narrow, in particular elongated,Expansion slots in the form of incisions penetrating and severing the material wall of the fuel nozzle in the radial direction in the direction of a nozzle-side end of the fuel nozzle and penetrating and severing a nozzle-side end face of the fuel nozzle.

[0041] Preferably, at the beginning of the manufacturing process in the first manufacturing step, the fuel nozzle with the radially outwardly facing and / or radially inwardly facing flow elements in the form of an air deflection groove and / or a stabilizing ring, in particular provided with teeth, is manufactured in a centrifugal casting process as a one-piece component.

[0042] In the second manufacturing step, the fuel tube section is then provided along its circumference preferably with 4 to 8 bores, depending on the circumference of the fuel nozzle, wherein the distance of the bores from a mouth-side end of the fuel nozzle corresponds in each case to approximately 1 / 3 to 2 / 3 of the total length of the fuel nozzle.

[0043] Starting from these bores, in a third manufacturing step, narrow, elongated expansion slots are cut toward the nozzle end of the fuel nozzle, preferably parallel to each other and parallel to a longitudinal axis of the fuel nozzle. By forming the expansion slots in the form of incisions penetrating the material wall and the nozzle end face of the fuel nozzle, the third manufacturing step further divides the air deflector groove, which widens conically radially outward toward the nozzle end, into individual air deflector segments, and the radially inward-facing stabilizing ring, which is particularly provided with teeth, into individual stabilizing segments.

[0044] The fuel nozzle according to the invention is suitable both for retrofitting or as a replacement part for burners, which are used in particular in existing fossil-fueled steam power plants. Alternatively, it is also conceivable to provide the fuel or primary air tube of a burner directly during its manufacture with expansion slots according to the invention arranged in the mouth area of the fuel or primary air tube.

[0045] In a burner of the type described in more detail at the outset, the above object is achieved according to the invention in that the burner comprises a fuel nozzle according to claim 1, wherein the burner has a fuel or primary air pipe and a jacket or secondary air pipe coaxially surrounding the fuel or primary air pipe, wherein the fuel or primary air pipe opens into the fuel nozzle and the fuel nozzle is designed as a cast part with a fuel pipe section assigned to the fuel or primary air pipe and a mouth section connected in one piece with the fuel pipe section and forming a mouth region of the fuel or primary air pipe, with a mouth-side end,wherein the orifice section of the fuel nozzle is designed radially outwardly as a flow element in the form of an air deflection groove that widens conically radially outwards in the direction of the orifice end of the fuel nozzle and has a radially inwardly facing, toothed stabilizing ring at its orifice end, wherein the fuel nozzle has expansion slots arranged along its circumference and extending axially in its longitudinal extent in the direction of the orifice end and terminating in an orifice end face of the fuel nozzle, and designed in the form of incisions that penetrate and sever the material wall of the fuel nozzle in the radial direction to compensate for thermally induced alternating loading of the fuel nozzle, wherein the orifice section of the fuel nozzle is divided into separate individual segments by means of the expansion slots,that the air deflection groove is divided into individual air deflection segments due to the expansion slots and the stabilizing ring is divided into individual stabilizing segments due to the expansion slots, wherein each stabilizing segment is delimited on the inside by a toothed ring arc connected in one piece with the respective stabilizing segment, and wherein the individual segments each form an air deflection segment on the outside and a stabilizing segment on the inside, and wherein the fuel tube section and the mouth section divided into the individual segments are connected to one another and formed in one piece by means of an unslotted cylindrical tube-shaped section of the fuel tube section formed on the side of the fuel tube section facing the fuel or primary air tube.

[0046] According to the invention, such a burner is characterized in that the fuel nozzle has expansion slots arranged along its circumference and extending axially in its longitudinal extent in the direction of the orifice-side end and ending in an orifice-side end face of the fuel nozzle and designed in the form of incisions penetrating and severing the material wall of the fuel nozzle in the radial direction to compensate for a thermally induced alternating load on the fuel nozzle.

[0047] The invention is fundamentally not limited to burners with a fuel or primary air tube whose fuel nozzle is designed as a separate, one-piece component. Thus, it is also conceivable to provide the orifice area of a fuel or primary air tube with an integral fuel nozzle with expansion slots according to the invention in order to compensate for the thermally induced alternating loads occurring there.

[0048] In an advantageous embodiment of the burner according to the invention, it is then provided that the fuel tube section of the fuel nozzle has a fuel tube-side end and the fuel or primary air tube is connected, in particular welded, to the fuel tube-side end of the fuel tube section.

[0049] Preferably, the burner according to the invention and its fuel nozzle are each manufactured as separate components, with the fuel nozzle, in particular, being provided with expansion slots during its manufacture. The fuel nozzle can then be welded, for example, to the end face of the fuel or primary air pipe using a circumferential weld seam. This design is particularly advantageous in that any radially outwardly and / or inwardly directed flow elements can be integrally formed onto the nozzle opening and / or the nozzle-side end of the fuel nozzle during manufacture.

[0050] Finally, the burner according to the invention according to claim 8 or 9 is further characterized in that the fuel nozzle is designed according to one of claims 2 - 6.

[0051] The invention is explained in more detail below with reference to the drawings, which show Figure 1 is a schematic perspective view of an exemplary embodiment of a fuel nozzle according to the invention with seven expansion slots and Figure 2 is a schematic side view of the exemplary embodiment of the fuel nozzle according to the invention from Figure 1 .

[0052] The Figure 1shows a schematic perspective view of an exemplary embodiment of a fuel nozzle 100 according to the invention. The fuel nozzle 100 shown has a fuel tube section 110, the fuel tube-side end 111 of which is suitable for connection to a fuel or primary air pipe 200, indicated by the dashed line, of a burner not shown in detail. During operation of the burner, a carrier gas, in particular air, mixed with a granular, powdery solid fuel such as coal and / or biomass, is conveyed in the fuel or primary air pipe 200. Adjacent to the fuel tube section 110 and formed as a one-piece component therewith, the fuel nozzle 100 further has an orifice section 120, the orifice-side end 121 of which is assigned to a combustion chamber (not shown) during operation of the burner.protrudes into the combustion chamber and thus forms an outlet region 210 of the fuel tube 200. Several expansion slots 160, here seven, are arranged at equal distances from one another along the circumference of the fuel nozzle 100. The expansion slots 160 run both parallel to one another and parallel to a longitudinal axis z of the fuel nozzle 100, or coaxially surround the longitudinal axis z of the fuel nozzle 100. The expansion slots 160 are designed in the form of narrow longitudinal sections and longitudinal slots extending along the longitudinal axis z.

[0053] A first end of each expansion slot 160 opens into a circular recess 161, in particular a bore, which radially penetrates the fuel tube section 110, i.e., through the material wall of the fuel nozzle 100, forms a connection from the outside of the fuel nozzle 100 to its interior. Starting from the associated recess 161, a respective expansion slot 160 extends axially in the direction of the orifice-side end 121 of the fuel nozzle 100. The distance between a recess 161 and the orifice-side end 121 of the fuel nozzle 100, or the length of an expansion slot 160, corresponds approximately to 2 / 3 of the total axial length of the fuel nozzle 100. The expansion slots 160 completely penetrate the fuel nozzle 100 in the radial direction, i.e.,They are designed to completely sever the material wall of the fuel nozzle 100 and end in the axial longitudinal direction in an orifice-side end face 122 of the fuel nozzle 100, so that a portion of the fuel tube section 110 and the orifice section 120 of the fuel nozzle 100 are divided into separate, independently movable individual segments 130 by means of the expansion slots 160. Due to the expansion slots 160, thermally induced volume changes in the material of the fuel nozzle 100 can be compensated for, so that overall stresses caused by thermal cycling are reduced, which leads to a reduction in crack formation and thus to greater durability of the fuel nozzle 100. Furthermore, the recesses 161 can be used to reduce stresses that occur at the end of a respective expansion slot 160 due to relative movements of various individual segments 130 to one another.

[0054] The fuel nozzle 100 is provided in its orifice section 120 with flow elements for specifying and defining the ignition conditions. At the orifice end 121, the orifice section 120 has radially inwardly facing stabilizing segments 150, which together form a toothed ring and are each separated or spaced from one another by an expansion slot 160 radially severing the material wall of the fuel nozzle 100. Each stabilizing segment 150 terminates in a toothed ring arc with inwardly facing teeth 151 or is delimited by the teeth 151. The stabilizing segments 150 with the associated teeth 151 are individually and independently movable to compensate for thermally induced stresses and, as a whole, form a stabilizing ring with teeth 151 for capturing, delaying, and redirecting the fuel guided in the fuel or primary air tube 200.

[0055] In the Figure 2, which is a schematic side view of the exemplary embodiment of the fuel nozzle 100 according to the invention from Figure 1It is clearly visible that the orifice section 120 has the shape of another flow element on the radial outside. Thus, the orifice section 120 is formed in the form of air deflection segments 140 that conically widen radially outward toward the orifice end 121. The air deflection segments 140 are each separated or spaced from one another by an expansion slot 160 and are independently movable to compensate for thermally induced stresses. As a whole, the air deflection segments 140 form a flow element in the form of an air deflection groove.Together with a jacket air or secondary air tube (not shown here), which typically coaxially surrounds the fuel or primary air tube 200 in burners for the combustion of pulverized carbon, the air deflection segments 140 enable an ignition process that proceeds without influencing the secondary air and is not disturbed by air fluctuations or turbulence. The fuel tube-side end 111, which delimits the fuel tube section 110 of the fuel nozzle 100, is designed for connection to the fuel or primary air tube 200 (see . Figure 1 ) of a burner and can be welded, for example, to the front side of the fuel or primary air pipe 200.

[0056] Like the Figure 1 and 2As can be seen, the entire fuel nozzle 100 is designed as a one-piece component and is preferably manufactured using a centrifugal casting process. In combination with the expansion slots 160 extending to the orifice-side end 121, a low-stress component is thus provided, which is suitable for use as a fuel nozzle 100 in the orifice region 210 of a fuel or primary air pipe 200 of a burner for a steam power plant, which is subject to particularly high thermal stress due to pronounced temperature fluctuations. Due to the reduced crack formation in the fuel nozzle 100 according to the invention, the service life of a burner equipped therewith can be significantly increased.

[0057] The fuel tube section 110 and the mouth section 120 are connected to one another lengthwise and by means of a circular, cylindrical tube-shaped section of the fuel tube section 110 which is formed on the side of the fuel or primary air tube 200 and does not have any expansion slots, or via such a section of the fuel tube section 110, so that the fuel nozzle 100 as a whole, but also the fuel tube section 110 together with the mouth section 120 cut into individual segments 130, are formed in one piece.

[0058] The shape of the incisions or expansion slots 160 does not have to be straight or elongated. The incisions or expansion slots 160 could also be curved, wavy, or similar.

[0059] Even if in the exemplary embodiment the bores or recesses 161 and thus the beginning of each expansion slot 160 are formed in the region of the fuel tube section 110, these, ie the bores and recesses 161 as well as the beginning of the expansion slots 160, can also be formed exactly in the transition from the fuel tube section 110 to the mouth section 120 or exclusively in the mouth section 120.

[0060] The holes 160 and the expansion slots 161 can be drilled and cut into the material wall by mechanical machining or can be formed in the material wall by means of a laser beam. List of reference symbols:

[0061] 100Fuel nozzle 110Fuel tube section 111Fuel tube end 120Mouth section 121Mouth end 122Mouth end face 130Single segment 140Air deflection segment 150Stabilization segment 151Teeth 160Expansion slot 161Recess 200Fuel or primary air tube 210Mouth area of the fuel or primary air tube zLongitudinal axis of the fuel nozzle

Claims

1. Fuel nozzle (100) for a burner for burning particulate fuel, in particular powdered, carbon-containing fuel such as coal or biomass, wherein the fuel nozzle (100) is formed as a cast portion having a fuel pipe portion (110) to be associated with a fuel pipe or primary air pipe (200) of the burner and an opening portion (120) integrally connected to the fuel pipe portion (110) and provided for forming an opening region (210) of the fuel pipe or primary air pipe (200), wherein the fuel pipe portion (110) comprises a fuel pipe side end (111) for connection to the fuel pipe or primary air pipe (200) and the opening portion (120) comprises an opening side end (121), and wherein the opening portion (120) of the fuel nozzle (100) radially on the outside is formed as a flow element in the form of an air deflection groove which widens conically in the direction of the opening side end (121) of the fuel nozzle (100) radially outward and comprises at its opening side end (121) a stabilizing ring provided with teeth (151), directed radially inwards, characterized in that the fuel nozzle (100) comprises expansion slits (160), which are arranged along its circumference and extend axially in the longitudinal extension thereof in the direction of the opening side end (121), and end in an opening side end face (122) of the fuel nozzle (100) and are formed in the form of incisions which penetrate and sever the material wall of the fuel nozzle (100) in the radial direction, for compensating for a thermally induced alternating load on the fuel nozzle (100), wherein the opening portion (120) of the fuel nozzle (100) is subdivided into separate individual segments (130) by means of the expansion slits (160) in such a way that the air deflection groove is subdivided due to the expansion slits (160) into individual air deflection segments (140) and the stabilizing ring is subdivided into individual stabilizing segments (150) due to the expansion slits (160), wherein a stabilizing segment (150) is respectively limited on the inside by a toothed rim arc integrally connected to the respective stabilizing segment (150), and wherein the individual segments (130) on the outside respectively form an air deflection segment (140) and on the inside respectively form a stabilizing segment (150), and wherein the fuel pipe portion (110) and the opening portion (120) subdivided into the individual segments (130) are connected to each other and formed integrally by means of an unslitted cylinder pipe shaped portion of the fuel pipe portion (110) formed on the side of the fuel pipe portion (110) facing the fuel pipe or primary air pipe (200).

2. Fuel nozzle (100) according to claim 1, characterized in that the axial length of the expansion slits (160) corresponds approximately to 1 / 3 to 2 / 3 of the axial overall length of the fuel nozzle (100).

3. Fuel nozzle (100) according to claim 1 or 2, characterized in that the number of the expansion slits (160) is in a range between 4 and 8.

4. Fuel nozzle (100) according to any one of the preceding claims, characterized in that the expansion slits (160) extend into the region of the fuel pipe portion (110) of the fuel nozzle (100) and respectively open into a circular recess (161).

5. Fuel nozzle (100) according to any one of the preceding claims, characterized in that the expansion slits (160) are arranged to extend in their longitudinal extension parallel to a longitudinal axis (z) of the fuel nozzle (100), in particular to extend parallel to one another, and to coaxially surround the longitudinal axis (z) of the fuel nozzle (100).

6. Fuel nozzle (100) according to any one of the preceding claims, characterized in that the fuel nozzle (100) is configured as a centrifugally cast component.

7. Method of producing a fuel nozzle (100), in particular a fuel nozzle (100) according to any one of the preceding claims, for a burner for burning particulate fuel, in particular powdered, carbon-containing fuel such as coal or biomass, wherein the fuel nozzle (100) is formed as a cast portion having a fuel pipe portion (110) to be associated with a fuel pipe or primary air pipe (200) of the burner and an opening portion (120) integrally connected to the fuel pipe portion (110) and provided for forming an opening region (210) of the fuel pipe or primary air pipe (200), wherein - in a first manufacturing step, the fuel nozzle (100) is cast as an integral component with an opening portion (120) formed as an air deflection groove widening conically in the direction of the opening side end (121) radially outward and with a stabilizing ring directed radially inward at the opening side end (121) of the opening portion (120) and provided, in particular, with teeth (151), characterized in that, - in a second manufacturing step following the first manufacturing step, circular recesses (161) are drilled along the circumference of the fuel nozzle (100) in the fuel pipe portion (110) penetrating through the material wall of the fuel nozzle (100), and - in a third manufacturing step following the second manufacturing step, starting from the circular recesses (161) drilled in the fuel pipe portion (110), expansion slits (160) in the form of incisions penetrating and severing the material wall of the fuel nozzle (100) in the radial direction are cut in the direction of an opening side end (121) of the fuel nozzle (100) and penetrating and severing an opening side end face (122) of the fuel nozzle (100).

8. Burner for burning particulate fuel, in particular powdered, carbon-containing fuel such as coal or biomass, having a fuel nozzle (100) according to claim 1, wherein the burner comprises a fuel pipe or primary air pipe (200) and a jacket pipe or secondary air pipe coaxially surrounding the fuel pipe or primary air pipe (200), the fuel pipe or primary air pipe (200) opening into the fuel nozzle (100) and being associated with the fuel pipe portion (110).

9. Burner according to claim 8, characterized in that the fuel pipe portion (110) of the fuel nozzle (100) comprises a fuel pipe side end (111) and the fuel pipe or primary air pipe (200) is connected, in particular welded, to the fuel pipe side end (111) of the fuel pipe portion (110).

10. Burner according to claim 8 or 9, characterized in that the fuel nozzle (100) is configured according to any one of claims 2 to 6.

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