Nozzle arrangement for a burner, and burner having such a nozzle arrangement

Abstract

The invention relates to a nozzle arrangement for a burner (12) having at least one pair of nozzles (43, 46) with a fuel gas nozzle (43) having a fuel gas nozzle longitudinal axis (62), for injecting fuel gas, the fuel gas nozzle (43) being connected to a fuel gas distribution device (17), and with a secondary gas nozzle (46) for injecting secondary gas, the secondary gas nozzle (46) being connected to a secondary gas distribution device (45), the fuel gas nozzle (43) being arranged along the fuel gas nozzle longitudinal axis (62) at least partially inside the secondary gas nozzle (46), and the secondary gas nozzle (46) surrounding the one fuel gas nozzle (43) in the circumferential direction around the fuel gas nozzle longitudinal axis (62).

Description

[0001] Nozzle arrangement for a burner and burner with such a nozzle arrangement

[0002] This patent application claims priority from German patent application DE 10 2023 202 665.1, the contents of which are incorporated herein by reference.

[0003] The invention relates to a nozzle arrangement for a burner, in particular a gas burner, and to a burner with such a nozzle arrangement.

[0004] In an asphalt production plant, various materials are processed, in particular heated, dried and / or mixed together. A large part of the energy input required for the subsequent asphalt mixing process is used to dry the materials during asphalt production. The materials are heated during drying. Depending on the type of asphalt to be mixed and in particular on the proportion of old asphalt granulate, which is also referred to as recycled material, the temperature level can be up to 450°C. Drying takes place in a rotary kiln, also known as a drying drum. Heat, which has been generated by means of a separate heating unit, is added to the rotary kiln. Heat generation is usually based on the combustion of fossil fuels such as natural gas, LPG, heating oil and / or coal dust. The combustion of fossil fuels is problematic from a climate technology perspective.

[0005] Other non-fossil fuels, especially non-fossil fuel gases such as hydrogen, have a high reaction rate and lead to high flame temperatures and thus to a high thermal load on the burner and to increased nitrogen oxide emissions.

[0006] It is the object of the present invention to enable the use of a fuel gas with a high reaction rate in a burner with efficient combustion, so that in particular the service life of the burner is not undesirably shortened and the burner can be operated in a particularly gentle manner.

[0007] This object is achieved according to the invention by a nozzle arrangement having the features specified in claim 1 and by a burner having the features specified in claim 11. According to the invention, it was recognized that efficient and advantageous combustion of gases is possible if the gases are advantageously injected into the burner. By means of a nozzle arrangement according to the invention, which comprises at least one pair of nozzles, a fuel gas and a secondary gas can be advantageously injected. Each pair of nozzles has a fuel gas nozzle with which fuel gas is injected, in particular into a combustion chamber of the burner. It is also conceivable for the fuel gas to be injected with the fuel gas nozzle directly into a working space that is to be heated with the burner flame. The working space can be, for example, a drying drum in an asphalt mixing plant. The fuel gas nozzle has a longitudinal fuel gas nozzle axis.The fuel gas nozzle is connected to a fuel gas distribution device, in particular to a fuel gas distribution chamber. The fuel gas distribution device can alternatively be designed as a pipeline, a distribution element, and / or a manifold. The fuel gas is made available to the fuel gas nozzle via the fuel gas distribution device. The fuel gas distribution chamber is designed to be annular, in particular with respect to a central longitudinal axis of the burner. The fuel gas nozzle is designed, in particular, as an internal nozzle.

[0008] The fuel gas used is a gas with a high reaction rate that can be burned efficiently and precisely to generate heat. The fuel gas has a high flame temperature in air. For hydrogen, the flame temperature in air is 2130°C. At a combustion temperature of 1400°C, nitrogen oxide emissions are produced, with their amount increasing approximately exponentially with increasing temperature. The fuel gas is typically hydrogen and / or acetylene.

[0009] Each nozzle pair further comprises a secondary gas nozzle. The secondary gas nozzle is designed, in particular, as an external nozzle and is arranged, in particular, around the fuel gas nozzle. The secondary gas nozzle serves to inject secondary gas into the combustion chamber of the burner. In particular, the secondary gas is different from air. In particular, the secondary gas does not contain any air. The secondary gas is air-free.

[0010] By using the secondary gas, the high reaction rate of the fuel gas can be specifically reduced, thus reducing flame temperatures and, in particular, local temperature peaks. By injecting the secondary gas, the combustion reaction in the burner can be specifically reduced. This means that the combustion reaction is slowed down by the addition of the secondary gas. In particular, the nozzle arrangement serves to locally influence the flame temperature of the burner flame through targeted injection.

[0011] In particular, the fuel gas nozzle and the secondary gas nozzle are arranged such that the fuel gas and the secondary gas are supplied separately from the air supply to the combustion chamber. In particular, the fuel gas and the secondary gas are supplied to the combustion chamber together, but separately from the air. In particular, a mixture of fuel gas and secondary gas is generated, and this mixture is supplied to the combustion chamber by means of the nozzle arrangement, where mixing with air takes place. In particular, mixing of air with the fuel gas and the secondary gas only occurs in the combustion chamber. In the nozzle arrangement, there is no mixing of the fuel gas with air. In particular, no air is supplied to the nozzle arrangement.

[0012] In addition to the fuel gas and the secondary gas, air is also processed in the burner. It is conceivable to add and burn an additional fuel gas, a so-called secondary fuel gas. In particular, only gas is processed in the burner. The burner is, in particular, a gas burner. Additionally, liquids and / or solids can be processed as fuels in the burner according to the invention.

[0013] According to the invention, it was recognized that the targeted injection of the secondary gas reduces the fuel conversion per volume. This reduces and, in particular, avoids high-temperature zones. By reducing the high-temperature zones, the combustion reaction is gentler on the burner. The service life of the burner is increased. The burner according to the invention is ecologically and economically advantageous. In particular, it was recognized that high-temperature zones are a significant cause of the formation of nitrogen oxide (NOx) emissions. By reducing nitrogen oxide emissions, the operation of the burner is particularly environmentally friendly. In particular, the formation of nitrogen oxides directly during combustion can be avoided.

[0014] The heat generated according to the invention is generated at least partially and in particular exclusively by the combustion of hydrogen as fuel gas. The combustion of hydrogen gas is carbon dioxide-free. No carbon dioxide is produced during the combustion of hydrogen gas. The combustion of hydrogen gas is climate-friendly. Harmful exhaust gases and / or emissions are reduced. It is particularly advantageous if the hydrogen gas is generated from renewable energies, i.e., if it is so-called green hydrogen.

[0015] The burner is used to supply heat to a rotary kiln in an asphalt production plant. For this purpose, the burner is coupled to the rotary kiln. A burner flame generated by the burner can burn directly in the rotary kiln. In this case, the burner and rotary kiln are physically coupled. In this case, the burner is arranged directly next to the rotary kiln. Alternatively, the burner flame can burn at a spatial distance from the rotary kiln, in particular in a hot gas generator. The heat generated in this way can be conducted as hot gas from the hot gas generator to the rotary kiln. The heat generated by the burner is supplied to the rotary kiln as hot gas. In this case, the burner is indirectly coupled to the rotary kiln, in particular via a hot gas line.

[0016] The secondary gas is, in particular, exhaust gas and / or inert gas. The exhaust gas is, in particular, exhaust gas from an asphalt production plant, in particular exhaust gas from the rotary kiln, which is to be supplied with heat by the burner. In this case, exhaust gas from the rotary kiln is returned directly to the burner via an exhaust gas recirculation line. This direct recirculation is referred to as recirculation. Additionally or alternatively, at least one further exhaust gas source can be present, from which exhaust gases are returned to the burner. The at least one further exhaust gas source is, in particular, another rotary kiln, a bucket conveyor, a chimney and / or a filter unit, in particular a filter dedusting system. In particular, there can be several exhaust gas recirculation lines that lead the various exhaust gas sources to the burner.In particular, an exhaust gas recirculation line system is provided, with which the rotary kiln and / or the at least one further exhaust gas source are fluidically connected, in particular at least indirectly, to the burner.

[0017] It is particularly advantageous if the recirculated exhaust gas has been previously cleaned, i.e., it contains essentially no dust particles. In particular, the recirculated exhaust gas is flue gas with a dust particle content of less than 20 mg / m 3 and in particular less than 10 mg / m 3 It was surprisingly found that purified exhaust gas, and in particular flue gas, is particularly advantageous for slowing down the combustion reaction.

[0018] Alternatively, the exhaust gas may be at least partially loaded with dust particles, the dust loading being in particular less than 35 mg / m 3

[0019] The secondary gas nozzle can also be used to inject inert gas. Inert gas refers to gases that have a higher inert gas content than ambient air. It has been found that the use of inert gas can be used to specifically slow down the combustion reaction in the burner. Examples of inert gases include nitrogen, water vapor, or noble gases such as helium, neon, argon, krypton, xenon, and / or radon.

[0020] The secondary gas nozzle is connected to a secondary gas distribution device, in particular to a secondary gas distribution chamber. The secondary gas distribution chamber is designed to be annular, in particular with respect to the central longitudinal axis of the burner. The secondary gas distribution device is designed to be spatially separated from the fuel gas distribution device.

[0021] In the nozzle pair, the fuel gas nozzle is arranged at least partially within the secondary gas nozzle along the longitudinal axis of the fuel gas nozzle. This means that the fuel gas injected by means of the fuel gas nozzle is first discharged into the secondary gas nozzle and from there, together with the secondary gas, is injected, in particular, into the combustion chamber. The fuel gas nozzle therefore in particular indirectly injects the fuel gas into the combustion chamber. In the secondary gas nozzle, the fuel gas is mixed with the secondary gas. This prevents the fuel gas from coming into direct contact with the combustion air. This in particular prevents undesirably high combustion temperatures from occurring. The mixing is particularly advantageous because the fuel gas nozzle is surrounded, in particular completely, in the circumferential direction around the longitudinal axis of the fuel gas nozzle.The secondary gas nozzle forms, in particular, a mixing chamber for mixing fuel gas and secondary gas. The mixing takes place directly and is particularly efficient. The gas mixture produced in this way is particularly well suited for combustion. It is particularly advantageous that there is no direct mechanical connection between the fuel gas nozzle and the secondary gas nozzle. The fuel gas nozzle is, in particular, attached directly to the fuel gas distribution chamber. The secondary gas nozzle is, in particular, attached directly to the secondary gas distribution chamber. The fuel gas nozzle is, in particular, arranged and held in the secondary gas nozzle without contact. This allows for uninterrupted gas flow, in particular the secondary gas flow through the secondary gas nozzle past the fuel gas nozzle.

[0022] A nozzle arrangement according to claim 2 enables further improved mixing of the gases. Mixing is improved by arranging a fuel gas discharge opening of the fuel gas nozzle within the secondary gas nozzle.

[0023] A nozzle arrangement according to claim 3 enables a specifically adjustable mixing of the gases. Because the fuel gas discharge opening is arranged with a sufficient opening spacing within the secondary gas nozzle, a sufficiently long common flow path of fuel gas and secondary gas in the secondary gas nozzle is ensured. In particular, the opening spacing, based on the length of the secondary gas nozzle, is at least 10%, in particular at least 20%, in particular at least 30%, in particular at least 40%, in particular at least 50%, in particular at least 60%, in particular at least 75%, and in particular at most 90%.

[0024] The fuel gas discharge opening has a cross-sectional area that is smaller than a cross-sectional area of ​​the secondary gas nozzle, in particular at the axial position of the fuel gas discharge opening. In particular, the cross-sectional area of ​​the fuel gas discharge opening is at most 70%, in particular at most 60%, in particular at most 50%, in particular at most 40%, in particular at most 30%, in particular at most 20%, and in particular at most 10% of the cross-sectional area of ​​the secondary gas nozzle.

[0025] Due to these different cross-sectional areas, the fuel gas has a higher flow velocity than the secondary gas, which is in particular at least twice, in particular at least three times, in particular at least five times, in particular at least eight times, and in particular at least ten times the flow velocity of the secondary gas. In particular, the flow velocity of the fuel gas is at least 500 m / s. The flow velocity of the secondary gas is in particular at least 50 m / s and in particular at most 100 m / s.

[0026] A nozzle arrangement according to claim 4 enables particularly advantageous flow conditions, in particular through the fuel gas nozzle and / or through the secondary gas nozzle on an outer side of the fuel gas nozzle. Because the fuel gas nozzle has a tapered section, losses in the flow to the fuel gas nozzle are reduced. In the tapered section, the fuel gas nozzle has a cross-sectional area that reduces along the longitudinal axis of the fuel gas nozzle. The cross-sectional area is reduced, in particular regressively. This means that the outer contour of the fuel gas nozzle is concave, i.e., in particular curved. Alternatively, a linear cross-sectional area reduction can be implemented, so that the outer contour of the fuel gas nozzle is conical. The cross-sectional shape of the tapered section of a plane perpendicular to the longitudinal axis of the fuel gas nozzle is, in particular, round.The cross-sectional shape, i.e. the inner contour of the fuel gas nozzle, can also be non-circular, for example without edges, in particular oval or polygonal, for example square or hexagonal.

[0027] A constant section adjoins the tapered section along the longitudinal axis of the fuel gas nozzle. The constant section has a constant cross-sectional area along the longitudinal axis of the fuel gas nozzle. The fuel gas discharge opening is located at a downstream end of the constant section. In particular, the cross-sectional area of ​​the constant section is identical to the cross-sectional area at the end of the tapered section. In particular, the transition from the tapered section to the constant section is stepless and, in particular, continuous. The fuel gas nozzle is essentially funnel-shaped or trumpet-shaped overall.

[0028] The change in the cross-sectional area of ​​the fuel gas nozzle in the tapered section and the arrangement of the fuel gas nozzle with the tapered section within the secondary gas nozzle result in a beneficial velocity reduction for the injection of the secondary gas due to the increased cross-sectional area. The mixing of the gases is further improved as a result of the velocity difference. Alternatively, it is conceivable for the fuel gas nozzle to be designed without a tapered section. In this case, the fuel gas nozzle can, in particular, have a constant cross-section along the longitudinal axis of the fuel gas nozzle.

[0029] A nozzle arrangement according to claim 5 enables a particularly advantageous influence on the flow velocities, in particular of the fuel gas.

[0030] A corresponding fuel gas nozzle, in particular, has an advantageous cross-sectional reduction along the longitudinal axis of the fuel gas nozzle. In particular, a minimum cross-sectional area of ​​the tapered section is at most 30% of a maximum cross-sectional area of ​​the tapered section, in particular at most 25%, in particular at most 20%, in particular at most 10%, in particular at most 5%, and in particular at least 1%.

[0031] A nozzle arrangement according to claim 6 enables uncomplicated supply of the secondary gas from the secondary gas distribution device, in particular the secondary gas distribution chamber. In particular, the secondary gas can flow directly into the secondary gas nozzle at the front. The nozzle arrangement has a compact and robust design. The nozzle arrangement can be easily integrated into the burner. The gas supply via the secondary gas distribution chamber is designed as an integral part and implemented in a straightforward manner.

[0032] A nozzle arrangement according to claim 7 is geometrically uncomplicated and allows for inexpensive production. In particular, the secondary gas nozzle itself is designed as a cylindrical sleeve. In particular, the inner contour of the secondary gas nozzle is cylindrical. It is conceivable for the secondary gas nozzle to be mounted in the burner on its outer wall in a non-circular, in particular non-cylindrical, manner and / or to have integrally formed mounting elements.

[0033] A concentric arrangement of the secondary gas nozzle according to claim 8 enables improved mixing of the gases. A nozzle arrangement according to claim 9 enables particularly uniform and, in particular, homogeneous injection of the fuel gas mixture. Several nozzle pairs are arranged in the circumferential direction around an arrangement center axis, in particular spaced from one another in the circumferential direction. In particular, the nozzle pairs are arranged evenly spaced from one another in the circumferential direction. The nozzle arrangement comprises, in particular, at least three, in particular at least four, in particular at least six, in particular at least eight, in particular at least twelve, in particular at least sixteen, and in particular at most fifty nozzle pairs. The number of nozzle pairs varies depending on the size of the burner and / or depending on the nozzle diameter. It is particularly advantageous if all nozzle pairs are identical.Depending on the burner flame to be generated, it is also conceivable to use at least two different nozzle geometries for the fuel gas nozzles and / or for the secondary gas nozzles. Geometrically differently designed nozzles, i.e., geometrically differently designed nozzle pairs, can be arranged alternately along the circumferential direction around the center axis of the arrangement, for example. It has been found that different nozzle geometries along the circumferential direction can advantageously result in homogeneous gas injection.

[0034] In particular, the nozzle pairs are arranged at a common axial position relative to the longitudinal axis of the burner. Additionally or alternatively, it is conceivable to arrange the nozzle pairs at different axial positions to enable a stepped fuel gas supply in the burner.

[0035] An inclined arrangement of the nozzle pairs according to claim 10 enables advantageous influencing of the burner flame geometry, in particular focusing of the burner flame. It is particularly advantageous if all combustion gas nozzles are arranged at the same angle of inclination relative to the arrangement's center axis. In particular, the longitudinal axes of the combustion gas nozzles of several combustion gas nozzles intersect at one point, in particular all longitudinal axes of the combustion gas nozzles intersect at a common point, which lies in particular on the arrangement's center axis. It is conceivable that the angles of inclination can be set differently for different nozzle arrangements. This allows the profile of the supplied gases to be influenced in a targeted manner. In particular, it is possible to specifically change the flame temperatures and, in particular, to change the geometry of the burner flame.

[0036] A burner according to claim 11 essentially has the advantages of the nozzle arrangement according to the invention, to which reference is hereby made. The burner has a burner head and a combustion chamber arranged in a burner housing. Air is sucked into the burner via an intake chamber. The combustion air is mixed with the gases injected by means of the nozzle arrangement in the burner head and burned there to form a burner flame. It is particularly advantageous if a swirling element is arranged upstream of the burner head in order to swirl the sucked-in air, in particular in a radial direction with respect to the burner's longitudinal axis. The swirling element is in particular designed to be static, i.e., arranged immovably in the burner.

[0037] A burner according to claim 12 enables advantageous cooling of the burner head, in particular by having sucked-in air flow as secondary air around a cooling cone from the outside. An annular gap is formed between the cooling cone and the burner head.

[0038] A burner according to claim 13 enables advantageous gas supply to the burner head. In particular, it ensures that the secondary air does not come into contact with the supplied gases before reaching the burner head. The nozzle arrangement allows the gases to be passed through the annular gap without contact. Furthermore, the secondary gas nozzles in the annular gap create a flow barrier for the secondary air, which is thereby additionally advantageously swirled.

[0039] A burner according to claim 14 enables advantageous integration of the fuel gas distribution chamber as a fuel gas distribution device and / or the secondary gas distribution chamber as a secondary gas distribution device on the burner housing. The arrangement of the distribution chambers on an outer side of the burner housing is straightforward and particularly possible retrofitting. The burner housing can be easily supplemented with the corresponding distribution chambers. A burner design according to claim 15 enables advantageous gas supply to the combustion chamber. In particular, the secondary gas nozzle opens directly into the combustion chamber with a secondary gas discharge opening.

[0040] Both the features specified in the patent claims and the features specified in the following embodiment of a nozzle arrangement according to the invention are suitable, either alone or in combination with one another, for further developing the subject matter of the invention. The respective combinations of features do not represent any limitation with regard to further developments of the subject matter of the invention, but are essentially merely exemplary in nature.

[0041] Additional features, advantageous embodiments, and details of the invention will become apparent from the following description of an embodiment with reference to the drawings. They show:

[0042] Fig. 1 is a schematic sketch of a plant for producing asphalt with a burner,

[0043] Fig. 2 is a schematic sectional view of a rotary kiln with a burner according to Fig. 1,

[0044] Fig. 3 is a view along section line III-III in Fig. 2,

[0045] Fig. 4 is an enlarged detailed view of a nozzle arrangement according to the invention according to detail IV in Fig. 2,

[0046] Fig. 5 is an enlarged, perspective detailed view of the nozzle arrangement according to Fig. 4.

[0047] A plant, shown as a whole with 1 in Fig. 1, is used to produce asphalt. The plant 1 comprises a first device 2 and a second device 3, which are each connected by an emission line 4 to a, in particular common, filter dedusting system 5. The plant 1 can also have only one device 2, 3 or more than two devices 2, 3. It is conceivable that the one or more devices 2, 3 are connected to the filter dedusting system 5 via a common emission line 4. In particular, the filter dedusting system 5 is a central filter dedusting system of the plant 1, with several and in particular all devices 2, 3 of the plant 1 being connected to the filter dedusting system 5. It is also conceivable that each device 2, 3 is assigned to a separate filter dedusting system 5 and connected thereto.

[0048] A condensate separator 6 is optionally connected to the filter dedusting system 5 and is connected to a chimney 8 via a fan 7. The condensate separator 6 can, as shown in Fig. 1, be arranged downstream of the filter dedusting system 5 and additionally or alternatively upstream of the filter dedusting system 5. In particular, in addition to the condensate separator 6, a recuperation unit (not shown) is provided, which serves to recover process heat, which is generated in particular in the condensate separator 6. For this purpose, the recuperation unit can be arranged, in particular, integrated into the condensate separator 6.

[0049] It has been found that the condensate separator 6 can be used advantageously in the system 1 if the exhaust air of the devices 2, 3 is comparatively clean, i.e. has a reduced emission load and in particular is less polluted with emissions than the exhaust air of a burner that burns fossil fuels.

[0050] Alternatively, the system 1 may be designed without a filter dust collector 5. In this case, the devices 2, 3 are directly connected to the condensate separator 6. It is also conceivable that several condensate separators 6 are present, in particular one condensate separator 6 per device 2, 3.

[0051] The first device 2 comprises a rotary kiln 9 in which material is dried. The rotary kiln 9 has a material inlet 10 and a material outlet 11. According to the exemplary embodiment shown, the material inlet 10 and the material outlet 11 are each arranged at the end, in particular opposite each other, of the rotary kiln 9. A burner 12 is coupled to the rotary kiln 9. The burner 12 is designed to burn hydrogen gas as fuel gas and to generate a burner flame 13, which is arranged at least in some regions in the rotary kiln 9. The burner 12 is a hydrogen burner. The fuel gas forms, in particular, a primary fuel. Primary fuel serves primarily, i.e., mainly, as fuel for heat generation in the burner 12. In particular, hydrogen is burned solely for heat generation in the burner 12.A fuel gas line 14 is connected to the burner 12, which is connected in particular to a fuel gas reservoir 15. The fuel gas reservoir 15 is in particular a storage container, in particular a storage tank, in which the fuel gas, i.e., hydrogen, in particular in gaseous form, is stored. The fuel gas reservoir 15 can also be designed as a connection to a fuel gas supply network.

[0052] The connection of a gas control section of the fuel gas line 14 is connected to a fuel gas distribution chamber 17 of the burner 12 by means of a compensator 16. The fuel gas distribution chamber 17 forms a fuel gas distribution device. Other designs of the fuel gas distribution device are also possible, for example, a pipeline, a distribution element, or a manifold. The compensator 16 is a flexible compensation element. The compensator 16 serves to compensate for movements of the fuel gas line 14, in particular as a result of thermal length changes, vibrations, wall penetrations, and / or settlement phenomena. The compensator 16 is arranged on a flange connection 18 between the fuel gas distribution chamber 17 and the fuel gas line 14.

[0053] An air line 19 is connected to the burner 12 to supply air, in particular ambient air.

[0054] A material conveying direction 20 through the rotary kiln 9 is directed from the material inlet 10 to the material outlet 11 and is oriented from right to left as shown in Fig. 1. A gas conveying direction 21 through the rotary kiln 9 is directed from the burner 12 to the emission line 4, i.e., from left to right as shown in Fig. 1. The material conveying direction 20 and the gas conveying direction 21 are oriented opposite to one another. The rotary kiln 9 is operated in countercurrent. The rotary kiln 9 can also be operated in cocurrent. A secondary fuel line 22 can be connected to the burner 12 to feed secondary fuel into the burner 12. Fossil energy sources such as natural gas, liquefied petroleum gas, heating oil, coal, in particular coal dust, synthetic fuels (BtL), and / or wood dust serve as secondary fuels, in particular. The secondary fuel line 22 is fed from a secondary fuel reservoir (not shown).The secondary fuel reservoir can be designed - similar to the fuel gas reservoir 15 - as a storage container and / or as a supply network.

[0055] The connection of the burner 12 to the secondary fuel line 22 and the gas control line there is made via a secondary fuel distribution chamber 23 by means of a compensator 16. The compensator 16 is essentially identical to the compensator 16 on the fuel gas line 14 and is arranged at a corresponding location between the secondary fuel line 22 and the secondary fuel distribution chamber 23.

[0056] The first device 2 further comprises an exhaust gas recirculation line 24 connected to the burner 12. The exhaust gas recirculation line 24 can additionally be directly connected, in particular via a branch line not shown, to the rotary kiln 9. The exhaust gas recirculation line 24 serves to recirculate exhaust gases to the burner 12. The exhaust gas recirculation line 24 serves, in particular, for the internal recirculation of exhaust gases from the rotary kiln 9. The exhaust gas recirculation line 24 is directly connected to the chimney 8. Exhaust gas, in particular purified exhaust gas, in particular flue gas, is recirculated to the burner 12 via the exhaust gas recirculation line 24. In addition, an exhaust gas bypass line 25 can be provided, connecting the emissions line 4 directly to the exhaust gas recirculation line 24. Dust-laden exhaust gas can be fed to the burner 12 via the exhaust gas bypass line 25.

[0057] The system 1 can have additional exhaust gas sources 26, such as filter elements. These additional exhaust gas sources can be connected directly to the exhaust gas recirculation line 24 via an exhaust gas bypass line 25. Additionally or alternatively, the exhaust gas sources 26 can be connected to the filter dedusting system 5 via an emissions line 4. This makes it possible to supply purified exhaust gas from the at least one exhaust gas source 26 to the burner 12. A separate fan 27 is arranged in the exhaust gas recirculation line 24 to improve the supply of the exhaust gas to the burner 12. One or more flaps 28 can be arranged along the exhaust gas recirculation line 24 to specifically control the exhaust gas flow and, in particular, to specifically adjust the amount of exhaust gas added. Additionally or alternatively, the exhaust gas flow rate can also be controlled using the fan 27 and, in particular, by means of a frequency converter connected to it.

[0058] According to the illustrated embodiment, the exhaust gas recirculation line 24 is branched, with a first branch leading directly into the rotary kiln 9. Another branch of the exhaust gas recirculation line 24 leads into the burner 12.

[0059] The rotary kiln 9 is designed to be driven in rotation about a rotation axis 29. The drives required for this purpose, in particular rotary drives, are known per se and are not shown in the figures for reasons of clarity.

[0060] The rotary kiln 9 has a burnout zone 30 extending along the rotation axis 29 in the region of the burner flame 13. The rotary kiln 9 further has a heat transfer zone 31 in which heat is transferred to the material by convection.

[0061] The second device 3 is constructed essentially identically to the first device 2, to which reference is hereby made. One difference is that the second device 3 comprises a hot gas generator 32 in addition to the burner 12. The hot gas generator 32 is connected to the rotary kiln 9 by means of a hot gas line 33. The hot gas generator 32 is arranged between the burner 12 and the rotary kiln 9. In the second device 3, the burner 12 is designed separately from the rotary kiln 9. In particular, the burner 12 is arranged completely outside the rotary kiln 9. Accordingly, the burner flame 13 is arranged in the hot gas generator 32. The burner flame 13 is arranged outside the rotary kiln 9 of the second device 3.

[0062] In the second device 3, recirculating air fans and / or exhaust air fans (not shown in detail) can be used for air guidance, in particular within the rotary kiln 9 and / or in the hot gas generator 32. The fans are arranged, in particular, outside the rotary kiln 9 and / or outside the hot gas generator 32, in particular along connecting lines. Accordingly, the burnout zone 30 is not required in the rotary kiln 9 of the second device 3. The rotary kiln 9 of the second device 3 essentially comprises only a heat transfer area 31.

[0063] Accordingly, an exhaust gas recirculation line 24 is provided from the chimney 8 to the burner 12 of the second device 3. According to the illustrated embodiment, the exhaust gas recirculation line 24 to the second device 3 is designed separately from the exhaust gas recirculation line 24 to the first device 2. It is also possible to design a common exhaust gas recirculation line 24 with corresponding branches. Accordingly, exhaust gas bypass lines 25 can be connected to the exhaust gas recirculation line 24 to the second device 3. In particular, the rotary kiln 9 of one device can represent an additional exhaust gas source for the other device.

[0064] In the illustrated embodiment, each device 2, 3 has its own separate fuel gas reservoir 15. It is possible for a common, centrally located fuel gas reservoir 15 to be available in the system 1, which is in fluid communication with several, and in particular with all, burners 12 of the system 1.

[0065] The system 1 accordingly has a central inert gas reservoir 34, which is also referred to as an inert gas source. Inert gas is stored in the inert gas reservoir 34. The inert gas has, in particular, a higher inert content than ambient air. Nitrogen is used, in particular, as the inert gas. The inert gas reservoir 34 is connected to the burners 12 of the first device 2 and the second device 3 via an inert gas line 35. It is understood that a separate inert gas reservoir 34 can also be designed for each burner 12. This makes it possible, in particular, to supply different inert gases to the respective burner 12.

[0066] The exhaust gas recirculation line 24 and the inert gas line 35 each form a secondary gas line for supplying secondary gas to the burner 12. Secondary gas within the meaning of the invention can be exhaust gas, in particular purified exhaust gas, and / or inert gas. The secondary gas can be used to specifically influence, in particular slow down, a combustion reaction in the burner 12.

[0067] The burner 12 has a mixing chamber 36, which is integrated into the burner 12. The mixing chamber 36 serves to mix the fuel gas with the secondary gas. The mixing chamber 36 is arranged, in particular, such that the fuel gas is first mixed with the secondary gas before air is supplied from the air line 19. In particular, the fuel gas line 14 and the exhaust gas recirculation line 24 and / or the inert gas line 35 are fluidly connected to the mixing chamber 36. It is also conceivable for the mixing chamber to be arranged outside the burner 12, in particular on the burner 12. The mixing chamber 36 can also be arranged externally and at a distance from the burner 12 and in particular upstream of the burner 12. It is conceivable to mix the fuel gas and secondary gas separately before feeding them into the burner 12.

[0068] The structure and function of the first device 2, in particular the burner 12, are explained in more detail below with reference to Fig. 2.

[0069] The burner 12 has a burner housing 38 having a longitudinal axis 37. The burner housing 38 has an intake chamber 39 at an end facing away from the rotary kiln 9, through which air, in particular ambient air, is sucked into the burner housing 38. For this purpose, the air line 19 and / or a silencer can be connected to the intake chamber 39. An air blower 40 is arranged along the burner housing 38, which, according to the exemplary embodiment shown, is designed as an axial blower. It is understood that the air blower 40 can also be designed as a different type of blower, in particular as a radial blower.

[0070] The burner 12 has, in particular, a flame sensor 41, which serves to monitor the burner flame 13. In particular, a plurality of flame sensors 41 can be implemented on the burner 12 and arranged at a distance from one another, in particular in the burner housing 38, in particular along the longitudinal axis 37. Furthermore, an ignition burner 42 is present in the burner housing 38, which serves to ignite the burner flame 13. The fuel gas line 14 is connected to the burner housing 38 via the fuel gas distribution chamber 17. The fuel gas distribution chamber 17 is arranged in a ring around the burner housing 38. At least one fuel gas nozzle 43 is connected to the fuel gas distribution chamber 17 in order to supply the fuel gas in a targeted manner into the burner housing 38. In particular, a plurality of fuel gas nozzles 43 are present.

[0071] Accordingly, at least one and in particular several secondary fuel nozzles 44 are connected to the secondary fuel distribution chamber 23. The secondary fuel nozzles 44 can be designed as gas lances and can be arranged in particular adjacent to the fuel gas nozzles 43 in the burner housing 38.

[0072] The secondary gas lines, i.e., the exhaust gas recirculation line 24 and / or the inert gas line 35, are connected to a secondary gas distribution chamber 45 of the burner 12. The secondary gas distribution chamber 45 forms a secondary gas distribution device and is designed analogously to the fuel gas distribution chamber 17, to which reference is hereby made. The secondary gas distribution chamber 45 extends, in particular, in a ring shape around the burner housing 38. At least one and, in particular, several secondary gas nozzles 46 are connected to the secondary gas distribution chamber 45, which serve for the targeted delivery of secondary gas into the burner housing 38.

[0073] The at least one fuel gas nozzle 43 and the at least one secondary gas nozzle 46 form a nozzle arrangement 47, which is shown purely schematically and in a simplified manner in Fig. 2.

[0074] In the area of ​​the nozzle arrangement 47, in particular upstream of the nozzle arrangement 47, a swirling element 48, likewise shown purely schematically, is arranged in the burner housing 38. The swirling element 48 serves to tangentially swirl the air. The swirling element 48 is designed in particular as a baffle plate, which in particular has a guide wheel. Depending on the fuel combination used, i.e. in particular depending on the secondary fuel, in particular a secondary combustion gas, the swirling element 48 can be designed differently in terms of diameter, shape and / or structural details. It is also conceivable to arrange the nozzle arrangement 47 upstream of the swirling element 48 and / or to arrange individual nozzles 43, 46 upstream and / or downstream of the swirling element 48.

[0075] The swirl element 48 is arranged in a cooling cone 49 of the burner 12. According to the exemplary embodiment shown, the cooling cone 49 has a cylindrical section whose outer diameter is at least 80% of the inner diameter of the burner housing 38 at this point. In particular, the outer diameter of the cooling cone 49 is at least 85%, in particular at least 90%, in particular at least 95%, and in particular at most 99% of the inner diameter of the burner housing 38 at this point. The cooling cone 49 is arranged in particular in a region of the burner housing 38 in which the burner housing 38 widens conically. The burner housing 38 has an expanding section 50 that merges into a cylindrical end section 51. The end section 51 and the expanding section 50 form a burner head 52.A circumferential, particularly conical, annular gap 53 is formed between an outer wall of the cooling cone 49 and an inner wall of the burner head 52. The air flowing through this annular gap 53 is referred to as secondary air. The secondary air thus flows past the cooling cone 49. The air flowing centrally through the cooling cone 49 is referred to as primary air. Because at least a portion of the air flows around the cooling cone 49 as secondary air, air staging is possible.

[0076] In the illustrated embodiment, the burner head 52 improves the mixing of the combustion gases, particularly hydrogen with air. The burner flame 13 forms downstream of the burner head 52, with the shape of the burner flame being influenced by the geometry of the burner head. This means that the shape of the burner flame 13 can be specifically adjusted by a suitable selection of the burner head geometry. In particular, the diameter DF of the burner flame 13 is larger, the larger the diameter at the outlet of the burner head 52.

[0077] The burner 12 is attached to an end wall 54 of the rotary kiln 9. The end wall 54 is referred to as the outlet end wall because the material outlet 11 is located in this area. The burner 12, in particular the burner housing 38, is attached to the end wall 54 by means of fastening elements not shown in detail. The end wall 54 is arranged on the rotary kiln 9 so as to overlap in the axial direction and / or in the radial direction relative to the axis of rotation 29. The end wall 54 forms a cover for a cylindrical opening of the rotary kiln 9. In particular, the rotary kiln 9 is not hermetically sealed by the end wall 54. A circumferential gap 55 remains between the end wall 54 and the rotary kiln 9. The circumferential gap 55 enables an additional supply of air, in particular ambient air, into the rotary kiln 9.

[0078] The burner 12 is arranged on the rotary kiln 9, in particular, such that its longitudinal axis 37 and the rotational axis 29 of the rotary kiln 9 coincide, i.e., are identical. The burner 12 is arranged concentrically with the rotary kiln 9. The burner 12 is attached directly to the rotary kiln 9 and is at least partially integrated therein. In particular, the burner head 52 and the burner flame 13 generated by the burner 12 are arranged, in particular entirely, within the rotary kiln 9.

[0079] The burner 12 has a burner frame 56, with which the burner 12 is placed on a base. According to the illustrated embodiment, the burner frame 56 is static, i.e., immobile, in particular fixed. The burner frame 56 can also be designed to be movable, in particular along the longitudinal axis 37. For this purpose, the burner frame 56 can have rollers on its underside, which can roll, in particular, on suitable rails. For axial displacement of the burner 12, an axial drive, in particular a pneumatic drive, is advantageous.

[0080] Along the longitudinal axis 37 or the rotational axis 29, the burner flame 13 has a length LF and a diameter DF oriented perpendicular thereto.

[0081] The rotary kiln 9 has an inner diameter Di. In the burnout zone 30, fire protection fittings 57 are provided, which are fastened to the inner wall of the rotary kiln 9. As a result of the fire protection fittings 57, a reduced inner diameter Dred results in the burnout zone 30. In the axial direction, the fire protection fittings 47 extend along a length LA that corresponds to the length of the burnout zone 30. It is essential that the length LA of the burnout zone 30 is greater than the length LF of the burner flame 13, and that the burner 12 is arranged on the rotary kiln 9 such that the burner flame 13 is arranged entirely within the burnout zone 30, in particular in the axial direction relative to the rotation axis 29. It is also essential that the diameter DF of the burner flame 13 is smaller than the reduced diameter D re d. Direct flame contact with the fire protection fittings 57 is avoided.

[0082] Throwing plates 58 are arranged in the heat transfer area 31 and are fastened in particular to the inside of the rotary kiln 9. The throwing plates 58 are open and serve to create a material curtain 59. It is particularly advantageous if the material curtain 59 is as dense as possible. The density of the material curtain 59 can be quantified indirectly, in particular by measuring the exhaust gas temperature. The lower the exhaust gas temperature, the greater the previous heat transfer to the material. This means that the material curtain 59 is denser the lower the exhaust gas temperature, and vice versa. The exhaust gas temperature results from the burner output, the pre-metering output, i.e. the mass flow of the material fed into the rotary kiln 9, and the material temperature. The material temperature serves in particular as an input variable for controlling the burner output.It has been found that it is advantageous if the exhaust gas temperature in the embodiment shown is at least 100°C.

[0083] It is understood that depending on the material used, the burner 12 used or the combustion gases used, the exhaust gas temperature for monitoring the material veil 59 can assume different values.

[0084] The nozzle arrangement 47 is explained in more detail below with reference to Figs. 3 to 5.

[0085] The nozzle arrangement 47 serves to inject gases into the burner 12, in particular into the burner head 52. The nozzle arrangement 47 has a plurality of nozzle pairs, 16 according to the exemplary embodiment shown, which are arranged in a ring arrangement, in particular concentrically to the longitudinal axis 37 of the burner housing 38. This ring arrangement has an arrangement center axis 60 that coincides with the longitudinal axis 37. In the circumferential direction around the arrangement center axis 60, the nozzle pairs are spaced apart and, in particular, evenly spaced from one another. It is understood that more or fewer than 16 nozzle pairs can be present. In particular, the circumferential distances from one another can be varied and, in particular, selected arbitrarily.

[0086] Each nozzle pair comprises a fuel gas nozzle 43 for injecting the fuel gas into a combustion chamber 61 of the burner 12. The combustion chamber 61 is understood to be the area of ​​the burner 12 surrounded by the burner head 52, which faces the opening of the burner 12. The fuel gas nozzle is connected to the fuel gas distribution chamber 17, i.e., is in fluid communication with the fuel gas distribution chamber 17. The fuel gas distribution chamber 17 is annular with respect to the longitudinal axis 37 of the burner housing 38. The fuel gas nozzle 43 has a fuel gas nozzle longitudinal axis 62, which is inclined with respect to the longitudinal axis 37 at an inclination angle n. In particular, the nozzle pairs are arranged with respect to the arrangement center axis 60 at the respective inclination angle n such that the fuel gas nozzle longitudinal axes 62 intersect. In particular, all fuel gas nozzle longitudinal axes 62 intersect at a common point P, which lies in particular on the arrangement center axis 60.

[0087] The fuel gas nozzle 43 is, in particular, an inner nozzle. The fuel gas nozzle 43 is arranged at least partially within the secondary gas nozzle 46 along the longitudinal axis 62 of the fuel gas nozzle.

[0088] Each nozzle pair further comprises a secondary gas nozzle 46 for injecting secondary gas into the combustion chamber 61. The secondary gas nozzle 46 is essentially hollow-cylindrical and, in particular, arranged concentrically to the combustion gas nozzle's longitudinal axis 62. The secondary gas nozzle 46 is, in particular, designed as a single piece and, in particular, as a cylindrical sleeve.

[0089] The secondary gas nozzle 46 is connected to the secondary gas distribution chamber 45. The secondary gas distribution chamber 45 extends annularly with respect to the longitudinal axis 37 of the burner housing 38. It is important that the secondary gas distribution chamber 45 is designed separately from the fuel gas distribution chamber 17.

[0090] In the circumferential direction around the longitudinal axis 62 of the fuel gas nozzle, the secondary gas nozzle 46 surrounds the fuel gas nozzle 43, in particular completely. The secondary gas nozzle 46 forms an outer nozzle arranged in a sleeve-like manner around the fuel gas nozzle 43. The secondary gas nozzle 46 is arranged at an axial distance from a side wall 63 of the fuel gas distribution chamber 17 with respect to the longitudinal axis 62 of the fuel gas nozzle. This spaced arrangement results in an inflow gap between the side wall 63 and the end opening 64 of the secondary gas nozzle 46 facing the secondary gas distribution chamber 45.

[0091] The fuel gas nozzle 43 has a fuel gas discharge opening 65 located within the secondary gas nozzle 46. This allows for pre-mixing of the fuel gas with the secondary gas in the secondary gas nozzle 46.

[0092] In particular, the fuel gas discharge opening 65 is arranged with an opening distance A oriented along the fuel gas nozzle longitudinal axis 62 from a secondary gas discharge opening 66 of the secondary gas nozzle 46. The opening distance A is at least 10% of a length Ls of the secondary gas nozzle 46.

[0093] The fuel gas nozzle 43 has a tapered section 67 and a constant section 68 extending along the longitudinal axis 62 of the fuel gas nozzle. The tapered section 67 faces the fuel gas distribution chamber 17. The fuel gas nozzle 43 is, in particular, constructed in one piece.

[0094] In the tapered section, the cross-sectional area of ​​the fuel gas nozzle 43 is reduced along the longitudinal axis 62 of the fuel gas nozzle. The cross-sectional area reduction is particularly regressive, but can also be linear. The outer contour of the tapered section 47 is correspondingly concave or conical. The cross-sectional shape perpendicular to the longitudinal axis 62 of the fuel gas nozzle is particularly round, but can also have a different shape, in particular oval or polygonal.

[0095] The constant section is designed to be cylindrical. It is essential that the transition from the tapered section to the constant section is continuous and, in particular, edge-free.

[0096] The fuel gas nozzle 43 is designed as a whole in a funnel-shaped or trumpet-shaped configuration. The minimum cross-sectional area of ​​the tapered section 67 is at most 50% of the maximum cross-sectional area of ​​the tapered section 67.

[0097] The operation of system 1, in particular the function of the burner 12 with the nozzle arrangement 47, is explained in more detail below.

[0098] In the first device 2, material is fed into the rotary kiln 9 via the material inlet 10 and conveyed through the rotary kiln 9 along the material conveying direction 20. In the heat transfer area 21, the throwing plates 58 create a dense, continuous, and homogeneous material veil 59, so that the material is arranged with a very large surface area within the rotary kiln 9. The material is heated by convection using the burner flame 13, with the burner flame 13 being arranged directly within the rotary kiln 9.

[0099] The burner flame 13 is generated by the burner 12, which uses hydrogen as the fuel gas. The addition of secondary gas, in particular recirculated exhaust gas and / or inert gas, can slow down the hydrogen gas combustion. This reduces the fuel gas conversion per volume. High-temperature zones are avoided. In particular, it is ensured that the high-temperature zones are located exclusively within the burnout zone 30.

[0100] Advantageous injection of the fuel gas on the one hand and the secondary gases on the other hand takes place by means of the nozzle arrangement 47 shown in Fig. 3 to 5. The fuel gas, in particular hydrogen, is provided in the burner 12 via the fuel gas distribution chamber 17 and injected via the fuel gas nozzles 43. Due to the special design of the fuel gas nozzle 43, in particular with the tapered section 67, the fuel gas is advantageously sucked in and discharged at the fuel gas nozzle discharge opening 65 at a comparatively high injection speed. The fuel gas is discharged into the secondary gas nozzle 46, which sucks in secondary gas from the secondary gas distribution chamber 45 via the end opening 64. The suction speed of the secondary gas is lower than the injection speed of the fuel gas. This speed difference between the fuel gas and the secondary gas results in improved mixing of the fuel gas with the secondary gas.Mixing occurs primarily within the secondary gas nozzle 46. The secondary gas nozzle 46 forms a mixing chamber for mixing the fuel gas and the secondary gas. It is also advantageous that the fuel gas is injected centrally, i.e., concentrically, into the secondary gas nozzle 46.

[0101] By adding the secondary gas, particularly purified exhaust gas and / or inert gas, high-temperature zones are reduced and thus the formation of nitrogen oxide. In particular, the nozzle arrangement according to the invention ensures advantageous mixing of fuel gas and secondary gas, especially before the fuel gas comes into contact with the combustion air in the combustion chamber 61. The fluid flows are shown schematically in Fig. 5. Flow arrows 69 indicate the fuel gas, flow arrows 70 the secondary gas, flow arrows 71 the primary air, and flow arrows 72 the secondary air.

Claims

Patent claims 1. Nozzle arrangement for a burner (12), the nozzle arrangement comprising at least one nozzle pair (43, 46) with a. a fuel gas nozzle (43) having a fuel gas nozzle longitudinal axis (62) for injecting fuel gas, the fuel gas nozzle (43) being connected to a fuel gas distribution device (17), b. a secondary gas nozzle (46) for injecting secondary gas, the secondary gas nozzle (46) being connected to a secondary gas distribution device (45), the fuel gas nozzle (43) being arranged at least partially within the secondary gas nozzle (46) along the fuel gas nozzle longitudinal axis (62), the secondary gas nozzle (46) surrounding the one fuel gas nozzle (43) in the circumferential direction around the fuel gas nozzle longitudinal axis (62).

2. Nozzle arrangement according to claim 1, characterized in that the fuel gas nozzle (43) has a fuel gas discharge opening (65) which is arranged within the secondary gas nozzle (46).

3. Nozzle arrangement according to claim 2, characterized in that the fuel gas discharge opening (65) is arranged with an opening distance (A) oriented along the fuel gas nozzle longitudinal axis (62) to a secondary gas discharge opening (66) of the secondary gas nozzle (46).

4. Nozzle arrangement according to one of the preceding claims, characterized in that the fuel gas nozzle (43) has a tapered section (67) and a constant section (68) adjoining the fuel gas nozzle longitudinal axis (62).

5. Nozzle arrangement according to claim 4, characterized in that a minimum cross-sectional area of ​​the tapered section (67) is at most 50% of a maximum cross-sectional area of ​​the tapered section (67).

6. Nozzle arrangement according to one of the preceding claims, characterized in that the secondary gas nozzle (46) is arranged at a distance from the fuel gas distribution device (17) with respect to the fuel gas nozzle longitudinal axis (62).

7. Nozzle arrangement according to one of the preceding claims, characterized in that the secondary gas nozzle (46) is cylindrical with respect to the fuel gas nozzle longitudinal axis (62).

8. Nozzle arrangement according to one of the preceding claims, characterized in that the secondary gas nozzle (46) is arranged concentrically with respect to the fuel gas nozzle longitudinal axis (62).

9. Nozzle arrangement according to one of the preceding claims, characterized by a plurality of nozzle pairs which are arranged spaced apart from one another in the circumferential direction around an arrangement center axis (60).

10. Nozzle arrangement according to claim 9, characterized in that the fuel gas nozzle longitudinal axes (62) are each arranged inclined at an angle of inclination (n) with respect to the arrangement center axis (60), wherein the fuel gas nozzle longitudinal axes (62) intersect, in particular at a common point (P), in particular on the arrangement center axis (60).

11. Burner with a. a burner housing (38) having a burner head (52) and a combustion chamber (61), b. an intake chamber (39) for intake of air, c. a nozzle arrangement according to one of the preceding claims arranged in the burner housing (38).

12. Burner according to claim 11, characterized in that the burner head (52) is surrounded by a cooling cone (49), an annular gap (53) being formed between the cooling cone (49) and the burner head (52).

13. Burner according to claim 12, characterized in that the secondary gas nozzle (46) crosses the annular gap (53).

14. Burner according to one of claims 11 to 13, characterized in that the fuel gas distribution device (17) and / or the secondary gas distribution device (45) are arranged on an outer side of the burner housing (38).

15. Burner according to one of claims 11 to 14, characterized in that the secondary gas nozzle (46) opens, in particular directly, into the combustion chamber (61).

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