Burner device for an installation for producing asphalt, installation with a burner device of this kind, and method for supplying heat to a rotary kiln of a burner device

Abstract

A burner device for an installation (1) for producing asphalt comprises a rotary kiln (9), which is rotationally driveable about a rotation axis (29), for drying material and a burner (12), which is coupled to the rotary kiln (9), for supplying heat to the rotary kiln (9), the burner (12) comprising an air line (19), which is connected to the burner (12), for supplying air, a combustion gas line (14), which is connected to the burner (12), for supplying combustion gas, and at least one secondary gas line (24, 35), which is connected to the burner (12), for supplying secondary gas.

Description

[0001] Burner device for a plant for the production of asphalt, plant with such a burner device and method of supplying heat into a rotary kiln of a burner device

[0002] This patent application claims priority from German patent application DE 10 2023 202 662.7, the contents of which are incorporated herein by reference.

[0003] The invention relates to a burner device for a plant for producing asphalt, a plant with such a burner device and a method for supplying heat into a rotary kiln of a burner device.

[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 generated by drying the materials during asphalt production. The materials are heated during drying. Depending on the type of asphalt being mixed and in particular on the proportion of old asphalt granulate, also known 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 generated by 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 fuel gases, such as hydrogen, have a high reaction rate and lead to high flame temperatures, so that conventional burners cannot simply be used for the combustion of such fuel gases.

[0006] The object of the present invention is to improve the provision of heat and its supply to a rotary kiln during asphalt production, particularly under climate-related aspects and, in particular, with a low-cost design. This object is achieved according to the invention by a burner device having the features specified in claim 1, by a system having the features specified in claim 9, and by a method having the features specified in claim 10.

[0007] According to the invention, it was recognized that a fuel gas can be efficiently and specifically combusted in a burner to generate heat if secondary gas is also supplied to the burner. Although the fuel gas, in particular hydrogen and / or acetylene, has a comparatively high reaction rate, so that high flame temperatures, particularly with local temperature peaks, can occur during combustion of the fuel gas alone, the combustion reaction rate in the burner can be specifically reduced by also combusting the secondary gas. This means that the combustion reaction in the burner is slowed down by the addition of the secondary gas.

[0008] 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.

[0009] In particular, the fuel gas and secondary gas are mixed in the absence of air. The mixture of fuel gas and secondary gas is then mixed with air in the combustion chamber.

[0010] Hydrogen has a flame temperature in air of 2130°C. Nitrogen oxides are formed at a combustion temperature of approximately 1400°C, with their amount increasing approximately exponentially with further increasing temperatures. The burner processes, in particular, the fuel gas as the primary fuel gas, the secondary gas, and air. In particular, the secondary gas differs from air. In particular, the secondary gas is air-free. Optionally, a secondary fuel gas can be added and co-combusted. It is essential that only gases are processed in the burner. The burner is, in particular, a gas burner. Liquids and / or solids as fuels are not processed in the burner according to the invention.

[0011] According to the invention, it was recognized that this reduces the fuel conversion per volume. As a result, high-temperature zones in the burner are reduced and, in particular, avoided. By reducing the high-temperature zones, the combustion reaction is gentler on the burner. The service life of the burner is increased. The burner device according to the invention is ecologically and economically advantageous. In particular, it was recognized that such high-temperature zones are a significant cause of the formation of nitrogen oxide (NOx) emissions. By reducing nitrogen oxide emissions, the process according to the invention is environmentally friendly. In particular, the formation of nitrogen oxides directly during combustion can be avoided.

[0012] According to the invention, the heat is generated at least partially and in particular exclusively by the combustion of hydrogen gas 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.

[0013] The burner is used to supply heat to a rotary kiln. 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 on 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.

[0014] The burner has an intake chamber for drawing air, in particular ambient air, into a burner housing. An air line is connected to the burner to supply air, in particular ambient air. This allows a mixture of fuel gas and combustion air to be generated in the burner to improve the combustion of the fuel gas.

[0015] An exhaust gas recirculation line according to claim 2 enables the uncomplicated provision of secondary gas. It has been recognized, in particular, that exhaust gas from the burner device can be advantageously used to slow down the combustion reaction.

[0016] A burner device according to claim 3 enables the integration of various exhaust gas sources. The rotary kiln itself can serve as an exhaust gas source for recirculating exhaust gases. In particular, the exhaust gases from the rotary kiln are returned directly to the burner via the exhaust gas recirculation line. Additionally or alternatively, at least one further exhaust gas source can be present, from which exhaust gases are conducted 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 deduster. In particular, several exhaust gas recirculation lines can be present, leading from different exhaust gas sources to the burner. In particular, an exhaust gas recirculation line system is present, 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] An exhaust gas purification unit according to claim 4 ensures that the recirculated exhaust gas has a reduced dust content. In particular, the exhaust gas is dust-free, i.e., it contains essentially no dust. The exhaust gas is, in particular, flue gas in which the proportion of dust particles is less than 20 mg / m 3 and in particular less than 10 mg / m 3 It has surprisingly been found that purified exhaust gas, and in particular flue gas, is particularly advantageous for slowing the combustion reaction. Alternatively, it is possible to allow at least partial dust loading of the exhaust gas. In particular, the dust loading is less than 35 mg / m 3 .

[0018] A natural gas pipeline according to claim 5 enables the targeted supply of inert gas to the burner. It has been discovered according to the invention that the use of the inert gas can specifically slow down the combustion reaction in the burner. Inert gas refers to gases that have a higher inert content than ambient air. Examples of inert gases that can be considered include nitrogen, water vapor, or noble gases such as helium, neon, argon, krypton, xenon, and / or radon.

[0019] In particular, the inert gas line is connected to an inert gas source, in particular an inert gas storage container.

[0020] A mixing chamber according to claim 6 improves the combustion process. The mixing chamber serves to mix fuel gas and secondary gas. The mixing chamber is arranged, in particular, upstream of the burner and / or integrated on or in the burner, in particular in a nozzle and in particular in a nozzle combination. The mixing chamber enables premixing of the fuel gas with the secondary gas, in particular before the fuel gas is mixed with air in the burner. The risk of an undesirable and uncontrolled increase in flame temperatures occurring, for example because fuel gas is inadvertently and undilutedly burned in the burner, is reduced and, in particular, eliminated.

[0021] Alternatively, it is possible to supply the fuel gas and secondary gas separately to the burner. It is particularly advantageous if the fuel gas and secondary gas are supplied in such a targeted manner that unwanted combustion of the fuel gas occurs alone, i.e., without the braking effect of the secondary gas. A targeted, separate supply of fuel gas and secondary gas can slow down the combustion reaction.

[0022] A burner device according to claim 7 simplifies the controlled slowing of the combustion of the fuel gas. By selectively supplying secondary gas to the mixing chamber and mixing it with the fuel gas, unwanted temperature peaks can be avoided.

[0023] A burner device according to claim 8 makes it possible to prevent undesirable, particularly undesirably premature, combustion of the fuel gas. Because the air is guided past the mixing chamber and only fed downstream of the combustion chamber, combustion of the fuel gas in the mixing chamber is eliminated.

[0024] A system according to claim 9 has the advantages of the burner device, to which reference is hereby made.

[0025] A method according to claim 10 ensures the efficient and advantageous combustion of a fuel gas.

[0026] Both the features specified in the patent claims and the features specified in the following embodiment of a burner device 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.

[0027] 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:

[0028] Fig. 1 is a schematic sketch of a plant for producing asphalt with a burner device according to the invention,

[0029] Fig. 2 is a schematic sectional view of a rotary kiln with a burner according to Fig. 1,

[0030] Fig. 3 is a view along section line III-III in Fig. 2, Fig. 4 is an enlarged detail view of detail IV in Fig. 2,

[0031] Fig. 5 is an enlarged, perspective detailed view of a nozzle arrangement according to Fig. 4.

[0032] A plant, shown as a whole in Fig. 1 at 1, is used for the production of asphalt. The plant 1 comprises a first device 2 and a second device 3, each of which is connected via an emission line 4 to a, in particular shared, filter dedusting system 5.

[0033] The system 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 system 1, with several and in particular all devices 2, 3 of the system 1 being connected to the filter dedusting system 5. It is also conceivable that each device 2, 3 is assigned to and connected to a separate filter dedusting system 5.

[0034] 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.

[0035] 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.

[0036] Alternatively, it is possible that system 1 is designed without filter dust removal 5. In this

[0037] 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.

[0038] 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 illustrated embodiment, the material inlet 10 and the material outlet 11 are each arranged at the end faces of the rotary kiln 9, in particular opposite one another.

[0039] 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 partially 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 a fuel for generating heat 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 and 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 with a connection to a fuel gas supply network.

[0040] 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.

[0041] An air line 19 is connected to the burner 12 for supplying air, in particular ambient air. 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 a countercurrent process. The rotary kiln 9 can also be operated in a cocurrent process.

[0042] A secondary fuel line 22 can be connected to the burner 12 to supply secondary fuel to the burner 12. Fossil fuels, such as natural gas, liquefied petroleum gas, heating oil, coal (especially coal dust), synthetic fuels (BtL), and / or wood dust, serve as secondary fuels. 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 tank and / or a supply network.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] A separate fan 27 is arranged in the exhaust gas recirculation line 24 to improve the supply of exhaust gas to the burner 12. One or more dampers 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 can also be controlled using the fan 27, in particular by means of a frequency converter connected to it.

[0047] 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.

[0048] 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.

[0049] The rotary kiln 9 has a burnout zone 30 extending along the rotational axis 29 in the region of the burner flame 13. The rotary kiln 9 further has a heat transfer region 31 in which heat is transferred to the material by convection. 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, in addition to the burner 12, a hot gas generator 32. 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.

[0050] 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.

[0051] 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.

[0052] In the embodiment shown, 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. 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 by 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The burner 12 has, in particular, a flame sensor 41, which serves to monitor the burner flame 13. In particular, several 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.

[0058] 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, several fuel gas nozzles 43 are provided.

[0059] 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.

[0060] 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.

[0061] 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. In the region of the nozzle arrangement 47, in particular upstream of the nozzle arrangement 47, a swirling element 48, also 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 fuel gas, the swirling element 48 can be designed differently in terms of diameter, shape and / or structural details.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 rotation axis 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 allows for an additional supply of air, in particular ambient air, into the rotary kiln 9.

[0067] 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.

[0068] The burner 12 has a burner frame 56 with which the burner 12 is placed on a base. According to the exemplary embodiment shown, 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. 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.

[0069] 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.

[0070] In the heat transfer area 31, throwing plates 58 are arranged and 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. It is possible to quantify the density of the material curtain 59 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.

[0071] It is understood that depending on the material used, the burner 12 used, or the fuel gases employed, the exhaust gas temperature for monitoring the material curtain 59 may assume different values. The nozzle arrangement 47 is explained in more detail below with reference to Figs. 3 to 5.

[0072] 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.

[0073] 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.

[0074] 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 fuel gas nozzle longitudinal axis 62.

[0075] 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 longitudinal axis 62 of the fuel gas nozzle. The secondary gas nozzle 46 is, in particular, designed as a single piece and, in particular, as a cylindrical sleeve. 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 essential that the secondary gas distribution chamber 45 is designed separately from the fuel gas distribution chamber 17.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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, particularly oval or polygonal.

[0081] 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.

[0082] The fuel gas nozzle 43 is overall funnel-shaped or trumpet-head-shaped.

[0083] 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.

[0084] The operation of system 1, in particular the function of the burner 12 with the nozzle arrangement 47, is explained in more detail below.

[0085] 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.

[0086] The burner flame 13 is generated by the burner 12, which is operated with hydrogen as the fuel gas. By adding secondary gas, in particular recirculated exhaust gas and / or inert gas, the hydrogen gas combustion can be slowed. 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. 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 Figs. 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 fuel gas and secondary gas results in improved mixing of the fuel gas with the secondary gas. Mixing takes place in particular within the secondary gas nozzle 46. The secondary gas nozzle 46 forms a mixing chamber for mixing the fuel gas and secondary gas. It is also advantageous that the fuel gas is injected centrally, i.e. concentrically, into the secondary gas nozzle 46.

[0087] By adding secondary gas, in particular purified exhaust gas and / or inert gas, high-temperature zones are reduced and thus the formation of nitrogen oxides.

[0088] In particular, the nozzle arrangement according to the invention ensures advantageous mixing of fuel gas and secondary gas, especially before contact of the fuel gas with the combustion air occurs 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. Burner device for a plant (1) for producing asphalt, the burner device comprising a. a rotary kiln (9) for drying material, which can be rotated about an axis of rotation (29), b. a burner (12) coupled to the rotary kiln (9) for supplying heat to the rotary kiln (9), the burner (12) comprising i. an intake chamber (39) for sucking in air, ii. a fuel gas line (14) connected to the burner (12) for supplying fuel gas, iii. at least one secondary gas line (24, 35) connected to the burner (12) for supplying secondary gas.

2. Burner device according to claim 1, characterized in that the at least one secondary gas line has an exhaust gas recirculation line (24) for recirculating exhaust gas from the burner device into the burner (12).

3. Burner device according to claim 2, characterized in that the exhaust gas recirculation line (24) is fluidically connected to the rotary kiln (9) and / or to at least one further exhaust gas source (9, 26) of the burner device.

4. Burner device according to claim 2 or 3, characterized in that the exhaust gas recirculation line (24) is connected to an exhaust gas purification unit (5, 6, 7, 8) 5. Burner device according to one of the preceding claims, characterized in that the at least one secondary gas line has an inert gas line (35) for supplying inert gas into the burner (12).

6. Burner device according to one of the preceding claims, characterized by a mixing chamber (36, 46) for mixing fuel gas and secondary gas.

7. Burner device according to claim 6, characterized in that the fuel gas line (14) and the secondary gas line (24, 35) are connected to the mixing chamber (36, 46).

8. Burner device according to claim 6 or 7, characterized in that an air line (19) is connected to the burner (12), wherein the air line (19) is in particular connected directly to the burner (12) and in particular is guided past the mixing chamber (36, 46).

9. Plant for producing asphalt with a burner device according to one of the preceding claims.

10. Method for supplying heat to a rotary kiln (9) of a burner device in an asphalt plant (1) with the method steps Supplying fuel gas into a burner (12) by means of a fuel gas line (14), supplying secondary gas into the burner (12) by means of a secondary gas line (24, 35), Supplying air to the burner (12), Combustion of the fuel gas and the air in the burner (12) in the presence of the secondary gas.

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