White mineral drying drum for heating white mineral for the production of asphalt, and plant with such a white mineral drying drum.

Abstract

White mineral drying drum (12; 12a) for heating white mineral for the production of asphalt by means of a system (1) with a flow guide unit (20), wherein the white mineral drying drum (12; 12a) is rotatable about a rotation axis (16), characterized in that a lamellar recuperator (22; 22a) with lamellar guide plates, which form an outer shell for a helical flow movement of exhaust gases and / or by-gases, is arranged in the white mineral drying drum (12; 12a).

Description

[0001] This patent application claims priority from German patent application DE 10 2016 217 738.9, the contents of which are incorporated herein by reference.

[0002] The invention relates to a white mineral drying drum for heating white mineral for producing asphalt and to a plant comprising such a white mineral drying drum.

[0003] For the production of asphalt, drying drums are used to heat old asphalt granulate. These dryers operate in direct current. Such a drying drum is known from DE 36 24 735 A1. A similar system is known from CN 2839358 Y.

[0004] WO 2015 / 082341 A1 discloses an apparatus and a method for heating old asphalt granulate to produce asphalt.

[0005] US 5,174,650 A discloses a method and a plant for drying and mixing old asphalt granules with two drying drums.

[0006] US 5,664,881 A discloses a countercurrent asphalt production plant with a multi-stage combustion zone overlapping a mixing zone.

[0007] Direct current means that the material to be heated and the heat are supplied in the same direction along the rotational axis of the drying drum. Upon exiting the drying drum, the waste asphalt material has a temperature of approximately 130°C. Exhaust gas generated by a burner as a heat source and fed into the drying drum has a temperature of approximately 150°C. Typically, a target temperature of approximately 160°C is aimed for for the waste asphalt material. An increase in the temperature level reduces the economic efficiency of heating the waste asphalt granulate. With increasing temperature, heat losses due to radiation increase to the fourth power of the temperature. The efficiency of the process at elevated temperatures is significantly reduced. An increase in temperature also leads to an additional increase in the pollutant content in the exhaust gas, particularly the proportion of unburned hydrocarbons (C ges), especially carbon monoxide (CO) and carbon dioxide (CO2). Furthermore, elevated exhaust gas temperatures could cause spontaneous combustion of fine particles in a dust extraction unit.

[0008] The invention is based on the object of improving the production of asphalt so that, in particular, pollutant levels in the exhaust gas are reduced and production is uncomplicated.

[0009] The object is achieved by the features of claims 1 and 9. The core of the invention is that exhaust gas is fed to a white mineral drying drum for heating white mineral and is burned there. The exhaust gas is guided into the white mineral drying drum by means of a flow guide unit. The combustion of pollutants in the exhaust gas in the white mineral drying drum is effective. The pollutant content in the exhaust gas is reduced. In particular, the proportion of hydrocarbons C gesis reduced because they are burned in the white mineral drying drum.

[0010] A finned recuperator improves the targeted combustion of pollutants in the exhaust and / or secondary exhaust gases. The finned recuperator features fin-like guide vanes that form an outer shell for the helical flow of the exhaust and / or secondary exhaust gases. The finned recuperator prevents pollutants in the exhaust and / or secondary exhaust gases from being ejected uncontrollably due to the centrifugal force of the swirling flow.

[0011] Further advantages of the invention emerge from the features of the dependent claims.

[0012] A plant with a direct-current drying drum for heating old asphalt material and with an exhaust device connected to the direct-current drying drum for extracting exhaust gas, with the white mineral drying drum connected to the exhaust device, enables old asphalt material to be heated in a direct-current drying drum. Exhaust gas from the direct-current drying drum is extracted by an exhaust device, fed to the white mineral drying drum to heat the white mineral, and burned there. The combustion of pollutants in the exhaust gas from the direct-current drying drum in the white mineral drying drum is effective. Surprisingly, it was found that a prior art plant for producing asphalt with a direct-current drying drum can be easily retrofitted by connecting the exhaust device for extracting the exhaust gas from the direct-current drying drum to the white mineral drying drum.It is possible to convert plants with high pollutant emissions into a plant according to the invention that has reduced pollutant emissions by converting it.

[0013] An exhaust hood, directly connected to the direct-current drying drum, enables improved extraction of exhaust gases from the direct-current drying drum. An exhaust fan of the extraction device improves the extraction of exhaust gases from the direct-current drying drum, and in particular from the exhaust hood, into the white mineral drying drum. The exhaust fan is arranged along an exhaust line, in particular between the exhaust hood and the white mineral drying drum.

[0014] A secondary exhaust line connected to the white mineral drying drum for the supply of secondary exhaust gases allows the supply of secondary exhaust gases that may arise in the plant, for example, from the extraction system of a mixer or from a loading silo, especially a mixed material loading silo. The total amount of pollutants in the exhaust gas is further reduced. The secondary exhaust line is part of the extraction system.

[0015] A burner in the white mineral drying drum enables uncomplicated and immediate heating of the white mineral. The combustion of the exhaust gases in the white mineral drying drum is improved.

[0016] A swirl chamber of the flow guide unit enables a swirling feed of the exhaust gases and / or secondary exhaust gases into the white mineral drying drum. Swirling feed means that the exhaust gases and / or secondary exhaust gases are fed eccentrically to the longitudinal axis of the white mineral drying drum. In particular, the exhaust gases and / or secondary exhaust gases are not fed directly to the burner flame. Due to the swirling feed, the exhaust gases and / or secondary exhaust gases are introduced essentially along a helical line around the longitudinal axis of the white mineral drying drum. The exhaust gases and / or secondary exhaust gases flow along a helical flow around the burner flame.

[0017] The design of the lamella recuperator with a tapered section, wherein a cylindrical section is arranged, in particular, along a longitudinal axis of the white mineral drying drum between an expanding section and the tapered section, ensures that the pollutant components in the exhaust gas and / or secondary exhaust gas are combusted in a controlled manner. In particular, along an expanding section, the helical flow of the exhaust gas and secondary exhaust gas can expand around the burner flame. Immediate combustion of the pollutant components after being fed into the white mineral drying drum is prevented. This prevents cooling of the flame core. This prevents incomplete combustion of the pollutant components. The pollutant components in the exhaust gas and / or secondary exhaust gas are heated within the expanding section, in particular as a result of the radiant heat of the lamella recuperator, and in particular become ignitable.In a tapered section, particularly one following the expansion section, the ignitable pollutants are fed to the burner flame tip and burned there. A cylindrical section arranged along a longitudinal axis of the white mineral drying drum between the expansion section and the tapered section enables targeted heating of the pollutant components in the exhaust gas and / or secondary exhaust gas. In particular, the pollutant components can be converted into vapor, thereby improving their combustion.

[0018] A design of the lamella recuperator with multiple tapered sections arranged one behind the other along the longitudinal axis ensures reliable removal of rock material, in particular old asphalt granulate, from the combustion chamber. In particular, multiple tapered sections are provided, which are arranged concentrically to one another and one behind the other along the longitudinal axis. The lamella recuperator is particularly funnel-shaped. In particular, the tapered sections arranged one behind the other are spaced apart along the longitudinal axis in such a way that a substantially annular end face gap is formed, which faces the burner flame. The rock material can exit the combustion chamber through this annular end face gap.

[0019] A flame tube for enveloping the burner flame is located primarily in the front area of ​​the burner flame and protects the flame from undesired cooling. This safeguards the combustion process. A further positive effect is that the flame tube is heated by the radiant heat of the burner flame and has a very high surface temperature. This heat can be transferred to the recuperator air. This heats the recuperator air to such an extent that any pollutants it contains evaporate and / or become ignitable. The flame tube is part of the flow control unit.

[0020] A heat / protection element, arranged along the longitudinal axis of the white mineral drying drum behind the flow guide unit, protects the throwing plate zone arranged in the white mineral drying drum along the longitudinal axis behind the flow guide unit from flame penetration. The heat / protection element is designed in particular as a cylindrical plate, in particular in the form of a baffle. The baffle is oriented in particular perpendicular to the longitudinal axis. The baffle allows heat to be transferred evenly and, in particular, over a large area into the white mineral drying drum via the baffle. Along the longitudinal axis, a dynamic pressure is created in the area of ​​the surface of the heat / protection element facing the flow guide unit, which leads, at least in some areas, to a forced flow of the recuperator air through the burner flame. As a result, a larger proportion of pollutants in the recuperator air are combusted.This reduces pollutant emissions and increases heat output.

[0021] A dust removal system, which is particularly located downstream of the white mineral drying drum, enables the reduction of the residual pollutants in the exhaust gas.

[0022] Both the features specified in the patent claims and the features specified in the following exemplary embodiments of the system according to the invention are suitable, either individually 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.

[0023] Further advantageous embodiments, additional features, and details of the invention will become apparent from the following description of exemplary embodiments with reference to the drawings. They show: Fig. 1 is a schematic representation of a plant with a white mineral drying drum according to the invention, Fig. 2 a sectional view according to section line II-II in Fig. 1, Fig. 3 a Fig. 1 corresponding schematic representation of a white mineral drying drum according to another embodiment.

[0024] One in Fig. 1 and Fig. Plant 1, shown schematically in Figure 2, is used to produce asphalt with the addition of old asphalt material, which is referred to as recycled material.

[0025] The system 1 comprises a direct current drying drum 2 for heating the old asphalt material. The direct current drying drum 2 is rotatable about a first rotation axis 3. At a Fig. 1, a material inlet 5 for supplying reclaimed asphalt material is provided on the end face 4 of the co-current drying drum 2 shown on the right. The reclaimed asphalt material passes through the co-current drying drum 2 along a material conveying direction 6, which is directed from the end face 4 into the interior of the co-current drying drum 2 and is oriented, in particular, parallel to the first rotational axis 3.

[0026] A first heat source in the form of a burner 7 is arranged on the front side 4. Heat is supplied directly to the direct-current drying drum 2 by means of the burner 7. The heat is conveyed through the direct-current drying drum 2 along a heat conveying direction 8. The heat conveying direction 8 is oriented parallel to and in the same direction as the material conveying direction 6. The direct-current drying drum 2 is operated using the direct-current method.

[0027] An extraction hood 9 is connected to the direct current drying drum 2 on a front side opposite the front side 4. Such an extraction hood 9, its details and mode of operation are known from German patent application DE 10 2015 217 845.5, to which reference is hereby made.

[0028] It is essential that the extraction hood 9 has an integrated particle separation unit for separating dust particles with a particle size of no more than 100 µm, in particular no more than 63 µm, and in particular no more than 20 µm. For this purpose, a collecting container 10 for collecting fine particles is arranged, in particular, below the extraction hood 9.

[0029] The extraction hood 9 has a substantially cylindrical housing 29, with a housing longitudinal axis 30 oriented substantially perpendicular to the rotational axis 3 of the direct-current drying drum 2. The housing longitudinal axis 30 is oriented substantially vertically. A collecting container 10 for fine particles is arranged in a lower region of the extraction hood 9. In a lower region facing away from the housing 29, the collecting container 10 is conical in design to improve the collecting effect and, in particular, the discharge of fine particles from the collecting container 10.

[0030] A conveying device with a screw conveyor can be arranged on an underside of the collecting container 10 facing away from the housing 29. The conveying device serves to remove material collected in the collecting container 18. The conveying device can further comprise a conveyor belt, which is loaded with the material from the collecting container 10 via the conveyor screw. Alternatively or in addition to the conveyor belt, the conveying device can comprise a trough screw conveyor.

[0031] The housing 29 of the extraction hood 9 has an inlet opening. Particle-containing gas from the cocurrent drying drum 2 can flow into the housing 29 through the inlet opening. The inlet opening is located in the outer cylindrical wall of the housing 29. The inlet opening is oriented essentially perpendicular to the rotation axis 3. The inlet opening is oriented essentially vertically.

[0032] The housing 29 has an outflow opening to which a suction line 11 is connected.

[0033] The outflow opening is arranged above the inflow opening along the housing's longitudinal axis 30. The inflow opening connects the outflow opening via a flow channel formed by the housing 29 of the extraction hood 9. The housing 29 has an inner diameter D A which defines a flow cross-sectional area of ​​the flow channel.

[0034] The flow channel is part of a flow control unit that is designed to be passive. The flow control unit is a particle separation unit. The flow control unit comprises a flow guide element, which is not shown in detail. The flow guide element is arranged in particular in the region of the inflow opening and is designed as a flap that can be pivoted about a pivot axis 30. The flow control unit can have a stop element against which the flow guide element can rest when there is no or insufficient exhaust gas flow from the co-current drying drum 2 into the extraction hood 9. The stop element is arranged in particular vertically below the axis of rotation, so that the flow guide element is oriented to hang vertically downwards in a non-actuated state. The flap is arranged such that a projection of the flap is arranged perpendicular to the inflow opening within the inflow opening.The flap clearly protrudes into the inflow cross-section formed by the inflow opening.

[0035] An extraction line 11 is connected to the extraction hood 9, which connects the extraction hood 9 to a white mineral drying drum 12. An extraction fan 13 is arranged along the extraction line 11 to extract exhaust gas from the extraction hood 9. A secondary exhaust line 14 opens into the extraction line 11, via which a secondary exhaust gas generator 15, in particular in a mix loading silo and / or a mixer, is connected to the extraction line 11.

[0036] The extraction hood 9, the extraction line 11 and the extraction fan 13 form an extraction device, which can optionally also include the secondary exhaust line 14.

[0037] The white mineral drying drum 12 is rotatable about a second rotational axis 16. A second heat source in the form of a second burner 17 is arranged concentrically to the second rotational axis 16 on the end face 18 of the white mineral drying drum 12. A white mineral inlet 19 for feeding white mineral into the white mineral drying drum 12 is provided on an end face opposite the end faces 18. The white mineral drying drum 12 is operated in a countercurrent process, with a white mineral conveying direction parallel but opposite to the heat conveying direction along the second rotational axis 16. A material outlet 31 for the heated white mineral is provided on the end face 18.

[0038] In the area of ​​the second burner 17, a flow guide unit 20 is arranged on the white mineral drying drum 12, which comprises a swirl chamber 21 and a lamella recuperator 22.

[0039] By means of the swirl chamber 21, the flow of exhaust gases from the extraction hood 9 and the secondary exhaust gases from the secondary exhaust gas generators 15 can be fed eccentrically with respect to the second rotational axis 16 of the white mineral drying drum 12 and introduced into the white mineral drying drum 12. The exhaust gases and secondary exhaust gases follow a helical flow around the second rotational axis 16 and thus around the flame of the second burner 17. The lamella recuperator 22 serves to guide the exhaust gas flow within the white mineral drying drum 12.

[0040] The lamella recuperator 22 has a length along the second axis of rotation 16 which essentially corresponds to a length of the burner flame 26 of the second burner 17.

[0041] The lamella recuperator 22 has an expanding section 23, a cylindrical section 24, and a tapered section 25 along the second rotational axis 16. The expanding section 23 is directly connected to the swirl chamber 21. The tapered section 25 is arranged facing away from the swirl chamber 21. The cylindrical section 24 is arranged on the rotational axis 16 between the expanding section 23 and the tapered section 25. The expanding section 23, the cylindrical section 24, and the tapered section 25 are arranged concentrically with respect to the second rotational axis 16.

[0042] The widening section 23, the cylinder section 24, and the tapered section 25 each have several, in particular eight, individual lamellae 32, which are arranged at least partially overlapping in the circumferential direction of the second rotation axis 16. This results in a radial overlap region 33 between two adjacent lamellae 32. Each overlap region 33 comprises an overlap opening 34, which has a surface normal oriented tangentially to a circular line around the rotation axis 3. Along the second axis of rotation 16, the respective overlap region 33 extends along the respective length of the widening section 23, the cylinder section 24 or the tapered section 25. In the circumferential direction 35 around the second axis of rotation 16, the overlap region 33 extends over approximately 5% to 10% of a circumferential length 33 of an individual lamella.

[0043] The overlap opening 34 is oriented such that during operation of the white mineral drying drum 12, material that has inadvertently entered the interior of the lamella recuperator 22 is automatically discharged from the lamella recuperator 22 through the overlap opening 34, in particular as a result of gravity.

[0044] Each lamella 32 is firmly connected to the rotary kiln 2 via two brackets 36. The brackets 36 are essentially identical. The brackets 36 are arranged spaced apart from one another along the second rotation axis 16. The brackets 36 ensure that each individual lamella 32 is connected to the white mineral drying drum 12 in a rotationally fixed manner with respect to the second rotation axis 16. In particular, the lamellae 32 are not directly connected to one another. The lamellae 32 are attached exclusively to the white mineral drying drum 12 via the brackets 36. The brackets 36 are designed such that a variable arrangement of the lamellae 32 relative to the white mineral drying drum 12 is possible. In particular, the brackets 36 serve to change the opening angle of the hopper. The brackets 36 are height-adjustable.

[0045] The individual slats 32 may have a curvature which can be seen from the illustrations Fig. 1 and Fig. 2. The lamella 32 extends linearly along an outer surface line of the lamella recuperator 22, so that the funnel of the lamella recuperator 22 has a conical, in particular a truncated cone-shaped, shape.

[0046] In the expansion section 23, the lamellae are arranged in a conical configuration with respect to the rotational axis 16, i.e., in the shape of a truncated cone. Along the rotational axis 16, the cross-sectional area in the expansion section 23 is designed to be conically widened.

[0047] According to the illustrated embodiment, the expansion angle at which the slats are arranged within the expansion section 23 in a conically widening manner relative to the second rotation axis 16 is approximately 15°. The expansion angle can in particular be between 5° and 45°.

[0048] Within the cylinder section 24, the fins are arranged substantially parallel to the second rotation axis 16. The cross-sectional area of ​​the fin recuperator 22 is substantially constant along the cylinder section 24.

[0049] Along the tapered section 25, the fins of the finned recuperator 22 are arranged in a conically tapered manner. Along the second rotational axis 16, the cross-sectional area of ​​the finned recuperator 22 tapers. According to the illustrated embodiment, a tapered angle at which the fins are arranged at an inclination relative to the second rotational axis is approximately -15°. The tapered angle can be, for example, between -5° and -45°. In particular, the expansion angle and the tapered angle are essentially identical in magnitude.

[0050] The design, in particular the dimensions of the expansion section 23, the cylinder section 24, and the tapered section 25, depend essentially on the geometry of the open burner flame 26 of the second burner 17. It is essential that the exhaust gases supplied via the swirl chamber 21 can move around the burner flame 26 in their helical flow, so that the exhaust gases are supplied to the burner flame 26, in particular to the burner flame tip, upon leaving the fin recuperator 22.

[0051] A dust removal unit 27 with a chimney 28 is arranged downstream of the white mineral drying drum 12. Cleaned exhaust gases are released into the environment via the chimney 28.

[0052] The function of system 1 is explained below. In the direct-current drying drum 2, reclaimed asphalt material fed through the material inlet 5 is heated and dried. Particles, particularly dust, are separated in the extraction hood 9 and collected in the collection container 10.

[0053] Particle-containing gas from the cocurrent drying drum 2 enters the extraction hood 9 via the inlet opening. The flow cross-sectional area of ​​the extraction hood 9 is selected to be large enough to result in a flow velocity of the incoming gas that, according to the illustrated embodiment, is less than 2 m / s. Due to the reduced flow velocity and, in particular, the fact that the upward-flowing gas flows from the inlet opening to at least the outlet opening, particles in the gas are automatically separated from the gas stream by gravity and collected in the collection container 10. The air discharged from the extraction hood 9 is pre-cleaned.

[0054] The flow guide element further improves particle separation. Due to the flow guide element, an exhaust gas stream from the cocurrent drying drum 2 cannot flow unhindered through the inlet opening into the extraction hood 9. The essentially horizontally flowing exhaust gas must flow around the flow guide element and is thereby accelerated downwards, at least in some areas, towards the collection container 10. Due to the downward acceleration, the exhaust gas flow in this area can reach up to approximately 6 m / s. The exhaust gas flow then changes direction towards the outlet opening. Due to the comparatively strong acceleration in the area of ​​the flow guide element and the deflection of the flow, particularly heavy particles are separated from the material stream. The exhaust gas flow then rises towards the outlet opening at a reduced flow velocity of approximately 2 m / s.

[0055] Exhaust gas from the extraction hood 9 is sucked through the extraction line 11 together with secondary exhaust gas from a secondary exhaust gas generator 15 by means of the extraction fan 13 and fed to the swirl chamber 21 of the flow guide unit 20. By means of the swirl chamber 21, the exhaust gases and secondary exhaust gases are forced into a helical flow around the burner flame 26. Due to the centrifugal force of the swirling flow of the exhaust gases, pollutant components are thrown radially outward from the rotation axis 16 and the burner flame 26. This prevents the exhaust gases, and in particular the pollutant components they contain, from being fed directly to the burner flame 26, which would cause the flame core to cool and result in incomplete combustion. The fins of the finned recuperator 22 prevent the exhaust gases, and in particular the pollutant components they contain, from being inadvertently thrown far outward, i.e., radially relative to the second rotation axis 16.The fins of the finned recuperator 22 prevent, in particular, the exhaust gases to be heated containing the pollutant components from coming into contact with the white mineral that is heated in the white mineral drying drum 12.

[0056] After expanding the swirling flow of the exhaust gases and secondary exhaust gases in the expansion section 23, the exhaust gases and secondary exhaust gases are guided around the burner flame 26 in the cylinder section 24. Within the cylinder section 24, the exhaust gases and in particular the pollutant components contained therein, in particular hydrocarbons C gesheated by the radiant heat of the finned recuperator. In the subsequent tapered section 25, the exhaust gases and secondary exhaust gases are directed conically closer to the second rotation axis 16 and the burner flame 26. The exhaust gases and pollutant components are additionally heated. The pollutant components in the exhaust gas thus become, in particular, vaporous and ignitable. The pollutants can be directed to the burner flame tip and burned there essentially pollutant-free. The cleaned exhaust gases from the white mineral drying drum 12 are directed to the dedusting unit 27, filtered, and released into the environment via the chimney 28.

[0057] The system 1 according to the invention creates the conditions for all pollutant components in the exhaust gas to be combusted. Pollutant emissions are reduced. A particular advantage of system 1 is that a hot gas generator can be arranged directly upstream of the white mineral drying drum 12.

[0058] It is surprising to find that an existing asphalt production plant can be easily converted into a plant according to the invention. This essentially requires connecting existing direct-current drying drums to the swirl chamber 21 with the lamella recuperator 22 on the white mineral drying drum 12 via the exhaust line 11 and the exhaust fan 13.

[0059] In the following, with reference to Fig. 3 describes a second embodiment of the invention. Structurally identical parts are given the same reference numerals as in the first embodiment, to the description of which reference is hereby made. Structurally different but functionally similar parts are given the same reference numerals with a suffix "a."

[0060] A significant difference compared to the first embodiment is that in the white mineral drying drum 12a, the lamella recuperator 22a has several tapered sections 25 arranged one behind the other along the second rotational axis 16. The tapered sections 25 are essentially identical, with the smaller outlet opening of the Fig. 3 left shown tapered section 25 along the second axis of rotation 16 into the larger receiving opening of the Fig.3, in particular protrudes into the rear tapered section 25 shown on the right. This results in an axial overlap region 40 directed in the axial direction of the second rotation axis 16, which has an annular end face through which material can exit the lamella recuperator 22a in a direction substantially parallel to the second rotation axis 16. This ensures that rock material, in particular old asphalt material, can be removed from the lamella recuperator 22a in sufficient quantities.

[0061] It is also conceivable to arrange only one tapered section 25 or more than two tapered sections 25 along the second axis of rotation 16.

[0062] A flame tube 41 is arranged in the area of ​​the burner flame 26. The flame tube 41 is designed as a cylindrical tube and is arranged in a front flame area of ​​the second burner 17. The flame tube 41 is made of a highly heat-resistant material, in particular a heat-resistant metal material, in particular a heat-resistant stainless steel alloy, which is available, for example, under the trade name Sicromal. These are high-alloy chromium steels, for example, with the material numbers 1.4713, 1.4724, 1.4742, 1.4749, 1.4762, 1.4878, 1.4828, 1.4821, 1.4841, or 1.4864.

[0063] The flame tube 41 protects the burner flame 26 from undesired cooling. The surface of the flame tube 41 is heated by the burner flame 26 in such a way that recuperation air, which is supplied to the front of the white mineral drying drum 12a via the swirl chamber 21, is heated. Pollutant components of the recuperation air evaporate and become ignitable. The flame tube 41 is fastened to a holding tube 43 via a holding device with several holding elements 42. The holding tube 43 and the flame tube 41 are arranged, in particular, concentrically to the axis of rotation 16. The holding tube 43 has a larger diameter than the flame tube 41. The holding elements 42 are arranged, in particular, spaced from one another along the axis of rotation 16. The holding elements 42 are arranged, in particular, parallel to one another. The holding elements 42 are designed, for example, as annular disks.The holding elements 42 can, for example, also be designed as radial webs and / or circular segment discs which are spaced apart from one another along the circumferential direction around the axis of rotation 16, but are arranged in a plane perpendicular to an axis of rotation 16.

[0064] The recuperation air flows via the swirl chamber 21 into an annular channel 44, which is bounded in the radial direction with respect to the rotation axis 16 on an inner side by the outer surface of the flame tube 41 and on an outer side by the inner surface of the holding tube 43.

[0065] Along the second rotational axis 16, a heat / protection element 45 in the form of a baffle is arranged at an end of the lamella recuperator 22a opposite the second burner 17. The baffle is attached to an inner side of the white mineral drying drum 12a by means of fastening elements (not shown). The baffle 45 is designed as a disc element or plate element and is arranged perpendicular to the second rotational axis 16 within the white mineral drying drum 12a. Recuperation air leaving the lamella recuperator 22a at the discharge opening 46 flows against the baffle 45. This prevents flames from the burner flame 26 from penetrating the deflection plate zone 47 arranged behind the baffle 45. In the area of ​​the discharge opening 46, the flow direction of the recuperation air is deflected and / or slowed down.In particular, the original flow direction, which is oriented essentially parallel to the second rotation axis 16, is deflected by up to 90° in a direction perpendicular to the second rotation axis 16. This creates a dynamic pressure on the recuperation air, so that the pollutants still contained in the recuperation air can be more effectively combusted.

[0066] The baffle 45 also improves heat distribution in the white mineral drying drum 12a. In particular, the heat from the burner flame 26 is distributed more evenly and over a larger area to the recuperation air. Heating of the white mineral drying drum 12a is more efficient and even. Material heating is thus improved.

Claims

[1] White mineral drying drum (12; 12a) for heating white mineral for the production of asphalt by means of a plant (1) with a flow guide unit (20), wherein the white mineral drying drum (12; 12a) is rotatable about a rotation axis (16), characterized by that a lamellar recuperator (22; 22a) with lamellar guide plates which form an outer shell for a helical flow movement of exhaust gases and / or secondary exhaust gases is arranged in the white mineral drying drum (12; 12a). [2] White mineral drying drum according to claim 1, wherein each lamella (32) is fixedly connected to the white mineral drying drum (12; 12a) by means of at least one holder (36). [3] White mineral drying drum according to one of claims 1 to 2, wherein the lamella recuperator (22) has a cylinder section (24) which is arranged in particular concentrically with respect to the axis of rotation (16). [4] White mineral drying drum according to claim 3, wherein the lamellae (32) are arranged within the cylinder section (24) parallel to the second axis of rotation (16). [5] A white mineral drying drum according to claim 3 or 4, wherein a cross-sectional area of ​​the lamella recuperator (22) is constant along the cylinder portion (24). [6] White mineral drying drum according to one of claims 1 to 5, wherein the white mineral drying drum (12; 12a) has a white mineral inlet (19) for feeding white mineral into the white mineral drying drum (12; 12a). [7] White mineral drying drum according to one of claims 1 to 6, wherein the white mineral drying drum (12; 12a) has a material outlet (31) for the heated white mineral. [8] White mineral drying drum according to claims 6 and 7, wherein the material outlet (31) is arranged on a first end face (18), wherein the white mineral inlet (19) is arranged on a second end face opposite the first end face (18), so that a white mineral conveying direction is defined which is directed parallel but opposite to the heat conveying direction along the second axis of rotation (16). [9] Plant with a white mineral drying drum according to one of claims 1 to 8 and with a burner (17) which is arranged on the first end face (18) of the white mineral drying drum (12; 12a) concentrically to the axis of rotation (16).

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