Apparatus for producing expanded granules

Abstract

An apparatus for producing expanded granules (2) from sandy mineral material (1) using an expanding agent, comprising a furnace (3) having a furnace shaft (4) with an upper end (5) and a lower end (6), a conveying path (7) passing through a plurality of heating zones (8) arranged separated from one another in a conveying direction (12) extending between the two ends, and at least one feeding means (10, 11) provided at one of the two ends for feeding at least unexpanded material into the furnace shaft in the direction of the one of the two ends. According to the invention, at least one guide element (13) is provided, arranged at least partially within the furnace shaft, which guide element forms a gap (15) with an inner wall (14) of the furnace shaft at least in the region of the one of the two ends, and the at least one feeding means is configured to feed the material into the gap.

Description

[Technical Field]

[0001] The present invention relates to an apparatus for producing expanded granules from sandy mineral material using an expanding agent, for example from perlite sand or obsidian sand using combined water as an expanding agent, the apparatus comprising a furnace having a substantially upright furnace shaft with an upper end and a lower end, a conveying path extending between the two ends through a plurality of heating zones arranged separately from one another in the conveying direction, the heating zones each having at least one heating element that can be controlled independently of one another for heating the material, in particular to a critical temperature, and expanding the sand granules, and at least one feeding means is provided, the feeding means being configured to feed at least unexpanded material into the furnace shaft at one of the two ends and in the direction of the other of the two ends of the furnace shaft in order to expand the material in the latter half of the conveying path, in particular in the last third, in the conveying direction. The device comprises at least one guide element arranged at least partially in the furnace shaft, the guide element forming a gap with the inner wall of the furnace shaft at least in the region of one of the two ends of the furnace shaft, and at least one feeding means configured to charge the unexpanded material into the gap. Regarding. [Background technology]

[0002] WO 2013 / 053635 A1 discloses a method and apparatus for expanding sandy mineral material, particularly closed-cell mineral material, using an expanding agent, such as bound water. The material is loaded from above into a furnace having a substantially upright furnace shaft. The material is transported by gravity along a conveying path from the upper end of the furnace shaft to its lower end in a conveying direction through the furnace shaft. The conveying path extends through a plurality of heating zones arranged separately from one another in the conveying direction, each of which has independently controllable heating elements for heating the material to a critical temperature and expanding the sand granules. The expanded granules are discharged at the lower end. Due to the buoyancy forces generated in the furnace shaft, particularly due to the chimney effect of the furnace shaft, which act to different degrees due to the different densities before and after expansion, this type of expansion is typically suitable for raw sand with a particle size of 75 μm or more, particularly 100 μm or more. With finer particle sizes, the buoyancy forces become too great and reliable expansion results are not achieved. Furthermore, fine particle size increases the risk of agglomeration on the furnace shaft walls, since particles that are too light or too dense remain suspended in the heating zone for too long. In this case, the particles continue to absorb energy after expansion and are unable to cool by isenthalpic shape changes, which also significantly increases the risk of agglomeration on the furnace shaft walls. This risk increases as the particle zone narrows, figuratively speaking, because there are no particles that are coarse and therefore heavy enough to carry away the fine particles against the buoyancy force.

[0003] To expand raw sand with a finer particle size, it is known from WO 2016 / 191788 A1 and WO 2018 / 191763 A1 that the material is charged or blown into the furnace shaft from bottom up together with a quantity of air and conveyed through the furnace shaft. When charging very fine particles in combination with blowing, it becomes clear that the different flows must be synchronized to obtain a uniform flow cross section through the furnace shaft and to avoid turbulence, which favors agglomerations at the side walls. Such agglomerations gradually "block" the shaft, thereby hindering heat radiation, which also worsens the expansion results. From WO 2021 / 060157 A1, a vertically arranged kiln for calcining lime, in particular limestone and dolomite, is known. This kiln has an outer tube and an inner tube through which the material to be calcined moves (by gravity), the material being introduced between the outer and inner tubes. This means that the tubes form a kind of gap between them into which the material is fed, the material being introduced into the kiln from above by a feeder. EP 0007977 A1 discloses a method and an annular shaft furnace for calcining lump materials such as limestone, dolomite, magnesite, etc., in which the annular shaft and the inner shaft are alternately filled with fresh air and calcination gas, and each is connected to an exhaust gas outlet. The annular gap and the inner shaft are formed by a shaft inserted into the furnace shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2013 / 053635 [Patent Document 2] International Publication No. 2016 / 191788 [Patent Document 3] International Publication No. 2018 / 191763 [Patent Document 4] International Publication No. 2021 / 060157 [Patent Document 5] European Patent Application Publication No. 0007977 Summary of the Invention

[0005] The object of the present invention is therefore to provide an apparatus for producing expanded granules which overcomes the above-mentioned drawbacks, in particular an apparatus which allows the expansion of raw sand having a fine grain size, preferably below 120 μm, particularly preferably in the range of 50 μm to 100 μm, and a narrow grain band, and in particular allows the production of expanded products of the same shape as possible.

[0006] To achieve the above object, there is provided an apparatus for producing expanded granules from sandy mineral material using an expanding agent, for example, from perlite sand or obsidian sand using combined water as an expanding agent, the apparatus comprising a furnace having a substantially upright furnace shaft with an upper end and a lower end, a conveying path extending between the two ends through a plurality of heating zones arranged separately from one another in the conveying direction, the heating zones each having at least one heating element independently controllable for heating the material, in particular to a critical temperature, and expanding the sand grains, and at least one supply means is provided, the supply means supplying at least unexpanded material to two of the furnace shafts in order to expand the material in the latter half of the conveying path, in particular the last third, in the conveying direction. In an apparatus according to the invention, at least one guide element is provided at least partially arranged in the furnace shaft, the guide element forming a gap with the inner wall of the furnace shaft at least in the region of one of the two ends of the furnace shaft, and the at least one feeding means is configured to charge the unexpanded material into the gap. Detachable mounting means are provided for the at least one guide element so that it can be removed from the furnace shaft and reinstalled as needed. It is intended that

[0007] The conveying direction is parallel to the vertical line or plumb line and can be from top to bottom or vice versa. That is, at least one guide element can be provided not only when the material is charged from above, but also when the material is charged from below. When charging from above, the material to be expanded is at least partially conveyed along the conveying path by gravity. When charging from below, the material to be expanded is typically charged into the furnace shaft together with a certain amount of air and conveyed through the furnace shaft.

[0008] The heating elements can be used to define the heating zones, as each of the different heating zones must have at least one heating element, and these heating elements must be controllable independently of each other.

[0009] For completeness, it is noted that the latter half is the second half, or the last third is the third third, as viewed in the conveying direction.

[0010] In principle, a single guide element can be provided, which can consist of several parts, in which case several smaller guide elements can jointly form or be integrated into a larger guide element, but it is also possible to provide several separate guide elements.

[0011] The at least one guide element is made from one or more materials that can withstand the temperatures occurring in the furnace shaft, and may include, for example, metals, in particular stainless steel or nickel-based alloys, or carbon fibers or ceramics, in particular high-performance ceramics.

[0012] It should be noted that the guide elements do not have to be located completely within the furnace shaft and, as will be explained in more detail below, they may partially protrude from the furnace shaft without impairing their function. For example, it is possible to provide for parts of the guide elements to protrude from the upper and / or lower ends of the furnace shaft for mounting purposes.

[0013] However, it is of course also possible to provide that at least one guide element is arranged completely within the furnace shaft and can only be mounted therein.

[0014] The inner wall defines the furnace shaft. The guide element is spaced from the inner wall of the furnace shaft, thereby forming at least in the region of one of the two ends of the furnace shaft, i.e., in the region of the end of the furnace shaft intended for the charging of the material to be expanded, the gap being in particular an annular gap. In this case, "annular gap" should be understood to extend in particular in the circumferential direction, and this does not mean that it is limited to a circular shape.

[0015] The guide element is thus arranged at least partially in the furnace shaft, forming a gap through which the unexpanded material is introduced, thereby moving the material or charge away from the radial center of the furnace shaft, at least in the region of the beginning of the conveying path. Here and below, "radial" should be understood regardless of the specific cross-sectional shape of the furnace shaft. That is, regardless of whether the cross-section of the furnace shaft normal to the conveying path or conveying direction is circular or not, for example, if the cross-section is elliptical, rectangular, or square, its center is called the radial center or radial middle. The radial direction therefore points outward from the radial middle.

[0016] Especially when charging is performed from above, in the radially middle region of the furnace shaft, there is typically an upward flow of heated air / gas ("stack flow") caused by the chimney effect, which prevents the material from being transported by gravity. However, said air or stack flow cannot hit or affect the material in the gap.

[0017] In addition, because it is a gap and not just a (particularly annular) opening, the material enters the furnace shaft and is guided therein.

[0018] The aforementioned guidance can extend over the entire conveying path, in particular if the guide elements extend over the aforementioned conveying path, in which case the length of the conveying path can typically be in the range from 3 m to 20 m, preferably from 5 m to 15 m, particularly preferably from 6 m to 10 m.

[0019] If the guide element, and therefore also the gap, extends only over a portion of the conveying path, for example over a few meters, the material is guided within the gap over said portion of the conveying path, while in this case there is typically also some guiding effect at least a little beyond the end of the guide element, due to the necessarily uniform movement, and in particular the direction of movement, of the individual material particles within the gap.

[0020] Accordingly, in the case of top loading, it is possible that the material does not yet come into contact with the air flow in the radial center even a little after it has left the gap.

[0021] However, even in the case of charging from below, the flow conditions and therefore the residence time of the particles and also the heat transfer to the particles in the furnace shaft can be influenced in an appropriate manner by means of at least one guide element.

[0022] The flow formed in the gap region, especially the annular gap flow, is characterized by the relatively narrow gap and the resulting increased flow velocity (Reynolds number Re>10 4 The turbulent flow (turbulence) favors heat transfer to the transport gas and therefore to the particles. The mixing in turbulence increases heat transfer (heat transfer coefficient α) compared to laminar flow.

[0023] That is to say, the guide elements favour the expansion of very fine and intimate charge fractions of material, which may in particular have a diameter of less than 120 μm, preferably less than 100 μm.

[0024] Another effect of the guide elements is that the entire material or charge, at least at the beginning of the conveying path, moves very close to the inner wall and thus relatively close to the heating element. This results in uniform heating of all grains of material in time and space, which also results in uniform expansion. This applies to both top- and bottom-loading.

[0025] Furthermore, the guide elements reflect or absorb a portion of the radiant energy and then re-emit it, allowing it to be irradiated by both the actively heated outer surface of the furnace or furnace shaft and the guide elements themselves, i.e., they can function as a passive heat source. The degree of reflection or emission can depend on the design of the guide elements, particularly the material of the guide elements, so that the guide elements form a passive heat source that is adjustable to some extent.

[0026] That is to say, the guide elements have many positive effects on the expansion result which can reinforce each other.

[0027] It becomes clear that different charge fractions of the material to be expanded may each require a different optimal guide element length, which may typically be one to several meters. Therefore, in a preferred embodiment of the device according to the invention, it is provided that at least one guide element extends, viewed in the conveying direction, up to the end of the first half, preferably up to the end of the first third, particularly preferably up to the end of the first quarter of the conveying path. In that case, according to the above explanation, the guide element can start from one of the two ends of the furnace shaft, or in the region of one of the two ends of the furnace shaft, or outside one of the two ends of the furnace shaft.

[0028] Such a limitation of the maximum extension of the guide elements seen in the conveying direction can be envisaged in particular in embodiments in which the charging of the material to be expanded takes place from above.

[0029] Alternatively or additionally, a minimum length of the guide element can be provided in order to achieve an optimal expansion result depending on the loading fraction, particularly in the case of embodiments in which the loading of the material to be expanded takes place from below.

[0030] Therefore, in a preferred embodiment of the device according to the invention, it is provided that at least one guide element extends over at least one quarter of the conveying path, preferably over at least one third of the conveying path, particularly preferably over the entire conveying path.

[0031] In a preferred embodiment of the device according to the invention, it is provided that the gap, viewed along the conveying direction, extends at least partially over the entire circumference around the radial center of the furnace shaft, so that the material to be expanded can be introduced into the furnace shaft without problems and, if necessary, simultaneously from all sides in very large quantities, in particular evenly distributed over the entire cross section of the gap or annular gap, which allows very high expansion or production rates.

[0032] If the guide elements are mounted only on the outside of the furnace shaft, the gap can also be formed over the entire length of the guide elements in the conveying direction, over the entire circumference relative to the radial center of the furnace shaft, which allows for maximum utilization of the space in the furnace shaft.On the other hand, if mounting elements for the guide elements must be provided inside the shaft, the gap can still be formed partially, viewed along the conveying direction, over the entire circumference around the radial center of the furnace shaft, i.e. in one or more sections where no mounting elements are provided.

[0033] In particular, the guide elements are formed radially, i.e., radially tight, particularly gas-tight, around the entire circumference around the radial center of the furnace shaft, i.e., in an angular range of 360°. According to the above explanation, this applies regardless of whether the furnace shaft has a circular cross section or not.

[0034] Thus, the outline shape of the gap need not be circular, but may be, for example, oval, rectangular, or square.

[0035] It should be noted here that the radial center of the furnace shaft and the radial center of the guide plate may generally coincide, and in that case, even if the guide plate does not completely surround this radial center, the radial center of the guide plate can be estimated, i.e., in some cases, the guide plate can be imaginarily extended to surround the radial center over the entire 360°.

[0036] In a preferred embodiment of the device according to the invention, it is provided that the gap varies in the conveying direction by at least 50%, preferably by at least 65%, particularly preferably by at least 80%, and the gap width is in particular at most 10 cm. The gap width corresponds to the distance between the inner wall of the furnace shaft and the guide element or the surface of the guide element facing the inner wall.

[0037] In particular, the gap width can be measured radially or normal to the guide element and / or the inner wall. In particular, the gap width at a point on the surface of the guide element facing the inner wall can be determined as the shortest distance between this point and the inner wall of the furnace shaft.

[0038] By varying the gap width in the conveying direction, i.e. over the conveying direction extension of the guide element in the gap-formed region, it is possible to precisely influence or adjust the residence time of the sand grains along the conveying path, in particular by increasing the gap width in a particular region of the conveying path, it is possible to adjust the residence time to be longer than in regions with a smaller gap width, and vice versa.

[0039] However, embodiments in which the gap width barely changes in the conveying direction or is essentially constant are of course also conceivable.

[0040] In any case, the shape of the guide element can be adapted to the shape of the cross section of the furnace shaft.

[0041] In that case, the range of variation mentioned above typically relates to the average gap width in the conveying direction or to a minimum or maximum gap width, the latter being in particular the case of the maximum possible gap width mentioned.

[0042] According to the above explanation, it is generally sensible to set the gap size relative to the actual size, i.e. not to set it to an exact centimeter value. However, in most cases, it may be sensible to set it based on absolute values. The design possible with the above-mentioned maximum gap width of 10 cm can provide particularly good or uniform expansion results for certain loading fractions, especially in embodiments where the loading of the material to be expanded is performed from above.

[0043] Similarly, in a preferred embodiment of the device according to the invention, the gap has a gap width that varies in the circumferential direction around the radial center of the furnace shaft by a maximum of 35%, preferably by a maximum of 10%, particularly preferably by a maximum of 5%, and it is particularly contemplated that the gap width is a maximum of 10 cm.

[0044] In that case, the range of variation mentioned above typically relates to the average value of the circumferential gap width or to a minimum or maximum gap width, the latter being in particular the case of the maximum possible gap width mentioned.

[0045] A small variation in the gap width in the circumferential direction proves to be advantageous for good, uniform expansion results, and vortices and therefore scorching of sand particles can be avoided particularly well.

[0046] Of course, variants are also conceivable in which the gap width does not vary at all in the circumferential direction or is substantially constant.

[0047] In a preferred embodiment of the device according to the invention, it is provided that the furnace shaft, along at least a portion of the conveying path, has an at least partially round, preferably substantially circular or substantially elliptical cross section defined by the inner wall transversely, in particular normal to, the conveying direction. With regard to warping stresses, a circular cross section is the most stable, while an ellipse has a much better ratio between circumference and cross section, in the sense that more "surface" (inner wall) is available for energy radiation.

[0048] The cross section of the furnace shaft is of course to be understood without any guide elements present.

[0049] In this case, "substantially" should be understood to mean that some deviation from a mathematically perfect circle or ellipse is possible and is usually even unavoidable from a manufacturing technology standpoint. If necessary, slight deviations from a mathematically perfect circle or ellipse can be intentionally provided.

[0050] In particular, the furnace shaft, which is hollow, has the above-mentioned cross-sectional shape along the entire transport path.

[0051] In that case, in each section, the cross-sectional shape may deviate from the round / circular / elliptical shape described above, for example, by connecting such section or section with a straight section or section.

[0052] Of course, the cross-sectional shape may be perfectly round / circular / oval along at least a portion of the transport path.

[0053] The transitions from one cross-section to another are designed in such a way that the flow vortices formed in the furnace shaft are particularly free from eddies.

[0054] Alternatively or additionally, the cross section may also have an angle. Thus, in a preferred embodiment of the device according to the invention, it is provided that the furnace shaft has an at least partially angular, preferably substantially rectangular or substantially square, cross section defined by the inner wall along at least a portion of the conveying direction and transversely, in particular normal to, the conveying direction. A relatively large cross-sectional circumference compared to the cross-sectional area may prove to be advantageous, since it makes room for a correspondingly large area of ​​heating elements and provides the material to be expanded with a larger area for energy transmission than would be the case with a purely or entirely circular cross section.

[0055] The cross section of the furnace shaft is of course to be understood in this case without any guide elements present.

[0056] In this case, "substantially" should be understood to mean that some deviation from a mathematically perfect rectangle or square is possible and usually even unavoidable from a manufacturing technology standpoint. In some cases, slight deviations from a mathematically perfect rectangle or square can be intentionally provided. In particular, it is possible to actually round the corners.

[0057] In particular, the furnace shaft, which is hollow, has the above-mentioned cross-sectional shape along a large part of the conveying path, preferably along the entire conveying path.

[0058] In that case, in some sections the cross-sectional shape may deviate from the angular / rectangular / square shape described above, for example, because such sections or sections are connected by rounded sections or sections.

[0059] Of course, the cross-sectional shape may be perfectly angular / rectangular / square along at least a portion of the transport path.

[0060] The transitions from one cross-section to another are designed in such a way that the flow vortices formed in the furnace shaft are particularly free from eddies.

[0061] In a preferred embodiment of the device according to the invention, the inner wall is formed by at least one boundary element, in particular made of high-temperature-resistant steel, and the at least one guide element is made of the same material as the at least one boundary element. This choice of material ensures that the boundary element fulfills the same performance requirements as the guide element. Furthermore, the same material results in the same thermal expansion coefficient, which prevents warping due to different thermal expansions and ensures a consistent gap shape.

[0062] In particular, the furnace is constructed radially behind the boundary elements from one or more other materials, in particular insulating materials.

[0063] High heat resistant steel is a type of stainless steel known per se.

[0064] By using the boundary element, it is possible to simply ensure in design that the material introduced into the furnace shaft cannot come into contact with the heating elements arranged behind the boundary element in the radial direction, while at the same time, any desired cross-sectional shape of the furnace shaft can be very easily realized by means of at least one boundary element and possibly adapted for different applications.

[0065] A correct or suitable choice of material for the boundary element allows its use in the entire temperature range in which it is actually intended to function, without its function being impaired or even damaged. Metallic materials are particularly conceivable when expanding perlite or obsidian. In this connection, it is also conceivable to manufacture the boundary element not from metal but from other suitable materials, such as carbon fiber or (high-performance) ceramics, especially in the case of other minerals that require higher firing temperatures.

[0066] As already mentioned several times, embodiments can be envisaged in which the material to be expanded is charged into the furnace shaft from below. Thus, in a preferred embodiment of the device according to the invention, at least one feed means is arranged to suck the unexpanded material into the furnace shaft at its lower end together with a quantity of air in the direction of its upper end, so that the quantity of air forms an air flow flowing from bottom to top, which air flow conveys the material from bottom to top along the conveying path and expands it in the upper (or second) half, in particular in the upper (or third) third of the conveying path.

[0067] For example, it would be conceivable to suck in a quantity of air by means of a vacuum source or a ventilator through a (suction) nozzle upstream of the furnace shaft and supply the material to the air flow entering the nozzle, for example by means of a chute. That is to say, the at least one supply means may comprise, for example, the aforementioned nozzle, means known per se for generating or sucking in a quantity of air, a vacuum source and / or an (air) ventilator, and a chute, the vacuum source or ventilator being connected downstream of the furnace shaft. In that case, the material can be supplied in a metered manner.

[0068] Therefore, in a particularly preferred embodiment of the device according to the invention, it is provided that the at least one supply means comprises at least one suction nozzle connected upstream of the furnace shaft and, in particular, a diffuser connected downstream of the suction nozzle.

[0069] In particular, the diffuser may be designed to disperse the material in a volume of air prior to the expansion process, reducing the relatively high flow velocity at the intake nozzle.

[0070] As already mentioned several times, embodiments can be envisaged in which the material to be expanded is charged into the furnace shaft from above. Thus, in a preferred embodiment of the device according to the invention, it is envisaged that at least one feed means is configured to charge the unexpanded material into the furnace shaft at the upper end thereof in the direction of the lower end thereof, so that the material is transported from top to bottom along the conveying path at least by gravity and is expanded in the lower half, in particular the lower third, of the conveying path.

[0071] Correspondingly, the at least one supply means may comprise, for example, a chute for supplying the material to be expanded.

[0072] The at least one supply means may further comprise at least one, in particular controllable, valve for the material, in particular to allow a particularly accurate metered supply of the material.

[0073] In addition to gravity, further supply or conveying means may be provided, such as process air or gas which flows from top to bottom or is blown or sucked into the furnace shaft.

[0074] For completeness' sake, it should be noted that, based on the recognition that the expansion process is an isenthalpic process accompanied by a temperature drop, the temperature drop can be accurately detected or located regardless of whether the expanded material is charged into the furnace shaft from above or below. This can also be used to determine the temperature treatment of the expanded sand grains after the actual expansion process, in particular to influence the surface properties of the expanded sand grains. For example, to prevent surface cracking, a new heating above a critical temperature can be prevented. Alternatively, if surface cracking of the sand grains is intentionally tolerated or even to be obtained, a new increase in such temperature can be intentionally initiated.

[0075] As mentioned above Apparatus according to the present invention fruitIn an embodiment, it is envisaged that detachable mounting means are provided for the at least one guide element so that the at least one guide element can be removed from the furnace shaft and reinstalled as needed, i.e. the guide element can be removed or reinstalled.

[0076] This allows the device to be used universally, since the guide elements can be completely removed without any problems when very coarse grains, especially those with diameters of several hundred micrometers or more, are to be expanded, while different guide elements, optimally matched to the respective feed fraction, can of course be easily attached / detached or replaced as required.

[0077] Typically, the removal or installation of each guide element is performed at a relatively low temperature, particularly at room temperature, and in some cases the device is allowed to cool first after the manufacturing process.

[0078] For the sake of order, we note that "detachable" should be understood in the usual sense to mean "non-destructively removable," thereby enabling reuse.

[0079] Correspondingly suitable attachment means are well known per se. In particular, a wide variety of screw connections and / or connections which function by form-fitting, such as hook-and-loop combinations, safety bolts or bayonet locks, or any combination of such connections, are conceivable as suitable attachment means.

[0080] As already mentioned above, the guide elements can be made from a wide variety of materials. In a preferred embodiment of the device according to the invention, at least one guide element is made from metal, in particular high-temperature-resistant steel. This ensures that the guide element can be used in the entire temperature range that is practically applicable, in particular when expanding perlite or obsidian, without its function being impaired or even damaged. On the other hand, the above-mentioned selection of the material for the guide element results in particularly good reflection or emission of heat or thermal radiation generated by the heating element. That is, the guide element is optimally suited as a passive heat source, as already explained in detail, which saves energy and costs.

[0081] In a preferred embodiment of the device according to the invention, it is provided that a free space is arranged in the furnace shaft along at least the entire extension of the at least one guide element, in particular along the entire extension of the at least one guide element, parallel to the conveying direction, between the at least one guide element and the radial center of the furnace shaft. It is not excluded that the guide element is formed outside the furnace shaft so that part of the guide element is arranged in the furnace shaft, typically in the region of the longitudinal axis of the furnace shaft, which extends exactly coaxially with the radial center of the furnace shaft.

[0082] The aforementioned free space allows air / gas, especially the chimney flow already mentioned, to escape from the furnace shaft in the radially central region, while the free space can be used to introduce forced air from the outside into the furnace shaft, which can influence the flow conditions in the furnace shaft and thus the residence time of the raw sand or of the expanded material in the furnace shaft after expansion.

[0083] The present invention will now be described in detail with reference to the following examples. The drawings are illustrative and represent the concept of the present invention, but are by no means intended to limit or completely represent the concept of the present invention. [Brief explanation of the drawings]

[0084] [Figure 1] FIG. 1 is a schematic cross-sectional view of one embodiment of an apparatus according to the invention for producing expanded granules, in which the granules to be expanded are charged or conveyed from top to bottom into or through a furnace shaft. [Figure 2] FIG. 2 is a schematic cross-sectional view of another embodiment of the device according to the invention for charging or conveying granules to be expanded into or through a furnace shaft from bottom to top. DETAILED DESCRIPTION OF THE INVENTION

[0085] FIG. 1 shows an apparatus according to the present invention for producing expanded granules 2 from sand-like mineral material using an expanding agent. In the illustrated embodiment, the material is perlite sand 1, to which water (so-called water of crystallization) is bound, acting as an expanding agent. The apparatus comprises a furnace 3 having a substantially upright furnace shaft 4 with an upper end 5 and a lower end 6. Between the two ends 5, 6, a conveying path 7 extends, indicated by a chain line in FIG. 1 (dashed line in FIG. 2), which also indicates the radial center 16 of the furnace shaft 4. The conveying path 7 passes through a plurality of heating zones 8 (indicated by horizontal dotted lines in FIG. 1) arranged separately from one another in the conveying direction 12. The heating zones 8 each have at least one independently controllable heating element 9 for heating the perlite sand 1, in particular to a critical temperature, and thereby expanding the perlite sand 1.

[0086] In the embodiment shown, the heating element 9 is electrically actuated and can be controlled by a regulation and control unit (not shown).

[0087] The apparatus further comprises a supply means, which in the embodiment of Fig. 1 includes a valve 10 for adjusting the charging of perlite sand 1 and process air 21, and is configured to charge unexpanded perlite sand 1 (together with process air 21) into the furnace shaft 4 at the upper end 5 of the furnace shaft 4 in the direction of the lower end 6 of the furnace shaft 4 in order to expand the perlite sand 1 in the latter half, particularly the last third, of the conveying path 7 as viewed in the conveying direction 12. That is, in the embodiment of Fig. 1, the perlite sand 1 is conveyed from top to bottom along the conveying path 7 mainly by gravity, and in some cases the falling movement of the perlite sand 1 is assisted by process air 21 blown or sucked in together with the perlite sand 1.

[0088] In this process, the process air 21 flowing from top to bottom through the furnace shaft 4 is heated. This could in principle increase the flow velocity within the furnace shaft 4, thereby shortening the residence time of all perlite sand particles 1 within the furnace shaft 4. To avoid this and to compensate for the increase in the flow velocity of the first process air or to keep the flow velocity approximately constant, in the embodiment of FIG. 1 the furnace shaft 4 is designed so that it is wider at the bottom than at the top. That is, the cross section of the furnace shaft 4 normal to the conveying direction 12 increases from the top end 5 to the bottom end 6.

[0089] However, it should be emphasized that, when the perlite sand 1 is charged at the upper end 5 of the furnace shaft 4, a furnace shaft 4 with a constant or nearly constant cross section is of course also possible.

[0090] The cross section of the furnace shaft 4 is defined by an inner wall 14 of the furnace shaft 4 which, in the embodiment shown, is formed by at least one boundary element made of high heat resistant steel.

[0091] The furnace shaft 4 or furnace 3 is insulated towards the outside by insulation 24 .

[0092] Temperature sensors 23 are arranged at vertically spaced locations 22, with at least one temperature sensor 23 in each heating zone 8. Thus, in the illustrated embodiment of FIG. 1, the temperature of the perlite sand 1 is sensed by the temperature in each heating zone 8.

[0093] The heating element 9 and the temperature sensor 23 are connected to a regulation and control unit (not shown), which determines the location or region 25 in the furnace shaft 4 where the expansion of the perlite sand granules 1 takes place based on the temperature data. At this location or region 25, a significant drop in temperature occurs in the expanded perlite sand 1, for example, a temperature drop of more than 100°C. This temperature drop is the result of an isenthalpic expansion process of the perlite sand 1, which occurs due to softening of the surface of the perlite sand granules 1 and the subsequent expansion process caused by the generation of water vapor or vapor pressure in the perlite sand granules 1. For example, the perlite sand 1 may be at about 780°C just before it expands, and only about 590°C immediately after the isenthalpic expansion process, i.e., a temperature drop of 190°C in this example. Depending on the material, this temperature drop is typically at least 20°C, in particular at least 100°C. To achieve the desired energy input, the heating elements 9 located after the temperature drop or area 25 as seen in the conveying direction 12 can be adjusted precisely or automatically by an adjustment and control unit (not shown).

[0094] It should be noted that this automatic adjustment may omit the use of the temperature sensor 23 to detect the temperature drop, since the temperature drop does not necessarily manifest itself as a temperature drop, but in some cases as an area where more energy is required to maintain the temperature.

[0095] In particular, these heating elements 9 can be adjusted so that the temperature of the expanded perlite sand or granules 2 does not rise further or again, or to ensure that the expanded granules 2 are closed-cell.

[0096] In the embodiment of Figure 1, the expanded granules 2 are discharged at the lower end 6 and fed via a water-cooled chute 20 into an entrained / suction flow 26 operated by cold air 27. The cold air 27 or cold air 28 containing the expanded perlite sand 2 is sucked in by, for example, a vacuum pump or ventilator (not shown).

[0097] The device according to the invention has at least one guide element 13 arranged at least partially in the furnace shaft 4, which guide element 13 forms a gap 15 with the inner wall 14 of the furnace shaft 4 at least in the region of one of the two ends 5, 6 of the furnace shaft 4, and at least one feeding means is configured to charge unexpanded perlite sand 1 into this gap 15.

[0098] 1, the guide element 13 is arranged accordingly in the region of the upper end 5. The valve 10 and the process air 21 are set up so that the perlite sand 1 is fed into the gap 15 in the region of the upper end 5, i.e., the perlite sand 1 enters the furnace shaft 4 when it enters the gap 15.

[0099] It should be emphasized that in the embodiment of FIG. 1, the perlite sand 1 is introduced into the entire gap 15 at the upper end 5, but in FIG. 1, for the sake of clarity, only the perlite sand 1 introduced into the gap 15 on the left side of the figure is shown.

[0100] The guide elements 13 protect the perlite sand 1 from the upward flow of heated air / gas ("chimney flow") that forms in the region of the radial center 16 of the furnace shaft 4. This prevents very fine grain sizes, less than 100 μm in diameter, especially less than 75 μm, from falling down due to the chimney flow and thus from expanding as desired. This is caused, in particular, by the fact that, without the guide elements 13, the perlite sand particles 1 would be heated again after cooling by an isenthalpic expansion process. This leads to a renewed softening of the perlite sand particles 1, but the perlite sand particles 1 are no longer able to cool isenthalpic- ically due to their shape change, and therefore the risk of agglomeration on the inner wall 14 increases.

[0101] The chimney flow can escape without problems upward from the furnace shaft 4 through a free space 19. This free space 19 is arranged or formed along the entire extension of the guide element 13, parallel to the conveying direction 12, between the guide element 13 and the radial center 16 of the furnace shaft 4.

[0102] Furthermore, the guide element 13 precisely guides the perlite sand 1 along the vicinity of the inner wall 14, so that all the perlite sand grains 1 are heated uniformly in time and place, which also results in uniform expansion.

[0103] In the embodiment of FIG. 1, the guide elements 13 extend in the furnace shaft 4 from the upper end 5 to approximately the end of the first third of the conveying path 7. However, the movement of the pearlite sand grains 1 in the gaps 15 caused by the guide elements 13, in particular the uniformity of the direction of movement, still acts a little past the end of the guide elements 13.

[0104] In the illustrated embodiment, the guide element 13 is made of high-temperature resistant steel and reflects the heat radiation caused by the heating element 9 accordingly well, i.e. the guide element 13 also serves as a passive heater for the perlite sand 1 located between the inner wall 14 and the guide element 13.

[0105] 1, the guide element 13 is arranged completely within the furnace shaft 4 and is therefore mounted there, for which purpose it is provided with removable mounting means (not shown) so that it can be removed from the furnace shaft 4 and reinstalled as required. Viewed along the conveying direction 12, the gap 15 extends over the entire circumference around the radial center 16 of the furnace shaft 4, with the exception of the region in which the above-mentioned mounting element is provided.

[0106] 1, the shape of the guide element 13 is adapted to the cross-section of the furnace shaft 4, in that the guide element 13 extends essentially parallel to the inner wall 14. Correspondingly, the gap 15 has a gap width 17 which varies only slightly, in particular is essentially constant, over the entire extension of the guide element 13 in the conveying direction 12 in the illustrated embodiment. However, it should be noted that embodiment variants are also possible in which the gap width 17 varies by at least 50% in the conveying direction 12 in order to precisely adjust the residence time of the perlite sand grains 1 in different regions along the conveying path 7.

[0107] Furthermore, in the embodiment of Fig. 1, the gap width 17 also varies little in the circumferential direction 18, and in particular remains essentially constant. This applies in particular to the region where the perlite sand 1 is charged, i.e., in the embodiment of Fig. 1, in the region of the upper end 5, at the position or region along the conveying path 7 where the guide elements 13 extend. However, it should be noted that embodiment variants are also possible in which the gap width 17 varies significantly in the circumferential direction 18, although typically by significantly less than in the conveying direction 12, for example by a maximum of 5%.

[0108] The obvious difference between the embodiment variant shown in FIG. 2 and that shown in FIG. 1 is that the perlite sand 1 to be expanded (not shown in FIG. 2 for clarity) is charged into the furnace shaft 4 from below, with the conveying direction 12 pointing from bottom to top. Correspondingly, at least one guide element 13 is arranged in the furnace shaft 4, at least in the region of the lower end 6 of the furnace shaft 4, where it forms a gap 15 together with the inner wall 14. In this case, the at least one supply means includes a suction nozzle 11 and a ventilator 34 connected upstream of the furnace shaft 4, and is configured to suck the unexpanded perlite sand 1 together with a quantity of air into the furnace shaft 4 at the lower end 6 in the direction of the upper end 5 of the furnace shaft 4, so that the perlite sand 1 is charged into the gap 15. This quantity of air then forms an upward airflow, which transports the perlite sand 1 along the conveying path 7 from bottom to top and expands it in the upper half, particularly the upper third, of the conveying path 7.

[0109] In the embodiment of Figure 2, the supply means further comprises a diffuser 30 connected downstream of the suction nozzle 11 and to which the lower end 6 of the furnace shaft 4 is connected. The diffuser 30 can contribute to dispersing the perlite sand 1 in a volume of air prior to the expansion process in order to achieve or support a uniform distribution of the perlite sand 1 in the air stream.

[0110] The suction nozzle 11 is supplied with perlite sand 1 via a vibrating trough 35, which is metered from a storage container 29 into the vibrating trough 35 via a metering screw 33. In addition, air is also sucked in via the suction nozzle 11 (using a ventilator 34), thereby forming a suction air flow 31. The air flow or suction air flow 31 can be adjusted by a suitable selection or design of the suction nozzle 11 and / or by selecting a suitable suction speed (using the ventilator 34). In principle, the above can also be performed automatically by means of an adjustment and control unit (not shown).

[0111] In the embodiment of Fig. 2, the guide elements 13 extend over approximately one-quarter or even the first quarter of the conveying path 7, but they can also be much larger and extend over the entire conveying path 7, in particular within the furnace shaft 4. The latter is indicated by dashed lines in Fig. 2.

[0112] The guide elements 13 are also essentially adapted to the cross-sectional shape of the furnace shaft 4 in the exemplary embodiment of Fig. 2. As in the exemplary embodiment of Fig. 1, the gap width 17 in the exemplary embodiment of Fig. 2 varies little in the circumferential direction 18 and is, in particular, essentially constant. This applies to all positions or regions along the conveying path 7 through which the guide elements 13 extend, in particular in the region where the perlite sand 1 is charged, i.e., in the region of the lower end 6 in the exemplary embodiment of Fig. 2. However, it should be noted that exemplary variants are also possible in which the gap width 17 varies significantly in the circumferential direction 18, although typically by a smaller amount than in the conveying direction 12, for example by a maximum of 5%.

[0113] Although FIG. 2 does not show the variation of the gap width 17 in the conveying direction 12, even in the embodiment shown in FIG. 2, the gap width 17 can be varied along the conveying path 7 or conveying direction 12 by a much larger amount than in the circumferential direction 18, for example by at least 50%, in order to precisely adjust the residence time of the perlite sand grains 1 in different regions along the conveying path 7.

[0114] However, in both illustrated embodiment variants, the gap width 17 is at most 10 cm.

[0115] In the embodiment of FIG. 2, the guide element 13 is in particular removably attached to the diffuser 30 .

[0116] Correspondingly, the gap 15 is provided over the entire circumference around the radial center 16 when viewed along the conveying direction 12 .

[0117] In the embodiment of Figure 2, an essentially absolute temperature measurement is performed (however, for the sake of clarity, a temperature sensor is not shown). In addition, the power consumption of the heating element 9 is determined, or how this power consumption varies along the conveying path 7. Immediately after the expansion process and the accompanying temperature drop, the temperature difference between the expanded granules 2 (not shown separately in Figure 2 for the sake of clarity) and the heating element 9 is much greater than that between the perlite sand 1 and the heating element 9 immediately before the expansion process.

[0118] Therefore, as long as the measured temperature remains constant, the heat flow also increases, i.e. the observed change in the heat flow or power consumption of the heating elements 9 from one heating zone 8 to the next is an increase, whereas the change in power consumption along the conveying path 7 is a decrease, due to the gradual heating of the perlite sand 1 before the expansion process.

[0119] The heating element 9 is connected to a regulation and control unit (not shown) for regulation, in particular for regulation along the remaining conveying path 7 after the temperature has dropped, so as to, for example, precisely prevent or allow the material temperature along the remaining conveying path 7 to increase up to or beyond a critical temperature.

[0120] The expanded granules 2 are discharged from the furnace shaft 4 (together with the warmed air) via a collection section 32 leading to the upper end 5 of the furnace shaft 4. The expanded granules 2 are further conveyed by an entrainment / suction flow 26 operating with cold air 27. As already mentioned, the cold air 27 or cold air 28 containing the expanded perlite sand 2 is then sucked in, for example, by a vacuum pump or ventilator (not shown). The inventions described in the original claims of this application are set forth below. [1] An apparatus for producing expanded granules (2) from sandy mineral material (1) using an expanding agent, for example, producing expanded granules (2) from perlite sand (1) or obsidian sand using combined water as an expanding agent, the apparatus comprising: a furnace (3) having a substantially upright furnace shaft (4) with an upper end (5) and a lower end (6); a conveying path (7) extending between the two ends (5, 6) through a plurality of heating zones (8) arranged separately from one another in a conveying direction (12); each of the heating zones (8) having at least one heating element (9) independently controllable to heat the material (1) to at least a critical temperature and expand the sand grains (1); and at least one supplying means (10, 11) for supplying the material (1) in the conveying direction (12). 1. An apparatus for feeding at least unexpanded material (1) into the furnace shaft (4) at one of the two ends (5, 6) of the furnace shaft (4) in the direction of the other of the two ends (6, 5) of the furnace shaft (4) in order to expand it in a second half, in particular in the last third, of the conveying path (7), characterized in that at least one guide element (13) is provided at least partially arranged in the furnace shaft (4), the guide element (13) forming a gap (15) with an inner wall (14) of the furnace shaft (4) at least in the region of one of the two ends (5, 6) of the furnace shaft (4), and the at least one feed means (10, 11) is configured to feed the unexpanded material (1) into the gap (15). [2] The device according to [1], characterized in that the at least one guide element (13) extends, in the conveying direction (12), up to the edge of the first half of the conveying path (7), preferably up to the edge of the first third, particularly preferably up to the edge of the first quarter. [3] The device according to [1] or [2], characterized in that the at least one guide element (13) extends over at least one-quarter of the conveying path (7), preferably over at least one-third of the conveying path (7), particularly preferably over the entire conveying path (7). [4] The device according to any one of [1] to [3], characterized in that the gap (15) extends, at least partially, over the entire circumference around the radial center (16) of the furnace shaft (4) when viewed along the conveying direction (12). [5] The device according to any one of [1] to [4], characterized in that the gap (15) has a gap width (17) that varies in the conveying direction (12) by at least 50%, preferably by at least 65%, particularly preferably by at least 80%, and in that the gap width (17) is in particular at most 10 cm. [6] The device according to any one of [1] to [5], characterized in that the gap (15) has a gap width (17) that varies in the circumferential direction (18) around the radial center (16) of the furnace shaft (4) by at most 35%, preferably at most 10%, particularly preferably at most 5%, and in particular the gap width (17) is at most 10 cm. [7] The apparatus according to any one of [1] to [6], characterized in that the furnace shaft (4) has, along at least a portion of the conveying path (7), an at least partially round, preferably substantially circular or substantially elliptical cross section defined by the inner wall (14) transversely, in particular normal to, the conveying direction (12). [8] The apparatus according to any one of [1] to [7], characterized in that the furnace shaft (4) has, along at least a part of the conveying direction (7), an at least partially angular, preferably substantially rectangular or substantially square, cross section defined by the inner wall (14) transversely, in particular normal to, the conveying direction (12). [9] The device according to any one of [1] to [8], characterized in that the inner wall (14) is formed by at least one boundary element made, in particular, from high-heat-resistant steel, and the at least one guide element (13) is made from the same material as the at least one boundary element.

[10] The device according to any one of [1] to [9], characterized in that the at least one supplying means (11) is configured to suck the unexpanded material (1) together with a quantity of air into the furnace shaft (4) at the lower end (6) of the furnace shaft (4) in the direction of the upper end (5) of the furnace shaft (4), whereby the quantity of air forms an air flow flowing from bottom to top, and the material (1) is transported from bottom to top along the conveying path (7) by the air flow, and is expanded in the upper half, in particular the upper third, of the conveying path (7).

[11] The device according to

[10] , characterized in that the at least one supply means comprises at least one suction nozzle (11) connected upstream of the furnace shaft (4) and, in particular, a diffuser (30) connected downstream of the suction nozzle (11).

[12] The device according to any one of [1] to [9], characterized in that the at least one feeding means (10) is configured to charge the unexpanded material (1) into the furnace shaft (4) at the upper end (5) of the furnace shaft (4) in the direction of the lower end (6) of the furnace shaft (4), so that the material (1) is conveyed from top to bottom along the conveying path (7) at least by gravity and expanded in the lower half, in particular the lower third, of the conveying path (7).

[13] An apparatus according to any one of [1] to

[12] , characterized in that detachable mounting means are provided for at least one guide element (13) so that the at least one guide element (13) can be removed from the furnace shaft (4) and reinstalled as needed.

[14] The device according to any one of [1] to

[13] , characterized in that the at least one guide element (13) is made of metal, in particular high-heat-resistant steel.

[15] The device according to any one of [1] to

[14] , characterized in that a free space (19) is arranged in the furnace shaft (4) between the at least one guide element (13) and the radial center (16) of the furnace shaft (4), at least along the entire extension of the at least one guide element (13), in particular along the entire extension of the at least one guide element (13), parallel to the conveying direction (12). [Explanation of symbols]

[0121] 1 perlite sand 2 Expanded granular material 3 furnace 4 Furnace shaft 5. Upper end of furnace shaft 6 Lower end of furnace shaft 7. Transport Route 8 Heating Zones 9 heating elements 10 valves 11 Suction nozzle 12 Conveying direction 13 Guide Elements 14 Furnace shaft inner wall 15 Gap 16 Radial center of furnace shaft 17 Gap width 18 Circumferential direction 19 Free space 20 Water-cooled Chute 21 Process Air 22 Temperature measurement position 23 Temperature Sensor 24 Insulation 25 Location or area of ​​temperature drop 26 Entrained Flow / Suction Flow 27 Entrained flow transport of cold air 28 Expanded perlite sand or cold air containing expanded granular material 29 Storage Container 30 Diffuser 31 Suction airflow 32 Collection Department 33 Metering screw 34 Ventilator 35 Vibrating Trough

Claims

1. 1. An apparatus for producing expanded granules (2) from sandy mineral material (1) using an expanding agent, the apparatus comprising: a furnace (3) having a substantially upright furnace shaft (4) with an upper end (5) and a lower end (6); a conveying path (7) extending between the upper end (5) and the lower end (6) through a plurality of heating zones (8) arranged separately from one another in a conveying direction (12), the heating zones (8) each having at least one heating element (9) independently controllable to heat the sandy mineral material (1) to at least a critical temperature and expand the sandy mineral material (1); and at least one supplying means (10, 11) for supplying at least one heating element (9) to expand the sandy mineral material (1) in a rear half of the conveying path (7) in the conveying direction (12). and a furnace shaft (4) configured to charge at least unexpanded sand-like mineral material (1) into the furnace shaft (4) at one of the upper end (5) and the lower end (6) of the furnace shaft (4) in the direction of the other of the upper end (5) and the lower end (6) of the furnace shaft (4), wherein at least one guide element (13) is provided at least partially arranged in the furnace shaft (4), the guide element (13) forming a gap (15) for guiding the sand-like mineral material (1) along an inner wall (14) of the furnace shaft (4) only in the region of one of the upper end (5) and the lower end (6) of the furnace shaft (4), and the at least one supply means (10, 11) is configured to charge the unexpanded sand-like mineral material (1) into the gap (15), 1. The device according to claim 1, wherein detachable mounting means are provided for at least one guide element (13) so that said at least one guide element (13) can be removed from said furnace shaft (4) and reinstalled.

2. 2. Device according to claim 1, characterized in that the at least one guide element (13) extends up to the edge of the front half of the conveying path (7) as seen in the conveying direction (12).

3. 3. Device according to claim 1 or 2, characterized in that the at least one guide element (13) extends over at least a quarter of the conveying path (7).

4. 3. The device according to claim 1 or 2, characterized in that the gap (15), viewed along the conveying direction (12), extends at least partially over the entire circumference around the radial center (16) of the furnace shaft (4).

5. 3. Apparatus according to claim 1 or 2, characterized in that the gap (15) has a gap width (17) which varies in the conveying direction (12) by at least 50% of the gap width (17).

6. 3. The device according to claim 1 or claim 2, characterized in that the gap (15) has a gap width (17) that varies in a circumferential direction (18) around the radial center (16) of the furnace shaft (4) by a maximum of 35% of the gap width (17).

7. 3. The apparatus according to claim 1 or 2, characterized in that the furnace shaft (4) has, along at least a portion of the conveying path (7), an at least partially round cross section defined by the inner wall (14) transversely to the conveying direction (12).

8. 3. The device according to claim 1 or 2, characterized in that the furnace shaft (4) has, along at least a portion of the conveying path (7), an at least partially rectangular cross section defined by the inner wall (14) transversely to the conveying direction (12).

9. 3. The device according to claim 1 or 2, characterized in that the inner wall (14) is formed by at least one boundary element, and the at least one guide element (13) is made from the same material as the at least one boundary element.

10. 3. The device according to claim 1, wherein the at least one supply means (11) is configured to suck the unexpanded sandy mineral material (1) at the lower end (6) of the furnace shaft (4) together with a quantity of air into the furnace shaft (4) in the direction of the upper end (5) of the furnace shaft (4), whereby the quantity of air forms an air flow flowing from bottom to top antiparallel to gravity in the vertical direction, and the air flow transports the sandy mineral material (1) from bottom to top along the conveying path (7) and causes it to expand in the upper half of the conveying path (7).

11. 11. Apparatus according to claim 10, characterized in that the at least one supply means comprises at least one suction nozzle (11) connected upstream of the furnace shaft (4).

12. 3. The device according to claim 1, wherein the at least one feeding means (10) is configured to charge the unexpanded sandy mineral material (1) into the furnace shaft (4) at the upper end (5) of the furnace shaft (4) in the direction of the lower end (6) of the furnace shaft (4), so that the sandy mineral material (1) is transported from top to bottom along the conveying path (7) parallel to gravity in a vertical direction and expanded in the lower half of the conveying path (7).

13. 3. Device according to claim 1 or 2, characterized in that the at least one guide element (13) is made of metal.

14. 3. The device according to claim 1, wherein a free space (19) is arranged in the furnace shaft (4) between the at least one guide element (13) and the radial center (16) of the furnace shaft (4) at least along the entire extension of the at least one guide element (13).

15. 6. The device according to claim 5, characterized in that the gap width (17) is at most 10 cm.

16. 7. Device according to claim 6, characterized in that the gap width (17) is at most 10 cm.

17. 10. The apparatus of claim 9, wherein said at least one boundary element is made from high heat resistant steel.

18. 12. Device according to claim 11, characterized in that said at least one supply means comprises a diffuser (30) connected downstream of said suction nozzle (11).

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