DEVICE FOR PRODUCING EXPANDED GRANULATED MATERIAL

Abstract

A device for producing expanded granulated material from grains of sand with an expanding agent includes a furnace with a furnace shaft, which has upper and lower ends. A conveying section extends between the ends and passes through separately-arranged heating zones in a conveying direction. At least one feeder charges at least the unexpanded material into the furnace shaft at one end toward the other end. At least one rotatable shaft insert is arranged at least in sections in the furnace shaft and has at least one scraper blade forming with an inner wall of the furnace shaft at least one gap having a gap width and being designed, during rotation of the at least one shaft insert in an operating state of the device, to remove caking on the inner wall at least in sections if a thickness of the caking is greater than the respective gap width.

Claims

1-13. (canceled)

14. A device for producing an expanded granulated material from mineral material in the form of grains of sand with an expanding agent, the device comprising a furnace with a substantially vertically standing furnace shaft having an upper end and a lower end, wherein a conveying section extends between the two ends, wherein further at least one feeding means is provided which is adapted to charge at least the unexpanded material at one of the two ends of the furnace shaft into the furnace shaft in the direction of the other of the two ends of the furnace shaft in order to expand the material, as seen in a conveying direction, in the last half of the conveying section, wherein at least one rotatable shaft insert is provided, which is arranged at least in sections in the furnace shaft and has at least one scraper blade, which forms with an inner wall of the furnace shaft at least one gap having a gap width and which is designed, during rotation of the at least one shaft insert in an operating state of the device, to remove caking on the inner wall in sections if a thickness of the caking is greater than the respective gap width, wherein the at least one shaft insert is rotatable about at least one axis of rotation which extends parallel to a longitudinal axis of the furnace shaft, wherein the conveying section leads through a plurality of heating zones which are arranged separately from one another in a conveying direction, wherein the heating zones each comprise at least one heating element which can be controlled independently of one another in order to heat the material at least to a critical temperature and to expand the sand grains, and wherein the at least one shaft insert each comprises a base body from which the at least one scraper blade projects with a directional portion parallel to a radial direction, wherein the radial direction lies in a plane normal to the axis of rotation of the respective shaft insert and, starting from the respective axis of rotation, faces away therefrom, wherein the respective base body, as viewed at least in the radial direction, is substantially closed.

15. The device according to claim 14, wherein the at least one shaft insert is rotatably mounted in the region of the upper end of the furnace shaft.

16. The device according to claim 14, wherein the at least one shaft insert has a plurality of scraper blades.

17. The device according to claim 16, wherein at least two of the scraper blades are arranged one behind the other as viewed in a circumferential direction around a radial center of the furnace shaft.

18. The device according to claim 16, wherein at least two of the scraper blades form gaps with the inner wall having different gap widths.

19. The device according to claim 14, wherein at least one drive means is provided for rotating the at least one shaft insert at a variable rotational speed.

20. The device according to claim 14, wherein the respective base body is essentially rotationally cylindrical.

21. The device according to claim 14, wherein the at least one scraper blade is arranged on the respective base body such that it can be extended/retracted and/or pivoted in order to be able to adjust the gap width.

22. The device according to claim 14, wherein the at least one scraper blade extends substantially in a straight line.

23. The device according to claim 14, wherein the at least one scraper blade extends at least in sections in a spiral or helical shape about an axis of rotation of the respective shaft insert.

24. The device according to claim 23, wherein, as viewed in a circumferential direction around a radial center of the furnace shaft, the gap width varies.

25. The device according to claim 14, wherein the gap width of the at least one gap varies as viewed in the conveying direction.

26. The device according to claim 14, wherein the inner wall is formed by at least one limiting element, and wherein the at least one shaft insert is made of the same material as the at least one limiting element.

27. The device according to claim 14, wherein the at least one axis of rotation coincides with the longitudinal axis.

28. The device according to claim 15, wherein the at least one shaft insert is floatingly mounted in the region of the lower end of the furnace shaft.

29. The device according to claim 16, wherein the at least one shaft insert has at most eight scraper blades.

30. The device according to claim 16, wherein the at least one shaft insert has two to four scraper blades.

31. The device according to claim 19, wherein the at least one drive means is adapted to set the rotational speed in the range from 0.125 rpm to 3 rpm.

32. The device according to claim 19, wherein the at least one drive means is adapted to set the rotational speed in the range from 0.5 rpm to 2 rpm.

33. The device according to claim 20, wherein, as seen in the conveying direction, upstream and/or downstream of the respective base body a shaft insert section tapering along the axis of rotation and away from the base body adjoins the respective base body.

34. The device according to claim 20, wherein, as seen in the conveying direction, upstream and/or downstream of the respective base body a shaft insert section tapering along the axis of rotation and away from the base body adjoins flush with the respective base body.

35. The device according to claim 22, wherein the at least one scraper blade extends parallel to the conveying direction.

36. The device according to claim 26, wherein the at least one limiting element is made of high-temperature steel.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The invention will now be explained in more detail by means of exemplary embodiments. The drawings are exemplary and are intended to illustrate the idea of the invention, but in no way to restrict it or even to reproduce it conclusively, wherein:

[0065] FIG. 1 shows a schematic sectional view of a first embodiment of the device according to the invention, wherein a longitudinal axis of a furnace of the device lies in the sectional plane.

[0066] FIG. 2 shows a schematic sectional view of the device from FIG. 1 from above, wherein the sectional plane is normal to the longitudinal axis.

[0067] FIG. 3 shows a schematic sectional view of a second embodiment of the device according to the invention, wherein the longitudinal axis of the furnace of the device is located in the sectional plane.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0068] FIG. 1 shows a first embodiment of a device according to the invention for producing an expanded granulated material 2 from mineral material in the form of grains of sand with an expanding agent. In the exemplary embodiments shown, the mineral material from which the expanded granulated material 2 is produced is perlite sand 1 containing bound water as an expanding agent.

[0069] The device comprises a furnace 3 having a substantially vertically disposed furnace shaft 4, which has an upper end 5 and a lower end 6, wherein between the two ends 5, 6 a conveying section 7 extends, which leads through several heating zones 8 arranged separately from one another in a conveying direction 10. The conveying direction 10 is substantially parallel to the direction of gravity and can in principle face in the direction of gravity or against the direction of gravity. In the exemplary embodiments shown, the conveying direction 10 faces against the direction of gravity, i.e. from the lower end 6 to the upper end 5.

[0070] The heating zones 8 each have at least one heating element 9 that can be controlled independently of one another in order to heat the perlite sand 1 to at least a critical temperature and to expand the perlite sand grains 1. In particular, the heating elements 9 may be electrical heating elements 9.

[0071] Furthermore, at least one feeding means (not shown) is provided, which is adapted to feed at least the unexpanded perlite sand 1 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 into the furnace shaft 4 in order to inflate the perlite sand 1, as seen in the conveying direction 10, in the last half, preferably in the last third, of the conveying section 7. In the exemplary embodiments shown, the feeding of the unexpanded perlite sand 1 takes place at the lower end 6 in the direction of the upper end 5, with the expanded granulated material 2 exiting at the upper end 5. A suction nozzle (not shown) cooperating with a fan can be provided, for example, as the feeding means for this, which nozzle is connected upstream of the furnace shaft 4 and is set up to suck the unexpanded perlite sand 1 together with a quantity of air at the lower end 6 of the furnace shaft 4 in the direction of the upper end 5 into the furnace shaft 4. The quantity of air thereby forms an air flow flowing from bottom to top, by means of which the perlite sand 1 is conveyed as a particle flow 25 from bottom to top along the conveying section 7 in order to be expanded in the upper half, preferably in the uppermost third, of the conveying section 7.

[0072] In an operating state of the device, caking 15 or agglomeration of perlite sand 1, some of which may already be expanded, occurs on an inner wall 13 of the furnace shaft 4.

[0073] In the illustrated exemplary embodiments of the device according to the invention, a rotatable shaft insert 11 is provided in each case, which is arranged in the furnace shaft 4, wherein a drive shaft 28 of the shaft insert 11 projects from the upper end 5 of the furnace shaft 4. The shaft insert 11 has at least one scraper blade 12, which forms at least one gap 14 with the inner wall 13 of the furnace shaft 4, having a gap width 18, and is set up to remove the caking 15 arranged in the gap 14 on the inner wall 13 in sections when the shaft insert 11 is rotated in the operating state of the device, if a thickness 16 of the caking 15, cf. FIG. 2, is greater than the respective gap width 18.

[0074] The gap width 18 is typically in the range of 2 mm to 5 mm.

[0075] This means that in the operating state of the device, when the perlite sand 1 is conveyed through the furnace shaft 4 and expanded therein, the gap 14 is covered with caking 15 within a short time. This caking 15 is then continuously removed by means of the at least one scraper blade 12 as the shaft insert 11 rotates. As a result of the removal, the thickness 16 of the caking 15 is limited and remains approximately constant, more precisely in a certain range around the gap width 18. This approximately constant, approximately uniform thickness 16 of the caking 15 guarantees an approximately constant radiation intensity which can be introduced into the furnace shaft 4 - through the caking 15 - by means of the heating elements 9. The resulting approximately or substantially constant energy input into the furnace shaft 4 in turn provides for a uniform expansion and ensures (substantially throughout the operation of the device) a substantially constant expansion result. The fact that the perlite sand grains 1 in the furnace shaft 4 move as a particle flow 25 along the conveying section 7 largely in well-defined movement ranges 29 between the at least one scraper blade 12, the remaining shaft insert 11 and the caking 15 also contributes to the uniform expanding or constant and defined expansion result. Accordingly, the residence time of the perlite sand grains 1 in the furnace shaft 4 - and thus the expansion process or the expansion result - can be determined or controlled quite precisely.

[0076] In the illustrated exemplary embodiments, the shaft insert 11 is rotatable in a direction of rotation 26 - and, optionally, also against the direction of rotation 26 - about an axis of rotation 20 that extends parallel to and coincides with a longitudinal axis 21 of the furnace shaft 4 and with a radial center 17 of the furnace shaft 4.

[0077] On the one hand, the drive shaft 28 serves to rotatably support the shaft insert 11 in the region of the upper end 5 of the furnace shaft 4. In the region of the lower end 6 of the furnace shaft 4, the shaft insert 11 is floatingly mounted, for example by means of a centering pin (not shown), which extends along the axis of rotation 20 and is movably supported parallel thereto.

[0078] On the other hand, drive means (not shown) may engage the drive shaft 28 to rotate the shaft insert 11. In the illustrated exemplary embodiments, the drive means are arranged to rotate the shaft insert 11 at a variable rotational speed, with the rotational speed preferably being in the range of 0.125 rpm to 3 rpm, particularly preferably in the range of 0.5 rpm to 2 rpm.

[0079] In the exemplary embodiments shown, the shaft insert 11 has a substantially rotationally cylindrical base body 22 from which the at least one scraper blade 12 projects with a directional portion parallel to a radial direction 24, wherein the radial direction 24 lies in a plane normal to the axis of rotation 20 of the shaft insert 11 and, starting from the axis of rotation 20, faces away therefrom. As viewed in the conveying direction 10, a respective tapering shaft insert section 23 is arranged upstream and downstream of the base body 22 and is flush with the base body 22. The taper is in each case along the axis of rotation 20 and faces away from the base body 22. The drive shaft 28 is connected to the rear shaft insert section 23 as seen in the conveying direction 10.

[0080] The base body 22 as well as the shaft insert sections 23 are substantially closed in shape, so that the perlite sand grains 1 cannot enter the shaft insert 11. Accordingly, the particle flow 25 can move practically exclusively in the movement ranges 29 along the conveying section 7, wherein the particle flow 25 is guided into and out of the movement ranges 29 in a flow-promoting manner by the tapering shape of the shaft insert sections 23. Preferably, the shaft insert 11 is hollow with an interior, wherein smaller pressure relief openings can be provided on the base body 22 and/or on the shaft insert sections 23 to allow air or gas, which is located in the interior of the shaft insert 11 and expands (or contracts) due to temperature, to pass out of (or into) the interior of the shaft insert 11 and thus effect pressure equalization.

[0081] In the exemplary embodiments shown, the shaft insert 11 is made of the same material as a limiting element 27 forming the inner wall 13, namely high-temperature steel. This ensures that the shaft insert 11, just like the inner wall 13, can easily withstand the temperatures that can occur in the operating state of the device in the furnace shaft 4 during expansion. Furthermore, the same choice of material also results in the same coefficients of thermal expansion, thus avoiding distortion due to different thermal expansion and ensuring a consistent shape or size of the gap 14. By forming the inner wall 13 by the limiting element 27, the geometry of the inner wall 13 or the (clear) cross-section of the furnace shaft 4 normal to the longitudinal axis 21 can be shaped in a well-defined manner, wherein said cross-section is substantially circular in the illustrated exemplary embodiments.

[0082] In the first exemplary embodiment shown in FIG. 1, four scraper blades 12 are provided which project uniformly from the base body 22 in a radial direction 24 and are arranged one behind the other as viewed in a circumferential direction 19 around the radial center 17, with an angular spacing between the scraper blades 12 being substantially constant. The scraper blades 12 thereby extend substantially rectilinearly and parallel to the conveying direction 10. Accordingly, there are four movement ranges 29 arranged symmetrically around the radial center 17 and extending rectilinearly parallel to the conveying direction 10.

[0083] The gap width 28 is correspondingly essentially constant as viewed in the conveying direction 10. The rotation of the shaft insert 11 creates an annular gap between the scraper blades 12 and the inner wall 13 bounding the circular clear cross-section of the furnace shaft 4, with the gap width 18 being essentially constant when viewed in the circumferential direction 19.

[0084] Accordingly, from a purely geometric point of view, without taking into account any turbulence that may occur in practice, perlite sand grains 1 in the particle flow 25 can move along straight lines parallel to the conveying direction 10 through the movement ranges 29. In FIG. 2, said symmetrical arrangement of the movement ranges 29 can be seen, wherein for reasons of clarity, the particle flow 25 is only indicated in two movement ranges 29.

[0085] The second exemplary embodiment, which is shown in FIG. 3, differs from the first exemplary embodiment only in the design of the scraper blades 12.

[0086] Unless explicitly stated otherwise, what has been said above about the first exemplary embodiment therefore also applies analogously to the second exemplary embodiment and will therefore not be repeated here.

[0087] As can be seen from FIG. 3, in the second exemplary embodiment, two scraper blades 12 are provided which project uniformly from the base body 22 in the radial direction 24 and each extend spirally about the axis of rotation 20 of the shaft insert 11. The two spiral or helical shapes of the scraper blades 12 are thereby nested within one another.

[0088] Accordingly, the resulting two movement ranges 29 also extend in a spiral or helical shape around the axis of rotation 20. Consequently, when the perlite sand grains 1 move through the movement ranges 29 in the particle flow 25, they must also follow the respective spiral or helical shape, which - from a purely geometrical point of view - results in a significantly longer path for the perlite sand grains 1 through the furnace shaft 4 compared to the first exemplary embodiment. The thermal treatment of the perlite sand grains 1 in the furnace shaft 4 can therefore be comparatively longer and thus even more precise in order to further optimize the expansion result.

[0089] It should also be noted that in the second exemplary embodiment shown, the gap width 28 is also essentially constant when viewed in the conveying direction 10. Likewise, the rotation of the shaft insert 11 creates an annular gap between the scraper blades 12 and the inner wall 13 delimiting the circular clear cross-section of the furnace shaft 4, with the gap width 18 being substantially constant when viewed in the circumferential direction 19.

[0090] Finally, it should be noted that in the second exemplary embodiment, the choice of the direction of rotation 26 offers a further possibility to influence the residence time of the perlite sand grains 1 in the furnace shaft 4 and thus the expansion result. If, in contrast to what is shown in FIG. 3, the direction of rotation 26 in interaction with the specific screw shape of the scraper blades 12 is such that the direction of movement of a corresponding screw along the axis of rotation 26 is opposite to the conveying direction 10, this can effectively reduce the path of the perlite sand grains 1 again. In fact, in purely theoretical terms, it would then be conceivable that with the “correct” rotational speed and the correct flow velocity, a linear movement of the perlite sand grains 1 in the particle flow 25 parallel to the conveying direction 10 could practically result. Conversely, in the second exemplary embodiment, the direction of rotation 26 shown in FIG. 3 leads to an extension of the residence time, since a spiral or helical particle flow 25 is forced.

[0091] A further aspect concerning the direction of rotation 26 is that, given the specific helical geometry of the scraper blades 12, this determines whether the caking 15 is primarily scraped off on a top side of the blade or on a bottom side of the blade, wherein in FIG. 3 the bottom side of the blade is in front of the top side of the blade 10 as viewed in the conveying direction 10. Preferably, as shown in FIG. 3, the direction of rotation 26 is selected in such a way that the underside of the blade assumes the stripping function, since the caking 15 then does not remain on the respective stripping blade 12 due to the force of gravity, but is transferred to the air flow and is discharged together with the expanded granulated material 2.

TABLE-US-00001 LIST OF REFERENCE SIGNS 1 Perlite sand 2 Expanded granulated material 3 Furnace 4 Furnace shaft 5 Upper end of the furnace shaft 6 Lower end of the furnace shaft 7 Conveying section 8 Heating zone 9 Heating element 10 Conveying direction 11 Shaft insert 12 Scraper blade 13 Inner wall of the furnace shaft 14 Gap 15 Caking 16 Caking thickness 17 Radial center of the furnace shaft 18 Gap width 19 Circumferential direction 20 Axis of rotation 21 Longitudinal axis of the furnace shaft 22 Base body 23 Tapering shaft insert section 24 Radial direction 25 Particle flow 26 Direction of rotation 27 Limiting element 28 Drive shaft 29 Movement range