Device for producing expanded granular material

Abstract

The invention relates to a device for producing an expanded granular material (2) from a sandy mineral material (1) by means of an expanding agent, comprising a furnace (3) with a furnace shaft (4) with an upper end (5) and a lower end (6), a conveying section (7) extending between the two ends and passing through a number of heating zones (8) arranged at a distance from one another in a conveying direction (10), at least one feeding means is also provided for filling the furnace shaft with at least unexpanded material at one of the two ends towards the other of the two ends. According to the invention, at least one rotatable shaft insert (11) is provided, arranged at least partially in the furnace shaft, with at least one scraper blade (12), which forms with the inner wall (13) of the furnace shaft at least one gap (14) with a gap width (18) and is designed to at least partially remove the consolidated material (15) on the inner wall during rotation of the at least one shaft insert in the operating state of the device, if the consolidated thickness (16) is greater than the respective gap width.

Description

Technical Field

[0001] The present invention relates to a device for producing an expanded granular material from a granular mineral material using an expanding agent, for example, for producing an expanded granular material from perlite sand or obsidian sand using bound water as an expanding agent. This device comprises a furnace having a substantially vertically standing furnace shaft with an upper end and a lower end, a conveying section extending between the two ends, and further, at least one supply means adapted to fill at least the unexpanded material into the furnace shaft in the direction of the other of the two ends of the furnace shaft at one of the two ends of the conveying section, preferably in the last half, preferably the last third, when viewed in the conveying direction, to expand the material. At least one rotatable shaft insert having at least one scraper blade is provided, which is at least partially disposed in the furnace shaft. The scraper blade forms at least one gap having a gap width between itself and the inner wall of the furnace shaft, and is designed to partially remove the solidified matter on the inner wall when the thickness of the solidified matter is greater than the respective gap width during the rotation of at least one shaft insert in the operating state of the device. At least one shaft insert is rotatable about at least one rotation axis extending parallel to the longitudinal axis of the furnace shaft, preferably at least one rotation axis coinciding with the longitudinal axis.

Background Art

[0002] According to WO2013 / 053635A1, a method and a device for expanding a granular mineral material containing an expanding agent such as bound water, in particular within a closed cell, are known. In this process, the material is fed from above into a furnace having a substantially vertical furnace shaft. By gravity, the material is transported in the transport direction along a transport section through the furnace shaft from its upper end to its lower end. The transport section passes through several heating zones which are arranged at a distance from each other in the transport direction and which are each provided with a separately controllable heating element for heating the material to the critical temperature and expanding the sand grains. The expansion process is isenthalpic and is accompanied by a corresponding detectable temperature drop. The expanded granular material is discharged from the lower end. The buoyancy force generated within the furnace shaft, which is caused in particular by the chimney effect of the furnace shaft and has different effects due to different densities before and after expansion, this type of expansion is typically suitable for raw sand having a particle size of 75 μm or more, in particular 100 μm or more. In the case of finer grains, the buoyancy force becomes too large for reliable expansion results. Also, when the particle size is fine, there is an increased risk of agglomeration or "caking" on the inner wall of the furnace shaft due to the lightweight and too-low-density particles continuing to float in the heating zone for a long time. In this case, the particles continue to absorb energy even after expansion and soften again without the isenthalpic shape change that causes cooling, so the risk of agglomeration or caking on the inner wall of the furnace shaft increases significantly. Figuratively speaking, this risk increases as the grain band narrows because there are no coarse and heavy enough particles to pull the fine particles against the buoyancy force.

[0003] In order to expand raw sand having a finer particle size, it is known from WO2016 / 191788A1 and WO2018 / 191763A1 to supply or inject a material together with a certain amount of air from the lower part to the upper part of a furnace shaft and convey it through the furnace shaft. When supplying in combination with blowing in very fine particles, it has been recognized that it is necessary to synchronize different flows in order to obtain a substantially uniform flow profile throughout the furnace shaft and to avoid turbulent flows that cause agglomeration / caking on the shaft wall. Such agglomeration / caking results in continuous "hypertrophy" of the shaft, which in turn hinders heat radiation and leads to insufficient expansion results.

[0004] Also, it should be noted that usually, even when expanding sand with a coarse particle size, it is impossible to completely avoid caking, which can have an adverse effect on the expansion result.

[0005] Each of US2625512A, US2521190A, and US2550877A describes a furnace having a vertical furnace shaft for expanding perlite sand. The perlite sand is supplied to the furnace shaft from above and heated for expansion at the upper part of the furnace shaft by an annular gas burner. A water cooling pipe is arranged in the furnace shaft and rotates around the vertical axis of the furnace shaft to scrape off the caked expanded perlite sand from the inner wall of the furnace shaft.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Accordingly, an object of the present invention is to provide a device for producing an expanded granular material that overcomes the above-mentioned drawbacks related to caking. In particular, it preferably enables uniform and constant expansion over as wide a range of granulation as possible.

Means for Solving the Problems

[0007] The core of the present invention is the consideration that since the consolidation ("agglomeration") of the granular mineral material on the inner wall of the furnace shaft is inevitable, it must be included in order to achieve a predetermined expansion process. For this purpose, in a device for producing expanded granular material from a granular mineral material using an expanding agent, for example, producing expanded granular material using bound water as an expanding agent from perlite sand or obsidian sand, the device comprises a furnace having a substantially vertically standing furnace shaft with an upper end and a lower end, a conveying section extending between the two ends, and further, at least one supply means adapted to supply at least the unexpanded material into the furnace shaft in the direction of the other of the two ends of the furnace shaft at one of the two ends of the furnace shaft, preferably in the last half, preferably the last third, of the conveying section when viewed in the conveying direction, at least one rotatable shaft insert having at least one scraper blade is provided, which is at least partially arranged in the furnace shaft, the scraper blade forms at least one gap with a gap width between it and the inner wall of the furnace shaft, and in the operating state of the device, during the rotation of at least one shaft insert, if the thickness of the solidified material is greater than the respective gap width, it is adapted to partially remove the solidified material on the inner wall, at least one shaft insert is rotatable about at least one rotation axis extending parallel to the longitudinal axis of the furnace shaft, at least one rotation axis preferably coincides with the longitudinal axis, according to the present invention, the conveying section passes through a plurality of heating zones arranged apart from each other in the conveying direction, each of the heating zones comprises at least one heating element that can be controlled independently of each other to heat the material to at least the critical temperature to expand the sand grains, and each of the at least one shaft inserts comprises a base body having a radially parallel direction portion where at least one scraper blade projects, the radial direction is in a plane perpendicular to the rotation axis of each shaft insert, and is directed away from the respective rotation axis starting therefrom, and each of the respective base bodies is defined to be substantially closed at least when viewed radially.

[0008] The conveying direction is substantially parallel to the vertical or plumb direction and may be from top to bottom or, conversely, from bottom to top. This means that at least one shaft insert can be provided both when the material is supplied from above and when the material is supplied from below. When supplied from above, the expanded material is at least partially conveyed along the conveying section by gravity, and a particle flow is formed in the furnace shaft. For example, in this case, a chute can be provided as a supply means for the expanded material. When supplied from below, the expanded material is usually supplied into the furnace shaft together with a certain amount of air and conveyed through the furnace shaft. In this case, the supply means may be, for example, a suction nozzle cooperating with a fan, which is connected upstream of the furnace shaft and is adapted to suck the unexpanded material together with a certain amount of air into the furnace shaft in the direction of the upper end at the lower end of the furnace shaft. The amount of air forms an air flow flowing from bottom to top, whereby the granular material is conveyed in the form of a particle flow passing through the furnace shaft from bottom to top along the conveying section so as to be expanded in the upper half of the conveying section, preferably in the uppermost one-third.

[0009] Each of the different heating zones needs to have at least one heating element, and since these heating elements need to be controllable independently, heating elements can be used to define the heating zones.

[0010] For the sake of completeness, note that, when viewed in the conveying direction, the last half is the second half, or the last one-third is the third one-third.

[0011] According to the present invention, the solidified matter is not regarded as disturbing the process, but its thickness is controlled by at least one shaft insert in order to bring a homogenizing effect to the expansion result. The shaft insert having at least one scraper blade forms a gap between the scraper blade and the inner wall of the furnace shaft. Typically, the gap width ranges from 2 mm to 5 mm.

[0012] In the operating state of the device, when the material is conveyed through the furnace shaft and expands within the furnace shaft, the gap is covered by the material solidified in a short period of time. This solidified material is then continuously removed by at least one scraper blade as at least one shaft insert rotates, and "removal" includes shearing, peeling, cutting, extrusion, or scraping off.

[0013] The thickness of the solidified material is limited by the removal and is maintained generally constant, precisely within a specific range near the gap width. This generally constant and generally uniform thickness of the solidified material ensures a generally constant radiation intensity that can be introduced into the furnace shaft through the solidified material by the heating element. As a result, a uniform expansion is brought about by inputting generally or substantially constant energy into the furnace shaft, and a substantially constant expansion result is ensured substantially throughout the operation of the device.

[0014] The fact that the removal is performed "at least partially" should be understood, on the one hand, such that it is not necessary for the removal to be performed simultaneously over the entire 360° angular range centered on the longitudinal axis in a specific plane perpendicular to the longitudinal axis of the furnace shaft. On the other hand, the term "partially" is actually used only when the entire thickness of the solidified material is not (locally) removed by a gap with a gap width greater than zero and a specific thickness of the solidified material is deliberately retained. This means that both the gap or gap width and the thickness are understood to be greater than zero.

[0015] In practice, due to manufacturing tolerances, it should be understood that the gap width may be within a specific gap width range or may vary slightly.

[0016] Therefore, in practice, the thickness of the solidified matter is also considered to be within the thickness range. Also, the actual thickness of the solidified matter at a specific point in a specific position within the furnace shaft is the result of a dynamic process, which means that on the one hand, new solidified matter is constantly added, and on the other hand, it is removed, so that the thickness is not constant at all positions at all times and changes within a specific range in terms of time and position. Therefore, an area where the thickness is greater than the gap width can temporarily occur until it is removed by at least one scraper blade.

[0017] The fact that the sand grains within the furnace shaft mainly move along the conveying section as a particle flow within a clearly defined movement range mainly between one or more scraper blades, other parts of the shaft insert, and the solidified matter also contributes to a uniform expansion or a certain defined expansion result. Therefore, the residence time of the sand grains within the furnace shaft, and the associated expansion process or expansion result, can be very precisely defined or controlled.

[0018] It is understood that the inner wall itself is maintained within a specific range with respect to its thickness without solidified matter. For example, in order to form the inner wall, a limiting element, especially in the form of a so-called steel liner, can be provided. In this context, although it is theoretically possible that the inner wall is not formed by the limiting element or the steel liner, but by one or more layers on the limiting element or the steel liner, this layer is not solidified matter with a controlled thickness. Therefore, the gap, together with its gap width, should be understood with respect to the specific inner wall without solidified matter.

[0019] The gap width and the thickness of the solidified matter are typically perpendicular to the longitudinal axis of the furnace shaft, which typically coincides with the longitudinal axis, and can be measured parallel to the radial direction facing outward from the radial center of the furnace shaft. Usually, this radial direction is perpendicular to the inner wall.

[0020] At least one shaft insert can be designed to be removable so as to be easily replaceable with different shaft inserts. The different shaft inserts can differ from each other, for example, by different scraper blades, especially with respect to the number and / or roughness and / or the resulting gap width and / or the resulting movement range of the abrasive grains.

[0021] At least one shaft insert is made of one or more materials that can withstand the temperature generated in the furnace shaft. The above materials may include, for example, metals, especially stainless steel or nickel-based alloys, or carbon fiber and ceramics, especially high-performance ceramics.

[0022] It should be noted that at least one shaft insert does not have to be completely arranged inside the furnace shaft and can partially protrude from the furnace shaft at the upper end and / or the lower end. Each part protruding from the furnace shaft can show advantages for the bearing and / or driving of each shaft insert.

[0023] However, it is also conceivable that at least one shaft insert is completely arranged inside the furnace shaft and stored only therein.

[0024] At least one shaft insert does not have to extend over the entire furnace shaft, or its entire length, or the entire conveying section.

[0025] As a rule, a single shaft insert can be provided. This can be composed of several parts or segments. Typically, in this case, the shaft insert can rotate around a rotation axis that coincides with the longitudinal axis of the furnace shaft. The same applies when several shaft inserts are provided and are arranged one behind the other when viewed in the conveying direction. In this case, for example, it is conceivable that different shaft inserts rotate at different speeds and / or form different gap widths. In these cases, in each case, the rotation of each shaft insert within the furnace shaft having a substantially circular cross-section (perpendicular to the longitudinal axis of the furnace shaft) effectively creates an annular gap between at least one scraper blade and the inner wall of the furnace shaft. Therefore, in the device according to the invention, it is defined that at least one shaft insert is rotatable about at least one rotation axis perpendicular to the longitudinal axis of the furnace shaft, preferably about at least one rotation axis that coincides with the longitudinal axis.

[0026] However, theoretically, in some examples of shaft inserts, several different rotation axes are also possible even when they are arranged at least partially one behind the other when viewed in the conveying direction.

[0027] In particular, it is also conceivable that several shaft inserts are provided that are arranged adjacent to each other and have different rotation axes when viewed in a cross-section perpendicular to the conveying direction or the longitudinal axis, and in each case, the rotation axes may extend parallel to the longitudinal axis of the furnace shaft.

[0028] Similarly to the above, in a preferred embodiment of the device according to the invention, it is defined that at least one shaft insert is rotatably mounted in the region of the upper end of the furnace shaft, preferably that at least one shaft insert is floatingly mounted in the region of the lower end of the furnace shaft.

[0029] The region at the upper end of the furnace shaft to which at least one shaft insert is rotatably attached can be arranged outside the furnace shaft. In addition to being a structurally simple and particularly stable mechanical bearing, this also enables a structurally simple (rotational) drive of the shaft insert.

[0030] In the operating state of the device, the floating bearing configuration ensures a particularly stable or constant defined gap over the entire length parallel to the conveying section at different rotational speeds of at least one shaft insert. Thereby, it is possible to realize a solidified material with a particularly accurately defined thickness, as a result, the uniformity of the process is particularly high, which has a good influence on the expansion result.

[0031] The region at the lower end of the furnace shaft to which at least one shaft insert is floatingly attached can be arranged outside the furnace shaft.

[0032] For example, for the floating bearing, a centering pin that can move along the rotation axis (''floatingly'') attached to the shaft insert can be provided. The centering pin extends along the rotation axis and is dimensioned such that a ''floating'' or movable bearing is ensured for all thermal expansions of the shaft insert, particularly at the length measured along the rotation axis.

[0033] In a preferred embodiment of the device according to the invention, it is determined that at least one shaft insert has several, preferably 8, particularly preferably 2 - 4 scraper blades. This means that the numbers shown can be regarded as the total number and / or the number of scraper blades per shaft insert (if several shaft inserts are to be provided). Multiple scraper blades are advantageous in terms of accuracy, whereby the expansion process can be adjusted. For example, multiple scraper blades can be used to provide different gaps along the conveying section in order to influence the expansion process.

[0034] The number of scraper blades for each shaft insert can also be variably designed, for example, in terms of the scraper blades being retractable / extendable or insertable / removable.

[0035] In particular, when several scraper blades are arranged one behind the other in the circumferential direction around the longitudinal axis or the radial center of the furnace shaft, a solidified material with a particularly uniform thickness can be achieved over the entire angular range around the radial center, thereby resulting in a particularly uniform expansion or expansion result. Thus, in a particularly preferred embodiment of the device according to the invention, it is defined that at least two of the scraper blades are arranged one behind the other in the circumferential direction around the radial center of the furnace shaft. It is understood that more than two scraper blades, in particular all scraper blades, may be arranged one behind the other in the circumferential direction.

[0036] Due to the above-described increased design possibilities with several scraper blades, in a particularly preferred embodiment of the device according to the invention, it is defined that at least two of the scraper blades form gaps with different gap widths between them and the inner wall. In this case, the gap width can vary when viewed in the conveying direction, i.e., gaps with different gap widths can be arranged at least partially one behind the other when viewed in the conveying direction. This can affect, for example, the residence time of the sand grains in zones of different temperatures.

[0037] Alternatively or additionally, the gap width may be different when viewed in the circumferential direction, i.e., gaps with different gap widths can be arranged at least partially one behind the other when viewed in the circumferential direction. By doing so, for example, the process of removing the solidified material can be optimized to set the desired thickness extremely precisely.

[0038] Depending on the temperature and the material to be expanded, the thickness of the solidified product can grow at different rates. Therefore, it may be necessary to accelerate or optionally decelerate the (partial) removal of the solidified product. In particular, the latter can also show advantages for setting the desired particle flow in the furnace shaft. Therefore, in a preferred embodiment of the device according to the invention, at least one drive means is provided for rotating at least one shaft insert at a variable rotational speed, the rotational speed preferably being in the range from 0.125 rpm ("revolutions per minute") to 3 rpm, more preferably in the range from 0.5 rpm to 2 rpm. For example, in practice, the rotational speed can be set or varied in the vicinity of 1 rpm.

[0039] Suitable drive means, which can be connected to at least one shaft insert via at least one drive shaft, for example, are known per se. For example, an electric motor is suitable as the drive means, and gears or a variable ratio or reduction can be provided to vary the rotational speed. It is also conceivable to use one or more electric motors whose rotational speed is varied by a frequency converter (or a plurality thereof) to vary the rotational speed of at least one shaft insert.

[0040] In the device according to the invention, in each case, at least one shaft insert has a substrate from which at least one scraper blade projects with a direction portion parallel to the radial direction, the radial direction being in a plane perpendicular to the rotational axis of each shaft insert, facing away from the respective rotational axis starting therefrom, and each substrate being substantially closed at least when viewed in the radial direction. According to this definition of the radial direction, there are an infinite number of radial directions in the above-mentioned plane perpendicular to the rotational axis of each shaft insert.

[0041] It is not excluded that other direction components are not zero such that at least one scraper blade projects "bent" from each substrate. However, preferably, the other direction components are zero.

[0042] The term "substantially closed" means a closure excluding, for example, a slight degree of opening that may inevitably exist to some extent due to the manufacturing process but can be ignored. The closure of the substrate, particularly in the radial direction, ensures that sand grains cannot escape from the moving area into the substrate. Therefore, the sand grains can be induced within the moving range at a predetermined distance from the inner wall or the solidified matter to ensure a defined energy input.

[0043] In a particularly preferred embodiment of the device according to the invention, each substrate is basically in the shape of a rotating cylinder. Preferably, a shaft insertion part that tapers in a direction away from the substrate along the rotation axis is adjacent to each substrate, particularly defined to be on the same plane as each substrate, when viewed in the conveying direction upstream and / or downstream of each substrate. However, in principle, other shaped substrates are also conceivable, in which case preferably in the shape of a rotating body, for example, a conical shape or a frustum of a cone shape.

[0044] The taper of the shaft insertion part(s) is in the direction away from each substrate, which is shown to be very favorable from the point of view of the flow. This means that the particle flow or sand grains are continuously guided in the direction of the substrate, and thus within the moving range, by the conical shape of each shaft insertion part, and then continuously guided in a direction away from the substrate again from the moving range.

[0045] In principle, various specific shapes regarding the shaft insertion part are conceivable. Preferably, the shaft insertion part is conical or frustum of a cone shaped.

[0046] The shaft insertion part(s) and the substrate represent different segments of the shaft insert (the "shaft insertion part").

[0047] The tapered shaft insertion part(s) (if plural) is / are also preferably at least basically closed when viewed in the radial direction. Thereby, sand or granular material is prevented from entering the shaft insert within the area of each shaft insertion part, and it is ensured that it can move only between the shaft insert and the solidified product (optionally the inner wall) through a furnace shaft having a direction part parallel to the conveying direction. In principle, there is no radial limitation for the shaft insert, but it can be defined that it is basically closed so that sand particles do not enter the shaft insert. Preferably, the shaft insert is designed as a hollow body having an internal space in order to reduce material and weight. Air or gas present inside the shaft insert and expanding (or contracting) due to temperature is enabled to pass from (or into) the inside of the shaft insert, and in order to bring about pressure equalization, small pressure relief openings can be provided in the shaft insert, particularly in the base body and / or the shaft insertion part(s).

[0048] To enhance the adjustability of the expansion process, in a particularly preferred embodiment of the device according to the invention, at least one scraper blade is defined to be extendable / retractable and / or rotatable on each base body so that the gap width can be adjusted. The extension to reduce the gap width or the contraction to increase the gap width can be performed with a direction component in the radial direction or with respect to the radial direction.

[0049] In any case, the rotation is preferably performed about a longitudinal axis or a rotation axis parallel to the respective rotation axis. Other arrangements of the respective rotation axes where the gap width changes due to the rotational movement of each scraper blade are of course conceivable.

[0050] To particularly simplify the design of at least one scraper blade, in a preferred embodiment of the device according to the invention, at least one scraper blade is defined to extend basically linearly, preferably parallel to the conveying direction.

[0051] In particular, each scraper blade may extend parallel to the longitudinal axis of the furnace shaft or the axis of rotation of each shaft insert.

[0052] In a preferred embodiment of the device according to the invention, in order to make the path through which sand or granular material has to pass particularly long and thereby enable the heat treatment of the granular material in the furnace shaft to be carried out particularly for a long time, at least one scraper blade is defined to extend at least partially spirally or helically about the axis of rotation of each shaft insert. The individual scraper blades do not have to extend around the entire circumference of the axis of rotation and may only cover an angular range substantially smaller than 360°.

[0053] According to the above, in the case of some shaft inserts, theoretically the spiral scraper blade may extend spirally at least partially about different axes of rotation.

[0054] It should be noted that in the case of some scraper blades, both straight - extending scraper blades and helically - extending scraper blades, i.e., some straight - extending scraper blades and / or some helically - extending scraper blades, may be provided. The movement area of the sand or granular material can be correspondingly designed in various ways.

[0055] It should be noted that, similar to what has been described above, the gap width may be made to vary circumferentially by an appropriate design of at least one spirally extending scraper blade. That is, in a particularly preferred embodiment of the device according to the present invention, it is defined that the gap width varies when viewed circumferentially about the radial center of the furnace shaft. In this case, the difference in the gap width of the gap formed by the spirally extending scraper blade and the inner wall is also brought about by the spiral or helical shape when viewed in the conveying direction. As described above, the radial center typically coincides with the longitudinal axis of the furnace shaft. This means that even when only a single spirally extending scraper blade is provided, the gap width can vary both when viewed circumferentially and when viewed in the conveying direction.

[0056] According to the above, in a preferred embodiment of the device according to the present invention, it is defined that the gap width of at least one gap varies when viewed in the conveying direction. This can be achieved with a scraper blade extending linearly or with a scraper blade extending at least partially spirally.

[0057] In particular, this allows for different expansion stages to be taken into account and for the residence time in various sections of the furnace shaft along the conveying direction to be affected. For example, a gap width that continuously increases or decreases when viewed in the conveying direction can be achieved.

[0058] In a preferred embodiment of the device according to the present invention, it is defined that the inner wall is preferably formed by at least one limiting element made of high-temperature steel, and that at least one shaft insert is made of the same material as the at least one limiting element. By selecting the above materials, the realization of the same performance requirements for the limiting element and the shaft insert is guaranteed. Also, by selecting the same material, the coefficient of thermal expansion becomes the same, thereby avoiding distortion due to different thermal expansions and ensuring a constant gap shape or gap size.

[0059] Preferably, when viewed radially, the furnace is composed of one or more other materials, especially heat insulating materials, on the back side of the limiting element.

[0060] The high-temperature steel is a well-known type of stainless steel.

[0061] On the one hand, the limiting element can ensure in a structurally simple way that the material supplied into the furnace shaft does not come into contact with the heating element arranged on the back side of the limiting element when viewed radially. On the other hand, at least one limiting element can very easily and as accurately as possible realize the desired, especially circular cross-sectional shape of the furnace shaft and can be adapted to different applications as required.

[0062] By a precise or appropriate selection of the material for the limiting element, it is possible to be used in all actual temperature ranges where the function of the limiting element is not impaired or damaged. When expanding perlite or obsidian, especially metal materials are considered. In this context, for other items that require particularly high firing temperatures, it is also conceivable to manufacture the limiting element from other suitable materials such as carbon fiber or (high-performance) ceramic instead of metal.

[0063] As described above, the shaft insert can be composed of several parts or segments. These can be assembled and disassembled, especially during the installation and removal of the shaft insert, simplifying each process. This also applies especially to the substrate. Therefore, in a particularly preferred embodiment of the device according to the invention, it is defined that the substrate is composed of a plurality of partial segments that are removably connected to each other. Thereby, it is possible to assemble and disassemble the substrate without difficulty during installation and removal. The removable connection of the partial segments can be realized in a method known per se, for example by screwing.

[0064] The present invention will be described in detail below using typical embodiments. The drawings are typical examples and are intended to illustrate the concept of the present invention, and are not intended to limit or reproduce the present invention deterministically.

Brief Description of the Drawings

[0065]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0066] FIG. 1 shows a first embodiment of a device according to the invention for producing expanded granular material 2 from granular mineral material using an expanding agent. In the illustrated typical embodiment, the mineral material from which the expanded granular material 2 is produced is perlite sand 1 containing bound water as the expanding agent.

[0067] The device comprises a furnace 3 having a furnace shaft 4 arranged substantially vertically with an upper end 5 and a lower end 6, and between the two ends 5, 6, a conveying section 7 extends through several heating zones 8 arranged spaced apart from each other in the conveying direction 10. The conveying direction 10 is substantially parallel to the direction of gravity and, in principle, may be directed towards or against the direction of gravity. In the illustrated typical embodiment, the conveying direction 10 is in a direction against the direction of gravity, i.e., from the lower end 6 towards the upper end 5.

[0068] Each of the heating zones 8 has at least one heating element 9 which can be controlled independently of each other to heat the perlite sand 1 to at least the critical temperature and expand the perlite sand grains 1. In particular, the heating element 9 may be an electric heating element 9.

[0069] Also, in order to expand the perlite sand 1 at least in the last half, preferably the last third, of the conveying section 7 as viewed in the conveying direction 10, at least one supply means (not shown) adapted to supply at least the unexpanded perlite sand 1 into the furnace shaft 4 in the direction of the other of the two ends 5, 6 of the furnace shaft 4 is provided at one of the two ends 5, 6 of the furnace shaft 4. In the illustrated typical embodiment, the supply of the unexpanded perlite sand 1 is performed in the direction of the upper end 5 at the lower end 6, and the expanded granular material 2 exits from the upper end 5. As a supply means for this, for example, a suction nozzle (not shown) cooperating with a fan may be provided, and this nozzle is connected upstream of the furnace shaft 4 and is configured to suck the unexpanded perlite sand 1 together with a certain amount of air into the furnace shaft 4 in the direction of the upper end 5 at the lower end 6 of the furnace shaft 4. Thereby, a certain amount of air forms an air flow flowing from the lower part to the upper part, and thereby the perlite sand 1 is conveyed as a particle flow from the lower part to the upper part along the conveying section 7 so as to be expanded in the upper half of the conveying section 7, preferably in the uppermost third.

[0070] In the operating state of the device, a solidified product 15 or lump of the perlite sand 1, which may already be in a partially expanded state, occurs on the inner wall 13 of the furnace shaft 4.

[0071] In the illustrated typical embodiment of the device according to the present invention, in any case, a rotatable shaft insert 11 disposed in the furnace shaft 4 is provided, and the 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 having a gap width 18 between the inner wall 13 of the furnace shaft 4, and when the shaft insert 11 rotates in the operating state of the device, as shown in FIG. 2, when the thickness 16 of the solidified product 15 is larger than the respective gap width 18, it is configured to partially remove the solidified product 15 disposed in the gap 14 of the inner wall 13.

[0072] The gap width is typically in the range of 2 mm to 5 mm.

[0073] This means that in the operating state of the device, when the perlite sand 1 is conveyed through the furnace shaft 4 and expands there, the gap 14 is covered by the solidified matter 15 in a short time. The solidified matter 15 is then continuously removed by at least one scraper blade 12 as the shaft insert 11 rotates. As a result of the removal, the thickness 16 of the solidified matter 15 is restricted and maintained approximately constant, more precisely within a specific range near the gap width 18. This approximately constant and approximately uniform thickness 16 of the solidified matter 15 ensures that an approximately constant radiation intensity can be introduced through the solidified matter 15 into the furnace shaft 4 by the heating element 9. The resulting approximately or substantially constant energy input into the furnace shaft 4 brings about a uniform expansion and guarantees a substantially constant expansion result (substantially throughout the operation of the device). The fact that the perlite sand grains 1 in the furnace shaft 4 move as a particle flow along the conveying section 7 mainly within a clearly defined movement range 29 between at least one scraper blade 12, other shaft inserts 11, and the solidified matter 15 also contributes to a uniform expansion or a constant and defined expansion result. Therefore, the residence time of the perlite sand grains 1 in the furnace shaft 4 and the associated expansion process or expansion result can be determined or controlled extremely precisely.

[0074] In the illustrated exemplary embodiment, the shaft insert 11 is rotatable about a rotation axis 20 that extends parallel to the longitudinal axis 21 of the furnace shaft 4 and coincides with the radial center 17 of the furnace shaft 4, and optionally, it is also rotatable in the direction opposite to the rotation direction 26.

[0075] 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 a centering pin (not shown) that extends along the rotation axis 20 and is movably supported parallel to the rotation axis 20.

[0076] On the one hand, the driving means (not shown) may engage the drive shaft 28 to rotate the shaft insert 11. In the illustrated exemplary embodiment, the driving means is arranged to rotate the shaft insert 11 at a variable rotatable speed, and the rotational speed is preferably in the range of 0.125 rpm to 3 rpm, particularly preferably in the range of 0.5 rpm to 2 rpm.

[0077] In the illustrated exemplary embodiment, the shaft insert 11 has a substantially rotationally cylindrical base body, from which at least one scraper blade 12 projects having a direction portion parallel to the radial direction 24, and the radial direction 24 is in a plane perpendicular to the rotation axis 20 of the shaft insert 11 and is directed away from the rotation axis 20. When viewed in the conveying direction 10, each tapered shaft insertion portion 23 is disposed upstream and downstream of the base body 22 and is in the same plane as the base body 22. In either case, the tapered portion is directed away from the base body 22 along the rotation axis 20. The drive shaft 28 is connected to the shaft insertion portion 23 on the rear side when viewed in the conveying direction 10.

[0078] The base body 22 and the shaft insertion portion 23 are in a substantially closed shape so that the pearlite sand grains 1 cannot enter the shaft insert 11. Accordingly, the particle flow 25 can move exclusively within the movement range 29 along the conveying section 7, and the particle flow 25 is guided to the inside and outside of the movement range 29 so as to promote the flow by the tapered shape of the shaft insertion portion 23. Preferably, the shaft insert 11 has a hollow interior, and the base body 22 and / or the shaft insertion portion 23 may be provided with smaller pressure relief openings, and air or gas existing inside the shaft insert 11 and expanding (or contracting) due to temperature can pass from (or into) the inside of the shaft insert 11 to enable pressure equalization.

[0079] In the illustrated exemplary embodiment, the shaft insert 11 is made of the same material as the restricting element 27 that forms the inner wall 13, namely high-temperature steel. This ensures that the shaft insert 11, like the inner wall 13, can easily withstand the temperatures that can occur in the furnace shaft 4 during expansion in the operating state of the device. Also, the selection of the same material results in the same coefficient of thermal expansion, avoiding strains due to different thermal expansions and ensuring a gap 14 of a constant shape or size. By forming the inner wall 13 with the restricting element 27, the inner wall 13 of the furnace shaft 4 perpendicular to the longitudinal axis 21 or the (explicit) cross-sectional geometry can be formed in a clearly defined manner, and the cross-section is substantially circular in the illustrated exemplary embodiment.

[0080] In the first exemplary embodiment shown in FIG. 1, four scraper blades 12 are provided that project uniformly radially 24 from the base 22 and are arranged one behind the other in the circumferential direction 19 about the radial center 17, and the angular spacing between the scraper blades 12 is substantially constant. Thereby, the scraper blades 12 extend substantially linearly and parallel to the conveying direction 10. Thus, there are four movement ranges 29 that are symmetrically arranged about the radial center 17 and extend linearly parallel to the conveying direction 10.

[0081] Accordingly, the gap width 28 is basically constant when viewed in the conveying direction 10. By the rotation of the shaft insert 11, an annular gap is created between the scraper blades 12 and the inner wall 13 that defines the clear circular cross-section of the furnace shaft 4, and the gap width 18 is basically constant when viewed in the circumferential direction 19.

[0082] Thus, without considering the turbulent flow that can occur in the particles, from a purely geometric point of view, the pearlite sand grains 1 in the particle flow 25 can move along a straight line parallel to the conveying direction 10 through the movement range 29. In FIG. 2, the above-described symmetric arrangement of the movement ranges 29 is shown, and for clarity, the particle flow 25 is shown only within two movement ranges 29.

[0083] The second exemplary embodiment shown in FIG. 3 differs only in the design of the scraper blade 12 from the first exemplary embodiment.

[0084] Therefore, unless otherwise specified, what has been described above with respect to the first exemplary embodiment is similarly applicable to the second exemplary embodiment, and thus will not be repeated here.

[0085] As can be seen from FIG. 3, in the second exemplary embodiment, two scraper blades 12 are provided that project uniformly in the radial direction 24 from the base 22 and each extend spirally about the axis of rotation 20 of the shaft insert 11. As a result, the two spiral or helical scraper blades 12 are nested within each other.

[0086] Therefore, the resulting two movement ranges 29 also extend spirally or helically about the axis of rotation 20. As a result, when the perlite grit 1 moves through the movement range 29 within the particle stream 25, it must follow each spiral or helical shape, which, purely from a geometric point of view, makes the path of the perlite grit 1 through the furnace shaft 4 significantly longer compared to the first exemplary embodiment. Therefore, the heat treatment of the perlite sand 1 within the furnace shaft 4 is relatively long and can be made even more precise in order to further optimize the expansion results.

[0087] Also, it should be noted that in the illustrated second exemplary embodiment, the gap width 28 is also basically constant when viewed in the conveying direction 10. Similarly, the rotation of the shaft insert 11 creates an annular gap between the scraper blade 12 and the inner wall 13 that defines the clear circular cross-section of the furnace shaft 4, and the gap width 18 is basically constant when viewed in the circumferential direction 19.

[0088] Finally, as a point to note, in the second exemplary embodiment, the selection of the rotation direction 26 provides the potential to further affect the residence time of the perlite sand grains 1 in the furnace shaft 4 and the associated expansion results. In contrast to what is shown in FIG. 3, the rotation direction 26 that interacts with the specific screw shape of the scraper blade 12 is such that the direction of movement of the corresponding screw along the rotation axis 26 is opposite to the conveying direction 10, whereby the path of the perlite sand grains 1 can be effectively reduced again. In fact, from a purely theoretical point of view, it is conceivable that with an "appropriate" rotational speed and appropriate flow rate, a linear movement parallel to the conveying direction 10 of the perlite sand grains 1 in the particle flow 25 can actually occur. Conversely, in the second exemplary embodiment, the rotation direction 26 shown in FIG. 3 results in an extension of the residence time by forcing a spiral or swirling particle flow 25.

[0089] A further aspect regarding the rotation direction 26 is determined by considering the specific spiral shape of the scraper blade 12 as to whether the solidified matter 15 is mainly scraped off on the upper side or the lower side of the blade. In FIG. 3, when viewed in the conveying direction 10, the lower side of the blade is in front of the upper side of the blade 10. Preferably, as shown in FIG. 3, the rotation direction 26 is selected such that the upper side of the blade assumes the peeling function, for the reason that the solidified matter 15 does not remain on the respective peeling blades 12 due to gravity, but moves into the air flow and is discharged together with the expanded granular material 2.

Explanation of Reference Numerals

[0090] 1 Perlite sand 2 Expanded granular 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 Solidified Matter 16 Thickness of Solidified Matter 17 Radial Center of Furnace Shaft 18 Gap Width 19 Circumferential Direction 20 Rotation Axis 21 Longitudinal Axis of Furnace Shaft 22 Substrate 23 Tapered Shaft Insertion Part 24 Radial Direction 25 Particle Flow 26 Rotation Direction 27 Limiting Element 28 Driving Shaft 29 Movement Range

Claims

Claim 1 A device for producing an expanded granular material (2) from a granular mineral material (1) using an expanding agent, for example for producing an expanded granular material (2) from perlite sand (1) or obsidian sand using bound water as the expanding agent, comprising a furnace (3) having a substantially vertically standing furnace shaft (4) with an upper end (5) and a lower end (6), a conveying section (7) extending between the two ends (5, 6), and further, at least one supply means adapted to fill at least the unexpanded material (1) into the furnace shaft (4) in a direction from one of the two ends (5, 6) of the furnace shaft (4) to the other of the two ends (6, 5) of the furnace shaft (4) in order to expand the material (1) in the last half, preferably the last third, of the conveying section (7) as seen in the conveying direction (10), at least one rotatable shaft insert (11) having at least one scraper blade (12) disposed at least partially within the furnace shaft (4), the scraper blade (12) forming at least one gap (14) having a gap width (18) between the scraper blade (12) and the inner wall (13) of the furnace shaft (4), and designed to at least partially remove the solidified matter (15) on the inner wall (13) when the thickness (16) of the solidified matter (15) is greater than the respective gap width (18) during rotation of the at least one shaft insert (11) in the operating state of the device, the at least one shaft insert (11) being rotatable about at least one rotation axis (20) extending parallel to the longitudinal axis (21) of the furnace shaft (4), preferably the at least one rotation axis (20) coinciding with the longitudinal axis (21). The conveying unit (7) passes through a plurality of heating zones (8) arranged at a distance from each other in the conveying direction (10), and each of the heating zones (8) is provided with at least one heating element (9) that can be independently controlled from each other to heat the material (1) and expand the sand grains (1). Each of the at least one shaft insert (11) is provided with a base body (22) on which the at least one scraper blade (12) projects with a direction portion parallel to the radial direction (24). The radial direction (24) is in a plane perpendicular to the rotation axis (20) of each of the shaft inserts (11), and is directed away from the rotation axis (20) of each of the shaft inserts (11). Each of the base bodies (22) is substantially closed at least when viewed in the radial direction (24). Device characterized by the above.

2. The at least one shaft insert (11) is rotatably attached in the region of the upper end (5) of the furnace shaft (4), and preferably, the at least one shaft insert (11) is floatingly attached in the region of the lower end (6) of the furnace shaft. The device according to claim 1, characterized in that it is attached.

3. The at least one shaft insert (11) has a plurality, preferably a maximum of 8, particularly preferably 2 to 4 scraper blades (12). The device according to any one of claims 1 to 2, characterized in that it has.

4. At least two of the scraper blades (12) are arranged one behind the other when viewed in the circumferential direction (19) centered on the radial center (17) of the furnace shaft (4). The device according to claim 3, characterized in that it is arranged.

5. At least two of the scraper blades (12) form a gap (14) having different gap widths (18) with the inner wall (13). The device according to any one of claims 3 to 4, characterized in that it forms.

6. At least one driving means is provided for rotating the at least one shaft insert (11) at a variable rotational speed, and the at least one driving means preferably sets the rotational speed in the range of 0.125 rpm to 3 rpm, particularly preferably in the range of 0.5 rpm to 2 rpm. The device according to any one of claims 1 to 5, characterized in that it is adapted to do so.

7. Each of the substrates (22) is basically rotationally cylindrical, and preferably, a shaft insertion portion (23) that tapers in a direction away from the substrate (22) along the rotation axis (20) when viewed in the transport direction (10) upstream and / or downstream of each of the substrates (22) is adjacent to each of the substrates (22), particularly on the same plane as each of the substrates (22). The device according to any one of claims 1 to 6.

8. The at least one scraper blade (12) is arranged on each of the substrates (22) so as to be extendable / contractible so as to be able to adjust the gap width (18) and / or rotatable. The device according to any one of claims 1 to 7.

9. The at least one scraper blade (12) preferably extends substantially linearly, preferably parallel to the transport direction (10). The device according to any one of claims 1 to 8.

10. The at least one scraper blade (12) extends at least partially spirally or helically around the rotation axis (20) of each of the shaft inserts (11). The device according to any one of claims 1 to 9.

11. The gap width (18) is different when viewed in the circumferential direction around the radial center (17) of the furnace shaft (4). The device according to claim 10.

12. The gap width (18) of the at least one gap (14) is different when viewed in the transport direction (10). The device according to any one of claims 1 to 11.

13. The inner wall (13) is preferably formed by at least one limiting element (27) made of high-temperature steel, and the at least one shaft insert (11) is made of the same material as the at least one limiting element (27). The device according to any one of claims 1 to 12.

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