METHOD AND DEVICE FOR PRODUCING AN EXPANDED GRANULATE

Abstract

A method for producing an expanded granulate made of a sand grain-shaped mineral material uses a propellant. The material is transported along a transport path through multiple heating zones in a furnace shaft, heated to a critical temperature at which the surfaces of the sand grains plasticize, and the sand grains are expanded based on the propellant. The material is fed from the bottom together with an amount of air; the material is transported from the bottom to the top along the transport path by the air quantity which flows from the bottom to the top in the furnace shaft and the sand grains are expanded in the upper half of the transport path. The material is heated such that the material immediately prior to entering into the furnace shaft is at a material entry temperature lower than the critical temperature and higher than the ambient temperature.

Claims

1: A method for producing an expanded granulate (2) from sand grain-shaped mineral material (1) having an expanding agent, for example for producing an expanded granulate from perlite sand (1) or obsidian sand; wherein the material (1) is fed into a furnace (3); wherein the material (1) is conveyed in a substantially vertically disposed furnace shaft (4) of the furnace (3) along a conveying path (5) through a plurality of heating zones (6) arranged vertically separated from one another, wherein each heating zone (6) can be heated with at least one independently controllable heating element (7); wherein the material (1) is thereby heated to a critical temperature at which the surfaces of the sand grains (1) become plastic and the sand grains (1) are expanded due to the expanding agent; wherein the expanded material (2) is discharged from the furnace (3), wherein furthermore the material (1) is fed together with a quantity of air from below, wherein the material (1) is conveyed from bottom to top along the conveying path (5) by means of the quantity of air flowing from bottom to top in the furnace shaft (4) and forming an air flow, and wherein the expansion of the sand grains (1) takes place in the upper half of the conveying path (5), wherein the material (1) is heated so that the material (1), immediately before its entry into the furnace shaft (4), has a material entry temperature (T3) which is lower than the critical temperature and higher than an ambient temperature (RT).

2: The method according to claim 1, wherein the quantity of air is heated to a second elevated temperature (T2) which is lower than the critical temperature and higher than the ambient temperature (RT).

3. (canceled)

4. (canceled)

5. (canceled)

6: The method according to claim 2, wherein at least the quantity of air heated to the second elevated temperature (T2) is provided as means for heating the material (1) to the material entry temperature (T3).

7. (canceled)

8. (canceled)

9. (canceled)

10. (canceled)

11. (canceled)

12. (canceled)

13: The method according to claim 1, wherein, upon detection of a first reduction in the temperature of the material (1) between two successive positions (10) along the conveying path (5), the heating elements (7) along the remaining conveying path (5) are regulated as a function of the critical temperature in order to prevent or selectively enable an increase in the material temperature along the remaining conveying path (5) to or above the critical temperature.

14: The method according to claim 1, wherein, after discharge, the size and/or density of the expanded sand grains (2) is determined, preferably continuously.

15: The method according to claim 14, wherein, in order to regulate the density of the expanded sand grains (2), the power of the at least one heating element (7) of a last heating zone (11) is controlled.

16: The method according to claim 13, wherein, in order to regulate a position of the detected first reduction in the temperature of the material (1) apart from the power of the at least one heating element (7) of a last heating zone (11), the powers of the heating elements (7) of all heating zones (6) are controlled.

17. (canceled)

18. (canceled)

19. (canceled)

20: The method according to claim 1, wherein the material entry temperature (T3) is at least 30% of the critical temperature.

21: The method according to claim 1, wherein the material entry temperature (T3) is at least 240 C.

22: The method according to claim 1, wherein additionally supply air (34) is injected and/or aspirated into the furnace shaft (4) from below in order to support the conveying of the material (1) along the conveying path (5), wherein the supply air (34) is preheated to a further elevated temperature (T4) before it enters the furnace shaft (4).

23. (canceled)

24: A device for producing an expanded granulate (2) from sand grain-shaped mineral material (1) having an expanding agent, for example for producing an expanded granulate from perlite (1) or obsidian sand, the device comprising a furnace (3) with a substantially vertically disposed furnace shaft (4), which has an upper end (12) and a lower end (13), wherein a conveying path (5) extends between the two ends (12, 13) through a plurality of heating zones (6) arranged vertically separated from one another, wherein the heating zones (6) each have at least one heating element (7) which can be controlled independently of one another in order to heat the material (1) to a critical temperature and to expand the sand grains (1), wherein furthermore at least one feed means (14) is also provided in order to expand the non-expanded material (1) together with a quantity of air at the lower end (13) of the furnace shaft (4) in the direction of the upper end (12) of the furnace shaft (4) into the furnace shaft (4) in such a way that the quantity of air forms an air flow flowing from bottom to top, by means of which the material (1) is conveyed from bottom to top along the conveying path (5) in order to be expanded in the upper half of the conveying path (5), wherein at least one means, upstream of the furnace shaft (4), for heating the material (1) is provided in order to ensure that the material (1), when it enters the furnace shaft (4), has a material entry temperature (T3) which is lower than the critical temperature and higher than an ambient temperature (RT).

25: The device according to claim 24, wherein at least one means is provided upstream of the furnace shaft (4) for heating the air quantity to a second elevated temperature (T2) which is lower than the critical temperature and higher than the ambient temperature (RT).

26. (canceled)

27. (canceled)

28. (canceled)

29: The device according to claim 25, wherein at least the quantity of air heated to the second elevated temperature (T2) is provided as means for heating the material (1) to the material entry temperature (T3).

30. (canceled)

31. (canceled)

32. (canceled)

33. (canceled)

34. (canceled)

35: The device according to claim 24, wherein material temperature measuring means (23, 24) are provided for directly and/or indirectly measuring the temperature and/or the temperature change of the material (1) along the conveying path (5) and a regulating and control unit (16) connected to the material temperature measuring means (23, 24) and to the heating elements (7) of the heating zones (6) in order to detect a first reduction of the temperature of the material (1) between two successive positions (10) along the conveying path (5), and wherein the heating elements (7) can be regulated by the regulating and control unit (16) as a function of the critical temperature in order to prevent an increase in the material temperature along the remaining conveying path (5) to or above the critical temperature or to make it possible in a targeted manner.

36: The device according to claim 24, wherein means (18, 19) are provided for the determination of the size and/or the density of the expanded sand grains (2).

37: The device according to claim 36, wherein a regulating and control unit (16) is provided which is designed in such a way that, in order to regulate the density of the expanded sand grains (2), the power of the at least one heating element (7) of a last heating zone (11) is controlled.

38. (canceled)

39: (canceled)

40. (canceled)

41. (canceled)

42: The device according to claim 24, wherein the material entry temperature (T3) is at least 30% of the critical temperature.

43: The device according to claim 24, wherein the material entry temperature (T3) is at least 240 C.

44: The device according to claim 24, wherein at least one means (35, 17) is provided in order to inject and/or aspirate supply air (34) from below into the furnace shaft (4) in order to support the conveying of the material (1) along the conveying path (5), and wherein at least one means (36) is provided for preheating the supply air (34) to a further elevated temperature (T4) which is connected upstream of the furnace shaft (4).

45. (canceled)

Description

SHORT DESCRIPTION OF THE FIGURES

[0059] The invention is now explained in more detail using embodiment examples.

[0060] The drawings are exemplary and are intended to illustrate the idea of invention, but in no way to restrict it or even render it conclusively, wherein:

[0061] FIG. 1 shows a flow diagram of a first embodiment of a device according to the invention for performing a first embodiment of the method according to the invention, wherein material to be expanded is heated by means of heated compressed air before it enters a furnace shaft from below, wherein the compressed air forms a quantity of air in which the material is dispersed before it enters the furnace shaft;

[0062] FIG. 2 shows a flow diagram of a second embodiment of the device according to the invention for carrying out a second embodiment of the method according to the invention, wherein the material to be expanded is heated by means of a heated storage container before it is dispersed and subsequently enters the furnace shaft;

[0063] FIG. 3 shows a flow diagram of a third embodiment of the device according to the invention for carrying out a third embodiment of the method according to the invention, wherein the material to be expanded is heated both by means of the heated compressed air and by means of the heated storage container before it enters the furnace shaft;

[0064] FIG. 4 shows a flow diagram of a fourth embodiment of the device according to the invention for carrying out a fourth embodiment of the method according to the invention, wherein, in contrast to the third embodiment according to FIG. 3, additionally preheated supply air is blown into the furnace shaft from below.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] FIG. 1 shows a schematic representation of a first embodiment of a device according to the invention with which a first embodiment of a method according to the invention for the production of expanded microspheres 2 or expanded granules 2 can be carried out. The starting material for the expanded microspheres 2 is a sand-like or powdery, in particular mineral, material with an expanding agent. In the embodiment example shown, perlite sand 1 is assumed to be the material, wherein water is bound in perlite and acts as an expanding agent in the expansion process. The diameter of the perlite sand grains 1 is typically smaller than 100 m.

[0066] To carry out the expansion process, the device according to the invention comprises a furnace 3 with a furnace shaft 4, which extends essentially verticallyi.e. a slight deviation from the vertical is possible, e.g. due to manufacturing fault tolerancesfrom a lower end 13 to an upper end 12 from bottom to top. A conveying path 5 extends between the ends 13, 12, which is indicated by a dotted line in FIG. 1. This line also marks a radial center of the furnace shaft 4.

[0067] In furnace shaft 4, several heating zones 6 are provided, arranged one above the other or one after the other in a conveying direction 19, through which the conveying path 5 passes. This means that heating zones 6 define furnace shaft 4 or furnace shaft 4 is the section of furnace 3 in which heating zones 6 are arranged.

[0068] Each heating zone 6 is equipped with at least one independently controllable heating element 7, which may in particular be an electric heating element 7. Using the heating elements 7, perlite sand 1 can be brought to a critical temperature in furnace 3 or furnace shaft 4 at which the surfaces of the perlite sand grains 1 become plastic and the perlite sand grains 1 are expanded due to the expanding agentin this case water vapor.

[0069] The perlite sand 1 is fed together with a quantity of air at the lower end 13 into the furnace 3 or furnace shaft 4 and blown in the direction of the upper end 12, i.e. from bottom to top. A solid/air nozzle 14 is provided for this injection. The perlite sand 1, which is stored in a storage container 8, is fed to said nozzle via a dosing screw 20. On the other hand, the solid/air nozzle 14 is supplied with compressed air 15 from a compressed air tank 21.

[0070] The solid/air nozzle 14 ensures that an air flow is formed from bottom to top, by means of which the perlite sand 1 is conveyed from bottom to top along the conveying path 5 in conveying direction 19. By conveying from bottom to top, it is generally prevented that the buoyancy forces that arise cause the residence time of perlite sand 1 or expanded granulate 2 in the furnace shaft 4 to become uncontrollably long. At the same time, it can be ensured that the expansion only takes place in the upper half, preferably in the upper third of the furnace shaft 4 or the conveying path 5, wherein a caking of the perlite sand 1 or the expanded granulate 2 on an inner wall of the furnace shaft 4 can be avoided as well as a sticking together of individual grains of the perlite sand 1 or the expanded granulate 2 among each other.

[0071] Perlite sand 1 typically has a temperature of approx. 780 C. immediately before its expansion. Since the expansion process, in which the perlite sand grains 1 expand, is an isenthalpic process, the perlite sand 1 cools down during expansion, typically to approx. 590 C., which is also referred to as a drop in temperature. Depending on the material, the temperature drop is at least 20 C., preferably at least 100 C. Detection of the temperature drop or detection of the position at which the temperature drop occurs in the furnace shaft 4 makes it possible to regulate the heating elements 7 in a targeted manner along the remaining conveying path 5, in particular to influence the surface structure or surface properties of the expanded granulate 2.

[0072] Accordingly, a large number of positions 10 are provided along conveying path 5 for temperature measurement in order to determine the position of the drop in temperature or the position of an initial reduction in the temperature of the material due to isenthalpic expansion. In the embodiment examples shown, temperature sensors 23 are provided for temperature measurement, which are connected to a regulating and control unit 16 (indicated by the dashed lines) and whose data are evaluated by the regulating and control unit 16.

[0073] However, it is also conceivable not to carry out an absolute temperature measurement but to determine the power consumption of the heating elements 7 or to determine how this power consumption changes along the conveying path 5. The corresponding power measurements can be carried out by means of current or power measuring instruments 24, which are provided for the heating elements 7 of the heating zones 6 in the illustrated embodiments. The current and power meters 24 are connected to the regulating and control unit 16 (indicated by the dashed lines), which can evaluate the data of the current and power meters 24, respectively.

[0074] Immediately after the expansion process and the resulting drop in temperature, the temperature difference between the expanded granulate 2 and the heating elements 7 is significantly greater than between the perlite sand 1 and the heating elements 7 immediately before the expansion process. The heat flow also increases accordingly. This means that the change in the heat flow or power consumption of the heating elements 7 from one heating zone 6 to the next is an increase, whereas the change in the power consumption along the conveying path 5 is a decrease due to the successive heating of perlite sand 1 before the expansion process.

[0075] The heating elements 7 are also connected to the regulating and control unit 16 (indicated by the dashed lines) for regulation, in particular for regulation along the conveying path 5 remaining after the temperature drop, so that an increase in the material temperature along the remaining conveying path 5 to or above the critical temperature can be specifically prevented or made possible.

[0076] The thus produced expanded microspheres 2 typically have a diameter of less than or equal to 150 m. In order to actually obtain individual expanded microspheres 2 in the end product and not too large particles in the form of agglomerates of expanded microspheres 2, it must be prevented that the perlite sand 1 in the furnace shaft 4 forms agglomerates which are then expanded to corresponding agglomerates of expanded microspheres 2. Agglomeration of perlite sand 1 is favored by moisture. Therefore, perlite sand 1 is typically processed before it reaches the storage container 8, wherein the processing includes a drying process. In addition, an agitator may be provided in the storage container 8 to prevent bridging between the perlite sand grains 1. Since, however, even in the dry state, it is hardly possible to convey the fine dust perlite sand 1 without forming agglomerates, the perlite sand 1 is dispersed in the air quantity with which it is fed into the furnace shaft 4 by means of the solid/air nozzle 14.

[0077] After the expansion process, the expanded granulate 2 is discharged together with the air heated in the furnace shaft 4 at the upper end 12 of the furnace shaft 4. This means that the expanded microspheres 2 are present in a gas-material stream 33.

[0078] Cooling air 27 is added to the gas-material flow 33 after it has left the furnace shaft 4. This cools the expanded granulate 2, preferably to a processing temperature of less than or equal to 100 C., which facilitates further handling of the expanded granulate 2, especially during further processing.

[0079] In order to be able to achieve an improved expansion result, in particular with increased uniformity, it is provided in accordance with the invention that the perlite sand 1 is heated before it enters the furnace shaft 4, so that the perlite sand 1 immediately before it enters the furnace shaft 4 has a material entry temperature T3 which is lower than the critical temperature and higher than an ambient temperature RT. As can be seen from the illustrations in FIG. 1 to FIG. 4, the ambient temperature RT is measured in the illustrated embodiments in the immediate vicinity of the area where the perlite sand 1 enters the furnace shaft 4.

[0080] Preferably, the material temperature T3 is at least 30%, especially preferred at least 90%, of the critical temperature. In particular, the material entry temperature T3 can be at least 240 C., preferably at least 720 C.

[0081] The amount of heat transferred from the perlite sand 1 to the quantity of air and thus the time of expansion can be regulated very sensitivelyeven within a heating zone 7by the amount of the heating. An increase in the material entry temperature T3 causes an earlier onset of expansion and usually also leads to lighter expanded granulate 2. A reduction in the material entry temperature T3 leads to opposite effects. A further advantage is that the reduced heat emission of perlite sand 1 to the quantity of air in furnace shaft 4 results in a more homogeneous temperature distribution in the perlite sand 1 to be expanded and thus a more evenly expanded granulate 2.

[0082] In the embodiment example of FIG. 1, compressed air 15 heated to the material entry temperature T3 is provided as at least one means provided upstream of the furnace shaft 4 for heating the perlite sand 1, which forms the air quantity heated to a second elevated temperature T2. To provide the air quantity heated to the second elevated temperature T2, a heating 22 of the compressed air tank 21 is provided. The heating 22 can be controlled by means of a controllable valve 32, which can be controlled by the regulating and control unit 16. The second elevated temperature T2 of the heated air quantity is monitored by a temperature sensor 23, which is also connected to the regulating and control unit 16 (indicated by the dashed line), so that the regulating and control unit 16 can regulate the heating 22 by means of the controllable valve 32 in such a way that the desired second elevated temperature T2 is reached. In the illustrated embodiment, the temperature sensor 23 measures the second elevated temperature T2 of the quantity of air directly in front of the solid/air nozzle 14, i.e. between the solid/air nozzle 14 and the compressed air tank 21. The quantity of air heated in this way heats the perlite sand 1 during dispersion to the material entry temperature T3, which will typically be lower than the second elevated temperature T2 in the embodiment example of FIG. 1.

[0083] In the second embodiment example according to FIG. 2 no compressed air tank 21and thus also no heating 22 of the compressed air tank 21is provided, but the compressed air 15 forming the quantity of air is fed directly to the solid/air nozzle 14 by means of the fan/compressor 25. To heat the perlite sand 1 to the material entry temperature T3, a heating 9 is provided in the storage container 8 instead to heat the perlite sand 1 in the storage container 8. The heating is carried out in such a way that the perlite sand 1 has a first elevated temperature T1 before entering the solid/air nozzle 14 or before dispersing.

[0084] This first elevated temperature T1 is less than the critical temperature and greater than the ambient temperature RT and can be measured using a temperature sensor 23 upstream of the solid/air nozzle 14. This temperature sensor 23, which measures the first elevated temperature T1 of perlite sand 1 between the dosing screw 20 and the solid/air nozzle 14 in the embodiment example shown, is connected to the regulating and control unit 16 (indicated by the dashed line). The heating 9 of the storage container 8 also has a controllable valve 32 which is connected to and controlled by the regulating and control unit 16 (indicated by the dashed line). The first elevated temperature T1 of the heated perlite sand 1 is monitored by the temperature sensor 23 of the regulating and control unit 16 so that the regulating and control unit 16 can regulate the heating 9 by means of the controllable valve 32 in such a way that the desired first elevated temperature T1 is reached. When dispersing with the (unheated) quantity of air, the perlite sand 1 typically cools down somewhat by heat transfer to the quantity of air, so that its material entry temperature T3 is typically somewhat lower than the first elevated temperature T1 in the embodiment example in FIG. 2.

[0085] The third embodiment example according to FIG. 3 is a combination of the embodiment examples from FIG. 1 and FIG. 2. On the one hand, the quantity of air is heated by means of the heating 22 of the compressed air tank 21, so that the quantity of air immediately before entering the solid/air nozzle 14 has the second elevated temperature T2. On the other hand, the perlite sand 1 in the storage container 8 is also heated by means of the heating 9, so that the perlite sand 1 immediately before entering the solid/air nozzle 14 has the first elevated temperature T1. The result is a particularly precise setting of the desired material entry temperature T3.

[0086] Preferably, the absolute value of a differential temperature, which is the difference between the first elevated temperature T1 and the second elevated temperature T2, is at most 50%, preferably at most 30%, particularly preferably at most 10%, of the first elevated temperature T1.

[0087] In the fourth embodiment example according to FIG. 4, compared to the third embodiment example according to FIG. 3, the supply of supply air 34 is additionally provided, which is blown into the furnace shaft 4 from below, in order to support the conveying of the perlite sand 1 or the expanded granulate 2 along the conveying path 5, wherein the supply air 34 is preheated to a further elevated temperature T4 before it enters the furnace shaft 4. Preferably, the further elevated temperature T4 is also higher than the ambient temperature RT and lower than the critical temperature. Preheating the supply air 34 prevents a large part of the heating of perlite sand 1 caused by the heating process from being transferred to the supply air 34 by convection. By heating or preheating the perlite sand 1 and the supply air 34 before each entry into furnace shaft 4, a shorter furnace shaft 4 can be built or regulated much more sensitively.

[0088] In the embodiment example in FIG. 4, a fan 35 and a pipe 17 are provided as means for supplying or injecting the supply air 34. The supply air 34 is blown into pipe 17 by means of fan 35, wherein a heating 36 is arranged in pipe 17 in order to preheat the supply air 34 to the further elevated temperature T4. The fan 35 and the heating 36 are therefore connected upstream of the furnace shaft 4. The heating 36 comprises a controllable valve 32 connected to and controlled by the regulating and control unit 16 (indicated by the dashed lines). The further elevated temperature T4 of the preheated supply air 34 is measured by means of a temperature sensor 23, preferably at a point in the pipe 17 downstream of the heating 36. This temperature sensor 23 is also connected to the regulating and control unit 16 (indicated by the dashed line), which evaluates its signals to control the heating 36 by means of the controllable valve 32 in such a way that the further elevated temperature T4 of the preheated supply air 34 has a desired value.

[0089] In the embodiment example shown, the pipe 17 leads into an area which is directly connected to the solid/air nozzle 14. This means that the pipe 17 is connected at least in sections on the one hand between the solid/air nozzle 14 and the furnace shaft 4 and on the other hand between the heating 36 and the furnace shaft 4 in order to be able to convey the preheated supply air 34 into a region between the solid/air nozzle 14 and the lower end 13 of the furnace shaft 4. In this way, the preheated supply air 34 is added to the dispersed perlite sand 1. Preferably, the further elevated temperature T4 of the preheated supply air 34 is selected so that it is at least as high as that of the dispersed perlite sand 1 in order to prevent the perlite sand 1 from cooling due to the addition of the preheated supply air 34. Accordingly, the desired material entry temperature T3 can be set with high precision.

[0090] In all the embodiment examples shown, the gas-material flow 33 is fed to a density measuring device 18, where at least part of the expanded granulate 2 carried in the gas-material flow 33 is separated. The density measuring device 18 has a sensor 31 which determines the density of this expanded granulate 2 in a manner known per se, e.g. optically. This expanded granulate 2 is discharged from the density measuring device 18 via a rotary valve 29 and can, for example, be fed to a silo (not shown).

[0091] In addition, a filter 28 downstream of the density measuring device 18 is provided in order to separate as completely as possible the expanded granulate 2 still present in the gas-material flow 33. Since the expanded granulate 2 or the gas-material flow 33 is cooled down by the cooling air 27, in particular to a temperature less than or equal to 120 C., it is possible to use inexpensive, in particular cleanable, filter hoses in filter 28. This expanded granulate 2 is also discharged from filter 28 via a rotary valve 29 and can, for example, be fed to a silo (not shown).

[0092] Exhaust air 30 cleaned by the filter 28 is released into the atmosphere via a fan 25 downstream of the filter 28.

[0093] The determination of the density of the expanded granulate 2 makes it possible to regulate the expansion or swelling process even more sensitively. The measurement allows the expansion result to be monitored continuously and process parameters to be adjusted immediately if the actual expansion result deviates from the desired expansion result. By connecting the regulating and control unit 16 also to the sensor 31 (indicated by the dashed line) and continuously evaluating its data, the density of the expanded microspheres 2 can be specifically regulated by means of the regulating and control unit 16 in order to guarantee the desired quality of the expansion result.

[0094] In particular, the power of at least one heating element 7 of a last heating zone 11 can be controlled to regulate the density of the expanded granulate 2, wherein its power is preferably controlled to a desired value or a value in a desired value range. This allows at least a coarse control of the density of the expanded granulate 2.

[0095] By means of the detection of the temperature drop described above, the heating elements 7 of the heating zones 6 before the last heating zone 11 are preferably regulated in such a way that the isenthalpic expansion process takes place before, in particular immediately before, the last heating zone 11. This means that the detection of the position of the temperature drop is used to at least roughly regulate this position to a desired position along the conveying path 5, namely to a position before, in particular immediately before, the last heating zone 11, by suitable control of the heating elements 7 by means of the regulating and control unit 16.

[0096] An extremely fine adjustment of the position of the temperature drop is made possible by the control of the material entry temperature T3, wherein the first elevated temperature T1 and/or the second elevated temperature T2 and/or the further elevated temperature T4 are suitably controlled by means of the regulating and control unit 16. Accordingly, for extremely fine regulation of the density of the expanded granulate 2, the first elevated temperature T1 and/or the second elevated temperature T2 and/or the further elevated temperature T4 can be suitably controlled by means of the regulating and control unit 16.

[0097] It should be noted that the homogeneity of the expanded granulate 2 can also be determined completely analogously to the determination of the density of the expanded granulate 2 and that this homogeneity can then be used as an alternative or additional regulating variable in order to guarantee the desired quality of the expansion result or the expanded granulate 2.

LIST OF REFERENCE NUMERALS

[0098] 1 Perlite sand [0099] 2 Expanded granulate/expanded microspheres [0100] 3 Furnace [0101] 4 Furnace shaft [0102] 5 Conveying path [0103] 6 Heating zone [0104] 7 Heating element [0105] 8 Storage container [0106] 9 Heating of the storage container [0107] 10 Position for temperature measurement along the conveying path [0108] 11 Last heating zone [0109] 12 Upper end of furnace shaft [0110] 13 Lower end of furnace shaft [0111] 14 Solid/air nozzle [0112] 15 Compressed air [0113] 16 Regulating and control unit [0114] 17 Pipe for supply air [0115] 18 Density measuring device [0116] 19 Conveying direction [0117] 20 Dosing screw [0118] 21 Compressed air tank [0119] 22 Heating of the compressed air tank [0120] 23 Temperature sensor [0121] 24 Current or power meter [0122] 25 Fan/compressor [0123] 26 Air supply [0124] 27 Cooling air [0125] 28 Filter [0126] 29 Rotary valve [0127] 30 Purified exhaust air [0128] 31 Sensor of the density measuring device [0129] 32 Controllable valve [0130] 33 Gas-material flow [0131] 34 Supply air [0132] 35 Fan [0133] 36 Heating for supply air [0134] T1 First elevated temperature (of the material) [0135] T2 Second elevated temperature (of the air quantity) [0136] T3 Material entry temperature [0137] T4 Further elevated temperature (of supply air) [0138] RT Ambient temperature