Method for the Thermal Treatment of Mineral Raw Materials

Abstract

A method for the thermal treatment of mineral raw materials such as limestone or dolomite is shown and described, which includes at least the following steps of a. providing a mineral bulk material and a conductive material and b. placing the mineral bulk material and the conductive material into a kiln, generating an electromagnetic field inside the kiln, thermally treating the mineral bulk material in the kiln by means of electromagnetic excitation of the conductive material in the electromagnetic field, and removing the thermally treated mineral bulk material and the conductive material from the kiln. Using the method described, even large quantities of mineral bulk material can be efficiently converted.

Claims

1. A method for the thermal treatment of mineral raw materials, comprising at least the steps of: a. providing a mineral bulk material and a conductive material, b. placing the mineral bulk material and the conductive material into a kiln, c. generating an electromagnetic field inside the kiln, d. thermally treating the mineral bulk material in the kiln by means of electromagnetic excitation of the conductive material in the electromagnetic field, and e. removing the thermally treated mineral bulk material and the conductive material from the kiln.

2. The method according to claim 1, wherein the mineral bulk material and the conductive material are mixed before being placed into the kiln.

3. The method according to claim 1, wherein the mineral bulk material comprises a hydroxide and/or a carbonate.

4. The method according to claim 1, wherein the mineral bulk material is selected from the group consisting of limestone, dolomite, magnesite, hydrated lime, carbonate ores and mixtures thereof.

5. The method according to claim 1, wherein the mineral bulk material has a bulk density of from 1.0 to 3.0 t/m3, in particular from 1.1 to 2.6 t/m3.

6. The method according to claim 1, wherein the has a melting point of at least 500° C. in particular at least 900° C. or at least 1000° C. or at least 1100° C. or at least 1200° C. or at least 1300° C.

7. The method according to claim 1, wherein the conductive material comprises at least one metal from the group consisting of iron, copper, tungsten, nickel, and cobalt, in particular iron.

8. The method according to claim 1, wherein the conductive material is substantially spherical.

9. The method according to claim 1, wherein that the conductive material has a mean particle size (d50) of from 1.0 to 70.0 mm, in particular from 2.0 to 50.0 mm.

10. The method according to claim 1, wherein the amount of mineral bulk material in method step a. is at least 10 wt. %. in particular at least 20 wt. % or at least 30 wt. % or at least 40 wt. %. based on the total amount of mineral bulk material and conductive material, and/or the amount of mineral bulk material in method step a. is a maximum of 90 wt. %. in particular a maximum of 80 wt. % or a maximum of 70 wt. % or a maximum of 60 wt. %, based on the total amount of mineral bulk material and conductive material.

11. The method according to claim 1, wherein the mineral bulk material in method step d. is exposed to a temperature of from 800 to 1500° C., in particular from 850 to 1450° C. or from 900 to 1250° C.

12. The method according to claim 11, wherein the conductive material has a melting point which is above the temperature to which the mineral bulk material in method step d. is exposed, in particular has a melting point which is at least 50° C. in particular at least 100° C. or at least 200° C. or at least 300° C. above the temperature to which the mineral bulk material is exposed.

13. The method according to claim 1, wherein the electromagnetic field in method step c. has a frequency of from 50 Hz to 30 MHz, in particular from 0.1 MHz to 2 MHz.

14. The method according to claim 1, wherein the gas which forms during the thermal treatment is extracted from the kiln, in particular is extracted from the kiln by means of a fan.

15. The method according to claim 14, wherein the gas comprises carbon dioxide.

16. The method according to claim 15, wherein at least part of the carbon dioxide extracted from the kiln is taken away for further use and/or storage.

17. The method according to claim 1, wherein the method comprises at least the steps of: f. cooling the removed mineral bulk material and the conductive material, and g. separating the conductive material from the thermally treated mineral bulk material.

18. The method according to claim 17, wherein, after method step g., the separated conductive material is placed back into the kiln.

19. A kiln comprising a kiln interior, a kiln wall, and a device for generating an electromagnetic field, wherein the device for generating an electromagnetic field is mounted outside the kiln interior and wherein the kiln has a wall thickness of a maximum of 50 cm.

20. The kiln according to claim 19, wherein the kiln comprises a fan for extracting gases.

21. The kiln according to either claim 19, wherein the kiln has an average inner diameter of 0.1 to 5 m, in particular 0.2 to 2 m, or 0.3 to 1.5 m.

22. A use of an electromagnetically excited conductive material for the thermal treatment of a mineral raw material.

23. The use according to claim 22, wherein the mineral raw material is a mineral bulk material and/or the electromagnetically excited conductive material.

24. The use according to either claim 22, wherein the electromagnetically excited conductive material is used for calcining limestone and/or dolomite.

25. The burnt lime and/or burnt dolomite which can be obtained from a method according to claim 1, wherein the mineral bulk material is selected from limestone and/or dolomite.

26. The apparatus for the thermal treatment of a mineral raw material, comprising a first metering installation containing a mineral bulk material, a second metering installation containing a conductive material, a supply system for the transport of the mineral bulk material and the conductive material, a kiln according to claim 20, at least one exhaust pipe connected to the kiln and the fan by means of which the extracted gas can be taken away, at least one inlet on the kiln by means of which the mineral bulk material and the conductive material can be conveyed into the kiln by the supply system, at least one gas-tight outlet on the kiln for removing the thermally treated mineral bulk material and the conductive material, a discharge system for taking away the thermally treated mineral bulk material and the conductive material, a separation system for separating the thermally treated mineral bulk material from the conductive material. a further conveyor system for the transport of the separated conductive material to the second metering installation.

27. The apparatus according to claim 26, wherein the inlet is a substantially gas-tight inlet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0113] The invention is explained in more detail below with reference to a drawing depicting a single preferred embodiment.

[0114] FIG. 1 is a schematic representation of a possible apparatus according to the invention.

DESCRIPTION OF THE INVENTION

[0115] FIG. 1 shows a schematic representation of a possible apparatus according to the invention as it can also be used in the method according to the invention. Conductive material 1 and mineral bulk material 2 are placed into the interior of the kiln 3. The kiln 3 can be, for example, a shaft kiln, crucible kiln, rotary kiln or fluidized bed kiln. It is preferably a shaft kiln. The device for generating an electromagnetic field 4, which is located outside the kiln interior, generates an electromagnetic field. The device for generating an electromagnetic field 4 can for example be a coil. The conductive material 1 and the mineral bulk material 2 are conveyed into the interior of the kiln 3 through the inlet 5 on the kiln 3. The thermally treated mineral bulk material as a product of the method and the conductive material 1 are removed from the kiln 3 through the outlet 6 of the kiln 3. The discharge system 7 serves to take away the thermally treated mineral bulk material and the conductive material 1. The discharge system 7 can, for example, be a transport system suitable for bulk materials. The thermally treated mineral bulk material and the conductive material are separated via the separation system 8. The separation system 8 can be designed, for example, as a magnetic separator and/or gravimetric sorting system and/or optical sorting system. It is preferably a magnetic separator. The optionally provided cooler 9 serves to cool the thermally treated mineral bulk material obtained. The mechanical unit 10 can mechanically separate mineral bulk material adhering to the separated conductive material 1. The mechanical unit 10 can be designed, for example, as a ball mill or a tube mill. The separated conductive material 1 is then conveyed on to the second metering installation 11. The cleaned conductive material 1 can thus be reused. New mineral bulk material 2 is added from the first metering installation 12 and conveyed into the kiln 3 via the supply system 13. The fan 14 can be used to extract gas which may arise during the thermal treatment in the course of the method according to the invention from the kiln interior, so that the thermal treatment is accelerated.

LIST OF REFERENCE SIGNS

[0116] 1 Conductive material

[0117] 2 Mineral bulk material

[0118] 3 Kiln

[0119] 4 Device for generating an electromagnetic field

[0120] 5 Inlet

[0121] 6 Outlet

[0122] 7 Discharge system

[0123] 8 Separation system

[0124] 9 Cooler

[0125] 10 Mechanical unit

[0126] 11 Second metering installation

[0127] 12 First metering installation

[0128] 13 Supply system

[0129] 14 Fan