AVOIDING OF EMISSIONS IN THE PRODUCTION OF ARTIFICIAL POZZOLANS MADE OF MINERAL MATERIAL, IN PARTICULAR CLAYS

Abstract

A device for thermal treatment comprises at least a preheater, a calciner, and a materials cooler, wherein a solids stream is guided into the preheater, from the preheater into the calciner, from the calciner into the materials cooler, and out of the materials cooler, wherein a gas stream is guided into the materials cooler, from the materials cooler into the calciner, from the calciner into the preheater, and out of the preheater, wherein the device comprises a combustion chamber, wherein the gas stream from the materials cooler is guided at least partially through the combustion chamber into the calciner, wherein a residence time device is arranged between the combustion chamber and the calciner.

Claims

1-22. (canceled)

23. A device for thermal treatment of mineral materials, comprising: a preheater; a calciner; a materials cooler, wherein a solids stream extends into the preheater, from the preheater into the calciner, from the calciner into the materials cooler, and out of the materials cooler, and wherein a gas stream extends into the materials cooler, from the materials cooler into the calciner, from the calciner into the preheater, and out of the preheater; and a combustion chamber, wherein the gas stream extends from the materials cooler at least partially through the combustion chamber into the calciner, wherein a residence time device is arranged between the combustion chamber and the calciner, and the combustion chamber is arranged outside the solids stream.

24. The device as claimed in claim 23, wherein at least one auxiliary combustion device is arranged between the combustion chamber and the residence time device and/or in the residence time device.

25. The device as claimed in claim 23, wherein a first reactant feed is arranged between the combustion chamber and the residence time device.

26. The device as claimed in claim 25, wherein at least the first reactant feed is configured for the supply of ammonia, urea, compounds thereof or solutions of these.

27. The device as claimed in claim 26, wherein the device comprises at least one first NO.sub.x analyzer and the device comprises at least one first control device, wherein the at least one first control device is configured for reading the at least one first NO.sub.x analyzer, wherein the at least one first control device is configured for actuating at least one first reactant feed in dependence on the NO.sub.x value detected by at least one first NO.sub.x analyzer by adapting the type and/or amount and/or concentration of the reactant.

28. The device as claimed in claim 27, wherein the device comprises at least one temperature sensor and the at least one first control device is configured for reading the temperature sensor, wherein the at least one first control device is configured for actuating at least one first reactant feed and/or at least one auxiliary combustion device and/or at least one water feed in dependence on the temperature detected by the temperature sensor by adapting the type and/or amount and/or concentration of the reactant.

29. The device as claimed in claim 28, wherein the device comprises at least one NH.sub.3 analyzer and the at least one first control device is configured for reading the at least one first NH.sub.3 analyzer, wherein the at least one first control device is configured for actuating at least one first reactant feed in dependence on the NH.sub.3 value detected by at least one first NH.sub.3 analyzer by adapting the type and/or amount and/or concentration of the reactant.

30. The device as claimed in claim 29, wherein the reactant feed is mounted at at least one addition point, in at least one height plane.

31. The device as claimed in claim 30, wherein the reactant feed is mounted at at least two addition points, in at least two different height planes.

32. The device as claimed in claim 31, wherein the first reactant feed is designed for a feed with a pressure of 0.5 bar to 5 bar and at least one first water feed is arranged adjacent to the first reactant feed.

33. The device as claimed in claim 23, wherein the residence time device has a length, so that the residence time in the residence time device is between 0.5 s and 10 s.

34. The device as claimed in claim 23, wherein the residence time device has a length, so that the residence time in the residence time device is between 1 s and 5 s.

35. The device as claimed in claim 23, wherein the residence time device has a length, so that the residence time in the residence time device is between 1.5 s and 2.5 s.

36. The device as claimed in claim 23, wherein a reduction device is arranged between the calciner and the materials cooler.

37. The device as claimed in claim 23, wherein the residence time device comprises a catalyst and also comprises at least one diversion and/or flow internals for the gas mixture.

38. The device as claimed in claim 23, wherein the residence time device comprises at least one second reactant feed, wherein the second reactant feed is arranged between the combustion chamber and the residence time device or at the residence time device.

39. The device as claimed in claim 23, wherein the device comprises a catalytic reactor, wherein the catalytic reactor is arranged in the gas stream downstream of the preheater.

40. A method for operating a device as claimed in claim 23, wherein a temperature in the residence time device is between 750 C. and 1300 C.

41. The method as claimed in claim 40, wherein the temperature in the residence time device is between 900 C. and 1050 C.

42. The method as claimed in claim 40, wherein a thermal treatment of clays or claylike substances takes place.

Description

[0038] The device of the invention is more closely elucidated hereinbelow with reference to an exemplary embodiment represented in the drawing.

[0039] FIG. 1 Device.

[0040] FIG. 1 provides a schematic representation of an illustrative device. The material to be treated, a clay for example, is supplied to the preheater 10 via a materials feed 110, introduced preheated into the calciner 20, and thermally treated there. From the calciner 20, the material enters an optional reduction device 100, where it undergoes optimization for color in particular, and enters the materials cooler 30, from which the finished product is then withdrawn via a product offtake 120. In countercurrent, the gas is guided via a gas supply 130 first into the materials cooler 30 and heated there by the product to be cooled. The heated gas enters the combustion chamber 40. There, for example, a substitute fuel, such as garbage, is burned. During combustion, nitrogen oxides can be produced solely due to the temperature and the presence of nitrogen and oxygen. Combustion chamber (40) and residence time device (50) are preferably equipped with temperature sensors. Furthermore, the gases are hottest on leaving the combustion chamber 40, and so this moment is ideally suited for decomposing the nitrogen oxides again. In order to compensate for fluctuations in the calorific value of the secondary fuel, the device comprises an auxiliary combustion device 60 (optionally a plurality of auxiliary combustion devices 60), which is operated, for example, with gas, liquid fuel or coal dust and is thus able to reliably adjust the temperature. In addition, the plant comprises a water feed 62, with which water can be supplied and thus the temperature can be lowered in a simple way. The combination of auxiliary combustion device 60 and water feed 62 thus enables particularly selective temperature adjustment. In addition, an ammonia solution is injected via a first reactant feed 70. As a result, a reaction between NO.sub.x and NH.sub.3 can take place in the residence time device 50 at for example 1000 C. In order to complete the reaction and not to generate an excess of ammonia (and thus introduce a new pollutant source), the device also comprises a second reactant feed 72, in which ammonia solution is injected again at a later point in the residence time device 50. In addition, an NO.sub.x analyzer 80 and an NH.sub.3 analyzer (82) are arranged in the residence time device. In addition, an NO.sub.x analyzer 80 and an NH.sub.3 analyzer (82) are arranged after the preheater. The NO.sub.x analyzers 80 and the NH.sub.3 analyzers (82) are connected to a first control device 90, which regulates the injection of ammonia solution through the first reactant feed 70 and the second reactant feed 72 in dependence on the NO.sub.x content detected by the NOx analyzer 80 and the NH.sub.3 content detected by the NH.sub.3 analyzer and also the temperature level detected via temperature sensors. From there, the hot gas, but freed of NOx and with only low NH.sub.3 content, enters the calciner 20. For certain products the calciner can be operated for example at 750 C., which would however be too low to convert NO.sub.x within the calciner 20. The gas is guided from the calciner 20 into the preheater 10, where it delivers its heat to the material supplied. The offgas from the preheater 10 is then delivered via a gas drain 140 and can be supplied, for example, to a further treatment, for dedusting, for example.

Reference Signs

[0041] 10 preheater [0042] 20 calciner [0043] 30 materials cooler [0044] 40 combustion chamber [0045] 50 residence time device [0046] 60 auxiliary combustion device [0047] 62 water feed [0048] 70 first reactant feed [0049] 72 second reactant feed [0050] 80 NO.sub.x analyzer [0051] 82 NH.sub.3 analyzer [0052] 90 control device [0053] 100 reduction device [0054] 110 materials feed [0055] 120 product offtake [0056] 130 gas supply [0057] 140 gas drain