Rotary Kiln and Method for Burning Carbonate-Containing Material, In Particular Limestone or Dolomite

Abstract

The present invention relates to a rotary kiln for burning carbonate-containing material, in particular limestone or dolomite, including a rotary tube having an inlet end for feeding the material to be burned and an outlet end for discharging the burnt material, and a burner unit arranged in the region of the outlet end, the rotary tube having an inlet zone at its inlet end and an outlet zone at its outlet end, a preheating zone and a combustion zone being arranged between the inlet zone and outlet zone in the direction of transport of the material. The rotary kiln is characterized according to the invention in that at least one projection is arranged in the outlet zone of the rotary tube, the at least one projection having a contour tapering in the direction of rotation of the rotary tube. The present invention further relates to a method for burning carbonate-containing material, in particular limestone or dolomite.

Claims

1-15. (canceled)

16. A rotary kiln for burning carbonate-containing material, in particular limestone or dolomite, comprising a rotary tube having an inlet end for feeding the material to be burned and an outlet end for discharging the burnt material, and a burner unit arranged in the region of the outlet end, the rotary tube having an inlet zone at its inlet end and an outlet zone at its outlet end, a preheating zone and a combustion zone being arranged between the inlet zone and outlet zone in the direction of transport of the material, at least one projection being arranged in the outlet zone of the rotary tube, the at least one projection having a contour tapering in the direction of rotation of the rotary tube, wherein an edge section is provided at the outlet end of the rotary tube, in which edge section no projection is arranged such that the intended ejection position of the burnt material is not changed relative to a rotary tube without projections.

17. The rotary kiln according to claim 16, wherein the at least one projection contains a refractory material, wherein the refractory material is optionally concrete, in particular refractory concrete.

18. The rotary kiln according to claim 16, wherein the at least one projection is V-shaped.

19. The rotary kiln according to claim 16, wherein the at least one projection has a prismatic geometry, in particular the geometry of a triangular prism, preferably an isosceles triangular prism, or the geometry of a truncated pyramid.

20. The rotary kiln according to claim 16, wherein the at least one projection is blunted or rounded in the direction of rotation of the rotary tube.

21. The rotary kiln according to claim 16, wherein the at least one projection has a height in the radial direction in relation to the rotary tube of between 50 mm and 500 mm, preferably of between 100 mm and 300 mm and particularly preferably of approximately 200 mm, and/or in that the at least one projection has a length in the circumferential direction of the rotary tube of between 50 mm and 2000 mm, in particular of between 100 mm and 1000 mm, preferably of between 300 mm and 500 mm and very particularly preferably of approximately 400 mm, and/or in that the at least one projection has a maximum width in the longitudinal direction of the rotary tube of between 50 mm and 600 mm, preferably of between 300 mm and 500 mm and particularly preferably of approximately 400 mm.

22. The rotary kiln according to claim 16, wherein the at least one projection is attached to the inner wall of the rotary tube by means of a metallic anchor, in particular a welded metallic anchor.

23. The rotary kiln according to claim 16, wherein a plurality of projections are provided in the outlet zone, wherein the projections are arranged in groups of 1 to 10, specifically 3 to 7, preferably 4 to 6 projections distributed over the circumference of the rotary tube, the projections of a group of projections optionally being arranged alternately offset in the longitudinal direction of the rotary tube, and/or a plurality of groups of projections being arranged one behind the other in the longitudinal direction of the rotary tube.

24. The rotary kiln according to claim 16, wherein a plurality of further projections are arranged in the preheating zone of the rotary tube, the further projections being arranged as groups, one behind the other, substantially parallel to the longitudinal axis of the rotary tube.

25. The rotary kiln according to claim 24, wherein further projections of adjacent groups of further projections arranged adjacent to one another in the circumferential direction of the rotary tube are arranged alternately offset in the longitudinal direction of the rotary tube, such that spiral-shaped transport paths for the material to be burned are formed in the preheating zone.

26. The rotary kiln according to claim 24, wherein at least some of the further projections have a prismatic geometry, in particular the geometry of a trapezoidal prism, preferably an isosceles trapezoidal prism.

27. The rotary kiln according to claim 24, wherein the groups of further projections arranged one behind the other substantially parallel to the longitudinal axis of the rotary tube can extend over a fifth to a third of the overall length of the rotary tube.

28. The rotary kiln according to claim 16, wherein at least one additional projection, preferably a plurality of additional projections, is provided in the inlet zone of the rotary tube, the at least one additional projection having at least one sliding surface inclined with respect to the longitudinal axis of the rotary tube for conveying the material to be burned from of the inlet zone to the preheating zone, a plurality of additional projections optionally being provided in the inlet zone of the rotary tube, the additional projections being arranged in a row as a group in such a way that the respective sliding surfaces of the additional projections form a common sliding surface for the material to be burned.

29. A method for burning carbonate-containing material, in particular limestone or dolomite, characterized by the following steps: introducing the carbonate-containing material into the rotary tube of a rotary kiln according to claim 16, burning the carbonate-containing material, the carbonate-containing material moving through the rotary tube from the inlet zone through the preheating zone and the combustion zone to the outlet zone, the rotary tube rotating in a direction of rotation, conveying the burnt material through the outlet zone, the at least one projection that is arranged in the outlet zone combing through the burnt material to improve cooling, an edge section being further provided at the outlet end of the rotary tube, in which edge section no projection is arranged, as a result of which the intended ejection position of the burnt material is not changed relative to a rotary tube without projections.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The invention is explained in more detail below in reference to a drawing depicting an exemplary embodiment. Shown are:

[0042] FIG. 1 the rotary tube of a rotary kiln in a perspective view,

[0043] FIG. 2 the rotary tube of FIG. 1 in truncated perspective longitudinal sectional view,

[0044] FIG. 3 an enlarged section of the outlet zone of the rotary tube of FIG. 1 in a perspective longitudinal sectional view,

[0045] FIG. 4 a projection in the outlet zone of the rotary tube of FIG. 1 in a perspective view,

[0046] FIG. 5 a two-dimensional truncated view of the unrolled kiln inner wall of the rotary tube of FIG. 2 in a starkly schematic form,

[0047] FIG. 6 an enlarged section of the preheating zone of the rotary tube of FIG. 1 in a perspective longitudinal sectional view,

[0048] FIG. 7 a projection in the preheating zone of the rotary tube of FIG. 1 in a perspective view,

[0049] FIG. 8 an enlarged section of the inlet zone of the rotary tube of FIG. 1 in a perspective longitudinal sectional view, and

[0050] FIG. 9 a projection in the inlet zone of the rotary tube of FIG. 1 in a perspective view.

DESCRIPTION OF THE INVENTION

[0051] In FIG. 1, the rotary tube 1 of a rotary kiln is shown with conventional mounting and drive components, which will not be discussed in more detail below. The rotary tube 1 comprises an inlet end 2ashown here on the frontand a rear outlet end 4a. Along the longitudinal extension of the rotary tube 1, the rotary tube 1 comprises an inlet zone 2, a preheating zone 3a (also called transition zone), a combustion zone 3b and an outlet zone 4 (see also FIGS. 2 and 5) in relation to the material feed, combustion and material discharge process. Arranged in the region of the outlet end 4a is a burner lance 5, by means of which a flame protruding into the rotary tube 1 is generated during operation of the rotary kiln. In one exemplary embodiment, the rotary tube 1 has an overall length of approximately 90 m, the length of the inlet zone 2 being approximately 2 m, that of the preheating zone 3a approximately 32 m, the length of the combustion zone 3b being approximately 53 m and that of the outlet zone 4 about 3 m. It goes without saying that these lengths are to be understood purely as examples. Different sized rotary tubes are also known from the prior art. The highest temperatures generated by the burner flame are achieved in the operation of the rotary kiln in the combustion zone 3b and are approximately 1500-1600? C., so that the predominant part of the calcination reaction takes place in this zone.

[0052] As shown in the perspective longitudinal sectional view of the rotary tube 1 in FIG. 2, the rotary tube 1 in the outlet zone 4 of the rotary tube 1 comprises a plurality of projections 8, which are arranged in groups 81 over the circumference of the rotary tube 1. Each projection 8 in turn has a contour tapering in the direction of rotation D of the rotary tube 1, as is shown in more detail in the detailed drawings of FIGS. 3 and 4. Specifically, the tapering contour of the projections 8 (also referred to as blades in technical terms) is formed as a truncated pyramid with the base area of an isosceles acute-angled triangle (see FIG. 4), the acute angle leading in the direction of rotation D of the rotary tube 1 and being slightly blunted for reasons of stability. This shape of the projections 8 makes it possible to comb through the burned material in the outlet zone 4 in the manner of a plow, with intensive intermixing occurring. This in turn means that no temperature spikes occur in the material, so that the risk of temperature-related damage that the burnt material causes to the components (not shown) downstream of the rotary tube 1, in particular the cooling units, is minimized. In order to ensure maximum temperature resistance, the projections 8 in the present case contain refractory concrete. Furthermore, each projection 8 is welded to the inner wall of the rotary tube 1 by means of a metallic anchor.

[0053] As can be seen in particular in the two-dimensional representation of the unwound open inner wall of the rotary tube 1 (FIG. 5), a group 81 of projections 8 comprises six projections, which in the present case are alternately offset in the longitudinal direction of the rotary tube 1. This is indicated in FIG. 5 by a zigzag line V. Furthermore, as shown in FIG. 5, a plurality of groups 81in the present case threeof projections 8 are arranged one behind the other in the longitudinal direction of the rotary tube 1, the group which is marginal with respect to the outlet end 4a of the rotary tube 1 comprising only 3 projections 8. In particular, the alternating offset of the projections 8 of a group 81 further increases the effectiveness of the intermixing of the burnt material in the outlet zone 4.

[0054] An edge section 4b that is approximately 400 mm wide is provided between the outlet end 4a of the rotary tube 1 and the peripheral group 81 of only three projections 8, in which edge section no projection 8 is arranged, so that the original discharge position into the cooling chute is not changed by the projections 8.

[0055] As further shown in FIG. 5, a plurality of further projections 7 (technically lugs) are provided in the preheating zone 3a of the rotary tube 1, the further projections 7 being arranged as groups 71, one behind the other, essentially parallel to the longitudinal axis of the rotary tube 1. In this case, further projections 7 of adjacent groups 71, which are arranged adjacent to one another in the circumferential direction of the rotary tube 1, are alternately offset with respect to one another in the longitudinal direction of the rotary tube 1, as represented by the zigzag line V. This alternately offset arrangement forms spiral transport paths S (shown in FIG. 5 as slanted lines) for the material to be burned in the preheating zone 3a. These serve to transport the material to be burned faster and with improved mixing through the preheating zone 3a with constant use of energy. They also serve to reduce the formation of dust in the preheating zone 3. The groups 71 of further projections 7 arranged one behind the other in the longitudinal direction of the rotary tube 1 can extend over a third to a fifth of the overall length of the rotary tube. As shown in the enlarged view of FIGS. 6 and 7, these further projections 7 (lugs) have the shape of a trapezoidal prism with inclined leg surfaces 7a and a length of approximately 400 mm in the present case and a height of approximately 200 mm in the present case. The angle of inclination of the leg surfaces 7a with respect to the lower trapezoidal base is approximately 76? in the present case. The trapezoidal design of the projections 7 ensures that the material intermixed by the projections 7 in the preheating zone 3a during kiln operation does not fall off the projections 7 with increased dust formation, but rather slides down along the leg surfaces 7a.

[0056] In the longitudinal sectional view of FIG. 2 and the two-dimensional view of FIG. 5, it can also be seen that a plurality of additional projections 6, which have a specific shape and are arranged in rows as groups 61 in a stepped form, are arranged in the inlet zone 2 of the rotary tube 1 as described below. The additional projections 6 are also referred to in technical terms as displacers.

[0057] As shown in FIGS. 1, 2, 5 and 8 and 9, the additional projections 6, in this case six of them, that are arranged in rows as a group 61, are essentially identical to one another and, according to FIG. 9, substantially have the shape of a triangular prism with the base of a right, isosceles triangle, the acute angles of the triangle being blunted for reasons of stability. Each additional projection 6 has a sliding surface 6a, which is arranged inclined with respect to the longitudinal axis of the rotary tube 1. An angle of inclination of approximately 45? is preferably selected. As mentioned, the additional projections 6 are arranged in rows in a stepped form in such a way that the individual sliding surfaces 6a of the additional projections 6 form a common sliding surface 6a*, which in the present case is also inclined at an angle of approximately 45? with respect to the longitudinal axis of the rotary tube 1.

[0058] Furthermore, the sliding surfaces 6a of the additional projections 6 and, accordingly, the common sliding surface 6a*, are oriented relative to the direction of rotation D of the rotary tube 1 in such a way that during operation of the kiln the material to be burned comes to rest on the sliding surfaces 6a, 6a* and, on the basis of the selected Inclination of the sliding surfaces 6a, 6a* with respect to the longitudinal axis of the rotary tube 1, slides rapidly in the direction of the preheating zone 3 by gravitational force without any undesirable rearward movement of the material to be burned in the direction of the inlet end 2a.

[0059] As shown in particular in FIGS. 1 and 5, six groups 61 of further projections 6 lined up in a row are provided distributed over the circumference on the inner wall of the rotary tube 1.