DEVICE FOR PRODUCING SUPPLEMENTARY CEMENTITIOUS MATERIAL

Abstract

The present invention relates to a device for heat-treating solid material, in particular in granular form, wherein the device comprises a kiln and an external heat generator, wherein said kiln comprises at least one sloped sliding surface on which a bed of said solid material slides down within said kiln due to gravity while a hot gas generated by the external heat generator is led through said solid material to heat said solid material to a desired temperature in order to change the substance properties of said solid material. According to the invention, said external heat generator for generating said hot gas is external to said kiln, wherein said kiln further comprises at least one kiln gas inlet through which said hot gas enters said kiln, such that the necessary temperature of said hot gas can be controlled precisely in that said hot gas is generated in said external heat generator, ensuring that the solid material does not experience temperatures above an allowed maximum temperature, and further such that the solid material is not exposed to radiation from a burner.

Claims

1. A device for heat-treating solid material in granular form, wherein the device comprises a kiln and an external heat generator wherein said kiln comprises at least one.-sloped sliding surface on which a bed of said solid material slides down within said kiln due to gravity while a hot gas generated by the external heat generator is led through said solid material to heat said solid material to a desired temperature in order to change the substance properties of said solid material, wherein said external heat generator generator for generating said hot gas is external to said kiln wherein said kiln further comprises at least one kiln gas inlet through which said hot gas enters said kiln such that the necessary temperature of said hot gas can be controlled precisely in that said hot gas is generated in said external heat generator ensuring that the solid material does not experience temperatures above an allowed maximum temperature, and further such that the solid materialis not exposed to radiation from a burner.

2. The device in according to claim 1 wherein the device further comprises a kiln and a heat generator, wherein said kilncomprises at least one sloped sliding surface on which said solid material slides down due to gravity while a hot gas generated by the heat generator is led through said solid material to heat said solid material to a desired temperature in order to change the substance properties of said solid material, wherein said sliding surface is adapted to allow an isokinetic motion of said solid material along said sliding surface.

3. The device according to claim 1 , wherein said kiln does not comprise any moving parts that come into contact with said solid material in order to effect movement of the solid material , such that the solid material automatically slides down along the sliding surface merely due to gravity and without the need of any pusher or moving means of the kiln.

4. The deice according to claim 1, wherein said sliding surface is formed by at least one grate plate through which said hot gas passes.

5. The device according to claim 4 , wherein said grate platecomprises a plurality of small gas openings through which said hot gas passes, wherein a combined flow cross-section of said plurality of small gas openings is smaller than a combined flow cross-section formed by spaces between the-overlying solid material .

6. The device according to claim 4 , wherein said grate plateplate comprises a plurality of overlapping slats.

7. The deviceaccording to claim 6 , wherein a sloping angle α between the horizontal plane and an upper surface of each slat is greater than or equal to 10°, or greater than or equal to 20°.

8. The device according to claim 6 , wherein a resulting angle β of the grate plate , the resulting angle β of the grate platebeing defined between the horizontal plane and an enveloping plane touching the lower ends of the overlapping slats , is less than or equal to 55°.

9. The device according to claim 6 , wherein the overlapping slats of the grate plate are held such that a gap is formed between a lower end of the respective overlapping slat and an upper end of the respective overlapped slat, the gaps between the overlapping slats forming gas openings through which said hot gas passes.

10. The device according to claim 1 , wherein said kiln comprises several sloped sliding surfaces arranged in a zigzag manner one above the other.

11. The device according to claim 1 , wherein kiln comprises several kiln sections, wherein each kiln section is provided with a separate kiln gas inlet .

12. The device according to claim 1 , wherein said device further comprises a preheater for preheating said solid material before it enters the kiln and a cooler for cooling said heat-treated solid material exiting said kiln, wherein the cooler , the kiln and the preheaterpreheater are arranged in vertical alignment one above the other, respectively.

13. The device (6) according to claim 12, wherein the device device further comprises at least one bypassbypass guiding cooling gas used for cooling the heat-treated solid material in the cooler, after having been heated by the heat-treated solid material, to the preheater.

14. The device Device according to claim 12 , wherein the preheater comprises several preheating sections in which preheating of the solid material occurs in several preheating steps, wherein the cooler comprises several cooling sections in which cooling of the solid material occurs in several cooling steps, and wherein the device is adapted and configured such that gas can be extracted or added in at least one or in all of said preheating and cooling steps.

15. The device Device according to claim 12 , wherein the device further comprises a discharging device for extracting said solid material at a lower end of said cooler at a controlled discharging rate.

16. The device Device according to claim 1 , wherein the devicecomprises at least one absorbing or catalyzing section in which the gas is led through an absorbent or catalyzing material in order to reduce emissions.

Description

[0031] Embodiments of the present invention shall be explained in more detail hereinafter with reference to the drawings.

[0032] FIG. 1 shows a perspective front view of a device according to a first embodiment of the present invention,

[0033] FIG. 2 shows a perspective rear view of the device shown in FIG. 1,

[0034] FIG. 3 shows a side view of the device shown in FIGS. 1 and 2,

[0035] FIG. 4 shows a longitudinal section view of the device shown in FIGS. 1 to 3 along section line IV indicated in FIG. 3,

[0036] FIG. 5 shows a detail view of neighboring grate plates of the device shown in FIG. 4,

[0037] FIG. 6 shows a side view of a grate plate of the device shown in FIGS. 1 to 5,

[0038] FIG. 7 shows a top view of the grate plate shown in FIG. 6,

[0039] FIG. 8 shows a section view of the grate plate shown in FIGS. 6 and 7 along section line VIII indicated in FIG. 7,

[0040] FIG. 9a shows a detail view of overlapping slats of the grate plate shown in FIG. 8,

[0041] FIG. 9b shows the detail view of FIG. 9a at a correct installation angle,

[0042] FIG. 10 shows a perspective front view of a device according to a second embodiment of the present invention,

[0043] FIG. 11 shows a side view of the device shown in FIG. 10,

[0044] FIG. 12 shows a longitudinal section view of the device shown in FIGS. 10 and 11,

[0045] FIG. 13 shows a detail view of the kiln section of the device as shown in section view of FIG. 12,

[0046] FIG. 14 shows a longitudinal section view of a device according to a third embodiment of the present invention,

[0047] FIG. 15 shows a longitudinal detail section view of the upper portion of the devices shown in FIGS. 4 and 14 according to a further embodiment, and

[0048] FIG. 16 shows a longitudinal detail section view of the upper portion of the devices shown in FIGS. 4 and 14 according to another embodiment.

[0049] A first embodiment of a device 1 according to the present invention is shown in FIGS. 1 to 4 whereas FIG. 1 shows a perspective front view, FIG. 2 shows a perspective rear view, FIG. 3 shows a side view, and FIG. 4 shows a longitudinal section view along the section line IV indicated in FIG. 3.

[0050] The device is configured as a vertical tower with a feeder 23 at its top end for feeding granular material into the device. The granular material, preferably shale, experiences a heat treatment when passing through the device such that the shale is calcinated. The finished product is discharged from the device at a lower end of the tower via a suitable discharging device 19 which may be formed by a reciprocating bar pushing the granular material out of the discharge opening at a certain controllable rate. As best shown in FIG. 4, the device 1 comprises an upper preheater 2, a kiln 3 in the middle, and a cooler section 4 forming a lower portion of the tower.

[0051] The granular material is first preheated in the preheater 2, then passes on to the kiln 3 in which the calcination takes place, and is subsequently cooled down in the cooler 4 to an acceptable outlet temperature. According to the invention, the hot gas required in the kiln 3 for calcining the granular material is not generated within the kiln by a burner as is conventional in the prior art. Instead, the hot gas is generated in an external heat generator 5. The external generation of hot gas has the advantage that the temperature can be precisely controlled such that the material experiences an ideal temperature or temperature range. The hot gas enters the kiln via the kiln gas inlets 8 shown in FIGS. 1 to 4.

[0052] Cooling gas for cooling the heat-treated or calcinated solid material in the cooler 4 is led into the cooler 4 via a gas inlet 21 at a lower end of the cooler 4. The cooling gas flows upwards within the tower while the solid material moves in a downward direction. At the upper end of the cooler 4, the cooling gas which has been heated up by then to a temperature slightly below the temperature of the hot gas used in the kiln may be bypassed via bypass 18 to the lower end of preheater 2 without passing through the kiln 3. A valve may be arranged within the bypass 18 for controlling the flow of bypassed heated cooling gas.

[0053] As shown in FIG. 4, a plurality of opposite sloped sliding surfaces formed by grate plates 7 are arranged within the tower such that the granular material can slide down through preheater 2, kiln 3 and cooler 4 in cascade from one grate plate 7 to another. In the exemplary embodiment, preheater and cooler each comprise four grate plates 7 whereas the kiln comprises two grate plates 7. Each grate plate 7 represents one section of preheater, kiln and cooler. As shown in FIG. 4, the kiln 3 comprises two sections. Each of these two sections is provided with a separate kiln gas inlet 8 such that each section is provided with fresh hot gas from below the respective grate plate 7. At the upper end of each kiln section, after heat-transfer between hot gas and solid material has taken place, the used and cooled down gas is extracted from the kiln via a bypass inlet 16. The cooled gas is led to the preheater 2 via a second bypass 15 and enters the preheater 2 via bypass outlet 17. The gas led to the preheater 2 is vented through gas outlet 22 at the upper end of the tower. Preferably, a suction fan is provided within the gas outlet in order to control the flow rate of the gas.

[0054] FIG. 5 shows a detail view of the grate plates 7 and the bed of solid granular material 6 sliding down along the upper surface of the sloped grate plates 7. The grate plates 7 are configured such that the bed of solid granular material 6 performs an isokinetic sliding motion. This means that no vertical mixing between the layers of the bed occurs. The isokinetic motion is a precondition for an efficient heat transfer. As shown in FIG. 5, the lower end 20 of each grate plate 7 forms a short vertical duct with the neighboring wall of the tower which allows tumbling of the granular material in a transition zone between two consecutive grate plates 7. The tumbling leads to a more uniform temperature within the granular solid material before the material enters the next section. FIG. 5 also shows that the height of the bed of solid material 6 is calibrated by the distance between the lower end of an upper grate plate and the upper end of the consecutive grate plate. According to an embodiment of the invention, the height of the bed of solid material 6 may be adjustable via a suitable adjusting mechanism which increases or decreases the distance between the lower end 20 of the upper grate plate and the upper end of the consecutive grate plate. As can be seen in FIG. 4, the height of the bed of solid material in the kiln sections is lower than the height of the bed of solid material in the preheater and cooler sections. The lower bed height in the kiln sections ensures that all the material layers are within a certain temperature window.

[0055] In FIGS. 4 and 5, the grate plates 7 are only schematically shown. FIG. 6 to 9b show the grate plates in more detail. Each grate plate 7 comprises a plurality of solid slats 14 that overlap each other in a roof tile manner in such a way that the solid granular material can slide down in an isokinetic motion. This means that no barriers or thresholds are present that would cause local blocking and tumbling of the solid granular material. As best shown in FIGS. 9a and 9b, a slot or gap 13 exists between two consecutive overlapping slats 14. The hot gas can pass through the grate plate 7 through these slots 13. According to a preferred embodiment of the present invention, the gas passes from underneath the grate plate through the slots 13 and the solid material to a space above the solid material. In this embodiment, blocking of the slots 13 by fine material is avoided. A sloping angle α between the horizontal plane and an upper surface of each slat is greater than or equal to 20°. In the embodiment shown in FIG. 9b, the sloping angle α is approximately 22°. The resulting angle β of the grate plate is defined between the horizontal plane and an enveloping plane touching the lower ends of the overlapping slats. The resulting angle β must be less than or equal to 55°. In the embodiment shown in FIG. 9b, the resulting angle β is approximately 31°. It must be ensured that the resulting angle β of the grate plate is less than the angle of repose of the solid material. Advantageously, the thickness of the gaps or slots 13 is in the range between 1 mm and 10 mm, preferably between 1.5 mm and 5.0 mm. Furthermore, the thickness d of the slats 14, at least of a portion of the slat that overlaps another slat, is within the range between 1 mm and 10 mm, preferably between 2 mm and 5 mm.

[0056] FIGS. 10 to 13 show an alternative second embodiment of the device 1 according to the present invention. We would like to stress that the drawings are only schematic. Instead of a vertical tower according to the embodiment shown in FIGS. 1 to 4, preheater 2, kiln 3 and cooler 4 are formed by a simple vertical pipe 9 that does is not equipped with grate plates. Instead, the inner wall 10 of the pipe (shown in FIGS. 12 and 13) forms a sliding surface along which the solid granular material slides down. The kiln section 3 shown in detail in FIG. 13 comprises a kiln gas inlet 8 consisting of a plurality of slots 11 extending parallel to the axis of pipe 9. In order to avoid blocking of the material in the kiln section, the pipe preferably widens slightly in a downward direction at least in the region of the slots 11. The hot gas generated in the external heat generator 5 is evenly distributed to the slots 11 via an annular manifold 12.

[0057] According to the invention and in order to increase the efficiency of the device, the device 1 is provided with a bypass 18 through which heated cooling gas from the upper end of cooler 4 is bypassed to the preheater 2. The devise is equipped with a similar discharging device as the discharging device 19 shown in FIG. 1, to ensure correct material retention time of the material to be heat treated.

[0058] FIG. 14 shows a device 1 according to a third embodiment of the present invention. The kiln 3 of the device 1 corresponds to the kiln of the embodiment shown in FIGS. 10 to 13 whereas preheater 2 and cooler 4 correspond to the design shown in FIGS. 1 to 5.

[0059] As shown in FIGS. 15 and 16, the device 1 may comprise an absorbing or catalyzing section 24 in which the emission of, for example, SO2, HCl, TOC, NOx etc. is reduced in that the gas used in cooler, kiln and preheater is led through an absorbing or catalyzing material 25 before it is released into the atmosphere. To this end, the absorbing or catalyzing material 25 is conveyed over a grate plate 26 similar to the grate plates 7. FIG. 15 shows an embodiment with the absorbing or catalyzing section being the top section of the preheater. The stream of absorbing or catalyzing material can run parallel to the first grate plate 7 of the preheater 2. The arrows symbolize the flow direction of the gas. FIG. 16 shows an embodiment with the absorbing or catalyzing section being arranged between two preheater sections (between two preheater grate plates). In this case, the flow of absorbing or catalyzing material runs into or out of the image plane. The vertical transition zone between the first two grate plates 7 is extended such that the solid material is bypassed past the absorbing or catalyzing section 24. The embodiments shown in FIGS. 15 and 16 are suitable for the devices shown in FIGS. 1 to 5 and 14.

LIST OF REFERENCE SIGNS

[0060] 1 heat-treating device [0061] 2 preheater [0062] 3 kiln [0063] 4 cooler [0064] 5 external heat generator [0065] 6 solid material [0066] 7 grate plate [0067] 8 kiln gas inlet [0068] 9 pipe [0069] 10 inner wall of pipe [0070] 11 kiln gas inlet slot [0071] 12 manifold [0072] 13 grate plate slot [0073] 14 solid grate plateslat [0074] 15 bypass [0075] 16 bypass IN [0076] 17 bypass OUT [0077] 18 bypass [0078] 19 discharging device [0079] 20 grate plate lower end [0080] 21 gas inlet [0081] 22 gas outlet [0082] 23 feeder [0083] 24 absorbing/catalyzing section [0084] 25 absorbing/catalyzing material [0085] 26 absorbing/catalyzing material grate plate [0086] d thickness of solid grate plate slat 14 [0087] α angle between solid grate plate slat 14 and the horizontal plane [0088] β angle between grate plate and the horizontal plane