Granular solids cooling line

Abstract

The invention relates to a line (1) for cooling hot granular solids, the temperature of which is greater than 1000°C, the cooling line (1) comprising in particular: - a first cooler (2) which is provided with at least one mesh (4) intended to receive the granular solids; - a second cooler (3) which is arranged downstream of the first cooler (2) in the direction of movement of the granular solids, the second cooler (3) being rotatable and comprising a material inlet (9) through which the granular solids enter and a material outlet (10) through which the granular solids leave, said cooling line (1) being configured so that the granular solids move successively from the first cooler (2) to the second cooler (3).

Description

[0001] DESCRIPTION

[0002] TITLE: Cooling line for granular solid materials

[0003] Technical field of the invention

[0004] The invention relates to a cooling line and a cooling method using the same. More concisely, the invention relates to a line for cooling granular solids having a temperature above 1000°C. In particular, the invention relates to the cement production industry, and the granular solids are clinker for cement production.

[0005] Technical background

[0006] Cooling lines are an integral part of cement production.

[0007] Clinker is a constituent of cement that is produced from a mixture of limestone and aluminosilicates.

[0008] Clinkering is a process in which a mixture of limestone and aluminosilicates becomes clinker. This process is carried out, depending on the production site and the surrounding geology, at a temperature of around 1500°C.

[0009] Clinkering is carried out in a rotary kiln. Once the clinker is obtained, it must be cooled. This cooling is carried out in a cooling line.

[0010] Cooling lines exist, for example, including grate coolers. These cooling lines are particularly energy-intensive from an electrical point of view, this being linked to the implementation of ventilation devices blowing through grates which present significant pressure losses.

[0011] In a context of reducing the environmental impact of clinker production units, cooling lines are a potential energy saving item.

[0012] The invention aims to reduce the energy consumption of cooling lines in order to improve the overall energy efficiency of clinker production facilities.

[0013] Summary of the invention

[0014] For this purpose, a cooling line for hot granular solid materials with a temperature above 1000°C is proposed firstly, the cooling line comprising:

[0015] - a first device for producing a first flow of cooling air,

[0016] - a first cooler provided with at least one grid intended to receive the granular solid materials, said grid being capable of being crossed by the first flow of cooling air,

[0017] - a second cooler arranged downstream of the first cooler in the direction of movement of the granular solid materials, said second cooler being rotatable and comprising a material inlet through which the granular solid materials enter and a material outlet through which the granular solid materials exit and in which a second cooling air flow circulates, the cooling line being configured so that the granular solid materials move successively from the first cooler to the second cooler, said cooling line comprising an air extraction circuit comprising an air extraction device, the air extraction circuit being capable of producing in part said second cooling air flow, the air extraction device being capable of extracting a first fraction of the second cooling air flow.

[0018] The cooling line ensures sufficient cooling efficiency. The cooling line also optimizes the electrical energy consumption required for its operation and also recovers at least part of the thermal energy present in the clinker.

[0019] Various additional features may be provided alone or in combination:

[0020] - the cooling line is arranged so that a second non-extracted fraction of the second air flow mixes with the first air flow in the first cooler to obtain a mixture;

[0021] - the cooling line includes means for recovering the mixture;

[0022] - the air extraction device is configured to extract air inside the second cooler;

[0023] - the air extraction device comprises an extraction end arranged inside the second cooler;

[0024] - the second cooler extends in a direction of extension substantially parallel to a direction of movement of the granular solid materials, said second cooler extending over a length L measured in the direction of extension, and in which the extraction end is arranged in the second cooler at a distance D greater than or equal to 0.5L measured in the direction of extension from the material outlet and said extraction end;

[0025] - the distance D is between 0.7L and 0.95L; - the extraction device comprises an extraction pipe arranged inside the second cooler, said extraction pipe extending substantially parallel to the second cooler;

[0026] - the extraction pipe and the second cooler are substantially concentric;

[0027] - at least one grid of the first cooler is fixed;

[0028] - the first cooler comprises at least one crusher for crushing the granular solid materials;

[0029] - the first cooler comprises a first portion and a second portion, separated from each other by the crusher, the at least one fixed grid of each portion being inclined so that the granular solid materials move under the effect of the Earth's gravity.

[0030] Secondly, a method is proposed for cooling granular solid materials using a cooling line as described above, in which it comprises the following operations:

[0031] - circulation of at least a first air flow in the first cooler through the at least one fixed grille,

[0032] - circulation of a second air flow in the second cooler produced in part by the air extraction circuit connected to the material outlet,

[0033] - extraction in the second cooler of a first fraction of the second air flow.

[0034] Various additional features may be provided alone or in combination:

[0035] - the extraction step is carried out so as to leave only a second fraction of the second air flow in the second cooler;

[0036] - the second fraction of the second air flow is directed towards the first air flow to be mixed therewith, said mixture being recovered for subsequent use by means for recovering said mixture;

[0037] - the first air flow contributes a share of the mixture between 50% and 60%, and the second fraction contributes a share of the mixture between 40% and 50%;

[0038] - the first air flow contributes a share of the mixture of approximately 55%, and the second fraction contributes a share of the mixture of approximately 45%;

[0039] - the first fraction extracted from the second air flow is between 65 and 80% of the second air flow.

[0040] Brief description of the figures

[0041] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which one will refer to the attached drawing in which:

[0042] [Fig 1] Figure 1 is a schematic representation of a cooling line according to the invention.

[0043] Detailed description of the invention

[0044] Figure 1 shows a cooling line 1 according to the invention.

[0045] Cooling line 1 comprises a first cooler 2 and a second cooler 3.

[0046] The first cooler 2 comprises several grates 4. These grates 4 are capable of receiving granular solid materials. In this case, the granular solid materials are clinker heated to a temperature above 1000°C in a kiln 5 adjacent to the first cooler 2.

[0047] As can be seen in Figure 1, the grids 4 are inclined in the direction of movement of the clinker, which direction of movement is represented by movement arrows 6. This inclination allows the clinker to move in the first cooler 2 under the effect of gravity and its geometric shape which is substantially spherical.

[0048] The cooling line 1 comprises at least one first device 7 for producing a first cooling air flow 8. The first device 7 for producing the first air flow 8 is arranged so that the first cooling air flow 8 passes through the grids 4. Thus the grids 4 are capable of being crossed by the first air flow 8. The grids 4 are in the form of perforated metal plates, the perforations of which have dimensions smaller than the clinker so that the latter cannot pass through the perforations.

[0049] The second cooler 3 is of the rotary type and is arranged downstream of the first cooler 2 in the direction of movement of the clinker. The second cooler 3 has a material inlet 9 through which the clinker leaving the first cooler 2 enters and which is adjacent to the first cooler 2. The second cooler 3 has a material outlet 10 through which the clinker leaves.

[0050] The cooling line 1 advantageously comprises an air extraction circuit 19 capable of producing in part a second flow 12 of cooling air. To do this, the air extraction circuit 19 comprises: - an air extraction device 17 capable of extracting a fraction of the second flow 12 of cooling air, and

[0051] - an extraction fan 23.

[0052] As shown in FIG. 1, the air extraction circuit 19 further comprises an extraction pipe 20, a heat exchanger 21, and a filter 22. The extraction pipe 20 is in fluid communication with the heat exchanger 21. The heat exchanger 21 is in fluid communication with the filter 22. The filter 22 is in fluid communication with the extraction fan 23.

[0053] The heat exchanger 21 is a backup exchanger to protect the filter 22 from possible overtemperatures.

[0054] Thus, the extraction circuit 19, in particular by means of the extraction fan 23, is capable of producing in part the second flow 12 of cooling air by drawing air directly into the second cooler 3. A part of the second flow 12 of cooling air can then move in the second cooler 3 in the opposite direction to the movement of the clinker, that is to say against the flow of the materials circulating in the second cooler 3 from the material inlet 9 to the material outlet 10.

[0055] The second cooler 3 is arranged substantially horizontally as can be seen in Figure 1. The second rotary cooler 3 advantageously comprises lifters 13 arranged on an inner face 14 of a rotary drum 15 of said second cooler 3. These lifters 13 have a profile which makes it possible to resuspend the clinker in the cooling air flow to improve the heat exchange. Thus the cooling line 1 is configured so that the clinker moves successively from the first cooler 2 to the second cooler 3.

[0056] This arrangement, which provides a first grate cooler 2 followed by a second rotary cooler 3 and in which the extraction device 17 makes it possible to extract a first fraction 27 from the second flow 12 of cooling air, makes it possible to reduce the electrical consumption while having acceptable clinker cooling kinetics and while maintaining an excellent recovery efficiency of the thermal energy contained in the clinker. The first grate cooler 2 is energy-intensive from an electrical point of view because the first air flow 8 is sent at high pressure to pass through the bed of clinker spread on the grates 4. The first cooler 2 is therefore used to quench the clinker and quickly reach a temperature slightly below 1000°C.Cooling is then completed in the second rotary cooler 3, which is less energy-intensive in terms of the power absorbed by the extraction device 17 or by any element connected to this extraction device 17. The extraction device 17 makes it possible to extract the first fraction 27 from the second air flow 12, the other fraction, hereinafter second fraction 28, preferably then mixing with the first air flow 8 in the first cooler 2, in order to obtain a mixture whose flow rate and temperature are suitable for use elsewhere in the clinker production process.

[0057] Thanks to these arrangements, the cooling line 1 described above allows significant savings in electrical energy as well as an increase in the overall efficiency of the cement plant.

[0058] Preferably, the cooling line 1 advantageously comprises at least one heating hood 16 which is in the form of a cavity. The heating hood 16 is in particular located at the location where the grids 4 are located and where a mixture comprising the first air flow 8 and the second fraction 28 of the second air flow 12 occurs. In addition, the cooling line 1 further preferably comprises one or more ducts 30 for recovering the mixture which can be arranged at different locations in the line 1, above the first cooler 2, according to specific temperature requirements of the mixture to be recovered. They make it possible in particular to capture the mixture comprising the first air flow 8 and the second fraction 28 of the second air flow 12.

[0059] It should be noted that the second fraction 28 of the second air flow 12 is directed towards the first cooler 2 insofar as the first cooler 2 comprises a depression zone produced, for example, by a draft fan of the furnace 5 and / or by the heating hood 16 and / or by the mixture recovery duct(s) 30 to which mixture recovery elements are generally connected.

[0060] According to an alternative embodiment, the air extraction device 17 is configured to extract air from inside the second cooler 3. More specifically, the extraction device 17 comprises an extraction end 18. The extraction end 18 is arranged inside the second cooler 3. The extraction of the air by the extraction end 18 arranged at this location advantageously makes it possible to reduce the quantity of air in the second air flow 12 before it mixes with the first air flow 8. Thus, the temperature of the mixture comprising the first air flow 8 and the second fraction 28 of the second air flow 12 is suitable for subsequent use in the cement production process. The second cooler 3 extends in an extension direction, hereinafter referred to as the X axis. The X axis is horizontal.

[0061] According to an alternative embodiment, the second cooler 3 is in the form of a tube mounted to rotate on fixed supports. The tube mounted to rotate has a slightly inclined slope, for example a slope of a few degrees, so as to allow the clinker to move in the second cooler 3 from the material inlet 9 to the material outlet 10. The second cooler 3 has a distance L measured between the material inlet 9 and the material outlet 10 and along the X axis.

[0062] According to an alternative embodiment, the extraction end 18 is arranged in the second cooler 3 at a distance D measured along the X axis. The distance D is measured between the material outlet 10 of the second cooler 3 and the extraction end 18.

[0063] Advantageously, the distance D is greater than or equal to 0.5L. By positioning the extraction end 18 at this distance D, the extraction of the first fraction 27 of the second air flow 12 is carried out so that the second air flow 12 has had time to cool the clinker in the second cooler 3.

[0064] In a preferred embodiment, the distance D is between 0.7L and 0.95L. This distance D advantageously allows efficient cooling of the clinker and makes it possible to obtain a good temperature of the second fraction 28 remaining and intended to be mixed with the first air flow 8 in the first cooler 2.

[0065] In the embodiment shown in Figure 1, the extraction pipe 20 is arranged inside the second cooler 3. As can be seen, the extraction pipe 20 extends substantially parallel to the second cooler 3. This arrangement is advantageous in that it makes it possible to position the extraction end 18 inside the second cooler 3. In addition, this arrangement makes it possible not to complicate the architecture of the extraction circuit 19 by overcoming the constraints inherent in the rotational movement of the rotating drum 15.

[0066] According to an alternative embodiment, the extraction pipe 20 is in the form of a tube. The extraction pipe 20 and the second cooler 3 are substantially concentric, which makes it possible to further overcome the constraints inherent in the rotational movement of the rotating drum 15. For example, a first part of the extraction pipe 20 and the rotating drum 15 are substantially concentric and rotate together, and a second part of the extraction pipe 20 is fixed relative to the rotational movement of the rotating drum 15 and connected to the first part of the extraction pipe 20 using a system of rotating joints.

[0067] The first cooler 2 comprises two portions 24, 25, namely a first portion 24 and a second portion 25. The first portion 24 and the second portion 25 each comprise one or more fixed grates 4. As can be seen in FIG. 1, the grates 4 are inclined so that the clinker moves under the effect of the Earth's gravity as previously mentioned.

[0068] The use of fixed 4 grids advantageously simplifies the operation of cooling line 1 and improves its reliability despite the high temperature of the clinker.

[0069] The cooling line 1 advantageously comprises a crusher 26. The crusher 26 is arranged between the first portion 24 and the second portion 25. The crusher 26 makes it possible to reduce the size of the clinker grains, in particular the crusting elements. The crusher 26 is arranged after the first portion 24 so that the clinker undergoes a reduction in temperature and this to preserve the crusher 26 by preventing it from being used at excessively high temperatures.

[0070] In the following, the operation of cooling line 1 will be described.

[0071] The clinker moves under the effect of gravity in the kiln 5, which is slightly inclined. The clinker then lands on the fixed grid 4 of the first portion 24 of the first cooler 2. Under the effect of gravity, the clinker moves and is crushed in the crusher 26. At the outlet of the crusher 26 the clinker falls onto the fixed grid 4 of the second portion 25 of the second cooler 3. The clinker moves in the second portion 25 of the first cooler 2 under the effect of gravity. The clinker then falls into the second cooler 3 where its temperature decrease continues throughout its journey in the second cooler 3.

[0072] At least a first air flow 8 is produced by the first air production device 7. This first air flow 8 is sent through the fixed grid 4 of the first portion 24 and the second portion 25. The first air flow 8 is sent at high pressure so that it can pass through the clinker bed spread over each fixed grid 4. This operation makes it possible to carry out a “clinker quenching” so that its temperature quickly drops below 1000°C. The first air flow 8 rises in temperature upon contact with the hot clinker.

[0073] A second air flow 12 is produced by means of the air extraction circuit 19 and the depression zone contained in the first cooler 2. This second air flow 12 is initiated in the second cooler 3 by the material outlet 10 as can be seen in the drawing. In the second cooler 3, a first fraction 27 of the second air flow 12 is extracted. This extraction is carried out via the extraction device 17 included in the air extraction circuit 19. The first fraction 27 of air which is extracted is sent to the heat exchanger 21. The first fraction 27 is then sent to the filter 22 to remove the clinker dust, then discharged into the atmosphere.

[0074] According to an alternative embodiment not illustrated in the figures, the energy, in particular thermal, of the first fraction 27 of the second air flow 12 is then used in the clinker or cement manufacturing process using ad hoc and known devices. For example, the energy of the first fraction 27 of the second air flow 12 can allow the drying of raw materials or fuels necessary for the clinker manufacturing process.

[0075] The second fraction 28 of the second air flow 12, which is preferably not extracted, enters the first cooler 2 where it mixes with the first air flow 8. This mixture is then recovered in the heating hood 16, and can also be recovered by one or more of the recovery ducts 30. This air mixture has temperature and flow characteristics which make it usable, for example, as a feed oxidant for a kiln burner, a combustion chamber integrated into a clinker production line, or even a precalciner by significantly increasing the energy efficiency of the clinker manufacturing process.

[0076] According to an alternative embodiment, the first air flow 8 contributes a portion of the mixture of between 50% and 60%. The second fraction 28 contributes a portion of the mixture of between 40 and 50%. According to an alternative embodiment, the first fraction 27 which is extracted from the second air flow 12 is between 65 and 80% of the second air flow 12.

[0077] In a preferred embodiment:

[0078] - the first air flow 8 contributes a share of the mixture of approximately 55%;

[0079] - the second fraction 28 contributes a share of the mixture of approximately 45%;

[0080] - the first fraction 27 extracted from the second air flow 12 is approximately 73%.

[0081] In a preferred embodiment and by way of example:

[0082] - the first flow 8 of injected air has a volume flow rate of 0.5 Nm 3 / kg of clinker;

[0083] - the second flow 12 of injected air has a volume flow rate of 1.5 Nm 3 / kg of clinker;

[0084] - the extraction of the first fraction 27 of the second air flow 12 is done at a flow rate of 1.1 Nm 3 / kg ;

[0085] - the second fraction 28 therefore has a flow rate of 0.4 Nm 3 / kg of clinker;

[0086] - the mixture of the first air flow 8 and the second fraction 28 therefore has a flow rate corresponding to their sum, i.e. 0.9 Nm 3 / kg .

Claims

CLAIMS 1. Line (1) for cooling hot granular solid materials whose temperature is greater than 1000°C, the cooling line (1) comprising: - a first device (7) for producing a first flow (8) of cooling air, - a first cooler (2) provided with at least one grid (4) intended to receive the granular solid materials, said grid (4) being capable of being crossed by the first flow (8) of cooling air, - a second cooler (3) arranged downstream of the first cooler (2) in the direction of movement of the granular solid materials, said second cooler (3) being rotatable and comprising a material inlet (9) through which the granular solid materials enter and a material outlet (10) through which the granular solid materials exit and in which a second flow (12) of cooling air circulates, said cooling line (1) being configured so that the granular solid materials move successively from the first cooler (2) to the second cooler (3), said cooling line (1) comprising an air extraction circuit (19) comprising an air extraction device (17), the air extraction circuit (19) being capable of producing in part said second flow (12) of cooling air, said air extraction device (17) being capable of extracting a first fraction (27) of the second flow (12) of cooling air.

2. Cooling line (1) according to claim 1 wherein said cooling line (1) is arranged so that a second fraction (28) not extracted from the second air flow mixes with the first air flow (8) in the first cooler (2) to obtain a mixture.

3. Cooling line (1) according to claim 2 wherein said cooling line (1) comprises means (16, 30) for recovering said mixture.

4. Cooling line (1) according to one of the preceding claims, in which the air extraction device (17) is configured to extract air inside the second cooler (3).

5. Cooling line (1) according to claim 4 wherein the air extraction device (17) comprises an extraction end (18) arranged inside the second cooler (3).

6. Cooling line (1) according to claim 5 wherein the second cooler (3) extends in a direction of extension substantially parallel to a direction of movement of the granular solid materials, said second cooler (3) extending over a length L measured in the direction of extension, and wherein the extraction end (18) is arranged in the second cooler (3) at a distance D greater than or equal to 0.5L measured in the direction of extension from the material outlet (10) and said extraction end (18).

7. Cooling line (1) according to claim 6 in which the distance D is between 0.7L and 0.95L.

8. Cooling line (1) according to any one of the preceding claims, in which the extraction device (17) comprises an extraction pipe (20) arranged inside the second cooler (3), said extraction pipe (20) extending substantially parallel to the second (3) cooler.

9. Cooling line (1) according to claim 8 in which the extraction pipe (20) and the second cooler (3) are substantially concentric.

10. Cooling line (1) according to any one of the preceding claims, in which the at least one grid (4) of the first cooler (2) is fixed. 1 1 . Cooling line (1) according to any one of the preceding claims, in which the first cooler (2) comprises at least one crusher (26) for crushing the granular solid materials.

12. Cooling line (1) according to claim 11 in which the first cooler (2) comprises a first portion (24) and a second portion (25), separated from each other by the crusher (26), the at least one fixed grid (4) of each portion (24, 25) being inclined so that the granular solid materials move under the effect of the Earth's gravity.

13. Method for cooling granular solid materials by means of a cooling line (1) according to any one of the preceding claims, in which it comprises the following operations: - circulation of at least a first flow (8) of air in the first cooler (2) through the at least one fixed grid (4), - circulation of a second flow (12) of air in the second cooler (3) produced in part by the air extraction circuit (19) connected to the material outlet (10), - extraction in the second cooler (3), of a first fraction (27) of the second flow (12) of air.

14. Cooling method according to claim 13 wherein the extraction step is carried out so as to leave only a second fraction (28) of the second air flow (12) in the second cooler (3).

15. Cooling method according to claim 14 wherein the second fraction (28) of the second air flow (12) is directed towards the first air flow (8) to be mixed therewith, said mixture being recovered for subsequent use by means (16, 30) for recovering said mixture.

16. Cooling method according to one of claims 14 or 15 in which the first flow (8) of air contributes to a part of the mixture of between 50% and 60%, and the second fraction (28) contributes a share of the mixture of between 40 and 50%.

17. Cooling method according to claim 16 wherein the first air flow (8) contributes a share of the mixture of approximately 55%, and the second fraction (28) contributes a share of the mixture of approximately 45%.

18. Cooling method according to one of claims 14 or 15 in which the first fraction (27) extracted from the second air flow (12) is between 65 and 80% of the second air flow (12).

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