FR3091661A1 - Grinding and drying device - Google Patents

Abstract

Device (1) for grinding and drying a material, in particular of mineral type, comprising: at least one grinding chamber (2); at least one entrance area (4); at least one line (7) for supplying a drying fluid to the inlet zone (4); at least one exit zone (9); at least a first branch (11) comprising an input (12) connected to the input zone (4) and an output (13) connected to the output zone (9); at least a second branch (17), comprising an inlet (18) connected to the line (7) for supplying the drying fluid, and an outlet (19) connected to the first branch (11), so that a part of the drying fluid is drawn into the first bypass (11) without entering the inlet zone (4) [Fig. 2]

Description

Grinding and drying device

The invention relates to a grinding and drying device, an installation comprising such a device, as well as to a process for grinding and drying a material implemented in such a device.

The invention relates to the field of material grinding, and more particularly the grinding and drying of mineral material, such as that used for the manufacture of cement, or the grinding and drying of a solid fuel such as petroleum coke or the coal.

Typically, clinker for making cement is obtained by firing a mineral material, itself being obtained by mixing materials such as clay and limestone.

Before firing the mineral material, it may require, and this is generally the case, to be dried and then ground before it can be fed into the clinker manufacturing process. Drying and grinding can be carried out in two separate devices. However, it is known to combine the two operations in a single drying and grinding device.

For example, the document FR2638105 proposes such a device called grinder-dryer, comprising successively a drying chamber and a pre-grinding chamber. A roller mill is combined with the mill-dryer to grind the pre-crushed and dried material. The material is introduced into the drying chamber of the mill-dryer with a hot gas. Once dried or partially dried, that is to say with a reduced humidity level, the material can be crushed more efficiently in the pre-crushing chamber, in this case by balls, then in the crusher, in this case by cylinders.

In order to increase the efficiency of the grinding, it is known that the particle size of the material to be ground must be controlled.

There is therefore a need for a drying and grinding solution overcoming the aforementioned drawbacks.

Technical problem

Indeed, in particular during ball milling as in the document FR2638105, too large a proportion of fine grains, that is to say of smaller size, has the effect of reducing the efficiency of the grinding.

In addition, the finest grains are also those with the highest moisture content. However, the speed of the drying gas in the dryer mill, and therefore the flow rate of drying gas, can only be increased up to a determined value, beyond which the drying gas degrades the grinding efficiency. Indeed, when the gas velocity is too high, it participates in the advancement of the material in the grinding chamber and causes the material to exit too quickly from the grinder, causing grains in suspension which should be ground, these grains escaping the grinding, so that the grinding is not carried out as desired. The drying gas at too high a speed can also be a source of obstruction of the partitions separating the successive drying and grinding chambers and can generate excessive pressure drops through these partitions. The consequences of these elements are a limitation of the drying potential of the known grinding-drying devices in a mill by attrition.

This known solution does not make it possible to optimize drying, in particular to increase the drying capacity of this type of pre-existing installation.

The invention improves this situation.

To this end, a first object of the invention is to propose a device and a method for grinding and drying a material in which the drying is optimized.

A second object of the invention is to provide a device and a method for grinding and drying a material in which the drying does not degrade the efficiency of the grinding.

A third object of the invention is to provide a device and a method for grinding and drying a material easily implemented on a pre-existing installation to increase its drying capacity.

A fourth object of the invention is to provide a device and a method for grinding and drying a material that does not or only slightly increase the costs of the installation.

The invention finds particular application for the grinding and drying of material of mineral type, in particular during the more general implementation of a cement clinker manufacturing process. The invention also finds an application for the grinding and drying of a solid fuel such as petroleum coke (“ petcoke ”) or coal.

Thus, according to a first aspect, the invention proposes a device for grinding and drying a material comprising:
- at least one grinding chamber comprising a material grinding system;
- at least one inlet zone, comprising at least one inlet for a drying fluid and an inlet for the material, the inlet zone being in communication with the grinding chamber so that the drying fluid and the material are brought into contact in the entry zone before passing, partly in the grinding chamber;
- at least one supply line for the drying fluid, adapted to be connected to a source of drying fluid and connected to the inlet for the drying fluid in the inlet zone;
- at least one exit zone comprising at least one exit for the drying fluid and an exit for the material, the exit zone being in communication with the grinding chamber so that the material and the drying fluid having passed through at least parts of the grinding chamber are recovered in the outlet area;
- at least a first bypass comprising an inlet connected to the inlet zone and an outlet connected to the outlet zone, so that a so-called fine part of the material is entrained by the drying fluid from the inlet zone to the exit zone without passing through the grinding chamber;
- at least one second bypass, comprising an inlet connected to the supply line for the drying fluid upstream of the inlet of the drying fluid in the inlet zone, and an outlet connected to the first bypass, so that part of the drying fluid is drawn into the first bypass without entering the inlet zone.

The combination of the first bypass and the second bypass allows effective and controlled drying of the material to be ground.

The characteristics exposed in the following paragraphs can, optionally, be implemented. They can be implemented independently of each other or in combination with each other:

According to one embodiment, the grinding system comprises a grinding system by attrition using grinding bodies. Such a grinding system is particularly suitable for grinding materials for the production of cement. Such materials require nearly complete drying before they can be incorporated into the downstream process.

According to one embodiment, the inlet zone comprises a system for controlling the quantity and/or the particle size of the fine part entrained in the first bypass, in order to control the quality of the drying. For this purpose, for example, the entry zone comprises a flight chamber connected to the material inlet so that the material passes through the flight chamber before entering the crushing chamber. The inlet to the first branch is connected to the flight chamber, and the control system includes a section restriction disposed in the flight chamber, downstream of the connection between the flight chamber and the first branch in the direction of material flow. Thus, the flow rate of the part of the drying fluid entraining the material in the first bypass is controlled. The section restriction may have an adjustable drying gas passage section making it possible to control the quantity and the particle size of the fine part entrained in the first bypass.

According to one embodiment, the second bypass advantageously comprises a system for regulating the flow rate of the drying fluid in the second bypass, making it possible in particular to adjust the flow rate according to drying needs.

According to one embodiment, the first bypass has an inverted V shape, limiting the problems of accumulation of material deposits.

According to one embodiment, the grinding and drying device comprises a drying chamber between the inlet zone and the grinding chamber

According to a second aspect, the invention proposes an installation for grinding and drying a material comprising a grinding and drying device as presented above. The installation also includes a selection system connected to the material outlet of the grinding and drying device. The selection system ensures in particular a selection between at least a so-called final fraction of the ground and dried material, whose particle size corresponds to a target particle size, and a so-called recirculated fraction, the selection assembly being connected to the inlet zone material to supply it with the recirculated fraction.

According to a third aspect, the invention proposes a method for grinding and drying a material using a grinding and drying device as presented above. The process may include:
- the supply of material to be ground and dried in the area of the grinding and drying device;
- the supply of drying fluid in the inlet zone of the grinding and drying device;
- entrainment of at least a so-called fine part of the material to be ground and dried from the entry zone into the first bypass by a first part of the drying fluid coming from the entry zone, up to the zone exit from the grinding and drying device, without passing through the grinding chamber, the other part of the material being carried separately into the grinding chamber where it is ground and dried by a second part of the drying fluid from the entrance area, separate from the first part;
- supplying the first branch with drying fluid comprising said first part of the drying fluid mixed with said at least one so-called fine part of the material to be ground and dried, as well as a third part of the drying fluid, separate from the first part and from the second part of the drying fluid, the said third part of the drying fluid being conveyed through the second bypass, without entering the inlet zone, joining the said first part of the drying fluid in the first derivation;
- the recovery of the material in the exit zone.

According to one embodiment (illustrated), the first part, the second part and the third part of the drying fluid can come from the same source of drying fluid, Alternatively these parts of the drying fluid, in this case the first and the second part, on the one hand, and the third part, on the other hand, can come from distinct sources of drying fluid (embodiment not illustrated).

According to one embodiment, said material to be ground is a mineral material or a solid fuel such as petroleum coke or coal.

The invention and the variants thereof can make it possible, in general, to optimize drying and to increase the drying capacity compared to the prior art known from FR2638105.

Other characteristics, details and advantages of the invention will appear on reading the detailed description below, and on analyzing the appended drawings, in which:

Fig. 1

is a schematic illustration of a grinding and drying device according to the state of the art.

Fig. 2

is a schematic illustration of a grinding and drying device according to an embodiment in accordance with the invention.

Fig. 3

is a schematic illustration of a grinding and drying installation comprising the device of Figure 2.

In what follows, the terms upstream and downstream, unless otherwise specified, must be understood in reference to the direction of movement of the material from upstream to downstream.

In Figure 1, there is shown schematically a device 100 for grinding and drying according to the state of the art. The device 100 comprises a drying chamber 101 in which the material 102 to be ground and dried arrives. Drying air 103 is also sent into the drying chamber 101. Downstream of the drying chamber 101, in the direction of movement of the material, the device 100 comprises a grinding chamber 104, in which grinding bodies 105, for example balls, ensure the grinding of the material. Finally, the crushed material passes into an outlet chamber 106, where it is recovered. The chambers 101, 104 and 106 are defined in a rotating drum 107 of the device 100, so as to ensure the advance of the material from the inlet chamber 101 to the outlet chamber 106. Grids 108 can be placed between the chambers 101, 104 and 106 in order in particular to retain the grinding bodies 105 in the grinding chamber 104.

In the drying chamber 101, the material comes into contact with the drying air, and most of the drying takes place in the drying chamber 101. The drying air passes through the grinding chamber 104 and the outlet chamber 106 where it is recovered for example to be cleaned. Although in FIG. 1 the material outlet and the air outlet from the outlet chamber 106 have been shown distinct from each other, they may be confused, the material/air separation taking place in a separation device. separation downstream of the grinding and drying device 100. More specifically, such a separation device may comprise a first stage making it possible to separate at least part of the material from the air, for example the largest particles of material. The air, then conveying the finest particles, can then be passed through at least one dust removal system in order to recover more material.

As presented in the introduction, a problem is that the flow of drying air that can be sent into the chambers 101, 104 and 106 is limited by the speed of movement of the material in the device 100. Consequently, the drying may be insufficient. .

In Figure 2, there is shown schematically a device 1 for grinding and drying according to one embodiment according to the invention. The grinding and drying device 1 is designed to dry and grind material, in particular of the mineral type, and finds a specific application in the grinding and drying of materials intended for the production of cement. Such a device can also make it possible to grind and dry a solid fuel such as petroleum coke or coal. The material which enters the grinding device 1 has an extended particle size spectrum, that is to say it comprises a mixture of particles which are fine enough not to have to be ground, and of particles which require grinding in order to be able to be used. for example for the production of cement.

According to the embodiment described, the device 1 comprises at least one grinding chamber 2 , for example in a rotating drum 3 . The grinding chamber 2 comprises a grinding system by attrition, using grinding bodies, such as balls. Optionally, a drying chamber can be formed in the rotating drum 3 upstream of the grinding chamber 2, as in the state of the art. The drying chamber can be made in the same rotating drum 3 as the grinding chamber 2, or as a device attached to the drum 3.

The device 1 comprises at least one inlet zone 4 , which zone 4 comprises an inlet 5 for a drying fluid, such as air, and an inlet 6 for the material to be dried and ground. The input zone 4 is in communication with the rotating drum 3, and more precisely with the grinding chamber 2, or possibly the drying chamber. The material and the drying fluid are thus brought into contact with each other in the entry zone 4 before entering the drum 3.

The inlet zone 4 may comprise both at least one rotating part mounted integral in rotation with the drum 3 and at least one fixed (non-rotating) part carrying said inlet 5 for the drying fluid and said inlet 6 for the material. to dry. A device is provided between the fixed part and the rotating part, having the function of limiting false air inlets between said fixed part and said rotating part.

The device 5 further comprises a pipe 7 for supplying the drying fluid, which is connected on the one hand to a source 8 of drying fluid and on the other hand to the inlet 5 of the fluid in the zone 4 of Entrance.

The device 1 also comprises an exit zone 9 , in communication with the grinding chamber 2 so that the crushed material is moved to the exit zone 9. Output zone 9 then comprises an output 10a for the drying fluid and an output 10b for the material.

The outlet zone 9 can comprise both at least one rotating part mounted integral in rotation with the drum 3 and at least one fixed (non-rotating) part carrying said outlet 10a for the drying fluid and outlet 10b for the material. A device is provided between the fixed part and the rotating part, having the function of limiting false air inlets between said fixed part and said rotating part.

Without this being explained any further in the rest of the description, it is understood that the drying fluid, once in contact with the material, can entrain the finest particles. Thus, although we speak in the following of drying fluid, it is understood that it may be a mixture of the drying fluid and particles of matter.

In order to increase the drying efficiency by selectively drying the thin part, the device 1 comprises a first bypass 11 . The first bypass comprises an inlet 12 connected to the inlet zone 4 and an outlet 13 connected to the outlet zone 9, so that the drying fluid partly passes through the first bypass 11, from the inlet zone 4 to the exit zone 9, without passing through the grinding chamber 2. Said input 12 can be embedded on the fixed part of the input zone 4 and said output 13 can be embedded on the fixed part of the zone 9, in the case of the rotating drum 3, so that the first bypass 11 is fixed .

Although the inlet zone 4 and the outlet zone 9 respectively are represented in FIG. 2 as directly located respectively upstream and downstream of the grinding chamber 2, they generally denote respectively the entire zone upstream and the entire the area downstream of the grinding chamber. In particular, the outlet 10a for the drying fluid, entraining the finest particles, may be a pipe connected to a downstream material/drying fluid separation device so as to recover the finest particles, as will be explained. further away. The outlet 13 of the first bypass 11 can then be connected to the pipe of the outlet 10a for the drying fluid, upstream and as close as possible to the material/drying fluid separation device.

The drying fluid passing through the first bypass 11 carries with it a so-called fine part of the material, that is to say the particles of smaller dimensions, which therefore do not pass through the grinding chamber 2 either. The thin part entrained in the first bypass 11 is thus effectively dried. Indeed, the quantity of drying fluid sent to the inlet zone 4 to dry the material can be greater than in the state of the art in which all of the drying fluid passes through the grinding chamber.

More precisely, and according to the embodiment of FIG. 2, the entry zone 4 comprises a system 14 for controlling the quantity and/or the particle size of the fine part entrained in the first diversion. For this purpose, the entry zone 4 comprises a flight chamber 15 connected to the material inlet 6, into which the material falls under the effect of gravity. The inlet 12 of the first bypass 11 is connected to the flight chamber 15. A section restriction 16 is arranged in the flight chamber 15, downstream of the inlet 12 of the first bypass in the direction of flow, in this case downhill, of the material in the flight chamber 15 .

Thus, the drying fluid entering the inlet zone 4 is partly driven into the flight chamber 15 according to a flow rate controlled by the section restriction 16. The flow rate of drying fluid driven into the flight chamber allows to adjust the quantity and/or the particle size of the thin part entrained in the first bypass 11. The section restriction 16 can be adjustable on the flight chamber 15, or can be pre-dimensioned according to predefined choices concerning the thin part.

It should be noted that in the flight chamber 15, the material circulates in a downward direction, under the effect of gravity, while the drying fluid circulates against the current of the material, i.e. say in the upward direction. As a result, the thin part is advantageously suspended in the drying fluid in the flight chamber 15, promoting its entrainment in the first bypass 11.

The material that is not entrained in the first bypass 11 continues the journey through the possible drying chamber and through the grinding chamber 2 where it undergoes a grinding stage as expected. The crushed material is moved to the exit zone 9, where the material having passed through the first bypass 11 joins it.

However, the drying of the thin part in the first bypass 11 may, when for example the material entering the device 1 is very wet, not be sufficient. As before, the flow rate of drying fluid at the inlet 5 of the inlet zone 4 is limited by the speed of advance of the material. It is also limited in the flight chamber 15, because if the flow rate is too high, the drying fluid can entrain coarse particles in the first bypass 11, which must pass through the grinding chamber.

Thus, the device further comprises a second bypass 17 , directly connecting the pipe 7 for supplying the drying fluid to the first bypass 11, so as to be able to increase the flow rate of drying fluid in the first bypass 11 without increasing the flow rate. of drying fluid passing through the grinding chamber 2 or the flow of drying fluid in the entry zone 4, that is to say in this case in the flight chamber 15 .

More specifically, the second bypass 17 comprises an inlet 18 connected to the pipe 7 for supplying drying fluid, upstream of the inlet 5 of drying fluid in the inlet zone 4, and an outlet 19 connected to the first branch 11, so that part of the drying fluid is drawn into the first branch 11 without entering the zone 4 of entry.

The outlet 19 of the second bypass 17 is arranged as close as possible to the inlet 12 of the first bypass 11, so that the drying fluid provided by the second bypass 17 comes into contact with the thin part drawn into the first bypass 11 as soon as possible.

Advantageously, the second branch 17 is provided with a system 20 for regulating the flow rate of the drying fluid in the second branch 17 in order to adjust the additional drying energy supplied by the second branch 17 into the first branch 11.

The device 1 thus described comprising the two bypasses 11 and 17 makes it possible to increase the efficiency of the drying of the material which enters the device 1, without disturbing the grinding process in the grinding chamber 2.

The device 1 can be integrated into a more complete installation 21 (FIG. 3), in which the device 1 is associated with a selection system 22 making it possible to recirculate the material to the grinding and drying device 1, in order to improve the grinding efficiency. More precisely, the selection system 22 makes it possible to operate a particle size selection, for example by aeraulics. It is connected to the material outlet 10b of the device 1, for example via an elevator. The drying fluid leaving the grinding and drying device 1 can be sent to the selection system 22, so as to carry out the aeraulic selection and to recover the particles present in the exiting drying fluid.

As a variant, the drying fluid leaving the grinding and drying device 1 can be sent to a separate system making it possible to recover the fines, and the aeraulic selection system 22 is supplied with fluid by another source. This variant makes it possible in particular to decorrelate the drying by the drying fluid and the particle size selection, simplifying the control.

As a further variant, the outlet 10a for the drying fluid and the outlet 10b for the material are combined, so that all of the material and the drying fluid is sent to the selection system 22.

The selection system 22 makes it possible to separate the ground and dried material into at least two fractions: a so-called final fraction 23 , whose particle size corresponds to a target particle size, to be sent to the rest of the process, in particular for the manufacture of cement, and a so-called recirculated fraction 24 , which is returned to the grinding and drying device 1, to the inlet zone.

Claims (10)

Device (1) for grinding and drying a material comprising:
- at least one grinding chamber (2) comprising a material grinding system;
- at least one inlet zone (4), comprising at least one inlet (5) for a drying fluid and an inlet (6) for the material, the inlet zone (4) being in communication with the chamber ( 2) grinding so that the drying fluid and the material are brought into contact in the entry zone (4) before passing, in part, into the grinding chamber (2);
- at least one line (7) for supplying the drying fluid, capable of being connected to a source (8) of drying fluid and connected to the inlet (5) for the drying fluid in the zone (4) input;
- at least one outlet zone (9) comprising at least one outlet (10a) for the drying fluid and one outlet (10b) for the material, the outlet zone (9) being in communication with the chamber (2) of grinding so that the material and the drying fluid having passed through at least part of the grinding chamber (2) are recovered in the outlet zone (9);
- at least one first branch (11) comprising an input (12) connected to the input zone (4) and an output (13) connected to the output zone (9), so that a so-called thin part of the material is entrained by the drying fluid from the inlet zone (4) to the outlet zone (9) without passing through the grinding chamber (2);
- at least one second bypass (17), comprising an inlet (18) connected to the pipe (7) for supplying the drying fluid upstream of the inlet (5) of the drying fluid in the zone (4) d inlet, and an outlet (19) connected to the first bypass (11), so that part of the drying fluid is drawn into the first bypass (11) without entering the inlet zone (4). Device (1) according to Claim 1, in which the grinding system comprises an attrition grinding system using grinding bodies. Device (1) according to any one of Claims 1 or 2, in which the entry zone (4) comprises a system (14) for controlling the quantity and/or the particle size of the fine part entrained in the first diversion (11). Device (1) according to Claim 3, in which the entry zone (4) comprises a flight chamber (15) connected to the material entry (6) so that the material passes through the chamber (15) d flight before entering the grinding chamber (2), in which the inlet (12) of the first bypass (11) is connected to the flight chamber (15), and in which a section restriction ( 16) is arranged in the take-off chamber (15), downstream of the connection between the take-off chamber (15) and the first bypass (11) in the direction of circulation of the material, so that the flow rate of the part of the drying fluid entraining the material in the first bypass (11) is controlled. Device (1) according to Claim 4, in which the section restriction (16) is of adjustable section. Device (1) according to any one of the preceding claims 1 to 5, in which the second bypass (17) comprises a system (20) for regulating the flow rate of the drying fluid in the second bypass (17). Device (1) according to any one of the preceding claims 1 to 6, comprising a drying chamber between the inlet zone (4) and the grinding chamber (2). Plant (21) for grinding and drying a material comprising a grinding and drying device (1) according to any one of the preceding claims 1 to 7, and comprising a selection system (22) connected to the outlet ( 10b) of material from the grinding and drying device (1), the selection system (22) ensuring a selection between at least one so-called final fraction (23) of the ground and dried material, the particle size of which corresponds to a target particle size , and a so-called recirculated fraction (24), the selection assembly being connected to the material inlet zone (4) to supply it with the recirculated fraction (24). Method of grinding and drying a material using a grinding and drying device (1) according to any one of Claims 1 to 7, comprising:
- the supply of material to be ground and dried in the zone (4) of the device (1);
- the supply of drying fluid in the inlet zone (4) of the device (1);
- entrainment of at least a so-called fine part of the material to be ground and dried from the entry zone (4) into the first bypass (11) by a first part of the drying fluid coming from the entry zone (4), as far as the outlet zone (9) of the grinding and drying device (1), without passing through the grinding chamber (2), the other part of the material being driven separately into the grinding chamber (2) where it is ground and dried by a second part of the drying fluid coming from the inlet zone (4), distinct from the first part;
- supplying the first bypass (11) with drying fluid comprising said first part of the drying fluid mixed with said at least one so-called fine part of the material to be ground and dried, as well as a third part of the fluid drying fluid, distinct from the first part and from the second part of the drying fluid, the said third part of the drying fluid being conveyed through the second bypass (17) without entering the inlet zone (4), joining the said first part of the drying fluid in the first bypass (11)
- the recovery of the material in the area (9) output. A method according to claim 9 wherein said material to be ground is mineral material or solid fuel.