METHOD FOR DISSOCIATING DIFFERENT CONSTITUENTS OF A HETEROGENEOUS ARTIFICIAL MATERIAL

Abstract

Method for dissociating different constituents of a heterogeneous artificial material, comprising the fragmentation of the material in a fragmentation machine (1) by material-bed compression, the machine (1) comprising at least one vibrator (8a, 8b, 8c, 8d) and a system (11) for controlling at least one parameter of the fragmentation force from the speed of rotation of the vibrator(s) (8a, 8b, 8c, 8d) and the phase shift angle between at least two vibrators (8a, 8b, 8c, 8d); the method being characterised in that the control system adjusts a rotation parameter of the vibrators (8a, 8b, 8c, 8d) so as to generate a fragmentation force by the machine (1) allowing to at least partially dissociate at least one of the constituents of the material from the other constituents.

Claims

1. A method for dissociating different constituents of heterogeneous artificial material, the method comprising the fragmentation of the material in a fragmentation machine (1) by material-bed compression under the effect of a fragmentation force, the machine (1) including: a tank (3) forming an internal fragmentation track (3a) about a longitudinal axis of the machine (1); a hub (5) forming an external fragmentation track (5a) about a longitudinal axis of the machine (1), the hub (5) being placed inside the tank (3); at least one vibrator (8a, 8b, 8c, 8d), rotated about a longitudinal axis of the machine (1), and connected to one or the other of the tank (3) and the hub (5); the method comprising: rotating the vibrator(s) (8a, 8b, 8c, 8d) of the fragmentation machine (1), such that the tank performs a movement in a transverse plane of the machine (1) relative to the hub (5); feeding the fragmentation machine (1) with material to be fragmented; fragmenting the material between the external fragmentation track (5a) and the internal fragmentation track (3a); the method being characterised in that the fragmentation machine comprises a system (11) for controlling at least one parameter of the fragmentation force from the speed of rotation of the vibrator(s) (8a, 8b, 8c, 8d) and the phase shift angle between at least two vibrators (8a, 8b, 8c, 8d); and this control system adjusts at least one rotation parameter of the vibrators (8a, 8b, 8c, 8d) so as to generate a fragmentation force by the machine (1) allowing to at least partially dissociate at least one of the constituents of the material from the other constituents.

2. The method according to claim 1, wherein the hub (5) is of a substantially conical shape and wherein the machine (1) comprises: a frame (2) intended to rest on the floor, the hub (5) being supported by the frame (2); a chassis (4) movable in translation at least in a transverse plane of the machine (1) relative to the frame (2), the tank being mounted on the movable chassis (4); at least one vibrator (8a, 8b, 8c, 8d) mounted on the chassis (4), and rotated about a longitudinal axis of the machine (1).

3. The method according to claim 1, wherein the hub (5) is of a substantially conical shape and wherein the machine (1) comprises: a frame (2) intended to rest on the floor, the hub (5) being supported by the frame (2); a chassis (4) movable in translation at least in a transverse plane of the machine (1) relative to the frame (2), the tank being mounted on the movable chassis (4), at least two vibrators (8a, 8b, 8c, 8d) mounted on the chassis (4), each vibrator (8a, 8b, 8c, 8d) being rotated about a longitudinal axis of the machine (1) by a motor (10), each motor (10) driving the vibrator (8a, 8b, 8c, 8d) to which it is associated independently of each other; a device for managing the motors (10) and a device for measuring the relative phase shift angle between the vibrators; method wherein the at least one rotation parameter of the vibrators (8a, 8b, 8c, 8d) adjusted by the control system is the relative phase shift angle between the vibrators (8a, 8b, 8c, 8d).

4. The method according to any one of the preceding claims wherein the at least one rotation parameter of the vibrators (8a, 8b, 8c, 8d) is adjusted in the following manner: determining in the material to be fragmented a target ratio between at least one constituent and the other constituents; recovering the fragmented material at the output of the fragmentation machine (1); determining at least one sorting criterion allowing to separate the at least one constituent from the other constituents; subjecting the fragmented material to a sorting by means of said sorting criterion determined so as to recover at least two fractions; determining an actual ratio between the at least two fractions; adjusting the at least one rotation parameter of the vibrators (8a, 8b, 8c, 8d) according to the difference between the target ratio and the actual ratio.

5. The method according to any one of the preceding claims, wherein the at least one rotation parameter of the vibrators (8a, 8b, 8c, 8d) is adjusted in the following manner: determining at least one property of at least one constituent of the material; from said determined property, calculating a target force allowing to dissociate the at least one constituent from the other constituents; adjusting the at least one rotation parameter of the vibrators (8a, 8b, 8c, 8d) to obtain the target force.

6. The method according to any one of the preceding claims, wherein all or part of at least one fraction of the fragmented material is recovered which is recirculated to feed the fragmentation machine (1).

7. The method according to claim 6, further comprising the following steps: determining at least one target flattening coefficient for at least one constituent of the material to be fragmented; recovering said at least one constituent after fragmentation; measuring said flattening coefficient of said at least one constituent; adjusting the flow rate and/or the granulometry range of the at least one fraction recirculated depending on the difference between the determined flattening coefficient and the measured flattening coefficient.

8. The method according to claim 6 or claim 7, further comprising the following steps: determining a cleaning rate for at least one constituent of the material to be fragmented; recovering said at least one constituent after fragmentation; measuring said cleaning rate of said at least one constituent; adjusting the flow rate and/or the granulometry range of the at least one fraction recirculated depending on the difference between the determined cleaning rate and the measured cleaning rate.

9. The method according to any one of the preceding claims, wherein the material to be fragmented is concrete and comprises a first constituent called gravel and a second constituent called mortar, the gravel being trapped in the mortar, the method comprising determining a target fragmentation force generating a constraint in the bed-material greater than or equal to the compressive strength of the concrete.

10. The method according to any one of the preceding claims, wherein the material to be fragmented is concrete and comprises a first constituent called gravel and a second constituent called mortar, the gravel being trapped in the mortar, the method comprising: recovering gravel and mortar at the output of the fragmentation machine; subjecting the gravel and mortar to a sorting between particles called coarse particles of a size greater than a given value corresponding to the minimum expected size of the gravel and particles called fine particles of a size less than said given value.

11. The method according to claim 10, further comprising the following step: subjecting the fine fraction to a second sorting to separate, on the one hand, particles of a size greater than a second given value corresponding to the minimum expected size for sand, and on the other hand, the particles of a size less than said second given value.

12. The method according to claim 10 or claim 11, further comprising the following step: subjecting the fine fraction to a second fragmentation step and to a sorting step to separate particles of a size greater than a second given value corresponding to the minimum expected size for sand and the particles of a size less than said second given value.

Description

[0072] Other effects and advantages of the invention will become apparent in light of the description of embodiments accompanied by figures wherein:

[0073] FIG. 1 is a schematic representation, in top view, of a fragmentation machine for implementing an embodiment of the method according to the invention.

[0074] FIG. 2 is a sectional view along line II-II of the machine of FIG. 1.

[0075] FIG. 3 is a schematic representation of different steps of an embodiment of the method according to the invention.

[0076] FIG. 4 is an illustration showing an example of a heterogeneous material.

[0077] FIGS. 1 and 2 show an example of a fragmentation machine 1 for a heterogeneous artificial material by material-bed compression adapted for implementing the method according to the invention. Fragmentation by material-bed compression is particularly, but not exclusively, adapted for the fragmentation of mineral materials.

[0078] Heterogeneous material here means a material comprising several constituents interconnected so as to form a block. In other words, by considering one of the constituents, it can be seen as being trapped in a matrix formed from the other constituents.

[0079] Generally, the constituents of a heterogeneous material can be distinguished according to their properties, for example their dimensions, their shape, their porosity, their wear resistance, their compressive strength or their hardness.

[0080] For the sake of simplification, the following description relates to the example of cement concrete as a heterogeneous artificial material, it being understood that the method which is the subject of the invention is not limited to this example. Thus, in what follows, it is considered that the cement concrete comprises aggregate particles trapped in the cement paste. The aggregate particles meet established criteria, such as those established in standard EN12620, and thus comprise gravel particles and sand particles, it being expected that the gravel particles are larger in size than those of the sand particles. Commonly, the mixture of sand and cement paste is called mortar, the mortar trapping the gravel.

[0081] The fragmentation machine 1 comprises in particular a frame 2, intended to rest directly on the floor, or indirectly via a movable platform resting on the floor. In addition, the machine 1 comprises a tank 3, the inner surface of which forms an interior fragmentation track 3a. The tank 3 is mounted on a chassis 4 which is movable in translation relative to the frame 2 at least in a transverse plane, which is in practice substantially the horizontal plane. To this end, the chassis 4 is mounted on the frame 2 via elastic studs 4a, deforming elastically both transversely and longitudinally to limit the transmission of vibrations to the frame 2. A hub 5, the outer surface of which forms an external fragmentation track 5a, is placed inside the tank 3. Preferably, the hub 5 is mounted on a shaft 6 extending along a longitudinal axis A, which is in practice substantially vertical, and supported by a secondary frame 2a. The secondary frame 2a is suspended from the chassis 4.

[0082] In what follows, longitudinal designates any axis parallel to the longitudinal axis A of the shaft 6, and transverse designates any direction perpendicular to the longitudinal axis A.

[0083] According to the machine of the example of FIGS. 1 and 2, and without limitation, the hub 5 is of a substantially conical shape. More specifically, the external track 5a describes a surface of revolution about the longitudinal axis A which is substantially conical, widening downwards. In this case, and advantageously, the internal track 3a also describes a surface which is substantially conical around a longitudinal axis, widening upwards.

[0084] The machine 1 is of the inertia type and to this end comprises a device 7 for vibrating the tank 3 relative to the frame 2 in a transverse plane. Thus, under the effect of the vibrating device 7, the tank 3 displaces in a transverse plane relative to the hub 5, so that the material is subjected to a fragmentation pressure between the internal track 3a and the external track 5a. According to one embodiment, the vibrating device 7 comprises at least one unbalance-type vibrator whose rotation about a longitudinal axis generates the movement of the tank 3 relative to the hub 5 in a transverse plane. Preferably, the vibrating device 7 comprises at least two vibrators.

[0085] More specifically, vibrator means here any device whose mass is not perfectly distributed over a volume of revolution and thus generates an unbalance force by rotation.

[0086] According to an embodiment which is that of the figures, the vibrating device 7 comprises four vibrators 8a, 8b, 8c, 8d distributed in a square on the chassis 4. Each vibrator 8a, 8b, 8c, 8d can be formed of two parts distributed on either side of a substantially transverse plane of the chassis 4, so that the vibrations of the tank 3 caused by the rotation of the vibrators 8a, 8b 8c, 8d remain substantially in this transverse plane. Each vibrator 8a, 8b, 8c, 8d is fixed on a shaft 9a, 9b, 9c, 9d with a longitudinal axis vibrator rotated relative to the chassis 4 by a motor 10, whose motors 10 of the vibrator shafts 9a, 9b are visible in FIG. 2. Thus, when the vibrators are rotated, the tank 3 is vibrated and describes a circular translational movement in a transverse plane.

[0087] Each motor 10 drives the corresponding vibrator independently of the other vibrators. More specifically, each motor 10 drives the position and the speed of rotation of the corresponding vibrator. Thanks to one or more sensors, it is possible to know at any time the position of each of the vibrators, and therefore to adjust the relative angular position between two vibrators, also called phase shift. Thus, each motor 10 is connected to a motor management device 10 so as to adjust the speed of rotation of the vibrators 8a, 8b, 8c, 8d. The machine 1 further comprises a device for measuring the relative phase shift angle between the vibrators 8a, 8b, 8c, 8d, which is connected to the motor management device 10 so as to control the phase shift between the vibrators 8a, 8b, 8c, 8d.

[0088] According to a variant, not shown in the figures, the vibrating device 7 comprises two vibrators rotated by a common motor and about the same longitudinal axis. The phase shift between the two vibrators, that is to say the relative angular position around their axis of rotation, is adjustable, for example manually when the machine is stopped or automatically during operation of the machine.

[0089] It is then possible to precisely adjust the force called the fragmentation force deployed by the fragmentation machine 1, that is to say the force deployed between the internal track 3a and the external track 5a by adjusting the rotation parameters of the vibrators. Indeed, in the fragmentation machine 1, the relative whose movement between the external fragmentation track 3a and the internal fragmentation track 5a is obtained by implementing a vibrator, the force deployed by the machine depends in particular on the frequency and the intensity of the vibrations, which in turn depend in particular on the speed of rotation of the vibrator, but also, when there are at least two vibrators, on the phase shift between the at least two vibrators.

[0090] Thus, the machine 1 further comprises a system 11 for controlling at least one parameter of the fragmentation force from the speed of rotation of the vibrator(s) and the phase shift angle between at least two vibrators. The fragmentation force implemented by the fragmentation machine 1 can thus be adjusted by adjusting the vibrators so as to release the aggregate from the concrete.

[0091] More specifically, it is possible to directly or indirectly determine a target force, or a range of values of the target force, of fragmentation to obtain the dissociation of the constituents of the material.

[0092] More generally, the fragmentation machine 1 with the fragmentation force adjusted as described allows to at least partially dissociate one constituent from the other constituents of the starting heterogeneous material, and to recover the original constituent in question. At least partially dissociate means here that at least part of the constituent in question is no longer trapped in the matrix formed by the other constituents, but is released. In the example of concrete, the fragmentation force thus allows to release, for example, the gravel particles from the mortar. In other words, the majority, if not all, of the gravel particles are individualised. Fragments of mortar may remain attached to the surface of the gravel particles, or may still connect gravel particles together. However, the amount of particles that are still interconnected by mortar is much less than the amount of individualised particles. Gravel particles may have been fragmented under the effect of the fragmentation force, but for a minority of the gravel particles. In other words, the gravel particles released and recovered are, for the most part, the original gravel particles, that is to say, those that were in the original concrete.

[0093] For example, to dissociate gravel from mortar, the target fragmentation force can be determined by theoretical calculation. Indeed, the compressive strength of the mortar is generally less than that of the gravel, so that it is possible to calculate a target fragmentation force allowing to break the mortar while limiting, or even avoiding, the fragmentation of the gravel. Generally, the target fragmentation force can be determined from the features of the constituents of the material to be fragmented.

[0094] It is also possible to calculate a target force corresponding to the bonding force between the gravel particles and the mortar, the target fragmentation force being greater than the bonding force but less than the limit compressive force of the gravel.

[0095] It is also possible to determine the target fragmentation force experimentally, on a sample of the initial concrete.

[0096] According to one embodiment, the target fragmentation force is reached by iteration, starting from an initial force of the machine and regulating it by acting on the speed of rotation of the vibrators or by acting on the phase shift between the vibrators until obtaining the dissociation between gravel and mortar.

[0097] For example, the fragmentation force is regulated from the ratio between gravel and mortar. Indeed, the proportion between gravel and mortar for a type of concrete is generally known. Thus, it is possible to determine a theoretical ratio depending on the type of concrete feeding the fragmentation machine 1. Once the concrete is fragmented in the machine 1, the fragmented material is recovered, and it is subjected to sorting according to a criterion allowing to separate the gravel from the mortar. Typically, the sorting can be a screening with a criterion on the size of the particles adapted to the recovery of the gravel, the particles of which are of sizes greater than those of the mortar. Two fractions are thus obtained after screening. By determining an actual ratio between these two fractions and comparing it with the theoretical ratio, the fragmentation force deployed by the machine can be regulated by approaching the actual ratio to the theoretical ratio.

[0098] It is also possible to use a criterion other than that of the ratio between gravel and mortar. For example, the presence of mortar implies an absorption of water all the more significant as the amount of mortar is significant. Thus, by evaluating at the output of the fragmentation machine 1 and after sorting, the amount of water absorbed by the fraction supposed to comprise the gravel, an evaluation of the amount of mortar which remains attached to the gravel is obtained, and the fragmentation force of the fragmentation machine 1 can be adjusted accordingly.

[0099] The adjustment of the fragmentation force by the speed or the phase shift of the vibrators 8a, 8b, 8c, 8d on the machine 1 as shown above allows to carry out a particularly reactive method, the fragmentation force deployed by the machine being modified in few seconds, without having to stop the machine or the material feed. Furthermore, thanks to the adjustment of the speed and phase shift of the vibrators 8a, 8b, 8c, 8d, it is possible to obtain a wide range of values for the fragmentation force deployed by the machine 1.

[0100] However, the method can be implemented on any material-bed compression and inertial fragmentation machine wherein the speed and/or the phase shift of the vibrators are manually or automatically adjustable during operation of the machine or at stop.

[0101] FIG. 3 illustrates an example of the implementation of the method according to the invention on the machine 1 presented above.

[0102] More specifically, the material 12 to be fragmented comprises at least two constituents, as schematically illustrated in FIG. 4. According to the example of concrete which is described here, the material 12 to be fragmented comprises a matrix 120 composed of the mortar, that is to say a mixture of sand and cement paste, and gravel particles 121 trapped in the mortar, that is to say that the surface of the gravel particles 121 is bonded to the mortar.

[0103] The material 12 passes between the internal fragmentation track 3a and the external fragmentation track 5a. The pressure exerted by the material bed on the mortar and the gravel allows to break the bond between the gravel particles and the mortar, releasing the gravel. The fragmented material is then subjected to sorting in a sorting device 13, for example based on size, it being expected that the gravel particles are of a size greater than those of the mortar. At the output of the sorting device 13, two fractions are recovered: a first fraction 14 comprising the particles of larger size, and called coarse fraction, and a second fraction 15 comprising the finer particles, called fine fraction.

[0104] The coarse fraction 14 thus comprises the gravel released from the mortar, and preferably gravel for the most part relative to the mortar. More specifically, mortar can stick to some gravel particles. However, by the flexibility of the fragmentation force adjustment of the machine, it is possible to determine an acceptable rate for the presence of mortar in the coarse fraction 14. Generally, the proportion of mortar varies between 10% and 70% by mass in the concrete feeding the fragmentation machine 1. After fragmentation, the coarse fraction can then contain less than 10% and preferably less than 5% by mass of mortar.

[0105] The fine fraction 15 then comprises mainly, and preferably exclusively, mortar which is in turn a mixture of sand and cement paste. Thus, in order to recover the sand, the fine fraction 15 can be sent to a second fragmentation machine 16, substantially similar to the machine 1 already described above, in order to dissociate the sand from the cement paste. As previously, the material recovered at the output of the second fragmentation machine 16 is subjected to sorting in a second sorting device 17 with a sorting criterion adapted for the separation between the sand and the cement paste. The passage in the second fraction machine 16 is optional, because it is possible that all the aggregate, that is to say the sand and the gravel, has already been sufficiently dissociated from the cement paste in the first fragmentation machine 1 so that the fine fraction 15 can be sent directly to the second sorting device 17. The sorting criterion can again be based on the size. Two fractions are then recovered again, namely a fraction comprising particles of a size greater than a given value corresponding to the minimum size expected for sand and another fraction comprising particles of a size smaller than this given value.

[0106] According to one embodiment, all or part of the fragmented material is recirculated, that is to say after it has passed through the fragmentation machine 1, in particular in order to homogenise the compression forces by multiplying the compression points on the gravel particles and therefore limit the production of particles with a particle size smaller than the expected particle size of the gravel.

[0107] More specifically, for example, part of the fragmented material is recovered directly from the output of the fragmentation machine 1 and returned to the feed of the machine 1.

[0108] Alternatively or in combination, the fragmented material is subjected to a sorting step, and all or part of one or more fractions recovered after sorting is returned to the feed of the machine 1.

[0109] In addition, the recirculation of a fraction to the machine 1 can be performed to improve what is called the flattening coefficient. The flattening coefficient allows to characterise the shape of particles, in particular for gravel particles in the field of cement concrete. However, this notion can be extended to all heterogeneous artificial materials. The flattening coefficient in particular gives an indication on the fragility of the gravel. Indeed, the more the shape is elongated and flat, the more the particle is fragile, ultimately making the concrete fragile. Thus, the higher the flattening coefficient, the more fragile the particles. Therefore, it is possible to determine a target value, or in any case a maximum value, for the expected flattening coefficient, for example for the gravel at the output of the machine. By measuring the flattening coefficient of the gravel after fragmentation, it is then possible to adjust the flow rate and/or the granulometry range of each fraction recirculated depending on the difference between the determined flattening coefficient and the measured flattening coefficient.

[0110] In addition, the recirculation, in particular of the fine fraction 15 in the case of concrete, can also promote the phenomenon of attrition, in particular on the mortar stuck to the gravel particles in the case of concrete, so as to improve the release of the gravel. For example, a cleaning rate can be defined which characterises the amount of mortar remaining attached to the gravel particles. For example, this may be the mass of mortar that is recovered by different techniques, such as scraping or chemical cleaning, on a sample of gravel particles. The cleaning rate can also be defined from the water demand. Thus, it is possible to determine a cleaning rate to be achieved, then to measure this cleaning rate on the gravel after fragmentation. The flow rate and/or the granulometry range of each recirculated fraction are then adjusted depending on the difference between the determined cleaning rate and the measured cleaning rate.

[0111] Alternatively or in combination, an adjuvant can be added to the feed of the fragmentation machine 1 in order to facilitate the dissociation between the gravel and the mortar. The adjuvant can have the effect, for example, of weakening the bond between the mortar and the gravel, or of preventing particles, both gravel and mortar, from clumping together, thus facilitating any screening.

[0112] The fragmentation machine 1 can easily be adjusted so as to obtain the desired result. The method thus allows to reliably obtain a fraction comprising gravel that can be used directly in the formulation of new concrete, without an additional cleaning step. The machine also allows to recover a fraction comprising sand and a fraction comprising cement paste, which can in turn be reused in the formulation of new concrete.

[0113] Although the description relates to the example of cement concrete, in particular thanks to the flexibility in the adjustment of the fragmentation force, the method can be implemented on any heterogeneous artificial material.