EP4467241A1 - Method for separating particles to be recycled - Google Patents

Abstract

A method of separating particles to be recycled comprising the following steps: (E1) providing a base material (1) comprising a plurality of particles, (E2) extracting a dense fraction (3) from the base material (1), the extraction being carried out by wetting and centrifuging the base material (1) in a hydrocyclone (5) then by removing the dense fraction (3) by sampling at a low point of the hydrocyclone (5), and (E3) separating the particles of the dense fraction (3) from the base material (1) on a vibrating table (9).

Description

Technical field

The present invention relates to a method for separating particles to be recycled. The particles are, for example, derived from composite material grinding activities.

Prior art

It is known to recover electrical cables and in particular telecommunications cables containing copper for recycling. This activity consists of separating by crushing, granulation, and densimetric table the elements constituting these cables.

This arrangement is satisfactory in that it allows the recovery of raw materials such as metallic particles like copper and aluminum, and non-metallic particles made of various plastic materials.

However, there is a difficulty in ensuring a quality separation between the various fine metal and non-metal particles and in obtaining a perfect separation of recycled materials. It is therefore common for non-metal materials resulting from separation to contain a residual quantity of metals of between 3 and 7%. The quantity of composite material less than 1 mm resulting from the recycling of copper cables is of the order of 14 to 18% of the volume of cable processed. In France, this ratio represents approximately 15,000 tonnes of composite waste, which corresponds to a deposit of approximately 950 tonnes of copper to be extracted from such waste.

There is therefore a need to improve the purity of composite recycling by-products, and in particular the recycling process of copper and aluminium cables. Indeed, it is desirable to improve the recycling of plastics, to recover residual metals and to limit environmental pollution by heavy metals.

Summary

• disposer d'une matière de base comprenant une pluralité de particules, chaque particule présentant une densité apparente propre qui est fonction d'une forme et d'une densité de matière de la particule,
• extraire une fraction dite « dense » de plus grande densité, de la matière de base, l'extraction étant réalisée par mouillage et centrifugeage de la matière de base dans un hydrocyclone, puis par prélèvement de la fraction dense en un point bas de l'hydrocyclone,
• séparer les particules de la fraction dense de la matière de base sur un plateau d'une table vibrante, la fraction dense de la matière de base étant disposée en un emplacement haut du plateau, le plateau présentant une pente s'étendant selon une direction d'extension entre l'emplacement haut et un emplacement bas du plateau, l'emplacement bas comportant une sortie basse pour recueillir une portion des particules de la fraction dense de densités apparentes les plus faibles, un écoulement d'eau suivant la direction d'extension déplaçant la portion dans le sens de la pente vers l'emplacement bas, la table vibrante comprenant une sortie latérale pour recueillir une seconde portion des particules de la fraction dense, de densités apparentes les plus élevées, la seconde portion étant déplacée vers la sortie latérale par vibration du plateau.

Embodiments relate to a method of separating particles to be recycled comprising the following steps:

• having a base material comprising a plurality of particles, each particle having an apparent density of its own which is a function of a shape and a material density of the particle,
• extract a so-called "dense" fraction of greater density from the base material, the extraction being carried out by wetting and centrifuging the base material in a hydrocyclone, then by collecting the dense fraction at a low point in the hydrocyclone,
• separating the particles of the dense fraction of the base material on a plate of a vibrating table, the dense fraction of the base material being arranged at a high location of the plate, the plate having a slope extending in a direction of extension between the high location and a low location of the plate, the low location comprising a low outlet for collecting a portion of the particles of the dense fraction of the lowest apparent densities, a flow of water following the direction of extension moving the portion in the direction of the slope towards the low location, the vibrating table comprising a lateral outlet for collecting a second portion of the particles of the dense fraction, of the highest apparent densities, the second portion being moved towards the lateral outlet by vibration of the plate.

Bulk density is the mass of a particle relative to the volume occupied by the particle, this volume including the volume made up of matter and the empty interstitial volume.

The base material may include metal particles and non-metal particles, and may come in several forms. It may be a shred, i.e. particles of different sizes resulting from the recycling by shredding of old electrical cables. This shred is also called plastic shot.

These may be finer particles called fines or suction dust or even filtration or settling sludge. These particles are of a finer caliber but they are made up of the same mixture of metallic and non-metallic material.

Preferably, the metal particles are copper or aluminum. The non-metal particles mainly comprise plastic particles. For example, for cables, these plastic particles may comprise polyvinyl chloride or PVC, cross-linked polyethylene or PE R, high-density polyethylene or HDPE, low-density polyethylene or LDPE, elastomer, and some other organic waste. Generally, these particles form a mixture of plastics having material densities of 0.85 to 1.7, and metals having material densities of between 2.7 and 9.

According to one embodiment, by hydrocyclone is meant a device also known as a hydraulic classifier comprising a conical shaped container with an inlet at a high point at the widest part of the cone and an outlet at the low point at the tip of the cone.

Preferably, the hydrocyclone is arranged so that the contents of the cone are rotated about a vertical axis which is also the axis of the cone. The base material is mixed inside the cone with a quantity of water or an equivalent fluid. This mixing step is called "wetting".

During the wetting step, a phenomenon of flotation of particles whose apparent density is less than 1 occurs, in the case where the wetting solution is water. Towards the low point, an aggregate of the densest particles forms. The dense fraction collected corresponds to all or part of this aggregate. The particles of intermediate densities concentrate above the aggregate on the periphery of the container or in the mass of moving water.

Wetting and centrifugation allow satisfactory separation of particles stuck or imbricated to each other. Only a small fraction of particles smaller than 100 µm can be trapped, the particles of this fraction remaining joined to other larger particles whose apparent density nevertheless remains greater than 1, according to current performances.

The dense fraction of the base material extracted at the low point of the hydrocyclone is then subjected to two mechanical forces tending to move the particles differently according to their density and shape, that is to say according to their apparent density, when passing over the vibrating table. The vibrating table can also be called an inclined water table.

The flow of water over the table carries the lighter particles to the lower location, while the heavier particles are essentially subject to gravity. The heaviest particles, or those with the highest apparent density, may be metallic particles. The lightest particles, or those with the lowest apparent density, may be non-metallic particles or polymers.

The passage of the dense fraction of the base material drawn off on the vibrating table makes it possible in this case to obtain a set of essentially metallic particles at the side outlet and a set of essentially non-metallic particles at the lower location of the vibrating table.

It should be noted that the side outlet may collect traces of non-metallic particles. For example, it may be a metal particle and a particle non-metallic particles solidly embedded in each other, or relatively dense non-metallic particles such as mineral materials also arriving at the side outlet. For example, manufacturers add calcium carbonate powders to trap hydrocarbons present in certain cables.

Similarly, the low location of the vibrating table may receive traces of metal particles, for example small particles which have been carried along by the flow of water.

This process allows for very efficient separation, the successive use of the hydrocyclone and the vibrating table allowing for excellent concentration of metal particles, particularly small ones (less than 800 µm).

Furthermore, this process is energy efficient, in the order of 225 KWh per tonne of raw material processed. Once the hydrocyclone and the vibrating table are in place, this process requires little human intervention because it is fully automatable.

Alternatively, a feedstock may be subjected to the process to separate particles according to their apparent densities.

According to one embodiment, the feed material may be transferred into the hydrocyclone through a feed hopper.

In the separation process, particles are conveyed using water or a solution with controlled density up to 1.35.

In this text, the term "particles" is used as a generic term to replace the formulation "metallic particles and/or non-metallic particles".

• une structure fixe,
• le plateau monté mobile sur la structure fixe,
• un moteur vibrant agencé pour faire vibrer le plateau.

According to one embodiment, the vibrating table comprises:

• a fixed structure,
• the tray mounted mobile on the fixed structure,
• a vibrating motor arranged to vibrate the plate.

The vibration of the plate allows, thanks to three main physical effects (spreading, stratification, displacement), the separation of particles and thus improves the precision of sorting between particles. The vibrating motor is for example an unbalance motor.

According to one embodiment, the vibrating table comprises a support for the vibrating motor secured to the plate and arranged under the plate on a side opposite the side outlet.

The location of the vibrating motor determines the movement of particles with the highest apparent density. These move away from the vibrating motor and thus towards the side outlet.

According to one embodiment, the support has the shape of a plate having an end secured to the underside of the plate and extending at a determined angle relative to the direction of extension of the plate.

The other end of the support is connected by a post to the table. This post of the vibrating table solidifies the structure and facilitates the movement of heavy particles towards the side outlet.

Preferably, the angle between the motor support and the extension direction is between 30 and 45°. In particular, the support is fixed to one end of the plate transversely to the extension direction.

The bracket has holes for mounting the vibration motor. The plate extends over a length of between 1.2 and 1.6 m transversely to the extension direction.

The vibrating table consists of four block cylinders connecting it to the fixed structure. Each block cylinder is mounted under the tabletop slightly set back from a corresponding corner of the tabletop.

According to one embodiment, the vibrating table top has grooves and/or ribs extending transversely to the extension direction.

This arrangement facilitates the stratification and flow of particles with high apparent densities towards the side outlet.

According to one embodiment, the vibrating motor is arranged to vibrate the plate at a frequency between 40 and 70 Hz.

This high frequency improves sorting. Preferably, the determined frequency is between 50 and 65 Hz for material from cable shredding.

According to one embodiment, the slope of the plate, extending in the direction of extension, has an angle of between 5 and 10° downwards relative to the horizontal plane.

According to one embodiment, the tray is inclined downward in a direction transverse to the direction of extension, from an edge of the tray comprising the side outlet to an opposite edge of the tray, at an angle of between 1 and 3° relative to a horizontal plane.

According to one embodiment, the sampling in the lowest zone of the hydrocyclone is carried out by an endless screw, and ideally associated with a lock.

This arrangement makes it possible to simplify and automate the collection of the dense fraction of the base material.

Preferably, the auger is mounted in a conduit connecting the lowest zone of the hydrocyclone to the high location of the vibrating table or an intermediate tank capable of discharging the dense fraction of the base material at the high location of the vibrating table.

According to one embodiment, the hydrocyclone comprises a mixing device configured to homogenize the solution inside the conical-shaped container of the hydrocyclone.

Preferably, the stirring device comprises two arms capable of setting the solution in motion inside the container.

Preferably, the mixing device comprises two scrapers integral with the axis, located at the base of the cone, capable of facilitating the flow of the dense fraction towards the low extraction point.

According to one embodiment, the vibrating table includes a distributor capable of generating the flow of water, the distributor comprising an alignment of openings for producing a plurality of parallel water jets forming the flow of water.

This arrangement allows non-metallic particles to be efficiently directed to the lower location.

Preferably, the alignment of openings is oriented along the direction of extension in the sense going from the low location to the high location.

The alignment of openings is shaped so that the water jets are introduced at the high location of the table to create a uniform water film whose flow is controlled by the outlet pressure of the water jets.

The water jets combined with the vibrations of the table allow all the particles present on the plate to be set in motion.

According to one embodiment, the intermediate tank is attached to the tray at the high location on the side opposite the side outlet transversely to the direction of extension.

Preferably, the bottom of the intermediate tank is the tray, a slot being provided between the tray and a wall of the intermediate tank for the passage of the dense fraction. A nozzle may be provided for projecting a curtain of pressurized water inside the intermediate tank, this nozzle being oriented towards the point of entry of the material into the tank, in order to facilitate its continuous exit.

In particular, the slot in the intermediate reservoir extends parallel to the direction of extension in order to generate a uniform and controlled exit of the dense fraction from the intermediate reservoir, transversely to the direction of extension.

According to one embodiment, the slot faces the distributor transversely to the direction of extension. Thus, when the dense fraction leaves the intermediate reservoir transversely to the direction of extension, the flow of water gives the dense fraction a trajectory in the direction of extension down the slope of the tray.

According to one embodiment, the separation method comprises a step carried out during the step of extracting the dense fraction of the base material and consisting of pumping a light fraction of the base material into the hydrocyclone, the light fraction comprising particles floating or suspended in the hydrocyclone after wetting and centrifuging the base material.

This arrangement allows particles to be sampled differently depending on their apparent density. Indeed, when the hydrocyclone is filled with water or an equivalent fluid, particles with a density lower than the density of the solution float or are suspended at the top of the water column in the hydrocyclone.

The particles of the light fraction mainly comprise PER, HDPE and LDPE for a solution with a density close to one. Traces of other particles may also be present, in particular the smallest metallic particles and non-metallic particles.

Following the step of collecting the light fraction of the base material, the collected particles can be directly conveyed to a corresponding container, the water or equivalent fluid being recovered in a corresponding recovery tank.

The same principle can be used for particles collected at the lower location of the vibrating table, these particles can be stored in a corresponding container. This principle also works with particles collected at the side outlet of the vibrating table.

According to one embodiment, the light fraction is sieved by a first sieve, for example under a jet of clear water, in order to facilitate the separation of the residual metal particles of small sizes, the particles of sizes greater than a sieving size of the first sieve being arranged in a corresponding container intended for non-metallic particles of low density.

The sieving caliber is of the order of one or several hundred microns, for example between 100 and 300 µm. The sieve used here is called a fine sieve.

The low density particles are mainly Polyethylene particles.

According to one embodiment, the portion coming from the low location of the table is sieved by a second sieve, for example under a jet of clear water, in order to facilitate the separation of the residual metal particles of small sizes, the particles of calibers greater than a sieving caliber of the second sieve being arranged in a corresponding container intended for non-metallic particles of medium density.

Medium density particles include all or part of the non-metallic particles mentioned above with the exception of HDPE and LDPE particles.

This arrangement allows the elimination of the smallest particles which may contain small metal particles, possibly aggregated with non-metallic particles.

The sieving caliber is of the order of one or several hundred microns, for example between 100 and 300 µm.

According to one embodiment, the step of arranging a base material is preceded by a step of sieving a raw material to obtain the base material, the sieving step consisting of eliminating particles of the raw material exceeding a determined size.

The separation process is intended for the separation and sorting of smaller particles, with larger particles being treated differently.

In practice, the raw material is first stored in an input silo, then transferred by a conveying system such as a worm screw to a sieve here called a coarse sieve.

The coarse screen can be a vibrating screen slightly inclined at a few degrees and driven by a vibratory movement in one or two dimensions.

Particles smaller than the intended size are collected by transfer to the hydrocyclone feed hopper or to an intermediate storage bin depending on the space available in the hydrocyclone.

One possibility is to choose a planned size smaller than 1.6 mm, i.e. any particle with a larger dimension is discarded to be treated in a different way.

This different treatment can be a crushing in order to correspond to the caliber lower than 1.6 mm or another type of sorting.

In particular, an electrostatic or eddy effect separator can be used to separate metallic particles from non-metallic particles.

According to one embodiment, the steps are repeated for several batches of base material.

According to one embodiment, each batch of base material, with the exception of the first, comprises a remainder of the previous batch still present in the hydrocyclone and a supplement of base material.

The rotation speed of the hydrocyclone is adjusted according to the apparent density of the particles: the speed is slowed down for particles in the hydrocyclone which are of lower average density.

The different aspects defined above which are not incompatible can be combined.

Brief description of the figures

• la figure 1 est une vue schématique d'un hydrocyclone et d'une table vibrante configurés pour réaliser le procédé de séparation ;
• la figure 2 est une vue schématique de dessus de la table vibrante ;
• la figure 3 est une vue schématique en coupe de la table vibrante selon un plan de coupe vertical transversal AA' montré sur la figure 2 ;
• la figure 4 est une vue arrière schématique de la table vibrante ;
• la figure 5 est une vue schématique similaire à la figure 1 et comprenant en plus des équipements pour la réalisation d'un tamisage préalable et d'une filtration finale.

The invention will be better understood with the aid of the detailed description which is set out below with reference to the appended figures, in which identical reference signs correspond to structurally and/or functionally identical or similar elements. In the figures:

• there figure 1 is a schematic view of a hydrocyclone and vibrating table configured to carry out the separation process;
• there figure 2 is a schematic top view of the vibrating table;
• there figure 3 is a schematic sectional view of the vibrating table along a transverse vertical section plane AA' shown in the figure 2 ;
• there figure 4 is a schematic rear view of the vibrating table;
• there figure 5 is a schematic view similar to the figure 1 and further comprising equipment for carrying out preliminary screening and final filtration.

Detailed description

In the detailed description which follows of the figures defined above, the same elements or elements fulfilling identical functions may retain the same references so as to simplify the understanding of the invention.

As illustrated in the figure 1 , a method for separating particles to be recycled comprises the steps described below. In the embodiment presented, these are metal particles and non-metallic particles which may be derived from residual fractions from the recycling of electric cables.

A first step E1 consists of having a base material 1 comprising a plurality of metallic 2 and non-metallic 4 particles.

Each particle 2, 4 has its own apparent density. The apparent density is a function of a shape and a density of matter of the particle 2, 4. The apparent density is the mass of a particle relative to the volume occupied by the particle, said volume comprising the volume consisting of matter and the empty interstitial volume.

A second step E2 consists of extracting a dense fraction 3 from the base material 1. The extraction is carried out by wetting and centrifuging the base material in a hydrocyclone 5, then by removing the dense fraction 3 by sampling at a low point 7 of the hydrocyclone 5.

A third step E3 consists in separating the particles of the highest apparent densities, that is to say for example comprising the metallic particles 2 and the particles of the lowest apparent densities, that is to say for example comprising the non-metallic particles 4 from the dense fraction 3 on a plate 29 of a vibrating table 9.

The dense fraction 3 of the base material 1 is arranged at a high location 11 of the plate 29. The plate 29 has a slope extending in a direction of extension 13 from the high location 11 to a low location 15 of the plate 29. The low location 15 is shaped to receive a less dense portion 6 of the particles of the dense fraction 3 of the lowest apparent densities, that is to say for example comprising the non-metallic particles 4.

A flow of water following the direction of extension 13 moves the less dense portion 6 following the slope of the plateau 29 towards the low location 15.

The vibrating table 9 comprises a lateral outlet 19 intended to collect another portion 8 of the particles of the dense fraction 3 of the highest apparent densities, that is to say for example comprising the metallic particles 2. The other densest portion 8 is moved by vibration of the plate 29.

The base material 1 here comprises metal particles 2 and non-metallic particles 4 which can be in several forms. It can be a ground material, i.e. particles of different sizes resulting from a grinding treatment of electric cables. This ground material is also called plastic shot.

These may be finer particles called fines or suction dust or even filtration or settling sludge. These particles are of a finer caliber but are also made up of a mixture of metallic and non-metallic matter.

The base material 1 may be derived from electric cables in which the conductor is a non-ferrous metal. The metal particles 2 may thus be made of copper or aluminum. The non-metallic particles 4 mainly comprise plastic particles. For example, for electric cables, the non-metallic particles 4 may comprise polyvinyl chloride or PVC, cross-linked polyethylene or PE R, high-density polyethylene or HDPE, low-density polyethylene or LDPE, elastomer, and some other organic waste.

By hydrocyclone 5 is meant a device also known as a hydraulic classifier comprising a conical shaped container with an inlet at a high point 21 at the widest part of the cone and an outlet at the low point 7 at the tip of the cone.

The hydrocyclone 5 is arranged so that the contents of the cone are rotated about a vertical axis which is also the axis of the cone. The base material 3 is mixed with a quantity of water 23 inside the cone. This mixing operation is called "wetting".

The hydrocyclone 5 comprises a stirring device configured to homogenize the interior of the container of the hydrocyclone 5. The stirring device may for example comprise two arms capable of being set in motion inside the container.

A phenomenon of flotation of particles whose apparent density is less than 1 occurs. Towards the low point 7 of the container, an aggregate of the densest particles forms. The dense fraction 3 taken at the low point 7 of the container corresponds to all or part of this aggregate. The particles of intermediate densities concentrate above the aggregate on the periphery of the container or in movement in the volume of water.

Wetting operations and centrifugation allow satisfactory separation of particles stuck or imbricated to each other. Only a small fraction of particles smaller than 100 µm can be trapped and remain attached to other larger particles whose apparent density nevertheless remains greater than 1, according to current performances.

The dense fraction 3 of the base material 1 taken is then subjected to two mechanical forces tending to move the particles differently according to their density and their shape, that is to say according to their apparent density when passing over the vibrating table. The vibrating table can also be called an inclined water table.

The flow of water on the vibrating table 9 carries away the particles least subject to gravity, while the heavier particles are essentially subject to gravity. The heaviest particles, or those with the highest apparent density, are essentially metallic particles and the lightest or those with the lowest apparent density are essentially non-metallic or polymeric particles.

We thus obtain a set comprising essentially metallic particles 2 at the side outlet 19 and a set comprising essentially non-metallic particles 4 at the lower location 15.

It should be noted that the side outlet 19 may collect traces of non-metallic particles. For example, these may be agglomerates comprising a metal particle and a non-metallic particle embedded in each other or relatively dense non-metallic particles 4.

Similarly, the low location 15 can collect traces of metal particles 2, for example particles of reduced sizes which have been deflected by the flow of water on the vibrating table 9.

The base material 1 can be transferred into the hydrocyclone 5 by a feed hopper 25.

In the separation process, the particles are conveyed using water or other equivalent fluid.

In this text, the term "particles" may be used as a generic term to designate "metallic particles 2 and/or non-metallic particles 4".

As illustrated in Figures 2 to 4 , the vibrating table 9 comprises a fixed structure 27 and the plate 29 mounted movably on the fixed structure 27. The plate 29 has an edge extending over the periphery of the plate and delimiting the lower outlet and the lateral outlet 19.

The tray 29 is fixed to the fixed structure 27 so as to be inclined downwards from the high location 11 to the low location 15 at an angle a of between 5 and 10° relative to a horizontal plane.

The tray 29 may also be fixed to the fixed structure 27 so as to be inclined downward from the lateral location 19 to the opposite lateral edge of the tray at an angle of between 1 and 3° relative to a horizontal plane. This arrangement makes it possible to limit the quantity of water exiting through the lateral outlet 19.

The vibrating table 9 also includes a vibrating motor 31 configured to vibrate the plate 29. The vibrating motor 31 is here an unbalance motor.

The vibrating table 9 comprises a support 32 for the vibrating motor 31 secured to the plate 29 and arranged under the plate 29 on a side opposite the lateral outlet 19.

The location of the vibrating motor 31 determines the movement of the particles with the highest apparent density. The latter move away from the vibrating motor 31 and thus head towards the side outlet 19.

According to one aspect of the invention, the support 32 has the shape of a plate comprising an end secured to the underside of the plate 29 and extending at a determined angle b relative to the direction of extension 13 of the plate 29.

The other end of the support 32 is connected by uprights 38 to the plate 29. The uprights 38 stiffen the structure and facilitate the movement of heavy particles towards the side outlet 19 by the transmission of vibrations from the vibrating motor 31.

Preferably, the angle b is between 30 and 45°. In particular, the support 32 is fixed to one end of the plate 29 transversely to the extension direction 13.

The support 32 has holes for mounting the vibrating motor 31. The plate 29 extends over a length of between 1.2 and 1.6 m transversely to the extension direction 13 and over a width along the extension direction 13 of between 0.8 and 1.2 m.

The vibrating table 9 comprises four block cylinders 36 connecting it to the fixed structure 27. Each block cylinder 36 is mounted under the plate 29 at a corresponding corner of the plate 29.

According to one embodiment, the plate 29 of the vibrating table 9 has grooves and/or ribs 33 extending transversely to the extension direction 13. The grooves and/or ribs 33 make it possible to facilitate the movement of the densest particles towards the lateral outlet 19 of the vibrating table, under the effect of the vibrations of the table 9.

The grooves may be shallower toward the high location 11 of the table 9. There may be both grooves and ribs 33 that define notches. These notches may be more pronounced toward the low location 15.

The vibrating motor 31 is arranged to vibrate the plate 29 at a determined frequency between 40 and 70 Hz. More precisely, the determined frequency is between 50 and 65 Hz.

The sampling in the lowest zone of the hydrocyclone 5 is carried out by an endless screw. The endless screw is mounted in a conduit connecting the lowest zone of the hydrocyclone and an intermediate tank 35 capable of discharging the dense fraction 3 of the base material to the high location 11 of the vibrating table 9.

The vibrating table 9 includes a distributor 37 capable of generating the flow of water, the distributor 37 comprising an alignment of openings or nozzles for generating a plurality of parallel water jets 17 distributed over the entire length (in the direction transverse to the direction of extension 13) of the plate 29 so as to form on the plate 29 a film of water of uniform thickness, the flow of which is controlled by the outlet pressure of the water jets 17 constituting the flow of water.

Preferably, the nozzle alignment is oriented in a direction opposite to the extension direction 13 and directed towards the edge 28 along the upper location 11 of the plate 29. Preferably, the nozzles are spaced from each other by 2 to 4 cm.

The water jets 17 make it possible to move the particles of the lowest apparent densities present on the plate 29 towards the lower location 15.

According to one embodiment, the intermediate tank 35 is arranged on the plate 29 at the high location 11 on the side opposite that of the side outlet 19.

The bottom of the intermediate tank 35 is formed by the plate 29, a slot 26 being provided between the plate 29 and a wall of the intermediate tank 35 for the passage of the dense fraction 3.

The slot 26 can extend parallel to the direction of extension 13 so as to provide an outlet for the dense fraction 3 from the intermediate reservoir 35 in the direction transverse to the direction of extension 13. The slot 26 is thus oriented opposite the distributor 37. In this way, when the dense fraction 3 leaves the intermediate reservoir 35 transversely to the direction of extension 13, the flow of water gives the dense fraction 3 a trajectory in the direction of extension 13 towards the bottom of the slope.

The separation process comprises a step E2' carried out during step E2 of extraction of the dense fraction 3 of the base material 1 and consisting of taking a light fraction 39 of the base material 1 in the hydrocyclone 5 by pumping.

The light fraction 39 comprises non-metallic particles 4 floating or suspended in the hydrocyclone 5 after wetting and centrifuging the base material 1.

Thus, when the hydrocyclone 5 is filled with water, the non-metallic particles 4 with a density less than one float or are suspended.

The particles of the light fraction 39 mainly comprise HDPE and LDPE. Traces of other particles may also be present, in particular the smallest or aggregated metallic particles 2 and non-metallic particles 4.

The non-metallic particles 4 of the dense fraction are thus essentially free of HDPE and LDPE.

Following the step of collecting the light fraction 39 of the base material 1, the non-metallic particles 4 collected can be directly conveyed to a corresponding container 41, the water being recovered in a corresponding recovery tank 43.

The same principle can be applied to the non-metallic particles 4 collected at the low location 15 of the vibrating table 9, the particles being able to be stored in a corresponding container 41'. Furthermore, the water can also be recovered in a corresponding recovery tank 43'. This principle can also be applied to the metallic particles 2 collected at the lateral outlet 19 of the vibrating table. For this purpose, the metallic particles 2 collected at the lateral outlet 19 can be directly conveyed to a corresponding container 41", the water being recovered in a corresponding recovery tank 43".

As illustrated in the figure 5 , the light fraction 39 can also be sieved using a sieve 45 under a jet of clear water in order to separate the residual metal particles of small sizes, the particles of sizes greater than the sieving size used being placed in the container 41 intended for the non-metallic particles 4 of low density.

This arrangement makes it possible to eliminate the smallest particles which may contain small metallic particles 2, possibly aggregated with non-metallic particles 4.

A 45' sieve under a jet of clear water can also be used to treat the least dense portion 6 taken from the low location 15 of the vibrating table 9, in order to separate the residual metal particles of small sizes, the particles of calibers greater than the sieving caliber used being placed in the container 41' intended for the non-metallic particles 4 of low density.

The sieving caliber is of the order of a hundred microns, for example between 100 µm and 300 µm. The 45, 45' sieves used here are called fine sieves.

Particles of sizes larger than the sieving size used are placed in a corresponding container 41 intended for non-metallic particles 4 of medium density.

Medium density particles include all or part of the non-metallic particles 4 mentioned above with the exception of HDPE and LDPE particles.

Step E1 of arranging a base material 1 may be preceded by a step E0 of sieving a raw material 49 to obtain the base material 1. The sieving of the raw material consists of eliminating the particles 2, 4 of the raw material 49 exceeding a determined size.

The separation process is intended for the separation and sorting of smaller particles, with larger particles being treated differently.

In practice, the raw material is first stored in an input silo 51 and then transferred by a conveying system such as a worm screw to a sieve here called a coarse sieve 53.

The coarse screen 53 may be a vibrating screen slightly inclined by a few degrees and driven by a vibratory movement in one or two dimensions.

Particles of a size smaller than the intended size are collected at the outlet of the coarse sieve 53 by transfer into the feed hopper 25 of the hydrocyclone 5 or into an intermediate storage tank 55 depending on the space available in the hydrocyclone 5.

One possibility is to choose a planned size smaller than 1.6 mm, i.e. any particle with a larger dimension is discarded by the coarse sieve 53 to be treated in a different way.

For example, electrostatic separator or eddy effect treatment can be used to separate metallic particles 2 from non-metallic particles 4.

The above detailed steps can be repeated for multiple batches of base material 1.

The method described above allows a very efficient separation of metal particles and non-metal particles, the successive use of the hydrocyclone 5 and the vibrating table 9 allowing an excellent concentration of the metal particles 2, even of small sizes (less than 500 µm). Thus, several samples taken at the side outlet 19 from various raw materials resulting from the grinding of cables, have the following average particle size distribution (percentages by weight): 4% of particles greater than 1 mm, 15% of particles between 1 and 0.5 mm, 19% of particles between 0.5 and 0.3 mm, 52% of particles between 0.3 and 0.1 mm, and 8% of particles less than 0.1 mm.

Furthermore, this process is energy-efficient, in the order of 225 kWh per tonne of raw material 1 processed. Once the hydrocyclone 5 and the vibrating table 9 are in place, this process requires little human intervention because it is fully automatable.

The vibration of the tray 29 combined with the flow of water on the tray improves the separation of particles and thus improves the accuracy of sorting between particles.

It goes without saying that the invention is not limited to the single embodiment described above as an example; on the contrary, it encompasses all variant embodiments.

Claims (14)

Method for separating particles to be recycled comprising steps consisting of: (E1) having a base material (1) comprising a plurality of particles, each particle having its own apparent density which is a function of a shape and a material density of the particle, (E2) extracting a dense fraction (3) of greater density from the base material (1), the extraction being carried out by wetting and centrifuging the base material (1) in a hydrocyclone (5), then by collecting the dense fraction (3) at a low point (7) of the hydrocyclone (5), and (E3) separating the particles of the dense fraction (3) of the base material (1) on a tray (29) of a vibrating table (9), the dense fraction (3) of the base material (1) being arranged at a high location (11) of the tray (29), the tray (29) having a slope extending in a direction of extension (13) between the high location (11) and a low location (15) of the tray (29), the low location (15) comprising a low outlet for collecting a first portion (6) of the particles of the dense fraction (3) of the lowest apparent densities, a flow of water following the direction of extension (13) moving the first portion (6) in the direction of the slope towards the low location (15), the vibrating table (9) comprising a lateral outlet (19) for collecting a second portion (8) of the particles of the dense fraction (3), of the highest apparent densities, the second portion (8) being moved towards the side exit by vibration of the plate (29). Separation method according to claim 1, in which the vibrating table (9) comprises: - a fixed structure (27), - the tray (29) mounted mobile on the fixed structure (27), - a vibrating motor (31) arranged to vibrate the plate (29). Separation method according to claim 2, in which the vibrating table (9) comprises a support (32) for the vibrating motor (31) secured to the plate (29) and arranged under the plate (29) on a side opposite the lateral outlet (19). Separation method according to one of claims 2 or 3, in which the plate (29) of the vibrating table (9) has grooves and/or ribs (33) extending transversely to the direction of extension (13) to facilitate the movement of the denser particles towards the side outlet (19). Separation method according to one of claims 2 to 4, in which the vibrating motor (31) is arranged to vibrate the plate (29) at a frequency between 40 and 70 Hz. Separation method according to one of claims 1 to 5, in which the slope of the plate (29), extending in the direction of extension (13) has an angle of between 5 and 10° downwards relative to the horizontal plane. Separation method according to one of claims 1 to 6, in which the tray (29) is inclined downwards in a direction transverse to the direction of extension (13), from an edge of the tray comprising the lateral outlet (19) to an opposite edge of the tray, at an angle of between 1 and 3° relative to a horizontal plane. Separation method according to one of claims 1 to 7, in which the sampling in the lowest zone of the hydrocyclone (5) is carried out by an endless screw. A separation method according to one of claims 1 to 8, wherein the vibrating table (9) includes a distributor (37) capable of generating the flow of water, the distributor (37) comprising an alignment of openings for producing a plurality of parallel water jets forming the flow of water. Separation method according to one of claims 1 to 9, comprising a step carried out during step (E2) of extracting the dense fraction (3) from the base material (1) and consisting of:
(E2') collecting a light fraction (39) of the base material (1) by pumping into the hydrocyclone (5), the light fraction (39) comprising particles floating or suspended in the hydrocyclone (5) after wetting and centrifuging the base material (1). A separation method according to claim 10, wherein the light fraction (39) is sieved by a first sieve (45), the particles of larger sizes to a sieving caliber of the first sieve being arranged in a corresponding container intended for non-metallic particles (4) of low density. Separation method according to one of claims 1 to 11, in which the portion (6) coming from the low location (15) is sieved by a second sieve (45'), the particles of sizes greater than a sieving size of the second sieve being arranged in a corresponding container intended for non-metallic particles (4) of low density. Separation method according to one of claims 1 to 12, in which the step (E1) of providing a base material (1) is preceded by a step (E0) of sieving a raw material (49) to obtain the base material (1), the sieving step consisting of eliminating the particles (2, 4) of the raw material (49) exceeding a determined size. Separation method according to one of claims 1 to 13, in which the steps are repeated for several batches of base material (1), each batch of base material (1), with the exception of the first, comprising a remainder of the previous batch still present in the hydrocyclone (5) and a complement of base material (1).

Images