METHOD FOR SEPARING THE COMPONENTS OF A MIXTURE OF FIBERS AND GRANULES BY ELECTROSTATIC NEUTRALIZATION AND SIEVING, AND CORRESPONDING INSTALLATION

Abstract

The invention relates to a separation process for separating the fibers from the granules of a mixture (1) containing fibers (2) and granules (3), said process comprising a supply step (S1), during which the mixture is brought into a receptacle (10) provided with a sieve (11), a dissociation step (S2), during which a substep (S201) of agitation is carried out simultaneously, according to which the mixture (1) contained in the receptacle (10) is mechanically stirred, and a substep (S202) of neutralization is carried out, according to which the mixture being stirred in the receptacle (10) is exposed to bipolar charges in order to neutralize electrostatic charges of the fibers (2) and granules (3),then a sieving step (S3) during which the mixture (1) treated according to the dissociation step (S2) is passed over the sieve (11) in order to retain in the receptacle (10) a first product (P1) enriched in fibers (2) while a second product (P2) enriched in granules (3) is discharged through the sieve (11). Figure 3,

Description

Title of the invention: METHOD FOR SEPARING THE COMPONENTS OF A MIXTURE OF FIBERS AND GRANULES BY ELECTROSTATIC NEUTRALIZATION AND SIEVING, AND CORRESPONDING INSTALLATION

[0001] The present invention relates to the general field of processes for separating the components of a mixture containing fibers and granules, which aim to recover said fibers separately on the one hand, and said granules separately.

[0002] The present invention finds particular application in the treatment of industrial waste in the form of a mixture containing fibers and granules, with a view to recycling the constituent materials of said fibers and granules, and more particularly in the treatment of mixtures which are obtained from the grinding of pneumatic tires and which contain textile fibers, in particular polyethylene terephthalate, and granules of rubber-based material.

[0003] The present invention finds more particularly application in the processing of mixtures whose components are of millimeter and sub-millimeter size, that is to say containing fibers whose diameter is between 10 pm and 1 mm for a length between 1 mm and 10 mm, and granules whose equivalent diameter is between 125 pm and 5 mm.

[0004] Many processes are known for recovering polymer material fibers from a mixture which contains said fibers among other components.

[0005] In particular, wet processes are known in which the mixture is dissolved in a solvent, and the resulting solution is then treated to recover the polymer. Such processes are generally quite polluting.

[0006] Other wet separation processes for the components of a mixture are also known, in which the mixture of granules and fibers is dispersed in an aqueous solution which is then subjected to decantation. However, these processes are limited to the treatment of mixtures whose components have distinct densities, one of which is strictly greater than the density of water.

[0007] Dry separation processes are also known, notably from document EP-2 937 200, which involve sieving the mixture through a vibrating sieve, and preferably several successive sievings through as many vibrating sieves, and which use a blow of air from below the sieve to carry the fibers and suck them into a hood located above the sieve.

[0008] Such sieving processes are certainly less polluting and less energy-intensive. of energy than wet processes, but they generally have unsatisfactory yields, and often only produce refined products of relatively poor quality, because many fibers and granules still remain agglomerated together.

[0009] The objects assigned to the invention therefore aim to remedy the aforementioned disadvantages and to propose a new separation process, and a corresponding new installation, which significantly improve the efficiency of the separation of fibers and granules, while being low in pollution and low in energy consumption.

[0010] The objects assigned to the invention are achieved by means of a separation process enabling the separation of said fibers from said granules from a mixture containing fibers and granules, said process comprising for this purpose a supply step (S1), during which the mixture is brought into a receptacle equipped with a sieve, a dissociation step (S2), during which a substep (S201) of agitation is carried out simultaneously, according to which the mixture contained in the receptacle is mechanically stirred, and a substep (S202) of neutralization is carried out, according to which the mixture being stirred in the receptacle is exposed to bipolar charges in order to neutralize electrostatic charges of the fibers and granules,then a sieving step (S3) during which the mixture treated in accordance with the dissociation step (S2) is passed over the sieve in order to retain in the receptacle a first product from the mixture, a first product which has a fiber content higher than that of the mixture, while a second product from the mixture, a second product whose granule content is higher than that of the mixture, is discharged through the sieve.

[0011] Advantageously, the inventors have found that, by combining on the one hand a mechanical mixing of the mixture, which makes it possible to overcome the adhesion forces of the Van der Waals type which keep the fibers and granules agglomerated, with on the other hand an electrostatic neutralization which makes it possible, at the same time, to reduce or even eliminate the electrical charges of the fibers and granules and thus to reduce or even eliminate the electrostatic attraction forces which tend to make the fibers and granules agglomerate, it is possible to effectively dissociate the fibers from the granules within the mixture, and to prevent the fibers and granules, once dissociated from each other, from re-agglomerating.

[0012] In this way, the mixture is perfectly prepared for sieving, in that the components of said mixture, namely the fibers and granules, are already well separated from one another when said mixture is presented to the sieve to be exposed to the action of said sieve, which makes said sieving particularly efficient and selective, since each individual component (fiber or granule) thus separated from the components which are close to it is properly exposed to the mesh of the sieve, without remaining attached to a neighboring component which could possibly prevent said component from passing through the sieve.

[0013] Preferably, the exposure of the mixture to the sieve occurs in a region of space, here in a portion of the receptacle, which is exposed to the combined actions of mechanical agitation and electrostatic neutralization, so that the mixture which is in contact with the sieve, and more particularly the different components of said mixture, including the fibers and granules which we wish to separate, are and remain permanently, including at the time when the sieving takes place, subject to the dissociation effect which results from this agitation and this neutralization.

[0014] It should also be noted that it is advantageously possible, as will be detailed below, to improve and reinforce the dissociation effect obtained by the mixing and neutralization actions carried out in accordance with the process according to the invention by also adding a blowing action, which helps to aerate the mixture and to diffuse the bipolar charges within said mixture.

[0015] In any event, the process proposed by the invention preferably constitutes a dry process, which makes it possible to obtain an efficient separation of the components of the mixture without involving any solvent or immersion of the mixture in any aqueous solution.

[0016] Other objects, features and advantages of the invention will become apparent in more detail from the following description and with the aid of the accompanying drawings, which are provided by way of illustration only and are not intended to be limiting, among which:

[0017] Fig. 1 illustrates, according to a perspective view with removal of a top wall and a side wall, an example of an installation allowing implementation of a process according to the invention and comprising for this purpose cylindrical screening drums mounted in rotation around a central axis which is substantially horizontal, as well as ionizing blowing bars which are located outside said screening drums and whose flow is directed towards the inside of said screening drums.

[0018] Fig. 2 is a cross-sectional perspective view of the installation of Fig. 1, in a cutting plane that is normal to the axis of rotation of the sieving drums.

[0019] Fig. 3 is a front view of the section of Fig. 2.

[0020] Fig. 4 is a schematic view, in a cutting plane perpendicular to the axis of rotation of the screening drum(s), of a variant embodiment of the installation of figures 1 to 3 in which ionizing blowing bars are located inside a screening drum.

[0021] Fig. 5 is a perspective view of the installation of Figures 1 to 3 with longitudinal section in a vertical cutting plane that is parallel to the axis of rotation of the sieving drums.

[0022] Fig. 6 is a partial side view of the installation of figures 1 to 3, in longitudinal section in a vertical sagittal plane which contains the axis of rotation of the sieving drums.

[0023] The present invention relates to a separation process enabling, from a mixture 1 containing fibers 2 and granules 3, the separation of said fibers 2 from said granules 3 (or, conversely, the separation of granules 3 from fibers 2).

[0024] The invention also relates, of course, to an installation 100 enabling the implementation of such a process.

[0025] The constituent material of the fibers 2 will be different from the constituent material of the granules 3, and, more particularly, the constituent materials of the fibers 2 on the one hand, and of the granules 3 on the other hand, will be such that the fibers 2 and the granules 3 can each carry an electrostatic charge, but of opposite sign.

[0026] Preferably, the process according to the invention will be designed to separate fibers 2, contained in the mixture 1, which have a length of between 1 mm and 10 mm, and a largest transverse dimension of between 10 µm and 1 mm. "Largest transverse dimension" means the largest of the dimensions of the fiber's cross-section, considered perpendicular to the fiber's length. In the case of a fiber 2 with a cylindrical shape and a circular base, the largest transverse dimension therefore corresponds to the diameter of the circular base, that is, the diameter of the cross-section of said fiber 2.

[0027] The fibers 2 shall have a thin and elongated shape, preferably substantially cylindrical.

[0028] More preferably, the fibers 2 will have a dimension, called length, which is significantly greater than the other two dimensions, called transverse dimensions, and more particularly which has a length at least 5 times, preferably at least 10 times, at least 20 times, or even at least 50 times or even 100 times greater than the largest of these transverse dimensions, that is typically to say the diameter of the fiber concerned.

[0029] The fibers 2 may be made of a natural or synthetic textile material, and more preferably of a polymer or a combination of polymers from among: polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS).

[0030] Preferably, the process will be designed to separate the aforementioned fibers 2 from the granules 3 in a mixture where said fibers 2 are mixed with, or even agglomerated with, granules 3 whose equivalent diameter is between 125 pm and 5 mm.

[0031] By “equivalent diameter” is meant the diameter that a fictitious sphere would have if it occupied the same volume as the volume occupied by the granule 3 considered.

[0032] Furthermore, the granules 3 will preferably have a form factor equal to or less than 2. The term "form factor" refers to the ratio between, on the one hand, the maximum Feret diameter, that is, the maximum observable distance for the granule in question between two parallel lines tangent to opposite sides of said granule, and, on the other hand, the minimum Feret diameter, that is, the minimum observable distance for the granule in question between two parallel lines tangent to opposite sides of said granule. This form factor provides a good indication of the slenderness of the granules. For reference, a form factor of 1 corresponds to a sphere, and a form factor equal to the square root of 2 corresponds to a cube.

[0033] Preferably, the granules 3 will be made of a rubber-based material.

[0034] Thus, the process is preferably applied to a mixture 1 which contains textile fibers 2, preferably polyethylene terephthalate, and granules 3 of rubber-based material.

[0035] More particularly, the invention can thus be applied to a process for recycling a pneumatic tire, said recycling process comprising a grinding step, during which at least a portion of the pneumatic tire concerned is reduced into a mixture 1 containing textile fibers 2 and granules 3 of rubber-based material and then a sorting step during which said mixture 1 is subjected to a separation process according to any one of the possibilities envisaged by the invention.

[0036] Indeed, as is known per se, used pneumatic tires contain both elastic structural elements, based on vulcanized rubber, and fibrous reinforcing elements. Shredding such tires thus makes it possible to obtain mixtures rich in both rubber granules and fibers, which it is useful to be able to separate in order to recycle the corresponding raw materials.

[0037] In all cases, regardless of the origin of the mixture and the purpose of the process in which the separation process according to the invention is involved, said separation process according to the invention includes first of all a supply step (SI), during which the mixture 1 is brought into a receptacle 10 equipped with a sieve 11.

[0038] The receptacle 10 and the sieve 11 may take any suitable shape. For example, the sieve may be formed by a flat plate, provided with edges delimiting the receptacle.

[0039] However, according to a preferred embodiment, and as can be clearly seen in Figures 1, 2, 3 and 5, the receptacle 10 shall have a cylindrical shape, preferably with a circular base, and the sieve 11 shall form all or part of the side wall A curved 10L container of the aforementioned cylindrical shape. Such a receptacle 10 will thus form a sieving drum. For ease of description, the receptacle 10 may be considered a sieving drum in the following text, and the same reference 10 may be used to designate either the receptacle or the sieving drum.

[0040] The sieve 11 shall preferably be made of an electrically insulating material, that is to say, one having an electrical resistivity greater than or equal to 1010 Ωm at a temperature of 300 Kelvin, so as not to hinder neutralization by bipolar charges. Furthermore, the material constituting the sieve 11 shall be sufficiently rigid to prevent the sieve 11 from deforming under the weight and movements of the mixture 1.

[0041] As can be seen in Figures 2 and 5, the receptacle 10 may include a rigid openwork frame 12, which will serve as a support for grid panels 13, here curved panels which follow substantially or even exactly the curvature of the side wall 10L of the sieving drum, which grid panels 13 fit the windows of the frame 12 so as to form as many portions of the sieve 11.

[0042] The supply of the receptacle 10 can be carried out by any suitable feeding system 15, for example by means of a screw conveyor, of the Archimedes screw type, which takes the mixture 1 from a nearby silo to transfer it into the receptacle 10, or by means of a hopper 16 which pours the mixture 1 into said receptacle 10, as shown schematically in figures 3 and 6.

[0043] It may be envisaged that the installation 100 be fed and therefore operated in batches, according to which a determined, finite quantity of mixture 1 is introduced into the receptacle 10, said quantity being called a "batch", and said batch is entirely processed before the installation is emptied and said installation is refilled with a new batch of mixture 1 to start a new separation cycle.

[0044] However, as a preferred variant, to improve the industrial efficiency of the installation 100 by reducing the downtime of said installation, a continuous feed may be considered, according to which a continuous supply of mixture 1 is made in the receptacle 10, for example at one of the axial ends of the screening drum, as the mixture 1 being processed in the receptacle 10 is screened and the products PI, P2 resulting from the processing of the mixture are removed from the receptacle 10, and more generally from the installation 100, for example by collecting said products PI, P2 at the other end of the screening drum and / or on suitable extraction conveyors.

[0045] The separation process according to the invention then comprises, after the supply step (S1), a dissociation step (S2), during which a substep (S201) of agitation is carried out simultaneously, in which the mixture 1 contained in the receptacle 10 is mechanically stirred, and a substep (S202) of neutralization is carried out, in which the mixture 1 being stirred is exposed. in the receptacle 10 to bipolar charges in order to neutralize electrostatic charges of the fibers 2 and granules 3.

[0046] Mechanical mixing of the mixture 1 can be obtained by any suitable means, and in particular either, preferably, by moving the receptacle 10 relative to the frame of the installation 100, for example by rotating the receptacle 10, or, alternatively, by stirring the mixture 1 by means of a stirring element, such as a stirring paddle, which would plunge into the receptacle 10 and be moved relative to the receptacle 10.

[0047] Preferably, a first cylindrical sieving drum 10 is used as a receptacle 10, delimited by a tubular side wall 10L which extends along and around a central axis X10 forming an angle of less than 30 degrees with the horizontal, at least a portion of which forms the sieve 11.

[0048] Advantageously, during the agitation substep (S201), a rotation RIO of the first sieving drum 10 on itself, around its central axis X10, can then preferably be used to cause mixing of the mixture 1.

[0049] By placing the mixture 1 in a horizontal cylindrical sieving drum 10 and using the rotation RIO of the drum on itself, rotation RIO which is preferably continuous and monotonous, that is to say carried out uninterrupted and always in one and the same direction, an efficient and gentle agitation of the mixture 1 is advantageously obtained, without jerks and without risk of compaction of the mixture 1, and this moreover without jerks or vibrations of the receptacle 10, or excessive noise, which improves the life, reliability and ease of use of the installation 100.

[0050] The rotation speed RIO is moderate, so as on the one hand to allow a natural mixing of the mixture 1, by self-collapse and permanent turning of the mixture on itself, under the joint action of the rotation RIO (which allows the lateral wall 10L to carry and raise a part of the mixture along said lateral wall, in the direction of the rotation RIO, seen in a section normal to the axis of rotation) and of gravity (which makes this part of the mixture raised by the rotation fall back onto the rest of the mixture), and on the other hand to avoid a centrifugal effect of the mixture 1 which would tend to compact said mixture 1 instead of dissociating it, or even to eject through the meshes of the sieve 11 certain aggregates of fibers 2 and granules 3 before said aggregates have been able to be properly dissociated into separate fibers 2 and granules 3.

[0051] Thus, the rotation speed RIO will preferably be chosen, depending on the internal diameter of the sieving drum 10, so that the centrifugal acceleration to which said rotation RIO subjects the mixture 1 remains less than 125 m / s², i.e., less than 12.75 times the acceleration due to gravity. In practice, for a granule 3 with a mass of approximately 0.15 grams, such an acceleration will generate on said granule 3 a centrifugal force of approximately 0.018 Newtons.

[0052] As an indication, particularly for a sieving drum diameter between 100 mm and 1000 mm, and more particularly between 120 mm and 240 mm, the RIO rotation speed will preferably be between 10 rpm and 150 rpm, more preferably between 30 rpm and 90 rpm.

[0053] Furthermore, it should be noted that, possibly, the radially internal face of the side wall 10L of the sieving drum 10 may be provided with protrusions, such as blades, which contribute to breaking up and stirring the mixture 1 during the rotation RIO.

[0054] According to one possible arrangement, at least some of these protuberances will correspond to the ledges formed by the frame 12 in relation to the panels 13 of the sieve 11.

[0055] Preferably, the angle formed by the central axis X10 of the first sieving drum 10 with respect to the horizontal is non-zero. By way of example, said angle may be between 5 degrees and 30 degrees.

[0056] This makes it possible to give said central axis X10, and therefore the first sieving drum 10, an inclination which places the inlet of the first sieving drum 10, corresponding to the open base of the cylinder located at one of the two axial ends of said first sieving drum, considered along the central axis X10, at an altitude greater than the altitude of the outlet of the first sieving drum, which corresponds to the open base of the cylinder forming the other axial end, opposite, of said first sieving drum 10.

[0057] Under the combined effect of the rotation RIO and gravity, this inclination of the sieving drum 10, and more specifically of the side wall 10L of said sieving drum, makes it possible to ensure a progressive and continuous transport of the mixture 1 from the inlet to the outlet of the first sieving drum 10, along the central axis X10, and thus allows continuous operation of the installation 100, and this with very low energy consumption.

[0058] It should be noted that, when the receptacle 10 is formed by a first sieving drum 10, care should be taken not to fill said first sieving drum to its entire height, that is, over the entire extent of its cross-section, in order to maintain sufficient emptiness in the upper part of the cylinder to allow the mixture 1 to be effectively stirred during the rotation RIO of the sieving drum 10, and, moreover, to be sufficiently exposed to the action of bipolar loads, and where applicable, to the action of the blowing. As an indication, the filling ratio will be such that the mixture occupies a height in the lower part of the cylinder less than or equal to 40% of the internal diameter of the first sieving drum 10, for example, a height between 25% and 30% of said internal diameter.

[0059] During the neutralization substep (S202), bipolar charges are produced, that is to say a set, globally neutral, of positive and negative ions, which is projected onto the mixture 1, for example by blowing or by gravity, in order to diffuse the said bipolar charges in the mixture 1, and to allow the ions to carry out an electronic exchange with the fibers 2 which are carriers of electrostatic charges, respectively with the granules 3 which are carriers of electrostatic charges of opposite sign to the charge of the fibers 2. Thus, it is advantageous to cancel the electrostatic charges of the components of the mixture 1 in order to be able to more easily separate the said components.

[0060] Indeed, the inventors have observed that the fibers 2 and granules 3 of the crude mixtures 1 are often electrically charged, in particular as a result of the friction which these fibers and granules have undergone during the operations of shredding, conveying, pouring, etc., and that, as long as these components carry residual electrostatic charges, it is almost futile to try to dissociate them from each other by simple mechanical action, insofar as the electrostatic attractive forces between components carrying charges of opposite signs have the effect of almost instantaneously re-agglomerating said components to each other.

[0061] The neutralization proposed according to the invention therefore makes it possible to significantly improve the effective dissociation of the components of mixture 1.

[0062] Preferably, the bipolar charges will be generated, by a neutralization device 40, by ionizing the ambient gaseous atmosphere in the vicinity of the receptacle 10, here therefore preferably by ionizing the ambient air which bathes the installation 100.

[0063] To obtain this ionization, the neutralization device 40 will preferably use an alternating electric field generator, the frequency of which will preferably be between 50 Hz and 60 Hz, and the amplitude preferably between 3 kV and 7 kV.

[0064] The separation process according to the invention then comprises, following the dissociation step (S2), a sieving step (S3) during which the mixture 1 treated in accordance with the dissociation step (S2) is passed over the sieve 11 in order to retain in the receptacle 10 a first product PI from the mixture 1, first product PI which has, as shown schematically in figures 3 and 6, a fiber content 2 greater than that of the mixture 1 while a second product P2 from the mixture 1 is discharged through the sieve 11, second product P2 having a granule content 3 greater than that of the mixture 1.

[0065] It will be noted in fact that the fibers 2 tend to intertwine and to be placed across the openings of the mesh of the sieve 11, which prevents their passage through said sieve 11.

[0066] It should also be noted that, in practice, sieving can preferably be carried out at the same location as, and therefore almost simultaneously with, the dissociation step (S2), in that the sieve 11 is located in a region of space subjected both to the mechanical stirring that agitates and to the ionic bombardment that neutralizes. Thus, as soon as they are dissociated, the fibers 2 and granules 3 are directly exposed to the action of the sieve 11, without having had the time or opportunity to re-agglomerate.

[0067] Preferably, the first cylindrical drum 10 shall have an axial length greater than its internal diameter, for example at least 1.5 times greater, preferably at least 2 times greater, or even at least 4 times greater or at least 5 times greater than its internal diameter. This will notably allow a significant quantity of mixture 1 to be held within the receptacle 10 while efficiently distributing the mixture 1 over a large surface area of ​​the sieve 11, in a relatively thin layer that is therefore easy to agitate and neutralize.

[0068] The sieve 11 equipping the side wall 10L of the first cylindrical sieving drum 10 will advantageously form an annular structure around the central axis X10, and will typically cover, in the same section normal to the central axis X10, and where appropriate considering the sum of the different grid panels 13 arranged around the central axis X10 in the section considered, a total angular coverage of at least 240 degrees or even at least 270 degrees around the central axis X10 (that is to say that at least two-thirds, preferably at least three-quarters, of the circumference of the side wall 10L are made up of one or more grids 13 of the sieve 11), preferably at least 300 degrees, or even at least 330 degrees.

[0069] Advantageously, this will allow a portion of the sieve 11 to be permanently in contact with the mixture 1, in the lower zone of the first sieving drum 10.

[0070] The mesh size of the sieve 11 will of course be defined in such a way as to ensure segregation of one of the components (here the fibers 2) with respect to the other component (here the granules 3).

[0071] As an indication, the mesh of the sieve 11 will preferably be between 2 mm and 6 mm.

[0072] It will be noted that the RIO rotation of the first sieving drum 10 promotes the action of the sieve 11, by allowing the mixture 1 to slide continuously in contact with the mesh of the sieve 11.

[0073] Of course, collectors can be provided to collect the first product PI on the one hand and, separately, the second product P2 on the other hand.

[0074] In particular, a first collector may be provided in the downstream extension of the first screening drum 10, opposite the lower axial end of said first screening drum 10, in order to collect the first product PI, here enriched in fibers 2 compared to the original mixture 1, as the production of said first PI product continues.

[0075] It will be noted that, by convention, the "contents" of fibers 2, respectively of granules 3, of the original mixture 1, and of the products PI, P2, will preferably correspond to the proportion by weight of the component considered (fiber or granule) in the mixture 1 or the product PI, P2 considered.

[0076] Preferably, the dissociation step (S2) comprises, simultaneously with the stirring substeps (S201) and neutralization substeps (S202), a blowing substep (S203), according to which the mixture 1 contained in the receptacle 10 is subjected to a forced gas flow F50, preferably a forced air flow, which on the one hand contributes to the mechanical mixing and aeration of said mixture 1, and on the other hand promotes the introduction and dissipation of bipolar charges within said mixture 1.

[0077] The blowing action advantageously enhances the effectiveness of the agitation and neutralization actions, and therefore ultimately the dissociation action. Thus, the three modes of action engaged jointly in accordance with the invention, namely mechanical mixing, electrostatic neutralization, and blowing, combine in perfect synergy to optimize dissociation.

[0078] It will be noted in particular that blowing makes it possible to obtain, mechanically, an aeration of the mixture 1, that is to say a reduction of the compactness of the mixture by the creation of voids, filled with the blown gas, here filled with air, between the components of the mixture, and also contributes to the movement of the components of the mixture relative to each other, which makes it possible to keep the fibers 2 separated from the granules 3.

[0079] The gas flow F50 also allows the bipolar charges to be transported to the mixture 1 and then facilitates the diffusion of said charges within the aerated mixture 1, which ensures a relatively homogeneous and deep neutralization of said mixture 1.

[0080] For this purpose, the gas flow F50 will preferably be directed towards the lower half of the first sieving drum 10, and in particular towards the lower portion of the side wall 10L, in the area where the mixture 1 being processed is located and where, in particular, the mixing and sieving take place.

[0081] Preferably, the sieving step (S3) described above forming a first sieving step, the separation process according to the invention comprises a second sieving step (S4), during which, as can be seen in particular in Figures 3 and 6, the second product P2 is sieved by means of a second sieving drum 20 having a diameter greater than that of the first sieving drum 10 so as to form a second tubular wall 20L surrounding said first sieving drum 10 at a radial distance from the tubular lateral wall 10L said first sieving drum 10, and which forms a second sieve 21 whose mesh is finer than that of the first sieve 11 used during the first sieving step (S3), so that a third product P3 is evacuated through the second sieve 21, the content of granules 3 being greater than that of the second product P2.

[0082] It is thus advantageous to obtain a third product P3 which is particularly well refined, by means of an installation 100 which remains particularly compact.

[0083] As an indication, the mesh of the second sieve 21 may preferably be less than 4 mm, or even less than 2 mm, and for example between 1 mm and 4 mm, or even between 1 mm and 2 mm.

[0084] Preferably, the second tubular wall 20L is coaxial with the first sieving drum 10. More generally, the second sieving drum 20 is therefore preferably coaxial with the first sieving drum 10.

[0085] Advantageously, the first and second sieving drums 10, 20 being lying down, preferably substantially horizontal, and more preferably inclined to ensure the conveyance of the mixture 1 and the products PI, P2 retained by the sieves 11, 21, and said first and second sieving drums 10, 20 overlapping axially, the components of the mixture 1, here mainly the granules 3, can pass successively through the first sieve 11 and then the second sieve 21 naturally, by gravity, in a generally radial direction with respect to the central axis X10.

[0086] The third product P3 thus falls naturally into a third collector 25 (or conveyor) placed under the second sieving drum 20, while the second product P2, or at least what remains of the second product P2 in the second sieving drum 20 after evacuation of the third product P3 through the second sieve 21, can be collected by a second collector (or conveyor) located at the downstream axial end of the second sieving drum 20, and separate from the first collector (or conveyor) which collects the first product PI at the outlet of the first sieving drum 10, so that the first product PI and the second product P2 do not mix.

[0087] According to a possible variant of the process, the second product P2, which will have been retained in the second sieving drum 20, can be recovered and reintroduced into the inlet of the first sieving drum 10 to be subjected to a new separation cycle, in order typically to recover, during this second pass through the first sieving drum 10, the fibers 2 which would have been released by the first sieving drum 10 during the first step (S3) of sieving the initial mixture 1.

[0088] Preferably, the second product P2 located in the second sieving drum 20 will also, like the first product PI and the mixture 1 contained in the first sieving drum 10, be subjected to an agitation action and an action of neutralization.

[0089] Preferably, the second sieving drum 20 will be driven in rotation for this purpose, preferably a rotation synchronous with, and more preferably a rotation linked to, the rotation RIO of the first sieving drum 10.

[0090] Similarly, the second sieving drum 20 will preferably be located in the area of ​​influence of the bipolar charges, and even more preferably on the path of the gas flow F50 ensuring the blowing action.

[0091] The dissociation of the fibers 2 and the granules 3, which begins in the first sieving drum 10, will thus be continued and ensured also within the second sieving drum 20.

[0092] Although the second sieving drum 20 has a diameter strictly greater than the first sieving drum 10, in order to contain the latter, the arrangement of said second sieving drum 20 may preferably be similar to that of the first sieving drum 10, for one, several, or even all of the characteristics described above, and may therefore be deduced mutatis mutandis from the arrangement of the first sieving drum 10.

[0093] Preferably, the receptacle 10, here therefore the first sieving drum 10, is located inside a chamber 60 which is delimited by walls 61.

[0094] Said chamber 60, which allows the functional components of the installation to be separated from the outside of the installation, advantageously contains the receptacle(s) 10, here the first and second screening drum 10, 20, their respective screens 11, 21, as well as the neutralization devices 40 and blowing devices 50, here in the form of blowing ionizing bars 52.

[0095] The process can then advantageously include a step (S5) of fiber recovery 2 during which one and / or the other of the walls 61 of the chamber 60 are scraped, for example by means of a scraper or a brush, in order to recover fibers 2 of the mixture 1 which have been projected out of the receptacle 10, or more generally out of one or the other of the first and second screening drums 10, 20, by the forced gas flow F50, and which have remained attached to said walls 61.

[0096] The inventors observed that the forced gas flow F50, and the movements induced by said gas flow in the relatively confined atmosphere of the chamber 60, had the effect of transporting fibers 2 from the mixture 1 to the walls 61 of the chamber, particularly to the vertical walls 61, and that these fibers 2 accumulated, by spontaneous adhesion to the inner faces of said walls 61, to form a fourth product, with a fluffy appearance, distinct from the first, second, and third products P1, P2, P3, and of very high purity, that is to say, consisting almost exclusively, or even exclusively, of fibers 2, and therefore almost devoid of granules 3, or even totally devoid of granules 3, so that it was It is particularly interesting to recover this fourth product.

[0097] Of course, the invention also relates as such to a separation installation 100 which is intended to receive a mixture of fibers 2 and granules 3 in order to separate said fibers 2 from said granules 3.

[0098] Said installation 100 comprises a receptacle 10 which is arranged to receive the mixture 1 and which is provided with a sieve 11, an agitation device 30 which allows the mixture 1 contained in the receptacle 10 to be stirred, a neutralization device 40 designed to emit bipolar charges towards the mixture 1 while said mixture 1 is being stirred in the receptacle 10, in order to be able to neutralize electrostatic charges of the fibers 2 and the granules 3, the agitation device 30 and the neutralization device 40 being arranged to act jointly on the mixture 1 so as to be able to dissociate agglomerates of fibers 2 and granules 3 and thus facilitate the sieving of the mixture 1 by the sieve 11.

[0099] Preferably, the stirring device 30 is designed to drive the sieve 11, and more generally the receptacle 10, into motion.

[0100] Preferably, as detailed above, the receptacle 10 is formed by a first cylindrical sieving drum 10 which is delimited by a tubular side wall 10L which extends along and around a central axis X10 forming with the horizontal an angle of less than 30 degrees, preferably non-zero, tubular side wall 10L of which at least a portion forms the sieve 11.

[0101] Preferably, the stirring device 30 can then be designed to drive said first sieving drum 10 in rotation RIO on itself, around its central axis X10, in order to cause mixing of the mixture 1.

[0102] Regardless of the form of the agitator used to cause the mixing of the mixture 1, and in particular if said mixing results from a movement of the receptacle 10, more particularly from a rotation RIO of the first sieving drum 10, the stirring device 30 may be equipped with a mixing motor 31, preferably an electric motor, to ensure the drive of the moving part(s) at the origin of the mixing, here typically the rotation of the first sieving drum 10.

[0103] Advantageously, the movement of the receptacle 10, and more particularly the rotation RIO of the sieving drum 10, allows, in addition to stirring the mixture 1 to dissociate it, to create a relative movement between said mixture 1 and the sieve 11, in order to create the sieving action.

[0104] Preferably, the installation 100 comprises a blowing device 50 arranged to generate a forced gas flow F50, preferably a forced air flow, and to direct said gas flow F50 onto the mixture 1 subjected to the combined action of the stirring device 30 and the neutralizing device 40, so that said gas flow F50 on the one hand contributes to the mixing of mixture 1 and to an aeration of said mixture, and on the other hand promotes the introduction and dissipation of bipolar charges within said mixture 1.

[0105] The gas flow F50 may take the form of an air curtain, or one or more jets emanating from as many nozzles 51, as can be seen in [Fig.6].

[0106] The flow rate of the gas flow F50 shall be chosen sufficiently high so that the power of said incident flow effectively produces a blowing effect on the components of the mixture, and in particular so that the gas flow 50 is powerful enough to be able to entrain and agitate the fibers 2, and detach said fibers 2 from the granules 3.

[0107] The blowing action will thus provide a second mechanical mixing component, in addition to the first mechanical mixing component which is provided by the movement, here by the rotation RIO, of the receptacle 10.

[0108] Preferably, the installation 100 comprises at least one ionizing blowing module 52, and preferably several ionizing blowing modules 52, each of which combines within the same sub-assembly, for example in the form of a blowing ionizing bar 52, both a blowing device 50 and a neutralization device 40.

[0109] Advantageously, such ionizing blowing bars are compact, directly available commercially, and their maintenance or replacement is particularly simple.

[0110] According to one arrangement possibility, and as illustrated in Figures 1 and 3, an ionizing blowing module 52, here an ionizing blowing bar oriented lengthwise parallel to the central axis X10, and more preferably two ionizing blowing modules 52, here two ionizing blowing bars parallel to each other and to the central axis X10, can be arranged outside the first sieving drum 10, and more preferably outside the assembly formed by the first and second sieving drums 10, 20.

[0111] Said blowing ionizing modules 52 will preferably be arranged higher than the central axis X10, or even above the crest line of the screening drum 10, 20 which is radially the outermost (in practice, here, the second screening drum 20 in a configuration with two nested screening drums 10, 20).

[0112] A height adjustment system may also be provided to allow the height of either of the ionizing blower modules 52 to be adjusted, in order to optimize the action of said modules.

[0113] Preferably, said blowing ionizing modules 52 shall be arranged symmetrically with respect to each other with respect to the vertical sagittal plane which contains the central axis X10.

[0114] The respective gaseous fluxes F50 generated by said blowing ionizing modules 52, which carry the bipolar charges, shall be pointed at the, respectively the, sieving drums 10, 20, preferably so that the initial directions of the gas flows F50 are transverse to the central axis X10, and therefore not parallel to said central axis X10, so that the gas flows interact efficiently with the mixture 1.

[0115] According to another arrangement possibility, illustrated in [Fig.4], one or more ionizing blowing modules 52, where appropriate all the ionizing blowing modules 52 equipping the installation 100, are implanted inside the first screening drum 10, and oriented so as to point their gas flow F50 and their flow of bipolar charges towards the lower portion of said first screening drum 10.

[0116] Said blowing ionizing modules 52 will of course be arranged above the filling level reached by the mixture 1 within the first sieving drum 10.

[0117] More specifically, these gas flows F50 will be directed so as to cover substantially a fictitious surface which is parallel to the central axis X10 and which is located at a height between 1 / 4 and 1 / 2 of the internal diameter relative to the lower line of the side wall 10L forming the bottom of the sieving drum 10. Thus, said gas flows F50 will cover substantially the entire surface of the mixture 1 contained in said receptacle 10.

[0118] In this respect, it should be noted that having two ionizing blowing modules 52, each pointing in a substantially opposite direction, makes it possible to cover a large area by means of the gaseous fluxes F50.

[0119] By arranging the blowing ionizing modules 52, and more particularly the blowing ionizing bars, inside the first sieving drum 10, one benefits advantageously from a compact arrangement, as well as a proximity between the source of the bipolar charges and the mixture 1, which improves the interaction of the bipolar charges with the mixture 1, in particular to carry out the first dissociation of said mixture 1.

[0120] If, on the contrary, the blowing ionizing modules 52, and more particularly the blowing ionizing bars, are placed outside the first sieving drum 10, and more generally outside the whole of the first and second sieving drums 10, 20, as can be seen in [Fig.3], then the flow of bipolar charges can advantageously cover more easily, and simultaneously, the two sieving drums 10, 20, and in particular the space between the first sieving drum 10 and the second sieving drum 20.

[0121] In particular, when the installation 100 includes a chamber 60, which forms part of the fixed frame of said installation 100, chamber 60 which is delimited by walls 61 and which contains the receptacle(s) 10, here the first and second screening drum(s) 10, 20, their respective screen(s) 11, 21, as well as the neutralization device(s) 40 and blowing device(s) 50, here the blowing ionizing bars 52, then the placement of Ionizing blowing bars 52 outside the sieving drum(s) 10, 20 will facilitate, by vortex effect, the diffusion of bipolar charges substantially throughout the internal volume of said chamber 60.

[0122] According to one possible embodiment, it will be possible to combine within the installation 100 a set of ionizing blowing bars 52 external to the second screening drum 20 and a set of ionizing blowing bars 52 internal to the first screening drum 10, in order to combine the aforementioned advantages.

[0123] Preferably, the installation 100 comprises a second cylindrical sieving drum 20, with a diameter greater than that of the first sieving drum 10, said second sieving drum 20 surrounding the first sieving drum 10, preferably in a coaxial arrangement with said first sieving drum 10, in order to form around said first sieving drum 10 a second receptacle 20 delimited by the tubular side wall 20L of the second sieving drum, which side wall 20L of the second sieving drum comprises a second sieve 21 whose mesh is finer than the mesh of the sieve 11 of the first sieving drum 10.

[0124] Said second sieving drum 20 is also driven in rotation about its central axis. This rotation could be different, and in particular at a different angular velocity than that of the first sieving drum 10, which would allow for additional mixing, particularly between the two sieving drums 10 and 20, thus improving the sieving. However, the two sieving drums 10 and 20 are preferably driven together in rotation, in the same direction and at the same angular velocity, which notably simplifies the structure of the installation 100 by providing a rotation support and / or a drive system that are common to both sieving drums 10 and 20.

[0125] Preferably, a single mixing motor 31 will be used, common to both sieving drums 10, 20.

[0126] Just like the first sieving drum 10, the second sieving drum 20 will preferably have an inclined central axis, in the same direction as the central axis X10 of the first sieving drum 10, and preferably coincident with the central axis X10 of the first sieving drum 10, in order to continuously convey the second product P2 towards the outlet, located lower than the inlet, of said second sieving drum 20.

[0127] Of course, the invention is by no means limited to the examples of embodiment described above, the person skilled in the art being able in particular to isolate or freely combine one or the other of the aforementioned characteristics, or to substitute equivalents for them.

Claims

Demands

1. A separation process for separating fibers (2) and granules (3) from a mixture (1), said fibers from said granules, said process comprising for this purpose a feeding step (S1), during which the mixture (1) is brought into a receptacle (10) provided with a sieve (11), a dissociation step (S2), during which a substep (S201) of agitation is carried out simultaneously, in which the mixture (1) contained in the receptacle (10) is mechanically stirred, and a substep (S202) of neutralization is carried out, in which the mixture (1) being stirred in the receptacle (10) is exposed to bipolar charges in order to neutralize electrostatic charges of the fibers (2) and granules (3),then a sieving step (S3) during which the mixture (1) treated in accordance with the dissociation step (S2) is passed over the sieve (11) in order to retain in the receptacle (10) a first product (PI) from the mixture (1), which first product (PI) has a higher fiber (2) content than the mixture (1), while a second product (P2) from the mixture (1) is discharged through the sieve (11), this second product (P2) having a higher granule (3) content than the mixture (1).

2. A method according to claim 1 characterized in that the dissociation step comprises, simultaneously with the substeps (S201) of agitation and (S202) of neutralization, a substep (S203) of blowing, according to which the mixture (1) contained in the receptacle (10) is subjected to a forced gas flow (F50), preferably a forced air flow, which on the one hand contributes to the mechanical mixing and aeration of said mixture (1), and on the other hand promotes the introduction and dissipation of bipolar charges within said mixture (1).

3. A method according to claim 2 characterized in that the receptacle (10) is located inside a chamber (60) which is delimited by walls (61), and in that the method includes a step (S5) of fiber recovery during which one and / or the other of the walls (61) of the chamber (60) is scraped in order to recover fibers (2) of the mixture (1) which have been projected out of the receptacle (10) by the forced gas flow (F50) and which have remained attached to said walls (61).

4. A method according to any one of claims 1 to 3 characterized in that a first sieving drum cy- is used as a receptacle (10) lindrique delimited by a tubular side wall (10L) which extends along and around a central axis (X10) forming with the horizontal an angle of less than 30 degrees, preferably non-zero, tubular side wall (10L) of which at least a portion forms the sieve (11), and in that, during the substep (S201) of stirring, a rotation (RIO) of the first sieving drum on itself, around its central axis (X10), is used to cause a mixing of the mixture (1).

5. The method according to claim 4 characterized in that it comprises a second sieving step (S4), in which the second product (P2) is sieved by means of a second sieving drum (20) which has a diameter greater than the first sieving drum (10) so as to form a second tubular wall (20L), preferably coaxial with the first sieving drum (10), a second tubular wall (20L) which surrounds said first sieving drum (10) at a radial distance from the tubular side wall (10L) of said first sieving drum, and which forms a second sieve (21) having a finer mesh than that of the first sieve (11) used in the first sieving step (S3), so that a third product (P3) with a granule content (3) greater than that of the second product (P2) is discharged through the second sieve (21).

6. A process according to any one of the preceding claims, characterized in that it applies to a mixture (1) which contains textile fibers (2), preferably polyethylene terephthalate, and granules (3) of rubber-based material.

7. A method according to any one of the preceding claims, characterized in that it allows the separation of fibers (2), contained in the mixture (1), which have a length which is between 1 mm and 10 mm, and a larger transverse dimension which is between 10 pm and 1 mm.

8. The method according to claim 7 characterized in that the fibers (2) are mixed with granules (3) having an equivalent diameter between 125 pm and 5 mm.

9. A method for recycling a pneumatic tire comprising a grinding step, during which at least a portion of said pneumatic tire is reduced into a mixture containing textile fibers (2) and granules (3) of rubber-based material and then a sorting step during which said mixture is subjected to a separation process according to any one of claims 1 to 8.