A method for the selective separation of constituents from a mixture of fragmented synthetic organic materials using a dense aqueous suspension stirred sequentially.

Abstract

The invention relates to a method for the selective separation of the constituents of a mixture of synthetic organic materials, namely polymers and / or copolymers, in particular used and to be recovered by recycling, in a fragmented form, comprising at least one step of separating the constituents by density difference in an aqueous suspension (100) of powdery solid particles dispersed in adequate quantity in an aqueous phase, to create a density level "ds" chosen as the separation threshold of the various fragmented synthetic organic materials to be selectively separated by type, the separation of the mixture being carried out in at least one hydraulic separator (1) comprising a separation tank (2) containing the aqueous suspension (100),characterized in that the aqueous suspension (100) contained in the separation tank (2) is subjected to sequential mixing by discontinuous upward external recirculation of the aqueous suspension (100) by means of a sampling pump (10) having an inlet diameter identical to the outlet diameter, the recirculation speed being defined to obtain a mixing flow rate of the aqueous suspension (100) within the separation tank (2) of between 25 m³ / h and 35 m³ / h, and preferably on the order of 30 m³ / h. Figure to be published with the abbreviation: Fig. 1,

Description

Title of the invention: Method for the selective separation of constituents of a mixture of fragmented synthetic organic materials using a dense aqueous suspension stirred sequentially. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the selective separation of constituents of mixtures of synthetic organic materials in a fragmented form.

[0002] The invention relates more particularly to a method for the selective separation of the constituents of a mixture of synthetic organic materials such as polymers and / or copolymers, in particular used and to be recovered by recycling, in a fragmented form, comprising at least one step of separating the constituents by difference in density in an aqueous suspension of powdery solid particles dispersed in adequate quantity in an aqueous phase, to create a density level "ds" chosen as the separation threshold of the various fragmented synthetic organic materials to be selectively separated by type, the separation of the mixture being carried out in at least one hydraulic separator comprising a separation tank containing the aqueous suspension. STATE OF THE ART

[0003] The used synthetic organic materials concerned generally originate from automotive shredding residues and end-of-life durable goods, in which a variety of types of synthetic organic materials, such as polymers and / or copolymers, filled or unfilled, flame-retardant or not, with or without additives, are considered recoverable, and in which a variety of other materials are considered troublesome contaminants, such as metals, minerals, and other miscellaneous contaminants that must be removed beforehand. Other waste, such as mixed industrial waste containing synthetic organic materials and packaging waste such as polymers and / or copolymers from municipal collections and also containing mixed polymer materials, can equally be considered potentially recoverable.

[0004] Among the processes for the selective separation of constituents of mixtures of synthetic organic materials in fragmented form, the one described in patent application EP1708819 is known.

[0005] The selective separation process described in the aforementioned application consists of selectively separating each of the constituents of a mixture of synthetic organic materials, particularly used materials intended for recycling and presented in fragmented form, by density difference using a dense liquid medium, which is an aqueous suspension of powdered particles dispersed in an aqueous phase. The separation by density difference is achieved by introducing the mixture into the dense liquid medium in an appropriate quantity within an aqueous phase to create a density level "ds" chosen as the separation threshold for the various fragmented synthetic organic materials to be selectively separated by type.

[0006] Although the separation process achieves satisfactory separation of each component of a mixture of synthetic organic materials, it nevertheless encounters a problem related to the dense medium used. This medium undergoes settling, resulting in uneven homogenization throughout the tank containing the dense medium.

[0007] The invention aims to remedy this problem by proposing a method for the selective separation of the constituents of an improved mixture of synthetic organic materials offering a homogeneity of the dense medium consisting of powdery particles dispersed in an aqueous phase into which the mixture of materials to be separated is poured. SUBJECT OF THE INVENTION

[0008] To this end, and according to a first aspect, the invention relates to a method for the selective separation of the constituents of a mixture of synthetic organic materials, namely polymers and / or copolymers, in particular used and to be recovered by recycling, in a fragmented form, comprising at least one step of separating the constituents by density difference in an aqueous suspension of powdery solid particles dispersed in adequate quantity in an aqueous phase, to create a density level "ds" chosen as the separation threshold of the various fragmented synthetic organic materials to be selectively separated by type, the separation of the mixture being carried out in at least one hydraulic separator comprising a separation tank containing the aqueous suspension,The selective separation process is remarkable in that the aqueous suspension contained in the separation tank is subjected to sequential mixing by discontinuous upward external recirculation of the aqueous suspension using a sampling pump with an inlet diameter identical to the outlet diameter, the recirculation speed being defined to obtain a mixing flow rate of the aqueous suspension within the separation tank of between 25 m³ / h and 35 m³ / h, and preferably on the order of 30 m³ / h.

[0009] Thus, thanks to the sequential mixing carried out, microcirculation is achieved at the level of the powdery particles of the aqueous suspension, making it possible to avoid vertical sedimentation of the powdery particles (at least over more than 2 millimeters) while keeping the powdery particles in suspension in the aqueous phase.

[0010] Advantageously, sequential mixing includes mixing sequences during a determined operating time of the sampling pump interspersed with a stopping time of the sampling pump greater than the operating time of the sampling pump.

[0011] According to a preferred embodiment, the operating time of the pump The sampling corresponds to 2 / 3 of the time of the mixing sequence.

[0012] Advantageously, the mixing sequences are cyclic.

[0013] Advantageously, the sampling pump is placed at a manometric height so as to expel, at each stop time and for at least 1 / 10th of the stop time of the sampling pump, the powdery particles stationary in front of the inlet of the sampling pump.

[0014] Advantageously, the external recirculation of the aqueous suspension is carried out by taking the suspension from the bottom of the separation tank and by reinjecting it into the upper part of said separation tank.

[0015] Advantageously, the sampling pump has a fully free passage.

[0016] Advantageously, the powder particles are of natural origin, synthetic or a mixture of particles of natural and synthetic origin.

[0017] Advantageously, the powdered particles are chosen from the group of mineral materials, and preferably from that of carbonates. According to an embodiment, the powdered particles may be derived from amorphous materials such as silicate.

[0018] Advantageously, a water-soluble agent for stabilizing the rheological characteristics and apparent density "ds" invariance of the aqueous suspension of powdered solid particles is introduced into said suspension in a dry weight / dry weight relative to the weight of powdered particles suspended, ranging from 0.02% to 20% depending on the particle composition chosen. Thus, the dry weight / dry weight of the water-soluble agent relative to the weight of powdered particles suspended is between 0.02% and 5%, and preferably between 0.1% and 2%, when the powdered particles are chosen from the group of mineral materials, and between 1% and 20%, and preferably between 2% and 15%, when the powdered particles are derived from amorphous materials such as silicate.

[0019] The invention also relates to the use of the separation selection process according to at least one of the characteristics previously described for the purpose of separating mixed polymer materials, in particular used, from the destruction of automobiles and / or end-of-life durable consumer goods. BRIEF DESCRIPTION OF THE FIGURES

[0020] Other features and advantages of the invention will become apparent from the detailed description of the invention which follows, given by way of example and with reference to the attached figure:

[0021] [Fig. 1] The [Fig. 1] represents a hydraulic separator for carrying out a selective separation of the constituents of a mixture of synthetic organic materials according to an example of an embodiment of the separation process according to the invention.

[0022] For greater clarity, identical or similar elements of the different embodiments are identified by identical reference signs throughout the figures. DETAILED DESCRIPTION OF THE INVENTION

[0023] In relation to the figure, a process and an associated hydraulic separator are described for selectively separating the constituents of a mixture of synthetic organic materials, such as polymers and / or copolymers, in particular used and to be recovered by recycling, which are in a fragmented form.

[0024] The selective separation process includes at least one step of separating the constituents by density difference in an aqueous suspension of powdered solid particles dispersed in an adequate quantity in an aqueous phase, to create a density level "ds" chosen as the separation threshold for the various fragmented synthetic organic materials to be selectively separated by type. According to the invention, the separation step includes a sequential stirring operation of the aqueous suspension.

[0025] The separation step is carried out in a hydraulic separator 1 as illustrated in [Fig.1].

[0026] The hydraulic separator 1 comprises a separation tank 2 containing the aqueous suspension 100 of powdery solid particles.

[0027] The selective separation suspension implemented consists of dimensionally selected powdered solid particles with a particle size of less than 50 µm. The powdered particles are of natural origin, synthetic origin, or comprise a mixture of particles of natural and synthetic origin. Advantageously, the powdered particles are chosen from the mineral group, preferably from the carbonate group, and in particular calcium carbonate (calcite), precipitated calcium carbonate, carbonate of Magnesium, dolomite (calcium and magnesium carbonate). Powdered particles can also be amorphous materials such as silicate. These will preferably have a particle size of around 20 µm.

[0028] In the illustrated example, the separation tank 2, generally polyhedral in shape with five faces, has a top face and four inclined lateral faces. The separation tank 2 has three openings for the passage of materials, namely an inlet opening 3 and two outlet openings 5, 6. In the illustrated embodiment, the inlet opening 3 is provided in the top face 4 of the separation tank 2, while the two outlet openings 5, 6 are provided on the lateral faces 7, 8, in their upper part and opposite each other.

[0029] The mixture of materials to be separated are introduced into the separation tank 2 through the inlet opening 3, the materials of the mixture having a density lower than the density "ds" of the aqueous suspension being discharged through the outlet opening 6, while the materials of the mixture having a density higher than the density "ds" will be discharged through the outlet opening 5 by means of a screw 9 which extends, in the illustrated example, on the lateral face 7 provided with the outlet opening 5, from the top of the separation tank 2 to the bottom of the latter.

[0030] The hydraulic separator 1 further comprises a sampling pump 10 connected to the separation tank 2 by a first fluid circuit 11 opening at the bottom of the separation tank 2, and a second fluid circuit 12 opening at the top of the separation tank 2, at the inlet opening 3. The sampling pump 10 and the first and second fluid circuits 11, 12 thus form a recirculation circuit external to the separation tank 2, the fluid recirculation being operated by said sampling pump 10.

[0031] The sampling pump 10 advantageously has an inlet diameter identical to the outlet diameter. It is placed at a manometric height such that, at each stoppage and for at least 1 / 10th of the stoppage time of the sampling pump 10, the powdery particles remaining in front of the inlet of the sampling pump 10 are expelled. Thus, according to one embodiment, the sampling pump will advantageously be placed at a manometric height of at least 3 meters, in order to allow, when the pump stops, a flushing effect lasting at least 2 seconds, thereby expelling the powdery particles remaining in front of the pump inlet.

[0032] Advantageously, the sampling pump 10 is a vortex-type pump with full free passage.

[0033] Advantageously, the hydraulic separator includes means for measuring the density of the aqueous solution. The measurement is preferably carried out continuously. In the event of a decrease in the density of the aqueous suspension in the tank of If the separation proves unacceptable, i.e., considered a drift in the density of the aqueous suspension, a specific quantity of a suitable correction medium is introduced to correct the observed drift upwards. Similarly, if an unacceptable increase in the density of the aqueous suspension in the separation cell is measured, i.e., considered a density drift, a specific quantity of a suitable correction medium is introduced to correct the observed drift downwards. For example, the correction medium used to lower the density of the aqueous solution would be water.

[0034] The separation process with the hydraulic separator just described is as follows.

[0035] The aqueous suspension 100 contained in the separation tank 2 is subjected to sequential mixing by discontinuous upward external recirculation of the aqueous suspension 100 by means of the sampling pump 10 through the first and second fluidic circuits 11, 12. The sequential mixing comprises mixing sequences during a determined operating time of the sampling pump 10 interspersed with a stopping time of the sampling pump 10 greater than the operating time of the sampling pump 10.

[0036] According to a preferred embodiment, the operating time of the sampling pump 10, which advantageously operates cyclically, corresponds to 2 / 3 of the mixing sequence time. "Operating" refers to the actual actuation of the sampling pump 10. Thus, for example, for an operating time of 20 seconds, the sampling pump will be stopped for 30 seconds before resuming a mixing sequence. Advantageously, the recirculation speed applied by the sampling pump 10 is defined so as to obtain a mixing flow rate of the aqueous suspension 100 within the separation tank 2 of between 25 m³ / h and 35 m³ / h, and preferably on the order of 30 m³ / h.

[0037] Due to its position at manometric height, the sampling pump 10 expels, at each rest cycle and for at least 1 / 10th of the stopping time of the sampling pump 10, the powdery particles stationary in front of the inlet of the sampling pump 10.

[0038] As illustrated, the external recirculation of the aqueous suspension 100 is carried out by taking the suspension from the bottom of the separation tank 2 and by reinjecting it into the upper part of said separation tank 2, through the inlet opening 3, by means of the sampling pump 10.

[0039] Advantageously, a water-soluble agent for stabilizing the rheological characteristics and apparent density invariance "ds" of the aqueous suspension 100 of powdered solid particles is introduced into said suspension according to a quantity by weight in dry weight / dry relative to the quantity by weight of powdery particles put into suspension of between 1% and 20%, and preferably between 0.02% and 5%, and preferably between 0.1% and 2% when the powdery particles are chosen from the group of mineral materials, and between 1% and 20% and preferably between 2% and 15% when the powdery particles are amorphous materials such as silicate.

[0040] Advantageously, the water-soluble agent for stabilizing the rheological characteristics and invariance of the apparent density "ds" of the suspension of powdered solid particles is chosen from the group consisting of phosphates and polyphosphates, alkylphosphate esters, alkylphosphonate, alkylsulfate, alkylsulfonate, lignin, lignosulfonates in the form of calcium, sodium, iron, chromium, iron and chromium salts, maleic anhydride and styrene sulfonic acid copolymers, substituted, neutralized, esterified or unsubstituted methylacrylamide and (methyl)acrylic acid copolymers, methylacrylamide-alkylsulfonic acid and (methyl)acrylamide copolymers, water-soluble diacrylic acid polymers implemented in the acidic form or, optionally, neutralized in whole or in part by alkaline agents. and / or alkaline earth metals, through amines salified by monovalent and / or polyvalent ions,and / or esterified or by water-soluble acrylic copolymers possessing phosphate, phosphonate, sulfate, or sulfonate functional groups.

[0041] Of course the invention is not limited to the described embodiment and alternative embodiments can be made without departing from the scope of the invention as defined by the claims.

[0042] Furthermore, the separation process has been described on the basis of separation carried out on a single hydraulic separator. It is clear that the separation can be carried out on several hydraulic separators in order to refine the separation of the mixture's components. In this case, the hydraulic separators will be placed in cascade (one after the other), each separator being operated with an aqueous suspension of powdered particles having a density threshold "ds" determined according to the components to be separated in the hydraulic separator concerned.

[0043] The invention is described above by way of example. It is understood that a person skilled in the art is able to carry out different embodiments of the invention without departing from the scope of the invention.

Claims

Demands

1. A method for the selective separation of the constituents of a mixture of synthetic organic materials, namely polymers and / or copolymers, in particular used and to be recovered by recycling, in a fragmented form, comprising at least one step of separating the constituents by density difference in an aqueous suspension (100) of powdery solid particles dispersed in an adequate quantity in an aqueous phase, to create a density level "ds" chosen as the separation threshold of the various fragmented synthetic organic materials to be selectively separated by type, the separation of the mixture being carried out in at least one hydraulic separator (1) comprising a separation tank (2) containing the aqueous suspension (100),characterized in that the aqueous suspension (100) contained in the separation tank (2) is subjected to sequential mixing by discontinuous upward external recirculation of the aqueous suspension (100) by means of a sampling pump (10) having an inlet diameter identical to the outlet diameter, the recirculation speed being defined to obtain a mixing flow rate of the aqueous suspension (100) within the separation tank (2) of between 25 m3 / h and 35 m3 / h, and preferably of the order of 30 m3 / h.

2. Selective separation method according to claim 1, characterized in that the sequential mixing comprises mixing sequences during a determined operating time of the sampling pump (10) interspersed with a stopping time of the sampling pump (10) greater than the operating time of the sampling pump (10).

3. Selective separation method according to claim 2, characterized in that the operating time of the sampling pump (10) corresponds to 2 / 3 of the time of the mixing sequence.

4. Selective separation method according to claim 2 or claim 3, characterized in that the mixing sequences are cyclic.

5. A selective separation method according to any one of claims 1 to 4, characterized in that the sampling pump (10) is placed at a manometric height so as to expel, at at each stop time and for at least 1 / 10th of the stop time of the sampling pump (10), the powdery particles are stationary in front of the inlet of the sampling pump (10).

6. A selective separation method according to any one of claims 1 to 5, characterized in that the external recirculation of the aqueous suspension (100) is carried out by taking the suspension from the bottom of the separation tank (2) and by reinjecting it into the upper part of said separation tank (2).

7. A selective separation method according to any one of claims 1 to 6, characterized in that the sampling pump (10) is fully free-flowing.

8. A process according to claim 1 to 7, characterized in that the powder particles are of natural origin, synthetic or a mixture of particles of natural and synthetic origin.

9. A method according to any one of claims 1 to 8, characterized in that the particles are chosen from the group of mineral materials, and advantageously from the group of carbonates.

10. A method according to any one of claims 1 to 8, characterized in that the particles are amorphous materials such as silicate.

11. A process according to at least one of claims 1 to 10 characterized in that a water-soluble agent for stabilizing the rheological characteristics and invariance of the apparent density "ds" of the aqueous suspension 100 of powdered solid particles is introduced into said suspension in a weight quantity in dry weight / dry relative to the weight quantity of powdered particles put into suspension of between 1% and 20%, and preferably between 2% and 15%.

12. A process according to claim 11, characterized in that the weight quantity in dry weight / dry of the water-soluble agent in relation to the weight quantity of powder particles put into suspension is between 0.02% and 5% and preferably between 0.1% and 2% when the powder particles are chosen from the group of mineral materials.

13. A process according to claim 11, characterized in that the weight quantity in dry / dry weight of the water-soluble agent relative to the weight quantity of powdered particles suspended

14. is between 1% and 20% and preferably between 2% and 15% when the powdery particles come from amorphous materials such as silicate. Use of the process according to at least one of claims 1 to 11, for the selective separation of mixed polymer materials, in particular used, from the destruction of automobiles and / or end-of-life durable consumer goods.

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