Method for selectively separating constituents of a mixture of fragmented organic synthetic materials by means of a dense sequentially stirred aqueous suspension

Abstract

The invention relates to a method for selectively separating the constituents of a mixture of organic synthetic materials that are in fragmented form, the method comprising at least one step of separating the constituents by difference in density in an aqueous suspension (100) of solid pulverulent particles contained in a separation tank (2), the aqueous suspension (100) being subjected to sequential stirring by discontinuous upward external recirculation by means of a sampling pump (10) having an inlet diameter identical to the outlet diameter, the recirculation speed being defined in order to obtain a rate of stirring of the aqueous suspension (100) within the tank of between 25 m3 / h and 35 m3 / h, the sequential stirring comprising sequences of stirring for a determined operating time of the sampling pump (10), interspersed with a stoppage time of the pump, which stoppage time is greater than the operating time of the pump.

Description

A method for the selective separation of constituents from 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 in question generally originate from automotive shredding residues and end-of-life consumer goods. These materials contain a variety of synthetic organic materials, including polymers and / or copolymers, filled or unfilled, flame-retardant or not, with or without additives, which are considered recoverable. A multitude of other materials, such as metals, minerals, and other contaminants, are considered problematic contaminants and must be removed beforehand. Other waste materials, such as mixed industrial waste containing synthetic organic materials and packaging waste containing polymers and / or copolymers from municipal collections, which also contain mixed polymer materials, can also be considered potentially recoverable.

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

[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 consisting of 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 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 being 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 by means of a sampling pump having 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 m, 3 / h and 35 m 3 / h, and preferably on the order of 30 m 3 / h and in that 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.

[0009] Thus, the combined implementation of (i) sequential mixing, in which each active sequence is followed by a pause longer than the operating time of the sampling pump, (ii) a symmetrical pump configuration (inlet diameter identical to outlet diameter), and (iii) an optimized recirculation flow rate results in effective microcirculation within the aqueous suspension. This microcirculation significantly prevents the vertical sedimentation of powdery solid particles (at least 2 millimeters in size) while keeping them suspended in the aqueous phase. Simultaneously, the extended pause promotes a backflow effect, allowing the spontaneous removal of any large or high-density materials (such as large polymer fragments), thereby considerably reducing the risk of clogging the pump and its recirculation line.This passive unclogging capability is enhanced by the pump's unique geometry, which, unlike standard pumps, does not reduce the outlet diameter, thus minimizing the tendency for particles to become stuck. Thanks to the synergy of these features, reliable, continuous, and durable separation of synthetic organic materials by density is achieved.

[0010] According to a preferred implementation, the operating time of the sampling pump corresponds to 2 / 3 of the time of the mixing sequence.

[0011] Advantageously, the mixing sequences are cyclical.

[0012] Advantageously, the sampling pump is placed at a manometric height so as to expel, at each stop time and for 1 / 10 ème at least during the time the sampling pump is stopped, the powdery particles are stationary in front of the inlet of the sampling pump.

[0013] Advantageously, external recirculation of the aqueous suspension is carried out by taking the suspension from the bottom of the separation tank and reinjecting it into the upper part of said separation tank.

[0014] Advantageously, the sampling pump has a completely free passage.

[0015] Advantageously, the powder particles are of natural origin, synthetic origin, or a mixture of particles of natural and synthetic origin.

[0016] Advantageously, the powdered particles are chosen from the group of mineral materials, and preferably from that of carbonates. According to an alternative embodiment, the powdered particles may be derived from amorphous materials such as silicate.

[0017] 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 silicates.

[0018] 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

[0019] 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:

[0020] Lare 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.

[0021] For clarity, identical or similar elements of the different embodiments are identified by identical reference symbols across all figures. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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, particularly used and to be recovered by recycling, which are in a fragmented form.

[0023] 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.

[0024] The separation step is carried out in a hydraulic separator 1 as illustrated in the.

[0025] The hydraulic separator 1 includes a separation tank 2 containing the aqueous suspension 100 of powdery solid particles.

[0026] The selective separation suspension used consists of dimensionally selected, powdery solid particles with a particle size of less than 50 mm. These powdery particles are of natural origin, synthetic origin, or a mixture of natural and synthetic particles. Advantageously, the powdery particles are chosen from the mineral group, preferably from the carbonate group, and in particular calcium carbonate (calcite), precipitated calcium carbonate, magnesium carbonate, and dolomite (calcium-magnesium carbonate). The powdery particles may also be amorphous materials such as silicates. These preferably have a particle size of approximately 20 mm.

[0027] 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.

[0028] 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.

[0029] The hydraulic separator 1 further includes 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.

[0030] The sampling pump 10 advantageously has an inlet diameter identical to the outlet diameter. It is positioned at a manometric height so as to expel, at each stop time and for 1 / 10 èmeat least during the stopping time of the sampling pump 10, the powdery particles stationed in front of the inlet of the sampling pump 10. Thus, according to an example of an embodiment, the sampling pump will advantageously be placed at a manometric height of at least 3 meters, in order to allow, when the said pump stops, a flushing phenomenon of at least 2 seconds, thus allowing the powdery particles stationed in front of the inlet of the pump to be expelled.

[0031] Advantageously, the sampling pump 10 is a vortex type pump with full free passage.

[0032] Advantageously, the hydraulic separator includes means for measuring the density of the aqueous solution. The measurement is preferably carried out continuously. If a decrease in the density of the aqueous suspension in the separation tank is found to be unacceptable, i.e., considered a density drift, a specified quantity of a suitable correction medium is introduced to correct the observed drift upwards. Similarly, if an increase in the density of the aqueous suspension in the separation tank is found to be unacceptable, i.e., considered a density drift, a specified 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.

[0033] The separation process with the hydraulic separator just described is as follows.

[0034] 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 includes 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.

[0035] 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 m 3 / h and 35 m 3 / h, and preferably on the order of 30 m 3 / h.

[0036] Due to its position at the manometric height, the sampling pump 10 expels during each rest cycle and for 1 / 10 èmeat least during the stopping time of the sampling pump 10, the powdery particles are stationary in front of the inlet of the sampling pump 10.

[0037] As illustrated, external recirculation of 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.

[0038] 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 in a weight quantity in dry weight / dry relative to the weight quantity of powdered particles suspended of between 1% and 20%, and preferably 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 amorphous materials such as silicate.

[0039] 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, copolymers of maleic anhydride and styrene sulfonic acid, copolymers of methylacrylamide and substituted (methyl)acrylic acid, neutralized, esterified or not, copolymers of methylacrylamide-alkylsulfonic acid and (methyl)acrylamide, water-soluble diacrylic acid polymers implemented in the acidic form or, possibly, neutralized in whole or in part by alkali and / or alkaline earth agents, by amines salified by monovalent and / or polyvalent ions,and / or esterified or by water-soluble acrylic copolymers having phosphate, phosphonate, sulfate, or sulfonate functional groups.

[0040] Of course the invention is not limited to the described method of implementation and alternative embodiments can be made without departing from the scope of the invention as defined by the claims.

[0041] Furthermore, the separation process has been described based on separation carried out using a single hydraulic separator. It is clear, of course, that the separation can be carried out using several hydraulic separators 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 specific density "ds" determined according to the components to be separated in the relevant hydraulic separator.

[0042] 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

A process for the selective separation of the constituents of a mixture of synthetic organic materials, namely polymers and / or copolymers, particularly 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),the aqueous suspension (100) contained in the separation tank (2) being subjected to sequential mixing by discontinuous upward external recirculation of the aqueous suspension (100) by means of a sampling pump (10), the recirculation speed being defined to obtain a mixing flow rate of the aqueous suspension (100) within the separation tank (2) of between 25 m, 3 / h and 35 m 3 / h, and preferably on the order of 30 m 3 / h, characterized in that the sequential mixing includes 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), the sampling pump (10) having an inlet diameter identical to the outlet diameter. Selective separation process according to claim 1, characterized in that the operating time of the sampling pump (10) corresponds to 2 / 3 of the time of the mixing sequence. Selective separation process according to claim 1 or claim 2, characterized in that the mixing sequences are cyclic. A selective separation method according to any one of claims 1 to 3, characterized in that the sampling pump (10) is placed at a manometric height such that it expels, at each stop time and for 1 / 10 ème at least during the stopping time of the sampling pump (10), the powdery particles are stationary in front of the inlet of the sampling pump (10). Selective separation process according to any one of claims 1 to 4, 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 reinjection into the upper part of said separation tank (2). Selective separation method according to any one of claims 1 to 5, characterized in that the sampling pump (10) is fully free-flowing. A process according to claim 1 to 6, characterized in that the powder particles are of natural origin, synthetic or a mixture of particles of natural and synthetic origin. A process according to any one of claims 1 to 7, characterized in that the particles are chosen from the group of mineral materials, and advantageously from the group of carbonates. A process according to any one of claims 1 to 7, characterized in that the particles are amorphous materials such as silicate. A process according to at least one of claims 1 to 9 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 powdery solid particles is introduced into said suspension in a weight quantity in dry weight / dry relative to the weight quantity of powdery particles put into suspension of between 1% and 20%, and preferably between 2% and 15%. A process according to claim 10, characterized in that the quantity by weight in dry weight of the water-soluble agent in relation to the quantity by weight of powdered particles put into suspension 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. A process according to claim 10, characterized in that the quantity by weight in dry weight of the water-soluble agent in relation to the quantity by weight of powdered particles put into suspension is between 1% and 20% and preferably between 2% and 15% when the powdered particles are derived from amorphous materials such as silicate. Use of the process according to at least one of claims 1 to 10, 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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