System and method for purifying a substance

Abstract

The invention relates to a system (100) for purifying a substance in a contaminated state, the system comprising a separation device (1) for separating a first material and a second material flowing through a channel between an inlet and a head, and a compressed fluid circuit (101) for causing compressed fluid to flow through the channel, wherein the first material and the second material are not miscible, wherein the second material has a viscosity greater than the viscosity of the first material, wherein the separation device (1) is suitable for being connected to an outlet port arranged in the channel, wherein the outlet port is suitable for allowing the first material to exit the channel, and wherein the separation device (1) comprises: - a body (2) comprising a bore (20), the bore (20) comprising a first end (21) suitable for being connected to the outlet port and a second end (22) suitable for allowing the first material to be discharged from the separation device (1); - at least one screw arranged in the bore (20) such that a free space is present between the screw (4) and the bore (20), wherein the screw (4), when rotated, is suitable for allowing selective discharge of the first material out of the channel (11) via the free space.

Description

[0001] SYSTEM AND METHOD FOR PURIFYING A SUBSTANCE

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the separation of two materials, in particular in the context of the recycling of a polluted substance, more precisely to a device for separating two materials advantageously adapted to be connected to a channel in which the two materials circulate, such as a barrel of an extruder or another type of pipe.

[0004] STATE OF THE ART

[0005] Recycling polluted substances, for example polluted polymers, is currently difficult or even impossible to implement. Due to a lack of recycling solutions, the substances can be burned or buried, which generates a lot of pollution. A polluted substance can also be recycled, for example using an extruder, and one or more solvents are used to extract the pollutants from the substance. However, the solvent pollutes the substance, which may be decontaminated of the initial pollutants but recontaminated by pollutants initially included in the solvent. Metal sintered filters are also known that can be used with an extruder to allow, for example, the evacuation of pollutants, for example entrained by a compressed fluid, from the extruder while leaving a decontaminated substance in the extruder barrel.However, this type of filter is not suitable when the pressure in the sheath is greater than 150 bars so that it becomes clogged. Consequently, this type of filter does not allow the recycling of substances requiring work at higher pressures, for example requiring the use of a compressed fluid at a pressure greater than 150 bars for the substance to be properly decontaminated. Other examples of separation systems are presented in US 3751527 A1 , FR 2364759 A1 , US 3738409 A1 and US 3799234 A1 .

[0006] There is therefore a need for a solution to recycle polluted substances, such as polymers.

[0007] STATEMENT OF THE INVENTION

[0008] An aim of the invention is to provide a system for purifying a substance in a polluted state so as to obtain a first material comprising pollutants and a second material corresponding to said substance in a purified state, the two materials having different viscosities and not being miscible, comprising a channel in which the substance circulates, such as a barrel of an extruder or another type of pipe.

[0009] Another object of the invention is to provide a method for separating two materials to purify a substance in a polluted state, implemented by the purification system.

[0010] According to a first aspect, there is provided a system for purifying a substance in a polluted state so as to obtain a first material comprising pollutants and a second material corresponding to said substance in a purified state, comprising:

[0011] - a separation system adapted to treat a substance so as to obtain the first material and the second material, the first material and the second material not being miscible, the second material having a viscosity greater than the viscosity of the first material, the system comprising:

[0012] - a channel extending between an inlet and a head adapted to allow the exit of the second material, the channel comprising an outlet orifice adapted to allow the exit of the first material from the separation system;

[0013] - a device for separating the first material and the second material circulating in the channel between the inlet and the head, the separation device being adapted to be connected to the outlet orifice and comprising:

[0014] - a body comprising a bore, the bore comprising a first end adapted to be connected to the outlet orifice and a second end adapted to allow the evacuation of the first material from the separation device,

[0015] - at least one screw arranged in the bore such that a free space is present between the screw and the bore, the screw being adapted to allow, when rotated, selective evacuation of the first material from the channel via the free space;

[0016] - a compressed fluid circuit comprising a fluid reservoir, a compression system adapted to compress the fluid, a first conduit in fluid connection with a compressed fluid inlet orifice in the channel of the separation system and a second conduit in fluid connection with the second end of the bore of the separation device, so as to cause a flow of compressed fluid in the channel between the compressed fluid inlet orifice and the outlet orifice to entrain the pollutants so as to form the first material; - a device for decontaminating the first material in fluid connection with the second conduit, adapted to separate the fluid from the pollutants of the first material.

[0017] According to advantageous and non-limiting characteristics, taken alone or in any combination: the screw of the separation device comprises a scraping element adapted to scrape the second material in contact with the bore; the screw of the separation device comprises a thread, the free space comprising said thread; the separation device comprises at least two screws, including a central screw and at least one peripheral screw, the at least one peripheral screw being arranged around the central screw, each screw comprising a respective thread, the thread of each peripheral screw being adapted to mesh with the thread of the central screw when the screws are rotated; the separation device comprises a motor adapted to rotate each screw; the motor is connected to each screw via a magnetic coupling so as to ensure sealing;the separation system comprises at least one screw extending into the channel and adapted to, when rotated, convey the substance from the inlet to the head; the separation system is an extruder.;

[0018] According to another aspect, there is provided a method of separating a first material and a second material to purify a substance in a polluted state, by means of a purification system as described above, the first material comprising pollutants and a compressed fluid and the second material corresponding to said substance in a purified state, the first material and the second material not being miscible, the second material having a viscosity greater than the viscosity of the first material, said method comprising:

[0019] - introducing the substance in the polluted state into the channel via the inlet, said substance comprising at least one polymer and pollutants;

[0020] - injecting compressed fluid into the channel through the compressed fluid inlet port;

[0021] - dissociating the at least one polymer and the pollutants from the substance in the channel, forming the first material comprising the compressed fluid and the pollutants and forming the second material comprising the at least one polymer; - discharging the first material via the free space between the at least one screw of the separation device and the bore;

[0022] - evacuation of the second material through the head of the separation system;

[0023] - separation of the fluid and pollutants from the first material leaving the separation system.

[0024] DESCRIPTION OF FIGURES

[0025] Other features and advantages of the present invention will become apparent upon reading the following description of a preferred embodiment. This description will be given with reference to the appended figures, including: Figure 1 illustrates a separation device of the purification system; Figure 2 illustrates a part of the separation device of Figure 1; Figure 3 is an enlarged view of Figure 1; Figure 4 illustrates a separation device of the purification system in another embodiment; Figure 5 illustrates a part of the separation device of Figure 4; Figure 6 corresponds to a perspective view of a part of the separation device of Figure 4; Figure 7 illustrates a purification system comprising a separation system.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] Device

[0028] With reference to Figures 1 and 4, the purification system comprises a device 1 for separating a first material and a second material. Typically, from a substance in a polluted state, the separation device 1 makes it possible to obtain a first material comprising pollutants and a second material corresponding to the substance in a purified state.

[0029] The first material and the second material are immiscible. In other words, the first material and the second material cannot mix, i.e. they cannot form a single homogeneous material together. In this way, they can be separated. Immiscible also means insoluble, for example, in the case where the first material is gaseous or in a supercritical state and the second material is liquid, or in the case where the first material is liquid and the second material is solid. Thus, if the first material is gaseous and the second material is liquid, the second material is not soluble in the first material. If the first material is liquid and the second material is solid, the second material is not soluble in the first material.

[0030] The second material has a viscosity greater than the viscosity of the first material. Advantageously, the viscosity of the second material is at least 1000 times greater, preferably at least 10,000 times greater, than the viscosity of the first material. Said viscosities are considered at the temperature to which the two materials are brought for the purpose of their separation.

[0031] Advantageously, the first material has a density different from the density of the second material. Preferably, the first material has a density lower than the density of the second material. Preferably, the first material has a density at least 0.6 lower than the density of the second material.

[0032] The first material is preferably gaseous, supercritical or liquid.

[0033] According to a certain embodiment, the first material comprises pollutants. Advantageously, the first material comprises a compressed fluid, or even a fluid in a supercritical state. The fluid may be, for example, carbon dioxide, nitrogen, a mixture of carbon dioxide and water, a mixture of carbon dioxide and nitrogen, etc.

[0034] The second material is preferably liquid or solid. The second material may be in the form of a powder or granules, or in a molten state.

[0035] Advantageously, the second material comprises at least one polymer. The at least one polymer may be polyolefin, polyethylene, polypropylene or polyamide.

[0036] The separation device 1 is adapted to separate two materials which circulate in a channel 11. The two materials circulate in the channel 11 for example under the effect of pressure or a worm screw. The channel 11 can be for example a barrel of an extruder or more generally a cylindrical pipe.

[0037] The separation device 1 is adapted to be connected to an outlet orifice 11 arranged in the channel 11, the outlet orifice 11 being adapted to allow the first material to exit from the channel 11.

[0038] The separation device 1 comprises a body 2 comprising a bore 20. The bore 20 comprises a first end 21 adapted to be connected to the outlet orifice 11 of the channel 11 and a second end 22 adapted to allow the evacuation of the first material from the separation device 1. The separation device 1, in particular the bore 20, is therefore adapted to allow the circulation of the first material from the first end 21 to the second end 22.

[0039] Advantageously, the body 2 is made of a material resistant to the effects of abrasion, corrosion, pressure and temperature. Alloy steels are advantageously used.

[0040] As illustrated in Figures 1 to 6, the separation device 1 comprises at least one screw 4. The screw 4 is arranged in the bore 20 so that a free space is present between the screw 4 and the bore 20. The free space corresponds to the free volume between the external surface of the screw 4 and the internal surface of the bore, i.e. between the external surface of the screw 4 and the surface delimiting the conduit formed by the bore.

[0041] By free space is meant at least the clearance between the screw 4 and the bore 20. Preferably, this clearance is at most 0.1 mm, preferably at most 0.05 mm.

[0042] According to an exemplary embodiment, the screw 4 has a diameter greater than or equal to 9 mm, or even greater than or equal to 10 mm, or even greater than or equal to 11 mm, or even greater than or equal to 12 mm. According to this embodiment, the screw has a length greater than or equal to 250 mm, or even greater than or equal to 300 mm. However, those skilled in the art will be able to adapt these dimensions according to the channel 11 to which it is desired that the separation device 1 be adapted to be connected and according to the pressure in the channel 11.

[0043] Advantageously, the screw 4 comprises a thread 40. The thread 40 is preferably helical. In this case, the free space further comprises the free volume between the screw 4 and the bore 20 formed by the thread 40.

[0044] The screw 4 is adapted to allow, when rotated, selective evacuation of the first material from the channel 11 via the free space. By selective, it is understood that the screw is adapted to allow the evacuation of the first material from the channel 11 while preventing the exit of the second material from the channel 11.

[0045] Indeed, the second material being more viscous than the first material, the screw 4 prevents the second material from entering the bore 20.

[0046] The separation device 1 is therefore suitable for allowing the separation of materials at a pressure greater than or equal to 300 bars, or even greater than or equal to 350 bars. Indeed, the screw(s) 4 of the separation device 1 operate in a similar manner to an endless screw of an extruder. This configuration allows a significant pressure drop (i.e. a significant pressure drop), thus making it possible to push the densest material (i.e. the second material) towards the channel 11. Thus, the separation device 1 allows the separation of materials that could not be separated at lower pressures. For example, to allow the extraction of pollutants from a polluted polymer so as to obtain a purified polymer comprising less than 10 ppm of pollutants, it is necessary to use a fluid compressed at a pressure greater than or equal to 300 bars, or even greater than or equal to 350 bars.The separation device 1 is adapted to allow the separation of a first material comprising the compressed fluid and the pollutants and a second material comprising the purified polymer.

[0047] According to the embodiment illustrated in figures 1 to 3, the separation device 1 comprises a single screw 4. This embodiment has a simpler and less bulky structure.

[0048] According to other embodiments, the separation device 1 comprises a plurality of screws 4 including a central screw 4e and at least one peripheral screw 4a, 4b, 4c, 4d. The peripheral screw(s) 4a, 4b, 4c, 4d are arranged around the central screw 4e. Each screw 4 comprises a respective thread 40. The thread 40 of each peripheral screw 4a, 4b, 4c, 4d is adapted to mesh with the thread 40 of the central screw 4e when the screws 4 are rotated. In such a way, if second material comes into contact with one of the screws 4, called the first screw 4, the screw(s) 4 whose thread is meshed with the thread of this first screw 4 makes it possible to scrape, i.e. detach, the second material. In other words, each screw 4 is cleaned by the screw(s) 4 which is in contact with it. This prevents the second material from circulating in the bore 20 which could clog it.

[0049] In the embodiment illustrated in Figures 4 to 6, the separation device 1 comprises a central screw 4e and four peripheral screws 4a, 4b, 4c, 4d.

[0050] Preferably, the separation device 1 comprises a motor adapted to drive the screw(s) 4 in rotation. Advantageously, in the case where the separation device 1 comprises a plurality of screws 4, the separation device 1 comprises a motor which drives one of the screws 4 in rotation and the rotation of this screw 4 drives the other screws 4 in rotation.

[0051] Preferably, the motor shaft is not directly connected to the screw(s) 4. Preferably, the motor is connected to the screw(s) 4 via a magnetic coupling in order to ensure sealing. It is advantageous to have a good seal between the motor and the screw(s) 4 of the separation device 1 to allow the purification of the first material during the separation process described below. Indeed, sealing is essential to extract the pollutants included in the first material, because it is necessary to solubilize them. The solubilization of the pollutants can be achieved by the use of carbon dioxide CO? under high pressure. Thus, a good seal between the motor and the separation device 1 makes it possible to achieve very high pressures and therefore densities of carbon dioxide, typically close to those of carbon dioxide in the liquid state.

[0052] Advantageously, the separation device 1 comprises a scraping element 41 adapted to scrape the second material in contact with a screw 4 or the bore 20.

[0053] According to a preferred embodiment illustrated in Figures 1 to 3, the screw 4 comprises the scraping element 41. The scraping element 41 is preferably a part projecting from the screw 4 towards the internal surface of the bore 20. Consequently, when the screw 4 is rotated, the scraping element 41 scrapes the second material in contact with the bore, in particular the first end 21 of the bore 20.

[0054] According to another embodiment, the body 2 comprises the scraping element 41. The scraping element 41 is then preferably a portion projecting from the internal surface of the bore 20 towards the screw 4. Consequently, when the screw 4 is rotated, the scraping element 41 scrapes the second material in contact with the screw 4, in particular at the first end 21 of the bore 20.

[0055] The scraping element 41 makes it possible to prevent the second material from circulating in the bore 20 which could block it.

[0056] In the case of a separation device 1 comprising several screws 4, the thread 40 of each screw 4 forms a scraping element 41.

[0057] Separation system

[0058] Referring to Figure 7, there is provided a separation system 10 adapted to process a substance so as to obtain the first material and the second material.

[0059] Advantageously, the separation system 10 is an extruder or more generally a cylindrical pipe.

[0060] The separation system 10 comprises a channel 11 extending between an inlet 13 adapted and a head 15 adapted to allow the exit of the second material. The inlet 13 is adapted to allow the introduction of the substance into the channel 11. In the case where the separation system 10 is an extruder, according to the usual terminology, the channel 11 corresponds to the barrel of the extruder 10.

[0061] The channel 11 further comprises an outlet orifice 11 adapted to allow the first material to exit from the separation system 10.

[0062] The channel 11 also includes a compressed fluid inlet 14 adapted to allow the introduction of compressed fluid into the channel 11.

[0063] The separation system 10 comprises at least one screw 12 extending into the channel 11. The screw 12 is adapted to, when rotated, convey the substance from the inlet 13 to the head 15. The separation system 10, for example when it is an extruder, may comprise a single screw 12 extending into the channel 11 or a plurality of screws 12 extending into the channel 11. The separation system 10 may be, for example, single-screw or twin-screw (the separation system 10 comprises two screws 12). In the case of a separation system 10 comprising several screws 12, the screws 12 may be co-rotating (the screws 12 are arranged to rotate in the same direction) or counter-rotating (the screws 12 are arranged to rotate in opposite directions).

[0064] The separation system 10 further comprises a separation device 1 presented previously. The separation device 1 is connected to the outlet orifice 11 of the separation system 10. The separation device 1 is therefore arranged between the inlet 13 and the head 15 of the separation system 10.

[0065] Purification system

[0066] With reference to FIG. 7, a system 100 is proposed for purifying a substance in a polluted state so as to obtain a first material comprising pollutants and a second material corresponding to said substance in a purified state.

[0067] The purification system 100 comprises a separation system 10 as presented previously.

[0068] The purification system 100 comprises a compressed fluid circuit 101 comprising a fluid reservoir 102. The fluid is not necessarily in a compressed state in the fluid reservoir 102.

[0069] The compressed fluid circuit 101 further comprises a compression system 103 adapted to compress the fluid.

[0070] The compressed fluid circuit 101 comprises a first conduit 104 in fluid connection with the compressed fluid inlet orifice 14 of the separation system 10. The compressed fluid circuit 101 further comprises a second conduit 105 in fluid connection with the second end 22 of the bore 20 of the separation device 1. The first conduit 104 and the second conduit 105 are thus adapted to cause a flow of compressed fluid in the channel 11 between the compressed fluid inlet orifice 14 and the outlet orifice 11 to entrain the pollutants so as to form the first material. The compressed fluid circuit 101 allows the circulation of the first material, which advantageously comprises the compressed fluid and pollutants, in the channel 11 of the separation system 10, then in the bore 20 of the separation device 1, then in the second conduit 105.

[0071] The purification system 100 further comprises a decontamination device 110 for the first material. The decontamination device 110 is in fluid connection with the second conduit 105 and is adapted to separate the fluid from the pollutants of the first material. In other words, the decontamination device 110 is adapted to extract the pollutants from the first material to obtain a first decontaminated material, consisting mainly of the fluid. The decontamination device 110 may for example be a separation column.

[0072] Separation process

[0073] A method of separating the first material and the second material is proposed, using the separation system 10 as presented previously.

[0074] The separation method may be a method for purifying a substance in a polluted state by means of the extruder 10 presented previously. The method for purifying advantageously makes it possible to depollute a substance in a polluted state comprising more than 800 g / mol of pollutants, or even more than 900 g / mol of pollutants, or even up to 1000 g / mol of pollutants. The separation system 10 and therefore the separation device 1 are preferably adapted to allow the depollution of a substance in a polluted state comprising more than 800 g / mol of pollutants, or even more than 900 g / mol of pollutants, or even up to 1000 g / mol of pollutants.

[0075] Preferably, the substance comprises at least one polymer and pollutants. The at least one polymer is, for example, polyolefin, polyethylene, polypropylene or polyamide. The separation process makes it possible to extract a second material from the substance and makes it possible to obtain, on the one hand, a first material and, on the other hand, the second material. The first material advantageously comprises a compressed fluid and pollutants and the second material comprises the at least one polymer. The second material therefore advantageously corresponds to the decontaminated substance.

[0076] The method comprises introducing the substance in the polluted state into the channel 11 via the inlet 13 of the separation system 10. The substance in the polluted state may be solid or liquid. The substance in the polluted state, when in the solid state, may be in the form of a powder or granules. It may be heated in the channel to change to the molten state.

[0077] In the case where the separation system 10 comprises a screw 12, the method advantageously comprises driving the screw 12 in rotation to circulate the substance between the inlet 13 and the head 15 and in particular to convey it from the inlet 13 to the head 15.

[0078] If the separation system 10 does not include a screw 12, the substance circulates between the inlet 13 and the head 15 and is conveyed from the inlet 13 to the head 15, for example under the effect of gravity.

[0079] The method comprises injecting compressed fluid into the channel 11. The compressed fluid is injected into the channel 11 via the compressed fluid inlet orifice 14. Advantageously, the flow rate of compressed fluid in the channel 11 is two to three times greater than the flow rate of the substance in the channel 11.

[0080] The compressed fluid can be in liquid, gaseous or supercritical state.

[0081] In the case where the method is implemented by means of the purification system 100 as presented previously, the fluid from the fluid reservoir 102 is advantageously compressed by the compression system 103. Then, the compressed fluid circulates in the first conduit 104 to the compressed fluid inlet orifice 14 of the separation system 10. The compressed fluid is thus injected into the channel 11 of the separation system 10.

[0082] Preferably, the compressed fluid has a pressure greater than or equal to 300 bars, or even greater than or equal to 350 bars. This makes it possible to increase the solubility of the pollutants of the substance in the polluted state with the fluid and therefore to improve the transport of the pollutants and thus to increase the efficiency of the decontamination of the substance (i.e. to extract more pollutants from the substance).

[0083] In the channel, the polymer containing the pollutants and the compressed fluid circulate as two distinct phases. Part of the fluid dissolves in the polymer, causing it to expand and the pollutants to migrate to the surface. Pollutants near the surface are then carried along by the compressed fluid circulating in the channel.

[0084] The method therefore allows, under the effect of the compressed fluid, the dissociation of the at least one polymer and the pollutants of the substance in the channel 11. This dissociation allows the formation of the first material on the one hand and the second material on the other hand. Advantageously, the first material comprises the compressed fluid and the pollutants and the second material comprises the at least one polymer which comprises few pollutants. By few pollutants, it is understood that the second material preferably comprises less than 100 ppm of pollutants, preferably less than 50 ppm of pollutants, more preferably less than 10 ppm of pollutants. Advantageously, the method therefore makes it possible to obtain a second material comprising the lowest possible level of pollutants. Thus, advantageously, the pollutants are extracted from the polymer so as to decontaminate the polymer.

[0085] The present method may be used to decontaminate a substance. However, the method may simply be used to separate two materials from a substance and a fluid, neither of which includes pollutants.

[0086] Advantageously, the flow rate of the first material in channel 11 is two to three times greater than the flow rate of the second material in channel 11.

[0087] The method comprises discharging the first material via the free space between the at least one screw 4 of the separation device 1 and the bore 20. For this, the method comprises rotating the at least one screw 4 of the separation device 1 so that the first material is selectively discharged from the channel 11 via the free space between the at least one screw 4 and the bore 20.

[0088] In other words, the first material flows from the first end 21 to the second end 22 of the bore 20 so that the first material exits the channel 11. The first material flows via the free space and advantageously, via the thread 40 of the screw(s) 4. In the case where the separation device 1 comprises a single screw 4 and this screw has a helical thread 40, the first material flows mainly in the thread, along a helical trajectory.

[0089] On the other hand, the second material is prevented from being introduced by the screw(s) 4. Indeed, due to the viscosity of the second material which is greater than the viscosity of the first material, the second material does not tend to be introduced into the bore 20.

[0090] Advantageously, one or more scraping elements 41 make it possible to scrape the second material which, despite everything, would attempt to enter the bore 20 via the first end 21 and which would be in contact with the screw 4 or the internal surface of the bore 20. Consequently, even if the second material enters the bore 20, it is scraped and does not block the separation device 1, in particular the bore 20.

[0091] Preferably, the first material exits the separation device 1 via the second end 22 of the bore 20 and then circulates in the second conduit 105.

[0092] The first material flows in the second conduit 105 to the decontamination device 110. The first material is decontaminated. In other words, the compressed fluid is separated from the pollutants of the first material at the outlet of the separation system 10.

[0093] The fluid is advantageously reinjected into the fluid reservoir 102 or can be directly reinjected into the separation system 10 via the compressed fluid inlet orifice 14.

[0094] The method comprises the evacuation of the second material through the head 15 of the separation system 10. The second material advantageously corresponds to the decontaminated substance.

[0095] The individual steps of the process are carried out continuously. In other words, the steps can take place simultaneously (for example, the second material can be discharged at the same time as compressed fluid is injected into the channel 11).

Claims

CLAIMS 1. System (100) for purifying a substance in a polluted state so as to obtain a first material comprising pollutants and a second material corresponding to said substance in a purified state, comprising: - a separation system (10) adapted to treat a substance so as to obtain the first material and the second material, the first material and the second material not being miscible, the second material having a viscosity greater than the viscosity of the first material, the system comprising: - a channel (11) extending between an inlet (13) and a head (15) adapted to allow the exit of the second material, the channel (11) comprising an outlet orifice (111) adapted to allow the exit of the first material from the separation system (10); - a separation device (1) for the first material and the second material circulating in the channel (11) between the inlet (13) and the head (15), the separation device (1) being adapted to be connected to the outlet orifice (111) and comprising: - a body (2) comprising a bore (20), the bore (20) comprising a first end (21) adapted to be connected to the outlet orifice (111) and a second end (22) adapted to allow the evacuation of the first material from the separation device (1), - at least one screw arranged in the bore (20) such that a free space is present between the screw (4) and the bore (20), the screw (4) being adapted to allow, when rotated, a selective evacuation of the first material out of the channel (11) via the free space; - a compressed fluid circuit (101) comprising a fluid reservoir (102), a compression system (103) adapted to compress the fluid, a first conduit (104) in fluid connection with a compressed fluid inlet orifice (14) in the channel (11) of the separation system (10) and a second conduit (105) in fluid connection with the second end (22) of the bore (20) of the separation device (1), so as to cause a flow of compressed fluid in the channel (11) between the compressed fluid inlet orifice (14) and the outlet orifice (111) to entrain the pollutants so as to form the first material; - a decontamination device (110) for the first material in fluid connection with the second conduit (105), adapted to separate the fluid from the pollutants of the first material.

2. Purification system (100) of a substance according to claim 1, wherein the screw (4) of the separation device (1) comprises a scraping element (41) adapted to scrape the second material in contact with the bore (20).

3. Purification system (100) of a substance according to any one of claims 1 and 2, wherein the screw (4) of the separation device (1) comprises a thread (40), the free space comprising said thread (40).

4. A purification system (100) for a substance according to any one of claims 1 to 3, wherein the separation device (1) comprises at least two screws (4), including a central screw (4e) and at least one peripheral screw (4a, 4b, 4c, 4d), the at least one peripheral screw (4a, 4b, 4c, 4d) being arranged around the central screw (4e), each screw (4) comprising a respective thread (40), the thread (40) of each peripheral screw (4a, 4b, 4c, 4d) being adapted to mesh with the thread (40) of the central screw (4e) when the screws (4) are rotated.

5. Purification system (100) of a substance according to any one of claims 1 to 4, in which the separation device (1) comprises a motor adapted to drive each screw (4) in rotation.

6. A system (100) for purifying a substance according to claim 5, wherein the motor is connected to each screw (4) via a magnetic coupling so as to ensure sealing.

7. A purification system (100) for a substance according to any one of claims 1 to 6, wherein the separation system (10) comprises at least one screw (12) extending into the channel (11) and adapted to, when rotated, convey the substance from the inlet to the head (15).

8. Purification system (100) of a substance according to any one of claims 1 to 7, wherein the separation system (10) is an extruder.

9. Method for purifying a substance in a polluted state, by means of a purification system (100) according to any one of claims 1 to 8, so as to obtain a first material comprising pollutants and a compressed fluid and a second material corresponding to said substance in a purified state, the first material and the second material not being miscible, the second material having a viscosity greater than the viscosity of the first material, said method comprising: - introducing the substance in the polluted state into the channel (11) via the inlet, said substance comprising at least one polymer and pollutants; - injecting compressed fluid into the channel (11) through the compressed fluid inlet orifice (14); - dissociating the at least one polymer and the pollutants from the substance in the channel (11), forming the first material comprising the compressed fluid and the pollutants and forming the second material comprising the at least one polymer; - the evacuation of the first material via the free space between the at least one screw (4) of the separation device (1) and the bore (20); - the evacuation of the second material through the head (15) of the separation system (10); - the separation of the fluid and pollutants from the first material leaving the separation system (10).

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