Method and facility for separating a mixture comprising at least one fluorinated fluid and one or more contaminants

Abstract

The invention relates to a method and a facility for recycling a mixture comprising at least one fluorinated fluid, the mixture comprising one or more fluorinated chemical components and one or more contaminants selected from among one or more hydrocarbons and / or one or more fluorinated contaminants, including a step of double membrane filtration for reducing the contaminant content of the mixture.

Description

[0001] METHOD AND INSTALLATION FOR THE SEPARATION OF A MIXTURE COMPRISING AT LEAST ONE FLUORINATED FLUID AND ONE OR MORE CONTAMINANTS

[0002] Technical field of the invention

[0003] The invention relates to the field of HydroFluoro-Carbides (HFC), HydroFluoro-Olefins (H FO) and / or hydroChloroFluoro-Olefins (HCFO) and relates to a process for recycling substances contained in mixtures comprising at least one fluorinated fluid and one or more contaminants.

[0004] Technological background

[0005] Fluorinated chemicals that can be used as refrigerants, aerosol propellants, fire extinguishing agents, or blowing agents are known as Hydrofluorocarbon (HFC) molecules (composed of hydrogen, fluorine, and carbon atoms), Hydrofluoroolefin (HFO), and Hydrochlorofluoroolefin (HCFO).

[0006] HFCs, HFOs and HCFOs enable the implementation of a thermodynamic cycle in a cold production device (such as a cold room, a freezer for example) or in a heat production device (such as a heat pump for example). They can also be used as aerosol propellants, extinguishing agents or blowing agents.

[0007] A fluorinated fluid commonly comprises a pure chemical component, or pure molecule, or a mixture of chemical components. Among the HFC / HFO / HCFO components, the most commonly known are R-1234yf / ze, R-134a, R-32, R-227ea, R-125, R-152a and R-143a used alone or in mixtures with other components.

[0008] WO 2022 / 078755 A1 describes a method for separating a plurality of chemical components from a chemical mixture, said chemical mixture comprising a plurality of fluorinated fluids, each fluorinated fluid comprising at least one fluorinated component. This method comprises a step of identifying at least two sub-mixtures, a primary distillation step and a secondary distillation step.

[0009] WO 2011 / 053449 A1 describes a process for separating 1,1,1,2-tetrafluoropropane from a mixture also comprising 1,1,1,2,3-pentafluoropropane and hydrogen fluoride by distillation. EP 1 038 857 A1 describes a process for separating a mixture comprising 1,1,1,3,3-pentafluorobutane and hydrogen fluoride by distillation.

[0010] Today, HFCs have replaced both chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) as refrigerants, spray propellants, and insulating foams because they do not deplete the ozone layer and have a lower global warming potential (GWP). However, their contribution to global warming is significant because, even though their lifespan is relatively short, their GWP over a hundred years can be several thousand times higher than that of CO2.

[0011] Thus, the F-Gas legislation limits their use and encourages the recycling and reuse of these products. Reducing their consumption, or at least their release into the atmosphere, is one of the challenges for the coming years. Indeed, HFC emissions have been increasing since the 1990s, while current regulations aim to reduce their use. Known alternatives to HFCs include, for example, the use of HFOs or the use of hydrocarbons such as propane (R290), which have a much lower GWP. For example, the GWP of R32 is 675 and that of R125 is 3500, while that of R290 is 3 according to the 4 ème IPCC report.

[0012] Unfortunately, the replacement of some of the fluorinated chemical components by hydrocarbons in refrigerants or refrigerant mixtures complicates the recycling process of the latter and in particular the possibilities of separating the different substances by conventional distillation means. A solution therefore remains to be found to improve the recycling of mixtures of mixed fluorinated fluids in that they include either different types of fluorinated chemical components, or both fluorinated chemical components and hydrocarbons.

[0013] The invention aims to provide a solution to one or more problems and drawbacks encountered in the prior art. In particular, the invention aims to propose a method for recycling a plurality of chemical components of a chemical mixture comprising at least one fluorinated chemical component and one or more contaminants chosen from one or more hydrocarbons and / or one or more fluorinated contaminants.

[0014] Presentation of the invention

[0015] To this end, according to a first aspect, the invention relates to a method for recycling a mixture comprising at least one fluorinated fluid, remarkable in that it comprises: a) the supply, in the form of an initial flow, of a mixture comprising at least one fluorinated fluid; the mixture comprising one or more fluorinated chemical components and one or more contaminants chosen from one or more hydrocarbons and / or one or more fluorinated contaminants; b) membrane filtration of the initial flow so as to obtain a purified flow comprising a contaminant content lower than the contaminant content of the initial flow and a contaminant-enriched flow, said membrane filtration comprising at least two membrane filtration sub-steps carried out successively; and c) recovery of the purified flow and / or the contaminant-enriched flow for the purpose of reusing and / or recycling them.

[0016] As will be understood from reading the definition just given, the invention proposes to carry out a double membrane filtration of a mixture comprising at least one fluorinated fluid in order to obtain a purified flow depleted in contaminants and a flow enriched in contaminants. According to the invention, the purified flow is the permeate and the flow enriched in contaminants (for example in hydrocarbons when they are present) is the retentate.

[0017] The invention finds a particular application in the decontamination of streams of refrigerant mixtures comprising hydrocarbon-type contaminants and in the separation of mixtures of fluorinated chemical compounds. The purified and / or enriched streams thus generated can be reused directly or directed to an additional recycling facility comprising one or more units for separating the fluorinated chemical components for recycling by conventional means.

[0018] The invention is remarkable in that it makes it possible, through this specific step of separating contaminants, to strengthen the overall efficiency of a process for recycling a mixture comprising at least one fluorinated fluid. Indeed, the contamination of mixtures comprising at least one fluorinated fluid by contaminants, such as hydrocarbons, could, when the content of the latter was too high, affect the efficiency of the distillation processes, or even make the recycling of certain mixtures impossible. It has been found that the implementation of a preliminary step of separating contaminants makes it possible to improve the distillation capacities and therefore makes it possible to improve the overall efficiency of the recycling process. In the case of fluorinated contaminants, the separation and purification of the fluorinated chemical components is improved.

[0019] According to one embodiment, the initial flow comprises one or more fluorinated fluids chosen from difluoromethane (R32), pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), 2,3,3,3-Tetrafluoropropene (R1234yf) and trans-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze).

[0020] According to one embodiment, the initial stream comprises one or more fluorinated contaminants and the, or at least one, fluorinated contaminant is 1,1,1,2,3,3,3-heptafluoropropane (R227ea) and / or the initial stream comprises one or more fluorinated contaminants and step c) comprises the recovery of the stream enriched in contaminants and its recycling.

[0021] According to one embodiment, the initial stream comprises one or more hydrocarbons selected from the group comprising propane and isobutane; and / or the initial stream comprises one or more hydrocarbons, and step c) comprises the recovery of the purified stream and its recycling.

[0022] Preferably, the initial stream comprises one or more fluorinated chemical components chosen from hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), hydrofluoroolefins (HFOs), and hydrochlorofluoroolefins (HCFOs); more preferably, the initial stream comprises one or more fluorinated chemical components chosen from hydrofluorocarbons (HFCs) and / or hydrofluoroolefins (HFOs).

[0023] According to the invention, membrane filtration step b) comprises at least two membrane filtration sub-steps carried out successively. Indeed, as shown in the examples, the implementation of two-stage filtration, i.e. in which at least two membrane filtration modules are arranged in series, makes it possible to significantly improve the separation of contaminants such as, for example, hydrocarbons. As will be understood, each filtration sub-step generating a permeate and a retentate, the second filtration sub-step is carried out on the permeate resulting from the first filtration sub-step.

[0024] Preferably, each membrane filtration sub-step generating a permeate and a retentate, the retentate from the second membrane filtration sub-step is recycled so as to be mixed into the initial flow.

[0025] According to a preferred embodiment, step b) of membrane filtration comprises at least one sub-step of filtration by means of a membrane comprising at least one layer of a material chosen from a polyethersulfone (PES), a polysulfone (PSU), a polyvinylidene fluoride (PVDF), a copolymer with polyether blocks and polyamide blocks (PEBA), a polypropylene (PP), a cellulose acetate (AC), a polytetrafluoroethylene (PTFE), a sulfonated polyphenylenesulfone (sPPSll), cellulose acetate butyrate (CAB), polyhedral oligomeric silsesquioxane (POSS), or a polydimethylsiloxane (PDMS). Preferably, step b) of membrane filtration comprises at least one sub-step of filtration by means of a membrane comprising at least one layer of a material chosen to be a copolymer with polyether blocks and polyamide blocks (PEBA) and / or a polyethersulfone (PES).For example, step b) of membrane filtration comprises at least one sub-step of filtration by means of a membrane comprising at least one layer of a material chosen to be a copolymer with polyether blocks and polyamide blocks (PEBA); preferably, the polyamide block comprises at least one polyamide chosen from polyamide 6, polyamide 11 and polyamide 12; preferably, polyamide 6.

[0026] For example, step b) of membrane filtration comprises at least one sub-step of filtration using a multilayer membrane comprising a layer of copolymer material with polyether blocks and polyamide blocks (PEBA), and a layer of polyethersulfone (PES); preferably, the polyamide block comprises at least one polyamide chosen from polyamide 6, polyamide 11 and polyamide 12; preferably, polyamide 6.

[0027] For example, the initial flux provided in step a) comprises a contaminant content greater than or equal to 0.5% by weight relative to the total weight of the initial flux; for example greater than or equal to 1.0%. For example, the initial flux provided in step a) comprises a contaminant content of 5.0% to 40% by weight relative to the total weight of the initial flux.

[0028] When the contaminant(s) consist of or comprise at least one fluorinated contaminant, the initial stream provided in step a) comprises a fluorinated contaminant content greater than or equal to 0.5% by weight relative to the total weight of the initial stream; for example greater than or equal to 1.0%. For example, the initial stream provided in step a) comprises a fluorinated contaminant content of 5.0% to 40% by weight relative to the total weight of the initial stream.

[0029] When the contaminant(s) consist of or comprise at least one hydrocarbon, the initial stream provided in step a) comprises a hydrocarbon content greater than or equal to 0.5% by weight relative to the total weight of the initial stream; for example greater than or equal to 1.0%. For example, step a) comprises a step of identifying one or more contaminants in the initial stream and that when the hydrocarbon content is greater than 40% by weight based on the total weight of the initial stream, it further comprises a sub-step of diluting the initial stream with another stream free of hydrocarbons in order to adjust the hydrocarbon content to be less than 40% by weight based on the total weight of the initial stream.

[0030] For example, the initial stream provided in step a) comprises a hydrocarbon content of 5.0% to 40% by weight relative to the total weight of the initial stream.

[0031] For example, step b) is carried out so as to obtain a hydrocarbon content of less than 5.0% by weight relative to the total weight of the purified stream; preferably less than or equal to 4.0% by weight; more preferably less than or equal to 3.0% by weight; more preferably less than or equal to 2.5% by weight. Indeed, it has been found that too high a hydrocarbon content such as a content greater than 5.0% by weight will degrade the distillation efficiency during the recycling of the purified mixture and / or the stream enriched in contaminants which can be carried out during step c).

[0032] For example, step b) is carried out so as to obtain a purified stream with a hydrocarbon content reduced by at least a factor of 4 compared to the hydrocarbon content of the initial stream, preferably by at least a factor of 5, more preferably by at least a factor of 6; more preferably by at least a factor of 8.

[0033] According to a preferred embodiment, the initial stream comprises at least two fluorinated chemical components and the recycling step c) comprises the separation of said fluorinated chemical components by distillation.

[0034] In an exemplary embodiment, the purified stream comprises a fluorinated component and step c) comprises recycling said purified stream by at least one purification step or sub-step; preferably the purification step is carried out by simple distillation on at least one simple distillation column.

[0035] In an exemplary embodiment, the purified stream is an azeotropic mixture and step c) comprises recycling said purified stream including one or more distillation sub-steps chosen from at least one simple distillation sub-step on a simple distillation column; and / or at least one advanced distillation sub-step by pressure balance; and / or at least one advanced distillation sub-step of extraction distillation.

[0036] Preferably, the purified stream is an azeotropic mixture and step c) comprises recycling said purified stream including one or more distillation sub-steps comprising at least one simple distillation sub-step on a simple distillation column followed by one or more advanced distillation sub-steps chosen from at least one advanced distillation sub-step by pressure balance; and / or at least one advanced distillation sub-step of extraction distillation.

[0037] For example, the step of separating fluorinated chemical components by distillation includes:

[0038] - a sub-step of identifying in the mixture of fluorinated chemical components at least two sub-mixtures, each sub-mixture being a simple sub-mixture comprising a single fluorinated chemical component (55) or a complex sub-mixture comprising a combination of chemical components, each complex sub-mixture being associated either with a first secondary distillation group by a pressure balance distillation method, or with a second secondary distillation group by an extraction distillation method,

[0039] - a primary distillation stage, using a simple distillation column, so as to separate each identified sub-mixture,

[0040] - a secondary distillation step, by at least two auxiliary columns, of each complex submixture of the first group and of the second group, the complex submixtures of the first group being separated by the pressure balance distillation method and the complex submixtures of the second group being separated, by means of a solvent, by the extraction distillation method.

[0041] According to a second aspect, the invention relates to an installation for implementing the method according to the first aspect, remarkable in that it comprises a membrane filtration unit comprising at least two membrane filtration modules arranged in series.

[0042] Preferably, the installation further comprises a distillation unit comprising: one or more simple distillation columns; and / or one or more columns configured to allow the implementation of advanced distillation by extraction, and / or one or more columns configured to allow the implementation of advanced distillation by pressure balance.

[0043] Preferably, the installation further comprises a distillation unit comprising: one or more simple distillation columns; and one or more columns configured to allow the implementation of advanced extraction distillation.

[0044] Presentation of figures

[0045] The invention will be well understood and other aspects and advantages will appear clearly on reading the following description given with reference to the figures annexed and listed below.

[0046] [Fig.1] Figure 1 illustrates an example of an installation according to the invention.

[0047] [Fig.2] Figure 2 is a representation of a thin-film composite membrane stage with a flow pattern in the feed and permeate streams. [Fig.3] Figure 3 is a graph showing the HFC+HFO concentration in the permeate stream versus HFC+HFO recovery as a function of feed pressure (1-8 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h -1 . Membrane thickness = 2 pm. Feed composition is 90% by weight HFC + HFO and 10% by weight HC (R600a + R290).

[0048] [Fig.4] Figure 4 is a graph of R32+R125 concentration in the permeate stream versus R32+R125 recovery as a function of feed pressure (1-8 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h -1 . Membrane thickness = 2 pm. The feed composition is 40 wt% R32, 40 wt% R125, 10 wt% R600a and 10 wt% R290.

[0049] [Fig.5] Figure 5 allows a comparison of one-stage and two-stage HFC+HFO purification: HFC+HFO concentration in the permeate stream versus HFC+HFO recovery as a function of feed pressure (1-8 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h' 1. Membrane thickness = 2 pm. Feed composition is 90% by weight HFC + HFO and 10% by weight HC (R600a + R290).

[0050] [Fig.6] Figure 6 allows a comparison of R32+R125 purification with one stage and two stages: R32+R125 concentration in the permeate stream versus R32+R125 recovery as a function of feed pressure (1-8 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h-1. Membrane thickness = 2 pm. The feed composition is 40 wt% R32, 40 wt% R125, 10 wt% R600a and 10 wt% R290.

[0051] [Fig. 7] Figure 7 allows a comparison of one-stage and two-stage R227ea purification: R227ea concentration in the retentate stream versus R227ea recovery as a function of feed pressure (1-4 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h-1. Membrane thickness = 2 pm. The feed composition is 70 wt% R227ea, 20 wt% R1234ze, and 10 wt% R134a.

[0052] Detailed Description In the following description, the term "comprise" is synonymous with "include" and is not limiting in that it allows for the presence of other elements in the installation described or other steps in the process to which it relates. It is understood that the term "comprise" includes the terms "consist of". Throughout the description, the different figures use the same reference signs to designate identical or similar entities.

[0053] The invention relates to a method for recycling a mixture comprising at least one fluorinated fluid and an installation for implementing such a method. The method and the installation will now be described jointly with reference to Figure 1.

[0054] According to the invention, the method for recycling a mixture 1 comprising at least one fluorinated fluid is remarkable in that it comprises: a) providing, in the form of an initial flow 3, a mixture 1 comprising at least one fluorinated fluid; the mixture 1 comprising one or more fluorinated chemical components (41, 43, 49, 51, 55) and one or more contaminants chosen from one or more hydrocarbons and / or one or more fluorinated contaminants; and b) membrane filtration of the initial flow 3 so as to obtain a purified flow 5 comprising a contaminant content lower than the contaminant content of the initial flow 3 and a contaminant-enriched flow 33, said membrane filtration comprising at least two membrane filtration sub-steps carried out successively; and c) recovering the purified flow 5 and / or the contaminant-enriched flow 33 for the purpose of reusing and / or recycling them.

[0055] In one embodiment, step c) comprises the recovery of the purified stream 5 and / or the stream enriched in contaminants 33 with a view to their reuse. Indeed, depending on the composition of the initial mixture, the purified stream 5 and / or the stream enriched in contaminants 33 can be recovered and reused as is (without any other additional separation or purification step).

[0056] In a preferred embodiment, step c) comprises the recovery of the purified stream 5 for recycling. The recycling of the purified stream 5 is carried out by separation and / or purification of the fluorinated chemical components (41, 43, 49, 51, 55) contained in the purified stream 5 by distillation.

[0057] In a preferred embodiment, step c) comprises recovering the contaminant-enriched stream 33 for recycling. The recycling of the contaminant-enriched stream 33 is carried out by separation and / or purification of the fluorinated contaminant(s) and / or the hydrocarbon(s) contained in the contaminant-enriched stream by distillation.According to one embodiment, the method for recycling a mixture 1 comprising at least one fluorinated fluid is remarkable in that it comprises: a) the supply, in the form of an initial flow 3, of a mixture 1 comprising at least one fluorinated fluid; the mixture 1 comprising one or more fluorinated chemical components (41, 43, 49, 51, 55) and one or more hydrocarbons; and b) the membrane filtration of the initial flow 3 so as to obtain a purified flow 5 comprising a hydrocarbon content lower than the hydrocarbon content of the initial flow 3, said membrane filtration comprising at least two membrane filtration sub-steps carried out successively; and c) the recovery of the purified flow and its recycling.

[0058] According to one embodiment, the method for recycling a mixture 1 comprising at least one fluorinated fluid is remarkable in that it comprises: a) providing, in the form of an initial flow 3, a mixture 1 comprising at least one fluorinated fluid; the mixture comprising one or more fluorinated chemical components (41, 43, 49, 51, 55) and one or more fluorinated contaminants; and b) membrane filtration of the initial flow 3 so as to obtain a purified flow 5 comprising a contaminant content lower than the contaminant content of the initial flow 3 and a contaminant-enriched flow 33, said membrane filtration comprising at least two membrane filtration sub-steps carried out successively; and c) recovering the contaminant-enriched flow 33 and recycling it.

[0059] The invention also relates to an installation for implementing the method, the installation comprising a membrane filtration unit 7 comprising at least two filtration modules (9, 11).

[0060] Preferably, the installation further comprises a distillation unit 13 comprising one or more simple distillation columns 15; and / or one or more columns (21, 23) configured to allow the implementation of advanced distillation by extraction, and / or one or more columns (17, 19) configured to allow the implementation of advanced distillation by pressure balance.

[0061] More preferably, the installation further comprises a distillation unit 13 comprising one or more simple distillation columns 15; and / or one or more columns (21, 23) configured to allow the implementation of advanced distillation by extraction.

[0062] Step a) of providing a mixture comprising at least one fluorinated fluid.

[0063] According to the invention, the initial flow 3 is a mixture 1 comprising at least one fluorinated fluid; the mixture comprising one or more fluorinated chemical components (41, 43, 49, 51, 55) and one or more contaminants chosen from one or more hydrocarbons and / or one or more fluorinated contaminants. Preferably, the initial flow 3 is a mixture 1 comprising one or more fluorinated chemical components (41, 43, 49, 51, 55) and one or more hydrocarbons. Preferably, the initial flow 3 is a mixture 1 comprising one or more fluorinated chemical components (41, 43, 49, 51, 55) and one or more fluorinated contaminants.

[0064] According to the invention, a fluorinated contaminant is a fluorinated fluid which can be separated from the mixture in that it is present mainly in the membrane filtration retentate.

[0065] According to the invention, a fluorinated chemical component is a fluorinated fluid which can be separated from the mixture in that it is present predominantly in the membrane filtration permeate.

[0066] The components of the mixture were previously used to enable the implementation of a thermodynamic cycle in a plurality of independent thermodynamic devices. A thermodynamic device is understood to mean a cold production device (such as a cold room, a freezer or a refrigerator), a heat production device (such as a heat pump), or even an aerosol propellant for example. The fluorinated fluids were used pure or in mixtures, then they were collected in separate collection tanks during a collective or selective recovery operation.

[0067] According to a preferred embodiment of the invention, the method further comprises a step of identifying one or more fluorinated fluids in the initial flow, this step being carried out before step b) of membrane filtration. In particular, the method comprises a step of identifying one or more contaminants chosen from one or more hydrocarbons and / or one or more fluorinated contaminants in the initial flow.

[0068] For example, the identification step is a qualitative and quantitative analysis step preferably carried out by chromatographic analysis and the installation further comprises an identification device, preferably a chromatographic analysis system.

[0069] For example, the initial stream 3 comprises one or more hydrocarbons selected from the group comprising methane (R50), ethane (R170), propane (R290), butane (R600), isobutane (R600a), pentane (R601), isopentane (R601a) and propene (R1270). Preferably, the initial stream 3 comprises propane (R290) and / or isobutane (R600a). In the context of the invention, the hydrocarbon(s) are contaminants in that they are present predominantly in the retentate.

[0070] For example, the initial stream 3 comprises at least one fluorinated contaminant being 1,1,1,2,3,3,3-heptafluoropropane (R227ea).

[0071] The contaminant content of the initial stream 3 is for example at least 0.3% by weight based on the total weight of the initial stream; preferably at least 0.5% by weight; more preferably at least 0.8% by weight; more preferably at least 1.0% by weight; more preferably at least 5.0% by weight and even more preferably at least 10.0% by weight.

[0072] For example, the contaminant content of the initial stream 3 is between 0.3 and 70% by weight based on the total weight of the initial stream; preferably, between 0.5 and 60% by weight; more preferably, between 1.0 and 50% by weight and more preferably between 5.0 and 40% by weight; or between 6.0 and 30% by weight.

[0073] When the contaminants comprise or consist of fluorinated contaminants, the fluorinated contaminant content of the initial stream 3 is for example at least 0.3% by weight based on the total weight of the initial stream; preferably at least 0.5% by weight; more preferably at least 0.8% by weight; more preferably at least 1.0% by weight; more preferably at least 5.0% by weight and even more preferably at least 10.0% by weight.

[0074] For example, the fluorinated contaminant content of the initial stream 3 is between 0.3 and 70% by weight based on the total weight of the initial stream; preferably, between 0.5 and 60% by weight; more preferably, between 1.0 and 50% by weight and more preferably between 5.0 and 40% by weight; or between 6.0 and 30% by weight.

[0075] When the contaminants comprise or consist of hydrocarbons, the hydrocarbon content of the initial stream 3 is for example at least 0.3% by weight based on the total weight of the initial stream; preferably at least 0.5% by weight; more preferably at least 0.8% by weight; more preferably at least 1.0% by weight; more preferably at least 5.0% by weight and even more preferably at least 10.0% by weight.

[0076] For example, the hydrocarbon content of the initial stream 3 is at most 70% by weight based on the total weight of the initial stream; preferably, at most 60% by weight; more preferably at most 50% by weight, more preferably at most 40% by weight; more preferably at most 30% by weight; and even more preferably at most 25% by weight. When the hydrocarbon content is too high, for example when the initial stream has a hydrocarbon content greater than 40% by weight based on the total weight of the initial stream, it is possible to carry out a sub-step of diluting the initial stream with another stream devoid of hydrocarbons in order to adjust the hydrocarbon content to be equal to or less than 40%, preferably less than 30% by weight. Such a dilution step makes it possible to increase the total efficiency of the process. Thus, step a) may comprise a sub-step of adjusting the hydrocarbon content.

[0077] For example, the hydrocarbon content of the initial stream 3 is between 0.3 and 70% by weight based on the total weight of the initial stream; preferably, between 0.5 and 60% by weight; more preferably, between 1.0 and 50% by weight and more preferably between 5.0 and 40% by weight; or between 6.0 and 30% by weight.

[0078] For example, the initial stream 3 comprises one or more fluorinated fluids chosen from hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), hydrofluoroolefins (HFOs), and hydrochlorofluoroolefins (HCFOs); more preferably, the initial stream 3 comprises one or more hydrofluorocarbons (HFCs) and / or one or more hydrofluoroolefins (HFOs).

[0079] According to one implementation of the invention, the initial flow 3 comprises at least one fluorinated chemical component (41, 43, 49, 51, 55) and preferably at least two distinct fluorinated chemical components (41, 43, 49, 51, 55).

[0080] In one embodiment, the initial flow 3 comprises one or more fluorinated fluids of the hydrofluorocarbon (HFC) type chosen from trifluoromethane (R23), difluoromethane (R32), pentafluoroethane (R125), 1,1,2,2-tetrafluoroethane (R134), 1,1,1,2-tetrafluoroethane (R134a), 1,1,1-trifluoroethane (R143a), 1,1-difluoroethane (R152a), 1,1,1,2,3,3,3-heptafluoropropane (R227ea), 1,1,1,2,3,3-hexafluoropropane (R236ea), 1,1,1,3,3,3-hexafluoropropane (R236fa), trifluoropropane (R263), difluoropropane (R272), fluoropropane (R281), and 1,1,1,3,3-pentafluorobutane (R365mfc).

[0081] Preferably, the initial stream 3 comprises one or more fluorinated fluids of hydrofluorocarbon (HFC) type chosen from difluoromethane (R32), pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), and 1,1,1-trifluoroethane (R143a). Preferably, the initial stream 3 comprises one or more fluorinated fluids of hydrofluorocarbon (HFC) type chosen from difluoromethane (R32), pentafluoroethane (R125), and 1,1,1,2-tetrafluoroethane (R134a). Preferably, the initial stream 3 comprises at least one HFC being difluoromethane (R32) and / or pentafluoroethane (R125). In one embodiment, the initial stream 3 comprises one or more fluorinated fluids of the hydrofluoroolefin (HFO) type chosen from cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z), trans-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-E), 2,3,3,3-Tetrafluoropropene (R1234yf) and trans-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze).Preferably, the initial stream 3 comprises at least one HFO being 2,3,3,3-Tetrafluoropropene (R1234yf) and / or trans-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze).

[0082] In one embodiment, the initial stream 3 comprises one or more fluorinated fluids of the hydrochlorofluorocarbon (HCFC) type chosen from chlorodifluoromethane (R22), chlorofluoromethane (R31), 2,2-dichloro-1,1,1-trifluoroethane (R123), 1-chloro-1,2,2,2-tetrafluoroethane (R124), 1-chloro-1,1,2,2-tetrafluoroethane (R124a), 1,1-dichloro-1-fluoroethane (R141b), 1-chloro-1,1-difluoroethane (R142b), and 1,3-dichloro-1,1,2,2,3-pentafluoropropane (R225cb).

[0083] In one embodiment, the initial stream 3 comprises one or more fluorinated fluids of the hydrochlorofluoroolefin (HCFO) type chosen from trans 1-chloro-3,3,3-trifluoropropene (R-1233zd(E)), cis-1-chloro-3,3,3-trifluoropropene (R-1233zd(Z)), and (Z)-1-Chloro2,3,3,3,-Tetrafluoropropene (R-1224yd(Z)).

[0084] For example, the initial stream 3 comprises one or more fluorinated fluids chosen from difluoromethane (R32), pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), 2,3,3,3-Tetrafluoropropene (R1234yf) and trans-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze).

[0085] The content of fluorinated chemical components (41, 43, 49, 51, 55) of the initial flux 3 is for example at least 20% by weight based on the total weight of the initial flux 3; preferably at least 30% or at least 40% by weight; more preferably at least 50% by weight and more preferably at least 60% by weight.

[0086] For example, the content of fluorinated chemical components (41, 43, 49, 51, 55) of the initial flux 3 is at most 97% by weight based on the total weight of the initial flux; preferably, at most 95% by weight; more preferably at most 92% by weight and more preferably at most 90% by weight.

[0087] For example, the content of fluorinated chemical components (41, 43, 49, 51, 55) of the initial stream 3 is between 30 and 97% by weight based on the total weight of the initial stream; preferably, between 40 and 95% by weight; more preferably, between 50 and 92% by weight and more preferably between 60 and 90% by weight. According to embodiments of the invention, step a) comprises at least one sub-step of pretreatment of the refrigerant mixture 1 to obtain the initial stream 3. It is understood that the pretreatment sub-step(s) are carried out before step b) of membrane filtration by means of a pretreatment unit 25.

[0088] For example, the mixture of fluorinated fluids 1 may be compressed for storage purposes or not. When the mixture of fluorinated fluids 1 is not compressed, step a) comprises a compression sub-step in a compression unit 27. In one embodiment of the invention, the initial flow 3 is compressed so as to exhibit a pressure of between 1 and 10 bars.

[0089] Preferably, before entering the membrane filtration unit 7, the initial stream 3 undergoes one or more pretreatment sub-steps to remove any traces of water, oil and particles that may damage the membrane surface. This task may be performed by one or more coalescence filters (29, 31) placed in series, for example two coalescence filters (29, 31) with 0.1 pm and 0.01 pm cartridges, respectively.

[0090] Alternatively, and according to an embodiment not shown, step a) comprises a sub-step of drying the refrigerant mixture in a dehydration unit. Advantageously, the dehydration sub-step is carried out using a molecular sieve. For example, the refrigerant mixture or a portion of the refrigerant mixture 1 is compressed so as to cause the condensation of at least a portion of the water it contains to produce a two-phase stream having liquid and gas phases. The gas phase is introduced into the dehydration unit so as to remove at least a portion of the water it contains and to produce a dried gas phase.

[0091] Whatever the pretreatment chosen, the person skilled in the art will have an advantage in ensuring that the initial flow 3 entering the membrane filtration unit 7 has a water content of at most 10 ppm by weight relative to the total weight of the initial flow.

[0092] For example, step a) comprises a sub-step of adjusting the hydrocarbon content of the refrigerant mixture 1 by mixing different streams of harvested refrigerants. Indeed, when the content of contaminants, for example hydrocarbons, is greater than 40% by weight relative to the total weight of the initial stream, the person skilled in the art will have an advantage in diluting the initial stream with another stream free of hydrocarbons.

[0093] Stage b) of membrane filtration and the membrane filtration unit

[0094] It will be understood that step b) of membrane filtration of the initial flow 3 so as to obtain a purified flow 5 comprising a hydrocarbon content lower than the hydrocarbon content of the initial flow 3, also makes it possible to obtain a contaminant-enriched flow 33. The membrane separation is carried out in a membrane filtration unit 7 comprising at least one filtration module 9, and preferably at least two filtration modules (9, 11) arranged in series. When the membrane filtration unit 7 comprises a single filtration module 9, the filtration is said to be single-stage. When the membrane filtration unit 7 comprises several filtration modules (9, 11) arranged in series, the filtration is said to be multi-stage. Figure 1 illustrates the embodiment in which the membrane filtration unit 7 comprises two filtration modules (9, 11) arranged in series.

[0095] Each filtration module (9, 11) comprises one or more membranes arranged in parallel. The membrane(s) may be single-layer or multi-layer, preferably with at least one selective layer allowing the separation of hydrocarbons. Two product streams exit a filtration module (9, 11): a permeate stream (5, 35) (or permeate) with the portion of the feed stream that passes through the membrane, and the retentate stream (33, 37) (or retentate) which contains the portion of the feed stream that does not pass through the membrane. According to the invention, the purified stream is the permeate and the stream enriched in contaminants (for example hydrocarbons) is the retentate. The retentate can then be treated as waste (e.g. in the case of a hydrocarbon contaminant) or purified by recycling for reuse (e.g. in the case of a fluorinated contaminant 1,1,1,2,3,3,3-heptafluoropropane (R227ea)).Thus, according to the invention, the method may further comprise the recovery of the filtration retentate obtained in step b) and the recycling of said retentate. Preferably, the recycling of the retentate may be carried out by distillation.

[0096] Filtration step b) may be a single-stage filtration comprising a single membrane filtration step or a multi-stage filtration in which a plurality of membrane filtration sub-steps are carried out successively.

[0097] According to the invention, membrane filtration step b) comprises at least two membrane filtration sub-steps carried out successively. Indeed, as shown in the examples, the implementation of multi-stage filtration, i.e. in which several filtration modules (9, 11) are arranged in series, makes it possible to improve the hydrocarbon separation performance.

[0098] According to the invention, the membrane filtration is carried out so that the contaminant(s) are predominantly in the filtration retentate (33, 37). Each filtration sub-step generating a permeate and a retentate, the filtration sub-steps in addition to the first are carried out on the permeate of the previous filtration sub-step. In the case of two-stage filtration, the second filtration sub-step is carried out on the permeate 35 of the first filtration sub-step. Preferably, the retentate of the filtration sub-steps in addition to the first is recycled so as to be mixed in the initial flow 3. In the case of two-stage filtration, the retentate 37 of the second filtration sub-step is recycled so as to be mixed in the initial flow 3.

[0099] Preferably, the retentate 33 from the first filtration sub-step is discharged for further processing.

[0100] Preferably, the membrane(s) of the filtration module(s) (9, 11) comprise at least one layer of a material chosen to be a polyethersulfone (PES), a polysulfone (PSU), a polyvinylidene fluoride (PVDF), a polyether block and polyamide block copolymer (PEBA), a polypropylene (PP), a cellulose acetate (CA), a polytetrafluoroethylene (PTFE), a sulfonated polyphenylenesulfone (sPPSll), cellulose acetate butyrate (CAB), polyhedral oligomeric silsesquioxane (POSS), or a polydimethylsiloxane (PDMS). More preferably, the membrane(s) of the filtration module(s) (9, 11) comprise at least one layer of a polymer or copolymer comprising repeating units of a tetramethylene oxide, propylene oxide, or ethylene oxide monomer. For example, the polymer or copolymer comprises repeating units according to formula (1): wherein PA is a polyamide selected from polyamide 6, polyamide 11 and polyamide 12, and PE is poly(ethylene oxide) or poly(tetramethylene oxide); preferably, PA is polyamide 6.

[0101] According to a preferred implementation of the invention, the material of the or at least one layer of the filtration membrane is chosen to be a copolymer with polyether blocks and polyamide blocks (PEBA). Preferably, the polyamide block comprises at least one polyamide chosen from polyamide 6, polyamide 11 and polyamide 12; preferably, polyamide 6.

[0102] As is known, polyamide block (PA) and polyether block (PE) copolymers result from the copolycondensation of polyamide blocks with reactive ends with polyether blocks with reactive ends. For example, it is possible to react: polyether diol, and a polyamide dicarboxylic acid, polyetherdiamine and a polyamide dicarboxylic acid, polyetherdiol and a polyamide diamine. Document FR 2 273 021 describes such copolymers formed from polyamide blocks and polyether blocks, the polyamide blocks and the polyether blocks being linked by an ester function. These products are sold under the trade name PEBAX® by the company ARKEMA. An example of PEBA that can be used in the context of the invention are PEBAX® 1074, PEBAX® 2533, and PEBAX® 1657, commercially available from the company ARKEMA.

[0103] Thus, according to a preferred embodiment, step b) of membrane filtration comprises at least one sub-step of filtration by means of a membrane comprising at least one layer of a material chosen from a polyethersulfone (PES), a polysulfone (PSU), a polyvinylidene fluoride (PVDF), a copolymer with polyether blocks and polyamide blocks (PEBA), a polypropylene (PP), a cellulose acetate (AC), a polytetrafluoroethylene (PTFE), a sulfonated polyphenylenesulfone (sPPSU), cellulose acetate butyrate (CAB), polyhedral oligomeric silsesquioxane (POSS), or a polydimethylsiloxane (PDMS). Preferably, step b) of membrane filtration comprises at least one sub-step of filtration by means of a membrane comprising at least one layer of a material chosen to be a copolymer with polyether blocks and polyamide blocks (PEBA) and / or a polyethersulfone (PES).

[0104] For example, step b) of membrane filtration comprises at least one sub-step of filtration using a multi-layer membrane comprising a layer of copolymer material with polyether blocks and polyamide blocks (PEBA), and a layer of polyethersulfone (PES).

[0105] Preferably, step b) is carried out so as to obtain a hydrocarbon content of less than 5.0% by weight relative to the total weight of the purified stream 5; preferably less than or equal to 4.0% by weight, more preferably less than or equal to 3.0% by weight; and even more preferably less than or equal to 2.5% by weight.

[0106] For example, the purified stream comprises a hydrocarbon content of between 0.01% and less than 5.0% by weight relative to the total weight of the purified stream 5; preferably between 0.01 and 4.0% by weight, more preferably between 0.01 and 3.0% by weight; more preferably between 0.01 and 2.5% by weight.

[0107] Step c) of recycling

[0108] The recycling step c) is carried out on the purified stream 5 and / or the stream enriched in contaminants 33. Preferably, when the initial stream 3 comprises one or more fluorinated contaminants, a recycling step is carried out on the stream enriched in contaminants 33. Preferably, when the initial stream 3 comprises one or more hydrocarbons, a recycling step is carried out on the purified stream 5. According to a preferred embodiment, the initial stream 3 comprises a single fluorinated chemical component (41, 43, 49, 51, 55) and one or more hydrocarbons, and the recycling step c) is carried out on the purified stream and is a step of purifying said fluorinated chemical component (41, 43, 49, 51, 55). This purification can be carried out by any means, preferably it is carried out by distillation.

[0109] According to a preferred embodiment, the initial stream 3 comprises at least two fluorinated chemical components (41, 43, 49, 51, 55) and one or more hydrocarbons, and the recycling step c) is at least carried out on the purified stream and comprises at least one step of separating the fluorinated chemical components (41, 43, 49, 51, 55). This separation can be carried out by any means, preferably it is carried out by distillation. Preferably, each separation step allowing the isolation of a fluorinated chemical component, or at least one of these separation steps, is followed by a step of purifying the fluorinated chemical component which has been isolated.

[0110] According to a preferred embodiment, the initial stream 3 comprises at least one fluorinated chemical component (41, 43, 49, 51, 55) and one or more fluorinated contaminants, and step c) comprises recycling the purified stream 5 and / or the stream enriched in contaminants 33. The recycling of each stream may be a step of purification or separation of the fluorinated contaminant(s) and the fluorinated chemical component(s).

[0111] According to the invention, a fluorinated contaminant is a fluorinated refrigerant that can be separated from the refrigerant mixture in that it is present predominantly in the membrane filtration retentate.

[0112] According to the invention, a fluorinated chemical component is a fluorinated refrigerant that can be separated from the refrigerant mixture in that it is predominantly present in the membrane filtration permeate.

[0113] Processes for separating fluorinated refrigerants by distillation are known to those skilled in the art. In the case of zeotropic mixtures, it is possible to separate the various components by a simple distillation process using simple distillation columns.

[0114] In the case of azeotropic or pseudo-azeotropic mixtures, two advanced distillation processes are known: by pressure balance (known as "pressure swing" in English), and by extraction using a driving agent, called solvent 45.

[0115] According to one implementation of the invention, the purified stream 5 is an azeotropic mixture and step c) is a step of separating a mixture of fluorinated chemical components (41, 43, 49, 51, 55) and / or fluorinated contaminants comprising one or more distillation sub-steps chosen from: a simple distillation sub-step on a simple distillation column 15, a pressure balance distillation sub-step using auxiliary distillation columns (17, 19), and an extraction distillation sub-step using auxiliary distillation columns (21, 23).

[0116] Preferably, the purified stream 5 is an azeotropic mixture and step c) is a step of separating a mixture of fluorinated chemical components (41, 43, 49, 51, 55) and / or fluorinated contaminants comprising at least one simple distillation sub-step and one or more advanced distillation sub-steps chosen from: a pressure balance distillation sub-step, and an extraction distillation sub-step.

[0117] Pressure balance distillation methods are known to those skilled in the art and use two distillation columns (17, 19) operating under different pressures.

[0118] More precisely, a complex sub-mixture 39 evolves successively, in a continuous circuit in two columns (17, 19) set at different pressures. Each column (17, 19) has the role of separating one of the components (41, 43) of the complex sub-mixture 39 according to the pressure at which it is set.

[0119] In the first distillation column 17, which is mainly used at low pressure (P1), one of the two components 41 can be removed at the bottom of the column 17, while the azeotrope is removed at the top of the column and is introduced into the second column 19 which operates at higher pressure (P2) which causes the azeotropic mixture to disappear. In the second column 19, the second compound 43 can be removed from the bottom, while an azeotropic mixture 57 is formed at the top. The latter again has a composition significantly different from that of the submixture 39. This azeotropic mixture 57 is reintroduced into the first column 17.

[0120] Extractive distillation uses a solvent 45, called an entraining agent, which increases the volatility of one of the components or strongly changes the activity coefficients of the substances to be separated in different directions and therefore the separation factor becomes significantly different from 1 (1 = azeotrope). Two columns (21, 23) are used. Usually, the solvent 45 is fed near the top of the first column 21 (called the extraction column) and the complex submixture 47 to be separated is introduced into a lower zone of this column 21 in order to obtain the best possible mixing. The solvent 45 can be withdrawn from the bottom of this same column 21 with one 51 of the substances to be separated. The second column 23 (called the regeneration column) is used to separate (regenerate) the solvent 45 and isolate the fluorinated chemical compound 51 to be extracted.

[0121] Such a method for separating a complex mixture of fluorinated chemical components (41, 43, 49, 51, 55) is known to those skilled in the art and is described for example in document FR3115036. Thus, preferably step c) of separation by distillation comprises the implementation of said method.

[0122] Preferably, the purified stream 5 is a complex mixture of fluorinated chemical components (41, 43, 49, 51, 55), and step c) comprises: a sub-step of identifying in the purified stream 5 at least two sub-mixtures (39, 47, 53), each sub-mixture being a simple sub-mixture 53 comprising a single fluorinated chemical component 55 or a complex sub-mixture (39, 47) comprising a combination of fluorinated chemical components (41, 43, 48, 51), each complex sub-mixture (39, 47) being associated either with a first secondary distillation group by a pressure balance distillation method, or with a second secondary distillation group by an extraction distillation method, a primary distillation step, by means of a simple distillation column 15, so as to separate each identified sub-mixture (39, 47, 53), and a secondary distillation step, by means of at least two auxiliary extraction columns, of each complex submixture (39,47) of the first group and of the second group, in which the complex sub-mixtures 39 of the first group are separated by the pressure balance distillation method and the complex sub-mixtures 47 of the second group are separated, by means of a solvent 45, by the extraction distillation method.,

[0123] According to one implementation of the invention, the same auxiliary columns can successively carry out the operations of distillation by pressure balance and distillation by extraction. Such a configuration is advantageous in that it makes it possible to reduce the number of columns in the installation and therefore the associated costs.

[0124] Preferably, the solvent 45 is chosen from the following solvents: n-pentane, dichloromethane, methyl isobutyl ketone (MIBK), methyl ethyl ketone (MEK), heptanone, pentanone, cyclohexanone and dimethyl ether. Preferably, the compound used is methyl isobutyl ketone (MIBK). Such a solvent advantageously makes it possible to benefit from a high separation factor and a high extraction capacity for advanced distillation and recovery of the chemical component. Preferably, several secondary distillation steps are carried out successively for each complex submixture (39, 47) of the first group and the second group.

[0125] Optionally, the separation of a fluorinated chemical component 55 from a simple submixture 53 comprises a purification step carried out on said simple submixture 53.

[0126] When step c) comprises both primary and secondary distillation sub-steps, the installation for implementing the method according to the invention comprises a distillation unit 13 comprising one or more simple distillation columns 15; preferably, the distillation unit 13 further comprises at least two auxiliary columns (17, 19, 21, 23) configured to allow the implementation of advanced distillation by extraction, and / or advanced distillation by pressure balance.

[0127] A procedure similar to that performed on the purified stream can be performed on the enriched stream when it includes one or more fluorinated contaminants.

[0128] Preferably, the installation comprises: a simple distillation column 15 configured to receive the purified stream 5 and carry out a primary distillation, so as to separate the purified stream 5 into at least two sub-mixtures, an electronic computer configured to:

[0129] • identify in the chemical mixture the different sub-mixtures (39, 47, 53), each sub-mixture being a simple sub-mixture 53 comprising a single chemical component 55 or a complex sub-mixture (39, 47) comprising a combination of chemical components (41, 43, 49, 51),

[0130] • associating each complex sub-mixture (39, 47) either with a first secondary distillation group by a pressure balance method, or with a second secondary distillation group by an extraction distillation method, at least two auxiliary columns (17, 19, 21, 23), configured to implement a secondary distillation and to allow extraction distillation by means of a carrier, and / or pressure balance distillation, so as to separate all the chemical components (41, 43, 49, 51) of each sub-mixture (39, 47).

[0131] Preferably, two auxiliary columns are configured to implement a secondary distillation and to allow successively an extraction distillation using an entrainer, then a distillation by pressure balance, so as to separate all the chemical components of each sub-mixture Examples

[0132] Example 1: Choice of membrane and refrigerant mixtures

[0133] The results presented in the examples below were obtained using simulation software based on ideal (non-competitive) experimental permeability and selectivity data obtained at laboratory scale.

[0134] The membrane material used in this project is a polyether block and polyamide block copolymer, namely a thermoplastic elastomer composed of flexible units of poly(ethylene oxide) (PEO, 60 wt%) and hard glassy segments of polyamide 6 (PA6, 40 wt%). The polyamide segments provide mechanical strength to the polymer and prevent crystallization of PEO, thus resulting in a polymer material with good film-forming properties and high gas permeability. The membrane thickness is 2 μm.

[0135] The analysis of experimental results concerning the pure permeation properties of 7 H FC and H FO and 2 hydrocarbons through the polymer membrane led to the definition of two mixtures of refrigerants M1 and M2 whose composition is given in Table 1. A mixture of fluorinated refrigerants is also indicated in M3.

[0136] Table 1: Composition of the different refrigerant mixtures in mass percentage relative to the total weight of the mixture

[0137] Blend M1 contains HFCs, HFOs, and hydrocarbons. It is an R448A blend in which 10% by weight of R32 has been replaced by hydrocarbons. Blend M2 contains HFCs and hydrocarbons. It is an R410A blend in which 20% by weight of HFCs has been replaced by hydrocarbons.

[0138] The M3 mixture contains a fluorinated HFC contaminant 1,1,1,2,3,3,3-heptafluoropropane (R227ea).

[0139] HFCs

[0140] R32: difluoromethane

[0141] R125: pentafluoroethane

[0142] R134a: 1,1,1,2-tetrafluoroethane

[0143] R227ea 1,1,1,2,3,3,3-heptafluoropropane

[0144] The H FO

[0145] R1234yf: 2,3,3,3-Tetrafluoropropene

[0146] R1234ze: trans-1,3,3,3-Tetrafluoroprop-1-ene

[0147] Hydrocarbons

[0148] R600a: isobutane

[0149] R290: propane

[0150] Example 2: Process using a single-stage membrane separation unit and hydrocarbons

[0151] The membrane separation step is carried out at a temperature of 25°C and under a maximum pressure of 8.0 bars.

[0152] The mathematical model for a membrane separation unit was constructed taking into account the following assumptions:

[0153] The gas permeability through the dense membrane layer is described by the solution-diffusion mechanism, which means that the permeability coefficient (P) is defined as the product of the sorption coefficient (S) and the diffusion coefficient (£). where S is an equilibrium term related to the concentration of a component in the polymer phase, and D is a kinetic term related to the molecular movement of the permeable component across the membrane.

[0154] Gas transport across a dense selective barrier is governed by the following expression. where Ji is the molar flux of component i, Pi is the gas permeability coefficient, S is the membrane thickness and p R i and p P i are the partial pressure of the component on either side of the membrane.

[0155] Gas permeability is independent of feed composition (ideal gas permeability), i.e., simulation results do not account for plausible competitive effects resulting from feeding the membrane with gas mixtures.

[0156] Gas permeability is pressure dependent. The permeability data of each HFC, HFO and HC were described as a function of the pressure gradient applied across the membrane (Apj) following an exponential function. where Po,i is a pre-exponential factor and m is a constant that provides information on the influence of pressure on gas permeability. A summary of the fitted parameter values ​​for each gas is provided in Table 2.

[0157] The plug flow concentration model is developed in both the feed gas and the permeate gas flowing through the channels on both sides of the membrane.

[0158] Negligible pressure losses of the gas phase along the supply side. Isothermal operation.

[0159] Table 2: Exponential fitting parameters to Eq. (3) of HFCs, HFOs and HCs.

[0160] The schematic diagram of the gas separation process through a flat thin-film composite membrane is shown in Figure 2.

[0161] The differential mass balances around each component in a slice of length dz are derived as follows, where Fj is the molar flow rate of component i, A is the membrane surface area, and z is the axial position along the module length. In addition, the transmembrane flux of each component (Jj) has been defined in Eq. 2. The proposed mathematical model is therefore formed by the system of equations (2), (3), (4), and (5).

[0162] Performance of the

[0163] The performance of the separation process is evaluated in terms of product purity and product recovery in the stream of interest (either retentate or permeate, depending on the case study). In each case study, product recovery is defined by Eq. (6) and purity is given by the mass concentration of the target component(s) in the product stream.

[0164] „ , , Flow rate of component im product stream

[0165] Product recovery = • - - — ~ — 7 — - ■ - —

[0166] Feed flowrate ot component /

[0167] (6)

[0168] Filtration of the M1 mixture

[0169] Figure 3 plots the HFC+HFO concentration in the permeate stream versus HFC+HFO recovery as a function of feed pressure (1-8 bar) and membrane area for Mixture 1. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg. h -1 . Membrane thickness = 2 pm. Feed composition is 90% by weight HFC + HFO and 10% by weight HC (R600a + R290).

[0170] Table 3 illustrates an example of the membrane separation performance for mixture M1

[0171] Table 3

[0172] As can be seen, the recovery and purity of HFC+HFO are 60.4% by weight (in the retentate) and 93.7% by weight (in the permeate) respectively. These product specifications are obtained with a feed pressure of 3.7 bar and a membrane module of 17 m 2 of permeation surface.

[0173] Filtration of the M2 mixture

[0174] Figure 4 plots the R32+R125 concentration in the permeate stream versus R32+R125 recovery as a function of feed pressure (1-8 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h' 1 . Membrane thickness = 2 pm. The feed composition is 40 wt% R32, 40 wt% R125, 10 wt% R600a and 10 wt% R290.

[0175] Table 4 illustrates an example of the membrane separation performance for the M2 mixture (membrane area: 5.1 m 2 ) Table 4

[0176] As can be seen, the HC content in the product stream can be reduced from 20 wt% to 5.5 wt% with a 5 m single-stage membrane unit 2 permeation surface applying a feed pressure of 7.4 bar. The recovery and purity of R32+R125 are 61.4% and 94.5% by weight respectively

[0177] Table 5 illustrates another example of membrane separation performance for the M2 mixture (membrane area: 17 m 2 )

[0178] Table 5

[0179] In this case, a much lower pressure of 3.6 bar must be applied in order to achieve R32+R125 recovery and purity of 60.2% and 92.6% by weight, respectively

[0180] Example 3: process using a 2-stage membrane separation unit and hydrocarbons

[0181] In the two-stage design, the permeate from the first membrane unit is usually recompressed and sent to a second membrane unit, where further separation is performed. The final permeate is then enriched twice. In addition, since the gas volume treated by the second-stage membrane unit is smaller than in the first stage, the membrane surface area of ​​the second stage is smaller and the required compression power does not increase significantly compared to the one-stage process.

[0182] Filtration of the M1 mixture

[0183] Figure 5 provides a comparison of one-stage and two-stage HFC+HFO purification. It illustrates HFC+HFO concentration in the permeate stream versus HFC+HFO recovery as a function of feed pressure (1-8 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h' 1. Membrane thickness = 2 pm. The feed composition is 90 wt% HFC + HFO and 10 wt% HC (R600a + R290). As can be seen, this configuration improves the product specifications compared to the single-stage process, as it would reduce the presence of HC in the permeate stream from the initial 10 wt% to a low hydrocarbon concentration (< 2 wt%) with HFC+HFO recoveries around 60%. A schematic representation of a two-stage membrane separation unit is given in Figure 1. The unit comprises two filtration modules connected in series, the first module having a membrane area of ​​57 m 2 and the second module having a membrane surface of 5 m 2The initial flow feeds the first module alone initially, then, as soon as it is available, the retentate from the second module is recycled to the inlet of the first module, adding to the initial flow and therefore modifying the composition of the flow entering the first module. The results given in Table 6 illustrate a situation at equilibrium.

[0184] Table 6

[0185] As can be seen, it is possible to achieve a target HFC+HFO purity of 98.3% by weight with a recovery of 68.8%. The specifications of this product are obtained with a feed pressure of 4.8 bar in the first stage and 8 bar in the second stage, and with 57 m modules 2 and 5 m 2 membrane surface. The initial hydrocarbon content of 10% by weight in the stream is less than 2% by weight in the second permeate (a decrease of a factor of 5).

[0186] Filtration of the M2 mixture

[0187] Figure 6 allows a comparison of R32+R125 purification with one stage and two stages. It illustrates the concentration of R32+R125 in the permeate stream versus the recovery of R32+R125 as a function of feed pressure (1-8 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h' 1 . Membrane thickness = 2 pm. The feed composition is 40 wt% R32, 40 wt% R125, 10 wt% R600a and 10 wt% R290.

[0188] The process illustrated in Figure 7 with recycling of the second retentate into the feed stream of the first module is also followed, with the difference that the membrane surface is 80 m 2 in the first module and 5 m 2 in the second filtration module. The results of the equilibrium situation are given in Table 7.

[0189] Table 7

[0190] As can be seen, the two-stage filtration step reduces the presence of HC from the initial 20 wt% to about 2 wt% (a decrease of a factor of 10) and achieves a higher recovery level (65%) than the single-stage separation. This separation is carried out with two membrane units of 80 and 5 m 2 , respectively. The recovery and purity of R32+R125 are 64.8% and 97.9% by weight, respectively. Example 4: Process using a 2-stage membrane separation unit and a fluorinated contaminant.

[0191] In the two-stage design, the permeate from the first membrane unit is typically recompressed and sent to a second membrane unit, where further separation is performed. The final permeate is then enriched twice. In addition, since the gas volume treated by the second-stage membrane unit is smaller than in the first stage, the membrane surface area of ​​the second stage is smaller, and the required compression power does not increase significantly compared to the one-stage process. When the contaminant is a fluorinated contaminant, it may be worthwhile to isolate this fluorinated chemical compound, which is labeled a contaminant, for recycling as well.

[0192] Filtration of the M3 mixture

[0193] Figure 7 allows a comparison of the separation of the fluorinated chemical compound R227ea with one stage and two stages. It illustrates the concentration of R227ea in the permeate stream versus the recovery of R227ea as a function of feed pressure (1-4 bar) and membrane area. Each data point represents a combination of feed pressure and membrane area. Feed flow rate = 10 kg h' 1 . Membrane thickness = 2 pm. The feed composition is 70% by weight R227ea, 20% by weight R1234ze and 10% by weight R134a.

[0194] The process illustrated in Figure 5 with recycling of the second retentate into the feed stream of the first module is also followed, with the difference that the membrane surface area is 15.3 m 2 in the first module and 21.8 m 2 in the second filtration module. The results of the equilibrium situation are given in Table 8.

[0195] Table 8

[0196] As can be seen, the two-stage filtration step allows recovery of the fluorinated chemical contaminant R227ea in the first and second retentates at 68% and 85% respectively. This contaminant can then be purified and recycled.

Claims

CLAIMS 1. A method for recycling a mixture (1) comprising at least one fluorinated fluid, characterized in that it comprises: a) providing, in the form of an initial flow (3), a mixture (1) comprising at least one fluorinated fluid; the mixture comprising one or more fluorinated chemical components (41, 43, 49, 51, 55) and one or more contaminants chosen from one or more hydrocarbons and / or one or more fluorinated contaminants; b) membrane filtration of the initial flow (3) so as to obtain a purified flow (5) comprising a contaminant content lower than the contaminant content of the initial flow (3) and a contaminant-enriched flow (33); said membrane filtration comprising at least two membrane filtration sub-steps carried out successively; and c) recovering the purified flow (5) and / or the contaminant-enriched flow (33) for reuse and / or recycling.

2. The recycling process according to claim 1 characterized in that the initial flow (3) comprises one or more fluorinated contaminants and the or at least one fluorinated contaminant is 1,1,1,2,3,3,3-heptafluoropropane (R227ea).

3. The recycling process according to claim 1 or 2 characterized in that the initial flow (3) comprises one or more fluorinated contaminants and step c) comprises the recovery of the flow enriched in contaminants (33) and its recycling.

4. The recycling method according to one of claims 1 to 3 characterized in that the initial flow (3) comprises one or more hydrocarbons chosen from the group comprising propane and isobutane.

5. The recycling process according to one of claims 1 to 4 in that the initial stream (3) comprises one or more hydrocarbons and step c) comprises the recovery of the purified stream (5) and its recycling.

6. The recycling method according to one of claims 1 to 5, characterized in that step b) of membrane filtration comprises at least one sub-step of filtration by means of a membrane comprising at least one layer of a polymer material chosen from a polyethersulfone, a polysulfone, a polyvinylidene fluoride, a copolymer with polyether blocks and polyamide blocks, a polypropylene, a cellulose acetate, a polytetrafluoroethylene, a sulfonated polyphenylenesulfone, acetate cellulose butyrate, polyhedral oligomeric silsesquioxane, or a polydimethylsiloxane.

7. The recycling method according to one of claims 1 to 6, characterized in that step b) of membrane filtration comprises at least one sub-step of filtration by means of a membrane comprising at least one layer of a material chosen to be a copolymer with polyether blocks and polyamide blocks; preferably, the polyamide block comprises at least one polyamide chosen from polyamide 6, polyamide 11 and polyamide 12; preferably, polyamide 6.

8. The recycling method according to one of claims 1 to 7, characterized in that the initial flow (3) comprises one or more fluorinated chemical components (41, 43, 49, 51, 55) chosen from hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), hydrofluoroolefins (HFOs), and hydrochlorofluoroolefins (HCFOs); more preferably, the initial flow comprises one or more fluorinated chemical components chosen from hydrofluorocarbons (HFCs) and / or hydrofluoroolefins (HFOs).

9. The recycling method according to one of claims 1 to 8 in that the initial flow (3) comprises one or more fluorinated fluids (41, 43, 49, 51, 55) chosen from difluoromethane (R32), pentafluoroethane (R125), 1,1,1,2-tetrafluoroethane (R134a), 2,3,3,3-Tetrafluoropropene (R1234yf) and trans-1,3,3,3-Tetrafluoroprop-1-ene (R1234ze).

10. The recycling method according to one of claims 1 to 9, characterized in that the initial flow supplied in step a) comprises a contaminant content greater than or equal to 0.5% by weight relative to the total weight of the initial flow (3); preferably, a contaminant content of 5.0% to 40% by weight relative to the total weight of the initial flow.

11. The recycling process according to one of claims 1 to 10 characterized in that the initial flow supplied in step a) comprises a hydrocarbon content greater than or equal to 0.5% by weight relative to the total weight of the initial flow (3); preferably between 5.0 and 40% by weight.

12. The recycling process according to one of claims 1 to 11, characterized in that the initial stream supplied in step a) comprises one or more hydrocarbons and in that step b) is carried out so as to obtain a hydrocarbon content of less than 5.0% by weight relative to the total weight of the purified stream (5).

13. The recycling method according to one of claims 1 to 12 characterized in that the initial flow (3) comprises at least two fluorinated chemical components (41, 43, 49, 51, 55) and in that step c) of recycling the purified flow (5) comprises the separation of said fluorinated chemical components (41, 43, 49, 51, 55) by distillation.

14. The recycling method according to claim 13 characterized in that the step of separating the fluorinated chemical components (41, 43, 49, 51, 55) by distillation comprises: - an identification sub-step in the mixture of fluorinated chemical components (41, 43, 49, 51, 55) of at least two sub-mixtures (39, 47, 53), each sub-mixture being a simple sub-mixture (53) comprising a single fluorinated chemical component (55) or a complex sub-mixture (39, 47) comprising a combination of chemical components (41, 43, 49, 51), each complex sub-mixture (39, 47) being associated either with a first secondary distillation group by a pressure balance distillation method, or with a second secondary distillation group by an extraction distillation method, - a primary distillation step, using a simple distillation column 15, so as to separate each identified sub-mixture (39, 47, 53), - a secondary distillation stage, by at least two auxiliary columns (17, 19, 21, 23), of each complex submixture (39, 47) of the first group and of the second group, the complex submixtures (39) of the first group being separated by the pressure balance distillation method and the complex submixtures (47) of the second group being separated, by means of a solvent (45), by the extraction distillation method.

15. The recycling method according to one of claims 1 to 14 characterized in that each membrane filtration sub-step generating a permeate and a retentate, the retentate from the second membrane filtration sub-step is recycled so as to be mixed in the initial flow.

16. The recycling method according to one of claims 1 to 15 characterized in that step a) comprises a step of identifying one or more contaminants in the initial stream and in that when the hydrocarbon content is greater than 40% by weight based on the total weight of the initial stream, it further comprises a sub-step of diluting the initial stream with another stream free of hydrocarbons in order to adjust the hydrocarbon content to be less than 40% by weight based on the total weight of the initial stream.

17. Installation for implementing the method of recycling a mixture (1) comprising at least one fluorinated fluid according to one of claims 1 to 16, characterized in that it comprises a membrane filtration unit (7) comprising at least two membrane filtration modules (9, 11) arranged in series.

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