Method for removing pfas comprised in waste

Abstract

The present invention relates to an industrial method for effectively removing a PFAS substance, in particular PFAS POPs, comprised in waste, while making it possible to effectively control the HF emissions induced by this removal.

Description

Description Title: PROCESS FOR ELIMINATING A PFAS INCLUDED IN WASTE Technical field

[0001] The present disclosure relates to the field of disposal of poly- and perfluoroalkyl substances ("Per- and polyfluoroalkyl substances" in English terminology, hereinafter referred to as PFAS), in particular included in waste.

[0002] PFAS are a large family of several thousand synthetic chemicals that have been commonly used since the 1950s for their non-stick properties, impermeability, and durability under extreme conditions (high heat, high pressure, and / or radiation).

[0003] According to a presentation dated February 7, 2023, by the European Chemicals Agency (hereinafter referred to as ECHA), PFAS are present in a wide variety of applications. For example, PFAS are used in various industrial processes, in the energy sector, in the oil and mining sectors, in the transport sector, in the surface treatment of materials (waterproofing, water repellent, anti-wetting), in fire-extinguishing foams, in lubricants, in electronic products and semiconductors. PFAS are also present in everyday objects, such as waterproof clothing (shoes, gloves, coats), non-stick pans, water-repellent stain-resistant textiles (tapestries, carpets), implantable medical devices, cosmetic products, medicines, plant protection products, and food packaging.Thus, according to this presentation, approximately 92,000 tonnes of PFAS were used in 2020.

[0004] However, even at very low doses, PFAS are particularly toxic. Indeed, according to the ECHA, PFAS are suspected of having multiple harmful effects in humans, such as causing cancer, reduced fertility, poor fetal development, and interference with the immune system.

[0005] Furthermore, due to their chemical structure made of carbon-fluorine bonds, which are among the strongest chemical bonds in organic chemistry, PFAS do not degrade after use or release into the environment. Some PFAS, such as perfluorooctanoic acid (hereinafter referred to as PFOA), perfluorooctane sulfonic acid (hereinafter referred to as PFOS) and perfluorohexane sulfonic acid (hereinafter referred to as PFHxS), are even called "Persistent organic pollutants" (hereinafter referred to as PFAS POPs). According to the European Commission, a POP is a chemical compound that persists in the environment, bioaccumulates in the food web and may have adverse effects on human health and the environment.

[0006] According to ECHA, most PFAS are also easily transported in the environment over long distances, far from their source of emission. PFAS contamination of groundwater, surface water, and soil has thus been frequently observed. If PFAS continue to be released into the environment, PFAS will continue to accumulate, particularly in drinking water and food.

[0007] PFAS are toxic, polluting, and accumulate in the environment, drinking water, and food. Banning them is currently under discussion in Europe, but is expected to take several years. In the short term, eliminating them is therefore a major health issue. Prior art

[0008] On July 27, 2022, the United Nations Environment Program (hereinafter UNEP) issued the technical guide "General technical guidelines on the environmentally sound management of wastes consisting of, containing or contaminated with persistent organic pollutants" which provides guidance for the environmentally sound management of wastes consisting of, containing or contaminated with PFAS POPs. In this patent application, this technical guide may be referred to as the technical guide issued by UNEP.

[0009] The technical guidance issued by UNEP defines two efficiencies to quantify the PFAS POP removal efficiency of a method. These two efficiencies are: - the destruction efficiency (hereinafter referred to as DE). This efficiency corresponds to the percentage of PFAS POPs contained in the waste which is destroyed or irreversibly transformed by a particular method or technology, and - the destruction and removal efficiency (hereinafter referred to as DRE). This efficiency only takes into account emissions into the air and corresponds to the percentage of original PFAS POPs transformed irreversibly and evacuated in the fumes.

[0010] In the field of the invention, there is a consensus to qualify as effective a method having a DE greater than or equal to 99.99% and a DRE greater than or equal to 99.9999%.

[0011] The publication "PFAS fate and destruction mechanisms during thermal treatment: a comprehensive review, Longendyyke, et al. Environ. Sci.: Processes Impact, 2022, 24, 196" presents different methods for PFAS removal. These methods are incineration, thermal desorption, pyrolysis, gasification, smoldering combustion, and hydrothermal liquefaction.

[0012] According to this publication: - thermal desorption and pyrolysis reduce the quantity of PFAS by 90%, - gasification generates volatile PFAS, - slow combustion can only reduce the amount of PFAS by about 80%, and - hydrothermal liquefaction can only reduce the amount of PFOA to 99% and the amount of PFOS to 86%.

[0013] A process for removing PFAS by gasification is described in US patent 11,339,337 B1. In particular, the waste used in this process is wastewater comprising biosolids and PFAS. The process comprises the following steps: - gasification of wastewater at a temperature of 480°C to 980°C to produce a synthesis gas including the PFAS not removed by gasification. Synthesis gas is a mixture of carbon monoxide (CO) and hydrogen (H2). Thus, unlike incineration carried out in an oxidizing medium, gasification is necessarily carried out in a reducing medium to produce synthesis gas, - combustion of the synthesis gas comprising the PFAS at a temperature of 870°C to 1420°C to produce a combustion gas comprising the PFAS not eliminated by combustion, - cooling the flue gas comprising the PFAS to a temperature of 205°C to 650°C to produce a cooled flue gas comprising the PFAS, and - contacting the cooled flue gas comprising the PFAS with hydrated lime to increase the decomposition of the PFAS from the cooled flue gas. Thus, as described in the publication "PFAS fate and destruction mechanisms during thermal treatment: a comprehensive review, Longendyyke, et al. Environ. Sci.: Processes Impact, 2022, 24, 196, the gasification step of the process of US patent 11,339,337 B1 generates volatile PFAS that need to be decomposed in two subsequent steps. The process of US patent 11,339,337 B1 therefore does not allow simple and effective elimination of PFAS.

[0014] Thus, thermal desorption, pyrolysis, gasification, slow combustion and hydrothermal liquefaction do not appear to be able to simply eliminate PFAS efficiently enough. Moreover, given the complexity of their implementation and the very large quantity of PFAS to be eliminated, these methods are difficult to envisage on an industrial scale.

[0015] Incineration, on the other hand, is a technique that can be considered on an industrial scale. Indeed, it is simple to implement and allows for the treatment of a very large quantity of waste, including waste containing PFAS. However, a study presented in this publication concludes that PFOA is not degraded by being subjected to 1000°C for 2 seconds.

[0016] Furthermore, according to this publication, the destruction, particularly thermal destruction, of PFAS generates hydrogen fluoride, hereinafter referred to as HF. HF is an extremely toxic and ecotoxic compound. In addition, HF can deteriorate the incineration unit by its corrosive action on metals or, as explained in this publication, by reacting with the silica-based coating of the reactors to produce silicon tetrafluoride.

[0017] In an industrial-scale test, the Applicant subjected waste containing PFAS to a temperature between 962°C and 979°C in an incineration unit. It found that some PFAS could be effectively removed but that, in return, the HF emissions are above the limit value of 1 mg / Nm 3 dry at 11% O2 indicated in Annex VI of Directive 2010 / 75 / EU of the European Parliament and of the Council of 24 November 2010. Technical problem

[0018] There is therefore still a need for an industrial solution to effectively eliminate PFAS while effectively controlling the HF emissions induced by this elimination.

[0019] It is therefore to the credit of the inventors that they found that it was possible to meet this need by subjecting the waste containing PFAS to heat treatment in the presence of an alkaline earth metal salt. Summary

[0020] Thus, a method is provided for removing a poly- and perfluoroalkylated substance included in a waste, the method comprising a step of: a) heat treatment of the waste at a temperature greater than or equal to 850°C, in particular from 900°C to 1100°C, more particularly from 950°C to 1050°C, step a) being carried out in the presence of a composition comprising an alkaline earth metal salt.

[0021] Surprisingly, the combination of the heat treatment carried out under the operating conditions of step a) and the alkaline earth metal salt advantageously allows: - to effectively and simply eliminate poly- and perfluoroalkyl substances, in particular the PFAS POPs PFOA, PFOS and PFHxS, and - to control the HF concentration in the smoke generated during step a) so that HF ​​emissions are below the limit value of 1 mg / Nm 3 dry at 11% O2 indicated in Annex VI of Directive 2010 / 75 / EU of the European Parliament and of the Council of 24 November 2010.

[0022] Without wishing to be bound by any theory, the inventors are of the opinion that the combination of the heat treatment carried out under the operating conditions of step a) and the alkaline earth metal salt gives the process its effectiveness by: - facilitating the degradation reactions of the poly- and perfluoroalkyl substance present in the waste and / or present in the smoke generated by the combustion of the waste during step a), and - effectively neutralizing the HF formed by this degradation. Indeed, under the conditions of step a), the heat treatment allows the combustion of the waste, the degradation of the poly- and perfluoroalkylated substance and the very rapid oxidation of the alkaline earth metal salt into alkaline earth metal oxide. The inventors are of the opinion that this oxide could then: - catalyze PFAS degradation reactions, thereby accelerating the kinetics of these reactions, and / or - react quickly with the products of these degradations, in particular with HF. In accordance with Le Chatelier's principle, the degradation reactions of PFAS would then be thermodynamically favored. Particularly convincing results have been obtained with calcium carbonate.

[0023] The method of the invention is also simple to implement on an industrial scale to treat a large quantity of waste. Indeed, the method of the invention can be implemented in a conventional waste incineration unit, known and mastered by the person skilled in the art. In addition, the flow rate of a combustion furnace of a conventional incineration unit can reach 15 T / h of waste.

[0024] The process of the invention is also economical. Indeed, it does not require heavy investment in equipment since it can be implemented in a conventional waste incineration unit and because the cost of the composition is low.

[0025] Also provided is a use of a composition comprising an alkaline earth metal salt for removing a poly- and perfluoroalkylated substance included in a waste. Brief description of the drawings

[0026] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analyzing the attached drawing, in which: Fig. 1

[0027] [Fig. 1] is a diagram illustrating an incineration unit. Description of the embodiments

[0028] Reference is now made to [Fig. 1].

[0029] According to a first aspect, there is provided a method for removing a poly- and perfluoroalkylated substance included in a waste, the method comprising a step of: a) heat treatment of the waste at a temperature greater than or equal to 850°C, in particular from 900°C to 1100°C, more particularly from 950°C to 1050°C, step a) being carried out in the presence of a composition comprising an alkaline earth metal salt.

[0030] For the purposes of the present invention, the term "poly- and perfluoroalkylated substance" means an organofluorine compound comprising one or more perfluorinated alkyl or polyfluorinated alkyl functional groups.

[0031] For the purposes of this invention, the singular forms "a", "an", "the" and "the" also encompass the plural forms of the terms to which they refer, unless the content clearly indicates otherwise.

[0032] The poly- and perfluoroalkylated substance used in the process of the present invention may be any PFAS. Thus, the PFAS may be chosen from a PFAS presented in Table 45-1 PFAS Target Analytes present in the US EPA method OTM-45 in its version of January 13, 2021, a PFAS listed in Directive 2020 / 2184 of the European Parliament and of the Council of December 16, 2020 relating to the quality of water intended for human consumption and their combination.

[0033] For example, the poly- and perfluoroalkyl substance may be at least one PFAS selected from:

[0034] According to one embodiment, the PFAS may be selected from PFAS POPs. Examples are PFOS, PFOA, PFHxS.

[0035] Thus, according to one embodiment, the PFAS may be PFOS, PFOA, PFHxS, a mixture of PFOS and PFOA, a mixture of PFOS and PFHxS, a mixture of PFOA and PFHxS or a mixture of PFOS, PFOA and PFHxS.

[0036] The process of the invention therefore makes it possible to effectively eliminate PFAS POPs and thus resolve a major health problem.

[0037] According to another embodiment, the poly- and perfluoroalkylated substance can be chosen from PFOS, PFOA, PFHxS, HFPO-DA, PFDS, PFBA and mixtures thereof.

[0038] The waste used in the process of the invention may be any type of waste comprising one or more PFAS. In particular, the waste may comprise at least 0.01 mg of PFAS per kg of waste, in particular from 0.10 mg of PFAS to 1000 mg of PFAS per kg of waste, more particularly from 0.90 mg of PFAS to 150 mg of PFAS per kg of waste.

[0039] The waste may be selected from hazardous waste, non-hazardous waste, POP waste, municipal sludge, industrial sludge and their mixtures, in particular hazardous waste, POP waste and their mixture, more particularly POP waste.

[0040] For the purposes of the present invention, "non-hazardous waste" means any waste which does not have any of the properties which make waste hazardous.

[0041] For the purposes of the present invention, "hazardous waste" means any waste which exhibits one or more of the hazardous properties listed in Annex III to Directive 2008 / 98 / EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain directives.

[0042] For the purposes of the present invention, "POP waste" means any waste comprising at least 50 mg of PFOS per kg of waste, at least 1 mg of PFOA per kg of waste and / or at least 1 mg of PFHxS per kg of waste.

[0043] For example, a non-hazardous waste that can be used in the method of the invention is an everyday object, such as waterproof clothing, a non-stick pan, a water-repellent stain-resistant textile, an implantable medical device, a cosmetic product, food packaging, an electronic product, a semiconductor and their mixtures. The clothing Waterproof can be a shoe, a glove, a coat or their combinations. Water-repellent stain-resistant textile can be a tapestry, a carpet or their combination.

[0044] A hazardous waste, which can be used in the method of the invention, can, for example, be a phytosanitary product, a lubricant, a paint, a used oil, a used acid, a used solvent, a paint sludge, a hydrocarbon tank bottom, an expired pesticide, a toxic gas waste and their mixtures.

[0045] The POP waste, which can be used in the process of the invention, can be the polluted soil of an industrial site, in particular of an industrial site for the manufacture of extinguishing powder.

[0046] The alkaline earth metal salt of the composition may comprise a cation selected from a magnesium cation, a calcium cation and mixtures thereof, preferably may be the calcium cation.

[0047] The anion of the alkaline earth metal salt may be selected from an acetate, an acrylate, a carbonate, a formate, a propionate and mixtures thereof, in particular from an acetate, an acrylate, a carbonate and mixtures thereof, more particularly the anion is a carbonate.

[0048] The alkaline earth metal salt may be selected from a magnesium salt, a calcium salt or a mixture thereof, particularly from magnesium carbonate, calcium carbonate or a mixture thereof, particularly calcium carbonate.

[0049] Advantageously, particularly convincing results have been obtained with calcium carbonate. In addition, the cost of calcium carbonate is advantageously low.

[0050] Calcium carbonate can be derived from chalk, limestone, lime, shell, mineral mud, or mixtures thereof, especially lime, shell, mineral mud, or mixtures thereof, especially lime.

[0051] The mineral sludge may be composed mainly of calcium carbonate and may, if necessary, be transformed into a powdery composition using one or more suitable chemical treatments. The chemical treatments are those known to those skilled in the art, such as, for example, washing, drying, and physicochemical treatments. A decarbonation sludge, a primary brine purification sludge, and their mixture are mineral sludges that are entirely suitable for use in the process of the invention.

[0052] Decarbonation sludge is a non-hazardous waste typically generated during the water decarbonation process, an operation carried out on industrial sites requiring softened water supplies. Each of these sites can generate 1000 to 3000 tonnes / year of decarbonation sludge. Advantageously, using decarbonation sludge as a source of calcium carbonate therefore makes it possible to recover waste that is not currently recovered and to create a circular economy through the availability of this waste around incinerators. This also makes it possible to substitute a natural resource (chalk, limestone and lime) with waste. Decarbonation sludge generally comprises approximately 65% ​​calcium carbonate, the remainder being water. To be used in step a) of the process the invention, it can therefore be dried so that the mass concentration of calcium carbonate in the dried sludge is greater than 90.0%.

[0053] Primary brine sewage sludge is a waste product resulting from electrolysis in the manufacture of chlorine. It contains calcium and magnesium carbonates as well as traces of pollutants, salts, and possibly metals. The pollutants, salts, and possible metals can be separated by specific operations known to those skilled in the art, such as successive washings or physicochemical treatments. Water can be removed by drying.

[0054] The composition may comprise at least 30% by mass of alkaline earth metal salt, in particular from 35% to 100% by mass of alkaline earth metal salt, more particularly from 50% to 99%.

[0055] The composition may, for example, be chosen from a powdery composition and a slurry and their combination.

[0056] For the purposes of the present invention, the term "powdery composition" means a composition in powder form. In particular, the maximum diameter of the volume distribution of 50% of the particles (d50) of the powdery composition according to the invention may be less than or equal to 50 pm, preferably from 2 pm to 20 pm, more preferably from 4 pm to 10 pm. The d50 value may be determined by liquid laser granulometry in distilled water with a Malvern-Mastersizer 2000 laser granulometer equipped with a 120 ml "small volume" cell, the signal is processed with the Mie mathematical model.

[0057] Advantageously, a particle size in the above ranges makes it possible to increase the contact surface of the powdered composition with the waste and with the smoke generated by the thermal treatment of the waste. This makes it possible to improve the efficiency of PFAS removal and to improve the efficiency of control of HF emissions induced by this removal.

[0058] The powdery composition may comprise at least 90% by mass of alkaline earth metal salt, in particular at least 95% by mass of alkaline earth metal salt.

[0059] According to a particular embodiment, the powdery composition consists essentially of the alkaline earth metal salt.

[0060] For the purposes of the present invention, "consisting essentially of" means that other specific elements may be present in the composition, in this case elements which do not materially affect the essential characteristics of the composition. Impurities are examples of elements which do not materially affect the essential characteristics of the composition.

[0061] For the purposes of the present invention, "slurry" means a viscous mixture of a solid material suspended in a liquid, in particular in water, the solid material comprising the alkaline earth metal salt.

[0062] For example, the slurry may be a suspension of a mineral slurry as described above.

[0063] The slurry may comprise at least 30% by mass of alkaline earth metal salt, in particular from 35% to 50% by mass of alkaline earth metal salt.

[0064] During step a) of the method of the invention, the heat treatment can be carried out for at least 2 seconds, in particular from 2 seconds to 30 seconds, more particularly from 2.2 seconds to 5 seconds.

[0065] This duration corresponds to the duration during which, during step a), the waste is subjected to a temperature greater than or equal to 850°C, in particular from 900°C to 1100°C, more particularly from 950°C to 1050°C.

[0066] Advantageously, the inventors have noted that the elimination of PFAS and the control of HF emissions induced by this elimination are all the more effective when the heat treatment of step a) of the process of the invention is carried out within these duration ranges.

[0067] Furthermore, such duration ranges are consistent with the implementation of the method of the invention in a conventional waste incineration unit 1. Indeed, certain units of a conventional waste incineration unit 1 operate: - at temperatures compatible with the operating conditions of step a) of the process of the invention, and - with stay times compatible with these duration ranges.

[0068] As shown schematically in [Fig. 1], an incineration unit 1 may comprise, in the direction of flow, a combustion furnace 11, for example rotary, a flue gas post-combustion chamber 12, a flue gas cooling unit comprising a boiler 13 then a cooling tower 14, a flue gas filtration unit 15, a flue gas ventilation and extraction unit 16 and a chimney 17.

[0069] The waste is conventionally burned in the combustion furnace 11, thus generating smoke. This smoke is then sent to the post-combustion chamber 12 to be burned there during a post-combustion step. The burned smoke from the post-combustion chamber 12 is then cooled and purified in the boiler 13 and the cooling tower 14, then purified in the smoke filtration unit 15. This purified smoke is then evacuated through the chimney 17 after passing through the ventilation and smoke extraction unit 16.

[0070] Incineration unit 1 can typically produce solid residues and gaseous residues.

[0071] For example, the solid residue may be clinker from the post-combustion chamber 12, fly ash from the boiler 13 and / or the cooling tower 14, ash from the flue gas filtration unit 15 or combinations thereof.

[0072] The gaseous residue may be the purified smoke discharged through the chimney 17.

[0073] The incineration unit 1 may further comprise an acid and / or basic flue gas scrubber between the flue gas filtration unit 15 and a flue gas ventilation and extraction unit 16. The flue gas scrubbing water from this acid and / or basic scrubber is a liquid residue produced by the incineration unit 1.

[0074] The heat treatment of step a) of the process of the invention may be an incineration step by oxidation.

[0075] Typically the temperature in the combustion furnace 11 is 850°C to 1200°C and the temperature in the post-combustion chamber 12 is 900°C to 1150°C.

[0076] Unlike the gasification reaction, the combustion reaction carried out in the combustion furnace 11 and the post-combustion reactions carried out in the post-combustion chamber 12 require the presence of oxygen. Thus, the oxygen content of the burnt smoke from the post-combustion chamber 12 may be from 1% to 10%, in particular from 2% to 9%, most particularly from 4% to 8% by volume relative to the volume of said burnt smoke.

[0077] Step a) of heat treatment of the process of the invention can be carried out in the combustion furnace 11 and / or in the post-combustion chamber 12 of the incineration unit 1. Due to their configuration, the combustion furnace 11 and the post-combustion chamber 12 of the incineration unit 1 are not suitable for carrying out a gasification step producing CO and H2. Indeed, these two compounds would oxidize immediately with the oxygen in the combustion air, which would be particularly dangerous in the case of H2.

[0078] Indeed, the temperature and / or the partial pressure of oxygen in the combustion furnace 11 and / or in the post-combustion chamber 12 are such that step a) of the method of the invention can be advantageously carried out there. In addition, with such a step a), it is not necessary to add to the incineration unit 1 a unit specifically dedicated to reducing the HF concentration in the combustion fumes. Consequently, such a step a) makes it possible not to complicate the incineration unit 1 and to increase the energy efficiency of the method of the invention.

[0079] A heat treatment duration of at least 2 seconds, in particular 2 seconds to 3 seconds, is suitable for carrying out step a) in the post-combustion chamber 12 of the incineration unit 1.

[0080] Indeed, advantageously, such a duration is in accordance with the conventional residence time of the fumes in the post-combustion chamber 12 of the incineration unit 1. Such a duration also allows the effective elimination of the PFAS and the effective control of the HF emissions induced by this elimination.

[0081] A heat treatment duration of at least 2 seconds, in particular from 2 seconds to 30 seconds, more particularly from 2.1 seconds to 3 seconds is suitable for carrying out step a) in the combustion furnace 11.

[0082] Indeed, advantageously, such a duration is in accordance with the duration during which the waste is conventionally subjected to the operating conditions of step a) in the combustion furnace 11 and with the conventional residence time of the fumes generated by the combustion of this waste in the combustion furnace 11. Such a duration also allows the effective elimination of the PFAS and the effective control of the HF emissions induced by this elimination.

[0083] A heat treatment duration of at least 2 seconds, in particular from 2 seconds to 30 seconds, more particularly from 2.2 seconds to 5 seconds is suitable for carrying out step a) in the combustion furnace 11 and in the post-combustion chamber 12 of the incineration unit 1.

[0084] Typically, during step a) of the method of the invention, the composition may be injected into the combustion furnace 11, at the interface between the combustion furnace 11 and the post-combustion chamber 12 and / or into the post-combustion chamber 12.

[0085] The powdery composition is suitable for injection into the post-combustion chamber 12 and / or at the interface between the combustion furnace 11 and the post-combustion chamber 12.

[0086] Thanks to its granulometry, the powdery composition has flowability properties allowing it to be injected well.

[0087] The slurry is suitable for injection into the combustion furnace 11, at the interface between the combustion furnace 11 and the post-combustion chamber 12 and / or into the post-combustion chamber 12, in particular into the combustion furnace 11.

[0088] Advantageously, injecting the slurry into the combustion furnace 11, in particular at the inlet of the combustion furnace 11, makes it possible to maximize the contact time between the waste and the alkaline earth metal salt and therefore to increase the efficiency of the elimination of the PFAS and the efficiency of the control of the HF emissions induced by this elimination.

[0089] The composition may be injected using an injection device such as a volumetric metering screw or a weight metering screw.

[0090] A mass flow meter may also be used to control the injection rate of the composition into the combustion furnace 11, at the interface between the combustion furnace 11 and the post-combustion chamber 12 and / or into the post-combustion chamber 12.

[0091] The ratio between the mass of the PFAS and the mass of the composition can be from 1:0.01 to 1:0.5, in particular from 1:0.03 to 1:0.25, more particularly from 1:0.06 to 1:0.08.

[0092] Advantageously, such a mass ratio allows efficient elimination of PFAS, efficient control of HF emissions induced by this elimination and does not alter the operation of incineration unit 1.

[0093] This mass ratio may depend on the waste flow rate in the combustion furnace 11 and the injection flow rate of the composition into the combustion furnace 11, at the interface between the combustion furnace 11 and the post-combustion chamber 12 and / or into the post-combustion chamber 12.

[0094] The person skilled in the art will be able to adapt these flow rates, in particular the injection flow rate of the composition to verify this mass ratio. Indeed, it is necessary to know the flow rate of waste in the combustion furnace 11 and the mass flow of the PFAS in the waste to then determine the injection flow rate of the composition.

[0095] Typically, the waste flow rate in the combustion furnace 11 may be greater than 0.1 t / h, in particular from 1.5 t / h to 15 t / h, more particularly from 5 t / h to 10 t / h.

[0096] The injection rate of the composition may be from 10 kg / h to 300 kg / h, in particular from 40 kg / h to 250 kg / h, more particularly from 50 kg / h to 200 kg / h.

[0097] According to another aspect, there is also provided a use of a composition comprising an alkaline earth metal salt for removing a poly- and perfluoroalkylated substance included in a waste.

[0098] The composition, the poly- and perfluoroalkylated substance and the waste are as described above in connection with the process of the invention.

[0099] For example, this use can be implemented at a temperature greater than or equal to 850°C, in particular from 900°C to 1100°C, more particularly from 950°C to 1050°C.

[0100] Advantageously, the process of the invention can be described as effective according to the consensus in force in the field of the invention. Indeed, for different poly- and perfluoroalkyl substances, in particular PFOS, PFOA, PFHxS, HFPO-DA, PFDS and PFBA, the process of the invention makes it possible to obtain a DRE greater than or equal to 99.9999% and a DE greater than or equal to 99.99%.

[0101] In accordance with the technical guide issued by UNEP, in this application and for each PFAS, the DRE and the DE are calculated according to the following formulas: in which: FMD is the hourly mass flux (in mg / h) of PFAS in the waste, FMRG is the hourly mass flux (in mg / h) of PFAS in the gaseous residue, FMRS is the hourly mass flux (in mg / h) of PFAS in the solid residue, and FMRL is the hourly mass flux (in mg / h) of PFAS in the liquid residue.

[0102] The hourly mass flux of PFAS in the waste is equal to the product of the average mass concentration of PFAS in the waste times the average mass flow rate of the waste, the waste being for example the waste used in combustion furnace 11 in [Fig. 1].

[0103] The hourly mass flux of PFAS in the solid residue is equal to the product of the average mass concentration of PFAS in the solid residue times the average mass flow rate of the solid residue, the solid residue being, for example, clinker from the post-combustion chamber 12, fly ash from the boiler 13 and / or the cooling tower 14, ash from the flue gas filtration unit 15 or combinations thereof in [Fig. 1].

[0104] The average mass concentration of PFAS in the waste and the average mass concentration of PFAS in the solid residue can be determined by applying Method 537M from the US EPA of 2020 to several samples, for example six samples, taken on the waste and the solid residue.

[0105] The hourly mass flux of PFAS in the gaseous residue is equal to the product of the average emission of PFAS in the gaseous residue (ng / Nm 3) by the average volume flow rate of the gaseous residue (Nm 3 / h), the gaseous residue being for example the smoke evacuated by the chimney 17 in [Fig. 1].

[0106] The average emission in the gaseous residue can be determined by applying the US EPA OTM-45 method in its version of January 13, 2021 to several samples, in particular several samples with a volume greater than 3 Nm3 dry, taken from the gaseous residue.

[0107] The hourly mass flux of PFAS in the liquid residue is equal to the product of the average mass concentration of PFAS in the liquid residue times the average mass flow rate of the liquid residue, the liquid residue being, for example, flue gas scrubbing water from an acid and / or basic scrubber.

[0108] The average mass concentration of PFAS in the liquid residue can be determined by applying US EPA Method 537 dated 2009 to several samples, for example six samples, taken from the waste and the liquid residue.

[0109] Unless otherwise indicated or incompatibility appears, the embodiments of the invention described above may be combined with each other.

[0110] The invention is described in more detail below, using the following example which is in no way limiting but is given by way of example only. Examples

[0111] This example describes an industrial-scale test of the process of the invention carried out in a combustion unit 1 which is an existing industrial line for the incineration of hazardous waste.

[0112] The combustion unit 1 used is shown in the diagram in [Fig. 1] and is composed of the following elements: - a rotary combustion furnace 11 with a maximum flow rate of 10t / h, - a post-combustion chamber 12, - a boiler 13, - a smoke cooling tower 14, - a smoke filtration unit 15 comprising two bag filters, - a ventilation and smoke extraction unit 16, and - a chimney 17.

[0113] Activated carbon is injected into both bag filters at a rate of 4 kg / h. Lime is injected into the second bag filter, in the direction of flow, at a rate of 175 to 300 kg / h.

[0114] For the tests, the powder composition tested was Desulfocarb P2-EC from Omya International AG. It contains more than 97% by mass of calcium carbonate and has a d50 value of 8 pm.

[0115] The powdered composition tested is stored in a silo with a capacity of 20 tonnes. The injection at the top of the post-combustion chamber 12 was carried out at two diametrically opposed points. This injection was carried out using two metering screws, themselves located downstream of a load cell placed under the silo to control and regulate the injection mass flow rates.

[0116] The waste tested is 65 tonnes of polluted soil from a former French site producing fire-extinguishing powders. The waste is introduced into rotary combustion furnace 11 using a grapple operated from the rotary combustion furnace 11 control room.

[0117] Six samples are taken from the polluted soil. Each sample is analyzed according to the 2020 US EPA Method 537M. The average mass concentration of each identified PFAS is then calculated.

[0118] As highlighted by Table 1 below, the tested waste is polluted by PFOS, PFOA, PFHxS, PFDS, PFBA and HFPO-DA. PFOS, PFOA, PFHxS are PFAS POPs. Considering the average mass concentration of each of these 3 PFAS POPs, the tested waste is a POP waste.

[0119] [Table 1]

[0120] The operating conditions are presented in Table 2 below.

[0121] The powdered composition tested is not injected into the post-combustion chamber 12 on days 1 and 2.

[0122] As highlighted in Table 2, the average temperature in the post-combustion chamber 12 varied by 17°C during the 4 days of testing. This temperature variation, less than 2%, is considered negligible and results from the conventional operation of the rotary combustion furnace 11 and the post-combustion chamber 12 and the control of the mixture of waste entering the rotary combustion furnace 11.

[0123] The test results are also presented in Table 2 below. Thus Table 2 shows: - the sum of the average mass concentrations of PFAS present in the solid residues (clinker from post-combustion chamber 12 and in the ash from the two bag filters of the flue gas filtration unit 15). These mass concentrations are determined by applying the 2020 US EPA method 537M on different samples of solid residues during the 4 days of testing, - the average emission of PFAS, measured in different samples of smoke from stack 17 by the US EPA OTM-45 method in its version of January 13, 2021 during the 4 days of testing, and - the average HF emission, measured in the smoke in different samples from chimney 17 by the NFX-43-304 method of 2007 during the 4 days of tests.

[0124] Table 3 presents the DRE values ​​calculated for each of the six PFAS present in the waste.

[0125] Table 4 presents the calculated DE values ​​for each of the six PFAS present in the waste.

[0126] The DRE and DE of each PFAS are determined using: - the hourly mass flow of each of the six PFAS present in the waste used in the rotary combustion furnace 11, - the hourly mass flux of each of the six PFAS present in the smoke from chimney 17, and - the sum of the hourly mass flows of each of the six PFAS present in the solid residues (clinker from the post-combustion chamber 12 and in the ash from the two bag filters of the smoke filtration unit 15). There is no liquid residue.

[0127] Tables 2 to 4 highlight the importance of the combination of the heat treatment carried out under the operating conditions of step a) and the powder composition tested comprising more than 97% by mass of calcium carbonate.

[0128] In particular, Table 2 highlights that the injection of the powdered composition tested into the post-combustion chamber 12 makes it possible to reduce: - PFAS emissions by a factor of 2.3 to 3.7, and - HF emissions by a factor of 2.3 to 3.7 to reach a value of 0.1 mg / Nm 3dry at 11% O2, i.e. a value well below the limit value of 1 mg / Nm 3 dry at 11% O2 indicated in Annex VI of Directive 2010 / 75 / EU of the European Parliament and of the Council of 24 November 2010.

[0129] Furthermore, according to Tables 3 and 4, on days 1 and 2, during which the tested powder composition is not injected into the afterburner 12, PFDS and PFBA are not effectively removed because the DE of PFDS and the DE of PFBA are less than 99.99% and the DRE of PFBA is less than 99.9999%. On the other hand, on days 3 and 4, during which the tested powder composition is injected into the afterburner 12, the six PFAS are effectively removed.

[0130] This example therefore demonstrates that the combination of thermal treatment of waste comprising PFAS under the conditions of step a) of the process of the invention and the powdery composition comprising calcium carbonate makes it possible to effectively eliminate the six PFAS while controlling HF emissions to comply with the limit value of 1 mg / Nm 3 dry to 11% O2 indicated in Annex VI of Directive 2010 / 75 / EU of the European Parliament and of the Council of 24 November 2010.

[0131] [Table 2]

[0132] [Table 3]

[0133] [Table 4]

Claims

Claims

1. A method of removing a poly- and perfluoroalkylated substance included in a waste, the method comprising a step of: a) heat treatment of the waste at a temperature greater than or equal to 850°C, step a) being carried out in the presence of a composition comprising an alkaline earth metal salt.

2. The method of claim 1 wherein the poly- and perfluoroalkylated substance is selected from PFOS, PFOA, PFHxS, HFPO-DA, PFDS, PFBA, PFPeA, PFHxA, PFHpA, PFNA, PFDA, PFUnDA, PFDoA, PFTrDA, PFTeDA, PFHxDA, PFODA, PFBS, PFPeS, PFHpS, PFNS, PFDoS, PFUnDS, PFDoDS, PFTrDS, FOSA, MeFOSA, EtFOSA, N-MeFOSE, N-EtFOSE, MeFOSAA, EtFOSAA, 4:2 FTS, 6:2 FTS, 8:2 FTS, 10:2 FTS, ADONA, 9CI-PF3ONS, 11CI- PF3OUdS, NFDHA, PFEESA, PFMBA, PFMPA, PFecHS, 8:2 FTUCA, 10:2 FDEA, 8:2 FTA, 6:2 FHUEA, 6:2 FTCA, 3:3 FTCA, 5:3 FTCA, 7:2 FTCA, PFECHS, 6:2 FTOH, 8:2 FTOH, C6O4 and mixtures thereof.

3. A method according to claim 1 or claim 2, wherein the waste is selected from hazardous waste, non-hazardous waste, POP waste, municipal sludge, industrial sludge and mixtures thereof.

4. A method according to any one of claims 1 to 3, wherein the composition comprises at least 30% by mass of alkaline earth metal salt.

5. A method according to any one of claims 1 to 4, wherein the alkaline earth metal salt is selected from a magnesium salt, a calcium salt and a mixture thereof.

6. A method according to any one of claims 1 to 5, wherein the composition is selected from a powdery composition, a slurry and a combination thereof.

7. The method of claim 6, wherein the powder composition has a maximum diameter of the 50% volume distribution of the particles (d50) of the powder composition is less than or equal to 50 pm.

8. A method according to any one of claims 1 to 7, wherein the ratio between the mass of the poly- and perfluoroalkylated substance and the mass of the composition is from 1:0.01 to 1:0.

5.

9. Method according to any one of claims 1 to 8, in which the heat treatment of step a) is carried out for at least 2 seconds.

10. Method according to any one of claims 1 to 9, in which step a) of heat treatment is carried out in a combustion furnace (11), and / or in a post-combustion chamber (12) of an incineration unit (1).

11. Use of a composition comprising an alkaline earth metal salt for removing a poly- and perfluoroalkylated substance included in a waste.

12. Use according to claim 11 at a temperature greater than or equal to 850°C.

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