Method for removing PFAS from waste

Abstract

The present invention relates to an industrial method for efficiently removing PFAS substances, particularly PFAS POP, from waste, while simultaneously enabling efficient control of HF emissions induced by this removal.

Description

Technical Field

[0001] The present disclosure relates to the field of disposal of poly and perfluoroalkyl substances (hereinafter referred to as PFAS), particularly those contained in waste.

[0002] PFAS is a large group of thousands of synthetic chemicals that have been widely used since the 1950s due to their non-stickiness, impermeability, and durability under extreme conditions (high heat resistance, high pressure resistance, and / or radiation resistance).

[0003] According to a submission by the European Chemicals Agency (hereinafter referred to as ECHA) on February 7, 2023, PFAS are present in numerous application fields. For example, PFAS are used in various industrial processes, in the energy sector, in the oil and mining sectors, in the transportation sector, in the surface treatment of materials (waterproofing, water repellents, anti-wetting), in fire-fighting foams, in lubricants, in electronic products, and in semiconductors. PFAS are also present in everyday items such as waterproof clothing (boots, gloves, coats), non-stick pans, water- and stain-resistant fabrics (upholstery, carpets), implanted medical devices, cosmetics, pharmaceuticals, crop protection products, and food packaging. Thus, according to that submission, approximately 92,000 metric tons of PFAS were used in 2020.

[0004] However, PFAS are particularly toxic even at very low doses. In fact, according to ECHA, there are suspicions that PFAS may have multiple adverse effects in the human body, such as cancer, reduced fertility, insufficient fetal development, and interference with the immune system.

[0005] Furthermore, due to their chemical structure, which consists of carbon-fluorine bonds, one of the strongest chemical bonds in organic chemistry, PFAS do not decompose after use or release into the environment. Some PFAS, such as perfluorooctanoic acid (hereinafter referred to as PFOA), perfluorooctanesulfonic acid (hereinafter referred to as PFOS), and perfluorohexanesulfonic acid (hereinafter referred to as PFHxS), are further referred to as "persistent organic pollutants" (hereinafter referred to as PFAS POPs). According to the European Commission, POPs are chemicals that persist in the environment and bioaccumulate in the food web, and can have adverse effects on human health and the environment.

[0006] According to ECHA, most PFAS are also easily transported to distant locations in the environment over long distances from their sources. Consequently, PFAS contamination of groundwater, surface water, and soil is frequently observed. If PFAS continue to be released into the environment, they will continue to accumulate, especially in drinking water and food.

[0007] PFAS are toxic and polluting, accumulating in the environment, in drinking water, and in food. Their ban is currently being discussed in Europe, but this is expected to take several years. Therefore, in the short term, their elimination is a major health concern. [Background technology]

[0008] On July 27, 2022, the United Nations Environment Programme (UNEP) issued the Technical Guideline, "General Technical Guidelines for the Environmentally Good Management of Waste Consisting with, Containing, or Contaminated with Persistent Organic Pollutants," which provides guidance on the environmentally good management of waste consisting of, containing, or contaminated with PFAS POP. In this patent application, this Technical Guideline may be referred to as the Technical Guideline issued by UNEP.

[0009] The technical guidance issued by UNEP defines two efficiencies to quantify the efficiency of methods for removing PFAS POP. These two efficiencies are as follows: - Decomposition efficiency (hereinafter referred to as DE). This efficiency corresponds to the percentage of PFAS POP contained in the waste that is decomposed or irreversibly converted by a specific method or technique, and, - Decomposition and removal efficiency (hereinafter referred to as DRE). This efficiency corresponds to the percentage of the original PFAS POP that was irreversibly converted and released into the flue gas, taking into account atmospheric emissions only.

[0010] In the field of the present invention, there is a consensus that a method is efficient if it has a DE of 99.99% or more and a DRE of 99.9999% or more.

[0011] The publication "PFAS fate and destruction mechanisms during thermal treatment: a comprehensive review," by Longendyyke et al., Environ. Sci.: Processes Impact, 2022, Vol. 24, p. 196, presents various methods for removing PFAS. These methods include incineration, thermal desorption, pyrolysis, gasification, fumigation, and hydrothermal liquefaction.

[0012] According to that publication, - Thermal desorption and thermal decomposition make it possible to reduce the amount of PFAS by 90%. - Gasification produces volatile PFAS. - Smoking can only reduce the amount of PFAS by about 80%, and, Hydrothermal liquefaction can only reduce the amount of PFOA by 99% and the amount of PFOS by 86%.

[0013] A method for removing PFAS by gasification is described in U.S. Patent No. 11,339,337B1. Specifically, the waste used in this method is wastewater containing biosolids and PFAS. The method is as follows: - A process of gasifying wastewater at temperatures between 480°C and 980°C to produce syngas containing PFAS that are not removed by gasification. Syngas is a mixture of carbon monoxide (CO) and hydrogen (H2). Therefore, unlike incineration which is carried out in an oxidizing medium, gasification must inevitably be carried out in a reducing medium to produce syngas; - A process of burning syngas containing PFAS at a temperature between 870°C and 1420°C to produce flue gas containing PFAS that is not removed by combustion; - A step of cooling flue gas containing PFAS to a temperature between 205°C and 650°C to produce cooled flue gas containing PFAS; and - The process includes contacting cooled flue gas containing PFAS with hydrated lime to increase the decomposition of PFAS in the cooled flue gas. Therefore, as described in the publication “PFAS fate and destruction mechanisms during thermal treatment: a comprehensive review,” Longendyyke et al., Environ. Sci.: Processes Impact, 2022, Vol. 24, p. 196, the gasification step of the method of U.S. Patent No. 11,339,337B1 generates volatile PFAS that must be decomposed in the following two steps. Therefore, the method of U.S. Patent No. 11,339,337B1 does not enable the simple and efficient removal of PFAS.

[0014] Therefore, thermal desorption, pyrolysis, gasification, fumigation, and hydrothermal liquefaction do not appear to be methods that can remove PFAS easily and efficiently. Moreover, given the complexity of their implementation and the very large quantities of PFAS to be removed, these methods are difficult to envision on an industrial scale.

[0015] Regarding incineration, it is a technology that can be assumed on an industrial scale. In fact, it is easy to implement and enables the treatment of very large amounts of waste and, consequently, waste containing PFAS. However, in the investigations presented in that publication, it was concluded that PFOA is not decomposed by exposure to 1000 °C for 2 seconds.

[0016] Furthermore, according to that publication, the decomposition of PFAS, especially thermal decomposition, generates hydrogen fluoride (hereinafter referred to as HF). HF is extremely toxic and an ecotoxic compound. Furthermore, HF may damage incineration facilities by its corrosive action on metals or, as explained in that publication, react with the silica-based coating of the reactor to generate silicon tetrafluoride.

[0017] During industrial-scale tests, the Applicant exposed waste containing PFAS to temperatures between 962 °C and 979 °C in an incineration facility. Although it became clear that some PFAS could be efficiently removed, instead, the HF emissions exceeded the limit value of 1 mg / Nm 3 at 11% O2 dry as shown in Annex VI of the Directive 2010 / 75 / EU of the European Parliament and of the Council of 24 November 2010.

Prior Art Documents

Patent Documents

[0018]

Patent Document 1

Non-Patent Documents

[0019]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0020] Therefore, there is still a need for an industrial solution that enables efficient removal of PFAS while allowing for efficient control of HF emissions induced by this removal.

Means for Solving the Problems

[0021] Therefore, it is the merit of the present inventors to have discovered that this need can be met by subjecting waste containing PFAS to heat treatment in the presence of an alkaline earth metal salt.

[0022] Therefore, a method is proposed for the removal of poly- and perfluoroalkyl substances contained in waste, and the method a) includes a step of heat-treating the waste at a temperature of 850 °C or higher, particularly between 900 °C and 1100 °C, especially between 950 °C and 1050 °C, and step a) is carried out in the presence of a composition containing an alkaline earth metal salt.

[0023] Surprisingly, the combination of the heat treatment carried out under the operating conditions of step a) and the alkaline earth metal salt advantageously enables the following. - Efficient and simple removal of poly- and perfluoroalkyl substances, particularly the following PFAS POPs: PFOA, PFOS and PFHxS; and - Controlling the HF concentration in the flue gas generated in step a) such that it is below the limit value of 1 mg / Nm of dry at 11% O2 shown in Annex VI of Directive 2010 / 75 / EU of the European Parliament and of the Council of 24 November 2010. 3 ​

[0024] Although not bound by any theory, the inventors believe that the method can be made more efficient by combining the heat treatment performed under the operating conditions of step a) with an alkaline earth metal salt. - To facilitate the decomposition reaction of poly and perfluoroalkyl substances present in the waste and / or in the flue gas produced by the combustion of the waste in step a), and - To efficiently neutralize the HF formed by this decomposition. In fact, under the conditions of step a), the heat treatment allows for the combustion of waste, the decomposition of poly and perfluoroalkyl materials, and the very rapid oxidation of alkaline earth metal salts to alkaline earth metal oxides. The inventors believe that in this case, this oxide is - It can catalyze the decomposition reaction of PFAS, thereby accelerating the reaction rate of these reactions, and / or - There is a view that these decomposition products, in particular, can be rapidly reacted with HF. According to Le Chatelier's principle, in that case, the decomposition reaction of PFAS is thermodynamically favorable. Particularly decisive results were obtained using calcium carbonate.

[0025] Furthermore, the method of the present invention is easy to implement on an industrial scale for processing large quantities of waste. In fact, the method of the present invention can be implemented in conventional waste incineration facilities known and understood by those skilled in the art. Moreover, the combustion furnace throughput in conventional incineration facilities can reach 15 tons of waste per hour.

[0026] Furthermore, the method of the present invention is economical. In fact, it can be implemented in conventional waste incineration facilities, and because the cost of the composition is low, it does not require a huge investment in equipment.

[0027] Furthermore, the use of compositions containing alkaline earth metal salts is proposed for removing poly and perfluoroalkyl substances from waste.

[0028] Other features, details, and advantages will become clear from reading the detailed description below and from analyzing the attached drawings. [Brief explanation of the drawing]

[0029] [Figure 1] This is a schematic diagram illustrating an incineration facility. [Modes for carrying out the invention]

[0030] Now, refer to Figure 1.

[0031] According to the first aspect, a method is proposed for the removal of poly and perfluoroalkyl substances contained in waste, and the method is a) The process includes a step of heat-treating the waste at a temperature of 850°C or higher, particularly between 900°C and 1100°C, and especially between 950°C and 1050°C, wherein step a) is carried out in the presence of a composition containing an alkaline earth metal salt.

[0032] For the purposes of this invention, the term "poly and perfluoroalkyl substances" means organofluorine compounds containing one or more perfluoroalkyl or polyfluoroalkyl functional groups.

[0033] For the purposes of this invention, the singular forms "a," "an," and "the" also encompass the plural forms of the terms they refer to, unless the content otherwise clearly indicates.

[0034] The poly and perfluoroalkyl substances used in the method of the present invention may be any PFAS. Accordingly, the PFAS may be selected from the PFAS listed in the PFAS target analytes in Table 45-1 of the 13 January 2021 edition of the US EPA's OTM-45 method, the PFAS listed in European Parliament and Council Directive 2020 / 2184 of 16 December 2020 relating to the quality of water intended for human consumption, and combinations thereof.

[0035] For example, the poly and perfluoroalkyl substances may be at least one PFAS selected from the following:

[0036] [Table 1A]

[0037] [Table 1B]

[0038] According to one embodiment, PFAS may be selected from among PFAS POPs. Examples include PFOS, PFOA, and PFHxS.

[0039] Therefore, according to one embodiment, 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.

[0040] Therefore, the method of the present invention enables the efficient removal of PFAS POP and thus solves major health problems.

[0041] According to another embodiment, the poly and perfluoroalkyl substances may be selected from PFOS, PFOA, PFHxS, HFPO-DA, PFDS, PFBA, and mixtures thereof.

[0042] The waste used in the method of the present invention may be any type of waste containing one or more types of PFAS. In particular, the waste may contain at least 0.01 mg of PFAS per kg of waste, more specifically 0.10 mg to 1000 mg of PFAS per kg of waste, and especially 0.90 mg to 150 mg of PFAS per kg of waste.

[0043] The waste may be selected from among hazardous waste, non-hazardous waste, POP waste, urban sludge, industrial sludge, and mixtures thereof, particularly hazardous waste, POP waste, and mixtures thereof, especially POP waste.

[0044] For the purposes of this invention, "harmless waste" means any waste that does not possess any of the properties that would make it harmful.

[0045] For the purposes of this invention, “hazardous waste” means any waste exhibiting one or more hazardous properties as enumerated in Annex III to Directive 2008 / 98 / EC and the repeal of certain Directives of the European Parliament and Council of 19 November 2008.

[0046] For the purposes of this invention, "POP waste" means any waste containing at least 50 mg of PFOS, at least 1 mg of PFOA, and / or at least 1 mg of PFHxS per kg of waste.

[0047] For example, harmless waste that may be used in the method of the present invention includes everyday items such as waterproof clothing, nonstick pans, water-repellent and stain-resistant fabrics, implantable medical devices, cosmetic products, food packaging, electronic products, semiconductors, and combinations thereof. Waterproof clothing may include shoes, gloves, coats, or combinations thereof. Water-repellent and stain-resistant fabrics may include upholstery, carpets, or combinations thereof.

[0048] Hazardous waste that may be used in the method of the present invention may include, for example, crop protection products, lubricants, paints, used oils, used acids, used solvents, paint sludge, fuel tank bottoms, expired pesticides, toxic gas waste, and mixtures thereof.

[0049] The POP waste that may be used in the method of the present invention may be contaminated soil from a factory site, particularly from a factory site where fire extinguishing agent powder is manufactured.

[0050] The alkaline earth metal salt in the composition may contain a cation selected from magnesium cations, calcium cations, and mixtures thereof; preferably, it may be a calcium cation.

[0051] The anion of the alkaline earth metal salt may be selected from acetate ions, acrylate ions, carbonate ions, formate ions, propionate ions, and mixtures thereof, particularly from acetate ions, acrylate ions, carbonate ions, and mixtures thereof; in particular, the anion is a carbonate ion.

[0052] The alkaline earth metal salt may be selected from among magnesium salts, calcium salts, or mixtures thereof, particularly from among magnesium carbonate, calcium carbonate, or mixtures thereof; in particular, it may be calcium carbonate.

[0053] Furthermore, particularly compelling results were obtained using calcium carbonate. Moreover, the low cost of calcium carbonate is advantageous.

[0054] Calcium carbonate may be derived from chalk, limestone, lime, seashells, mineral sludge, or mixtures thereof, in particular from lime, seashells, mineral sludge, or mixtures thereof, in particular from lime.

[0055] The mineral sludge may consist mainly of calcium carbonate and, if necessary, may be converted into a powder composition by one or more suitable chemical treatments. These chemical treatments are known to those skilled in the art, such as washing, drying, and physicochemical treatments. Carbonate-removed sludge, primary brine-purified sludge, and mixtures thereof are suitable mineral sludges for use in the method of the present invention.

[0056] Decarbonate sludge is typically a harmless waste generated during operations that remove carbonates from water, operations performed at factory sites requiring the supply of softened water. Each of these sites may produce 1,000 to 3,000 metric tons of decarbonate sludge per year. Therefore, advantageously, using decarbonate sludge as a calcium carbonate source enables the recycling of waste that is currently not recycled and creates a cyclical economy due to the availability of this waste around incinerators. This also allows the use of waste instead of natural resources (chalk, limestone, and lime). Decarbonate sludge generally contains approximately 65% ​​calcium carbonate, with the remainder being water. For use in step a) of the method of the present invention, it can therefore be dried so that the mass concentration of calcium carbonate in the dried sludge exceeds 90.0%.

[0057] Primary brine wastewater sludge is a waste product obtained as a result of electrolysis during chlorine production. It contains calcium and magnesium carbonates, as well as trace amounts of contaminants, salts, and occasionally metals. Contaminants, salts, and any metals may be separated by specific operations known to those skilled in the art, such as continuous washing or physicochemical treatment. Water can be removed by drying.

[0058] The composition may contain at least 30% by mass of an alkaline earth metal salt, particularly between 35% by mass and 100% by mass, and especially between 50% by mass and 99% by mass.

[0059] The composition may be selected from, for example, a powder composition, a slurry, and a combination thereof.

[0060] For the purposes of this invention, the term "powder composition" is understood to mean a composition in powder form. In particular, the maximum diameter (d50) of the powder composition according to the present invention at 50% of the volume distribution of particles may be 50 μm or less, preferably between 2 μm and 20 μm, and more preferably between 4 μm and 10 μm. The d50 value may also be determined by laser particle size analysis in distilled water using a Malvern-Mastersizer 2000 laser particle size analyzer equipped with a 120 ml "small volume" cell; the signal is processed using the Mie mathematical model.

[0061] Advantageously, the particle size range described above allows for an increase in the contact area of ​​the powder composition with the waste and the flue gas generated by the heat treatment of the waste. This improves the efficiency of PFAS removal and the efficiency of controlling the HF emissions induced by this removal.

[0062] The powder composition may contain at least 90% by mass of an alkaline earth metal salt, and in particular at least 95% by mass of an alkaline earth metal salt.

[0063] According to one particular embodiment, the powder composition is essentially composed of alkaline earth metal salts.

[0064] For the purposes of this invention, "essentially composed of ~" means that other specific elements may be present in the composition, in which case these elements do not affect the essential properties of the composition. Impurities are an example of elements that do not affect the essential properties of the composition.

[0065] For the purposes of this invention, the term "slurry" is understood to mean a viscous mixture of solid substances containing alkaline earth metal salts suspended in a liquid, particularly in water.

[0066] For example, the slurry may be a suspension of mineral slurry as described above.

[0067] The slurry may contain at least 30% by mass of alkaline earth metal salts, particularly between 35% and 50% by mass of alkaline earth metal salts.

[0068] In step a) of the method of the present invention, the heat treatment may be performed for at least 2 seconds, particularly between 2 and 30 seconds, and especially between 2.2 and 5 seconds.

[0069] This duration corresponds to the duration during which the waste is exposed to temperatures above 850°C, particularly between 900°C and 1100°C, and especially between 950°C and 1050°C, during process a).

[0070] Advantageously, the inventors have found that the removal of PFAS and the control of HF emissions induced by this removal become increasingly efficient when the heat treatment in step a) of the method of the present invention is carried out within these duration ranges.

[0071] Furthermore, such a duration range is not inconsistent with the implementation of the method of the present invention in conventional waste incineration facilities 1. In fact, certain equipment in conventional waste incineration facilities 1, - At a temperature that is compatible with the operating conditions of step a) of the method of the present invention, and - Operate using residence times that match these duration ranges.

[0072] As schematically shown in Figure 1, the incineration facility 1 may include, in the direction of flow, a combustion furnace 11, for example a rotary furnace, a flue gas post-combustion tank 12, a boiler 13 and a flue gas cooling system including a cooling tower 14 thereafter, a flue gas filtration system 15, a flue gas ventilation and extraction system 16, and a stack 17.

[0073] The waste is incinerated in the conventional furnace 11, thereby generating flue gas. This flue gas is then sent to the post-combustion tank 12, where it is incinerated in the post-combustion process. The burnt flue gas from the post-combustion tank 12 is then cooled and purified in the boiler 13 and cooling tower 14, and then purified in the flue gas filtration equipment 15. This purified flue gas then passes through the flue gas aeration and extraction equipment 16 and is released through the stack 17.

[0074] Incineration equipment 1 may generate solid residue and gaseous residue as in the conventional manner.

[0075] For example, the solid residue may be combustible material from the post-combustion tank 12, fly ash from the boiler 13 and / or the cooling tower 14, ash from the flue gas filtration equipment 15, or a combination thereof.

[0076] The gaseous residue may be purified flue gas released through stack 17.

[0077] Incineration equipment 1 may further include a flue gas filtration system 15 and an acid and / or alkaline flue gas scrubber between the flue gas aeration and extraction system 16. The scrubbing water from this acid and / or alkaline flue gas scrubber is the liquid residue produced by incineration equipment 1.

[0078] The heat treatment in step a) of the method of the present invention may be a step of incineration by oxidation.

[0079] Typically, the temperature in the combustion furnace 11 is between 850°C and 1200°C, and the temperature in the post-combustion tank 12 is between 900°C and 1150°C.

[0080] Unlike the gasification reaction, the combustion reaction carried out in the combustion furnace 11 and the post-combustion reaction carried out in the post-combustion tank 12 require the presence of oxygen. Therefore, the oxygen content of the combustible flue gas from the post-combustion tank 12 may be between 1% and 10% by volume, particularly between 2% and 9% by volume, and especially between 4% and 8% by volume, relative to the volume of the combustible flue gas.

[0081] The heat treatment step a) of the method of the present invention may be performed in the combustion furnace 11 and / or post-combustion tank 12 of the incineration facility 1. Due to their configuration, the combustion furnace 11 and post-combustion tank 12 of the incineration facility 1 are not suitable for carrying out the gasification process that produces CO and H2. In fact, these two compounds oxidize immediately with oxygen in the combustion air, and are particularly harmful in the case of H2.

[0082] In fact, the temperature and / or partial pressure of oxygen in the combustion furnace 11 and / or post-combustion tank 12 are such that step a) of the method of the present invention can be advantageously carried out therein. Furthermore, using such step a) eliminates the need to add special dedicated equipment to the incineration plant 1 to reduce the HF concentration in the combustion flue gas. Consequently, such step a) does not increase the complexity of the incineration plant 1 and makes it possible to increase the energy efficiency of the method of the present invention.

[0083] A heat treatment duration of at least 2 seconds, particularly 2 to 3 seconds, is suitable for carrying out step a) in the post-combustion tank 12 of the incineration equipment 1.

[0084] In fact, advantageously, such a duration is not inconsistent with the conventional residence time of flue gas in the post-combustion tank 12 of the incinerator 1. Such a duration also enables efficient removal of PFAS and efficient control of HF emissions induced by this removal.

[0085] A heat treatment duration of at least 2 seconds, particularly 2 to 30 seconds, and especially 2.1 to 3 seconds, is suitable for performing step a) in the combustion furnace 11.

[0086] In fact, advantageously, such a duration is not inconsistent with the duration for which the waste is conventionally subjected to the operating conditions of process a) in the combustion furnace 11, nor is it inconsistent with the conventional residence time of the flue gas produced by the combustion of this waste in the combustion furnace 11. Such a duration also enables efficient removal of PFAS and efficient control of HF emissions induced by this removal.

[0087] A heat treatment duration of at least 2 seconds, particularly 2 to 30 seconds, and especially 2.2 to 5 seconds, is suitable for performing step a) in the combustion furnace 11 and post-combustion tank 12 of the incineration facility 1.

[0088] Typically, in step a) of the method of the present invention, the composition may be injected into the combustion furnace 11 and / or into the post-combustion tank 12 at the interface between the combustion furnace 11 and the post-combustion tank 12.

[0089] The powder composition is suitable for injection into the post-combustion tank 12 and / or at the interface between the combustion furnace 11 and the post-combustion tank 12.

[0090] Due to its particle size, the powder composition has fluidity that allows for appropriate injection.

[0091] The slurry is suitable for injection into the combustion furnace 11, at the interface between the combustion furnace 11 and the post-combustion tank 12, and / or into the post-combustion tank 12, particularly into the combustion furnace 11.

[0092] Advantageously, the injection of slurry into the combustion furnace 11, particularly at the inlet of the combustion furnace 11, maximizes the contact time between the waste and the alkaline earth metal salts, thus increasing the efficiency of PFAS removal and the efficiency of HF emission control induced by this removal.

[0093] The composition may be injected using an injection device such as a volumetric metering screw or a mass metering screw.

[0094] A mass flow meter may also be used to control the rate at which the composition is injected into the combustion furnace 11, at the interface between the combustion furnace 11 and the post-combustion tank 12, and / or into the post-combustion tank 12.

[0095] The ratio of the mass of PFAS to the mass of the composition may be between 1:0.01 and 1:0.5, particularly between 1:0.03 and 1:0.25, and especially between 1:0.06 and 1:0.08.

[0096] Advantageously, such a mass ratio allows for the efficient removal of PFAS, efficient control of HF emissions induced by this removal, and does not impair the operation of incineration plant 1.

[0097] This mass ratio may depend on the flow rate of waste in the combustion furnace 11 and the injection rate of the composition into the combustion furnace 11 at the interface between the combustion furnace 11 and the post-combustion tank 12 and / or in the post-combustion tank 12.

[0098] Those skilled in the art know how to adapt these flow rates, in particular, the injection rate of the composition, to satisfy this mass ratio. In fact, to determine the injection rate of the composition at that time, it is necessary to know the flow rate of the waste in the combustion furnace 11 and the material flux of PFAS in the waste.

[0099] Typically, the waste flow rate in the combustion furnace 11 may exceed 0.1 t / hour, and may be particularly between 1.5 t / hour and 15 t / hour, and especially between 5 t / hour and 10 t / hour.

[0100] The injection rate of the composition may be between 10 kg / hour and 300 kg / hour, particularly between 40 kg / hour and 250 kg / hour, and especially between 50 kg / hour and 200 kg / hour.

[0101] In another embodiment, the use of a composition comprising an alkaline earth metal salt for removing poly and perfluoroalkyl substances contained in waste is also provided.

[0102] Poly and perfluoroalkyl substances, as well as waste compositions, are related to the method of the present invention as described above.

[0103] For example, this use may be carried out at temperatures above 850°C, particularly between 900°C and 1100°C, and especially between 950°C and 1050°C.

[0104] Advantageously, the methods of the present invention can be described as efficient in accordance with the consensus used in the art of the present invention. In fact, for various poly and perfluoroalkyl substances, particularly PFOS, PFOA, PFHxS, HFPO-DA, PFDS, and PFBA, the methods of the present invention make it possible to obtain 99.9999% or more DRE and 99.99% or more DE.

[0105] According to the technical guidance issued by UNEP, in this application and for each PFAS, DRE and DE are calculated according to the following formulas.

[0106]

number

[0107] Here, FMD is the hourly material flux (mg / hour) of PFAS in waste. FMRG is the hourly mass flux (mg / hour) of PFAS in the gaseous residue. FMRS is the hourly mass flux (mg / hour) of PFAS in solid residue. FMRL is the hourly mass flux (mg / hour) of PFAS in the liquid residue.

[0108] The hourly mass flux of PFAS in the waste is equal to the product of the average mass concentration of PFAS in the waste and the average mass flow rate of the waste, and the waste is, for example, the waste used in the combustion furnace 11 in Figure 1.

[0109] 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 and the average mass flow velocity of the solid residue, where the solid residue is, for example, fuel clumps from the post-combustion tank 12, fly ash from the boiler 13 and / or cooling tower 14, ash from the flue gas filtration equipment 15, or a combination thereof as shown in Figure 1.

[0110] The average mass concentration of PFAS in waste and the average mass concentration of PFAS in solid residue may be determined by applying the US EPA's 2020 Method 537M to several samples, e.g., six samples, collected from the waste and solid residue.

[0111] The hourly mass flux of PFAS in the gaseous residue is equal to the average emission of PFAS in the gaseous residue (ng / Nm³). 3 ) and the average volume flow velocity (Nm) of the gaseous residue. 3 This is equal to the product of (time), where the gaseous residue is, for example, the flue gas released from stack 17 in Figure 1.

[0112] The average emissions in the gaseous residue were measured using the US EPA's OTM-45 method, January 13, 2021 edition, collected from several samples, particularly the gaseous residue, at a dry 3 Nm³. 3 This may be determined by applying it to several samples having a volume exceeding [a certain value].

[0113] 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 and the average mass flow rate of the liquid residue, where the liquid residue is, for example, flue gas scrubbing water from an acid and / or alkali scrubber.

[0114] The average mass concentration of PFAS in the liquid residue may be determined by applying Method 537 of the US EPA dated 2009 to several samples, e.g., six samples collected from waste and liquid residue.

[0115] Unless otherwise specified, or unless there is an obvious incompatibility, the embodiments of the present invention described above may be combined with each other.

[0116] The present invention is described in more detail below with the help of the following examples, which are given merely as illustrations, and is by no means limited. [Examples]

[0117] This embodiment describes an industrial-scale test of the method of the present invention conducted in a combustion facility 1, which is an existing industrial incineration pipeline for hazardous waste.

[0118] The combustion equipment 1 used is shown in the schematic diagram in Figure 1 and consists of the following elements: - Rotary combustion furnace 11 having a maximum flow rate of 10 t / hour, - after-combustion tank 12, - Boiler 13, - Flue gas cooling tower 14, - Flue gas filtration system 15 including two baghouses, - Flue gas ventilation and extraction equipment 16, and - Stack 17.

[0119] Activated carbon is injected into the two baghouses at a flow rate of 4 kg / hour. Lime is injected into the second baghouse along the direction of the flow at a rate of 175-300 kg / hour.

[0120] For the test, 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 μm.

[0121] The powder composition to be tested was stored in a silo with a capacity of 20 tons. Injection was carried out from two opposing locations on top of the post-combustion tank 12. This injection was performed using two metering screws located downstream of a spring scale placed below the silo, and it was possible to control and adjust the mass flow rate of the injection.

[0122] The waste tested consisted of 65 tons of contaminated soil from a French site that had previously produced fire extinguishing agent powder. The waste was introduced into the rotary incinerator 11 using a grapple operated from the control room of the rotary incinerator 11.

[0123] Six samples were collected from the contaminated soil. Each sample was analyzed according to the US EPA's 2020 Method 537M. The average mass concentration of each identified PFAS was then calculated.

[0124] As highlighted in Table 1 below, the waste samples to be tested were contaminated with PFOS, PFOA, PFHxS, PFDS, PFBA, and HFPO-DA. PFOS, PFOA, and PFHxS are PFAS POPs. Given the average mass concentrations of each of these three PFAS POPs, the waste samples to be tested are POP waste.

[0125] [Table 2]

[0126] The operating conditions are shown in Table 2 below.

[0127] On the first and second days, the powder composition to be tested was not injected into the post-combustion tank 12.

[0128] As shown in Table 2, the average temperature in the post-combustion tank 12 fluctuated by 17°C over the four days of the test. Temperature fluctuations of less than 2% are considered negligible and are thought to result from the conventional operation of the rotary combustion furnace 11 and the post-combustion tank 12, as well as the control over the mixture of waste entering the rotary combustion furnace 11.

[0129] The test results are shown in Table 2 below. Therefore, Table 2 shows the following: - The sum of the average mass concentrations of PFAS present in the solid residue (combustion clumps in ash from the post-combustion tank 12 and from two baghouses of the flue gas filtration system 15). These mass concentrations were determined by applying US EPA Method 537M 2020 to various samples of solid residue over a four-day test. - In a 4-day trial using the January 13, 2021 edition of US EPA Method OTM-45, the average PFAS emissions measured in various samples of flue gas from stack 17, and - Average HF emissions measured in flue gas in various samples from stack 17 by using the 2007 NFX-43-304 method in a 4-day test.

[0130] Table 3 presents the DRE calculation values ​​for each of the six types of PFAS present in the waste.

[0131] Table 4 presents the DE calculation values ​​for each of the six types of PFAS present in the waste.

[0132] Use the following to determine the DRE and DE for each PFAS: - The hourly material flux of each of the six types of PFAS present in the waste processed in the rotary incinerator 11, - The hourly mass flux of each of the six PFAS present in the flue gas from stack 17, and - The sum of the hourly material fluxes of each of the six types of PFAS present in the solid residue (combustion masses in the ash from the post-combustion tank 12 and from the two baghouses of the flue gas filtration equipment 15). There is no liquid residue.

[0133] Tables 2 to 4 (Table 5) highlight the importance of combining the heat treatment performed under the operating conditions of step a) and the powder composition to be tested, which contains more than 97% by mass of calcium carbonate.

[0134] In particular, Table 2 shows the injection of the powder composition to be tested into the post-combustion tank 12. - PFAS emissions with a coefficient of 2.3 to 3.7, - Demonstrated that a reduction in HF emissions is possible with a coefficient of 2.3 to 3.7, and a dry filtration rate of 0.1 mg / Nm³ at 11% O2. 3 It reaches the value of 1 mg / Nm³ dry in 11% O2, as specified in Annex VI of Directive 2010 / 75 / EU of the European Parliament and the Council of 24 November 2010. 3 This value is well below the limit.

[0135] Furthermore, according to Tables 3 and 4, on days 1 and 2, when the powder composition to be tested is not injected into the post-combustion tank 12, the DE of PFDS and PFBA is less than 99.99%, and the DRE of PFBA is less than 99.9999%, indicating that the removal of PFDS and PFBA is not efficient. On the other hand, during days 3 and 4, when the powder composition to be tested is injected into the post-combustion tank 12, the six types of PFAS are efficiently removed.

[0136] Therefore, this embodiment controls HF emissions while achieving a dry filtration rate of 1 mg / Nm³ at 11% O2 as specified in Annex VI of Directive 2010 / 75 / EU of the European Parliament and the Council of 24 November 2010. 3 To satisfy the limit values, the combination of the heat treatment of waste containing PFAS under the conditions of step a) of the present invention and a powder composition containing calcium carbonate enables the efficient removal of six types of PFAS.

[0137] [Table 3]

[0138] [Table 4]

[0139] [Table 5] [Explanation of symbols]

[0140] 1 Incineration equipment 11 Combustion furnace 12 After-combustion tank 13 Boiler 14 Cooling Tower 15 Filtration equipment 16. Ventilation and extraction equipment 17 stacks

Claims

1. A method for removing poly and perfluoroalkyl substances from waste, wherein the method is a) A step of heat-treating the waste at a temperature of 850°C or higher, A method wherein step a) is carried out in the presence of a composition containing an alkaline earth metal salt.

2. The poly and perfluoroalkyl substances are 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 The method according to claim 1, comprising a selection from FTS, ADONA, 9Cl-PF3ONS, 11Cl-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. The method according to claim 1 or claim 2, wherein the waste is selected from hazardous waste, non-toxic waste, POP waste, urban sludge, industrial sludge, and mixtures thereof.

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

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

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

7. The method according to claim 6, wherein the maximum diameter (d50) of the powder composition at 50% of the volume distribution of the particles of the powder composition is 50 μm or less.

8. The method according to any one of claims 1 to 7, wherein the ratio of the mass of the poly and perfluoroalkyl substances to the mass of the composition is between 1:0.01 and 1:0.

5.

9. The method according to any one of claims 1 to 8, wherein the heat treatment in step a) is performed for at least 2 seconds.

10. The method according to any one of claims 1 to 9, wherein step a) of the heat treatment is performed in the combustion furnace (11) and / or in the post-combustion tank (12) of the incineration equipment (1).

11. Use of a composition containing an alkaline earth metal salt to remove poly and perfluoroalkyl substances contained in waste.

12. Use according to claim 11 at a temperature of 850°C or higher.

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