Removing PFAS from contaminated soil

Abstract

The present invention includes a method for remediating soil containing PFAS. The method includes steps a) to d). In step a), sludge and a first gas stream are heated in a first entrained bed incinerator to produce a raw material for ceramic articles and a first gas stream containing the first exhaust gas and having a temperature of at least 800°C. In step b), the first gas stream containing the first exhaust gas is heat exchanged with a second gas stream in an air-to-air heat exchanger to produce a second gas stream having a temperature of at least 500°C. In step c), the soil containing PFAS is contacted with the second gas stream in a dryer to vaporize PFAS from the soil, producing clean soil and a second gas stream containing PFAS. In step d), the second gas stream containing PFAS is further heated in a second entrained bed incinerator to a temperature of at least 1000°C to produce a second gas stream containing decomposed PFAS.

Description

[Technical field]

[0001] The present invention relates to a process for remediation of soil containing PFAS and the use of an entrained bed incinerator in the process. [Background technology]

[0002] Since the 1960s, many new chemicals have been developed and used in various industrial and household products. One example is the family of per- and polyfluoroalkyl substances (PFAS). These substances have been used for their unique properties: they are both water- and oil-repellent, and for example resistant to heat and acid. There are many different types of PFAS, and the family of substances currently includes more than 6000 compounds.

[0003] The uses of these compounds in industrial and household products are very diverse. They have been used as stain repellents in carpets, water repellent textiles, in metal processing processes, in the manufacture of non-stick materials, and as auxiliary substances in certain types of fire extinguishing foams. However, since about 2000, the PFAS family of substances has attracted increasing attention, as scientific studies have revealed that these substances are persistent, bioaccumulative, and toxic (PBT). Furthermore, measurements have revealed that these substances exist on a large scale in the environment.

[0004] Basically, PFAS consist of chains of carbon (C) and fluorine (F) atoms with specific substance groups attached. The best known substances are PFOS (perfluorooctane sulfonic acid) and PFOA (perfluorooctanoic acid). Until recently, PFOS was used, for example, in fire extinguishing foams. PFOS forms an aqueous film between the liquid and the foam, and it can withstand very high temperatures. For this reason, this type of fire-fighting foam was formulated in airports, fuel depots, drilling platforms, and other facilities that use large amounts of liquid fuel. PFOA is an adjuvant in the production of Teflon and has been used in many other products, as it contributes to its excellent oil and water repellency.

[0005] In the Netherlands, the use of PFOS and PFOA is prohibited by law wherever possible. Despite a phase-out, these substances are still present in the environment. Moreover, they are being replaced by other PFASs that are still in use and, to a lesser extent, are still PBTs.

[0006] Technologies capable of decomposing PFAS contaminants are limited. Many of the technologies available for conventional contaminants cannot be used for PFAS due to their low volatility and degradability. Feasibility testing with the most common ex-situ remediation methods indicates that extractive remediation (soil washing) is currently the only viable method for remediating excavated soils. Soil washing is an ex-situ remediation technique that removes harmful contaminants from soils by washing the soil with a liquid (often with chemical additives), scrubbing the soil, and then separating the clean soil from the contaminated soil and wash water. PFAS can then be removed from the liquid phase by adsorption onto activated carbon or other materials. However, caution remains regarding the subsequent treatment of the contaminated carbon. Very high temperatures (1000-1200°C) are required to completely decompose PFAS, and therefore the additional waste streams from PFAS processing are very energy intensive and therefore expensive to decompose.

[0007] The high decomposition temperatures of PFAS are also the reason why, for example, conventional thermal soil washing (vaporization of the contaminated compounds at 500-600 °C followed by post-combustion at about 750 °C) has proven ineffective for soils contaminated with PFOS and PFOA (Een handelingskader voor PFAS - Expertisecentrum PFAS - 25-6-2018 - ISBN / EAN: 978-90-815703-0-5).

[0008] Currently, there are only a limited number of patent publications related to PFAS removal from contaminated soil. For example, US Patent Application Publication No. 2018 / 319685, US Patent Application Publication No. 2019 / 300387, and WO 2019 / 113268 disclose methods in which soil contaminated with PFAS is remediated by washing the soil. Also, the cyclodextrin of US Patent Application Publication No. 2018 / 282530 is used in a liquid medium. US Patent Application Publication No. 2019 / 314876 differs in that it discloses first heating the soil at a temperature in the range of 225-440 °C to vaporize the PFAS. Water vapor is added to the vaporized PFAS to produce a concentrated aqueous PFAS solution. Thus, US Patent Application Publication No. 2019 / 314876 does not disclose washing the soil, but the PFAS is obtained in the aqueous phase. Thus, all of the above mentioned methods suffer from the drawback of generating additional waste streams, the decomposition of which requires large energy inputs.

[0009] US 2021 / 106860 discloses decontaminating contaminated solid materials, such as soil contaminated by PFAS, by heating under vacuum at a temperature that can volatilize the contaminants. WO 2021 / 102519 discloses decontaminating soil contaminated with PFAS by pyrolysis. US 2018 / 345338 and Duchesne et al. (Environ. Sci. Technol. 2020, 54, 12631) also disclose all thermal destruction methods. Smoldering combustion is used to decontaminate soil containing PFAS. The soil is treated with a solid fuel that contains organic material. The mixture is heated to 200°C-400°C to initiate smoldering and an oxidant gas is forced through the heated mixture to sustain smoldering until the mixture reaches the PFAS decomposition temperature and the perfluoroalkylated substances are thermally decomposed. The resulting flue gas releases hydrogen fluoride and other fluorine gases and requires treatment. US 2018 / 345338 notes that there is no mechanism to utilize energy from the treatment of other wastes, such as hydrocarbon-impacted soils, coal tar, or other fuels, to reduce the energy and cost burden. This is consistent with what was reported in Een handelingskader voor PFAS - Expertisecentrum PFAS - 25-6-2018 - ISBN / EAN: 978-90-815703-0-5, namely, that scrubbing methods appear to be the only viable method. Summary of the Invention

[0010] Due to the high associated costs, facilities that accept waste contaminated with PFAS are limited.However, due to the large amount of PFAS present in the environment and the stringent requirements related to the acceptable level of PFAS contamination in soil, new and more cost-effective methods of PFAS remediation are needed.The object of the present invention is to provide an improved method and system for remediating soil containing PFAS, or at least provide a useful alternative.

[0011] The present invention further provides a method for remediating soil containing PFAS, the method comprising: a) heating the sludge and a first gas stream in a first entrained bed incinerator, thereby incinerating organic material in the sludge and producing a raw material for ceramic articles and a first gas stream comprising a first exhaust gas, said first gas stream comprising a first exhaust gas having a temperature of at least 800°C; b) exchanging the first gas stream comprising the first exhaust gas with a second gas stream in an air-to-air heat exchanger, thereby producing a second gas stream having a temperature of at least 500° C.; c) contacting the soil containing PFAS with the second gas stream having a temperature of at least 500° C. in a dryer, thereby vaporizing the PFAS from the soil and producing clean soil and a second gas stream containing PFAS; d) decomposing the PFASs contained in the second gas stream in a second entrained bed incinerator at a temperature of at least 1000° C., thereby producing a second gas stream containing decomposed PFASs; Includes.

[0012] Surprisingly, it has been found that, contrary to the general view that energy generated from the treatment of other wastes cannot be advantageously used in the remediation of PFAS-contaminated soils, gas streams, including exhaust gases generated in the process of preparing raw materials for ceramic articles from sludge, can be advantageously used in the remediation process of soils containing PFASs. Due to a unique combination of features, namely, heating the PFASs in two stages (first in a dryer in step c) and then at a higher temperature in an entrained bed incinerator in step d), the temperature in step d) can be increased to a value at which the PFASs from the contaminated soils can be decomposed without the need for an aqueous phase in the process of removing the PFASs from the contaminated soils, thus reducing the amount of these waste streams and the required cleaning steps compared to conventional PFAS remediation techniques. [Brief description of the drawings]

[0013] [Figure 1] 2 is a flow chart of a method according to the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] From WO 2019 / 160409 a method for preparing a raw material for ceramic articles from sludge is known. This application discloses a method for preparing a ceramic article comprising industrial, domestic or natural sludge. The sludge has been pretreated by a process including the optional steps of drying the sludge to a moisture content of up to 10% by weight to obtain a dried sludge and heating the sludge or the dried sludge in an entrained bed incinerator to reduce the organic matter content to less than 5% by weight to obtain the raw material for the ceramic article.

[0015] In the present invention, energy generated from a similar pretreatment process of sludge is advantageously used in a method for remediating soil containing PFAS.

[0016] In step a) of the method according to the invention, the sludge and the first gas stream are heated in a first entrained bed incinerator. The first and second gas streams preferably contain oxygen, more preferably at least 5% oxygen, even more preferably at least 10% oxygen, for example at least 15% or 20% oxygen. Preferably, the first and / or second gas streams are airstreams. Preferably, the first and second gas streams are at ambient temperature (e.g. 0°C to 30°C) before entering the process in steps a) and b), respectively, but may be preheated, for example to a temperature of at least 50°C, 70°C or 90°C.

[0017] Sludge is a common waste material that is incorporated into construction materials. Sludge can come from a variety of sources. Domestic sludge (including agricultural sludge) is primarily organic and biodegradable, whereas industrial sludge is often inorganic (e.g. marble sludge, masonry sludge, ceramic sludge). The organic component of industrial sludge is usually not biodegradable. Another form of sludge is natural sludge, which, like domestic sludge, may contain organic and biodegradable components. Domestic sludge is related to human waste and includes, for example, sewage sludge, sludge from wastewater treatment plants, or other forms of sludge treating human waste. Domestic and natural sludges generally contain a large amount of water and biodegradable organic matter. The water content is usually 60-90%. The dry content of organic matter is usually 40-80% by weight of the dry matter. Industrial sludge may contain combustible organic matter. The industrial sludge used in the present invention may have a dry content of combustible organic matter ranging from 40 to 80% by weight of dry matter. Preferably, the sludge is dried to a moisture content of up to 10% by weight to obtain a dry sludge, which is then heated in a first entrained bed incinerator. Preferably, the sludge is sludge resulting from a wastewater treatment process.

[0018] Entrained bed incinerators are a form of Dynamic Thermal Oxidation (DTO). Incineration in an entrained bed incinerator is a dynamic process. The air velocity and temperature within the incinerator's combustion chamber ensure the "cutting" of the material. The chamber geometry provides a thermally driven circulation so that the feed particles undergo thermal treatment over their entire surface area. A combination of air velocity, temperature, specific gravity and specific gravity of the particles controls the residence time and "unloading" point of the treated particles. Typically, the feedstock has a caloric value of at least 4 MJ, either by itself or with the addition of fuel.

[0019] Preferably, the sludge has a calorific value of at least 4 MJ. Therefore, preferably, no extra fuel is fed to the first entrained bed incinerator. If extra fuel is required to continue the combustion process, preferably, the fuel is solid recovered fuel (SRF) or refuse derived fuel (RDF). RDF is produced from domestic and commercial waste and includes biodegradable materials and plastics. Non-burnable materials such as glass and metals are removed and the residue is crushed. SRF is a high-quality alternative to fossil fuels, produced mainly from commercial waste such as paper, card, wood, textiles and plastics. Solid recovered fuel has undergone additional processing to improve its quality and value. SRF has a higher calorific value than RDF. Additionally or alternatively, the fuel may be a conventional fuel, such as a conventional solid fuel, liquid fuel or gaseous fuel. Examples of solid fuels include wood, coal, peat, dung, coke, charcoal, etc. Examples of liquid fuels include petroleum, diesel, gasoline, kerosene, LPG, coal tar, naphtha, ethanol, etc. Examples of gaseous fuels include natural gas, hydrogen, propane, methane, coal gas, water gas, blast furnace gas, coke oven gas, CNG, etc.

[0020] Entrained bed incinerators are known. For example, Russian Patent No. 2249763 describes fire-chambers with entrained beds that can be used in heat power engineering. The fire-chambers with entrained beds of this document include a cylindrical combustion chamber, the height of which is 10-15% of the height of the cone, the inclination angle of the cone wall to the vertical is 10-20°, and the height of the cone is 3-5 times its average inner diameter. Below the combustion chamber is an ignition chamber with tangential connecting pipes for the supply of air and exhaust gases and injectors for pre-ignition of the pulverized fuel. The gas flow velocity along the height of the combustion chamber varies, so that the fuel particles are located in the cone according to the values ​​of their liquefaction and airborne velocities depending on the size of the particles. The burning fuel particles are thrown onto a stabilizer-deflector made in the form of a radial shutter. In the process, part of the particles is deflected and returned to the cone. The particles that have passed through the stabilizer-deflector are fed together with the exhaust gases into a high-temperature cyclone separator arranged outside the firebox. Entrained-bed incinerators are also known from US Pat. No. 4,047,883 and the technical literature cited therein. Furthermore, entrained-bed incinerators are used for example for the incineration of (hazardous) waste by the EM Group in Gelijn, The Netherlands (http: / / www.emgroup.nl / en / products / incinerators / (Link)).

[0021] Typically, the temperature in an entrained bed incinerator ranges from 900 to 1250 °C. Typically, the residence time in an entrained bed incinerator ranges from 1 to 10 seconds. The gas velocity is at least 10 m / s. The capture of the final treated material is usually performed by a cyclone driven by combustion air. The cyclone transports the treated material via air flow and gravity, for example to a storage or further conveying operation. By using an entrained bed incinerator, complete incineration of organic material is achieved without the side effect of sintering inorganic material. The product of step a), i.e. the pretreated sludge or raw material of ceramic articles captured by the use of a cyclone or similar gas / solid separator, can be applied to bricks without fear of deterioration of properties.

[0022] The raw material for the ceramic article produced in step a) represents a first stream of material produced by the first entrained bed incinerator. The second stream of material is a first gas stream comprising hot gas, i.e. a first exhaust gas, which is produced by the combustion and subsequent gasification of organic matter. Due to the high temperatures in the entrained bed incinerator, the first gas stream comprising the first exhaust gas has a temperature of at least 800°C, for example at least 850°C, preferably at least 900°C. For example, the temperature of the first gas stream comprising the first exhaust gas is between 800 and 1400°C, preferably between 850 and 1350°C, more preferably between 900 and 1100°C. If the second gas stream is fed to an air-to-air heat exchanger for heating the second gas stream, the second gas stream may be heated to a temperature of at least 500°C. This is step b) of the method of the present invention, which results in a second gas stream having a temperature of at least 500°C, preferably at least 550°C, more preferably at least 600°C (e.g. 500-900°C, preferably 550-850°C, more preferably 600-800°C).

[0023] In the heat exchanger, the first gas stream comprising the first exhaust gas is cooled to a cooled first gas stream comprising the first exhaust gas. The cooled first gas stream comprising the first exhaust gas may be purified in a first purifier. The first purifier may include, for example, a scrubber, activated carbon, a zeolite, or a combination of one or more thereof.

[0024] In step c), the soil containing PFAS is contacted with a second gas stream in a dryer. The dryer may be, for example, a rotating drum or a sieve. By contacting with the second gas stream, the PFAS and other contaminant compounds are effectively and efficiently vaporized and then transported by the second gas stream to the second entrained bed incinerator. The use of a gas stream for heating is advantageous over other heating methods such as direct combustion or indirect heating through the dryer wall. Such heating methods usually result in localized high temperatures that may result in sintering of parts of the soil. In the method of the present invention, sintering is avoided by the use of a gas stream. Thus, the clean soil produced is not sintered and does not adversely affect the soil grain size. The vaporized PFAS and other contaminant compounds are then transported by the second gas stream to the second entrained bed incinerator.

[0025] In step d), the second gas stream is further heated in a second entrained bed incinerator to a temperature of at least 1000°C, for example at least 1100°C, preferably at least 1150°C, thereby producing a second gas stream containing decomposed PFAS. The decomposed PFAS includes hydrogen fluoride, among other low molecular weight compounds. The second gas stream containing decomposed PFAS can be discharged from the second entrained bed incinerator through a cyclone or similar gas / solid separator and purified in a second purifier. The second purifier can include, for example, a scrubber, activated carbon, zeolite, or a combination of one or more of these. A small amount of solids stream can be discharged from the cyclone or similar gas / solid separator. Preferably, this solids stream is recycled to step c), i.e., the solids stream can be mixed with the soil containing PFAS before or during contact with the second gas stream.

[0026] Preferably, excess fuel is fed to the second entrained bed incinerator, which fuel is preferably SRF or RDF. Additionally or alternatively, the fuel may be a conventional fuel, such as a conventional solid fuel, liquid fuel, or gaseous fuel. The additional fuel fed to the second entrained bed incinerator is preferably SRF, RDF, or natural gas, most preferably natural gas.

[0027] The method of the present invention results in clean soil with a content of each PFAS compound of less than 3.0 μg / kg, such as less than 1.4 μg / kg, or even less than 0.1 μg / kg. Thus, the clean soil may contain, for example, 2.5 μg / kg pfPFOS, 2.5 μg / kg PFOA, and 2.5 μg / kg of one or more other individual PFAS compounds.

[0028] The present invention further relates to the use of an entrained bed incinerator in a method for remediating soil containing PFAS. In an embodiment, an entrained bed incinerator is used to raise the temperature of a gas stream containing PFAS to a temperature suitable for decomposition of the PFAS (i.e., at least 1000°C), the gas stream having an initial temperature of at least 500°C, preferably between 500 and 900°C.

[0029] Detailed Description of the Drawings The flow chart of FIG. 1 shows an embodiment of the method according to the invention. A first entrained bed incinerator (DTO1) is fed with sludge and any fuel. The sludge is preferably dried to a moisture content of at most 10%. In the first entrained bed incinerator, the organic matter in the sludge and any fuel are combusted with a first gas stream, such as an air stream (air 1), typically at ambient temperature, at a temperature of 800-1400°C, with a residence time of, for example, 1-10 seconds, and with a gas velocity of at least 10 m / s. This results in a treated sludge suitable for use as a raw material for the manufacture of ceramic articles, such as bricks (raw material). The first gas stream (hot air + exhaust gas 1) comprising the first exhaust gas has a temperature of at least 800°C, for example 800-1400°C.

[0030] In an air-to-air heat exchanger (heat exchanger), heat is exchanged between a first gas stream containing the first exhaust gas and a second gas stream (air 2), which is usually at ambient temperature. This results in a cooled gas stream containing the first exhaust gas (cooled air + exhaust gas 1) and a second gas stream (hot air 2). The cooled gas stream containing the first exhaust gas has a temperature of about 200-300°C and is purified in a first purifier (purifier 1), such as a scrubber, to obtain a first clean gas stream (clean air 1).

[0031] The second gas stream has a temperature of at least 500°C, for example 500-900°C. The second gas stream is used in a dryer (heater) to heat the soil containing PFAS (soil + PFAS) to vaporize the PFAS from the soil. The clean soil (clean soil) is discharged from the dryer at an elevated temperature of at least about 500°C and cooled in a cooler (chiller) to a temperature typically less than 50°C to produce cooled clean soil (cooled clean soil) containing less than 3.0 μg / kg, for example less than 1.4 μg / kg, typically less than 0.1 μg / kg of PFAS per individual compound. This clean soil may then be transported and is ready for use in applications such as road construction. Optionally, heat from the cooler can be used to preheat the first gas stream and / or the second gas stream.

[0032] The PFAS are discharged from the dryer in the form of a second gas stream (hot air 2 + PFAS) containing the PFAS. This second gas stream typically has a temperature of at least 500 °C, for example 500-900 °C. The gas stream containing the PFAS is then further heated in a second entrained bed incinerator (DTO2), which reaches a temperature of at least 1000 °C due to the combustion of the PFAS and other impurities contained in the gas stream, and the addition of an optional second fuel (fuel 2). Discharged from the second entrained bed incinerator is a second gas stream (hot air 2 + decomposed PFAS) containing the decomposed PFAS. The second gas stream is purified in a second purifier (purifier 2), such as a scrubber, to obtain a second clean gas stream (clean air 2).

[0033] In the diagram, the grey arrows show the path of the sludge through the process, the grey dotted arrows show the path of the first gas stream, the dark dotted arrows show the path of the second gas stream, and the black arrows show the path of the soil.

[0034] (term) In the present invention, the term "first gaseous stream" can be read interchangeably with "first gas stream". The term "first gaseous stream containing the first exhaust gas" can be read interchangeably with "second gaseous stream containing the first exhaust gas". The term "second gaseous stream" can be read interchangeably with "third gaseous stream". The term "second gaseous stream having a temperature of at least 500°C" can be read interchangeably with "fourth gaseous stream having a temperature of at least 500°C". The term "second gaseous stream containing PFAS" can be read interchangeably with "fifth gaseous stream containing PFAS". The term "second gaseous stream containing decomposed PFAS" can be read interchangeably with "sixth gaseous stream containing decomposed PFAS". Thus, the present invention also relates to the following clauses.

[0035] Section 1: A method for remediating soil containing PFAS, comprising: a) heating the sludge and a first gas stream in a first entrained bed incinerator, thereby incinerating organic matter in the sludge and producing a raw material for ceramic articles and a second gas stream comprising the first exhaust gas, said second gas stream having a temperature of at least 800°C; b) exchanging the second gas stream comprising the first exhaust gas with a third gas stream in an air-to-air heat exchanger, thereby producing a fourth gas stream having a temperature of at least 500° C.; c) contacting the soil containing PFAS with the fourth gas stream having a temperature of at least 500° C. in a dryer, thereby vaporizing the PFAS from the soil and producing clean soil and a fifth gas stream containing PFAS; d) decomposing the PFASs contained in the fifth gas stream in a second entrained bed incinerator at a temperature of at least 1000° C., thereby producing a sixth gas stream comprising decomposed PFASs; A method comprising:

[0036] Item 2: The method according to item 1, wherein the temperature of the first gas stream containing the first exhaust gas is 800°C to 1400°C, preferably 850°C to 1350°C, and more preferably 900°C to 1100°C.

[0037] Item 3: The method according to item 1 or 2, wherein the temperature of the second gas stream having a temperature of at least 500°C is 500°C to 900°C, preferably 550°C to 850°C, more preferably 600°C to 800°C.

[0038] Clause 4: The method according to any one of clauses 1 to 3, wherein after step b), the first gas stream comprising the first exhaust gas is cooled to become a cooled first gas stream comprising the first exhaust gas, and the cooled first gas stream comprising the first exhaust gas is purified in a first purifier.

[0039] Paragraph 5: The method of any one of paragraphs 1 to 4, wherein after step d), the second gas stream containing the decomposed PFAS is purified in a second purifier.

[0040] Paragraph 6: The method of any one of paragraphs 1 to 5, wherein a solids stream is discharged from the second entrained bed incinerator and in step c) the solids stream is mixed with the soil containing PFAS.

[0041] Paragraph 7: The method according to any one of paragraphs 1 to 6, wherein additional heat for the heating in step a) is generated by combustion of a first fuel, preferably solid recovered fuel (SRF) or refuse derived fuel (RDF).

[0042] Item 8: The method of any one of items 1 to 7, wherein the heat for decomposing PFAS in step d) is generated by combustion of a second fuel, preferably solid recovered fuel (SRF), refuse derived fuel (RDF) or natural gas, most preferably natural gas.

[0043] Clause 9: The method of any one of clauses 1 to 8, wherein the clean soil contains less than 3.0 μg / kg, preferably less than 1.4 μg / kg, more preferably less than 0.1 μg / kg of each individual PFAS compound.

[0044] Item 10: Use of an entrained bed incinerator in a method for remediating soil containing PFAS, the use being for decomposing PFAS, the entrained bed incinerator being used to increase the temperature of a gas stream containing PFAS to a temperature suitable for decomposing PFAS, the gas stream having an initial temperature of at least 500°C, preferably between 500°C and 900°C.

Claims

1. A method for remediating soil containing PFAS, comprising: a) heating the sludge and a first gas stream in a first entrained bed incinerator, thereby incinerating organic matter in the sludge and producing a first gas stream comprising a raw material for ceramic articles and a first exhaust gas, said first gas stream having a temperature of at least 800°C; b) exchanging heat between the first gas stream containing the first exhaust gas and a second gas stream in an air-to-air heat exchanger, thereby producing a second gas stream having a temperature of at least 500°C; c) contacting the soil containing PFAS with the second gas stream having a temperature of at least 500°C in a dryer, thereby vaporizing the PFAS from the soil and producing clean soil and a second gas stream containing PFAS; d) decomposing the PFAS contained in the second gas stream in a second entrained bed incinerator at a temperature of at least 1000°C, thereby producing a second gas stream containing decomposed PFAS; A method comprising:

2. 2. The method of claim 1, wherein the temperature of the first gas stream comprising the first exhaust gas is between 800°C and 1400°C, preferably between 850°C and 1350°C, more preferably between 900°C and 1100°C.

3. 3. The method of claim 1 or claim 2, wherein the temperature of the second gas stream having a temperature of at least 500°C is between 500°C and 900°C, preferably between 550°C and 850°C, more preferably between 600°C and 800°C.

4. 3. The method of claim 1 or claim 2, wherein after step b), the first gas stream comprising the first exhaust gas is cooled to form a cooled first gas stream comprising the first exhaust gas, and the cooled first gas stream comprising the first exhaust gas is purified in a first purifier.

5. 3. The method of claim 1 or claim 2, wherein after step d), the second gas stream containing decomposed PFAS is purified in a second purifier.

6. The second gas stream containing decomposed PFAS is passed through a gas / solid separator to separate the second gas stream. a solids stream is discharged from the gas / solids separator while the entrained bed incinerator is discharged; 3. The method of claim 1 or claim 2, wherein a solids stream is mixed with the soil containing PFAS in step c).

7. 3. The method according to claim 1 or claim 2, wherein the additional heat for the heating in step a) is generated by combustion of a first fuel, preferably solid recovered fuel (SRF) or refuse derived fuel (RDF).

8. 3. The method according to claim 1 or claim 2, wherein the heat for decomposing the PFAS in step d) is generated by combustion of a second fuel, preferably solid recovered fuel (SRF), refuse derived fuel (RDF) or natural gas, most preferably natural gas.

9. 3. The method of claim 1 or claim 2, wherein the clean soil contains less than 3.0 μg / kg, preferably less than 1.4 μg / kg, more preferably less than 0.1 μg / kg of each individual PFAS compound.

10. 1. Use of an entrained bed incinerator in a method for remediating soil containing PFAS, wherein the entrained bed incinerator is used to raise the temperature of a gas stream containing PFAS to a temperature suitable for decomposing the PFAS, thereby decomposing the PFAS, and the gas stream has an initial temperature of at least 500°C, preferably between 500°C and 900°C.

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