Apparatus for PFAS degradation and method for PFAS degradation

Abstract

An apparatus (10) for PFAS degradation, which comprises: - a burner (11), fluidically connected to an assembly (12) for feeding an aerosol of a PFAS-contaminated liquid solution, - the assembly (12) for feeding comprising means (13) for generating the aerosol of the PFAS-contaminated liquid solution.

Description

[0001] APPARATUS FOR PFAS DEGRADATION AND METHOD FOR PFAS

[0002] DEGRADATION

[0003] The present invention relates to an apparatus for PFAS degradation (with PFAS standing for Poly- and Per- Fluorinated Alkylated Substances).

[0004] The invention also relates to a method for PFAS degradation.

[0005] The term PFAS identifies a class of synthetic chemical compounds belonging to the category of “Emerging Contaminants” (ECs).

[0006] Such compounds are constituted by an alkyl chain of variable length, completely or partially fluorinated.

[0007] PFASs can be found in the liquid, gaseous or solid state, as a function of the length of their chain, of their functional groups, etc.

[0008] In the liquid state, these substances are heavier than water and can be mixed with most organic solvents.

[0009] PFASs form a group of several thousand man-made substances used in a vast range of industrial applications, by virtue of their proofing properties against water and oils and their capacity to withstand extreme environmental conditions.

[0010] Although PFASs have hydrophobic properties, which leads to their use for their water-repellent characteristics, their functional groups (carboxyl and sulfonic) render them hydrophilic and, as such, soluble in water and extremely pollutant, with consequent considerable environmental impact and grave risks for human health.

[0011] For these reasons, nowadays techniques for degradation of PFAS are used.

[0012] Such techniques include:

[0013] - immobilization of PFASs: this is used mainly for contaminated soils, and entails stabilization of PFASs by means of, for example, cements, fly ash or pozzolans,

[0014] - adsorption / separation of PFAS: this is used mainly for aquifers, and can entail in turn: - physical adsorption of PFASs by means of, for example, granular activated charcoal, carbon fibers and carbon nanotubes, organic polymers or ion-exchange resins,

[0015] - filtration, such as, for example, ultra-filtration, nano-filtration, micro-filtration or reverse osmosis,

[0016] - capture, by means of cyclodextrins,

[0017] - precipitation and settling by means of coagulants,

[0018] - destruction of PFASs: this can entail in turn:

[0019] - biological treatments by means of, for example, funguses, enzymes and bacteria,

[0020] - mechanical methods by means of, for example, ball-mills,

[0021] - chemical / physical methods by means of, for example, chemical oxidation and reduction, sonolysis, ozonation, photolysis or use of non-thermal plasma,

[0022] - thermal methods such as, for example, incineration.

[0023] Such conventional techniques have a number of drawbacks.

[0024] In fact, none of the conventional techniques described above is capable of completely degrading PFASs owing to the strength of the carbonfluorine bond, which is determined by the high electronegativity of fluorine (3.98).

[0025] In particular, when considering heat treatments, conventional incinerators degrade organic substances solely as an effect of heat: the flame of the incinerator generates heat, and the principle of incineration is a function of the temperatures reached in the combustion chamber and the time the substance remains in the chamber.

[0026] However, it has been seen that conventional incinerators do not successfully result in the complete destruction of PFASs, as the effect of heat alone does not fully degrade fluorinated molecules.

[0027] In these plants, therefore, at the end of the incineration process, the fluorinated molecules undergo only a partial degradation, resulting in the generation of reduced-chain PFASs or other fluorinated organic compounds, which further complicate the problem and the management of PFASs, since short-chain PFASs are more mobile in the environment and harder to degrade.

[0028] The aim of the present invention is to provide an apparatus for PFAS degradation and a method for PFAS degradation that are capable of improving the known art in one or more of the above mentioned aspects.

[0029] Within this aim, an object of the invention is to provide an apparatus for PFAS degradation that the complete degradation of PFASs possible.

[0030] Another object of the invention is to provide a method for PFAS degradation that makes the complete degradation of PFASs possible.

[0031] Furthermore, the present invention sets out to overcome the drawbacks of the background art in a manner that is alternative to any existing solutions.

[0032] Another object of the invention is to provide an apparatus for PFAS degradation and a method for PFAS degradation that are highly reliable, easy to implement, and low cost.

[0033] This aim and these and other objects which will become better apparent hereinafter are achieved by an apparatus for PFAS degradation, characterized in that it comprises:

[0034] - a burner, fluidically connected to an assembly for feeding an aerosol of a PFAS -contaminated liquid solution,

[0035] - said assembly for feeding comprising means for generating said aerosol of said PFAS-contaminated liquid solution.

[0036] This aim and these and other objects which will become more apparent hereinafter are achieved by a method for PFAS degradation, which consists in:

[0037] - generating an aerosol of a PFAS-contaminated liquid solution by virtue of means for generating an aerosol,

[0038] - conveying said aerosol of said PFAS-contaminated liquid solution inside a burner,

[0039] - making said aerosol of said PFAS-contaminated liquid solution pass through a flame of said burner, so converting the PFAS to hydrofluoric acid.

[0040] Further characteristics and advantages of the invention will become better apparent from the detailed description that follows of a preferred, but not exclusive, embodiment of the apparatus for PFAS degradation, according to the invention, which is illustrated for the purposes of nonlimiting example in the accompanying drawings wherein:

[0041] - Figure 1 is a partially cross-sectional view of the apparatus for PFAS degradation, according to the invention;

[0042] - Figure 2 is an enlarged view of a detail of Figure 1;

[0043] - Figure 3 is a view of a component of the apparatus of Figure 1;

[0044] - Figure 4 is a cross-sectional view of a portion of the component of Figure 3;

[0045] - Figures 5a and 5b are two different views of an element of the apparatus of Figure 1.

[0046] With reference to the figures, an apparatus for PFAS degradation, according to the invention, is generally designated by the reference numeral 10.

[0047] One of the peculiarity of the invention consists in that the apparatus 10 comprises:

[0048] - a burner 11, fluidically connected to an assembly 12 for feeding an aerosol of a PFAS-contaminated liquid solution, not shown in the figures,

[0049] - the assembly 12 for feeding comprising means 13 for generating the aerosol of the PFAS-contaminated liquid solution.

[0050] In the present description, the term “aerosol” means a suspension constituted by liquid and / or solid particles, with indicative dimensions between 0.01 pm and 10 pm, dispersed in a carrier gas.

[0051] In particular, the burner 11 comprises:

[0052] - a first tubular element 14, - a second tubular element 15, concentric to the first tubular element

[0053] 14 and surrounding the latter.

[0054] A mixing chamber M is defined between the second tubular element

[0055] 15 and the first tubular element 14.

[0056] The first tubular element 14 has:

[0057] - a first end 16, arranged at least partially within the assembly 12 for feeding and provided with an inlet 17 for the aerosol of the PFAS- contaminated liquid solution, the inlet 17 being fluidically connected to the assembly 12 for feeding,

[0058] - a second end 18, opposite the preceding one, the second end 18 defining an outlet 36 for the aerosol of the PFAS-contaminated liquid solution.

[0059] The second tubular element 15 has:

[0060] - a first end 19, arranged proximate to / at the assembly 12 for feeding and closed around the first tubular element 14,

[0061] - a second end 20, which is opposite to the preceding one and corresponds to the second end 18 of the first tubular element 14, the second end 20 defining an outlet 37 for the flame of the burner 11.

[0062] The second tubular element 15 has a portion 21 with a substantially annular profile, and a widened cross-section, proximate to / at its first end 19.

[0063] This portion 21 has:

[0064] - a first inlet 22, which is lateral and has an axis of extension perpendicular to the axis of extension of the second tubular element 15, the first inlet 22 being adapted for the introduction of a fuel and being connected to means for feeding the fuel into the mixing chamber M, not shown in the figures,

[0065] - a second inlet 23, which is lateral and has an axis of extension perpendicular to the axis of extension of the second tubular element 15 and is adjacent to the first inlet 22, the second inlet 23 being adapted for the entry of an oxidizer into the mixing chamber M, such as atmospheric air. The fuel is, for example, methane.

[0066] Advantageously, the first tubular element 14 and the second tubular element 15 have a vertical configuration for use, as shown in Figure 1.

[0067] It should be noted that the apparatus 10 and the method, according to the invention, can be operated both with the flame directed upwards and with the flame directed downwards.

[0068] The assembly 12 for feeding comprises a box-like body 24, which has:

[0069] - a top 25,

[0070] - a base 30, which is opposite with respect to the top 25 and is arranged below it in the configuration for use,

[0071] - two opposite sides 28a, 28b, arranged between the base 30 and the top 25, on planes of arrangement which are perpendicular to the plane of arrangement of the base 30,

[0072] - a front wall and a rear wall, not shown in the figures, arranged between the base 30 and the top 25 and between the two sides 28a, 28b, on planes of arrangement which are perpendicular to the plane of arrangement of the base 30.

[0073] Arranged on the top 25 of the box-like body 24 are:

[0074] - a first hole 26, into which the first tubular element 14 is at least partially inserted at the first end 16 thereof,

[0075] - one or more third inlets 27, with an axis of extension parallel to the axis of extension of the first tubular element 14, for the entry of a carrier gas (air), the one or more third inlets 27 being connected to means for feeding the carrier gas, not shown in the figures, such as for example pipes fluidically connected to a tank.

[0076] In the example shown in the figures, the box-like body 24 has a parallelepiped shape; however, in other embodiments not shown in the figures the box-like body can also have a different shape, for example cylindrical, cubic etc. At least one of said two sides 28a, 28b is provided with at least one fourth inlet 29, for the entry of the PFAS-contaminated liquid solution, the fourth inlet 29 being arranged proximate to the base 30 of the box-like body 24 and being connected to means for feeding the PFAS-contaminated liquid solution, not shown in the figures, such as for example a hermetically-sealed tank.

[0077] In particular, the apparatus 10 comprises means of control of the level of the PFAS-contaminated liquid solution.

[0078] These means of control of the level of the PFAS-contaminated liquid solution comprise, for example, a vertical pipe, not shown in the figures, which is fluidically connected and interposed between the fourth inlet 29 and the tank of PFAS-contaminated liquid solution, also not shown in the figures, which is closed hermetically.

[0079] When the level of liquid inside the box-like body 24 drops below the level of the fourth inlet 29, a bubble of gas ascends along the pipe until it reaches the tank of PFAS-contaminated liquid solution, so allowing a certain quantity of liquid to descend and to enter the box-like body 24.

[0080] In this manner it is possible to constantly control the quantity of liquid that interacts with the means 13 for generating an aerosol, so optimizing the work of the latter means.

[0081] Arranged inside the box-like body 24, on the base 30, are the means 13 for generating an aerosol, which comprise an ultrasound generator 31.

[0082] The ultrasound generator 31 is arranged, in the configuration for use, below the first hole 26 and resting on the base 30.

[0083] In this manner, during use, the ultrasound generator 31 generates an aerosol of the PFAS-contaminated liquid solution, which is conveyed toward the first tubular element 14 of the burner 11 by means of a flow of carrier gas entering the box-like body 24 through the third inlets 27.

[0084] Another of the peculiarities of the invention consists in that the apparatus 10 comprises an annular element 32 which surrounds the first tubular element 14, inside the second tubular element 15 and the mixing chamber M, and arranged between the first tubular element 14 and the second tubular element 15.

[0085] The annular element 32 is arranged proximate to the second end 18 of the first tubular element 14.

[0086] Such annular element 32 has a plurality of second holes 33, which are through holes and are:

[0087] - arranged along a circumference which surrounds the first tubular element 14, and

[0088] - have an axis of extension parallel to the axis of the first tubular element 14.

[0089] Furthermore, the annular element 32 has a plurality of slots 34 along its outer perimetric profile 35.

[0090] These slots 34 have an axis of extension which is inclined with respect to the plane of arrangement of the annular element 32.

[0091] In particular, all the slots 34 have an axis of extension which has the same inclination as the plane of arrangement of the annular element 32.

[0092] Specifically, the second holes 33 and the slots 34 create paths for the mixture of fuel and oxidizer which are adapted to determine an inward convergence of the flame, i.e. toward the axis of extension of the first tubular element 14, and the outlet 36 of the first tubular element 14.

[0093] In this way, a more effective contact is ensured between the radicals in the flame and the fluorinated contaminants present in the droplets of aerosol of the PFAS -contaminated liquid solution that passes through the flame, so maximizing the degradation of the fluorinated contaminants present.

[0094] The flame, in fact, is not a physical object, but a surface and / or a volume wherein chemical reactions occur.

[0095] These reactions are all produced by means of free radicals, i.e. unstable and highly reactive chemical compounds which determine the rapidity of the combustion process. The high reactivity of these radicals makes them adapted to bond chemically with other molecules, including stable molecules like PFASs.

[0096] In particular, in the apparatus according to the present invention, differently from what occurs in conventional burners, the flame is not used exclusively as a heat source, but as a reactant, i.e. as a source of radicals that act directly on the fluorinated molecule of the PFASs, breaking the carbon / fluorine bonds and as a consequence maximizing the conversion of the PFAS to hydrofluoric acid.

[0097] Therefore, with the apparatus according to the present invention the PFASs undergo a chemical, in addition to thermal, attack, differently from traditional incineration, wherein the attack is purely thermal.

[0098] Furthermore, by virtue of the slots 34 of the annular element 32, the resultant flame is vortex-like, in that the gas mixture (fuel / oxidizer) is forced to rotate, which increases turbulence and considerably shortens the flame, making it hotter.

[0099] This phenomenon makes it possible to considerably increase the density of radicals proximate to / at the outlet 36 of the first tubular element 14, while at the same time increasing the possibilities for attacking the fluorinated compounds present in the droplets of aerosol exiting from the first tubular element 14.

[0100] Also, by modulating the flow of carrier gas entering the box-like body 24 it is possible to stabilize the speed with which the aerosol of the PFAS- contaminated solution passes through the flame, in so doing manipulating the contact time between the radicals in the flame and the fluorinated substances in the PFASs.

[0101] In this manner, the aerosol can pass through the flame much more slowly than atomized liquid from a nozzle, as in the background art, so maximizing the conversion of the PFASs to hydrofluoric acid.

[0102] Droplets of aerosol, furthermore, are on average finer than droplets of atomized liquid and this aspect too ensures a higher yield of hydrofluoric acid, at the end of the treatment, with respect to what occurs in the background art.

[0103] The apparatus 10 is also provided with means for igniting the flame, not shown in the figures, which are per se known and can be manual or automatic.

[0104] The operation of the apparatus 10, according to the invention, is as follows.

[0105] A PFAS-contaminated liquid solution is introduced into the box-like body 24 through the fourth inlet 29, filling the box-like body 24 with a sufficient head of PFAS-contaminated liquid solution to ensure the correct operation of the means 13 for generating an aerosol.

[0106] Here, the ultrasound generator 31 generates an aerosol of the PFAS- contaminated liquid solution, which is conveyed toward the first tubular element 14 by virtue of one or more flows of a carrier gas entering through the third inlets 27.

[0107] The aerosol ascends through the first tubular element 14 and exits from it through its outlet 36.

[0108] A flame develops around the outlet 36 and above it. This flame is lit by means of ignition and is generated by the fuel / oxidizer mixture. This mixture:

[0109] - is produced by mixing fuel, which enters the second tubular element 15 through the first inlet 22, and oxidizer, which enters the second tubular element 15 through the second inlet 23, and

[0110] - passes through the second tubular element 15 and exits from the annular element 32.

[0111] The aerosol that flows out from the outlet 36 of the first tubular element 14 therefore passes through the flame, starting from the bottom and center of the flame.

[0112] In passing through, the droplets of aerosol come into contact with the radicals of the flame and, by virtue of the considerable density of radicals present and the efficacious contact between the fluorinated compounds present in the droplets of aerosol and the radicals in the flame, the carbon / fluorine bonds are broken, so converting the PFASs to hydrofluoric acid.

[0113] The invention also relates to a method for PFAS degradation.

[0114] Such method can be executed by means of the apparatus 10 and consists of:

[0115] - generating an aerosol of a PFAS-contaminated liquid solution by virtue of means 13 for generating an aerosol,

[0116] - conveying the aerosol of the PFAS-contaminated liquid solution inside a burner 11 ,

[0117] - making the aerosol of the PFAS-contaminated liquid solution pass through a flame of the burner 11, so converting the PFASs to hydrofluoric acid.

[0118] In particular, the flame has a vortex-like extension and the aerosol passes through the flame starting from the base and from the center of said flame.

[0119] In practice it has been found that the invention fully achieves the intended aim and objects by providing an apparatus for PFAS degradation that makes the complete degradation thereof possible.

[0120] With the invention, a method for PFAS degradation has also been devised that makes the complete degradation of PFASs possible.

[0121] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

[0122] In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art.

[0123] The disclosures in Italian Patent Application No. 102024000021816 from which this application claims priority are incorporated herein by reference.

[0124] Where technical features mentioned in any claim are followed by reference signs, such reference signs have been inserted for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

CLAIMS1. An apparatus (10) for PFAS degradation, characterized in that it comprises:- a burner (11), fluidically connected to an assembly (12) for feeding an aerosol of a PFAS-contaminated liquid solution,- said assembly (12) for feeding comprising means (13) for generating said aerosol of said PFAS-contaminated liquid solution.

2. The apparatus (10) according to claim 1, characterized in that said burner (11) comprises:- a first tubular element (14),- a second tubular element (15), which is concentric to said first tubular element (14) and surrounds it, a mixing chamber (M) being defined between said second tubular element (15) and said first tubular element (14).

3. The apparatus (10) according to claim 2, characterized in that:- said first tubular element (14) has:- a first end (16), arranged at least partially within said assembly (12) for feeding and provided with an inlet (17) for said aerosol of said PFAS-contaminated liquid solution, said inlet (17) being fluidically connected to said assembly (12) for feeding,- a second end (18), opposite the preceding one, said second end (18) defining an outlet (36) for said aerosol of said PFAS-contaminated liquid solution,- said second tubular element (15) has:- a first end (19), arranged proximate to / at said assembly (12) for feeding and closed around said first tubular element (14),- a second end (20), which is opposite to said first end (19) and corresponds to said second end (18) of said first tubular element (14), said second end (20) defining an outlet (37) for the flame of said burner (11).

4. The apparatus (10) according to claim 3, characterized in that said second tubular element (15) has a portion (21) with a substantially annularprofile proximate to / at said first end (19) thereof, said portion (21) with a substantially annular profile having:- a first inlet (22), which is lateral and has an axis of extension perpendicular to the axis of extension of said second tubular element (15), said first inlet (22) being adapted for the introduction of a fuel and being connected to means for feeding said fuel into said mixing chamber (M),- a second inlet (23), which is lateral and has an axis of extension perpendicular to the axis of extension of said second tubular element (15) and is adjacent to said first inlet (22), said second inlet (23) being adapted for the entry of an oxidizer into said mixing chamber (M).

5. The apparatus (10) according to claim 3, characterized in that said assembly (12) for feeding comprises a box-like body (24), said box-like body (24) having:- a top (25), on said top (25) there being:- a first hole (26), into which said first tubular element (14) is at least partially inserted at said first end (16) thereof,- one or more third inlets (27), with an axis of extension parallel to the axis of extension of said first tubular element (14), for the entry of a carrier gas, said one or more third inlets (27) being connected to means for feeding said carrier gas,- a base (30), which is opposite with respect to said top (25) and is arranged below it in the configuration for use,- two opposite sides (28a, 28b), arranged between said base (30) and said top (25) on planes of arrangement which are perpendicular to the plane of arrangement of said base (30), at least one of said two sides (28a, 28b) being provided with at least one fourth inlet (29), for the entry of said PFAS- contaminated liquid solution, said fourth inlet (29) being connected to means for feeding said PFAS-contaminated liquid solution,- a front wall and a rear wall, arranged between said base (30) and said top (25) and between said two sides (28a, 28b) on planes of15 arrangement which are perpendicular to the plane of arrangement of said base (30).

6. The apparatus (10) according to claim 5, characterized in that said means (13) for generating said aerosol, which comprise an ultrasound generator (31), are arranged inside said box-like body (24).

7. The apparatus (10) according to claim 3, characterized in that it comprises an annular element (32) which surrounds said first tubular element (14), inside said second tubular element (15) and said mixing chamber (M), said annular element (32) being arranged between said first tubular element (14) and said second tubular element (15) proximate to said second end (18) of said first tubular element (14).

8. The apparatus (10) according to claim 7, characterized in that said annular element (32) has:- a plurality of second holes (33), said second holes (33) being through holes and:- being arranged along a circumference which surrounds said first tubular element (14),- having an axis of extension that is parallel to the axis of said first tubular element (14),- a plurality of slots (34) along its outer perimetric profile (35), said slots (34) having an axis of extension that is inclined with respect to the plane of arrangement of said annular element (32).

9. A method for PFAS degradation, consisting in:- generating an aerosol of a PFAS-contaminated liquid solution by virtue of means (13) for generating an aerosol,- conveying said aerosol of said PFAS-contaminated liquid solution inside a burner (11),- making said aerosol of said PFAS-contaminated liquid solution pass through a flame of said burner (11), so converting the PFASs to hydrofluoric acid.1610. The method according to the claim 9, characterized in that said flame has a vortex-like extension and said aerosol passes through said flame starting from the base and from the center of said flame.

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