Patent Application
20240059860
The invention relates to clean, safe and efficient methods and systems for utilizing thermolysis methods to process various per- and polyfluoroalkyl substances (PFAS) in various waste sources. The methods and systems beneficially convert the waste sources containing PFAS and other halogenated compounds into a Clean Fuel Gas and Char source. The thermolysis methods and system provide an advanced pyrolysis methodology for heating and converting these waste sources including a multicomponent and multistep, energy-assisted, chemical reaction as disclosed herein.
Various waste sources in need of safe and efficient processing and/or recycling contain high levels of fluorine, often in addition to chlorine and other halogens/halogenated compounds. This presents a significant challenge as these fluorine sources often contain synthetic chemicals that are classified as perfluoroalkyl substances or polyfluoroalkyl substances (PFAS). As referred to herein PFAS can also be referred to as PFOS (which are specifically the water soluble and most difficult to destroy or remove) of the family of perfluoro compounds. PFAS chemicals are known as “forever chemicals” because of their long half-life and remarkable stability. PFAS represents a family of synthetic perfluoro compounds possessing incredible persistence in both the environment and the human body. The carbon-fluorine bond is one of the strongest bonds in organic chemistry (due to the low molecular weight of the fluorine, where the molecular weight is inversely related to the C-halogen bond strength). For example, the C—F bond strength is 115.8 kcal/mole whereas the C—Br bond strength is only 65.9 kcal/mole. As a result, the C—F bond is chemically resistant to a broad range of organic and inorganic solvents, acids, bases, enzymes, biologicals, UV radiation and other approaches used in traditional chemical decomposition.
PFAS are considered to be very stable fluoro compounds and are therefore difficult to decompose. Fluoropolymers like Teflon (polytetrafluoroethylene) manufactured since the 1940s have been widely used in residential and commercial applications. Their “non-stick” characteristics have unparalleled resistance to heat, oils, stains, and cleaning products. This has enabled companies to develop and commercialize over 9000 perfluorinated compounds. These compounds are also used as soil and stain repellants for fabrics, carpet, leather, paints, cardboard, food packaging, fire suppression gasses and foams (AFFF), wiring, plumbing and chemical processing seals, gaskets, coatings, etc. These products end up in landfills and the PFAS eventually leaches into ground water.
An additional example are PFAS surfactant foams (AFFF) that have been broadly used in firefighting especially around airports, military installations, and locations with inventories of highly combustible fuel oils and chemicals. The water-soluble foams are highly effective in the high energy fires but seep into ground water and eventually in drinking water sources.
There are myriad additional types of PFAS widely used for more than 60 years in various types of plastics, foams (e.g. fire retardant foams), lubricants, and various other stain-resistant, waterproof, and/or nonstick products. Accordingly there is a massive amount of materials and waste sources that have accumulated and contain PFAS in need of processing and/or recycling. These PFAS-containing materials are in need of clean, safe and efficient methods for process and recycling. This is needed to address various environmental considerations, which are exhibited by PFAS compounds now identified at varying concentrations in waste streams, ground water, soil, and the like.
Attempted processing of PFAS compounds has included several destruction approaches over the years, including chemical and biological disassociation, UV radiation, biological activity, and incineration. High temperature incineration is extremely expensive and often results in incomplete destruction with toxic air dispersion emissions of shorter-chain fluoro-compounds. There is no “silver bullet” available for treatment or complete destruction of PFAS. Accordingly, it is an objective of the methods and systems described herein to solve the problem and need in the art for clean, safe and efficient methods for processing PFAS-containing materials.
A further object of the disclosure is to provide methods and systems for utilizing thermolysis methods to safely and efficiently convert various PFAS-containing materials into a Clean Fuel Gas and Char source without generation (and further the removal of) toxic byproducts. As a result, the methods and systems would meet even the most rigid environmental standards that may be set forth for recycling and/or processing of such waste sources.
In particular, the generation of a Clean Fuel Gas provides a desirable waste-to-energy pathway from a previously unutilized waste source through the recycling of tars and oils to generate Clean Fuel Gas to thereby reuse the energy that went into the original fabrication of the PFAS-containing waste sources. In a further application, the generation of the Char source is suitable for further recycling and/or use of the Char source for further separation of desirable components for various applications as disclosed pursuant to the invention.
A further object of the invention is to utilize thermolysis methods to remove all halogen compounds, including fluorine, bromine and chlorine compounds, while beneficially not generating any additional toxic compounds.
A further object of the invention is to utilize thermolysis methods to generate clean, useable fuel gas sources substantially-free or free of halogens (including fluorine, bromine and chlorine) and other halogenated organic compounds (including VOCs).
Other objects, advantages and features of the present invention will become apparent from the following specification taken in conjunction with the accompanying drawings.
An advantage of the invention is the clean and efficient methods and systems for utilizing a multicomponent, energy-assisted, chemical reaction to safely and efficiently convert PFAS material and/or PFAS-containing waste source to Clean Fuel Gas and Char source. It is a further advantage of the present invention that the waste sources are converted by destroying halogenated compounds and halogens including fluorine and any hazardous byproducts from the PFAS compounds; clean, reusable fuel gas sources substantially-free or free of halogens and other VOCs are generated; and a Char source containing valuable materials are further generated.
In a further aspect, products produced by the described methods for converting PFAS materials and/or PFAS-containing waste source are provided.
While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.
Various embodiments of the present invention are described in detail with reference to the drawings, wherein like reference numerals represent like parts throughout the several views. Reference to various embodiments does not limit the scope of the invention. FIGS. represented herein are not limitations to the various embodiments according to the invention and are presented for exemplary illustration of the invention.
The embodiments of this invention are not limited to particular methods and systems, and/or the resultant products for thermolysis methods to safely and efficiently convert PFAS materials and PFAS-containing waste sources, which can vary and are understood by skilled artisans. It is further to be understood that all terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting in any manner or scope. For example, as used in this specification and the appended claims, the singular forms “a,” “an” and “the” can include plural referents unless the content clearly indicates otherwise. Further, all units, prefixes, and symbols may be denoted in its SI accepted form. Numeric ranges recited within the specification are inclusive of the numbers defining the range and include each integer within the defined range.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which embodiments of the invention pertain. Many methods and materials similar, modified, or equivalent to those described herein can be used in the practice of the embodiments of the present invention without undue experimentation, the preferred materials and methods are described herein. In describing and claiming the embodiments of the present invention, the following terminology will be used in accordance with the definitions set out below.
The term “about,” as used herein, refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or use solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients used to make the compositions or carry out the methods; and the like. The term “about” also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term “about”, the claims include equivalents to the quantities.
As used herein, the term “exemplary” refers to an example, an instance, or an illustration, and does not indicate a most preferred embodiment unless otherwise stated.
The term “substantially-free,” as used herein may refer to a minimal amount of a non-desirable and/or toxic component in a material, such as a fluorinated salts, clean fuel gas and Char generated by the methods, processes and systems of the invention. In an aspect, a material is substantially-free of a defined component if it contains less than a detectable amount of the defined component, or less than about 10 parts per billion (ppb), or more preferably less than about 1 ppb. In an embodiment, fluorinated salts, Char and fuel gas generated according to the processing of PFAS material and PFAS-containing waste is substantially-free of toxins, including halogens, having less than about the detection limit of about 10 ppb, or more preferably less than about 1 ppb of the toxin, including halogens. For toxic and/or hazardous materials, free represents an amount below the detection limit of the appropriate material within experimental error. In an aspect of the invention the fluorinated salts, Char source and fuel gas source generated according to the processing of PFAS material and PFAS-containing waste are free of toxins, indicating that there is a non-detectable amount of toxins in the measured source.
The term “substantially-free,” as used herein referring to oxygen in the thermolysis methods refers to a minimal amount of oxygen or air. In an aspect, a system is substantially-free of oxygen if it contains less than about 4 wt.-%, and preferably less than about 2 wt.-%.
The term “thermolysis” as used herein is generally referred to as a thermal-chemical decomposition conversion process employing heat to an input source in need of conversion to a Clean Fuel Gas and Char source. Thermolysis refers generally to thermal-chemical decomposition of organic materials at temperatures >300° C. and in some instances in the absence of external oxygen to form gases, tars, and oils and Chars that can be used as chemical feedstocks or fuels. Tars and oils represent groups of volatile organic compounds, viscous liquids, paraffins, waxes, aromatics, aliphatics, fats and other petrochemical based organic mixtures for example. The thermolysis methods disclosed according to the present invention are an advancement over conventional pyrolysis and/or thermolysis methods, which employ fire or a heat source and include an oil as an output. As described herein no oil is generated as an output of the thermolysis methods of the present invention. As disclosed in further detail herein, the present thermolysis methods employ at least a reprocessing of any tars and oils. Based on at least these distinctions between the thermal conversion methods, the terms thermolysis and pyrolysis are not synonymous, as thermolysis provides various beneficial improvements not previously achieved by pyrolysis methods and/or conventional thermolysis methods.
The term “weight percent,” “wt.-%,” “percent by weight,” “% by weight,” and variations thereof, as used herein, refer to the concentration of a substance as the weight of that substance divided by the total weight of the composition and multiplied by 100. It is understood that, as used here, “percent,” “%,” and the like are intended to be synonymous with “weight percent,” “wt.-%,” etc.
The methods and systems of the present invention may comprise, consist essentially of, or consist of the components and ingredients of the present invention as well as other ingredients described herein. As used herein, “consisting essentially of” means that the methods and systems may include additional steps, components or ingredients, but only if the additional steps, components or ingredients do not materially alter the basic and novel characteristics of the claimed methods, processes and/or systems.
It should also be noted that, as used in this specification and the appended claims, the term “configured” describes a system, apparatus, or other structure that is constructed or configured to perform a particular task or adopt a particular configuration. The term “configured” can be used interchangeably with other similar phrases such as arranged and configured, constructed and arranged, adapted and configured, adapted, constructed, manufactured and arranged, and the like.
The methods and systems of the present invention relate to thermolysis methods, namely a multicomponent and multistep, energy-assisted, chemical reaction, to safely and efficiently convert various PFAS materials and/or PFAS-containing waste sources to a Clean Fuel Gas and Char source. Beneficially, the methods and systems provide significant and unexpected advances beyond conventional thermolysis methods, as well as conventional incineration or pyrolysis methods. For example, conventional combustion processes which burn waste sources are highly unpredictable and difficult to control. Although advancements in thermolysis have been made in the prior art, the present invention beneficially exceeds the capabilities of known thermolysis methods in converting PFAS materials and/or PFAS-containing waste sources into valuable outputs which beneficially destroy (and do not generate any new) toxic PFAS byproducts, halogens and halogenated organic compounds present in the waste sources, in particular fluorine, such as those depicted in
Moreover, the thermolysis methods of the invention include the use of multiple reactors, reinjection and cracking of any and all tars and oils that are created. As a further benefit, the methods and systems generate clean, useable fuel gas sources substantially-free or free of halogenated organic compounds. As a still further benefit, Char is generated along with the fluorinated salts. Notably, the methods and systems of the present invention do not simply reduce the amounts of fluorinated (and other halogenated compounds) and other toxins, instead these are removed as salts (with no additional generation) from the treated waste sources while further providing the useful and valuable outputs of the invention defined further herein.
PFAS Materials and PFAS-Containing Waste Sources
The methods and systems described herein relate to novel processes using thermolysis methods too safely and efficiently convert PFAS materials and PFAS-containing waste sources into Clean Fuel sources and Char sources. PFAS compounds have a very strong carbon-fluorine chemical bond that is challenging to safely break and thereafter destroy the fluorine compound without generating hazardous gases or other harmful byproducts, making their complete destruction difficult.
Exemplary PFAS compounds include, for example, poly vinyl fluoride (PVF, C2H3F)n) and poly vinylidene fluorine (PVF/PVDF). PVF is available under the tradename Kynar and is commonly used to coat chemical pipes, tanks, and the like to provide extreme chemical resistance. Additional listing of PFAS compounds are shown in Table 1.
PFAS materials can be employed for various applications (and therefore found in various waste sources), including for example: various types of plastics, foams (e.g. fire retardant foams and other concentrated film forming foam (AFFF)), liquid crystals, chemical crop protectants, lubricants, and various other stain-resistant, waterproof, other surface repellant products for fabrics, carpet, leather, paints, cleaning products, food packaging, and/or nonstick products. It is estimated that as many as 9000 or more products containing fluorinated organic compounds have been produced in the past 40 years. As a result there is a variety of PFAS materials and PFAS-containing waste sources.
PFAS materials are often comingled with various other components in need of the processing and/or recycling, making up the PFAS-containing waste sources. For example, additional waste sources and components often include metals, film or fiber layers including other polymers, etc. Additional exemplary polymers that are often used in combination with PFAS materials include polymeric coatings, including for example, ethyl vinyl acetate (EVA), polyethylene terephthalate (PET), polyvinyl chlorine (PVC), and the like.
As one skilled in the art will ascertain, the waste sources can differ based upon factors including the metals, polymer types, thickness and/or density of the waste source, etc. that are employed. The methods and systems are able to process and recycle to convert the myriad waste sources into desirable outputs.
Thermolysis Methods
The methods relate to multicomponent and multistep, energy-assisted, chemical reaction using thermolysis methods to safely and efficiently process and recycle materials in order to convert PFAS materials and PFAS-containing waste sources to gas/vapor mixtures and carbonaceous materials, namely a Clean Fuel Gas source and a Char. Beneficially, the gas/vapor including halogens (in particular fluorine) are cleaned and removed as disposable (or reusable and salable byproduct) salts. In addition various materials, such as metals are recovered substantially in their original form and most have not been melted. As a result of the methods described herein, a clean Char source, Clean Fuel Gas and fluoride salts are the only products of the system.
Beneficially, the methods provide for complete defluorination of the PFAS compounds. According to the methods described herein, at least 99% or at least 99.9% of the PFAS compounds in the PFAS material and/or PFAS-containing waste source are destroyed. Moreover, the at least 99% or at least 99.9% of the destroyed PFAS compounds include any PFAS byproducts formed during the methods. These destroyed compounds include toxic residues from the destruction of the PFAS compounds. This includes for example, any short-chain PFAS byproducts, also referred to as short-chain fluorinated molecules (e.g., CF4), gas byproducts (e.g., HF), highly electronegative fluorine atoms and free radicals, and halogenated dioxins and furans. These byproducts are often more volatile that the PFAS compounds and present an extreme environmental hazard. Therefore, it is critical that the methods destroy these byproducts in addition to the PFAS compounds. Beneficially, the destruction or neutralization of these byproducts prevents the need for any further incineration and/or landfilling in a hazardous waste facility.
The methods provide for the complete defluorination of the PFAS compounds through use of the multicomponent and multistep, energy-assisted, chemical reaction in the thermolysis system. As referred to herein the thermolysis system and methods employ a continuous, oxygen-free thermal processing for the PFAS material and/or PFAS-containing waste sources using heat energy. Beneficially, the methods and systems convert the PFAS material and/or PFAS-containing waste sources by destroying PFAS compounds and not generating additional toxic byproducts including halogenated organic compounds. As a further benefit, the methods generate clean, useable fuel gas sources substantially-free or free of PFAS byproducts including halogenated organic compounds. As a still further benefit, the methods and systems generate a Char containing carbon and other valuable metals and components (depending upon the makeup of the PFAS-containing waste source) which are substantially-free or free of PFAS byproducts and halogenated organic compounds and which can be extracted to obtain further value from the methods.
As a still further benefit, the invention providing for the generation of a Clean Fuel Gas and Char without the formation of (along with the destruction of) halogenated compounds beneficially prolongs the life span of the systems employed for the thermolysis methods. Without being limited according to a particular mechanism, the reduction of formation of PFAS byproducts and halogenated compounds reduces the corrosive damage caused to the systems, such as valves, filters, reactors and the like.
In an embodiment, the methods of using a multicomponent and multistep, energy-assisted, chemical reaction to defluorinate PFAS compounds in the PFAS material and/or PFAS-containing waste source include the steps of inputting the material and/or waste sources into the thermolysis system, cleaving the C—C and the C—H bonds (resulting in an abundance of H2 along with C1-C4 aliphatic chains) and cleaving the C—F bonds by providing an excess of H2 in the reactor(s) to drive the formation of HF. The H—F bond is the strongest of the fluorine bonds. The fluorinated polymer fragments continue to process in the reactor until all fluorine is converted to HF.
In some embodiments the waste source is further saturated with an excess of hydrogen (protons) to drive the reaction with highly electronegative fluorine atoms to rapidly form HF. Without being limited to a particular mechanism of action, with the abundant presence of H2 from the polymer decomposition and the high electronegativity of the fluorine atom, there will be strong chemical force to form HF. In an embodiment, excess hydrogen can be provided to the reactor(s) to create a further abundance of hydrogen to drive the formation of the preferred stable form of HF.
In an exemplary embodiment, a source of hydrogen, such as polymeric olefins (or olefin polymers), including for example HDPE, LDPE, polyethylene, polypropylene, polystyrene, PVC or combinations thereof, is added to the reactor system. In an embodiment, a ratio of PFAS material (e.g. fluorinated polymer) to excess hydrogen source can be from about 1 to about 2, about 1 to about 3, about 1 to about 4, about 1 to about 5, or greater.
In a further exemplary embodiment, a PFAS material may need to be saturated (e.g. providing an organic material such a cellulose) with a hydrogen source. In an exemplary embodiment a PFAS material (e.g. PFOS used in AFFF foams or liquids) can be combined with an organic material that absorbs the PFOS, such as sawdust (wood), to enable the fluorine atoms to react with the hydrogen atoms that are produced from the cellulose source upon thermolysis. In an embodiment, a ratio of PFAS material (e.g. fluorinated polymer) to organic material for saturation is at least about 1 to about 1 (1:1), or can be from about 1 to about 5 to about 5 to about 1.
In an embodiment it is desired to have a fluorine concentration in the mixture that is less than about 10% fluorine, less than about 9% fluorine, less than about 8% fluorine, or less than about 7% fluorine. The fluorine concentration of the PFAS material and/or PFAS-containing waste source can be adjusted by saturating the material as described to provide excess hydrogen.
Thereafter the HF (which is in the form of a hot gas at the temperature of the reactor, e.g. 600-650° C.) is captured and converted to the gas scrubber(s) within the system. Beneficially, in embodiments the HF gas does not need to be cooled before entering the gas scrubber; instead, it goes from an oil-water scrubber to a water scrubber where the temperature is less than about 100° C. There the HF is neutralized with a mineral basic compound. The mineral basic compound can include an aqueous solution, such as calcium base. In embodiments a mineral basic compound can be a sodium or potassium fluoride which is soluble in water, with the addition of a further removal step. It is desirable to add a water soluble source of calcium to precipitate a fluoride salt. Examples of water soluble calcium ions can include Ca Acetate (34.7 g/100 ml water solubility), Ca(NO3)2 (121 g/100 ml), and Ca Nitrite, etc. Preferably, a water-soluble calcium compound is utilized to precipitate CaF2 for removal. This final step removes the fluorine halogens in a basic aqueous scrubber. In an embodiment, the neutralized HF is converted to a non-toxic mineralized salt, namely a fluoride salt (e.g. CaF2) and can be disposed or reused. Again, without being limited to a particular mechanism of action, the high hydration/solvation energy of the H-halogen species causes them to dissolve immediately and then they are safely removed by basic neutralization into non-toxic mineral salts (e.g. calcium or sodium fluoride). In an embodiment, the neutralized ionic mineral salts could be further repurposed as a building block (or raw material) for synthesis of other fluorinated compounds.
In an aspect the systems and apparatuses utilized for the methods and processes of the present invention includes at least the following components as substantially depicted in
In an aspect the methods and systems include the steps as substantially depicted in
The methods and systems of the present invention may optionally include one or more of the following steps: an initial separation of components of the waste source, such as removing metal framing and/or glass panels for reuse/recycle; drying the waste input; suturing a waste input (e.g. adding wood chips or saw dust to a AFFF for PFAS destruction); removing any other valuable components from the waste source (e.g. the solar cells or portions thereof); extraction of metals or other components from the ground and/or shredded waste input; separation steps and/or additional gas scrubbers; and/or collection and separation of components from the Char (e.g. metals, silicon).
The methods and systems of the present invention can be carried out in a variety of apparatus for thermolysis. An exemplary device or series of reactors, further including oil and other separators, char/oil separators, gas scrubbers, evaporators, and the like are shown for example in U.S. Pat. No. 9,631,153, which is incorporated herein by reference in its entirety. As a benefit, the systems can be scaled for small, transportable systems for deployment to clean and process waste sources at remote contaminated sites and/or provide law scale facility thermolysis systems to process 10, 50, or near 100 tons of waste sources per day. As a further benefit, the methods utilizing these systems provide a far more cost-effective (in addition to safe) processing of the waste sources, including less than one tenth the cost of high temperature incineration.
In an aspect the invention includes an initial optional step of separating components of the PFAS-containing waste source for processing according to the invention. In an aspect, one or more portions of the waste may be separated for independent processing, recycling and/or reuse. This separation can be a manual or automatic process.
In an aspect, the invention includes an initial shredding, chopping and/or grinding step of the waste source, each of which may be referred to herein as shredding. The scope of the invention is not limited with respect to this initial processing step to reduce the size of the waste and provide a substantially uniform input source. In an aspect, the waste source can be placed directly into a grinder or shredder. In an aspect, the grinding and/or shredding step provides substantially uniform pieces of the input source. In an aspect, the grinding and/or shredding step provides pieces of the input source having an average diameter of less than about 2 inches. In an aspect, the shredding and/or grinding can include a first coarse step followed by a fine shredding and/or grinding step. In an alternative aspect, the shredding and/or grinding can include a single processing step. Various conventional shredding and/or grinding techniques may be employed without limiting the scope of the invention described herein.
Beneficially, according to the invention a variety of PFAS material and/or PFAS-containing waste sources can be processed according to the invention without substantial extraction steps to remove or separate various components for distinct and separate processing. This is a significant benefit over processing systems and techniques of the prior art requiring substantial sorting and separation of components of waste sources.
In an aspect, the invention includes an optional extraction step for the removal of certain metals (or other components) from the ground and/or shredded waste source input. In an aspect, a step for extraction of metals (or other components) immediately follows the shredding and/or grinding of the waste source. The removal step may include any techniques known to those skilled in the art to which the invention pertains, including a combination of mechanical and/or manual removal. In an aspect, the separation may include the use of magnet separators, including magnetic and high magnetism separators, for the attraction and removal of ferrous metals. In a further aspect, the use of eddy current can be used to remove metals, such as copper and aluminum. In an aspect, the separation may include the use of electrostatic separation. In an aspect, the separation may include the use of specific gravity separation. In an aspect, the separation may include the use of an air or fluid sorting device.
In an aspect, the methods and systems involve a reactor or series of thermolysis reactors using a substantially oxygen-free (or oxygen-free) continuous, low pressure, thermolysis process using heat energy. In an aspect, low pressure includes from about 10 to about 100 millibar, or any range therein. In an aspect, the invention involves an oxygen-free continuous, low pressure, thermolysis process in a reactor or series of reactors. As referred to herein, the oxygen-free process in the reactor(s) does not include air or oxygen in contact with the waste input source. Beneficially, as a result of the reduction and/or elimination of oxygen from the methods and systems of the present invention, the waste input sources are not exposed to flame and/or fires or plasma source and therefore do not form hazardous byproducts, polycyclic aromatic hydrocarbons (PAHs), halogenated dibenzodioxins, halogenated dibenzofurans, biphenyls, and/or pyrenes, or other halogenated (fluorinated) organics.
In an aspect, the invention employs the substantially oxygen-free or oxygen-free continuous, low pressure thermolysis process with supply of heat energy. Thermolysis methods are known to employ different methods and amounts of heat energy, including for example: Low temperature thermolysis with a process temperature below 500° C.; medium-temperature thermolysis in the temperature range 500 to 800° C.; and melting thermolysis at temperatures of 800 to 1,500° C. According to aspects of the present invention, the substantially oxygen-free or oxygen-free continuous, low pressure thermolysis process applies indirect heating. In an aspect, the heating includes processing the waste source input at temperatures of about 400° C.-800° C., preferably about 450° C.-650° C., and more preferably about 600° C.-650° C. The disclosed temperature ranges beneficially gasify the halogenated aliphatic and aromatic compounds by thermally decomposing these compounds.
Beneficially, the use of a lower temperature thermolysis process places less stress on a reactor(s) (such as steel reactors), requires less energy to run the continuous process according to the invention, and further maintains metals in contact with the system at lower temperature ranges which improves longevity, processing, etc. within a plant facility.
In an aspect, a reactor or series of reactors (also referred to as cascading reactors) allows for the thermolysis processing over the lower range of temperatures from about 400° C. to about 800° C., preferably about 450° C.-600° C., and more preferably about 600° C.-650° C. As one skilled in the art understands, there is not a single processing temperature for an input source according to the invention; instead, a range of temperatures within a reactor (or series of reactors) is obtained. In preferred aspects, the reactor(s) employed according to the methods of the invention do not require design for withstanding high temperature/pressure, as the relatively low temperature and pressures are employed (such as on average about 650° C. and ambient pressures of on average about 50 mbar).
The continuous thermolysis process is carried out in at least one reactor to undergo at least partial gasification. Various reactors known in the art can be employed, including for example, rotary drum reactors, shaft reactors, horizontal reactors, entrained-flow gasifiers, fixed-bed gasifiers, entrained-flow gasifiers, or the like. Exemplary reactors are disclosed, for example in, U.S. Pat. No. 9,631,153, Publication No. 2014/0182194 and DE 100 47 787, DE 100 33 453, DE 100 65 921, DE 200 01 920 and DE 100 18 201, which are herein incorporated by reference in its entirety. As one skilled in the art will ascertain the number, sequence and scale of the reactors employed according to the invention can be adapted pursuant to the scale and volume of PFAS material and/or PFAS-containing waste source inputted, which are embodied within the scope of the invention.
In some embodiments, a primary reactor employed according to the invention may comprise, consist of or consist essentially of input region with distributor, reactor mixing chamber, high-temperature region, high-temperature chamber, heating jacket chamber with burners, conversion section, inner register, and/or heat transfer register. In exemplary embodiments, a secondary (or tertiary) reactor employed and may comprise, consist of or consist essentially of gas compartment with dome, high-temperature chamber with vertical conveying device, inner register and outer register, conversion section with conveyor device, heating jacket chamber and/or combustion chamber.
In an aspect, the reactor(s) are jacket heated. In an aspect, the reactors are vertically and horizontally disposed. In an aspect, at least two reactors are employed. In an aspect, at least three reactors are employed. In an aspect, the reactor(s) may optionally undergo agitation. In a preferred aspect, at least one reactor or a primary reactor is vertical with a moving bed design and counter-current flow for the fuel gas along the heated walls into secondary reactors. Without being limited according to an embodiment of the invention, such designs minimize the creation of undesirable tars and fuel oils. In a further preferred embodiment, a moving bed design is further employed for a secondary horizontal reactor which extends the controlled reaction time and temperature of the fuel gas and char from improved solid/gas and gas/gas reactions according to the invention.
The PFAS material and/or PFAS-containing waste source undergo the conversion in the reactor(s) for an amount of time sufficient to provide at least partial conversion and substantially as set forth according to the methods of U.S. Pat. No. 9,631,153. In an aspect, the amount of retention time in a reactor(s) varies from at least about 10 minutes, at least about 20 minutes, at least about 30 minutes, or more as may vary based upon factors including for example the fluorine content (% fluorine in waste source), size of the input source which impacts the gasification reaction, and the like.
In an aspect, the pressure in the reactor(s) is held constant within a pressure range from about 10 to about 100 millibar, or preferably from about 20 to about 50 millibar.
In an aspect, the methods further include a tar and oil cracking step. As one skilled in the art appreciates, tars and oils are an unavoidable product of the pyrolysis process, which are a non-heterogenous mixture of olefins and paraffins, which contain tars and hazardous component. These hazardous components include carcinogenic benzene, toluene and chlorinated-brominated components, if PVC and/or flame retardants are present in the plastics feedstock. The pyrolytic oils have a low flash point and are known to be extremely hazardous (often requiring hazardous regulatory permits in various countries).
Beneficially, according to the invention such unavoidably created tars and oils are merely an intermediate and are subsequently cracked. As referred to herein, “cracking” refers to the process whereby complex organic molecules are broken down into simpler molecules, such as light hydrocarbons, by the breaking of carbon-carbon bonds in the precursors. Thus, cracking describes any type of splitting of molecules under the influence of heat, catalysts and solvents. Accordingly, tars and oils are not collected or an output of the thermolysis methods of the invention. In an aspect, a further gas converter (cracking reactor) will be employed, such as where higher organic components are further degraded. This removal and conversion of these heavy oils or tars into Clean Fuel Gas is desired to remove these materials which selectively absorb halogenated hazardous substances. In an aspect, the step recycles tars and oils in order to remove the hazardous halogenated compounds. In a further aspect, the tar and oil cracking step has the beneficial effect of creating more clean fuel gas.
In an aspect, the generated tars and oils are processed in the presence of an optional catalyst, such as for example zeolite. In an embodiment, the cracking step separates light and heavy oils, such as disclosed for example in U.S. Pat. No. 9,631,153, which is incorporated herein by reference in its entirety.
In an aspect, the methods may further include an optional cooling step for the gas. In some embodiments, the gas will be cooled due to further processing in a scrubbing stage. For example, a cooled conversion chamber may be in connection with a reactor according to the methods of the invention. In an aspect, a gas at a temperature from about 400° C.-800° C. is cooled to a temperature below about 100° C., or preferably below about 80° C. The gas may further thereafter be cooled to an ambient temperature, such as in an adjacent water scrubber to remove any excess water and/or steam from the gas. In other embodiments a cooling step is not required. For example in some embodiments, the piping of the system can be lined with heat resistant PFAS material, such as PVP lining.
In an aspect, the invention further includes a cleaning step for the further processing of the generated fuel gas. Such step may be referred to as a “wet scrubbing” step. In an aspect, the gas is introduced as a gas flow into a wet scrubber for purification. In an aspect, the gas scrubber(s) separate tars, oils and Char from the product gas flow. In a further aspect, the gas scrubber(s) can further cool the product gas, for example to a temperature below about 80° C. The scrubber(s) may further be employed for a final removal step for any toxic compounds in the fuel gas product.
In an aspect, the produced fuel gas/water vapor mixture enters the gas cleaning, i.e. scrubber system. In an aspect, each reactor line has its own first gas cleaning unit. The gas streams are combined after the first scrubber units and will enter the additional scrubbers afterwards.
In an aspect, the gas cleaning units include or consist of scrubbers, vessels, pumps, oil discharge units and heat exchangers. Water combined with additives, such as for example an alkalinity source (e.g. Ca(OH)2 or other alkaline compounds whose fluoride salt is insoluble in water) or other source such as limestone for removal of sulfur, which are known to those skilled in the art of incineration technologies. Notably, the heating methods according to the invention are distinct from incineration as external heating is provided. For clarity, the methods of the invention do not employ incineration. Those skilled in the incineration arts understand scrubbing using water containing alkaline materials to remove acidic components are distinct methods. These are used in a closed loop system to clean condensates and contaminants out of the gas stream and to cool the gas down. The condensates contain olefins, aromatics and paraffins as solids and water. The standard system includes or consists of five gas cleaning systems. This amount can be reduced or increased depending on the feedstock specifications employed according to embodiments of the invention. The scrubbed components like tar will be the feedstock of the cracking reactors, the light oil fraction of aromatic oil and olefins will be separated from the solids/water and reprocessed in the gasification system and the water will be pre-cleaned and reused.
In an aspect, the invention will further include a recycling step for the recycling of any oils and tars created from the methods described herein. In an aspect, the recycling of the oils and tars involves cracking them and then reprocessing the shorter chain molecules into a main reactor to be converted into additional Clean Fuel Gas. In a beneficial aspect of the invention, such generated Clean Fuel Gas is suitable for use in maintaining operation of the processes of the invention at a point of use (i.e. facility employing the methods and systems of the present invention).
In an aspect, the infeed screw conveyor has a conventional design, and the temperature of the co-product is the main parameter for its specification. The temperature of the co-product will be increased by indirect heating and controlled air supply before it enters the rotary calciner.
In an aspect, the rotary calciner has a basic design of an elongated drum with two bearings, an inner drum with flights and a central output screw conveyor. Input and output are symmetrical located. The drive is at the head of the rotary calciner. Input and output of the material is done via the shaft and thus gas proof to the atmosphere. A pipe register in two levels inside the drum will cool the process. The material can be transported by the inner flights into the output screw conveyor. The material can be continuously transported through the rotary calciner at a constant temperature and constant cooling. Moreover, carbon oxidizes to CO2 in this process.
In an aspect, the output screw conveyor has a conventional design with a cooling jacket and connected to the storage vessel.
In an aspect, the exhaust gas cleaning module has a conventional particulate removal system and can be optionally equipped with a gas scrubber with solid removal. A fan can be added if necessary, before entering the stack.
In an aspect, the fuel gas is transported through the gas cleaning system by increasing the pressure, such as to about 100 mbar by ventilation systems. In an aspect, 100 mbar is the limit value for the system employed according to the invention.
In an aspect, the wastewater treatment includes or consists of a physical and biological treatment segment. The wastewater can be discharged after pre-treatment and cleaning.
In an aspect, the safety system transports the fuel gas to a flare in case of an emergency. In an aspect, all the pipelines have valves, which automatically open in case of a power failure. In a further aspect, the connecting pipes to the flare are equipped with burst discs, which will prevent excessive pressure in the reactors and the gas cleaning systems. In case of an emergency, this system will help to shut down the system in a safe manner.
Generated Outputs of the Thermolysis Methods
In an aspect, the methods and systems process and/or recycle PFAS material and/or PFAS-containing waste sources into fluoride salts, Char, and a Clean Fuel Gas source. Beneficially, the hydrocarbon materials from the waste inputs are converted to the Clean Fuel Gas while the metals and carbon-coke will be collected as “Char.” As a further benefit, any oils and tars created are recycled into the secondary reactor and cracking reactor to be converted into additional fuel gas, such as may be employed to maintain operation of the processes of the invention at a point of use (i.e. facility employing the methods and systems of the present invention).
Fluoride Salts
The methods according to the invention employing the thermolysis methods beneficially provide fluorinated salts (e.g. CaF2). In an aspect, the salts are substantially-free of (or free of) toxic chemicals and halogens and/or halogenated compounds.
Char
The methods according to the invention employing the thermolysis methods beneficially provide a processed Char comprising carbon and metals, or other fittings or materials of construction or design of the items containing the PFAS compounds (i.e. shoes, a rainproof jacket, carpet, etc.) In an embodiment at least 90% or greater, 95% or greater, or more of the Char will be carbon. The Char can further comprise carbon particulates/fine matter, and/or combinations of the same. In an aspect, the Char is a non-hazardous material. In an aspect, the Char is substantially-free or free of toxic chemicals. The Char must be cooled down before opening to air to prevent formation of hazardous dioxins and furans (such as for example to less than about 120° C.).
In an aspect, the Char is substantially-free of (or free of) toxic chemicals and halogens and/or halogenated compounds.
In a further aspect and depending upon the waste source containing the PFAS material, at least 50% recovery of any metals are recovered from the Char through separation methods, preferably at least about 55%, preferably at least about 60%, preferably at least about 65%, preferably at least about 70%, preferably at least about 75%, preferably at least about 80%, preferably at least about 85%, preferably at least about 90%, or most preferably at least about 95%.
Fuel Source
The methods according to the invention employing the thermolysis methods beneficially provide a clean fuel source. In an aspect, the fuel gas source is a clean, non-hazardous material. In an aspect, the fuel gas source is substantially-free of toxic chemicals. In an aspect, the fuel gas source is substantially-free of halogens and/or halogen compounds and other toxic chemicals. In an aspect, the fuel gas source is free of toxic chemicals. In an aspect, the fuel gas source is free of halogens and/or halogen compounds. In a further aspect, the fuel gas source is free of toxic chemicals, halogens and halogen compounds. In an aspect, the fuel source is substantially-free or free of polycyclic aromatic hydrocarbons (PAHs), halogenated dibenzodioxins, halogenated dibenzofurans, biphenyls, and/or pyrenes.
In an embodiment, the fuel gas generated is utilized for heating the reactor(s) for the system and methods of the thermolysis methods of the invention. In an aspect, the heat for the reactor(s) is supplied by about 10-50% of the generated fuel gas, about 10-40% of the generated fuel gas, or about 20-30% of the generated fuel gas.
In an embodiment, the fuel gas generated has a composition as set forth in the Tables in the examples.
In an aspect, the fuel gas is a superior product as a result of no air or external oxygen introduced into the reactors, such as is common in pyrolysis and/or partial oxidation systems.
In an embodiment of the invention the thermolysis of PFAS materials and/or PFAS-containing waste sources can provide at least about 100 BTU per pound, at least about 500 BTU per pound, at least about 1,000 BTU per pound, or greater, producing a Clean Fuel Gas as an energy source. As one skilled in the art will ascertain based on the disclosure of the invention set forth herein, differences in PFAS material and waste sources will impact the BTUs per pound.
In an aspect, the generation of the fuel gas is suitable for various applications of use. In an embodiment, the generated fuel source can be used to generate electricity using engines or gas turbines to power a manufacturing plant and/or boilers as a replacement for natural gas and/or electricity. In another aspect, the fuel gas can be used for burners, or steam and electricity production and/or distribution. Many examples of such uses are well known to practitioners of the art.
The present disclosure is further defined by the following numbered paragraphs:
Embodiments of the present invention are further defined in the following non-limiting Examples. It should be understood that these Examples, while indicating certain embodiments of the invention, are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the embodiments of the invention to adapt it to various usages and conditions. Thus, various modifications of the embodiments of the invention, in addition to those shown and described herein, will be apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims.
The disclosure of each reference set forth herein this patent application is incorporated herein by reference in its entirety.
Early studies of thermal degradation of poly(vinylfluoride) (PVF) was studied by Chatfield and reported in The Pyrolysis and Nonflaming Oxidative Degradation of Poly (vinylfluoride), Journal of Polymer Science: Polymer Chemistry Edition, Vol. 21, 1681-1691 (1983). Table 2 shows the summary of low-boiling volatiles from pyrolysis and nonflaming oxidative degradation of PVF at 450° C., where (a) shows Mol % based on all low-boiling volatile degradation products, and (b) shows Mol % excluding CO, CO2, and H2O.
As shown in Table 1 HF is the predominant compound from the thermal degradation of PVF. However various other degradation products are formed, including lower-molecular-weight halogen-containing compounds (e.g. partially-reacted fluorinated compounds) and various other residues. This demonstrates a need for further processing and/or improved processing to ensure that a waste source including PVF is able to completely break down to HF (and no other fluorinated compounds), along with also cracking and removing any tars and oils to provide outputs that only include Clean Fuel Gas and Char that are substantially-free of halogenated organic compounds and do not include tars and/or oils.
As shown in
This is further illustrated in Table 3.
C—F has the shortest bond distance of the C—X families. Further, increasing the number of fluorine atoms on a carbon also increases the stability and disassociation energy C—F4>C—F3>C—F2>C—F. All of these factors contribute to fluorinated organics being among the most chemically resistant and difficult to break the C—F bonds.
Additional TGA of PFAS-containing materials are shown in
Assessment of various PFAS-containing waste sources will be analyzed, including solar panels containing PVP and PVDP, to review and analyze the components of these waste sources that become inputs for processing. Table 4 lists component pieces of a solar panel subjected to processing by the Thermolysis systems showing how the material can be processed:
Systems and apparatus for processing PFAS-containing solar panel waste sources. Apparatus and processing system has been evaluated to assess the product features and material balances as disclosed pursuant to the embodiments of the invention. Materials of construction have been selected to be halogen tolerant, such as steel or liners inside piping of the scrubbers. Testing will be completed to demonstrate the technical capabilities of a plant with a continuous feed of the shredded waste source to yield specific product and operating parameter for further evaluation. The methods according to the invention were evaluated to confirm gas output having a suitable composition with high methane, hydrogen and carbon monoxide content for further usage, and toxic components neutralized in the gas scrubbers with sodium hydroxide. The methods according to the invention will be evaluated to confirm complete and safe removal of fluorine and other toxic compounds in the Char as non-detectable. The methods according to the invention will be evaluated to confirm complete removal of fluorine, VOCs and other toxic components, along with the measurement of any potentially hazardous components and VCOs to assess suitability of the processes for use in factories. The methods according to the invention will be evaluated to assess ability to collect silicon and metal particles from the Char through mechanical separation.
Parameters of the test operation. Feedstock will be received and inspected. After any removal of the metal frames and/or glass panels, the feedstock will be shredded to approximately less than 2 inches. The reactor substantially as depicted in
Continuous processing. A continuous plant operation will be conducted after heating the system up with controlled feedstock input and product discharge. The operating parameters will be adjusted to the requirements of the feedstock. The resulting materials and media will be sampled and documented. Gas samples, a feedstock sample and a Char sample will be obtained for further analysis. The analysis of the samples will be carried out by a certified independent laboratory.
Standard operating conditions of the plant included the following preparation of the plant for the operation: Start-up of the plant: 6:30 am; Feedstock Input: from 11:00 am; Sampling between 13:00 and 15:30 pm; Completion of plant operation: until 18:00 pm; Discharge of products and media, Recording of the yielded products for the mass balance.
General conditions. The feedstock will be shredded and was fed according to the test protocol. The start-up process included the heating of the reactors and the adjustments of the gas scrubbing units and adjacent plant components. The operating conditions will be adjusted to the test plant as outlined below.
Plant conditions. The plant operation during the test will use the standard configuration of the system and specific adjustments for this feedstock.
Special conditions of the test operation. The selected basic operating parameters will be continuously monitored and needed only miniscule adjustments. The Infeed volume of the feedstock will be increased during the second phase of the test. The feedstock input will be continuous—in selected intervals.
Summary of apparatus and process set-up. The feedstock reacts quickly in the main reactor at these temperature conditions and gasifies rapidly. This gasification profile will be monitored by the pressure increase shortly after the feedstock is fed into the system. The observed pressure increase is not critical and can be equalized by a more constant feedstock input for a commercial size unit. Beneficially, the gasification and reaction speed of the tested feedstock described herein enables a high throughput volume. The generated gas is piped from the reactor into the gas scrubbing units, which remove the condensates from the gas stream. The condensates are then collected in the scrubbers and their viscosity is suitable for reinjection into the process as a fuel source. Residual tars are not left over in the scrubbers.
Various operational parameters will be adjusted including: throughput volumes for the Infeed screw conveyors; adjustments of the steam injections to balance out the reactions in the reactor; reactor temperatures; volume of feedstock input; and residence time dependent on Char removal. With these adjustments and the set-up described a stable plant operation will be achieved.
The plant operation volumes will be measured and recorded to assess input total (kg) and average output (kg/h).
Exemplary processing of PFAS containing waste sources are depicted in
Benchtop testing for Teflon processing. A sample of 0.52 g of Teflon and 0.52 g of polyethylene (PE) were put into a 6″ long 316 stainless steel tube and enclosed by two fine stainless steel wool plugs inside a 4″ tube furnace. The plugs constrained the Teflon and PE to be in the center of the furnace. This testing that was not completed in the thermolysis system is an example to demonstrate the methods for safely processing and/or recycling PFAS materials and/or PFAS-containing waste sources under similar processing conditions on a small scale. The use of the Thermolyzer system will provide significantly enhanced residence time of the Tedlar or Teflon (or other PFAS materials) and will provide more hydrogen atoms to complete the reactions to HF.
In this evaluation the 1:1 mass ratio assured that there was a hydrogen/fluorine ratio of about 3:1. The excess of hydrogen coupled with the high HF bond strength promotes scission of the fluorine bonds in the Teflon and formation of HF to precipitate as CaF2 in the bubblers. The tube was flushed with He to remove all air. The furnace was heated at about a 90° C./min heating rate. The high heating rate was chosen to maximize the likelihood that sufficient hydrogen atoms from the decomposition of PE were present to enable scission of the fluorine atoms from the Teflon. After 6 minutes of heating, the temperature was stabilized at 550° C. The furnace gradually increased to 574° C. When a temperature of 450° C. was reached, the He flow was shut off and periodic gas samples were taken as the gas bubbled thru the Ca acetate solution. The bubblers each held 30 ml of water containing 3.14 g of Ca acetate. The solution had been degassed. Then the furnace was turned off A yellow waxy material was observed in the exit tube A cloudiness in the first bubbler was observed, indicating that HF had formed in the reaction chamber. When cool, the tube was weighed. Starting weight was 116.76 g and the weight after heating was 115.92 g for a weight loss of 0.84 g. The waxy material was collected and weighed 0.16 g. The stoppers on each end of the tube were blackened and showed surface damage. The cloudy Ca acetate solution was filtered onto paper. After drying, the mass of the cloudy material was 0.02 g. The steel wool plugs removed easily and were a bluish color on the side facing the center of the tube.
The next day the bubblers were washed thoroughly and refilled with 30 ml each of a solution containing 3.14 g of Ca acetate in each bubbler. A new stainless steel tube was loaded with 0.54 g of Teflon and 0.62 g of PE. Two steel wool plugs constrained the samples to be in the center of the tube. Two end stoppers and an exit tube placed in one. That side connects to the bubblers. A flow of He was passed thru the tube to remove all air. The tube weighed 117.41 g at the start and 116.95 g when the test was over for a weight loss of 0.46 g. The furnace was heated at 75° C./min. The temperature stabilized at 500° C. and then gradually increased to 550° C. At 400° C. the flow of He was stopped. Bubbling continued and gas samples were taken. Samples were taken by briefly opening the gas collection tank valve. Care had to be taken not to evacuate the gas line or the Ca acetate solution would be sucked back into the hot reaction tube. The gas sampling stopped when the bubbling stopped as best determined. A very slight cloudiness appeared in the first bubbler, but it was too dilute to attempt to recover. The temperature in this test did not rise as high as the test on the first day, explaining why a smaller amount of precipitate formed in the Ca acetate solution.
On the second day of testing increased bubbling at a lower temperature was observed and the heat was turned off at 400° C. instead of 450° C. This was done to capture more syngas for analysis and was not critical to the results of the experiment.
The gas bottles and chain of custody documents were packaged and shipped overnight for analysis by Eurofins. The gas sample from the Teflon processing was too small to interpret as only methane and CO2 were measured. This is a small scale showing of defluorination of the waste source even with the small gas sample evaluated.
Analysis of the Char source will be conducted to show that the methods of the invention maintain the form of the metals and other elements, without introducing any contaminants and/or other hazardous materials, including PFAS byproducts. This beneficially, preserves the value of the metals and other elements. The Fresenius Institute will validate the destruction of and complete defluorination of the waste source using a mass and energy balance of the Char.
Additional analysis of the Clean Fuel Gas processed according to the methods described herein will be conducted to show that the methods of the invention generate gas that is suitable for use as a clean energy source, without introducing any contaminants and/or other hazardous materials, including PFAS byproducts. Measurement of at least the following components as shown in Table 5 will be made to demonstrate complete defluorination of the waste source (validated by the Fresenius Institute) and expected ranges are shown:
This application claims priority under 35 U.S.C. § 119 to provisional application U.S. Ser. No. 63/199,507 filed Jan. 4, 2021, herein incorporated by reference in its entirety. The entire contents of this patent application are hereby expressly incorporated herein by reference including, without limitation, the specification, claims, and abstract, as well as any figures, tables, or drawings thereof.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/011106 | 1/4/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63199507 | Jan 2021 | US |
