Systems and methods for stabilizing, storing, and transporting pyrolysis oil

Abstract

Provided here are systems and methods for limiting gum formation and removing gum impurities from pyrolysis oil during storage and / or transport, as well as improved techniques for removing gum deposits from the interior surfaces of storage and / or transport containment vessels. One such method includes the steps of loading a containment vessel with a dispersant and pyrolysis oil, the dispersant being a polar surfactant that is non-miscible with the pyrolysis oil. The steps include contacting the pyrolysis oil with the dispersant inside the containment vessel to yield stabilized pyrolysis oil and to form water-dispersible gum deposits on interior surfaces of the containment vessel. In certain examples, after removing the stabilized pyrolysis oil from the containment vessel, the steps include applying an aqueous fluid to the interior surfaces of the containment vessel to disperse and remove the water-dispersible gum deposits from the interior surface of the containment vessel.

Description

SYSTEMS AND METHODS FOR STABILIZING, STORING, AND TRANSPORTING PYROLYSIS OILCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to and the benefit of European Application No. EP23205932.9, filed on October 25, 2023. The contents of the referenced application are incorporated into the present application by reference.TECHNICAL FIELD

[0002] The present disclosure generally relates to systems and methods of stabilizing, storing, and transporting pyrolysis oil. More specifically, the present disclosure relates to systems and methods for limiting gum formation and removing gum impurities from pyrolysis oil during storage and / or transport, as well as improved techniques for removing gum deposits from the interior surfaces of storage and / or transport containment vessels.BACKGROUND

[0003] Pyrolysis oil originates from the chemical recycling of mixed plastic waste (MPW). For example, pyrolysis oil can be formed by pyrolyzing MPW at sufficiently elevated temperatures (e.g., between 400 °C and 500 °C) under anaerobic conditions. Pyrolysis oil predominantly contains small hydrocarbon molecules that can include a number of different heteroatoms, such as oxygen, nitrogen, and halide (e.g., chloride, bromide, fluoride) atoms, depending on the composition of the MPW and the pyrolysis process. Additionally, atmospheric gases, including oxygen (O2), can dissolve in the pyrolysis oil, for example, when the pyrolysis oil is being transferred to a container for storage or transport. It is presently recognized that the heteroatoms and / or the dissolved oxygen content of the pyrolysis oil can lead to undesirable gum formationwithin the pyrolysis oil during storage and / or transport. In general, these heteroatoms are more electronegative than carbon, which reduces electron density of a carbon atom that is bound to a heteroatom, rendering it more susceptible to oxidation.

[0004] As the pyrolysis oil is oxidized during storage or transport, the pyrolysis oil begins to form gum, which are solid particles of oxidized pyrolysis oil that are insoluble in the remaining liquid pyrolysis oil. When the pyrolysis oil is subsequently removed from a container after storage or transport, a substantial portion of the gum remains as deposits on the interior surface of the storage or transport container, and these containers are typically cleaned to remove the gum deposits before the container can be used for other purposes. The cleaning of storage or transport containers used for pyrolysis oil takes about three times as long compared to the amount of time involved in cleaning the storage or transport container after use with other hydrocarbons, which undesirably increases operational costs and delays. Additionally, a considerable volume of organic solvent (e.g., acetone) is typically used to dissolve and remove the gum deposits from the interior of these containers after the pyrolysis oil is removed, which undesirably increases operational costs related to the purchasing, application, and disposal of the organic solvent. In some cases, depending on the organic solvent that is used, certain protection, ventilation, and monitoring equipment may also be used to limit and / or monitor organic solvent exposure, further increasing operational costs.SUMMARY

[0005] Applicant recognized the need to limit gum formation within pyrolysis oil during storage and transport, and facilitate cheaper and easier cleaning of gum deposits from storage and transport containers used to store or transport pyrolysis oil. Provided here are systems and methods toaddress these shortcomings of the art and provide other additional or alternative advantages. Examples include systems and methods for limiting gum formation and removing gum impurities from pyrolysis oil during storage and / or transport, as well as improved techniques for removing gum deposits from the interior surfaces of storage and / or transport containment vessels. One such method includes the steps of loading a containment vessel with a dispersant and pyrolysis oil, the dispersant being a polar surfactant that is non-miscible with the pyrolysis oil. The steps include contacting the pyrolysis oil with the dispersant inside the containment vessel to extract gum impurities of the pyrolysis oil to yield stabilized pyrolysis oil and to form water-dispersible gum deposits on interior surfaces of the containment vessel. In certain examples, the steps include pumping or draining the stabilized pyrolysis oil from the containment vessel, wherein the water- dispersible gum deposits remain on the interior surfaces of the containment vessel. In some examples, after removing the stabilized pyrolysis oil from the containment vessel, the steps include applying an aqueous fluid to the interior surfaces of the containment vessel to disperse and remove the water-dispersible gum deposits from the interior surface of the containment vessel. For example, applying the aqueous fluid can include hydro jetting or pressure washing the interior surfaces of the containment vessel to remove the water-dispersible gum deposits. In some examples, the aqueous fluid does not include acetone or other organic solvents.

[0006] In certain examples, the pyrolysis oil is derived from pyrolysis of mixed plastic waste. In certain examples, the stabilized pyrolysis oil removed from the containment vessel contains between 1 weight percent (wt.%) and 10 wt.% fewer heteroatoms relative to the pyrolysis oil, wherein the heteroatoms comprise oxygen atoms, nitrogen atoms, or halogen atoms, or a combination thereof. In some examples, the stabilized pyrolysis oil comprises less than 1 wt.% the gum impurities. In certain examples, the dispersant contains a polyalkylene oxide block copolymerhaving a hydrophilic-lipophilic balance (HLB) value greater than 10. In some examples, the dispersant contains a poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEO- PPO-PEO) block co-polymer having a HLB between 18 and 23.

[0007] One such system or apparatus is a containment vessel for storage or transport pyrolysis oil, wherein the containment vessel contains pyrolysis oil and a dispersant, the dispersant being a polar surfactant that is non-miscible with the pyrolysis oil. In certain examples, interior surfaces of the containment vessel are coated with the dispersant prior to the containment vessel being loaded with the pyrolysis oil for storage or transport. In certain examples, interior surfaces of the containment vessel contain water-dispersible gum deposits that are formed as gum impurities of the pyrolysis oil contact the dispersant. In some examples, the dispersant is a polyalkylene oxide block copolymer having a hydrophilic-lipophilic balance (HLB) value between 18 and 23. In some examples, the containment vessel is a road tanker, a railroad tanker, or an ocean tanker.

[0008] Aspects and advantages of these exemplary examples and other examples, are discussed in detail herein. Moreover, it is to be understood that both the foregoing information and the following detailed description provide merely illustrative examples of various aspects and examples, and are intended to provide an overview or framework for understanding the nature and character of the claimed aspects and examples. Accordingly, these and other objects, along with advantages and features of the present disclosure, will become apparent through reference to the following description and the accompanying drawings. Furthermore, it is to be understood that the features of the various examples described herein are not mutually exclusive and may exist in various combinations and permutations.BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The accompanying drawings, which are included to provide a further understanding of the examples of the present disclosure, are incorporated in and constitute a part of this specification, illustrate examples of the present disclosure, and together with the detailed description, serve to explain principles of the examples discussed herein. No attempt is made to show structural details of this disclosure in more detail than may be necessary for a fundamental understanding of the examples discussed herein and the various ways in which they may be practiced. According to common practice, the various features of the drawings discussed below are not necessarily drawn to scale. Dimensions of various features and elements in the drawings may be expanded or reduced to more clearly illustrate examples of the disclosure.

[0010] FIG. 1 is a diagrammatic representation of a process for stabilizing pyrolysis oil stored in a containment vessel and subsequently cleaning water-dispersible gum deposits from the containment vessel, according to an example.

[0011] FIG. 2 is a diagrammatic representation of a process for stabilizing pyrolysis oil in a containment vessel during transport and subsequently cleaning water-dispersible gum deposits from the containment vessel, according to an example.

[0012] FIG. 3A is a diagrammatic representation of a containment vessel prior to being loaded with pyrolysis oil, according to an example.

[0013] FIG. 3B is a diagrammatic representation of the containment vessel of FIG. 3A after being loaded with pyrolysis oil, according to an example.

[0014] FIG. 3C is a diagrammatic representation of the containment vessel of FIG. 3B after the pyrolysis oil is removed and the water-dispersible gum deposits remain on the interior surfaces of the containment vessel, according to an example.

[0015] FIG. 3D is a diagrammatic representation of the containment vessel of FIG. 3C as the water-dispersible gum deposits that remain on the interior surfaces of the containment vessel are dispersed and removed using an aqueous fluid, according to an example.DETAILED DESCRIPTION

[0016] The present disclosure describes various examples related to systems and methods for limiting gum formation and removing gum impurities from pyrolysis oil during storage and / or transport, as well as improved techniques for removing gum deposits from the interior surfaces of storage and / or transport containment vessels. The description may use the phrases “in certain examples,” “in various examples,” “in an example,” or “in examples,” which may each refer to one or more of the same or different examples. Furthermore, the terms “comprising,” “including,” “having,” and the like, as used with respect to examples of the present disclosure, are synonymous. The term “plurality” as used herein refers to two or more items or components. The terms “about” or “approximately” are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting example, these terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0017] The terms “removing,” “removed,” “reducing,” “reduced,” or any variation thereof, when used in the claims and / or the specification includes any measurable decrease of one or more components in a mixture to achieve a desired result. The use of the words “a” or “an” when used in conjunction with any of the terms “comprising,” “including,” “containing,” or “having,” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” The terms “wt.%”, “vol.%”, or “mol.%” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight,the total volume of material, or total moles, which includes the component. In a non-limiting example, 10 grams of component in 100 grams of the material is 10 wt.% of component.

[0018] Examples include systems and methods for limiting gum formation and removing gum impurities from pyrolysis oil during storage and / or transport, as well as improved techniques for removing gum deposits from the interior surfaces of storage and / or transport containment vessels. One such method includes the steps of loading a containment vessel with a dispersant and pyrolysis oil, the dispersant being a polar surfactant that is non-miscible with the pyrolysis oil. The steps include contacting the pyrolysis oil with the dispersant inside the containment vessel to extract gum impurities of the pyrolysis oil to yield stabilized pyrolysis oil and to form water-dispersible gum deposits on interior surfaces of the containment vessel. In certain examples, the steps include pumping or draining the stabilized pyrolysis oil from the containment vessel, wherein the water- dispersible gum deposits remain on the interior surfaces of the containment vessel. In some examples, after removing the stabilized pyrolysis oil from the containment vessel, the steps include applying an aqueous fluid to the interior surfaces of the containment vessel to disperse and remove the water-dispersible gum deposits from the interior surface of the containment vessel. For example, applying the aqueous fluid can include hydro jetting or pressure washing the interior surfaces of the containment vessel to remove the water-dispersible gum deposits. In some examples, the aqueous fluid does not include acetone or other organic solvents.

[0019] In certain examples, the pyrolysis oil is derived from pyrolysis of mixed plastic waste. In certain examples, the stabilized pyrolysis oil removed from the containment vessel contains between 1 wt.% and 10 wt.% fewer heteroatoms relative to the pyrolysis oil, wherein the heteroatoms comprise oxygen atoms, nitrogen atoms, or halogen atoms, or a combination thereof. In some examples, the stabilized pyrolysis oil comprises less than 1 wt.% the gum impurities. Incertain examples, the dispersant contains a polyalkylene oxide block copolymer having a hydrophilic-lipophilic balance (HLB) value greater than 10. In some examples, the dispersant contains poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEO-PPO-PEO) block co-polymer having a HLB between 18 and 23.

[0020] One such system or apparatus is a containment vessel for storage or transport pyrolysis oil, wherein the containment vessel contains pyrolysis oil and a dispersant, the dispersant being a polar surfactant that is non-miscible with the pyrolysis oil. In certain examples, interior surfaces of the containment vessel are coated with the dispersant prior to the containment vessel being loaded with the pyrolysis oil for storage or transport. In certain examples, interior surfaces of the containment vessel contain water-dispersible gum deposits that are formed as gum impurities of the pyrolysis oil contact the dispersant. In some examples, the dispersant is a polyalkylene oxide block copolymer having a hydrophilic-lipophilic balance (HLB) value between 18 and 23. In some examples, the containment vessel is a road tanker, a railroad tanker, or an ocean tanker.

[0021] FIG. 1 is a diagrammatic representation of an example of a process 100 for stabilizing pyrolysis oil stored in a containment vessel and subsequently cleaning water-dispersible gum deposits from the containment vessel. For the illustrated example, the process 100 begins with the step 102 of pyrolyzing mixed plastic waste (MPW) to yield pyrolysis oil. For example, the MPW may be heated to temperatures ranging from 400 °C to 500 °C under anaerobic conditions to yield pyrolysis oil. As noted, while pyrolysis oil predominantly contains small hydrocarbon molecules, at least some of these molecules can also contain heteroatoms, such as oxygen, nitrogen, and halide (e.g., chloride, bromide, fluoride) atoms, depending on the composition of the MPW and the pyrolysis process. Additionally, in certain cases, atmospheric O2 can be dissolved in the pyrolysis oil. It is presently recognized that the heteroatoms and / or the dissolved oxygen content of thepyrolysis oil can lead to undesirable gum formation within the pyrolysis oil during storage and / or transport.

[0022] For the illustrated example, the process 100 continues with the step 104 of combining pyrolysis oil with a dispersant. More specifically, the dispersant is a polar surfactant that is non- miscible (i.e., not miscible) with pyrolysis oil. As discussed below, the dispersant is also an emulsifier that is capable of forming and / or stabilizing oil-in-water emulsions in the presence of an aqueous fluid. The dispersant generally has a hydrophilic-lipophilic balance (HLB) value (calculated in accordance with Davies’ method) greater than 10, such as between 10 and 30, between 15 and 25, or between 18 and 23, in some examples. In certain examples, the dispersant is a polyalkylene oxide block copolymer. For example, the dispersant may be a poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEO-PPO-PEO) block co-polymer. In some examples, the dispersant is Synperonic PeP105 (e.g., Chemical Abstracts Service (CAS) Number 9003-11-6) having an approximate molecular weight of 6500 grams per mole (g / mol), in which approximately half of the dispersant is PEO by weight. In some examples, the dispersant is in the form of a paste, and the paste may be dissolved in a small quantity of organic solvent (e.g., toluene) to ease handling and mixing of the dispersant with the pyrolysis oil.

[0023] For the illustrated example, the process 100 continues with the step 106 of disposing the pyrolysis oil and the dispersant within a containment vessel. In certain examples, the dispersant and the pyrolysis oil are combined prior to being loaded into the containment vessel, while in other examples, the dispersant and the pyrolysis oil are combined within the containment vessel itself. The dispersant combines with and separates gum impurities from the pyrolysis oil, yielding stabilized pyrolysis oil generally having lower gum content and lower heteroatom content. More specifically, the combination of the gum impurities and the dispersant form water-dispersible gumdeposits on interior surfaces of the containment vessel, isolating the gum impurities from the stabilized pyrolysis oil. In certain examples, after being exposed to the dispersant for at least 24 hours, the stabilized pyrolysis oil contains between 1 wt.% and 10 wt.% fewer heteroatoms (e.g., nitrogen, oxygen, and / or halide atoms) relative to the pyrolysis oil initially formed in step 102. In certain examples, after being exposed to the dispersant for at least 24 hours, the stabilized pyrolysis oil includes less than 1 wt.% gum impurities (e.g., less than 5 wt.%, less than 3 wt.%, less than 2 wt.%, or less than 1 wt.% gum impurities). In some examples, the stabilized pyrolysis oil is lighter in color and / or demonstrates a higher optical transmission than the pyrolysis oil formed in step 102 or pyrolysis oil that is stored or transported in a containment vessel without the dispersant. Additionally, this reduced level of gum impurities can be maintained indefinitely as long as the pyrolysis oil remains in contact with a sufficient quantity of the dispersant.

[0024] Because the dispersant is non-miscible with the pyrolysis oil, the dispersant is present as a separate phase when combined with the pyrolysis oil. For example, the dispersant may form a higher-density layer or phase that sits below the pyrolysis oil within the containment vessel, such as between the pyrolysis oil and the interior surfaces of the containment vessel. Additionally, the polarity of the dispersant is sufficient to enable polar gum impurities that form in the pyrolysis oil to be removed from the pyrolysis oil by dissolving within the separate phase. It is presently recognized that, in the absence of the disclosed dispersant, once gum formation has started within a batch of fresh pyrolysis oil, the initial insoluble gum particulates that form serve as seeds that promote further gum formation at their surfaces. By providing a separate layer or phase that captures and sequesters the initial gum particulates that form, the disclosed dispersant purifies and stabilizes the pyrolysis oil while limiting further gum formation or reducing the gum formation rate within the pyrolysis oil. Further, it is recognized that the inner surfaces of a containment vessel(e.g., a metal or glass containment vessel) can also serve as a surface that promotes gum formation within pyrolysis oil. As such, since certain examples the dispersant can provide a separate layer or phase that can isolate the pyrolysis oil from directly contacting the interior surfaces of the containment vessel, it is believed that the dispersant can further limit gum formation or reduce the gum formation rate within the pyrolysis oil. Furthermore, it is presently recognized that the disclosed aforementioned effects of the dispersant are surprising and unexpected, as those skilled in the art would not generally be inclined to combine pyrolysis oil with a non-miscible dispersant and expect beneficial results.

[0025] For the illustrated example, the process 100 continues with the step 108 of removing the stabilized pyrolysis oil from the containment vessel. For example, the stabilized pyrolysis oil may be pumped or drained from the containment vessel. Once the pyrolysis oil is removed, the water- dispersible gum deposits formed from the mixture of the gum impurities and the dispersant remain adhered to the interior surfaces of the containment vessel. Unlike the gum deposits formed from pyrolysis oil alone that require an organic solvent (e.g., acetone) to remove, because of the presence of the dispersant, the water-dispersible gum deposits are readily dispersed in an aqueous fluid as an oil-in-water emulsion.

[0026] For the illustrated example, the process 100 concludes with the step of applying an aqueous fluid to the interior surfaces of the containment vessel to disperse and remove the water- dispersible gum deposits from the interior surfaces of the containment vessel. In some examples, the aqueous fluid may include a detergent or additional surfactants. However, in most examples, water alone is sufficient to remove the water-dispersible gum deposits, which advantageously reduces operational cost and complexity. In some examples, the aqueous fluid may be applied to the interior surfaces of the containment vessel using hydrojetting or pressure washing to enhanceremoval of the water-dispersible gum deposits, which may desirably reduce cleaning time and / or the total volume of aqueous fluid consumed to wash the containment vessel. In some examples, the aqueous fluid may be heated to between 60 °C and 95 °C to promote removal of the water- dispersible gum deposits, while in other examples, the aqueous fluid remains at ambient temperatures to desirably reduce power consumption. The resulting wash fluid includes the gum impurities that were sequestered from the stabilized pyrolysis oil, wherein these gum impurities are dispersed within oil droplets that are emulsified by the dispersant within the aqueous fluid. The wash fluid is removed (e.g., pumped, drained) from the containment vessel, resulting in a containment vessel in which the interior surfaces are free of gum deposits. In certain examples, the wash fluid is directed to a water treatment system, which purifies the wash fluid by removing the emulsified oil droplets. In some examples, the water treatment system further recovers water from the wash fluid to be recycled for use in cleaning of a containment vessel or another industrial process.

[0027] FIG. 2 is a diagrammatic representation of an example of a process 200 for stabilizing pyrolysis oil in a containment vessel during transport and subsequently cleaning water-dispersible gum deposits from the containment vessel. For the illustrated example, the process 200 begins with the step 202 of pyrolyzing mixed plastic waste (MPW) to yield pyrolysis oil, as discussed above. The process 200 continues with the step 204 of loading a containment vessel of a vehicle with a dispersant and the pyrolysis oil prior to transport. In certain examples, the containment vessel is a road tanker, a railroad tanker, or an ocean tanker. As noted, the dispersant is a polar surfactant and is non-miscible with the pyrolysis oil. In certain examples, the dispersant is applied to the interior surfaces of the containment vessel prior to the pyrolysis oil being added to the containment vessel. For example, the dispersant may be in the form of a paste, and the paste maybe brushed or rolled onto the interior surfaces of the containment vessel to form a waxy layer that isolates the pyrolysis oil from directly contacting the interior surfaces of the containment vessel. In some examples, the dispersant is dissolved in at least a minimal amount of organic solvent and sprayed onto the interior surfaces of the containment vessel, and after the organic solvent evaporates, the dispersant forms a waxy layer that blocks or prevents the pyrolysis oil from directly contacting the interior surfaces of the containment vessel. In some examples, the dispersant and the pyrolysis oil are combined before, during, or after the pyrolysis oil is loaded into the containment vessel.

[0028] For the illustrated example, the process 200 continues with the step 206 of using the vehicle to transport the containment vessel from a first location to a second location. For example, the containment vessel may be transported by road, rail, or water, enabling the pyrolysis oil to contact the dispersant for at least 24 hours. In some examples, the motion (e.g., acceleration, vibrations, oscillations) associated with transporting the containment vessel promotes enhanced contact between the pyrolysis oil and the dispersant. While in contact within the pyrolysis oil during transport, the dispersant combines with gum impurities of the pyrolysis oil to form water- dispersible gum deposits on interior surfaces of the containment vessel and yield stabilized pyrolysis oil, as discussed above.

[0029] For the illustrated example, after arriving at the second location, the process 200 continues with the step 208 of unloading the containment vessel of the vehicle by pumping or draining the stabilized pyrolysis oil from the containment vessel. As discussed above, the water- dispersible gum deposits remain on the interior surfaces of the containment vessel after the stabilized pyrolysis oil is removed. The process 200 concludes with the step 210 of applying an aqueous fluid to the interior surfaces of the containment vessel to disperse and remove the water-dispersible gum deposits from the interior surfaces of the containment vessel. As noted, in some examples, the aqueous fluid may be applied to the interior surfaces of the containment vessel using hydrojetting or pressure washing to enhance removal of the water-dispersible gum deposits, which may desirably reduce cleaning time and / or the total volume of aqueous fluid consumed to wash the containment vessel. As noted, in certain examples, after applying the aqueous fluid, the resulting wash fluid is directed to a water treatment system, which purifies the wash fluid by removing the emulsified oil droplets and recovers water to be recycled. In certain examples, when the properties of the dispersant are conducive to surface application, the interior surfaces of the cleaned containment vessel are subsequently coated with the dispersant to prepare the containment vessel to receive another batch of pyrolysis oil for transport.

[0030] FIG. 3A is a diagrammatic representation of an example of a containment vessel 300 prior to being loaded with pyrolysis oil. More specifically, the illustrated example of the containment vessel 300 is a transport containment vessel (e.g., a road tanker) that is coupled to a truck 302 for transport, while in other examples, the containment vessel 300 may be associated with a railroad car or ocean liner for transport. For the example illustrated in FIG. 3A, the interior surfaces of the containment vessel 300 have been coated with the dispersant 304. For example, as noted, in certain examples, the dispersant is applied to the interior surfaces using a brushing, rolling, spraying, or any other suitable application technique to form a waxy layer of dispersant over the interior surfaces of the containment vessel 300. While the dispersant 304 is illustrated as covering all of the interior surfaces of the containment vessel 300 for the example illustrated in FIG. 3A, in other examples, only a portion of the interior surfaces of the containment vessel 300 (e.g., only a portion that will contact the pyrolysis oil during transport) are coated with the dispersant.

[0031] FIG. 3B is a diagrammatic representation of the example of the containment vessel 300 of FIG. 3 A after being loaded with pyrolysis oil 306. For the illustrated example, the lack of miscibility between the pyrolysis oil 306 and the dispersant 304 results in the dispersant remaining near the interior surfaces of the containment vessel 300. As such, for the illustrated example, the dispersant generally isolates the pyrolysis oil 306 from directly contacting the interior surfaces of the containment vessel 300. For other examples in which the dispersant is instead mixed with the pyrolysis oil prior to or upon being loaded into the containment vessel 300, the dispersant will similarly separate into a distinct layer or phase that isolates the pyrolysis oil from contacting at least a portion of the interior surfaces of the containment vessel 300. In either case, once the pyrolysis oil 306 and the dispersant 304 are in contact with one another within the containment vessel 300, the dispersant 304 combines with and sequesters gum impurities from the pyrolysis oil 306 as water-dispersible gum deposits on the interior surfaces of the containment vessel 300 throughout transport. As noted, this lowers the amount of gum impurities and / or heteroatoms in the pyrolysis oil, which results in stabilization and / or purification of the pyrolysis oil 306 during storage and transport.

[0032] FIG. 3C is a diagrammatic representation of the example of the containment vessel 300 of FIG. 3B after the pyrolysis oil 306 has been removed. For example, as noted, the pyrolysis oil 306 that was stabilized during transport may be pumped or drained from the containment vessel 300. Once removed, in some cases, the containment vessel 300 may still include some dispersant 304 that did not contact or combine with gum impurities from the pyrolysis oil 306. The dispersant 304 that combined with the gum impurities of the pyrolysis oil 306 forms water-dispersible gum deposits 308 that remain on the interior surfaces of the containment vessel 300. As noted, since the presence of gum impurities can act to promote further gum formation within pyrolysis oil, it ispresently recognized that the interior surfaces of the containment vessel 300 should be cleaned to remove any gum deposits before the containment vessel 300 is used to transport additional pyrolysis oil or other hydrocarbon fluids.

[0033] FIG. 3D is a diagrammatic representation of the example of the containment vessel 300 of FIG. 3C as the water-dispersible gum deposits that remain on the interior surfaces of the containment vessel 300 are dispersed and removed using an aqueous fluid 310. For the example illustrated in FIG. 3D, the aqueous fluid is mostly water (or entirely consists of water) that is delivered to the interior of the containment vessel 300 using a hydrojetting system 312. The hydro jetting system 312 enables the aqueous fluid to be manually or robotically directed to the interior surfaces of the containment vessel 300 to remove and disperse the water-dispersible gum deposits 308 into emulsified oil droplets 314 that are suspended within the wash fluid 316. Additionally, any residual dispersant 304 that remained within the containment vessel 300 is also removed by the aqueous fluid 310 and aids in emulsifying the oil droplets 314. The wash fluid 316 is subsequently drained or pumped from the cleaned containment vessel 300. For the illustrated example, the wash fluid 316 is delivered to a water treatment system 318 that processes the wash fluid 316 to remove the emulsified oil droplets 314 from the wash fluid 316. In certain examples, the water treatment system 318 recovers at least a portion of the water 320 from the wash fluid 316, and this recovered water can be used to form at least a portion of the aqueous fluid 310 used to remove water-dispersible gum deposits during the cleaning of another containment vessel.EXAMPLES

[0034] A set of experiments were performed to model the ability of the dispersant to stabilize pyrolysis oil and form water-dispersible gum deposits on the interior surfaces of containment vessels. For these experiments, various concentrations of a dispersant (Synperonic PeP105) werecombined with 50 milliliters (mL) of fresh pyrolysis oil within glass containment vessels. The dispersant was first dissolved in toluene before being combined with the pyrolysis oil, such that the concentration of the dispersant ranged between 50 part-per-million-by-weight (ppmw) and 5000 ppmw. After the dispersant and the pyrolysis oil were combined, each of the containment vessels were exposed to air for an equal amount of time (e.g., 10 minutes) before being sealed. The performance of the dispersant within the pyrolysis oil was evaluated over a two-week period relative to a control sample that lacked the dispersant. At the conclusion of the two-week period, the stabilized pyrolysis oil was removed (e.g., drained, poured) from the containment vessels, leaving water-dispersible gum deposits along the interior surfaces of the containment vessels. It was observed that dispersant concentrations as low as 50 ppmw were effective at forming the water-dispersible gum deposits, and it is believed that even lower concentration (e.g., 5 ppmw) may also be effective, depending on the composition of the pyrolysis oil in certain implementations. It was further observed that dispersant concentrations of 200 ppmw and above were highly effective at forming the water-dispersible gum deposits, and these deposits were readily removed and dispersed when the containment vessels were washed with water alone.

[0035] Other objects, features, and advantages of the disclosure will become apparent from the foregoing figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific examples of the disclosure, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from the detailed description. In further examples, features from specific examples may be combined with features from other examples. For example, features from one example may be combined with features from any of the otherexamples. In further examples, additional features may be added to the specific examples described herein.

Claims

CLAIMSWhat is claimed is:

1. A method, comprising: loading a containment vessel with a dispersant and pyrolysis oil, the dispersant being a polar surfactant that is non-miscible with the pyrolysis oil; and contacting the pyrolysis oil with the dispersant inside the containment vessel to extract gum impurities of the pyrolysis oil to yield stabilized pyrolysis oil and to form water- dispersible gum deposits on interior surfaces of the containment vessel.

2. The method of claim 1, wherein the pyrolysis oil is derived from pyrolysis of mixed plastic waste.

3. The method of claims 1 or 2, comprising: pumping or draining the stabilized pyrolysis oil from the containment vessel, wherein the water-dispersible gum deposits remain on the interior surfaces of the containment vessel.

4. The method of claim 3, comprising: after removing the stabilized pyrolysis oil from the containment vessel, applying an aqueous fluid to the interior surfaces of the containment vessel to disperse and remove the water-dispersible gum deposits from the interior surface of the containment vessel.

5. The method of claim 4, wherein applying the aqueous fluid includes hydrojetting or pressure washing the interior surfaces of the containment vessel to remove the water- dispersible gum deposits.

6. The method of claim 4, wherein the aqueous fluid does not include acetone or other organic solvents.

7. The method of any of claims 1 to 6, wherein the stabilized pyrolysis oil contains between 1 weight percent (wt.%) and 10 wt.% fewer heteroatoms relative to the pyrolysis oil, wherein the heteroatoms comprise oxygen atoms, nitrogen atoms, or halogen atoms, or a combination thereof.

8. The method of any of claims 1 to 6, wherein the stabilized pyrolysis oil comprises less than 1 wt.% of the gum impurities.

9. The method of any of claims 1 to 6, wherein the dispersant contains a polyalkylene oxide block copolymer having a hydrophilic-lipophilic balance (HLB) value greater than 10.

10. The method of any of claims 1 to 6, wherein the dispersant contains a poly(ethylene glycol)-poly(propylene glycol)-poly(ethylene glycol) (PEO-PPO-PEO) block co-polymer having a HLB between 18 and 23.

11. A containment vessel for storage or transport of pyrolysis oil, wherein the containmentvessel contains pyrolysis oil and a dispersant, the dispersant being a polar surfactant that is non-miscible with the pyrolysis oil.

12. The containment vessel of claim 11, wherein interior surfaces of the containment vessel are coated with the dispersant prior to the containment vessel being loaded with the pyrolysis oil for storage or transport.

13. The containment vessel of claims 11 or 12, wherein interior surfaces of the containment vessel contain water-dispersible gum deposits that are formed as gum impurities of the pyrolysis oil contact the dispersant.

14. The containment vessel of any of claims 11 to 13, wherein the dispersant is a polyalkylene oxide block copolymer having a hydrophilic-lipophilic balance (HLB) value between 18 and 23.

15. The containment vessel of any of claims 11 to 14, wherein the containment vessel is a road tanker, a railroad tanker, or an ocean tanker.

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