Methods for disposing of liquefied waste plastics

Abstract

The present invention relates to an improved method for processing liquefied waste plastics, comprising the steps of: providing a volume of liquefied waste plastic oil; subjecting the volume of the LWP oil to heat treatment; separating the volume of the resulting heat-treated mixture into a first aqueous phase volume and a first oil phase volume; isolating the first aqueous phase volume; adjusting the pH of the first aqueous phase volume to pH 9.0 or less; and separating the pH-adjusted volume into at least a second aqueous phase volume and a second oil phase volume.

Description

Technical Field

[0001] The present invention relates to an improvement in the treatment of liquefied waste plastic. More specifically, the present invention relates to an improved method for treating crude (untreated) liquefied waste plastic with a high-temperature alkaline aqueous medium. Background Art

[0002] Refining liquefied waste plastic (LWP) to obtain more valuable (pure) substances, and converting liquefied waste plastic (LWP) into more valuable materials, have been studied for several years.

[0003] For example, Finnish Patent No. 128848 discloses a method comprising pretreating a liquefied waste plastic material at a high temperature in the presence of an alkaline aqueous medium, followed by liquid-liquid separation, hydrotreatment and post-treatment to provide a steam cracker feed.

[0004] Although pretreatment of liquefied waste plastic has been used over the past several years, this process is still under development to maximize yield and / or purity and minimize the environmental impact of the process. In particular, contaminated wastewater poses significant environmental impacts due to complex and / or very energy-intensive post-treatment. Summary of the Invention Problem to be Solved by the Invention

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide an improved method for treating liquefied waste plastic. Means for Solving the Problem

[0006] The problem underlying the present invention is solved by the subject-matter set out in the independent claims. Further advantageous developments are set out in the dependent claims. In summary, the present invention relates to one or more of the following items.

[0007] 1. A method for processing liquefied waste plastics (LWP), (i) A step of providing a volume of liquefied waste plastic oil (A), (ii) A step of subjecting the volume of LWP oil (A) together with the volume of alkaline aqueous medium (B) to heat treatment (1) to provide the volume (C) of the heat-treated mixture, (iii) A step (2) of separating the volume (C) of a heat-treated mixture into at least two separate phase volumes (D, E), wherein one of the separated phase volumes is a first aqueous phase volume (D) and the other separated phase volume is a first oil phase volume (E), (iv) Step (2) to isolate the first aqueous phase volume (D), (v) A step of forming a pH-adjusted volume (G) by adding an acidic medium (F) to the first aqueous phase volume (D) to adjust the pH of the first aqueous phase volume (D) to pH 9.0 or less (3), (vi) A step (4) of separating the pH adjustment volume (G) into at least two separate phase volumes (H, I), wherein one of the separated phase volumes is the second aqueous phase volume (I) and the other separated phase volume is the second oil phase volume (H), Methods that include...

[0008] 2. The method according to item 1, wherein the acidic medium (F) comprises an organic acid and / or inorganic acid such as hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), phosphoric acid (H3PO4), sulfamic acid (H3NSO3), or a carboxylic acid.

[0009] 3. The method according to item 1 or 2, wherein the acidic medium (F) is a solution of acid.

[0010] 4. The method according to any one of items 1 to 3, wherein the acidic medium (F) is an aqueous solution of an acid.

[0011] 5. The method according to item 3 or 4, wherein the acid is at least one selected from the group consisting of hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), phosphoric acid (H3PO4), sulfamic acid (H3NSO3), or carboxylic acid, preferably at least sulfuric acid or hydrochloric acid.

[0012] 6. The method according to item 5, wherein the acid is at least sulfuric acid.

[0013] 7. The method according to any one of items 3 to 6, wherein the solution of the acid has a concentration of 1 to 98% by mass, preferably 1 to 96% by mass, and more preferably 50 to 70% by mass.

[0014] 8. The method according to any one of items 1 to 7, wherein the phase separation (2) in step (iii) is carried out at a temperature in the range of 15°C to 200°C, preferably 40°C to 200°C, 50°C to 175°C, or 60°C to 150°C.

[0015] 9. The method according to any one of items 1 to 8, wherein the phase separation (2) in step (iii) is carried out at a pressure in the range of 1 bar (absolute) to 15 bar (absolute), preferably 2 bar (absolute) to 15 bar (absolute).

[0016] 10. The method according to any one of items 1 to 9, wherein the residence time of the pH adjustment volume (G) in phase separation (4) of step (vi) is in the range of 1 minute to 600 minutes, for example, 1 minute to 240 minutes or 2 minutes to 180 minutes.

[0017] 11. The method according to any one of items 1 to 10, wherein the phase separation (4) in step (vi) is carried out at the same temperature as or lower than the phase separation (2) in step (iii).

[0018] 12. The method according to any one of items 1 to 11, wherein the first oil phase volume (E) and / or the second oil phase volume (H) are further subjected to washing, preferably water washing.

[0019] 13. The method according to any one of items 1 to 12, wherein the first oil phase volume (E) and the second oil phase volume (H) are each separately subjected to washing, preferably water washing.

[0020] 14. The method according to any one of items 1 to 13, wherein the second aqueous phase volume (I) is further subjected to evaporation to obtain an impurity concentrate residue and a waste water stream.

[0021] 15. The method according to any one of items 1 to 14, further comprising combining at least a portion of the second oil phase volume (H) with at least a portion of the first oil phase volume (E) to provide a combined oil phase volume (K).

[0022] 16. The method according to item 15, further comprising subjecting at least a portion of the combined oil phase volume (K) to further processing and / or conversion processes.

[0023] 17. The method according to any one of items 1 to 16, further comprising subjecting at least a portion of the second oil phase volume (H) and / or at least a portion of the first oil phase volume (E) to further processing and / or conversion processes.

[0024] 18. The method according to any one of items 1 to 17, wherein the pH of the first aqueous volume (D) is adjusted in step (iii) to a pH of 8.7 or lower, for example 8.5 or lower, 8.3 or lower, or 8.0 or lower.

[0025] 19. The method according to any one of items 1 to 18, wherein the pH of the first aqueous volume (D) is adjusted in step (iii) to a pH of 1.5 or higher, preferably 2.0 or higher, more preferably 3.0 or higher, 4.0 or higher, 5.0 or higher, 6.0 or higher, or 7.0 or higher.

[0026] 20. The method according to any one of items 1 to 19, wherein the pH of the first aqueous volume (D) is adjusted in step (iii) to a pH of 3.0 or higher, for example 4.0 or higher, 5.0 or higher, 6.0 or higher, or 7.0 or higher.

[0027] 21. The method according to any one of items 1 to 20, wherein the pH of the first aqueous volume (D) is adjusted in step (iii) to a pH in the range of 1.5 to 9.0, preferably 2.0 to 9.0, 3.0 to 9.0, 4.0 to 8.7, 5.0 to 8.5, 6.0 to 8.3, or 7.0 to 8.0.

[0028] 22. The method according to any one of items 1 to 21, wherein the pH of the first aqueous volume (D) is adjusted in step (iii) to a pH in the range of 3.0 to 9.0, for example, 3.0 to 8.7, 4.0 to 4.7, 5.0 to 8.7, 5.0 to 8.5, 6.0 to 8.3, or 7.0 to 8.0.

[0029] 23. The method according to any one of items 1 to 22, wherein the alkaline aqueous medium (B) is an aqueous solution of an alkaline substance.

[0030] 24. The method according to any one of items 1 to 23, wherein the alkaline aqueous medium (B) is an aqueous solution of a metal hydroxide.

[0031] 25. The method according to any one of items 1 to 24, wherein the alkaline aqueous medium (B) is an aqueous solution of a metal hydroxide, and the metal hydroxide is selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

[0032] 26. The method according to any one of items 1 to 25, wherein the alkaline aqueous medium (B) is an aqueous solution of a metal hydroxide, and the metal hydroxide is selected from the group consisting of KOH, NaOH, LiOH, Ca(OH)2, Mg(OH)2, RbOH, Sr(OH)2, and Ba(OH)2.

[0033] 27. The method according to any one of items 1 to 26, wherein the alkaline aqueous medium (B) is an aqueous solution of a metal hydroxide, and the metal hydroxide is NaOH.

[0034] 28. The method according to any one of items 1 to 27, wherein the alkaline aqueous medium (B) contains an amount of alkaline substance in the range of 0.5% to 15.0% by weight, for example, 0.5% to 10.0% by weight, 1.0% to 6.0% by weight, or 1.5% to 6.0% by weight.

[0035] 29. The method according to any one of items 1 to 28, wherein the alkaline aqueous medium (B) comprises at least 50% by weight of water, preferably at least 70% by weight of water, more preferably at least 85% by weight of water, at least 90% by weight of water, or at least 95% by weight of water.

[0036] 30. The method according to any one of items 1 to 29, wherein the water-oil ratio between the volume of alkaline aqueous medium (B) and the volume of liquefied waste plastic oil (A) in the heat treatment (1) of step (ii) is in the range of 0.1 to 1.4 by weight, preferably in the range of 0.2 to 1.0, for example, 0.2 to 0.7.

[0037] 31. The method according to any one of items 1 to 30, further comprising the step of cooling the volume (C) of the heat-treated mixture before or during the separation (2) in step (iii).

[0038] 32. The method according to any one of items 1 to 31, wherein the separation (2) in step (iii) includes liquid-liquid separation.

[0039] 33. The method according to any one of items 1 to 32, wherein the total volume of liquefied waste plastic oil (A) and the volume of alkaline aqueous medium (B) in the heat treatment (1) of step (ii) is 85 to 100% by weight, preferably 90 to 100% by weight, 95 to 100% by weight, 97 to 100% by weight, or 99 to 100% by weight.

[0040] 34. The method according to any one of items 1 to 33, wherein heat for performing the heat treatment (1) in step (ii) is provided to a volume of LWP oil (A), a volume of alkaline aqueous medium (B), and / or a mixture of the volume of LWP oil (A) and the volume of alkaline aqueous medium (B), in a reactor and / or a heating section as an independent unit preceding the reactor.

[0041] 35. The method according to item 34, wherein heat is provided by indirect heating and / or by blowing steam (hot water vapor) into a volume of LWP oil (A), a volume of alkaline aqueous medium (B), and / or a mixture of a volume of LWP oil (A) and a volume of alkaline aqueous medium (B).

[0042] 36. The method according to any one of items 1 to 35, wherein the heat treatment (1) is carried out in a reactor, and the residence time of the mixture of volume LWP oil (A) and volume alkaline aqueous medium (B) at high temperature is at least 10 minutes, preferably in the range of 10 to 600 minutes, for example, 10 to 300 minutes, 15 to 180 minutes, 15 to 120 minutes, or 20 to 60 minutes.

[0043] 37. The method according to any one of items 1 to 36, wherein the heat treatment (1) in step (ii) is carried out at a temperature of 150°C or higher, preferably 180°C or higher, for example, 200°C or higher, 220°C or higher, or 240°C or higher.

[0044] 38. The method according to any one of items 1 to 37, wherein the heat treatment (1) in step (ii) is carried out at a temperature of 450°C or lower, preferably 400°C or lower, 350°C or lower, 320°C or lower, or 300°C or lower.

[0045] 39. The method according to any one of items 1 to 38, wherein the heat treatment (1) in step (ii) is carried out at a temperature in the range of 150°C to 450°C, preferably 180°C to 450°C, 200°C to 400°C, 210°C to 350°C, 220°C to 330°C, 240°C to 320°C, or 260°C to 300°C.

[0046] 40. The method described in any one of items 1 to 39, wherein the method is performed as a batch process.

[0047] 41. A method according to any one of items 1 to 40, wherein the method is carried out as a continuous process.

[0048] 42. The method according to any one of items 1 to 41, wherein the separation (2) in step (iii) includes separation based on gravity, such as decantation, or separation by centrifugation.

[0049] 43. The method according to any one of items 1 to 42, wherein the second aqueous phase volume (I) is at least partially recycled and returned to form part of the volume of the alkaline aqueous medium (B) after optional purification.

[0050] 44. The method according to any one of items 1 to 43, wherein the volume of the LWP oil (A) has a 5% boiling point of 25°C or higher, preferably 30°C or higher, or 35°C or higher, for example, in the range of 25°C to 120°C, 25°C to 100°C, 30°C to 90°C, or 35°C to 80°C.

[0051] 45. The method according to any one of items 1 to 44, wherein the volume of the LWP oil (A) has a 95% boiling point in the range of 700°C or less, preferably 650°C or less, 600°C or less, or 550°C or less, for example, 180°C to 700°C, 250°C to 700°C, 300°C to 650°C, 350°C to 600°C, 380°C to 500°C, or 400°C to 500°C.

[0052] 46. ​​The volume of LWP-type oil (A) measured at 15°C is 0.780~0.850 kg / m³. 3 The method described in any one of items 1 to 45, having a density within the range of [specified range].

[0053] 47. The method according to any one of items 1 to 46, wherein the volume of LWP-based oil (A) has an olefin content of 5% by weight or more, for example, 10% by weight or more, 15% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, or 50% by weight or more.

[0054] 48. The method according to any one of items 1 to 47, wherein the volume of LWP-based oil (A) has an olefin content of 85% by weight or less, for example, 80% by weight or less, 70% by weight or less, or 65% by weight or less.

[0055] 49. The method according to any one of items 1 to 48, wherein the chlorine content by volume of LWP oil (A) is in the range of 1 ppm by weight to 4000 ppm by weight, for example, 100 ppm by weight to 4000 ppm by weight, or 300 ppm by weight to 4000 ppm by weight.

[0056] 50. The method according to any one of items 1 to 49, wherein the separation (4) in step (vi) includes liquid-liquid separation.

[0057] 51. The method according to any one of items 1 to 50, wherein the separation (4) in step (vi) includes separation based on gravity, such as decantation, or separation by centrifugation.

[0058] 52. The method according to any one of items 1 to 51, wherein the phase separation (4) in step (vi) is carried out at a temperature in the range of 15°C to 200°C, preferably 30°C to 200°C, 40°C to 175°C, 50°C to 150°C or 60°C to 140°C.

[0059] 53. The method according to any one of items 1 to 52, wherein the phase separation (4) in step (vi) is carried out at a pressure in the range of 1 bar (absolute) to 15 bar (absolute), preferably 2 bar (absolute) to 15 bar (absolute).

[0060] 54. The method according to any one of items 1 to 53, further comprising subjecting at least a portion of the second aqueous phase volume (I) to evaporation.

[0061] 55. The method according to any one of items 1 to 54, further comprising (5) adjusting the pH of the second aqueous phase volume (I) to pH 9.5 or higher, preferably 10.0 or higher, or 10.5 or higher.

[0062] 56. The method according to any one of items 1 to 55, further comprising (5) adjusting the pH of the second aqueous phase volume (I) to pH 11.0 or higher, preferably 11.5 or higher, or 12.0 or higher.

[0063] 57. The method according to item 55 or 56, wherein the pH is adjusted by adding an alkaline medium (L).

[0064] 58. The method according to item 57, wherein the alkaline medium (L) for adjusting the pH of the second aqueous phase volume (5) is an aqueous solution of a metal hydroxide.

[0065] 59. The method according to item 57 or 58, wherein the alkaline medium (L) for adjusting the pH of the second aqueous phase volume (5) is an aqueous solution of a metal hydroxide, and the metal hydroxide is selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

[0066] 60. The method according to any one of items 57 to 59, wherein the alkaline medium (L) for adjusting the pH of the second aqueous phase volume (5) is an aqueous solution of a metal hydroxide, and the metal hydroxide is selected from the group consisting of KOH, NaOH, LiOH, Ca(OH)2, Mg(OH)2, RbOH, Sr(OH)2 and Ba(OH)2.

[0067] 61. The method according to any one of items 57-60, wherein the alkaline medium (L) for adjusting the pH of the second aqueous phase volume (5) is an aqueous solution of a metal hydroxide, and the metal hydroxide is NaOH.

[0068] 62. The method according to any one of items 57 to 61, wherein the alkaline medium (L) for adjusting the pH of the second aqueous phase volume (5) contains an amount of alkaline substance in the range of 1% to 100% by weight, for example, 1% to 99% by weight, 2% to 90% by weight, 5% to 70% by weight, 10% to 65% by weight, 15% to 60% by weight, or 20% to 55.0% by weight.

[0069] 63. The method according to any one of items 57 to 62, wherein the alkaline medium (L) for adjusting the pH of the second aqueous phase volume (5) comprises at least 1% by weight of water, preferably at least 10% by weight of water, at least 15% by weight of water, at least 20% by weight of water, or at least 25% by weight of water.

[0070] 64. The method according to any one of items 55 to 63, comprising (5) adjusting the pH and then evaporating at least a portion of the second aqueous phase volume (M) to provide at least one condensate (N) and at least one evaporation residue (P).

[0071] 65. The method of item 64, wherein evaporation (6) is carried out in one, two, or more steps.

[0072] 66. The method according to item 64 or 65, further comprising subjecting at least a portion of at least one condensate (N) to further post-treatment, preferably ammonia removal, such as at least stripping treatment, in particular steam stripping treatment.

[0073] 67. The method according to any one of items 64 to 66, further comprising subjecting at least a portion of at least one condensate (N) to wastewater treatment after an optional further post-treatment.

[0074] 68. The method according to any one of items 1 to 67, wherein the alkaline aqueous medium has a pH of at least 9.5, preferably at least 10.0, at least 10.5, at least 11.0, more preferably at least 12.0, at least 12.5, or at least 13.0.

[0075] 69. The method according to any one of items 1 to 68, wherein the alkaline aqueous medium has a pH in the range of 9.5 to 14.0, 10.0 to 14.0, 11.0 to 14.0, 12.0 to 14.0, 12.5 to 14.0, 13.0 to 14.0, or 13.0 to 13.9.

[0076] 70. The method according to any one of items 1 to 69, further comprising the step of subjecting the isolated first aqueous phase volume (D) of step (iv) to preliminary separation to provide an oil-reduced aqueous phase volume and an oil-enriched aqueous phase volume, wherein at least the oil-enriched aqueous phase volume is sent to step (v) as the first aqueous phase volume (D).

[0077] 71. The method according to item 70, wherein the preliminary separation includes at least one of cooling and centrifugation.

[0078] 72. The method according to item 70 or 71, wherein the preliminary separation includes at least cooling in a heat exchanger and subsequent phase separation.

[0079] 73. The method according to any one of items 70 to 72, wherein the oil-reduced aqueous phase volume is separated as a translucent liquid.

[0080] 74. The method according to any one of items 70-73, wherein the oil-enriched aqueous phase volume is separated as an opaque (turbid / milky white) liquid. [Brief explanation of the drawing]

[0081] [Figure 1] This is a flowchart showing one embodiment of the method and system of the present invention. [Figure 2] This flowchart shows one embodiment of wastewater handling. [Modes for carrying out the invention]

[0082] Liquefied waste plastics (LWP) (by volume), such as the pyrolysis products of recovered waste plastics (e.g., pyrolysis products of recovered consumer plastics), contain large and varied amounts of contaminants that may be harmful in downstream processes. Such contaminants include, among others, halogens (e.g., chlorine and bromine) derived from halogenated plastics (e.g., PVC and PTFE) or flame retardants, sulfur derived from crosslinking agents of rubbery polymers (e.g., in end-of-life tires), and metal or metalloid (e.g., Si, Al) contaminants derived from composite materials and additives (e.g., films coated with metals or metal compounds, end-of-life tires, or plastic processing aids). These contaminants may exist in elemental form, ionic form, or as part of organic or inorganic compounds.

[0083] These impurities should be removed before the LWP is subjected to further processing. The inventors of the present invention have previously proposed a method comprising contacting (crude) LWP with an alkaline aqueous medium at high temperature (hereinafter also referred to as heat treatment (HT) processing), followed by phase separation. HT processing is sometimes called “reactive extraction.” That is, the inventors have found that a suitable combination of high pH (of the alkaline aqueous medium) and heat (in the process of HT processing) results in a reaction of impurities (e.g., organically bonded impurities), and therefore provides more benefits than simple “water washing” or “neutralization treatment” of the LWP. In particular, the reactive extraction process is useful for removing silicon compounds (organosilicon compounds are especially problematic), as well as at least some chlorine compounds (in organic and inorganic forms) and nitrogen-containing compounds. That is, reactive extraction converts (organic) impurities into water-soluble forms so that they can be removed (separated) together with the aqueous phase.

[0084] The present invention is based on the above-mentioned HT processing and provides an improved post-treatment of the aqueous phase (hereinafter referred to as the "first aqueous phase volume") resulting from the HT processing after phase separation. Specifically, the inventors have surprisingly found that a considerable amount of LWP is "lost" along with the aqueous phase, leading to both yield problems and wastewater post-treatment problems. The inventors have surprisingly found that by acidifying the first aqueous phase (volume) to a pH of 9.0 or lower, it becomes possible to separate an additional amount (volume) of the oil phase in the subsequent (second) phase separation step. Therefore, the yield of the final LWP increases, the purity of the aqueous phase increases (total organic carbon content decreases), and thus post-treatment becomes easier. Based on this finding, the inventors have completed the present invention.

[0085] In the context of this invention, liquefied waste plastic (LWP) means the product discharge from a liquefaction process that includes at least the depolymerization of waste plastic. Therefore, LWP is a material obtained by depolymerizing waste plastic. LWP may also be called polymer waste oil or liquefied waste plastic. Furthermore, whenever LWP (used as an abbreviation for "LWP oil") is referred to, it shall naturally include "volume of liquefied waste plastic oil." The same applies to the (volume) of the alkaline aqueous medium, the (volume) of the first / second aqueous phase, the (volume) of the first / second oil phase, the (volume) of the pH adjustment (aqueous) phase, etc.

[0086] Waste plastics may originate from any source, such as (recycled or recovered) consumer plastics, (recycled or recovered) industrial plastics, or (recycled or recovered) end-of-life tires (ELT). In particular, the term waste plastics refers to organic polymer materials that are no longer suitable for use or have been discarded for other reasons. More specifically, waste plastics may refer to end-of-life tires (including naturally occurring rubber), recovered consumer plastics (consumer plastics refer to any organic polymer materials in consumer goods, even if they do not possess “plastic” properties of their own), recovered industrial polymer waste, or any combination thereof. In the sense of the present invention, the terms waste plastics or “polymers” generally do not include purely inorganic materials (otherwise sometimes called inorganic polymers). Polymers in waste plastics may be of natural and / or synthetic origin, and may be based on renewable and / or fossil raw materials. Collected consumer plastics or waste plastics that are municipal waste are generally considered to have undergone mechanical sorting, and therefore cellulosic materials (paper, cardboard) and metals may be present in low-quality waste plastic supplies and should be considered contaminants.

[0087] The liquefaction process is typically carried out at high temperatures, preferably under non-oxidative conditions. The liquefaction process may also be carried out under high pressure. The liquefaction process may be carried out in the presence of a catalyst. The waste products from the liquefaction process may be used directly as liquefied waste plastics, or they may be subjected to fractional distillation (or separation) to provide fractions (or separated liquids) of the waste products as liquefied waste plastics. For example, LWP may be hydrothermally liquefied (HTL) oil or a fraction thereof. Similarly, multiple fractional distillations may be performed. Furthermore, two or more liquefaction process waste products and / or fractions thereof may be combined to obtain LWP. These waste products and / or fractions may have the same or similar boiling point ranges, or they may have different boiling point ranges. In this context, fractional distillation includes fractional distillation and / or fractional evaporation and / or fractional condensation.

[0088] In addition to liquid (NTP) hydrocarbons, i.e., hydrocarbons that are liquid at room temperature and pressure (NTP, 20°C, 101.325 absolute kPa), typical product emissions from the liquefaction process include gaseous (NTP) hydrocarbons and hydrocarbons that are waxy or solid in NTP but become liquid when heated, for example, to 80°C.

[0089] In the context of this disclosure, depolymerization of waste plastics means typically decomposing or degrading the polymer backbone of the waste plastic, typically at least thermally, to the extent that it produces polymer and / or oligomer species that have a lower molecular weight compared to the starting waste plastic, but still contain at least liquid (NTP) hydrocarbons. In other words, as used herein, liquefied waste plastics do not encompass plastics in liquid form obtained only by melting or dissolution in a solvent, because such liquid forms of plastics do not involve sufficient cleavage of the polymer backbone, nor do they encompass waste plastics that have been completely depolymerized to the monomer level and are therefore, for example, in gaseous (NTP) form. Depolymerization of waste plastics may also involve cleavage of covalently bonded heteroatoms such as O, S, and N from heteroatom-containing compounds that are optionally present.

[0090] First, each type of waste plastic in the waste plastic or mixed waste plastic to be liquefied is usually in a solid state and typically has a melting point in the range of 100°C or higher, as measured by DSC, as described by Larsen et al. ("Determining the PE fraction in recycled PP", Polymer Testing, Vol. 96, April 2021, 107058). However, the waste plastic or each type of waste plastic may be at least partially melted before and / or during depolymerization.

[0091] Solid waste plastics may contain a variety of further components, such as fillers, pigments, printing inks, flame retardants, stabilizers, antioxidants, plasticizers, lubricants, labels, metals, paper, cardboard, cellulosic fibers, glass fibers, and even additives and reinforcing materials including sand or other contaminants. Some of these further components may be removed from solid waste plastics, molten waste plastics, and / or liquefied waste plastics using commonly known methods, as needed.

[0092] Preferably, the (solid) waste plastic that will be subjected to the liquefaction process (depolymerization) and is therefore the base material for LWP (LWP-based oil) has an oxygen content of 15% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less, of the total weight of the (solid) waste plastic. In other words, LWP-based oil is preferably derived from waste plastic having the oxygen content described above. The oxygen content may be 0% by weight, and preferably in the range of 0% to 15% by weight or 0% to 10% by weight. The oxygen content (by weight) can be determined by the difference using the formula 100% by weight - (CHN content + ash content), where the CHN content refers to the total content of carbon, hydrogen, and nitrogen as determined according to ASTM D5291, and the ash content refers to the ash content as determined according to ASTM D482 / EN15403.

[0093] In this disclosure, all embodiments of the present invention (e.g., all preferred values ​​and / or ranges within the embodiments and even from the examples) may be combined to give (preferred) embodiments, unless otherwise specified, or unless such combinations do not result in a conflict.

[0094] LWP preferably mainly consists of hydrocarbons, typically in an amount of more than 50% by weight relative to the total weight of the LWP. Typically, LWP contains two or more hydrocarbon species selected from paraffins, olefins, naphthenes, and aromatics. The composition of LWP may vary depending, for example, on the composition of the waste plastic, the type and conditions of the liquefaction process. Furthermore, combinations of impurities associated with various types of waste plastics and recovered waste may result in the presence of impurities in the LWP, including varying amounts of silicon, sulfur, nitrogen, halogens, and oxygen-related substances.

[0095] The LWP (LWP-based oil) of the present invention is derived from (crude) LWP, and may be, for example, crude LWP (i.e., the liquid fraction that comes directly from the liquefaction process) or a fraction of crude LWP.

[0096] LWP oils specifically refer to oils or oil-like products obtained from the liquefaction of (solid) waste plastics using non-oxidative thermal depolymerization or thermal catalytic depolymerization (followed by optional subsequent fractional distillation). In other words, LWP oils are sometimes called "depolymerized polymer waste" or "liquefied polymer waste."

[0097] The liquefaction method is not particularly limited as long as it is a depolymerization process, and examples include thermal depolymerization processes such as thermal decomposition of waste plastics (e.g., fast thermal decomposition) or hydrothermal liquefaction of waste plastics.

[0098] Furthermore, in this invention, the term "pH" refers to the pH value of an aqueous medium measured at 20°C (or converted to a value corresponding to measurement at 20°C). pH can be measured according to the Finnish standard SFS 3021.

[0099] The present invention relates to a method for treating liquefied waste plastics (LWP), the method comprising: (i) providing a volume of liquefied waste plastic oil; (ii) subjecting this together with a volume of alkaline aqueous medium to a heat treatment to provide a volume of heat-treated mixture; (iii) separating the phases to provide at least a first aqueous phase volume and a first oil phase volume; (iv) isolating (at least) the first aqueous phase volume; (v) adjusting (reducing) its pH to 9.0 or less by adding an acidic medium (for example, by mixing the first aqueous phase volume with the acidic medium); and subsequently, (vi) separating the obtained pH-adjusted volume into at least a second oil phase volume and a second aqueous phase volume. In the phase separation, the aqueous phase is usually the heavy phase and the oil phase is usually the light phase.

[0100] The method of the present invention can increase the total yield of purified LWP, reduce the TOC content (second aqueous phase volume) of wastewater, and thus facilitate further post-treatment.

[0101] The alkaline aqueous medium preferably has a pH of 9.5 or higher, for example, 10.0 or higher, 10.5 or higher, or 11.0 or higher. More preferably, the alkaline aqueous medium has a pH of 12.0 or higher, 12.5 or higher, or 13.0 or higher. For example, the pH may be in the range of 9.5 to 14.0, 10.0 to 14.0, 11.0 to 14.0, 12.0 to 14.0, 12.5 to 14.0, 13.0 to 14.0, or 13.0 to 13.9. Alkaline aqueous mediums, especially strongly alkaline aqueous mediums, have been shown to have very good efficiency in removing contaminants (impurities), particularly with respect to problematic contaminants such as silicon (e.g., organosilicon compounds). Furthermore, when using a strongly alkaline aqueous medium (for example, having a pH of 12.0 or higher, 12.5 or higher, or 13.0 or higher), good impurity removal can be achieved while simultaneously keeping the water-to-oil ratio low so that almost no contaminating water is generated.

[0102] The alkaline aqueous medium (hereinafter sometimes simply referred to as the aqueous medium) may be an aqueous solution of an alkaline substance. This means that the alkaline substance is dissolved in the aqueous medium, i.e., the aqueous medium contains the alkaline substance in a dissolved form. The aqueous medium may be an aqueous solution of a metal hydroxide in particular (the alkaline substance may be a metal hydroxide). The metal hydroxide is preferably selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides. In particular, the aqueous medium (B) may be an aqueous solution of a metal hydroxide, and the metal hydroxide is selected from the group consisting of KOH, NaOH, LiOH, Ca(OH)2, Mg(OH)2, RbOH, Sr(OH)2, and Ba(OH)2. The metal hydroxide is preferably NaOH.

[0103] Preferably, the aqueous medium contains an amount of alkaline substance (such as a metal hydroxide) in the range of 0.5% to 15.0% by weight, for example, 0.5% to 10.0% by weight, 1.0% to 6.0% by weight, or 1.5% to 6.0% by weight. The aqueous medium (B) may contain at least 50% by weight of water, preferably at least 70% by weight of water, more preferably at least 85% by weight of water, at least 90% by weight of water, or at least 95% by weight of water.

[0104] Preferably, the total amount of alkaline substance and water in the alkaline aqueous medium is 90% by weight or more (90-100% by weight), more preferably 95% by weight or more, or 99% by weight or more (relative to the alkaline aqueous medium as a whole).

[0105] While such ranges have been shown to be useful, it is also important that the concentration of the alkaline substance in the heat treatment remains within a certain range. That is, if heating is achieved at least partially by steam injection, as will be discussed later, this inevitably leads to the addition of water, and thus dilutes the alkaline substance in the aqueous medium to some extent. Therefore, this method preferably takes into account water added in the form of steam. This can be achieved by any suitable means, for example, by calculating the concentration of the alkaline substance considering the volume of steam added and the volume of aqueous medium added. The amount added (e.g., steam for heating) can be calculated or obtained from tabular values ​​(or both).

[0106] In the present invention, it is preferable that the aqueous component of the mixture subjected to heat treatment has a pH of 9.5 or higher, for example, 10.0 or higher, 11.0 or higher, 12.0 or higher, or 13.0 or higher, or a pH in the range of 9.5 to 14.0, 10.0 to 14.0, 11.0 to 13.9, 12.0 to 13.9, or 13.0 to 13.9.

[0107] The water-to-oil ratio (water-to-oil ratio = amount of "water" / amount of "oil") between the volume of alkaline aqueous medium in the heat-treated mixture and the liquefied waste plastic is in the range of 0.1 to 1.4 by weight, preferably in the range of 0.2 to 1.0, for example, 0.2 to 0.7. In this context, "water" refers to the total amount of alkaline aqueous medium (including the mixed aqueous medium and optionally water from injected steam), and "oil" refers to the volume of LWP. The water-to-oil ratio may also be calculated from the feed (mixing / injection) volume.

[0108] The heat treatment in step (ii) is preferably carried out at a temperature of 150°C or higher, more preferably 180°C or higher, for example, 200°C or higher, 220°C or higher, or 240°C or higher. The heat treatment may also be carried out at a temperature of 450°C or lower, preferably 400°C or lower, 350°C or lower, 320°C or lower, or 300°C or lower. Thus, the heat treatment may be carried out at a temperature in the range of 150°C to 450°C, preferably 180°C to 450°C, 200°C to 400°C, 210°C to 350°C, 220°C to 330°C, 240°C to 320°C, or 260°C to 300°C. Such high temperatures (especially 180°C or higher, and even more so 200°C or higher) have been shown to result in “reactive extraction” rather than mere water washing and / or neutralization of the acidic LWP oil, along with the use of an alkaline aqueous medium. Since the heat treatment is typically carried out at a temperature high enough to observe vapor formation, it is preferably performed under pressurized conditions, the pressure of which may vary depending on the operating conditions. The pressurized conditions are preferably such that the mixture of LWP and aqueous medium is maintained in a liquid state during the heat treatment.

[0109] The heat for the heat treatment in step (ii) may be supplied to a volume of LWP oil, a volume of alkaline aqueous medium (B), and / or a mixture of the volume of LWP oil and the volume of alkaline aqueous medium. The heat may be supplied within the reactor and / or within a heating section as a separate unit (prior to the reactor). The heat is supplied by indirect heating and / or direct heating. Direct heating can be achieved, in particular, by blowing steam (hot steam) into a volume of LWP oil, a volume of alkaline aqueous medium, and / or a mixture of the volume of LWP oil and the volume of alkaline aqueous medium. Direct heating using steam offers the particular benefit of significantly reducing adhesion fouling due to (localized) excessive heat.

[0110] Preferably, the total amount of liquefied waste plastic and alkaline aqueous medium in the material subjected to heat treatment in step (ii) (and therefore in the volume of the heat-treated mixture) is 85-100% by weight, preferably 90-100% by weight, 95-100% by weight, 97-100% by weight, or 99-100% by weight. In other words, it is preferable that the material subjected to heat treatment in step (ii) consists essentially of liquefied waste plastic and alkaline aqueous medium (the latter, in some cases, is assumed to include steam used for heating, even if steam is added only to the LWP). In other words, no significant amount (15% by weight or less, preferably 10% by weight or less, 5% by weight or less, 3% by weight or less, or 1% by weight or less) of co-feeds or additives is desired.

[0111] The method may further include holding (maintaining) the volume of the heat-treated mixture preferably in a reactor (for treatment). The reactor is preferably a tubular reactor. The reactor may be a packed reactor or an unpacked reactor, for example, a packed tubular reactor or an unpacked tubular reactor. The heating for the heat treatment in step (ii) may be carried out in the reactor and / or in a dedicated (separate) heating section(s). The heating step may be carried out both in the heating section and (subsequently or further) in the reactor. Providing a dedicated heating section may facilitate temperature control and handling (as well as integration into an existing process line), while reducing the equipment required for heating in the reactor.

[0112] The residence time of the volume of the heat-treated mixture (such as the residence time in the reactor) is preferably at least 10 minutes, more preferably in the range of 10 to 600 minutes, for example, 10 to 300 minutes, 15 to 180 minutes, 15 to 120 minutes, or 20 to 60 minutes. Residence time can be defined as the time that the volume of the heat-treated mixture is maintained at a high temperature in the reactor.

[0113] The heat treatment step (ii) may include a heating step in which the temperature of the volume of the mixture of LWP-based oil and alkaline aqueous medium is raised from an initial temperature T1 to a temperature T2 by injecting (blowing) steam, thus forming a heated volume of the mixture, and as a result, a volume of heat-treated mixture (C) is obtained. The temperature T2 is preferably 180°C or higher, for example 200°C or higher, 220°C or higher, or 240°C or higher. The temperature T2 is preferably 450°C or lower, or preferably 400°C or lower, 350°C or lower, 320°C or lower, or 300°C or lower. The temperature T2 is appropriately in the range of 180°C to 350°C, for example 200°C to 350°C, 210°C to 350°C, 220°C to 330°C, 240°C to 320°C, or 260°C to 300°C. It has been found that (reaction) temperatures within the above limits enable efficient pretreatment of liquefied waste plastics.

[0114] The method may further include a preheating step before the heat treatment step (ii). In the preheating step, the volume of the mixture is preheated to a temperature T1. Preheating can be achieved in a dedicated (separate) preheating section(s), in a heating section(s), or in a reactor for heat treatment, as long as it is achieved before the heating step. Typically, preheating is performed after mixing the volume of LWP oil (A) and the volume of alkaline aqueous medium (B), but it may be performed partially or completely before such mixing (i.e., preheating the volume of alkaline aqueous medium alone and / or the volume of LWP oil alone).

[0115] The difference between temperature T2 and temperature T1 (T2-T1) may be, for example, 5°C or more, preferably 10°C or more, and may be in the range of 5°C to 300°C, 10°C to 240°C, or 15°C to 200°C.

[0116] The method of the present invention may be carried out in batches (as a batch process) or continuously (also called a continuous flow process). A combination of both, for example, continuous heat treatment, batch or semi-batch phase separation, and continuous pH adjustment and subsequent (second) phase separation are possible.

[0117] As will be apparent to those skilled in the art, the terms “before” or “preceding” (or similar) can be rephrased as “before in time” in batch processes and “upstream” in continuous processes; “after” (or similar) can be rephrased as “after in time” in batch processes and “downstream” in continuous processes; and “volume” (or quantity such as relative amount) can be rephrased as (relative) “batch size” (or “supply amount”) in batch processes and (relative) “flow rate” (or “flow rate ratio”) in continuous processes. The same applies to all expressions used herein.

[0118] The method of the present invention includes a separation step of separating a volume (C) of a heat-treated mixture into an oil phase volume (first oil phase volume) and an aqueous phase volume (first aqueous phase volume). The oil phase volume mainly contains "oil" (i.e., refined LWP), for example, mainly hydrocarbons. The aqueous phase volume mainly contains water, as well as oily materials (dissolved and / or emulsified and / or dispersed organic compounds) and alkaline substances and / or their reaction products. In this regard, the term "mainly" means "at least 50% by weight," for example, at least 60% by weight or at least 70% by weight. The separation is preferably carried out after the volume of the heat-treated mixture has been cooled to a temperature and pressure suitable for separation. Specifically, the phase separation in the separation step of separating the volume of the heat-treated mixture is preferably carried out at a temperature in which the LWP-based oil (A) in the volume (C) of the heat-treated mixture is in liquid form, more preferably 15°C to 200°C, preferably 40°C to 200°C, for example 50°C to 175°C or 60°C to 150°C. Phase separation may be carried out at a pressure in the range of 1 absolute bar to 15 absolute bars, for example, 2 absolute bars to 15 absolute bars. The separation pressure is not particularly important. Most appropriately, the pressure is adjusted so that no or substantially no gas / vapor formation occurs at the separation temperature. The separation temperature is preferably within the above range. The temperature is best selected depending on the LWP oil being refined, and is particularly high enough to maintain the liquid state of the LWP oil (i.e., to avoid solidification or precipitation). Furthermore, higher temperatures can accelerate phase separation as they reduce the viscosity of the liquid being separated. The separation step preferably includes liquid-liquid separation.

[0119] The separation in step (iii) is preferably carried out after giving the volume of the heat-treated mixture sufficient time to react (see residence time above for a useful period) by, for example, maintaining the volume of the heat-treated mixture at or near the heat-treatment temperature.

[0120] The method may further include a step of cooling the volume of the heat-treated mixture. Cooling is particularly preferred to facilitate phase separation. Cooling is performed after the reaction is complete (i.e., after the residence time). For ease of reference, the volume of the heat-treated mixture is still referred to as the "volume of the heat-treated mixture" even after cooling. Cooling (temperature reduction) can also occur in the transfer line or storage container. Phase separation is performed at a temperature below the temperature during heat treatment. Preferably, the method further includes phase separation of the volume of the heat-treated mixture into a first oil volume and a first aqueous volume. The separation step may include gravity-based separation (non-forced separation), such as decantation, or forced separation, such as separation by centrifugation. In other words, separation can be achieved by letting the volume of the heat-treated mixture settle (by natural gravity), or by forcing separation, for example, by centrifugation.

[0121] During the phase separation process, the first aqueous phase is isolated. That is, not only are the phases separated, but there is no longer any contact between the oil phase and the aqueous phase, and for example, both the oil phase and the aqueous phase are extracted separately from the phase separator.

[0122] After isolation, the pH of the first aqueous volume is adjusted to pH 9.0 or less in step (iii) by adding an acidic medium. The pH is preferably adjusted to 8.5 or less, for example, 8.0 or less, 7.5 or less, or 7.0 or less. In other words, the pH of the resulting pH-adjusted volume is preferably within the range described above after adjustment. To avoid excessive use of the acidic medium, the pH of the first aqueous volume is appropriately adjusted to pH 1.5 or higher, preferably 2.0 or higher, more preferably 3.0 or higher, 4.0 or higher, 5.0 or higher, 6.0 or higher, or 7.0 or higher. The pH of the first aqueous volume may be adjusted to a pH in the range of 1.5 to 9.0, preferably 2.0 to 9.0, 3.0 to 9.0, 4.0 to 8.7, 5.0 to 8.5, 6.0 to 8.3, or 7.0 to 8.0.

[0123] The inventors have surprisingly found that by adjusting the first aqueous phase volume to a pH of 9.0 or less, the separation of a significant additional amount of oil phase (second oil phase volume) becomes significantly easier (or possible). The reason for this effect is not fully understood, and it is undesirable to be bound by theory, but it is assumed that some components of the (crude) LWP oil react with the alkaline aqueous medium to yield water-soluble or water-dispersible compounds, some of which may even act as surfactants for emulsifying hydrocarbon compounds (considering that LWP mainly consists of nonpolar hydrocarbon compounds that are expected to be water-insoluble in practice, regardless of pH). Furthermore, it is assumed that such dissolved / dispersed compounds are converted to a water-insoluble form, and / or the dispersion state of the dispersed compounds is destabilized by lowering the pH to 9.0 or less, for example, close to neutral or even acidic. Thus, these compounds can be separated after pH adjustment. The inventors have surprisingly found that a significant amount of oil phase (within the range of several percent of the original LWP oil volume) that would otherwise be lost can be recovered.

[0124] The acidic medium preferably comprises at least one organic acid and / or at least one inorganic acid. Suitable acids are at least one (preferably just one) selected from the group consisting of hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), phosphoric acid (H3PO4), sulfamic acid (H3NSO3), and carboxylic acids.

[0125] The acidic medium may be a solution of an acid. In particular, the acidic medium may be an aqueous solution of an acid. The acid is preferably at least one (more preferably just one) selected from the group consisting of hydrochloric acid (HCl), nitric acid (HNO3), sulfuric acid (H2SO4), phosphoric acid (H3PO4), sulfamic acid (H3NSO3), or carboxylic acid, and preferably at least sulfuric acid or hydrochloric acid. The acid is particularly preferably at least sulfuric acid.

[0126] The acid solution preferably has an acid concentration in the range of 1 to 98% by mass, more preferably 1 to 96% by mass, and more preferably 50 to 70% by mass.

[0127] In a preferred embodiment, the method further includes subjecting the isolated first aqueous phase volume from step (iv) to a preliminary separation to provide an oil-reduced aqueous phase volume and an oil-enriched aqueous phase volume. Typically, no heating occurs between the (first) phase separation and the preliminary separation, but cooling may occur, for example, in a heat exchanger or transfer line. At least the oil-enriched aqueous phase volume (and preferably only the oil-enriched aqueous phase volume) is sent to an acidification step (v) as the first aqueous phase volume for pH adjustment. That is, the inventors have surprisingly found that a portion of the separated aqueous phase (first aqueous phase volume) can be further separated into an aqueous phase that is substantially oil-free (or has a significantly reduced oil content) and an aqueous phase with a significantly increased oil content (oil-enriched aqueous phase). Not intended to be bound by theory, the oil-enriched aqueous phase is assumed to contain mainly water and dispersed or emulsified oil. In other words, this phase separation does not form a separate oil phase and a separate aqueous phase, but rather forms at least an intermediate phase (oil-enriched aqueous phase) that contains substantial amounts of both water and oil.

[0128] Next, this oil-enriched aqueous phase may be subjected to pH adjustment (in this case, referred to as the first aqueous phase used in step (v)). This offers the advantage that significant oil recovery can be achieved with only a small amount of acidic medium required for pH adjustment. Thus, this embodiment offers further improvements in terms of economic and ecological aspects. Furthermore, this procedure is expected to further improve the quality of the second oil phase because the amount of impurities that may return to the oil phase during acidification is minimized.

[0129] While not intended to be theoretically bound, the inventors observed that as the oil-reduced aqueous phase decreases, it becomes more transparent (less opaque), allowing for visual inspection of the progression of phase separation (and thus the decrease in oil content in the volume of the oil-reduced aqueous phase). This transparent (but usually dark) liquid is also called a translucent liquid. Simultaneously, an opaque (cloudy / milky, and sometimes even solid) oil-enriched phase is formed.

[0130] The preliminary separation may include at least one of cooling and centrifugation. The preliminary separation may include both of these, and / or further include other processes. Preferably, the preliminary separation includes at least phase separation after cooling or centrifugation.

[0131] After pH adjustment in step (v), further phase separation is performed in step (vi) using the pH-adjusted (aqueous) volume. The further (second) phase separation results in a second oil phase volume and a second aqueous phase volume. As already stated for the first oil / aqueous phase volume, the oil phase volume mainly contains "oil" (i.e., refined LWP), e.g., mainly hydrocarbons. The aqueous phase volume mainly contains water, as well as oily materials (dissolved and / or emulsified and / or dispersed organic compounds) and alkaline substances and / or their reaction products. Again, the term "mainly" in this respect means "at least 50% by weight," e.g., at least 60% by weight, at least 70% by weight, or at least 80% by weight.

[0132] The residence time of the pH-adjusted volume in the phase separation (in the phase separator) of step (vi) is preferably in the range of 1 minute to 600 minutes, for example, 1 minute to 240 minutes, or 2 minutes to 180 minutes. That is, depending on the pH and temperature, for example, the phase separation may proceed quite quickly spontaneously (or forcibly), or it may take some time. The phase separation in step (vi) preferably includes liquid-liquid separation. The phase separation in step (vi) may include gravity-based separation such as decantation, or separation by centrifugation.

[0133] Preferably, the phase separation in step (vi) is carried out at the same temperature as or lower than the phase separation in step (iii). The phase separation in step (vi) is preferably carried out at temperatures in the range of 15°C to 200°C, for example, 30°C to 200°C, 40°C to 175°C, 50°C to 150°C, or 60°C to 140°C. The phase separation may be carried out at a pressure in the range of 1 (absolute) bar to 15 (absolute) bar, preferably 2 (absolute) bar to 15 (absolute) bar.

[0134] After phase separation in step (iv), the second oil phase volume may be subjected to further washing, for example, water washing.

[0135] The method may further include combining at least a portion (e.g., all) of the second oil phase volume with at least a portion (e.g., all) of the first oil phase volume to provide a combined oil phase volume. In other words, the resulting oil phase volumes can be combined. The method may further include subjecting at least a portion of the combined oil phase volume to a further processing and / or transformation process. The further processing or transformation process may include any known process (or series of processes), including known petrochemical processes such as fractional distillation, cracking (e.g., steam cracking or hydrocracking), finish, and hydrotreatment.

[0136] The method may optionally or additionally include a step of subjecting at least a portion of the second oil phase volume and / or at least a portion of the first oil phase volume to a further processing and / or transformation process. In other words, the oil phases may be further used (or processed) separately, together, or both. Unless otherwise specified, the processing (and use) of the first and / or second oil phase volumes described herein also applies to the first oil phase volume alone, the second oil phase volume alone, and the combined oil phase volumes. Furthermore, such processing (or use) may be performed separately on the first and second oil phase volumes, and only thereafter these (processed) volumes may be optionally combined.

[0137] In one embodiment, the second oil phase volume and the first oil phase volume are subjected separately to cleaning, for example, water cleaning, and then optionally combined.

[0138] The second aqueous phase volume may be further subjected to evaporation to obtain impurity concentrates, residues, and wastewater flow. Depending on local regulations and / or standards, the wastewater flow may be ready for disposal, such as being released into nature. However, in most cases, the wastewater flow is further treated before disposal (e.g., by conventional wastewater treatment) to minimize its environmental impact. Wastewater treatment may include biological purification (microbial treatment), such as bacterial digestion or decomposition of organic materials (organic compounds).

[0139] The first and / or second (preferably second) aqueous volumes may be recycled back into the process (to form part of the alkaline aqueous medium) after optional purification, for example, by recycling to the heat treatment of step (ii). In this case, the recycled aqueous volume (amount) is counted as part of the alkaline aqueous medium (volume), even if it is mixed separately with the LWP.

[0140] The method may further include subjecting at least a portion (e.g., all) of the second aqueous phase volume to evaporation. Evaporation provides at least one condensate (evaporate) and further provides at least one evaporation residue. At least one of the condensates(s) is the aqueous phase volume (purified water). The majority of impurities are concentrated in the evaporation residue.

[0141] Evaporation may be suitable for further separating oily components and / or other impurities from the second aqueous phase volume. In any case, evaporation is suitable for providing further purified water (which, depending on the use case, is more suitable for wastewater treatment or direct use as "fresh" water), although the evaporation residue typically contains at least inorganic compounds (such as residual alkaline or acidic substances or their reaction products) and high-boiling point reaction products of LWP.

[0142] The inventors have surprisingly found that evaporation of the second aqueous phase volume obtained immediately after phase separation in step (vi) (and therefore having a pH of 9.0 or less, and often near neutral or even acidic) can result in the significant presence of organic compounds in the purified water (condensate). The reason for this phenomenon is not fully understood, and it is undesirable to be bound by theory, but for example, carboxylic acids and / or phenols present in protonated forms in the second aqueous phase volume are assumed to evaporate under evaporation conditions.

[0143] Next, the inventors found that adjusting the pH of the second aqueous phase volume to a basic pH, more specifically 9.5 or higher, preferably 10.0 or higher, or 10.5 or higher, most appropriately 11.0 or higher, for example 11.5 or higher, or 12.0 or higher, significantly reduces the TOC (total organic carbon) in the purified water (evaporated product). Therefore, such adjustment of the pH of the second aqueous phase volume is preferable, especially when the second aqueous phase is subsequently subjected to evaporation.

[0144] In this step (pH adjustment of the second aqueous phase volume), the pH may be adjusted by adding an alkaline medium. The alkaline medium may be an aqueous solution of a metal hydroxide. The alkaline medium may be an aqueous solution of a metal hydroxide, and this metal hydroxide may be selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides. The alkaline medium may be an aqueous solution of a metal hydroxide. The metal hydroxide may be selected from the group consisting of KOH, NaOH, LiOH, Ca(OH)2, Mg(OH)2, RbOH, Sr(OH)2, and Ba(OH)2. Specifically, the alkaline medium may be an aqueous solution of NaOH.

[0145] The alkaline medium (used for pH adjustment of the second aqueous phase volume) preferably contains an amount of alkaline substance in the range of 1% to 100% by weight, for example, 1% to 99% by weight, 2% to 90% by weight, 5% to 70% by weight, 10% to 65% by weight, 15% to 60% by weight, or 20% to 55% by weight. Preferably, the concentration of alkaline substance in the alkaline medium in this step is higher than the concentration of alkaline substance in the alkaline aqueous medium used in step (ii), in order to ensure easy pH adjustment and considering that precise adjustment in this step is not important. For example, the alkaline medium contains at least 1% by weight of water, preferably at least 10% by weight of water, at least 15% by weight of water, at least 20% by weight of water, or at least 25% by weight of water. Preferably, the total amount of alkaline substance and water in the alkaline medium used to adjust the pH of the second aqueous phase volume is 90% by weight or more (90-100% by weight), more preferably 95% by weight or more, or 99% by weight or more (relative to the alkaline aqueous medium as a whole). Most appropriately, stirring is performed during and / or after pH adjustment.

[0146] The method preferably involves adjusting the pH and then evaporating at least a portion of the second aqueous phase volume to provide at least one condensate and at least one evaporation residue. Evaporation may be carried out in one, two, or more stages. Preferably, at least a portion of the at least one condensate is subjected to further post-treatment. Further post-treatment may include at least ammonia removal, preferably stripping, and especially steam stripping. Stripping is particularly suitable for removing ammonia or amines.

[0147] At least a portion of at least one condensate (purified water) may be sent to wastewater treatment after optional further post-treatment.

[0148] The liquefied waste plastic oil, which is the feed to be (pre)treated by the method of the present invention, may have a 5% boiling point of 25°C or higher, preferably 30°C or higher, or 35°C or higher, for example, in the range of 25°C to 120°C, 25°C to 100°C, 30°C to 90°C, or 35°C to 80°C. The liquefied waste plastic oil may have a 95% boiling point of 700°C or lower, preferably 650°C or lower, 600°C or lower, or 550°C or lower, for example, in the range of 180°C to 700°C, 250°C to 700°C, 300°C to 650°C, 350°C to 600°C, 380°C to 500°C, or 400°C to 500°C. The LWP may be crude LWP or a fraction thereof.

[0149] LWP was measured at 15°C and was 0.780-0.850 kg / m³. 3 LWP may have a density in the range of 5% by weight or more, for example, 10% by weight or more, 15% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, or 50% by weight or more of olefins. LWP may have an olefin content of 85% by weight or less, for example, 80% by weight or less, 70% by weight or less, or 65% by weight or less. Such olefin content is typical for thermally produced LWP (e.g., pyrolysis oil or HTL oil), but can vary depending on the depolymerization temperature. The chlorine content of LWP may be in the range of 1 ppm by weight to 4000 ppm by weight, for example, 100 ppm by weight to 4000 ppm by weight, or 300 ppm by weight to 4000 ppm by weight.

[0150] Preferred embodiments of the present invention will be briefly described below with reference to the drawings.

[0151] Figure 1 shows a flowchart of the base process of the present invention. In this embodiment, a volume of liquefied waste plastic oil (A) and a volume of alkaline aqueous medium (B) are subjected to heat treatment (1). The heat treatment may be carried out in a reactor. After completion, the volume of the heat-treated mixture obtained (C) is sent to phase separation (2) to obtain a first aqueous phase volume (D) and a first oil phase volume (E). The first oil phase volume (E) may be used as is (as purified LWP), as shown in Figure 1, or it may be combined with a second oil phase volume (H) obtained later. Separation and isolation of the first aqueous phase volume (D) can be achieved by a separator. The isolated first aqueous phase volume (D) is subjected to pH adjustment (3), and the pH is adjusted to pH 9.0 or less by adding an acidic medium (F) to the first aqueous phase volume (D). The resulting pH-adjusted volume (G) is sent to a further phase separation (4) to provide a second aqueous phase volume (I) and a second oil phase volume (H). As shown in Figure 1, the second oil phase volume (H) may be combined with the first oil phase volume (E) to provide a combined oil phase volume (K).

[0152] Figure 2 shows a further post-treatment procedure in a preferred embodiment of the present invention. In this embodiment, the second aqueous phase volume (I) resulting from phase separation (4) is subjected to pH adjustment (5) by adding an alkaline medium (L). The second aqueous phase (M) obtained after pH adjustment is then evaporated to provide a condensate (purified water, N) and an evaporation residue (P). The residue (P) may be discarded or incinerated (not shown). [Examples]

[0153] The present invention will be further described by example below. The examples represent preferred embodiments of the present invention and may use numerical values ​​for specific process steps, which may be combined with values ​​or ranges disclosed in the specification or claims to generate more limited (e.g., preferred) ranges. However, it should be understood that the present invention is defined by the appended claims and is not limited to the examples illustrated.

[0154] Example 1 LWP samples were heat-treated with an aqueous NaOH solution in a continuous flow tubular reactor system (test reactor). The reactor had an inner diameter of 23 mm and an effective capacity of approximately 325 ml. The reactor was a packed reactor containing a woven steel wire matrix (200 micrometer wire) to facilitate the dispersion / mixing of the LWP-alkaline water mixture. The conditions for the test run are shown in the table below. The absolute amount of NaOH (flow rate and concentration) was set so that the pH value of the first aqueous phase after the heat treatment process and phase separation was at least 12. [Table 1]

[0155] After leaving the reactor, the discharge flow (volume of heat-treated mixture) was cooled and reduced to 2.5 bar (gauge). The discharge flow was then directed to a vertical decanter (42 mm in diameter, 500 mm in height) for phase separation. The decanter had two outlets: one for removing the spent NaOH solution (heavy phase, volume of the first aqueous phase) at the bottom of the decanter, and the other (350 mm from the bottom) for removing the product LWP (light phase, volume of the first oil phase). The levels of both liquid phases could be set independently and were controlled by a combination of control valves and level / interface measurements within the decanter. The pH in the continuous decanter heavy phase (aqueous phase) flow was approximately pH 13. The residence time for phase separation within the decanter was an average of 1 hour. In this example, the decanter was operated continuously for 12 hours at a temperature of 100°C and a pressure of 2 bar (gauge). To maintain the desired level for the heavy phase, the average runoff during the 12-hour experiment was approximately 60 g / hour (heavy phase). The water content of the light phase was measured to be an average of 0.87 wt%. This resulted in a calculated LWP yield loss of approximately 5.46 wt% to the heavy phase (first aqueous phase volume).

[0156] After the separation test run was completed, a 200g sample of the first aqueous phase volume was taken from the integrated aqueous phase recovered during the test run (approximately 12 hours), placed in a 500ml glass container, stirred using magnetic stirring, and heated to 80°C. The pH of this sample was then adjusted to approximately 8.9 over 5 minutes by the dropwise addition of 50 wt% sulfuric acid. Subsequently, 10 wt% sulfuric acid was added over 5 minutes until a change in color / appearance (from opaque yellowish to translucent / transparent brown) was observed at approximately pH 7.4. The neutralized mixture was then allowed to settle, and spontaneous phase separation was performed for 60 minutes (gravity sedimentation) to ensure complete separation. The amount of oil separated from the 200g sample was approximately 42.4g.

[0157] After allowing the acidified mixture to settle for 60 minutes, the water content of the light phase (second oil phase volume) was analyzed at 30.1 wt%. The overall yield of the treated LWP from the process increased from its original value of 94.5 wt% (after the first separation and before acidification) to approximately 99.7 wt% (after acidification and the second separation).

[0158] While this value may not be 100% accurate due to the small sample size of this test run, it is clear that the method of the present invention provides a significant increase in yield and, as a result, an aqueous phase with a significantly reduced TOC (total organic carbon) content.

[0159] Example 2 To evaluate preferred embodiments of the present invention, a test run was performed in a pilot plant. 149 kg of LWP and 45 kg of 2 wt% NaOH aqueous solution were transferred to a 500 liter mixed batch reactor vessel. The reactor was packed to approximately 46 vol%. The mixture was heated to 240°C and then maintained at that temperature for 30 minutes. The reactor pressure at 240°C was approximately 41 bar (g). After the heat treatment, the reactor mixture was cooled to approximately 70°C. After reaching 70°C, mixing was stopped, and the light phase (first oil phase) and heavy phase (first aqueous phase) were separated and isolated by gravity.

[0160] The pH of the first aqueous phase volume thus produced was adjusted to approximately 8 using 50% by weight sulfuric acid. The mixture was subjected to spontaneous (gravity) phase separation, and the precipitated oil was recovered or removed from the aqueous solution.

[0161] A portion of the first aqueous phase, which was nearly neutral (pH approximately 8), was directly subjected to evaporation according to the procedure described below. For the second portion, the pH was adjusted to approximately 12 using a 50 wt% NaOH aqueous solution before evaporation.

[0162] Both evaporation tests were performed in a 10-liter rotary evaporator at a constant pressure of 200 mbar (absolute). The condensates were collected in three stages, and each sample was separately analyzed for total organic carbon (TOC, SFSEN1484), chemical oxygen demand (COD, ISO15705), and phenol content (ISO14402) using the respective standards.

[0163] Table 2 below shows the results from an experiment where the pH value of the evaporated feed (second aqueous phase volume) was 8. In this evaporation, the yield of the evaporated residue was 5% by weight of the original feed. [Table 2]

[0164] Table 3 below shows the results from an experiment where the pH value of the evaporated feed (second aqueous phase volume after pH adjustment) was approximately 13. [Table 3]

[0165] Comparing the results, it can be clearly observed that the TOC, COD, and phenol concentrations in the condensate obtained with the pH-adjusted second aqueous phase volume were significantly lower than those obtained using the second aqueous phase volume without pH adjustment. In other words, when evaporating the second aqueous phase volume from a neutralized LWP pretreatment for improved oil recovery, a better quality condensate can be obtained after readjusting the pH value of the solution back to the basic conditions before evaporation, thus providing further benefits to the present invention.

Claims

1. A method for processing liquefied waste plastics (LWP), (i) A step of providing a volume of liquefied waste plastic oil (A), (ii) A step of subjecting the aforementioned volume of LWP oil (A) together with the volume of alkaline aqueous medium (B) to a heat treatment (1) to provide a heat-treated mixture volume (C), (iii) A step (2) of separating the volume (C) of the heat-treated mixture into at least two separated phase volumes (D, E), wherein one separated phase volume is a first aqueous phase volume (D) and the other separated phase volume is a first oil phase volume (E), (iv) Step (2) to isolate the first aqueous phase volume (D), (v) A step of forming a pH-adjusted volume (G) by adding an acidic medium (F) to the first aqueous phase volume (D) to adjust the pH of the first aqueous phase volume (D) to pH 9.0 or less (3), (vi) A step (4) of separating the pH adjustment volume (G) into at least two separated phase volumes (H, I), wherein one separated phase volume is a second aqueous phase volume (I) and the other separated phase volume is a second oil phase volume (H), Methods that include...

2. The acidic medium (F) is hydrochloric acid (HCl), nitric acid (HNO) ３ ), sulfuric acid (H ２ SO ４ ), phosphoric acid (H ３ PO ４ ), sulfamic acid (H ３ NSO ３ The method according to claim 1, comprising an organic acid such as a carboxylic acid and / or an inorganic acid.

3. The method according to claim 1 or 2, wherein the acidic medium (F) is a solution of an acid, preferably an aqueous solution of an acid.

4. The acid is hydrochloric acid (HCl), nitric acid (HNO ３ ), sulfuric acid (H ２ SO ４ ), phosphoric acid (H ３ PO ４ ), sulfamic acid (H ３ NSO ３ ), or a carboxylic acid, which is at least one selected from the group consisting of, preferably at least sulfuric acid or hydrochloric acid, the method according to claim 3.

5. The method according to claim 3 or 4, wherein the solution of the acid has a concentration of 1 to 98% by mass, preferably 1 to 96% by mass, and more preferably 50 to 70% by mass.

6. The method according to any one of claims 1 to 5, wherein the phase separation (2) in step (iii) is carried out at a temperature in the range of 15°C to 200°C, preferably 40°C to 200°C, 50°C to 175°C, or 60°C to 150°C.

7. The method according to any one of claims 1 to 6, wherein the first oil phase volume (E) and / or the second oil phase volume (H) are further subjected to washing, preferably water washing.

8. The method according to any one of claims 1 to 7, wherein the pH of the first aqueous volume (D) is adjusted in step (iii) to a pH in the range of 1.5 to 9.0, preferably 2.0 to 9.0, more preferably 3.0 to 9.0, 4.0 to 8.7, 5.0 to 8.5, 6.0 to 8.3, or 7.0 to 8.

0.

9. The method according to any one of claims 1 to 8, wherein the alkaline aqueous medium (B) is an aqueous solution of a metal hydroxide, and the metal hydroxide is selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

10. The method according to any one of claims 1 to 9, wherein the water-oil ratio between the volume of the alkaline aqueous medium (B) and the volume of the liquefied waste plastic oil (A) in the heat treatment (1) of step (ii) is in the range of 0.1 to 1.4 by weight, preferably in the range of 0.2 to 1.0, for example, 0.2 to 0.

7.

11. The method according to any one of claims 1 to 10, wherein the heat treatment (1) in step (ii) is performed at a temperature in the range of 150°C to 450°C, preferably 180°C to 450°C, 200°C to 400°C, 210°C to 350°C, 220°C to 330°C, 240°C to 320°C, or 260°C to 300°C.

12. The method according to any one of claims 1 to 11, further comprising a step (5) of adjusting the pH of the second aqueous phase volume (I) to pH 9.5 or higher, preferably 10.0 or higher, or 10.5 or higher, and preferably a step (6) of evaporating at least a portion of the second aqueous phase volume (M) after the step (5) of adjusting the pH to provide at least one condensate (N) and at least one evaporation residue (P).

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