FI130739B1

FI130739B1 - Improved heating concept for treatment of liquefied waste plastic

Info

Publication number: FI130739B1
Application number: FI20226186A
Authority: FI
Inventors: Ville Paasikallio; Antti Pasanen; Mathijs Pelsma; Saga Suntio
Original assignee: Neste Oyj
Priority date: 2022-12-30
Filing date: 2022-12-30
Publication date: 2024-02-21
Also published as: FI20226186A1; WO2024141698A1

Abstract

Disclosed is an improved heating concept in treating liquefied waste plastics (LWP). The method comprises the steps of providing a volume of the liquefied waste plastics (A) and a volume of an aqueous medium (B), admixing said volume of the liquefied waste plastics (A) and said volume of the aqueous medium (B) to form an admixture volume (C), and heating the admixture volume (C) by injecting steam (D) into said admixture volume (C) to form a heated admixture volume (E).

Description

IMPROVED HEATING CONCEPT FOR TREATMENT OF LIQUEFIED

WASTE PLASTIC

Technical Field

The present invention relates to improvements in the heating concept of liquefied waste plastic treatment. More specifically, the invention relates to an improved method of treating crude (untreated) liquefied waste plastics with an aqueous medium at elevated temperature.

Background of the Invention

In the conventional method of providing heat to streams in chemical processing, heat exchangers are relied upon with the existing apparatuses.

In particular, the concerned material can be heated by heat exchangers as this provides an easy setup of apparatus without the need of further modifications.

While such prior art technique is a convenient method which can be easily integrated into existing procedures, the heat exchangers need to have a very high temperature and/or surface area in order to transfer the heat to the process stream.

The inventors found that fouling in the treatment of crude liquefied plastics occurs mainly in the heat exchangers and concluded that the high surface temperatures of the heat exchangers is one reason for fouling. & Further, WO 2020/016400 A1 discloses a method of purifying a recycled or a renewable organic material. US 2022235276 A1 discloses a method for = preparing fuel components from waste pyrolysis oil. CN 115353904 A ? discloses a method and device for liquefying plastic garbage to prepare oil & 30 through a superheated steam system. 2

N Brief description of drawings & FIG. 1 is a flow chart showing an embodiment of the method and system of the present invention.

FIG. 2A-2C are flow charts showing embodiments of the method and system of the present invention, wherein the steam injection unit is provided within (as a part of) the reactor.

FIG. 3A and 3B are flow charts showing embodiments of the method and system of the present invention, wherein mixing unit, steam injection unit and reactor are combined in a combined unit.

FIG. 4 is a flow chart showing an embodiment of the method and system of the present invention, wherein mixing unit, steam injection unit, reactor and separator are combined in a combined unit.

FIG. 5A and 5B are a flow charts showing embodiments of the method and system of the present invention, in which the heating section is provided in the mixing unit (FIG. 5A, 5B), in a heating section preceding the reactor (FIG. 5B) and/or in the reactor (FIG. 5A).

Brief description of the invention

The present invention was made in view of the above-mentioned problems and it is an object of the present invention to provide an improved heating concept for treatment of liquefied waste plastics.

The problem underlying the invention is solved by the subject-matters set forth in the independent claims. Further beneficial developments are set forth in dependent claims.

In brief, the present invention relates to one or more of the following items:

Q 25 < 1. A method for treating liquefied waste plastics (LWP), said method = comprises the steps of

S (i) providing a volume of the liguefied waste plastics (A) and a volume of

E an agueous medium (B),

W 30 (ii) admixing said volume of the liquefied waste plastics (A) and said = volume of the agueous medium (B) to form an admixture volume (C),

N (iii) heating the admixture volume (C) by injecting steam (D) into said

N admixture volume (C) to form a heated admixture volume (E).

2. The method according to item 1, wherein the aqueous medium (B) is an acidic aqueous medium (B), a neutral aqueous medium (B) or an alkaline aqueous medium (B). 3. The method according to item 1 or 2, wherein the aqueous medium (B) is an alkaline aqueous medium (B). 4. The method according to any one of the preceding items, wherein the aqueous medium (B) is an aqueous solution of an alkaline substance. 5. The method according to any one of the preceding items, wherein the agueous medium (B) is an agueous solution of a metal hydroxide. 6. The method according to any one of the preceding items, wherein the agueous medium (B) is an agueous solution of a metal hydroxide and the metal hydroxide is selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides. 7. The method according to any one of the preceding items, wherein the agueous medium (B) is an agueous 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).. en 25 8. The method according to any one of the preceding items, wherein the

S agueous medium (B) is an agueous solution of a metal hydroxide and the = metal hydroxide is NaOH. > = 9. The method according to any one of the preceding items, wherein the

W 30 aqueous medium (B) contains the alkaline substance in an amount in the = range of from 0.5 wt.-% to 15.0 wt.-%, such as from 0.5 wt.-% to 10.0 wt.-

N %, 1.0 wt.-% to 6.0 wt.-%, or 1.5 w.-% to 4.0 wt.-%.

Al

10. The method according to any one of the preceding items, wherein the aqueous medium (B) comprises at least 50 wt.-% water, preferably at least 70 wt.-% water, more preferably at least 85 wt.-% water, at least 90 wt.-% water or at least 95 wt.-% water. 11. The method according to any one of the preceding items, wherein the heated admixture volume (E) contains the alkaline substance in an amount in the range of from 0.5 wt.-% to 10.0 wt.-%, such as from 1.0 wt.-% to 6.0 wt.-%, or 1.5 w.-% to 4.0 wt.-%, relative to the total amount of water and alkaline substance contained in the heated admixture volume (E). 12. The method according to any one of the preceding items, wherein water-oil-ratio between the water in the heated admixture volume (E) and the liquefied waste plastics in the heated admixture volume (E) is in the range of from 0.1 to 1.4 by weight, preferably in the range of 0.2 to 1.0, such as 0.2 to 0.7. 13. The method according to any one of the preceding items, wherein the method further comprises a cooling step and a separation step of separating the heated admixture volume (E; F) into a treated LWP volume (H) and a contaminated agueous volume (G). 14. The method according to item 13, wherein the cooling step is performed before the separation step, and the temperature of the heated © 25 admixture volume (E) is reduced to 180°C or less. & = 15. The method according to item 13 or 14, wherein the separation step

S comprises liguid-liguid separation. fz © 30 16. The method according to any one of the preceding items, wherein the = total amount of liguefied waste plastics (A), agueous medium (B) and steam

N (D) in the heated admixture volume (E) is 85% to 100% by weight, preferably

Al

90% to 100% by weight, 95% to 100% by weight, 97% to 100% by weight, or 99% to 100% by weight. 17. The method according to any of the preceding items, wherein the 5 heating step (iii) is performed in a reactor (3) and/or in a heating section (2) as an independent unit preceding a reactor (3). 18. The method according to any of the preceding items, wherein the heating step (iii) is performed in a reactor (3). 19. The method according to any one of the preceding items, wherein the heating step (iii) is performed in a heating section (2) and the heated admixture volume (E) is then forwarded to a reactor (3). 20. The method according to any one of the preceding items, wherein the heated admixture volume (E) is held in a reactor (3) and the residence time of the heated admixture volume (E) in the reactor (3) may be at least 10 minutes, preferably in the range of 10 minutes to 600 minutes, such as in the range of 10 minutes to 300 minutes, 15 minutes to 180 minutes, 15 minutes to 120 minutes, or 20 minutes to 60 minutes. 21. The method according to any one of the preceding items, wherein the heating step (iii) increases the temperature of the admixture volume (C) from an initial temperature T1 to form the heated admixture volume (E) having a en 25 temperature T2, and the temperature T2 is 180°C or more, such as 200°C or

O more, 220°C or more, or 240°C or more.

S 22. The method according to any one of the preceding items, wherein the = heating step (iii) increases the temperature of the admixture volume (C) from

W 30 an initial temperature T1 to form the heated admixture volume (E) having a = temperature T2, and the temperature T2 is 450°C or less, preferably 400°C

N or less, 350°C or less, 320°C or less, or 300°C or less.

Al

23. The method according to item 21 or 22, wherein the temperature T2 is in the range of 180°C to 450°C, preferably 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. 24. The method according to any one of the preceding items, further comprising a preheating step (ii') in which the admixture volume (C) is preheated to a temperature T1 before the heating step (iii). 25. The method according to any one of the preceding items, further comprising a preheating step (ii') in which the admixture volume (C) is preheated to a temperature Ti before the heating step (iii), wherein the difference (T2-T1) between temperature T2 and temperature T1 is 5°C or more, preferably 15°C or more, or 30°C or more, such as in the range of from 5°C to 150°C, 15°C to 125°C or 30°C to 100°C. 26. The method according to any one of the preceding items, further comprising a preheating step (ii') in which the volume of the liquefied waste plastics (A) and/or the volume of the aqueous medium (B) is/are preheated. 27. The method according to any one of the preceding items, wherein the method is carried out as a batch process. 28. The method according to any one of the preceding items, wherein the method is carried out as a continuous process. & 29. The method according to any one of the preceding items, wherein said s method further comprises a step of cooling the heated admixture volume (E). 3 - 30. The method according to any one of the preceding items, wherein the & 30 method further comprises a separation step of separating the heated 2 admixture volume (E; F) into a treated LWP volume (H) and a contaminated

N agueous volume (G). oo

Al

31. The method according to item 30, wherein the separation step is a gravity-based separation, such as decantation, or a separation by means of centrifugation. 32. The method according to item 13, 14, 15, 30 or 31, wherein the contaminated aqueous volume (G) is at least partially recycled, after optional purification, back to form part of the (heated) admixture volume (C, E). 33. The method according to any one of the preceding items, wherein the steam (D) has a temperature of at least 250°C, such as in the range of 250- 350°C, preferably in the range of from 270-350°C, 290-340°C, or 310-330°C. 34. The method according to any one of the preceding items, wherein the liquefied waste plastics (A) has a 5% boiling point of 25°C or more, preferably 30% or more, or 35°C or more, such as in the range of from 25°C to 120°C, in the range of from 25°C to 100°C, in the range of 30°C to 90°C, or in the range of from 35°C to 80°C. 35. The method according to any one of the preceding items, wherein the liquefied waste plastics (A) has a 95% boiling point of 700°C or less, preferably 650°C or less, 600°C or less, or 550°C or less, such as in the range of from 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. en 25 36. The method according to any one of the preceding items, wherein the

S liquefied waste plastics (A) has a density, as measured at 15°C in the range = of from 0.780 to 0.850 kg/m". > = 37. The method according to any one of the preceding items, wherein the

W 30 liquefied waste plastics (A) has an olefins content of 5 wt.-% or more, such = as 10 wt.-% or more, 15 wt.-% or more, 20 wt.-% or more, 30 wt.-% or

N more, 40 wt.-% or more, or 50 wt.-% or more.

Al

38. The method according to any one of the preceding items, wherein the liquefied waste plastics (A) has an olefins content of 85 wt.-% or less, such as 80 wt.-% or less, 70 wt.-% or less, or 65 wt.-% or less. 39. The method according to any one of the preceding items, wherein the chlorine content of the liquefied waste plastics (A) is in the range of from 1 wt.-ppm to 4000 wt.-ppm, such as 100 wt.-ppm to 4000 wt.-ppm, or 300 wt.-ppm to 4000 wt.-ppm. 40. A system for treating liquefied waste plastics (LWP), said system comprising - a mixing unit (1) configured to mix liquefied waste plastics volume (A) and aqueous medium volume (B) to form an admixture volume (C), - a steam injection unit (6) configured to inject steam (D) into the admixture volume (C), - a reactor (3) for holding a heated admixture volume (E). 41. The system according to claim 40, wherein the system further comprises a heating section (2). 42. The system according to claim 40 or 41, wherein the steam injection unit (6) is implemented in the mixing unit (1) and/or the heating section (2) and/or the reactor (3). en 25 43. The system according to any one of the claims 40 to 42, wherein the

S system further comprises a pre-heating section (5) for pre-heating prior to = the reactor (3). > = 44. The system according to claim 43, wherein the pre-heating section (5)

W 30 is an indirect heat exchanger or a plurality of indirect heat exchangers = configured to receive heat from a flow of the reactor (3) output (E; F), and/or

N from an independent external heat source such as thermal oil system or high

N pressure steam system.

45. The system according to any one of claims 40 to 44, wherein the system further comprises a separator (4) configured to phase separate the reacted admixture volume (F) into a phase separated treated liquefied waste plastic volume (H) and a contaminated aqueous volume (G). 46. The system according to claim 45, wherein the separator (4) is one or more gravity settling vessels in series, or one or more decanter centrifuge in series. 47. The system according to any one of claims 40 to 46, wherein the mixing unit (1) is a static in-line mixer or rotor in-line mixer or agitated continuous stirred tank or in-line rotor mixer (high shear mixer). 48. The system according to any one of claims 40 to 47, wherein the steam injection unit (6) is a conical steam jet. 49. The system according to any one of claims 40 to 48, wherein the reactor (3) is one or more continuous tube reactors in series, or one or more stirred tank reactors in series. 50. The system according to any one of claims 40 to 49, wherein the mixing unit (1), the steam injection unit (6) and the reactor (3) are a combined unit (7) such that the steam (D) and liquefied waste plastics volume (A) and an en 25 aqueous medium volume (B) are fed directly to the combined unit (7) and

S the separation step is performed in said combined unit (7).

S 51. A use of a steam injection unit for heating a liquefied waste plastics = volume (A), or an admixture volume (C) of liquefied waste plastics volume

W 30 (A) and aqueous medium volume (B).

S

Detailed description of the invention

A (volume of) liquefied waste plastics (LWP), such as a pyrolysis product of collected consumer plastics, contains large and varying amounts of contaminants which would be detrimental in downstream processes. Such contaminants include, among others, halogens (e.g. chlorine and bromine) originating from halogenated plastics (such as PVC and PTFE) or flame retardants, sulphur originating from cross-linking agents of rubbery polymers (e.g. in end-of-life tires) and metals or metalloids (e.g. Si, Al) contaminants originating from composite materials and additives (e.g. films coated with metals or metal compounds, end-of-life tires, or plastics processing aids).

These contaminants may be present in elemental form, in ionic form, or as a part of organic or inorganic compounds.

These impurities should be removed before the LWP is subjected to further processing. The present invention focusses on an improved heating concept in a method of removing such impurities (or contaminants) by treatment of an LWP with an aqueous medium at elevated temperature (also referred to as heat treatment (HT) processing in the following). The HT processing requires that the LWP is heated to a high temperature T2. The inventors found that conventional heating means (e.g. comprising a heat exchanger system in which heat is exchanged from a heating medium and/or from a product) tend to cause fouling near the heating surface over time as well as process efficiency deterioration. The inventors observed that such fouling was caused by excessively high temperatures of the heat exchanger surface, which needs © 25 to be considerably higher (e.g. 20°C to 100°C higher) than the target heating < temperature, in order to allow rapid heating. The inventors thus searched for = possibilities to reduce the heat load on the LWP and found that direct injection

S of steam causes much less heat load and thus significantly reduces fouling as = well as process efficiency deterioration. Based on this finding, the inventors

W 30 completed the invention. ©

A

N In the context of the present invention, liguefied waste plastics (LWP) means

N a product effluent from liquefaction process comprising at least depolymerising waste plastics. LWP is thus a material which is obtainable by depolymerizing waste plastics. LWP may also be referred to as polymer waste-based oil or as liquefied waste plastic. Moreover, whenever reference is made to the LWP, this shall of course encompass the “volume of liquefied waste plastics”. The same applies to the (volume) of aqueous medium, the admixture (volume), the heated admixture (volume) and so on.

The waste plastics may be derived from any source, such as (recycled or collected) consumer plastics, (recycled or collected) industrial plastics or (recycled or collected) end-life-tires (ELT). In particular, the term waste plastics refers to an organic polymer material which is no longer fit for its use or which has been disposed of for any other reason. Waste plastics may more specifically refer to end-life tires, collected consumer plastics (consumer plastics referring to any organic polymer material in consumer goods, even if not having “plastic” properties as such), collected industrial polymer waste.

In the sense of the present invention, the term waste plastics or “polymer” in general does not encompass purely inorganic materials (which are otherwise sometimes referred to as inorganic polymers). Polymers in the waste plastics may be of natural and/or synthetic origin and may be based on renewable and/or fossil raw material.

The liquefaction process is typically carried out at elevated temperature, and preferably under non-oxidative conditions. The liquefaction process may be carried out at elevated pressure. The liquefaction process may be carried out © 25 in the presence of a catalyst. The effluent from the liquefaction process may < be employed as the liquefied waste plastic as such or may be subjected to = fractionation (or separation) to provide a fraction (or separated liquid) of the

S effluent as the liguefied waste plastics. For example, the LWP may be a = hydrothermal liquefaction oil or a fraction thereof. Similarly, multiple

W 30 fractionations may be carried out. In addition, two or more liquefaction = process effluents and/or fractions thereof may be combined to give the LWP.

N These effluents and/or fractions may have the same or similar boiling range

N or may have different boiling ranges. In this context, fractionation comprises fractional distillation and/or fractional evaporation and/or fractional condensation.

In addition to liquid (NTP) hydrocarbons, i.e. hydrocarbons being liquid at normal temperature and pressure (NTP; 20°C, 101.325 kPa absolute), typical product effluents from liquefaction processes comprise gaseous (NTP) hydrocarbons, and hydrocarbons that are waxy or solid at NTP but become liquids upon heating, for example upon heating to 80°C.

In the context of the present disclosure, depolymerizing waste plastic means decomposing or degrading the polymer backbones of the waste plastic, typically at least thermally, to the extent yielding polymer and/or oligomer species of smaller molecular weight compared to the starting waste plastic, but still comprising at least liquid (NTP) hydrocarbons. In other words, as used herein, the liquefied waste plastic does not cover plastics in liquid form obtained merely by melting or by dissolving into a solvent, as these do not involve sufficient cleavage of the polymer backbones, nor waste plastics depolymerized completely to the monomer-level and thus being e.g. of gaseous (NTP) form. Depolymerizing waste plastics may also involve cleavage of covalently bound heteroatoms such as O, S, and N from optionally present heteroatom-containing compounds.

Initially the waste plastics, or each waste plastics species in mixed waste plastics, to be subjected to liquefaction, is usually in solid state, typically © 25 having a melting point in the range of 100°C or more 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 plastics,

S or each waste plastics species, may be at least partially melted before and/or = during the depolymerisation. o 30 5 Solid waste plastics may contain various further components such as

N additives, reinforcing materials, etc., including fillers, pigments, printing inks,

N flame retardants, stabilizers, antioxidants, plasticizers, lubricants, labels,

metals, paper, cardboard, cellulosic fibres, fibre-glass, even sand or other dirt. Some of the further components may be removed, if so desired, from the solid waste plastics, from melted waste plastic, and/or from liquefied waste plastic using commonly known methods.

Preferably, the (solid) waste plastics to be subjected to the liquefaction process (depolymerisation), and thus being the base material of the LWP, has an oxygen content of 15 wt.-% or less, preferably 10 wt.-% or less, more preferably 5 wt.-% or less, of the total weight of the (solid) waste plastics.

The oxygen content may be 0 wt.-% and may preferably be in the range of 0 wt.-% to 15 wt.-% or O wt.-% to 10 wt.%. Oxygen content in wt.-% can be determined by difference using the formula 100 wt.-% - (CHN content + ash content), wherein CHN content refers to combined content of carbon, hydrogen and nitrogen, as determined in accordance with ASTM D5291, and ash content refers to ash content as determined in accordance with ASTM

D482/EN15403.

In the present disclosure, when reference is made to a standard, the latest revision available on January 31, 2022 shall be meant, unless stated to the contrary. Furthermore, all embodiments (such as all preferred values and/or ranges within the embodiments, even from Examples) of the present invention may be combined with each other to give (preferred) embodiments, unless explicitly specified otherwise or unless such a combination would result in a contradiction.

Q 25 < The LWP preferably comprises primarily hydrocarbons, typically more than = 50 wt.-% based on the total weight of the LWP. Typically the LWP comprises

S two or more hydrocarbon species selected from paraffins, olefins, naphthenes = and aromatics. The composition of the LWP may vary depending e.g. on the

W 30 composition of the waste plastics, liguefaction process type and condition. = Further, the assortment of various species of waste plastics and impurities

N associated with collected waste may result in a presence of impurities

Al including silicon, sulphur, nitrogen, halogens and oxygen related substances in various quantities in the LWP.

The LWP of the present invention is derived from (crude) LWP and may, for example, be crude LWP (i.e. the liquid fraction directly emerging from the liquefaction process), or a fraction of crude LWP.

The LWP may specifically refer to an oil or an oil-like product obtainable from liquefaction using non-oxidative thermal or thermocatalytic depolymerisation of (solid) waste plastics (followed by optional subsequent fractionation). In other words, the LWP may also be referred to as "depolymerized polymer waste” or “liquefied polymer waste”.

The method of liquefaction is not particularly limited as long as it is a depolymerisation process and one may mention thermal depolymerisation processes, such as pyrolysis (e.g. fast pyrolysis) of waste plastics, or hydrothermal liquefaction of waste plastics.

Further, in the present invention, the term “pH” refers to the pH value of an aqueous medium measured at (or converted to a value corresponding to measurement at) 20°C. The pH can be measured in accordance with Finnish standard SFS 3021.

The present invention relates to a method for treating liquefied waste plastics © 25 (LWP), said method comprises the steps of (i) providing a volume of the < liquefied waste plastics (A) and a volume of an aqueous medium (B), (ii) = admixing said volume of the liquefied waste plastics (A) and said volume of 2 the agueous medium (B) to form an admixture volume (C), (iii) heating the = admixture volume (C) by injecting steam (D) into said admixture volume (C) a © 30 to form a heated admixture volume (E). 0 e

N Using the method of the present invention, the heating in step (iii) is

N accomplished by injecting steam into the LWP and the process feed (LWP) is heated up directly, thus improving heat transfer, decreasing fouling and increasing safety. In particular, since the steam may provide energy by both its own temperature and its heat of condensation, the direct heating in the present invention is highly efficient. More importantly, the direct injection of steam can minimize direct contact of the LWP (feed) with hot surfaces (e.g. of heat exchangers) and thus significantly reduces fouling.

The aqueous medium (B) may be an acidic aqueous medium (B) (pH below 7), a neutral aqueous medium (B) (pH of about 7) or an alkaline aqueous medium (B) (pH above 7). In one embodiment of the present invention, the pretreatment process employs an alkaline medium. Alkaline aqueous media have been found to have very good contaminants removal efficiency, in particular with respect to problematic contaminants, such as silicon (e.g. organosilicon compounds).

The (alkaline) aqueous medium (B) 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 dissolved form. The aqueous medium (B) may particularly be an aqueous solution of a metal hydroxide (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 2 25 KOH, NaOH, LiOH, Ca(OH)z, Mg(OH)2, RbOH, Sr(OH)> and Ba(OH).. The metal < hydroxide is preferably NaOH.

S Preferably, the agueous medium (B) contains the alkaline substance (such as

E metal hydroxide) in an amount in the range of from 0.5 wt.-% to 15.0 wt.-

W 30 %, such as from 0.5 wt.-% to 10.0 wt.-%, 1.0 wt.-% to 6.0 wt.-%, or 1.5 = w.-% to 4.0 wt.-%. The aqueous medium (B) may comprise at least 50 wt.-

N % water, preferably at least 70 wt.-% water, more preferably at least 85 wt.-

N % water, at least 90 wt.-% water or at least 95 wt.-% water.

While such ranges have been shown to be useful, it is more important that the concentration of the alkaline substance in the heated admixture (volume) (C) (i.e. after addition of steam) be within a certain range. That is, the injection of steam inevitably results in addition of water to the admixture volume and thus dilutes the alkaline (or, as the case may be, acidic) substance in the aqueous medium to a certain extent. Thus, the method of the present invention takes into account the water added in the form of steam. This can be accomplished by any suitable means, e.g. calculating the concentration of the alkaline substance in consideration of added steam volume and added volume of aqueous medium. Addition amounts (of e.g. steam for required heating) can be calculated or taken from tabulated values or both.

Accordingly, in the present invention, it is preferable that the heated admixture volume (E) contains the alkaline substance (e.g. metal hydroxide, such as NaOH) in an amount in the range of from 0.5 wt.-% to 10.0 wt.-%, such as from 1.0 wt.-% to 6.0 wt.-%, or 1.5 w.-% to 4.0 wt.-%, relative to the total amount of water and metal hydroxide contained in the heated admixture volume (E). As a result of containing the alkaline substance, the aqueous component of the heated admixture volume (E) may adopt a pH of 8.0 or more, such 9.0 or more, 10.0 or more, 11.0 or more, 12.0 or more, or 13.0 or more, or in the range of from 8.0 to 14.0, 9.0 to 13.9, 10.0 to 13.9, 11.0 to 13.9, 12.0 to 13.9, or 13.0 to 13.9. 2 25 < The water-oil-ratio (water to oil ratio = amount of “water” / amount of "oil”) = between the water in the heated admixture volume (E) and the liquefied

S waste plastics in the heated admixture volume (E) is in the range of from 0.1

E to 1.4 by weight, preferably in the range of 0.2 to 1.0, such as 0.2 to 0.7. In

W 30 this context, the “water” refers to the total amount of water (from admixed = agueous medium and from injected steam); and the "oil” refers to the volume

N of liguefied waste plastics. The water-oil-ratio may be calculated from the

N feed (admixing / injection) amounts.

The method of the present invention may further comprise a separation step of separating the heated admixture volume (E; F) into a treated LWP volume (H) and a contaminated aqueous volume (G). The separation is preferably carried out after cooling down the heated admixture volume (E; F) to a temperature which is suitable for separation (as within the skilled person's knowledge). The separation step preferably comprises liquid-liquid separation. The separation is preferably carried out after giving the heated admixture volume (E) sufficient time to reaction (see residence time below for useful time durations), e.g. by maintaining the heated admixture volume (E) at or close to the temperature shortly after steam injection.

Favourably, the total amount of liquefied waste plastics (A), aqueous medium (B) and steam (D) in the heated admixture volume (E) 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. In other words, it is preferable that the admixture volume (C) predominantly consists of liquefied waste plastics (A) and aqueous medium (B) and that the heated admixture volume (E) predominantly consists of liquefied waste plastics (A), aqueous medium (B) and steam (D). Put in even other words, no significant amounts (15 wt.-% or less, preferably 10 wt.-% or less, 5 wt.-% or less, 3 wt.-% or less or 1 wt.-% or less) of co-feeds or additives are desired.

The method may further comprise holding (maintaining) the heated © 25 admixture volume in a reactor (for treatment). The heating step (iii) may be < performed in a reactor and/or in a dedicated (separate) heating section(s). = The heating step may be performed in both the heating section and

S (subseguently or further) in the reactor. Providing a dedicated heating section = may facilitate temperature control and handling (as well as integration into

W 30 existing process lines) while heating within the reactor may require less : equipment. & When the heating step (iii) is performed in heating section(s), the heated admixture volume (E) is preferably thereafter forwarded to a reactor.

Alternatively, or in addition, the heating section maybe implemented as a part of the reactor.

The residence time of the heated admixture volume (E) in the reactor is preferably at least 10 minutes, more preferably in the range of 10 minutes to 600 minutes, such as in the range of 10 minutes to 300 minutes, 15 minutes to 180 minutes, 15 minutes to 120 minutes, or 20 minutes to 60 minutes.

The residence time may be defined as the time for which the heated admixture volume (E) is maintained in the reactor at elevated temperatures.

The heating step (iii) increases the temperature of the admixture volume (C) from an initial temperature T1 to a temperature T2, thus forming the heated admixture volume (E). The temperature T2 is preferably 180°C or more, such as 200°C or more, 220°C or more, or 240°C or more. The temperature T2 is preferably 450°C or less, preferably 400°C or less, 350°C or less, 320°C or less, or 300°C or less. The temperature T2 is suitably in the range of 210°C to 350°C, preferably 220°C to 330°C, 240°C to 320°C, or 260°C to 300°C. It has been found that a (reaction) temperature within the above limits allows efficient pretreatment of the liquefied waste plastics.

The method may further comprise a preheating step (ii') before the heating step (iii). In the preheating step (ii”), the admixture volume (C) is preheated to the temperature T1. Preheating may be accomplished in a dedicated (separate) preheating section(s), in the heating section(s) or in the reactor, © 25 as long as it is accomplished before the heating step (iii). Usually, the < preheating will be carried out after the admixing step (ii) but it may be partly = or fully carried out before the admixing step (i.e. preheating the aqueous

S medium and/or the LWP before admixing). fz © 30 Suitably, the difference (T2-T1) between temperature T2 and temperature T1 = is 5°C or more, preferably 10°C or more, such as in the range of from 5°C to

N 300°C, 10°C to 240°C or 15°C to 200°C.

Al

That is, the effects of the present invention can be achieved even if only the final heating (e.g. the last 5°C temperature increase) is accomplished by direct steam injection while the effects are more pronounced if more (optionally all) of the heating is accomplished by steam injection. As a matter of course, the maximum difference (T2-T1) cannot be higher than the temperature difference between the (non-heated) admixture volume (C) and the temperature T2.

The method of the present invention may be carried out batchwise (as a batch process) or continuously (a continuous process, also referred to as continuous flow process). A combination of both is possible, e.g. batchwise admixing, continuous steam injection and semi-batchwise reaction (filling one reactor after another with the stream from steam injection) or continuous mixing and then batchwise steam injection and reaction.

As will be apparent to the skilled person, a term like "before” or "preceding” (or similar) can be translated to "earlier in time” in a batch process and “upstream” in a continuous process, “afterwards” (or similar) can be translated to "later in time” in a batch process and "downstream” in a continuous process, a “volume” (or amount, such as relative amount) may be translated to (relative) "batch size” (or "feed amount”) in a batch process and to (relative) “flow rate” (or “flow rate ratio”) in a continuous process. The same applies similarly to all expressions used herein. en 25 The method may further comprise a step of cooling the heated admixture

S volume (E). Cooling is particularly favourable to facilitate (phase) separation. = Cooling is carried out after the reaction is finished (i.e. after the residence

S time). Note that for ease of reference, the heated admixture volume (E) is = called “heated admixture volume (E)” even after cooling. The method

W 30 preferably further comprises a separation step of separating the heated = admixture volume (E; F) into a treated LWP volume (H) and a contaminated

N agueous volume (G). The separation step may be a gravity-based separation

N (non-forced separation), such as decantation, or a forced separation, such as separation by means of centrifugation. In other words, it is possible to let the heated admixture volume (E) settle (by natural gravity) to achieve separation or to force the separation e.g. by centrifugation.

The contaminated aqueous volume (G) is preferably at least partially recycled, after optional purification, back to the process (to form part of the admixture volume and/or the heated admixture volume), e.g. by recycling it into the aqueous medium. In this case, the (amount of the) recycled contaminated aqueous volume (G) is counted as being part of the (volume of the) aqueous medium, even if admixed with the LWP separately.

Suitably, the steam (D) has a temperature of at least 250°C, such as in the range of 250-350°C, preferably in the range of from 270-350°C, 290-340°C, or 310-330°C. Usually, the steam temperature should be at least T2 or higher than T2 to allow efficient heating.

The liquefied waste plastics (A), which is a feed to be (pre)treated by the method of the present invention, may have a 5% boiling point of 25°C or more, preferably 30°C or more, or 35°C or more, such as in the range of from 25°C to 120°C, in the range of from 25°C to 100°C, in the range of 30°C to 90°C, or in the range of from 35°C to 80°C. The liquefied waste plastics (A) may have a 95% boiling point of 700°C or less, preferably 650°C or less, 600°C or less, or 550°C or less, such as in the range of from 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 © 25 to 500°C. The LWP may particularly be a crude LWP or a fraction thereof. & = The liquefied waste plastics (A) may have a density, as measured at 152C, in

S the range of from 0.780 to 0.850 kg/m”. The liquefied waste plastics (A) may = have an olefins content of 5 wt.-% or more, such as 10 wt.-% or more, 15

W 30 wt.-% or more, 20 wt.-% or more, 30 wt.-% or more, 40 wt.-% or more, or = 50 wt.-% or more. The liguefied waste plastics (A) may have an olefins

N content of 85 wt.-% or less, such as 80 wt.-% or less, 70 wt.-% or less, or

N 65 wt.-% or less. Such an olefins content is usual for thermally produced LWP

(e.g. pyrolysis oil or HTL oil) but may vary with depolymerisation temperature.

The chlorine content of the liquefied waste plastics (A) may be in the range of from 1 wt.-ppm to 4000 wt.-ppm, such as 100 wt.-ppm to 4000 wt.-ppm, or 300 wt.-ppm to 4000 wt.-ppm.

The present invention furthermore relates to a system for treating liquefied waste plastics (LWP), said system comprising mixing unit (1) configured to mix liquefied waste plastics volume (A) and aqueous medium volume (B) to form an admixture volume (C), a steam injection unit (6) configured to inject steam (D) into the admixture volume (C), and a reactor (3) for holding a heated admixture volume (E).

The system is preferably configured to carry out the method of the present invention, including the preferred embodiments of the method depicted in the items. Similarly, embodiments of the system, as recited in the present disclosure, may be implemented as embodiments of the method of the invention, as will be apparent to the skilled person.

The system may further comprise a heating section (2). The heating section is preferably provided preceding the reactor (3), as illustrated e.g. in FIG. 1.

The heating section (2) may alternatively (or in addition) be provided as a part of the reactor (3).

Q 25 < The steam injection unit (6) may be implemented in the mixing unit (1) (as = shown in FIG. 5A and 5B) and/or in a heating section (2) preceding the

S reactor (as shown in FIG. 5B) and/or in the reactor (3) (as shown in FIG. 5A). = when the steam injection unit (6) is provided in the reactor (3), the steam

W 30 injection unit may be provided as a part of a heating section within the eo] o reactor.

S

The system may further comprise a pre-heating section (5) for pre-heating prior to the reactor (3), such as pre-heating the admixture volume (C), the liquefied waste plastics volume (A) and/or the aqueous medium volume (B).

Pre-heating is carried out prior to the final steam injection (unit), e.g. in case multiple steam injection units (6) are provided.

For example, as illustrated e.g. in FIG. 1, the system may comprise a pre- heating section (5) for preheating the admixture volume (C), and the pre- heating section (5) is implemented in between the mixing unit (1) and the reactor (3) (including the steam injection unit (6)).

As illustrated e.g. in FIG. 2C, 3A, and 4, the system may also comprise a pre- heating section (5) for pre-heating the liguefied waste plastics volume (A) and/or the agueous medium volume (B), and this pre-heating section (5) is implemented preceding the mixing unit (1). Although not shown in the FIGs., it is possible that only the liguefied waste plastics volume (A) or only the agueous medium volume (B) is subjected to pre-heating in the pre-heating section (5) before mixing and/or that separate pre-heating units be provided for pre-heating the liquefied waste plastics volume (A) and the aqueous medium volume (B), respectively. The system may also contain both a pre- heating section (5) for pre-heating the liguefied waste plastics volume (A) and/or the agueous medium volume (B) and a pre-heating section (5) for heating the admixture volume (C), as shown e.g. in FIG. 2B. © 25 The pre-heating section(s) (5) may be an indirect heat exchanger or a < plurality of indirect heat exchangers. The heat exchanger(s) may be = configured to receive heat from a flow of the reactor (3) output (E; F). In this

S case, the heat exchangers may furthermore act for cooling the reactor output = before phase separation. The heat exchanger(s) may be configured to receive

W 30 heat from an independent external heat source such as thermal oil system or = high pressure steam system.

In the embodiments of FIG. 3A, 3B and 4, the mixing section (1) is furthermore integrated with the reactor (3) and steam injection unit (6) and provided as a combined unit (7). That is, the mixing unit (1), the steam injection unit (6) and the reactor (3) may be provided as a combined (single) unit (7), i.e. a single unit capable of performing the functions of the mixing and heating. In this case, the steam (D), liquefied waste plastics volume (A) and aqueous medium volume (B) are fed directly to the combined unit (7).

The system may further comprise a separator (4) configured to phase separate the reacted admixture volume (E; F) into a (phase separated) treated liquefied waste plastic volume (H) and a contaminated aqueous volume (G). As shown in FIG. 4, the separation step may further be performed in the above-mentioned combined unit (7). In such a combined unit, the separation may for example be carried out by batch-wise operation in a single vessel.

The separator (4) may be one gravity settling vessel or may be two or more gravity settling vessels in series. The separator (4) may be one decanter centrifuge or two or more decanter centrifuges in series. It is also possible to provide gravity settling vessel(s) and decanter centrifuge(s) in series.

The mixing unit (1) may be a static in-line mixer or rotor in-line mixer or agitated continuous stirred tank or in-line rotor mixer (high shear mixer). The steam injection unit (6) may be a conical steam jet. 2 25 < The reactor (3) may be one, two or more continuous tube reactor(s) in series, = or one, two or more stirred tank reactor(s) in series. In the case of tube

S reactors, the product flow may be, for example, top-down or bottom-up. fz © 30 The above constitutions for arrangement of units and sections of the system = of the invention (and corresponding method steps) are similarly applicable to

N the method and/or use of the invention and vice versa.

Al

Claims

1. A method for treating liquefied waste plastics (LWP), said method comprises the steps of (i) providing a volume of the liguefied waste plastics (A) and a volume of an agueous medium (B), (ii) admixing said volume of the liquefied waste plastics (A) and said volume of the agueous medium (B) to form an admixture volume (C), characterized in that the method comprises (iii) heating the admixture volume (C) by injecting steam (D) into said admixture volume (C) to form a heated admixture volume (E).

2. The method according to claim 1, wherein the aqueous medium (B) is an alkaline aqueous medium (B), such as an aqueous solution of an alkaline substance.

3. The method according to claim 1 or 2, wherein the agueous medium (B) is an aqueous solution of a metal hydroxide, such as an aqueous solution of a metal hydroxide selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, in particular selected from the group consisting of KOH, NaOH, LiOH, Ca(OH)>, Mg(OH)2, RbOH, Sr(OH)> and Ba(OH),, preferably an aqueous solution of NaOH.

4. The method according to any one of the preceding claims, wherein the heated admixture volume (E) contains the alkaline substance in an & amount in the range of from 0.5 wt.-% to 10.0 wt.-%, such as from 1.0 a 25 —wt.-% to 6.0 wt.-%, or 1.5 w.-% to 4.0 wt.-%, relative to the total amount = of water and alkaline substance contained in the heated admixture volume O : (E).

2 5. The method according to any one of the preceding claims, wherein N 30 — water-oil-ratio between the water in the heated admixture volume (E) and & the liquefied waste plastics in the heated admixture volume (E) is in the range of from 0.1 to 1.4 by weight, preferably in the range of 0.2 to 1.0, such as 0.2 to 0.7.

6. The method according to any one of the preceding claims, wherein the method further comprises a separation step, such as a liguid-liguid separation step, of separating the heated admixture volume (E; F) into a treated LWP volume (H) and a contaminated agueous volume (G).

7. The method according to any one of the preceding claims, wherein the total amount of liguefied waste plastics (A), agueous medium (B) and — steam (D) in the heated admixture volume (E) 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.

8. The method according to any of the preceding claims, wherein the heated admixture volume (E) is maintained in a reactor (3) for a residence NN time of at least 10 minutes, preferably in the range of 10 minutes to 600 minutes, such as in the range of 10 minutes to 300 minutes, 15 minutes to 180 minutes, 15 minutes to 120 minutes, or 20 minutes to 60 minutes.

9. The method according to any one of the preceding claims, wherein the heated admixture volume (E) is heated to a temperature T2 by the injected steam, and the temperature T2 is 180°C or more, such as 200°C or more, 220°C or more, or 240°C or more, and/or 450°C or less, preferably en 25 400°C or less, 350°C or less, 320°C or less, or 300°C or less, such as in the S range of 210°C to 350°C, preferably 220°C to 330°C, 240°C to 320°C, or = 260°C to 300°C. > =

10. The method according to any one of the preceding claims, further W 30 comprising a preheating step (ii') in which the admixture volume (C) is = preheated to a temperature T1 before the heating step (iii).

11. The method according to any one of the preceding claims, wherein said method further comprises a step of cooling the heated admixture volume (E).

12. The method according to any one of the preceding claims, wherein the method further comprises a separation step of separating the heated admixture volume (E; F) into a treated LWP volume (H) and a contaminated aqueous volume (G), wherein the separation step is preceded by a cooling step. —

13. The method according to any one of the preceding claims, wherein the steam (D) has a temperature of at least 250°C, such as in the range of 250-350°C, preferably in the range of from 270-350°C, 290-340°C, or 310- 330°C.

14. The method according to any one of the preceding claims, wherein NN the liquefied waste plastics (A) has a 5% boiling point of 25°C or more, preferably 30°C or more, or 35°C or more, such as in the range of from 25°C to 120°C, in the range of from 25°C to 100°C, in the range of 30°C to 90°C, or in the range of from 35°C to 80°C; and/or the liquefied waste plastics (A) has a 95% boiling point of 700°C or less, preferably 650°C or less, 600°C or less, or 550°C or less, such as in the range of from 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; and/or © 25 the liquefied waste plastics (A) has a density, as measured at 15°C in < the range of from 0.780 to 0.850 kg/m3; and/or = the liquefied waste plastics (A) has an olefins content of 5 wt.-% or S more, such as 10 wt.-% or more, 15 wt.-% or more, 20 wt.-% or more, 30 = wt.-% or more, 40 wt.-% or more, or 50 wt.-% or more; and/or W 30 the liguefied waste plastics (A) has an olefins content of 85 wt.-% or = less, such as 80 wt.-% or less, 70 wt.-% or less, or 65 wt.-% or less; N and/or &

the chlorine content of the liquefied waste plastics (A) is in the range of from 1 wt.-ppm to 4000 wt.-ppm, such as 100 wt.-ppm to 4000 wt.- ppm, or 300 wt.-ppm to 4000 wt.-ppm.

15. A system for treating liquefied waste plastics (LWP), said system comprising - a mixing unit (1) configured to mix liquefied waste plastics volume (A) and aqueous medium volume (B) to form an admixture volume (C), and — - areactor (3) for holding a heated admixture volume (E), characterized in that the system comprises - a steam injection unit (6) configured to inject steam (D) into the admixture volume (C).

16. The system according to claim 15, wherein the system further H comprises a heating section (2).

17. The system according to claim 15 or 16, wherein the steam injection unit (6) is implemented in the mixing unit (1) and/or the heating section (2) and/or the reactor (3).

18. The system according to any one of the claims 15 to 17, wherein the system further comprises a pre-heating section (5) for heating the en 25 admixture volume (C), and is implemented in between the mixing unit (1), S the heating section (2) and the reactor (3). S

19. The system according to claim 18, wherein the pre-heating section = (5) is an indirect heat exchanger or a plurality of indirect heat exchangers W 30 configured to receive heat from a flow of the reactor (3) output (F), and/or = from an independent external heat source such as thermal oil system or N high pressure steam system. Al

20. The system according to any one of claims 15 to 19, wherein the system further comprises a separator (4) configured to phase separate the reacted admixture volume (E; F) into a phase separated treated liquefied waste plastic volume (H) and a contaminated aqueous volume (G).

21. The system according to claim 20, wherein the separator (4) is one or more gravity settling vessels in series, or one or more decanter centrifuge in series.

22. The system according to any one of claims 15 to 21, wherein the — reactor (3) is one or more continuous tube reactors in series, or one or more stirred tank reactors in series.

23. The system according to any one of claims 15 to 22, wherein the mixing unit (1), the steam injection unit (6) and the reactor (3) are a combined unit (7) such that the steam (D) and liguefied waste plastics NN volume (A) and agueous medium volume (B) are fed directly to the combined unit (7) and a separation step is optionally further performed in said combined unit (7).

24. A use of a steam injection unit for heating a liquefied waste plastics volume (A), or an admixture volume (C) of liquefied waste plastics volume (A) and aqueous medium volume (B). 0 N O N O 0 I = O 0 © N N O N