Separation of a water soluble compound through fluid bed pyrolysis

Abstract

The disclosure relates to a method for separating at least one water soluble compound from a heteropolymer mixture in a thermal pyrolysis. In addition, the disclosure relates to an apparatus for separating at least one water soluble compound from a heteropolymer mixture in a thermal pyrolysis.

Description

[0001] A method for separating a water soluble compound

[0002] Technical field

[0003] The disclosure relates to a method for separating at least one water soluble compound from a heteropolymer mixture in a thermal pyrolysis. In addition, the disclosure relates to an apparatus for separating at least one water soluble compound from a heteropolymer mixture in a thermal pyrolysis.

[0004] Background

[0005] There is a great need to develop methods for separating and recovering water soluble compounds from heteropolymer mixtures in a thermal pyrolysis in order to refine and / or enable the re-use of the water soluble compounds as well as the organic hydrocarbon mixture and thus reduce the environmental burden caused by the synthesis of such organic compounds. There is also a need to find simple and economic methods for separating and recovering water soluble compounds from heteropolymer mixtures in a thermal pyrolysis.

[0006] Summary

[0007] It is an aim of this disclosure to provide a new method for separating at least one water soluble compound from a heteropolymer mixture in a thermal pyrolysis. The method enables separation of one or more water soluble compound which can then be re-used as a raw material, for example. Further, with the method disclosed herein water soluble compounds can be separated from the organic hydrocarbon mixture containing phase which is then more easy to handle in separate further processing steps.

[0008] Accordingly, the present disclosure provides a method for separating at least one water soluble compound from a heteropolymer mixture in thermal pyrolysis by using a carrier gas comprising steam.

[0009] Further, it is an aim of this disclosure to provide an apparatus for separating at least one water soluble compound from a heteropolymer mixture in thermal pyrolysis by using a carrier gas comprising steam.In the course of this disclosure, the expression ‘steam’ should be understood to refer to steam originating from water, i.e. , water vapor. In other words, the expression ‘steam’ is used interchangeably with and as a synonym to water vapor.

[0010] The main embodiments are characterized in the independent claims. Various embodiments are disclosed in the dependent claims. The embodiments and examples disclosed herein are mutually freely combinable unless otherwise explicitly stated. The embodiments and examples not in the scope of the claims are embodiments and examples not part of the invention, but useful for understanding the invention.

[0011] Brief description of the drawings

[0012] Figure 1 shows a flowchart of the present method.

[0013] Figure 2 shows the water content analysis of Example 1

[0014] Figure 3 shows the amount of caprolactam in the water phase and in the organic phase of Example 1.

[0015] Detailed description

[0016] The solution is described in the following in more detail with reference to some embodiments, which shall not be regarded as limiting.

[0017] In this disclosure, separation of at least one water soluble compound from a heteropolymer mixture in thermal pyrolysis is described. Water soluble compounds enriched into the aqueous phase formed during the thermal pyrolysis from the heteropolymer mixture can be separated from hydrocarbon-based hydrophobic condensation products by using a carrier gas comprising steam in the pyrolysis. The water soluble compounds can thus be separated from the main stream containing the hydrocarbon-based hydrophobic condensation products, which are then more easy to handle in separate further processing steps.

[0018] The method enables separation of one or more water soluble compounds which can then be refined and / or re-used as raw materials, for example. Further, with the method disclosed herein water soluble compounds can beseparated from the organic hydrocarbon mixture containing phase which is then more easy to handle in separate further processing steps.

[0019] Thus, the present disclosure provides a method for separating at least one water soluble compound from a heteropolymer mixture in thermal pyrolysis by using a carrier gas comprising steam. The method comprises feeding heteropolymer mixture and a carrier gas comprising steam into a fluidized bed pyrolysis reactor. The method further comprises treating the heteropolymer mixture with steam in thermal pyrolysis at a temperature in the range of 475°C to 650°C to produce / obtain condensable pyrolysis products, condensing the condensable pyrolysis products to obtain a water phase and a hydrocarbon-based organic phase, separating the water phase from the hydrocarbon-based organic phase and recovering at least one water soluble compound from the water phase. A residence time of the heteropolymer mixture in the fluidized bed pyrolysis reactor is from 0.5 to 5 seconds during the thermal pyrolysis.

[0020] More specifically, the present disclosure relates to a method which comprises the steps of:

[0021] - feeding a heteropolymer mixture (1) into a fluidized bed pyrolysis reactor (2),

[0022] - feeding a carrier gas comprising steam (3) into the fluidized bed pyrolysis reactor (2),

[0023] - treating the heteropolymer mixture with steam in thermal pyrolysis to obtain condensable pyrolysis products (4),

[0024] - condensing (5) the condensable pyrolysis products to obtain a water phase and an organic phase,

[0025] - separating (8) the organic phase (6) and the water phase (7),

[0026] - recovering at least one water soluble compound (10) from the water phase (7),

[0027] wherein a residence time of the heteropolymer mixture in the fluidized bed pyrolysis reactor is from 0.5 to 5 seconds during the thermal pyrolysis.

[0028] In this disclosure, also the separation of caprolactam from the polyamide 6 containing polymer mixture is described. Caprolactam is a building block of polyamide 6 (PA6) plastic and also a degradation product thereof in thermal pyrolysis. Hydrophilic caprolactam formed during thermal pyrolysis from thepolyamide 6 containing polymer mixture can be selectively separated from hydrocarbon-based hydrophobic condensation products by using a carrier gas comprising steam in thermal pyrolysis. Aqueous phase is enriched with caprolactam which can be separated from the main stream containing the hydrocarbon-based hydrophobic condensation products.

[0029] Caprolactam is the main raw material for the production of polyamide 6 fiber as well as resin and films. The synthesis of caprolactam is a complex multistage process which heavily pollutes the environment. There is a great need to develop methods for separating and recovering caprolactam from polyamide 6 containing polymer mixtures in order to enable the re-use of caprolactam and reduce the environmental burden of caprolactam production. In addition, there is a need to purify the polyamide 6 containing polymer mixture to allow the reuse of the organic hydrocarbon mixture. By using a carrier gas comprising steam in thermal pyrolysis, caprolactam can be dissolved into the water fraction, resulting in phase separation from the main stream containing the hydrocarbon-based hydrophobic condensation products.

[0030] The present disclosure also provides a method for separating caprolactam from a polyamide 6 containing polymer mixture in thermal pyrolysis by using a carrier gas comprising steam. The method comprises feeding polyamide 6 containing polymer mixture and the carrier gas comprising steam into a fluidized bed pyrolysis reactor. The method further comprises treating the polyamide 6 containing polymer mixture with steam in thermal pyrolysis at a temperature in the range of 475°C to 650°C to produce / obtain condensable pyrolysis products, condensing the condensable pyrolysis products to obtain a water phase and an organic phase, separating the water phase from the organic phase and recovering caprolactam from the water phase. A residence time of the polyamide 6 containing polymer mixture in the fluidized bed pyrolysis reactor is from 0.5 to 5 seconds during the thermal pyrolysis.

[0031] More specifically, the present disclosure may relate to a method, which comprises the steps of:

[0032] - feeding polyamide 6 containing polymer mixture into a fluidized bed pyrolysis reactor,- feeding a carrier gas comprising steam into the fluidized bed pyrolysis reactor,

[0033] - treating the polyamide 6 containing polymer mixture with steam in thermal pyrolysis to obtain condensable pyrolysis products,

[0034] - condensing the condensable pyrolysis products to obtain a water phase and an organic phase,

[0035] - separating the water phase and the organic phase, and

[0036] - recovering caprolactam from the water phase,

[0037] wherein a residence time of the polyamide 6 containing polymer mixture in the fluidized bed pyrolysis reactor is from 0.5 to 5 seconds during the thermal pyrolysis.

[0038] Polyethylene terephthalate (PET) is a common thermoplastic resin of the polyester family. PET is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins. PET is commonly used as multilayer films combined with other polymers to reduce its oxygen permeability for packaging applications, for example. Thermal degradation of PET may produce a variety of compounds as degradation products, including acetaldehyde, carbon oxides (CO, CO2), water, and various hydrocarbons such as methane, ethylene, and benzoic acid.

[0039] The present disclosure also provides a method for separating benzoic acid from a polyethylene terephthalate (PET) containing polymer mixture in thermal pyrolysis by using a carrier gas comprising steam. The method comprises feeding PET containing polymer mixture and the carrier gas comprising steam into a fluidized bed pyrolysis reactor. The method further comprises treating the PET containing polymer mixture with steam in thermal pyrolysis at a temperature in the range of 475°C to 650°C to produce / obtain condensable pyrolysis products, condensing the condensable pyrolysis products to obtain a water phase and an organic phase, separating the water phase from the organic phase and recovering benzoic acid from the water phase. A residence time of the PET containing polymer mixture in the fluidized bed pyrolysis reactor is from 0.5 to 5 seconds during the thermal pyrolysis.More specifically, the present disclosure may relate to a method, which comprises the steps of:

[0040] - feeding polyethylene terephthalate (PET) containing polymer mixture into a fluidized bed pyrolysis reactor,

[0041] - feeding a carrier gas comprising steam into the fluidized bed pyrolysis reactor,

[0042] - treating the polyethylene terephthalate (PET) containing polymer mixture with steam in thermal pyrolysis to obtain condensable pyrolysis products,

[0043] - condensing the condensable pyrolysis products to obtain a water phase and an organic phase,

[0044] - separating the water phase and the organic phase, and

[0045] - recovering benzoic acid from the water phase,

[0046] wherein a residence time of the polyethylene terephthalate (PET) containing polymer mixture in the fluidized bed pyrolysis reactor is from 0.5 to 5 seconds during the thermal pyrolysis.

[0047] In the methods of the present disclosure the temperature is from about 475°C to about 650°C during the thermal pyrolysis. In other words, the pyrolysis may be carried out at a temperature in the range of 475°C to 650°C. In one embodiment, the temperature is from about 500°C to about 600°C during the thermal pyrolysis. In one embodiment, the temperature is from about 500°C to about 550°C during the thermal pyrolysis. In one embodiment, the temperature is about 550°C during the thermal pyrolysis. In one embodiment, the temperature is about 500°C during the thermal pyrolysis.

[0048] In the method of the present disclosure, a residence time of the heteropolymer mixture in the fluidized bed pyrolysis reactor is from about 0.5 second to about 5 seconds during the thermal pyrolysis. In other words, the pyrolysis in the method is a fast pyrolysis. In one embodiment, the residence time is about 3 seconds. In one embodiment, the residence time is from about 1 second to about 3 seconds during the thermal pyrolysis. In one embodiment, the residence time is from about 1 second to about 2 seconds during the thermal pyrolysis. In the presented method, the temperature is from about 475°C to about 650°C and the residence time is from about 0.5 second to about 5 seconds during the thermal pyrolysis. In one embodiment, the temperature isfrom about 500°C to about 600°C and the residence time is from about 1 second to about 2 seconds during the thermal pyrolysis. In one embodiment, the temperature is from about 500°C to about 550°C and the residence time is from about 1 s to about 3 s during the thermal pyrolysis.

[0049] The specified temperatures and residence times bring about several advantages. The specified temperature and residence time enable the pyrolysis reaction to be complete, while suppressing the occurrence of undesired secondary reactions. In other words, if the temperature is lower and / or if the residence time is shorter than specified here, the conversion of the polymer mixture into the condensable pyrolysis products may be incomplete and a part of the polymer mixture may remain unreacted. On the other hand, if the temperature is higher and / or if the residence time is longer than specified here, undesired secondary reactions may take predominance over the desired pyrolysis condensation, which may increase the number of components condensing into the water phase. This may in turn decrease the yield of the desired condensable pyrolysis products. A high number of components in the water phase may also complicate the separation of the components. In other words, the specified temperatures and / or residence times may ensure efficient and simple recovery of the at least one water-soluble compound from the water phase.

[0050] In the methods of the present disclosure the amount of steam needs to be sufficient for the water-soluble products to dissolve into water fraction. In one embodiment the carrier gas contains steam, N2 and / or at least one noncondensable gas. In one embodiment the carrier gas contains steam and N2 and at least one non-condensable gas. In one embodiment the carrier gas contains steam and N2. In one embodiment, a minimum required ratio is 50 / 50 (vol / vol) of steam and N2 or some other carrier gas component. In one embodiment the carrier gas comprises steam and N2. In one embodiment, the ratio of steam to the other carrier gas component is >50 / 50, such as 60 / 40, 70 / 30, 80 / 20 or 90 / 10 (vol / vol). In one embodiment, the carrier gas comprises steam at least 50% (vol-%). In one embodiment the steam content of the carrier gas is 50% to 100% (vol-%). In one embodiment the steam content of the carrier gas is 55%, 60%, 65%, 70% 75%, 80%, 85%, 90% 95% or 100% (vol-%). In pyrolysis where water-soluble components are formed, steam actsas dissolving medium and attracts other polar components to the water fraction. In addition, when components that have tendency to dissolve to both polar and non-polar medium can change the solubility of the medium to dissolve components into water fraction that would not normally dissolve. Steam, in high temperature, enhances solubility of the components to water that have tendency to dissolve both polar and non-polar media, or even non-polar only. An advantage of thermal pyrolysis in comparison to catalytic pyrolysis is that polymers can be converted to their original starting monomers with high yield.

[0051] In the methods of the present disclosure condensing the condensable pyrolysis products may be performed in at least one scrubbing step. In one embodiment condensing the condensable pyrolysis products may be performed in in two consecutive scrubbing steps.

[0052] In the methods of the present disclosure the at least one water soluble compound is recovered from the water phase by a separation step. In one embodiment the separation step is a distillation step. In one embodiment, the separation step is an extraction step. In one embodiment the separation step is a crystallization step. In one embodiment the separation step includes any combination of distillation, extraction and crystallization.

[0053] In the methods of the present disclosure, also other components which are separated into the water phase can be recovered. Typically such components are hetero atoms containing compounds, i.e., compounds that contain in addition to carbon and hydrogen also other atoms. Examples of heteroatoms containing compounds are N- and / or O-containing compounds and / or impurities, such as ketones, nitriles, amides, carboxylic acids, and halogens. The condensation of water-soluble impurities into the water phase may further simplify the further purification and usage of the condensed organic phase. Components of the organic phase may be utilized as raw materials in further chemical synthesis. Thus, it is beneficial for the organic phase to contain as little heteroatom containing compounds or impurities as possible. It is desired for the organic phase to comprise hydrocarbons to an extent as high as possible.When the at least one water soluble compound is recovered from the water phase, the thus treated and partly purified water phase can be recycled into the pyrolysis as steam, optionally after some further purification steps. The further purification steps may include different types of filtration, neutralization, and / or distillation. The need for further purification depends, for example, on the origin of heteropolymer mixture, such as the polyamide 6 containing polymer mixture or the PET containing polymer mixture. These polymer mixtures can contain also other compounds and materials, such as solids and non-condensable compounds, for example.

[0054] In the methods of the present disclosure, the organic phase can be recovered. In the methods of the present disclosure, also components which are condensed into the organic phase can be recovered.

[0055] Within context of this disclosure, the term heteropolymer mixture refers to any polymer mixture that has potential of producing water soluble compounds during thermal pyrolysis. In one embodiment, the heteropolymer mixture is a plastic containing material or waste. In one embodiment, the heteropolymer mixture is any mixture comprising ethylene vinyl alcohol (EVOH), polylactide (PLA), polyethylene terephthalate (PET), polyamide (PA), polycarbonate (PC), polyurethane (Pll), acrylonitrile butadiene styrene (ABS), polyvinylchloride (PVC), polytetrafluoroethylene (PTFE) and / or polyvinylidene chloride (PVDC). In one embodiment, the heteropolymer mixture comprises impurities, such as metals and / or solids.

[0056] Within context of this disclosure, the origin of the heteropolymer mixture is not limited. Any commercially or otherwise available heteropolymer mixture is suitable for the method disclosed herein. In one embodiment, the heteropolymer mixture is derived from a multilayer plastic film material. Within context of this disclosure, the origin of the polyamide 6 containing polymer mixture or the polyethylene terephthalate (PET) containing mixture is not limited. Any commercially or otherwise available polyamide 6 containing polymer mixture or PET containing polymer mixture is suitable for the method disclosed herein. In one embodiment, the polyamide 6 containing polymer mixture or the PET containing polymer mixture is derived from a multilayer plastic film material. In one embodiment, the polyamide 6 containing polymermixture or the polyethylene terephthalate (PET) containing mixture is derived from municipal solid plastic waste (MSW plastic waste) material.

[0057] The pyrolysis reactor used in the methods of the present disclosure is a fluidized bed pyrolysis reactor. The terms ‘fluidized bed pyrolysis reactor’, ‘fluidized bed reactor’, and ’pyrolysis reactor’ may in the course of the present disclosure be used interchangeably. In one embodiment, the pyrolysis reactor is a bubbling fluidized bed reactor. In one embodiment, the pyrolysis reactor is a circulating fluidized bed reactor.

[0058] Using a fluidized bed reactor in the presented method allows to combine the fast pyrolysis, i.e., the specified residence times and the pyrolysis temperatures, with the use of steam as a functional carrier gas. The carrier gas is used in the presented method to fluidize both the support bed and the gaseous products. This combination may not be possible in other reactor types. It has been surprisingly found that water-soluble compounds may condense from the gaseous phase to the condensed water phase directly during the pyrolysis, which enables the simple recovery of the water-soluble compounds by simply separating the water phase from the organic phase.

[0059] The present disclosure also provides an apparatus for separating at least one water soluble compound from a heteropolymer mixture in a thermal pyrolysis. In one embodiment, the present disclosure provide an apparatus for separating caprolactam from an organic hydrocarbon mixture originating from a polyamide 6 containing polymer mixture in a thermal pyrolysis.

[0060] More specifically, the present disclosure relates to an apparatus for separating at least one water soluble compound from organic hydrocarbon mixture originating from a heteropolymer mixture, wherein the apparatus comprises: - a fluidized bed pyrolysis reactor in which the heteropolymer mixture is treated using a carrier gas comprising steam in thermal pyrolysis,

[0061] - at least one inlet / device for feeding the heteropolymer mixture into the fluidized bed pyrolysis reactor,

[0062] - at least one inlet / device for feeding the carrier gas comprising steam into the fluidized bed pyrolysis reactor,

[0063] - at least one condenser,- at least one phase separation unit,

[0064] - at least one outlet / device for the condensed water phase, and

[0065] - at least one outlet / device for the condensed organic phase.

[0066] The present disclosure also relates to an apparatus for separating caprolactam from organic hydrocarbon mixture originating from a polyamide 6 containing polymer mixture, wherein the apparatus comprises:

[0067] - a fluidized bed pyrolysis reactor in which the polyamide 6 containing polymer mixture is treated using a carrier gas comprising steam in thermal pyrolysis,

[0068] - at least one inlet / device for feeding the polyamide 6 containing polymer mixture into the fluidized bed pyrolysis reactor,

[0069] - at least one inlet / device for feeding the carrier gas comprising steam into the fluidized bed pyrolysis reactor,

[0070] - at least one condenser,

[0071] - at least one phase separation unit,

[0072] - at least one outlet / device for the condensed water phase,

[0073] - at least one outlet / device for the condensed organic phase, and

[0074] - at least one recovery unit for recovering at least one water soluble compound from the condensed water phase.

[0075] The present disclosure also relates to an apparatus for separating benzoic acid from organic hydrocarbon mixture originating from a polyethylene terephthalate (PET) containing polymer mixture, wherein the apparatus comprises:

[0076] - a fluidized bed pyrolysis reactor in which the polyethylene terephthalate (PET) containing polymer mixture is treated using a carrier gas comprising steam in thermal pyrolysis,

[0077] - at least one inlet / device for feeding the polyethylene terephthalate (PET) containing polymer mixture into the fluidized bed pyrolysis reactor,

[0078] - at least one inlet / device for feeding the carrier gas comprising steam into the fluidized bed pyrolysis reactor,

[0079] - at least one condenser,

[0080] - at least one phase separation unit,

[0081] - at least one outlet / device for the condensed water phase,

[0082] - at least one outlet / device for the condensed organic phase, and- at least one recovery unit for recovering at least one water soluble compound from the condensed water phase.

[0083] The inlet / device for feeding the carrier gas comprising steam, the inlet / device for feeding the heteropolymer mixture, the inlet / device for feeding the polyamide 6 containing polymer mixture, and / or the inlet / device for feeding the polyethylene terephthalate (PET) containing polymer mixture into the fluidized bed pyrolysis reactor may be any suitable device for feeding the carrier gas comprising steam, the heteropolymer mixture, the polyamide 6 containing polymer mixture, and / or the polyethylene terephthalate (PET) containing polymer mixture into the fluidized bed pyrolysis reactor. Suitable inlets / devices are known to a skilled person.

[0084] In one embodiment, the condenser comprises at least one scrubber. The use of a scrubber as the condenser may provide an advantage of improved contact between the gaseous pyrolysis products and the liquid phase when compared to other types of condensers, thus providing efficient liquid extraction for the water-soluble compounds. In other words, the water-soluble compounds may be extracted into the water phase with a higher yield when using a scrubbertype condenser.

[0085] In the presented apparatus, the pyrolysis reactor is a fluidized bed pyrolysis reactor. The terms ‘fluidized bed pyrolysis reactor’ and ‘fluidized bed reactor’ may in the course of the present disclosure be used interchangeably. In one embodiment, the pyrolysis reactor is a bubbling fluidized bed reactor. In one embodiment, the pyrolysis reactor is a circulating fluidized bed reactor.

[0086] The phase separation unit may be any suitable means for separating the water phase and the organic phase from each other. In one embodiment the phase separation unit is a decanter.

[0087] The outlet / device may be any suitable outlet for taking out the condensed water phase and the condensed organic phase from the phase separator unit. Suitable outlets / devices are known to a skilled person.The recovery unit for recovering at least one water soluble compound from the condensed water phase may be any suitable unit known to a skilled person.

[0088] Finally, the present disclosure also relates to use of the recovered caprolactam in manufacture of polyamide 6.

[0089] Example 1

[0090] In this example, plastic containing material was treated in fluidized-bed reactor. A mixture of nitrogen and steam was used as carrier gas. Used heat carrier was common joint sand with no catalytic properties. Temperature was in a range of 500-550 °C with residence time of approximately 3 s.

[0091] During the experiment, the raw material comprised of either pure LDPE (low-density polyethylene) or multilayer film which included polymers PE, PP, EVOH and PA-6 (denoted as multilayer plastic, MLP). In Figure 2 water content results are shown with different feeds. The results indicated that with the presence of MLP feed, some components were dissolved to the water fraction which could be seen as decreased water content in the analysis. The major degradation component from PA-6, caprolactam, was seen in excessive amounts in water phase, compared to organic (oil) phase (Figure 3). Caprolactam dissolves both polar and non-polar phases which allows the separation of valuable component to water phase during pyrolysis step. In addition, some other components such as ketones, nitriles, amides and carboxylic acids were found from the water phase (Table 1), suggesting that water can act as purification step during pyrolysis which increases the value of organic stream and makes the downstream processing easier.

[0092] Upon examining the water and oil fraction, it was observed that caprolactam concentration was at least 5 wt% in the water phase compared to the concentration around 0.5 wt% in the organic phase.Table 1

[0093]

[0094] n.a = not analyzed

[0095] Example 2

[0096] Condensation of benzoic acid from PET containing multilayer film was simulated in this experiment. The PET containing multilayer film was composed of PA (12.8 wt-%), PE (41.5 wt-%), PP (15.3 wt-%), EVOH (4.5 wt-%), and amorphous PET (APET) (26 wt-%).

[0097] The PET containing multilayer film was treated in a fluidized bed reactor. Nitrogen was used as a carrier gas.

[0098] After the pyrolysis reaction, the organic fraction was extracted with water at a selection of temperatures. This subsequent water extraction simulates a situation where steam would be used as the carrier gas. In other words, a similar extraction of water-soluble compounds is expected in the water extraction following the pyrolysis reaction than in a pyrolysis reaction with steam as a carrier gas.

[0099] Concentration of benzoic acid was measured from the water phase after the extraction. The results are shown in Table 2.Table 2. Benzoic acid content of water phase after extraction at different temperatures

[0100]

[0101] The results show that benzoic acid is extractable into the water phase. The obtained water phase contained up to 4.66 wt-% of benzoic acid (of the total mass of the water phase) when the extraction temperature was 80°C.

[0102] Example 3

[0103] Municipal solid plastic waste (MSW plastic waste) was treated in a fluidized bed reactor. The MSW plastic waste was composed of PET (18 wt-%), PP (28 wt-%), and PE (47 wt-%). Traces of other polymers was also observed in the feed material.

[0104] The MSW plastic waste was treated in the fluidized bed reactor at 530°C using a residence time of 1 s. Steam was used as a carrier gas.

[0105] After the pyrolysis, the composition of both the organic phase and the water phase was characterized. The water phase was shown to dissolve heteroatom-containing organic compounds. This was observed from a visual color change of the water phase. Karl Fischer titration analysis confirmed an increase of organic share in the water phase. The water phase was observed to have a water content of 98.7 wt-%, confirming the dissolution of other compounds in the water phase.

[0106] The organic phase, the water phase and the solid (char) phase were analyzed for their halogen and sulfur content. Table 3 presents the distribution of each element into the different phases, with respect to the total weight of said element in the sample. The proportion of each element in the gas phase was calculated from the measured data for the other phases.Table 3. Distribution of halogens and sulfur into the water phase, the organic phase, the solid (char) phase and the gaseous phase in the pyrolysis reactor

[0107]

[0108] n.a = not analyzed

[0109] The results show that the proportion of Cl, B r, and S transferred into the water phase is larger than the proportion remaining in the organic phase. In other words, the halogen and sulfur impurity concentration in the organic phase is reduced by the presented method (compared to, e.g. a process utilizing nitrogen as the carrier gas).

[0110] Furthermore, composition analysis of the water phase revealed that the water phase contained several heteroatom containing organic compounds, including carboxylic acids such as acetic acid (1440 mg / L) and benzoic acid (310 mg / l), aldehydes such as acetaldehyde (6490 mg / L) and benzaldehyde (125 mg / L), ketones such as acetone (248 mg / L) and 1 -hydroxy-2-propanone (600 mg / L), and caprolactam (510 mg / L).

[0111] The results show that several different kinds of water-soluble heteroatom organic compounds may be recovered from MSW plastic waste. With further processing, one or more of the heteroatom organic compounds may be separated from the water phase for utilization, e.g., as raw materials for new product syntheses.

Claims

Claims:

1. A method for separating at least one water soluble compound from a heteropolymer mixture, wherein the method comprises:- feeding the heteropolymer mixture (1) into a fluidized bed pyrolysis reactor (2),- feeding carrier gas comprising steam (3) into the fluidized bed pyrolysis reactor (2)- treating the heteropolymer mixture with a carrier gas comprising steam in thermal pyrolysis at a temperature in the range of 475°C to 650°C to obtain condensable pyrolysis products (4),- condensing (5) the condensable pyrolysis products to obtain a water phase and an organic phase,- separating (8) the organic phase (6) and the water phase (7), - recovering (9) at least one water soluble compound (10) from the water phase (7),wherein a residence time of the heteropolymer mixture (1) in the fluidized bed pyrolysis reactor (2) is from 0.5 to 5 seconds during the thermal pyrolysis.

2. The method according to claim 1 , wherein the temperature is from 500°C to 600°C during the thermal pyrolysis.

3. The method according to claim 1 or claim 2, wherein the residence time is from 1 second to 3 seconds, preferably from 1 second to 2 seconds during the thermal pyrolysis.

4. The method according to any one of claims 1-3, wherein the residence time is from 1 second to 2 seconds, and the temperature is from 500°C to 600°C during the thermal pyrolysis.

5. The method according to any one of claims 1-4, wherein condensing of condensable pyrolysis product is performed in at least one scrubbing step.

6. The method according to any one of claims 1 -5, wherein the water phase comprises hetero atoms-containing compounds.

7. The method according to any one of claims 1-6, wherein the at least one water soluble compound is recovered from the water phase by distillation, extraction and / or crystallization.

8. The method of any one of claims 1 -7, wherein the method further comprises recovering the organic phase.

9. An apparatus for separating at least one water soluble compound from organic hydrocarbon mixture originating from a heteropolymer mixture by the method according to any of claims 1-8, wherein the apparatus comprises;- a fluidized bed pyrolysis reactor in which the heteropolymer mixture is treated using a carrier gas comprising steam in thermal pyrolysis, - at least one device for feeding the heteropolymer mixture into the fluidized bed pyrolysis reactor, and- at least one device for feeding the carrier gas comprising steam into the fluidized bed pyrolysis reactor,- at least one condenser,- at least one phase separation unit,- at least one outlet for the condensed water phase,- at least one outlet for the condensed organic phase, and- at least one recovery unit for recovering at least one water soluble compound from the condensed water phase.

10. The apparatus according to claim 9, wherein the condenser comprises at least one scrubber.

11. The method of any one of claims 1 -8 or the apparatus of claim 9 or 10, wherein the heteropolymer mixture is a polyamide 6 containing polymer mixture and the at least one water soluble compound is caprolactam.

12. The method or apparatus according to claim 11, wherein the polyam ide 6 containing polymer mixture is derived from a multilayer plastic film material.

13. Use of the caprolactam obtained by the method or apparatus of claim 11 or 12 as a raw material for producing polyamide 6.

14. The method of any one of claims 1-8 or the apparatus of claim 9 or 10, wherein the heteropolymer mixture is a polyethylene terephthalate (PET) containing polymer mixture and the at least one water soluble compound is benzoic acid.

15. The method or apparatus according to claim 14, wherein the polyethylene terephthalate (PET) containing polymer mixture is derived from municipal solid plastic waste.

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