Depolymerization method and system

Abstract

The depolymerization process includes the sequential steps of pyrolyzing a polymer-containing feed material in a pyrolysis reactor to produce a hot gas stream, removing solid and liquid impurities from the gas stream in a separator and condensing monomers contained in the gas stream in a condenser. The gaseous stream is transferred from the separator to the condenser by a transfer column provided with internal components. A cold monomer in a liquid state is injected into the transfer column, the internal member is configured such that the cold monomer flows downward inside the transfer column by gravity, and heavy contaminants contained in the gas stream condense in a liquid state on the internal member and flow back by gravity toward the bottom of the transfer column and into the separator.

Description

[0001] The project leading to the present application has received funding from the European Union's Horizon2020 research and innovation programme under grant agreement No. 820687.

[0002] The present invention relates to the field of depolymerization for the recovery of monomers from feed materials containing polymers having monomers as components.

[0003] The present invention more particularly relates to a thermal depolymerization process comprising pyrolysis of a feed material, ie, heating the feed material in the substantial absence of oxygen to at least partially vaporize the feed material. The pyrolysis of the feed material produces a gas stream comprising monomer vapors.

[0004] A problem with such depolymerization processes is that the gas stream produced by pyrolysis may contain impurities (eg dust, droplets, remaining polymer chains, oligomers and / or contaminants) in addition to the evaporated monomers.

[0005] Such impurities may alter components of the depolymerization system located downstream of the pyrolysis reactor, thus negatively affecting productivity and cycle times between cleanings, or contaminate the monomer obtained from the evaporated monomer (eg recovered as so-called "crude monomer" or "pyrolysis oil").

[0006] JP3210323 and DE3146194 each disclose a depolymerization method for recovering monomers from polymers, comprising the steps of pyrolyzing a feed material containing a polymer in a pyrolysis reactor to produce a gas stream containing monomer vapor, and passing the gas stream through a separator to remove impurities from the gas stream.

[0007] WO2016 / 030460 discloses a depolymerization method for recovering monomers from polymers, which comprises the following steps: pyrolyzing a feed material containing a polymer in a pyrolysis reactor to produce a gas stream containing monomer vapor and passing the gas stream through a contactor containing a perforated plate, wherein the perforated plate is arranged to allow long-chain components to flow back to the pyrolysis reactor.

[0008] US10731080 discloses a depolymerization method for recovering monomers from polymers, which comprises the following steps: pyrolyzing waste materials containing polymers to produce a gas stream, quenching the gas stream output from a pyrolysis reactor in a quenching device to remove oligomers from the gas stream and returning the oligomers to the pyrolysis reactor.

[0009] EP2679654A1 discloses a device for carrying out a pyrolysis process of waste plastics and / or rubber waste and / or organic waste, the device comprising a pyrolysis reactor.

[0010] WO2014040634A1 discloses an apparatus for recycling plastic waste, which comprises a pyrolysis reactor, a separator and a condenser.

[0011] EP 3 031 881 A1 discloses an apparatus for processing polymer waste, the apparatus comprising a thermal reactor, a cyclone separator, a first condenser, a second condenser and a filter column arranged in series.

[0012] US10301235B1 discloses an apparatus for processing plastic waste, the apparatus comprising a pyrolysis reactor, a quenching device and a condenser, a portion of the condensate being supplied to the quenching device.

[0013] One of the objects of the present invention is to propose a depolymerization process which allows the production of monomers with satisfactory quality and satisfactory productivity, in particular as crude monomers or pyrolysis oils.

[0014] To this end, the present invention proposes a depolymerization process for recovering monomers from polymers, the depolymerization process comprising the following sequential steps: pyrolyzing a feed material containing a polymer in a pyrolysis reactor to generate a hot gas stream, removing solid and liquid impurities from the gas stream in a separator and condensing the monomers contained in the gas stream in a condenser,

[0015] wherein the gas stream is transferred from the separator to the condenser via a transfer column, the transfer column extending upward from a lower end connected to the outlet fluid of the separator to an upper end connected to the inlet fluid of the condenser,

[0016] wherein cold monomer in liquid state is injected into a transfer column, the transfer column is provided with internals, the internals being configured so that the cold monomer flows downwards inside the transfer column by gravity, heavy pollutants contained in the gas stream are condensed in liquid state on the internals and flow back by gravity toward the bottom of the transfer column and are then transferred to a separator, and the temperature of the gas stream decreases from the lower end to the upper end of the transfer column, and

[0017] The temperature of the gas stream at the outlet of the separator and the inlet of the transfer column is maintained above the boiling point of the monomer and the temperature of the gas stream at the outlet of the transfer column is maintained between the boiling point of the monomer and the boiling point of the monomer + 50°C.

[0018] In a specific embodiment, the depolymerization method includes one or several of the following optional features, which are used alone or in any technically feasible combination:

[0019] - the temperature of the gas stream at the outlet of the separator and at the inlet of the transfer column is maintained at least at the boiling point of the monomer + 20°C, in particular at least at the boiling point of the monomer + 30°C, more particularly at least at the boiling point of the monomer + 40°C, even more particularly at least at the boiling point of the monomer + 50°C;

[0020] - the temperature of the gas stream at the outlet of the transfer column is maintained between the boiling point of the monomer and the boiling point of the monomer + 50° C., in particular between the boiling point of the monomer and the boiling point of the monomer + 40° C., in particular between the boiling point of the monomer and the boiling point of the monomer + 30° C., in particular between the boiling point of the monomer and the boiling point of the monomer + 20° C., in particular between the boiling point of the monomer and the boiling point of the monomer + 10° C.;

[0021] - the internals comprise a mesh filter or a plurality of mesh filters arranged in cascade inside the transfer column;

[0022] - the internals comprise structured packing and / or random packing, for example random packing comprising saddles and / or rings, in particular ball rings;

[0023] -The internal structure includes a series of baffles;

[0024] - the internal member comprises a series of baffles, said baffles comprising internally heated baffles, preferably alternating with unheated baffles;

[0025] - injecting the cold monomer in liquid state at the upper end of the transfer column and / or at one or several intermediate positions between the lower end and the upper end of the transfer column;

[0026] - it comprises a step of filtering the cold monomer before injecting it into the transfer column;

[0027] - it comprises a step of introducing thermal energy into the interior of the transfer column and / or into the separator by heating the gas and / or liquid present inside the transfer column and / or inside the separator;

[0028] - It comprises heating the liquid collected in the separator using a heater located inside the separator and / or a heater located outside the separator for evaporating the monomer contained in the liquid and returning the monomer to the separator;

[0029] -Heating of liquids using:

[0030] - a heater provided in the form of an electric heater, which is arranged outside the separator and is used to heat the liquid collected inside the separator;

[0031] a heater provided in the form of an evaporator, in particular a wiped film evaporator, preferably arranged inside the separator, the evaporator being supplied with liquid collected from the separator; and /

[0032] or

[0033] - a heater provided in the form of a heated screw extruder, to which the liquid collected from the separator is supplied, and a gas generated by the heater provided in the form of a heated screw extruder is supplied to the separator.

[0034] - the rate of cold monomer injection into the transfer column is at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90% of the equivalent feed rate of the monomer;

[0035] - the fraction of cold monomer injected into the transfer column is less than 153%, preferably less than 103%, preferably less than 93%, preferably less than 83%, preferably less than 73%, preferably less than 63%, preferably less than 53% of the equivalent feed rate of monomer;

[0036] - the temperature of the gas stream at the inlet of the separator is equal to or higher than 250° C.;

[0037] - the temperature of the gas stream at the outlet of the separator is between 100° C. and 280° C., preferably between 110° C. and 180° C.;

[0038] - the pressure inside at least one or each of the pyrolysis reactor, separator and condenser is between 0.3 and 2.0 bar, preferably between 0.4 and 1.5 bar, more preferably between 0.5 and 1.2 bar.

[0039] The present invention also relates to a depolymerization system configured for recovering monomers from a polymer, the depolymerization system comprising: a pyrolysis reactor configured for pyrolyzing a feed material containing a polymer to produce a gas stream; a separator fluidly connected to the pyrolysis reactor for receiving the gas stream from the pyrolysis reactor and configured for removing impurities from the gas stream; and a condenser fluidly connected to the separator for receiving the gas stream from the separator and configured for condensing monomers contained in the gas stream received from the separator, wherein the depolymerization system comprises a transfer column for transferring the gas stream from the separator to the condenser, the transfer column extending upward from a lower end connected to the outlet fluid of the separator to an upper end connected to the inlet fluid of the condenser, the transfer column being configured for injecting cold monomers in a liquid state into the interior of the transfer column and provided with internal components, the internal components being configured so that in operation the cold monomers flow downwardly by gravity inside the transfer column, heavy pollutants contained in the gas stream are deposited on the internal components in a liquid state and flow back toward the separator by gravity, in particular through the bottom of the transfer column, and the temperature of the gas stream decreases from the lower end to the upper end of the transfer column.

[0040] The invention and its advantages will be better understood by reading the following description given by way of non-limiting example only and with reference to the accompanying drawings, in which:

[0041] - Figure 1 is a schematic diagram illustrating a depolymerization system for carrying out a depolymerization method for recovering monomers from a feed material containing a polymer having the monomers as its components;

[0042] - Figure 2 is available in Figure 1 A schematic side view of a separator used in a depolymerization system;

[0043] - Figure 3 yes Figure 2 A schematic top view of an alternative separator;

[0044] - Figure 4 yes Figure 3 A schematic exploded side view of a separator;

[0045] - Figure 5 is a schematic side view of the separator;

[0046] - Figure 6 is a schematic side view of the separator;

[0047] - Figure 7 is a schematic top view of the separator and the primary separator;

[0048] - Figure 8 is a schematic side view of a primary separator;

[0049] - Fig. 9 is a schematic exploded view of the separator;

[0050] - Fig.10 is a schematic side view of a depolymerization system, more particularly illustrating a transfer column having a lower end fluidly connected to an outlet of a separator and an upper end fluidly connected to an inlet of a condenser, the transfer column having internals including packing;

[0051] - Fig.11 is a schematic side view of a transfer column having internal components including a grid, filter, or perforated plate;

[0052] - Fig.12 is a schematic side view of a transfer column having internal components including a baffle;

[0053] - Fig.13 is a schematic side view of a transfer column having internal components including a baffle, the baffle comprising a jacketed baffle;

[0054] - Fig.14 is a schematic side view of a separator including a thin film evaporator for heating liquid collected from the separator and returned to the separator.

[0055] - Fig.15 is a schematic diagram illustrating the use of a reheat extruder for reheating liquid collected from a separator to be returned to the separator.

[0056] Figure 1The illustrated depolymerization system 10 is configured for use in performing a depolymerization process for recovering monomers from a feed material containing a polymer comprising the monomers as a component.

[0057] The depolymerization system 10 includes: a pyrolysis reactor 12 configured to generate a gas stream from a feed material containing a polymer, a separator unit 15 configured to remove liquid and solid impurities from the gas stream, a condenser 16 configured to condense gaseous monomers contained in the gas stream into liquid monomers, and a transfer column 18 configured to transfer the gas stream from the separator 14 to the condenser 16.

[0058] The pyrolysis reactor 12, the separator 14, the transfer column 18 and the condenser 16 are fluidly connected in series in sequence.

[0059] The depolymerization process includes the following sequential steps: pyrolyzing a feed material in a pyrolysis reactor 12 for generating a gas stream from the feed material containing a polymer, the gas stream containing monomers in a gaseous state, which are components of the polymer, directing the gas stream from the pyrolysis reactor 12 to a separator 14 for removing liquid and solid impurities from the gas stream, and transferring the gas stream from the separator 14 to a condenser 16 for condensing the monomers in a gaseous state contained in the gas stream into monomers in a liquid state.

[0060] During the implementation of the depolymerization process, the pyrolysis is operated so that the gas stream supplied to the separator 14 contains monomers in a gaseous state, which are also referred to below as "gaseous monomers".

[0061] During the performance of the depolymerization process, the condensate provided by the condenser 16 contains monomers in a liquid state, which are also referred to hereinafter as “liquid monomers” or “cold monomers”.

[0062] The condensate containing liquid monomer resulting from the depolymerization of the polymer is also referred to as "crude monomer" or "pyrolysis oil".

[0063] The monomers make up, for example, at least 20% by weight of the crude monomers, preferably at least 50% by weight of the crude monomers, still preferably at least 80% by weight of the crude monomers, and in particular at least 90% by weight of the crude monomers.

[0064] According to the depolymerization process, the gas stream is transferred from the separator 14 to the condenser 16 via a transfer column 18 extending upward from a lower end 18A fluidly connected to the gas outlet 14B of the separator 14 to an upper end 18B fluidly connected to the gas inlet 16A of the condenser 16 .

[0065] According to the depolymerization method, cold monomers in a liquid state are injected into a transfer column 18, and the transfer column 18 is provided with internal components, which are configured so that the cold monomers flow downwardly by gravity inside the transfer column 18, and heavy pollutants contained in the gas stream flowing upward through the transfer column 18 are condensed on the internal components in a liquid state and flow back toward the lower end 18A of the transfer column 18 by gravity, and then are transferred to the separator 14, and the temperature of the gas stream decreases from the lower end 18A to the upper end 18B of the transfer column 18.

[0066] The depolymerization system 10 includes, for example, a reinjection loop 20 configured to collect liquid monomers from the condenser 16 , more particularly from the condensate outlet 16B of the condenser 16 , and inject the liquid monomers into the transfer column 18 , particularly the upper end 18B of the transfer column 18 .

[0067] like Figure 1 As shown, the reinjection loop 20 includes a reinjection line 20A for reinjecting liquid monomer at the upper end 18B of the transfer column 18 .

[0068] Optionally, reinjection loop 20 is configured for reinjecting liquid monomer collected from condenser 16 at one or several intermediate injection points between lower end 18A and upper end 18B of transfer column 18 , at gas inlet 16A of condenser 16 , and / or in separator 14 .

[0069] like Figure 1 As shown, the reinjection loop 20 includes: a reinjection line 20B for reinjecting liquid monomer at an intermediate point along the transfer column 18, a reinjection line 20C for reinjecting liquid monomer at the gas inlet 16A of the condenser 16 and / or a reinjection line 20D for reinjecting liquid monomer in the separator 14.

[0070] Optionally, the depolymerization process includes filtering the cold monomer withdrawn from condenser 16 prior to reinjecting the cold monomer into transfer column 18 and optional condenser 16 and / or separator 14 .

[0071] like Figure 1 As shown, the reinjection loop 20 comprises a filtering device 22 for filtering the liquid monomer withdrawn from the condenser 16 before reinjection into the transfer column 18 and optional condenser 16 and / or separator 14. The filtering device 22 comprises, for example, one filter or two filters fluidly connected in parallel.

[0072] According to the depolymerization method, the temperature of the gas stream at the separator gas outlet 14B of the separator 14 and the lower end 18A of the transfer column 18 is maintained greater than the boiling point of the monomer and the temperature of the gas stream at the upper end 18B of the transfer column 18 is maintained between the boiling point of the monomer and the boiling point of the monomer + 50°C.

[0073] For example, the depolymerization process is operated so that the temperature of the gas stream at the gas outlet 14B of the separator 14 and the lower end 18A of the transfer column 18 is maintained, for example, at least at the boiling point of the monomer + 20°C, particularly at least at the boiling point of the monomer + 30°C, more particularly at least at the boiling point of the monomer + 40°C, even more particularly at least at the boiling point of the monomer + 50°C.

[0074] Preferably, for example, the depolymerization process is operated so that the temperature of the gas stream at the upper end 18B of the transfer column 18 is maintained between the boiling point of the monomer and the boiling point of the monomer+50°C, particularly between the boiling point of the monomer and the boiling point of the monomer+40°C, particularly between the boiling point of the monomer and the boiling point of the monomer+30°C, particularly between the boiling point of the monomer and the boiling point of the monomer+20°C, particularly between the boiling point of the monomer and the boiling point of the monomer+10°C.

[0075] Preferably, depending on the depolymerization process, the rate of cold monomer injected into transfer column 18 is at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90% of the equivalent feed rate of monomer produced by depolymerization.

[0076] The equivalent feed rate of monomer is defined as the flow rate of pyrolysis monomer produced by depolymerization and entering the inlet 14A of the separator 14 .

[0077] Preferably, the fraction of cold monomer withdrawn from condenser 16 and reinjected into transfer column 18 is less than 153%, preferably less than 103%, preferably less than 93%, preferably less than 83%, preferably less than 73%, preferably less than 63%, preferably less than 53% of the equivalent feed rate of the monomer.

[0078] Preferably, the depolymerization process is carried out so that the temperature of the gas stream at the inlet 14A of the separator 14 is equal to or higher than 250°C, preferably equal to or higher than 300°C, still preferably equal to or higher than 350°C, more preferably equal to or higher than 400°C, and even more preferably equal to or higher than 420°C.

[0079] The temperature of the gas stream at the inlet 14A of the separator 14 varies in particular with the operation of the pyrolysis reactor 12, which is configured for heating the feed material, as will be explained later.

[0080] Preferably, the depolymerization process is operated such that the temperature of the gas stream at outlet 14B of separator 14 is between 100°C and 280°C, preferably between 110°C and 180°C.

[0081] Preferably, the depolymerization process is operated such that the pressure inside the pyrolysis reactor 12, separator 14, transfer column 18 and condenser 16 is between 0.3 and 2.0 bar, preferably between 0.4 and 1.5 bar, more preferably between 0.5 and 1.2 bar.

[0082] The pyrolysis reactor 12 includes a reactor inlet 12A for receiving a feed material and a reactor outlet 12B for providing a gas stream generated by pyrolysis of the feed material.

[0083] The depolymerization system 10 comprises, for example, a feeding device 23 for supplying a polymer-containing material to the pyrolysis reactor 12, in particular to the reactor inlet 12A. The feeding device 23 comprises at least one feeder. The feeding device 23 comprises, for example, one feeder, or preferably at least two feeders, which feed into the pyrolysis reactor 12 in parallel.

[0084] The pyrolysis reactor 12 is configured to heat feed material received at a reactor inlet 12A at an elevated temperature, thereby vaporizing the feed material to produce a gas stream provided at a reactor outlet 12B.

[0085] Optionally, pyrolysis reactor 12 is configured to mechanically treat the feed material. In addition to heating the feed material, mechanically treating the feed material also facilitates the generation of a gas stream.

[0086] Mechanical treatment of the feed material in the pyrolysis reactor 12 may, for example, include stirring and / or extruding the feed material. Thus, the pyrolysis reactor 12 is, for example, configured to stir the feed material and / or to extrude the feed material.

[0087] The pyrolysis reactor 12 is configured, for example, as a heated screw extruder, in particular a heated twin-screw extruder.

[0088] The heated screw extruder comprises a tubular barrel, at least one screw extending inside the barrel and rotatably driven to extrude a feed material along a tubular chamber, and a heating system for heating the feed material contained in the barrel.

[0089] A heated twin-screw extruder is a heated screw extruder comprising two screws extending side by side in a barrel, the flights of the screws preferably intermeshing, the screws either co-rotating (rotating in the same direction about their respective axes) or counter-rotating (rotating in opposite directions about their respective axes).

[0090] The separator unit 15 has an internal flow channel for the gas stream. The gas stream flows through the separator unit 15 via its internal flow channel.

[0091] The separator 14 includes a separator gas inlet 14A for receiving a gas stream produced by the pyrolysis reactor 12 and a separator gas outlet 14B for providing a gas stream to be transferred to the condenser 16 via a transfer column 18 .

[0092] Optionally, the separator 14 comprises at least one impurity outlet 14C for collecting impurities separated from the gas stream in the separator 14 .

[0093] The separator 14 has an internal flow passage for flowing gas from the separator gas inlet 14A to the separator gas outlet 14B. The internal flow passage of the separator 14 has an upstream section adjacent to the separator gas inlet 14A and a downstream section adjacent to the separator gas outlet 14B.

[0094] The internal flow passage of the separator 14 defines at least a portion of the internal flow passage of the separator unit 15 .

[0095] The internal flow passage of separator unit 15 (including or consisting of the internal flow passage of separator 14) has a cross section that is substantially perpendicular to the gas flow in the internal flow passage. The cross section has an area (ie a measure of the cross-sectional extent).

[0096] The area of ​​the cross section of the internal flow passage of the separator unit 15 or separator 14 may be constant along the internal flow passage or vary along the internal flow passage.

[0097] In the following, the “maximum cross section” of the internal flow passage of the separator unit 15 or the separator 14 refers to the cross section of the internal flow passage of the separator unit 15 or the separator 14 which has the cross section as the maximum area.

[0098] The condenser 16 includes a gas inlet 16A for receiving the gas stream provided by the separator 14 and a condensate outlet 16B for providing a condensate (ie, a product condensed in the condenser 16 ).

[0099] Condenser 16 is configured to condense a gas stream received at gas inlet 16A and provide condensate at condensate outlet 16B.

[0100] The condenser 16 optionally includes a gas outlet 16C for providing non-condensable products that pass through the condenser 16 without condensation.

[0101] The depolymerization process is preferably carried out so that the gas stream in separator 14 is at a temperature equal to or greater than the boiling temperature of the monomers.

[0102] When the inlet flow channel is provided, the gas stream generated by the pyrolysis travels along the inlet flow channel of the separator 14 and gradually cools down. The temperature of the gas stream in the separator 14 is lowest in the downstream section of the separator 14.

[0103] In such cases, the depolymerization process is preferably carried out so that the temperature of the gas stream in the section downstream of separator 14 is equal to or higher than the boiling temperature of the monomers.

[0104] This will promote the evaporation of any liquid monomer present in the gas stream into gaseous monomer and this will prevent polymerization of the monomer.

[0105] The gas stream may contain dimers or trimers, ie chains of two or three monomers. Such dimers or trimers may be due to incomplete depolymerization during the pyrolysis process or due to oligomerization or polymerization of the monomers.

[0106] Typically, the boiling temperatures of dimers and trimers of a monomer are strictly higher than the boiling temperature of the monomer.

[0107] Preferably, the depolymerization process is carried out such that the temperature of the gas stream in the section downstream of separator 14 is at a temperature strictly below the boiling temperature of the trimers of the monomers and / or below the boiling temperature of the dimers of the monomers.

[0108] This will cause a majority of the dimers and / or trimers present in the gas stream to condense in separator 14 , thereby retaining the dimers and trimers in separator 14 and limiting or preventing their flow to transfer column 18 and condenser 16 .

[0109] The depolymerization process is carried out, for example, with polymethyl methacrylate (PMMA), which refers to a homopolymer or copolymer of methyl methacrylate (MMA) containing at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, advantageously at least 80% by weight and even more advantageously at least 90% by weight of methyl methacrylate.

[0110] In the case of PMMA (polymer) and MMA (monomer), the boiling temperature of MMA is about 100° C., and the boiling temperatures of the dimer and trimer are about 200° C. and 300° C., respectively, at atmospheric pressure.

[0111] Thus, in this case, the depolymerization process is carried out such that the temperature of the gas stream at the separator outlet 14B and at the lower end 18A of the transfer column 18 is above 100°C.

[0112] It is also preferred to carry out the depolymerization process such that the temperature of the gas stream in the downstream section of the inlet flow channel of the separator 14 is between 100°C and 280°C, in particular between 110°C and 180°C.

[0113] Advantageously, the depolymerization process comprises spraying the liquid monomer withdrawn from the condenser 16 into the separator 14, spraying the liquid monomer into the gas stream and preferably facing the gas stream.

[0114] Optionally, the depolymerization process includes spraying a portion of the liquid monomers recovered by condenser 16 into separator 14 .

[0115] Spraying the liquid monomer recovered through the condenser 16 into the separator 14 provides a cleaning effect in the separator 14 (eg, on the wall of the separator 14 or on a demisting device provided inside the separator 14).

[0116] Preferably, the spraying of the liquid monomer recovered by the condenser 16 into the separator 14 is performed intermittently, for example during the cleaning phase.

[0117] In this case, the depolymerization system 10 is configured to spray a portion of the liquid monomers recovered by the condenser 16 into the separator 14 , for example, via the reinjection line 20D of the reinjection loop 20 .

[0118] Preferably, the liquid monomer is sprayed into the separator 14 so that the ratio of the mass rate of the liquid monomer sprayed into the separator 14 to the mass rate of the gas stream is equal to or less than 93%, still preferably equal to or less than 83%, still preferably equal to or less than 73%, still preferably equal to or less than 63%, still preferably equal to or less than 53%.

[0119] Preferably, the liquid monomer is sprayed into the separator 14 so that the mass rate of the liquid monomer sprayed into the separator 14 is equal to or greater than 10%, still preferably equal to or greater than 20%, preferably equal to or greater than 30%, still preferably equal to or greater than 40%, still preferably equal to or greater than 50% of the mass rate of the gas stream.

[0120] Optionally, instead of or in addition to spraying liquid monomer into the interior of separator 14, the depolymerization process includes spraying liquid water into the interior of separator 14. The benefits are similar to those of spraying liquid monomer into the interior of separator 14.

[0121] The pyrolysis reactor 12 is configured to process a feed material having a maximum mass flow rate, and therefore provide a gas stream having a maximum mass flow rate.

[0122] Further, in any section of the internal flow channel of the separator unit 15, the gas stream flowing in the separator unit 15 has a linear velocity, which is determined by the volume of gas produced by the pyrolysis reactor 12 per unit time divided by the cross-sectional area of ​​the section of the internal flow channel of the separator unit 15.

[0123] Preferably, the depolymerization process is carried out such that the linear velocity of the gas stream in the separator unit 15 is below the maximum linear velocity at least in the section of the internal flow channel of the separator unit 15 having the largest cross section.

[0124] In a particular embodiment, the section of the internal flow channel of the separator unit 15 having the largest cross section is the downstream section of the internal flow channel of the separator unit 15 .

[0125] In one embodiment, in particular if the polymer is PMMA, the maximum line speed is 0.50 m / s, preferably 0.15 m / s, in particular 0.10 m / s.

[0126] The linear velocity of the gas stream in any section of the internal flow passage of the separator unit 15 is a function of the mass flow rate of the gas stream or the volume flow rate of the gas stream and the cross-sectional area of ​​the section of the internal flow passage of the separator unit 15. The mass flow rate is related to the volume flow rate and mass density of the gas stream at the operating pressure.

[0127] The volumetric flow rate of the gas stream varies with the feed rate to the pyrolysis reactor 12, the depolymerization temperature of the polymer, and the molar mass of the polymer.

[0128] Advantageously, the area of ​​the maximum cross-section of the internal flow channel of the separator unit 15 is selected, for example, based on the maximum feed rate of the pyrolysis reactor 12, the depolymerization temperature of the polymer and the molar mass of the polymer, so that the linear velocity of the gas stream in the maximum cross-section of the internal flow channel of the separator unit 15 is lower than the maximum linear velocity at the maximum feed rate of the pyrolysis reactor.

[0129] Preferably, the maximum cross-section of the internal flow channel of the separator unit 15 has an area of ​​at least 0.001 times the maximum mass flow rate of the gas stream provided by the pyrolysis reactor 12, the area being measured in square meters (m2). 2 ), and the maximum mass flow rate is expressed in kilograms per hour (kg / h).

[0130] Preferably, the area of ​​the largest cross section of the internal flow channel of the separator unit 15 is at least ten times the area of ​​the smallest cross section in the separator unit 15 .

[0131] These parameters allow limiting the linear velocity of the gas stream in the separator unit 15, thus favoring the deposition of dust and droplets carried by the gas stream and thus separating these droplets from the gas stream. In fact, the lower the linear velocity of the gas stream, the less likely the droplets and dust are to be carried by the gas stream.

[0132] Advantageously, the depolymerization process comprises gradually decelerating the gas flow inside the separator unit 15 .

[0133] This is achieved, for example, by gradually increasing the cross-section of the internal flow passage of the separator 14 from the separator gas inlet 14A to the separator gas outlet 14B.

[0134] In such a case, the downstream section of the internal flow channel of the separator 14 is the section of the internal flow channel of the separator 14 having the largest cross section.

[0135] Advantageously, the residence time of the gas stream in the separator unit 15 is between 1 s and 30 s, preferably between 5 s and 25 s, still preferably between 10 s and 20 s.

[0136] The residence time is the time required for the gas stream to flow through the separator unit 15 .

[0137] The residence time varies with the length of the internal flow channel of the separator unit 15 , the average temperature, the mass flow rate or volume flow rate, and the molecular weight, and also with the internal volume of the separator unit 15 .

[0138] The gas stream produced by the pyrolysis reactor 12 may contain a mist formed by droplets. The droplets may form around dust particles present in the gas stream. The dust particles may be due to impurities in the feed material containing the polymer to be depolymerized. The droplets present in the gas stream may contain liquid monomers, liquid dimers, or liquid trimers carried on the dust particles present in the gas stream.

[0139] Advantageously, the depolymerization process comprises demisting the gas stream (eg passing the gas stream through a demister or demisting device) and / or desublimating the gas stream (ie passing the gas stream through a desublimator or desublimating device).

[0140] Demisting is different from condensing monomers in the gaseous state into monomers in the liquid state. Demisting consists in collecting droplets in the liquid state that are already present in the gas stream, such as droplets in a mist.

[0141] For example, demisting can be achieved by favoring the coalescence of mist droplets present in the gas stream, such as by defining small channels to force the droplets to flow closer to each other and then coalesce.

[0142] Demisting is performed, for example, by providing at least one demisting device, each demisting device being configured to favor coalescence of the mist droplets so that the mist droplets become too heavy to be transported by the gas stream.

[0143] Each demisting device may comprise a cyclonic effect chamber, at least one grid, at least one mesh, at least one piece of foam, at least one porous monolith and / or at least one baffle for capturing the mist droplets, for example by facilitating their coalescence.

[0144] Optionally, the depolymerization process includes demisting the gas stream inside separator 14 .

[0145] In this case, the separator 14 comprises an internal demisting device located inside the separator 14 .

[0146] Optionally, the depolymerization process includes demisting the gas stream downstream of the condenser 16 (ie, the gas stream collected from the condenser gas outlet 16C of the condenser 16).

[0147] In this case, the depolymerization system 10 comprises a demisting unit 24 comprising at least one downstream demisting device 24A, 24B arranged downstream of the condenser 16, each downstream demisting device 24A, 24B being configured for removing droplets present in the gas stream.

[0148] The demisting unit 24 includes, for example, two demisting devices 24A, 24B arranged in series on a fluid line (collecting gas from the condenser gas outlet 16C of the condenser 16 ).

[0149] The upstream demisting device 24A is, for example, configured to demist the gas at the temperature of the gas, and the downstream demisting device 24B is, for example, configured to cool and demist the gas simultaneously using cold, for example, provided by the cold generator 26 .

[0150] Desublimation differs from demisting in that it provides for the retention of the gaseous portion of the gas stream as solids.

[0151] Desublimation involves passing a gas stream through a chamber containing sheets or fins, cooling the sheets or fins so that the product to be separated from the rest of the gas stream desublimates near or below its triple point and adheres to the sheets or fins in crystalline form.

[0152] The desublimator is gradually charged with the separation product in crystalline or solid form and can be discharged by heating so that the crystalline or amorphous solid separation product melts. This requires that the separation product to be captured can be heated to melt without polymerization.

[0153] In the case of PMMA depolymerization, provision of a desublimator may be suitable for removing terephthalic acid from dimethyl terephthalate which may result from PET contamination and be present in the gas stream.

[0154] Providing a desublimator may be appropriate, for example, where there is a risk of contamination with polyolefins (eg PE), which may produce wax having a high melting point and which may be captured in the condenser 16 .

[0155] The desublimation unit may comprise two desublimators fluidly connected in parallel, such that one of the two desublimators may be maintained in operation while the other is emptied, thus allowing the depolymerization system 10 to operate continuously.

[0156] Optionally, the depolymerization process includes passing the gas stream through a desublimator to capture contaminants present in the gas stream.

[0157] If a desublimation unit is provided, the latter is preferably installed in series between the separator 14 and the condenser 16 .

[0158] like Figure 1As shown, the depolymerization system 10 optionally includes a desublimation unit 25 provided between the separator 14 and the condenser 16 to process the gas stream flowing from the separator 14 to the condenser 16 .

[0159] The desublimation unit 25 comprises, for example, one desublimator or two desublimators fluidly connected in parallel between the separator 14 and the condenser 16. Each desublimator can process a gas stream while discharging the other desublimator.

[0160] Optionally, the depolymerization system 10 comprises a side container 27 in fluid connection with the separator 14 in order to indicate the liquid level in the separator 14 .

[0161] The side container 27 is fluidly connected to the separator 14, for example, via a liquid pipeline 29A for collecting liquid from the bottom of the separator 14 (preferably heating the liquid connection pipeline 29A) and optionally via a gas pipeline 29B for returning gas to the separator 14.

[0162] Optionally, the depolymerization process includes a primary separation between the pyrolysis reactor 12 and the separator 14 for separating dust from the gas stream before supplying the gas stream to the separator 14 .

[0163] Accordingly, the separator unit 15 optionally comprises a primary separator 100 which is inserted in series between the pyrolysis reactor 12 and the separator 14 and is configured to separate dust from a gas stream generated by the pyrolysis reactor 12 before the gas stream enters the separator 14 .

[0164] The deagglomeration system 10 preferably comprises a solid particle collector 90 connected to the primary separator 100 for collecting dust.

[0165] The solid particle collector 90 is removably connected to the primary separator unit 100 , for example, preferably via a valve 35 configured to allow exchange with another solid particle collector 90 during an ongoing process, ie, during operation of the depolymerization system 10 .

[0166] The primary separator 100 must be considered to determine the ratio between the maximum cross-section of the internal channels of the separator unit 15 and the maximum flow rate of the gas stream provided by the pyrolysis reactor 12 , and to determine the residence time of the gas stream in the separator unit 15 .

[0167] Thus, preferably, the residence time of the gas stream in the separator unit 15 (comprising the separator 14 and, if appropriate, the primary separator 100 ) is between 1 s and 30 s, preferably between 5 s and 25 s, still preferably between 10 s and 20 s.

[0168] Furthermore, preferably, the maximum cross-section of the internal flow passage of the separator unit 15 (comprising the separator 14 and, if appropriate, the primary separator 100) has an area of ​​at least 0.001 times the maximum mass flow rate of the gas stream provided by the pyrolysis reactor 12, the area being expressed in square meters (m2). 2 ), and the maximum mass flow rate is expressed in kilograms per hour (kg / h).

[0169] Optionally, the depolymerization system 10 includes an inert gas feed assembly 37 configured for supplying an inert gas, such as nitrogen or argon, into the depolymerization system 10 during shutdown of the depolymerization system 10 and maintaining a lower oxygen partial pressure in the unit.

[0170] The inert gas feed assembly 37 , for example, is configured to inject an inert gas into the separator 14 .

[0171] The depolymerization system 10 preferably comprises a pump for forcing the fluid to flow into the depolymerization system 10. Figure 1 As shown, the depolymerization system 10 comprises, for example, a pump arranged at the condensate outlet 16B of the condenser 16 , a pump on the reinjection loop 20 and / or a pump on the reheating loop 11 .

[0172] Optionally, the depolymerization process includes injecting liquid monomer withdrawn from a liquid monomer reservoir, for example, at the upper end 18B of the transfer column 18, at one or several intermediate injection points between the lower end 18A and the upper end 18B of the transfer column 18, at the condenser inlet 16A, and / or in the separator 14 during a cleaning phase or a start-up phase.

[0173] To this end, the depolymerization system 10 comprises, for example, a liquid monomer reservoir 39 fluidly connected to the reinjection loop 20 for providing liquid monomer during a cleaning phase or a start-up phase.

[0174] The depolymerization system 10 includes the necessary pumps 140 , 142 , 144 that are required to force fluid flow through the components, lines, and circuits of the depolymerization system 10 .

[0175] like Figure 1 As shown, a pump 140 is provided on the reinjection loop 20, and a pump 142 is provided on the condensate outlet 16B for the produced liquid monomer. A pump 144 is also provided on the reheating loop which will be described in detail later.

[0176] The portion of the cold monomer withdrawn by the condensate outlet 16B defines the “produced” cold monomer which is collected to be used as a final product or to be further processed, in particular to be distilled. The produced cold monomer is pumped here by means of a pump 142 .

[0177] A portion of the cold monomers withdrawn at the condensate outlet 16B is collected by a reinjection loop 20 for reinjection in the depolymerization system 10 , in particular the upper end 18B of the transfer column 18 .

[0178] Preferably, the depolymerization process comprises injecting a stabilizer into the produced cold monomer.

[0179] Stabilizers are formulated to prevent polymerization of cold monomers during storage or further processing such as distillation.

[0180] Optionally, the depolymerization process includes injecting a stabilizer into the reinjected cold monomer.

[0181] The stabilizer injected into the re-injected cold monomer is, for example, the same stabilizer injected into the production cold monomer, has the same dosage or a different dosage, or is different from the stabilizer injected into the production cold monomer.

[0182] If the stabilizer injected into the produced cold monomer is the same as the stabilizer injected into the reinjected cold monomer, this stabilizer is, for example, injected into the condensate outlet 16B upstream of the branch of the reinjection loop 20, whereby the dosage is the same, or the stabilizer is injected into the condensate outlet 16B downstream of the branch of the reinjection loop 20 on the one hand and into the reinjection loop 20 on the other hand, whereby the dosage is the same or different dosages are used.

[0183] If different stabilizers are used, one stabilizer is injected at the condensate outlet 16B downstream of the branching of the reinjection loop 20 , and the other stabilizer is injected in the reinjection loop 20 .

[0184] The stabilizer injected in the produced cold monomer is, for example, selected from one of the following families: phenothiazines, hydroquinones, topanol and butylated hydroxytoluene (or "BHT").

[0185] The stabilizer injected in the re-injected cold monomer is preferably from the phenothiazine family or any other stabilizer that can be used in the absence of oxygen.

[0186] Figure 2 A separator 14 suitable for use in a depolymerization system 10 for carrying out the depolymerization process is shown.

[0187] The separator 14 includes an internal flow passage 30 configured for circulating a gas stream between the separator inlet 14A and the separator outlet 14B.

[0188] In one example, if Figure 2 As shown, the pyrolysis reactor outlet 12B is directly connected to the separator inlet 14A, so that the gas stream generated by the pyrolysis reactor 12 flows directly out of the pyrolysis reactor outlet 12B.

[0189] Preferably, when the pyrolysis reactor 12 has at least one extrusion screw, the extrusion screw is inserted or protruded into the separator inlet 14A to avoid clogging of the reactor outlet 12B by impurities.

[0190] In other words, the pyrolysis reactor outlet 12B is directly fluidly connected to the separator inlet 14A, so that the gas stream generated by the pyrolysis reactor 12 flows directly from the pyrolysis reactor outlet 12B directly connected to the separator inlet 14A without passing through any other fluid conducting elements.

[0191] The separator 14 includes, for example, a separation chamber 32 extending around a central axis A. The separator 14 is configured such that a gas stream circulates around the central axis A in the separation chamber 32 .

[0192] The separator 14 is thus configured to implement a cyclone effect in the separation chamber 32 .

[0193] With such a configuration, the gas stream flows faster at the periphery of the separation chamber 32 and slower at the center of the separation chamber 32 , whereby impurities present in the gas stream tend to stay at the periphery of the separation chamber 32 .

[0194] The separator 14 includes, for example, an inlet conduit 34 configured to receive a gas stream produced by the pyrolysis reactor 12. The inlet conduit 34 extends from the separator inlet 14A, which defines an upstream end of the inlet conduit 34. The inlet conduit 34 forms an upstream section of the interior volume 30 of the separator 14.

[0195] With a view to promoting a circular flow of the gas stream in the separation chamber 32 , an inlet duct 34 is for example present in the separation chamber 32 , thereby imparting a rotational movement about the central axis A to the gas stream in the separation chamber 32 .

[0196] In a particular embodiment, the inlet conduit 34 opens into the separation chamber 32 such that the gas stream emerges into the separation chamber 32 along an inlet direction defining a non-zero angle with a radial direction that is radial relative to the central axis A.

[0197] In a variant in which the separator 14 has no inlet duct 34 , the separator inlet 14A opens, for example, into the separation chamber 32 , thereby imparting a rotational movement about the central axis A to the gas stream in the separation chamber 32 .

[0198] In a particular embodiment, the separator inlet 14A opens into the separation chamber 32 , for example, such that the gas stream emerges into the separation chamber 32 along an inlet direction that defines a non-zero angle with a radial direction that is radial relative to the central axis A.

[0199] Advantageously, the inlet duct 34 extends around a central axis A. This allows obtaining a cyclonic or rotating effect in the inlet duct 34 .

[0200] The separator 14 is preferably configured for collecting the gas stream at the center of the separation chamber 32 and for providing the gas stream collected at the center of the separation chamber 32 to the separator outlet 14B.

[0201] The separator 14 includes, for example, a collecting pipe 36 located at the center of the separation chamber 32, which extends along the central axis A and has at least one inlet opening 38 for allowing the gas stream present in the separation chamber 32 to enter the collecting pipe 36, and the collecting pipe 36 is fluidically connected to the separator outlet 14B for providing the collected gas stream to the separator outlet 14B.

[0202] The collecting tube 36 is provided, for example, with at least one inlet section 40 , each inlet section 40 comprising one inlet opening 38 or several inlet openings 38 which are distributed circumferentially around the inlet section 40 of the collecting tube 36 .

[0203] The collecting tube 36 is provided, for example, with a plurality of inlet sections 40 distributed along the collecting tube 36 , each inlet section 40 comprising one inlet opening 38 or several inlet openings 38 distributed circumferentially around the inlet section 40 of the collecting tube 36 .

[0204] In a preferred embodiment, the collecting tube 36 is provided with at least one frustoconical baffle 42 , each having an upper edge of smaller diameter connected to the collecting tube 36 and a free lower edge of larger diameter, the baffle 42 extending around the respective inlet section 40 .

[0205] Preferably, each inlet section 40 is associated with a respective frustoconical baffle 42 extending around the inlet section 40 .

[0206] Preferably, the upper edge of each frustum baffle 42 is located above each inlet opening 38 of the corresponding inlet section 40 , and the lower edge of the frustum baffle 42 is located below each inlet opening 38 of the corresponding inlet section 40 .

[0207] Each frustoconical baffle 42 forces the gas stream to flow below the lower edge of the frustoconical baffle 42 before entering the inlet opening 38 of the corresponding inlet section 40 .

[0208] Each frustum baffle 42 facilitates impurities to fall to the bottom of the separation chamber 32 and / or to be deposited on the frustum baffle 42 .

[0209] Preferably, each inlet opening 38 has a width between 3 and 79 mm. 2 Between, and preferably between 12 and 51 mm2 The area between.

[0210] Preferably, each inlet opening 38 has a circular profile with a diameter between 2 and 10 mm, preferably between 4 and 8 mm.

[0211] Preferably, the cumulative area of ​​the inlet openings 38 (i.e., the sum of the areas of all inlet openings 38) is between 0.01 times and 1.0 times the area of ​​the cross-section of the upstream section of the internal flow channel 30 of the separator 14, in particular between 0.01 times and 0.1 times the area of ​​the cross-section of the upstream section of the internal flow channel 30 of the separator 14.

[0212] exist Figure 2 In the separator 14 of FIG. 1 , the upstream section of the internal flow passage 30 of the separator 14 corresponds to the upstream end of the inlet conduit 34 .

[0213] Advantageously, the separator 14 is configured such that the largest cross section of the separator 14 is located in the downstream section of the separator 14 .

[0214] exist Figure 2 In the separator 14 shown, a downstream section of the separator 14 is defined by a separation chamber 32 .

[0215] In one example where the separator 14 includes an inlet conduit 34 and a separation chamber 32 , the inlet conduit 34 has a cross-section that gradually increases from an upstream end of the inlet conduit 34 that receives the gas stream to a downstream end of the inlet conduit 34 that opens into the separation chamber 32 .

[0216] Therefore, the gas stream gradually decelerates in the inlet conduit 34 until the gas stream reaches the separation chamber 32 .

[0217] The inlet duct 34 has, for example, a height that gradually increases in the downstream direction and / or a width that gradually increases along the inlet duct 34 in the downstream direction so as to increase the cross-sectional area of ​​the inlet duct 34 in the downstream direction.

[0218] Advantageously, if Figure 2 As shown, the separator 14 is configured for spraying liquid monomer into the gas stream inside the separator 14 .

[0219] The separator 14 is configured to inject one or several spray jets into the gas stream inside the separator 14 .

[0220] To this end, the separator 14 includes at least one spray nozzle 44 for spraying the liquid monomer inside the separator 14. Each spray nozzle 44 is configured to spray a spray stream.

[0221] The direction of each spray stream can be parallel, perpendicular or oblique to the gas stream. In one example, each spray stream faces the gas stream, i.e., sprays toward the upstream of the gas stream.

[0222] Each spray nozzle 44 is fluidly connected to the condenser 16 , and more specifically, to the return line 20D.

[0223] Each injection nozzle 44 is, for example, arranged to inject liquid monomer into the separation chamber 32 .

[0224] like Figure 2 As shown, the separator 14 comprises, for example, an injection nozzle 44 arranged to inject liquid monomer at the inlet of the separation chamber 32 (ie where the inlet conduit 34 connects to the separation chamber 32, here in the upstream direction of the gas stream).

[0225] Advantageously, the separator 14 comprises internal demisting means 46 located inside the separator 14 for depositing the mist droplets transported by the gas stream.

[0226] The internal demisting device 46 comprises, for example, at least one grid 48 extending across the cross section of the separator 14 , such that the gas stream flows through openings of the grid 48 .

[0227] In an example where the separator 14 includes the inlet duct 34 , each grid 48 is located, for example, within the inlet duct 34 .

[0228] like Figure 2 As shown, the separator 14 comprises two grids 48 arranged in the inlet duct 34. The two grids 48 are located along the inlet duct 34 at a distance from each other.

[0229] The inlet duct 34 is defined between a lower surface 50 and an upper surface 52 .

[0230] In one example, the conduit lower surface 50 is sloped and / or the conduit upper surface 52 is sloped.

[0231] Specifically, the duct lower surface 50 is sloped and / or the duct upper surface 52 is sloped such that the cross-section of the inlet duct 34 increases from the upstream end of the inlet duct 34 toward the downstream end of the inlet duct 34 .

[0232] like Figure 2 As shown, the conduit lower surface 50 is sloped such that it descends from the upstream end of the inlet conduit 34 toward the downstream end of the inlet conduit 34. Mist droplets deposited on the conduit lower surface 50 will tend to flow by gravity toward the separation chamber.

[0233] In one example, the inlet conduit 34 extends around the separation chamber 32 over at least a portion of the circumference of the separation chamber 32 .

[0234] like Figure 3 As shown, the inlet conduit 34 extends around the separation chamber 32 about the central axis A over approximately 270°.

[0235] In operation, the gas stream is hot when it enters the separator 14, and due to heat losses, the temperature of the gas stream tends to decrease as it passes through the separator 14, even if the separator 14 is properly insulated. If liquid monomer is sprayed into the separator 14, such spraying tends to further cool the gas stream in the separator 14 due to the evaporation of the liquid monomer sprayed into the hot gas stream.

[0236] The inlet conduit 34 partially surrounding the separation chamber 32 facilitates maintaining the gas stream in the separator 14 , and in particular in the separation chamber 32 , sufficiently hot.

[0237] like Figure 4 As shown, in one exemplary embodiment, the separator 14 includes a bottom portion 60 and a top portion 62 assembled to the bottom portion 60 for forming the separator 14 .

[0238] The bottom portion 60 comprises a bottom 64 and a peripheral wall 66 extending upward from the periphery of the bottom 64, the peripheral wall 66 defining an upper opening 68 and an inner volume 70. The peripheral wall 66 is provided with a side opening defining the inlet opening 14A of the separator 14. The peripheral wall 66 is, for example, cylindrical and has a circular cross section.

[0239] The top portion 62 includes a cover 72 for closing the upper opening 68 and an internal structure 74 extending downwardly from the cover 72 for mounting within the bottom portion 60 when the upper opening 68 is closed by the cover 72. The internal structure 74 is configured to define the separation chamber 32 and the inlet conduit 34 within the interior volume 70 of the bottom portion 60.

[0240] The internal structure 74 includes: a partition wall 76 extending downward from the cover 72 along the central axis A, for internally defining the separation chamber 32 and externally defining the inlet duct 34 separated by the peripheral wall 66; and a duct element 78 extending around the partition wall 76, for defining the lower surface 50 of the inlet duct 34, and the upper surface 52 of the inlet duct 34 is defined by the peripheral area below the cover 72.

[0241] The partition wall 76 has an inner face 74A defining a side wall of the separation chamber 34 and an outer face 76B defining a side wall of the inlet duct 34 .

[0242] When viewed along the central axis A, the partition wall 76 extends around the central axis A. Figure 3 The upper angle is approximately 270°.

[0243] The inlet duct 34 is defined between the partition wall 76 , the peripheral wall 66 , the duct element 78 and the cover 72 .

[0244] The peripheral wall 66 is provided with a connector 67 for connection to the outlet of the pyrolysis reactor 12. The connector 67 is outlined in dashed lines as S to show its position relative to the upstream end of the inlet conduit 34.

[0245] The cover 72 is perpendicular to the central axis A, and the duct element 78 extends around the central axis A, wherein the top surface of the duct element 78 is inclined relative to the central axis A, so that the height of the inlet duct 34 gradually increases from the upstream end of the inlet duct 34 to the outlet end of the inlet duct 34, and the cross-section of the inlet duct 34 gradually increases from the upstream end of the inlet duct 34 to the outlet end of the inlet duct 34.

[0246] The duct element 78 extends, for example, helically around the central axis A of the separation chamber 32 .

[0247] Viewed along the central axis A, the partition wall 76 extends, for example, along a portion of a circle or along a portion of a spiral, wherein the inlet duct 34 delimited by the partition wall 76 approaches the central axis A in the downstream direction.

[0248] A circular extension of the partition wall 76 serves, for example, to define an inlet duct 34 of constant width in the downstream direction of the inlet duct 34 , and a helical extension of the partition wall 76 serves, for example, to define an inlet duct 34 of increasing width in the downstream direction of the inlet duct 34 .

[0249] The bottom 64 of the bottom portion 60 defines a lower surface of the separation chamber 32 .

[0250] The bottom 64 is provided with an evacuation opening 80 for evacuating impurities separated from the gas stream in the separator.

[0251] Preferably, the bottom 64 is shaped for impurities to fall toward the evacuation opening 80 by gravity. Figure 4 As shown, the bottom 64 is a frustum that tapers downwardly to the evacuation opening 80 .

[0252] Optionally, the separator 14 includes a collection tank 82 configured to be mounted below the bottom portion 60 for collecting impurities that fall into the evacuation opening 80 .

[0253] Preferably, the collection tank 82 is movably connected to the bottom 64. Therefore, the collection tank 82 can be removed to empty the collection tank 82.

[0254] Optionally, the evacuation opening 80 is equipped with a valve 83, such as a sliding valve, arranged for selectively closing or opening the evacuation opening 80. This allows disconnecting the collection tank 82 after closing the valve 83 while the separator 14 is still in operation.

[0255] The collection tank 82 may be equipped with a gas purge line and / or the collection tank 82 may be actively cooled to allow it to be safely removed and replaced.

[0256] In one example, the separator 14 is provided with a scraping device configured to scrape the product deposited in the separator 14 to the evacuation opening. The scraping device is configured to scrape the bottom of the separator 14, for example.

[0257] like Figure 2 and 4 As shown, the scraping device 84 is configured, for example, to scrape products deposited on the bottom wall 64 of the bottom portion 60 towards the evacuation opening 80 .

[0258] The separator 14 is not limited to Figure 2-4 Examples are shown, other variations or options are possible.

[0259] Figure 5 The separator 14 (in which similar elements are numbered the same) is connected to Figure 2-4 The separator 14 of FIG. 1 is different in that the inlet duct 34 is delimited by a lower surface 50 and an upper surface 52 , wherein the lower surface 50 extends along a plane perpendicular to the central axis A and the upper surface 52 is inclined to rise from the upstream end of the inlet duct 34 to the downstream end of the inlet duct 34 .

[0260] Figure 5 The separator 14 and Figure 2-4 The separator 14 in FIG. 1 is different in that the spraying device 42 is arranged to spray the liquid monomer at a position close to the central axis A, in particular, around the central axis A. The spraying device 42 includes a plurality of spray nozzles 44 distributed around the central axis A, for example.

[0261] If Figure 5 As shown, a collecting tube 36 is provided, and the spraying device 42 is configured to spray the liquid monomer around the collecting tube 36, for example.

[0262] Spraying liquid monomer withdrawn from the condenser 16 into the separator 14 can be used to prevent clogging of one or several demisting grids 48 provided inside the separator 14 over time, in particular by spraying the liquid monomer onto the demisting grids 48 .

[0263] Figure 6 The separator 14 , in which like elements are numbered the same, comprises a spray nozzle 44 oriented to spray liquid monomer withdrawn from the condenser 16 onto a most downstream demisting grid 48 provided in the inlet duct 34 of the separator 14 .

[0264] Optionally, as Figure 6As shown, the separator 14 comprises one or several spray nozzles 44 arranged to spray the liquid monomer withdrawn from the condenser 16 onto the face of the most upstream demisting grid 48 provided in the inlet duct 34 of the separator 14 .

[0265] Optionally, as Figure 6 As shown, the separator 14 includes one or several spray nozzles 44, which are arranged to spray the liquid monomer withdrawn from the condenser 16 into the intermediate space defined between two demister grids 48 provided in the inlet pipe 34 of the separator 14, preferably spraying the liquid monomer onto one or both of the two demister grids 48.

[0266] Optionally, as Figure 6 As shown, the separator 14 comprises a demisting grid 48 provided in a downstream section of the separator, in particular around the collecting pipe 36 .

[0267] The demisting grid 48 is, for example, arranged in a tubular shape and installed around the collecting pipe 36 , so that the gas stream must pass through the demisting grid to reach the collecting pipe 36 .

[0268] The gas stream entering the separator 14 may contain solid particles due to impurities in the raw materials being depolymerized in the pyrolysis reactor 12 .

[0269] Optionally, the separator 14 is provided with at least one solid particle collector 90 , which is preferably arranged in the inlet duct 34 of the separator 14 , preferably upstream of a demisting grid 48 provided in the inlet duct 34 of the separator 14 .

[0270] Each solid particle collector 90 comprises a collection tank 92 connected to the separator 14, for example, by a collection pipe 94, so that the solid particles fall by gravity into the collection tank 92. The collection pipe 94 is connected to the lower wall 50 of the inlet pipe 34 of the separator 14, for example.

[0271] The collection tank 92 is preferably movably connected to the separator 14. This allows the collection tank 92 to be emptied or replaced with a new one when solid particles are collected in the collection tank 92. The collection tank may be equipped with one or two valves to separate it from the separator 14 and allow replacement of the collection tank.

[0272] Preferably, each solid particle collector 90 is located in a climate chamber 96 that is controlled to maintain a temperature therein that is equal to or higher than the boiling temperature of the monomer.

[0273] The separator 14 may be provided with one or several solid particle collectors 90 .

[0274] like Figure 6As shown, the separator 14 is provided with two solid particle collectors 90 , each connected to the inlet conduit 34 of the separator 14 at a respective location along the inlet conduit 34 of the separator 14 .

[0275] When a plurality of solid particle collectors 90 are provided, each solid particle collector may be connected to the inlet duct 34 of the separator 14 upstream of a corresponding one of a plurality of demisting grids 48 provided in the inlet duct 34 of the separator 14 .

[0276] like Figure 6 As shown, the separator 14 is provided with two demisting grids 48 extending across the inlet duct 34 of the separator 14 , and with two solid particle collectors 90 , each connected to the inlet duct 34 of the separator 14 upstream of a respective one of the two demisting grids 48 .

[0277] One of the solid particle collectors 90 is connected to the inlet duct 34 upstream of the first demisting grid 48 , and one of the solid particle collectors 90 is connected to the inlet duct 34 between the two demisting grids 48 .

[0278] When a plurality of solid particle collectors 90 are provided, they may be housed in the same climate chamber 96 .

[0279] like Figure 6 As shown, the separator 14 is provided with two solid particle collectors 90 arranged in the same climate chamber 96 .

[0280] like Figure 7 and 8 As shown, the separator unit 15 advantageously comprises a primary separator 100 configured to separate dust from the gas stream produced by the pyrolysis reactor 12 before the gas stream enters the separator 14 .

[0281] The primary separator 100 comprises a separation chamber 102 having a gas inlet 101 connected to the pyrolysis reactor 12 , a gas outlet 103 connected to the gas inlet 14A of the separator 14 , and a dust outlet 105 for collecting dust.

[0282] like Figure 7 and 8 As shown, the gas inlet 101 is, for example, coaxial with the gas outlet 103 so that in operation the gas flows along a straight line from the gas inlet 101 to the gas outlet 103 , and the dust outlet 105 is formed in the bottom wall of the separation chamber 102 .

[0283] The solid particle collector 90 is connected to the dust outlet 105 for collecting dust.

[0284] In operation, dust that is too heavy to flow with the gas stream through the separation chamber 102 falls into the dust outlet 105 and is collected in the solid particle collector 90 .

[0285] The gas inlet 101 is provided, for example, with a first flange 104 for movable connection with the separator 14 , and the gas outlet 103 is provided, for example, with a second flange 106 for movable connection with the pyrolysis reactor 12 .

[0286] like Fig. 9 As shown, the separator 14 may include a demisting grid 48 that extends across the internal flow passage 30 at the connection between the inlet duct 34 and the chamber 32 .

[0287] The demisting grid 48 is, for example, arranged on the top section 62 , which is attached to the partition wall 76 and the duct element 78 .

[0288] Preferably, the demister grid 48 is arcuate, so that the demister grid 48 bulges in the upstream direction. The demister grid 48 has, for example, two straight vertical side edges and an arcuate top edge and bottom edge. This provides a larger free cross section for the gas to pass through the demister grid 48.

[0289] like Fig. 9 As shown, a tubular demisting grid 48 is also provided inside the chamber 32 and around the collecting tube 36 to cover the collecting tube 36 .

[0290] like Fig.10 As shown, in an alternative example of the primary separator 100 , the separation chamber 102 is configured to force the gas flow to change direction at least once between the gas inlet 101 and the gas outlet 103 of the separation conduit 102 so as to facilitate separation of dust.

[0291] Advantageously, the separation chamber 102 is configured for the gas stream to enter the gas inlet 101 horizontally and be forced to change direction to flow upwards towards the gas outlet 103 , wherein a dust outlet 105 is provided at the bottom of the separation chamber 102 .

[0292] Due to the interaction of the dust particles, the direction of the gas stream in the separation chamber 102 is changed to promote separation. The dust particles tend to hit the side walls of the separation chamber 102 and fall into the dust outlet 105 provided at the bottom of the separation chamber 102.

[0293] As noted above, the primary separator 100, and in particular the separation chamber 102, must be taken into account to determine the ratio between the maximum cross-section of the internal passage of the separator unit 15 (including the separator 14 and (if appropriate) the primary separator 100) and the maximum flow rate of the gas stream provided by the pyrolysis reactor 12, and to determine the residence time of the gas stream in the separator unit 15.

[0294] Fig.10 A transfer column 18 suitable for carrying out the depolymerization method is illustrated in FIG.

[0295] The transfer column 18 includes a lower end 18A fluidly connected to the gas outlet 14B of the separator 14 (for receiving the gas stream exiting the gas outlet 14B of the separator 14 ) and an upper end 18B fluidly connected to the gas inlet 16A of the condenser 16 .

[0296] The depolymerization system 10 comprises a return line 20A fluidly connecting the condenser 16 with the upper end 18B of the transfer column 18 for injecting liquid monomer into the upper end 18B, in this example via a filtering device 22 .

[0297] Optionally, one or several intermediate injection return lines 20B are provided for injecting liquid monomer into the transfer column 18 at one or several injection points located between the lower end 18A and the upper end 18B of the transfer column 18 .

[0298] The lower end 18A of the transfer column 18 is fluidly connected to the separator 14 such that liquid collected at the lower end 18A of the transfer column 18 is transferred to the separator 14 , in particular to the separation chamber 32 and / or to the inlet conduit 34 of the separator 14 .

[0299] The transfer column 18 includes an internal component 110, which is configured so that in operation, the gas stream flows upward from the lower end 18A to the upper end 18B, the cold monomer injected in the transfer column 18 flows downward inside the transfer column 18 by gravity, the heavy pollutants contained in the gas stream are condensed in a liquid state in the internal component 110 and refluxed toward the lower end 18A of the transfer column 18 by gravity, and then are transferred to the separator 14, and the temperature of the gas stream decreases from the lower end 18A to the upper end 18B of the transfer column 18.

[0300] The function of the internals 110 provided in the transfer column 18 is to increase the contact surface area of ​​the gas stream flowing upward in the transfer column 18 and the liquid stream flowing downward in the transfer column 18 .

[0301] The internal member 110 includes, for example, a packing 112. The packing 112 may include a random packing and / or a structured packing.

[0302] Known types of random and structured packings are described, for example, on the Internet page http: / / chemiopedia.com / packed-bed-column-and-its-types.

[0303] The internal member 110 comprises, for example, a random packing, which comprises, for example, so-called rings and / or saddles. The rings and / or saddles of the internal member 110 are preferably made of metal or ceramic. The use of metal or ceramic allows to withstand the temperatures encountered in the transfer column 18.

[0304] The internals 110 comprise, for example, a random packing comprising or consisting of rings, in particular so-called ball rings. Rings, in particular ball rings, provide a good interaction between gas and liquid.

[0305] Structured packing comprises, for example, alternating layers of mesh, gauze, or finely corrugated board.

[0306] Known filler providers are, for example, the companies Sulzer, Montz and Koch-Gl i tsch Intalox. The internals 110 of the transfer column 18 may contain different types of fillers in the various sections of the transfer column 18. The internals 110 may contain, for example, a first filler of a first type in a first section of the transfer column 18 and a second filler of a second type in a second section of the transfer column 18, the first type being different from the second type and the first section being different from the second section.

[0307] In particular, it is advantageous to adjust the internal components 110 of the transfer column 18 to impart higher fouling resistance to the lower section of the transfer column 18 as compared to the upper section of the transfer column 18, and to provide improved distribution in the upper section of the transfer column 18 as compared to the lower section of the transfer column 18.

[0308] In addition, the pyrolysis reactor 12 is Fig.10 A heated screw extruder is shown above and the separator 14 is represented by a spiral inlet conduit 34 and a collecting pipe 36 provided with a baffle 42 and extending in the separation chamber 34, which is fluidly connected to the lower end of the transfer column 18 for supplying the transfer column 18 with a gas stream.

[0309] These features are optional and exemplary, and the depolymerization system 10, particularly the pyrolysis reactor 12 and the separator 14, can be according to the examples and variations as discussed above.

[0310] Fig.11 The transfer column 18 is different from Fig.10 The transfer column 18 is characterized in that the internals 110 comprise a series of filters 123 distributed along the transfer column 18, each filter 123 (provided with holes or defined holes) being arranged inside the transfer column 18 for forcing the cycle gas stream and the liquid to pass through said holes.

[0311] Each filter 123 is, for example, flat or cylindrical. Each filter 123 is provided in the form of a grid, a porous plate or a net, for example.

[0312] Such internals 110 force the gas stream and the liquid stream to circulate through the pores of the filter 123 in contact with each other.

[0313] like Fig.11As shown, the lower end 18A of the transfer column 18 is connected to the collecting pipe 36 of the separator 14 , for example, so that the gas stream leaving the separator 14 is directly circulated to the transfer column 18 and the liquid flowing downward in the transfer column 18 is returned to the separator 14 via the collecting pipe 36 .

[0314] Fig.12 The transfer column 18 is different from Fig.10 The transfer column 18 is characterized in that the internal component 110 includes a series of plates or baffles distributed along the transfer column 18 .

[0315] The baffles are configured to force the upwardly flowing gas stream and the downwardly flowing liquid stream to contact each other. In particular, the baffles are preferably configured to force the gas stream and the liquid stream to flow across a tortuous path.

[0316] The baffles include, for example, first baffles 124 alternating with second baffles 126 along the transfer column 18, each first baffle 124 is annular and defines a central channel for gas flow and liquid flow, each second baffle 126 is circular and defines an annular channel for gas flow and liquid flow, and the inner diameter of the first baffle 124 is preferably smaller than the outer diameter of the second baffle 126.

[0317] Such first and second baffles 124 and 126 force the gas stream to flow through the liquid stream flowing by gravity, falling from the edges of the first and second baffles 124 and 126 .

[0318] The depolymerization process optionally includes inputting heat energy into the interior of the transfer column 18 and / or the separator 14 by heating the gas stream and / or the liquid present inside the transfer column 18 and / or inside the separator 14 .

[0319] The input of heat energy obviously enables control of the temperature range of the gas streams in the separator 14 and in the transfer column 18 .

[0320] like Fig.13 As shown, the transfer column 18 is configured, for example, for inputting thermal energy by heating the gas and liquid streams circulating in the transfer column 18 .

[0321] Fig.13 The transfer column 18 is different from Fig.12 The transfer column 18 comprises at least a portion of the baffles configured for heating the baffles, hereinafter referred to as "heated baffles".

[0322] The heated baffles are for example jacketed, ie provided with internal conduits for circulating a heated fluid F.

[0323] like Fig.13As shown, the first baffle 124 (which is annular) is a heated baffle, in particular a jacketed baffle. Optionally or alternatively, the second baffle 126 (which is circular) is a heated baffle, in particular a jacketed baffle.

[0324] Heated baffles may be provided in the transfer column 18 all along the transfer column 18 or only in sections of the transfer column 18 .

[0325] like Fig.13 As shown, heated baffles are provided all along the transfer column 18. Alternatively, heated baffles are provided only in the lower section of the transfer column 18, with the upper section of the transfer column 18 containing only unheated baffles or filler.

[0326] The jacketed heated baffles contain internal pipes 127 for circulating heated fluid F. Each jacketed baffle 124 is, for example, hollow, and the internal pipes 127 defining the interior of the hollow jacketed baffle 124 are used for circulating heated fluid F.

[0327] The heated fluid F preferably circulates in a closed loop in a heating circuit 123 which comprises jacketed baffles and also contains a heater and / or heat exchanger 125 and a pump 129 for heating said heated fluid F.

[0328] The circulation of the gas stream flowing from the lower end 18A to the upper end 18B and the liquid monomer flowing from the upper end 18B to the lower end 18A are respectively Fig.13 As shown by arrows G and L.

[0329] The internal components 110 of the transfer column 18 may include one type of internal component 110 such as a packing 112 ( Fig.10 ), perforated plates or grids ( Fig.11 )、Baffle( Fig.12 ), which may include or consist of heated baffles ( Fig.13 ).

[0330] The internal components 110 of the transfer column 18 may include a combination of different types of internal components 110 , with each type of internal component 110 being located at each section of the transfer column, for example.

[0331] Optionally, the depolymerization method includes heating the liquid present or accumulated inside the separator 14 to a temperature greater than the boiling temperature of the monomers, thereby evaporating the monomers present in the liquid, the liquid inside the separator 14 is heated to evaporate the monomers inside the separator and / or heated outside the separator 14, and the evaporated monomers are returned to the separator 14, so that the evaporated monomers flow together with the gas feed stream circulating inside the separator 14.

[0332] The liquid present in the separator 14 is provided from the transfer column 18 or from condensation inside the separator 14 , for example on the surface of the separator 14 .

[0333] At least partially vaporizing the liquid withdrawn from transfer column 18 or condensed in separator 14 is also referred to as "reboiling" or "reheating."

[0334] Accordingly, the depolymerization system 10 optionally comprises a reheating device 114 configured to vaporize the liquid present and / or accumulated in the separator 14, and the reheating device 114 is configured so that the gas generated by the vaporization is generated in the separator 14 and / or returns to the separator 14, and thus flows to the transfer column 18 together with the gas stream.

[0335] like Figure 1 As shown, the depolymerization system 10 includes, for example, a heating device 114 configured to heat the liquid outside the separator 14 and to reinject the gas generated by reheating inside the separator 14 .

[0336] The heating device 114 includes a heater 116 arranged outside the separator 14 , and the heater 116 reheats the liquid collected from the separator 14 .

[0337] The depolymerization system 10 includes, for example, a reheating loop 111 configured to collect liquid from the separator 14 , heat the liquid in a reheater 116 to obtain a gas fraction, and reinject the gas and liquid generated from the reheating into the separator 14 .

[0338] Under stable operating conditions, most of the monomers in liquid state condensed in the separator 14 or arriving in liquid state from the transfer column 18 will be re-evaporated in the reheater 116 so that there is no accumulation of monomers.

[0339] Optionally, the reheating loop 111 comprises a filtering device 113. The filtering device comprises, for example, one filter or two filters fluidly connected in parallel.

[0340] Preferably, the reheating loop 111 comprises a pump 144 for forcing the fluid in the reheating loop 111 to circulate.

[0341] Optionally, the depolymerization system 10 comprises a liquid monomer reservoir 117 for feeding liquid monomer into the reheating loop 111 , for example during a start-up phase and / or a cleaning phase.

[0342] Preferably, the depolymerization system 10 comprises a collection storage 119 connected to the reheat loop 111 , preferably via a heated line 121 , for collecting heavies that accumulate in the reheat loop 111 over time.

[0343] like Figure 10-14 As shown, the reheating device 114 is configured, for example, to heat the liquid inside the separator 14 .

[0344] The reheating device 114 is, for example, configured for heating the liquid collected on a collecting surface 115 of the separator 14 , on which the liquid present in the separator 14 collects by gravity.

[0345] The collecting surface 115 is, for example, the bottom surface of the separator 14 on which the liquid present in the separator 14 collects, in particular the bottom of the separation chamber 32 of the separator 14 .

[0346] like Figure 10-14 As shown, the reheating device 114 comprises an electric heater 116 arranged outside the separator 14 along a collecting surface 115 of the separator 14 , on which the liquid present in the separator 14 collects by gravity.

[0347] Preferably, the depolymerization system 10 comprises a discharge device 118 configured for discharging heavy liquid accumulated on the collecting surface 115 of the separator 14 , on which the liquid present in the separator 14 is collected by gravity.

[0348] like Fig.14 As shown, the reheating device 114 comprises a reheater 116 installed inside the separator 14 , in particular in the chamber 32 of the separator 14 , and is configured to evaporate the liquid present in the separator 14 .

[0349] The reheater 116 is, for example, an evaporator, in particular a wiped film evaporator, which includes: a hollow cylinder 130, which extends vertically and is configured to receive hot oil inside the cylinder 130; a reheating loop 111, which is configured to supply the liquid collected in the separator 14 to the upper end of the hollow cylinder 130 to form a liquid film flowing on the outer surface of the cylinder 130 by gravity; a rotating wiper 134 coupled to a drive motor 136, which is used to rotate the rotating wiper 134 around the cylinder 130 and scrape the liquid film onto the outer surface of the cylinder 130.

[0350] The reheating device 114 preferably includes a collector 138 for collecting liquid dripping from the cylinder 130 and evaporating the liquid out of the separator 14, preventing the liquid from returning to the collection surface 115 of the separator 14.

[0351] The reheating device 114 allows evaporation of the liquid present in the separator 14 for the purpose of recovering any monomers that will still be present in this liquid and of draining the heavies outside the separator 14 .

[0352] In one example, if Fig.15As shown, the reheating device 114 includes a reheater 116 provided in the form of a screw extruder, which is fluidly connected to the separator 14 for receiving the liquid collected in the separator 14 and squeezing the liquid to at least partially evaporate the monomer and return the gaseous monomer to the separator 14, for example, to the gas inlet 14A of the separator 14.

[0353] The screw extruder is capable of processing high viscosity liquids and produces a solid residue and gaseous monomer. The gaseous monomer is returned to the separator 14, while the solid / heavy residue is disposed of, for example.

[0354] Advantageously, if Fig.15 As shown, the liquid withdrawn from the separator 14 is supplied to a reheater 116 , which is provided in the form of a screw extruder, and the outlet of the reheater 116 provided in the form of a screw extruder is connected to the separator 14 , in particular the gas inlet of the separator 14 , for example via the primary separator 100 .

[0355] The heater 116 of the reheating device 114 may be located outside the separator 14 and used to heat the liquid present inside the separator 14 ( Fig.10 ), or located outside the separator 14 for heating the liquid collected from the separator 14 ( Figure 1 and 15 ), or inside the separator 14 ( Fig.14 ).

[0356] Furthermore, different types of heaters 116 may be provided, including, for example, extruders or evaporators, in particular thin film evaporators. Example

[0357] Examples 1 and 2

[0358] The first embodiment is implemented in a depolymerization system 10 comprising a pyrolysis reactor 12 , and a separator 14 , a condenser 16 , and a transfer column 18 .

[0359] The pyrolysis reactor 12 is provided in the form of a twin-screw extruder, wherein the screws rotate in the same direction and the screws intermesh.

[0360] The twin-screw extruder includes a screw extending through a barrel, an electric heater installed around the barrel to provide heating energy, and a thermocouple also installed in the barrel for temperature control. The barrel is formed, for example, of barrel segments.

[0361] The twin screw extruder (and in particular its heater) is configured to produce a temperature profile along the screws, with the highest profile temperature being in the middle section along the screws.

[0362] The twin screw extruder is a TEX 44 with a screw diameter of 47 mm. For industrial lines, a TEX 90 with a screw diameter of 96.5 mm can be used depending on the required feed rate. The TEX extruder is sold by The Japan Steel Works, Ltd, which also offers larger equipment.

[0363] The material to be depolymerized is fed into the twin screw extruder at the hopper barrel by a gravity screw feeder. The material provided to the gravity screw feeder is previously crushed to a size of about 5 to 10 mm.

[0364] A twin screw extruder has a melting section along its length followed by a depolymerization section.

[0365] In operation, the material is melted in the melting zone of the twin-screw extruder by the shear stress from the screws and the heat from the heater, and then the molten material is conveyed to the depolymerization section.

[0366] The depolymerization section of the pyrolysis reactor 12 may achieve a temperature of 550°C.

[0367] The PMMA mixture is fed in the form of crushed granules via a gravity feeder. Two to four separate feeders are loaded with cast, injected and / or extruded PMMA.

[0368] The following operating conditions were used in the comparative examples and the inventive examples: the feed rate of the material in the pyrolysis reactor 12 was between 50 and 100 kg / h, the rotation speed of the screw of the pyrolysis reactor 12 was about 800 rpm, and the maximum distribution temperature in the pyrolysis reactor 12 was 470°C or lower.

[0369] For Examples 1 and 2, the transfer between the separator 14 and the condenser 16 was performed via a transfer column 18 having an inner diameter of 5.08 cm, into which an internal member provided in the form of a filter mesh was inserted. The filter mesh was a cylindrical grid having holes with a diameter of 1 mm. The filter mesh was inserted into the transfer column at an angle so that the gas stream was filtered through the filter mesh. The filter mesh was placed in the upper part of the transfer column 18, closer to the condenser 16 than the separator 14.

[0370] Gas chromatography was used to analyze the results of the examples using three different procedures, referred to below as the first GC procedure, the second GC procedure, and the third GC procedure.

[0371] Gas chromatography was performed using a gas chromatograph HP7890 sold by Agilent Technologies equipped with a flame ionization detector (FID)

[0372] The first GC run was used to quantify products such as methyl methacrylate (MMA), methanol (MeOH), methyl acrylate, and ethyl acetate.

[0373] In the first step, a calibration curve was prepared using reference materials and 2-butanol as internal standard. The samples were diluted in m-xylene.

[0374] The analysis was completed by gas chromatography using an HP5 GC column sold by Agilent Technologies. The HP5 GC column was 30 m long, with a 0.25 mm diameter and a 0.5 μm film thickness. The injector was operated at 250° C. in a separation mode (separation ratio of 50). A flame ionization detector (FID) was operated at 320° C., and a hydrogen flow rate of 40 ml / min and an air flow rate of 350 ml / min. The sample was located on an automatic sampler.

[0375] The analysis lasted 42 minutes, with the GC column temperature starting at 40°C, then increasing to 100°C after 13 minutes, and the carrier gas flow rate increasing from 0.8 ml / min to 1.5 ml / min after 18 minutes. The temperature was increased to 280°C after 31 minutes and kept at this level until the end.

[0376] A second GC procedure was used to quantify all other products based on gas chromatography peak areas. In this second GC procedure, the sample was diluted in dichloromethane. The analysis was performed using the same equipment and GC protocol as the first GC procedure.

[0377] The third GC procedure was used to quantify methacrylic acid and acetic acid and utilized a different GC column and analytical method.

[0378] The third GC run was performed using a HP-INNOWax GC column sold by Agilent Technologies with a length of 29 m, a diameter of 0.32 mm and a film thickness of 0.25 μm, wherein the sample was diluted in dichloromethane.

[0379] The analysis was performed by gas chromatography using an HP5 GC column with a length of 30 m, a diameter of 0.25 mm and a film thickness of 0.5 μm. The injector was operated at 250° C. in a split mode (split ratio of 50). The flame ionization detector (FID) was operated at 320° C. with a hydrogen flow of 45 ml / min and an air flow of 400 ml / min.

[0380] The analysis lasted 32 minutes, with the GC column temperature starting at 40° C., then increasing to 115° C. after 13.274 minutes, then to 130° C. after 20.875 minutes and 230° C. after 27.542 minutes. The carrier gas flow rate was 1.3 ml / min.

[0381] Quantification was performed using an external standard, meaning by comparing the peak area with a reference sample.

[0382] Embodiment 1 (comparison):

[0383] In Example 1, the filter was operated "dry," meaning that no liquid cold monomer (MMA) was injected into the transfer column.

[0384] Use scrap car tail light PMMA, collected at car dismantling sites, and crushed into small particles. It contains mainly PMMA and some contaminants of other polymers such as ABS. The average age of cars arriving at the dismantling site is about 17 years, so the scrap contains all kinds of PMMA, pigments and additives from all past and present suppliers.

[0385] The feed rate of the injection waste was 50 kg / h, the maximum temperature of the pyrolysis reactor 12 extruder was set at 470° C., the screw speed was 800 rpm, and the depolymerization system 10 was operated at atmospheric pressure.

[0386] The color of the collected crude MMA product was dark red. Color was measured according to ASTM D1500-07 standard method. The value reported was L3.0 ASTM color.

[0387] Example 2 (according to the present invention):

[0388] The previous example is continued, but at the upper end of the transfer column 18, 10 kg / h of liquid cold monomer (MMA) is injected through the filter screen and towards the separator 14. The other operating parameters remain the same.

[0389] The color of the crude MMA product collected at the outlet of condenser 16 was dark red. The color was measured according to ASTM D1500-07 standard method. The value reported was L2.5 ASTM color.

[0390] The gas temperature at the gas inlet 16A of the condenser 16 was reduced by 51° C. compared with that in Comparative Example 1. This indicates that the liquid MMA sent to the transfer column 18 has a cooling effect.

[0391] In addition, after the test, the filter was checked. It was clean, unlike in Example 1.

[0392] In both Examples 1 and 2, the crude MMA temperature at the bottom outlet of condenser 16 was maintained between 12 and 13°C.

[0393] Table 1 below reports the analysis of the samples by gas chromatography. The main differences detected are in the heavy compounds (determined by GC based on retention time). The products collected at MMA retention time + 2 minutes and above are much higher in the case of Example 1 than in the case of Example 2.

[0394] Table 1: Characteristics and GC analysis after depolymerization

[0395]

[0396] As previously described, the color of the crude MMA of Example 1 and Example 2 was dark red, however, as noted in Table 1, the color of Example 2 was more transparent than that of Example 1. Additionally, GC analysis showed less unknown heavies and very heavies products in the sample from Example 2 compared to the sample from Example 1, indicating a purer product of better quality in Example 2 compared to Example 1.

[0397] Examples 3 to 6 (according to the present invention)

[0398] For Examples 3 to 6, use according to Figure 1 and Fig.10 of Depolymerization system The pyrolysis reactor 12 is provided in the form of a twin screw extruder Tex44 sold by Japan Steel Works and is connected to a primary separator 100 for separating solids from hot gases. The main separator 14 has a Figure 7 and Fig. 9 In the main separator 14, two demister grids 48 are installed in the path of the hot gases: one demister grid 48 at the end of the spiral path and one demister grid 48 surrounding the central collecting pipe 36, which has a diameter of 12,7 cm and is equipped with a frustum baffle 42 for forcing the hot gases to pass through the inlet opening 38 drilled in the collecting pipe 36. The hot gases then circulate through the transfer column 18 with an internal diameter of 20 cm and a length of 2.8 m and to the condenser 16.

[0399] The crude MMA withdrawn from the condenser 16 is returned to the top of the transfer column 18. The temperature of the gas at the top of the transfer column 18 is monitored and controlled by adjusting the crude MMA flow rate.

[0400] The transfer column 18 was filled with a packing comprising a ball ring having a diameter of 16 mm over a length of 2,500 mm. The crude MMA was distributed on the top of the transfer column 18 by a shower type distributor.

[0401] The condenser 16 is provided in the form of a tube and shell heat exchanger, with cold water being used as the heat exchanger fluid. The temperatures at the inlet and outlet of the condenser 16 are monitored.

[0402] During operation, heavy pollutants condensed in the transfer column 18 flow down the transfer column 18 and return to the main separator 14 via the bottom of the transfer column 18 .

[0403] The heavy pollutants deposited at the bottom of the main separator 14 are pumped and circulated through an oil bath to reheat them.

[0404] Such heating is recommended only on experimental or "pilot" depolymerization systems, as there will be significant heat losses, particularly on a cold start with each new sample or condition tested.

[0405] The temperature of the heavy pollutants in liquid state at the bottom of the main separator 14 is controlled to maintain below 200°C, preferably below 150°C and above 100°C during the test.

[0406] This configuration of the deaggregation system is further identified as the "first deaggregation system".

[0407] Example 3 (according to the invention): Transparent cast PMMA sheet

[0408] PMMA (sample A) from cast transparent sheet was depolymerized in pyrolysis reactor 12 at a depolymerization temperature of 450°C and then increased to a depolymerization temperature of 470°C, wherein at the same time the feed rate was 50 kg / h to 90 kg / h and the rotation speed of the screw of pyrolysis reactor 12 was increased from 500 revolutions / minute (rpm) to 800 rpm. During the test, the pressure at the inlet of main separator 14 and condenser 16 was maintained between 1.0 and 1.1 bar and increased to a maximum of 1.2 bar when adjusting the process conditions. The temperature of the condensed crude MMA was maintained at about 20°C and varied between 17°C and 22°C when adjusting the process conditions. The temperature of the hot gas phase in the main separator 14 varied between 250°C and 350°C (at the measuring point), while the temperature of the liquid phase varied between 125°C and 150°C, which was consistent with the liquid composition in the main separator 14 containing both MMA and heavier compounds.

[0409] When the PMMA feed rate is 50 kg / h, the crude MMA returned to the transfer column 18 is adjusted to about 35 L / h. When the PMMA feed rate is 90 kg / h, the crude MMA returned to the transfer column 18 is adjusted to about 70 L / h (+ / - 5 L / h).

[0410] For each depolymerization temperature A sample of crude MMA was taken out from the condenser 16 and analyzed by gas chromatography. The following Table 2 shows the results of the GC analysis.

[0411] The purity of the collected crude MMA was greater than 98% (based on GC peak area analysis). The crude MMA sample contained ethyl acetate, which was due to some PMMA sheets being made from materials containing this compound, which was not expected in cast sheets.

[0412] The primary separator 100 remained clean during the testing with no polymer accumulation therein.

[0413] Table 2: Depolymerization characteristics and GC analysis of sample A

[0414]

[0415]

[0416] In the GC analysis, several unidentified products were grouped together according to their respective retention times. These were "very lights" with retention times less than the MMA retention time minus 2 minutes, "lights" with retention times between the MMA retention time minus 2 minutes and the MMA retention time, "light heavies" with retention times between the MMA retention time and the MMA retention time plus 2 minutes, "heavies" with retention times between the MMA retention time plus 2 minutes and the MMA retention time plus 8 minutes, and "very heavy" with retention times greater than the MMA retention time plus 8 minutes.

[0417] The crude MMA collected in the condenser 16 is not only clear, transparent and colorless, but also has a high MMA purity (as a peak area percentage) of more than 98% and a low content of heavy and very heavy substances. The sum of heavy and very heavy substances was kept below 0.5% in the test. The contents of acetic acid and methacrylic acid were also extremely low (not detected).

[0418] Example 4 (according to the invention): White cast PMMA sheet

[0419] A white cast PMMA sheet (Sample B) was used in this test.PMMA was depolymerized in the pyrolysis reactor 12 at 470°C using a feed rate of 90 kg / h and two different screw rotation speeds, namely 800 and 650 rpm.

[0420] During the test, the pressure in the main separator 14 and at the inlet of the condenser 16 was maintained between 1.0 and 1.1 bar most of the time and increased to a maximum of 1.2 bar when the process conditions were adjusted. The temperature of the condensed crude MMA was maintained at about 20° C. and varied between 19 and 21° C. when the process conditions were adjusted. The temperature of the hot gas in the main separator 14 varied between 260 and 300° C. during the test, while the temperature of the liquid phase varied between 125 and 150° C., which was consistent with the liquid composition in the main separator 14 containing both MMA and heavier compounds.

[0421] When the PMMA feed rate is 90 kg / h, the flow rate of the crude MMA returned from the condenser 18 to the transfer column 18 is adjusted to about 90 L / h (+ / - 5 L / h).

[0422] A sample of crude MMA was taken from the condenser 16 and analyzed by gas chromatography. The purity of the collected sample of crude MMA was greater than 98% (GC peak area basis) as shown in Table 3 below.

[0423] The primary separator 100 remained clean during the test with no polymer accumulation therein, but fine white dust was collected therein. This represented the white pigment used in the white PMMA cast sheet. The amount of white solids collected represented about 1 to 2 weight % of the processed PMMA.

[0424] Table 3 - Depolymerization characteristics and GC analysis of sample B

[0425]

[0426] The MMA content in the crude MMA is greater than 99%. The crude MMA is clear and transparent, without solid suspension and color. The amount of heavy and very heavy substances in the crude MMA is very small. No acetic acid or methacrylic acid was detected. The initial sample may be slightly contaminated by the remaining product from the previous sample processed in the equipment because the amount of ethyl acetate is slightly higher than the other two samples. The last one of the three samples (i.e., Example 4c) represents stable conditions. The three samples were spaced 50 and 30 minutes respectively, and the sample of Example 4c was taken out 30min after the sample of Example 4b.

[0427] Example 5 (according to the invention): Mixture of 80 wt.% cast PMMA - 20 wt.% extruded PMMA, mixed colors and suppliers, representing European mixed waste from sheets.

[0428] Crude MMA was obtained by depolymerization of a waste mixture of cast sheets and extruded sheets collected from two different companies that collected sheet cuttings generated when the sheets were cut into sizes and various products were prepared from them, with a ratio of about 80% by weight of cast sheets and 20% by weight of extruded sheets.

[0429] The mixture treated represents the average composition of material that can be collected from companies of this type in Europe.

[0430] This example is considered to represent post-consumer waste because the waste is collected from multiple sources and mixed together, unlike post-industrial waste.

[0431] Wastes from two different sources were mixed in a 50 / 50 ratio using two separate screw feeders providing PMMA waste to the pyrolysis reactor 12 (Sample C).

[0432] PMMA was depolymerized in the pyrolysis reactor 12 operated at 470°C with a feed rate of 90 kg / h.

[0433] The flow of crude MMA from the condenser 16 to the top of the transfer column 18 was adjusted to about 85 L / h (+ / - 5 L / h). The temperature at the top of the transfer column 18 varied between 100 and 102° C., while the temperature at the bottom of the transfer column 18 varied between 103 and 105° C. At the end of the test, the temperature at the bottom of the transfer column 18 began to increase as soon as the flow of crude MMA from the condenser to the top of the transfer column 18 was stopped.

[0434] A first sample of crude MMA (Example 5A) and then a second sample of crude MMA (Example 5b) were taken from the condenser 16 at intervals of about 30 minutes. They were analyzed by gas chromatography (GC) using a flame ionization detector (FID). The results of the analysis are indicated in Table 4 below.

[0435] Table 4: Depolymerization characteristics and GC analysis of sample B

[0436]

[0437] The crude MMA sample was clear, transparent and colorless. The purity (MMA content) was greater than 98%. The sum of heavies and very heavies remained below 0.5% during the test. The acetic acid and methacrylic acid contents were also extremely low (not detected).

[0438] Example 6 (according to the invention): Injected PMMA scrap from post-industrial automotive taillights containing red, black and transparent particles (sample D).

[0439] Crude MMA was obtained from injected PMMA waste from car tail lamps containing red, black and transparent particles - taken from post-industrial waste (Sample D).PMMA was depolymerized in a pyrolysis reactor 12 operated at 470°C with a feed rate of 50 kg / h and 800 rpm.

[0440] The flow rate of crude MMA from condenser 16 back to the top of transfer column 18 was adjusted to 45 L / h (+ / - 3 L / h) during the test. The temperature in transfer column 18 varied between 101 and 105°C at the bottom and between 99 and 103°C at the top of transfer column 18.

[0441] Samples of crude MMA were taken from the condenser 16 at different times over 45 min and analyzed by gas chromatography (GC) equipped with a flame ionization detector.

[0442] Table 5: Depolymerization characteristics and GC analysis of sample D

[0443]

[0444] The colored PMMA material of the waste material of self-injection molding leads to MMA purity (GC peak area percentage) greater than 98%. In addition, the amount of heavy and very heavy materials is kept below 0.5%. All crude MMA collection samples are clear and colorless, while the processed PMMA waste is a mixture containing red and black materials. The acetic acid and methacrylic acid content are also extremely low (not detected).

[0445] Comparative Examples were performed using a depolymerization method and a depolymerization system not according to the present invention.

[0446] Example 7 (Comparative Example)

[0447] Crude MMA was obtained from the depolymerized PMMA, and a depolymerization system obtained from the first depolymerization system was completed by omitting the primary separator 100, replacing the transfer column 18 with an empty tube having a diameter of 5.08 cm, and suppressing the reheating of the heavy materials accumulated in the main separator 14. This depolymerization system is referred to as a "second depolymerization system".

[0448] Sample A and Sample A1, which is similar to Sample A but from another batch, were used. Both were clear cast sheets.

[0449] Table 6: Characteristics and GC analysis of depolymerization of sample A1 and sample A using the second depolymerization system

[0450]

[0451] The MMA content (GC peak area) in all crude samples was less than 98%. In addition, the amount of heavy and very heavy substances was much greater than 1%. Methacrylic acid was also detected in the crude samples.

[0452] Example 8 (Comparative Example): White cast

[0453] In Example 8, the depolymerization system is further modified, wherein the pyrolysis reactor 12 is directly connected to the condenser 16. The main separator 14 is set to a dead end, and the condenser 12 is connected via a pipe between the extruder and the separator instead. This depolymerization system is referred to as the "third depolymerization system".

[0454] Sample B1, similar to Sample B but from another batch, was used in Example 8.

[0455] Table 7: Characteristics and GC analysis of depolymerization of sample B1 using cell arrangement 3

[0456]

[0457] Crude MMA The MMA content in all samples of the crude samples was lower than 98.5% or much lower than that of the first depolymerization system used in the examples according to the present invention. In addition, all samples were colored. The heavies and very heavies were also greater than 1%. Methacrylic acid was also detected in the crude samples.

[0458] Example 9 (Comparative Example): White Casting

[0459] For this Example 9, a second deagglomeration system and sample B 1 were used. The two samples reported in Table 8 were collected on two different days.

[0460] Table 8: Characteristics and GC analysis of depolymerization of sample B1 using the second depolymerization system

[0461]

[0462] The crude MMA produced was turbid (solids suspended) and the MMA content was less than 98%. In addition, the sum of heavies and very heavies was greater than 2%. Methacrylic acid and acetic acid were detected in the crude sample.

[0463] Example 10 (Comparative Example): White cast

[0464] For this Example 10, Sample B1 was used in a second depolymerization process (as in Example 9), wherein the pressure was adjusted to 1.5, 1.0 and 0.5 bar.

[0465] Table 9: Characteristics and GC analysis of depolymerization of sample B1 using the second depolymerization system and pressure variation

[0466]

[0467]

[0468] The collected crude MMA was yellow and turbid, and the MMA content in the crude MMA was less than 98%. In addition, methacrylic acid and acetic acid were detected, and the sum of heavy and very heavy substances was much greater than 2%.

[0469] Example 11 (Comparative Examples 5 and 6): Mixed Casting and Extrusion (80 / 20 wt / wt Ratio)

[0470] For this example, the third deagglomeration system used sample C1 and sample C2, which were similar to sample C. In several cases, samples were analyzed twice.

[0471] Table 10 Characteristics and GC analysis of depolymerization of samples C1 and C2 using unit arrangement 3

[0472]

[0473] All samples had a dark color and the crude MMA purity was less than 98%. Methacrylic acid was detected in the crude MMA and the sum of the heavies and very heavies content was greater than 1.5% in all cases.

[0474] At the end of the test, a lot of solid deposits were recovered at the inlet of the condenser.

[0475] Example 12 (Comparative Example): Mixed Casting and Extrusion (80 / 20 wt / wt Ratio)

[0476] In this example, a second depolymerization system was used to feed a mixture of cast and extruded PMMA from sample C1 in a 80 / 20 wt / wt ratio using a depolymerization temperature of 500°C and different pressures.

[0477] Table 11: Characteristics and GC analysis of depolymerization of samples C1 and C2 using cell arrangement 2

[0478]

[0479] All collected samples of crude MMA had an MMA content well below 98% and they had a brown turbid color. Methacrylic acid was detected in the product and the amount of heavies and very heavies was greater than 3% in all cases.

[0480] Embodiment 13 (comparative example):

[0481] In this example, a second depolymerization system was used, wherein the feed material was from Sample D as in Example 6.

[0482] Table 12: Depolymerization characteristics and GC analysis of sample D

[0483]

[0484] The crude MMA had an MMA content of less than 98% and had a dark turbid color. The sum of the heavies and very heavies was greater than 3%, and methacrylic acid was detected in the crude MMA.

[0485] The depolymerization process and the corresponding depolymerization system 10 for carrying out the depolymerization process allow the production of liquid monomers from feed materials containing the corresponding polymers, obtaining satisfactory purity and maximizing the operating time of the depolymerization system 10 .

[0486] Indeed, the provision of a separator 14 allows the capture of impurities that may be present in the gas stream and avoids these impurities from clogging the components of the depolymerization system 10 situated downstream of the separator 14 .

[0487] The gas stream reaching the condenser 16 is kept clean by providing a transfer column 18, in which impurities in the cold monomer flowing by gravity are captured and returned to the separator 14. Backwashing the transfer column 18 with cold monomer thus limits the risk of plugging.

[0488] Inputting heat energy into separator 14 (eg, via heating device 114) and / or transfer column 118 (eg, via heated baffles) avoids wasting too much cold monomer as it is circulated in transfer column 18 to capture impurities present in the gas stream.

[0489] The separator 14 may be used as a reheater for boiling liquid returning to the separator 14 , in particular when the separator 14 is provided with a reheating device 114 comprising a heater 116 .

[0490] The input of thermal energy into the separator 14 and / or the transfer column 18 allows increasing the amount of cold monomer injected into the transfer column 18 and thus reducing the risk of clogging of the transfer column 18 .

[0491] Operating the separator 14 and the transfer column 18 within a specific temperature range allows avoiding any condensation and polymerization of the monomers in the separator 14 and the transfer column 18 and promotes good operation of the separator and the transfer column 18. This further allows spraying cold liquid monomers into the interior of the separator 14 for controlling the temperature of the gas stream inside the separator 14.

[0492] The quality of the finally obtained cold monomer is increased, with less impurities, less dimers, less trimers and less wax present in the cold monomer.

[0493] The deagglomeration system can be operated with longer cycle times between cleaning operations.

[0494] Some specific arrangements of the separator 14 and the transfer column 18, such as the limited linear velocity of the gas stream, the separation chamber 32, the inlet conduit 14 having a varying cross-section and / or extending around the separation chamber 32, the collecting pipe 36 having a specific structure and / or the internal demisting device 46, the internal components of the transfer column 18 and / or the injection of the cold monomer withdrawn from the condenser 16 into the transfer column 18, allow for efficient capture of impurities while managing the temperature of the gas stream and allowing the gaseous monomer to flow to the separator outlet 14B for supplying the condenser 16 via the transfer column 18.

Claims

1. A depolymerization process for recovering monomers from polymers, said depolymerization process comprising the following sequential steps: pyrolyzing a feed material containing said polymer in a pyrolysis reactor (12) to produce a hot gas stream, removing solid and liquid impurities from said gas stream in a separator (14) and condensing the monomers contained in said gas stream in a condenser (16), wherein the gas stream is transferred from the separator to the condenser via a transfer column (18), the transfer column (18) extending upward from a lower end connected to the outlet fluid of the separator (14) to an upper end connected to the inlet fluid of the condenser (16), wherein cold monomer in liquid state is injected into the transfer column (18), the transfer column is provided with internal components, the internal components are configured so that the cold monomer flows downwardly by gravity inside the transfer column (18), heavy pollutants contained in the gas stream are condensed in liquid state on the internal components and flow back downwardly toward the bottom of the transfer column (18) by gravity, and then transferred to the separator (14), and the temperature of the gas stream decreases from the lower end to the upper end of the transfer column (18), and The temperature of the gas stream at the outlet of the separator (14) and the inlet of the transfer column (18) is maintained greater than the boiling point of the monomer, and the temperature of the gas stream at the outlet of the transfer column (18) is maintained between the boiling point of the monomer and the boiling point of the monomer + 50°C.

2. The depolymerization process according to claim 1, wherein the temperature of the gas stream at the outlet of the separator (14) and the inlet of the transfer column (18) is maintained at least at the boiling point of the monomer + 20°C, particularly at least at the boiling point of the monomer + 30°C, more particularly at least at the boiling point of the monomer + 40°C, even more particularly at least at the boiling point of the monomer + 50°C.

3. The depolymerization method according to claim 1 or 2, wherein the temperature of the gas stream at the outlet of the transfer column (18) is maintained between the boiling point of the monomer and the boiling point of the monomer+50°C, in particular between the boiling point of the monomer and the boiling point of the monomer+40°C, in particular between the boiling point of the monomer and the boiling point of the monomer+30°C, in particular between the boiling point of the monomer and the boiling point of the monomer+20°C, in particular between the boiling point of the monomer and the boiling point of the monomer+10°C.

4. Depolymerization process according to any one of the preceding claims, wherein the internals comprise a mesh filter or a plurality of mesh filters arranged in cascade inside the transfer column.

5. Depolymerization process according to any one of the preceding claims, wherein the internals comprise structured packing and / or random packing, such as random packing comprising saddles and / or rings, in particular ball rings.

6. A depolymerization process according to any one of the preceding claims, wherein the internals comprise a series of baffles.

7. A depolymerization process according to any one of the preceding claims, wherein the internals comprise a series of baffles comprising internally heated baffles, preferably alternating with unheated baffles.

8. The depolymerization process according to any one of the preceding claims, wherein cold monomers in liquid state are injected at the upper end of the transfer column and / or at one or several intermediate positions between the lower end and the upper end of the transfer column.

9. The depolymerization method according to any one of the preceding claims, comprising the step of filtering the cold monomers before injecting them into the transfer column (18).

10. The depolymerization process according to any one of the preceding claims, comprising a step of inputting thermal energy into the interior of the transfer column (18) and / or into the separator (14) by heating the gas and / or liquid present inside the transfer column (18) and / or inside the separator (4).

11. The depolymerization method according to any one of the preceding claims, comprising heating the liquid collected in the separator (14) using a heater located inside the separator and / or a heater located outside the separator (14) for evaporating the monomers contained in the liquid, and returning the monomers to the separator (14).

12. The depolymerization process according to claim 10, wherein the heating of the liquid is carried out using: - a heater provided in the form of an electric heater, arranged outside the separator (14) for heating the liquid collected inside the separator (14); a heater provided in the form of an evaporator, in particular a wiped film evaporator, preferably arranged inside the separator, to which the liquid collected from the separator is fed; and / or - a heater provided in the form of a heated screw extruder, to which the liquid collected from the separator (14) is supplied, and to which the gas generated by the heater provided in the form of a heated screw extruder is supplied.

13. A depolymerization process according to any one of the preceding claims, wherein the rate of cold monomer injected into the transfer column (18) is at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90% of the equivalent feed rate of the monomer.

14. A depolymerization process according to any of the preceding claims, wherein the fraction of cold monomer injected into the transfer column (18) is less than 153%, preferably less than 103%, preferably less than 93%, preferably less than 83%, preferably less than 73%, preferably less than 63%, preferably less than 53% of the equivalent feed rate of the monomer.

15. Depolymerization process according to any one of the preceding claims, wherein the temperature of the gas stream at the inlet of the separator (14) is equal to or higher than 250°C.

16. Depolymerization process according to any of the preceding claims, wherein the temperature of the gas stream at the outlet of the separator (14) is between 100 and 280°C, preferably between 110 and 180°C.

17. The depolymerization process according to any one of the preceding claims, wherein the pressure inside at least one or each of the pyrolysis reactor (12), the separator (14) and the condenser (16) is between 0.3 and 2.0 bar, preferably between 0.4 and 1.5 bar, more preferably between 0.5 and 1.2 bar.

18. The depolymerization process according to any one of the preceding claims, wherein the pyrolysis reactor is a heated twin-screw extruder.

19. A depolymerization system configured for recovering monomers from a polymer, the depolymerization system comprising: a pyrolysis reactor (12) configured for pyrolyzing a feed material containing the polymer to produce a gas stream; a separator (14) fluidly connected to the pyrolysis reactor (12) for receiving the gas stream from the pyrolysis reactor (12) and configured for removing impurities from the gas stream; and a condenser (16) fluidly connected to the separator (14) for receiving the gas stream from the separator and configured for condensing monomers contained in the gas stream received from the separator (14), The depolymerization system comprises a transfer column (18) for transferring the gas stream from the separator (14) to the condenser (16), the transfer column (18) extending upward from a lower end connected to the outlet fluid of the separator to an upper end connected to the inlet fluid of the condenser (16), the transfer column (18) being configured to inject cold monomer in a liquid state into the interior of the transfer column (18) and the transfer column (18) being provided with internal components, the internal components being configured so that in operation the cold monomer flows downwardly by gravity inside the transfer column (18), heavy pollutants contained in the gas stream are deposited in a liquid state on the internal components and flow back by gravity toward the separator (14), in particular via the bottom of the transfer column (18), and the temperature of the gas stream decreases from the lower end to the upper end of the transfer column (18).

20. The depolymerization system according to claim 19, comprising a primary separator (100) inserted in series between the pyrolysis reactor (12) and the separator (14).

Images