Disambiguation method and system

Abstract

The recombination method includes a series of steps: pyrolyzing a feedstock containing a polymer in a pyrolysis reactor to generate a high-temperature 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. The gas stream is transferred from the separator to the condenser through a moving tower provided with internal elements. The low-temperature monomers in a liquid state are injected into the moving tower. The internal elements are configured such that the low-temperature monomers flow downward in the moving tower by gravity, and the heavy impurity substances contained in the gas stream condense in a liquid state on the internal elements and flow back downward toward the bottom of the moving tower and enter the separator.

Description

Technical Field

[0001] The project leading to this application has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 820687.

[0002] The present invention relates to the field of depolymerization for recovering monomers from feedstocks containing polymers of which the monomers are constituents.

[0003] More particularly, it relates to a thermal depolymerization method comprising the thermal decomposition of a feedstock, i.e. heating the feedstock so as to at least partially vaporize the feedstock in the substantial absence of oxygen, which thermal decomposition of the feedstock generates a gas stream containing monomer vapors.

Background Art

[0004] A problem with such depolymerization methods is that the gas stream generated by thermal decomposition can contain impurities such as dust, mist droplets, remaining polymer chains, oligomers, and / or contaminants in addition to the vaporized monomers.

[0005] Such impurities can change the components of the depolymerization system located downstream of the thermal decomposition reactor and thus can adversely affect the productivity and the cycle time between cleanings, or can contaminate the monomers recovered, for example, as so-called "crude monomers" or "pyrolysis oils" obtained from the vaporized monomers.

[0006] JP3210323 and DE3146194 each disclose a depolymerization method for recovering monomers from polymers, comprising the steps of thermally decomposing a feedstock containing a polymer in a thermal decomposition reactor so as to generate a gas stream containing monomer vapors, and passing the gas stream through a separator so as to remove impurities from the gas stream.

[0007] WO2016 / 030460 discloses a depolymerization method for recovering monomers from polymers, which includes the steps of pyrolyzing a feedstock containing polymers in a pyrolysis reactor to generate a gas stream containing monomer vapor, and passing the gas stream through a contactor containing a perforated plate arranged according to the flow of long-chain components to return to the original pyrolysis reactor.

[0008] US10731080 discloses a depolymerization method for recovering monomers from polymers, which includes the steps of pyrolyzing waste materials containing polymers to generate a gas stream, quenching the gas stream from the pyrolysis reactor in a quenching device to remove oligomers from the gas stream, and transferring the oligomers back to the original pyrolysis reactor.

[0009] EP2679654A1 discloses a facility for carrying out a pyrolysis process of waste plastics and / or rubber waste and / or organic waste, which includes a pyrolysis reactor.

[0010] WO2014040634A1 discloses a facility for recycling plastic waste, which includes a pyrolysis reactor, a separator, and a condenser.

[0011] EP3031881A1 discloses a facility for treating polymer waste, which includes a thermal reactor, a cyclone separator, a first condenser, a second condenser, and a filtration tower arranged in series.

[0012] US10301235B1 discloses a facility for treating plastic waste, which includes a pyrolysis reactor, a quenching device, and a condenser, and a condensate fraction is supplied to the quenching device.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0014] One object of the present invention is to propose a depolymerization method for producing monomers, particularly crude monomers or pyrolysis oils, with satisfactory quality and productivity.

Means for Solving the Problems

[0015] Therefore, the present invention is a depolymerization method for recovering monomers from a polymer, comprising: a step of pyrolyzing a feedstock containing a polymer in a pyrolysis reactor to generate a high-temperature gas stream; a step of removing solid and liquid impurities from the gas stream in a separator; and a step of condensing the monomers contained in the gas stream in a condenser; including the continuous steps of the gas stream moves from the separator to the condenser through a moving tower that extends upward from the lower end fluidly connected to the outlet of the separator to the upper end fluidly connected to the inlet of the condenser. The low-temperature monomer in the liquid state is injected into the moving tower, and the moving tower is provided with internal elements configured such that the low-temperature monomer flows downward in the moving tower by gravity. Heavy impurity substances contained in the gas stream condense into the liquid state on the internal elements and flow back downward toward the bottom of the moving tower by gravity, and then move to the separator. The temperature of the gas stream decreases from the lower end to the upper end of the moving tower, and the temperature of the gas stream at the outlet of the separator and the inlet of the moving tower is maintained above the boiling point of the monomer, and the temperature of the gas stream at the outlet of the moving tower is maintained between the boiling point of the monomer and the boiling point of the monomer + 50°C. A depolymerization method is proposed.

[0016] In a specific embodiment, the depolymerization method includes one or several of the following optional features, individually or in any technically feasible combination: - The temperature of the gas stream at the outlet of the separator and the inlet of the moving tower is maintained at at least the boiling point of the monomer + 20°C, particularly at least the boiling point of the monomer + 30°C, more particularly at least the boiling point of the monomer + 40°C, and even more particularly at least the boiling point of the monomer + 50°C; - The temperature of the gas stream at the outlet of the moving tower 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, and particularly between the boiling point of the monomer and the boiling point of the monomer + 10°C; - The internal elements include one mesh filter or a plurality of mesh filters arranged stepwise in the moving tower; - The internal elements include structured packing and / or random packing, for example, random packing including saddles and / or rings, particularly Pall rings; - The internal elements include continuous baffles; - The internal elements preferably include continuous baffles including internally heated baffles arranged alternately with unheated baffles; - The low-temperature monomer in the liquid state is injected at the upper end of the moving tower and / or at one or more intermediate positions between the lower and upper ends of the moving tower; - Before injecting the low-temperature monomer into the moving tower, it includes the step of filtering the low-temperature monomer; - It includes the step of inputting thermal energy into the moving tower and / or into the separator by heating the gas and / or liquid existing in the moving tower and / or in the separator; - Heating the liquid collected in the separator using a heater positioned inside the separator and / or a heater positioned outside the separator to evaporate the monomer contained in the liquid and return the monomer to the separator; - The step of heating the liquid is: - With a heater provided as an electric heater, arranged and configured outside the separator, for heating the liquid collected in the separator; - With a heater provided as an evaporator, particularly a wiped-film evaporator, preferably an evaporator arranged and configured inside the separator, where the liquid collected from the separator is supplied; and / or - With a heater provided as a heated screw extruder, to which the liquid collected from the separator is supplied, and the gas generated by the heater provided as the heated screw extruder is supplied to the separator; performed, - The speed of the low-temperature monomer injected into the moving tower is at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90% of the equivalent supply speed of the monomer; - The ratio of the low-temperature monomer injected into the moving tower 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 supply speed of the monomer; - The temperature of the gas flow at the inlet of the separator is equal to or higher than 250 °C; - The temperature of the gas flow at the outlet of the separator is included between 100 °C and 280 °C, preferably between 110 °C and 180 °C; - 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.

[0017] The present invention is a depolymerization system configured to recover monomers from a polymer, a pyrolysis reactor configured to pyrolyze a feedstock containing a polymer to generate a gas stream, a separator fluidly connected to the pyrolysis reactor to receive the gas stream from the pyrolysis reactor and configured to remove impurities from the gas stream, and a condenser fluidly connected to the separator to receive the gas stream from the separator and configured to condense the monomers contained in the gas stream received from the separator including, this depolymerization system includes a transfer column for moving the gas stream from the separator to the condenser, the transfer column extends upward from a lower end fluidly connected to the outlet of the separator to an upper end fluidly connected to the inlet of the condenser, the transfer column is configured to inject a low-temperature monomer in a liquid state into the transfer column, and during operation, heavy impurity substances contained in the gas stream are deposited in a liquid state on internal elements and flow back towards the separator by gravity, particularly configured to flow back through the bottom of the transfer column so that the low-temperature monomer flows downward in the transfer column by gravity, Also related to a depolymerization system in which the temperature of the gas stream decreases from the lower end to the upper end of the transfer column.

[0018] The present invention and its advantages will be better understood by reading the following description, which is presented as a non-limiting example only, and by referring to the accompanying drawings.

Brief Description of the Drawings

[0019]

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DETAILED DESCRIPTION OF THE INVENTION

[0020] The depolymerization system 10 shown in FIG. 1 is configured to implement a depolymerization method for recovering monomers from a feedstock containing a polymer whose monomers are its constituents.

[0021] The depolymerization system 10 includes a pyrolysis reactor 12 configured to generate a gas stream from a feedstock containing a polymer, a separator unit 15 including a separator 14 configured to remove liquid and solid impurities from the gas stream, a condenser 16 configured to condense the 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.

[0022] The pyrolysis reactor 12, the separator 14, the transfer column 18, and the condenser 16 are fluidly connected in series in this order.

[0023] The depolymerization method includes a step of pyrolyzing the feedstock in the pyrolysis reactor 12 to generate a gas stream containing gaseous monomers (which are the constituents of the polymer), a step of directing the gas stream from the pyrolysis reactor 12 to the separator 14 to remove liquid and solid impurities from the gas stream, and a step of transferring the gas stream from the separator 14 to the condenser 16 to condense the gaseous monomers contained in the gas stream into liquid monomers, which are consecutive steps.

[0024] During the implementation of the depolymerization method, the pyrolysis is operated such that the gas stream provided to the separator 14 contains gaseous monomers, which are also referred to as "gaseous monomers" hereinafter.

[0025] During the implementation of the depolymerization method, the condensate provided by the condenser 16 contains liquid monomers, which are also referred to as "liquid monomers" or "low-temperature monomers" hereinafter.

[0026] The condensate containing liquid monomers generated from the depolymerization of the polymer is also referred to as "crude monomer" or "pyrolysis oil".

[0027] The monomer constitutes, for example, at least 20% by mass of the crude monomer, preferably at least 50% by mass of the crude monomer, more preferably at least 80% by mass of the crude monomer, and particularly at least 90% by mass of the crude monomer.

[0028] According to the depolymerization method, the transfer of the gas flow from the separator 14 to the condenser 16 is performed via a transfer tower 18 that extends 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.

[0029] According to the depolymerization method, the low-temperature monomer in the liquid state is injected into the transfer tower 18, and the transfer tower 18 is provided with internal elements configured such that the low-temperature monomer flows downward in the transfer tower 18 by gravity. The heavy impurity substances contained in the gas flow flowing upward through the transfer tower 18 condense into the liquid state on the internal elements and flow back downward toward the lower end 18A of the transfer tower 18 by gravity, and then move to the separator 14. The temperature of the gas flow decreases from the lower end 18A to the upper end 18B of the transfer tower 18.

[0030] The depolymerization system 10 includes a reinjection loop 20 configured to collect, for example, the liquid monomer from the condenser 16, and more specifically from the condensate outlet 16B of the condenser 16, and inject this liquid monomer into the transfer tower 18, particularly at the upper end 18B of the transfer tower 18.

[0031] As shown in FIG. 1, the reinjection loop 20 includes a reinjection line 20A for reinjecting the liquid monomer at the upper end 18B of the transfer tower 18.

[0032] Optionally, the reinjection loop 20 is configured to reinject the liquid monomer collected from the condenser 16 at one or several intermediate injection points located between the lower end 18A and the upper end 18B of the transfer tower 18, at the gas inlet 16A of the condenser 16, and / or into the separator 14.

[0033] As shown in FIG. 1, the reinjection loop 20 includes a reinjection line 20B for reinjecting the liquid monomer at an intermediate point along the moving tower 18, a reinjection line 20C for reinjecting the liquid monomer at the gas inlet 16A of the condenser 16, and / or a reinjection line 20D for reinjecting the liquid monomer into the separator 14.

[0034] Optionally, the depolymerization method includes a step of filtering the cold monomer obtained from the condenser 16 before injecting the cold monomer into the moving tower 18 and optionally the condenser 16 and / or the separator 14.

[0035] As shown in FIG. 1, the reinjection loop 20 includes a filtering device 22 for filtering the liquid monomer obtained from the condenser 16 before reinjecting it into the moving tower 18 and optionally the condenser 16 and / or the separator 14. The filtering device 22 includes, for example, a filter or two filters fluidly connected in parallel.

[0036] According to the depolymerization method, the temperatures of the gas flows at the separator gas outlet 14B of the separator 14 and the lower end 18A of the moving tower 18 are maintained above the boiling point of the monomer, and the temperature of the gas flow at the upper end 18B of the moving tower 18 is maintained between the boiling point of the monomer and the boiling point of the monomer + 50°C.

[0037] The depolymerization method is operated, for example, such that the temperatures of the gas flows at the gas outlet 14B of the separator 14 and the lower end 18A of the moving tower 18 are maintained at, for example, at least the boiling point of the monomer + 20°C, in particular at least the boiling point of the monomer + 30°C, more particularly at least the boiling point of the monomer + 40°C, and even more particularly at least the boiling point of the monomer + 50°C.

[0038] Preferably, the depolymerization method is operated, for example, such that the temperature of the gas flow at the upper end 18B of the moving tower 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, and in particular between the boiling point of the monomer and the boiling point of the monomer + 10°C.

[0039] Preferably, according to the depolymerization method, the rate of the low-temperature monomer injected into the moving tower 18 is at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90% of the equivalent supply rate of the monomer generated by the depolymerization.

[0040] The equivalent supply rate of the monomer is defined as the flow rate of the pyrolysis monomer generated by the depolymerization and entering the inlet 14 of the separator 14.

[0041] Preferably, the ratio of the low-temperature monomer obtained from the condenser 16 and reinjected into the moving tower 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 supply rate of the monomer.

[0042] Preferably, the depolymerization method is carried out such that the temperature of the gas flow at the inlet 14A of the separator 14 is equal to or higher than 250 ° C, preferably equal to or higher than 300 ° C, more 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.

[0043] The temperature of the gas flow at the inlet 14A of the separator 14 is, in particular, a function of the operation of the configured pyrolysis reactor 12 for heating the feedstock, as will be described later.

[0044] Preferably, the depolymerization method is operated such that the temperature of the gas flow at the outlet 14B of the separator 14 is included between 100 ° C and 280 ° C, preferably between 110 ° C and 180 ° C.

[0045] Preferably, the depolymerization method is operated such that the pressures in the pyrolysis reactor 12, the separator 14, the moving tower 18, and the condenser 16 are included between 0.3 and 2.0 bar, preferably between 0.4 and 1.5 bar, and more preferably between 0.5 and 1.2 bar.

[0046] The pyrolysis reactor 12 includes a reactor inlet 12A for receiving the feedstock and a reactor outlet 12B for providing a gas stream obtained from the pyrolysis of the feedstock.

[0047] The depolymerization system 10 includes, for example, a supply device 23 for feeding a material containing a polymer to the pyrolysis reactor 12, particularly to the reactor inlet 12A. The supply device 23 includes at least one feeder. The supply device 23 includes, for example, one feeder or preferably at least two feeders for feeding the pyrolysis reactor 12 in parallel.

[0048] The pyrolysis reactor 12 is configured to heat the feedstock received at the high-temperature reactor inlet 12A so as to vaporize the feedstock in order to generate the gas stream provided at the reactor outlet 12B.

[0049] Optionally, the pyrolysis reactor 12 is configured to mechanically process the feedstock. The mechanical processing of the feedstock in addition to heating the feedstock promotes the generation of the gas stream.

[0050] The mechanical processing of the feedstock in the pyrolysis reactor 12 may include, for example, agitation and / or extrusion of the feedstock. Thus, the pyrolysis reactor 12 is configured to, for example, agitate the feedstock and / or extrude the feedstock.

[0051] The pyrolysis reactor 12 is configured as, for example, a heated screw extruder, particularly as a heated twin-screw extruder.

[0052] The heated screw extruder includes a tubular barrel in which at least one screw extends into a barrel that is rotationally driven to extrude the feedstock along a tubular chamber, and a heating system for heating the feedstock contained in this barrel.

[0053] The heated twin-screw extruder is a heated screw extruder that includes twin screws extending side by side within a barrel, and the threads of these screws preferably mesh with each other, and the screws rotate co-rotating (rotating in the same direction about their respective axes) or counter-rotating (rotating in opposite directions about their respective axes).

[0054] The separator unit 15 has an internal flow path for a gas flow. The gas flow flows within the separator unit 15 through its internal flow path.

[0055] The separator 14 includes a separator gas inlet 14A for receiving the gas flow generated by the pyrolysis reactor 12 and a separator gas outlet 14B for providing a gas flow that will move to the condenser 16 via the moving tower 18.

[0056] Optionally, the separator 14 includes at least one impurity outlet 14C for collecting impurities separated from the gas flow within the separator 14.

[0057] The separator 14 has an internal flow path for the gas flow from the separator gas inlet 14A to the separator gas outlet 14B. The internal flow path 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.

[0058] The internal flow path of the separator 14 defines at least one section of the internal flow path of the separator unit 15.

[0059] The internal flow path of the separator unit 15 (including or consisting of that of the separator 14) has a cross-section obtained substantially perpendicular to the flow of the gas within the internal flow path. The cross-section has an area (i.e., a measure of the extent of the cross-section).

[0060] The area of the cross-section of the internal flow path of the separator unit 15 or the separator 14 may be constant along the internal flow path or may vary along the internal flow path.

[0061] During flow, the "maximum cross-section" of the internal flow path of the separator unit 15 or the separator 14 refers to the section of the internal flow path of the separator unit 15 or the separator 14 having the cross-section as the maximum area.

[0062] The condenser 16 includes a gas inlet 16A for receiving the gas flow provided by the separator 14 and a condensate outlet 16B for providing the condensate, i.e., the product condensed in the condenser 16.

[0063] The condenser 16 is configured to condense the gas flow received at the gas inlet 16A and provide the condensate at the condensate outlet 16B.

[0064] The condenser 16 optionally includes a gas outlet 16C for providing a non-condensable product that passes through the condenser 16 without being condensed.

[0065] The depolymerization method is preferably carried out such that the gas flow in the separator 14 is at a temperature equal to or higher than the boiling temperature of the monomer.

[0066] When the inlet flow path is provided, the gas flow generated by pyrolysis moves along the inlet flow path of the separator 14 while being gradually cooled. The temperature of the gas flow in the separator 14 is the lowest in the downstream section of the separator 14.

[0067] In such a case, the depolymerization method is preferably carried out such that the temperature of the gas flow in the downstream section of the separator 14 is equal to or higher than the boiling temperature of the monomer.

[0068] This will promote the evaporation of any liquid monomer present in the gas flow into the gaseous monomer and prevent the polymerization of the monomer.

[0069] The gas flow may contain dimers or trimers, i.e., chains of two or three monomers. Such dimers or trimers may result from incomplete depolymerization during pyrolysis or from oligomerization or polymerization of the monomer.

[0070] Generally, the boiling temperatures of the dimer and trimer of a monomer are strictly higher than that of the monomer.

[0071] Preferably, the depolymerization method is realized such that the temperature of the gas stream in the downstream section of the separator 14 is strictly lower than the boiling temperature of the trimer of the monomer and / or lower than the boiling temperature of the dimer of the monomer.

[0072] This will condense most of the dimer and / or trimer present in the gas stream in the separator 14, so that the dimer and trimer are retained in the separator 14, restricting or avoiding their flow to the transfer column 18 and the condenser 16.

[0073] The depolymerization method is realized with polymethyl methacrylate (PMMA) which refers to a homo- or copolymer of methyl methacrylate (MMA) containing at least 50%, preferably at least 60%, more preferably at least 70%, advantageously at least 80%, more advantageously at least 90% by mass of methyl methacrylate.

[0074] In the case of PMMA (polymer) and MMA (monomer), at atmospheric pressure, 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.

[0075] Therefore, in such a case, the depolymerization method is realized such that the temperature of the gas stream at the separator outlet 14B and the lower end 18A of the transfer column 18 is higher than 100 °C.

[0076] Moreover, preferably, the depolymerization method is realized such that the temperature of the gas stream in the downstream section of the inlet flow path of the separator 14 is included between 100 °C and 280 °C, particularly between 110 °C and 180 °C.

[0077] Advantageously, the depolymerization method includes the step of spraying the liquid monomer obtained from the condenser 16 into the separator 14, and this liquid monomer is to be sprayed into the gas stream, preferably facing the gas stream.

[0078] Optionally, the depolymerization method includes a step of spraying a part of the liquid monomer recovered by the condenser 16 into the separator 14.

[0079] Spraying the liquid monomer recovered by the condenser 16 into the separator 14 results in a cleaning operation in the separator 14, for example, on the wall of the separator 14 or on a mist removal device provided in the separator 14.

[0080] Preferably, the spraying of the liquid monomer recovered by the condenser 16 into the separator 14 is performed intermittently, for example, during a cleaning stage.

[0081] In such a case, the depolymerization system 10 is configured to spray a part of the liquid monomer recovered by the condenser 16 into the separator 14, for example, via the reinjection line 20D of the reinjection loop 20.

[0082] Preferably, the liquid monomer is sprayed into the separator 14 such that the ratio of the mass flow rate of the liquid monomer sprayed into the separator 14 to the mass flow rate of the gas stream is equal to or lower than 93%, more preferably equal to or lower than 83%, more preferably equal to or lower than 73%, more preferably equal to or lower than 63%, more preferably equal to or lower than 53%.

[0083] Preferably, the liquid monomer is sprayed into the separator 14 such that the mass flow rate of the liquid monomer sprayed into the separator 14 is equal to or higher than 10% of the mass flow rate of the gas stream, more preferably equal to or higher than 20%, preferably equal to or higher than 30%, more preferably equal to or higher than 40%, more preferably equal to or higher than 50%.

[0084] Optionally, instead of or supplementing the spraying of the liquid monomer in the separator 14, the depolymerization method includes a step of spraying liquid water into the separator 14. The benefits are similar to those when spraying the liquid monomer in the separator 14.

[0085] The pyrolysis reactor 12 is configured to process the feedstock at the maximum mass flow rate and thus provide a gas flow at the maximum mass flow rate.

[0086] Furthermore, in any section of the internal flow path of the separator unit 15, the gas flow flowing into the separator unit 15 has a linear velocity determined as the value obtained by dividing the volume of the gas generated by the pyrolysis reactor 12 per unit time by the cross-sectional area of the said section of the internal flow path of the separator unit 15.

[0087] Preferably, the depolymerization method is realized such that the linear velocity of the gas flow in the separator unit 15 is lower than the maximum linear velocity in the section of the internal flow path of the separator unit 15 having at least the maximum cross-section.

[0088] In a particular embodiment, the section of the internal flow path of the separator unit 15 having the maximum cross-section is the downstream section of the internal flow path of the separator unit 15.

[0089] In one embodiment, particularly when the polymer is PMMA, the maximum linear velocity is 0.50 m / s, preferably 0.15 m / s, particularly 0.10 m / s.

[0090] The linear velocity of the gas flow in any section of the internal flow path of the separator unit 15 is a function of the mass flow rate or the volume flow rate of the gas flow and the cross-sectional area of the said section of the internal flow path of the separator unit 15. The mass flow rate is related to the volume flow rate and the mass density of the gas flow at the operating pressure.

[0091] The volume flow rate of the gas flow is a function of the feed rate of the pyrolysis reactor 12, the depolymerization temperature of the polymer, and the molar weight of the polymer.

[0092] Advantageously, the area of the maximum cross-section of the internal flow path of the separator unit 15 is selected as a function of, for example, the maximum feed rate of the pyrolysis reactor 12, the depolymerization temperature of the polymer, and the molar weight of the polymer, such that the linear velocity of the gas flow at the maximum cross-section of the internal flow path of the separator unit 15 is made lower than the maximum linear velocity at the maximum feed rate of the pyrolysis reactor.

[0093] Preferably, the maximum cross-section of the internal flow path of the separator unit 15 has an area that is at least 0.001 times the maximum mass flow rate of the gas flow provided by the pyrolysis reactor 12, the area being expressed in square meters (m 2 ), and the maximum mass flow rate being expressed in kilograms per hour (kg / h).

[0094] Preferably, the maximum cross-section of the internal flow path of the separator unit 15 is at least 10 times the area of the minimum cross-section of the separator unit 15.

[0095] These parameters make it possible to limit the linear velocity of the gas flow in the separator unit 15, thus promoting the deposition of dust and droplets retained by the gas flow, and thus separating these droplets from the gas flow. In fact, the lower the linear velocity of the gas flow, the less easily droplets and dust are retained by the gas flow.

[0096] Advantageously, the depolymerization method includes a step of gradually slowing down the gas flow within the separator unit 15.

[0097] This is obtained, for example, by gradually increasing the cross-section of the internal flow path of the separator 14 from the separator gas inlet 14A to the separator gas outlet 14B.

[0098] In such a case, the downstream section of the internal flow path of the separator 14 is the section of the internal flow path of the separator 14 having the maximum cross-section.

[0099] Advantageously, the residence time of the gas flow in the separator unit 15 is included between 1 second and 30 seconds, preferably between 5 seconds and 25 seconds, more preferably between 10 seconds and 20 seconds.

[0100] The residence time is the time required for the gas flow to flow through the separator unit 15.

[0101] The residence time is a function of the length of the internal flow path, the average temperature, the mass flow rate or the volume flow rate and the molecular weight of the separator unit 15, and thus is a function of the internal volume of the separator unit 15.

[0102] The gas flow generated by the pyrolysis reactor 12 may contain mist formed by mist droplets. The mist droplets can be formed around the dust particles present in the gas flow. The dust particles can be due to impurities in the feed material containing the polymer intended to be depolymerized. The mist droplets present in the gas flow may contain liquid monomers, liquid dimers, or liquid trimers carried on the dust particles present in the gas flow.

[0103] Advantageously, the depolymerization method includes the steps of removing the mist of the gas flow (for example, by passing the gas flow through a mist eliminator or a mist removal device), and / or condensing the gas flow (i.e., by passing the gas flow through a condenser or a condensation device).

[0104] Mist removal is different from the condensation of monomers in the gaseous state to monomers in the liquid state. Mist removal consists of collecting the droplets already in the liquid state present in the gas flow, such as the droplets in the fog.

[0105] Mist removal is obtained, for example, by promoting the coalescence of the mist droplets present in the gas flow, for example by defining small passages that force the droplets to flow closer to each other and then coalesce.

[0106] Mist removal is performed, for example, by providing at least one mist removal device, each mist removal device being configured to be very heavy so as to promote the coalescence of the mist droplets and transport the mist droplets with the gas stream.

[0107] Each mist removal device may include a cyclone effect chamber, at least one grid, at least one mesh, at least one foam sheet, at least one porous monolith, and / or at least one baffle, for example, for capturing mist droplets by promoting the coalescence of the mist droplets.

[0108] Optionally, the depolymerization method includes a step of performing mist removal of the gas stream in the separator 14.

[0109] In such a case, the separator 14 includes an internal mist removal device positioned within the separator 14.

[0110] Optionally, the depolymerization method includes a step of performing mist removal of the gas stream downstream of the condenser 16, i.e., the gas stream collected from the condenser gas outlet 16C of the condenser 16.

[0111] In such a case, the depolymerization system 10 includes a mist removal unit 24 including at least one downstream mist removal device 24A, 24B arranged and configured downstream of the condenser 16, each downstream mist removal device 24A, 24B being configured to remove droplets present in the gas stream.

[0112] The mist removal unit 24 includes, for example, two mist removal devices 24A, 24B arranged in series on a fluid line for collecting gas from the condenser gas outlet 16C of the condenser 16.

[0113] The upstream mist removal device 24A is configured to remove the mist of the gas by, for example, the temperature of the gas, and the downstream mist removal device 24B is configured to cool and remove the mist of the gas, for example, simultaneously, using the cold air provided by the cold air generator 26.

[0114] Condensation results in the retention of the gaseous portion of the gas stream as a solid component, and thus is different from mist removal.

[0115] Condensation includes passing the gas stream through a chamber containing a cooled thin plate or fin so as to condense the product to be separated from the rest of the gas stream near or below its triple point and adhere it to the thin plate or fin in a crystalline form.

[0116] In the condenser, the separated product in crystalline or solid form is gradually introduced and can be discharged by heating so that the separated product of crystallization or amorphous solid melts. It is necessary that the separated product to be captured can be heated to melt without polymerization.

[0117] In the case of the depolymerization of PMMA, providing a condenser can be appropriate for removing terephthalic acid of dimethyl terephthalate that can be generated by PET contamination and present in the gas stream.

[0118] Providing a condenser is appropriate, for example, when there is a risk of contamination by polyolefins such as PE that can generate wax having a high melting point and can be trapped in the condenser 16.

[0119] The condensation unit may include two condensers fluidly connected in parallel such that one of the two condensers can be maintained in an operating state while the other is discharged, thus enabling continuous operation of the depolymerization system 10.

[0120] Optionally, the depolymerization method includes passing the gas stream through a condenser to capture contaminants present in the gas stream.

[0121] When a condensation unit is provided, the latter is preferably installed in series between the separator 14 and the condenser 16.

[0122] As illustrated in FIG. 1, the depolymerization system 10 optionally includes a condensation 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.

[0123] The condenser 25 includes, for example, one condenser or two condensers fluidly connected in parallel between the separator 14 and the condenser 16. Each condenser can process the gas stream when the other condenser is discharging.

[0124] Optionally, the depolymerization system 10 includes a side tank 27 fluidly connected to the separator 14 so as to indicate the liquid level of the separator 14.

[0125] The side tank 27 is fluidly connected to the separator 14 via a liquid line 29A, for example, to collect liquid from the bottom of the separator 14. The liquid connection line 29A is preferably heated and optionally via a gas line 29B for returning gas to the separator 14.

[0126] Optionally, the depolymerization method includes a step of performing primary separation between the pyrolysis reactor 12 and the separator 14 to separate dust from the gas stream before supplying the gas stream to the separator 14.

[0127] Accordingly, the separator unit 15 optionally includes a primary separator 100 that is interposed in series between the pyrolysis reactor 12 and the separator 14 and is configured to separate dust from the gas stream generated by the pyrolysis reactor 12 before the gas stream enters the separator 14.

[0128] The depolymerization system 10 preferably includes a solid particle collector 90 connected to the primary separator 100 to collect dust.

[0129] The solid particle collector 90 is removably connected, for example, to the primary separator unit 100 via a valve 35 configured to be replaceable with another solid particle collector 90 during operation, i.e., during the operation of the depolymerization system 10.

[0130] The primary separator 100 must be considered to determine the ratio between the maximum cross-sectional area of the internal passage 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.

[0131] Thus, preferably, the residence time of the gas stream in the separator unit 15 (including the separator 14 and, where applicable, the primary separator 100) is included between 1 second and 30 seconds, preferably between 5 seconds and 25 seconds, and more preferably between 10 seconds and 20 seconds.

[0132] Furthermore, preferably, the maximum cross-sectional area of the internal flow path of the separator unit 15 (including the separator 14 and, where applicable, 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, and the area is expressed in square meters (m 2 ), and the maximum mass flow rate is expressed in kilograms per hour (kg / h).

[0133] Optionally, the depolymerization system 10 includes an inert gas supply assembly 37 configured to supply an inert gas, such as nitrogen or argon, to the depolymerization system 10 during the shutdown of this depolymerization system 10 and to maintain a lower oxygen partial pressure within the unit.

[0134] The inert gas supply assembly 37 is configured, for example, to inject an inert gas into the separator 4.

[0135] The depolymerization system 10 preferably includes a pump for forcing the fluid flow towards the depolymerization system 10. As shown in FIG. 1, the depolymerization system 10 includes, for example, a pump disposed 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.

[0136] Optionally, the depolymerization method includes the step of injecting liquid monomer obtained from the liquid monomer reservoir at the upper end 18B of the moving tower 18, at one or several intermediate injection points positioned between the lower end 18A and the upper end 18B of the moving tower 18, at the condenser inlet 16A, and / or within the separator 14, for example during a purification stage or a start-up stage.

[0137] For this purpose, the depolymerization system 10 includes a liquid monomer reservoir 39 fluidly connected to the reinjection loop 20 to provide liquid monomer, for example during a purification stage or a start-up stage.

[0138] The depolymerization system 10 includes essential pumps 140, 142, 144 that are necessary to force the fluid to flow through the components, lines, and loops of the depolymerization system 10.

[0139] As shown in FIG. 1, the pump 140 is provided on the reinjection loop 20, and the pump 142 is provided on the condensate outlet 16B for the produced liquid monomer. The pump 144 is also provided on the reheating loop, which will be detailed later.

[0140] A part of the low-temperature monomer obtained at the condensate outlet 16B defines the "produced" low-temperature monomer that is collected for use as the final product or for further processing, especially for distillation. The produced low-temperature monomer is here pumped out by the pump 142.

[0141] A part of the low-temperature monomer obtained at the condensate outlet 16B is collected by the reinjection loop 20 for reinjection in the depolymerization system 10, especially at the upper end 18B of the moving tower 18.

[0142] Preferably, the depolymerization method includes a step of injecting a stabilizer into the generated low-temperature monomer.

[0143] The stabilizer is configured to prevent the low-temperature monomer from polymerizing during storage or further processes such as distillation.

[0144] Optionally, the depolymerization method includes a step of injecting a stabilizer into the re-injected low-temperature monomer.

[0145] The stabilizer injected into the re-injected low-temperature monomer is, for example, the same as the stabilizer injected into the generated low-temperature monomer at the same dosage or a different dosage, or different from the stabilizer injected into the generated low-temperature monomer.

[0146] When the stabilizer injected into the generated low-temperature monomer and the stabilizer injected into the re-injected low-temperature monomer are the same, this stabilizer is injected into the condensate outlet 16B upstream of the branch of the re-injection loop 20, for example, so that the dosage is the same, or the stabilizer is injected into the condensate outlet 16B downstream of the branch of the re-injection loop 20 on one hand and into the re-injection loop 20 on the other hand, so that the dosage is the same or different dosages are used.

[0147] When various stabilizers are used, one type of stabilizer is injected into the condensate outlet 16B downstream of the branch of the re-injection loop 20, and the other stabilizer is injected into the re-injection loop 20.

[0148] The stabilizer injected into the generated low-temperature monomer is selected, for example, from one of the following families: phenothiazine, hydroquinone, topanol, and butylated hydroxytoluene (or "BHT").

[0149] The stabilizer injected into the re-injected low-temperature monomer is preferably from the family of phenothiazine or any other stabilizer that can be used in the absence of oxygen.

[0150] A separator 14 suitable for use in a depolymerization system 10 to implement a depolymerization method is shown in FIG. 2.

[0151] The separator 14 includes an internal flow path 30 configured for circulation of a gas flow between a separator inlet 14A and a separator outlet 14B.

[0152] In one embodiment, as shown in FIG. 2, the pyrolysis reactor outlet 12B opens directly into the separator inlet 14A such that the gas flow generated by the pyrolysis reactor 12 flows directly from the pyrolysis reactor outlet 12B.

[0153] Preferably, when the pyrolysis reactor 12 has at least one extrusion screw, the extrusion screw is inserted into or protrudes into the separator inlet 14A to avoid blockage of the reactor outlet 12B by impurities.

[0154] In other words, the pyrolysis reactor outlet 12B is directly fluidly connected to the separator inlet 14A such that the gas flow 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 element.

[0155] The separator 14 includes, for example, a separation chamber 32 extending around a central axis A, and the separator 14 is configured such that the gas flow flows annularly around the central axis A into the separation chamber 32.

[0156] Thus, the separator 14 is configured to achieve a cyclone effect in the separation chamber 32.

[0157] With such a configuration, the gas flow 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 flow tend to remain at the periphery of the separation chamber 32.

[0158] Separator 14 includes, for example, an inlet duct 34 configured to receive the gas flow generated by pyrolysis reactor 12. Inlet duct 34 extends from a separator inlet 14A that defines the upstream end of inlet duct 34. Inlet duct 34 forms an upstream section of the internal volume 30 of separator 14.

[0159] In view of promoting an annular flow of the gas flow in separation chamber 32, inlet duct 34 is, for example, made to appear in separation chamber 32 and impart a rotational movement about central axis A to the gas flow in separation chamber 32.

[0160] In a particular embodiment, inlet duct 34 is opened into separation chamber 32 such that the gas flow appears in separation chamber 32 along an inlet direction that defines a non-zero angle with respect to the radial direction in which the gas flow is radial with respect to central axis A.

[0161] In a variant where separator 14 does not have an inlet duct 34, separator inlet 14A is opened, for example, into separation chamber 32 so as to impart a rotational movement about central axis A to the gas flow in separation chamber 32.

[0162] In a particular embodiment, separator inlet 14A is opened, for example, into separation chamber 32 such that the gas flow appears in separation chamber 32 along an inlet direction that defines a non-zero angle with respect to the radial direction in which the gas flow is radial with respect to central axis A.

[0163] Advantageously, inlet duct 34 extends around central axis A. This makes it possible to obtain a cyclone or rotational effect with inlet duct 34.

[0164] Separator 14 is preferably configured to collect the gas flow at the center of separation chamber 32 and to provide the gas flow collected at the center of separation chamber 32 to separator outlet 14B.

[0165] The separator 14 includes, for example, a collecting pipe 36 positioned at the center of the separation chamber 32. The collecting pipe 36 extends along the central axis A and has at least one inlet opening 38 for the gas flow existing in the separation chamber 32 to enter the collecting pipe 36. The collecting pipe 36 is fluidly connected to the separator outlet 14B to provide the collected gas flow to the separator outlet 14B.

[0166] The collecting pipe 36 is provided with, for example, at least one inlet section 40. Each inlet section 40 includes one inlet opening 38 or several inlet openings 38 distributed circumferentially around the inlet section 40 of the collecting pipe 36.

[0167] The collecting pipe 36 is provided with, for example, a plurality of inlet sections 40 distributed along the collecting pipe 36. Each inlet section 40 includes one inlet opening 38 or several inlet openings 38 distributed circumferentially around the inlet section 40 of the collecting pipe 36.

[0168] In a preferred embodiment, the collecting pipe 36 is provided with at least one frustoconical baffle 42. Each frustoconical baffle 42 has an upper edge with a smaller diameter connected to the collecting pipe 36 and a lower edge with a free and larger diameter. The baffles 42 extend around the respective inlet sections 40.

[0169] Preferably, each inlet section 40 is associated with a respective frustoconical baffle 42 that extends around this inlet section 40.

[0170] Preferably, the upper edge of each frustoconical baffle 42 is positioned above each inlet opening 38 of the corresponding inlet section 40, and the lower edge of the frustoconical baffle 42 is positioned below each inlet opening 38 of the corresponding inlet section 40.

[0171] Each frustoconical baffle 42 forces the gas flow to flow below the lower edge of the frustoconical baffle 42 before entering the inlet opening 38 of the corresponding inlet section 40.

[0172] Each frustoconical baffle 42 promotes the fall of impurities to the bottom of the separation chamber 32 and / or the deposition of impurities on the frustoconical baffle 42.

[0173] Preferably, each inlet opening 38 has an area included between 3 and 79 mm 2 and preferably between 12 and 51 mm 2 inclusive.

[0174] Preferably, each inlet opening 38 has a circular profile with a diameter included between 2 and 10 mm, preferably between 4 and 8 mm.

[0175] Preferably, the cumulative area of the inlet openings 38 (i.e., the sum of the areas of all the inlet openings 38) is included between 0.01 and 1.0 times, particularly between 0.01 and 0.1 times, the cross-sectional area of the upstream section of the internal flow path 30 of the separator 14.

[0176] In the separator 14 of FIG. 2, the upstream section of the internal flow path 30 of the separator 14 corresponds to the upstream end of the inlet duct 34.

[0177] Advantageously, the separator 14 is configured such that the maximum cross-section of the separator 14 is positioned in the downstream section of the separator 14.

[0178] In the separator 14 shown in FIG. 2, the downstream section of the separator 14 is defined by the separation chamber 32.

[0179] In one embodiment where the separator 14 includes an inlet duct 34 and a separation chamber 32, the inlet duct 34 has a cross-section that gradually increases from the upstream end of the inlet duct 34 that receives the gas flow to the downstream end of the inlet duct 34 that opens into the separation chamber 32.

[0180] Thus, the gas flow gradually slows down in the inlet duct 34 until the gas flow reaches the separation chamber 32.

[0181] 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, with a value such that the cross-sectional area of the inlet duct 34 increases in the downstream direction.

[0182] Advantageously, as shown in Figure 2, the separator 14 is configured to spray the liquid monomer into the gas flow within the separator 14.

[0183] The separator 14 is configured to spray one or several spray jets into the gas flow within the separator 14.

[0184] For this purpose, the separator 14 includes at least one spray nozzle 44 for spraying the liquid monomer within the separator 14. Each spray nozzle 44 is configured to spray a spray jet.

[0185] The direction of each spray jet can be parallel or perpendicular or oblique to the gas flow. In one embodiment, each spray jet faces the gas flow, i.e., is sprayed upstream of the gas flow.

[0186] Each spray nozzle 44 is fluidly connected to the condenser 16, more specifically, to the return line 20D.

[0187] Each spray nozzle 44 is arranged and configured to spray the liquid monomer, for example, within the separation chamber 32.

[0188] As shown in Figure 2, the separator 14 includes spray nozzles 44 arranged and configured to spray the liquid monomer, for example, at the inlet of the separation chamber 32, i.e., the inlet duct 34 is connected to the separation chamber 32 here in the upstream direction of the gas flow.

[0189] Advantageously, the separator 14 incorporates an internal mist removal device 46 positioned within the separator 14 for depositing the droplets of the mist transported by the gas flow.

[0190] The internal mist removal device 46 includes at least one grid 48 extending across the cross-section of the separator 14 such that, for example, a gas flow passes through the openings of the grid 48.

[0191] In one embodiment where the separator 14 includes the inlet duct 34, each grid 48 is positioned, for example, within the inlet duct 34.

[0192] As shown in FIG. 2, the separator 14 includes two grids 48 arranged in the inlet duct 34. The two grids 48 are positioned at a distance from each other along the inlet duct 34.

[0193] The inlet duct 34 is bounded between a lower surface 50 and an upper surface 52.

[0194] In one embodiment, the duct lower surface 50 is inclined and / or the duct upper surface 52 is inclined.

[0195] In particular, the duct lower surface 50 is inclined and / or the duct upper surface 52 is inclined such that the cross-section of the inlet duct 34 increases from the upstream end of the inlet duct 34 towards the downstream end of the inlet duct 34.

[0196] As shown in FIG. 2, the duct lower surface 50 is inclined so as to descend from the upstream end of the inlet duct 34 towards the downstream end of the inlet duct 34. The mist droplets deposited on the duct lower surface 50 tend to flow towards the separation chamber due to gravity.

[0197] In one embodiment, the inlet duct 34 extends around the separation chamber 32 and over at least a portion of the circumference of the separation chamber 32.

[0198] As shown in FIG. 3, the inlet duct 34 extends around the separation chamber 32 for approximately 270° about a central axis A.

[0199] During operation, the gas stream is hot when entering the separator 14, and the temperature of the gas stream tends to decrease as it moves through the separator 14 due to heat loss, even if the separator 14 is properly insulated. When spraying of liquid monomers into the separator 14 is effected, this spraying tends to further cool the gas stream within the separator 14 due to vaporization of the liquid monomers sprayed into the hot gas stream.

[0200] The inlet duct 34 that partially surrounds the separation chamber 32 is beneficial for maintaining the gas stream at a sufficiently high temperature within the separator 14, particularly within the separation chamber 32.

[0201] As shown in FIG. 4, in one exemplary embodiment, the separator 14 includes a bottom 60 and an upper portion 62 that fits onto the bottom 60 to form the separator 14.

[0202] The bottom 60 includes a bottom portion 64 and a peripheral wall 66 that extends upwardly from the periphery of the bottom portion 64, the peripheral wall 66 defining an upper opening 68 and an internal volume 70. The peripheral wall 66 is provided with a side opening that defines the inlet opening 14A of the separator 14. The peripheral wall 66 is, for example, cylindrical and has a circular cross-section.

[0203] The upper portion 62 includes a lid 72 for closing the upper opening 68 and an internal structure 74 that extends downwardly from the lid 72 for fitting inside the bottom 60 when the upper opening 68 is closed by the lid 72. The internal structure 74 is configured to define the separation chamber 32 and the inlet duct 34 within the internal volume 70 of the bottom 60.

[0204] The internal structure 74 includes a partition wall 76 that extends downwardly from the lid 72 along a central axis A for defining the boundary of the separation chamber 32 internally and the boundary of the inlet duct 34 externally, separated by the peripheral wall 66, and a duct element 78 that extends around the partition wall 76 for defining the boundary of the bottom surface 50 of the inlet duct 34, and the upper surface 52 of the inlet duct 34 is bounded by a peripheral region of the lower surface of the lid 72.

[0205] The partition wall 76 has an inner surface 74A that defines the side wall of the separation chamber 34 and an outer surface 76B that defines the side wall of the inlet duct 34.

[0206] When viewed along the central axis A, the partition wall 76 extends approximately 270° around the central axis A as shown in FIG. 3.

[0207] The inlet duct 34 is bounded by the partition wall 76, the peripheral wall 66, the duct element 78, and the lid 72.

[0208] The peripheral wall 66 is provided with a connector 67 for connection to the outlet of the pyrolysis reactor 12. The contour of the connector 67 is represented by a dotted line such as S to indicate its position relative to the upstream end of the inlet duct 34.

[0209] The lid 72 is perpendicular to the central axis A, and the duct element 78 extends around the central axis A with its upper surface inclined with respect to the central axis A such that the height of the inlet duct 34 gradually increases from the upstream end to the outlet end of the inlet duct 34 and the cross-section of the inlet duct 34 gradually increases from the upstream end to the outlet end of the inlet duct 34.

[0210] The duct element 78 extends, for example, spirally around the central axis A of the separation chamber 32.

[0211] When viewed along the central axis A, the partition wall 76 extends, for example, along a part of a circle or along a part of a spiral, and is made to approach the central axis A in the downstream direction of the inlet duct 34 bounded by the partition wall 76.

[0212] The circular extension of the partition wall 76 is used, for example, to define an inlet duct 34 of a constant width in the downstream direction of the inlet duct 34, and the spiral extension of the partition wall 76 is used, for example, to define an inlet duct 34 of a gradually increasing width in the downstream direction of the inlet duct 34.

[0213] The bottom 64 of the bottom 60 defines the lower surface of the separation chamber 32.

[0214] On the bottom 64, an exhaust opening 80 is provided for exhausting impurities separated from the gas flow within the separator.

[0215] Preferably, the bottom 64 is shaped such that impurities fall by gravity towards the exhaust opening 80. As shown in FIG. 4, the bottom 64 is frustoconical in a downwardly tapered state towards the exhaust opening 80.

[0216] Optionally, the separator 14 includes a collection pot 82 configured to fit under the bottom 60 for collecting impurities that have fallen into the exhaust opening 80.

[0217] Preferably, the collection pot 82 is removably connected to the bottom 64. Thus, the collection pot 82 can be removed to empty it.

[0218] Optionally, the exhaust opening 80 is provided with a valve 83, such as a slide valve, arranged and configured to selectively open and close the exhaust opening 80. This allows for disconnecting the collection pot 82 after closing the valve 83 while keeping the separator 14 operating.

[0219] The collection pot 82 may be provided with a gas purge line and / or the collection pot 82 may be actively cooled so as to be safely removable and replaceable.

[0220] In one embodiment, the separator 14 is provided with a removal device configured to remove the product deposited on the separator 14 towards the exhaust opening. The removal device is configured to remove, for example, the bottom of the separator 14.

[0221] As shown in FIGS. 2 and 4, the removal device 84 is configured to remove, for example, the product deposited on the bottom wall 64 of the bottom 60 towards the exhaust opening 80.

[0222] The separator 14 is not limited to the embodiments shown in FIGS. 2 to 4, and other modifications or alternatives are possible.

[0223] Separator 14 in FIG. 5, which has the same reference numerals for similar elements, is different from the separators in FIGS. 2 to 4. That is, the inlet duct 34 is bounded by a lower surface 50 extending in a plane perpendicular to the central axis A and an upper surface 52 inclined so as to rise from the upstream end to the downstream end of the inlet duct 34.

[0224] Separator 14 in FIG. 5 is different from the cases of FIGS. 2 to 4 in that a spraying device 42 is arranged and configured to spray the liquid monomer, particularly around the central axis A, at a location close to the central axis A. The spraying device 42 includes, for example, a plurality of spray nozzles 44 distributed around the central axis A.

[0225] When the collecting pipe 36 is provided as shown in FIG. 5, the spraying device 42 is configured, for example, to spray the liquid monomer around the collecting pipe 36.

[0226] The spraying of the liquid monomer obtained from the condenser 16 into the separator 14 can be useful for preventing clogging of one or several mist removal grids 48 provided in the separator 14 over time, particularly by spraying the liquid monomer onto the mist removal grid 48.

[0227] Separator 14 in FIG. 6, which has the same reference numerals for similar elements, includes spray nozzles 44 oriented to spray the liquid monomer obtained from the condenser 16 onto the lowermost mist removal grid 48 provided in the inlet duct 34 of the separator 14.

[0228] Optionally, as shown in FIG. 6, the separator 14 includes one or several spray nozzles 44 arranged and configured to spray the liquid monomer obtained from the condenser 16 at the surface of the uppermost mist removal grid 48 provided in the inlet duct 34 of the separator 14.

[0229] Optionally, as shown in FIG. 6, the separator 14 is arranged to spray the liquid monomer obtained from the condenser 16 in an intermediate space defined by a boundary between two mist removal grids 48 provided in the inlet duct 34 of the separator 14, preferably by spraying the liquid monomer onto one or both of these two mist removal grids 48, and includes one or several spray nozzles 44.

[0230] Optionally, as shown in FIG. 6, the separator 14 includes a mist removal grid 48 provided in the downstream section of the separator, particularly a mist removal grid 48 surrounding the collection pipe 36.

[0231] This mist removal grid 48 is arranged, for example, in a tube shape and fitted around the collection pipe 36 so that the gas flow passes through this mist removal grid and reaches the collection pipe 36.

[0232] The gas flow entering the separator 14 may contain solid particles due to impurities in the raw material being depolymerized in the pyrolysis reactor 12.

[0233] Optionally, the separator 14 is provided with at least one solid particle collector 90, preferably in the inlet duct 34 of the separator 14, preferably arranged upstream of the mist removal grid 48 provided in the inlet duct 34 of the separator 14.

[0234] Each solid particle collector 90 includes, for example, a collection pot 92 connected to the separator 14 by a collection pipe 94 such that solid particles fall into the collection pot 92 by gravity. The collection pipe 94 is connected, for example, to the lower wall 50 of the inlet duct 34 of the separator 14.

[0235] The collection pot 92 is preferably removably connected to the separator 14. This enables the collection pot 92 to be emptied when solid particles have been collected inside or when the collection pot 92 is replaced with a new one. The collection pot can be provided with one or two valves that isolate it from the separator 14, allowing for the replacement of the collection pot.

[0236] Preferably, each solid particle collector 90 is positioned within a climate chamber 96 that is controlled to maintain the temperature inside equal to or higher than the boiling temperature of the monomer.

[0237] The separator 14 may be provided with one or several solid particle collectors 90.

[0238] As shown in FIG. 6, the separator 14 is provided with two solid particle collectors 90 that are respectively connected to the inlet duct 34 of the separator 14 at respective positions along the inlet duct 34 of the separator 14.

[0239] 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 each one of a plurality of mist elimination grids 48 provided in the inlet duct 34 of the separator 14.

[0240] As shown in FIG. 6, the separator 14 is provided with two mist elimination grids 48 that extend across the inlet duct 34 of the separator 14, and two solid particle collectors 90 that are respectively connected to the inlet duct 34 of the separator 14 upstream of each one of these two mist elimination grids 48.

[0241] One of the solid particle collectors 90 is connected to the inlet duct 34 upstream of the first mist elimination grid 48, and one of the solid particle collectors 90 is connected to the inlet duct 34 between the two mist elimination grids 48.

[0242] When a plurality of solid particle collectors 90 are provided, they can be housed in the same climate chamber 96.

[0243] As shown in FIG. 6, the separator 14 is provided with two solid particle collectors 90 arranged and configured in the same climate chamber 96.

[0244] As shown in FIGS. 7 and 8, the separator unit 15 includes a primary separator 100 configured to separate dust from the gas flow generated from the pyrolysis reactor 12 before the gas flow enters the separator 14.

[0245] The primary separator 100 includes a cavity 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.

[0246] As shown in FIGS. 7 and 8, the gas inlet 101 is coaxial with the gas outlet 103, for example, and is arranged such that the gas flows linearly from the gas inlet 101 to the gas outlet 103 during operation. The dust outlet 105 is formed in the bottom wall of the separation cavity 102.

[0247] The solid particle collector 90 is connected to the dust outlet 105 for collecting dust.

[0248] During operation, the dust that is too heavy to flow with the gas flow in the separation cavity 102 falls at the dust outlet 105 and is collected by the solid particle collector 90.

[0249] The gas inlet 101 is provided with a first flange 104, for example, for a detachable connection to the separator 14, and the gas outlet 103 is provided with a second flange 106, for example, for a detachable connection to the pyrolysis reactor 12.

[0250] As shown in FIG. 9, the separator 14 may include a mist removal grid 48 that extends across the internal flow path 30 at the junction between the inlet duct 34 and the chamber 32.

[0251] The mist removal grid 48 is provided, for example, at the upper part 62 while being attached to the partition wall 76 and the duct element 78.

[0252] Preferably, the mist removal grid 48 is arcuate such that the mist removal grid bulges in the upstream direction. The mist removal grid 48 has, for example, two straight vertical side edges and an arcuate upper edge and bottom edge. This provides a larger free cross-section for the passage of gas through the mist removal grid 48.

[0253] As shown in FIG. 9, a tubular mist removal grid 48 is provided within the chamber 32 and around the collection pipe 36 to cover the collection pipe 36.

[0254] As shown in FIG. 10, in an alternative embodiment of the primary separator 100, the separation cavity 102 is configured such that the gas flow is forced to change direction at least once between the gas inlet 101 and the gas outlet 103 of the separation duct 102, such as to facilitate the separation of dust.

[0255] Advantageously, the separation cavity 102 is configured such that the gas flow enters horizontally at the gas inlet 101 and is forced to flow upwardly towards the gas outlet 103, and the dust outlet 105 is provided at the bottom of the separation cavity 102.

[0256] The change in the direction of the gas flow within the separation cavity 102 promotes separation due to the interaction of the dust particles, which tend to strike the side walls of the separation cavity 102 and fall at the dust outlet 105 provided at the bottom of the separation cavity 102.

[0257] As indicated above, the primary separator 100, in particular the separation cavity 102, must be considered in determining the ratio between the maximum cross-section of the internal passage of the separator unit 15 (including the separator 14 and, where applicable, the primary separator 100) and the maximum gas flow rate provided by the pyrolysis reactor 12, and in determining the residence time of the gas flow within the separator unit 15.

[0258] A moving tower 18 suitable for implementing the depolymerization method is shown in FIG. 10.

[0259] The moving tower 18 includes a lower end 18A fluidly connected to the gas outlet 14B of the separator 14 to receive the gas flow 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.

[0260] The depolymerization system 10 includes a return line 20A that fluidly connects the condenser 16 to the upper end 18B of the moving tower 18, in this embodiment via a filtration device 22, for injecting liquid monomer into the upper end 18B.

[0261] Optionally, one or several intermediate injection return lines 20B are provided for injecting liquid monomer into the moving tower 18 at one or several injection points positioned between the lower end 18A and the upper end 18B of the moving tower 18.

[0262] The lower end 18A of the moving tower 18 is fluidly connected to the separator 14 such that the liquid collected at the lower end 18A of the moving tower 18 moves to the separator 14, in particular to the separation chamber 32 of the separator 14 and / or to the inlet duct 34.

[0263] The moving tower 18 includes internal elements 110 configured such that during operation, the gas flow flows upward from the lower end 18A to the upper end 18B. The low-temperature monomer injected into the moving tower 18 flows downward within the moving tower 18 by gravity. Heavy impurity substances contained in the gas flow are condensed in a liquid state on the internal elements 110 and flow back downward by gravity toward the lower end 18A of the moving tower 18, and then move to the separator 14. The temperature of the gas flow decreases from the lower end 18A to the upper end 18B of the moving tower 18.

[0264] The function of the internal elements 110 provided in the moving tower 18 is to increase the contact surface area between the gas flow flowing upward within the moving tower 18 and the liquid flow flowing downward within the moving tower 18.

[0265] The internal elements 110 include, for example, packing materials 112. The packing materials 112 may include random packing materials and / or structured packing materials.

[0266] Random packing materials and structured packing materials of the known type are described, for example, on the web page https: / / chemiopedia.com / packed-bed-column-and-its-types.

[0267] The internal element 110 includes, for example, random packing materials, which include, for example, so-called rings and / or saddles. The rings and / or saddles of the internal element 110 are preferably made of metal or ceramic. The use of metal or ceramic can withstand the temperatures encountered in the moving tower 18.

[0268] The internal element 110 includes, for example, a random packing material that includes or consists of rings, especially so-called Pall rings. Rings, especially Pall rings, provide good interaction between gas and liquid.

[0269] The structured packing material includes, for example, meshes, gauzes, or finely corrugated sheets with alternating layers.

[0270] Well-known packing material suppliers are, for example, Sulzer, Montz, and Koch-Glitsch Intalox. The internal element 110 of the moving tower 18 may include different types of packing materials in each section of the moving tower 18. The internal element 110 may include, for example, a first packing material of a first type in a first section of the moving tower 18 and a second packing material of a second type in a second section of the moving tower 18, where the first type is different from the second type, and the first section is clearly distinguished from the second section.

[0271] In particular, it is advantageous to adjust the internal element 110 of the moving tower 18 so as to give the moving tower 18 higher fouling resistance in the lower section of the moving tower 18 compared to the upper section, and to provide improved distribution in the upper section of the moving tower 18 compared to the lower section.

[0272] Furthermore, the pyrolysis reactor 12 is represented in FIG. 10 as a heated screw extruder, and the separator 14 is represented with a spiral inlet duct 34 and a collection pipe 36 provided with baffles 42 and extending into the separation chamber 34, the collection pipe 36 being fluidly connected to the lower end of the moving tower 18 to supply a gas stream to the moving tower 18.

[0273] These features are optional and exemplary, and the depolymerization system 10, particularly the pyrolysis reactor 12 and the separator 14, may be according to the embodiments and variations discussed above.

[0274] The moving tower 18 of FIG. 11 differs from that of FIG. 10 in that the internal element 110 includes a series of filters 123 distributed along the moving tower 18, and each filter 123 provided with holes or having its hole boundaries defined is arranged and configured within the moving tower 18 to force the circulation of the gas stream and the liquid through the holes.

[0275] Each filter 123 is, for example, flat or cylindrical in shape. Each filter 123 is provided, for example, as a grid, a perforated plate, or a mesh.

[0276] Such an internal element 110 forces the circulation of the gas stream and the liquid stream through the holes of the filters 123 in contact with each other.

[0277] As shown in FIG. 11, the lower end 18A of the moving tower 18 is connected, for example, to the collection pipe 36 of the separator 14, and thus the gas stream exiting the separator 14 is made to circulate directly into the moving tower 18, and the liquid flowing downward in the moving tower 18 is made to return to the separator 14 via the collection pipe 36.

[0278] The moving tower 18 of FIG. 12 differs from that of FIG. 10 in that the internal element 110 includes a series of plates or baffles distributed along the moving tower 18.

[0279] The baffle is configured to force the gas flow to flow upward and the liquid flow to flow downward for contact. In particular, the baffle is preferably configured to force the gas flow and the liquid flow to compulsorily follow a crossed and meandering path.

[0280] The baffle includes, for example, a first baffle 124 alternating with a second baffle 126 along the moving tower 18. Each first baffle 124 is annular and defines the boundary of the central passage for the gas flow and the liquid flow. Each second baffle 126 is circular and defines the boundary of the annular passage for the gas flow and the liquid flow. The inner diameter of the first baffle 124 is preferably smaller than the outer diameter of the second baffle 126.

[0281] Such first baffle 124 and second baffle 126 cause the gas flow to drop from the edges of the first baffle 124 and the second baffle 126 and force it into the liquid flow flowing by gravity.

[0282] The cracking polymerization method optionally includes a step of inputting thermal energy into the moving tower 18 and / or the separator 14 by heating the gas flow and / or the liquid present inside the internal elements of the moving tower 18 and / or the separator 14.

[0283] The step of inputting thermal energy particularly enables controlling the temperature range of the gas flow inside the separator 14 and the moving tower 18.

[0284] As shown in FIG. 13, the moving tower 18 is configured, for example, to input thermal energy by heating the gas and liquid flows circulating inside the moving tower 18.

[0285] The moving tower 18 in FIG. 13 is different from the case of FIG. 12 in that at least a part of the baffle is configured to heat these baffles, which are hereinafter referred to as "heating baffles".

[0286] The heating baffle is, for example, jacketed, that is, provided with an internal conduit for circulating the heating fluid F.

[0287] As shown in FIG. 13, the first baffle 124 which is annular is a heating baffle, particularly a jacketed baffle. Optionally or alternatively, the second baffle 126 which is circular is a heating baffle, particularly a jacketed baffle.

[0288] The heating baffle is provided in the moving tower 18 along the entire moving tower 18 or in only one section of the moving tower 18.

[0289] As shown in FIG. 13, the heating baffle is provided along the entire moving tower 18. Alternatively, the heating baffle is provided only in the lower section of the moving tower 18, and the upper section of the moving tower 18 includes only a non-heating baffle or a filler.

[0290] The jacketed heating baffle includes an internal duct 127 for circulating the heating fluid F. Each jacketed baffle 124 is, for example, hollow, and the internal duct 127 defines the boundary within the hollow jacketed baffle 124 for the circulation of the heating fluid F.

[0291] The heating fluid F preferably circulates in a closed loop of a heating circuit 123 which includes a jacketed baffle and further includes a heater and / or a heat exchanger 125 and a pump 129 for heating the heating fluid F.

[0292] The circulation of the gas flow from the lower end 18A to the upper end 18B and the circulation of the liquid monomer from the upper end 18B to the lower end 18A are respectively indicated by the arrows G and L in FIG. 13.

[0293] The internal elements 110 of the moving tower 18 may include one type of internal element 110 such as a filler 112 (FIG. 10), a perforated plate or a grid (FIG. 11), and perhaps a heating baffle (FIG. 13) or a baffle (FIG. 12) including or consisting of a heating baffle.

[0294] The internal elements 110 of the mobile column 18 may include combinations of different types of internal elements 110, and each type of internal element 110 is positioned, for example, in respective sections of the mobile column.

[0295] Optionally, the depolymerization method includes heating the liquid present in or accumulating in the separator 14 above the boiling temperature of the monomer so as to evaporate the monomer present in the liquid. This liquid is heated in the separator 14 and / or outside the separator 14 so as to evaporate the monomer in the separator, and the evaporated monomer is returned to the separator 14 so as to flow with the gas stream in which the evaporated monomer circulates inside the separator 14.

[0296] The liquid present in the separator 14 is provided, for example, on the surface of the separator 14 from the mobile column 18 or from condensation within the separator 14.

[0297] At least partially evaporating the liquid obtained from the mobile column 18 or condensed within the separator 14 is also known as "reboiling" or "reheating".

[0298] Accordingly, the depolymerization system 10 optionally includes a reheating device 114 configured to evaporate the existing liquid and / or accumulate it within the separator 14. The reheating device 114 is configured such that the gas resulting from evaporation is generated within the separator 14 and / or returns to the separator 14, and thus flows to the mobile column 18 together with the gas stream.

[0299] As shown in FIG. 1, the depolymerization system 10 includes, for example, a heating device 114 configured to heat the liquid outside the separator 14 and reinject the gas obtained from reheating within the separator 14.

[0300] 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.

[0301] The depolymerization system 10 includes, for example, a reheating loop 111 configured to collect liquid from a separator 14, heat the liquid in a reheater 116 to obtain a gas fraction, and reinject the gas and liquid obtained from the reheating in the separator.

[0302] Under stable operating conditions, most of the monomers in the liquid state that are condensed in the separator 14 or reach in the liquid state from the moving tower 18 will be re-evaporated in the reheater 116, and thus there is no accumulation of monomers.

[0303] Optionally, the reheating loop 111 includes a filtration device 113. The filtration device includes, for example, one filter or two filters fluidly connected in parallel.

[0304] Preferably, the reheating loop 111 includes a pump 144 that forces fluid circulation in the reheating loop 111.

[0305] Optionally, the depolymerization system 10 includes a liquid monomer reservoir 117 for supplying liquid monomers in the reheating loop 111, for example, during the start-up phase and / or the purification phase.

[0306] Preferably, the depolymerization system 10 includes a collection reservoir 119 connected to the reheating loop 111, preferably via a heating line 121, for occasionally collecting heavy substances that accumulate in the reheating loop 111.

[0307] As shown in FIGS. 10 to 14, the reheating device 114 is configured to heat liquid, for example, in the separator 14.

[0308] The reheating device 114 is configured to heat, for example, the liquid collected on a collection surface 115 of the separator 14 where the liquid present in the separator 14 is collected by gravity.

[0309] The collection surface 115 is, for example, the bottom surface of the separator 14 where the liquid present in the separator 14 is collected, in particular, the bottom surface of the separation chamber 32 of the separator 14.

[0310] As shown in Figures 10-14, the reheating device 114 includes an electric heater 116 arranged outside the separator 14 along a collection surface 115 of the separator 14 where liquid exiting the separator 14 is collected by gravity.

[0311] Preferably, the depolymerization system 10 includes a drainage device 118 configured to drain heavy liquid accumulated on the collection surface 115 of the separator 14, where the liquid present in the separator 14 is collected by gravity.

[0312] As shown in FIG. 14, the reheating device 114 includes a reheater 116 disposed within the separator 14, specifically within the chamber 32 of the separator 14, and configured to evaporate liquid present in the separator 14.

[0313] The reheater 116 is, for example, an evaporator, specifically a wiped film evaporator, including a hollow cylinder 130 extending vertically and configured to receive hot oil within the cylinder 130, a reheat loop 111 configured to feed liquid collected in the separator 14 to the top end of the hollow cylinder 130 to form a liquid film that flows by gravity on the outer surface of the cylinder 130, and a rotating wiper 134 connected to a drive motor 136 for rotating the rotating wiper 134 around the cylinder 130 and wiping the liquid film onto the outer surface of the cylinder 130.

[0314] The reheating device 114 preferably includes a collector 138 for collecting liquid dripping from the cylinder 130 and draining the liquid outside the separator 14, preventing the liquid from returning to the collection surface 115 of the separator 14.

[0315] The reheat device 114 makes it possible to evaporate the liquid present in the separator 14 in order to capture any monomers that may still be present in this liquid and to expel the heavier materials out of the separator 14.

[0316] In one embodiment, as shown in FIG. 15, the reheating device 114 includes a reheater 116 provided as a screw extruder fluidly connected to the separator 14 for receiving the liquid collected in the separator 14 and extruding this 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.

[0317] The screw extruder is capable of handling highly viscous liquids and produces solid residues and gaseous monomers. The gaseous monomers are returned to the separator 14 while the solid / heavy residues are, for example, discarded.

[0318] Advantageously, as shown in FIG. 15, the liquid obtained from the separator 14 is supplied to the reheater 116 provided as a screw extruder, and the outlet of the reheater 116 provided as a screw extruder is connected to the separator 14, in particular to the gas inlet of the separator 14, for example via a primary separator 100.

[0319] The heater 116 of the reheating device 114 may be positioned outside the separator 14 to heat the liquid present within the separator 14 (FIG. 10), or may be positioned outside the separator 14 to heat the liquid collected from the separator 14 (FIGS. 1 and 15), or may be positioned within the separator 14 (FIG. 14).

[0320] Moreover, various types of heaters 16 may be provided, including, for example, an extruder or an evaporator, in particular a thin-film evaporator.

Example

[0321] (Examples 1 and 2) The first embodiment was implemented in a depolymerization system 10 including a pyrolysis reactor 12, and a separator 14, a condenser 16, and a transfer column 18.

[0322] The pyrolysis reactor 12 is provided as a twin-screw extruder by co-rotation of the screws and cross-reversal of the screws.

[0323] The twin-screw extruder includes a screw extending through the barrel, an electric heater provided around the barrel to provide heating energy, and a thermocouple for temperature control also provided on the barrel. The barrel is formed, for example, by barrel segments.

[0324] The twin-screw extruder, especially its heater, is configured to generate a temperature profile along the screw with the maximum profile temperature in an intermediate section along the axis.

[0325] The twin-screw extruder is a TEX44 with a screw diameter of 47 mm. In an industrial production line, a TEX90 with a screw diameter of 96.5 mm can be used according to the required feed rate. TEX extruders are also sold by Nippon Steel Works, Ltd. which offers larger units.

[0326] The material to be depolymerized is fed into the twin-screw extruder in the hopper barrel by a gravimetric screw feeder. The material provided to the gravimetric screw feeder is pre-crushed to a size of about 5 to 10 mm.

[0327] The twin-screw extruder has a melting section and a subsequent depolymerization section along its length.

[0328] During operation, the material melts in the twin-screw melting section pushed by the shear stress from the screw and the heat from the heater, and then the molten material is transferred to the depolymerization section.

[0329] The depolymerization section of the pyrolysis reactor 12 can achieve a temperature of 550 °C.

[0330] The PMMA mixture in the form of crushed particles is fed through a gravimetric feeder. 2 to 4 independent feeders are charged with cast, injected, and / or extruded PMMA.

[0331] The following operating conditions were used in the comparative examples and the examples of the present invention: The feed rate of the material in the pyrolysis reactor 12 was included between 50 and 100 kg / h, the rotational speed of the screw of the pyrolysis reactor 12 was about 800 revolutions per minute, and the maximum profile temperature in the pyrolysis reactor 12 was 470 °C or less.

[0332] In Examples 1 and 2, the transfer between the separator 14 and the condenser 16 was carried out via a transfer column 18 having an inner diameter of 5.08 cm into which an internal element provided as a filter mesh was inserted. The filter mesh is a cylindrical grid having holes with a diameter of 1 mm. The filter mesh is inserted into the transfer column at an angle such that the gas flow is filtered through the filter mesh. The filter mesh is disposed at the upper part of the transfer column 18 closer to the condenser 16 than the separator 14.

[0333] The results of the examples were analyzed using gas chromatography, and three different procedures called the first GC procedure, the second GC procedure, and the third GC procedure were used as follows.

[0334] Gas chromatography was performed using a gas chromatograph HP7890 sold by Agilent Technologies, and this gas chromatograph is equipped with a flame ionization detector (FID).

[0335] The first GC procedure was used to quantify products such as methyl methacrylate (MMA), methanol (MeOH), methyl acrylate, and ethyl acrylate.

[0336] In the first procedure, a calibration curve was created with 2-butanol as a reference material and an internal standard. The sample was diluted with meta-xylene.

[0337] The analysis is performed by gas chromatography using an HP5 GC column sold by Agilent Technologies. The HP5 GC column is 30 m in length, has a diameter of 0.25 mm and a film thickness of 0.5 μm. The injector operates at 250 °C and is in split mode with a split ratio of 50. The flame ionization detector (FID) operates at 320 °C, the hydrogen flow rate is 40 ml / min, and the air flow rate is 350 ml / min. The sample is positioned on an automatic sampler.

[0338] The analysis was continued for 42 minutes, starting the GC column temperature at 40 °C and then increasing it to 100 °C after 13 minutes, and increasing the carrier gas flow rate from 0.8 ml / min to 1.5 ml / min after 18 minutes. The temperature was increased to 280 °C after 31 minutes and held at that level until the end.

[0339] The second GC procedure is used for the quantification of all other products based on the gas chromatography peak area. In this second GC procedure, the sample is diluted with dichloromethane. The analysis is performed using the same equipment and GC protocol as the first GC procedure.

[0340] The third GC procedure is for the quantification of methacrylic acid and acetic acid and utilizes a different GC column and analytical method.

[0341] The third GC procedure is performed using an HP-INNOWax GC column sold by Agilent Technologies, which has a length of 29 m, a diameter of 0.32 mm, and a film thickness of 0.25 μm, and the sample is diluted with dichloromethane.

[0342] The analysis is performed by gas chromatography using an HP5 GC column that has a length of 30 m, a diameter of 0.25 mm, and a film thickness of 0.5 μm. The injector is operated at 250 °C and its split mode has a split ratio of 50. The flame ionization detector (FID) is operated at 320 °C, the hydrogen flow is 45 ml / min and the air flow is 400 ml / min.

[0343] The analysis was continued for 32 minutes. The GC column temperature started at 40 °C, then increased to 115 °C after 13.274 minutes, then to 130 °C after 20.875 minutes, and to 230 °C after 27.542 minutes. The carrier gas flow rate was 1.3 ml / min.

[0344] Quantification was performed by external standard, meaning comparison of peak areas with a reference sample.

[0345] (Example 1 (Comparative Example)) In Example 1, the filter was operated “dry,” which means there was no injection of liquid cryogenic monomer (MMA) in the moving bed.

[0346] Tail lamp PMMA from end-of-life vehicles collected at an automobile disassembly site and crushed into small particles was used. Most contained PMMA, and some were contaminated with other polymers such as ABS. The average age of the vehicles arriving at the disassembly site was about 17 years, so the scrap contained all types of PMMA, pigments, and additives from all past and current suppliers.

[0347] The supply rate of the injected scrap was 50 kg / h. The maximum temperature of the pyrolysis reactor 12 extruder was set at 470 °C, its screw rotation speed was 800 revolutions per minute, and the depolymerization system 10 was operated at atmospheric pressure.

[0348] The color of the collected crude MMA product was dark red. The color was measured according to the ASTM D1500-07 standard method. The recorded value was L3.0 ASTM color.

[0349] (Example 2 (According to the Invention)) Continuing with the previous example, 10 kg / h of liquid cryogenic monomer (MMA) was injected into the upper end of the moving bed 18 through the filter mesh and towards the separator 14. The other operating parameters remained the same.

[0350] The color of the crude MMA product collected at the outlet of the condenser 16 was dark red. The color was measured according to the ASTM D1500-07 standard method. The recorded value was L2.5 ASTM color.

[0351] The temperature of the gas at the gas inlet 16A of the condenser 16 dropped by 51 °C compared to Comparative Example 1. This indicates that the liquid MMA sent to the moving tower 18 has a cooling effect.

[0352] Furthermore, the filter was checked after the test. Unlike Example 1, it was clean.

[0353] In both Example 1 and Example 2, the temperature of the crude MMA at the outlet at the bottom of the condenser 16 remained between 12 and 13 °C.

[0354] The following Table 1 reports the analysis of the samples by gas chromatography. The main differences detected were in the heavy compounds (determined by GC based on retention time). The products collected at MMA retention time +2 minutes and above were much higher in the case of Example 1 than in the case of Example 2.

[0355]

Table 1

[0356] As already mentioned, the color of the crude MMA for Example 1 and Example 2 was dark red. However, as shown in Table 1, the color of Example 2 was clearer than that of Example 1. Furthermore, the GC analysis showed fewer unknown heavy and very heavy substance products in the sample from Example 2 compared to the sample from Example 1, indicating a purer product with better quality in Example 2 compared to Example 1.

[0357] (Examples 3 to 6 (according to the present invention)) In Examples 3 to 6, the depolymerization system according to FIGS. 1 and 10 was used. The pyrolysis reactor 12 was provided as a twin-screw extruder Tex44 sold by Nippon Steel Corporation and connected to a primary separator 100 for separating solids from the hot gas. The main separator 14 had a spiral shape as shown in FIGS. 7 and 9. Inside the main separator 14, two mist removal grids 48 were installed in the path of the hot gas: one mist removal grid 48 was at the end of the spiral path, and one mist removal grid 48 was around a central collection pipe 36 having a diameter of 12.7 cm and provided with a frustoconical baffle 42 for forcing the hot gas to pass through an inlet opening 38 perforated in the collection pipe 36. The hot gas then circulated through a moving tower 18 having an inner diameter of 20 cm and a length of 2.8 m to the condenser 16.

[0358] The crude MMA obtained from the condenser 16 returns to the top of the moving tower 18. The temperature of the gas at the top of the moving tower 18 was monitored and controlled by adjusting the crude MMA flow rate.

[0359] The moving tower 18 was charged with a packing material containing Pall rings having a diameter of 16 mm over a length of 2,500 mm. The crude MMA was distributed to the top of the moving tower 18 by a shower distributor.

[0360] The condenser 16 was provided as a tube and shell heat exchanger, and cold water was used as the heat exchange fluid. The inlet and outlet temperatures of the condenser 16 were monitored.

[0361] During operation, the heavy contaminants that condense in the moving tower 18 flow down the moving tower 18 and return to the main separator 14 through the bottom of the moving tower 18.

[0362] The heavy contaminants deposited at the bottom of the main separator 14 were pumped out and reheated by recirculating them through an oil bath.

[0363] Such heating is proposed on an experimental or "pilot" depolymerization system because there is significant heat loss, especially under low-temperature start-up or test conditions for all new samples.

[0364] The temperature of the heavy contaminants in the liquid state at the bottom of the main separator 14 was controlled to be below 200 °C, preferably below 150 °C, and above 100 °C during the test.

[0365] This configuration of the depolymerization system is further specified as the "first depolymerization system".

[0366] (Example 3 (According to the present invention)): Clear cast PMMA sheet PMMA, sample A, from the cast clear sheet was depolymerized in the pyrolysis reactor 12 at a depolymerization temperature of 450 °C, then raised to a depolymerization temperature of 470 °C, and at the same time its feed rate was from 50 kg / h to 90 kg / h, and the rotational speed of the screw of the pyrolysis reactor 12 was increased from 500 revolutions per minute (rpm) to 800 rpm. During the test, the pressure in the main separator 14 and at the inlet of the condenser 16 remained between 1.0 and 1.1 bar for most of the time and increased up to 1.2 bar when the process conditions were adjusted. The temperature of the condensed crude MMA remained at about 20 °C and varied between 17 °C and 22 °C when the process conditions were adjusted. The temperature of the high-temperature gas phase in the main separator 14 varied between 250 °C and 350 °C (at the measurement point), while the temperature of the liquid phase varied between 125 °C and 150 °C, which is consistent with the liquid composition in the main separator 14 containing both MMA and heavier compounds.

[0367] When the PMMA feed rate was 50 kg / h, the crude MMA returning to the moving tower 18 was adjusted to about 35 L / h. When the PMMA feed rate was 90 kg / h, the crude MMA returning to the moving tower 18 was adjusted to about 70 L / h (+ / - 5 L / h).

[0368] Samples of crude MMA were obtained from condenser 16 for each depolymerization temperature and analyzed by gas chromatography. Table 2 below shows the results of the GC analysis.

[0369] The crude MMA collected had a purity above 98% (by GC peak area analysis). The crude MMA samples contained ethyl acrylate, which was not predicted in the cast sheet, due to some PMMA sheets made of materials containing this compound.

[0370] Primary separator 100 remained clean during the test and no polymer accumulated inside.

[0371] [Table 2]

[0372] In the GC analysis, several unspecified products are grouped together according to their respective retention times. These are "very light substances" with a retention shorter than 2 minutes minus the MMA retention time, "light substances" with a retention time between 2 minutes minus the MMA retention time and the MMA retention time, "slightly heavy substances" with a retention time between the MMA retention time and 2 minutes plus the MMA retention time, "heavy substances" with a retention time between 2 minutes plus the MMA retention time and 8 minutes plus the MMA retention time, and "very heavy substances" with a retention time longer than 8 minutes plus the MMA retention time.

[0373] The crude MMA collected in condenser 16 is not only transparent-clear and colorless, but also has a high MMA purity (as peak area percentage) above 98%, and low contents of heavy and very heavy substances. The total of heavy and very heavy substances remained below 0.5% in the test. The acetic acid and methacrylic acid contents were also extremely low (not detected).

[0374] (Example 4 (According to the present invention)): White cast PMMA sheet A white cast PMMA sheet (Sample B) was used in this test. The PMMA was depolymerized in a thermal decomposition reactor 12 at 470 °C at a feed rate of 90 kg / h and at two different screw rotation speeds, namely 800 and 650 rpm.

[0375] During the test, the pressure inside the main separator 14 and at the inlet of the condenser 16 remained between 1.0 and 1.1 bar for most of the time and increased up to 1.2 bar at most when the process conditions were adjusted. The temperature of the condensed crude MMA remained at about 20 °C and varied between 19 and 21 °C when the process conditions were adjusted. The temperature of the hot gas inside 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 is consistent with the liquid composition in the main separator 14 containing both MMA and heavier compounds.

[0376] When the PMMA feed rate was 90 kg / h, the flow rate of the crude MMA returning from the condenser 18 to the transfer column 18 was adjusted to about 90 L / h (+ / - 5 L / h).

[0377] Samples of the crude MMA were obtained from the condenser 16 and analyzed by gas chromatography. The samples of the collected crude MMA had a purity higher than 98% (based on the GC peak area), as shown in Table 3 below.

[0378] The primary separator 100 remained clean during the test and there was no accumulation of polymer inside, but fine white dust was collected inside. This represents the white pigment used in the white PMMA cast sheet. The amount of the collected white solid represented about 1 to 2 mass% of the treated PMMA.

[0379]

Table 3

[0380] The MMA content in the crude MMA is higher than 99%. The crude MMA is transparent and clear, without solid suspensions and color. The amounts of heavy and very heavy substances in the crude MMA are very small. Neither acetic acid nor methacrylic acid was detected. The first sample was slightly contaminated with the remaining product from the previous sample processed in the unit, as the amount of ethyl acrylate was slightly higher than in the case of the other two samples. The last of the three samples, i.e., Example 4c, represents stable conditions. The three samples were separated at 50 and 30 minutes respectively, and the sample of Example 4c was obtained 30 minutes after the sample of Example 4b.

[0381] (Example 5 (according to the present invention)): A mixture of 80% by weight of cast PMMA - 20% by weight of extruded PMMA, representative of the mixed color and supplier, and European mixed scrap from the sheet. The crude MMA was obtained from the depolymerization of a mixture of approximately 80% by weight of cast sheets and 20% by weight of extruded sheets, which were scrap collected from two different companies that collect the edge materials of the sheets produced when cutting the sheets into several dimensions and making various products therefrom.

[0382] The treated mixture represents the average composition that can be collected in Europe from this type of company.

[0383] This example is considered representative of consumer waste, as opposed to the case where it could be industrial waste, because the waste is collected from multiple sources and mixed together.

[0384] Wastes from two different sources were mixed in a 50 / 50 ratio (Sample C) using two individual screw feeders that supply the PMMA scrap to the pyrolysis reactor 12.

[0385] The PMMA was depolymerized in a pyrolysis reactor 12 at 470 °C operating at a feed rate of 90 kg / h.

[0386] The flow of crude MMA from the condenser 16 to the top of the moving tower 18 was adjusted to approximately 85 L / h (+ / - 5 L / h). The temperature at the top of the moving tower 18 varied between 100 and 102 °C, while the temperature at the bottom of the moving tower 18 varied between 103 and 105 °C. At the end of the test, as soon as the flow of crude MMA from the condenser to the top of the moving tower 18 was stopped, the temperature at the bottom of the moving tower 18 began to rise.

[0387] The first sample of crude MMA (Example 5A), and then the second sample of crude MMA (Example 5b) were obtained from the condenser 16 at approximately 30-minute intervals. They were analyzed by gas chromatography (GC) using a flame ionization detector (FID). The results of the analysis are shown in Table 4 below.

[0388] [Table 4]

[0389] The crude MMA samples were clear and colorless. The purity (MMA content) was higher than 98%. The total of heavy and very heavy substances remained below 0.5% in the test. The contents of acetic acid and methacrylic acid were also extremely low (not detected).

[0390] (Example 6 (according to the present invention)): Injection PMMA scrap (Sample D) from a car tail light, which is industrial waste, containing red, black, and transparent particles Crude MMA was obtained from injection PMMA scrap from a car tail light (Sample D), which is industrial waste and contains red, black, and transparent particles. The PMMA was depolymerized in a thermal decomposition reactor 12 at 470 °C operating at a feed rate of 50 kg / h and 800 rpm.

[0391] During the test, the flow rate of the crude MMA returning from the condenser 16 to the top of the moving tower 18 was adjusted to 45 L / h (+ / - 3 L / h). The temperature inside the moving tower 18 varied between 101 and 105 °C at the bottom and between 99 and 103 °C at the top of the moving tower 18.

[0392] Samples of crude MMA were obtained from condenser 16 at various times over 45 minutes and analyzed by gas chromatography (GC) equipped with a flame ionization detector.

[0393] [Table 5]

[0394] The colored PMMA material derived from injection molding scrap reached an MMA purity higher than 98% (GC peak area percentage). Furthermore, the amounts of heavy and very heavy substances remained below 0.5%. All crude MMA collection samples were clear and colorless, while the treated PMMA waste was a mixture containing red and black materials. The contents of acetic acid and methacrylic acid were also extremely low (not detected). Comparative examples were conducted using a depolymerization method and a depolymerization system not according to the present invention.

[0395] (Example 7 (Comparative Example))

[0396] Crude MMA was obtained from depolymerized PMMA. The depolymerization system was obtained from the first depolymerization system by omitting the primary separator 100 and replacing the moving tower 18 with an empty tube having a diameter of 5.08 cm, and suppressing the reheating of the heavy substances accumulated in the main separator 14. This depolymerization system is referred to as the "second depolymerization system".

[0397] Sample A and sample A1, which was similar to sample A but from another batch, were used. Both were transparent cast sheets.

[0398] [Table 6]

[0399] The MMA content (GC peak area) in all crude samples is lower than 98%. Furthermore, the amount of heavy and very heavy substances is sufficiently higher than 1%. Methacrylic acid is also detected in the crude samples.

[0400] (Example 8 (Comparative Example)): White cast In Example 8, the depolymerization system was further modified by a pyrolysis reactor 12 directly connected to the condenser 16. The main separator 14 was arranged as a dead end, and the condenser 12 was instead connected by a tube positioned between the extruder and the separator. This depolymerization system is referred to as the "third depolymerization system".

[0401] Sample B1, which is similar to Sample B but from a different batch, was used in Example 8.

[0402] [Table 7]

[0403] The MMA content in all samples of the crude MMA crude samples is lower than 98.5% or even lower than in the case of using the first depolymerization system used in the examples according to the present invention. Furthermore, all the samples were colored. The heavy and very heavy substances were also above 1%. Methacrylic acid was also detected in the crude samples.

[0404] (Example 9 (Comparative Example)): White cast In this Example 9, the second depolymerization system and Sample B1 were used. Two samples reported in Table 8 were collected on two different days.

[0405] [Table 8]

[0406] The crude MMA produced was turbid (solids in suspension), and the MMA content was below 98%. Furthermore, the total of heavy and very heavy substances was above 2%. Methacrylic acid and acetic acid were detected in the crude sample.

[0407] (Example 10 (Comparative Example)): White cast In this Example 10, Sample B1 was used in the second depolymerization system with the pressure adjusted to 1.5, 1.0, and 0.5 bar (as in Example 9).

[0408] [Table 9]

[0409] The collected crude MMA was yellow and turbid, and the MMA content in the crude MMA was below 98%. Furthermore, methacrylic acid and acrylic acid were detected, and the total of heavy and very heavy substances was sufficiently high above 2%.

[0410] (Example 11 (Comparative Examples 5 and 6)): Mixed casting and extrusion (80 / 20 mass / mass ratio) In this example, a third depolymerization system was used with Samples C1 and C2 similar to Sample C. In some cases, the samples were analyzed twice.

[0411] [Table 10]

[0412] All samples had a deep color, and the purity of the crude MMA was below 98%. Methacrylic acid was detected in the crude MMA, and the total content of heavy and very heavy substances was above 1.5% in all cases.

[0413] At the end of the test, many solid deposits were recovered at the inlet of the condenser.

[0414] (Example 12 (Comparative Example)): Mixed casting and extrusion (80 / 20 mass / mass ratio) In this example, a second depolymerization system was used with a feed of a 80 / 20 mass / mass ratio mixture of cast and extruded PMMA from sample C1 at a depolymerization temperature of 500 °C and various pressures.

[0415] [Table 11]

[0416] All collected samples of crude MMA had an MMA content well below 98% and they had a brownish cloudy color. Methacrylic acid was detected in the product and the amount of heavy and very heavy substances was above 3% in all cases.

[0417] (Example 13 (Comparative Example)) In this example, a second depolymerization system was used with a feed of the material from sample D as in Example 6.

[0418] [Table 12]

[0419] The crude MMA had an MMA content below 98% and had a dark cloudy color. The total of heavy and very heavy substances was above 3% and methacrylic acid was detected in the crude MMA.

[0420] The depolymerization method and the corresponding depolymerization system 10 for implementing the depolymerization method enable the production of liquid monomers from a feed material containing the corresponding polymer, obtain a satisfactory purity, and maximize the operating time of the depolymerization system 10.

[0421] In fact, by providing the separator 14, it becomes possible to capture impurities that may be present in the gas stream and avoid these impurities from clogging the components of the depolymerization system 10 located downstream of the separator 14.

[0422] By providing the moving tower 18, the gas flow reaches the condenser 16 cleanly, and impurities of the low-temperature monomer flowing by gravity in the moving tower 118 are captured, and these impurities are returned to the separator 14. The moving tower 18 is backwashed with the low-temperature monomer, and thus the risk of clogging is limited.

[0423] The input of thermal energy in the separator 14 (e.g., via the heating device 114) and / or the moving tower 118 (e.g., via the heated baffle) avoids wasting a lot of low-temperature monomer due to the circulation of the low-temperature monomer in the moving tower 18 for capturing impurities present in the gas flow.

[0424] The separator 14 can be used as a reheater for boiling the liquid returning to the separator 14, especially when the separator 14 is provided with a reheating device 114 including a heater 116.

[0425] The input of thermal energy in the separator 14 and / or the moving tower 18 increases the amount of low-temperature monomer injected into the moving tower 18, and thus reduces the risk of clogging of the moving tower 18.

[0426] The operation of the separator 14 and the moving tower 18 in a specific temperature range avoids any condensation and polymerization of the monomer in the separator 14 of the moving tower 18 and promotes the good operation of the separator and the moving tower 18. This further sprays the low-temperature liquid monomer in the separator 14 to control the temperature of the gas flow in the separator 14.

[0427] The quality of the finally obtained low-temperature monomer is increased, and there are few impurities, few dimers, few trimers, and few waxes present in the low-temperature monomer.

[0428] The depolymerization system can operate with a longer cycle time during the purification operation.

[0429] Certain specific arrangements of the separator 14 and the moving tower 18, such as a gas flow with a limited linear velocity, the separation chamber 32, having various cross-sections and / or an inlet duct 14 extending around the inlet of the separation chamber 32, the collecting pipe 36 with a specific structure and / or an internal mist removal device 46, the internal elements of the moving tower 18 and / or the injection of the cryogenic monomer obtained from the condenser 16 into the moving tower 18 enable the efficient capture of impurities while maintaining the temperature of the gas flow and flowing the gaseous monomer to the separator outlet 14B for supply to the condenser 16 via the moving tower 18.

Explanation of Signs

[0430] 10 Depolymerization system 12 Pyrolysis reactor 12A Reactor inlet 12B Reactor outlet 14 Separator 14A Inlet 14B Gas outlet 15 Separator unit 16 Condenser 16A Gas inlet 16B Condensate outlet 18 Moving tower 18A Lower end 18B Upper end 20 Re-injection loop 20A Re-injection line 20B Re-injection line 20C Re-injection line 20D Re-injection line 22 Filtration device 23 Supply device 24 Removal unit 24A Downstream mist removal device 24B Downstream mist removal device 26 Cold air generator 27 Side tank 27 29A Liquid connection line 29B Gas line 30 Internal volume 32 Separation chamber 34 Inlet duct 35 Valve 36 Collection pipe 37 Inert gas supply assembly 38 Inlet opening 40 Inlet section 42 Frustum-shaped baffle 44 Spray nozzle 48 Grid 90 Solid particle collector 100 Primary separator 111 Reheating loop 113 Filtration device 116 Heater 117 Liquid monomer reservoir 119 Collection reservoir 140 Pump 142 Pump 144 Pump A Central axis

Claims

1. A depolymerization method for recovering monomers from a polymer, comprising: a step of pyrolyzing a feedstock containing the polymer in a pyrolysis reactor (12) to generate a high-temperature gas stream; a step of removing solid and liquid impurities from the gas stream in a separator (14); and a step of condensing the monomer contained in the gas stream in a condenser (16); wherein the method includes the above-described continuous steps, the gas stream moves from the separator to the condenser through a moving tower (18) that extends upward from a lower end fluid-connected to an outlet of the separator (14) to an upper end fluid-connected to an inlet of the condenser (16), a low-temperature monomer in a liquid state is injected into the moving tower (18), and the moving tower is provided with internal elements configured such that the low-temperature monomer flows downward in the moving tower (18) by gravity, heavy impurity substances contained in the gas stream condense in a liquid state on the internal elements and flow back downward by gravity toward the bottom of the moving tower (18), and then move to the separator (14), and the temperature of the gas stream decreases from the lower end to the upper end of the moving tower (18), and the temperature of the gas stream at the outlet of the separator (14) and the inlet of the moving tower (18) is maintained above the boiling point of the monomer, and the temperature of the gas stream at the outlet of the moving tower (18) is maintained between the boiling point of the monomer and the boiling point of the monomer + 50°C; a depolymerization method.

2. The depolymerization method according to claim 1, wherein the temperature of the gas stream at the outlet of the separator (14) and the inlet of the moving tower (18) is maintained at at least the boiling point of the monomer + 20°C, particularly at least the boiling point of the monomer + 30°C, more particularly at least the boiling point of the monomer + 40°C, and even more particularly at least 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 moving tower (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, and particularly between the boiling point of the monomer and the boiling point of the monomer + 10°C.

4. The method of separating polymers according to any one of claims 1 to 3, wherein the internal element includes one mesh filter or a plurality of mesh filters arranged stepwise in the moving tower.

5. The method of separating polymers according to any one of claims 1 to 4, wherein the internal element includes a structured packing and / or a random packing, such as saddles and / or rings, in particular a random packing including Pall rings.

6. The method of separating polymers according to any one of claims 1 to 5, wherein the internal element includes continuous baffles.

7. The method of separating polymers according to any one of claims 1 to 6, wherein the internal element includes continuous baffles including internally heated baffles (preferably internally heated baffles arranged alternately with unheated baffles).

8. The method of separating polymers according to any one of claims 1 to 7, wherein the low-temperature monomer in a liquid state is injected at the upper end of the moving tower and / or at one or several intermediate positions between the lower end and the upper end of the moving tower.

9. The method of separating polymers according to any one of claims 1 to 8, including a step of filtering the low-temperature monomer before injecting the low-temperature monomer into the moving tower (18).

10. The method of separating polymers according to any one of claims 1 to 9, including a step of inputting thermal energy into the moving tower (18) and / or into the separator (14) by heating the gas and / or liquid present in the moving tower (18) and / or in the separator (14).

11. The method of separating polymers according to any one of claims 1 to 10, including a step of heating the liquid collected in the separator (14) using a heater positioned inside the separator and / or a heater positioned outside the separator (14) to evaporate the monomer contained in the liquid and return the monomer to the separator (14).

12. The step of heating the liquid is - a heater provided as an electric heater, arranged outside the separator (14), for heating the liquid collected in the separator (14), - an evaporator, in particular a wiped film evaporator, preferably an evaporator arranged inside the separator and provided as a heater for the evaporator to which the liquid collected from the separator is supplied, and / or - A heater provided as a heated screw extruder to which the liquid collected from the separator (14) is supplied, wherein the gas generated by the heater provided as the heated screw extruder is supplied to the separator (14). The depolymerization method according to claim 10, which is performed.

13. The depolymerization method according to any one of claims 1 to 12, wherein the speed of the low-temperature monomer injected into the moving tower (18) is at least 50%, preferably at least 60%, preferably at least 70%, preferably at least 80%, preferably at least 90% of the equivalent supply speed of the monomer.

14. The depolymerization method according to any one of claims 1 to 13, wherein the ratio of the low-temperature monomer injected into the moving tower (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 supply speed of the monomer.

15. The depolymerization method according to any one of claims 1 to 14, wherein the temperature of the gas flow at the inlet of the separator (14) is equal to or higher than 250 °C.

16. The depolymerization method according to any one of claims 1 to 15, wherein the temperature of the gas flow at the outlet of the separator (14) is between 100 °C and 280 °C, preferably between 110 °C and 180 °C.

17. The depolymerization method according to any one of claims 1 to 16, 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 method according to any one of claims 1 to 17, wherein the pyrolysis reactor is a heated twin-screw extruder.

19. A depolymerization system configured to recover monomers from a polymer, A pyrolysis reactor (12) configured to pyrolyze a feedstock containing the polymer to generate a gas flow, A separator (14) fluidly connected to the pyrolysis reactor (12) to receive the gas flow from the pyrolysis reactor (12) and configured to remove impurities from the gas flow, and A condenser (16) that is fluidly connected to the separator (14) to receive a gas stream from the separator and is configured to condense monomers contained in the gas stream received from the separator (14) comprising The depolymerization system includes a transfer column (18) for moving the gas stream from the separator (14) to the condenser (16). The transfer column (18) extends upward from a lower end fluidly connected to the outlet of the separator to an upper end fluidly connected to the inlet of the condenser (16). The transfer column (18) is configured to inject a cryogenic monomer in a liquid state into the transfer column (18), and during operation, the cryogenic monomer flows downward in the transfer column (18) by gravity, and heavy impurity substances contained in the gas stream are deposited in a liquid state on an internal element and flow back toward the separator (14) by gravity, particularly configured to flow back through the bottom of the transfer column (18), and is provided with an internal element. A depolymerization system in which the temperature of the gas stream decreases from the lower end to the upper end of the transfer column (18). **Claim 20** The depolymerization system according to claim 19, comprising a primary separator (100) interposed in series between the pyrolysis reactor (12) and the separator (14).

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