Apparatus for chemical recycling of polymeric materials in the presence of molten metal and / or salts

Abstract

The present invention relates to an apparatus to convert a polymeric material into the starting monomer(s) with high rate of conversion, high purity of the obtained monomer(s) and by minimizing the utilities and energy consumption equipped with a reaction section (200), an ash flotation section (300) and an external closed loop for molten metal circulation (800) and characterized in that it further comprises, in combination, at least one pre-mixing section (100), at least one vapor disengagement chimney (400), at least one produced gas collecting section (500), at least one produced solid ashes collecting section (600) and at least one molten metal collecting section (700); and wherein the reaction section (200) is placed inside the ash flotation section (300) and said reaction section (200) is jointed with the at least one vapor disengagement chimney (400) for the quick disengagement of the produced gaseous monomer toward the at least one produced gas collecting system (500), thus preventing, at least reducing, the flow of said produced gaseous monomer through the ash flotation section (300), which would negatively affect the ash flotation phenomenon and also allowing to decrease depolymerization gases residence time in the reaction section (200), therefore avoiding their recombination or degradation, wwiitthh consequent loss of depolymerization yield into the target monomer.

Description

" HIGH EFFICIENCY APPARATUS FOR CHEMICAL RECYCLING OF POLYMERIC MATERIALS”Summary

[0001] The present invention relates to an apparatus to convert a polymeric material into the starting monomer(s) with high selectivity of the obtained monomer(s).Technical field

[0002] The technical field is the recovery, depolymerization and reuse of thermoplastic, thermoplastic based materials, such as poly-methyl-methacrylate (PMMA), polystyrene, polyolefin in general or similar and crosslinked materials.Background art

[0003] The correct management of waste materials is one of the most important global environmental challenges.

[0004] The continuous increase in the world population, together with economic growth and the associated improvement in living conditions experienced by millions of people, mainly in developing countries, is leading, on a global level, to an exceptional increase in waste production.

[0005] According to some studies, plastic waste is approximately up to 10% of the total municipal solid waste produced annually.

[0006] Further studies have also highlighted that in the last 50 years the production of plastic waste has increased considerably and that the incorrect management of this type of waste causes significant environmental damage, including the pollution of marine ecosystem.

[0007] Among the practices and technologies currentlyused for the management of plastic waste, mechanical recycling, thermal recovery and landfill disposal are well known.

[0008] The recycling of plastic polymeric materials is a specific sector of waste recycling, and consists of a set of operations carried out on waste composed of plastic materials to obtain new material to be reintroduced into production processes.

[0009] Following the separate collection phase, the plastic is transferred to the first selection and treatment plants where it is sorted from other components and impurities, and further divided by type of polymer.

[0010] In particular, mainly poly-ethylene-terephthalate (PET) and poly-olefins (PO) are sorted, namely low-density poly-ethylene (LDPE), high density poly-ethylene (HDPE), and poly-propylene (PP).

[0011] Unlike other types of waste, such as glass or metals, it is estimated that plastic waste cannot be recycled indefinitely and only 50% of the total plastic waste can be validly reused in the supply chain, while the remaining 50% is not suitable for various reasons such as, for example, but not limited to, the excessive degree of contamination of the plastics, the loss of technical properties due to past recycling / reuse cycles, the consistent amount of fine fraction (whose particle size is too small to allow an efficient polymer sorting).

[0012] Said remaining 50% of plastic waste is currently disposed of through waste-to-energy or landfill disposal.

[0013] Waste-to-energy and landfill disposal are currently the two most widespread practices worldwide for the management of plastic waste, although they are inefficientmanagement methods, with high negative impacts from both an economic and environmental point of view.

[0014] Indeed, both practices are ranked at the lowest levels of the waste treatment hierarchy aimed at developing a circular economy, for which, practices and applications aimed at reusing materials / waste and their chemical recycling for the generation of further products / raw materials are favored.

[0015] Plastic-To-Fuel (PTF) technologies consisting of processes aimed at converting waste and plastic materials into liquid fuels, or synthetic petroleum, are well known and consists of the two processes of simple thermal pyrolysis and catalytic pyrolysis.

[0016] Thermal pyrolysis technologies use only thermal energy to promote the breaking of the molecular bonds of polymers and, therefore, to produce lower-molecular weight hydrocarbon / organic molecules suitable for transformation into liquid hydrocarbons, after a condensation or distillation process, with conversion yields generally comprised between 50% and 70%.

[0017] Usually, the products obtained by PTF technologies based on thermal pyrolysis are heavy fuel oils that do not have proper quality to be used directly as fuels in the energy sector and in the transport sector, or as raw materials in the industrial sector.

[0018] Catalytic technologies are instead based on the combined action of both thermal energy and the presence of a catalyst to perform the breaking of molecular bonds of polymers and, therefore, to produce lower-molecular weight hydrocarbon / organic molecules with higher selectivity to desired components due to the presence of the catalyst.

[0019] In both cases, the downstream purification step is usually complex and highly energy-intensive.

[0020] When depolymerization of multi-plastic material (a mixture of various types of plastic) is performed, the depolymerization product is typically a mixture of several families of hydrocarbons / organic molecules and not only aliphatic hydrocarbons.

[0021] On the contrary, when considering pure plastics (of a single type), it would not be convenient to use them to produce hydrocarbons, so it is preferable to use them for obtaining new monomers (depolymerization) or reuse them directly, instead of relying on repeated processing.

[0022] The selectivity, yield, recovery rate and purity in a depolymerization process are maximized by the optimization of operating and design parameters, aiming to maximize both the polymeric material conversion and the selectivity of depolymerization into the desired monomer.

[0023] In addition, the presence of impurities in the feedstock, either as external contaminants or as co-monomers and additives inside polymer formulation, can result in the formation of solid by-products, as ashes, and liquid (hydrocarbons / organic compounds) by-products in the recovered monomer, affecting the overall process performance.

[0024] Moreover, analyzing in detail the reaction mechanism, the thermal decomposition of plastic polymers can be considered as a macromolecular cracking into free radicals, whose composition depends on the following factors:• the type of catalyst used in the process (in the case of catalytic cracking);• the temperature and residence time or contact time;• the ratio between the plastic material flowrate and thevolume of the catalyst (in the case of catalytic cracking);• the plastic material composition and its level of impurities.

[0025] Indeed, it is matter of fact that a uniform temperature inside the depolymerization reactor, upon optimization of such operating parameter, can help to maintain the optimal thermal conditions to convert the polymer while ensuring the selectivity to the desired molecule, thereby avoiding the presence of hot spots that could affect the maximization of selectivity, even increasing the formation of unwanted ashes and other hydrocarbons / organics (by-products).

[0026] On the other side, it is well known in the state of the art, for example in the steam crackers plants, that when dealing with hydrocarbons chain bond breaking, short contact time in the reactor can increase the selectivity to less stable (and desired) molecules (olefins), thereby avoiding further degradation to more thermodynamically stable molecules with production of solid carbon, the most stable species.

[0027] In the end, when strictly necessary, the presence of a catalyst, carefully optimized case by case, can increase the selectivity to the desired molecule, addressing the reaction mechanism through the formation of the desired species, reducing the byproducts and improving the polymeric material conversion.

[0028] Patent US 6423878 B2 discloses a process and apparatus for the controlled pyrolysis of plastic materials, comprising the first two main steps of:i. bringing the polymeric material into a plastic state; ii. immersing the polymeric material in plastic waste in a molten metal bath at a certain depth, thereby obtaininggaseous products which migrate in a gas phase above the bath.

[0029] In such patent, the molten metal bath is kept continuously agitated, like a sort of continuous stirred tank reactor.

[0030] Patents WO 2022 / 136334 Al and WO 2023 / 247286 Al disclose a char handling section and depolymerization process associated therewith.

[0031] An extruder system is installed upstream the reactor inlet, however, in these cases the reactor is kept under continuous agitation, and it is not equipped with a molten metal bath.

[0032] Patent WO 2020 / 084522 Al discloses a process for depolymerization plastic material for the production of hydrocarbons and a plant therefor.

[0033] Also in this case, the use of an extruder is coupled with a depolymerization reactor but without the use of molten metal.

[0034] The depolymerization of plastic waste material in a molten medium is already known for example, patent EP 3645664 Bl discloses a process and relevant apparatus characterized by the use of a molten medium (in first instance, molten lead) loaded into the depolymerization reactor with a continuous injection of polymeric material to be treated.

[0035] The main role of the molten medium is to provide depolymerization heat to plastic waste by direct mixing (with extremely high heat-transfer coefficient), in order to maintain the plastic waste material uniformly at the optimal operating temperature for reaction, thereby avoiding hot spots effects that can result in a detrimental loss ofselectivity.

[0036] In addition, if properly selected, the molten metal, both pure metal or metal alloys, could have a catalytic effect to increase the process selectivity.

[0037] The second main feature of the above process consists in the fact that the molten metal is kept in continuous flow, making this type of process distinctive when compared to other examples in the literature already using molten metal for depolymerization of polymeric material.

[0038] Further, the technological concept behind such solution makes it applicable to a variety of polymeric materials.

[0039] The main limitation of such solution is the potential accumulation of solid by-product (ashes) in the molten metal circuit, due to the continuous operation of the reactor.

[0040] This effect is highly evidenced in particular when dealing with a polymeric material feedstocks characterized by high quantity of external impurities.

[0041] By considering the PMMA plastic material as example, the most frequent external impurities that can be found are: PVC, PC, PS, ABS, Polyolefins, PET, metals, Glass, Silicone, Paper / Cardboard.

[0042] While several of these contaminations have the defect of generation of byproducts that can affect the final monomer quality but can be easily removed by upstream optical sorting, other external contaminants like metals, glass, silicone, and paper / cardboard, not removable by optical sorting systems, are responsible either for their accumulation in the molten medium (like metals) or for the production of ashes that shall be eliminated, even if notimpacting the final monomer purity.

[0043] In both cases a resulting level of accumulation of impurities in the molten metal circuit is expected.

[0044] It is worth to mention that the ashes formation is a chemical process not completely avoidable, therefore the presence of technological solutions implemented on the molten metal circuit for their continuous or discontinuous removal (such as by filtration) is anyway mandatory, also to deal with chemical contamination (that cannot be removed) and that can be decomposed to ashes.

[0045] However, if the formation of ashes is not controlled upstream at a certain extent, the overall reliability and operability of the plant could be affected, due to the need to periodically and frequently stop the plant to perform the filter regeneration or replacement.Technical problem

[0046] The aim of the present invention is an apparatus for plastic waste chemical recycling through depolymerization process in a molten metal and / or molten salts continuous flow, with a high conversion efficiency and selectivity, easily tunable for the recycle of a huge variety of plastic waste, optimized to reduce the effect of the impurities, contained in the feedstock, on the overall process performance, and optimized to reduce the amount of produced wastes to be sent to disposal.Solution to problem

[0047] According to the present invention, the solution is an innovative depolymerization reactor which can enhance both mass and heat-transfer and, at the same time, can minimize the byproducts formation, particularly ashes, capable to separate a portion of the solid impurities frommolten metal and / or salts., also increasing the selectivity of the obtained monomer(s).Brief description of the drawings

[0048] A better understanding of the invention will be achieved from the following detailed description and with reference to the accompanying drawings showing, by way of a non-limiting example, a preferred embodiment.

[0049] In the drawings:Figure 1 shows a preferred embodiment of the present invention.Detailed description of the invention

[0050] The apparatus according to the present invention is an innovative depolymerization reactor able to depolymerize several polymeric materials.

[0051] Said depolymerization reactor uses molten system in continuous flow as heating medium in order to provide heat for the depolymerization reaction.

[0052] In the following apparatus description, reference is made to a reactor for a “generic polymer” conversion, wherein the term "generic polymer” indicates the thermoplastic and cross-linked materials.Feedstock

[0053] According to the present invention, the polymeric materials suitable to be treated with the present apparatus are thermoplastic or thermoplastic based materials such as poly-methyl-methacrylate (PMMA), polystyrene, polyolefin in general or similar and cross-linked materials.

[0054] The polymeric material feedstock in a solid or liquid form, for example scraps or polymer melt, but not limited to, is routed to the reactor inlet.Molten metal and / or molten salts

[0055] According to the present invention, the depolymerization process is performed by means of a molten metal and / or molten salts continuous flow.

[0056] In the preferred embodiment disclosed, but not limiting, the molten metal used for providing the reaction heat is selected from the group consisting of lead, tin, zinc, antimony, cadmium, magnesium, bismuth and mixtures thereof, optionally mixed with other metals and / or an acid component, such as silicates and / or metallic carbonates.

[0057] Moreover, according to the present invention the molten salts used for providing the reaction heat are selected between potassium chloride, magnesium chloride, lithium chloride, copper chloride, sodium nitrate and potassium nitrate.Embodiment

[0058] In the preferred embodiment disclosed, but not limiting, the apparatus is a depolymerization reactor comprising the following:• At least one mixing section (100);• At least one reaction section (200);• At least one ash flotation section (300);• At least one vapor disengagement chimney (400);• At least one produced gas collecting section (500);• At least one produced solid ashes collecting section (600);• At least one molten metal collecting section (700);• An external closed loop for molten metal circulation and heating (800).

[0059] The following is a description of the arrangement of the embodiment according to the present invention.Mixing section (100)

[0060] In the preferred embodiment disclosed, the incoming polymeric material feedstock is routed, together with the recycled molten metal, into a mixing section (100).

[0061] According to the preferred embodiment disclosed, said mixing section (100) is designed in order to provide the best mixing for the incoming feed, in solid or liquid form, with the recycled molten metal and / or salt.

[0062] Specifically, when the polymeric material feedstock is in a solid form said mixing section (100) is at least an eductor, optionally coupled with a static mixer in order to deeply mixing the incoming polymeric material with the recirculated molten metal and / or salts.

[0063] When the polymeric material feedstock is in a liquid form, specifically polymer melt, said pre-mixing section (100) is at least an injection device, optionally coupled with a static mixer in which polymeric feedstock and recirculated molten metal and / or salts are closely mixed.

[0064] In addition, the injection of solid polymeric material into the molten metal according to the current technological solution may imply the oxygen intake into the circuit, thereby leading to the potential formation of lead oxides due to the high reaction temperature that can affect the metallurgy of the plant piping for corrosion effect.

[0065] For this reason, according to the present invention, inert gas injection is provided when solid polymeric material is fed to the mixing section (100).

[0066] According to a preferred embodiment, but not limiting, said inert gas is nitrogen.Reaction section (200)

[0067] According to the present invention, the at leastone reaction section (200), namely where the depolymerization reaction takes place, is connected with the at least one vapor disengagement chimney (400), allowing quick and effective depolymerization products disengagement from reacting medium and molten metal and avoiding both ashes and molten metal entrainment in vapor phase.

[0068] In the preferred embodiment disclosed said reaction section (200) comprises the following:• One inlet section (201);• One closed-end section (202);• A plurality of connecting holes (203a / 203b / .. / 203n);• A plurality of longitudinal / axial channels (204a / 204b / .. / 204n).

[0069] In the preferred embodiment disclosed, said at least one reaction section (200) is tubular.

[0070] Moreover said at least one reaction section (200) is dipped inside the at least one ash flotation (300), and is connected with said ash flotation section (300) by means of said plurality of longitudinal / axial channels (204) located close to said closed-end section (202) of the reaction section (200), said closed-end section (202) being located at the opposite side from the inlet (201) of the reaction zone.

[0071] The closed-end of the reaction section (202) is designed as a conical deflector to avoid or reduce direct injection of liquid flow into the ash flotation section (300), which could negatively affect the ash flotation; however, steady flow from section (200) is guaranteed by longitudinal / axial channels (204a / 204b / .. / 204n) provided in the last part of the section, allowing liquid / solid material to leave radially into a larger ash flotation section (300) with consequent decrease of axial velocity because of highercross-section.

[0072] In the preferred embodiment disclosed, but not limiting, the volume of the reaction zone (200) between the inlet (201) and the closed-end section (202) is equipped with a plurality of connecting holes (203a / 203b / .. / 203n) placed on the top of the surface of said reaction section (200).Ash flotation section (300)

[0073] In said ash flotation section (300) take place the flotation and stratification of produced ashes above the molten metal, said flotation occurring by gravity and based on the high density difference between ash and liquid metal as driving force.

[0074] Moreover, the horizontal portion of the reactor corresponding to the ash flotation section (300), carefully designed taking into account vertical rising / dragging velocity resulting from the balance of vertical forces acting on each ash particle, is long enough to allow flotation of the ash particles, coming from the axial channels (204), to the molten metal / salt free surface.Vapor disengagement chimney (400)

[0075] According to the present invention, the top part of the reaction zone (200), included between its inlet (201) and its closed end (202) is equipped with one disengagement chimney (400) for each connecting hole (203), thus connecting the reaction section (200) with the at least one gas collecting section (500), allowing depolymerization vapor products (bubbles) to smoothly leave molten metal / solid flow as soon as they are formed, along the whole length / longitudinal axis of the tubular section (200).

[0076] In the preferred embodiment disclosed, but not limiting, the volume of the reaction zone (200) between theinlet (201) and the closed-end section (202) is equipped with a plurality of connecting holes (203a / 203b / .. / 203n), said plurality connecting the reaction zone with a corresponding plurality of disengagement chimneys (400a / 400b / .. / 400n).

[0077] The number of disengagement chimneys (400a / 400b / .. / 400n) and of the connecting holes (203a / 203b / .. / 203n) is determined by considering both the reactor capacity, the nature of incoming feedstock, the reaction kinetics, concerning the depolymerization process into gaseous monomer, and the residence time of the stream at the inlet of the reaction section, said stream comprising both the molten metal and also the feedstock.

[0078] The total area of channels and the number and of the connecting holes (203a / 203b / ... / 203n) along the longitudinal axis are carefully designed to allow quick disengagement of vapor flow from the top of reaction section (200) as soon as they are formed by ongoing depolymerization reaction.

[0079] Said arrangement is designed:a. to allow the uniform disengagement of the depolymerization gases from the reaction zone (200), through disengagement chimney (400) towards the gas collecting zone (500) and preventing, at least reducing, the flow of said produced gaseous monomer through the ash flotation section (300), which would negatively affect, interfere with, the ash flotation phenomenon;b. to decrease depolymerization gases residence time in the reaction section (200), therefore avoiding their recombination or degradation, with consequent loss of depolymerization yield into the target monomer;c. to avoid the increase of axial velocity of molten metalflow inside the tubular reactor (200), due to the presence low density monomer bubbles trapped in the metal flow.

[0080] Moreover, the length of the portion of pipe corresponding to the disengagement chimney (400) depends on the level of the ash flotation section (300) above the reaction section (200), thus on the reactor capacity.Gas collecting section (500)

[0081] The at least one produced gas collecting section (500) is located above the ash flotation section (300).

[0082] Said gas collecting section (500) is equipped with at least one gas exit nozzle (501) on the top.

[0083] In addition, the horizontal cross-section of the gas collecting zone (500) is designed large enough to reduce the rising velocity of depolymerization vapors in the collecting zone itself, allowing smooth operation and avoiding both ash and liquid metal entrainment in the vapor phase towards the gas exit nozzle (501).Produced ash collecting section (600)

[0084] According to the preferred embodiment disclosed, at least one produced ash collecting section (600) is located in a dedicated compartment (601) within the flotation zone (300), where ash ends-up by overflow from flotation section (300) and are accumulated before final disposal.

[0085] Moreover, said ash collecting section (600) is equipped with at least one ashes exit section (602) aimed to remove cyclically the collected ashes from the compartment (601).

[0086] In the preferred embodiment disclosed, but not limiting, the cross-section of said compartment (601), perpendicular to the molten metal flow, is shaped as a circular segment.

[0087] Additionally, said compartment (601) is open on top / upper surface: therefore, the lateral surface of the compartment itself, perpendicular to the molten metal flow, acts like a weir for the molten metal, allowing only the overflow of the floating ashes from the opened top, which can accumulate in the compartment itself for collection and disposal.

[0088] According to the present invention, the ashes fall in said compartment (601) dragged by the molten metal slip stream; when the compartment is completely full of ash and molten metal, its whole content is sent, via ashes exit (602), to a dedicated auxiliary system where the separation between metal and ashes takes place (the ashes floating on molten metal are vented by nitrogen pressure and / or sucked by vacuum).

[0089] Finally, the molten metal (free of ashes) is recycled to the reactor apparatus.Molten metal collecting section (700)

[0090] According to the preferred embodiment disclosed, the at least one molten metal collecting section (700) is located below the ash flotation section (300); due to:(a) its low positioning and(b) considering that this zone is sheltered from horizontal / axial flow of molten metal flowing from axial holes (204) of closed end of reactor.

[0091] Both (a) and (b) guarantee the lowest ashes content in molten metal and therefore make this area the optimal location for collection of molten metal with the lowest content of solid impurities.

[0092] The bottom of the at least one molten metal collecting section (700) is connected in closed loop withtubular reaction section (200) inlet for molten metal circulation and heating (800).

[0093] The position of the molten metal collecting section (700) below the ash flotation section (300) allows the collection of molten metal from a point far away from (lower than) both metal / ash interface and metal / ash horizontal flow thus limiting, if not avoiding, the recirculation of ash and solid impurities in the closed loop (800) together with molten metal.External closed Loop (800)

[0094] According to the invention, the external closed loop (800) comprises the following:• At least one circulation pump (801);• At least one heat exchanger (802);• Means for molten metal flow control (e.g. a control valve).

[0095] The molten metal fetched at the bottom of said molted metal collecting section (700) is routed, by means of circulating pump (801), toward the mixing section (100), after the metal temperature control by means of heat exchanger (802).Preferred arrangement

[0096] According to a preferred embodiment, but not limiting, the arrangement of all the above-mentioned sections of the depolymerization reactor comprises a tubular reaction zone (200) provided with a plurality of connecting holes (203a / 203b / .. / 203n) along its upper surface; said reaction section (200) is located inside the ash flotation section (300).

[0097] Moreover, in said arrangement a plurality of vapor disengagement chimneys (400a / 400b / .. / 400n) are provided.

[0098] Each of said plurality of connecting holes(203a / 203b / .. / 203n) joints the reaction zone with each of the plurality of disengagement sections (400a / 400b / .. / 400n).

[0099] The gas collecting section (500) is located above the ash flotation section (300); the ashes collection section (600) is an open-top cylindrical segment located inside the ash flotation section (300), while the molten metal collection zone (700) is located below the ash flotation zone (300).

[0100] The gaseous monomer obtained from depolymerization, outcomes from the reaction section (200) by the disengagement sections (400a / 400b / .. / 400n) and directly reaches the gas collecting section (500), without passing through the ash flotation section (300).

[0101] In the preferred embodiment disclosed, the gas collecting section (500) is located on the top of the ash flotation section (300), in turn located around the reaction section (200), thus avoiding any drag of solid by-product or molten metal.Residence time control

[0102] The optimal residence time of the polymer in the reaction section (200) depends on the polymer nature, the specific decomposition kinetics and the heat transfer that depends on polymer state.

[0103] The control of said residence time in the reaction section (200) is performed by modulating the molten metal flow inside the external molten metal recirculation closed loop (800); in this way the apparatus can convert many different polymer feedstocks into the corresponding monomers, by simply adjusting the residence time of the polymer inside the reaction section (200) by modulating the molten metal flow.Temperature control

[0104] Moreover, the temperature of the molten metal is controlled by acting on the duty of the molten metal heat exchanger (802).Advantages

[0105] A first advantage of the present invention regards the compactness of the overall apparatus: indeed, said compact reactor / separator set-up is able to:• separate the gaseous product as soon as it is formed, minimizing its residence time in the reaction section and therefore potential side-reactions causing monomers recombination;• obtain a proper disengagement volume (characterized by lower turbulence level) for the ash / molten metal stream;• collect the solid ashes into a dedicated compartment, to be removed cyclically by a slip stream with minimum gas and molten metal entrainment.

[0106] Moreover, the quick disengagement of the produced gaseous monomer from the reaction section (200) toward the gas collecting section (500) thus avoiding retain of said produced gas in the ash flotation section (300) allows to minimize, if not eliminate, the byproducts and solid ashes production.

[0107] Thus, the combined effect of the modulation of the ratio between polymer feedstock and molten metal flow before the reactor inlet, the control of the molten metal flow and temperature, the presence of at least one produced gas monomer quick disengagement chimney (400), allows to reduce the kinetics of side reactions leading to hydrocarbons and organic by-products and solid formation (mainly char and ash), thus acting on the selectivity in the obtained monomer(s).

[0108] According to the present invention, the disclosed apparatus allows to an optimization of all the required steps necessary for the polymer decomposition into the respective monomer; said optimization results in a high conversion yield of the feedstock polymer and in a high purity of the recovered monomer.

Claims

Claims1. An apparatus for the depolymerization of polymeric material into the corresponding gaseous monomer by cracking with molten metal and / or salts, equipped with a reaction section (200), an ash flotation section (300) and an external closed loop for molten metal circulation (800), characterized in that said apparatus further comprises in combination:• At least one mixing section (100)• At least one vapor disengagement chimney (400);• At least one produced gas collecting section (500); • At least one produced solid ashes collecting section (600);• At least one molten metal collecting section (700); whereinsaid reaction section (200) is placed inside the ash flotation section (300) and is jointed with the at least one disengagement chimney (400) for the quick disengagement of the produced gaseous monomer toward the at least one produced gas collecting system (500).

2. The apparatus according to claim 1 wherein said mixing section (100) corresponds to an eductor when the polymeric material feedstock is in a solid form.

3. The apparatus according to claim 2 wherein inert gas injection is provided when solid polymeric material is fed to the mixing section (100), preferably nitrogen injection.

4. The apparatus according to claim 1 wherein said mixing section (100) corresponds to a injection device when the polymeric material feedstock is in a liquid form.

5. The apparatus according to claims from 2 to 4 wherein theeductor or the injection device are coupled with a static mixer in order to deeply mixing the incoming polymeric material with the recirculated molten metal and / or salts.

6. The apparatus according to one or more of the previous claims wherein the reaction zone (200) comprises:• One inlet section (201);• One closed end section (202);• A plurality of connecting holes (203a / 203b / .. / 203n);• A plurality of longitudinal / axial channels (204a / 204b / .. / 204n).

7. The apparatus according to one or more of the previous claims wherein the length of the portion of apparatus corresponding to the ash flotation section (300) is designed to allow gravity flotation of ash particles, coming from the axial channels (204), to the molten metal free surface.

8. The apparatus according one of more of the previous claims wherein said at least one vapor disengagement chimney (400) directly connects said reaction section (200) with said produced gas collecting system (500), thus bypassing the ash flotation (300) and also preventing, at least reducing, the flow of said produced gaseous monomer through the ash flotation section (300), which would negatively affect the ash flotation phenomenon and also allowing to decrease depolymerization gases residence time in the reaction section (200), therefore avoiding their recombination or degradation, with consequent loss of depolymerization yield into the target monomer.

9. The apparatus according one or more of the previous claims wherein said gas collecting section (500) is equipped with at least one gas exit nozzle (501) on the top.

10. The apparatus according one of more of the previous claims wherein the at least one produced ashes collecting section (600) is located in a dedicated compartment (601) within the separation zone (300)whereinsaid compartment (601) is shaped as a circular segment and is open on top / upper surface, thus, the lateral surface of the compartment itself, perpendicular to the molten metal flow, acts like a weir for the molten metal, allowing only the overflow of the floating ashes from the opened top, which can accumulate in the compartment itself for collection and disposal,and whereinsaid ashes collecting section (600) is equipped with at least one ashes exit section (602) aimed to remove cyclically the collected ashes from the compartment (601).

11. The apparatus according one or more of the previous claims wherein said at least one molten metal collecting section (700) is located below the ash flotation section (300) and is sheltered from horizontal / axial flow of molten metal flowing from axial holes (204) of closed end of reactor thus allowing the lowest ashes content in molten metal and therefore ensuring that this area is the optimal location for collection of molten metal with the lowest content of solid impurities.

12. The apparatus according one or more of the previous claims wherein the external closed loop (800) comprises:• At least one circulation pump (801);• At least one heat exchanger (802);• Means for flow regulation / control,and whereinthe molten metal fetched at the bottom said molted metal collecting section (700) is routed, by means of circulating pump (801), toward the mixing section (100), after the metal temperature regulation by means of heat exchanger (802).

13. The apparatus according one or more of the previous claims wherein the polymeric materials suitable to be used as feedstock for the process are thermoplastic, thermoplastic based materials such as poly-methyl-methacrylate (PMMA), polystyrene and polyolefin in general or similar.

14. The apparatus according one or more of the previous claims wherein the polymeric materials suitable to be used as feedstock for the process are cross-linked materials.

15. The apparatus according one or more of the previous claims wherein the molten metal is selected from the group consisting of lead, tin, zinc, antimony, cadmium, magnesium, bismuth and mixtures thereof, optionally mixed with other metals and / or an acid component, such as silicates and / or metallic carbonates, preferably is lead.

16. The apparatus according one or more of the previous claims wherein the molten salts are selected from potassium chloride, magnesium chloride, lithium chloride, copper chloride, sodium nitrate and potassium nitrate.

17. The apparatus according one or more of the previous claims wherein the control of said residence time in the reaction section (200) is performed by modulating the molten metal flow inside the external molten metal recirculation closed loop (800) allowing the apparatus to convert many different polymer feedstocks into the correspondingmonomers, by simply adjusting the residence time of the polymer inside the reaction section (200) by modulating the molten metal flow.

18. The apparatus according one or more of the previous claims wherein the temperature control is performed by acting on the duty of the molten metal and / or salts heat exchanger (802).

19. The apparatus according one or more of the previous claims wherein the reaction zone (200), the ash flotation section (300), the at least one vapor disengagement chimney (400), the at least one produced gas collecting section (500), the at least one produced solid ashes collecting section (600) and the at least one molten metal collecting section (700) are configured in a kettle arrangement.

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