Method for processing plastic waste

Abstract

The invention relates to a method for processing plastic waste. The method comprises providing plastic waste material with a proportion of thermoplastics of at least 50 wt. %, heating and melting the plastic waste material by means of a single-shaft single-screw extrusion device, separating non-melted solid matter from the plastic material melt by means of the filtration device and heating the filtered plastic material melt further by means of a multi-shaft extrusion device. After the further heating, the filtered plastic material melt is transferred by means of the multi-shaft extrusion device to a continuous pyrolysis furnace reactor and is pyrolysed in said continuous pyrolysis furnace reactor at a pyrolysis temperature. Before transfer to the continuous pyrolysis furnace reactor, the filtered plastic material melt is heated by means of the multi-shaft extrusion device to a discharge temperature which is 50 °C lower to 20 °C higher than the pyrolysis temperature in the continuous pyrolysis furnace reactor.

Description

[0001] PROCESS FOR TREATMENT OF PLASTIC WASTE

[0002] The invention relates to a method for processing plastic waste.

[0003] Depending on their intended application or use, plastic materials often contain other substances in addition to the actual polymeric materials, such as fillers, pigments, plasticizers, stabilizers, fibers, and so on. Blends of different polymers are also frequently used. Furthermore, plastic materials are naturally subject to a certain degree of degradation during use, for example, due to mechanical stress or UV radiation. For all these reasons, the direct reuse of plastic waste, for example, by melting and molding into new products, is often not possible, even if it would be desirable.

[0004] An alternative method for processing plastic waste is pyrolysis, i.e., the chemical decomposition of macromolecular substances at high temperatures under at least minimal oxygen exclusion. Pyrolysis can be used to decompose plastic materials into recyclable, low-molecular-weight substances. As is well known, the pyrolysis of plastic materials generally produces gaseous and solid pyrolysis products, and depending on the type of pyrolytically decomposed plastic waste, liquid decomposition products may also be obtained. The resulting pyrolysis products can then be recycled, for example, for the further production of polymers. Thermal utilization of such pyrolysis products, for example, by using them as fuel gas, is also a possibility.

[0005] Pyrolysis is usually carried out in a pyrolysis reactor, which is maintained under negative pressure or purged with inert gas and heated by means of heating media, such as electrical resistance heaters or heating gases. Agitation media are often used to move the material to be pyrolyzed within a pyrolysis reactor. Such pyrolysis processes are very energy-intensive and, due to the high energy input required to heat the material to be pyrolyzed, very difficult to thermally control. In particular, fluctuations due to the very different types of plastic waste to be processed can pose problems in terms of process or control technology. WO 2013 / 171510 proposes carrying out the pyrolysis of plastic waste entirely in a twin-screw reactor.A significant portion of the thermal energy required for pyrolysis can be generated by converting mechanical energy generated by the kneading of the plastic material in the twin-screw reactor. However, the use of such a twin-screw reactor for pyrolysis also brings with it several disadvantages. For example, such a twin-screw pyrolysis reactor must be very long to achieve a sufficient residence time for complete pyrolysis of the plastic material. This, of course, also requires the use of very long shafts. The correspondingly high torques lead to significant twisting of the screws, which also severely limits the choice of screw materials.Furthermore, the required high pyrolysis temperatures, typically from approximately 400 °C to approximately 700 °C, place an additional, significant strain on such a twin-screw pyrolysis reactor. The shafts of such a pyrolysis reactor are therefore subjected to both severe mechanical and thermal stress, making them highly susceptible to damage due to the high temperatures and the resulting reduced strength, coupled with the high mechanical stress. Furthermore, very precise control of the process parameters is required, especially in such a twin-screw reactor, to handle fluctuations in the type of plastic material being fed.

[0006] The object of the present invention was to overcome the disadvantages of the prior art and to provide a process by means of which a wide range of different plastic waste can be pyrolytically processed in an energy-efficient manner with high throughput and at the same time in a process-stable and reliable manner.

[0007] This object is achieved by a method according to the claims.

[0008] The process for processing plastic waste includes the following steps:

[0009] - Providing plastic waste material with a thermoplastic content of at least 50 wt.%

[0010] - Heating and melting the plastic waste material by means of a single-screw extrusion device to form a plastic material melt,

[0011] - Transferring the plastic material melt from the single-screw extrusion device into a filtration device and separating non-melted solids from the plastic material melt by means of the filtration device,

[0012] - Transferring the filtered plastic material melt into a multi-screw extrusion device and further heating the filtered plastic material melt by means of the multi-screw extrusion device.

[0013] The method provides that the filtered plastic material melt, after further heating by means of the multi-screw extrusion device, is transferred to a continuous or continuously operating pyrolysis furnace reactor and pyrolyzed in this continuous or continuously operating pyrolysis furnace reactor at a pyrolysis temperature. The filtered plastic material melt is heated by means of the multi-screw extrusion device before transferring, in particular immediately before transferring, to the continuous or continuously operating pyrolysis furnace reactor to a discharge temperature that is 50 °C lower to 20 °C higher than the pyrolysis temperature in the continuous or continuously operating pyrolysis furnace reactor.

[0014] The specified process steps are not to be considered exclusive. In particular, the process may include further process steps that can be performed before, after, or even between two of the specified process steps.

[0015] The specified process measures and steps enable energy-efficient, yet highly reliable and stable processing of plastic waste. Since each of the specified process steps is carried out using a separate device, the individual process steps can be accomplished using devices optimized for that purpose. This ensures a high level of process reliability during the execution of the individual process steps, which in turn also enables high throughput and processing rates. By successively heating or melting the plastic waste material to be processed using extrusion devices and further heating it to at least approximately the pyrolysis temperature, a process with high energy efficiency can also be provided.In particular, heating of the plastic waste material can be enabled at least partially by converting mechanical energy through the kneading of the plastic waste material in the extrusion devices. Preferably, the process can be controlled such that the pyrolysis is carried out at least largely, for example, to over 90% or even entirely, in the continuous pyrolysis furnace reactor, and that only a small amount, for example, 10% or less, or even no pyrolysis takes place in the upstream, multi-screw extrusion device. This can prevent excessive mechanical stress, particularly on the shafts of the multi-screw extrusion device.

[0016] As has been demonstrated, the process allows for pyrolysis in the continuous pyrolysis furnace reactor to be carried out with high process reliability and stability. In particular, very precise temperature control and regulation of the temperatures in the continuous pyrolysis furnace reactor can be ensured without the need for complex or expensive control interventions or measures. Because the molten and filtered plastic waste material is introduced into the continuous pyrolysis furnace reactor at at least approximately the pyrolysis temperature, the continuous pyrolysis furnace reactor can be operated with long-term stability at a very uniform temperature throughout the entire pyrolysis furnace reactor. This, in turn, enables complete pyrolysis with a very high yield of the desired decomposition products.The formation of decomposition products that can no longer be recycled can therefore be effectively prevented by or through the specified process.

[0017] The resulting pyrolysis gases can be discharged from the continuous pyrolysis furnace reactor via one or more vents, as is known per se, and then recycled. For example, the pyrolysis gases can be thermally and / or materially recycled directly or at a later time. Alternatively, the pyrolysis gases can also be condensed and temporarily stored for later recycling. Solid pyrolysis products, usually in crumbly form and often referred to as pyrolysis coal or coke, and optionally liquid pyrolysis products, usually with a bitumen-like consistency, can also be discharged from the continuous pyrolysis furnace reactor via discharge openings in a known manner and then recycled.

[0018] Furthermore, the specified process steps also enable the process to achieve a high degree of tolerance towards fluctuations in the type of plastic materials provided. In other words, a wide range of different plastic waste or plastic waste materials can be processed using the process. In this context, it can certainly also be provided that the provision of plastic waste material also includes the provision of a mixture of several different plastic waste materials, and that such a mixture of plastic waste materials is also processed simultaneously or jointly using the following process steps. This also includes the provision of plastic waste material with several different polymers.

[0019] By means of the filtration device, in particular non-melted solids with a particle size of 1 mm or more, preferably 0.5 mm or more, can be separated.

[0020] In a preferred embodiment of the method, it can be provided that the filtered plastic material melt is heated to the discharge temperature only in the last 20% of a total extrusion section of the multi-screw extrusion device.

[0021] This measure ensures that only a very small portion of the multi-screw extrusion device is operated at a high temperature level, thus further reducing the material load, particularly on the shafts of the multi-screw extrusion device. Preferably, the filtered plastic melt is heated to the discharge temperature only in the last 10%, in particular only in the last 3%, of the entire extrusion path of the multi-screw extrusion device.

[0022] In a further advantageous embodiment of the method, it can also be provided that the filtered plastic material melt is heated by means of the multi-screw extrusion device before being transferred into the continuous pyrolysis furnace reactor to a discharge temperature which is 50 °C to 5 °C lower than the pyrolysis temperature in the continuous pyrolysis furnace reactor.

[0023] This measure virtually eliminates the possibility of undesired pyrolysis starting in the multi-screw extrusion device before transfer to the continuous pyrolysis furnace reactor. This measure also effectively protects the multi-screw extrusion device from excessive stress and allows for gentle operation. In this context, it is preferable to heat the filtered plastic melt by means of the multi-screw extrusion device to a discharge temperature that is 50 °C to 10 °C lower than the pyrolysis temperature in the continuous pyrolysis furnace reactor before transfer to the continuous pyrolysis furnace reactor.

[0024] In a further development of the method, it can be provided that the further heating of the filtered plastic material melt is carried out by means of a twin-screw extrusion device with an L / D ratio of 12 to 32.

[0025] This measure allows further heating to be accomplished over a very short extrusion path and, with a corresponding extrusion device, only slight twisting is required to introduce the mechanical energy into the plastic material melt.

[0026] In addition, it can be advantageous in the process that the further heating of the filtered plastic material melt is carried out by means of a twin-screw extrusion device, the conveyor segments of which have a radially effective clearance SKG between the screw crest of one of the two screws and the screw base of the other of the two screws of 0.5 mm to 2 mm, preferably 1 mm to 2 mm.

[0027] This measure allows the mechanical stress during further heating to be kept to a minimum. As has been demonstrated, this is achieved while largely preserving the self-cleaning properties of the two screws. Material blockage, particularly in the overlapping working area of ​​the two screws, and thus jamming, can be effectively prevented by this measure. The specified radial clearance SKG is specified, for example, in Klemens Kohlgrüber's "Der gleichlaufende Doppelschneckenextruder" (The Co-Rotating Twin-Screw Extruder), ISBN: 978-3-446-43361-8, and reference is made to this literature at this point.

[0028] In a further preferred embodiment of the method, it may be expedient for the filtered and further heated plastic material melt to be transferred from the multi-screw extrusion device into the continuous pyrolysis furnace reactor via an inlet opening arranged in a ceiling region of a reactor chamber of the continuous pyrolysis furnace reactor, and for solid and / or liquid pyrolysis products produced by the pyrolysis to be transported by means of a spiral conveyor screw along a horizontally or at least approximately horizontally oriented floor region in the interior of the reactor chamber, in the direction of a discharge opening horizontally offset from the inlet opening and arranged in the floor region.

[0029] A process using such a continuous pyrolysis furnace reactor allows for continuous and very uniform pyrolysis, including a continuous discharge of solid and, if necessary, liquid pyrolysis products. Because the plastic melt and the solid pyrolysis products generated during pyrolysis are only displaced in the bottom area of ​​the reactor chamber, virtually no mechanical stress occurs at the high pyrolysis temperatures in the continuous pyrolysis furnace reactor. Furthermore, the surface of the plastic material to be pyrolyzed can be continuously renewed, thereby increasing the efficiency of pyrolysis. This allows the pyrolysis itself to be carried out in a very gentle yet complete manner.

[0030] In this context, it may further be advantageous if the solid pyrolysis products produced by the pyrolysis are transferred via the discharge opening into a discharge device having a discharge screw, and are transported away from the continuous pyrolysis furnace reactor by means of the discharge device.

[0031] This measure allows the solid pyrolysis products to be continuously and rapidly discharged from the continuous pyrolysis furnace reactor and transported away from the reactor. Advantageously, the solid pyrolysis products can also be cooled during the transport process.

[0032] In a further development of the method, it can also be provided that the filtration device is heated by means of one or more heating devices during the separation of the non-melted solids from the plastic material melt.

[0033] This effectively prevents excessive temperature drops during deposition, thus eliminating the need for disadvantageous additional heating using the multi-screw extrusion device. This is also advantageous because the required length of the multi-screw extrusion device can be kept as short as possible, allowing the multi-screw extrusion device to be operated with the lowest possible torque.

[0034] Furthermore, it may be expedient if the plastic material melt is heated by means of one or more heating devices during the transfer from the single-screw single-screw extrusion device to the filtration device and / or if the filtered plastic material melt is heated by means of one or more heating devices during the transfer from the filtration device to the multi-screw extrusion device.

[0035] These measures can effectively prevent cooling during the respective transfers, and the plastic material melt or the filtered plastic material melt does not have to be additionally heated or heated up.

[0036] In addition, the process can also provide for the filtered and further heated plastic material melt to be heated by means of one or more heating devices during the transfer from the multi-screw extrusion device into the continuous pyrolysis furnace reactor.

[0037] This measure, above all, allows pyrolysis in the continuous pyrolysis furnace reactor to be carried out at very uniform and stable temperature conditions throughout the entire pyrolysis furnace reactor. This allows for highly reliable and complete pyrolysis without the need for complex control interventions or adjustments to stabilize the temperature in the continuous pyrolysis furnace reactor.

[0038] For a better understanding of the invention, it is explained in more detail using the following figure.

[0039] It shows in a highly simplified, schematic representation:

[0040] Fig. 1 An exemplary embodiment of a plant for processing plastics waste to illustrate the method. By way of introduction, it should be noted that in the variously described embodiments, identical parts are provided with identical reference symbols or identical component designations, whereby the disclosures contained in the entire description can be transferred mutatis mutandis to identical parts with identical reference symbols or identical component designations. Furthermore, the positional information chosen in the description, such as top, bottom, side, etc., relates to the directly described and illustrated figure, and if the position changes, these positional information must be transferred mutatis mutandis to the new position.

[0041] In the process for processing plastic waste, a plastic waste material is initially provided. As is usual with the recycling of plastic waste, the plastic waste material to be processed can be provided in comminuted form, for example, produced by shredding plastic objects into flakes. Mixtures of several different plastic waste materials can also be provided. This also includes providing plastic waste material with several different polymers. For the purpose of further processing or processing, the plastic waste material must be provided with a total proportion of thermoplastic plastics or thermoplastic polymers of at least 50 wt.%. This is particularly important to ensure extrusion capability.

[0042] As illustrated schematically in Fig. 1, the provided plastic waste material can then be filled or continuously metered into a single-screw extrusion device 2 via a filling opening 1. By means of this single-screw extrusion device 2, the plastic waste material is then heated and melted into a plastic material melt. The melting of the plastic waste material should therefore be carried out by means of a single-screw extrusion device 2 because such a single-screw extrusion device 2 is very robust against damage caused by non-melting, particulate components of the plastic waste material. Such particles are transported or conveyed in the single-screw extrusion device 2 with the molten thermoplastic(s).

[0043] The single-screw extrusion device 2, as is known per se, has a screw 4 mounted in a housing 3 for kneading, melting, and conveying the provided plastic waste material. After melting, the resulting plastic melt is transported or conveyed by this screw 4 in a working cavity 5 of the single-screw extrusion device 2 toward a discharge opening 6 of the housing 3. The plastic melt can typically have a temperature of approximately 200°C to 350°C upon discharge from the single-screw extrusion device 2.

[0044] In Fig. 1, the single-screw extrusion device 2 and its components are shown only very schematically and partly incompletely. Of course, the single-screw extrusion device 2 can, as is known per se, be provided with thermal insulation, for example (not shown in detail in Fig. 1). The screw 4 of the single-screw extrusion device 2 is also shown only roughly schematically and, as is also known, can, for example, be designed in sections without a transport thread, and instead have sections or portions such as kneading zones or, in some sections, other screw elements which are not designed for conveying the plastic material melt, for example. As shown in Fig.As shown in Figure 1, the single-screw extrusion device 2 can further comprise one or more heating devices 7, for example, electrical resistance heating elements or heating devices that can be supplied with heating fluids, in order to also externally heat the plastic waste material or the plastic melt in the working cavity 5. Furthermore, one or more vents 8 can also be provided to remove volatile components from the working cavity 5 or the plastic melt transported therein.

[0045] As further shown in Fig. 1, the plastic material melt formed by the single-screw extrusion device 2 is transferred from the single-screw extrusion device 2 into a filtration device 9. This can be accomplished, as outlined in Fig. 1, via a connection 10, for example, a piece of pipe. Preferably, the plastic material melt can be heated during the transfer from the single-screw extrusion device 2 into the filtration device 9, for example, again by means of one or more heating devices 7. The connection 10 can, of course, also be thermally insulated from the environment.

[0046] By means of or in the filtration device 9, non-melted solids are separated from the plastic material melt. The filtration device can be used to separate non-melted solids with a particle size of 1 mm or more, preferably 0.5 mm or more.

[0047] In principle, any filtration device 9 suitable for filtering plastic melts can be used. A preferred embodiment of a filtration device 9 can comprise a cylindrical filter 12 arranged rotatably or rotatably in a likewise cylindrical housing 11 and designed for the continuous filtering of a plastic melt, as shown schematically in Fig. 1. Furthermore, a filtration device can expediently comprise one or more scrapers for removing filtered-out solids from the filter 12 and a discharge device for removing these filtered-out solids from the filtration device 12 (not shown in detail in Fig. 1).

[0048] As illustrated in Fig. 1, the filtration device 9 can preferably be heated by one or more heating devices 7 during the separation of the unmelted solids from the plastic material melt, in order to prevent or prevent a drop in the temperature of the plastic material melt during filtration. For the same reason, the filtration device can also be equipped with thermal insulation.

[0049] After separating non-melted solids, the filtered plastic material melt is transferred to a multi-screw extrusion device 13, as illustrated in Fig. 1. The transfer can again take place via a connection 14, for example, a piece of pipe, whereby such a connection 14 can again be thermally insulated. Furthermore, the filtered plastic material melt can be heated during the transfer from the filtration device 9 to the multi-screw extrusion device 13, for example, by means of one or more heating devices 7, as shown in the embodiment according to Fig. 1.

[0050] The filtered plastic material melt is further heated by means of the multi-screw extrusion device 13. Preferably, however, only a small amount of the total pyrolysis takes place in the multi-screw extrusion device 13 itself, for example, 10% or less of the total pyrolysis, or even no pyrolysis at all. Instead, the method provides for the filtered plastic material melt, after further heating by means of the multi-screw extrusion device 13, to be extruded as shown in Fig.

[0051] 1, is transferred to a continuous or continuously operating pyrolysis furnace reactor 15 and pyrolyzed in this pyrolysis furnace reactor 15 at a pyrolysis temperature. Depending on the plastic waste material initially provided, the pyrolysis temperature can typically be approximately 400°C to 750°C.

[0052] In the process, the filtered plastic material melt is heated by means of the multi-screw extrusion device 13 before being transferred or immediately before being transferred into the continuous or continuously operating pyrolysis furnace reactor 15 to a discharge temperature which is 50 °C lower to 20 °C higher than the pyrolysis temperature in the continuous pyrolysis furnace reactor 15. The multi-screw extrusion device 13 is accordingly used only or mainly for heating the filtered plastic material melt to near the pyrolysis temperature, while the predominant part of the pyrolysis, for example over 90%, or even the pyrolysis entirely, is carried out in the continuous pyrolysis furnace reactor.

[0053] The multi-screw extrusion device 13 can preferably be designed as a twin-screw extruder with co-rotating screws 16, as is also shown in the embodiment according to Fig. 1. The two screws 16 of such a twin-screw extrusion device 13 can thus rotate in the same direction of rotation, wherein the two axes of rotation of the screws 16 can be arranged parallel to one another. As in the case of the single-screw extrusion device 2, the two screws 16 of the twin-screw extrusion device 13 can also be designed in sections without a transport thread and instead have sections or portions such as kneading zones or other screw elements in sections which are not designed, for example, for conveying the plastic material melt or for reclaiming the plastic material melt. As an alternative to the embodiment shown in Fig.In addition to the co-rotating twin-screw extruder shown in Figure 1, a twin-screw extrusion device 13 can also be designed, for example, as a counter-rotating twin-screw extruder or as a twin-screw extruder with tapered screws. In principle, other variants of multi-screw extrusion devices, such as so-called ring extruders or planetary roller extruders, are also conceivable for further heating the filtered plastic material melt.

[0054] The filtered plastic material melt is conveyed or transported in a working cavity 17 of the multi-screw extrusion device 13 toward an outlet opening 18, and is further heated to the discharge temperature by means of the multi-screw extrusion device 13. This heating can be achieved primarily through internal friction in the filtered plastic material melt due to the intensive kneading of the same in the multi-screw extrusion device 13. As is known per se, this can be accomplished particularly efficiently using a twin-screw extruder. Nevertheless, it can also be provided that the filtered plastic material melt is additionally further heated by means of one or more heating devices 7, as can also be seen from the embodiment shown in Fig. 1. The multi-screw extrusion device 13 can also be thermally insulated from the environment.In addition, the multi-screw extrusion device 13 may also comprise degassing openings 8 for removing volatile components from the filtered plastic material melt.

[0055] Specifically, the further heating of the filtered plastic material melt can be carried out using a twin-screw extrusion device 13 with an L / D ratio of 12 to 32. Such an embodiment of the twin-screw extrusion device 13 has proven particularly advantageous with regard to the torques required by the two screws 16. This is because the torques required can be kept low while still achieving heating to the respective discharge temperature.

[0056] The further heating of the filtered plastic material melt can be carried out in particular by means of a twin-screw extrusion device 13, the conveyor segments of which have a radially effective clearance SKG between the screw crest 20 of one of the two screws 16 and the screw base 32 of the other of the two screws 16 of 0.5 mm to 2 mm, preferably 1 mm to 2 mm.

[0057] Preferably, in the process, the filtered plastic material melt can only be heated to the discharge temperature in the last 20% of an entire extrusion section 19 of the multi-screw extrusion device 13. Specifically, the filtered plastic material melt can only be heated to the discharge temperature in the last 10%, in particular only in the last 3%, of an entire extrusion section 19 of the multi-screw extrusion device 13.

[0058] In addition, the filtered plastic material melt can preferably be heated by means of the multi-screw extrusion device 13 before being transferred into the continuous pyrolysis furnace reactor 15 to a discharge temperature which is 50 °C to 5 °C, particularly preferably 50 °C to 10 °C lower than the pyrolysis temperature in the continuous pyrolysis furnace reactor 15, since this prevents the pyrolysis from starting in the multi-screw extrusion device 13 and protects the multi-screw extrusion device 13.

[0059] During the further heating of the filtered plastic melt, additives can also be added to the same in the multi-screw extrusion device 13. These additives can be, for example, stabilizers or catalysts for the subsequent pyrolysis. Such additives can preferably be added toward the beginning of the entire extrusion section 19 in order to achieve the most homogeneous distribution of these additives in the filtered plastic melt. For example, such additives can be added to the filtered plastic melt in the first 50%, preferably the first 30%, of the entire extrusion section 19 of the multi-screw extrusion device 13.

[0060] After further heating to the discharge temperature by means of the multi-screw extrusion device 13, as already mentioned, the filtered and further heated plastic material melt is transferred to the continuous pyrolysis furnace reactor 15, for example via a further connection 21, as can be seen from the exemplary embodiment shown in Fig. 1. This connection 21 can also be, for example, a piece of pipe, and this connection can also be thermally insulated from the environment. Furthermore, in this context, it can also be provided that the filtered and further heated plastic material melt is heated by one or more heating devices 7 during the transfer from the multi-screw extrusion device 13 to the continuous pyrolysis furnace reactor 15, as illustrated in Fig. 1.1 shows a particularly preferred embodiment of a continuous or continuously operating pyrolysis furnace reactor 15 to illustrate a preferred process control for the actual pyrolysis.

[0061] As can be seen from the exemplary embodiment shown in Fig. 1, the filtered and further heated plastic material can preferably be transferred from the multi-screw extrusion device 13 into the continuous pyrolysis furnace reactor 15 via an inlet opening 24 arranged in a ceiling region 22 of a reactor chamber 23 of the continuous pyrolysis furnace reactor 15. In the illustrated exemplary embodiment, the connection 21 can, for example, open into this inlet opening 24.

[0062] The reactor chamber 23 of the continuous pyrolysis furnace reactor 15 can, for example, be heated by one or more heating devices 25 or brought to or maintained at a desired pyrolysis temperature, and the continuous pyrolysis furnace reactor 15 can, of course, also have thermal insulation. In the preferred embodiment shown in Fig. 1, a heating device 25, for example again an electrical resistance heating element, can be provided only in a base region 26 of the continuous pyrolysis furnace reactor 15. This heating device 25 can also be designed to be low-power, since the plastic material melt to be pyrolyzed is already introduced into the reactor chamber 23 of the continuous pyrolysis furnace reactor 15 at at least approximately the pyrolysis temperature. As an alternative to the embodiment shown in Fig.1, other methods for heating the reactor chamber 23 of the pyrolysis furnace reactor 15 are also conceivable, such as heating with a heating gas via a heat exchanger or introducing a heating gas directly into the reactor chamber 23.

[0063] Through pyrolysis, the introduced plastic material melt is thermally decomposed in the reactor chamber 23 of the continuous pyrolysis furnace reactor 15. This produces, on the one hand, pyrolysis gases, which, as shown in the embodiment according to Fig. 1, can be discharged from the reactor chamber 23 via one or more gas outlets 27. These pyrolysis gases can then be directly recycled for material and / or thermal purposes, for example, polymerized again into macromolecular substances. Alternatively, the pyrolysis gases can also be fed to condensation devices so that these condensates can be temporarily stored for later recycling, for example. Furthermore, the pyrolysis of the plastic waste in the reactor chamber generally also produces solid pyrolysis residues and, depending on the plastic waste material provided, possibly also liquid residues.As can be seen from the exemplary embodiment according to Fig. 1, these solid and / or liquid pyrolysis products resulting from the pyrolysis can each be transported along a horizontally or at least approximately horizontally oriented bottom surface 28 inside the reactor chamber 23 by means of a spiral conveyor screw 29 that meshes only with the bottom surface 28 and rotates in the reactor chamber, in the direction of a discharge opening 30 that is horizontally offset from the inlet opening 24 and arranged in the bottom region 26 of the reactor chamber 23. The transport of the solid and optionally also liquid pyrolysis products can be carried out by means of a very slowly rotating spiral conveyor screw 29 in order to ensure a sufficient residence time in the reactor chamber 23 of the continuous pyrolysis furnace reactor 15 and thus to be able to carry out the most complete pyrolysis possible.

[0064] Any liquid pyrolysis products resulting from the pyrolysis can, for example, be discharged from the continuous pyrolysis furnace reactor 15 via an outlet 31 arranged in the bottom region 26 of the reactor chamber 23, as shown in the embodiment according to Fig. 1.

[0065] The solid pyrolysis products produced by the pyrolysis can preferably be transferred via the discharge opening 30 into a discharge device 32 having a discharge screw 33, and transported away from the continuous pyrolysis furnace reactor 15 by means of the discharge device 32, as is also illustrated by the embodiment shown in Fig. 1.

[0066] After discharge from the continuous pyrolysis furnace reactor 15, the solid and any resulting liquid pyrolysis products can then be subjected to material and / or thermal recycling.

[0067] Unlike the embodiment shown in Fig. 1, the process can also be carried out using more than just one single-screw extrusion device 2, filtration device 9, twin-screw extrusion device 13, and / or pyrolysis furnace reactor 15. Rather, several of the aforementioned devices 2, 9, 13, 15 can be used in combination to carry out the process, whereby a different number of the respective devices 2, 9, 13, 15 can also be used in combination.In particular, the method can provide for the use of a plurality of single-screw, single-screw extrusion devices 2 for heating and melting the plastic waste material, wherein the plastic material melt formed thereby is then transferred, preferably via one or more filtration devices 9, into a single, multi-screw extrusion device 13, and after further heating in this single, multi-screw extrusion device 13, can then be introduced into a single, continuous pyrolysis furnace reactor 15.

[0068] The embodiments show possible embodiments, whereby it should be noted at this point that the invention is not limited to the specifically illustrated embodiments thereof, but rather various combinations of the individual embodiments with each other are also possible and this possibility of variation lies within the skill of the person skilled in the art in this technical field due to the teaching of technical action by means of the objective invention.

[0069] The scope of protection is determined by the claims. However, the description and drawings must be used to interpret the claims. Individual features or combinations of features from the various embodiments shown and described may represent independent inventive solutions. The problem underlying these independent inventive solutions can be derived from the description.

[0070] All information on value ranges in this description is to be understood as including any and all sub-ranges thereof, e.g. the information 1 to 10 is to be understood as including all sub-ranges starting from the lower limit of 1 and the upper limit of 10, ie all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g. 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0071] For the sake of clarity, it should be noted that some elements have been shown not to scale and / or enlarged and / or reduced in size to improve understanding of the structure.

[0072] Filling opening 31 Outlet

[0073] Single screw extrusion device - 32 screw base

[0074] Housing

[0075] Snail

[0076] Working cavity

[0077] Discharge opening

[0078] Heating device

[0079] Degassing opening

[0080] Filtration device

[0081] Connection

[0082] Housing

[0083] filter

[0084] Extrusion device

[0085] Connection

[0086] Pyrolysis furnace reactor

[0087] Snail

[0088] Working cavity

[0089] Outlet opening

[0090] Extrusion line

[0091] Snail comb

[0092] Connection

[0093] Ceiling area

[0094] reactor chamber

[0095] Entry opening

[0096] Heating device

[0097] Floor area

[0098] Gas outlet

[0099] Floor area

[0100] Spiral conveyor screw

[0101] discharge opening

Claims

Patent claims 1. Process for the treatment of plastic waste, comprising the process steps - Providing plastic waste material with a thermoplastic content of at least 50% by weight - heating and melting the plastic waste material by means of a single-screw extrusion device (2) to form a plastic material melt, - transferring the plastic material melt from the single-screw extrusion device (2) into a filtration device (9) and separating non-melted solids from the plastic material melt by means of the filtration device (9), - Transferring the filtered plastic material melt into a multi-screw extrusion device (13) and further heating the filtered plastic material melt by means of the multi-screw extrusion device (13), characterized in that the filtered plastic material melt, after further heating by means of the multi-screw extrusion device (13), is transferred into a continuous pyrolysis furnace reactor (15) and is pyrolyzed in this continuous pyrolysis furnace reactor (15) at a pyrolysis temperature, wherein the filtered plastic material melt is heated by means of the multi-screw extrusion device (13) to a discharge temperature before being transferred to the continuous pyrolysis furnace reactor (15), which discharge temperature is 50 °C lower to 20 °C higher than the pyrolysis temperature in the continuous pyrolysis furnace reactor (15).

2. Method according to claim 1, characterized in that the filtered plastic material melt is heated to the discharge temperature only on the last 20% of an entire extrusion section (19) of the multi-screw extrusion device (13).

3. Method according to one of claims 1 or 2, characterized in that the filtered plastic material melt is extruded by means of the multi-screw extrusion device (13) before being transferred into the continuous pyrolysis furnace reactor (15) to a discharge temperature, which discharge temperature is 50 °C to 5 °C lower than the pyrolysis temperature in the continuous pyrolysis furnace reactor (15).

4. Method according to one of the preceding claims, characterized in that the further heating of the filtered plastic material melt is carried out by means of a twin-screw extrusion device (13) with an L / D ratio of 12 to 32.

5. Method according to one of the preceding claims, characterized in that the further heating of the filtered plastic material melt is carried out by means of a twin-screw extrusion device (13), the conveyor segments of which have a radially effective clearance SKG between the screw crest (20) of one of the two screws (16) and the screw base (32) of the other of the two screws (16) of 0.5 mm to 2 mm.

6. Method according to one of the preceding claims, characterized in that the filtered and further heated plastic material melt is transferred from the multi-screw extrusion device (13) into the continuous pyrolysis furnace reactor (15) via an inlet opening (24) arranged in a ceiling region (22) of a reactor chamber (23) of the continuous pyrolysis furnace reactor (15), and in that solid and / or liquid pyrolysis products resulting from the pyrolysis are each transported along a horizontally or at least approximately horizontally oriented bottom surface (28) in the interior of the reactor chamber (23) by means of a spiral conveyor screw (29) which meshes only with the bottom surface (28) and rotates in the reactor chamber (23), in the direction of a discharge opening (30) which is horizontally offset from the inlet opening (24) and arranged in a bottom region (26) of the reactor chamber (23).

7. The method according to claim 6, characterized in that the solid pyrolysis products produced by the pyrolysis are transferred via the discharge opening (30) into a discharge device (32) having a discharge screw (33) and are transported away from the continuous pyrolysis furnace reactor (15) by means of the discharge device (32).

8. Method according to one of the preceding claims, characterized in that the filtration device (9) is heated by means of one or more heating devices (7) during the separation of the non-melted solids from the plastic material melt.

9. Method according to one of the preceding claims, characterized in that the plastic material melt is heated by means of one or more heating devices (7) during the transfer from the single-screw single-screw extrusion device (2) to the filtration device (9) and / or that the filtered plastic material melt is heated by means of one or more heating devices (7) during the transfer from the filtration device (9) to the multi-screw extrusion device (13).

10. Method according to one of the preceding claims, characterized in that the filtered and further heated plastic material melt is heated by means of one or more heating devices (7) during the transfer from the multi-screw extrusion device (13) into the continuous pyrolysis furnace reactor (15).

Images