Method and recycling plant for recycling plastic waste material

Abstract

In a method for recycling plastic waste material (MW), plastic waste material (MW) is supplied to a first screw machine (2) and is melted in the screw machine to give a plastic waste material melt (SW). The plastic waste material melt (SW) is supplied to a second multi-shaft screw machine (3) by means of a supply unit (55) and is processed therein together with plastic raw material (MV) to give a plastic material melt (S).

Description

[0001] Process and recycling plant for the recycling of plastic waste material

[0002] This patent application claims priority from German patent application DE 10 2022 201 398.0, the contents of which are incorporated herein by reference.

[0003] The invention relates to a method and a recycling plant for recycling plastic waste material, in particular polyolefin waste material.

[0004] DE 10 2019 127 827 A1 discloses a process for producing plastic products from a recycled plastic material and an unrecycled virgin plastic material. Production takes place using an extrusion system. The basic material for the plastic products is a polymeric raw material, such as polyolefins. To produce the plastic products, a granulate of the recycled plastic material and a granulate of the unrecycled virgin plastic material are fed into the extrusion system in specific proportions. The extrusion system uses the supplied granules to produce, for example, new compounds or films as plastic products.

[0005] The invention is based on the object of creating a method that enables simple, flexible, qualitatively reliable, and energy-efficient recycling of plastic waste material, in particular polyolefin waste material. This object is achieved by a method having the features of claim 1. The plastic waste material to be recycled, in particular the polyolefin waste material to be recycled, is first fed to the first screw extruder, in particular the first multi-shaft screw extruder, and melted by the first screw extruder to form a plastic waste material melt. The plastic waste material is made from plastic products that have been shredded and / or cleaned or washed. The plastic waste material is in particular in bulk form, for example as flakes and / or pellets.In particular, the plastic waste material was not already processed by a screw machine before being fed to the first screw machine. In particular, the plastic waste material is not plastic waste material granulate produced from processed and granulated plastic waste material.

[0006] Preferably, the residence time of the plastic waste melt in the first screw extruder is adjustable by means of a throttle device. The throttle device is arranged in particular downstream of the first screw extruder. The throttle device comprises at least one throttle element for adjusting a flow resistance of the plastic waste melt. The position of the at least one throttle element is adjustable or variable for this purpose. A higher flow resistance leads to a longer residence time and vice versa. By increasing the residence time, the plastic waste melt is mixed and homogenized for a longer and thus more intensively in the first screw extruder, which has a positive effect on the quality of the plastic waste melt.Parallel to the melting of the plastic waste material, plastic raw material is fed to the second multi-shaft screw extruder, which is then processed into a plastic raw material melt by the second multi-shaft screw extruder. The plastic raw material can be fed to the second multi-shaft screw extruder as bulk material, for example as powder and / or granules, or already in a melted state. If the plastic raw material is fed as bulk material, the processing involves melting the plastic raw material. If, on the other hand, the plastic raw material is fed already in a melted state, the processing involves conveying and the associated mixing of the plastic raw material melt. At least one additive can also be fed to the second multi-shaft screw extruder.

[0007] The plastic waste material melt is also fed to the second multi-shaft screw extruder. Preferably, the plastic waste material is fed to the second multi-shaft screw extruder in a conveying direction downstream of the feed of the plastic raw material. The plastic waste material melt is fed in particular into the plastic raw material melt. Subsequently, the plastic raw material melt and the plastic waste material melt are mixed or homogenized by the second multi-shaft screw extruder to form a plastic material melt. The plastic material melt is then discharged from the second multi-shaft screw extruder. The discharged plastic material melt is either further processed directly into a plastic product or fed to a granulating device, which produces plastic granules or polyolefin granules from the plastic material melt.The process is simple and energy-efficient because the plastic waste material is melted by the first screw extruder and then fed to the second multi-screw extruder without the intermediate step of granulation. The second multi-screw extruder mixes the melt with the plastic raw material melt to produce the resulting product. Because the proportions of plastic waste material and plastic raw material can be flexibly adjusted depending on the initial quality of the plastic waste material, the quality of the plastic melt can be reliably guaranteed.

[0008] A method according to claim 2 ensures simple, flexible, qualitatively reliable, and energy-efficient recycling. Because the plastic waste melt is filtered by means of a filter device before being fed into the second multi-shaft screw extruder, contaminants and / or agglomerates are not mixed with the plastic raw material melt. The quality of the plastic material melt is thereby increased. The filter device preferably comprises at least two filter elements. Alternatively, the filter device comprises at least one filter element with continuous cleaning and / or a backflushing function. This allows at least one filter element to be cleaned and / or replaced during operation. The filter device is preferably designed as a screen-changing device.

[0009] A method according to claim 3 ensures simple, flexible, qualitatively reliable, and energy-efficient recycling. Preferably, the at least one determined parameter characterizes at least one quality feature of the plastic waste material melt. This enables the determination of a quality measure for the plastic waste material melt. The at least one determined parameter is transmitted in particular to a control device. By means of the at least one sensor, in particular, a pressure, a temperature, and / or a viscosity of the plastic waste material melt is determined. Preferably, by means of at least one sensor, a pressure, a temperature, and / or a viscosity of the plastic waste material melt is measured immediately downstream of the first screw machine and / or immediately upstream of the filter device and / or downstream of the filter device.The measurement immediately after the first screw extruder provides information about the flow properties of the unpurified plastic waste melt. The measurement immediately before the filter device provides information about the pressure increase over time and / or the degree of contamination of the plastic waste melt depending on the filtration fineness of the filter device. The filtration fineness of the at least one filter element is selected depending on the required quality of the plastic melt. The measurement after the filter device, in particular the viscosity measurement or the online viscosity measurement, provides information about the flow properties of the filtered plastic waste melt and the expected viscosity of the plastic melt.The viscosity can be adjusted in particular by adjusting the residence time of the plastic waste material melt in the first screw machine and / or by adding plastic raw material to the first screw machine.

[0010] A method according to claim 4 ensures simple, flexible, qualitatively reliable, and energy-efficient recycling. Based on the quality measure, the quality of the plastic waste melt can be assessed and / or the plastic waste melt can be classified into different quality classes. This makes it possible to control the recycling depending on the quality measure(s). In particular, an inadequate quality of the plastic waste melt can be responded to immediately, for example by controlling a feed device and / or a throttle device. In the simplest case, the quality measure is the at least one parameter. The measured values ​​of the at least one parameter can be signal-processed by the control device. The quality measure is, for example, the measured viscosity of the plastic waste melt downstream of a filter device.

[0011] A method according to claim 5 ensures simple, flexible, qualitatively reliable, and energy-efficient recycling. Because at least one feed device and / or a throttle device is controlled as a function of the determined at least one parameter or the determined quality measure, an immediate response can be made to insufficient quality or an insufficient quality measure of the plastic waste material melt. The at least one feed device prevents, for example, the feeding of the plastic waste material melt into the second multi-shaft screw extruder if the determined quality measure lies outside a predefined range. Furthermore, the at least one feed device feeds, for example, plastic raw material and / or at least one additive into the first screw extruder in order to increase the quality measure.The throttle device increases, for example, the flow resistance of the plastic waste melt, so that the residence time of the plastic waste melt in the first screw extruder is increased, which leads to longer and more intensive mixing or homogenization and thus to an increase in quality. A method according to claim 6 ensures simple, flexible, qualitatively reliable, and energy-efficient reprocessing. The plastic waste melt is fed to the second multi-shaft screw extruder by means of a feed device. The feed device for feeding the plastic waste melt comprises, in particular, at least one switching element that can be switched between a first switching position and a second switching position. The switching is controlled, in particular, by means of a control device. The feed device preferably comprises a drive for actuating the switching element.

[0012] In the first switching position, the plastic waste melt is fed to the second multi-shaft screw extruder. The first switching position is selected when the determined quality measure lies within a predefined range. In the second switching position, the plastic waste melt is not fed to the second multi-shaft screw extruder. The second switching position is selected when the determined quality measure lies outside the predefined range. In the second switching position, the plastic waste melt can, for example, be fed to a granulator, which granulates the plastic waste melt into granules. The granules have a comparatively low quality but can still be further processed.Because the feed device for feeding the plastic waste melt is controlled depending on the determined quality measure, the plastic waste melt is only fed to the second multi-shaft screw extruder if the quality is sufficient. A method according to claim 7 ensures simple, flexible, qualitatively reliable, and energy-efficient reprocessing. To increase the quality of the plastic waste melt, plastic raw material and / or at least one additive can be fed to the first screw extruder by means of a feed device. By feeding plastic raw material and / or at least one additive, the quality of the plastic waste melt is increased, thus improving the determined quality measure.If the quality level returns to the predefined range, the plastic waste material melt can be fed back to the second multi-shaft screw machine by switching a switching element.

[0013] A method according to claim 8 ensures simple, flexible, qualitatively reliable, and energy-efficient recycling. By ensuring that the plastic waste melt is of high quality and / or the quality of the plastic waste melt is monitored, a high proportion (mw) of plastic waste material can be recycled. The proportion (mw) defines, in particular, an average weight proportion based on the plastic melt discharged from the second multi-shaft screw extruder.

[0014] Furthermore, the invention is based on the object of creating a recycling plant which enables simple, flexible, qualitatively reliable and energy-efficient recycling of plastic waste material, in particular polyolefin waste material.

[0015] This object is achieved by a recycling plant having the features of claim 9. The advantages of the recycling plant according to the invention correspond to the already described advantages of the method according to the invention for recycling plastic waste material, in particular polyolefin waste material. The recycling plant can be further developed, in particular, with at least one feature described in connection with the method according to the invention. Accordingly, the method according to the invention can be further developed with at least one feature described in connection with the recycling plant according to the invention.

[0016] The first screw extruder comprises, in particular, at least one treatment element shaft. The first screw extruder is preferably designed as a multi-shaft extruder. The first multi-shaft extruder comprises, in particular, at least two treatment element shafts that are co-rotating and / or closely intermeshing. The first multi-shaft extruder is preferably designed as a co-rotating twin-shaft extruder. The first screw extruder comprises, in particular, an intake zone, a melting zone, a degassing zone, and a discharge zone. The first screw extruder comprises, in particular, at least one feed opening for feeding the plastic waste material and / or for feeding plastic raw material and / or for feeding at least one additive.The first screw extruder preferably comprises a first feed opening for feeding the plastic waste material and a second feed opening for feeding the plastic raw material and / or the at least one additive. For feeding the plastic waste material, the reprocessing plant comprises, in particular, a feed screw extruder that opens into the first feed opening. The second multi-shaft screw extruder particularly comprises at least two treatment element shafts that are designed to rotate in the same direction and / or to mesh tightly. The second multi-shaft screw extruder is preferably designed as a co-rotating twin-shaft screw extruder. The second multi-shaft screw extruder particularly comprises a first feed zone with the first feed opening, a melting zone, a second feed zone with the second feed opening, a homogenization zone, and a discharge zone.

[0017] The first screw machine can in particular be retrofitted to an existing second multi-shaft screw machine.

[0018] A reprocessing plant according to claim 10 ensures simple, flexible, qualitatively reliable, and energy-efficient reprocessing. The throttle device is arranged in particular downstream of the first screw extruder and enables adjustment of the residence time of the plastic waste material melt in the first screw extruder. The throttle device comprises at least one throttle element for adjusting a flow resistance of the plastic waste material melt. The position of the at least one throttle element is adjustable or changeable for this purpose. A higher flow resistance leads to a longer residence time and vice versa. By increasing the residence time, the plastic waste material melt in the first screw extruder is mixed and homogenized for a longer and thus more intensively, which has a positive effect on the quality of the plastic waste material melt.A reprocessing system according to claim 11 ensures simple, flexible, qualitatively reliable, and energy-efficient reprocessing. The filter device comprises, in particular, at least two filter elements. Alternatively, the filter device comprises at least one filter element with continuous cleaning and / or a backwash function. This enables the cleaning and / or replacement of at least one filter element during operation. The filter device is designed, in particular, as a screen-changing device. The filter device is arranged, in particular, between the first screw extruder and the second multi-shaft screw extruder.

[0019] A reprocessing plant according to claim 12 ensures simple, flexible, qualitatively reliable, and energy-efficient reprocessing. The determined at least one parameter characterizes, in particular, a quality feature of the plastic waste material melt. By determining at least one parameter of the plastic waste material melt, the determination of a quality measure is made possible. The at least one sensor is, in particular, in signal communication with a control device. This allows the measured parameter values ​​to be transmitted to the control device. The at least one sensor is, in particular, a pressure sensor for measuring a pressure of the plastic waste material melt, a temperature sensor for measuring a temperature of the plastic waste material melt, and / or a viscosity sensor for measuring a viscosity of the plastic waste material melt.The at least one sensor is arranged in particular immediately after the first screw extruder and / or immediately before a filter device and / or after a filter device. Preferably, a pressure, a temperature and / or a viscosity of the plastic waste material melt is measured immediately after the first screw extruder and / or immediately before the filter device and / or after the filter device by means of at least one sensor. The measurement immediately after the first screw extruder provides information regarding the flow properties of the unpurified plastic waste material melt. The measurement immediately before the filter device provides information regarding the pressure increase as a function of time and / or the degree of contamination of the plastic waste material melt as a function of the filtration fineness of the filter device.The filtration fineness of the at least one filter element is selected depending on the required quality of the plastic melt. The measurement downstream of the filter device, in particular the viscosity measurement or the online viscosity measurement, provides information about the flow properties of the filtered plastic waste melt and the expected viscosity of the plastic melt. The viscosity can be adjusted in particular by adjusting the residence time of the plastic waste melt in the first screw extruder and / or by adding plastic raw material to the first screw extruder.

[0020] A reprocessing system according to claim 13 ensures simple, flexible, qualitatively reliable, and energy-efficient reprocessing. The control device enables the determination of a quality measure for assessing the quality of the plastic waste material melt. Furthermore, the control device enables the control of at least one feed device and / or a throttle device depending on the determined at least one parameter and / or depending on the determined quality measure. A reprocessing system according to claim 14 ensures simple, flexible, qualitatively reliable, and energy-efficient reprocessing. Because the feed device comprises at least one switching element, the feed device or the at least one switching element can be switched at least between a first switching position and a second switching position.In the first switching position, the feed device forms a first channel, which is connected to the second feed opening and opens into the second multi-shaft screw extruder. The plastic waste melt is thus fed into the second multi-shaft screw extruder in the first switching position. In the second switching position, the feed device forms a second channel, which does not open into the second multi-shaft screw extruder. The second channel leads, for example, to a granulation device. The feed device is designed, for example, as a diverter and / or valve.

[0021] A recycling plant according to claim 15 ensures simple, flexible, qualitatively reliable, and energy-efficient recycling. The feed device enables the feeding of plastic raw material and / or the feeding of at least one additive into the first screw extruder, so that the quality and / or color of the plastic waste material melt can be influenced. The feed device comprises, in particular, at least one dosing device. The at least one dosing device is designed, for example, to be volumetric and / or gravimetric. The at least one additive comprises, for example, powdered carbon black (FCB: Free Carbon Black), color pigments, peroxide, UV stabilizers, and / or antioxidants. A recycling plant according to claim 16 ensures simple, flexible, qualitatively reliable, and energy-efficient recycling.The control is carried out in particular as a function of at least one parameter of the plastic waste melt and / or a determined quality measure of the plastic waste melt. Because the control device is in signal communication with the feed device for feeding the plastic waste melt into the second multi-shaft screw extruder, the feed device can be controlled such that the plastic waste melt is fed into the second multi-shaft screw extruder if the plastic waste melt is of sufficient quality, and such that the plastic waste melt is not fed into the second multi-shaft screw extruder if the plastic waste melt is of insufficient quality.Because the control device is in signal communication with the feed device for feeding plastic raw material and / or for feeding at least one additive into the first screw extruder, if the quality of the plastic waste melt is insufficient, plastic raw material and / or at least one additive can be fed into the first screw extruder, thus improving the quality of the plastic waste melt. Because the control device is in signal communication with the throttle device, a residence time of the plastic waste melt in the first screw extruder can be set. By increasing the residence time, the plastic waste melt in the first screw extruder is mixed and homogenized for longer and thus more intensively, which has a positive effect on the quality of the plastic waste melt.Further features, advantages, and details of the invention will become apparent from the following description of an exemplary embodiment. It shows:

[0022] Fig. 1 is a schematic representation of a recycling plant for recycling plastic waste material, in particular polyolefin waste material, with a first multi-shaft screw machine for melting the plastic waste material to a plastic waste material melt and a second multi-shaft screw machine for mixing the plastic waste material melt with a plastic raw material melt,

[0023] Fig. 2 a side view of the first multi-shaft screw machine,

[0024] Fig. 3 is a partially sectioned plan view of the first multi-shaft screw machine in Fig. 2,

[0025] Fig. 4 is a sectional view of a throttle device of the reprocessing plant,

[0026] Fig. 5 is a side view of the second multi-shaft screw machine, and

[0027] Fig. 6 is a partially sectioned plan view of the second multi-shaft screw extruder in Fig. 5. A recycling plant 1 for recycling plastic waste material Mw, in particular polyolefin waste material, comprises a first screw extruder 2 and a second multi-shaft screw extruder 3. The screw extruder 2 is designed as a multi-shaft screw extruder. Alternatively, the screw extruder 2 can also be designed as a single-shaft screw extruder.

[0028] The first multi-shaft screw extruder 2 serves to melt the plastic waste material Mw into a plastic waste material melt Sw, in particular into a polyolefin waste material melt. The first multi-shaft screw extruder 2 is designed as a twin-shaft screw extruder. The first multi-shaft screw extruder 2 has a housing 4 comprising several successively arranged and mutually fastened housing sections. Two housing bores 5, 6 are formed in the housing 4, which penetrate one another and have the shape of a horizontal figure eight in cross-section. Two closely meshing treatment element shafts 7, 8 are arranged in the housing bores 5, 6 and can be driven for rotation about associated axes of rotation 9, 10. The treatment element shafts 7, 8 are driven in the same direction, i.e., in the same directions of rotation, by a drive motor 13 via a transfer case 11 and a clutch 12.

[0029] The first multi-shaft screw machine 2 has, in a conveying direction 14, a feed zone 15, a melting zone 16, a degassing zone 17 and a discharge zone 18.

[0030] In the intake zone 15, a first feed opening 19 is formed laterally in the housing 4. The first feed opening 19 serves to feed the plastic waste material Mw. For feeding plastic raw material Mv and / or for feeding at least one additive A, a second feed opening 20 is formed in the housing 4 in the intake zone 15. The second feed opening 20 is formed upstream of the first feed opening 19. A hopper 21 is connected to the second feed opening 20. In the intake zone 15, the treatment element shafts 7, 8 have screw elements.

[0031] The melting zone 16 serves to melt the plastic waste material Mw and / or the plastic raw material Mv and to melt or mix in any additive A or additives A that may be added. In the melting zone 16, the treatment element shafts 7, 8 have screw elements and / or kneading elements.

[0032] The degassing zone 17 serves to homogenize and degas the produced plastic waste material melt Mw. In the degassing zone 15, degassing openings 22 are formed in the housing 4, to which degassing devices 23 are connected. In the degassing zone 17, the treatment element shafts 7, 8 have screw elements and / or kneading elements.

[0033] The discharge zone 18 serves to discharge the plastic waste material melt Sw from the first multi-shaft screw extruder 2 through a discharge opening s. In the discharge zone 18, the treatment element shafts 7, 8 have screw elements. To heat the housing 4, the first multi-shaft screw extruder 2 comprises heating devices 24, which are connected to the housing 4 in the feed zone 15, the melting zone 16, the degassing zone 17, and the discharge zone 18.

[0034] The reprocessing plant 1 comprises a first feed device 25, which is assigned to the first multi-shaft screw extruder 2. The first feed device 25 comprises a twin-shaft feed screw extruder 26. The feed screw extruder 26 is designed as a side-loading machine. The feed screw extruder 26 is connected laterally to the housing 4 and opens into the first feed opening 19.

[0035] The feed screw machine 26 comprises a housing 27 with housing bores 28, 29, in which screw shafts 30, 31 are arranged so as to be rotatable in the same direction. The screw shafts 30, 31 are driven in the same direction, i.e., in the same directions of rotation, by a drive motor 33 via a distributor gear 32 about corresponding axes of rotation. A feed opening 34 is formed in the housing 27, which opens into the housing bores 28, 29 and to which a hopper 35 is connected. The feed screw machine 26 serves to feed the plastic waste material Mw.

[0036] The first feed device 25 further comprises a first dosing device 36 for feeding plastic raw material Mv and a second dosing device 37 for feeding at least one additive A through the second feed opening 20 into the first multi-shaft screw extruder 2. The dosing devices 36, 37 are designed gravimetrically, for example. The reprocessing system 1 comprises a throttle device 38, which is arranged downstream of the first multi-shaft screw extruder 2 with respect to the conveying direction 14. The throttle device 38 is attached to the housing 4. The throttle device 38 is designed as a start-up valve throttle device.Between the first multi-shaft screw extruder 2 and the throttle device 38, a first pressure sensor 53, which measures a pressure pi of the plastic waste material melt Sw immediately after the first multi-shaft screw extruder 2, and a first temperature sensor 56, which measures a temperature Ti of the plastic waste material melt Sw immediately after the first multi-shaft screw extruder 2, are arranged.

[0037] The throttle device 38 comprises a housing 39 in which a cylindrical housing recess 40 is formed. Arranged in the housing recess 40 is a correspondingly cylindrical switching element 41 which can be pivoted about a pivot axis 43 in the housing recess 40 by means of a drive 42. An inlet channel 44 is formed in the housing 39 and connects the housing bores 5, 6 to the housing recess 40. The switching element 41 forms a through-channel 45 which, in a discharge position shown in Fig. 4, connects the inlet channel 44 to a discharge channel 46. The switching element 41 further forms an outlet channel 47 which, in an outlet position, connects the inlet channel 44 to the environment. To switch between the discharge position and the discharge position, the switching element 41 can be pivoted about the pivot axis 43 by means of the drive 42.

[0038] A throttle element 48 is arranged in the discharge channel 46 and can be pivoted about a pivot axis 50 by means of a drive 49. Only a drive shaft of the drive 49 is visible in Fig. 4. In the discharge position, the throttle element 48 serves to adjust the residence time of the plastic waste material melt Sw in the first multi-shaft screw extruder 2. The throttle device 38 can also be designed according to the start-up valve throttle devices described in EP 3 552 798 A1. The disclosure content of EP 3 552 798 A1 is incorporated by reference into this patent application.

[0039] The recycling plant 1 comprises a melt pump 51, which is arranged downstream of the throttle device 38 with respect to the conveying direction 14. The melt pump 51 is designed, for example, as a gear pump. The melt pump 51 serves to increase the pressure of the plastic waste material melt Sw.

[0040] The recycling plant 1 further comprises a filter device 52, which is arranged downstream of the melt pump 51 with respect to the conveying direction 14. The filter device 52 comprises at least two filter elements. The filter device 52 is designed, for example, as a screen-changing device. The filter device 52 comprises a second pressure sensor 53', which measures a pressure p2 of the plastic waste melt Sw upstream of the filter device 52. The filter device 52 further comprises a second temperature sensor 56', which measures a temperature T2 of the plastic waste melt Sw upstream of the filter device 52.

[0041] The filter device 52 is connected to a second feed device 55 via a pipeline 54. A measuring region M is formed in the pipeline 54, in which various parameters of the plastic waste melt Sw are determined or measured by means of sensors 57, 58, 59. A pressure ps of the plastic waste melt Sw downstream of the filter device 52 is determined or measured by means of a third pressure sensor 57. The temperature T3 of the plastic waste melt Sw is determined or measured by means of a third temperature sensor 58. Furthermore, a viscosity p is determined or measured by means of a viscosity sensor 59.

[0042] The reprocessing plant 1 comprises a control device 60. The sensors 53, 53 56, 56', 57, 58, 59 are in signal connection with the control device 60.

[0043] The second feed device 55 comprises a housing 61 in which a housing recess 62 is formed. A switching element 63 is arranged in the housing recess 62 and can be displaced within the housing recess 62 by means of a drive 64. An inlet channel 65 is formed in the housing 61 and is connected to the pipeline 54. Furthermore, a first discharge channel 66, a discharge channel 67, and a second discharge channel 68 are formed in the housing 61.

[0044] A first through-channel 69 is formed in the switching element 63, which, in a first switching position of the switching element 63, connects the inlet channel 65 to the first discharge channel 66. The first switching position is shown in Figure 1. The first discharge channel 66 is connected to the second multi-shaft screw extruder 3 via a pipeline 70.

[0045] Furthermore, the switching element 63 comprises a second through-channel 71, which, in a second switching position, connects the inlet channel 65 to the second discharge channel 68. The second discharge channel 68 is connected to a first granulating device 74 via a pipeline 73. The first granulating device 74 is designed, for example, as an underwater granulating device.

[0046] The switching element 63 further comprises a third through-channel 72, which, in a third switching position, connects the inlet channel 65 with the discharge channel 67. The discharge channel 67 opens into the environment.

[0047] The second feed device 55 further comprises a first dosing device 91 for feeding plastic raw material Mv and a second dosing device 92 for feeding at least one additive A into the second multi-shaft screw machine 3. The dosing devices 91, 92 are designed gravimetrically, for example.

[0048] The second multi-shaft screw extruder 3 is designed as a twin-shaft screw extruder. The second multi-shaft screw extruder 3 has a housing 75 comprising several successively arranged and mutually secured housing sections. Two housing bores 76, 77 are formed in the housing 75, which penetrate one another and have the shape of a horizontal figure eight in cross-section. Two closely meshing treatment element shafts 78, 79 are arranged in the housing bores 76, 77 and can be driven in the same direction of rotation about associated axes of rotation 80, 81. The treatment element shafts 78, 79 are driven in the same direction, i.e., in the same directions of rotation, by a drive motor 84 via a transfer case 82 and a coupling 83.

[0049] The second multi-shaft screw extruder 3 has, in a conveying direction 85, a first feed zone 86, a melting zone 87, a second feed zone 88, a homogenization zone 89, and a discharge zone 90. In the first feed zone 86, a first feed opening 93 is formed in the housing 75. A hopper 94 is connected to the first feed opening 93. The first feed opening 93 opens into the housing bores 76, 77 and serves to feed plastic raw material Mv and / or the at least one additive A. The dosing devices 91, 92 open into the hopper 94. In the first feed zone 86, the treatment element shafts 78, 79 comprise screw elements.

[0050] The melting zone 87 serves to melt the plastic raw material Mv and, if applicable, the additive A or additives A. In the melting zone 87, the treatment element shafts 78, 79 comprise screw elements and / or kneading elements.

[0051] In the second feed zone 88, a second feed opening 95 is formed in the housing 75. The second feed opening 95 opens into the housing bores 76, 77. The second feed opening 95 serves to feed the plastic waste material melt Sw. The pipeline 70 is connected to the second feed opening 95. In the second feed zone 88, the treatment element shafts 78, 79 comprise screw elements.

[0052] The homogenization zone 89 serves to homogenize the plastic raw material melt Sv and the plastic waste material melt Sw and to degas the resulting plastic material melt S. For degassing, degassing openings 96 are formed in the housing 75, to each of which a degassing device 97 is connected. In the degassing zone 89, the treatment element shafts 78, 79 comprise screw elements and / or kneading elements. The discharge zone 90 serves to discharge the plastic material melt S through a discharge opening of the second multi-shaft screw extruder 3. In the discharge zone 90, the treatment element shafts 78, 79 comprise screw elements.

[0053] For heating the housing 75, the second multi-shaft screw machine 3 comprises heating devices 99 which are connected to the housing 75 in the melting zone 87, the second feed zone 88, the homogenization zone 89 and the discharge zone 90.

[0054] The recycling plant 1 comprises a second granulation device 98 for granulating the plastic material melt S. The second granulation device 98 is arranged downstream of the second multi-shaft screw extruder 3 and connected to the discharge opening. The second granulation device 98 serves to produce granules from the plastic material melt S. The second granulation device 98 is designed, for example, as an underwater granulation device.

[0055] The multi-shaft screw machines 2, 3, the feeding devices 25, 55 and the throttle device 38 are in signal connection with the control device 60 for control.

[0056] The following describes the operation of the recycling plant 1 and the process for recycling the plastic waste material Sw:

[0057] The plastic waste material Mw is fed to the first multi-shaft screw extruder 2 by means of the first feed device 25. For this purpose, the plastic waste material Mw, present as bulk material, is fed via the feed opening 34 to the feed screw extruder 26, which conveys the plastic waste material Mw via the first feed opening 19 into the housing bores 5, 6 of the first multi-shaft screw extruder 2. The plastic waste material Mw was produced from plastic products that were washed and / or shredded. The plastic waste material Mw is present, in particular, as shreds and / or pellets. The plastic waste material Mw is degassed and compacted in the feed screw extruder 26.

[0058] If required, plastic raw material Mv and / or at least one additive A can be fed to the first multi-shaft screw machine 2 via the second feed opening 20 by means of the dosing device 36 and / or by means of the dosing device 37.

[0059] In the melting zone 16, the plastic waste material Mw and optionally the plastic raw material Mv or the at least one additive A are melted and mixed. The housing 4 is heated by means of the heating devices 24, and the melting is assisted. The resulting plastic waste material melt Sw is homogenized and degassed in the degassing zone 17. The plastic waste material melt Sw is then discharged from the first multi-shaft screw extruder 2 via the discharge zone 18 and the associated discharge opening. The pressure pi and the temperature Ti of the plastic waste material melt Sw are monitored immediately downstream of the multi-shaft screw extruder 2 by means of the first pressure sensor 53 and the first temperature sensor 56.After starting up the first multi-shaft screw extruder 2, the gate element 41 of the metering device 38 is transferred from the discharge position to the discharge position, so that the plastic waste material melt Sw flows from the inlet channel 44 through the through-channel 45 into the discharge channel 46. The flow resistance in the discharge channel 46 can be adjusted by means of the throttle element 48, which in turn adjusts the residence time of the plastic waste material melt Sw in the first multi-shaft screw extruder 2. With a longer residence time of the plastic waste material melt Sw in the first multi-shaft screw extruder 2, a longer and more intensive mixing and homogenization of the plastic waste material melt Sw takes place, which has a positive effect on the viscosity and quality of the plastic waste material melt Sw.

[0060] The plastic waste melt Sw is pumped through the filter device 52 by the melt pump 51 and filtered therein. The pressure p2 of the plastic waste melt Sw upstream of the filter element is monitored by the second pressure sensor 53', so that a filter element replacement can be initiated if it becomes contaminated. Furthermore, the temperature T2 of the plastic waste melt Sw is monitored by the second temperature sensor 56'.

[0061] In the measuring range M, various parameters are measured by means of sensors 57, 58, 59. The measured parameters include, in particular, the pressure ps, the temperature T3, and the viscosity p of the plastic waste material melt Sw. The measured parameters are fed to the control device 60 via the signal connection. The control device 60 determines a quality measure Q for the plastic waste material melt Sw as a function of at least one parameter of the plastic waste material melt Sw. The quality measure Q is assigned to one of several quality classes Qi, Q2, Q3 by means of the control device 60. The first feed device 25, the throttle device 38, and / or the second feed device 55 are controlled by the control device 60 as a function of the determined quality measure Q.The quality class Qi indicates a high quality, the quality class Q2 a medium quality and the quality class Q3 a low quality of the plastic waste material melt Sw.

[0062] For example, the quality measure Q is the measured viscosity p of the plastic waste material melt Sw. If necessary, the measured values ​​can be processed by the control device 60, for example by suppressing noise through signal processing. If the viscosity p is within a predefined range, the quality class Qi is present. If, on the other hand, the viscosity p is outside the predefined range, the quality class Q2 or Q3 is present. The quality class Q3 is present, for example, if the quality measure Q or the viscosity p is outside a predefined usability range of the plastic waste material melt Sw. The assessment of the quality of the plastic waste material melt Sw depends in particular on the predefined requirements for the plastic material melt S.

[0063] If the control device 60 determines a quality measure Q corresponding to the quality class Qi, the control device 60 controls the drive 64 such that the switching element 63 is moved to the first switching position. In the first display position, the plastic waste material melt Sw is fed to the second multi-shaft screw machine 3.

[0064] If the control device 60 determines a quality measure Q associated with the quality class Q2, the throttle device 38 is controlled by the control device 60 in such a way that the flow resistance and thus the residence time of the plastic waste material melt Sw in the first multi-shaft screw extruder 2 increases. Furthermore, the first feed device 25 is controlled by the control device 60 in such a way that the quality of the plastic waste material melt Sw increases through the supply of plastic raw material Mv and / or at least one additive A. The drive 64 of the second feed device 55 is controlled by the control device 60 in such a way that the switching element 63 is moved into the second switching position.In the second switching position, the plastic waste material melt Sw is fed via the pipeline 73 to the granulating device 74, which produces a granulate of low quality from the plastic waste material melt Sw, which can, however, still be further processed.

[0065] If the control device 60 determines a quality measure Q corresponding to quality class Q3, the throttle device 38 and the first feed device 25 are controlled such that the quality of the plastic waste melt Sw increases. This control has already been described in connection with quality class Q2. Furthermore, the drive 64 of the second feed device 55 is controlled by the control device 60 such that the switching element 63 is shifted to the third switching position. In the third switching position, the plastic waste melt Sw is discharged into the environment and disposed of, since further processing is not possible. Parallel to the production of the plastic waste melt Sw by means of the first multi-shaft screw extruder 2, a plastic raw material melt Sv is produced by means of the second multi-shaft screw extruder 3.The second multi-shaft screw extruder 3 is fed with plastic raw material Mv and, optionally, at least one additive A via the first feed opening 93 by means of the dosing devices 91, 92. The plastic raw material Mv is fed in particular as bulk material, in particular as powder and / or granules. The plastic raw material Mv and the at least one additive A are melted and mixed in the melting zone 87 to form a plastic raw material melt Sv. Alternatively, a plastic raw material melt Sv can already be fed via the first feed opening 93.

[0066] In the second feed zone 88, the plastic raw material melt Sv is fed to the plastic waste material melt Sw via the pipeline 70 and the second feed opening 95. In the homogenization zone

[0067] 89, the plastic raw material melt Sv and the plastic waste material melt Sw are mixed and homogenized together and degassed via the degassing openings 96 by means of the degassing devices 97. The housing 75 is heated by means of the heating devices 99. The resulting plastic material melt S is discharged into the discharge zone

[0068] 90 is discharged through the discharge opening and fed to the granulating device 98. The granulating device 98 produces high-quality granules from the plastic material melt S, which can be further processed.

[0069] The plastic waste material Mw has a proportion mw of the plastic material melt S, where: 5 wt.% < mw < 50 wt.%, in particular 10 wt.% < mw < 45 wt.%, in particular 15 wt.% < mw < 40 wt.%, and in particular 20 wt.% < mw < 35 wt.%.

[0070] By feeding a plastic waste melt Sw to the second multi-shaft screw extruder 3, the recycling of plastic waste Mw is simple and energy-efficient. Measuring and assessing the quality of the plastic waste melt Sw and controlling the recycling plant 1 based on the determined quality also ensures flexible and qualitatively reliable recycling of plastic waste Mw. The quality measurement and / or quality assessment are performed online, i.e., during operation of the recycling plant 1. The first screw extruder 2 can also be retrofitted. The quality measurement and quality assessment prevent an existing second multi-shaft screw extruder 3 from being subjected to increased loads due to the plastic waste melt Sw.For example, colorant can be fed into the second multi-shaft screw machine 3 via the first screw machine 2, so that the second multi-shaft screw machine 3 is hardly contaminated by the colorant.

[0071] The reprocessing plant 1 has, in particular, a throughput of plastic material melt S of at least 10 t / h, in particular of at least 20 t / h and of at most 150 t / h, of which at least 5%, in particular at least 10%, is a recycled content.

Claims

Patent claims 1. Method for the reprocessing of plastic waste material, in particular polyolefin waste material, comprising the following steps: - Providing a first screw machine (2), in particular a first multi-shaft screw machine, and a second multi-shaft screw machine (3), - Feeding plastic waste material (Mw) into the first screw machine (2) and melting the plastic waste material (Mw) by means of the first screw machine (2) to a plastic waste material melt (Sw), - Feeding plastic raw material (Mv) into the second multi-screw machine (3) and processing the plastic raw material (Mv) by means of the second multi-screw machine (3) to a plastic raw material melt (Sv), - Feeding the plastic waste material melt (Sw) into the second multi-screw machine (3), and - Mixing the plastic raw material melt (Sv) and the plastic waste material melt (Sw) using the second multi-shaft screw machine (3) to form a plastic material melt (S).

2. Method according to claim 1, characterized in that the plastic waste material melt (Sw) is filtered by means of a filter device (52) before being fed into the second multi-shaft screw machine (3).

3. Method according to claim 1 or 2, characterized in that, that at least one parameter (pi, p2, ps, Ti, T2, T3, r|) of the plastic waste material melt (Sw) is determined by means of at least one sensor (53, 53 56, 56', 57, 58, 59).

4. Method according to claim 3, characterized in that, depending on the determined at least one parameter (pi, P2, p3, Ti, T2, T3, r|) of the plastic waste material melt (Sw), a quality measure (Q) for the plastic waste material melt (Sw) is determined by means of a control device (60).

5. Method according to claim 3 or 4, characterized in that, depending on the at least one parameter (pi, p2, p3, Ti, T2, T3, r|) and / or the determined quality measure (Q), at least one feeding device (25, 55) and / or a throttling device (38) is controlled.

6. Method according to at least one of claims 3 to 5, characterized in that, depending on the at least one parameter (pi, p2, p3, Ti, T2, T3, r|) and / or the determined quality measure (Q), a feeding device (55) for feeding the plastic waste material melt (Sw) is controlled such that - the plastic waste material melt (Sw) is fed to the second multi-screw machine (3) if at least one parameter (pi, p2, p3, Ti, T2, T3, r|) and / or the determined quality measure (Q) lies within a predefined range (Qi), and - the plastic waste material melt (Sw) is not fed to the second multi-screw machine (3) if at least one parameter (pi, p2, ps, Ti, T2, T3, r|) and / or the determined quality measure (Q) is outside the predefined range (Qi). Method according to at least one of claims 3 to 6, characterized in that, depending on the at least one parameter (pi, p2, p3, Ti, T2, T3, r|) and / or the determined quality measure (Q), a feeding device (25) for feeding plastic raw material (Mv) and / or for feeding at least one additive (A) is controlled such that plastic raw material (Mv) and / or at least one additive (A) is fed to the first screw machine (2) when the at least one parameter (pi, p2, p3, Ti, T2, T3, r|) and / or the determined quality measure (Q) lies outside a predefined range (Qi).A method according to at least one of the preceding claims, characterized in that the plastic waste material (Mw) has a proportion mw in the plastic material melt (S), wherein: 5 wt.% < mw < 50 wt.%, in particular 10 wt.% < mw < 45 wt.%, in particular 15 wt.% < mw < 40 wt.%, and in particular 20 wt.% < mw < 35 wt.%. A reprocessing plant for reprocessing plastic waste material, in particular polyolefin waste material, comprising. - a first screw machine (2), in particular a first multi-screw machine, for melting the plastic waste material (Mw) to a plastic waste material melt (Sw), - a second multi-shaft screw machine (3) with — a first feed opening (93) for feeding plastic raw material (Mv) and — a second feed opening (95) for feeding the plastic waste material melt (Sw), - a feeding device (55) for feeding the plastic waste material melt (Sw) into the second multi-screw machine (3). Reprocessing plant according to claim 9, characterized by a throttling device (38) for setting a residence time of the plastic waste material melt (Sw) in the first screw machine (2). Reprocessing plant according to claim 9 or 10, characterized by a filter device (52) for filtering the plastic waste material melt (Sw) before feeding it into the second multi-screw machine (3). Reprocessing plant according to at least one of claims 9 to 11, characterized by at least one sensor (53, 53', 56, 56', 57, 58, 59) for determining at least one parameter (pi, p2, ps, Ti, T2, T3, r|) of the plastic waste material melt (Sw). A reprocessing plant according to claim 12, characterized by a control device (60) for determining a quality measure (Q) for the plastic waste material melt (Sw) as a function of the determined at least one parameter (pi, p2, ps, Ti, T2, T3, r|) of the plastic waste material melt (Sw). A reprocessing plant according to at least one of claims 9 to 13, characterized in that the feeding device (55) for feeding the plastic waste material melt (Sw) comprises at least one switching element (63). A reprocessing plant according to at least one of claims 9 to 14, characterized by a feeding device (25) for feeding plastic raw material (Mv) and / or for feeding at least one additive (A) into the first screw machine (2).Reprocessing plant according to at least one of claims 9 to 15, characterized in that a control device (60) for controlling in signal connection with the feed device (55) for feeding the plastic waste material melt (Sw) and / or with a feed device (25) for feeding plastic raw material (Mv) and / or for feeding at least one additive (A) into the first screw machine (2) and / or with a throttling device (38).

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