Method and plant for recycling plastic waste

Abstract

Plastic waste (M W In a method for recycling plastic waste (M W ) is fed to a first screw machine (2) and melted there to produce a plastic waste melt (S W ) is formed. W ) is fed by a feeding device (55) to a second multi-axis screw machine (3) where it is mixed with plastic raw material (M V ) to form a plastic material melt (S).

Description

[Technical field]

[0001] This patent application claims the priority of DE 10 2022 201 398.0 A1, the content of which is incorporated herein by reference.

[0002] The present invention relates to a method and a recycling plant for recycling plastic waste, in particular polyolefin waste. [Background technology]

[0003] Patent document 1 discloses a method for producing a plastic product from recycled plastic material and non-recycled virgin plastic material. The product is produced using an extrusion plant. The base material of the plastic product is a polymeric raw material such as polyolefin. To produce the plastic product, granules of the recycled plastic material and granules of the non-recycled virgin plastic material are fed to the extrusion plant in a specific ratio. The extrusion plant produces, for example, a new composite or film as the plastic product from the fed granules. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] DE 10 2019 127 827 A1 [Patent Document 2] European Patent Application Publication No. 3 552 798 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to provide a method which allows the recycling of plastic waste, in particular polyolefin waste, which is simple, flexible, qualitatively reliable and energy efficient. [Means for solving the problem]

[0006] This object is achieved by a method having the features of claim 1. Firstly, the plastic waste to be treated, in particular the polyolefin waste to be treated, is fed to a first screw machine, in particular a first multi-shaft screw machine, where it is melted into a plastic waste melt. The plastic waste consists of chopped and / or washed or rinsed plastic products. The plastic waste is in particular present as bulk material, for example as flakes and / or pellets. In particular, the plastic waste has not yet been treated by a screw machine before being fed to the first screw machine. In particular, this plastic waste is not a plastic waste granulate, which has been produced by treating and granulating the plastic waste.

[0007] Preferably, the throttling device allows the residence time of the waste plastics melt in the first screw machine to be adjusted. In particular, the throttling device is arranged downstream of the first screw machine. The throttling device comprises at least one throttling element for adjusting the flow resistance of the waste plastics melt. For this purpose, the position of the at least one throttling element can be adjusted or changed. The higher the flow resistance, the longer the residence time and vice versa. By increasing the residence time, the waste plastics melt in the first screw machine is mixed and homogenized for a longer time and therefore more intensively, which has a positive effect on the quality of the waste plastics melt.

[0008] In parallel with the melting of the plastic waste material, the plastic raw material is fed to the second multi-screw machine and processed by the second multi-screw machine into a plastic raw material melt. The plastic raw material can be fed to the second multi-screw machine as a bulk material, e.g. powder and / or granules, or already as a melt. If the plastic raw material is fed as a bulk material, the processing includes melting of the plastic raw material. On the other hand, if the plastic raw material is fed already as a melt, the processing includes conveying and associated mixing of the plastic raw material melt. In addition, at least one additive can be fed to the second multi-screw machine.

[0009] The plastic waste melt is also fed to a second multi-shaft screw machine. Preferably, the plastic waste is fed to the second multi-shaft screw machine downstream of the feed of the plastic raw material in the conveying direction. In particular, the plastic waste melt is fed to the plastic raw material melt. The plastic raw material melt and the plastic waste melt are then mixed or homogenized by the second multi-shaft screw machine to form a plastic material melt. The plastic material melt is then discharged from the second multi-shaft screw machine. The discharged plastic material melt is either processed directly into a plastic product or fed to a pelletizing device, which produces plastic pellets or polyolefin pellets from the plastic material melt.

[0010] The method is simple and energy-efficient, since the plastic waste is melted by a first screw machine, and then the plastic waste melt is fed to a second multi-shaft screw machine without an intermediate pelletizing step, and processed by mixing with the plastic raw material melt by the second multi-shaft screw machine. The ratio of the plastic waste to the plastic raw material can be flexibly adjusted according to the initial quality of the plastic waste, so that the quality of the plastic material melt can be reliably guaranteed.

[0011] The method according to claim 2 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. The plastic waste melt is filtered by a filtering device before being fed to the second multi-screw machine, so that contaminants and / or agglomerates are not mixed with the plastic raw material melt. This improves the quality of the plastic material melt. The filtering device preferably comprises at least two filtering elements. Alternatively, the filtering device comprises at least one filtering element with continuous cleaning and / or backwashing capabilities. This allows cleaning and / or replacing at least one filtering element during operation. Preferably, the filtering device is designed as a screen-replaceable device.

[0012] The method according to claim 3 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. Preferably, the at least one determined parameter characterizes at least one quality property of the plastic waste melt. This makes it possible to determine a quality index for the plastic waste melt. In particular, the determined at least one parameter is transmitted to a control device. In particular, by means of at least one sensor the pressure, temperature and / or viscosity of the plastic waste melt are determined. Preferably, the pressure, temperature and / or viscosity of the plastic waste melt are measured by at least one sensor immediately downstream of the first screw machine and / or immediately upstream of the filtering device and / or downstream of the filtering device. The measurement immediately downstream of the first screw machine provides information on the flow properties of the uncleaned plastic waste melt. The measurement immediately upstream of the filtering device provides information on the pressure rise as a function of time and / or on the degree of contamination of the plastic waste melt as a function of the filtering accuracy of the filtering device. The filtering accuracy of the at least one filtering element is selected depending on the required quality of the plastic material melt. Measurements downstream of the filtering device, in particular viscosity measurements or online viscosity measurements, provide information about the flow properties of the filtered plastic waste melt and the expected viscosity of the plastic material melt. In particular the viscosity can be adjusted by setting the residence time of the plastic waste melt in the first screw machine and / or by adding plastic raw material to the first screw machine.

[0013] The method according to claim 4 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. Based on the quality indicators 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 indicators or quality classes. In particular, an inadequate quality of the plastic waste melt can be immediately responded to, for example by activating a feed device and / or a throttling device. In the simplest case, the quality indicator is at least one parameter. The measured value of the at least one parameter can be signal processed by the control device. The quality indicator is, for example, the measured viscosity of the plastic waste melt downstream of the filtering device.

[0014] The method according to claim 5 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. The at least one feeding device and / or throttling device can be operated depending on the at least one determined parameter or the determined quality indicator, thereby providing an immediate response to an inadequate quality or an inadequate quality indicator of the plastic waste melt. The at least one feeding device prevents the feeding of the plastic waste melt to the second multi-shaft screw machine, for example, if the determined quality indicator is outside a predefined range. Furthermore, the at least one feeding device feeds, for example, plastic raw materials and / or at least one additive to the first screw machine in order to increase the quality indicator. The throttling device increases, for example, the flow resistance of the plastic waste melt, which extends the residence time of the plastic waste melt in the first screw machine, resulting in a longer and more intense mixing or homogenization and thus an improved quality.

[0015] The method according to claim 6 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. The plastic waste melt is fed to the second multi-screw machine by a feeding device. The feeding device for feeding the plastic waste melt comprises in particular at least one switching element which can be switched between a first switching position and a second switching position. The switching is in particular controlled by a control device. Preferably, the feeding device comprises a drive for actuating the switching element.

[0016] In the first switching position, the waste plastics melt is fed to the second multi-shaft screw machine. The first switching position is set when the determined quality indicator is within a predefined range. In the second switching position, the waste plastics melt is not fed to the second multi-shaft screw machine. The second switching position is set when the determined quality indicator is outside of a predefined range. In the second switching position, the waste plastics melt can for example be fed to a pelletizing device which pelletizes the waste plastics melt into pellets. The pellets can be further processed, although they are of relatively low quality. The feeding device for feeding the waste plastics melt is activated depending on the determined quality indicator, such that the waste plastics melt is fed to the second multi-shaft screw machine only if it is of sufficient quality.

[0017] The method according to claim 7 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. In order to increase the quality of the plastic waste melt, the first screw machine can be fed with a plastic raw material and / or at least one additive by means of a feeding device. By feeding the plastic raw material and / or the at least one additive, the quality of the plastic waste melt is increased and, as a result, the determined quality indicator is improved. If the quality indicator returns to the predefined range, the plastic waste melt can be fed again to the second multi-shaft screw machine, in particular by switching a switching element.

[0018] The method according to claim 8 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. Due to the high quality of the plastic waste melt and / or the quality of the plastic waste melt being monitored, a high ratio m W of plastic waste can be recycled. In particular, at a ratio of m W defines the average weight fraction of the plastic material melt exiting the second multi-screw machine.

[0019] Another object of the present invention is to provide a recycling plant that allows the recycling of plastic waste, in particular polyolefin waste, which is simple, flexible, qualitatively reliable and energy efficient.

[0020] 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 mentioned advantages of the method according to the invention for recycling plastic waste, in particular polyolefin waste. In particular, the recycling plant can be further embodied with at least one feature as mentioned in relation to the method according to the invention. Correspondingly, the method according to the invention can be further embodied with at least one feature as mentioned in relation to the recycling plant according to the invention.

[0021] In particular, the first screw machine comprises at least one processing element shaft. Preferably, the first screw machine is designed as a multi-shaft screw machine. In particular, the first multi-shaft screw machine comprises at least two processing element shafts, which are designed to rotate in the same direction and / or to be positively intermeshed. Preferably, the first multi-shaft screw machine is designed as a twin-shaft screw machine rotating in the same direction. In particular, the first screw machine comprises an intake zone, a melting zone, a degassing zone and a discharge zone. In particular, the first screw machine comprises at least one feed opening for feeding the plastic waste and / or for feeding the plastic raw material and / or for feeding at least one additive. Preferably, the first screw machine comprises a first feed opening for feeding the plastic waste and a second feed opening for feeding the plastic raw material and / or the at least one additive. To feed the plastic waste, the recycling plant comprises in particular a feed screw machine opening into the first feed opening.

[0022] In particular, the second multi-screw machine comprises at least two processing element shafts, which are designed to rotate in the same direction and / or to be positively intermeshed. Preferably, the second multi-screw machine is designed as a twin-screw machine rotating in the same direction. In particular, the second multi-screw machine comprises a first intake zone with a first feed opening, a melting zone, a second intake zone with a second feed opening, a homogenization zone and a discharge zone.

[0023] In particular, the first screw machine may be retrofitted to an existing second multi-screw machine.

[0024] The recycling plant according to claim 10 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. In particular, the throttling device is arranged downstream of the first screw machine and allows for the adjustment of the residence time of the plastic waste melt in the first screw machine. The throttling device comprises at least one throttling element for adjusting the flow resistance of the plastic waste melt. For this purpose, the position of the at least one throttling element can be adjusted or changed. The higher the flow resistance, the longer the residence time and vice versa. By increasing the residence time, the plastic waste melt in the first screw machine is mixed and homogenized for a longer time and therefore more intensively, which has a positive effect on the quality of the plastic waste melt.

[0025] The recycling plant according to claim 11 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. In particular, the filtering device comprises at least two filtering elements. Alternatively, the filtering device comprises at least one filtering element with continuous cleaning and / or backwashing function. This makes it possible to clean and / or replace at least one filtering element during operation. The filtering device is designed in particular as a screen-replacement device. In particular, the filtering device is arranged between the first screw machine and the second multi-shaft screw machine.

[0026] The recycling plant according to claim 12 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. The at least one determined parameter characterizes in particular a quality property of the plastic waste melt. Determining the at least one parameter of the plastic waste melt makes it possible in particular to determine a quality indicator. In particular, the at least one sensor is in signal connection with the 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 the pressure of the plastic waste melt, a temperature sensor for measuring the temperature of the plastic waste melt and / or a viscosity sensor for measuring the viscosity of the plastic waste melt. In particular, the at least one sensor is arranged immediately downstream of the first screw machine and / or immediately upstream of the filtering device and / or downstream of the filtering device. In particular, at least one sensor is used to measure the pressure, temperature and / or viscosity of the plastic waste melt immediately downstream of the first screw machine and / or immediately upstream of the filtering device and / or downstream of the filtering device. The measurement immediately downstream of the first screw machine provides information about the flow properties of the uncleaned plastic waste melt. Measurements immediately upstream of the filtering device provide information on the pressure rise as a function of time and / or on the degree of contamination of the plastic waste melt as a function of the filtering quality of the filtering device. The filtering quality of the at least one filtering element is selected depending on the required quality of the plastic material melt. Measurements downstream of the filtering device, in particular viscosity measurements or online viscosity measurements, provide information on the flow properties of the filtered plastic waste melt and the expected viscosity of the plastic material melt. In particular the viscosity can be adjusted by setting the residence time of the plastic waste melt in the first screw machine and / or by adding plastic raw material to the first screw machine.

[0027] The recycling plant according to claim 13 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. The control device makes it possible to determine a quality indicator for assessing the quality of the plastic waste melt. Furthermore, the control device makes it possible to operate at least one feeding device and / or throttling device depending on the determined at least one parameter and / or depending on the determined quality indicator.

[0028] The recycling plant according to claim 14 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. Due to the inclusion of at least one switching element in the feeding device, the feeding device or the at least one switching element can be switched between at least a first switching position and a second switching position. In the first switching position, the feeding device forms a first channel, which is connected to a second feeding opening and opens into the second multi-shaft screw machine. Thus, the plastic waste melt is fed into the second multi-shaft screw machine in the first switching position. In the second switching position, the feeding device forms a second channel, which does not open into the second multi-shaft screw machine. The second channel leads, for example, to a pelletizing device. The feeding device is designed, for example, as a diverter valve and / or a valve.

[0029] The recycling plant according to claim 15 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. The feeding device allows the feeding of the plastic raw material to the first screw machine and / or the feeding of at least one additive, which can influence the quality and / or the color of the plastic waste melt. In particular, the feeding device comprises at least one dosing unit. The at least one dosing unit is, for example, designed volumetrically and / or gravimetrically. The at least one additive comprises, for example, powdered carbon black (FCB), color pigments, peroxides, UV stabilizers and / or antioxidants.

[0030] The recycling plant according to claim 16 ensures a simple, flexible, qualitatively reliable and energy-efficient recycling. In particular, the operation is performed depending on at least one parameter of the waste melt and / or the determined quality indicator of the waste plastic melt. The control device is in signal connection with a feed device for feeding the waste plastic melt to the second multi-shaft screw machine, so that the feed device can be operated in such a way that the waste plastic melt is fed to the second multi-shaft screw machine if the waste plastic melt is of sufficient quality and that the waste plastic melt is not fed to the second multi-shaft screw machine if the waste plastic melt is not of sufficient quality. The control device is in signal connection with a feed device for feeding the first screw machine with a plastic raw material and / or with at least one additive, so that the plastic raw material and / or at least one additive can be fed to the first screw machine if the quality of the waste plastic melt is insufficient, thereby improving the quality of the waste plastic melt. The control device is in signal connection with a throttling device, so that the residence time of the waste plastic melt in the first screw machine can be set. By increasing the residence time, the plastic waste melt in the first screw machine is mixed and homogenized for a longer period and therefore more intensively, which has a positive effect on the quality of the plastic waste melt.

[0031] Further features, advantages and details of the invention are set forth in the following description of exemplary embodiments. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a schematic diagram of a recycling plant for recycling plastic waste, in particular polyolefin waste, comprising a first multi-screw machine for melting the plastic waste to form a plastic waste melt and a second multi-screw machine for mixing the plastic waste melt with a plastic raw material melt. [Diagram 2]FIG. 1 is a side view of a first multi-screw machine. [Diagram 3] FIG. 3 is a partial cross-sectional plan view of the first multi-axis screw machine in FIG. 2. [Figure 4] FIG. 1 is a cross-sectional view of a squeezing device of a recycling plant. [Diagram 5] FIG. 2 is a side view of a second multi-screw machine. [Figure 6] FIG. 6 is a partial cross-sectional plan view of the second multi-screw machine of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] Plastic waste material M W The recycling plant 1, in particular for recycling polyolefin waste, comprises a first screw machine 2 and a second multi-screw machine 3. The screw machine 2 is designed as a multi-screw machine. Alternatively, the screw machine 2 can also be designed as a single-screw machine.

[0034] The first multi-axis screw machine 2 is a machine for processing plastic waste material M W The plastic waste melt S W , in particular for the melting of polyolefin waste materials. The first multi-screw machine 2 is designed as a twin-screw machine. It has a housing 4, which comprises a number of housing parts arranged in series and fixed to one another. In the housing 4, two housing bores 5, 6 are formed, which interpenetrate each other and have a horizontal "8" cross-sectional shape. In the housing bores 5, 6, two positively intermeshing processing element shafts 7, 8 are arranged and can be driven in rotation about associated rotation axes 9, 10. The processing element shafts 7, 8 are driven in the same rotation direction by a drive motor 13 via a transmission gear 11 and a coupling 12.

[0035] The first multi-screw machine 2 has, in succession along the conveying direction 14 , an intake zone 15 , a melting zone 16 , a degassing zone 17 and a discharge zone 18 .

[0036] In the suction area 15, a first feed opening 19 is formed laterally in the housing 4. The first feed opening 19 allows the plastic waste material M W Used to supply plastic raw materials M V A second feed opening 20 is formed in the housing 4 in the suction zone 15 for feeding the first feed opening 19 and / or for feeding the at least one additive A. The second feed opening 20 is formed upstream of the first feed opening 19. A funnel 21 is connected to the second feed opening 20. In the suction zone 15, the processing element shafts 7, 8 have screw elements.

[0037] The melting zone 16 is a melting zone for melting plastic waste material M W and / or plastic raw material M V and optionally melting or mixing additive A. In the melting zone 16, the processing element shafts 7, 8 comprise screw elements and / or kneading elements.

[0038] The degassing section 17 is for removing the generated plastic waste melt S W In the degassing section 17, a degassing opening 22 is formed in the housing 4, to which a degassing device 23 is connected. In the degassing section 17, the processing element shafts 7, 8 have screw elements and / or kneading elements.

[0039] The discharge section 18 receives the plastic waste melt S from the first multi-screw machine 2 through a discharge opening. W In the discharge section 18 the processing element shafts 7, 8 have screw elements.

[0040] For heating the housing 4 , the first multi-screw machine 2 comprises a heating device 24 , which is connected to the housing 4 in the suction zone 15 , the melting zone 16 , the degassing zone 17 and the discharge zone 18 .

[0041] The recycling plant 1 comprises a first feeding device 25, which is associated with a first multi-shaft screw machine 2. The first feeding device 25 comprises a two-shaft feeding screw machine 26. The feeding screw machine 26 is designed as a side-feed machine. The feeding screw machine 26 is connected to a side of the housing 4 and opens into a first feeding opening 19.

[0042] The feed screw machine 26 includes a housing 27 having housing bores 28, 29 in which screw shafts 30, 31 are arranged to be driven in the same rotational direction. The screw shafts 30, 31 are driven in the same direction, i.e. in the same rotational direction, about associated rotation axes by a drive motor 33 via a transmission gear 32. A feed opening 34 is formed in the housing 27, the feed opening 34 opens into the housing bores 28, 29, and a hopper 35 is connected to the feed opening 34. The feed screw machine 26 feeds the plastic waste material M W Used to supply

[0043] The first supply device 25 supplies the plastic raw material M V and a second dosing unit 37 for supplying at least one additive A to the first multi-screw machine 2 through the second feed opening 20. The dosing units 36, 37 are, for example, designed gravimetrically.

[0044] The recycling plant 1 comprises a throttling device 38, which is arranged downstream of the first multi-screw machine 2 with respect to the conveying direction 14. The throttling device 38 is mounted in the housing 4. The throttling device 38 is designed as a start-up valve throttling device. The plastic waste melt S immediately downstream of the first multi-screw machine 2 is W a first pressure sensor 53 for measuring the pressure p1 of the plastic waste melt S immediately downstream of the first multi-shaft screw machine 2; WA first temperature sensor 56 for measuring the temperature T1 of the first multi-screw machine 2 is arranged between the first multi-screw machine 2 and the throttling device 38.

[0045] The throttling device 38 comprises a housing 39 in which a cylindrical housing recess 40 is formed. A suitably cylindrical switching element 41 is arranged in the housing recess 40 and can be pivoted about a pivot axis 43 in the housing recess 40 by a drive 42. The housing 39 is formed with an inlet channel 44 connecting the housing bores 5, 6 to the housing recess 40. The switching element 41 forms a through channel 45 which connects the inlet channel 44 to a discharge channel 46 in the discharge position shown in FIG. 4. The switching element 41 further forms a discharge channel 47 which connects the inlet channel 44 to the surrounding environment in the discharge position. To switch between the discharge position and the discharge position, the switching element 41 can be pivoted about the pivot axis 43 by the drive 42.

[0046] A throttling element 48 is arranged in the discharge channel 46, which can be pivoted about a pivot axis 50 by a drive 49. In FIG. 4, only the drive shaft of the drive 49 can be seen. In the discharge position, the throttling element 48 is arranged to direct the plastic waste melt S in the first multi-shaft screw machine 2. W The throttling device 38 may also be designed according to the start-up valve throttling device described in US Pat. No. 5,399,633, the disclosure of which is incorporated herein by reference.

[0047] The recycling plant 1 comprises a melt pump 51, which is arranged downstream of the throttling 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 pumps the plastic waste melt S W It is used to increase the pressure.

[0048] Furthermore, the recycling plant 1 comprises a filtering device 52, which is arranged downstream of the melt pump 51 with respect to the conveying direction 14. The filtering device 52 comprises at least two filtering elements. The filtering device 52 is designed, for example, as a screen-changing device. The filtering device 52 comprises a second pressure sensor 53', which detects the pressure of the plastic waste melt S upstream of the filtering device 52. W Furthermore, the filtering device 52 includes a second temperature sensor 56', which measures the pressure p2 of the plastic waste melt S upstream of the filtering device 52. W The temperature T2 is measured.

[0049] The filtering device 52 is connected via a pipe 54 to a second supply device 55. In the pipe 54, a measuring area M is formed, in which the plastic waste melt S W Various parameters of the melt are determined or measured by sensors 57, 58, 59. The third pressure sensor 57 measures the pressure of the plastic waste melt S downstream of the filtering device 52. W The third temperature sensor 58 is used to determine or measure the pressure p3 of the plastic waste melt S W The temperature T3 of the liquid is determined or measured. Furthermore, the viscosity η is determined or measured by the viscosity sensor 59.

[0050] The recycling plant 1 includes a control device 60. The sensors 53, 53', 56, 56', 57, 58, 59 are in signal connection with the control device 60.

[0051] The second supply 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 the switching element 63 can be displaced within the housing recess 62 by a drive 64. An inlet channel 65 is formed in the housing 61, the inlet channel 65 being connected to the pipe 54. Furthermore, a first discharge channel 66, a discharge channel 67 and a second discharge channel 68 are formed in the housing 61.

[0052] 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 a first discharge channel 66. The first switching position is shown in Figure 1. The first discharge channel 66 is connected via a pipe 70 to the second multi-axis screw machine 3.

[0053] Furthermore, the switching element 63 comprises a second through-channel 71, which in the second switching position connects the inlet channel 65 to a second discharge channel 68. The second discharge channel 68 is connected via a pipe 73 to a first pelletizing device 74. The first pelletizing device 74 is designed, for example, as an underwater pelletizing device. The switching element 63 further comprises a third through-channel 72, which in the third switching position connects the inlet channel 65 to a discharge channel 67. The discharge channel 67 opens to the environment.

[0054] The second supply device 55 supplies the plastic raw material M V and a second dosing unit 92 for supplying at least one additive A to the second multi-screw machine 3. The dosing units 91, 92 are, for example, designed gravimetrically.

[0055] The second multi-screw machine 3 is designed as a twin-screw machine. It has a housing 75, which comprises a number of housing parts arranged in series and fixed to one another. Two housing bores 76, 77 are formed in the housing 75, which interpenetrate each other and have a horizontal "8" cross-sectional shape. Two processing element shafts 78, 79 are arranged in the housing bores 76, 77, which are positively intermeshed and can be driven in the same rotational direction around associated rotation axes 80, 81. The processing element shafts 78, 79 are driven in rotation in the same direction, i.e. in the same rotational direction, by a drive motor 84 via a transmission gear 82 and a coupling 83.

[0056] The second multi-screw machine 3 comprises, in sequence in the conveying direction 85 , a first suction zone 86 , a melting zone 87 , a second suction zone 88 , a homogenization zone 89 and a discharge zone 90 .

[0057] In the first suction area 86, a first supply opening 93 is formed in the housing 75. A hopper 94 is connected to the first supply opening 93. The first supply opening 93 opens into the housing bores 76, 77 and supplies the plastic raw material M. V and / or is used to supply at least one additive A. The dosing units 91, 92 open into a hopper 94. In the first suction zone 86, the processing element shafts 78, 79 comprise screw elements.

[0058] The melting zone 87 is a melting zone for melting plastic raw material M V and optionally used to melt Additive A. In the melting section 87, the processing element shafts 78, 79 include screw elements and / or kneading elements.

[0059] In the second suction area 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 allows the plastic waste melt S W The pipe 70 is connected to a second feed opening 95. In the second suction section 88, the processing element shafts 78, 79 include screw elements.

[0060] The homogenization section 89 is a section for homogenizing the plastic raw material melt S V and plastic waste melt S W and degassing 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 section 89 the processing element shafts 78, 79 comprise screw elements and / or kneading elements.

[0061] The discharge section 90 is used for discharging the plastic material melt S through a discharge opening of the second multi-screw machine 3. In the discharge section 90 the processing element shafts 78, 79 comprise screw elements.

[0062] To heat the housing 75 , the second multi-screw machine 3 includes a heating device 99 that is connected to the housing 75 in the melting zone 87 , the second suction zone 88 , the homogenization zone 89 and the discharge zone 90 .

[0063] The recycling plant 1 comprises a second pelletizing device 98 for pelletizing the plastic material melt S. The second pelletizing device 98 is arranged downstream of the second multi-shaft screw machine 3 and connected to the discharge opening. The second pelletizing device 98 is used to produce pellets from the plastic material melt S. The second pelletizing device 98 is, for example, designed as an underwater pelletizing device.

[0064] The multi-screw machines 2, 3, the feed devices 25, 55 and the throttling device 38 are in signal connection with a control device 60 for operation purposes.

[0065] The function principle of the recycling plant 1 and the plastic waste M W Here's how to recycle it:

[0066] Plastic waste material M W is fed to the first multi-screw machine 2 by a first feeding device 25. For this purpose, plastic waste material M W is fed to the feed screw machine 26 through the feed opening 34, and the feed screw machine 26 feeds the plastic waste material M W is conveyed through the first feed opening 19 into the housing bores 5, 6 of the first multi-axis screw machine 2. W is generated from washed and / or shredded plastic products. Wis present especially as chips and / or pellets. W is degassed and compressed in the feed screw machine 26.

[0067] If necessary, the dosing unit 36 ​​feeds the plastic raw material M to the first multi-screw machine 2 through the second feed opening 20. V and / or at least one additive A can be provided by the dosing unit 37.

[0068] In the melting zone 16, plastic waste material M W And plastic raw material M as necessary V Or at least one additive A is melted and mixed. A heating device 24 is used to heat the housing 4 to assist the melting process. The resulting plastic waste melt S W is homogenized and degassed in the degassing section 17. The plastic waste melt S W is discharged from the first multi-screw machine 2 through the discharge section 18 and the associated discharge openings. W The pressure p1 and temperature T1 are monitored.

[0069] After the first multi-shaft screw machine 2 is started, the switching element 41 of the dosing device 38 is moved from the discharge position to the discharge position, whereby the plastic waste melt S W 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 a throttle element 48, so that the plastic waste melt S in the first multi-shaft screw machine 2 W The residence time of the plastic waste melt S in the first multi-shaft screw machine 2 can be set. W The longer the residence time of the plastic waste melt S W The mixing and homogenization of the plastic waste melt S is carried out longer or more intensively. WThis has a positive effect on the viscosity or quality of the product.

[0070] Plastic waste melting material S W is conveyed by the melt pump 51 through the filtering device 52 where it is filtered. W A second pressure sensor 53' is used to monitor the pressure p2 of the plastic waste melt S, and the filter element can be replaced if it becomes contaminated. W The temperature T2 of the second temperature sensor 56' is monitored.

[0071] In the measuring area M, various parameters are measured using sensors 57, 58, 59. The measured parameters include, in particular, the amount of the plastic waste melt S W The measured parameters include the pressure p3, the temperature T3 and the viscosity η of the mixture. The measured parameters are provided to the control device 60 via signal connections.

[0072] The control device 60 controls the plastic waste melt S W Depending on at least one parameter of the plastic waste melt S W The quality index Q is assigned by the control device 60 to one of a number of quality classes Q1, Q2, Q3. Depending on the determined quality index Q, the first supply device 25, the throttling device 38 and / or the second supply device 55 are activated by the control device 60. The quality class Q1 is a quality class that is assigned by the control device 60 to a quality class Q1, Q2, Q3 for the plastic waste melt S. W quality class Q1 characterizes high quality, quality class Q2 characterizes medium quality, and quality class Q3 characterizes low quality.

[0073] For example, the quality index Q is the melting point of plastic waste S Wis the measured viscosity η of the plastic waste melt S. If necessary, the measured values ​​can be processed by the control device 60, for example by suppressing noise by signal processing. If the viscosity η is within a predefined range, a quality class Q1 is provided. On the other hand, if the viscosity η is outside the predefined range, a quality class Q2 or Q3 is provided. For example, if the quality index Q or the viscosity η of the plastic waste melt S W If the melted plastic is outside the specified usable range, it is given quality class Q3. W The assessment of the quality of depends in particular on the given requirements for the plastic material melt S.

[0074] If the control device 60 determines a quality indicator Q that is associated with a quality class Q1, the control device 60 activates the drive 64 such that the switching element 63 is moved to a first switching position. In the first switching position, the plastic waste melt S W is fed into a second multi-screw machine 3.

[0075] If the control device 60 determines a quality index Q associated with a quality class Q2, the plastic waste melt S in the first multi-shaft screw machine 2 is W The throttling device 38 is operated by the control device 60 so that the flow resistance of the plastic raw material M increases and thus the residence time increases. V and / or by the addition of at least one additive A to the plastic waste melt S W The first supply device 25 is actuated by the control device 60 such that the quality of the waste plastic melt S is increased. The drive 64 of the second supply device 55 is actuated by the control device 60 such that the switching element 63 is moved to the second switching position. In the second switching position, the waste plastic melt S W is fed through a pipe 73 to a pelletizing device 74, which pelletizes the plastic waste melt S W This produces low quality pellets which can be further processed.

[0076] If the control device 60 determines a quality indicator Q associated with the quality class Q3, the plastic waste melt S W The throttling device 38 and the first supply device 25 are activated in such a way that the quality of the plastic waste melt S is increased. This activation has already been described in connection with the quality class Q2. Furthermore, the drive 64 of the second supply device 55 is activated by the control device 60 in such a way that the switching element 63 is moved to the third switching position. In the third switching position, no further processing is possible, so that the plastic waste melt S is not replenished. W is released into the environment and disposed of.

[0077] Plastic waste melt S by the first multi-screw machine 2 W In parallel with the production of the plastic raw material melt S by a second multi-screw machine 3 V Plastic raw material M V and optionally at least one additive A are fed to the second multi-screw machine 3 by dosing units 91, 92 through the first feed opening 93. V is supplied in particular as bulk material, in particular as powder and / or pellets. In the melting zone 87, the plastic raw material M V and at least one additive A is melted and mixed to obtain a plastic raw material melt S V Alternatively, the plastic raw material melt S V may already be dispensed through the first dispense opening 93.

[0078] In the second suction zone 88, the plastic raw material melt S V The plastic waste melt S is fed through the pipe 70 and the second feed opening 95. W In the homogenization section 89, the plastic raw material melt S V and plastic waste melt S Wand are mixed, homogenized by a degassing device 97 and degassed through a degassing opening 96. The housing 75 is heated by a heating device 99. The resulting plastic material melt S is discharged through a discharge opening in the discharge area 90 and fed to a pelletizing device 98. The pelletizing device 98 produces high quality pellets from the plastic material melt S, which can be further processed.

[0079] Plastic waste material M W is the ratio m of the plastic material melt S W and the following applies: 5% by weight≦m W ≦50% by weight, in particular 10% by weight≦m W ≦45% by weight, in particular 15% by weight≦m W ≦40% by weight and in particular 20% by weight≦m W ≦35% by weight.

[0080] Plastic waste melting material S W is fed to the second multi-shaft screw machine 3, whereby the plastic waste material M W Recycling of plastic waste melting is simple and energy efficient. W The system is flexible and qualitatively reliable, by measuring and evaluating the quality of the plastic waste material M and controlling the recycling plant 1 according to the determined quality. W The recycling of the plastic waste melt S is also ensured. The quality measurement and / or quality evaluation is carried out online, i.e. while the recycling plant 1 is in operation. The first screw machine 2 can also be retrofitted. The quality measurement and quality evaluation are carried out on the plastic waste melt S W This does not increase the load on the existing second multi-shaft screw machine 3 due to the first screw machine 2. For example, a colorant can be supplied to the second multi-shaft screw machine 3 through the first screw machine 2, and the second multi-shaft screw machine 3 is hardly contaminated by the colorant.

[0081] In particular, the recycling plant 1 has a throughput of at least 10 tonnes / hour, in particular at least 20 tonnes / hour and up to 150 tonnes / hour of plastic material melt S, of which at least 5%, in particular at least 10%, is recycled. [Explanation of symbols]

[0082] 1. Recycling Plant 2. The first screw machine 3. The second multi-screw machine 25, 55 Supply Device 38 Aperture Device 52 Filtration Devices 53, 53', 56, 56', 57, 58, 59 Sensors 55 Supply Device 60 Control Device 93 First supply opening 95 Second supply opening A Additive p1, p2, p3, T1, T2, T3, η parameter Q quality index Q1 Prescribed range S V Plastic raw material melt S W Plastic waste melting M V Plastic Raw Materials M W Plastic waste

Claims

1. A method for recycling plastic waste, particularly polyolefin waste, comprising: - providing a first screw machine (2) and a second multi-screw machine (3); - The first screw machine (2) is fed with plastic waste material (M Ｗ ) is fed, and the plastic waste material (M Ｗ ) is melted to produce a plastic waste melt (S Ｗ ) forming a - the second multi-screw machine (3) is fed with a plastic raw material (M Ｖ ) is supplied to the second multi-screw machine (3), and the plastic raw material (M Ｖ ) to produce a plastic raw material melt (S Ｖ ) forming a - the plastic waste melt (S Ｗ ) into the second multi-screw machine (3); - The second multi-screw machine (3) mixes the plastic raw material melt (S Ｖ ) and the plastic waste melt (S Ｗ ) to form a plastic material melt (S); A method comprising:

2. The melted plastic waste (S Ｗ 2. The method according to claim 1, characterized in that the raw material (1) is filtered by a filtering device (52) before being fed to the second multi-screw machine (3).

3. The melted plastic waste (S Ｗ ) at least one parameter (p １ , p ２ , p ３ , T １ , T ２ , T ３ , η) is determined by at least one sensor (53, 53′, 56, 56′, 57, 58, 59), or 2. The method according to claim 1, characterized in that at least one parameter (p 1 , p 2 , p 3 , T 1 , T 2 , T 3 , η) of the plastic waste melt (S W ) is determined by at least one sensor (53, 53', 56, 56', 57, 58, 59), and a quality index (Q) for the plastic waste melt (S W ) is determined by a control device (60) in response to the determined at least one parameter (p 1 , p 2 , p 3 , T 1 , T 2 , T 3 , η) of the plastic waste melt (S W ).

4. At least one supply device (25, 55) and / or throttle device (38) controls the at least one parameter (p １ , p ２ , p ３ , T １ , T ２ , T ３ 4. The method according to claim 3, characterized in that it is operated in dependence on the determined quality indicator (Q) and / or on the determined quality indicator (η).

5. The at least one parameter (p １ , p ２ , p ３ , T １ , T ２ , T ３ , η) and / or the plastic waste melt (S Ｗ a supply device (55) for supplying said at least one parameter (p １ , p ２ , p ３ , T １ , T ２ , T ３ , η) and / or the determined quality index (Q) is within a predetermined range (Q １ ), the plastic waste melt (S Ｗ ) is fed to the second multi-screw machine (3), and said at least one parameter (p １ , p ２ , p ３ , T １ , T ２ , T ３ , η) and / or the determined quality index (Q) is within the predetermined range (Q １ ), the plastic waste melt (S Ｗ ) is not fed to the second multi-screw machine (3); 5. The method according to claim 3 or 4, characterized in that it is operated as follows:

6. The at least one parameter (p １ , p ２ , p ３ , T １ , T ２ , T ３ , η) and / or the plastic raw material (M Ｖ ) and / or the supply device (25) for supplying at least one additive (A) is adapted to adjust said at least one parameter (p １ , p ２ , p ３ , T １ , T ２ , T ３ , η) and / or the determined quality index (Q) is within a predetermined range (Q １ ), if it is outside the plastic raw material (M Ｖ 5. The method according to claim 3 or 4, characterized in that the first screw machine (2) is operated so that the first screw machine (2) is supplied with the additive (A) and / or at least one additive (B).

7. The plastic waste material (M Ｗ ) is the ratio m of the plastic material melt (S) Ｗ and 5 wt.%≦m Ｗ 5. The method according to claim 1, wherein the content of the hydroxybenzoates is ≦50% by weight.

8. A recycling plant for recycling plastic waste, comprising: - the plastic waste material (M Ｗ ) is melted to produce plastic waste melt (S Ｗ a first screw machine (2) for forming a a second multi-screw machine (3), -- Plastic raw materials (M Ｖ a first feed opening (93) for feeding -- The melted plastic waste (S Ｗ a second feed opening (95) for feeding the first multi-screw machine (3); - the plastic waste melt (S Ｗ a feeding device (55) for feeding the second multi-screw machine (3) with the raw material; Recycling plants, including:

9. The plastic waste melt (S) in the first screw machine (2) Ｗ 9. A recycling plant according to claim 8, characterized in that it has a throttle device (38) for adjusting the residence time of the wastewater.

10. The melted plastic waste (S Ｗ ) is fed to the second multi-screw machine (3), Ｗ 10. A recycling plant according to claim 8 or 9, characterized in that it comprises a filtering device (52) for filtering out the wastewater.

11. The melted plastic waste (S Ｗ ) at least one parameter (p １ , p ２ , p ３ , T １ , T ２ , T ３ η), or 10. A recycling plant as claimed in claim 8 or 9, characterized in that it has at least one sensor (53, 53', 56, 56', 57, 58, 59) for determining at least one parameter (p1, p2, p3, T1, T2, T3, η) of the plastic waste melt (S W ), and a control device (60) for determining a quality index (Q) for the plastic waste melt (S W ) depending on the determined at least one parameter (p1, p2, p3, T1, T2, T3, η) of the plastic waste melt (S W ).

12. The melted plastic waste (S Ｗ 12. The recycling plant according to claim 11, characterized in that the supply device (55) for supplying ) comprises at least one switching element (63).

13. The first screw machine (2) is fed with a plastic raw material (M Ｖ 10. A recycling plant according to claim 8 or 9, characterized in that it has a supply device (25) for supplying the wastewater treatment plant (10) and / or for supplying at least one additive (A).

14. A control device (60) for operating the plastic waste melt (S Ｗ ) to the feeding device (55) and / or the first screw machine (2) to feed the plastic raw material (M Ｖ 10. The recycling plant according to claim 8 or 9, characterized in that it is in signal connection with a supply device (25) for supplying the at least one additive (A) and / or a throttle device (38).

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