METHOD AND RECYCLING PLANT FOR RECYCLING PLASTIC WASTE MATERIAL

Abstract

In a method for recycling plastic waste material, plastic waste material is supplied to a first screw machine and melted therein to form a plastic waste material melt. The plastic waste material melt is supplied to a second multi-shaft screw machine by means of a supply device and is processed therein together with plastic raw material to form a plastic material melt.

Claims

1. A method for recycling plastic waste material, comprising the following steps: providing a first screw machine and a second multi-shaft screw machine, p1 supplying plastic waste material into the first screw machine and melting of the plastic waste material by means of the first screw machine to form a plastic waste material melt, supplying plastic raw material into the second multi-shaft screw machine and processing of the plastic raw material by means of the second multi-shaft screw machine to form a plastic raw material melt, supplying the plastic waste material melt into the second multi-shaft screw machine, and mixing the plastic raw material melt and the plastic waste material melt by means of the second multi-shaft screw machine to form a plastic material melt.

2. A method according to claim 1, wherein the plastic waste material melt is filtered by means of a filter device before being supplied into the second multi-shaft screw machine.

3. A method according to claim 1, wherein at least one parameter of the plastic waste material melt is determined by means of at least one sensor.

4. A method according to claim 3, wherein a quality measure for the plastic waste material melt is determined by means of a control device in dependence on the determined at least one parameter of the plastic waste material melt.

5. A method according to claim 3, wherein at least one of at least one supplying device and a throttling device is actuated in dependence on at least one of the at least one parameter and a determined quality measure.

6. A method according to claim 3, wherein in dependence on at least one of the at least one parameter and a determined quality measure, a supplying device for supplying the plastic waste material melt is actuated in such a manner that the plastic waste material melt is supplied to the second multi-shaft screw machine if at least one of the at least one parameter and the determined quality measure is within a predefined range, and the plastic waste material melt is not supplied to the second multi-shaft screw machine if at least one of the at least one parameter and the determined quality measure (Q) is outside the predefined range (Q.sub.1).

7. A method according to claim 3, wherein in dependence on at least one of the at least one parameter and a determined quality measure, a supplying device for at least one of supplying plastic raw material and for supplying at least one additive is actuated in such a manner that at least one of plastic raw material and at least one additive is supplied to the first screw machine if at least one of the at least one parameter and the determined quality measure is outside a predefined range.

8. A method according to claim 1, wherein the plastic waste material has a proportion m.sub.W of the plastic material melt(S), wherein: 5 wt. %m.sub.W50 wt. %,

9. A recycling plant for recycling plastic waste material, comprising a first screw machine for melting the plastic waste material to form a plastic waste material melt, a second multi-shaft screw machine with a first supply opening for supplying plastic raw material and a second supply opening for supplying the plastic waste material melt, a supplying device for supplying the plastic waste material melt into the second multi-shaft screw machine.

10. A recycling plant according to claim 9, comprising a throttling device for adjusting a dwell time of the plastic waste material melt in the first screw machine.

11. A recycling plant according to claim 9, comprising a filter device for filtering the plastic waste material melt before it is supplied into the second multi-shaft screw machine.

12. A recycling plant according to claim 9, comprising at least one sensor for determining at least one parameter of the plastic waste material melt.

13. A recycling plant according to claim 12, comprising a control device for determining a quality measure for the plastic waste material melt in dependence on the determined at least one parameter of the plastic waste material melt.

14. A recycling plant according to claim 9, wherein the supplying device for supplying the plastic waste material melt comprises at least one switching element.

15. A recycling plant according to claim 9, comprising a supplying device for at least one of supplying plastic raw material and for supplying at least one additive into the first screw machine.

16. A recycling plant according to claim 11, wherein a control device for actuation has a signal connection with at least one of the supplying device for supplying the plastic waste material melt and with a supplying device for at least one of supplying plastic raw and for supplying at least one additive into the first screw machine and with a throttling device.

17. A method according to claim 1, wherein the recycling plastic waste material is polyolefin waste material.

18. A method according to claim 1, wherein the first screw machine is a first multi-shaft screw machine.

19. A recycling plant according to claim 11, wherein the plastic waste material is a polyolefin waste material.

20. A recycling plant according to claim 11, wherein the first screw machine is a first multi-shaft screw machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 shows 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 form 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,

[0046] FIG. 2 shows a side view of the first multi-shaft screw machine,

[0047] FIG. 3 shows a partially sectioned plan view of the first multi-shaft screw machine in FIG. 2,

[0048] FIG. 4 shows a sectional view through a throttling device of recycling plant,

[0049] FIG. 5 shows a side view of the second multi-shaft screw machine, and

[0050] FIG. 6 shows a partially sectioned plan view of the second multi-shaft screw machine in FIG. 5.

DETAILED DESCRIPTION

[0051] A recycling plant 1 for recycling plastic waste material M.sub.W, in particular polyolefin waste material, comprises a first screw machine 2 and a second multi-shaft screw machine 3. The screw machine 2 is designed as a multi-shaft screw machine. Alternatively, the screw machine 2 can also be designed as a single-shaft screw machine.

[0052] The first multi-shaft screw machine 2 serves to melt the plastic waste material M.sub.W into a plastic waste material melt S.sub.W, in particular into a polyolefin waste material melt. The first multi-shaft screw machine 2 is designed as a two-shaft screw machine. The first multi-shaft screw machine 2 has a housing 4, which comprises a plurality of housing portions arranged in succession and fastened to one another. Two housing bores 5, 6 are formed in the housing 4, which penetrate each other and have the shape of a horizontal figure eight in cross-section. Two tightly intermeshing treatment element shafts 7, 8 are arranged in the housing bores 5, 6 and can be driven in rotation about associated axes of rotation 9, 10. The treatment element shafts 7, 8 are driven in the same direction of rotation by a drive motor 13 via a transfer gear 11 and a coupling 12.

[0053] The first multi-shaft screw machine 2 has an intake zone 15, a melting zone 16, a degassing zone 17 and a discharge zone 18 successively in a conveying direction 14.

[0054] In the intake zone 15, a first supply opening 19 is formed laterally in the housing 4. The first supply opening 19 serves to supply the plastic waste material M.sub.W. A second supply opening 20 is formed in the housing 4 in the intake zone 15 for supplying plastic raw material M.sub.V and/or for supplying at least one additive A. The second supply opening 20 is formed upstream of the first supply opening 19. A funnel 21 is connected to the second supply opening 20. In the intake zone 15, the treatment element shafts 7, 8 have screw elements.

[0055] The melting zone 16 serves to melt the plastic waste material M.sub.W and/or the plastic raw material M.sub.V and to melt or mix in any additive A or additives A that may have been added. In the melting zone 16, the treatment element shafts 7, 8 have screw elements and/or kneading elements.

[0056] The degassing zone 17 serves to homogenize and degas the produced plastic waste material melt M.sub.W. 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.

[0057] The discharge zone 18 serves to discharge the plastic waste material melt S.sub.W from the first multi-shaft screw machine 2 through a discharge opening. In the discharge zone 18, the treatment element shafts 7, 8 have screw elements.

[0058] For heating the housing 4, the first multi-shaft screw machine 2 comprises heating devices 24, which are connected to the housing 4 in the intake zone 15, the melting zone 16, the degassing zone 17 and the discharge zone 18.

[0059] The recycling plant 1 comprises a first supplying device 25, which is associated with the first multi-shaft screw machine 2. The first supplying device 25 comprises a two-shaft supply screw machine 26. The supply screw machine 26 is designed as a side-feed machine. The supply screw machine 26 is connected to the side of the housing 4 and opens into the first supply opening 19.

[0060] The supply screw machine 26 comprises a housing 27 with housing bores 28, 29, in which screw shafts 30, 31 are arranged to be driven in the same direction of rotation. The screw shafts 30, 31 are driven in the same direction, i.e. in the same direction of rotation, by a drive motor 33 around associated axes of rotation via a transfer gear 32. A feed opening 34 is formed in the housing 27, which feed opening 34 opens into the housing bores 28, 29 and to which a hopper 35 is connected. The supply screw machine 26 is used for supplying the plastic waste material M.sub.W.

[0061] The first supplying device 25 further comprises a first dosing unit 36 for supplying plastic raw material M.sub.V and a second dosing unit 37 for supplying at least one additive A through the second supply opening 20 into the first multi-shaft screw machine 2. The dosing units 36, 37 are designed to be gravimetric, for example.

[0062] The recycling plant 1 comprises a throttling device 38, which is arranged downstream of the first multi-shaft screw machine 2 with respect to the conveying direction 14. The throttling device 38 is attached to the housing 4. The throttling device 38 is designed as a start-up valve throttling device. A first pressure sensor 53, which measures a pressure p.sub.1 of the plastic waste material melt S.sub.W immediately downstream of the first multi-shaft screw machine 2, and a first temperature sensor 56, which measures a temperature T.sub.1 of the plastic waste material melt S.sub.W immediately downstream of the first multi-shaft screw machine 2, are arranged between the first multi-shaft screw machine 2 and the throttling device 38.

[0063] The throttling device 38 comprises a housing 39 in which a cylindrical housing recess 40 is formed. A correspondingly cylindrical switching element 41 is arranged in the housing recess 40, which can be swivelled about a swivel axis 43 in the housing recess 40 by means of a drive 42. In the housing 39, an inlet channel 44 is formed, which connects the housing bores 5, 6 with the housing recess 40. The switching element 41 forms a passage channel 45 which, in a discharge position shown in FIG. 4, connects the inlet channel 44 with a discharge channel 46. The switching element 41 further forms an ejection channel 47, which connects the inlet channel 44 to the surroundings in a discharge position. To switch between the ejection position and the discharge position, the switching element 41 can be swivelled about the swivel axis 43 by means of the drive 42.

[0064] In the discharge channel 46, a throttling element 48 is arranged, which can be swivelled about a swivel axis 50 by means of a drive 49. Only a drive shaft of the drive 49 can be seen in FIG. 4. In the discharge position, the throttling element 48 serves to set the dwell time of the plastic waste material melt S.sub.W in the first multi-shaft screw machine 2. The throttling device 38 can also be designed in accordance with the start-up valve throttling 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.

[0065] 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 serves to increase the pressure of the plastic waste material melt S.sub.W.

[0066] Further, the recycling plant 1 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.

[0067] The filter device 52 comprises a second pressure sensor 53, which measures a pressure p2 of the plastic waste material melt S.sub.W upstream of the filter device 52. Further, the filter device 52 comprises a second temperature sensor 56, which measures a temperature T.sub.2 of the plastic waste material melt S.sub.W upstream of the filter device 52.

[0068] The filter device 52 is connected to a second supplying device 55 via a pipe 54. A measuring region M is formed in the pipe 54, in which various parameters of the plastic waste material melt S.sub.W are determined or measured by means of sensors 57, 58, 59. A third pressure sensor 57 is used to determine or measure a pressure p.sub.3 of the plastic waste material melt S.sub.W downstream of the filter device 52. By means of a third temperature sensor 58, the temperature T.sub.3 of the plastic waste material melt S.sub.W is determined or measured. Further, a viscosity is determined or measured by means of a viscosity sensor 59.

[0069] The recycling plant 1 comprises a control device 60. The sensors 53, 53, 56, 56, 57, 58, 59 have a signal connection with the control device 60.

[0070] The second supplying device 55 comprises a housing 61 in which a housing recess 62 is formed. In the housing recess 62, a switching element 63 is arranged, which can be displaced in the housing recess 62 by means of a drive 64. An inlet channel 65 is formed in the housing 61, which is connected to the pipe 54. Further, a first discharge channel 66, an ejection channel 67 and a second discharge channel 68 are formed in the housing 61.

[0071] In the switching element 63, a first passage channel 69 is formed, which connects the inlet channel 65 to the first discharge channel 66 in a first switching position of the switching element 63. The first switching position is shown in FIG. 1. The first discharge channel 66 is connected to the second multi-shaft screw machine 3 via a pipe 70.

[0072] Furthermore, the switching element 63 comprises a second passage 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 pelletizing device 74 via a pipe 73. The first pelletizing device 74 is designed, for example, as an underwater pelletizing device. The switching element 63 further comprises a third passage channel 72 which, in a third switching position, connects the inlet channel 65 to the discharge channel 67. The ejection channel 67 opens into the environment.

[0073] The second supplying device 55 further comprises a first dosing unit 91 for supplying plastic raw material M.sub.V and a second dosing unit 92 for supplying at least one additive A into the second multi-shaft screw machine 3. The dosing units 91, 92 are designed to be gravimetric, for example.

[0074] The second multi-shaft screw machine 3 is designed as a two-shaft screw machine. The second multi-shaft screw machine 3 has a housing 75 which comprises a plurality of housing portions arranged in succession and fastened to one another. Two housing bores 76, 77 are formed in the housing 75, which penetrate each other and have the shape of a horizontal figure eight in cross-section. Two tightly intermeshing 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 rotation in the same direction, i.e. in the same directions of rotation, by a drive motor 84 via a transfer gear 82 and a coupling 83.

[0075] The second multi-shaft screw machine 3 has a first intake zone 86, a melting zone 87, a second intake zone 88, a homogenizing zone 89 and a discharge zone 90 in succession in a conveying direction 85.

[0076] In the first intake zone 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 serves to supply plastic raw material M.sub.V and/or the at least one additive A. The dosing units 91, 92 open into the hopper 94. In the first intake zone 86, the treatment element shafts 78, 79 comprise screw elements.

[0077] The melting zone 87 serves to melt the plastic raw material M.sub.V and, if necessary, the additive A or additives A. In the melting zone 87, the treatment element shafts 78, 79 comprise screw elements and/or kneading elements.

[0078] In the second intake zone 88, a second supply opening 95 is formed in the housing 75. The second supply opening 95 opens into the housing bores 76, 77. The second supply opening 95 serves to supply the plastic waste material melt S.sub.W. The pipe 70 is connected to the second supply opening 95. In the second intake zone 88, the treatment element shafts 78, 79 comprise screw elements.

[0079] The homogenizing zone 89 serves to homogenize the plastic raw material melt S.sub.V and the plastic waste material melt S.sub.W 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.

[0080] The discharge zone 90 serves to discharge the plastic material melt S through a discharge opening of the second multi-shaft screw machine 3. In the discharge zone 90, the treatment element shafts 78, 79 comprise screw elements.

[0081] 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 intake zone 88, the homogenizing zone 89 and the discharge zone 90.

[0082] 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 is connected to the discharge opening. The second pelletizing device 98 serves to produce pellets from the plastic material melt S. The second pelletizing device 98 is designed, for example, as an underwater pelletizing device.

[0083] The multi-shaft screw machines 2, 3, the supplying devices 25, 55 and the throttling device 38 have a signal connection with the control device 60 for actuation purposes.

[0084] The functional principle of the recycling plant 1 and the method for recycling the plastic waste material S.sub.W are described below:

[0085] The plastic waste material M.sub.W is supplied to the first multi-shaft screw machine 2 by means of the first supplying device 25. For this purpose, the plastic waste material M.sub.W, which is present as bulk material, is supplied via the feed opening 34 to the supply screw machine 26, which conveys the plastic waste material M.sub.W via the first supply opening 19 into the housing bores 5, 6 of the first multi-shaft screw machine 2. The plastic waste material M.sub.W has been produced from plastic products that have been washed and/or shredded. The plastic waste material M.sub.W is present in particular as shreds and/or pellets. The plastic waste material M.sub.W is degassed and compacted in the supply screw machine 26.

[0086] If required, plastic raw material M.sub.V can be supplied to the first multi-shaft screw machine 2 via the second supply opening 20 by means of the dosing unit 36 and/or at least one additive A can be supplied by means of the dosing unit 37.

[0087] In the melting zone 16, the plastic waste material M.sub.W and, if necessary, the plastic raw material M.sub.V or the at least one additive A are melted and mixed. The heating devices 24 are used to heat the housing 4 and support the melting process. The resulting plastic waste material melt S.sub.W is homogenized and degassed in the degassing zone 17. The plastic waste material melt S.sub.W is then discharged from the first multi-shaft screw machine 2 via the discharge zone 18 and the associated discharge opening. By means of the first pressure sensor 53 and the first temperature sensor 56, the pressure p.sub.1 and the temperature T.sub.1 of the plastic waste material melt S.sub.w are monitored immediately downstream of the multi-shaft screw machine 2.

[0088] After the first multi-shaft screw machine 2 has started up, the switching element 41 of the dosing device 38 is transferred from the ejection position to the discharge position, so that the plastic waste material melt S.sub.W flows from the inlet channel 44 through the passage channel 45 into the discharge channel 46. The flow resistance in the discharge channel 46 can be adjusted by means of the throttling element 48, which in turn allows the dwell time of the plastic waste material melt S.sub.W in the first multi-shaft screw machine 2 to be set. With a longer dwell time of the plastic waste material melt S.sub.W in the first multi-shaft screw machine 2, a longer or more intensive mixing and homogenization of the plastic waste material melt S.sub.W takes place, which has a positive effect on the viscosity or quality of the plastic waste material melt S.sub.W.

[0089] The plastic waste material melt S.sub.W is conveyed through the filter device 52 by means of the melt pump 51 and filtered therein. The second pressure sensor 53 is used to monitor the pressure p.sub.2 of the plastic waste material melt S.sub.W upstream of the filter element, so that the filter element can be replaced if it becomes contaminated. Further, the temperature T.sub.2 of the plastic waste material melt S.sub.W is monitored by means of the second temperature sensor 56.

[0090] Various parameters are measured in the measuring region M using the sensors 57, 58, 59. The measured parameters include, in particular, the pressure p.sub.3, the temperature T.sub.3 and the viscosity of the plastic waste material melt S.sub.W. The measured parameters are supplied to the control device 60 via the signal connection.

[0091] The control device 60 determines a quality measure Q for the plastic waste material melt S.sub.W in dependence on at least one parameter of the plastic waste material melt S.sub.W. The quality measure Q is assigned to one of multiple quality classes Q.sub.1, Q.sub.2, Q.sub.3 by means of the control device 60. Depending on the determined quality measure Q, the first supplying device 25, the throttling device 38 and/or the second supplying device 55 are actuated by the control device 60. The quality class Q.sub.1 characterizes a high quality, the quality class Q.sub.2 a medium quality and the quality class Q.sub.3 a low quality of the plastic waste material melt S.sub.W.

[0092] For example, the quality measure Q is the measured viscosity 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 is within a predefined range, the quality class Q.sub.1 is provided. If, on the other hand, the viscosity is outside the predefined range, the quality class Q.sub.2 or Q.sub.3 is provided. The quality class Q.sub.3 is provided, for example, if the quality measure Q or the viscosity is outside a predefined usability range of the plastic waste material melt S.sub.W. The assessment of the quality of the plastic waste material melt S.sub.W depends in particular on the predefined requirements for the plastic material melt S.

[0093] If the control device 60 determines a quality measure Q associated with the quality class Q.sub.1, the control device 60 actuates the drive 64 in such a manner that the switching element 63 is moved to the first switching position. In the first switching position, the plastic waste material melt S.sub.W is supplied to the second multi-shaft screw machine 3.

[0094] If the control device 60 determines a quality measure Q associated with the quality class Q.sub.2, the throttling device 38 is actuated by the control device 60 in such a manner that the flow resistance and thus the dwell time of the plastic waste material melt S.sub.W in the first multi-shaft screw machine 2 is increased. Further, by means of the control device 60, the first supplying device 25 is actuated in such a manner that the quality of the plastic waste material melt S.sub.W is increased by the supply of plastic raw material M.sub.V and/or at least one additive A. The drive 64 of the second supplying device 55 is actuated by the control device 60 in such a manner that the switching element 63 is moved to the second switching position. In the second switching position, the plastic waste material melt S.sub.W is supplied via the pipe 73 to the pelletizing device 74, which produces a low-quality pellet from the plastic waste material melt S.sub.W, which can, however, still be processed further.

[0095] If the control device 60 determines a quality measure Q associated with the quality class Q.sub.3, the throttling device 38 and the first supplying device 25 are actuated in such a manner that the quality of the plastic waste material melt S.sub.W is increased. This actuation has already been described in connection with the quality class Q.sub.2. Further, the drive 64 of the second supplying device 55 is actuated by the control device 60 in such a manner that the switching element 63 is moved to the third switching position. In the third switching position, the plastic waste material melt S.sub.W is discharged into the environment and disposed of, since further processing is not possible.

[0096] Parallel to the production of the plastic waste material melt S.sub.W by means of the first multi-shaft screw machine 2, a plastic raw material melt S.sub.V is produced by means of the second multi-shaft screw machine 3. Plastic raw material M.sub.V and, if necessary, at least one additive A are supplied to the second multi-shaft screw machine 3 by means of the dosing units 91, 92 via the first supply opening 93. The plastic raw material M.sub.V is supplied in particular as bulk material, in particular as powder and/or pellets. The plastic raw material M.sub.V and the at least one additive A are melted and mixed in the melting zone 87 to form a plastic raw material melt S.sub.V.

[0097] Alternatively, a plastic raw material melt S.sub.V can already be supplied via the first supply opening 93.

[0098] In the second intake zone 88, the plastic raw material melt S.sub.V is supplied with the plastic waste material melt S.sub.W via the pipe 70 and the second supply opening 95. In the homogenizing zone 89, the plastic raw material melt S.sub.V and the plastic waste material melt S.sub.W are mixed together and homogenized 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 in the discharge zone 90 via the discharge opening and supplied to the pelletizing device 98. The pelletizing device 98 produces high-quality pellets from the plastic material melt S, which can be further processed.

[0099] The plastic waste material M.sub.W has a proportion m.sub.W of the plastic material melt S, wherein the following applies: [0100] 5 wt. %m.sub.W50 wt. %, in particular 10 wt. %m.sub.W45 wt. %, in particular 15 wt. %m.sub.W40 wt. %, and in particular 20 wt. %m.sub.W35 wt. %.

[0101] Due to the fact that a plastic waste material melt S.sub.W is supplied to the second multi-shaft screw machine 3, the recycling of plastic waste material M.sub.W is simple and energy-efficient. By measuring and assessing the quality of the plastic waste material melt S.sub.W and controlling the recycling plant 1 in dependence on the determined quality, flexible and qualitatively reliable recycling of plastic waste material M.sub.W is also ensured. The quality measurement and/or the quality assessment are carried out online, i.e. during operation of the recycling plant 1. The first screw machine 2 can also be retrofitted. The quality measurement and quality assessment do not increase the load on an existing second multi-shaft screw machine 3 due to the plastic waste material melt S.sub.W. Colourant can be supplied into the second multi-shaft screw machine 3 via the first screw machine 2, for example, so that the second multi-shaft screw machine 3 is hardly contaminated by the colourant.

[0102] In particular, the recycling plant 1 has 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 proportion.