EP1300200B1 - Method and apparatus for indentification and separation of plastic particles - Google Patents

Description

The present invention relates to a method for the separation of materials according to part 1 of claim 1. In particular, it relates to the separation of plastics of various types such. As the selection of polyethylene terephthalate in blends with polyolefins, polycarbonate, polyvinyl chloride, etc., as well as for the sorting of colored with different colors plastics under colorless plastics and for the elimination of metals and other substances such. As aluminum, wood, paper, etc. in process streams that are designed for the recycling of valuable materials. The process is an example of the recycling process of plastics, which originate from beverage bottles and have already been filled at least once with mineral water or soft drinks or misappropriated with pollutants explained. However, it is equally suitable for the separation of various constituents of other free-flowing multicomponent mixtures.

For the production of plastic beverage bottles - eg. From polyethylene teraphthalate PET is usually new material, which originates from polymerization processes, used in recent time, however, it goes to the already used as food packaging containers after a recycling process again for the packaging of food, especially for beverage bottles. The advantage of this approach is on the one hand in a cheaper price for the recycled PET material compared to new material and on the other hand therein. that the disposal problem for used plastics is eliminated. However, in order to guarantee the quality of food, additional sensor system measures must be taken with the aim of sorting out inadmissible components which comply with the regulations of international legislation

According to the prior art currently being recycled plastic parts, eg. B. beverage bottles or other food packaging, crushed into small pieces with the edge lengths of 5 to 12 mm, subjected to a continuous cleaning process and then tested with a camera systems on colors. All colored plastic parts are blown out of the plastic stream via air nozzles in a subsequent sorter and to lower quality plastics further processed. In further developed arrangements according to the state of the art, a sorting out of PVC plastic parts takes place in addition, by making use of the fact that, due to heating, a blackening of this type of plastic occurs which is recognized by the color sorter.

The basic principle of sorters according to the prior art is that the material to be sorted when passing parabolic orbits in the air in the case of bad detection of perpendicular to the trajectory nozzle jet pulses have been deflected so that they land in a separate collection container for low-grade plastics. Because of the statistically strongly fluctuating shape and fluctuating weight of the plastic pieces, however, the respective trajectory of the plastic pieces deviates in part greatly from the parabolic shape, which is why the sorting nozzles must be mounted to avoid collisions with the plastic pieces at a great distance from the ideal trajectory. From this distance, the passing bad substances are no longer selectively detected by the concentrated nozzle jet immediately in front of the nozzle opening, but deflected uncertainly only by an expanded and turbulence-afflicted, weak jet together with nearby accepts. The result is a mixture of high and low-grade plastics associated with a loss of quality and a loss of quantity of high-quality plastic fraction. Both disadvantages lead to economic problems that jeopardize the economy of the overall process.

From the EP 0461616A a color detection for colored glass fragments is known, wherein particles pass on a smooth slide a color detection device and a pneumatic separator is operated with a smooth inclined plane by the color detection device with multiple measuring points. Only colored glass can be sorted and no other material recognition is possible.

The WO 9606690A also refers to pure glass separation of broken glass fragments. A pure color detection is carried out and then corresponding ejection stations are operated, which operate on a vibrating rail arrangement. From conveyor belts 3a and 3b, the waste glass parts are guided through a subsequent measuring and control arrangement, which is sorted and then in the ejection device ejects pneumatically. US Pat. No. 6,060,677A is able to quickly and roughly detect a wide variety of materials by means of diffusely reflected IR spectra or other electromagnetic radiation spectra. For this purpose, the particles are guided on an inclined plane over a slot where there is a separate IR source at each detection point. The IR sources emit from optical fibers and transmit through the conveyed material, whereby the thus influenced IR radiation is directed to the detector. Downstream of the detection points air nozzles can then be activated, which can eject objects. The plant can also roughly sort plastics, a finer distinction is impossible due to the inaccuracy of the IR spectroscopy. Sorting of the waste particles can be done via the strength of air streams from nozzles. US 4848590 A describes the sorting of metal parts by an inclined plane or grid, which has a lateral boundary and is not suitable for plastics. WO 0100333 A explains gutters in a vibrating table, which causes the products to fall down in parallel rows - but there is no exact plastic separation. US 4549659 A describes the charging of free-flying particles by corona discharge for a rotationally symmetric distribution.
US 5917585 A deals with the distinction of polyethylene naphthalate (PEN) from other plastics, such as polyolefins and especially the similar polyethylene terephthalate (PET), by fluorescence measurements at certain wavelengths without spectrometer. Others, this accompanying plastics, such as PVC; Polyolefins, polyamides, etc. can not be determined or separated therefrom. Thus, the system is the US Pat. No. 5,917,585 A Exclusively for the isolation of PEN, but not for the separation of different plastics. DE 42 31 477 A refers exclusively to the fluorescent colorful marking of plastic particles for a fluorescence spectral analysis to be carried out later and subsequent separation. Thereafter, the skilled artisan learns that undyed plastics are not or only poorly sortable. GB 2 264 558 A describes that the admixing of a dye which fluoresces in FIR or NIR to plastics for their later sortability is a conditio sine qua non. As a result, it is possible GB 2264 558 in no way the task to separate normal plastic waste to solve.

It is accordingly an object of the present invention to avoid the disadvantages of the prior art.

The object is achieved by a method having the features of claim 1.
Furthermore, the invention also relates to an apparatus for carrying out the method with the features of claim 9. Advantageous developments emerge from the dependent claims. In the evaluation of different spectral regions or physical phenomena for the identification of the particles to be separated, the material particles are irradiated by radiation sources having a different emission spectrum and the resulting optical transmission / reflection beam is detected by at least one suitable spectrometer. The spectrometers are eg fluorescence spectrometers, IR spectrometers, UV / VIS spectrometers. According to the invention, in addition to a light source illuminating the plastic parts for generating fluorescent light, a further light source is used for irradiating the plastic particles and in particular for the efficient improvement of the recognition of colors and for the detection of non-fluorescent and / or non-transparent substances, such as Wood or metal particles, serves. The separation unit comprises a plurality of channel-shaped channels, in which, for example, in the low point of the cross-sectional profile, nozzles, in particular clocked nozzles for sorting out characteristic material particles are integrated into at least two material fractions. In this case, a plurality of nozzles in each channel groove may be accommodated on a surface which is not larger than the area of the smallest material particle to be sorted. Preferably, in the region of the nozzle, the channel channels have a depression in order to guide the particles to the nozzle. The inclined plane has channel troughs, wherein in each Channel gutter, preferably several nozzles are housed on a surface which is not larger than the area of the smallest material particle to be sorted.

• Fig. 1 ein Beispiel einer Vorrichtung gemäß der vorliegenden Offenbarung;
• Fig. 2 Eine weitere Ausführungsform einer erfindungsgemäßen Vorrichtung
• Fig. 3 eine Detailansicht der Düsen in Fig. 2
• Fig 4a/4b: Detailansichten der schiefen Ebene der Fig. 2
• Fig. 4c eine Detailansicht einer Partikeltrennung durch elektrostatische Ladung, und
• Fig. 5: eine Detailansicht einer Transmissionsmessung in der schiefen Ebene In den Figuren werden gleich wirkende Einrichtungen mit gleichen Bezugszeichen bezeichnet.

Advantageously, the nozzles are designed as supersonic nozzles. All nozzles are preferably supplied with compressed air via a common transverse pipe (18) and pulsed on and off under the control of the analysis unit. For example. However, the material particles can also be lifted out of the channel via a weak jet and then sucked off via a hood pressurized with negative pressure.
In this case, the channels of the inclined plane may be closed in the section between material application and the separating device on the top, wherein within the channels, a gas stream is generated, which assists the acceleration of the material particles during the slide down and keeps at a steady speed in the course.
It may be useful that the channels of the inclined plane ends immediately after the nozzles and the trajectories of the material supports supported by a baffle directly in the collection containers. Together with the jet stream method, the separation unit can spray an electrical charge on the material particles to be sorted via a corona discharge on a metal tip over the material flow in each channel and subsequently deflecting these selectively charged material particles through an electric field during a free fall and thus separating them. By the invention it is possible to achieve an improved separation of the different material fractions. It may also be expedient that the material particles which have been lifted out of the channel via a weak nozzle jet are subsequently sucked off via a hood acted upon by a vacuum. According to the invention, the plastic parts sliding on an inclined plane are illuminated with optical radiation, the spectrum of the plastics emitted by the plastic parts as a consequence of the illumination being determined by spectral analysis, If necessary, the color and possible contamination of the respective plastic particle as a result of foreign substances are determined and as inferior recognized plastic parts are ejected from an integrated in the inclined plane nozzle with a compressed air pulse. Essential for the invention is the fact that the integrated in the inclined plane compressed air opening as a nozzle for generating a concentrated bundled high-speed flow, even at supersonic speed, for example, as a Laval nozzle is formed.
Hereinafter, preferred embodiments of the invention with reference to the following description and the drawings are explained in more detail, to which this is by no means limited. Showing:

• Fig. 1 an example of a device according to the present disclosure;
• Fig. 2 Another embodiment of a device according to the invention
• Fig. 3 a detailed view of the nozzles in Fig. 2
• Fig. 4a / 4b : Detailed views of the inclined plane of the Fig. 2
• Fig. 4c a detailed view of a particle separation by electrostatic charge, and
• Fig. 5 : a detailed view of a transmission measurement in the inclined plane In the figures, like-acting devices are denoted by the same reference numerals.

In the Fig. 1 illustrated system for carrying out the method has a conveyor unit 4 for the material particles 14, an inclined plane 13 with supersonic nozzles 15, lighting devices 6, 7 for fluorescence, a separation unit for high-quality and low-grade material, an optical spectrometer 10 with beam scanner, evaluation and valve control is , as in FIG. 1 shown in a reservoir 1 to be analyzed optically analyzed and then separated into different fractions 2 and 3 to be separated particulate material 14 with a conveyor system 4 on the inclined plane 5, on which it slides down by gravity. When illuminated with the light sources 6 and 7 with a high UV component, most of the plastic material particles emit fluorescent light 8, which is detected by a known scanner system 9 transversely to the transport direction over the entire width of the inclined plane and directed onto an optical spectrometer 10. A likewise known per se analysis system 11 calculated from the spectra both the type of the respective plastic, as well as the color, as well as any contamination of the plastic particles, eg by gasoline, diesel, engine oil, paint thinner, urine, pesticides, etc. If pure, ie for Food packaging suitable plastic material, such as polyethylene, it travels by gravity in the channel 2 and is supplied to the plastic recycling for beverage bottles or other food packaging. If contamination or coloring or other plastic materials are present, the so classified material particles are deflected by supersonic jet into the channel 3 and used in the context of a recycling for the production of minor plastics.
Here, in the region of the nozzle, the channel grooves on a recess, as seen from Fig. 4a seen. The channels of the inclined plane end immediately after the nozzles 21 and the trajectories of the material particles 14 end, supported by a separating plate directly in the collecting containers.
Here all nozzles 15 are supplied with compressed air via a common transverse pipe 18 and are pulsed on and off under the control of the analysis unit. In the process for the separation of the material particles according to the invention by a multiple supersonic nozzle system according to Fig. 2 . Fig. 3 and Fig. 4a / b, the particle material 14 reaching the inclined plane 13 from the vibratory linear conveyor 12 is sorted by gravity through the supersonic nozzle 15 into the recycling channel 16 for inferior plastics or, alternatively, into the recycling channel 17 for food grade plastics. Transverse to the transport direction, a plurality of identical nozzles 15 are not shown in their entirety in the figures, arranged at a distance from the dimensions of the material components 14. All nozzles 15, 25 are supplied with oil-free, dry compressed air via the transverse channel 18. The respective nozzle 15 is connected via a branch line 19 and the quick-acting valve 20 to the transverse channel 18. The opening and closing function of the respective quick-acting valve 20 takes place according to control by the analysis unit 11 Fig. 1 , An essential part of the invention is based on the use of high-speed, in particular supersonic nozzles 15. The latter is due to the fact that for economic reasons, a minimum mass flow of material particles 14 must be supported by the arrangement. such that the particle velocity on the inclined plane 13 reaches values requiring a maximum velocity of a supersonic jet 21 to prevent. that too many high-quality material particles 14 are passed undesirably into the inferior fraction before or after the blow-out process of the particle to be sorted out. The inclined plane 13 off Fig.2 exists according to Fig. 4a / b of numerous channel-shaped tracks 30, which are concave in cross section 31 and ensure a precise guidance of the material particles 14 relative to the nozzle openings 15. Advantageously, each nozzle unit is according to Fig. 4a / b provided with a plurality of nozzle openings 15. This ensures that the critical expansion ratio required for supersonic speed is achieved in any case and that a mechanical force impulse evenly distributed over the material particle surface results.

The lighting of the material ponds 14 takes place here for excitation with light from both sides Fig. 2 by means of two light sources 36 and 37. To ensure the passage of light through the channel-shaped tracks 30, 31, the latter are provided with a translucent disc 23 made of quartz glass, which has a smaller angle of inclination relative to the channel in order to ensure a trouble-free transition between Ridge and glass to reach. The respectively on the spectrometer with analysis system 11 according to Fig.1 The fluorescent light beam is incident through the rays 22 in the Figures 2 and 3 shown.
To optimize the color detection is in the embodiment of the Fig. 5 a light source 41, which transilluminates the material particles, with a downstream color spectrometer, for example, the existing of milky polyolefins or aluminum caps of beverage bottles are identified. With this arrangement, in particular, contaminants such as wood and metal foils can be identified and removed. For this purpose, the passage of light through the channel 30 through a UV radiation-reflecting filter 38, which directs the radiation of the light source for exciting fluorescent light on the underside of the plastic parts, in combination with an optical high-pass filter 40, which light a halogen light source 41 above a Wavelength of about 480 nm for spectral analysis passes allows. The filter 38 is protected by a protective plate 42 against wear, in particular mechanical.

In a particular embodiment of the invention, the particle separation is carried out together with the jet stream process and that the particles to be sorted out according to Fig. 4c an electric charge is sprayed on a metal tip 44 via a high-voltage corona discharge 43 and these electrostatically charged material particles are subsequently deflected by an electric field 45 during the free fall and thus high-grade 46 and low-grade plastics 47 are separated into the fractions.
While the invention has been described in terms of a preferred embodiment and possible alternatives, various alternative arrangements and embodiments for carrying out the invention as defined by the claims will be obvious and familiar to those skilled in the art to which this description pertains.

LIST OF REFERENCE NUMBERS

1

reservoir

2

Faction or channel

3

fraction

4

conveyor system

5

inclined plane

6

light source

7

light source

8th

fluorescent light

9

scanner system

10

spectrometer

11

Analysis system or analysis unit

12

Linear vibratory conveyor

13

slide level

14

particulate

15

Supersonic nozzle or nozzle opening

16

recycling channel

17

recycling channel

18

Querkanal

19

stub

20

Fast switching valve

21

Supersonic jet

22

beam

23

disc

25

Supersonic nozzle or nozzle opening

30

Traces, gutters

31

Cross section through 30

36

light source

37

light source

38

filter

39

UV-light source

40

High Pass Filter

41

light source

42

windscreen

43

High-voltage corona discharge

44

metal tip

45

electric field

46

plastics

47

plastics

Claims (8)

1. Method for identifying and separating plastics material particles having at least two light sources (6, 7) for producing fluorescent light (8) and for irradiating the plastics material particles, wherein the at least two light sources have different emission spectrums,
   an optical recognition system comprising at least one optical spectrometer (10) onto which the fluorescent light (8) emitted by the plastics material particles is directed and at least one additional spectrometer which detects the transmitted and/or reflected light from the plastics material particles,
   an analysis system (11) for evaluating spectrums, wherein the analysis system (11) by means of spectral analysis using the light (8) absorbed by the spectrometers (10) calculates the type of the respective plastics material, the colour and impurities of the plastics material particles,
   a separation unit having an inclined plane for conveying and separating the plastics material particles, wherein the plastics material particles during their path on the inclined plane (13) are classified by the optical recognition system in accordance with the signals of the at least two optical spectrometers (10) and are separated into at least two material fractions in accordance with the classification, wherein the inclined plane has channel grooves, wherein at least one nozzle is arranged in each channel groove, wherein the surface-area of the nozzle in the channel groove and the surface-area of the smallest plastics material particle which is intended to be sorted are adapted to each other in such a manner that the surface-area of the nozzle is no greater than the surface-area of the smallest material particle which is intended to be sorted.
2. Method according to claim 1, characterised in that the separation unit sprays an electrical charge onto the material particles (14) which are intended to be sorted via a corona discharge (43) at a metal tip (44) above the material flow in each channel and these material particles (14) which are selectively charged in this manner are subsequently redirected during a free fall by an electrical field (45) and consequently separated.
3. Method according to claims 1 to 2, characterised in that the material particles are lifted out of the channel by means of a weak nozzle jet and subsequently drawn away via a hood which is acted on with reduced pressure.
4. Method according to claims 1 to 3, characterised in that the channels of the inclined plane (13) are closed in the portion between the material charging member and the separation device at the upper side and there is produced within the channels a gas flow which supports the acceleration of the material particles (14) while they slide down and subsequently maintains a uniform speed.
5. Method according to claims 1 to 4, characterised in that the channels of the inclined plane (13) terminate directly downstream of the nozzles (15, 25) and the flight paths of the material particles (14), supported by a partition sheet, terminate directly in the collection containers.
6. Method according to claims 1 to 5, characterised in that all the nozzles (15) are supplied with compressed air via a common transverse pipe (18) and the nozzles (15) are switched on and off in a pulsed manner by means of control by the analysis unit.
7. Method according to claims 1 to 6, characterised in that the at least one spectrometer is selected from fluorescence spectrometers, IR spectrometers, UV/VIS spectrometers.
8. Device for identifying and separating plastics material particles, suitable for carrying out a method according to at least one of claims 1 to 7, comprising
   at least two light sources (6, 7) for producing fluorescent light (8) and for irradiating the plastics material particles, wherein the at least two light sources have different emission spectrums,
   an optical recognition system having at least one optical spectrometer (10) onto which the fluorescent light (8) emitted by the plastics material particles is directed and at least one additional spectrometer which detects the transmitted and/or reflected light from the plastics material particles,
   and having an analysis system (11) for evaluating spectrums, wherein the analysis system (11) is constructed, by means of spectral analysis using the light (8) absorbed by at least two spectrometers (10), to calculate the type of the respective plastics material, the colour and impurities of the plastics material particles,
   a separation unit having an inclined plane for conveying and separating the plastics material particles, wherein
   the plastics material particles during their path on the inclined plane (13) are classified by the optical recognition system in accordance with the signals of the at least two optical spectrometers (10) and are separated by means of the separation unit into at least two material fractions in accordance with the classification, wherein the inclined plane has channel grooves, wherein at least one nozzle is arranged in each channel groove, wherein the surface-area of the nozzle in the channel groove and the surface-area of the smallest plastics material particle which is intended to be sorted are adapted to each other in such a manner that the surface-area of the nozzle is no greater than the surface-area of the smallest material particle which is intended to be sorted.

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