DE19949656A1 - Separating scrap plastics from vehicles, electronics and other areas according to type, has two stages of separation which use sensors to determine material sort and position on a belt or carousel - Google Patents

Abstract

Separating scrap plastics involves using two stages of separation which use sensors to determine material sort and position on a belt or carousel. Scrap parts are shredded to a uniform size and evenly distributed on a conveyer belt which passes sensors (2) for determining the type of plastic and position on the belt. Identified parts in one or two materials are ejected at the end of the conveyer and collected. The remaining fraction is conveyed (8) to a sorting carousel (9) which carries individual pieces past sensors (10,11) for identifying further predetermined plastics. Identified plastics of different types are ejected into containers (12) or transporting systems.

Description

The invention relates to a method and a device for separating plastic fen, metals and glasses or their composites according to the type.

The auto industry uses a variety of different plastics. This includes poly vinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyethylene (PE), acrylonitrile / Butadiene / styrene (ABS), polycarbonate (PC), polyamide (PA), polyurethane (PUR), poly phenyloxide (PPO), polybutylene terephthalate (PBT) and polymethyl methacrylate (PMMA). A dominant type of plastic with a share of over 50%, like the polyolefins Making PP and PE in household waste does not exist. In addition, products come from Plastic mixtures (blends), parts with layers of paint and bodies colored in black, the identification of which has caused major problems so far.

Safety requirements, the effort to lightweight construction and the high In the automotive industry, cost pressures lead to a growing use of Plastic parts. The proportion of plastic in cars grew from 10% in the 1970s to currently 15%. For the next few years there will be a growing proportion of plastic up to expected to be around 25% in 2005.

Conventional car recycling takes place directly from the scrap yard to the Shredder. After shredding, a quarter of the amount of scrap must be used as so-called Shredder light fraction are separated out. It's a mixture of plastics Glass, upholstery, rubber and other materials unsuitable for steel production, one Total amount of approx. 450,000 t per year, which is becoming increasingly scarce in Germany future landfill space must be disposed of. This development is in Contradiction to the Recycling Management and Waste Act (KrW- / AbfG), which the Calls for the closure of production cycles. Much of the plastics in the car can be used as a high-quality secondary raw material can be used.

There are highly selective separation processes for the large number of different plastics required that the advantages of automation in terms of sorting quality and productivity to use.

Some have started to recycle plastics in cars Recycling companies that process plastic bumpers made of polypropylene and a produce high quality regrind. The plastic is separated according to a process developed by A. Bahr [A. Bahr, V. Vogt, sorting technology at Plastic waste ", Industrieanzeiger 99 (1997) 100, p. 2021]. Polypropylene has one lower density than water and consequently floats in a water basin. the the vast majority of other plastics such as polystyrene and polyvinyl chloride have a higher density and sink in the water basin. This so-called swim-sink Technology can be used to separate plastics from one another or also weed out other heavier materials like metals. By adding salt the density of the water can be changed and on other separation tasks be adjusted.

The different density of the plastics is also used in hydrocyclones for separation of the parts used. The crushed plastics are suspended in water and reach the hydrocyclone (inlet) via a pressure booster pump. Through its tangential arrangement, a centrifugal field is generated in the hydrocyclone. The particles with the higher density accumulate near the outer wall. The particles with lower density migrate to the center. The resulting from the tangential inlet downward particle trajectory is called the primary vortex. The outlet opening on lower end of the cyclone (underflow) is designed so that it acts as a throttle and does not let the entire amount of incoming suspension escape. Only that flows like this near the wall, which contains the heavy fraction, from the cyclone. The largest Amount of water, together with the particles accumulating further inside, is in the Hydrocyclone forced to reverse. The resulting central vortex is called Secondary vortex and is directed upwards in the opposite direction to the primary vortex. By an overflow nozzle at the top of the arrangement leaves the water with the lighter particles the plant.

The hydrocyclone is widely used for separating granules from household waste Technology. Large systems are sold by Thyssen-Hentschel.

The plastics of the auto industry are often made by additives, fillers or Reinforcement fibers modified. This changes the density of the plastics and a reliable assignment of the density to the type of plastic becomes impossible.

In addition, there is the already mentioned variety of varieties, which is a multi-level extraordinary requires expensive separation plant, which leads to uneconomical solutions.

Try the plastic parts using an identifier or specifically used ones Marking and sorting fluorescent markers could not be widely used Find. The reasons for this are the necessary global regulations for marking of production, which are difficult to implement for competitive reasons.

Plastics can be determined well with analytical methods. Deployed Methods are mass spectroscopy, X-ray fluorescence spectroscopy, UV VIS absorption spectroscopy, atomic emission spectroscopy, MIR absorp tion spectroscopy (MIR = medium infrared) and NIR absorption spectroscopy (NIR = near infrared).

In mass spectroscopy, polymers are pyrolytically processed Molecular fragments transferred into the spectrometer and the corresponding masses detected. The plastic can be identified from the mass spectrogram. That Method requires measuring times that are well over a minute. One Sample preparation is required. For automatic sorting systems that is Measurement method unsuitable.

X-ray fluorescence measures the atomic lines excited by hard X-rays of the elements contained in the sample. A recognition of the polymeric structure of Plastics is not possible. Plastic additives can be measured using the Identify elements. The measurement requires a few seconds, with the sample too fix is. The method is used to measure flame retardants in mobile Measuring car used.

The oscillation bands of the polymer molecules can be in the wave range between 200 and 400 nm measured in re-emission and used to identify the plastics will. As a rule, however, the plastics are colored and the result is strong Superimposition of the absorption bands by fluorescence spectra of the dyes that exclude secure identification. The UV-VIS spectroscopy has therefore to Plastic measurement not found widespread.

Laser Induced Plasma Spectroscopy (LIPS), often also called Laser Induced Breakdown Spectroscopy (LIBS) is a new method of the Atomic emission spectroscopy, which is comparable to X-ray fluorescence spectroscopy on the measurement of the atomic composition of additives and fibers in plastics can identify. The method can handle fast moving parts without sample preparation measure and is suitable as process measurement technology.

Floating spark spectroscopy, another method of atomic emission spectroscopy, was used to identify polymers and additives. To measure, electrodes are pressed onto the plastic parts and onto their Surface sliding sparks generated. Surface contamination is to be excluded. the Measurement time is a few seconds. This is different for automatic sorting systems Procedure due to the low productivity.

Of all spectroscopic methods is for the material identification of Plastics, IR spectroscopy is of outstanding importance.

An IR spectrum can be divided into two broad areas:

• - Above 1500 cm ^-1 there are absorption bands that are assigned to individual functional groups.
• - Below 1500 cm ^-1 there are bands that characterize the molecule as a whole.

In the first area are the stretching vibrations of the functional building blocks of C, H, O or N and, as an exception, the NH deformation vibrations. Deformation, other valence and combination vibration bands are below 1500 cm ^-1.

This area is therefore referred to as the "fingerprint" region. While the area of the stretching vibrations of the functional groups contains more pronounced and more intense bands, the "fingerprint" area is more significant for the identification of the molecule. The identification of substances by means of infrared spectra is carried out by evaluating the bands of the functional groups and the bands of the "fingerprint" area. The measurement below 1500 cm ^-1 requires complex cooling systems.

FTIR spectrometers (FTIR = Fourier Transform Infrared) is used. The absorption spectra are measured in Re-emission. The sample must be prepared and fixed for measurement. Identification times of a few seconds and more are common.

Newer IR spectrometers use acousto-optically tunable filters (AOTF = Acousto Optical Tunable Filter) to record spectra in the short-wave range of the IR spectrum (2500 cm ^-1 to 4000 cm ^-1 ), which only require fractions of a second for measurement and at a measuring distance can work from 20 cm. The use of these so-called AOTF spectrometers suggests that progress will be made in identifying black plastics. Due to the strong absorption of the fundamental vibrations, the plastics are measured in the immediate vicinity of the surface. Contamination of the plastics has a considerable negative impact on the analysis result and must be ruled out.

The near infrared spectral range (NIR) begins above 4000 cm ^{-1 (<2.5 µm).} There is extensive literature on vibration spectroscopy in the NIR and its application in a wide variety of areas, comprehensively reported in a work by KA Martin in Recent Advances in Near-Infrared Reflectance Spectroscopy, Appl. Spectrosc. Rev., 27, 325-383 (1992).

With broadband irradiation in the NIR, polymers show a characteristic absorption spectrum that corresponds to the overtone or combination oscillations of the molecules. They are much weaker than the fundamental bands. Interpretation and assignment is also more difficult. The decisive advantages of the spectroscopic measurement in the NIR are, however

• - a high detection sensitivity and a high temporal resolution of the available radiation detectors (measurement of moving parts is possible),
• - the beam is guided by common media such as glass and quartz,
• - the suitability of commercial IR radiation sources and
• - the insensitivity to atmospheric influences and against Impurities on the surface of the plastic body.

After spectral analysis of plastics with different Fillers, soiling and different coloring, a NIR- spectroscopic method for the identification of plastics on fast moving Conveyor belts developed. Essential components of the procedure are standard Halogen lamps as IR light sources, fiber optics to capture the re-emitted Light, holographic concave grating, IR photodetector lines and an ultra-fast one spectrometric software. Based on this conception, the NIR Spectrometer KUSTA 2001, KUSTA 2002, KUSTA 4001 and KUSTA 4002 developed.

The KUSTA 2001 and KUSTA 4001 spectrometers are handheld measuring devices for Sample measurements.

For the process measurement of plastics on fast moving belts or rotating plates, the measuring systems KUSTA 2002 and KUSTA 4002 were developed. All plastics commonly used in the packaging industry such as PE, PP, PS, PA, PET, PVC and ABS can be reliable regardless of the coloring and soiling be identified. For the measurement of the absorption bands, IR detector lines are used made of PbS photoresistors or InGaAs diodes. The determination time of the type of plastic is less than 10 ms. The measuring system is able to Reliably identify plastic parts up to a speed of 4 m / s.

A system concept for sorting DSD plastics was created by H. Lucht, K. Löbe, in Material recycling of plastics with the NIR spectrometer KUSTA, Conference report: UTECH Berlin 1995, seminar "Plastic Recycling II", BC Berlin- Consults GmbH, pages 1-12. It contains segmented conveyor belts. The plastic bodies are poured onto an underfloor belt and over a Vertical conveyor guided onto a pair of conveyor belts arranged in a V-shape. The two Belts move at different speeds, forcing the parts in a lying position. The plastic parts fall from this pair of belts onto another Pair of belts that run at a much higher speed and the parts pull apart. This belt is transferred to another belt, the in the area of sensor technology. This tape is through partitions in many divided into small segments, into which only one plastic part falls. For smaller parts there can also be two parts per segment. The segmented band with the Plastic parts are fed past the measuring head. The measuring head measures the Material properties of the plastic parts and in a controller is the variety determined. The signal is then fed to a pneumatic separating system that uses the identified plastic part in the right place from the conveyor belt into one Container or transported to another belt. There are two parts different types of plastic in one segment, these are identified by the Measuring system recognized and both parts sorted into a residual fraction. This residual fraction can be sorted again.

The use of segmented belts results in the pneumatic separation more reliable results.

The identification of plastics as they are in the Scrap cars occur frequently. This includes the detection of dark materials, of Blends and additives. The signal / noise ratio and the spectral resolution of the The previously used NIR spectrometer is not sufficient for this task.

Another problem with recycling vehicle scrap is the shape and variety of sizes as well as the appearance of extremely unwieldy parts. the Automation of the material flow, as practiced with DSD goods, fails here. A comminution to a uniform level proves to be essential for the Invention. Crushers or shredders can be used for this. the Automation of material flows from broken or shredded Plastics is still unexplored. It is a fundamental requirement for that material recycling of plastics from electronics and Motor vehicle scrap.

One aim of the invention is a system for sorting plastics from motor vehicle scrap, which fully automatically separates comminuted material into ultra-pure fractions. If necessary, the system can carry out a gray grading (black sorting). The system is shown schematically in FIG .

A modular structure of the system is provided so that specific, different tasks can be solved in the different expansion stages. The system shown enables

• - the simultaneous separation of coarsely shredded plastic parts user-specific range specifications,
• - the separation of the plastics into light and dark,
• - the freely programmable selection of sorting classes,
• - learning new types of plastic,
• - a reliable mechanical separation and separation of the plastic parts and highest purity of the sorted materials.

The system shown is composed of two basic components (NIR spectroscopic image processing, type separator):
NIR spectroscopic image processing, with the assemblies

• - Material feed for the shredded plastic parts
• - Belt conveyor
• - NIR spectroscopic image processing (used to sort out two Main factions used)
• - Control Panel
• - pneumatic system
• - Container

Sort separator, with the assemblies

• - Conveyor for separating the plastic parts
• - mechanical stress device
• - Separation device
• - sorting device
• - several containers

The roughly broken plastic parts (no larger than 8 × 8 cm and no smaller than 3 × 3 cm) are placed on the entrance chute. From there they'll get through Vibration conveyed and as evenly as possible on a 1 m wide belt conveyor transfer. A transport speed of approx. 2 m / s causes a Pulling apart the items to be sorted and largely overlaps avoided. This high transport speed is also required in order to To generate a sufficiently large trajectory parabola of the goods to be sorted at the end of the conveyor belt. the Trajectory parabola leads via pneumatic ejectors, the two pre-selected plastic Take the main fractions from the material flow. A NIR- arranged spectroscopic image processing. The recorded images will be evaluated ultrafast according to defined criteria and used to control the pneumatic ejectors are used.

The fraction of the remaining plastic parts fall on a conveyor for separating the Plastic parts. If necessary, a mechanical stress device can be used in this area be added, which mechanically stresses the parts. This stress should on the one hand, improve the identification of black plastics through embrittlement, on the other hand, separate alliances. From the conveyor the parts fall to one Sorting carousel. The sorting carousel has receptacles that are symmetrical around a Rotation axis are arranged. A suitable setting of the conveyor should be a Even and aligned feeding of the plastic parts to the sorting carousel secured. Findings known in the construction of pick and place machines are taken into account. The shapelessness of the parts and the high throughput are new of at least 5 plastic parts per second.

When the carousel rotates, the parts reach the MIR measuring head. The measuring head measures the material properties of the plastic parts and in an industrial PC the Variety determined. The system control is informed via a serial interface which point the identified parts are to be sorted out. The system shows 4 Ejection chutes for the identified plastic parts as well as an acceptance point for the remaining fraction. The sorted goods are collected in the containers.

The exemplary NIR spectrometer consists of the NIR measuring head and the measuring device. The measuring head combines the light sources with the focus on the sample and the Fiber optics to capture the light from the sample. The measuring device contains the Spectrographs with the NIR detector line, the line supply and analog Signal processing, the calibration device, an industrial PC with the spectrometric software, the control of the measuring system, the power supply and the interfaces to the system control.

InGaAs photodiode lines with a signal / noise ratio have been known since 1995, which is about an order of magnitude better than that of the PbS resistors. the Detector size is an order of magnitude smaller than with the PbS used up to now Lines. The known spectrometers are too faint for these new lines. It makes sense to develop spectrometers where the largest possible Sample area is imaged on a small detector. This task can be done with holographic optical elements are realized specifically for these tasks are tailored. Building on photodiode lines up to 512 elements and one Seya-Namiaka spectrometer with a holographic concave grating is said to be an NIR measuring system to be developed, the higher resolution and higher detection sensitivity than that previously known spectrometer. The planned arrangement is intended to trigger a trip of 2 nm / pixel in the range between 1.5 and 2.2 µm can be achieved. Small Differences in the absorption spectra of e.g. B. Nylon6 and Nylon66 can do so can be safely measured. Another advance is in the identification of Flame retardants to be expected, which so far have only been measured in the mid-infrared could.

The 10 times better signal / noise ratio of the InGaAs detectors can can only be used because the associated analog signal path has the required Sensitivity as well as the necessary dynamic range. The line camera shows a 16-bit analog / digital converter.

The light intensity of the optical paths in the measuring room is optimized. Halogen lamps are for Radiation sources suitable for the NIR range. They are cheap and always on sale available. The electrical parameters for operating the lamps are to the effect optimized to ensure maximum radiation intensity on the sample. Furthermore, the focusing of the lamps on the samples as well as the collection of the light from the Sample optimized for the fiber optics.

The light sources, the optical arrangement and the sensors show drift phenomena or aging effects. In order to impair the ability to identify prevent optical measuring systems are regularly calibrated. The measuring system shows a calibration device, which the measuring arrangement at regular intervals automatically recalibrated.

According to the invention, an identification time of less than 4 ms should be achieved if possible. Ultra-fast spectrometric software is provided for this purpose. The software shows the following conceptual structures:

• - Pre-processing of the spectra via normalization and fuzzification of the measured values
• - Classification of the spectra with neural networks
• - plausibility check
• - Use of a digital signal processor to increase the speed
• - Development of a variety database
• - Spectrometric software for the determination of plastic blends.

This makes plastics with a graphite content of up to 0.5% in one Movement up to 4 m / s reliably identified.

Black plastics with a graphite content over 0.5% are used in the area of Fundamental waves measured in the mid-infrared range. For this task comes a AOTF spectrometer for use.

Exemplary configurations or applications of the invention for tasks in the Recycling area

For the automotive industry, this method solves the material Recycling of plastics from motor vehicle scrap the existing problem, the to recycle the constantly increasing mountain of plastic waste productively and economically. By the possibility of sorting shredded plastics can manual dismantling and sorting work is no longer necessary.

So far, there is a lack of high-performance plastics from electronic scrap Sorting process for material recycling. Again, make a lot different shapes of parts, a wide range of polymers and additives and black coloring extreme demands on the sorting mechanics and the Identification sensors. The invention can be modified without substantial changes can be used directly for plastics from electronic scrap.

For the processing of scrap when recycling metals, especially aluminum scrap, the purity of types is a decisive factor. Smelters and foundries usually feed scrap from their own test casts, separated feeders, risers, etc. back into their own weld pool without any problems. Primary scrap from other companies, in which it is sorted and collected accordingly, is also recycled without any problems. So z. B. new profile waste from the material AlMgSi0.5 collected separately from window and door manufacturers and recycled. In the scrap metal trade, these secondary raw materials are valued at significantly higher prices than comparable scrap metals from the scrap collection point with unknown composition, adhesions, impurities and foreign matter proportions. As an example, here are some wholesale purchase prices for aluminum scrap from 03/20/96 in DM / 100 kg:

Alu. new, poor in Cu 180-190 Pure aluminum wire 220-225 Cast scrap, max. 2% Fe 135-140 Aluminum sheet waste, max. 2% foreign material 120-125 Aluminum chips, max. 5% foreign matter. 110-115 Aluminum profile waste, AlMgSi0.5 225-230 Cast aluminum alloy No. 225 216-250 Cast aluminum alloy No. 226 225-252 Cast aluminum alloy No. 231 240-264 Cast aluminum alloy No. 233 277

The usual sorting practice of the scrap metal wholesalers differs according to the Conditions caused by the quality of the secondary materials and are determined by trade agreements with buyers and recyclers. So far, there has usually been a pre-sorting by inspection and one subsequent shredding. The result is an aluminum scrap that is not in a class can be classified and its sale is only possible at significantly reduced prices. According to the invention, it is possible to separate the high-quality aluminum scrap parts as single-type Separate fractions and add the remaining fraction in the analytical composition determine. This means that the Al smelters can be offered a defined quality and good Prices can be obtained. The profit for the recycling company can be considerable increase.

The system for sorting shredded plastics can be used accordingly for Realize shredded light metals. To identify the chemical The NIR sensor can assemble the Al parts using a laser plasma sensor be replaced.

Electronic scrap contains large amounts of technical glass. Alone in In Germany there are around 5 million picture tubes for disposal every year. The picture tubes consist of special glasses that represent high quality secondary raw materials. Nevertheless, the majority of these glasses are still deposited. Even those in modern ones Shards that have been cleaned of toxic fluorescent substances are delivered to the Usually only an inferior raw material because of the large number of types of glass used with a wide variety of chemical compositions, a direct material one Recycling of the mixed glass fraction prevented.

The laser plasma sensor is used for sorting technical glasses into single-origin Recycling of high pressure lamp glasses is particularly suitable according to the invention. It is a coarse sorting according to the type of glass through a simple qualitative analysis of the chemical components (Table 1) as well as an exact quantitative determination possible.

It was possible to obtain single-variety glasses that were used directly in the glassworks Production of new lamp glasses can be used.

The possibility of differentiating between different classes within one type of glass depending on the concentration of individual oxide components, allows one Manufacturer-specific sorting. For example, a distinction can also be made staggered according to the lead or barium oxide content, their determination at the Disposal of cone or screen glasses of various picture tubes from Meaning is to be done.

By constantly measuring the chemical composition of broken Mixed glass fractions by means of laser spectroscopic rapid analysis are in the Composition known glass fractions achievable and thus their Can be recycled as a high-quality secondary raw material.

The NIR sensor is removed from the plastic sorting system by the Laser plasma sensor replaced and with it the sorting system for broken cullet the picture tube area.

Fig. 1 shows a schematic representation of a system for automatic sorting of plastics from the motor vehicle scrap.

This plant is suitable plastic body in size smaller than 8 × 8 cm, larger than 3 × 3 cm, in two stages, the first stage having two main fractions and the second Level 5 shows fractions to separate safely. The materials PVC, PS, PP, PE, ABS, PC, PA, PUR, PPO, PMMA and others recognized and the basis of Sorting done. The sorting purity of the plastic type becomes better than 99% achieved. The system requires a footprint of 10 m × 5 m and can handle approx. 1 t / h process and sort.

List of reference symbols

1

Feed facility

2

NIR measuring head line, sensor line

3rd

Row of halogen lights

4th

Row of pneumatic ejectors

5

Control cabinet for process measurement technology and process control

6th

Container for single-type, separated plastic parts

7th

Slide for separated plastic parts

8th

Vibratory conveyor for plastic parts

9

Sorting carousel

10

NIR measuring head with halogen lamps

11

MIR measuring head with infrared lights

12th

Container for single-origin fractions

13th

Plastic residue

14th

Gripper for plastic parts

Claims (2)

1. A method for separating plastics and composites according to the type, with sensors to identify the type of plastic and actuators for the mechanical separation of the plastics, characterized in that the plastic parts are crushed to a uniform size in a first process step,
that the shredded parts are placed on a conveyor belt and distributed there as evenly as possible,
that the parts are guided past a row of sensors that determine the position on the belt and the type of plastic parts,
that the identified and localized parts are dropped at the end of the conveyor belt via trajectory parabolas,
that at this point one or two predetermined plastic fractions are separated from the material flow and processed further as single-type fractions,
that the remaining fraction is picked up by a subsequent transport system and transported to a sorting carousel,
that the sorting carousel predominantly picks up one plastic part at a time and guides it past one or more sensors,
and that the identified plastic parts are collected according to predetermined criteria via actuators at dropping stations, sorted by type, in containers or transport systems. 2. The method according to claim 1, characterized in that
that the sensor line is a line of NIR measuring heads that is connected to an NIR spectrometer via an optical multiplexer, which is located in the control cabinet for the process measurement technology and process control,
that the signals picked up by the measuring head line are used in the computer for process control to determine the position on the tape and to identify the plastic parts and
that the process control activates mechanical or pneumatic ejectors on the basis of this information, which blow out predetermined plastic parts according to freely selectable criteria.