EP1533045B1 - Process and device for improved sorting of waste paper and cardboard - Google Patents

Abstract

A waste recycling assembly recovers wood and paper products for use as incinerator fuel. Waste products are transported by a conveyer belt under a halogen lamp where they are registered by a CCD camera coupled through a lens and spectrograph. The camera registers lines transverse to the direction of refuse travel. The camera registered selected wavelengths coinciding with the target products. The target residues are subsequently discharged by the belt into a sorting assembly operating on the basis of the wavelengths detected by the CCD camera. The lamp emits light in the wavelength from infrared to ultra-violet. Residues including plastics are separated into two fractions. Also claimed is a commensurate assembly with a CCD or NIR camera.

Description

The invention relates to a method for detecting, detecting and sorting objects of a material flow, from waste paper and old cardboard according to the preamble of claim 1, and to an apparatus for detecting, detecting and sorting objects of a material flow according to the preamble of claim 7.

Thermally recyclable waste mixtures are often used for the energetic use of incineration. From the point of view of the sustainable use of valuable raw materials, it makes sense, however, to sort out recyclable materials from the corresponding waste material mixes and to supply them to recycling. The use of recovered paper and cardboard in the paper industry has been known for a long time and is now being intensively pursued.

When collecting waste paper and cardboard, these two main components are mixed. However, it is inevitable that other material, which is not necessarily immediately and easily recognizable as foreign material, flows into the collection. However, such foreign material (eg films of general or plastic-coated papers) can not be used for paper production and therefore has to be sorted out manually by hand. Furthermore, for the production of higher and high quality paper, the cardboard fraction of the collection is not suitable, this can only be used to produce inferior papers or cardboard. In order to allow a meaningful use of the amount of paper and cardboard collected, therefore, a separation of the amount collected in these two fractions makes sense and economically.

Methods which separate the paper from the cardboard fraction from the collection of the paper collection are already known and are based essentially on optoelectronic systems which separate these two fractions by means of color and / or structure recognition (using visible light). This is done by the individual parts of the mixed material flow are placed in a single layer on a sorting belt, irradiated by radiation sources (preferably light sources) and the reflected radiation is received by evaluation and compared with reference values, which then assign these pieces of the respective fraction, whereupon These are then detected by transducers or supplied by Druckluftblas- or suction nozzles to a predetermined storage space.

A procedure of this kind is about EP 1 048 363 A2 known. In this case, the material stream to be sorted is moved in front of radiation sources and through the detection range of cameras along a rectilinear movement direction, wherein the cameras detect the wavelengths of the radiation emitted by the objects of the material flow and their intensity and serve to control subsequent sorting devices. It is proposed that first the wavelength of the radiation reflected by the objects is determined, an assignment of the object to a certain fraction is attempted, and in the event that it can not be unambiguously assigned to a fraction, then the intensity differences of the reflected radiation from different partial areas of the object are determined. If, for example, large differences in intensity of the reflected radiation from different object areas are evident, this indicates printed paper, while slight differences in intensity are more likely to be due to cardboard, since cardboard is generally hardly printed with small letters.

In EP 1 048 363 A2 Furthermore, the idea is expressed to use a line scan camera, which images only a strip of an object, with a movement of the object a plurality of strips are detected sequentially, so as to obtain information about the entire object. In particular, the reflected wavelength of such a stripe is integrally detected, but a differentiation with respect to the reflected wavelengths of different portions of a stripe is not made.

The fact that in such a view, for example, colorfully printed or pure white cardboard boxes are assigned to the paper fraction and obviously wrongly eliminated, reduces the sorting success and thus the quality of the sorted fractions. In addition, any foreign matter (foils, laminated cardboard boxes, composite cartons, multilayer cartons with metal or plastic foils) that may appear in the groupage can not be identified and sorted out.

Due to changed consumer behavior and rationalization in the collection, a further substantial increase of contaminants can be observed. An economic processing of the collected goods, taking into account the required final quality of the individual sorted fractions is therefore increasingly difficult. For example, the inadequacy of the available systems requires complex process solutions, such as the use of multiple cameras.

It is therefore an object of the invention to avoid the complexity of conventional process solutions, so as not for each separation phase (paper board, plastic paper, plastic 1 plastic 2, etc.) its own separation device with radiation source, evaluation and discharge or To provide blowout device. Furthermore, it is the object of the invention to provide recognition and evaluation methods, which, when irradiated by only one radiation source, make it possible to establish definite material properties according to which the individual fractions can be sorted out.

These objects are achieved by the characterizing features of claim 1. Claim 1 relates generically to a method for detecting, detecting and sorting objects of a material stream, in particular wood waste and wood fiber products such as paper and cardboard, in front of radiation sources and through the detection range of at least one camera, which serves to drive subsequent sorting devices, along a rectilinear movement direction is moved, wherein the detection range of the at least one camera stripe-shaped extending transversely to the direction of movement of the objects and the at least one camera detects the wavelengths of the radiation emitted by the objects of the material flow. According to the invention, claim 1 provides that, for a plurality of regions of this strip-shaped section, the intensity of the radiation emitted by an object of the material flow is detected for several wavelengths using spatially resolved spectroscopy and the control of the subsequent sorting devices is performed by comparing the detected wavelength spectra with previously measured wavelength spectra, wherein only selected, discrete wavelength ranges are used to control the subsequent sorting devices. In contrast to known methods, therefore, not only the intensity for different subareas of an object strip is ascertained for the purpose of determining intensity differences, but the entire wavelength spectrum. Through the use of spatially resolved spectroscopy, a larger variety of data is created, which ultimately allows a more accurate assignment to different object fractions, but also allows a greater diversity of the material flow to be separated.

According to the invention, it is provided that the control of the subsequent sorting devices is carried out by means of comparison of the detected, location-dependent wavelength spectra with previously measured wavelength spectra. On the basis of these comparisons of the ascertained location-dependent, spectral reflection intensities of the measured object with previously ascertained product samples, a classification of the object can be carried out. Various materials can be predefined, taught and then assigned to material classes. On the basis of the classified measuring strips, the movement of the objects in the conveying direction of the sorting belt and the rapid repetition of the measurement, the result is a classification-capable image of the object to be recognized. This image is evaluated by algorithms and assigned according to the specifications of the user of a pass or a discharge fraction. After the assignment, at the end of the sorting belt, exhaust nozzles or suction nozzles are activated in time and place according to the sorting task. After activation of the discharge elements, the object is separated from the rest of the material flow via a separating edge, separating roller or separating belt.

According to the invention, a reduction in the amount of data to be evaluated is provided by using only selected, discrete wavelength ranges for driving the subsequent sorting devices.

Furthermore, it often proves necessary to irradiate the objects with electromagnetic radiation in certain wavelength ranges to generate reflection spectra, which are particularly advantageous for further classification. It is therefore provided according to claim 4 that the wavelengths of the radiation emitted by the radiation sources comprise a wavelength range from near infrared to ultraviolet light.

Due to a spatially resolving spectroscopy according to claim 1 and the thus created, greater data diversity ultimately the sorting of a greater variety of material to be separated flow can be handled. According to claim 3, it is therefore provided that the material flow to be sorted additionally comprises plastics so as to make better use of the possibilities of the method according to the invention. Accordingly, according to claim 4 also provided that the material flow is sorted into more than two fractions, which are discharged along different transport directions.

The generation of evaluable wavelength spectra can be done in different ways. For example, it is provided according to claim 5 that the wavelength of the radiation emitted by the objects of the material flow is detected as a reflection spectrum. According to claim 6 it is provided that the wavelength of the radiation emitted by the objects of the material flow is detected as a transmission spectrum. The decision on the choice of one of these two methods will have to be made depending on the composition of the material flow.

Claim 7 finally provides a device for detecting, detecting and sorting objects of a material flow, from waste paper and old cardboard before, the radiation sources and at least one camera for controlling subsequent sorting devices comprises. The detection range of the at least one camera, through which the flow of material is moved along a rectilinear direction of movement, is formed in a strip-shaped manner transversely to the direction of movement of the objects. The at least one camera is a detector for the wavelengths of the radiation emitted by the objects of the material flow. According to the characterizing features of claim 7, it is provided in devices of this kind that the at least one camera is a spatially resolving spectrometer which, for several regions of an object, which are each simultaneously within this strip-shaped section, measures the intensity of the Allow this object emitted radiation for several wavelengths. According to claim 8, an NIR area camera is used for this purpose.

• Fig. 1 eine schematische Seitenansicht einer Ausführungsform eines Sortieranlagenabschnittes zur Durchführung des erfindungsgemäßen Verfahrens,
• Fig. 2 eine schematische Seitenansicht einer weiteren Ausführungsform eines Sortieranlagenabschnittes zur Durchführung des erfindungsgemäßen Verfahrens,
• Fig. 3 eine perspektivische Darstellung der Anordnung von Strahlungsquellen, Kamera und Sortierband, und
• Fig. 4 eine schematische Darstellung eines für das erfindungsgemäße Verfahren geeigneten Spektrographen.

The invention will be explained in more detail below with reference to the accompanying figures. Show it

• Fig. 1 a schematic side view of an embodiment of a sorting plant section for carrying out the method according to the invention,
• Fig. 2 a schematic side view of another embodiment of a sorting plant section for carrying out the method according to the invention,
• Fig. 3 a perspective view of the arrangement of radiation sources, camera and sorting belt, and
• Fig. 4 a schematic representation of a suitable spectrograph for the inventive method.

Fig. 1 shows a schematic side view of an embodiment of a sorting plant section for sorting thermo energetically usable objects 7, 8, 9 such as wood waste, wood fiber products (eg waste paper, cardboard, fabric remnants), plastic waste (eg PET bottles, films) and mixed fractions of different quality and texture, at For example, different existing substances, such as paper 8, cardboard 9 or plastics 7 are on at least one sorting belt 1 and transported along a direction of movement 2. At least one region of the sorting belt surface is irradiated by at least one radiation source 3. The radiation sources 3 can for this purpose also be provided with reflectors 4. The radiation reflected by the individual objects 7, 8, 9 is detected by a camera 5 and the objects 7, 8, 9 are assigned to a specific material class or fraction 11, 12 on the basis of the determined data, as will be explained in more detail below. Due to this assignment, sorting devices 10, 14, such as suction or blowing nozzles, are activated. The physical separation of the objects 7, 8, 9 can in this case be supported by apparatus measures such as separating rollers, separating strips or separating edges 13.

Fig. 2 shows an alternative embodiment, which unlike the in Fig. 1 embodiment shown allows separation of the mixed material into three fractions. This is achieved, for example, by providing a further conveying device 15, to which approximately all cardboard boxes 9 are lifted by means of a first sorting device 10, 14 and are transported in the direction 16 to a collecting location. By means of a second sorting device 10, 14, the further fractions, such as paper 8 and plastic 7 are subsequently separated. The separation of the different fractions by means of a suitable arrangement of suction and blowing nozzles or other conveyors can be made in many ways, however, are a precise and reliable control of the sorting devices 10, 14 necessary, which in turn requires a rapid and reliable assignment of the objects to the different fractions 11 or 12. The method according to the invention is capable of this.

It envisages the use of spatially resolved spectrometer systems. In this case, transmissive spectrometer systems are used which essentially comprise an objective 17, an imaging spectrograph 18 and a matrix detector 19 (eg a CCD camera) (see Fig. 4 ). When using conventional, non-spatially resolved spectrometers, the measuring head has to be moved over the object or the object under the measuring head has to be moved in different directions in order to obtain locally differentiated spectral information. In contrast, spatially resolved spectrometer systems, also referred to here as camera 5 or spectrometer 5, are measuring devices which permit simultaneous recording of spectral and local information of an object surface.

The detection area 6 of the camera 5 is preferably in the form of a line or strip. This is achieved in a known manner by suitable arrangement of lenses 17, which image the radiation emitted by the object 7, 8, 9 onto the input slot of the spectrograph 18. The length of the imaged strip can vary from a few millimeters to several meters, using either commercially available microscope objectives or conventional camera lenses. The spatial resolution varies accordingly from micrometers for measurements in the millimeter range up to several millimeters for measurements in the meter range. Typically, the spectral image is captured by a monochrome CCD camera 19. In this case, in a first dimension, the location information defined by the input slot, ie the position information within a certain strip, imaged and in a second dimension of the wavelength range to be examined. The location-dependent intensities for different wavelengths can thus be represented as a three-dimensional image. Each pixel corresponds to a particular location on the imaged strip of the object 7, 8, 9 and an intensity at a particular wavelength. Usually, the spatial axis is placed in the x-direction and the spectral axis in the y-direction of the detector 19. The spatial resolution is then determined by the number of pixels in the x-direction, while the number of wavelength bands is determined by the number of pixels in the y-direction. In addition, there remains a need to move the measurement object relative to the strip-shaped detection area to accommodate a surface. In contrast to conventional spectrometers, however, the measurement object only has to be moved in one direction.

The matrix detector 19, usually a CCD camera, preferably has a uniform sensitivity over the widest possible wavelength range. CCD cameras 19 having such a characteristic at least in the visible wavelength range are commercially available. In addition, there are also specialized CCD cameras that have good measuring characteristics from the ultraviolet and blue wavelengths to the near infrared. For the determination of chemical composition of material mixtures also spatially resolved spectroscopy is used, but in the near infrared (NIR) range. This technology works up to a wavelength of 2500 nm. In these cases, a NIR surface camera is the preferred instrument. For example, an FPA (Focal Plane Array) detector based on InGaAs and thermoelectric cooling can be used.

It is therefore sometimes because of the different measuring characteristics of commercially available CCD cameras 19 indicated to use multiple spectrometers 5 to cover the entire wavelength range from near infrared to sometimes in the UV range, since different materials for generating evaluable spectra must sometimes be examined in different wavelength ranges. In this case, however, material flows can be sorted, which are composed of diverse fractions. As an alternative to CCD cameras and CMOS, CID or "diode array" cameras are conceivable, although at least currently available systems of this kind have significantly lower sensitivity than conventional CCD cameras.

Converting analog to digital data can be accomplished using conventional 8-bit digitizing PC frame grabber cards, but for more sophisticated sorting tasks, using 12- to 16-bit resolutions is beneficial. Alternatively, a conversion of the analog measurement signal into a digital signal can take place, and sometimes also PC frame grabber cards can be dispensed with.

The amount of data collected can sometimes be considerable, depending on the desired spatial and spectral resolution. It will therefore be to optimize the speed of data processing, which can be achieved by appropriate data processing and special evaluation algorithms. However, it proves to be sufficient in practice not to digitize and evaluate the entire spectral information at each pixel of the measured object strip, but to limit itself to selected wavelength ranges. As a result, the scope of the data to be processed can be significantly reduced and the conveying speed of the sorting belt 1 can be increased. If, for example, the number of coordinate points of the matrix detector 19 to be evaluated is reduced by a factor of 10, then a reduction of the data processing times by a factor of 100 usually appears.

Since, in the method according to the invention, the light emitted by the surface of the objects 7, 8, 9 is analyzed as a function of location and wavelength, a higher irradiation intensity is generally necessary than in the case of RGB cameras, for example. The required irradiation intensity with the aid of the radiation sources 3 depends in particular on the properties of the camera optics, the camera sensitivity, the spectral resolution, the integration time (ie the measuring time of a strip which depends on the conveying speed of the sorting belt 1), the f-number of the objective 17 and of the spectrograph 18 and the spatial dimensions of the detection area 6 from. It is important to ensure the most uniform possible illumination of the detection area 6. This can be achieved with the help of fiber optic lamps or tungsten halogen lamps with linear parabolic or elliptical reflectors 4 with downstream cylindrical lenses.

The illumination by means of the radiation sources 3 should have a stable (and "flat") emission spectrum over the entire wavelength range of the emitted radiation. Since the sensitivity in the blue wavelength range decreases with many commercially available CCD cameras, the illumination by means of the radiation sources 3 can also ensure that the intensity is stronger in the blue wavelength range. Halogen lamps provide a very stable spectrum and have a relatively long lifetime, but have low emission in the blue wavelength range. With the aid of a red filter, however, the emission intensity over the entire wavelength range can be somewhat compensated. Xenon lamps produce a very flat visible spectrum but are more unstable than halogen lamps and also require a high voltage supply. Xenon flash lamps can as well be used. They have a long life and are high power radiation sources, but variations in intensity of 1-2% and spectral instabilities in the flashes can occur.

On the basis of comparisons of the spectrally divided reflection intensities of the object 7, 8, 9 obtained with product samples already taught, a classification of the measuring object 7, 8, 9 can be carried out. The classifiers are capable of learning, i. Various materials can be predefined, taught in and then assigned to material classes. On the basis of the classified strips, the movement of the objects 7, 8, 9 in the conveying direction 2 of the sorting belt 1 and the rapid repetition of the measurement results in a classified image of the object to be recognized 7, 8, 9. This image is evaluated by algorithms and accordingly assigned to the user's specifications of a run or a discharge fraction. After the assignment, at the end of the sorting belt 1 time and place correct exhaust nozzles or suction nozzles 10, 14 are activated depending on the sorting task. After activation of the discharge organs, the object is separated by a separating roller, separating belt or separating edge 13 from the other material flow.

The method according to the invention thus represents a comparatively simple process solution, in which an individual separation device with radiation source, evaluation unit and discharge or blow-out device need not be provided for each individual separation phase (paper board, plastic paper, plastic 1 plastic 2, etc.) , Instead, sufficient data is collected via spatially resolved spectroscopy to ensure reliable classification. It is also possible to determine 3 unique material properties when irradiated by only one radiation source, after which the individual fractions 11, 12 can be sorted out. So can also about the groupage Appearing foreign substances such as foils, laminated cardboard, composite boards, multi-layer cardboard boxes with metal or plastic films recognized us to be sorted out.

Claims (8)

1. A method for detecting, recognizing and sorting objects (8, 9) of a flow of material which is made of waste paper (8) and waste cardboard (9) and which is moved along a straight direction of movement (2) in front of radiation sources (3) and through the detection area (6) of at least one camera (5) which are used for triggering subsequent sorting devices (10, 14), with the detection area (6) of the at least one camera (5) extending in the form of strips transversally to the direction of movement (2) of the objects (8, 9) and the at least one camera (5) detecting the wavelengths of the radiation emitted from the objects (8, 9) of the flow of material, characterized in that with the help of imaging spectroscopy the intensity of the radiation emitted from this object (8, 9) is detected for several wavelengths, and the triggering of the subsequent sorting devices (10, 14) is made by means of comparison of the detected wavelength spectra with previously measured wavelength spectra, with only selected discrete wavelength ranges being used for triggering the subsequent sorting devices (10, 14).
2. A method according to claim 1, characterized in that the wavelengths of the radiation emitted by the radiation sources (3) comprise a wavelength range of near infrared up to ultraviolet light.
3. A method according to claim 1 or 2, characterized in that the flow of materials additionally comprises plastic materials (7).
4. A method according to claim 3, characterized in that the flow of material is sorted into more than two fractions which are removed along different directions of transport.
5. A method according to one of the claims 1 to 4, characterized in that the wavelength of the radiation emitted from the objects (7, 8, 9) of the flow of material is detected as a reflection spectrum.
6. A method according to one of the claims 1 to 4, characterized in that the wavelength of the radiation emitted from the objects (7, 8, 9) is detected as a transmission spectrum.
7. An apparatus for detecting, recognizing and sorting objects (8, 9) of a flow of material made of waste paper (8) and waste cardboard (9), comprising radiation sources (3) and at least one camera (5) for triggering subsequent sorting devices (10, 14), with the detection area (6) of the at least one camera (5), through which the flow of material is moved along a straight direction of movement (2), being arranged in the form of strips transversally to the direction of movement (2) of the objects (8, 9) and the at least one camera (5) are detectors for the wavelength of the radiation emitted from the objects (8, 9) of the flow of material, characterized in that the at least one camera (5) is an imaging spectrometer which allows the measurement of the intensity of the radiation emitted from said object (8, 9) for several wavelengths for several areas of said object (8, 9) which each lie simultaneously within said strip-like section (6).
8. An apparatus according to claim 7, characterized in that the at least one camera (5) is an NIR area camera.

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