AT501020A1 - SORTING DEVICE AND SORTING METHOD FOR PIECE GOODS - Google Patents

Abstract

A loose goods (1) sorting unit has an energy dispersive detector (5) unit (5) with single channel analyser (6) set to the characteristic X ray (4) emission line of a chemical element in the part and producing an analogue signal to control (7) the sorter (8) by comparison with a reference channel (11).

Description

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The invention relates to a sorting device and a sorting method for piece goods, which is introduced via a conveyor belt or the like, wherein the piece goods are exposed to X-radiation and emitted from the unit X-ray radiation is measured, and wherein a sorting process is controlled on the basis of the measurement signal.

From US 6,506,991 Bl, for example, a sorting system for various types of waste paper is known, which supplies the pieces of paper with a conveyor belt of an irradiation device. This has two radiation sources, as well as a detector which detects the radiation emanating from the sample. For the radiation source both visible light, infrared radiation and X-rays can be used. Tuned to the radiation source, the detector may be a simple camera, but also a device with which the wavelength of the emitted measuring radiation can be detected. Depending on the measurement signal detected by the analysis device, for example, an air nozzle is actuated with which the piece goods are conveyed into different containers.

Furthermore, from US 3,872,306 a sorting plant for crops is known, with which, for example, potatoes can be separated from stones and other impurities. The mixture of rocks, crops, and soil is fed to a well in which it passes through the radiation field of a radiation source (e.g., X-rays). The different attenuation of the output radiation due to the different material densities is measured and used as a control signal for deflecting elements, which sort out the stones and impurities. The sorting method is suitable only for piece goods with sufficiently different material density or for materials with distinguishable absorption coefficients for the radiation used.

Finally, from US 5,339,962 a waste separator (inter alia polyester and PVC) is known, which has an electromagnetic radiation source, for example an X-ray tube, and is based on different absorption values and penetration depths of the radiation used in the different materials.

The object of the invention is, starting from known sorting and sorting devices to propose improvements that allow sorting material with very similar values for the material density or similar penetration depth for the ionizing radiation used safely separated even at a rapid throughput, the analysis effort should be kept low ,

This object is achieved in that the measurement is limited to one or a few characteristic X-ray emission lines of a predetermined chemical element in the piece goods whose radiation intensity is detected with a single-channel measurement and from an analog measurement signal is derived, based on a predetermined threshold of the analog Measuring signal of the sorting process is initiated. The advantage is that no X-ray fluorescence analysis has to be carried out since, in the best case, the sorting process is based on the measurement of only one characteristic X-ray emission line whose intensity is detected with a single-channel measurement. In the separation of PET bottles and vinyl bottles is sufficient, for. the measurement of the intensity of the CI Κα-line to win a unique sorting signal.

It is advantageous if at least one reference measured value in the emission spectrum outside the energy range of the characteristic X-ray emission line is detected with a single-channel measurement and at least one analog reference signal is derived therefrom. For example, the measurement signal can be normalized with the aid of the reference signal. For this purpose, the reference signal can be obtained in the region of the anode radiation.

A sorting device according to the invention is characterized in that the detection device has at least one energy-dispersive detector, which is followed by at least one single-channel analyzer, which is set to a characteristic X-ray emission line of a predetermined chemical element in the piece goods, the analog measurement signal optionally via a control and Evaluation device controls the sorting device.

According to an advantageous development of the sorting device according to the invention, the detector is followed by at least one further single-channel analyzer, which is set to a region outside the energy range of the characteristic X-ray emission line whose analog reference signal is used to normalize the measurement signal.

The invention is explained in more detail below with reference to schematic representations and diagrams.

2 shows a detail of FIG. 1 in a schematic representation, FIG. 3 shows a variant of the sorting device according to the invention in a view transversely to the conveyor belt, FIG. 4 shows the diagram of a measurement result, the chlorine content 5 shows the spectra of samples with and without chlorine, and FIG. 6 shows a diagram for determining the minimum detection level (MDL) for chlorine. ···· ♦ + ···· ♦ +

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The sorting device for piece goods 1 shown in FIG. 1 has a conveying device (not shown) with a conveyor belt 2, with which the piece goods 1 are moved in the direction of movement 3. The conveyor belt 2 is an X-ray source 4 for exciting the piece goods 1 with X-radiation, and associated with a detection device 5 for detecting the output of the piece goods 1 measuring radiation. The detection device 5 has at least one energy-dispersive detector 5 ', which is followed by a Einkanalanalysator 6, which is set to a characteristic X-ray emission line of a predetermined chemical element in the article 1. The analogue output signal of the single-channel analyzer 6 is fed either directly or via a control and evaluation device 7 to a sorting device 8. The sorting device 8 has a drive 9 for a pivotable flap 10, so that upon reaching a predetermined threshold value in the analog measurement signal of the sorting process can be triggered. Of course, other known sorting devices can be used, for example, air nozzles, which are controlled by the signal of the control and evaluation device 7.

According to FIG. 1, the energy-dispersive detector 5 'is followed by at least one further single-channel analyzer 11, which is set to a region outside the energy range of the characteristic X-ray emission line whose analog reference signal is used to normalize the measurement signal. For example, a ratio signal can be formed in the control and evaluation unit 7 from the measurement signal and the reference signal.

According to a specific embodiment variant (FIG. 2), the output signal of the detector 5 'is fed via a preamplifier 12 to a discriminator circuit, which in the example illustrated decomposes the fluorescence spectrum into six energy windows. One of the single-channel measurements is made in the area of the Cl emission line, others in the area of the flanks or the top of the Fe line. The single-channel measurements outside the Cl line are used to standardize the measurement signal.

Fig. 3 shows a section of the sorting device transverse to the width b of the conveyor belt 2, wherein in a linear sequence detectors 5 'and x-ray sources 4 are arranged so that the cargo 1 on the conveyor belt 2 are subjected to the smallest possible radiation exposure to the environment as homogeneously as possible with x-rays can.

In Fig. 4 is shown as a measurement example, the measurement of a vinyl-plastic bottle containing chlorine. In the field of view of the detector field, the bottle generates a Cl signal whose signal height is the distance between the measuring spot on the bottle and the detectors, as well as the different thickness of the material in the

Neck and floor area depends. In comparison, a PET plastic bottle would not generate a signal, so that a sorting process can be initiated due to the analog measurement signal from the detectors.

FIG. 5 shows a fluorescence spectrum of a sample with chlorine, as well as a sample without chlorine, wherein the energy in keV is plotted on the x-axis. The chlorine Κα line is clearly recognizable at 2.6 keV, which is absent in the sample without chlorine (solid line). The peak to the right of the chlorine line comes from the Bremsstrahlung of the X-ray tube.

Finally, FIG. 6 shows the attainable detection limit (minimum detection level) for chlorine, whereby an MDL of less than 1% can be achieved.

Claims (9)

. ··· PATENT CLAIMS 1. Sorting method for piece goods (1), which is introduced via a conveyor belt (2) or the like, wherein the cargo (1) is exposed to X-radiation and measured by the cargo (1) X-ray radiation is measured, and wherein the sorting process is controlled on the basis of the measurement signal, characterized in that the measurement is limited to one or a few characteristic X-ray emission lines of a predetermined chemical element in the article (1) whose radiation intensity is detected by a single-channel measurement and an analog measurement signal is derived therefrom is initiated on the basis of a predetermined threshold value of the analog measurement signal of the sorting process. 2. Sorting method according to claim 1, characterized in that at least one reference measured value in the emission spectrum outside the energy range of the characteristic X-ray emission line is detected with a single-channel measurement and at least one analog reference signal is derived therefrom. 3. Sorting method according to claim 1 and 2, characterized in that the measuring signal is normalized with the aid of the reference signal. 4. Sorting method according to claim 2 or 3, characterized in that the reference signal is obtained in the region of the anode radiation. 5. Sorting method according to one of claims 1 to 4, characterized in that for the determination of chlorine in the article (1) the intensity of the CI Κα-line is measured. 6. sorting device for piece goods (1) having a conveyor belt (2) having conveyor for the piece goods (1), a conveyor belt (2) associated X-ray source (4) for exciting the piece goods (1) with X-radiation, a detection device (5) for detecting the measuring radiation emanating from the article (1) and a sorting device (8) controlled by the measuring signals of the detection device (5), characterized in that the detection device (5) has at least one energy-dispersive detector (5 ') which at least one Downstream of a single-channel analyzer (6), which is set to a characteristic X-ray emission line of a predetermined chemical element in the piece goods (1), the analog measuring signal possibly via a control and evaluation device (7) controls the sorting device (8). • · • · ♦ · ··· · ♦ · 7. Sorting device according to claim 6, characterized in that the detector (5 ') at least one further single-channel analyzer (11) is connected downstream, which is set to a region outside the energy range of the characteristic X-ray emission line whose analog reference signal is used to normalize the measurement signal , 8. Sorting device according to claim 6 or 7, characterized in that a linear sequence of detectors (5 ') and X-ray sources (4) is provided, which is arranged transversely or obliquely with respect to the direction of movement (3) of the conveyor belt (2) , 9. Sorting device according to one of claims 6 to 8, characterized in that the set on a characteristic X-ray emission line single-channel analyzer (6) is set to the CI Κα line. 2004 10 18 Fu / Sc A-1150 Vienna, Marie Hilf er Gürtel 39/17 Tel .: (4431) 892 89 33 * 0 Fax: (+43 1) 892 89 333 e-mail: oatemebabelak.at Patent AttorneyDipl.-Ing. Mag. Michael Babeluk