SORTING OUT WASTE GLASS CULLET WITH A HIGHER IRON OXIDE CONTENT

Abstract

Method and sorting system for sorting out waste glass cullet with a higher content of iron oxide from a single-layer material stream of waste glass cullet. The material stream contains waste glass cullet with a higher and a lower content of iron oxide. The material stream is irradiated with visible light and the visible transmission light passing through the waste glass cullet is detected, the material stream is irradiated with infrared light in a frequency range of at least 1100-1200 nm and the infrared transmission light passing through the waste glass cullet is detected, a waste glass cullet is classified as having a higher content of iron oxide if the ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light exceeds or falls below a predetermined threshold value, and the cullet classified in this way is separated from other waste glass cullet.

Claims

1. A method for sorting out waste glass cullet with a higher content of iron oxide from a single-layer material stream of waste glass cullet, wherein the material stream contains waste glass cullet with a higher and with a lower content of iron oxide, comprising: irradiating the material stream with visible light and detecting the visible transmission light passing through the waste glass cullet, irradiating the material stream with infrared light in a frequency range of at least 1100-1200 nm and detecting the infrared transmission light passing through the waste glass cullet, wherein a piece of waste glass cullet is classified as having a higher iron oxide content if when the ratio of an intensity of the infrared transmission light to an intensity of the visible transmission light exceeds or falls below a predetermined threshold value, and wherein the piece of waste glass cullet classified in this way is separated from other waste glass cullet.

2. The method according to claim 1, wherein an intensity of a red, a green and a blue spectral range is determined when detecting the visible transmission light passing through the waste glass cullet, and either the highest value or a mean value of the three intensities is used as the intensity of the visible transmission light.

3. The method according to claim 1, wherein the intensity of the infrared transmission light is determined as the mean value of an intensity in the frequency range of 1100-1200 nm.

4. The method according to claim 1, wherein the intensity of the infrared transmission light is the intensity in a sub-range of the frequency range of 1100-1200 nm.

5. The method according to claim 1, wherein a further subdivision of waste glass cullet classified as having a higher content of iron oxide is carried out on the basis of the ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light.

6. The method according to claim 5, wherein at least one further threshold value is specified for the further subdivision, which threshold value the ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light exceeds or falls below.

7. The method according to claim 1, wherein the visible light for irradiating the material stream is white light and the visible transmission light passing through the waste glass cullet is detected in a color camera.

8. The method according to claim 1, wherein the visible light for irradiating the material stream is alternately red, green and blue light and the visible transmission light passing through the waste glass cullet is detected in a monochrome camera.

9. The method according to claim 1, wherein the visible transmission light passing through the waste glass cullet and/or the infrared transmission light passing through the waste glass cullet is detected in the form of an image of several pieces of waste glass cullet.

10. The method according to claim 1, wherein the predetermined threshold value for the ratio of the intensity of the infrared transmission light normalized to 1 to the intensity of the visible transmission light normalized to 1 is greater than or equal to 0.9, and a piece of waste glass cullet is classified as having a higher content of iron oxide when the ratio of the intensity of the infrared transmission light normalized to 1 to the intensity of the visible transmission light normalized to 1 is below the predetermined threshold value.

11. A sorting system for carrying out a method according to claim 1, comprising: a first light source for visible light, with which a single-layer material stream of waste glass cullet is to be illuminated, a first detector for visible light, with which the visible transmission light passing through the waste glass cullet is detectable, a second light source, from which infrared light in a frequency range of at least 1100-1200 nm is to be emitted, a second detector for infrared light, with which the infrared transmission light passing through the waste glass cullet is detectable, a device for producing a single-layer material stream from waste glass cullet, with which the material stream is guidable past the two light sources, and a device for sorting out, which then classifies a piece of waste glass cullet as having a higher content of iron oxide and separates it from other waste glass cullet of the material stream when the ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light exceeds or falls below a predetermined threshold value.

12. The sorting system according to claim 11, wherein the first light source for visible light is designed to emit white light and the first detector is a color camera.

13. The sorting system according to claim 11, wherein the first light source for visible light is designed alternately to emit red, green and blue light and the first detector is a monochrome camera.

14. A computer program product comprising: a program loadable directly into a memory of a central computing unit of a sorting system, where the sorting system includes at least a first light source for visible light, with which a single-layer material stream of waste glass cullet is to be illuminated, a first detector for visible light, with which the visible transmission light passing through the waste glass cullet, is detectable, a second light source from which infrared light in a frequency range of at least 1100-1200 nm is to be emitted, a second detector for infrared light, with which the infrared transmission light passing through the waste glass cullet is detectable, a device for producing a single-layer material stream from waste glass cullet, with which the material stream is guidable past the two light sources, and a device for sorting out, which then classifies a piece of waste glass cullet as having a higher content of iron oxide and separates the piece of waste glass cullet from other waste glass cullet of the material stream if the ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light exceeds or falls below a predetermined threshold value, wherein, when executed by the central computing unit, the program carrying out the method according to claim 1.

15. The method according to claim 8, wherein the visible light for irradiating the material stream is alternately red, green and blue light and the visible transmission light passing through the waste glass cullet is detected in a same monochrome camera.

16. The method according to claim 10, wherein the predetermined threshold value for the ratio of the intensity of the infrared transmission light normalized to 1 to the intensity of the visible transmission light normalized to 1 is greater than or equal to 0.92.

17. The sorting system according to claim 11, wherein the visible transmission light passing through the waste glass cullet is detectable in a form of an image of several pieces of waste glass cullet, and wherein the infrared transmission light passing through the waste glass cullet is detectable in a form of an image of several pieces of waste glass cullet.

18. The sorting system according to claim 14, wherein the visible transmission light passing through the waste glass cullet is detectable in a form of an image of several pieces of waste glass cullet, and wherein the infrared transmission light passing through the waste glass cullet is detectable in a form of an image of several pieces of waste glass cullet.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0072] The invention will now be explained in more detail with the aid of schematic figures, which show exemplary embodiments of a sorting system according to the invention. The backlight method is used for the visible light and the infrared light, i.e., the light source and detector are arranged on opposite sides of the material stream.

[0073] FIG. 1 shows a sorting system according to the invention,

[0074] FIG. 2 shows spectra of the transmission light of various pieces of waste glass cullet with different iron oxide contents,

[0075] FIG. 3 shows a diagram of the ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light according to the spectra of the waste glass cullet from FIG. 2.

DETAILED DESCRIPTION

[0076] In FIG. 1, a first light source 1 for visible light and a second light source 2, which can emit infrared light in a frequency range of at least 1100-1200 nm, are arranged in such a way that waste glass cullet 3 can be irradiated through an inclined glass pane 7. The visible transmission light from the first light source 1 that passes through the waste glass cullet 3 is detected in a first visible light detector 4. The infrared transmission light from the second light source 2 passing through the waste glass cullet 3 is detected in a second detector 5 for infrared light. The waste glass cullet 3 is fed onto a conveyor belt or conveyor trough 6 and conveyed by it onto the inclined glass pane 7, where it slides downwards by gravity. After the lower end of the glass pane 7, at least one blow-out nozzle 9 is arranged, which either blows the waste glass cullet 3 falling from the glass pane 7 on the basis of the control signals (see arrows) from the evaluation and control unit 8, so that it falls to the left of a partition wall 10 downwards into a first container 11 for the first fraction, e.g. for waste glass cullet 3 with a higher iron oxide content, or which waste glass cullet 3 falling from the glass pane 7 is not blown on the basis of the control signals (see arrows) of the evaluation and control unit 8, so that it falls undisturbed to the right of a partition wall 10 downwards into a second container 12 for the second fraction, e.g. for waste glass cullet 3 with a lower iron oxide content.

[0077] It is understood that it would also be possible for the blow-out nozzles 9 to be arranged (exclusively or also) on the opposite side of the material stream and, optionally, to blow on waste glass cullet 3 so that it falls downwards to the right of the partition wall 10 into the second container 12, while other waste glass cullet 3 is not blown on and falls into the first container 11.

[0078] The way in which the waste glass cullet 3 with different iron oxide contents is mechanically separated from one another is not essential to the invention.

[0079] The first light source 1 here emits white light in the range from at least 400 to 650 nm. The first light source 1 can be formed by one orin particular in order to cover the entire width of the material stream of waste glass cullet 3a plurality of LED lights.

[0080] The second light source 2 emits light in the infrared range, covering at least the wavelength range of 1100-1200 nm. Light sources can be used that cover a broad infrared spectrum, e.g., the range of 600-1300 nm, for example by means of one orin particular to cover the entire width of the material stream of waste glass cullet 3several infrared halogen emitters. However, light sources can also be used that are tuned to the required range, e.g., covering the range from 1100 to 1300 nm, for example by means of infrared LED lights.

[0081] The glass pane 7 serves as a chute for the waste glass cullet 3 to be examined. When the sorting system according to the invention is installed, it has an inclination of approximately 60. The waste glass cullet 3 slides down it and is illuminated by the two light sources 1, 2. It is essential that the material for the glass pane 7 serving as a chute is translucent at least in the range of 400-1200 nm.

[0082] The spatial distance between the visible transmission light to be detected and the infrared transmission light to be detected should be as small as possible so that both detectors 4, 5, the one for visible light and the one for infrared light, can generate an image of the waste glass cullet 3 that matches as closely as possible.

[0083] The first detector 4 for detecting the visible transmission light is sensitive in a wavelength range of 400-650 nm; if necessary, the sensitivity can be narrowed to this wavelength range using filters. The first detector 4 is usually designed as a color camera. For example, it can be designed as a so-called RGB camera. The measurement results of the color camera can be divided into the color ranges red, green and blue by means of internal filtering. This means that the colors red, green and blue are each transmitted or stored in a separate channel.

[0084] The first detector 4 must at least be able to provide data for an image of the waste glass cullet 3 in shades of gray in order to detect the position and shape of the individual pieces of waste glass cullet 3. This can then be used to determine the position and shape of the individual pieces of waste glass cullet 3, which are necessary to remove them from the material stream by means of downstream units for deflecting cullet, in this case blow-out nozzles 9.

[0085] The first detector 4 could also be designed as a monochrome camera if the first light source 1 does not emit white light, but alternately red, green and blue light. The intensity of the transmitted light in the red, green and blue frequency range can then be determined in succession, in each case using a monochrome image.

[0086] The second detector 5 is usually an infrared camera and is sensitive at least in the 1100-1200 nm range.

[0087] The data detected by the two detectors 4, 5 are fed to the evaluation and control unit 8, which evaluates the two images and assigns the individual pieces of waste glass cullet 3 to the various fractions and controls the blow-out nozzles 9, which transfer the waste glass cullet 3 to the corresponding containers 11, 12.

[0088] Both the exposure time for the first detector 4 for visible light and for the second detector 5 for infrared light is in the order of 2 microseconds to 10,000 microseconds, for example. This enables a high image line rate or a high-resolution image to be achieved.

[0089] The obliquely aligned glass pane 7 could also be shortened. In this case, the area where the light from the two light sources 1, 2 hits the waste glass cullet 3 could be provided in the direction of movement of the waste glass cullet 3 (from top to bottom in FIG. 1) after the glass pane 7, i.e., below the lower edge of the glass pane 7. This would have the advantage that no translucent material is required for the chute and that any contamination of the chute does not affect the measurement result. The disadvantage of the shortened chute is that the waste glass cullet 3 is guided shorter, which can have a negative effect on the discharge efficiency, especially with small cullet 3.

[0090] FIG. 1 shows the connection of the detectors 4, 5 to the evaluation and control unit 8, generally a computing unit (e.g., computer), which can, for example, form the central computing unit of a sorting system, and which executes the program according to the invention. This evaluation and control unit 8 assembles the image lines of the detectors 4, 5 into images and carries out the evaluation according to the invention.

[0091] Depending on this evaluation, the units for deflecting are controlled, such as one or more blow-out nozzles 9 in this case. These are arranged below the glass pane 7 (or below a chute made of non-transparent material) and below the area where the waste glass cullet 3 is irradiated.

[0092] It would also be conceivable to separate the waste glass cullet 3 into three fractions, wherein the waste glass cullet 3 with a higher content of iron oxide is further subdivided, e.g., into a fraction with a medium content of iron oxide and a fraction with a high content of iron oxide.

[0093] In FIG. 2, the intensity of the transmission light in the wavelength range of approx. 380-1680 nm is standardized for various pieces of waste glass cullet 3, here in the range of 0-100%. The intensities were determined in test measurements. Thirteen different types of waste glass with a low iron oxide content were measured, see dashed spectra LI-101 to LI-113, thirteen different types of waste glass with a medium iron oxide content, see solid spectra MI-201 to MI-213, and one type of waste glass with a high iron oxide content, see dotted spectrum HI-301.

[0094] It can be seen that the intensity in the visible wavelength range is generally slightly higher than in the infrared range around 1100-1200 nm for most waste glass cullet 3 of the waste glass types with a low iron oxide content, but the difference is not very large, only a few percentage points. The difference between the intensity in the visible wavelength range and in the infrared range around 1100-1200 nm is already greater for waste glass cullet 3 of the waste glass types with a medium iron oxide content. However, the difference between the intensity in the visible wavelength range and in the infrared range around 1100-1200 nm is greatest for the waste glass type with a high iron oxide content. Here, the maximum intensity in the green spectral range around 530 nm is approx. 88% (or 0.88 when normalized to 1), while in the infrared range around 1100-1200 nm it is approx. 67% (or 0.67 when normalized to 1).

[0095] In FIG. 3, the ratio of the intensity of the infrared transmission light in the 1100-1200 nm range to the maximum intensity, which occurs either in the red, green or blue spectral range, is shown as a percentage for the individual spectra from FIG. 2. This ratio serves as a measure of the transparency due to the iron oxide content and is used as a characteristic for classifying the iron oxide content.

[0096] The ratios for waste glass types with a low iron oxide content are shown on the left, the ratios for waste glass types with a medium iron oxide content are shown in the middle and the ratio for waste glass types with a high iron oxide content is shown on the far right. The iron oxide content increases from left to right in groups (LI, MI, HI). The individual ratios are connected by the solid line and tend to decrease from left to right. If a threshold value of e.g., 93% (or 0.93 when normalized to 1) is now definedknowing the iron oxide content and the intensities measured in the test measurements, see dashed horizontal linethe ratios on the left-hand side of FIG. 3 are largely above this threshold value, while the ratios on the right-hand side of FIG. 3 are largely below this threshold value.

[0097] According to this example, in the industrial application of the method according to the invention to any waste glass cullet, those pieces of waste glass cullet where the ratio is above 93% (or above 0.93 when normalized to 1) are classified as pieces of waste glass cullet with a lower content of iron oxide and those pieces of waste glass cullet where the ratio is below 93% (or below 0.93 when normalized to 1) are classified as pieces of waste glass cullet with a higher content of iron oxide.

[0098] Since the iron oxide content and the corresponding intensities were determined during the test measurements, a further threshold value could also be defined for industrial applications, e.g., at 80% (or at 0.8 when normalized to 1). Waste glass cullet with a ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light of more than 93% (or 0.93) is classified in this example as having a low iron oxide content. Waste glass cullet with a ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light of less than 93% (or 0.93) but more than 80% (or 0.8) is classified as having a medium iron oxide content. Waste glass cullet with a ratio of the intensity of the infrared transmission light to the intensity of the visible transmission light of less than 80% (or less than 0.8) is classified as having a high iron oxide content.

LIST OF REFERENCE SIGNS

[0099] 1 First light source for visible light [0100] 2 Second light source (for infrared light) [0101] 3 Piece of waste glass cullet [0102] 4 First detector for visible light [0103] 5 Second detector for infrared light [0104] 6 Conveyor trough [0105] 7 Glass pane (chute) [0106] 8 Evaluation and control unit (device for sorting out) [0107] 9 Blow-out nozzle (device for sorting out) [0108] 10 Partition wall (device for sorting out) [0109] 11 First container for first fraction (device for sorting out) [0110] 12 Second container for second fraction (sorting device)