JP2001208704A - Method of detecting foreign matter of used plastic, method of removing foreign matter, and compression packing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique related to the detection and removal of a foreign matter mixedly existing in a used plastic suited to recycling and a technique related to the compression of the used plastic. SOLUTION: The hard foreign matter mixedly existing in a used plastic is detected and removed by judging the presence of foreign matter on the basis of the transmitted X-ray data which is obtained by irradiating the used plastic with X-rays. A used plastic compression package reduced in the content of foreign matter is manufactured by compression packing of the used plastic from which the detected foreign mater is remove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting and removing foreign substances mixed in used plastics in a process for recycling used plastics discharged from households and the like, In addition, the present invention relates to a method for easily manufacturing a used plastic compressed package with less foreign matter.

[0002]

2. Description of the Related Art Polyethylene, polystyrene and other plastics are used in various applications such as packaging, containers, cases of home electric appliances, toys and the like because of their excellent moldability and durability. However, at the same time, it is also being disposed of in large quantities as waste. Plastics generated as waste include waste plastics (hereinafter referred to as waste plastics) generated from processing steps such as leftover molds and cutting residues during molding, as well as container and packaging plastics and product plastics. There is used recovered plastic to be discarded (hereinafter referred to as used plastic).

[0003] The generation of a large amount of plastic waste has become a major social problem at present, and particularly an environmental and resource problem. In other words, when these waste plastics are incinerated as waste, the combustion temperature rises too much, damaging the incinerator,
There is a problem of generating harmful gas or dioxin.
In addition, there is a problem that the soil does not solidify even when the landfill treatment is performed because the plastic does not rot.

[0004] Therefore, recycling these waste plastics solves the above-mentioned problems and is advantageous from the viewpoints of energy saving and resource saving. Therefore, various methods have been implemented. For example, as a method of material recycling, a method of using a polyethylene terephthalate bottle as a raw material of a plastic or a twisted yarn, a method of gasifying at a high temperature, and other methods are used. Regarding recycling to fuel, it is common to use a granulated product produced by compression molding after removing vinyl chloride as fuel for boilers and industrial furnaces.

To recycle waste plastic as a fuel or a raw material, there are a method of performing processing such as molding at a site where the waste plastic is generated, and a method of processing the waste plastic at a place remote from the place where the waste plastic is generated. In particular, in a method of processing at a remote place from the place where the waste occurs, a pre-compression packing may be performed in order to efficiently transport the used plastic.

[0006] When performing pre-compression packing, it is an important requirement to manufacture and recycle compressed plastics with less foreign substances. In other words, when foreign materials are mixed when transporting used plastic compressed packages and reusing them at a recycling factory, problems such as damage to processing machines and deterioration in the quality of recycled products will occur. Had occurred.

[0007]

It is common that used plastics contain foreign matter, and when used in a small amount, 2 to 5% by mass, and in large cases, 30% by mass.
Foreign matter is mixed. The foreign matter is kitchen waste, sand, glass dust, paper, metal pieces, and the like. The problem is particularly large with hard foreign matter. These are metal plates,
Bolts, wires, blades, ceramic parts of about 5 mm or more, and other metals and ceramics. If this large hard foreign substance is present in the used plastic, the crushing machine may stop due to biting during the plastic crushing process, the crushing blade may be broken, or if it is severe, the shaft of the crushing blade may be damaged. It often causes serious equipment and operational problems such as bending.

In the prior art, various methods have been adopted as a method for removing foreign substances such as kitchen waste, sand, glass dust, paper and the like, for example, as described in JP-A-51-11089. However, this method is not suitable for removing the hard foreign matter described above. On the other hand, in the case of recycling plastic bottles that can be easily separated from foreign matter, see Japanese Patent Application Laid-Open
As described in US Pat. No. 19933, mechanical separation methods have been relatively established. However, none of the conventional techniques has a good technique for efficiently detecting and removing hard foreign matter. In the case of used plastic, which can be mixed with the handle of vinyl umbrellas and even small household appliances, if hard foreign matter is not removed, the waste plastic crusher will be damaged, and the recycling plant will start operation. There was a problem that the rate dropped significantly.

Therefore, in the conventional method, as a countermeasure for the trouble of the crusher caused by the hard foreign matter, after removing the packing of the used plastic which has been received and removing the hard foreign matter, the low speed for sorting by humans is used. It has been common practice to spread used plastic on a belt conveyor (hereinafter, referred to as a hand-selecting conveyor) and have several workers remove large foreign matter from the used plastic. In addition,
In the case of waste plastic discharged from factories, etc. where the brand can be identified, foreign matter countermeasures can be taken only by removing iron pieces by a magnetic separator, but in the case of used plastic, the magnetic material in the used plastic can be eliminated. Because the tape wrapped around the magnetic separator in large quantities, the function of the magnetic separator could not be exhibited, and non-magnetic hard foreign substances, such as stainless steel knives and ceramics, could not be removed,
As described above, a method that relied on people was used.

Therefore, there is a need for a new technique for detecting and removing hard foreign materials mixed in used plastics, which can minimize the number of sorting operators for eliminating the effects of hard foreign materials on equipment and operation. Was.

When recycling used plastics, compression packing may be performed after removing foreign substances from the used plastics as an intermediate treatment.
This is because the used plastic has an extremely low bulk specific gravity, and in severe cases, is only 0.03 kg / liter or less, and is difficult to transport to a recycling plant. In this case, the used plastic bag containing the collected bags is broken, and the foreign matter is removed manually and in a mechanical separation process such as a magnetic separation period. And had

At this time, there is a problem that labor is required due to the operation relying on manual work, and there is a problem that large foreign substances are mixed in the compressed package due to missing foreign substances. Also, used plastic in bags is well packed and does not spill from between ties when compressed and packed, but used plastic that has broken the bag falls apart and is poorly tied and spills from between ties. There were also many problems. In other words, there has been a demand for a new method of detecting and removing foreign substances in used plastics, which is capable of inspecting and removing foreign substances even in a bag, and a method of compressing and packing with little foreign substances.

[0013]

The present invention is as described in (1) to (13). (1) Place the used plastic on a moving means with a mass per square meter of 60 kg or less, irradiate the area including the used plastic with X-rays, and transmit the transmitted X-ray intensity to the X-ray detection sensor. A method for detecting foreign matter by detecting an electrical signal that changes in accordance with the transmitted X-ray intensity, and detecting the foreign matter by determining the electrical signal. (2) The transmitted X-ray intensity detected by the X-ray detection sensor is 2
The method according to (1), wherein the presence of foreign matter is determined by forming a three-dimensional image. (3) Irradiate used plastics with X-rays, generate electric signals that change according to the intensity of transmitted X-rays, analyze the electric signals, and generate information signals corresponding to the X-ray transmission characteristics of the image field of view. Wherein the information signal is electrically compared with specific comparison information stored in advance in a storage device by a data analyzer having an arithmetic function. Detection method. (4) The data analysis device having the arithmetic function performs image processing on the two-dimensional transmission image of the transmission X-ray signal intensity obtained by the X-ray detection sensor, and determines the actual image and the judgment information stored in the storage device in advance. (2) The method for detecting foreign matter in a used plastic according to (2), wherein the presence or absence of foreign matter is automatically determined by comparing and referencing the data of density and shape. (5) A method for removing foreign matter from used plastics, comprising operating a device for removing a load on the moving means based on the determination information obtained by the method for detecting foreign matter from used plastic described in (1). (6) The apparatus according to (5), wherein a device for removing a load on the moving means is automatically operated based on the determination information obtained by the used plastic foreign matter detection method described in (3). A method for removing foreign matter from used plastic. (7) The apparatus according to (5), wherein a device for removing a load on the moving means is automatically operated based on the determination information obtained by the used plastic foreign matter detection method described in (4). A method for removing foreign matter from used plastic. (8) Separately collected used plastic in a bag with a mass per square meter of 60 kg or less is placed on moving means, and the used plastic is irradiated with X-rays without breaking the bag and transmitted. A method for compressing and packing used plastics, comprising determining an X-ray intensity signal detected by an X-ray sensor receiving X-rays, and compressing and packing the used plastics in a bag only when a predetermined standard is met. . (9) Separated collected plastic bags with X
Irradiates the X-rays and irradiates the electric signal information, which changes according to the intensity of the transmitted X-rays, with comparison information indicating the presence or absence of a foreign substance to be removed stored in advance in a storage device, using a data analyzer having an arithmetic function. Only when it is judged electrically that there is no foreign matter to be removed, the used plastic in the bag is compressed and packed without breaking the bag (8).
Compressed packing method for used plastic as described. (10) The method according to (8), wherein only the used plastic in a bag, which is determined to be free of foreign matter by the method for detecting foreign matter in used plastic described in (2), is compressed and packed. Compression packing method for used plastic. (11) Tube voltage of irradiation tube 30 to 320 kV and tube current 5 to 20
The method for detecting foreign matter in used plastic according to (1), wherein an X-ray generator for irradiating X-rays of mA is used. (12) Tube voltage of irradiation tube 30 to 320 kV and tube current 5 to 20
(5) The method for removing foreign matter from used plastic according to (5), wherein an X-ray generator irradiating X-rays of mA is used. (13) Tube voltage of irradiation tube 30 to 320 kV and tube current 5 to 20
The method for compressing and packing used plastic according to (8), wherein an X-ray generator for irradiating X-rays of mA is used.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention uses an apparatus described below to detect foreign matter in used plastic and remove the foreign matter. How to do it. First, FIGS. 1 and 2 are used to describe a method for detecting foreign matter mixed in used plastic according to the present invention.

FIG. 1 shows an example of a detection device using X-rays of hard foreign matter in used plastic in a bag state.
In this example, an embodiment is shown in which the transmission intensity of X-rays is displayed as a two-dimensional image and the presence of a foreign substance is determined by performing data analysis.

The used plastic bag 2 placed on the plastic conveyor 1 is placed in the X-ray shielding frame 6. Here, X-rays are radiated from the X-ray irradiator 4 toward the used plastic bag 2, the transmitted X-rays are detected by the X-ray detector 5, and this electric signal is converted by the signal converter 7. It is converted into an image signal and displayed on the monitor 9 as an X-ray transmission image. Since the hard foreign material 3 is an iron plate, a damaged tool, or a ceramic product, it contains iron, nickel, titanium, and other atoms having a large atomic number, and is hard to transmit X-rays as compared with plastic. The image is displayed on the monitor 9 as a portion having a high image density. This image is judged by a human to detect hard foreign matter. As another determination method of foreign matter detection, a signal obtained by the signal converter 7 is subjected to signal processing by the data analysis device 8 to automatically determine presence of foreign matter. As a specific method, a condition for determining a transmitted X-ray pattern of a foreign substance to be detected is incorporated in a memory device of the data analyzer 8 so that actual detection of transmitted X-rays transmitted from the signal converter 7 is performed. The presence of a foreign substance is detected by comparing and judging the signal electrically.
If it is determined in these determinations that foreign matter to be detected is present in the used plastic bag 2, the used plastic bag to be recycled is removed by removing the used plastic bag from the plastic conveyor 1. Foreign substances are prevented from being mixed in the inside.

FIG. 2 shows an example in which the bag is broken and the used plastic is placed in a layer on the plastic conveyor 1. It is also a diagram showing an embodiment in which a data analysis device performs shape determination of an image-processed image in the case of automatically detecting foreign matter.

The used plastic in the bag is broken in the previous step, and the used plastic contained therein is placed on the plastic conveyor 1 in a layered manner. X-rays are projected onto the used plastic layer 10 and transmitted X-rays are detected by the X-ray detector 5. This is converted into an image signal by the signal converter 7. Further, the image signal is subjected to image processing by the data analysis device 8 to clarify the image. At the same time, the information obtained by the image pattern recognition can be compared with reference data stored in advance so that the foreign matter can be automatically determined. Here, at the time of automatic judgment,
The thickness, size, and shape of the hard foreign material represented by the density of the shadow of the transmission image are used as determination criteria in the determination logic.

The present inventors have conducted studies on the amount of X-rays irradiated on hard foreign matter in used plastic and the amount of plastic and obtained the following conclusions.

Here, the foreign matter in the used plastic to be detected is an iron plate having a thickness of about 1 to 3 mm or more, a bolt, and a ceramic product having a thickness of 10 mm or more. The present inventors have observed the X-ray transmission image of the foreign matter by changing the mass of plastic per unit area, and when the state is 40 kg or less per square meter, the foreign matter image can be visually identified, In addition, automatic determination in image processing was performed. The mass of plastic is 40-6 per square meter
In the case of 0 kg, the image of a thin foreign substance becomes unclear,
Judgment was a little difficult. This is because the X-ray transmittance of plastic is 1/5 to that of heavy elements such as iron.
Since it is about 1/20, it has been clarified that if the effective thickness of the plastic (corresponding to the mass per unit area) increases, the whole image becomes dark and the shadow portion becomes unclear.

Further, it has been clarified that even with the above-mentioned plastic mass per unit area, it is difficult to obtain a clear image unless the tube voltage and current of the X-ray generator are set within appropriate ranges. In other words, they found that the tube voltage and the tube current of the X-ray generator were the conditions for determining the quality of the transmitted image, and repeated various experiments. As a result, if the X-ray is too strong and the transmission is too good, the shadow of the foreign matter becomes thin and unclear,
In addition, when the X-rays were too weak and the transmission was insufficient, the X-ray absorption of the plastic resulted in a dark image as a whole, and it was found that foreign substances could not be sufficiently detected. Therefore, the present inventors have conducted various studies and found that, due to the difference in the X-ray transmission characteristics between the substance to be detected and the plastic, the condition under which a clear image is easily obtained is that the tube voltage is 30 to 300 kV and the tube voltage is 30 to 300 kV. It was revealed that the X-rays had a current of 3 to 20 mA.

Hereinafter, a method of removing foreign matter from the used plastic using the foreign matter determination apparatus using the X-ray and a method of compressing and packing the used plastic in a bag after removing the foreign matter will be described. FIG. 3 shows an apparatus diagram used in this method. The upper figure is a plan view, and the lower figure is a side view.

The used plastic bag 2 is conveyed by the plastic conveying conveyor 1, and an X-ray device in the X-ray shielding frame 6 obtains a transmitted X-ray signal of the used plastic bag 2. The transmitted X-ray signal is converted by the signal converter 8 into two-dimensional transmitted X-ray intensity distribution information. The transmitted X-ray intensity distribution information is used by the data analysis device 9 to determine the presence of foreign matter, and the used plastic bag 2 in which hard foreign matter is detected is removed by the used plastic bag removal device 11 to the plastic transport conveyor 1.
Eliminate from. Here, the used plastic bag 2 in which the hard foreign matter is detected is used plastic bag bucket 1
Moved to 2. The used plastic bag 2 in which hard foreign matter was not detected is transferred as it is on the plastic transport conveyor 1 and compressed by the compression packing machine 13 into the compressed package 14.
To manufacture.

In the present invention, the compressed packaged product 14 of the used plastic manufactured is transported by truck to a recycling factory, where it is recycled into raw plastic and chemical raw materials.

[0025]

EXAMPLE As an example using the present invention, an operation was performed with the apparatus shown in FIG. This equipment detects hard foreign substances at the stage of used plastic bags.
In the apparatus of the present invention, the presence of metal bolts, large iron plates, kitchen knives, home appliances, and other items is automatically determined. Although not shown in the figure, a monitoring monitor was provided in the operation room at another position, and the image of the foreign matter could be confirmed in the same shape. When it was determined that a foreign substance was present, the used plastic bag removing device 11 was activated, and the used plastic bag was removed from the plastic transport conveyor 1. The used plastic bags, which were not removed without detecting foreign matter, were directly compressed into packages by the compression packaging device 13.

Conventionally, there was no hard foreign matter detection device, so four hard foreign matter sorting personnel were arranged and the sorting was performed on a manually selected belt conveyor. However, since the hard foreign matter is constantly monitored, the sorting is performed. Personnel were tired and were often overlooked. As a result, even in this separation system,
A hard foreign object caused a plastic crusher to break down on average 18 times a month at a remote recycling plant, and the plant was shut down for an average of 19.3 hours a month on average. On the other hand, by using this device, only one monitor / monitoring person is required for sorting, and the breakdown of the plastic crusher at a remote recycling factory due to hard foreign matter is not required. It has decreased to 3.4 times on average on a monthly basis, and equipment failures have been suspended on an average of 2.2 times per month.
It was time.

As described above, according to the present invention, hard foreign substances can be reliably eliminated from used plastics, and the failure of a used plastic crusher at a recycling factory can be greatly reduced to 1/5 or less. In addition, since the determination of hard foreign matter was facilitated, the number of sorting personnel was significantly reduced.

[0028]

According to the present invention, the use of the used plastic foreign matter judging apparatus and the foreign matter removing apparatus according to the present invention makes it possible to reliably detect and eliminate foreign substances, and to compress and pack used plastics with little foreign substances. In addition, since the determination of the foreign matter was facilitated, the number of personnel for separating foreign matter could be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the structure of an X-ray foreign matter detector for detecting foreign matter present in a used plastic bag.

FIG. 2 is a diagram illustrating a structure of an X-ray foreign matter detector that detects foreign matter present in a used plastic layer on a belt conveyor.

FIG. 3 is a diagram showing a used plastic compression packing facility provided with an X-ray foreign matter detector for detecting foreign matter present in a used plastic bag.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Plastic conveyor 2 Used plastic bag 3 Hard foreign object 4 X-ray projection device 5 X-ray detection device 6 X-ray shielding frame 7 Signal converter 8 Data analysis device 9 Monitor 10 Used plastic layer 11 Used plastic bag removal device 12 Used plastic bag bucket 13 Compression packing machine 14 Plastic packing

Continued on the front page F term (reference) 2G001 AA01 BA11 CA01 FA01 HA13 JA09 JA13 KA06 LA05 LA09 PA11 RA06 RA10 3F079 AD00 CA44 CB07 DA12 4D004 AA07 AB03 CA03 CA08 CA43 CB45 DA01 DA02 DA03 DA20

Claims (13)

[Claims] 1. A method in which a used plastic is placed on a moving means with a mass per square meter of 60 kg or less and X-rays are irradiated to a range including the used plastic, and a transmitted X-ray intensity is detected by X-ray. A method for detecting foreign matter in a used plastic, comprising detecting an electrical signal that varies according to the intensity of the transmitted X-rays, detecting the foreign matter by detecting the sensor, and detecting the electrical signal. 2. The method for detecting foreign matter in a used plastic according to claim 1, wherein the presence of foreign matter is determined by forming a two-dimensional image of the transmitted X-ray intensity detected by the X-ray detection sensor. 3. Irradiating used plastic with X-rays,
An electric signal that changes according to the intensity of the transmitted X-ray is generated, and the electric signal is analyzed to generate an information signal corresponding to the X-ray transmission characteristic of the image field of view. 2. The method according to claim 1, wherein the specific comparison information is electrically compared with a data analysis device having an arithmetic function. 4. A data analysis device having an arithmetic function,
The image processing is performed on the two-dimensional transmission image of the transmission X-ray signal intensity obtained by the line detection sensor, and the actual image is compared with the density and shape data, which is the determination information stored in the storage device in advance, so as to be referred to. 3. The method according to claim 2, wherein the presence of foreign matter is automatically determined. 5. An apparatus for removing foreign matter from used plastics, wherein the apparatus for removing a load on the moving means is operated based on the determination information obtained by the method for detecting foreign matter from used plastics according to claim 1. Method. 6. The apparatus for automatically removing a load on a moving means based on the determination information obtained by the method for detecting foreign matter in a used plastic according to claim 3. The method for removing foreign matter from used plastic described in the above. 7. An apparatus for automatically removing a load on a moving means based on the determination information obtained by the method for detecting foreign matter in a used plastic according to claim 4. The method for removing foreign matter from used plastic described in the above. 8. A method of placing a separated and collected bag of used plastic on a moving means in a state where the mass per square meter is 60 kg or less and irradiating the used plastic with X-rays without breaking the bag. X to receive transmitted X-ray
A method for compressing and packing used plastics, comprising determining an X-ray intensity signal detected by a ray sensor and compressing and packing the used plastics in a bag only when a predetermined standard is met. 9. A method of irradiating X-rays on separately collected and used bagged used plastics, and detecting electric signal information that changes according to the intensity of the transmitted X-rays, the presence / absence of foreign matter to be removed previously stored in a storage device. Is compared electrically with a data analyzer having an arithmetic function, and only when it is determined that there is no foreign substance to be removed, the used plastic in the bag is compressed and packed without breaking the bag. 9. The method for compressing and packing used plastic according to claim 8, wherein: 10. The method for detecting foreign matter in a used plastic according to claim 2, wherein only the used plastic in a bag, which is determined to contain no foreign matter, is compressed and packed. Compressed packing method for used plastic as described. 11. The method for detecting foreign matter in used plastic according to claim 1, wherein an X-ray generator for irradiating X-rays with a tube voltage of 30 to 320 kV and a tube current of 5 to 20 mA is used. . 12. The method according to claim 5, wherein an X-ray generator for irradiating X-rays having a tube voltage of 30 to 320 kV and a tube current of 5 to 20 mA is used. . 13. The used plastic according to claim 8, wherein an X-ray generator for irradiating X-rays having a tube voltage of 30 to 320 kV and a tube current of 5 to 20 mA is used. Compression packing method.