JP3782797B2 - Plastic material identification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plastic material identification device, and more particularly to a plastic material identification device applied to the separation and collection of specific plastics from waste plastics discharged from households and waste plastics as industrial waste.
[0002]
[Prior art]
Conventionally, regarding the separation of waste plastics, it has been known to separate plastics by utilizing a specific gravity difference of plastics using a liquid cyclone. Specifically, polyethylene (specific gravity 0.93) and polystyrene (specific gravity 1.05) have a density of 98.6% which is lighter than upper discharge, and 94.7% of polystyrene which has a higher specific gravity than lower discharge. It has been. In addition, wind sorting and sinking sorting are efficiently performed in the same way as using the specific gravity difference. FIG. 5 shows an example of a conventional waste plastic discrimination method.
[0003]
Waste plastic (raw material) 1 is first supplied to a crusher 2. The waste plastic 1 after crushing is sent to the storage tank 3 and temporarily stored. Thereafter, the waste plastic 1 is supplied to the agitation storage tank 5 from a fixed amount supply device 4 disposed on the lower side of the storage tank 3. A constant amount of water 6 is supplied to the stirring storage tank 5 and adjusted to a constant concentration. Next, the mixture of the plastic and water is quantitatively supplied to the hydrocyclone 8 by the centrifugal pump 7 whose rotational speed is controlled, and the low specific gravity plastic is discharged from the upper part of the cyclone to the washing and dehydrator 9, and the water and plastic are mixed. The low specific gravity plastic is stored in the circulating water tank 11 in the low specific gravity storage 10. Also, the high specific gravity plastic and water are discharged from the lower part of the liquid cyclone 8, and the water and the plastic are separated by the washing dehydrator 12. The high specific gravity plastic is temporarily stored in the circulating water tank 11 in the specific storage 13. . As a product, the specific gravity larger plastic than the specific gravity large savings 13, also the specific gravity small plastic is taken out from the specific gravity small savings 10.
[0004]
[Patent Document 1]
Japanese National Patent Publication No. 06-506149 [Patent Document 2]
US Pat. No. 5,134,291 [Patent Document 3]
Japanese Patent Laid-Open No. 06-210632 [Patent Document 4]
Japanese Patent Laid-Open No. 61-192380
[Problems to be solved by the invention]
However, according to the prior art, there are the following problems.
(1) Polyethylene (0.93) and polypropylene (0.90 to 0.91) having substantially the same specific gravity cannot be separated. Further, in the prior art, it has been difficult to separate plastics having a small specific gravity difference (small). Furthermore, if not pulverized, the fluidity in the hydrocyclone is poor, clogging occurs, and separation is impossible.
[0006]
(2) When the material of waste plastic is identified using a near-infrared identification device, it is very difficult to line up by type without overlapping each other on the conveyor.
(3) When recycling waste plastic, it is necessary to separate the identified materials at high speed.
[0007]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a plastic material identification device that can separate plastics having a small difference in specific gravity and can separate plastics without being crushed.
[0008]
[Means for Solving the Problems]
The solution of the present invention includes a pretreatment sorting device for roughly separating plastic, a transport device for aligning and transporting the pretreated plastic, a light source for irradiating the plastic with near infrared rays, and irradiation light from the light source. A light receiving element for detecting transmitted light or reflected light from the plastic, comprising: an identification device for identifying a material by absorbance at a specific wavelength by the plastic; and a separation device controlled by the identification device , wherein the identification When discriminating by the apparatus, the specific wavelength of transmitted light or reflected light from the plastic is 1660 to 1669 nm when it is polyethylene terephthalate (PET), and 1677 to 1698 nm when it is polystyrene (PS). One absorption peak appears, 171 for polypropylene (PP) Two absorption peaks appearing at ˜1726 nm and 1726-1735 nm, and two absorption peaks appearing at 1716-1729 nm and 1746-1754 nm for polyvinyl chloride (PVC), and appearing at 1710-1735 nm for polyethylene (PE) The plastic material identification device is characterized in that the type of plastic is identified by one absorption peak .
[0010]
Solution of the present invention, further the pretreatment sorting device, preferably a material identifying apparatus pulp plastic to have a mobile device and a pulse air nozzle of the plastic.
[0011]
Solution of the present invention, further the pretreatment sorting apparatus, and blown by the wind selection fan moves the plastic on the vibrating screen conveyor, moving plastic material identifying the plastic that is configured to be selected by pulse air nozzle An apparatus is preferred .
[0012]
Solution of the present invention preferably further the transfer device and the material identifying apparatus of the pulse in the balloon side of the air nozzle consists of a plurality of conveyors arranged in parallel flow Help plastics.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a plastic material identification device according to an embodiment of the present invention will be described with reference to FIGS. Here, FIG. 1 is an explanatory diagram of a pre-processing sorting device which is one configuration of the identification device, and FIG. 2 is an explanatory diagram of a near infrared type identification device and a sorting device which are one configuration of the identification device.
[0014]
First, the pretreatment sorting device 21 will be described with reference to FIG. Reference numeral 22 in the figure denotes a wind selection fan that disperses waste plastic (hereinafter abbreviated as waste plastic) sent from a raw material waste plastic hopper on a conveyor as described later. Waste plastic that has passed through the vibrating screen conveyor 23 by the wind selection fan 22 is roughly classified by a plurality of pulsed air nozzles 24 having a constant pressure. That is, heavy waste plastics such as bottles 25 are only blown to near (within 1 m) and reach the conveyor 26a, and light waste plastics such as trays 27 are blown far (1 m or more) and reach the conveyor 26b. Further, small waste plastics, for example, those having a size of 30 mm × 30 mm or less (small items such as caps 28) are small in quantity and are dropped from the vibrating screen conveyor 23 and excluded. This improves the performance of the entire system (preprocessing, identification and sorting device) (accuracy is improved and the amount of processing is increased). As described above, the pretreatment sorting device 21 is mainly composed of the wind sorting fan 22, the vibrating screen conveyor 23, and the pulsed air nozzle 24. The conveyors 26a and 26b are arranged in parallel on the blowing side of the pulse air nozzle 24, and function as a conveying device.
[0015]
Next, the near-infrared discrimination device 29 and the sorting device 30 will be described with reference to FIG. The near-infrared discriminator 29 is a halogen tungsten lamp (light source) 31 that emits near-infrared light, and a light reception made of PbS and InGaAs that detects transmitted light or reflected light from the waste plastic of the light emitted from the light source 31. An element 32 and a spectroscope 33 such as a filter disposed between the light source 31 and the light receiving element 32 are configured. Here, among the waste plastics, heavy ones such as bottles and light ones such as trays, vinyl, and films were aligned on the belt conveyor 34, and then the materials were identified by absorption of near-infrared rays of a specific wavelength. An amplifier circuit 35, a personal computer 36, and an aerial converter 37 are sequentially and electrically connected to the light receiving element 32, and an electromagnetic valve 39 provided on a header 38 is connected to the aerial converter 37.
[0016]
The sorting apparatus 30 includes a sorting box 40 having a plurality of partitioned rooms 40a to 40d. Waste plastics identified by material are controlled by high pressure air (for example, 6 kg / cm @ 2) by a solenoid valve 39, and the high pressure air is discharged from the pulse air nozzle 41 in a pulsed manner to each room 40a-40d of the sorting box 40. Blown away. For example, a PET bottle is stored in the room 40a, a PVC bottle is stored in the room 40b, a PE bottle is stored in the room 40c, and other bottles such as detergent and mayonnaise are stored in the room 40d.
[0017]
As described above, the plastic material identification device according to the above embodiment roughly sorts plastic, and includes a pretreatment sorting device 21 including a wind sorting fan 22, a vibrating screen conveyor 23, a pulse air nozzle 24, and the like. Conveyors 26a and 26b for transporting the preprocessed plastics in alignment, a light source 31 for irradiating the plastic with near infrared rays, and a light receiving element for detecting transmitted light or reflected light from the plastic of the light irradiated from the light source 31 The configuration includes an identification device 29 having 32 and a separation device 30 having a separation box 40 for separating and storing various plastics identified by the identification device 29 with high-pressure air from the pulse air nozzle 41.
[0018]
The operation of the plastic material identification device having the above-described configuration is as follows. When a waste plastic is identified using a near-infrared type identification device, it is necessary to align the plastics without overlapping each other on the belt conveyor, but it is very difficult to align. However, in the material identification device of the present application, the pretreatment sorting device 21 separates the caps 28 and the like from the waste plastic, or mechanically pretreats the bottles 25 and the trays 27, so that the near infrared of the wake The accuracy of the expression identification device 29 is improved.
[0019]
Specifically, out of 100 waste plastics, for example, 10 caps (small ones) were dropped from the vibrating screen conveyor 23 of 30 mm × 30 mm or less. Next, 50 heavy items (30 PET bottles and 20 other bottles) were dropped on a nearby conveyor 26a using a wind fan 22 and a pulse air nozzle 24, and 40 light items (20 trays, 10 vinyls, 10 films, etc.) were dropped onto a distant conveyor 26b using a wind-selecting fan 22 and a pulsed air nozzle 24. As a result, the waste plastic collected from the conveyor 26a was 100% bottles. In this way, since there is a small amount of light waste plastic (for example, cap 28) of 30 mm x 30 mm or less, the performance of the entire system (pretreatment, identification and separation device) can be reduced by dropping it off the vibrating screen. Improve (accuracy increases and throughput increases).
[0020]
In the near-infrared type identification device 29, the aligned bottles are irradiated with a near-infrared ray by the light source 31 and then the light-receiving element 32 receives a light transmission amount of a wavelength peculiar to the sample by the spectroscope 33. The absorbance of each wavelength for each sample is calculated by the following formula (1) to identify the material.
[0021]
A = log (T1 / T2) (1)
Here, T1: the amount of transmitted light when there is no sample T2: the amount of transmitted light when there is a sample A: Absorbance By the way, infrared light is light having a wavelength of 2.5 μm to 16 μm, and this is now irradiated with infrared light Sometimes, when the vibration period of infrared rays and the vibration period of an atom do not coincide with each other, the infrared rays do not affect the plastic molecules and only pass through as they are. However, if the periods are the same, each atom or group absorbs its energy according to its period and the vibration changes from the ground state to the excited state. It appears as absorption of infrared spectrum.
[0022]
However, if water adheres to the plastic as shown in Japanese Patent Application No. 5-5042, the accuracy decreases rapidly. By using light called near-infrared light having a short wavelength (0.8 to 2.5 μm, high frequency), it is common to weaken the water absorbance and maintain accuracy. However, as shown in FIG. 3, the absorption peak is shown to overlap from 1662 nm to 1748 nm, and high measurement accuracy and an advanced algorithm are required. In the present invention, as an advanced discrimination and algorithm, the material is not comprehensively determined only by the wavelength of the absorption peak, but is comprehensively determined by using the ratio of the number of absorption peaks and the height of each absorption peak. .
[0023]
Next, the high-pressure air (6 Kg / cm ² ) in the wake is controlled by the solenoid valve 39 based on the identified signal, and the high-pressure air is jetted out by the pulse air nozzle 41 in a pulsed manner, and the sample is separated into each room of the separation box 40 Sprinkle into 40a-40b. The material in each room was tested with a total of 100 samples and 10 each of PET, PVC, and PE, but they were separated with 100% accuracy.
[0024]
【Example】
Example 1 Example 1 is an example using a light receiving element made of PbS (lead sulfide). No. For five samples 1 to 5, five types of materials of PP (No. 1), PE (No. 2), PVC (No. 3), PS (No. 4) and PET (No. 5) are determined. For this purpose, the sample was irradiated with near infrared light at an incident angle of 45 degrees, and the reflected light was received by the light receiving element 32 at a reflection angle of 50 degrees. The absorbance A was calculated from the amount of light R (sample reflected light amount) based on the amount of light R (mirror reflected light amount) when totally reflected by the mirror, using the following equation (2).
[0025]
A = logR (mirror reflected light amount) −logR (sample reflected light amount) (2)
Next, in order to obtain the absorption peak wavelength, the absorbance A ′ (no unit) was calculated by the following equation (3).
[0026]
A ′ = (A−Amin) / (Amax−Amin) (3)
However, Amax: the maximum amount of absorbance within the integral range Amin: the minimum amount of absorbance within the integral range The results are shown in FIG. As shown in FIG. 3, No. 1 has one absorption peak in the range of 1600 nm to 1800 nm. 2 PE, no. 4 PS, no. 5 and its peaks are 1732 nm, 1682 nm and 1662 nm, respectively. The two absorption peaks are No. 1 PP, no. 3 for PVC, appearing at 1710 nm and 1730 nm for PP and 1716 nm and 1748 nm for PVC. Therefore, from the number of peaks and the peak wavelength, No. 1-No. The material of 5 types of plastics up to 5 could be judged 100%.
[0027]
(Embodiment 2) Embodiment 2 is an example using a light receiving element made of InGaAs (indium gallium arsenide). The same No. 1 as in Example 1. 1-No. The samples were irradiated with near-infrared light perpendicularly to the five types of materials, and the transmitted light was received by the light receiving element 32. The absorbance A was calculated from the amount of light T (sample) based on the transmitted light amount T (reference) of air by the following equation (4).
[0028]
A = log T (reference) −log T (sample) (4)
Next, in order to determine the absorption peak wavelength, the absorbance A ′ was calculated from the above equation (3). The result is shown in FIG. From FIG. 3, when absorbance A is converted to absorbance A ′ in the range of 1641 nm to 1863 nm, 1726 nm is 1.0, and when absorbance A is converted to absorbance A ′ in the range of 1735 nm to 1663 nm, 1735 nm is 1.0 and 1766 nm 0.0, and the difference between 1745 nm and 1754 nm was 0.05 or less, and it was determined that the material was PVC.
[0029]
No. For 1, the absorbance A ′ at 1716 nm, 1726 nm, and 1735 nm is 0.88 or higher when the absorbance A is converted to the absorbance A ′ in the range from 1641 nm to 1663 nm, and it can be determined that the material is PP. .
[0030]
No. As for 2, when the absorbance A was converted to the absorbance A ′ in the range of 1641 nm to 1663 nm, 1735 nm was 1.0, and it was determined that the material was PE.
[0031]
No. Similarly, when the absorbance A was converted to the absorbance A ′ in the range from 1641 nm to 1663 nm, 1688 nm was 1.0, and it was determined that the material was PS.
[0032]
Finally, no. Similarly, when the absorbance A was converted to the absorbance A ′ in the range of 1641 nm to 1663 nm, 1669 nm was 1.0, and it was determined that the material was PET.
[0033]
In addition, the numerical value of the measurement wavelength is 9 to 10 jumps because near infrared rays are irradiated for each wavelength of 9.4 nm, and is due to rounding to the first decimal place. As described above, according to the above embodiment, determining the material of the waste plastic from the wavelength and number of absorption peaks in the absorbance spectrum of the present invention and the height of the peaks has the following effects.
[0034]
(1) Polyethylene (specific gravity 0.93) and polypropylene (specific gravity 0.90) have almost no difference in specific gravity, and cannot be separated by a hydrocyclone or the like that uses the specific gravity difference. However, in the present invention, the absorption peak of polyethylene is one peak from 1710 nm to 1735 nm, and the absorption peak of polypropylene is two absorption peaks appearing from 1710 nm to 1726 nm and from 1726 nm to 1735 nm. Can be identified. After identification, the material placed on the conveyor can be separated by blowing off with high-pressure air or the like.
[0035]
(2) The specific gravity difference is also small for PVC bottles (specific gravity 1.17 to 1.25 soft) and PET bottles (specific gravity 1.38), and it is difficult to separate PVC and PET by the specific gravity difference. However, in the present invention, identification is possible as in (1) above.
[0036]
【The invention's effect】
As described in detail above, according to the present invention, for example , i) small bottles and the like, ii) light items such as trays, vinyl and films, and iii) heavy items such as bottles. Perform pre-processing such as large separation, cut out the pre-processed sample on the conveyor, align the plastic samples one by one without overlapping the plastic samples , irradiate the plastic with near infrared rays, and from the irradiated light plastic When the transmitted light or reflected light is detected, the material is identified by the absorbance at a specific wavelength by the plastic, and the identification device identifies the material, when the specific wavelength of the transmitted light or reflected light from the plastic is polyethylene terephthalate (PET) One absorption peak appearing at 1660 to 1669 nm and 1 appearing at 1677 to 1698 nm for polystyrene (PS) In the case of polypropylene (PP), two absorption peaks appearing at 1710 to 1726 nm and 1726 to 1735 nm, and in the case of polyvinyl chloride (PVC), two absorption peaks appearing at 1716 to 1729 nm and 1746 to 1754 nm. In the case of polyethylene (PE), the type of plastic is identified by one absorption peak appearing at 1710 to 1735 nm, so that it is possible to identify a plastic material that is difficult to identify with specific gravity and the like with high accuracy and high throughput.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a pretreatment sorting device which is a configuration of a plastic material identification device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a near-infrared type identification device and a sorting device which are one configuration of a plastic material identification device according to an embodiment of the present invention.
FIG. 3 is a characteristic diagram showing the relationship between the absorbance (reflection type) of plastic and the wavelength.
FIG. 4 is a characteristic diagram showing the relationship between the absorbance (transmission type) of plastic and the wavelength.
FIG. 5 is an explanatory view of a conventional waste plastic discrimination method.
[Explanation of symbols]
21 ... Pretreatment sorting device
22… Wind selection fan
23… Vibrating screen conveyor
24 ... Pulse air nozzle
29… Near infrared type identification device
30 ... Separation device
31 ... Light source
32 ... Light receiving element
33 ... Spectroscope
34… Conveyor belt
35 ... Amplifier circuit
36 ... PC
37… Aeroelectric converter
38 ... Header
39… Solenoid valve
40 ... Separation box
41 ... Pulse air nozzle

Claims (1)

A pre-treatment sorting device for roughly separating plastic, a transport device for aligning and transporting the pre-treated plastic, a light source for irradiating the plastic with near-infrared light, and light transmitted from the light source or transmitted light from the plastic or A light receiving element for detecting reflected light, comprising: an identification device for identifying a material by absorbance at a specific wavelength by the plastic; and a separation device controlled by the identification device. The specific wavelength of transmitted or reflected light from the plastic is one absorption peak appearing at 1660 to 1669 nm for polyethylene terephthalate, one absorption peak appearing at 1677 to 1698 nm for polystyrene, and 1710 for polypropylene. Tables at 1726 nm and 1726-1735 nm By two absorption peaks that, by two absorption peaks appearing in 1716~1729nm and 1746~1754nm when the PVC, the single absorption peak appearing in 1710~1735nm When polyethylene, to identify the type of plastic material identifying equipment plastic characterized by.

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