JP3124142B2 - Waste plastic discrimination method and waste plastic removal method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for discriminating waste plastic.
The present invention relates to a method used for a sexing apparatus applied to the separation of waste plastic as industrial waste.

[0002]

2. Description of the Related Art Conventionally, regarding the separation of waste plastics, it has been known to separate plastics by utilizing the difference in specific gravity of plastics using a hydrocyclone.

[0003] Specifically, polyethylene (specific gravity 0.9
3) and polystyrene (specific gravity 1.05) were obtained at a concentration of 98.6% for polyethylene lighter than the upper discharge and at a concentration of 94.7% for polystyrene heavier than the lower discharge. In addition, wind sorting and sinking sorting are also efficiently performed using the difference in specific gravity in the same manner. FIG. 2 shows an example of a conventional waste plastic discriminating method.

[0004] Waste plastic 1 as a raw material is first supplied to a crusher 2. The waste plastic 1 after crushing is sent to the storage tank 3 and is temporarily stored. After that, the waste plastic 1 is supplied to the stirring storage tank 5 from the fixed amount supply device 4 arranged on the lower side of the storage tank 3. A fixed amount of water 6 is supplied to the stirring storage tank 5 and adjusted to a fixed concentration. Next, the mixture of plastic and water is quantitatively supplied to the liquid cyclone 8 by the vortex pump 7 having a controlled number of revolutions, and low-density plastic is discharged from the upper part of the cyclone to the washing and dehydrating machine 9 to remove water and plastic. Separated, the low specific gravity plastic is stored in the circulating water tank 11 in the small specific gravity storage 10. Also,
High specific gravity plastic and water are discharged from the lower part of the hydrocyclone 8 together with water, and water and plastic are separated by a washing and dehydrating machine 12. High specific gravity plastic is temporarily stored in a circulating water tank 11 in a specific storage 13. As a product, specific gravity plastic is extracted from specific gravity storage 13 and specific gravity plastic is extracted from specific gravity storage 10.

[0005]

However, according to the prior art, polyethylene (0. 0. 1) having almost the same specific gravity is used.
93) and polypropylene (0.90 to 0.91) cannot be separated. Further, in the prior art, it was difficult to separate plastic having no (small) difference in specific gravity. In addition, if not pulverized, the fluidity in the hydrocyclone is poor, so that clogging occurs and separation cannot be performed.

[0006] The present invention has been made in view of such circumstances, and it is possible to separate plastic having a small difference in specific gravity, and to separate waste plastic without pulverization.
An object of the present invention is to provide a method for determining ticks .

[0007]

Means for Solving the Problems The present inventors have focused on the molecular structural formula of plastic, and have tried to determine the functional group of plastic by near-infrared light to determine the type (material) of plastic. That is, the present invention is:

(1) For waste plastic to which water adheres
Illuminate near infrared rays with a wavelength of 0.6 μm to 2.5 μm from the projector
Light from the waste plastic
Then, the discarding means is connected to the light-receiving element by the discriminating means.
Officials based on the molecular structure of certain plastics in tics
Near-infrared absorption peaks due to functional groups
Waste plastic discriminating method characterized by discriminating the type of waste plastic by comparing the near infrared absorption peak previously determined for the stick ,

(2) Waste plastic to which water has adhered
When burning in a furnace, pouring is performed according to the determination method described in (1) above.
The Cl group of polyvinyl chloride is converted to a wavelength of 0.6 μm to 2.5 μm.
Judgment by near-infrared absorption, and then based on this judgment
Removing only polyvinyl chloride from waste plastic
A method for removing waste plastic ,

(3) Waste plastic to which water has adhered
When burning in a furnace, nitrogen is determined by the determination method described in (1) above.
Nitrogen compounds in nitrogen-containing plastics at wavelengths from 0.6 μm
Judgment was made by absorption of near-infrared light of 2.5 μm.
Only nitrogen compounds from waste plastics
A method for removing waste plastic ,

(4) Water is determined by the determination method described in (1) above.
Determine the type of waste plastic to which
A method of discriminating waste plastic, characterized in that the waste plastic is discriminated into high calorie plastic and low calorie plastic based on another result .

[0012]

The infrared light is light having a wavelength of from 2.5 μm to 16 μm. If the vibration cycle of the infrared ray does not match the vibration cycle of a certain atom when this is irradiated with the infrared ray, the infrared ray is generated by plastics. It does not affect the molecule, it just passes through. However, if the periods match, the individual atoms or atomic groups absorb their energy according to each period, and the vibration changes from the ground state to the excited state. And appears as absorption in the infrared spectrum.

For example, polyvinyl chloride (PVC) as a plastic has the following chemical formula (1) as a molecular structural formula.
725 cm for monochloro compound due to the stretching vibration of Cl
^An absorption peak appears at ^-1 (13.8 μm).

[0014]

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[0015]

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Accordingly, when the plastic is irradiated with light of 725 cm ^-1 (13.8 μm), the absorption of the sample can be determined from the reflected light, whereby the sample can be confirmed to be PVC.

[0017] The polystyrene (PS) molecular structure, is a following "Formula 3", the following "Formula 4" as a functional group is - plane deformation vibration of a benzene ring having a substituent is 755 cm ^{- An} absorption peak appears at ¹ (13.2 μm).

[0018]

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[0019]

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Further, polypropylene (PP) has the following chemical formula (Chemical Formula 5) as a molecular structural formula, and the following chemical formula (Chemical Formula 6) as a functional group has a symmetric bending vibration of CH ₃ of a hydrocarbon of 138.
An absorption peak appears at 0 cm ^-1 (7.2 μm).

[0021]

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[0022]

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Next, from the near infrared region of 0.6 μm to 2.
At 5 μm, an absorption peak appears as an overtone and a combined sound of the reference vibration in the infrared region, so that the intensity to be absorbed is reduced and the wavelength range is reduced. Also, the chemical structure of plastic can be determined by light without being affected by water absorption.

That is, as the accuracy, the infrared ray is simple and excellent, so that the infrared ray is usually used. However, if water adheres, the accuracy rapidly decreases. If moisture adheres to the plastic after washing, for example, near-infrared rays are used to weaken the absorbance of water to ensure accuracy.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) This embodiment shows an example in a fluidized bed combustion furnace.

Reference numeral 21 in the figure denotes a collection vehicle, and waste plastic from a plastic maker factory or a plastic primary processing factory is collected. A receiving / supplying conveyor 22 is arranged near the collection vehicle 21, and waste plastic from the collection vehicle 21 is charged. The waste plastic on the conveyor 22 is irradiated with light having a specific wavelength, for example, 13.8 μm in the case of polyvinyl chloride from the light projector 23, and the reflected light is received by the light receiving element 24.

After the light signal is converted into an electric signal by the light receiving element 24, the electric signal is sent to an arithmetic and control unit (CPU) 25. In the arithmetic and control unit 25, the type of the waste plastic is determined to be, for example, polyvinyl chloride,
The result is stored in the actuator 26 connected to the CPU 25.
Tell This actuator 26 moves a sorting conveyor 27 which is a part of the receiving / supplying conveyor 22, and a polyvinyl chloride is moved to a hopper 28 below the conveyor 22.
Is dropped and removed.

In the first stage, the absorption of chlorinated hydrocarbon C-Cl of polyvinyl chloride is 725 cm, as shown in FIG.
^-1 (13.8 μm). 1470 cm ^-1 and 2800 cm ^-1 in Figure 4, the absorption of such following "Formula 7" is a linkage other than a C-Cl bond PVC have we table, 725 cm
^-1 was found to represent a C-Cl bond. 725cm
^The plastic was irradiated with light having a wave number of ⁻¹ , the absorption of the sample was determined from the reflected light, and after confirming that it was PVC, it was removed.

[0029]

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FIG. 1 shows that in the first stage the PVC is removed and then the remaining plastic is fed to the compression feeder 29, but if necessary a plastic other than PVC, for example polystyrene, is fed in the second stage and the third stage. It is not shown to remove the polypropylene at the step
A third projector, a light receiving element, a calculation / control unit, an actuator, a sorting conveyor, and a hopper can be provided.

Specifically, in the second stage, as shown in FIG. 5, the frequency of the out-of-plane bending vibration of the benzene ring having a -substituent in the polystyrene shown in the above "Chemical Formula 3" is 755 cm @ -1 (1
3.2 μm), the light of that wavelength is absorbed, the absorption is determined, and after confirming that it is polystyrene (PS),
Can be removed.

1470 cm ^-1 and 2800 cm in FIG.
^-1 is the absorption represents a bond "of 7" above, other ^{550cm -1, 700cm -1, 1490cm -1} , 1600cm
Per ^-1 was investigated the absorption of benzene rings result, 755 cm ^-1
The strongest absorption occurred and the accuracy was high.

In the third stage, the absorption of CH ₃ as a functional group of the polypropylene (PP) was shown at 1380 cm −1 (7.2 μm) as shown in FIG. Of the infrared spectrum of PP shown in FIG.
70cm ^-1 and 2800 cm ^-1 is the absorption of the "reduction 7", absorption of the CH ₃ most strongly absorbing a 1380 cm ^-1, the accuracy was the highest. By the absorption of light having a wave number of 1380 cm ^-1 , the determination of PP can be made, and the PP can be removed by the above-described method.

Further, although not shown in FIG. 1, after confirming that the required plastic is finally obtained, it can be put into the compression feeder 29. For example, when only polyethylene is required, the following “Chemical Formula 8”, which is a polymethylene chain characteristic of polyethylene, is used as a third light emitter,
In the third light receiving element, the absorption is 640 cm as shown in FIG.
^-1 (15.6 μm) is determined. Other plastics can be removed by the third operation / control unit, the third actuator, and the third sorting conveyor, and can be put into the third hopper.

[0035]

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In the infrared spectrum of PE shown in FIG.
Absorption of 470 cm ^-1 and 2800 cm ^-1 is the absorption of the "reduction 7" above, is not a PE specific absorption peak. 1280cm
^-1, 1730 cm ^-1, absorption peaks such as 1220 cm ^-1, P
E was determined to be an absorption peak specific to E, and 640 cm ^-1 was determined to be PE.
Was the most accurate to determine Therefore, 640 cm
The absorption was determined using light having a wave number of ⁻¹ , and after confirming that it was PE, it was placed in a compression feeder 29, and after compression, subjected to impact crushing and shear crushing with a shredder 30. After that, the crushed waste plastic was separated from the waste plastic by a vibration conveyor 31 from a supply conveyor 32 and supplied to a fluidized-bed furnace 33 and burned.

In the fluidized bed furnace 33, the calorie can be adjusted by the sensing device according to the present invention (for example, PE).
Has a high calorific value of 11,000 Kcal / Kg, and PVC is 430
It is as low as 0 Kcal / Kg). In addition, harmful substances such as HCl, NOx, dioxin and the like in the exhaust gas could be reduced. For example, HCl and dioxin could be reduced by removing PVC. NOx could be reduced by removing the nitrogen compound plastic. In the fluidized bed furnace 33, a blower
Supply air 35 by 34, burn waste plastic,
Exhaust gas 36 was discharged. (Example 2)

Referring to FIG. However, (a) both primary and secondary sensing separations were separated by the method of the present invention. (b) The method of the present invention was applied only to the secondary, and (c) the method of the present invention was applied only to the secondary.

As shown in FIG. 3, as (a), in a plastic maker factory, a plastic primary processing factory, and a plastic secondary processing factory, extraordinary products, by-products, cleaning debris, etc. are collected and sent to a recycling factory. It was confirmed that the purity of the recycled plastic was increased by performing the primary sensing separation and the secondary sensing before being applied to the regenerator at the recycling factory. Next, as shown in (b), the type of plastic is determined by the sensing device, and after sorting according to the type, it is sent to each recycling factory for each type. It was confirmed that the purity increased without performing the secondary sorting of No. 3 as compared with the case where the sensing fractionation of the present invention was not performed. Further, as shown in FIG. 3C, the molding waste, the cleaning waste, and the cleaning waste sent without performing the primary sensing in FIG.
Prior to the use of a regenerator, extraneous products and the like were separated by type of plastic by secondary sensing and classification according to the method of the present invention.

Of course, when both the primary sensing and the secondary sensing shown in FIG. 3 were carried out, the purity was higher than either one or only one. In some cases, extraneous products, by-products, cleaning debris, etc. are collected and then washed before sensing / sorting so that impurities such as dust are not contained in the recycled plastic.

When water is attached to the plastic after washing, the absorption peak of water is large in the infrared region and 3200.
cm ^-1 ~3600cm ^-1 (2.78μm~3.13μm),
1630cm ^-1 ~1650cm ^-1 (6.06μm~6.13
μm) and 900 cm ^{−1 to} 650 cm ⁻¹ (11.1 μm to ¹
(5.4 μm) over a wide wavelength range, so that plastic absorption was weak. If there is no water absorption, as the accuracy, the infrared range corresponds to the type of plastic,
Infrared light is used because the absorption peak appears clearly and the accuracy increases. If water adheres, using near-infrared (0.6 μm to 2.5 μm), which is the overtone and combined sound range, the absorption of water is weak and limited in a short wavelength range. Did not receive.

In the conversion between the unit “cm ⁻¹ ” and the unit “μm”, the wave number 1 cm ^{−1 corresponds} to the wavelength 1 cm (0.01 m).
Therefore, the wave number 3200 cm ^-1 is 1/3200 cm,
3.125 × 10 ⁻⁴ cm = 3.125 μm. (Example 3)

A near-infrared spectrum was taken of a sample in which water was attached to four types of plastics, PP, PE, PS, and PVC. FIG. 8 shows the result. Water absorption is
1450 nm (1.45 μm) and 1905 nm (1.90 μm)
5 μm). The absorption peaks of the four types of plastics indicate that the PS benzene ring has a 1677 nm (1.677 nm).
μm), and CH ₂ —CH _{2 of} PE is 1710 nm (1.71 nm).
μm), and the Cl group of PVC is 1729 nm (1.729 μm).
m), PP of CH ₃ had a strong absorption peak at 1829 nm (1.829 μm), indicating high accuracy.

Therefore, it was possible to separate PS, PE, PVC and PP by using near-infrared rays even with plastic to which water adhered. From FIG. 8, the absorption peak of PP appeared at 1704 nm, but it was close to 1710 nm of PE. Since 1829 nm did not absorb PE, PVC, and PP, the accuracy of PP at 1829 nm was higher.

In PVC, a peak having the same size as 1729 nm is at 1863 nm.
Since there are three kinds of absorption peaks of S and PVC and separation by a third party has not been performed, 1729 nm has high accuracy. That is, as described above, PS, PE, and PV in various near infrared regions.
Of the C and PP spectra, 1677 nm and 171 respectively
0 nm, 1729 nm, and 1829 nm could be judged with the highest accuracy. Further, the absorption peak of the oil appeared at 1723 nm, which was different from the above-mentioned wavelength, so that the above four kinds of separation were possible even if the oil was attached. (Embodiment 4) When waste plastics are burned in a furnace, the following substances containing nitrogen are separated and removed to remove NO
Reduce x. For example, the chemical structural formula of nylon is

-[-CO- [CH ₂ ] ₅ -NH-] _n-
And the absorption of —CH ₂ —NH— is 1410 cm ⁻¹ (7.
09 μm). Therefore, in order to separate and remove nylon, the sample was irradiated with light having a wavelength of 1410 cm ^-1 , the light absorption of the sample was measured from the reflected light (or transmitted light), and the nylon was judged. The chemical structural formula of polyurethane is

[—O—R′—CO—NH—R ″ —NH—
CO—] _n and the absorption of —CO—NH— is 3400 cm.
^-1 (2.94 μm). Therefore, to separate and remove polyurethane, irradiate light with a wavelength of 3400 cm ^-1 ,
Based on the reflected light (or transmitted light), the absorption in the sample was measured to determine the polyurethane. PAN: 1- (2-pyridylazo) resorcinol has the following chemical structural formula, and the absorption of the following chemical formula was shown at 2270 cm ^-1 .

[0048]

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[0049]

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Therefore, to separate and remove PAN, it is necessary to use 22
The sample was irradiated with light having a wavelength of 70 cm ^-1 (4.405 μm), and the light reflected by the sample (or the transmitted light) was used to measure the absorption of light in the sample, thereby determining PAN.

ABS: acrylonitrile-butadiene-
The chemical structural formula of acrylonitrile of the styrene copolymer resin is CH ₂ ＣＨCHCN, and —CH ＝ CH—CN is 223
Absorption was shown at a wavelength of 0 cm ^-1 (4.484 μm). Next, the light of the wavelength was applied, the light absorption in the sample was measured from the reflected light (or transmitted light), and the ABS was determined. The effects of the above embodiment are as listed below.

(1) When waste plastics are burned in a furnace such as a fluidized bed furnace, harmful substances in exhaust gas can be reduced. For example, by separating and removing PVC, HCl and dioxin could be eliminated from exhaust gas and ash.

(2) Similarly, when a waste plastic is burned in a furnace, a nitrogen content such as ABS (acrylonitrile-butadiene-styrene copolymer resin), polyurethane, nylon,
PAN (1- (2-pyridylazo) -2-naphthol)
The generation of NOx was suppressed by fractionating and removing.

(3) The calorie of the furnace can be adjusted when the waste plastic is burned in the furnace. For example, PE is 11000Kcal /
Because of the high calorific value of kg, high-efficiency combustion was possible. (4) The purity of recycled products from a waste plastic recycling plant has been improved. (5) By using near-infrared rays, even if water (oil) adhered to the plastic, the type of plastic could be determined. (6) Even if the waste plastic was not crushed and reduced in size, it could be separated as it was. (7) Even plastic with a small difference in specific gravity could be efficiently separated.

[0055]

As described above in detail, according to the present invention, when burning waste plastic, it is possible to reduce harmful substances of exhaust gas, and to suppress the generation of NOx by separating and removing nitrogen in the combustion of waste plastic in a furnace. Thus, it is possible to provide a waste plastic discriminating method having various effects such that the calorie of the furnace can be adjusted when the waste plastic is burned in the furnace, and even a plastic having a small difference in specific gravity can be efficiently separated.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a method for determining waste plastic according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional waste plastic discriminating method.

FIG. 3 is an explanatory diagram of a method for determining waste plastic according to a second embodiment of the present invention.

FIG. 4 is an infrared spectrum diagram of polyvinyl chloride.

FIG. 5 is an infrared spectrum diagram of polystyrene.

FIG. 6 is an infrared spectrum diagram of polypropylene.

FIG. 7 is an infrared spectrum of polyethylene.

FIG. 8 is a near-infrared spectrum diagram of polyvinyl chloride, polystyrene, polypropylene, and polyethylene.

[Explanation of symbols]

21… Collection truck, 22… Receiving / supplying conveyor, 23
... Sender, 24 ... Light-receiving element, 25 ... Calculation / control unit,
26 ... actuator, 27 ... sorting conveyor, 28 ...
Hopper, 29 ... Compression feeder,
30 Shredder, 31 Vibration conveyor, 32 Feeder conveyor, 33 Fluid bed furnace, 34 Blower,
35 ... air, 36 ... exhaust gas.

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI B29K 79:00 (58) Field surveyed (Int.Cl. ⁷ , DB name) B29B 17/00-17/02 B07C 5/34 -5/342 G01N 21/25-21/39 G01N 33/44

Claims (4)

(57) [Claims] 1. Light is emitted to waste plastic to which water adheres.
Irradiates near-infrared light with a wavelength of 0.6 μm to 2.5 μm from a container
Light reflected from the waste plastic by the light receiving element or
The transmitted light is received, and the discriminating means connected to this light receiving element
Molecular structure of specific plastic in the waste plastic
Near-infrared absorption peak due to functional group based on formula and known
A method of discriminating waste plastics, comprising comparing a plurality of plastics with near-infrared absorption peaks obtained in advance to determine the type of waste plastics. 2. Waste plastic to which water has adhered is placed in a furnace.
When burning, polychlorinated by the determination method according to claim 1.
Near-infrared light with a wavelength of 0.6 μm to 2.5 μm
The waste plastic is then determined based on this determination.
Features to remove only polyvinyl chloride from sticks
Waste plastic removal method. 3. A waste plastic to which water has adhered is placed in a furnace.
At the time of combustion, nitrogen is contained by the determination method according to claim 1.
Near infrared of wavelength 0.6μm ~ 2.5μm
Is determined based on the absorption of
Remove only nitrogen-containing plastics from sticks
And a method for removing waste plastic. 4. Water adheres according to the method of claim 1.
The type of waste plastic used and the result of this determination
A method of discriminating the waste plastics into high calorie plastics and low calorie plastics based on