JPH08309749A - Discrimination of waste plastics by type and discrimination device - Google Patents

Abstract

PURPOSE: To discriminate plastics of specified type positively from waste plastics. CONSTITUTION: This discrimination device consists of a crushing device which crushes waste plastics to a specified size, a heating-up furnace which preheats crushed plastic pieces, a microwave heating device 3 which heats the preheated plastic pieces M1 by microwave, a radiation pyrometer 6 which measures the temperature of the plastic piece M1, and a discrimination part 5 which discriminates plastics based on the results of temperature measurement. The microwave heating device 3 is equipped with a microwave generation device 41 which heats the plastic piece M1 on a conveyor belt 32. The discrimination part 5 is equipped with a first cylinder 51, a second cylinder 52 and a third chute 38 which discriminate PVC by pressing and discharging the plastic piece M1 from the conveyor belt 32 based on the temperature measurement results of the plastic piece M1 after heating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for sorting plastic waste (waste plastic) by type.

[0002]

2. Description of the Related Art Wastes, which are discharged in enormous amounts every day, are classified into combustible wastes, large-scale wastes, and non-combustible wastes depending on the treatment method. According to the above classification, plastic waste falls into the category of flammable waste, and most of them have been subjected to incineration. However, from the viewpoint that plastic causes damage to combustion equipment due to its high calorific value, and from the viewpoint of resource recycling, nowadays plastics are tended to be sorted from combustible waste and recycled in a separate system. In many cases, due to facility restrictions, plastic waste is still incinerated while being mixed with other combustible waste.

By the way, plastic wastes are classified into chlorine-based plastics, which generate highly corrosive chlorine when decomposed, and other non-chlorine-based plastics, which do not generate chlorine. From the viewpoint of processing, it is preferable that the plastic is separated into chlorine-based plastic and non-chlorine-based plastic.

Particularly, when a combustible waste mixed with plastic is used as a fuel for generating exhaust gas for driving a waste heat turbine, if chlorine-based plastic is mixed in the fuel, high-temperature chlorine gas generated from it There is an inconvenience that the waste heat turbine is corroded by this, which causes stress corrosion cracking and the like. Therefore, in order to reduce the corrosive activity of chlorine gas, the exhaust gas temperature is lowered from a normal temperature of approximately 800 ° C to approximately 450 ° C. However, there is a problem in that waste heat cannot be fully utilized. To do. In order to solve such problems, it is preferable to remove chlorine-based substances in advance when the plastic waste is incinerated.

However, it is extremely difficult to sort out plastic wastes having very similar properties by type.

[0006] Conventionally, regarding the selection of plastic waste, for example, Japanese Patent Laid-Open Nos. 46-53371 and 5
1-15577, JP-A-48-95654, JP-A-52-84260, JP-A-58-20.
No. 5552, No. 4-326955, JP-A-6-
As described in Japanese Patent No. 126743, Japanese Unexamined Patent Publication No. 6-182251, etc., a specific gravity separation method, which focuses on the fact that the specific gravity differs depending on the type of plastic, has been the mainstream. Specifically, a plastic waste is put into a solution having a specific gravity and separated by floating and sinking, a plastic having a specific gravity larger than the specific gravity of the solution is settled, and a plastic having the same small specific gravity is Since it floats, the specific gravity of the solution can be appropriately selected to select the solution.

Further, in Japanese Patent Laid-Open No. 6-3260, paying attention to the existence of an optical spectrum peculiar to a substance, the plastic waste is irradiated with infrared rays, and the reflected light is dispersed by a spectroscope to form a spectral pattern. A method for separating plastics by type by discriminating is described.

[0008]

By the way, when the plastic waste is sorted by using the above-mentioned specific gravity separation method, the dirt component of the waste is dissolved in the separation liquid, which causes the specific gravity of the separation liquid to change. Therefore, it becomes impossible to reliably separate the plastics by type. If you try to avoid this, you have to increase the replacement frequency of the separated liquid,
There is a problem that a large amount of separated liquid is required, which is economically disadvantageous.

In addition, in the method of selecting plastic waste based on the above infrared reflected light spectrum, since the stain on the surface of the plastic waste affects the spectrum of reflected light, accurate selection cannot be performed. There is a problem. Furthermore, it is necessary to input the reflected light of the ultraviolet rays applied to the plastic waste to a predetermined measuring device. For that purpose, it is preferable that the reflection surfaces of the plastic waste always face in the same direction, but they are sent sequentially. It is difficult to always make the reflecting surface of the incoming plastic waste the same direction.

The present invention has been made in order to solve the above problems, and a method and a sorting apparatus for selecting a type of waste plastic capable of reliably selecting a predetermined type of plastic from plastic waste. Is intended to provide.

[0011]

A method for selecting a type of waste plastic according to claim 1 of the present invention comprises a crushing step of crushing plastic into a substantially predetermined size in advance, and raising the crushed plastic piece to a predetermined temperature. Preheating process for heating, electromagnetic heating process for heating preheated plastic pieces by irradiating them with electromagnetic waves, and measuring the temperature of the plastic pieces heated by electromagnetic waves, and identify from the magnitude of the measured value of this temperature The present invention is characterized in that it comprises a selection step of selecting different types of plastic pieces.

According to a second aspect of the present invention, there is provided a waste plastic type sorting method, wherein the waste plastic type sorting method according to the first aspect uses the plastic pieces sorted by the sorting step as a sorting liquid having a predetermined specific gravity. It is characterized in that a specific gravity selection step is provided in which the specific gravity is supplied and additionally selected according to the specific gravity difference.

According to a third aspect of the present invention, there is provided a waste plastic type sorting apparatus which includes a temperature raising unit for raising the temperature of a plastic piece that has been crushed to a substantially predetermined size to a predetermined temperature. It consists of an electromagnetic wave heating part that radiates electromagnetic waves and heats it, a thermometer that measures the temperature of the plastic piece heated by the electromagnetic wave, and a sorting part that sorts out a specific type of plastic piece based on the measured value of this temperature. It is characterized by being present.

The waste plastic type sorting device according to the fourth aspect is the waste plastic type sorting device according to the third aspect, wherein the electromagnetic wave heating section uses microwaves for electromagnetically heating the plastic pieces being transferred by the conveyor belt. An irradiating section is provided, and the sorting section is configured to sort only plastic pieces of a specific type from the conveyor belt to different sorting paths.

[0015]

According to the method for selecting the type of waste plastics described in claim 1, the various plastics supplied to the crushing step are crushed here into plastic pieces of substantially a predetermined size, and the following preheating is performed. Introduced into the process. The plastic piece introduced in this step is heated to a predetermined temperature in advance and supplied to the next electromagnetic wave heating step. In this step, the plastic piece is heated by electromagnetic wave heating and the temperature is measured. Then, in the final sorting step, the plastic pieces are sorted based on the measured temperature.

According to the waste plastic type sorting method of the second aspect, the plastic pieces sorted in the sorting step are supplied to a sorting liquid having a predetermined specific gravity and further sorted by the difference in specific gravity. Even if other types of plastic are mixed in the sorted products obtained by the sorting in the sorting step, the other types of plastic are removed by the sorting based on the difference in specific gravity.

According to the waste plastic type sorting apparatus of the third aspect, the crushed plastic pieces having a substantially predetermined size are introduced into the temperature raising section, where they are heated to a predetermined temperature in advance. , Is supplied to the next electromagnetic wave heating unit. Here, the plastic piece is electromagnetically heated and the temperature is measured. Then, in the final sorting device, the plastic pieces are sorted based on the measured temperature.

According to the waste plastic type sorting apparatus of the fourth aspect, the plastic pieces are transferred by the conveyor belt in the casing of the electromagnetic wave heating section, and the microwave is irradiated from the microwave irradiation section during the transfer. Received and heated. Then, the heating temperature is measured by a thermometer, selected based on the magnitude of the measured value, and only a specific type of plastic piece is distributed from the conveyor belt to a predetermined sorting path.

[0019]

The present invention is a phenomenon in which a substance is internally heated by irradiating an insulator with an electromagnetic wave such as a high frequency wave or a microwave to vibrate molecules constituting the insulator (electromagnetic wave heating), and the kind of the substance. It was made based on the fact that the degree of internal heating differs depending on the type.

A substance generates heat by dielectric heating when it is irradiated with electromagnetic waves, for example, high frequency waves. Heat value P at this time
(W / cm ² ) is represented by P = ((5/9) / 10 ¹² ) · f · E ² · ε · tan δ. Where f is the frequency of the high frequency, E is the strength of the electric field (V / cm), ε is the dielectric constant, tan δ is the dielectric loss angle, and in particular (ε × tan δ) is called the dielectric loss coefficient. There is. From the above equation, the heat generation amount P is proportional to the square of the strength of the electric field (E ² ) and the loss coefficient (ε × tan δ). When the strength of electrolysis is constant, the larger the loss coefficient, the more heat is generated. The amount will increase.

FIG. 1 is a graph showing an example of the relationship between temperature and the numerical value related to the dielectric constant of plastics. (A) shows the relationship between temperature and the dielectric constant, (b) shows the relationship between temperature and the dielectric loss angle. , (C) show the relationship between the temperature and the dielectric loss coefficient.

Then, as shown in the graph of (a), the value of the dielectric constant gradually increases as the temperature rises from 0 ° C. to 60 ° C., then rapidly increases from 60 ° C. to 100 ° C., and exceeds 100 ° C. The behavior gradually increases again. The value of the dielectric loss angle is gradually decreased from 0 ° C to 40 ° C as shown in the graph (b), and then 9 °
The behavior is such that the temperature rapidly increases until reaching 0 ° C. and then rapidly decreases. Therefore, the dielectric loss coefficient, which is the product of the dielectric constant and the dielectric loss angle, seems to have amplified the behavior of the dielectric loss angle in the graph (b), and the maximum value appears near 90 ° C. .

Since the behavior of such a dielectric loss coefficient is expected to vary depending on the type of plastic near 90 ° C., which shows the limit value, if the value of the dielectric loss coefficient near 90 ° C. is used as an index, It is expected that sorting by type of plastic will be facilitated.

FIG. 2 shows typical plastics.
It is a graph which illustrates each dielectric loss coefficient. This graph is a bar graph showing the dielectric loss coefficient of various plastics at room temperature so as to correspond to the ordinate scale. As shown in this graph, the dielectric loss coefficient differs depending on the type of plastic. For example, the phenol resin shows a very large value of 0.7, while the fluororesin shows a very small value of 0.0004, and the phenol resin and the fluororesin are different from each other. There are various plastics that exhibit values for the dielectric loss factor.

Therefore, when a certain kind of plastic is selected, if the electromagnetic waves are radiated under the same conditions, the heating values of the respective plastics are different because the calorific values generated are different. Therefore, by detecting the heating temperature of each plastic, it becomes possible to specify the type of the plastic.

Therefore, various plastics were actually irradiated with electromagnetic waves to carry out a test for examining the temperature rise. In this test, a microwave generator with an output of 1.1 Kw that generates a microwave having a frequency of 2.45 GHz was used. In addition, polyvinyl chloride (vinyl chloride: PVC), acrylonitrile butadiene styrene copolymer (ABS), polystyrene (PS), polyethylene (PE) and methacrylic resin (PMMA), which are typical plastics, were adopted as samples. Test pieces of substantially the same rectangular parallelepiped shape were prepared from these plastics, and these were preheated from room temperature by a conventional method until they reached a predetermined temperature, and then the microwave from the microwave generator was applied. After irradiation for a predetermined time, the temperature was measured using a known radiation thermometer (for example, infrared thermometer). Table 1 shows the measurement results. A graph of Table 1 is shown in FIG. In addition, in FIG. 3, when the test piece is not preheated, when it is preheated to 40 ° C.,
A line graph is shown for each of the case of preheating to 80 ° C. and 80 ° C. Regarding the preheating, the test piece was loaded into a normal soaking furnace and the temperature was gradually raised. Therefore, the temperature rises at the same heating rate regardless of the type of plastic until the preheating temperature is reached.

[0027]

[Table 1]

As can be seen from Table 1 and FIG. 3, when the test piece is not preheated and microwaves are irradiated for a predetermined time from room temperature, a notable temperature difference depending on the type of plastic is not recognized. Therefore, when the test piece is preheated, the temperature of the test piece after being irradiated with microwaves for a predetermined time largely varies depending on the type of plastic, and a more preferable tendency for detecting the type of plastic is shown. You can see that it shows.

When preheating is performed before microwave heating, for example, PE has a lower temperature than the initial temperature, but this is due to the heat between microwave heating and natural heat dissipation. It is considered that the natural cooling is superior to the balance in terms of balance.

Further, the reason why the temperature difference between the types of plastics becomes large by performing the pre-heating is that the pre-heating causes the difference in the dielectric loss coefficient of the plastic as described above with reference to FIG. It is considered that this is because the increase in the value increases the rate of temperature increase, which in turn increases the temperature variation among the types of plastic.

The present invention has been completed based on the above findings. The first embodiment of the present invention will be described below with reference to FIG.
~ It demonstrates in detail based on FIG. FIG. 4 is a process diagram showing the first embodiment of the present invention, and FIG. 5 is a partially cutaway perspective view showing an example of a configuration applied to the electromagnetic wave heating process and the sorting process.

First, as shown in FIG. 4, according to the present invention, a crushing step P1 for crushing a plastic waste material M and a plastic piece M1 crushed to a substantially predetermined size in this crushing step P1 are brought to a predetermined temperature. A preheating step P2 for preheating, an electromagnetic wave heating step P3 for heating by irradiating the plastic piece M1 derived from the preheating step P2 with microwaves, and a plastic piece heated in the electromagnetic wave heating step P3. Measure the temperature of M1,
Based on this measurement result, a PVC piece (see the sorting step P4 in FIG.
To the right) and a non-PVC piece (indicated by an arrow extending downward from the screening step P4 in FIG. 4) to a sorting step P4.

In the crushing step P1, a known crushing device 1 is used.
Is provided, and the plastic waste raw material M introduced in the crushing step P1 is crushed by the crushing device 1 to a substantially predetermined size. In this embodiment, a plastic piece M1 of approximately 5-10 cm3 is prepared by the above crushing. By crushing the plastic waste material M to a substantially predetermined size in this way, variations in the heating effect in the electromagnetic wave heating step P3 are suppressed as much as possible.

As the crushing device 1, a shearing type crusher that shears the plastic waste material M pressed and supplied by a pusher at a predetermined pitch with a reciprocating or rotating shearing blade, and rotates at high speed around the axis. Any of the impact type crushers that sequentially supplies the plastic waste material M to the rotating disk and crushes the plastic waste material M by tapping with a plurality of hammers attached to the rotating disk can be adopted. In this embodiment, the former one suitable for obtaining the plastic piece M1 having a substantially predetermined size is adopted.

A known temperature raising furnace (temperature raising part) 2 is applied to the preheating step P2, and the plastic piece M1 introduced in the preheating step P2 is heated by the preheating step 2 by the heating furnace 2.
The temperature is raised to 0 ° C. and is sent out toward the electromagnetic wave heating step P3. In this embodiment, a hot air tunnel system in which hot air is supplied is adopted as the temperature raising furnace 2. The temperature raising furnace 2 is composed of a temperature raising chamber whose temperature is adjusted to be slightly higher than 80 ° C., and a transfer means such as a belt conveyor which is provided so as to penetrate the temperature raising chamber. Then, the plastic piece M1 led out from the crushing device 1 is introduced into the temperature raising furnace 2 by the above-mentioned transfer means, heated to 80 ° C., and then maintained at this temperature. ) 3 is supplied.

FIG. 5 is a partially cutaway perspective view showing an example of the configuration from the electromagnetic wave heating section to the selection section. The microwave heating device 3 as an electromagnetic wave heating unit includes a box-shaped casing 31 arranged on the floor F, a conveyor belt 32 stretched inside the casing 31, and a preheating process P.
The microwave irradiation unit 4 for heating the plastic piece M1 from 2 in the microwave, and the temperature of the plastic piece M1 and the selection unit 5 for selecting the plastic piece M1 heated by the microwave irradiation unit 4 It comprises a radiation thermometer 6 to be measured, and a control unit 7 which outputs a control signal to the selection unit 5 based on the measurement result of the radiation thermometer 6.

On the upstream side (left side) of the casing 31, an inclined portion is formed which is inclined downward, and a take-over portion 31a extending horizontally from the lower end of the inclined portion is provided. This take-over portion 31a has a plastic piece M1.
An input port 31b for inputting the
Is connected to a connecting chute 21 that is connected to the downstream end of the temperature raising furnace 2 (FIG. 4). Then, the plastic piece M1 preheated to a predetermined temperature in the temperature raising furnace 2 is supplied onto the conveyor belt 32 in the casing 31 through the connecting chute 21 and the charging port 31b.

The conveyor belt 32 has the casing 3
1 is stretched over a plurality of rollers 33 provided at appropriate places within 1,
An inclined portion is formed along the inclined portion of the casing 31 on the upstream side. One of the plurality of rollers 33 is a drive roller 33a that is driven to rotate by the drive of the drive motor 33b, and the forward rotation of the conveyor belt 32 is changed from the left side to the right side in FIG. 5 by the drive rotation of the drive roller 33a. It is designed to move.

On the surface of the conveyor belt 32, a plurality of partition projecting plates 32a are projected at equal pitches in the longitudinal direction.
An accommodating portion 32b for accommodating the plastic piece M1 is formed between the partition projecting plates 32a. This housing 32
b is dimensioned to have a capacity sufficient to accommodate one plastic piece M1.

A receiving hopper 34 is provided around the upstream end of the conveyor belt 32, and the plastic piece M1 passes through the connecting chute 21 and receives the receiving hopper 34.
Once, and is picked up by the conveyor belt 32. Also, the conveyor belt 32
The required length of the support plate 3 is located at the position just below the forward belt.
5 is provided, and this support plate 35 effectively prevents the forward belt from bending downward. A pair of left and right side walls 35a for sandwiching the conveyor belt 32 from the width direction are erected on the upper surface side of the support plate 35. The side walls 35a prevent the plastic piece M1 from falling out of the accommodating portion 32b. There is.

Further, a first cutout portion 36 and a second cutout portion 37 are sequentially provided on the downstream side of the pair of left and right side walls 35a, and by selection based on the temperature measurement result by the radiation thermometer 6, The plastic piece M1 other than the specific type is led out from any of the cutout portions 36 and 37. The specific type of plastic piece M1 that has not been led out to the outside from the notches 36 and 37 is transferred to the downstream end as it is by driving the conveyor belt 32, and is led out (selected) to the outside from here. There is.

On the side of the casing 31, the first
A first chute (sorting path) 36a for guiding the plastic piece M1 led out from the notch 36, and a second notch 37
A second chute (sorting path) 37a for guiding the plastic piece M1 led out from the third chute 38 for guiding the plastic piece M1 led out from the downstream end of the conveyor belt 32 is provided. Three
7a and 38 are connected to corresponding transfer means such as a conveyor belt (not shown).

In this embodiment, the conveyor belt 32
Is made of polytetrafluoroethylene (PTFE). Since PTFE is a very tough material, has a very small dielectric loss coefficient of about 0.0004, and is hardly heated even by irradiation with microwaves, it is suitable as a member for transferring the plastic piece M1.

The microwave irradiator 4 has a microwave generator 41 installed on the floor F and a microwave generated by the microwave generator 41 in the casing 3.
It is configured by a waveguide 42 that guides inside 1 and a microwave heating furnace 43 to which a tip portion of the waveguide 42 is connected. The tip of the waveguide 42 is penetrated through a microwave irradiation hole 31c formed in the ceiling of the casing 31, and is connected to a microwave heating furnace 43 below the microwave irradiation hole 31c.

The conveyor belt 32 and the supporting plate 35
Are provided so as to penetrate through the microwave heating furnace 43 in the front-rear direction. Therefore, the plastic piece M1 passing through the microwave heating furnace 43 is microwave-heated by the microwave irradiation from the waveguide 42.

The radiation thermometer 6 is the microwave heating furnace 4
Immediately after the downstream of 3, the measurement direction is provided on the ceiling of the casing 31 downward, and the radiation thermometer 6 measures the temperature of the plastic piece M1.
The radiation thermometer 6 is a thermometer that receives infrared radiant energy emitted from an object, can measure the object in a non-contact and fast response, and has no restriction on the shape of the object. , A thermometer suitable for applications such as the present invention.

The sorting section 5 is provided with a first cylinder 51 provided at one side of each position corresponding to the first and second cutouts 36, 37 on the downstream side of the radiation thermometer 6.
And a second cylinder 52.

The first cylinder 51 has a cylinder rod 51a having a pressing member 51b at the tip thereof.
By pushing the cylinder rod 51a forward, the pressing member 51b guides the plastic piece M1 in the housing portion 32b to the first chute 36a via the first notch portion 36. Similarly, the second cylinder 52 is
Cylinder rod 52a having a pressing member 52b at the tip
When the cylinder rod 52a is moved forward, the pressing member 52b guides the plastic piece M1 in the accommodating portion 32b to the second chute 37a via the second cutout portion 37. . Further, the third chute 38 is adapted to receive the one falling from the downstream end.

The temperature measurement results of the radiation thermometer 6 are input into the control unit 7 one by one, and the first cylinder 51 or the second cylinder 52 receives them based on the temperature measurement results. A drive signal for driving is output. Specifically, the temperature condition of the plastic piece M1 that drives the cylinders 51 and 52 is input into the control unit 7 in advance, and the temperature of the plastic piece M1 detected by the radiation thermometer 6 is input to the control unit 7. Then, the control unit 7 determines whether the temperature should drive the cylinder or which cylinder should be driven by comparing the temperature with the above temperature condition, and a drive signal is output to the required cylinder. It has become so.

In a proper place in the casing 31,
When the housing 32b is located below the radiation thermometer 6,
Partition projecting plate 3 of the conveyor belt 32 of the accommodating portion 32b
An unillustrated passage detector for detecting passage of 2a is provided, and a detection signal of this passage detector is input to the control unit 7 one by one. On the other hand, each time the passage detector detects the partition plate 32a, the control unit 7 outputs a temperature measurement command signal to the radiation thermometer 6, so that the plastic piece M1 is placed directly below the radiation thermometer 6. Only when the radiation thermometer 6 passes, the radiation thermometer 6 detects the temperature of the plastic piece M1 and inputs the detection signal to the control unit 7.

In the control unit 7, the delay storage unit 71, the first drive command unit 72 and the second drive command unit 7 are included.
3 are provided, and by these, the temperature detection result of the radiation thermometer 6, the first cylinder 51 and the second cylinder 5 are provided.
I am trying to cooperate with the driving of 2.

The delay storage unit 71 is composed of, for example, four serially connected flip-flops (hereinafter referred to as FFs), and the storage contents of the first stage FF are the storage unit 32b immediately below the radiation thermometer 6. The second stage FF corresponds to the housing portion 32b facing the first cylinder 51, and
The accommodating portion 32b in which the FF in the stage is opposed to the second cylinder 52
It corresponds to.

In this embodiment, "1", "2" or "0" is used as the cylinder drive signal, "1" is a signal for driving the first cylinder 51, and "2" is for the second cylinder 52. The driving signal, "0", is for both cylinders 51,
52 is determined as a signal that is not driven. Therefore,
The delay storage unit 7 is used according to the temperature measurement result of the radiation thermometer 6.
"1", "2", or "0" is input to the 1st stage FF.

The stored content of each FF is triggered by a detection signal of a passage detector (not shown) that detects the passage of the partitioning projection plate 32a of the conveyor belt 32, and the stored content is sequentially transferred to the subsequent stage by the input of this trigger. It will be transferred.

In the first drive command section 72, when the passage detector detects the partition plate 32a, the radiation thermometer 6 detects the temperature of the plastic piece M1 and the delay storage section 71 is obtained as a result of the temperature comparison described later. The cylinder drive signal is input to the first-stage FF and the cylinder drive signal transferred to the second-stage FF is referred to. Then, when it is "1", a drive signal is output to the first cylinder 51. In addition, the second drive command unit 73
Like the first drive command unit 72, refers to the cylinder drive signal transferred to the FF in the fourth stage, and when it is “2”, outputs the drive signal to the second cylinder 52. ing.

Therefore, when FF is "0", the cylinders 51 and 52 are not driven, whereby the plastic piece M1 is transferred as it is to the downstream end by the conveyor belt 32 and is guided to the outside through the third chute. It will be.

The control by the control unit 7 will be described below with reference to specific examples. In this example,
A PVC piece is selected from the plastic piece M1. Therefore, 98 ° C. is set as the temperature (T ° C.) condition of the plastic piece M1 selected by driving the first cylinder 51, and 92 ° C. is set as the temperature condition of the plastic piece M1 selected by driving the second cylinder 52. It is set.

Such a temperature condition is set because PVC which has been preheated to 80 ° C. is heated to about 95 ° C. by microwave heating, so that the temperature is also raised to 92 ° C. by microwave heating. Less than plastic piece M
1, and the PVC pieces are selected by removing the plastic pieces M1 above 98 ° C. by microwave heating.

First, when a temperature measurement command signal is output from the control unit 7 to the radiation thermometer 6, the temperature of the plastic piece M1 located immediately below the radiation thermometer 6 is detected, and the detection signal is sent to the control unit 7. Is entered. Then, the detected temperature T is 98
It is determined whether the temperature is higher than 90 ° C, lower than 93 ° C, or higher than 93 ° C and lower than 98 ° C. When the temperature exceeds 98 ° C, the cylinder selection signal "1" is lower than 93 ° C. When “2” is 93 ° C. or higher and 98 ° C. or lower, “0” is input to the delay storage unit 71. Thereafter, when the next temperature measurement command signal is output in synchronization with the movement of the conveyor belt 32, the temperature of the next plastic piece M1 is detected, and the cylinder selection signal "1" in the delay storage unit 71 is sequentially detected each time. "2" or "0" is each F
It is input in synchronization with the transfer of the stored contents to the subsequent stage of F.

In this way, the temperature of the plastic piece M1 is sequentially detected as the conveyor belt 32 moves.
In the delay storage unit 71, for example, “0”, as a cylinder drive signal, is supplied to the first stage FF to the fourth stage FF.
If "1", "2", and "2" are stored, the drive signal is output from the first drive command unit 72 to the first cylinder 51 because the FF in the second stage is "1". The cylinder rod 51a reciprocates by the pressure member 51b.
Presses the plastic piece M1 on the conveyor belt 32 and is discharged to the outside from the first chute 36a through the first cutout portion 36.

Since the FF in the fourth stage is "2", a drive signal is output from the second drive command section 73 to the second cylinder 52, whereby the cylinder rod 52a reciprocates and the plastic piece M1 is pressed by the pressing member 52b and is discharged to the outside from the second chute 37a via the second cutout portion 37.

Since the above-described first embodiment is configured as described above, by appropriately setting the temperature range in which the first cylinder 51 and the second cylinder 52 are driven, plastic waste that has been very difficult in the past has been difficult. This makes it possible to sort by type very easily, and as a result, it becomes possible to reliably select the desired type of plastic, which is convenient for recycling plastic waste.

In the above selection control, a delay storage unit 71, a first drive command unit 72, and a second drive command unit 73 are provided in the control unit 7, and the detection result of the radiation thermometer 6 and the Although the drive of the first cylinder 51 and the drive of the second cylinder 52 are coordinated, instead of providing the delay storage unit 71 and the like, all the storage units 32b are provided.
An absolute address is assigned to the partition using the passage detector of the partition plate 32a, a data area corresponding to this absolute address is provided in the control unit 7, and the temperature measurement result of the radiation thermometer 6 is set in these data areas. A cylinder drive signal based on the absolute address is taken in, and the first cylinder 51 and the second cylinder 52 correspond to the absolute address while always confirming the absolute address using a similar passage detector provided here. Whether or not to drive may be determined based on the cylinder drive signal in the data area.

FIG. 6 is a side sectional view showing another example of the selecting section. In the case of this example, the selection unit 50 distributes the plastic pieces M1 using the injection pressure of compressed air. Specifically, the transfer device 8 is continuously provided at the downstream end (right side) of the casing 31, and the first conveyor belt (sorting path) 81 and the second conveyor belt (sorting) are vertically arranged in the transfer device 8 in two stages. 82) is provided. The first conveyor belt 81 has an upstream end slightly lower than the downstream end of the forward belt of the conveyor belt 32, and is horizontally spaced so that the plastic piece M1 can drop from the downstream end of the conveyor belt 32. Is being done,
The second conveyor belt 82 is provided such that its upstream end projects further upstream than the upstream end of the first conveyor belt 81, and the plastic piece M that falls from the conveyor belt 32.
Positioned so that it can receive 1.

On the other hand, the microwave heating device 3 and the transfer device 8
Of the second conveyor belt 82 above the upstream end of the second conveyor belt 82 at a position where it interferes with the plastic piece M1 falling from the conveyor belt 32.
An injection nozzle 501 for injecting compressed air toward is provided. The air volume and pressure of the injection nozzle 501 are the same as those of the plastic piece M1 falling from the conveyor belt 32.
It is set so that the plastic piece M1 can be blown to the first conveyor belt 81 by the pressure by injecting compressed air toward the first conveyor belt 81.

A high pressure tank 503 in which air of a predetermined pressure is stored by a compressor 502 is provided behind the injection nozzle 501. This high pressure tank 503.
And the injection nozzle 501 are connected by a high-pressure pipe 504. An electromagnetic valve 505 is provided in the high-pressure pipe 504, and by opening / closing the electromagnetic valve 505, the pressurized air in the high-pressure tank 503 is jetted from the jet nozzle 501 or stopped.

In this embodiment, based on the temperature measurement result of the radiation thermometer 6, the control unit 7 causes the solenoid valve 50 to
The drive signal is output to the terminal 5. Specifically, when the temperature detected by the radiation thermometer 6 is within a preset temperature range, a drive signal for opening the valve is output from the control unit 7 to the solenoid valve 505, and when the temperature is outside the set temperature range. A drive signal for closing the valve is output to the solenoid valve 505.

Therefore, the plastic piece M1 transferred to the downstream end by the conveyor belt 32 has the radiation thermometer 6
Depending on the result of the temperature measurement by, the pressure air is ejected from the ejection nozzle 501 or the ejection is stopped, whereby the plastic piece M1 is sorted, the PVC piece is transferred by the first conveyor belt 81, and the non-PVC piece is Second
It will be delivered by the conveyor belt 82.

It should be noted that the above-mentioned injection nozzle 501 is provided in the selection unit 50.
Instead of providing the above, a damper rotatable about a horizontal axis is provided between the upstream end of the first conveyor belt 81 and the downstream end of the conveyor belt 32, and the posture of this damper is changed so that The plastic piece M1 of the first conveyor belt 81 through the damper.
To the second conveyor belt 8 without using a damper.
You may make it fall on 2 above.

FIG. 7 is a process chart showing the second embodiment of the present invention. As shown in this figure, the second embodiment is similar to the first embodiment up to the sorting step P4, but the sorting step P4
4 is further added with a specific gravity separation step P5 in which the specific gravity separation device 30 is provided. Then, the plastic pieces selected as PVC are further subjected to specific gravity separation in the specific gravity separation step P5, so that the P mixed in the selection step P4 is mixed.
Make sure to remove the plastic pieces other than VC. This is done by using PVC, as can be seen in FIG.
This is because ABS, PMMA and the like, which have similar temperature conditions, may be erroneously mixed as PVC pieces.

By the way, FIG. 8 is a graph showing the specific gravity of various plastics. As can be seen from this graph,
While PVC has a specific gravity of 1.4, PMMA has a value of about 1.2, and ABS has a value of about 1.1, which is significantly smaller than that of PVC. Therefore, for example, by preparing a sorting liquid having a specific gravity of about 1.3 and supplying the plastic pieces derived from the sorting step P4 into this sorting liquid, PV
The C piece settles in the liquid and the non-PV mixed by mistake.
Since the C piece floats, PV with more reliably removed impurities
The C piece is collected. In addition, if it is intended to sort the accidentally mixed phenol resin or the like by specific gravity separation, the specific gravity of the sorting liquid may be set to about 1.38 as shown by the alternate long and short dash line in FIG.

Although the above embodiments have been described focusing on sorting plastic waste into PVC and other plastics, the present invention sorts plastic waste into PVC and other plastics. The present invention is not limited to the above, and it is possible to select a specific plastic other than PVC by changing the setting temperature of the plastic selection variously.

In the above embodiment, the plastic piece M1 after the crushing step P1 is preheated by the hot air tunnel type temperature raising furnace 2. However, the present invention is not limited to the preheating of the plastic piece M1. The heating furnace 2 as described above is not limited to the application, and a heater may be provided in the furnace or electromagnetic wave heating may be applied. Note that the preheating causes the water adhering to the surface of the plastic piece M1 to evaporate, so that the plastic piece M1 in the electromagnetic wave heating step P3 on the downstream side is evaporated.
There is also an advantage that the heating temperature of is not affected by moisture.

Further, in the above embodiment, the selection unit 5
A first cylinder 51 and a second cylinder 52 are provided, and those exceeding the upper limit temperature of the plastic pieces M1 to be sorted are removed by the first cylinder 51, and those below the lower limit temperature are removed by the second cylinder 52. However, the two cylinders 51,
Instead of providing 52, only one of them may be provided, and the plastic piece M1 may be bisected depending on whether or not it is within a certain temperature range.

Further, in the above-mentioned embodiment, the plastic pieces M1 are arranged in a line and transferred by the conveyor belt 32, and the plastic pieces sorted by the temperature are removed from the conveyor belt 32 by driving the cylinders 51 and 52. However, instead of lining them up in a line, they are placed randomly so that they do not overlap on the conveyor belt, and the temperature and position of the plastic pieces are detected by image processing, and operation is performed based on the detected temperature and position. The robot may be used to perform the sorting operation of the plastic pieces.

Further, in this embodiment, the radiation thermometer 6 is applied as a thermometer for detecting the temperature of the plastic piece M1 provided in the microwave heating device 3, but in the present invention, the thermometer is the radiation temperature. The thermometer is not limited to the total of 6, but other thermometers such as a thermometer using a temperature sensitive element that directly contacts the plastic piece M1 to detect the temperature may be used. The detection of the temperature may be performed immediately before the exit of the microwave heating furnace 43.

In the present embodiment, the partition belt 32a is provided on the conveyor belt 32. However, when the forward belt of the conveyor belt 32 is set to move horizontally, the partition blade 32a is particularly used. Need not be provided. However, when the partition plate 32a is not provided, the conveyor belt 32 is provided with at least one detection piece for position detection in order to detect the position of the conveyor belt 32, and the detection piece is stored as a reference for time management. Part 32
You may make it position b.

Furthermore, although microwaves are used for the heat treatment in the electromagnetic wave heating step P3 in the above embodiment, high frequencies may be used instead of microwaves.

Further, in the case of the type (for example, FIG. 6) in which selection is performed depending on the temperature condition range, a selection section such as a cylinder or an injection nozzle may be arranged directly in the accommodation section 32b at the temperature measurement position. This eliminates the need for a delay circuit and facilitates control for selection.

[0080]

As described in detail above, according to the method and apparatus for selecting the type of waste plastics according to claims 1 and 3 of the present invention, the waste plastic is crushed to a substantially predetermined size in the crushing step, and the pre-heating step (raising The plastic piece, which has been heated to a predetermined temperature in the warm part), is further heated by the irradiation of electromagnetic waves in the electromagnetic wave heating step (electromagnetic wave heating section), and the increased temperature is measured, and the sorting step ( Since the sorting section) sorts the plastics based on the above measurement results, the temperature conditions for the sorting can be set according to the type of plastic that is desired to be separated from other types. Compared with the specific gravity separation, etc., the target type of plastic can be selected very easily.

Therefore, if this method is applied to the selection of plastic waste, it is possible to prevent chlorine-containing plastics, which have many problems in the incineration and recycling of plastics, from being mixed with non-chlorine-containing plastics. It is convenient for incineration and recycling of plastics.

According to the method for sorting waste plastics of the second aspect of the present invention, the plastic pieces sorted by the sorting step are supplied to a sorting liquid having a predetermined specific gravity, and further sorted by the difference in specific gravity. Therefore, even if other types of plastics are mixed in the sorted products obtained in the sorting process, other types of plastics are removed by the sorting due to the difference in specific gravity, and the target sorted products become impurities. It is effective in making things without.

According to the waste plastic type sorting apparatus of the fourth aspect of the present invention, by supplying the plastic pieces to the conveyor belt in the casing, the plastic pieces are sequentially transferred and the microwave from the microwave generator is transferred. Is heated by the thermometer, and the temperature is measured by the thermometer, and the sorting section sorts the pieces sequentially based on the temperature measurement results. It is convenient for saving labor of sorting work.

[Brief description of drawings]

FIG. 1 is a graph showing an example of the relationship between temperature and a numerical value related to the dielectric constant of plastics, where (a) is the relationship between temperature and the dielectric constant, (b) is the relationship between temperature and the dielectric loss angle, and )
Indicates the relationship between the temperature and the dielectric loss coefficient, respectively.

FIG. 2 is a graph illustrating the dielectric loss coefficient of various plastics.

FIG. 3 is a graph showing temperature rise of a typical plastic due to microwave heating.

FIG. 4 is a process drawing showing the first embodiment of the present invention.

FIG. 5 is a partially cutaway perspective view showing an example of a microwave heating device provided with a selection unit.

FIG. 6 is a transverse cross-sectional view showing another example of the selection unit.

FIG. 7 is a process drawing showing a second embodiment of the present invention.

FIG. 8 is a graph showing the specific gravity of various plastics.

[Explanation of symbols]

 P1 Crushing process P2 Pre-heating process P3 Electromagnetic wave heating process P4 Sorting process P5 Specific gravity separation process M Plastic waste raw material M1 Plastic piece 1 Crushing device 2 Heating furnace 21 Connecting chute 3 Microwave heating device 31 Casing 31a Handover part 31b Input hole 31c Microwave irradiation hole 32 Conveyor belt 34 Receiving hopper 35 Support plate 36 1st notch part 37 2nd notch part 38 3rd chute (separation path) 4 Microwave irradiation part 41 Microwave generator 42 Waveguide 43 Micro Wave heating furnace 5,50 Sorting unit 51 First cylinder 52 Second cylinder 501 Injection nozzle 6 Radiation thermometer 7 Control unit 8 Transfer device 81 First conveyor belt 82 Second conveyor belt 501 Injection nozzle

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // B29K 105: 26

Claims (4)

[Claims] 1. A crushing step of crushing plastic into a substantially predetermined size in advance, a pre-heating step of heating the crushed plastic piece to a predetermined temperature, and irradiating electromagnetic waves to the pre-heated plastic piece. Waste plastic characterized by comprising an electromagnetic wave heating step of heating by electromagnetic waves and a selection step of measuring the temperature of the plastic piece heated by the electromagnetic wave and selecting a specific type of plastic piece based on the measured value of this temperature. Type selection method. 2. The method for selecting a type of waste plastic according to claim 1, further comprising a specific gravity selecting step of supplying the plastic pieces selected by the selecting step to a selecting liquid having a predetermined specific gravity and additionally selecting by a difference in specific gravity. A method for selecting the type of waste plastic, which is characterized in that 3. A heating unit for raising the temperature of a plastic piece crushed to a substantially predetermined size to a predetermined temperature, an electromagnetic wave heating unit for irradiating the heated plastic piece with electromagnetic waves to heat the plastic piece, and electromagnetic wave heating. A type selection device for waste plastics, comprising a thermometer for measuring the temperature of the cut plastic pieces and a sorting section for sorting plastic pieces of a specific type according to the magnitude of the measured value of the temperature. 4. The electromagnetic wave heating unit includes a microwave irradiation unit that electromagnetically heats plastic pieces being transferred by a conveyor belt, and the sorting unit distributes only specific types of plastic pieces from the conveyor belt to different sorting paths. 4. The structure according to claim 3, wherein
Equipment for sorting the types of waste plastic described.