JP3264200B2 - Recycling of waste plastic - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling waste, and more particularly to a method for recycling plastic in waste (hereinafter referred to as "waste plastic").
The present invention relates to a method for removing chlorine-containing plastics from waste plastics for recycling.

[0002]

2. Description of the Related Art Plastics contained in wastes are generally incinerated as combustible waste or disposed of by landfill. In order to incinerate waste plastics as combustible waste, chlorine-containing plastics such as PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride) in plastics are thermally decomposed during incineration, and hydrogen chloride gas is generated. Therefore, it is necessary to equip the equipment for recovering and neutralizing the hydrogen chloride. In addition, regarding landfill disposal of waste plastic, shortage of disposal sites has become a major social problem in recent years.

[0003]

As mentioned above, the processing of plastics in wastes has a very low recycling rate. However, in recent years, for example, oil liquefaction processing technology of plastic has been developed,
2. Description of the Related Art In an ironworks, a technique has been developed in which plastic is formed into a predetermined shape as a substitute for coke, processed and then blown from a blast furnace tuyere and used as a reducing agent for an iron source. In these recycling techniques, there is a problem of corrosion of pipes due to chlorine, and therefore, a step of removing chlorine-containing plastic before use is still required.

Conventionally, as a technique for removing chlorine-containing plastics from various types of mixed plastics, a wet separation method (sink float) utilizing a difference in specific gravity of plastics is known. According to this method, it is possible to separate PVC and PVDC whose specific gravity is higher than that of water of the specific gravity liquid from most other plastics whose specific gravity is lower than that of water. However, on the other hand, most of the raw materials for plastic bottles are PET (polyethylene terephthalate).
Since ET and PVC and PVDC have substantially the same specific gravity, PVC and PVDC and P
It was impossible to separate from ET. Therefore, P
There is a problem that the PET bottle is discarded without being recycled in the process of removing VC and PVDC.

[0005] Accordingly, an object of the present invention is to selectively remove PVC and PVDC from plastic in waste without removing PET bottles in view of the above situation.
It is an object of the present invention to provide a method for effectively recycling plastic in waste.

[0006]

According to the first aspect of the present invention,
The waste plastic in the mixed state is separated into a solid plastic and a lighter plastic lighter than the solid plastic by a rocking repulsion sorter, and then the solid plastic thus sorted is chlorinated by a dry separation method. The content plastic is removed, and the lightweight plastic is characterized in that chlorine-containing plastic is removed by wet sorting using a specific gravity difference of a specific gravity liquid with respect to water.

A second aspect of the present invention is characterized in that the chlorine-containing plastic obtained by selectively removing the chlorine-containing plastic by the method of the first aspect is processed into a predetermined shape and used as a raw material for a blast furnace. .

[0008] Wastes of mixed plastics are roughly classified into solid plastics mainly composed of plastic bottles, plastics in the form of films, and plastics in tray systems such as firing trays. By using an oscillating sorter, film-based plastic and tray-based plastic are collected as lightweight plastics as light-weight materials, and solid plastics are collected as heavy-weight materials. The chlorine-containing plastic can be removed by wet sorting using a specific gravity difference with respect to water, and the solid plastic can be removed by a dry sorting method. The removed chlorine-containing plastic can be processed into a predetermined shape and used as a raw material for a blast furnace as a reducing material for an iron source.

[Operation] In the swing type sorting machine, when an object to be sorted is put on an inclined repulsion plate attached to a crankshaft and swinging, a trajectory repelled by a difference in weight, shape and hardness of the object is formed. This is a sorting device that sorts by utilizing different things, and has a structure in which a heavy object is collected below a slope and a lightweight object is collected above a slope. When the waste of the mixed plastic is put into the oscillating sorter, a solid plastic is collected as a heavy material, and a film-based plastic and a tray-based plastic are collected as a light-weight material.

[0010] The solid plastic recovered as a heavy material is subjected to dry-selection to selectively remove chlorine-containing plastic. The use of the dry sorting method is based on the fact that in the wet separation method, PET, which accounts for the majority of the raw material of the bottle, and PV
This is because it is impossible to distinguish between C and PVDC.

As a dry sorting method, for example, a method of measuring and determining an absorption spectrum when irradiating near infrared rays is disclosed in JP-A-6-210632 and JP-A-6-308.
Various methods have been developed and disclosed in Japanese Unexamined Patent Publication No. 022 and the like.
By using this method, it is possible to selectively remove chlorine-containing plastics of PVC and PVDC without removing PET.

On the other hand, PVC and PVDC are removed from the film-based plastic and the tray-based plastic collected as lightweight materials by a wet separation method using a difference in specific gravity of water with respect to water. P for film plastic
Since almost no ET is contained, even if wet separation is used, P
There is no risk of removing ET. It should be noted that the wet separation method can be implemented with smaller and simpler equipment than the dry separation method.

[0013]

Next, an embodiment of the present invention will be described with reference to the drawings. [Embodiment 1] FIG. 1 is a processing step diagram showing Embodiment 1 of the present invention, and FIG. 2 is a side view showing a principle of sorting of a swing repulsion type sorting machine used for this sorting.

As shown in FIG. 2, a swing repulsion type sorting machine 1
Is attached to the crankshaft 2 with an inclination of 0 degree when one or a plurality of repulsion plates 3 attached to the crankshaft 2 are small and about 20 degrees when large. A sieve hole 4 can be set in the repulsion plate 3 as needed,
A small diameter object can be taken out by this sieve effect. Since the crankshaft 2 is rotated in the direction of the arrow by an electric motor (not shown), the movement of the crankshaft causes the repulsion plate 3 to swing. The sorting principle of the oscillating type sorting machine 1 is based on the difference in the trajectory when the object 7 falling on the repulsion plate 3 that oscillates rebounds on the repulsion plate 3.
Since the direction of rebound is greatly affected by the inclination angle of the repulsion plate 3, the rebound direction falls below the inclination.
Since the bounce on the repulsion plate 3 is small, is repelled by the swinging motion of the repulsion plate 3 and is conveyed to an upper part of the slope, and is collected as lightweight plastic. Further, the small-diameter object 8 is sieved by a sieve hole on the repulsion plate 3 and collected just below the repulsion plate 3. According to experiments, the optimum inclination angle of the rebound plate 3 for separating waste plastic in the present embodiment is about 5 to 15 degrees. The rotation speed of the crankshaft is 100
About 200 rpm is appropriate.

As shown in FIG. 1, if necessary, a bag breaking machine 9
Alternatively, the waste plastic unpacked by the crusher is put into the oscillating sorter 1. As for the waste plastic put into the oscillating sorter 1, solid plastic mainly composed of bottle plastic is collected on the heavy material side, and film-based and tray-based plastics are collected on the light-weight side as lightweight plastic. In addition, due to the sieving effect of the sieve holes set on the repulsion plate, improper sorting residues such as sand particles, pebbles, and glass fragments are sorted out.

The solid plastic collected below the rebound plate is sent to a dry sorting step after collecting metals by a magnetic separator 10. The dry sorting process usually includes an alignment device 11, a sensor unit 12, an information processing device 13, and a sorting device 14. That is, the alignment unit 11 uses the sensor units 12 one by one.
Is irradiated with near-infrared light, the information processing device 13 determines the absorption spectrum peculiar to the substance, the type is determined, and the sorting device 14 removes chlorine-containing PVC and PVDC.

The lightweight plastic collected above the rebound plate is sent to a wet separation process, where PV having a specific gravity greater than water is used.
C and PVDC are removed. This wet separation process,
For example, it is constituted by a crusher 15, a mixing tank 16, and a separation tank 17. The crusher 15 is provided with a metal removing device as needed. In the wet separation process, PVC and PVDC having a higher specific gravity than water are settled and taken out from below, and other plastics having a lower specific gravity than water are collected from above as lightweight plastic.

In the dry sorting method in the embodiment, the method of near-infrared irradiation has been described, but it goes without saying that other dry sorting methods, for example, a method of observing the transmission spectrum of ultraviolet rays, can be applied in the same manner. No.

[Embodiment 2] FIG. 3 is a process chart showing Embodiment 2 of the present invention. As shown in FIG. 3, the plastic from which the chlorine-containing plastic has been removed in the first embodiment can be used as a reducing agent for an iron source in a steel plant as an alternative raw material for coal. That is, the solid plastic sorted by the rocking repulsion sorter 1 is used to remove PVC and PVDC by a dry sorter, and then crushed by a crusher 18.
, It can be cut into a predetermined shape and blown from the tuyere of the blast furnace. Further, the plastics of the film type and the tray type collected as the lightweight plastics by the rocking type sorting machine 1 are removed by the wet sorting utilizing the difference in the specific gravity with the water to remove PVC and PVDC having a higher specific gravity than the water. After it is shaped into a predetermined shape using a granulator, it can be blown from the tuyere of a blast furnace.

[0020]

As described above, according to the present invention, by using a repulsion type rejection type separator, a solid plastic having a high PET content and a film-based or tray-based plastic containing no PET are separated and separated. It is possible to remove chlorine-containing plastics without substantially losing valuable resources, so that it is possible to effectively use plastics that have been incinerated or landfilled. Since the plastic is removed, the plastic can be used as a raw material for replacing iron as a raw material for iron making, and thus has an industrially useful effect.

[Brief description of the drawings]

FIG. 1 is a process chart showing a first embodiment of the present invention.

FIG. 2 is a side view showing a sorting principle of a swing repulsion type sorting machine used for sorting according to the first embodiment of the present invention.

FIG. 3 is a process chart showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillating repulsion sorter 2 Crankshaft 3 Repulsion plate 4 Sieve hole 5 Heavy material 6 Light and flexible material 7 Sorted material 8 Small diameter material 9 Bag breaker 10 Magnetic separator 11 Alignment device 12 Sensor part 13 Information processing device 14 Sorting device 15 Crusher 16 Mixing tank 17 Separation tank

Continued on the front page (72) Inventor Shigeki Yamazaki 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Yoji Ogaki 1-2-1-2 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Makoto Arimoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-6-126743 (JP, A) JP-A-57-167772 (JP, A JP-A-54-36666 (JP, A) JP-A-53-130873 (JP, A) JP-A-56-84078 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29B 17/00-17/02 C08J 11/00-11/28 B07B 13/10

Claims (2)

(57) [Claims] 1. A waste plastic in a mixed state is separated into a solid plastic and a lighter plastic which is lighter than the solid plastic by a rocking repulsion sorter, and then the solid plastic thus sorted is dried. The chlorine-containing plastic is removed by the sorting method of
A method for recycling waste plastics, comprising removing chlorine-containing plastics from the lightweight plastics by wet sorting using a specific gravity difference of a specific gravity liquid with respect to water. 2. The method according to claim 1, wherein the chlorine-containing plastic sorted and removed by the method according to claim 1 is processed into a predetermined shape and used as a raw material for a blast furnace.