JP2000117732A - Method and apparatus for granulation of plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To granulate a melt of waste plastic discharged from a dechlorination apparatus so as to improve removing efficiency of hydrogen chloride and to decrease treating processes until granulation is performed. SOLUTION: A melt 1a of waste plastic continuously discharged from a discharging nozzle 4 of a screw extruder 2 is cut into small pieces at right angles to the discharging direction by means of a wire 9 under stretched condition constituting a granulating machine 10 to prepare pellets 1d. The pellets 1d are received by a cooling water tank 11 positioned below to perform cooling with water. As the melt 1a is cut into small pieces immediately after discharging to prepare small pellets 1d, the pellets have large surface area through which hydrogen chloride easily comes out to be able to decrease remaining chlorine in the pellets and as granulation work is immediately performed from the melt 1a discharged from the discharging nozzle 4, treating processes for granulation can be remarkably decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for granulating plastics, which are used for granulating a melt of waste plastics for thermal recycling.

[0002]

2. Description of the Related Art In recent years, disposal of waste plastic has become a major problem. One of the methods for solving this problem is to use waste plastic as fuel (or auxiliary fuel) for blast furnaces and cement kilns. Thermal recycling has been proposed and implemented.

[0003] Since the above waste plastics usually contain polyvinyl chloride, in the case of processing for use as a fuel, a plastic melt detoxified and detoxified as a pretreatment is granulated as a pretreatment. There is a need to.

Since the polyvinyl chloride is thermally decomposed at about 350 ° C., conventionally, as shown in FIG. 2A, a charging hopper 3 is provided on one end in the longitudinal direction and a discharge port is provided on the other end. In a horizontally elongated reaction tube 5 provided with a discharge nozzle 4, two screws 6 having different blade directions are housed in parallel so that they can be rotated in opposite directions by driving a motor 7. Using a screw-type extruder 2 having a configuration in which a heating device 8 is assembled on the outer peripheral wall of the tube 5 as a dechlorinator, the raw material (flake-like waste plastic) 1 supplied into the reaction tube 5 through the charging hopper 3 is supplied. The plastic melt 1a extruded from the discharge nozzle 4 is water-cooled and dried while being heated by the heating device 8 while being melted and pyrolyzed while being moved to be pushed toward the downstream side by the rotation of the screw 6. It recovered as a large lump 1b as shown in FIG. 2 (b), and further crushed The mass 1b at crusher, so that make the small particle 1c as shown in FIG. 2 (c).

[0005]

In the method shown in FIG. 2, however, the hydrogen chloride on the surface of the large lump 1b is removed, but the hydrogen chloride entering the lump 1b stays without being completely removed. Therefore, a step of crushing the melt lump 1b, granulating and granulating the small granules 1c, immersing them again in water, washing and dehydrochlorinating, and then drying is required. A number of processing steps are required until hydrogenation and granulation, resulting in a problem of increased time and cost. Therefore, there has been a demand for how to remove a large amount of hydrogen chloride from the waste plastic melt to reduce residual chlorine and reduce the number of treatment steps.

Accordingly, the present invention is intended to increase the efficiency of removing hydrogen chloride from the waste plastic melt discharged from a dechlorinator such as a screw type extruder to reduce residual chlorine and efficiently granulate. It is an object of the present invention to provide a plastic granulation method and apparatus capable of reducing the number of processing steps.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is to cut a molten plastic waste continuously discharged from an outlet of a dechlorination apparatus into fine pellets immediately after discharging. After the granulation, the pellets are water-cooled in a cooling water tank.

[0008] Since the melt discharged from the outlet of the dechlorination apparatus is immediately cut into small pieces, the conventional crushing step is not required, and the cut melt has an increased surface area, thereby improving the desalination efficiency. In addition, since water cooling is performed, re-washing and re-drying after crushing and granulation are not required.

Further, by using a wire tensioned for cutting the melt of waste plastic as a granulator, the melt can be reliably cut because the melt does not adhere to the wire. By being mounted between the outer ends of the rotating bodies arranged to face left and right as much as possible, the melt can be cut continuously to a certain size.

[0010]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1 (a) and 1 (b) show an embodiment of a plastic granulating apparatus according to the present invention, in which a raw material 1 made of flake-shaped waste plastic is melted and thermally decomposed while being pushed and moved. Degas hydrogen chloride and melt 1
A horizontal screw type extruder 2 as a dechlorination device having the same configuration as that shown in FIG. 2 (a) in which a is extruded and discharged, and a melt 1a discharged from the screw type extruder 2 As a granulator for finely cutting and pelletizing into pellets 1d, a plurality of wires 9 are tensioned in the left-right direction, and a plurality of wires 9 are arranged at the same radial position and rotated while rotating.
a granulator 10 that cuts a, and a cooling water tank 11 that receives the pellets 1d that have been granulated and dropped by the granulator 10 and water-cooled.

The granulator 10 is shown in detail in FIG.
(B) As shown in (b), a gantry 14 having a required opening 13 formed in a base plate 12 on the upper surface is installed close to the level below the discharge nozzle 4 of the screw type extruder 2, and the discharge nozzle 4 so as to face the opening 13, and the melt 1 a from the discharge nozzle 4 is positioned above the opening 13.
The rotating shaft 15 is arranged in a direction orthogonal to the discharge direction of the base plate, and is supported by a bearing 16 installed on the base plate 12. Further, the disk 17 as two rotating bodies is mounted on the rotating shaft 15. At the same time, the wires are fixed so as to face each other at a required interval in the left-right direction, and four wires 9 are equally spaced in the circumferential direction between the outer peripheral edges of the two discs 17 and are tensioned in parallel with the rotating shaft 15. Attach, and connect one end of the rotating shaft 15 to the base plate 1
2 and connected to the output shaft of the motor 18
By rotating the rotating shaft 15 by the drive of the
The wire 9 can be rotated integrally with the wire 7.

Further, in the cooling water tank 11, one end in the longitudinal direction provided with the cooling water supply port 20 is located directly below the opening 13 inside the gantry 14, and the other end in the longitudinal direction is
It is configured such that it is guided to the outside of the gantry 14 to form a pellet outlet 19, and a cooling water outlet 21 partitioned by a screen 22 is provided on the bottom side of the pellet outlet 19.

When the raw material 1 is charged into the reaction tube 5 of the screw type extruder 2 through the charging hopper 3, the raw material 1 is moved by the rotation of the screw 6 so as to be pushed downstream. During the movement, it is heated to the set temperature by the heating device 8 and melted. Therefore, at this time, the polyvinyl chloride is thermally decomposed.

Next, the melt 1a is continuously discharged as it is pushed out from the discharge nozzle 4, and the discharged melt 1a is cut by a granulator 10 and granulated immediately. To do. In this case, in the granulator 10, the driving force of the motor 18 is transmitted to the rotating shaft 15 to keep the disk 17 in a rotated state, so that the melt 1a continuously discharged from the discharge nozzle 4 is discharged. Immediately thereafter, each of the wires 9 in a tensioned state that rotates integrally with the rotation of the disk 17 is finely cut into a certain dimension at right angles to the discharge direction and is dropped as pellets 1d.

Further, the pellets 1d are put into the lower cooling water tank 11 by dropping, and are washed at the same time as water cooling. Thereafter, they are collected and dried.

In the above, the melt 1a in the screw-type extruder 2 is in a state in which the polyvinyl chloride contained therein is thermally decomposed, and when the melt 1a is discharged from the discharge nozzle 4, hydrogen chloride is degassed. And then collected by a scrubber or the like.
By cutting into pellets 1d, the surface area is increased and the hydrogen chloride contained therein is easily released, so that an efficient desalination step can be performed. Further, since the pellet 1d is washed at the same time as being cooled in the cooling water tank 11, the hydrogen chloride still remaining in the pellet 1d can be sufficiently removed. By the way,
According to the experiment of the present inventor, when a raw material containing 4 to 5% chlorine was treated by the present apparatus, only about 0.15% of hydrogen chloride remained in the pellet 1d after washing in the cooling water tank 11. Has not been confirmed.

As described above, in the present invention, the plastic melt 1a immediately after being melted and discharged by the screw type extruder 2 is cut by the wire 9 and immediately granulated, so that the plastic melt 1a is granulated as in the conventional method. The step of re-watering and re-drying, and the step of crushing the lump can be dispensed with. Also, since the wire 9 has a very small adhesion area of the melt 1a, the wire 9 can be cut. It can be done reliably.

In the above embodiment, the case where four wires 9 are used as the configuration of the granulator 10 has been described.
By selecting the number of these wires 9 and the rotation speed of the disk 17, the melt 1a can be cut to an arbitrary length, and the disk 17 is shown as a rotating body. Arms are arranged radially and wires 9
May be attached with tension, and
The strained wire is an example, and is not limited to this. A thin cutter or another thing may be used. In the embodiment, the case where the screw-type extruder 2 is used as the dechlorination apparatus has been described. However, as long as the waste plastic is melted and desalted, other types may be employed, and of course, various changes can be made without departing from the gist of the present invention. .

[0020]

As described above, according to the method and the apparatus for granulating plastic of the present invention, the melt of waste plastic continuously discharged from the discharge port of the dechlorination apparatus is finely cut immediately after discharging. After granulating into pellets, the pellets are cooled with water, so the pellets formed by cutting have a large surface area so that hydrogen chloride can easily escape, and hydrogen chloride can be removed even when cooling with water. In addition, it is possible to remarkably improve the desalination efficiency and eliminate the need for a re-watering step and a re-drying step after crushing and granulation as in the conventional method, thereby reducing the number of treatment steps and reducing costs. Further, if the melt of waste plastic is cut with a strained wire, the melt does not easily adhere to the wire, so that the wire can be cut reliably. The pellets of a certain size continuously and efficiently by mounting the rotors at equal intervals in the circumferential direction between the outer ends of the rotating body arranged to face the left and right so as to be rotatable. It has excellent effects such as

[Brief description of the drawings]

FIG. 1 shows an embodiment of a plastic granulator according to the present invention, in which (A) is a schematic cut-away side view, and (B) is a view taken in the direction of arrows AA in (A).

FIG. 2 shows a conventional plastic granulation method.
(A) is a schematic diagram showing a state in which raw materials are melted by a screw type extruder, (B) is a diagram showing a lump of a recovered melt,
(C) is a view showing a grain formed by crushing a lump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material 1a Melt 1d Pellet 2 Screw type extruder (dechlorination apparatus) 4 Discharge nozzle (discharge port) 9 Wire 10 Granulator 11 Cooling water tank 17 Disk (rotating body)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiharu Shitara 1-Shin-Nakahara-cho, Isogo-ku, Yokohama-shi, Kanagawa Prefecture Ishikawajima-Harima Heavy Industries, Ltd. F-term (reference) 4F201 AA14 AA50 AH81 BA02 BA04 BC01 BC02 BC13 BC25 BD05 BL09 BL37 BL42 BL43 BN12 BN39 BN44 4F301 AA17 AD02 BA21 BD09 BE11 BE18 BE31 BF16 BF20 BF31

Claims (4)

[Claims] 1. A waste plastic melt continuously discharged from a discharge port of a dechlorination apparatus is finely cut immediately after discharge, granulated into pellets, and then cooled with water. Plastic granulation method. 2. A dechlorination apparatus configured to melt and thermally decompose a raw material made of waste plastic to continuously discharge a molten material from an outlet, and a dechlorination apparatus installed near a discharge port of the dechlorination apparatus. It has a configuration provided with a granulator that cuts the melt discharged from the discharge port into small pieces and granulates them into pellets, and a cooling water tank that receives the granulated pellets and water-cools them. A plastic granulator characterized by the above-mentioned. 3. The plastic granulator according to claim 2, wherein the granulator is configured to rotate the strained wire to cut the waste plastic melt. 4. The plastic granulating apparatus according to claim 3, wherein both ends of the wire are attached between outer ends of rotating bodies which are rotatably arranged on the left and right sides so as to be rotatable.