JP2002194364A - Method for decomposing waste plastic and device for decomposing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for decomposing waste plastics, which enables the treatment of a large amount of the waste plastics, the removal of carbon produced in a process for producing evaporated components from a liquid phase polymer, and the efficient recovery of a desired evaporated component. SOLUTION: The waste plastics are decomposed in a waste plastic- decomposing device in which a liquid phase polymer obtained by heating the waste plastics is supplied from a melting chamber, and which has a horizontally formed bottom surface 6a, has a decomposition chamber capable of being heated from the outside, and has plate-like stirring plates 13a in the decomposition chamber. The stirring of the liquid phase polymer and the scraping of residues are carried out with the stirring plates. The liquid surface of the liquid phase polymer is placed at a lower place than the upper ends of the stirring plates whose lower ends are approximately linearly brought into contact with the bottom surface.

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 decomposing waste plastic and recovering it as fuel oil or fuel gas.

[0002]

2. Description of the Related Art In recent years, how to treat waste has become a very important issue. In particular, waste plastics generate a high temperature when incinerated and damage the incinerator, so that a method of treating the waste plastic is being sought as a difficult-to-treat waste. By the way, many waste plastics, for example, polyethylene and polystyrene, are converted into a liquid phase polymer by performing a thermal decomposition treatment, and can be recovered as a fuel oil or a fuel gas by further performing thermal decomposition.
Since recovering these useful materials from waste is the best means of waste treatment, development of an apparatus capable of recovering fuel oil and fuel gas from waste plastic at a reasonable cost is desired.

[0003] From such a viewpoint, various studies on the decomposition treatment of waste plastics have been conducted, but the actual situation has not yet reached a full-scale practical stage. This is due to the following problems specific to this technology.

[0004] The biggest problem in the current decomposition treatment of waste plastics is how to increase the throughput. This is because if the processing amount is small, the processing per unit time becomes high in cost, and the practicality is poor. However, in the processing using a bathtub type apparatus which is currently the mainstream, if the decomposition apparatus is simply enlarged in order to increase the processing amount, the temperature gradient in the decomposition apparatus becomes large. For this reason, uniform heating of the waste plastic cannot be performed, and stable thermal decomposition treatment is difficult. Therefore, measures have been taken to increase the processing amount by arranging two disassembly devices, but in this case, the initial cost becomes enormous and is not suitable for practical use. As another type of decomposition device, there is a screw type in which a screw is disposed inside a cylindrical body, but this type of decomposition device also does not have a sufficient area for heating the liquid phase polymer, so that large-scale processing is not possible. It is not expected. Therefore, there is a need for a decomposition apparatus that can be processed in a large amount and does not require an initial cost.

[0005] Another conventional problem is the generation of carbon. Carbon is generated in the process of thermal decomposition of waste plastic. Decomposition of waste plastics is achieved by heating the liquid phase polymer to break the higher-order structure of the polymer into a lower-order structure, and by further heating this to generate a vaporized component according to the decomposition temperature, and cooling this vaporized component. By doing so, various fuel oils and fuel gases are obtained.

[0006] In the case where low-molecular-weight vaporized components generated by decomposition of the liquid-phase polymer during such heat treatment cannot be separated from the liquid-phase polymer quickly, the vaporized components are excessively present at the contact portion with the heating surface. It is generated by heating. Since this carbon acts as a heat insulating material by being deposited and laminated on the heating surface, it becomes difficult to control the decomposition of the liquid phase polymer, particularly to control the decomposition temperature. In addition, since the inside of the decomposition device needs to be cleaned to remove carbon, continuous operation becomes impossible, and the running cost increases. Further, if carbon is mixed into the recovered oil, the quality of the recovered oil is reduced, and the economic value of the recovered material is reduced.

Further, in the conventional decomposition apparatus, it is difficult to control the degree of decomposition of the liquid phase polymer when performing the decomposition reaction, and it is difficult to selectively obtain a recovered material having a desired composition. This is because it is difficult to maintain the temperature of the entire liquid phase polymer uniformly, so that temperature control can be performed accurately, and only high value-added products can be selectively recovered. Is preferred.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to enable a large amount of waste plastics to be treated, to eliminate carbon generated in the process of producing a vaporized component from a liquid phase polymer, and to reduce the temperature of the entire liquid phase polymer. An object of the present invention is to provide a method and an apparatus for decomposing waste plastic, which can efficiently collect desired vaporized components by performing a decomposition reaction in a uniform state.

[0009]

According to the method for decomposing waste plastic of the present invention which solves the above-mentioned problems, a liquid-phase polymer obtained by heating waste plastic is supplied from a melting chamber and formed horizontally. The liquid polymer is thermally decomposed by a waste plastic decomposer having a decomposed chamber having a bottom surface and heatable from the outside, and a plate-shaped stirring plate provided inside the decomposed chamber. This is performed so as to generate a vaporized component that becomes oil or fuel gas. Then, the temperature of the entire liquid phase polymer is made uniform, the residue is physically scraped off, and the liquid phase polymer is decomposed in such an amount that the generation of the residue itself can be suppressed. In other words, the agitating plate moves while being substantially in line contact with the bottom surface and the end, so that the stirring of the liquid phase polymer at the time of performing the decomposition and the scraping of the residue generated by the decomposition are performed, and the liquid The decomposition is performed while the liquid level of the phase polymer is lower than the upper end of the stir plate that is substantially in line contact with the bottom surface at the end.

According to this method for decomposing waste plastic, decomposition is performed by forming a thin layer of the liquid-phase polymer on the bottom surface formed on a plane so as to obtain a large contact area between the liquid-phase polymer and the heating surface. Therefore, the distance between the liquid polymer and the heating surface can always be kept small, and it is possible to obtain a large amount of vaporized components at a time while maintaining a uniform temperature by suppressing the temperature gradient in the liquid polymer. Become. In addition, in this method for decomposing waste plastic, the liquid phase polymer is heated while being stirred using the stirring plate, so that the temperature uniformity of the entire liquid phase polymer can be further maintained. Also,
Since the agitating plate moves while being substantially in line contact with the bottom surface of the decomposition chamber, it is possible to scrape off the residue attached to the bottom surface. As a result, the decomposition reaction can be performed in a state where the temperature of the entire liquid phase polymer is made uniform while suppressing generation of carbon, so that a desired vaporized component can be selectively and efficiently recovered.

In the method for decomposing waste plastic according to the present invention, the endless track device having a rotating endless belt is provided inside the decomposition chamber, and the stirring plate is attached to the endless belt at a predetermined interval, whereby the endless belt is attached. By moving the stirring plate with the rotation of the belt, it is possible to agitate the liquid phase polymer at the time of decomposition and scrape off the residue generated due to the decomposition. It is of course possible to move the stirring plate inside the decomposition chamber by other means, but by moving the stirring plate using the rotation of the endless belt in the endless track device, stirring of the liquid phase polymer and residue By performing the scraping, the movement of the stirring plate can be easily realized. Particularly in this case, the residue discharge pipe is arranged in parallel with the end of the stirring plate at a position in contact with the trajectory of the end of the stirring plate that moves with the rotation of the endless belt, and along the bottom surface of the decomposition chamber. It is preferable that the residue separated from the liquid phase polymer by the moving stirring plate is discharged to the outside through the residue discharge pipe. According to this, the residue carried by the stirring plate, particularly the solid residue, can be continuously discharged to the outside from the residue discharge pipe, so that the residue is reliably and efficiently discharged to the outside of the decomposition chamber. become able to.

Further, in the method for decomposing waste plastic according to the present invention, an inclined surface having an upward inclination is provided on a part of the bottom surface, and a residue connected to the outside of the decomposition chamber is provided above the inclined surface. By providing the discharge pipe, the residue separated from the liquid-phase polymer can be discharged to the outside through the residue discharge pipe by moving the stirring plate along the inclined surface. According to this method, not only the residue is scraped off with the stirring plate, but also the scraped residue can be efficiently discharged to the outside by concentrating the scraped residue in one place. At this time, the inclined surface is useful for separating the solid residue from the liquid polymer flowing down along the inclined surface.

A melting chamber having the same structure as the decomposition chamber is provided for the decomposition chamber as described above, and the waste plastic is heated and decomposed by the melting chamber to produce a liquid phase polymer. You may make it supply as it is.
That is, the melting chamber has a horizontally formed bottom surface, and a plate-shaped stirring plate is provided therein, and the stirring plate moves while being substantially in line contact with the bottom surface and the end of the melting chamber. Alternatively, the liquid phase polymer may be agitated at the time of the decomposition, and the residue generated along with the decomposition may be scraped off. The stirring plate in the melting chamber may be constituted by using an endless track device similarly to the stirring plate in the decomposition chamber. Further, vaporized components generated at a relatively low temperature may be generated in the melting chamber.

In the above-mentioned method for decomposing waste plastic, a substance serving as an abrasive may be used in order to scrape off residues more efficiently. That is, a granular material serving as an abrasive may be charged into the decomposition chamber, and the residue generated on the bottom surface may be scraped off by the granular material stirred with the movement of the stirring plate. It is sufficient that the particulate matter does not melt at a temperature inside the decomposition chamber such as sand. Granules are
It will be discharged to the outside together with the scraped residue.

Further, the waste plastic decomposing apparatus of the present invention has a melting chamber configured to heat a waste plastic to obtain a liquid phase polymer, and heat decomposes the liquid phase polymer supplied from the melting chamber. A decomposition chamber configured to heat the waste plastic supplied while stirring in the melting chamber to generate the liquid-phase polymer, and supplied while stirring in the decomposition chamber. The liquid phase polymer is thermally decomposed to generate a vaporized component that becomes a fuel oil or a fuel gas. In this decomposition apparatus, the decomposition chamber and the melting chamber have the same structure, and the waste plastic is thermally decomposed by the melting chamber to generate a liquid phase polymer, and the liquid phase polymer is supplied to the decomposition chamber as it is. Is configured. That is, the decomposition chamber and the melting chamber are
It has a horizontally formed bottom surface, and inside it is provided a plate-shaped stir plate that moves while making approximate line contact with the bottom surface and at the end, and this stir plate allows the liquid-phase polymer to be decomposed. And the scraping of the residue generated by the decomposition can be performed. Both the stirring plate in the melting chamber and the stirring plate in the decomposition chamber may be configured using an endless track device. Further, vaporized components generated at a relatively low temperature may be generated in the melting chamber.

Further, on a part of the bottom surface of the decomposition chamber and the melting chamber,
Moving the stir plate along the inclined surface by providing an inclined surface inclined upward and providing a residue discharge pipe connected to the outside of the decomposition chamber and the melting chamber above the inclined surface. Thus, the residue separated from the waste plastic can be discharged to the outside through the residue discharge pipe. By providing one residue discharge pipe through the decomposition chamber and the melting chamber, if one is provided, the residue generated in the decomposition chamber and the melting chamber can be discharged to the outside of the decomposition apparatus.

The decomposition chamber and the melting chamber are adjacent to each other with a partition wall provided therebetween. By providing a through hole for connecting the decomposition chamber and the melting chamber with the partition wall, a certain amount of the liquid phase polymer can be contained inside the melting chamber. When the liquid accumulates, the liquid phase polymer can be supplied into the decomposition chamber from the through hole. The through hole is
A notch may be provided in the upper part, or an opening may be provided.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a waste plastic decomposing device according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a plan view of an apparatus for decomposing waste plastic according to the present invention as viewed from above. This decomposition apparatus is composed of a decomposition chamber A for thermally decomposing a liquid-phase polymer to produce a vaporized component, and a melting chamber B for juxtaposing and adjoining the decomposition chamber A for thermally decomposing waste plastic to form a liquid-phase polymer.
And a partition 1 separating the decomposition chamber A and the melting chamber B. In the partition 1, a through-hole 2 as shown in FIG. 2 is formed to supply the liquid phase polymer in the melting chamber B to the decomposition chamber A. Although the through-hole 2 is shown as a notch in FIG. 2, it may be an opening, or may be an open-close type provided with an open-close mechanism such as a valve. The decomposition chamber A and the melting chamber B are surrounded by a casing 3 made of a heat insulating material. The casing 3 is provided with a burner 4 capable of heating the decomposition chamber A and the melting chamber B. Further, the decomposition chamber A and the melting chamber B are respectively provided with stirrers 5a and 5b for stirring the liquid phase polymer and scraping the residue.

FIG. 3 is a side view of the waste plastic disassembling apparatus shown in FIG. 1 and shows the inside of the disassembling chamber A from a section taken along a dashed line I. The melting chamber B has the same internal structure as the decomposition chamber A.

The decomposition chamber A is formed with an inclined surface 7a extending upward from the bottom surface 6a and inclined upward, and a direction penetrating the melting chamber B and the decomposition chamber A is provided above the inclined surface 7a. And a residue discharge pipe 8 for discharging the residue generated inside to the outside.

A supply pipe 9 for supplying waste plastic from the outside is provided in the melting chamber B, and a vaporization component discharge pipe 10 for discharging a vaporization component generated by heating the liquid phase polymer is provided in the decomposition chamber A. Is provided. The vaporized component discharge pipe 10 may be provided also in the melting chamber B. The vaporized component discharge pipe 10 is connected to a cooling device (not shown).

The stirrer 5a of the decomposition chamber A has a shape as shown in FIG. 4, and includes a belt 11a, a rotating body 12a and a stirring plate 1a.
3a. The stirrer 5a is an endless track device including a rotating body 12a formed in a drum shape rotatable by a driving unit (not shown) inside the belt 11a, and a belt that rotates with the rotation of the rotating body 12a. On the outside of the belt 11a, stirring plates 13a are attached at regular intervals perpendicular to the traveling direction of the belt 11a by rotation. The stirrer 5a is mounted in a positional relationship such that the end of the stirrer plate 13a substantially contacts the bottom surface 6a of the decomposition chamber A. Substantially line contact means that the linear end of the plate-like stirring plate 13a is close enough to scrape off the residue adhering to the bottom surface 6a of the decomposition chamber A. The stirrer 5b of the melting chamber B has the same structure as the stirrer 5a.

Next, the operation of the waste plastic decomposing apparatus of the present invention having the above-mentioned stirrers 5a and 5b inside the decomposition chamber A and the melting chamber B will be described.

The waste plastic is first supplied into the melting chamber B through a supply pipe 9 by a conveying means such as a screw conveyor. The melting chamber B is heated to a temperature at which the waste plastic is melted by the burner 4b, and the waste plastic is thermally decomposed in the melting chamber B to become a liquid phase polymer. The temperature in the melting chamber B is 200 ° C to 350 ° C.
In this case, the waste plastic is liable to become a liquid phase polymer.
Further, a vaporized component may be generated in the melting chamber B. The waste plastic that has been liquid-phase polymerized is stored in the melting chamber B. In order to store the liquid phase polymer in the melting chamber B,
Subsequent waste plastic is easily melted.

The liquid-phase polymer accumulated in the melting chamber B naturally flows into the decomposition chamber A when accumulated to the position of the through-hole 2 formed in the partition wall 1. The liquid phase polymer that has flowed in stays thinly on the bottom surface 6a of the decomposition chamber A, and is further heated by the burner 4b until a vaporized component is generated. When the temperature in the decomposition chamber A is, for example, 300 to 400 ° C., a vaporized component can be obtained while suppressing generation of carbon. The vaporized components are mainly generated on the heating surface of the decomposition chamber A, and the stirring plate 13a
Also occurs from above. The vaporized component generated from the stirring plate 13a is generated when the stirring plate 13a comes out of the liquid polymer by the operation of the stirrer 5a. Stir plate 13a
Since is not heated strongly, the generation of carbon is suppressed even when a vaporized component is generated. The thickness of the liquid-phase polymer flowing into the decomposition chamber A varies depending on the processing amount and the heating temperature. However, when the liquid level L is substantially in line contact with the bottom surface 6a of the decomposition chamber A, the liquid level L The thickness is set so that it is lower than the upper end. Specifically, a thickness of about 3 cm for polyethylene, polypropylene, or polystyrene, or about 2 cm for ABS or the like is good for generating vaporized components.

During the above-described decomposition reaction, the stirrers 5a and 5b in the decomposition chamber A and the melting chamber B are operating. The decomposition chamber A and the melting chamber B have the same shape, and the stirrers 5a and 5b perform the same operation.
Only the operation of the stirrer 5a will be described, and the description of the operation of the melting chamber B will be omitted.

The belt 11a of the stirrer 5a is
It rotates in conjunction with the rotation of a. When the belt 11a rotates, the stirring plate 13a attached thereto also rotates, and the rotating stirring plate 13a stirs the liquid-phase polymer accumulated on the bottom surface 6a of the decomposition chamber A. The stirring enables uniform heating of the liquid-phase polymer, eliminates the temperature gradient, and suppresses carbon generated when excessively heated at the contact portion with the heating surface.
By suppressing the generation of carbon, the decomposition temperature of the liquid phase polymer can be controlled without any trouble. In addition, it becomes easier to selectively obtain a recovered material having a desired composition. Stir plate 13
Since a is attached such that its tip is substantially in line with the bottom surface 6a of the decomposition chamber A, the residue a is scraped off from the bottom surface 6a of the decomposition chamber A and transferred to the residue discharge pipe 8 at the same time as stirring. An inclined surface 7a having an inclination is formed from the bottom surface 6a to the residue discharge pipe 8, and the residue scraped off by the agitating plate 13a is collected in one place by the inclined surface 7a, so that it can be efficiently and easily discharged to the outside. Is discharged to Also, the inclined surface 7a
Is also useful for separating the solid residue from the liquid phase polymer flowing down along the inclined surface 7a. If the trajectory of the tip of the stirring plate 13a at the time of operating the stirrer 5a corresponds to the shape of the bottom surface 6a, the residue can be discharged more efficiently. The residue discharge pipe 8 separates the liquid phase polymer and the solid residue from the liquid phase polymer by a conveying means such as a screw conveyor, and discharges only the residue to the outside of the decomposition chamber A. Residue discharge pipe 8
Is a tube with a built-in screw conveyor, it is possible to squeeze out the liquid phase polymer by compressing the residue.

The scraping of the residue can be performed more efficiently by putting granular materials, such as sand, which do not melt at the temperature in the decomposition chamber into the decomposition chamber A. This is because when the granular material put in the decomposition chamber A scrapes the bottom surface 6a in the decomposition chamber A with the stirring plate 13a, the bottom surface 6a is stirred by the stirring plate 13a.
This is because it functions as an abrasive for removing a. Granules are
A residue discharge pipe 8 is provided by the stirring plate 13a together with the scraped residue.
And discharged to the outside of the decomposition chamber A.

The liquid-phase polymer on the bottom surface 6a of the decomposition chamber A is heated and decomposed by the burner 4a and vaporized. By discharging the vaporized component from the vaporized component discharge pipe 10 and cooling it, various fuel oils and fuel gases are obtained. By heating while stirring, the decomposition reaction can be performed while keeping the temperature of the entire liquid phase polymer uniform while suppressing the generation of carbon.
Control of the decomposition temperature is facilitated, and a desired vaporized component is obtained.

[0031]

According to the waste plastic decomposition apparatus of the present invention, the bottom of the decomposition chamber is formed horizontally, and a stirrer is provided in the decomposition chamber so that the residue can be discharged to the outside while stirring the liquid phase polymer. In addition, the generation of carbon in a large amount of liquid phase polymer can be suppressed, and the decomposition temperature of the liquid phase polymer can be controlled without any trouble. For this reason, the vaporized component can be rapidly and massively separated from the liquid phase polymer. Also,
The decomposition reaction is performed in a state where the temperature of the entire liquid phase polymer is made uniform, and the desired vaporized component can be efficiently recovered. Since a large amount of waste plastic can be processed, processing costs and running costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a waste plastic decomposition apparatus of the present invention as viewed from above.

FIG. 2 is a perspective view showing a partition used in the disassembling apparatus of FIG.

FIG. 3 is a side view of the waste plastic decomposing device of the present invention as viewed from a cut surface along a dashed line I in FIG.

FIG. 4 is a perspective view schematically showing a stirrer used in the decomposition apparatus shown in FIGS. 1 and 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Partition wall 2 Through-hole 3 Casing 4a, 4b Burner 5a, 5b Stirrer 6 Bottom surface 7 Slope 8 Residue discharge pipe 9 Supply pipe 10 Vaporization component discharge pipe 11a, 11b Belt 12a Rotating body 13a, 13b Stirring plate A Decomposition chamber B Melting Chamber I Cutting surface L Liquid level

Claims (9)

[Claims] 1. A liquid phase polymer obtained by heating a waste plastic is supplied from a melting chamber, and a decomposition chamber having a horizontally formed bottom surface and capable of being heated from the outside is provided. A method for decomposing waste plastic in which a liquid-phase polymer is heated and decomposed by a decomposer for waste plastic provided with a plate-shaped stirring plate in an interior to generate a vaporized component that becomes a fuel oil or a fuel gas. The plate is moved while being substantially in line contact with the bottom surface and the end, thereby stirring the liquid-phase polymer when performing the decomposition and scraping off the residue generated due to the decomposition, and the liquid of the liquid-phase polymer. A method for disassembling waste plastics, wherein the disintegration is performed while the surface is lower than the upper end of the agitating plate which is substantially in line contact with the bottom surface at the end. 2. An endless track device having a rotating endless belt is provided inside the decomposition chamber, and the stirring plate is attached to the endless belt at a predetermined interval. The method for decomposing waste plastic according to claim 1, wherein the stirring of the liquid-phase polymer at the time of decomposition and the scraping of the residue generated by the decomposition are performed by moving the stirring plate. 3. A residue discharge pipe connected to the outside of the decomposition chamber in a direction parallel to the end of the stirring plate at a position in contact with the trajectory of the end of the stirring plate that moves with the rotation of the endless belt. The method for decomposing waste plastic according to claim 2, wherein a residue separated from the liquid-phase polymer by a stirring plate moving along the bottom surface of the decomposition chamber is discharged outside through the residue discharge pipe. 4. A part of the bottom surface is provided with an inclined surface inclined upward, and a residue discharge pipe connected to the outside of the decomposition chamber is provided above the inclined surface. The method according to claim 2, wherein the residue separated from the liquid-phase polymer is discharged to the outside through the residue discharge pipe by moving the stirring plate along the surface. 5. The melting chamber has a horizontally formed bottom surface, and a plate-like stirring plate is provided inside the melting chamber, whereby the stirring plate is substantially in line contact with the bottom surface of the melting chamber at an end. The method for decomposing waste plastic according to claim 1, wherein the liquid plastic is stirred while the liquid phase polymer is being decomposed, and the residue generated during the decomposition is scraped off. 6. The method for decomposing waste plastic according to claim 1, wherein a granular material is charged into the decomposition chamber, and a residue generated on the bottom surface is scraped off by the granular material agitated as the stirring plate moves. . 7. A melting chamber configured to heat a waste plastic to obtain a liquid phase polymer, and a decomposition chamber configured to thermally decompose a liquid phase polymer supplied from the melting chamber, The waste plastic supplied while being stirred in the melting chamber is heated to generate the liquid phase polymer, and the liquid polymer supplied while being stirred in the decomposition chamber is thermally decomposed to produce a fuel oil. Or a waste plastic decomposer configured to generate a vaporized component that becomes a fuel gas, wherein the decomposition chamber and the melting chamber have a horizontally formed bottom surface, and the inside thereof has the bottom surface and A plate-like agitating plate that moves while making approximate line contact at the end is provided. This agitating plate is used to agitate the liquid-phase polymer during the decomposition and scrape off the residue generated by the decomposition. DOO decomposition apparatus constructed waste plastic to allow the. 8. A part of the bottom surface of the decomposition chamber and the melting chamber is provided with an inclined surface inclined upward, and the decomposition chamber and the melting part are provided above the inclined surface. A residue discharge pipe connected to the outside of the melting chamber is provided, and by moving the stirring plate along the inclined surface, the residue separated from the waste plastic is discharged to the outside through the residue discharge pipe. The waste plastic decomposer according to claim 7, wherein the waste plastic is decomposed. 9. The decomposition chamber and the melting chamber are adjacent to each other with a partition wall provided therebetween, and the partition wall is provided with a through hole connecting the decomposition chamber and the melting chamber. Waste plastic decomposition equipment.