Vent device

Abstract

The present invention provides a method and system for the thermal decomposition of resin materials, which can perform the thermal decomposition treatment of resin materials continuously and efficiently. [Solution] The thermal decomposition treatment system for resin materials includes an extruder having a cylinder 12 into which the resin material is fed, a heat source unit provided in the cylinder 12 for thermally decomposing the resin material, a screw positioned inside the cylinder 12 for transporting the resin material, a vent section 14a for exhausting gas containing multiple components generated inside the cylinder 12 when the resin material is thermally decomposed, and a first heat exchanger 14b connected to the vent section 14a for liquefying a portion of the gas, and a second heat exchanger 15 for cooling and liquefying the remainder of the gas that has passed through the first heat exchanger 14b in gaseous form.

Description

Technical Field

[0001] The present invention relates to a thermal decomposition treatment method for resin materials and a thermal decomposition treatment system for resin materials.

Background Art

[0002] Currently, plastic products are used in a very wide range of fields, and the amount used is enormous. On the other hand, disposal of plastic products incurs high costs, and the leakage of their components into rivers, marine areas and the like caused by leaving them in the natural environment has also made the impact on the environment a problem.

[0003] Therefore, various studies have been conducted on effective utilization of resources by recycling various resins. For example, when treating waste plastics, there is a known technique in which an extruder having a screw used for resin extrusion molding is used, and gas generated in the cylinder of the extruder is discharged to the outside through a vent provided on the cylinder (see, for example, Japanese Patent Laid-Open No. 2005-349838 (Patent Document 1), Japanese Patent Laid-Open No. 2008-302555 (Patent Document 2), etc.).

Prior Art Literature

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0005] As described above, the treatment and recycling of resin materials such as waste plastics have been promoted in recent years, and there is a demand for efficient decomposition treatment of resin materials.

[0006] Therefore, the present invention aims to provide a method and system for the thermal decomposition of resin materials that can perform the thermal decomposition treatment of resin materials continuously and efficiently. Other challenges and novel features will become apparent from the description and accompanying drawings in this specification. [Means for solving the problem]

[0007] The thermal decomposition treatment method for a resin material disclosed in this application includes: (a) a step of thermally decomposing the resin material in the cylinder of an extruder having a screw; (b) a step of exhausting a gas containing multiple components generated by the thermal decomposition of the resin material from a vent after step (a); (c) a step of cooling and liquefying a portion of the gas with a first heat exchanger after step (b); and (d) a step of cooling and liquefying the remaining portion of the gas with a second heat exchanger after step (c).

[0008] The thermal decomposition treatment system for resin materials disclosed in this application comprises (a) an extruder and (b) a second heat exchanger. The extruder comprises a cylinder into which the resin material is fed, a heat source provided in the cylinder for thermally decomposing the resin material, a screw located inside the cylinder for transporting the resin material, a vent for exhausting gas containing multiple components generated inside the cylinder as the resin material is thermally decomposed, and a first heat exchanger connected to the vent for liquefying a portion of the gas. The second heat exchanger cools and liquefies the remainder of the gas that has passed through the first heat exchanger in gaseous form.

[0009] The extruder venting device disclosed herein comprises a vent section connected to an extruder; and a heat exchanger provided in the vent section for cooling and liquefying a portion of the exhaust gas discharged from the vent section. [Effects of the Invention]

[0010] The thermal decomposition treatment method and thermal decomposition treatment system for resin materials disclosed herein allow for the continuous and efficient thermal decomposition treatment of resin materials such as waste plastics.

[0011] The extruder venting device disclosed in this application provides a venting device suitable for an extruder as a component used to efficiently carry out thermal decomposition in the above-mentioned thermal decomposition treatment method and thermal decomposition treatment system. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows a schematic configuration of a thermal decomposition treatment system for resin materials in one embodiment. [Figure 2] This figure shows a schematic configuration of a cylinder used in the thermal decomposition treatment system for resin materials shown in Figure 1. [Figure 3] This figure shows an overview of the internal structure of the venting device shown in Figure 1. [Figure 4] This figure shows the configuration of a thermal decomposition treatment system for resin materials in another embodiment. [Figure 5] This figure shows a modified example of the thermal decomposition treatment system for resin materials shown in Figure 4. [Figure 6] This figure shows a schematic configuration of a thermal decomposition treatment system for resin materials in another embodiment. [Modes for carrying out the invention]

[0013] The embodiments will be described in detail below with reference to the drawings. In all the drawings used to describe the embodiments, the same reference numerals are used for members having the same function, and repeated descriptions of them will be omitted. In addition, in the following embodiments, descriptions of the same or similar parts will not be repeated unless it is particularly necessary.

[0014] <Embodiment 1> The overall configuration of the thermal decomposition treatment system for resin materials in this embodiment and the method for thermal decomposing resin materials using the same will be described with reference to Figure 1.

[0015] [Thermal decomposition treatment system for resin materials] Fig. 1 is an explanatory diagram (side view) showing a schematic configuration of a thermal decomposition treatment system 10 for resin materials according to Embodiment 1. The thermal decomposition treatment system 10 for resin materials is an apparatus used to thermally decompose a resin material to be decomposed by heating the resin material inside the system, separate monomers and low-molecular-weight compounds generated by the decomposition according to their properties (gas or liquid), and perform recovery and treatment on the compounds.

[0016] This thermal decomposition treatment system 10 for resin materials comprises a resin material supply unit 11, a cylinder 12 having a screw, a rotation drive mechanism 13 for driving the screw of the cylinder 12, a vent device 14 composed of a vent portion 14a and a heat exchanger 14b, a heat exchanger 15, a liquid recovery container 16, and a solid recovery container 17.

[0017] The resin material supply unit 11 is a member that supplies the resin material to be decomposed to the cylinder 12. In the present embodiment, for example, thermoplastic resins and thermosetting resins are supplied as the resin material to be decomposed. As the supplied resin material, those in various forms such as pellets, powder, and flakes are used. For example, the resin material is charged from above into the resin material supply unit 11 having a hopper 11a by a feeder or the like, and then supplied into the cylinder 12.

[0018] The cylinder 12 has a space formed therein for conveying the resin material, and is provided with a screw 12a for conveying the resin material in the space. Fig. 2 shows a cross-sectional view of the cylinder 12 so that the internal structure of the cylinder 12 of the thermal decomposition treatment system 10 for resin materials in Fig. 1 can be understood. The cylinder 12 is provided with an opening 12b that allows gas generated inside the cylinder 12 to be discharged to the outside of the cylinder 12, a tip portion 12c that can discharge residues, and a plurality of heaters (heat source units) 12d that can heat the cylinder 12 for each cylinder block. These members constitute an extruder. The vent device 14, which will be described in detail later, is provided in the opening 12b.

[0019] By rotating the screw 12a of the cylinder 12, the resin material supplied to the resin material supply unit 11 is gradually conveyed inside the cylinder 12 toward the tip 12c side (downstream side) of the cylinder 12.

[0020] The cylinder 12 is composed of, for example, multiple cylinder blocks connected together, and each cylinder block has a space inside that can transport resin material. A screw 12a is provided in this space, and the screw 12a is connected to a rotary drive mechanism 13. This rotary drive mechanism 13 rotates the screw 12a, allowing the resin material to be disassembled to be transported within the cylinder 12.

[0021] Furthermore, the cylinder 12 is equipped with a heat source such as a heater so that its temperature can be adjusted. The resin material to be decomposed is transported from the resin material supply unit 11 toward the tip unit 12c, and at that time, it is gradually heated by the heater, etc., and becomes a molten plasticized resin material. The molten plasticized resin material thus obtained can be easily transported within the cylinder 12 and is transported downstream while being further heated. In this embodiment, the heating temperature is gradually increased until the resin material is heated to a temperature at which it undergoes thermal decomposition.

[0022] Furthermore, the molten resin in cylinder 12 may be pressurized and heated simultaneously by screw 12a. Simultaneous heating and pressurization can further accelerate the thermal decomposition of the resin material. The resin material is then decomposed by thermal decomposition into monomers and other low-molecular-weight compounds that make up the resin. At this time, some of the low-molecular-weight compounds become gas within cylinder 12. This gas generally contains several components produced during the decomposition process of the resin material.

[0023] The tip section 12c is the part that discharges the residue of the resin material that has been transported and thermally decomposed inside the cylinder 12, which remains in a molten state and does not turn into gas, into the solid recovery container 17. This residue is a liquid substance heated to a high temperature, and if the resin material contains fillers or the like, it may be discharged in a state mixed with solids.

[0024] The rotary drive mechanism 13 is a device for rotating the screw 12a located inside the cylinder 12. By utilizing the screw rotated by the rotary drive mechanism 13, the resin material of the object to be disassembled can be transported inside the cylinder 12.

[0025] The extruder may be a twin-screw extruder with two screws in the cylinder 12, or a single-screw extruder with one screw. In the case of a twin-screw extruder, the two screws are arranged parallel to each other and rotate. The two shafts may be arranged to mesh with each other, or they may be arranged not to mesh with each other.

[0026] Twin-screw extruders are preferable because, for the same screw diameter, they can achieve a higher extrusion rate than single-screw extruders due to their high raw material transport efficiency and high mixing performance. They also have various advantages, such as the flexibility to freely change operating conditions such as screw rotation speed and barrel temperature. Here, the direction of extension of cylinder 12 and the direction of extension of the screw within cylinder 12 are the same.

[0027] The venting device 14 is a device comprising a vent section 14a provided on the cylinder 12 and a heat exchanger 14b. The vent section 14a is a component that exhausts the gas generated inside the cylinder 12 to the outside of the cylinder 12, and can be configured in the same way as the vent sections provided in known extruders. In this embodiment, the vent section 14a is provided so that the gas is sequentially subjected to heat exchange treatment by the heat exchanger 14b and the heat exchanger 15, which will be described later.

[0028] The heat exchanger 14b is integrally provided above the vent section 14a to constitute the venting device 14. This heat exchanger 14b is a device that cools and liquefies a portion of a gas containing multiple components. For example, in this case, the temperature is controlled so that the component with a high boiling point (high-boiling point gas component) is liquefied, while the component with a lower boiling point (low-boiling point gas component) passes through as a gas.

[0029] The temperature of the heat exchanger 14b can be controlled by supplying and discharging a refrigerant (cooling medium) maintained at a predetermined temperature through piping installed inside it. In Figure 1, the flow of this refrigerant supply and discharge is indicated by arrows. As described above, the temperature of this refrigerant is controlled to be lower than the boiling point of the high-boiling point gas component and above the melting point of the high-boiling point gas component, so that a portion of it can be cooled and liquefied in the heat exchanger 14b. This allows the high-boiling point gas component to be cooled and liquefied by the heat exchanger 14b.

[0030] Furthermore, it is preferable to control the temperature of the refrigerant so that it is higher than the boiling point of the low-boiling-point gas component. By controlling the temperature in this way, the high-boiling-point gas component and the low-boiling-point gas component can be separated, and it is particularly preferable that the high-boiling-point gas component is not included in the gas supplied to the heat exchanger 15. Here, the remaining gas that has passed through the heat exchanger 14b without being liquefied is supplied to the heat exchanger 15 through the piping 18.

[0031] The venting device 14 can be installed at any position on the cylinder 12. In order to efficiently process the generated gas, it is preferable to install the venting device 14 in a location within the cylinder 12 where the amount of gas generated is high, or downstream of that location (towards the tip 12c of the cylinder 12).

[0032] The heat exchanger 15 is a device that cools and liquefies the gas (the remaining gas) that was not liquefied in the heat exchanger 14b, which contains multiple components. For example, the temperature is controlled here to liquefy the low-boiling point gas components among the multiple components.

[0033] The temperature of the heat exchanger 15 can be controlled in the same way as the heat exchanger 14b by supplying and discharging a refrigerant maintained at a predetermined temperature through piping installed inside it. In Figure 1, the flow of this refrigerant supply and discharge is indicated by arrows.

[0034] The temperature of this refrigerant is controlled to be lower than the boiling point of the low-boiling point gas component and higher than the melting point of the low-boiling point gas component, as described above, so that the remaining gas can be cooled and liquefied in the heat exchanger 15. As a result, the low-boiling point gas component is cooled and liquefied in the heat exchanger 15. By controlling the temperature in this way, the low-boiling point gas component becomes liquid and can be separated and recovered as a liquid.

[0035] Furthermore, it is preferable that the temperature of the refrigerant is lower than the melting point of the high-boiling-point gas components. In this case, conditions for the formation of solids in the heat exchanger, which has been a problem in the past, can occur. However, according to this embodiment, the high-boiling-point gas components are not included in the gas (the remainder of the gas) processed in the heat exchanger 15, so such problems do not occur.

[0036] As described above, this heat exchanger 15 liquefies low-boiling point gas components. However, if multiple types of low-boiling point gas components are present, it may be configured to liquefy only a portion of them and release the gas components with even lower boiling points into the atmosphere, or to perform other treatments such as exhaust gas treatment. Release into the atmosphere should only be carried out if it does not have an adverse effect on the environment. The gas components liquefied in the heat exchanger 15 are collected in the liquid recovery container 16 via the piping 19.

[0037] Furthermore, the temperature control of the refrigerants in the heat exchangers 14b and 15 described above can be achieved by providing control units that manage their temperatures and maintaining the set temperatures (for example, temperatures at which the high-boiling-point and low-boiling-point gas components can be liquefied, as described above).

[0038] The liquid recovery container 16 is a container for storing the components liquefied in the heat exchanger 15. This liquid recovery container 16 should be made of a material that can stably store the liquefied components. The liquid recovery container 16 may be open to the atmosphere or sealed. A sealed system is preferable if contact with air could cause deterioration of the recovered liquid or other problems.

[0039] As described above, the solid recovery container 17 is a container for storing the residue of the resin material that is not gasified by thermal decomposition due to heating in the cylinder 12 and is discharged from the tip 12c of the cylinder 12.

[0040] The residue recovered in this solid recovery container 17 is in a molten state (liquid) when heated to a high temperature, and if the resin material contains fillers, etc., it is discharged as a liquid mixture containing solids. On the other hand, once this residue is discharged into the solid recovery container 17, it is gradually cooled and solidified inside the container, and the solid residue accumulates sequentially at the bottom of the solid recovery container 17.

[0041] The solid recovery container 17 should be made of a material capable of stably storing the liquid flowing out from the tip 12c of the cylinder 12 and the cooled and solidified solid. The solid recovery container 17 may be open to the atmosphere or closed to the atmosphere. A closed system is preferable if contact with air could cause the residue to deteriorate or pose a risk of combustion. A cooling source may also be provided to promote the solidification of the residue.

[0042] <Method for thermal decomposition of resin materials> Next, the thermal decomposition treatment method for resin materials according to this embodiment will be explained, using the case where the resin material thermal decomposition treatment system 10 described above is used as an example.

[0043] First, the resin material is thermally decomposed in the cylinder 12 of the extruder ((a) step; thermal decomposition step). In this step, the resin material to be decomposed is supplied to the inside of the cylinder 12 of the thermal decomposition processing system 10 via the resin material supply unit 11, and the resin material is thermally decomposed by heating it inside the cylinder 12. Here, the resin material supplied into the cylinder 12 is gradually heated and thermally decomposed as it is conveyed by the screw 12a towards the tip 12c inside the cylinder 12.

[0044] The resin products to be decomposed are not particularly limited as long as they are resins that can be thermally decomposed by heating. Examples include polyethylene (PE) resin, polypropylene (PP) resin, polyamide 6 (PA6) resin, polycarbonate (PC) resin, polyethylene terephthalate (PET) resin, and polybutylene terephthalate (PBT) resin.

[0045] A heat source, such as a heater, is provided on the outer circumference of the cylinder 12, and the resin material is configured to gradually reach a high temperature as it is transported by this heater. Furthermore, as it is heated, the resin material becomes molten and plasticized, making it easy to transport by the screw 12a.

[0046] Although it varies depending on the resin material used, the heating temperature in this thermal decomposition is preferably such that the resin temperature reaches approximately 250 to 400°C. Furthermore, pressurization may be applied during this thermal decomposition process. Pressurization is preferable as it facilitates further thermal decomposition. If pressurization is applied, it is preferable to pressurize the machine to an internal pressure of 0.3 to 20.0 MPa.

[0047] As described above, when thermal decomposition is carried out by heating, the bonds in the resin material are broken down, resulting in a reduction in molecular weight. Through this thermal decomposition, the resin material is broken down into monomers and other low-molecular-weight compounds that constitute the resin. The monomers and low-molecular-weight compounds produced by the decomposition become gas in cylinder 12. The gas produced at this time usually contains multiple components.

[0048] Next, the gas containing multiple components generated by thermal decomposition is exhausted from the vent section 14a provided in the cylinder 12 ((b) step; exhaust step). This step involves discharging the gas generated by the thermal decomposition of the resin material inside the cylinder 12 to the outside of the cylinder 12. When the resin material is decomposed as in this embodiment, the resin material is heated and thermally decomposed, that is, the chemical bonds of the constituent resin are broken and it becomes low molecular weight, so a large amount of gas is generated.

[0049] The gas generated in this manner is the gas to be processed in this embodiment, and the generated gas is exhausted to the outside of the cylinder 12 through the opening 12a. Known extruders also have a vent section for exhausting gas generated in the cylinder, and similarly, a vent section 14a can be provided for exhaust.

[0050] The vent section 14a is positioned at the opening 12a of the cylinder 12, allowing the gas inside the cylinder 12 to be exhausted to the outside of the cylinder 12 through the vent section 14a at this opening 12a. In this embodiment, a heat exchanger 14b is provided in the vent section 14a, forming a venting device 14.

[0051] Therefore, in this embodiment, the gas exhausted from the vent section 14a is directly introduced into the heat exchanger 14b. In this heat exchanger 14b, a portion of the gas containing multiple components is cooled and liquefied, while the remainder is allowed to pass through as a gas ((c) step; liquefaction step 1).

[0052] For example, a gas containing multiple components has a unique boiling point for each component, and the gas contains a mixture of components with relatively high boiling points (high-boiling-point gas components) and components with lower boiling points (low-boiling-point gas components).

[0053] As described above, in order to cool and liquefy a portion of the gas containing multiple components, for example, the temperature of the heat exchanger 14b is controlled to a temperature at which the high-boiling point gas component liquefies. Specifically, the temperature of the heat exchanger 14b is controlled to be lower than the boiling point of the high-boiling point gas component, but higher than the melting point of the high-boiling point gas component. As a result, the high-boiling point gas component is cooled in the heat exchanger 14b and becomes a liquid.

[0054] Furthermore, it is preferable to control the temperature of the heat exchanger 14b so that it is higher than the boiling point of the low-boiling-point gas component. By controlling the temperature in this way, the high-boiling-point gas component and the low-boiling-point gas component can be separated, and it is particularly preferable that the high-boiling-point gas component is not included in the gas supplied to the heat exchanger 15. The remaining gas that has passed through the heat exchanger 14b without being liquefied is supplied to the heat exchanger 15 through the piping 18.

[0055] Finally, the gas that was not liquefied in step (c) above (the remaining gas) is introduced into the heat exchanger 15, where it is cooled and liquefied (step (d); liquefaction step 2). In other words, the temperature is controlled here to liquefy the low-boiling point gas component among the multiple components mentioned above. As a result, the low-boiling point gas component is cooled in the heat exchanger 15 and becomes a liquid.

[0056] Furthermore, it is preferable that the temperature of the heat exchanger 15 is lower than the melting point of the high-boiling-point gas component. In this case, the conditions for solidification in the heat exchanger, which has been a problem in the past, can occur. However, according to this embodiment, the high-boiling-point gas component is not included in the gas processed by the heat exchanger 15 (the remainder of the gas), so such a problem does not occur.

[0057] The liquid obtained in step (d) is collected in the liquid recovery container 16. The recovered liquid can be used as a raw material (monomer) for the manufacture of new resin (polymerization reaction) or as a material for other reactions, or, if it is to be disposed of, it can be treated for disposal.

[0058] Furthermore, if the gas exhausted from cylinder 12 contains three or more components, the high-boiling-point and low-boiling-point gas components can be arbitrarily determined according to the purpose. Also, if the gas contains three or more components, in step (d), a portion may be liquefied, allowing the gas components with lower boiling points to pass through as they are and be released into the atmosphere, or further processed by an exhaust gas treatment device. Release into the atmosphere should only be carried out if it does not have an adverse effect on the environment. Here, the gas components liquefied in heat exchanger 15 are collected in liquid recovery container 16 through piping 19.

[0059] Furthermore, if a gas component with a lower boiling point is passed through the heat exchanger 15 in step (d), the same liquefaction process can be performed one or more times to further separate the components in order.

[0060] Meanwhile, any resin material that is not gasified from the thermal decomposition process in the cylinder 12 moves through the cylinder 12 as a heated liquid to the tip 12c, and is discharged from the tip 12c into the solid recovery container 17. The discharged residue is gradually cooled and solidified in the solid recovery container 17.

[0061] As residue accumulates in the solid recovery container 17 during processing, it is replaced with an empty container 17 after a certain period of processing or depending on the amount of residue contained in the container. The residue contained inside the solid recovery container 17 is then disposed of. Note that this replacement of the solid recovery container 17 is performed by temporarily stopping the operation of the resin material thermal decomposition processing system, and after the replacement, the system can be restarted to continue the thermal decomposition processing of the resin material.

[0062] [Function of a heat exchanger] The configuration and operation of heat exchangers 14b and 15 have already been described above, but they will be explained in more detail below with reference to Figure 3.

[0063] Figure 3 is a cross-sectional view showing the internal structure of the venting device 14. As already explained, the vent section 14a is provided in the cylinder 12 and is a component that contains the gas generated in the cylinder 12 and introduces it to the heat exchanger 14b.

[0064] The heat exchanger 14b has a lower opening 141 that connects to the vent section 14a and an upper opening 142 that connects to the heat exchanger 15 via piping. The heat exchanger 14b also has a refrigerant inlet 143 for introducing refrigerant into the interior, a refrigerant flow pipe 144 for circulating the introduced refrigerant, and a refrigerant outlet 145 for discharging the refrigerant after it has circulated through the refrigerant flow pipe 144.

[0065] Then, a gas containing multiple components generated in the cylinder 12 is introduced into the heat exchanger 14b through the vent section 14a and the lower opening 141. A portion of the introduced gas is liquefied, while the remainder passes through as a gas. The components that are liquefied at this time are determined by the temperature of the heat exchanger 14b, and this temperature is controlled by the temperature of the refrigerant used.

[0066] For example, if a gas containing high-boiling-point and low-boiling-point gas components is introduced into the heat exchanger 14b, and the refrigerant temperature is set so that the temperature inside the heat exchanger 14b is below the boiling point of the high-boiling-point gas component and above the boiling point of the low-boiling-point gas component, the heat exchanger 14b will perform the following actions.

[0067] First, when the gas is introduced into the heat exchanger 14b from the lower opening 141, the gas comes into contact with the refrigerant flow pipe 144 (indirectly coming into contact with the refrigerant), and the high-boiling point gas components contained in the gas are cooled and liquefied. The liquefied high-boiling point gas components then drip downward due to gravity. The dripped liquid moves in the opposite direction to the gas flow direction, returns to the cylinder 12 via the lower opening 141 and the vent section 14a, and is reintroduced into the heated molten material.

[0068] On the other hand, the low-boiling-point gas components in the gas do not liquefy even when they come into contact with the refrigerant flow pipe 144 (indirectly coming into contact with the refrigerant), but are discharged as gas from the upper opening 142 and sent to the heat exchanger 15 via the piping 18.

[0069] The temperature control of the heat exchanger 14b is determined appropriately depending on the type of resin material to be thermally decomposed, but it is controlled to a relatively high temperature of 100°C or higher. For this reason, a fluid that can circulate as a liquid even at high temperatures of 100°C or higher, such as oil, is used as the refrigerant. When such oil is used, the refrigerant inlet 143 and refrigerant outlet 145 are generally connected to a hot oil unit, and this hot oil unit is configured to control the heat exchanger 14b to a predetermined temperature while circulating the refrigerant oil.

[0070] By directly installing the heat exchanger 14b above the vent section 14a, and allowing the liquefied components to fall back directly to the cylinder 12 as described above, the high-boiling-point gas components are remixed into the molten material in the cylinder 12, thereby further promoting demolecularization through thermal decomposition. Such a configuration is preferable because it allows for more efficient thermal decomposition.

[0071] The heat exchanger 15 has a different controlled temperature, but it can have the same configuration as the heat exchanger 14b. However, unlike the heat exchanger 14b, the liquefied gas component is discharged through a separate outlet from the gas (remaining gas) inlet. In this respect, it is preferable to use a heat exchanger 15 with a configuration that is generally known as a heat exchanger. Furthermore, if there is gas that has not been liquefied in the heat exchanger 15, another outlet is provided to separate the liquid component from the gas component.

[0072] Here, if a gas containing low-boiling-point gas components that has passed through heat exchanger 14b is introduced into heat exchanger 15, and the refrigerant temperature is set so that the temperature inside heat exchanger 15 is below the boiling point of the low-boiling-point gas components, the following effects will occur.

[0073] First, when the gas (the remaining gas) is introduced into the heat exchanger 15, this gas comes into contact with the refrigerant flow pipe (indirectly into contact with the refrigerant), and the low-boiling point gas components contained in the gas are cooled and liquefied. The liquefied low-boiling point gas components are sent to the liquid recovery container 16.

[0074] At this time, all components in the gas containing low-boiling-point gaseous components may be liquefied, or a portion of them may be liquefied and recovered, while components with even lower boiling points than the low-boiling-point compounds may be released as gaseous waste. The exhaust may be released into the atmosphere as long as it does not have an adverse effect on the environment, or it may be recovered and reused or disposed of.

[0075] The temperature control of this heat exchanger 15 is appropriately determined depending on the type of resin material to be thermally decomposed, but is controlled to a relatively low temperature of less than 100°C. Therefore, the refrigerant used here can be water or other commonly used refrigerants, and generally, the refrigerant inlet and outlet are configured to circulate while being controlled to a predetermined temperature by a chiller unit or the like.

[0076] [Explanation of resin materials and compounds produced by thermal decomposition] Next, regarding the above-mentioned thermal decomposition and liquefaction treatments, we will describe the compounds produced by thermal decomposition in specific resin materials and the conditions for their treatment.

[0077] <Polycarbonate (PC)> When the resin material to be thermally decomposed is polycarbonate (PC), water is added as a reaction aid or additive, and the thermal decomposition treatment is carried out in cylinder 12. At this time, the temperature of cylinder 12 is heated to, for example, 260 to 320°C to carry out the thermal decomposition treatment.

[0078] This thermal decomposition generates bisphenol A (melting point: 159°C, boiling point: 220°C) and phenol (melting point: 40.5°C, boiling point: 182°C) from the polycarbonate (PC). The gas introduced into the heat exchanger 14b contains the above-mentioned compounds and unreacted water (melting point: 0°C, boiling point: 100°C).

[0079] Therefore, for example, the temperature of heat exchanger 14b is set to 182°C or higher and less than 220°C to liquefy bisphenol A, and the temperature of heat exchanger 15 is set to less than 182°C to liquefy phenol. At this time, by setting the temperature of heat exchanger 15 to 100°C or higher and less than 182°C, the phenol can be recovered as a liquid, and the water (steam) can be released into the atmosphere.

[0080] If bisphenol A is reintroduced into the molten material in cylinder 12, it will be recovered in solid recovery container 17. However, in this case, separation and recovery from other residues becomes difficult. Therefore, in the case of polycarbonate, it is preferable to use the system configuration described in Embodiment 3 below and recover it in liquid recovery container 42 (Figure 6).

[0081] <Polyamide 6 (PA6)> When the resin material to be thermally decomposed is polyamide 6 (PA6), water is added as a reaction aid or additive, and the thermal decomposition treatment is carried out in cylinder 12. At this time, the temperature of cylinder 12 is heated to, for example, 230 to 350°C to carry out the thermal decomposition treatment.

[0082] This thermal decomposition produces caprolactam (melting point: 69°C, boiling point: 267°C) from polyamide 6 (PA6), and the gas introduced into the heat exchanger 14b includes the generated compound and unreacted water (melting point: 0°C, boiling point: 100°C).

[0083] Therefore, for example, the temperature of heat exchanger 14b is set to 100°C or higher and less than 267°C to liquefy caprolactam, and the temperature of heat exchanger 15 is set to less than 100°C to liquefy water vapor. <Polyethylene terephthalate (PET)>

[0084] When the resin material to be thermally decomposed is polyethylene terephthalate (PET), water or ethylene glycol is added as a reaction aid or additive, and the thermal decomposition treatment is carried out in cylinder 12. At this time, the temperature of cylinder 12 is heated to, for example, 255 to 320°C to carry out the thermal decomposition treatment.

[0085] (2) When ethylene glycol is added, polyethylene terephthalate (PET) is converted to bis(2-hydroxyethyl) terephthalate (melting point: 106°C, boiling point: 317°C or higher) through this thermal decomposition, and the gas introduced into the heat exchanger 14b includes the above compound that was generated and unreacted ethylene glycol (melting point: -10°C, boiling point: 244°C).

[0086] Therefore, for example, the temperature of heat exchanger 14b is set to 244°C or higher and less than 317°C to liquefy bis(2-hydroxyethyl) terephthalate, and the temperature of heat exchanger 15 is set to less than 244°C to liquefy ethylene glycol.

[0087] <Polyethylene (PE), Polypropylene (PP)> When the resin material to be thermally decomposed is polyethylene (PE) or polypropylene (PP), the thermal decomposition process is carried out in cylinder 12. At this time, the temperature of cylinder 12 is heated to, for example, 390 to 430°C to allow the thermal decomposition process to proceed.

[0088] This thermal decomposition breaks down polyethylene (PE) and polypropylene (PP) into various hydrocarbon compounds with different numbers of carbon atoms. Examples of hydrocarbons that gasify at this time are the compounds shown in Table 1, and the melting and boiling points of these hydrocarbon compounds are also shown in Table 1.

[0089] [Table 1]

[0090] In this case, the gas generated in cylinder 12 will be a gas containing various hydrocarbon compounds with 1 to 21 carbon atoms as described above. Depending on the temperature conditions, hydrocarbon compounds with a large number of carbon atoms will not be gasified in cylinder 12 but will remain in a molten state and will be discharged from the tip 12c of cylinder 12 into the solid recovery container 17 for recovery.

[0091] The generated gas is then introduced into the heat exchanger 14b, as described above. At this time, any compound can be selected as the high-boiling point gas component to be liquefied, but the decision should be made considering the control temperature in the heat exchanger 15. For example, if the control temperature in the heat exchanger 15 is set to 15°C, then if the gas component cooled in the heat exchanger 15 has a melting point of 15°C or higher, solid matter will precipitate in the heat exchanger 15. Therefore, in this case, if hydrocarbons with more carbon atoms than pentadecane (melting point: 9.9°C), which has 15 carbon atoms (hydrocarbons with 16 or more carbon atoms) are included, solid matter will adhere inside the heat exchanger 15, and if the process continues, the efficiency of the thermal decomposition process will decrease. Furthermore, if the adhesion of solid matter progresses and accumulates, it may eventually lead to blockage, making it difficult to continue the thermal decomposition process.

[0092] Therefore, under the above conditions, the high-boiling point gas component liquefied in the heat exchanger 14b is a hydrocarbon with 16 carbon atoms (hexadecane, chemical formula: C 16 H 34 It is preferable to set it as follows. In this case, since hexadecane is liquefied in the heat exchanger 14b, hexadecane is not included in the gas components introduced into the heat exchanger 15. Therefore, even if the control temperature of the heat exchanger 15 is set to 15°C, since there are no components with a melting point of 15°C or higher, there are no components that solidify in the heat exchanger 15, and the above-mentioned problems can be prevented.

[0093] When processing in this manner, the control temperature of the heat exchanger 14b should be, for example, set to a temperature above its melting point but below its boiling point (18°C or higher and less than 287°C). However, this thermal decomposition process includes compounds with similar molecular weights and similar melting and boiling points. Therefore, it is preferable to efficiently liquefy the target compound and avoid including as many compounds with lower boiling points than the target compound as possible, thereby preventing the mixing of unnecessary compounds. For this reason, it is preferable to set the control temperature of the heat exchanger 14b to around 230-260°C when performing thermal decomposition under the above conditions. As a result, hydrocarbon compounds with 16 or more carbon atoms are returned to the cylinder 12 and reintroduced into the molten material in the extruder. Upon reintroduction, they receive thermal energy again in the heated cylinder 12 and are further thermally decomposed into hydrocarbon compounds with 15 or fewer carbon atoms.

[0094] <Embodiment 2> The overall configuration of the thermal decomposition treatment system for resin materials in this embodiment and the method for thermal decomposing resin materials using it will be described with reference to Figure 4.

[0095] Figure 4 is an explanatory diagram (side view) showing the schematic configuration of the resin material thermal decomposition treatment system 20 of Embodiment 2. The resin material thermal decomposition treatment system 20 is a resin material thermal decomposition treatment system that has the same configuration as the resin material thermal decomposition treatment system 10 of Figure 1 described above, except that it has two sets of venting devices 14, heat exchangers 15, and liquid recovery containers 16.

[0096] In other words, the resin material thermal decomposition treatment system 20 shown in Figure 4 includes a resin material supply unit 11, a cylinder 12 having a screw, a rotary drive mechanism 13 that drives the screw of the cylinder 12, a venting device 14 consisting of a venting unit 14a and a heat exchanger 14b, a heat exchanger 15, a liquid recovery container 16, and a solid recovery container 17. The elements constituting the device are the same as those in the above embodiment. Hereinafter, the description of components that are the same as those already described will be omitted, and the differences will be described in detail.

[0097] As described above, the thermal decomposition treatment system 20 for resin materials differs from the thermal decomposition treatment system 10 for resin materials in that it is equipped with two sets of venting devices 14, heat exchangers 15, and liquid recovery containers 16.

[0098] By providing two such sets, the thermal decomposition treatment system 20 for resin materials has an upstream vent device 14 and a downstream vent device 14. In this case, the gas generated in the cylinder 12 is first subjected to heat exchange treatment in the upstream vent device 14, a portion of which is liquefied and re-mixed into the cylinder 12, while the remainder is sent to the heat exchanger 15.

[0099] The liquefied and re-mixed components are compounds that have not been sufficiently broken down into smaller molecules, and are further thermally decomposed in the cylinder 12 to break them down into even smaller molecules. The monomers and low-molecular-weight compounds produced by this re-mixing and re-thermal decomposition treatment are then subjected to heat exchange treatment in the downstream venting device 14, where some of them are liquefied and re-mixed into the cylinder 12, while the remainder is sent to the heat exchanger 15.

[0100] In the thermal decomposition treatment apparatus 20 of this embodiment of resin materials, as described above, the upstream venting device 14 removes sufficiently decomposed components from the cylinder 12, and components that have not been sufficiently decomposed are returned to the cylinder 12 and subjected to thermal decomposition treatment again. Subsequently, the downstream venting device 14 removes sufficiently decomposed components from the cylinder 12, and components that have not been sufficiently decomposed are returned to the cylinder 12.

[0101] In this way, energy can be selectively supplied to components that require thermal decomposition treatment depending on the degree of molecular decomposition of the gas components. Furthermore, from the perspective of the resin material, components that were not sufficiently decomposed into small molecules can be subjected to further thermal decomposition treatment. Therefore, by adopting the configuration of this embodiment, thermal decomposition treatment can be carried out more efficiently.

[0102] From this perspective, the relative positions of the upstream vent device 14 and the downstream vent device 14 can be arbitrarily determined depending on the state of thermal decomposition of the resin material inside the cylinder 12. If the two vent devices 14 are placed too close together, the above-mentioned effects cannot be fully exerted, so it is preferable to ensure that there is enough time for further decomposition of the material.

[0103] Furthermore, the upstream venting device 14 and the downstream venting device 14, and the upstream heat exchanger 15 and the downstream heat exchanger 15 may be controlled to the same temperature for processing, or they may be controlled to different temperatures for processing.

[0104] Furthermore, as shown in Figure 5, the thermal decomposition treatment system 30 for resin materials, compared to the thermal decomposition treatment system 20 for resin materials described in Figure 4, can also be treated by a single heat exchanger 15 with the gas discharged from the two venting devices 14.

[0105] The thermal decomposition treatment system 30 for resin materials includes a resin material supply unit 11, a cylinder 12 having a screw, a rotary drive mechanism 13 for driving the screw of the cylinder 12, a venting device 14 consisting of a venting unit 14a and a heat exchanger 14b, a heat exchanger 15, a liquid recovery container 16, and a solid recovery container 17. The elements constituting the device are the same as those in the above embodiment.

[0106] By using only one heat exchanger 15, the installation space for the device can be reduced, and maintenance and other tasks can be simplified, which is preferable.

[0107] <Embodiment 3> The overall configuration of the thermal decomposition treatment system for resin materials in this embodiment and the method for thermal decomposing resin materials using the same will be described with reference to Figure 6.

[0108] Figure 6 is an explanatory diagram (side view) showing the schematic configuration of the resin material thermal decomposition treatment system 40 of Embodiment 3. The resin material thermal decomposition treatment system 40 is a resin material thermal decomposition treatment system that has the same configuration as the resin material thermal decomposition treatment system 10 of Figure 1 described above, except that the heat exchanger 14b of the vent device 14 is separated from the vent section 14a and connected through piping.

[0109] In other words, the thermal decomposition treatment system 40 for resin materials shown in Figure 6 includes a resin material supply unit 11, a cylinder 12 having a screw, a rotary drive mechanism 13 that drives the screw of the cylinder 12, a vent unit 14a, a heat exchanger 15, a liquid recovery container 16, a solid recovery container 17, a heat exchanger 41, and a liquid recovery container 42. The elements constituting the apparatus are the same as those in the above embodiment. Below, the description of components that are the same as those already described will be omitted, and the differences will be described in detail.

[0110] As described above, the thermal decomposition treatment system 40 for resin materials differs from the thermal decomposition treatment system 10 for resin materials in that the vent section 14a and the heat exchanger 14b are separated and provided as separate elements. Specifically, a heat exchanger 41 is provided instead of the heat exchanger 14b, the vent section 14a and the heat exchanger 41 are connected by piping 43, and a liquid recovery container 42 is connected to the heat exchanger 41 by piping 44. Furthermore, the heat exchanger 41 is connected to the heat exchanger 15 via piping 18.

[0111] With the above configuration, in this thermal decomposition treatment system 40 for resin materials, the gas exhausted from the vent section 14a is introduced to the heat exchanger 41 via piping 43, where the high-boiling point gas components are cooled and liquefied. The liquefied high-boiling point gas components are recovered by a liquid recovery container 42 via piping 44. The remaining gas that was not liquefied in the heat exchanger 41 is sent to the heat exchanger 15 via piping 18. The subsequent processing is the same as in the above embodiment.

[0112] In this embodiment as well, since the gas is introduced into the heat exchanger 15 with the solidifying components removed, problems such as blockage of the heat exchanger 15 can be avoided. Furthermore, by separating the vent section 14a and the heat exchanger 41 in this way, cleaning of each component becomes easier, improving maintainability and thus reducing maintenance costs.

[0113] In the above explanation, the liquid high-boiling point gas component is recovered in the liquid recovery container 42, but it may also be returned to the cylinder 12 and subjected to further thermal decomposition treatment.

[0114] Although the present invention has been specifically described above with reference to embodiments and examples, it goes without saying that the present invention is not limited to these embodiments and examples, and can be modified in various ways without departing from its spirit. [Explanation of Symbols]

[0115] 10, 20, 30, 40 Thermal decomposition treatment system for resin materials 11 Resin material supply section 12 cylinders 12a Screw 12b opening 12c Tip 13 Rotary drive mechanism 14. Venting device 14a Vent section 14b,15,41 Heat exchanger 16,42 Liquid recovery containers 17 Solid recovery containers 18,19,43,44 Piping

Claims

1. A venting device connected to an extruder, which includes a cylinder into which a resin material is fed, a screw disposed inside the cylinder for transporting the resin material, an opening for exhausting gas generated inside the cylinder as the resin material is thermally decomposed, and a first heat exchanger into which the gas is introduced, A vent portion is provided at the opening, A second heat exchanger is provided above the aforementioned vent section, Equipped with, The vent section and the second heat exchanger are connected between the cylinder and the first heat exchanger. The second heat exchanger cools the gas exhausted from the opening, thereby liquefying a portion of the gas and re-mixing it into the cylinder. A venting device that introduces the remaining portion of the gas that has passed through the second heat exchanger in its gaseous state into the first heat exchanger.

2. In the venting device according to Claim 1, The aforementioned gas comprises a high-boiling-point gas component and a low-boiling-point gas component having a lower boiling point than the high-boiling-point gas component. A portion of the aforementioned gas is the high-boiling point gas component, The remaining portion of the gas is the low-boiling point gas component, in a venting device.

3. In the venting device according to Claim 2, A venting device wherein the control temperature of the second heat exchanger is lower than the boiling point of the high-boiling point gas component and higher than the melting point of the high-boiling point gas component.

4. In the venting device according to claim 3, A venting device in which the control temperature of the second heat exchanger is higher than the boiling point of the low-boiling point gas component.

5. In the venting device according to claim 4, A venting device wherein the control temperature of the first heat exchanger is lower than the boiling point of the low-boiling point gas component and higher than the melting point of the low-boiling point gas component.

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