Plastic oil-making method and oil-making device, and oil-lowering device

Abstract

A method for converting plastics into oil is provided, which improves the yield of low-molecular-weight oils. [Solution] A primary cracking process is carried out in which plastics are thermally or hydrothermally cracked in cracking devices 20, 20', 30 to generate primary cracked gas, which is then cooled to a first cooling temperature (153°C in the example) in a first coagulation tower 40 to recover a high molecular weight oil (diesel oil), and the primary cracked gas from which the high molecular weight oil has been recovered is further cooled to a second cooling temperature (40°C or 20°C in the example) in a second coagulation tower 50 to recover a low molecular weight oil (naphtha). The high molecular weight oil (diesel oil) recovered in this primary cracking process is further decomposed into secondary cracked gas to reduce its molecular weight using hydrothermal treatment including subcritical water or supercritical water, and the secondary cracked gas is cooled to recover the oil, thereby increasing the yield of low molecular weight oil recovered from plastics.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for converting plastics into oil, and an apparatus for reducing the molecular weight of oil, and more specifically to a method and apparatus for converting plastics into oil that can improve the yield of low-molecular weight oils with high added value, and an apparatus for reducing the molecular weight of oil that is suitable for use in said method and apparatus. [Background technology]

[0002] Due to a growing sense of crisis about environmental issues such as climate change and global warming, there is a need to reduce the consumption of limited resources and reduce the burden on the environment by recycling resources in a circular manner.

[0003] Due to these demands, the importance of recycling plastics, which are used as packaging containers and discarded in large quantities, is also increasing.

[0004] Currently, approximately 60% of plastic recycling in Japan is carried out as so-called "thermal recycling," which reuses waste plastic as fuel for the purpose of energy recovery, such as using waste incineration heat, waste incineration for power generation, conversion into cement raw materials and fuel, and conversion into solid fuels such as RPF (Refuse Paper & Plastic Fuel) and RDF (Refuse Derived Fuel).

[0005] However, plastics that have been subjected to thermal recycling are lost through combustion and can no longer be recycled.

[0006] Therefore, from the perspective of recycling resources, it is desirable to first aim for recycling by subjecting waste plastics to "material recycling," in which they are recycled while remaining in their plastic state, or "chemical recycling," in which they are decomposed chemically and reused, and then to recover energy through "thermal recycling" as a final recycling method for the remaining waste plastics that cannot be recycled in this way, thereby making full use of petroleum resources without waste.

[0007] On the other hand, even if material recycling or chemical recycling were possible, it would require the input of a huge amount of new resources and result in the emission of large amounts of CO2 gas, which would actually increase the burden on the environment. Furthermore, even if these problems could be overcome, recycling that ignores economic efficiency cannot be expected to become widespread.

[0008] The conversion of plastics into oil, which is the subject of this invention, is positioned as a type of "chemical recycling" among the aforementioned recycling methods, and since it aims to reuse plastics manufactured from petroleum as raw materials by returning them to the hydrocarbon oil that was the raw material, it can be said to be the recycling method that is most consistent with the perspective of cyclical use of resources.

[0009] Conventionally, the general method for converting such plastics into oil has been to thermally decompose the plastics and recover the oil from the decomposition gas obtained by this thermal decomposition by cooling and condensing it, etc. Patent Document 1 listed below proposes a batch-type oil conversion method for thermally decomposing such plastics, while Patent Document 2 proposes a continuous-type oil conversion method.

[0010] Furthermore, Patent Document 3, listed below, proposes an oil-making method in which plastics are decomposed by hydrothermal treatment instead of the aforementioned decomposition by heating. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-285635 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-306974 [Patent Document 3] Special Publication No. 2023-551608 Summary of the Invention [Problem to be solved by the invention]

[0012] In the method of pyrolyzing plastics by heating, as described in Patent Documents 1 and 2 cited above, not only does the equipment configuration become large and require a large initial investment, but in order to pyrolyze the plastics, they must be heated to temperatures of 400°C or higher under atmospheric pressure, which consumes a lot of energy to obtain pyrolysis gas and increases running costs, and there is also a risk of bad odors and harmful gases being generated during pyrolysis.

[0013] In contrast, the hydrothermal treatment employed in the oil production method described in Patent Document 3 cited above uses special water in a subcritical, critical, or supercritical state to decompose plastic, which is an organic substance. This not only enables plastic to be decomposed in a clean manner without generating foul odors, noise, or harmful gases, but also makes it possible to reduce the energy consumption required for decomposing plastic and to recover oil (diesel oil and gasoline, as examples) at a high yield of approximately 85 to 90% by weight from the waste plastic (see Tables 1, 4, and 7 of Patent Document 3, etc., for oil yields).

[0014] However, when examining the breakdown of the oil recovered in the examples described in Patent Document 3, it is found that in addition to gasoline, the recovered oil contains more than 40% diesel oil, which has a higher carbon content than gasoline, is polymeric, and has low economic value (see Tables 1, 4, and 7 of Patent Document 3, etc.).

[0015] Therefore, if we can reduce the yield of such diesel oil (high molecular weight oil) and increase the yield of low molecular weight oils such as naphtha, which have lower molecular weights and higher economic value than diesel oil (high molecular weight oil), we can further improve the economic viability of plastic recycling through oilification, and further accelerate its spread.

[0016] Therefore, the present invention has been made to eliminate the drawbacks of the above-mentioned conventional technology, and aims to provide a method and apparatus for oiling plastics that can reduce the yield of relatively high molecular weight oils (also referred to as "high molecular weight oils" in the present invention) such as diesel oil among the oils recovered by the oiling of plastics, and can improve the yield of low molecular weight oils (also referred to as "low molecular weight oils" in the present invention) compared to the above-mentioned high molecular weight oils such as naphtha, as well as an oil low molecular weight apparatus suitable for use in the method and apparatus. [Means for solving the problem]

[0017] The means for solving the problems are described below together with the reference numerals used in the description of the embodiment of the invention. These reference numerals are intended to clarify the correspondence between the claims and the description of the embodiment of the invention, and needless to say, are not used to restrict the interpretation of the technical scope of the present invention.

[0018] In order to achieve the above object, the method for converting plastics into oil of the present invention comprises the steps of: In a plastic oil recovery method in which plastic is chemically decomposed and recovered as oil, The oil production method includes a primary decomposition process in which plastic is decomposed and the oil is separated into high molecular weight oil and low molecular weight oil and recovered; A low molecular weight process is included in which the high molecular weight oil obtained in the primary cracking process is further cracked, The primary decomposition treatment comprises: a plastic decomposition step of decomposing the plastic to produce a primary decomposition gas; a polymer oil recovery step of cooling the primary cracked gas obtained in the plastic cracking step to a first cooling temperature (153°C in the example) to condense and recover the polymer oil (diesel oil in the example) from the primary cracked gas; a low molecular weight oil recovery step of cooling the primary cracked gas after the high molecular weight oil has been recovered to a second cooling temperature (40°C or 20°C in the examples) lower than the first cooling temperature to condense and recover the low molecular weight oil (naphtha in the examples) from the primary cracked gas; The low molecular weight treatment a polymer oil cracking step in which the polymer oil (diesel oil in this embodiment) recovered in the polymer oil recovery step of the primary cracking treatment is further cracked, for example, by hydrothermal treatment, to produce a secondary cracked gas; The method is characterized by including a secondary recovery step of cooling the secondary cracked gas obtained in the high molecular weight oil cracking step, and condensing and recovering oil from the secondary cracked gas (claim 1; see FIG. 1).

[0019] In the present invention, low molecular weight oil refers to oil that is relatively low molecular weight compared to the oil (high molecular weight oil) that is the target of low molecular weight processing. As an example, in the configuration of an embodiment in which diesel oil is the high molecular weight oil that is the target of low molecular weight processing, naphtha and / or kerosene, which are lower molecular weight compared to diesel oil, can be used as the low molecular weight oil, and preferably naphtha can be used as the low molecular weight oil.

[0020] In addition, the combination of low molecular weight oil and high molecular weight oil may be, for example, heavy oil as the high molecular weight oil and one or more of naphtha, kerosene, and light oil as the low molecular weight oil, and is not limited to the above examples as long as the combination is such that the low molecular weight oil is relatively low molecular weight compared to the high molecular weight oil.

[0021] The decomposition of the plastic in the plastic decomposition step can be carried out by thermal decomposition (claim 2).

[0022] Alternatively, the decomposition of the plastic in the plastic decomposition step may be carried out by hydrothermal treatment including subcritical water or supercritical water (claim 3).

[0023] In any of the above oil-recovery methods, a dechlorination / deoxidation step for dechlorinating and / or deoxidizing the plastic can be further included before the primary decomposition treatment (claim 4).

[0024] In this case, the dechlorination and deoxidation process and the plastic decomposition process can be carried out in the same reaction vessel (claim 5).

[0025] Furthermore, when the above-mentioned dechlorination and deoxidation process is carried out, it is desirable to carry out the dechlorination and deoxidation process under processing conditions (e.g., heating temperature and heating time) that do not reduce the oil yield in the primary decomposition process (Claim 6).

[0026] In addition, a volume reduction process can be further included before the primary decomposition process (before the dechlorination and deoxidation process if the aforementioned dechlorination and deoxidation process is included) in which the plastic is heated at a temperature of 50°C to 200°C, which does not cause thermal decomposition, to reduce its volume (Claim 7).

[0027] This volume reduction process may be carried out when the plastic is collected (claim 8), or may be carried out when the plastic is transported and / or during intermediate processing (claim 9).

[0028] When decomposing plastics by thermal decomposition, the polymer oil recovered in the primary decomposition treatment is successively decomposed in the polymer oil decomposition step in the low molecular weight treatment, The secondary decomposition gas produced in the high molecular weight oil decomposition process may be merged with the primary decomposition gas prior to the high molecular weight oil recovery process, so that the high molecular weight oil recovery process and the low molecular weight oil recovery process are carried out on the secondary decomposition gas together with the primary decomposition gas, thereby carrying out the secondary recovery process (Claim 10; see Figure 9).

[0029] In addition, when decomposing plastics by hydrothermal decomposition, the plastic decomposition process in the primary decomposition treatment is carried out continuously, and The polymer oil produced in the primary decomposition process may be decomposed sequentially together with the plastic through hydrothermal treatment in the plastic decomposition step, thereby allowing the secondary decomposition process to be carried out simultaneously with the primary decomposition process (claim 11; see Figure 10).

[0030] Furthermore, when decomposing plastics by hydrothermal decomposition, it is desirable that the plastics that are decomposed in the primary decomposition step of the primary decomposition treatment are plastics that have been melted in advance to a flowable state (see Claim 12; Figure 3).

[0031] In addition, the plastic oil-making device 1 of the present invention is In a plastic oil production system 1, plastic is chemically decomposed and recovered as oil. The oil-producing device 1 includes a primary decomposition means 10 that decomposes plastics and separates the oil into high molecular weight oil and low molecular weight oil for recovery; a low molecular weight means (70) for further decomposing the high molecular weight oil obtained by the primary decomposition means (10), The primary decomposition means 10 a plastic decomposition device 20, 20', 30 for decomposing the plastic to generate a primary decomposition gas; a first condensation tower 40 for recovering polymer oil (diesel oil in the example) from the primary cracked gas obtained in the plastic cracking units 20, 20', 30 by cooling the primary cracked gas to a first cooling temperature (153°C in the example); The primary cracked gas after the high molecular weight oil is recovered is cooled to a second cooling temperature (40°C or 20°C in the embodiment) lower than the first cooling temperature to recover a coagulated low molecular weight oil (naphtha in the embodiment) from the primary cracked gas. The molecular weight reduction means 70 a polymer oil cracking device 71 that further cracks the polymer oil (diesel oil in this embodiment) recovered in the first coagulation tower 40 of the primary cracking means 10, for example, by hydrothermal treatment, to generate a secondary cracked gas; The system is characterized by including a secondary recovery means 76 for cooling the secondary cracked gas obtained in the polymer oil cracking unit 71 and condensing and recovering oil from the secondary cracked gas (claim 13; see FIG. 1).

[0032] In the oil production apparatus 1 having the above-described configuration, the plastic decomposition devices 20, 20' of the primary decomposition means 10 can be configured to decompose the plastic by thermal decomposition (Claim 14; see Figures 2, 3, and 9).

[0033] Alternatively, the plastic decomposition device 30 of the primary decomposition means 10 may be configured to decompose the plastic by hydrothermal treatment including subcritical water or supercritical water (Claim 15; see Figures 4 and 10).

[0034] Either of the above-described configurations of the oil production apparatus 1 may further include a dechlorination / deoxidation means for dechlorinating and / or deoxidizing the plastic before the plastic is decomposed by the plastic decomposition devices 20, 20', 30 of the primary decomposition means 10 (Claim 16).

[0035] In this case, the dechlorination and deoxidation means may be realized by the plastic decomposition devices 20, 20', 30 of the primary decomposition means 10 by having the plastic decomposition devices 20, 20', 30 perform the dechlorination and / or deoxidation (Claim 17).

[0036] When dechlorination and deoxidation are carried out in this manner, a control means (not shown) may be provided to control the processing conditions (e.g., heating temperature and heating time) in the dechlorination and deoxidation means so as not to reduce the oil yield in the primary decomposition means 10 (claim 18).

[0037] The primary decomposition means 10 may further include a volume reduction means for reducing the volume of the plastic by heating the plastic at a temperature of 50°C to 200°C that does not cause thermal decomposition before the plastic is decomposed by the plastic decomposition devices 20, 20', 30 (Claim 19).

[0038] The volume reduction means may reduce the volume of the plastic when it is collected (Claim 20), or may reduce the volume of the plastic when it is transported and / or during intermediate processing (Claim 21).

[0039] When a thermal decomposition type configuration is adopted as the plastic decomposition device 20, 20', the polymer oil decomposition device 71 is configured as a continuous type that sequentially decomposes the polymer oil recovered by the primary decomposition means 10, and a confluence flow path 81 is provided for confluence of the secondary cracked gas generated in the polymer oil cracking device 71 with the primary cracked gas before being introduced into the first coagulation tower 40; The first coagulation tower 40 and the second coagulation tower 50 may be used to realize the secondary recovery means 76 that condenses and recovers oil from the secondary cracked gas (claim 22; see FIG. 9).

[0040] In addition, when a hydrothermal decomposition type is adopted as the plastic decomposition device 30, the plastic decomposition device 30 in the primary decomposition means 10 is formed as a continuous type that continuously decomposes the plastic, and By providing a reflux flow path 80 that sequentially introduces the polymer oil recovered by the primary decomposition means 10 into the plastic decomposition device 30, the polymer oil decomposition device 71 can be realized by the plastic decomposition device 30, and the secondary recovery means 76 can be realized by the first coagulation tower 40 and the second coagulation tower 50 (Claim 23: see Figure 10).

[0041] Furthermore, if a hydrothermal decomposition type is adopted as the plastic decomposition device 30, a plastic melt supply means (e.g., a screw extruder 35) may be provided to introduce plastic that has been melted in advance to make it flowable into the plastic decomposition device 30 (Claim 24: see Figure 4).

[0042] Furthermore, the oil low molecular weight device 70 of the present invention is a pressure vessel, namely a reaction vessel 72; a heater 73 surrounding the outer periphery of the reaction vessel 72; high-pressure pumps 74a and 74b for introducing oil and, if necessary, water into the reaction vessel 72 from one end side of the reaction vessel 72; and an oil decomposition device 71 equipped with an outlet pipe 75 communicating with the space inside the reaction vessel 72 at the other end side of the reaction vessel 72, for decomposing the oil in the reaction vessel 72. The oil decomposition apparatus is characterized by comprising a secondary recovery means 76 for cooling the cracked gas discharged through the discharge pipe 75 of the oil decomposition apparatus 71 to condense and recover oil (claim 25: see Figs. 7 and 8).

[0043] The oil decomposition device 70 having the above-described configuration includes a temperature detection means T and a pressure detection means P for detecting the temperature and pressure in the reaction vessel 72 of the oil decomposition device 71, A control means (not shown) may be provided to control the temperature detected by the temperature detection means T and the pressure detected by the pressure detection means P to be a predetermined temperature and pressure set in advance within the range of 200 to 600°C and 0.1 to 30 MPa absolute pressure (Claim 26). [Effects of the Invention]

[0044] With the configuration of the present invention described above, high molecular weight oil (diesel oil, as an example) recovered by primary decomposition of plastics is further decomposed by hydrothermal treatment, for example, including subcritical water or supercritical water, to reduce the molecular weight, and then cooled and coagulated to recover the low molecular weight oil.In conventional methods, even when hydrothermal decomposition was used to convert the oil to oil, more than 40% of the recovered oil was high molecular weight oil (diesel oil).However, with this method, the yield of diesel oil (high molecular weight oil) was reduced to 20% or less, and the yield of naphtha (low molecular weight oil) was improved to more than 80%.

[0045] As a result, the yield of low molecular weight oils with higher economic value was increased, which improved the economic efficiency of recycling by oilification.

[0046] The primary decomposition of plastics may be carried out by thermal decomposition, but by carrying out the primary decomposition of plastics by hydrothermal treatment including subcritical water or supercritical water, not only can the amount of fuel consumed for the primary decomposition be reduced compared to when the primary decomposition of plastics is carried out by thermal decomposition, but it is also possible to prevent the generation of bad odors, noise, harmful gases, etc. during the process.

[0047] In a configuration that further includes a dechlorination / deacidification process in which the plastic is dechlorinated and / or deacidified before the plastic decomposition process, it is possible to prevent chlorine and acid from being mixed into the recovered diesel oil or naphtha, thereby recovering high-quality oil.

[0048] By carrying out this dechlorination and deoxidation process in the same reaction vessel as the subsequent plastic decomposition process, the equipment configuration can be simplified by sharing components, thereby making it possible to keep the initial costs low when introducing the oil production method and oil production equipment of the present invention.

[0049] Furthermore, by controlling the dechlorination and deacidification processes to processing conditions (e.g., heating temperature and heating time) that do not reduce the oil yield in the primary cracking process, it was possible to recover high-quality oil without reducing the oil yield.

[0050] Prior to the plastic decomposition process, for example, when collecting or transporting waste plastic, if a volume reduction process is carried out at an intermediate treatment plant or the like, in which the plastic is heated to a temperature of 50 to 200°C, which does not cause thermal decomposition, to reduce its volume, the costs of collection and transportation can be significantly reduced without reducing the oil yield.

[0051] In a configuration in which the primary decomposition of plastics is carried out by thermal decomposition, the high molecular weight oil produced by the primary decomposition process is sequentially subjected to secondary decomposition, and the secondary decomposition gas is merged with the primary decomposition gas before passing through the first condensation tower 40, and the high molecular weight oil is recovered from the secondary decomposition gas together with the primary decomposition gas by the first condensation tower 40 and the low molecular weight oil is recovered by the second condensation tower 50, thereby carrying out a secondary recovery process for the secondary decomposition gas.In this configuration, it is possible to share some of the components between the primary decomposition means 10 that performs the primary decomposition of plastics and the low molecular weight reduction means 70 that reduces the molecular weight of the high molecular weight oil recovered by the primary decomposition means 10, which simplifies the device configuration of the oil production device 1 and keeps the initial investment costs low.

[0052] In a configuration in which primary decomposition of plastics is carried out by hydrothermal treatment, the plastic decomposition process is carried out continuously, and the polymer oil produced in the plastic decomposition process is sequentially subjected to hydrothermal treatment together with the plastic in the plastic decomposition process for secondary decomposition.This makes it possible to carry out primary decomposition of plastics, recovery of oil from the primary decomposition gas produced in the primary decomposition, and secondary decomposition of polymer oil (diesel oil) and recovery of oil from the secondary decomposition gas simultaneously and using common equipment, which makes it possible to further simplify the equipment configuration and further reduce initial investment costs.

[0053] Since the decomposition of plastic by hydrothermal treatment is carried out in a reaction vessel 72 consisting of a pressure vessel, if a configuration is adopted in which solid plastic is continuously introduced to cause primary decomposition, it is necessary to adopt a configuration in which solid plastic can be continuously introduced into the reaction vessel 72 while maintaining the pressure inside the reaction vessel 72.

[0054] However, by melting the plastic into a fluid state before introducing it into the reaction vessel 72, it was possible to easily introduce the plastic continuously while maintaining the pressure inside the reaction vessel 72. [Brief explanation of the drawings]

[0055] [Figure 1] FIG. 1 is an explanatory diagram of the method for converting plastics into oil according to the present invention. [Figure 2] An explanatory diagram of an example of the configuration of a thermal decomposition type plastic decomposition device (batch type). [Figure 3] An explanatory diagram of an example of the configuration of a thermal decomposition type plastic decomposition device (continuous type). [Figure 4] An explanatory diagram of an example of the configuration of a hydrothermal decomposition type plastic decomposition device (continuous type). [Figure 5] FIG. 2 is an explanatory diagram showing an example of the configuration of a coagulation tower. [Figure 6] FIG. 10 is an explanatory diagram showing another configuration example of the coagulation tower. [Figure 7] FIG. 2 is an explanatory diagram showing a configuration example of a molecular weight reduction means. [Figure 8] FIG. 10 is an explanatory diagram showing another example of the configuration of the molecular weight reduction means. [Figure 9] FIG. 1 is an explanatory diagram showing an example of the configuration of an apparatus for producing oil from plastics according to the present invention (an example of the configuration in which primary decomposition is carried out by thermal decomposition). [Figure 10] FIG. 1 is an explanatory diagram showing an example of the configuration of an apparatus for producing oil from plastics according to the present invention (an example of the configuration in which primary decomposition is carried out by hydrothermal decomposition). DETAILED DESCRIPTION OF THE INVENTION

[0056] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0057] [Outline of methods for converting plastics into oil] An outline of the method for converting plastics into oil according to the present invention is shown in FIG.

[0058] The method for converting plastics into oil of the present invention includes a primary cracking process in which plastics are primarily cracked to recover high molecular weight oil ("diesel oil" in this embodiment) and low molecular weight oil ("naphtha" in this embodiment), and a low molecular weight process in which the high molecular weight oil obtained as a cracking product in the primary cracking process is further cracked by hydrothermal treatment to reduce the molecular weight of the oil obtained, and the resulting oil is recovered.By going through this two-stage cracking and oil recovery process, it is possible to reduce the yield of high molecular weight oil in the recovered oil and increase the yield of low molecular weight oil, which has higher economic value.

[0059] The primary decomposition process includes a "plastic decomposition process" in which plastic is decomposed to produce primary decomposition gas, a "polymer oil recovery process" in which the primary decomposition gas obtained in the plastic decomposition process is cooled to a first cooling temperature (153°C in the example) to condense and recover polymer oil, and a "low molecular weight oil recovery process" in which the primary decomposition gas after the polymer oil has been recovered is further cooled to a second cooling temperature (40°C or 20°C in the example) lower than the first cooling temperature to condense and recover low molecular weight oil from the primary decomposition gas.

[0060] In addition, the low-molecular-weight processing includes a "polymer oil decomposition process" in which the polymer oil ("diesel oil" in this embodiment) recovered in the primary decomposition process is decomposed by hydrothermal treatment using, for example, subcritical water or supercritical water to produce secondary decomposition gas, and a "secondary recovery process" in which the secondary decomposition gas obtained in the polymer oil decomposition process is cooled and oil is condensed and recovered from the secondary decomposition gas.

[0061] The method for converting plastics into oil according to the present invention may further include a pretreatment step carried out before the primary decomposition step, if necessary.

[0062] [Plastics to be treated] Examples of plastics that can be converted into oil in this invention include, but are not limited to, waste plastics that have been discarded after being used as product packaging containers, etc. By treating such waste plastics, it becomes possible to recycle plastics using the oil conversion method of this invention.

[0063] It is desirable to treat plastics that are olefin-based resins, such as polyethylene (PE) and polypropylene (PP), but it is also possible to treat plastics that contain synthetic resins other than olefin-based resins, such as polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET).

[0064] When waste plastics are to be treated, it is preferable that the collected waste plastics be subjected to a predetermined pretreatment before being treated.

[0065] This pre-treatment may include a volume reduction step to reduce the volume of the recovered plastic.

[0066] The volume of the plastic is reduced in the volume reduction process by heating it to a temperature of about 50°C to 200°C, at which the plastic does not undergo thermal decomposition or produce harmful substances, preferably at a temperature of 120°C to 200°C.Such heating may be carried out using a liquid such as water or oil as a heat medium, or a solid such as silica sand as a heat medium, and there are no particular restrictions on the method as long as it can heat the plastic to the aforementioned temperature.

[0067] Such volume reduction can be installed in facilities that generate or handle waste plastic on a certain scale, such as office buildings, factories, material recycling facilities, resource collection sites established in each region, and intermediate processing facilities, or volume reduction means can be installed on garbage collection trucks so that volume reduction can be carried out while collecting and transporting waste plastic.

[0068] In this way, by reducing the volume of recovered plastic, it becomes possible to transport waste plastic to a plant or the like equipped with the oil production apparatus of the present invention efficiently and at low cost.

[0069] In addition, examples of the above-mentioned pre-treatment include rough separation of the recovered waste plastic by material, rough separation to remove foreign matter such as metal pieces mixed in the waste plastic using known sorting methods such as magnetic sorting or infrared sorting, and crushing, washing, drying, and gravity sorting of the plastic after this rough separation.By going through these processes, PVC, PET, metals, etc. can be removed and the waste plastic consisting only of olefin-based resins can be processed.

[0070] Furthermore, when the plastics to be processed contain PVC and PET in addition to olefin resins, in order to prevent deterioration of quality due to the inclusion of chlorine or acid in the recovered oil, the plastics after crushing, washing, drying, etc. may be subjected to dechlorination and / or deoxidation treatment before the primary decomposition described below, and the pretreatment may further include a dechlorination and deoxidation treatment process.

[0071] Such dechlorination and deoxidation can be carried out by various known methods, for example, by placing plastics including PVC and PET into a reaction vessel together with hydrated lime and heating them at atmospheric pressure at a temperature of, for example, about 350°C, but the methods of dechlorination and / or deoxidation are not limited to these.

[0072] When dechlorination and deoxidation are carried out by heating as described above, it is preferable to control the heating temperature and heating time so that the process is carried out under pre-set processing conditions (temperature, time, etc.) so as to obtain the effects of dechlorination and deoxidation while not allowing the thermal decomposition of the plastic to progress to the extent that it would reduce the oil yield in the subsequent primary separation process.From this perspective, the temperature inside the reaction vessel can be adjusted to an appropriate temperature by adjusting the heat output of the burner that heats the reaction vessel or the temperature of the heater, based on the temperature inside the reaction vessel detected by a temperature detection means such as a temperature sensor, and the control means for controlling heating to be carried out for an appropriate processing time can be realized by having a computer system execute a specified program.

[0073] Furthermore, as in the prior art shown in Patent Document 1 and Patent Document 2 above, it is also possible to configure the system so that a common reaction vessel is used to decompose plastics following dechlorination, and in this case, as in the device configuration described in Patent Document 1, for example, the gas generated by heating during the dechlorination process (for example, heating to about 350°C) can be used as fuel to heat the plastics, and by configuring the system in this way, it is possible to reduce the amount of new fuel consumed for recycling plastics.

[0074] In addition, if primary decomposition of plastics is performed using a reaction vessel different from the one used for dechlorination or deoxidation, it will be necessary to transfer the plastics from the reaction vessel used for dechlorination or deoxidation to the reaction vessel used for primary decomposition of plastics.

[0075] This type of work may be carried out, for example, by manually removing the plastic from the dechlorination or deoxidation reaction vessel and transferring it to the primary decomposition reaction vessel, but it may also be possible to connect the dechlorination or deoxidation reaction vessel and the primary decomposition reaction vessel via, for example, a pipe so that the plastic can be transferred directly via this pipe.

[0076] In this case, a heater is wrapped around the outer periphery of the aforementioned piping that connects the dechlorination / deoxidation reaction vessel with the primary decomposition reaction vessel, and the heating temperature of the heater is controlled to melt all or part of the plastic in the reaction vessel into a flowable state during or after dechlorination / deoxidation, and the fluid state within the piping can be maintained by heating with the heater so that the molten plastic can move within the piping.By configuring in this way, it is possible to continuously introduce plastic after dechlorination / deoxidation into the primary decomposition reaction vessel and continuously carry out primary decomposition of the plastic.

[0077] [Primary decomposition treatment] The plastics that have undergone the above-mentioned pretreatment are subjected to primary decomposition treatment by primary decomposition means 10.

[0078] In this primary decomposition process, plastics are subjected to a plastic decomposition process using plastic decomposition units 20, 20', 30, where they are subjected to primary decomposition to generate primary decomposition gas, and the primary decomposition gas generated in the plastic decomposition process is introduced into a first coagulation tower 40 and cooled to a first cooling temperature (for example, 153°C) to recover condensed high molecular weight oil (diesel oil), and the primary decomposition gas after the high molecular weight oil has been recovered is further introduced into a second coagulation tower 50 and cooled to a second cooling temperature (for example, 40°C or 20°C) to recover condensed low molecular weight oil (naphtha), which is then subjected to a low molecular weight oil recovery process.

[0079] (1) Plastic decomposition process The plastic decomposition process in which plastic is decomposed to generate primary decomposition gas may be carried out by either thermal decomposition or hydrothermal decomposition.

[0080] (1-1) Decomposition of plastics by pyrolysis The decomposition of plastics by thermal decomposition can be carried out by heating the plastics to a temperature of, for example, about 400°C under atmospheric pressure in a reaction vessel 21 provided in the plastic decomposition device 20, 20'.

[0081] Such thermal decomposition of plastics may be carried out by either a batch method or a continuous method, and an example of the configuration of a batch type plastic decomposition device 20 is shown in FIG.

[0082] The plastic decomposition device 20 shown in Figure 2 is configured to pyrolyze plastic by heating a reaction vessel 21, into which the amount of plastic to be processed at one time has been put, from the outside using a burner, electric heater, etc. so that the internal temperature reaches approximately 400°C, and to extract the primary decomposition gas produced by this pyrolysis through an outlet pipe 22 connected to the reaction vessel 21.

[0083] In addition, the configuration of such a batch-type plastic decomposition device may be the same as that of the thermal decomposition device described in Patent Document 1, above, so that the thermal decomposition of plastic can be carried out following the dechlorination and deoxidation treatment carried out as a pretreatment in a common reaction vessel.

[0084] FIG. 3 shows an example of the configuration of a continuous plastic decomposition device 20'.

[0085] The plastic decomposition device 20' shown in Figure 3 is equipped with a cylindrical reaction vessel 21 and a screw conveyor 23 that rotates within the reaction vessel 21, as well as a burner or electric heater that heats the reaction vessel 21 from the outside so that the temperature inside the reaction vessel 21 becomes approximately 400°C.Plastic is fed into a raw material feed port 24 located at one end of the reaction vessel 21 and transported by the screw conveyor 23 toward the other end of the reaction vessel 21, so that the primary decomposition gas generated by the thermal decomposition of the plastic during transport can be extracted from the outlet pipe 22, and the residue generated by the thermal decomposition can be discharged outside the machine through the residue discharge port 25.

[0086] The configuration of such a continuous plastic decomposition device 20' may be the same as that of the thermal decomposition device described in Patent Document 2, whereby the processes from the dechlorination and deoxidation treatments carried out as pretreatment to the thermal decomposition of plastics can be carried out continuously in a single device.

[0087] The configuration examples of the decomposition devices 20, 20' used when thermally decomposing plastics are not limited to the configurations described above, and various known configurations of thermal decomposition devices can be adopted.

[0088] (1-2) Decomposition of plastics by hydrothermal decomposition The decomposition of plastics may be carried out by hydrothermal treatment instead of the thermal decomposition described above.

[0089] In this hydrothermal treatment, the inside of the reaction vessel 31, which is a pressure vessel into which water is introduced along with the plastic, is subjected to an absolute pressure of 0.1 MPa to 30 MPa and a temperature of 200 to 600°C, and the plastic, which is an organic substance, is decomposed by the hydrothermal treatment using subcritical or supercritical water generated in the reaction vessel 31.

[0090] The decomposition of plastics by such hydrothermal decomposition can be carried out by either a batch method or a continuous method, and Figure 4 shows an example of the configuration of a plastic decomposition device 30 that continuously decomposes raw plastics by such hydrothermal decomposition.

[0091] The plastic decomposition device 30 shown in Figure 4 is configured so that the inside of a cylindrical reaction vessel 31, which is a pressure vessel, can be heated by covering the outer periphery of the reaction vessel 31 with a heater 33, and is configured so that plastic, water pressurized by a high-pressure pump 34, and nitrogen gas as a purge gas can be introduced from one end of the reaction vessel 31, and is provided with an outlet pipe 32 connected to the inside of the reaction vessel 31 at the other end, so that the primary decomposition gas generated by the hydrothermal decomposition of plastic can be extracted via the outlet pipe 32.

[0092] In the embodiment shown in Figure 4, a screw extruder 35 is provided which is connected to a raw material inlet 36 provided in the reaction vessel 31, and the plastic extruded in a molten state by this screw extruder 35 can be forced into the reaction vessel 31, but the continuous type configuration is not limited to this method.

[0093] Furthermore, when such a screw extruder 35 is provided and configured to introduce molten plastic into the reaction vessel 31, the aforementioned dechlorination and deoxidation may also be performed at the same time as melting using this screw extruder.

[0094] By continuously introducing plastic and water while controlling the pressure and temperature inside the reaction vessel 31 of the plastic decomposition device 30 configured in this manner to a predetermined pressure and temperature within the aforementioned range, continuous hydrothermal decomposition of plastic can be achieved.

[0095] (2) Oil separation process The primary cracked gas generated by thermal cracking or hydrothermal cracking in the plastic cracking units 20, 20', 30 described above is cooled to condense and recover oil.

[0096] In this type of condensation oil recovery, as shown in Figure 1, two condensation towers (first condensation tower 40, second condensation tower 50) with different cooling temperatures are arranged in series so that the cooling temperatures decrease sequentially, and the temperature of the primary cracked gas is gradually lowered.This allows the high-molecular-weight oil with a high boiling point (diesel oil as an example) and the low-molecular-weight oil with a low boiling point (naphtha as an example) to be recovered separately.

[0097] (2-1) Recovery of polymer oil from primary cracked gas (polymer oil recovery process) In order to recover diesel oil, which is a polymer oil, from the primary cracking gas produced by thermally or hydrothermally cracking plastics in the plastic cracking units 20, 20', 30, the primary cracking gas extracted from the plastic cracking units 20, 20', 30 is introduced into the first coagulation tower 40 and cooled.

[0098] The cooling temperature in the first coagulation tower 40 is set to a temperature slightly lower than the lower limit of the boiling point temperature range of polymer oil, and in this embodiment in which diesel oil is recovered as polymer oil, it is cooled to a temperature (153°C in this embodiment, as an example) slightly lower than 170°C, which is the lower limit of the boiling point range of diesel oil (170°C to 370°C), and the polymer oil (diesel oil in this embodiment) coagulated by this cooling is recovered in the first coagulation tower 40.

[0099] In the embodiment shown in Figure 1, the primary decomposition gas generated by the plastic decomposition devices 20, 20', 30 is pre-cooled in a heat exchanger 61 and then introduced into the first condensation tower 40, so that the primary decomposition gas can be cooled to a first set temperature (for example, 153°C) in the first condensation tower 40 in a short period of time.However, it is also possible to introduce the primary decomposition gas directly into the first condensation tower 40 without pre-cooling it using the heat exchanger 61.

[0100] The configuration of the first coagulation tower 40 is not particularly limited as long as it can cool the primary cracked gas to the first cooling temperature and recover the coagulated polymer oil (diesel oil).As an example, various known cooling tower configurations can be adopted.

[0101] As an example of the configuration of such a first coagulation tower 40, the structure shown in FIG. 5 can be adopted.

[0102] The coagulation tower 40 shown in Figure 5 contains a spiral pipe 42 through which the primary decomposition gas passes, inside a cooling water tank 41 filled with cooling water, and is capable of controlling the temperature inside the cooling water tank 41 by supplying and discharging cooling water to and from the cooling water tank 41.The primary decomposition gas is cooled to the first cooling temperature (153°C, for example) mentioned above in the process of passing through the spiral pipe 42, so that the polymer oil can be coagulated and recovered in the polymer oil recovery tank 43.

[0103] In addition, the first coagulation tower 40 may be configured as shown in Figure 6, with a cooling chamber 44 whose outer wall is covered with a refrigerant flow path 45, and a cooler 46 that cools and circulates the refrigerant in the refrigerant flow path 45, and by introducing the primary decomposition gas into the cooling chamber 44 while circulating a refrigerant such as cooling water cooled by the cooler 46 within the refrigerant flow path 45, the primary decomposition gas can be cooled to the above-mentioned first cooling temperature (for example, 153°C), thereby coagulating the polymer oil and recovering it in the polymer oil recovery tank 43.

[0104] By cooling in this first condensation tower 40, among the oils contained in the primary cracked gas, high molecular weight oil (diesel oil in this embodiment) having a relatively high boiling point temperature is condensed.

[0105] The polymer oil (diesel oil) coagulated in the first coagulation tower 40 is cooled to an appropriate temperature by passing it through a heat exchanger or the like as necessary, and then recovered in the polymer oil recovery tank 43.

[0106] (2-2) Recovery of low molecular weight oil from primary cracked gas (low molecular weight oil recovery process) The primary cracked gas after passing through the first condensation tower 40 and having the high molecular weight oil removed is further introduced into the second coagulation tower 50, where it is cooled to a temperature near the lower limit of the boiling point range of the low molecular weight oil.

[0107] In this embodiment, diesel oil is recovered as high molecular weight oil, and the low molecular weight oil (naphtha in this embodiment) is condensed and recovered by cooling to a temperature near the lower limit of the boiling point range (30°C to 180°C) of naphtha to be recovered as low molecular weight oil (for example, 40°C or 20°C in this embodiment).

[0108] In the embodiment shown in Figure 1, the primary cracked gas after the polymer oil has been separated by the first concentrating tower 40 is pre-cooled by a heat exchanger 62 before being introduced into the second concentrating tower 50, so that the primary cracked gas can be cooled to a second set temperature (for example, 40°C or 20°C) in the second concentrating tower 50 in a short period of time.However, it is also possible to introduce the primary cracked gas after passing through the first concentrating tower 40 directly into the second concentrating tower 50 without pre-cooling by the heat exchanger 62.

[0109] The configuration of the second coagulation tower 50 is not particularly limited as long as it can cool the primary cracked gas to the second cooling temperature and recover the coagulated low molecular weight oil (naphtha in this embodiment), and various configurations can be adopted.As an example, the configuration of the first coagulation tower 40 described with reference to Figures 5 and 6 can also be adopted in the second coagulation tower 50.

[0110] Furthermore, the first coagulation tower 40 and the second coagulation tower 50 may be used in combination with towers having similar structures, or may be used in combination with towers having different structures.

[0111] By cooling in this second condensation tower 50, the low molecular weight oil (naphtha in this embodiment) with a relatively low boiling point temperature among the oils contained in the primary cracking gas is condensed, and the condensed low molecular weight oil is recovered in the second condensation tower 50.

[0112] The low molecular weight oil flocculated in the second flocculation tower 50 is recovered in a low molecular weight oil recovery tank 53.

[0113] [Low molecular weight processing] The high molecular weight oil (diesel oil in this embodiment) recovered from the primary cracking gas in the above manner is further decomposed by hydrothermal cracking to reduce the molecular weight, and secondary recovery is performed in which the secondary cracking gas produced by this secondary cracking is cooled to condense the oil and recover it.

[0114] This reduces the yield of high molecular weight oils recovered from plastics, while increasing the yield of low molecular weight oils, thereby improving the economic viability of plastic recycling through oilification.

[0115] Figure 7 shows an example configuration of a low molecular weight means (low molecular weight means) 70 equipped with a high molecular weight oil cracking device 71 that performs secondary cracking of such high molecular weight oil and a secondary recovery means 76 for recovering oil from the secondary cracking gas produced in the high molecular weight oil cracking device 71.

[0116] The polymer oil decomposition device 71 provided in the low molecular weight means 70 is equipped with a cylindrical reaction vessel 72 which is a pressure vessel, and a heater 73 which covers the outer periphery of the reaction vessel 72, and is configured so that the reaction vessel 72 can be heated by heating with the heater 73.

[0117] High-pressure pumps 74a and 74b are connected to the bottom side of the reaction vessel 72, and these high-pressure pumps 74a and 74b are configured to pressurize and introduce water and diesel oil recovered by the primary decomposition process into the reaction vessel 72, and in the illustrated example, are configured to introduce nitrogen gas as a purge gas.

[0118] On the other hand, an outlet pipe 75 connected to the inside of the reaction vessel 72 is provided on the upper end side of the reaction vessel 72, and is configured so that the secondary decomposition gas generated by hydrothermal decomposition of polymer oil (diesel oil) can be introduced through this outlet pipe 75 into a cooling tower 77 that constitutes the secondary recovery means 76.

[0119] The pressure and temperature inside the reaction vessel 72 are controlled to a pressure of 0.1 MPa to 30 MPa absolute and a predetermined pressure and temperature selected within the range of 200 to 600°C. In this embodiment, a control means (not shown) controls the heat output of the heater 73 based on the detection signal of the temperature sensor T that detects the temperature inside the reaction vessel 72, thereby controlling the temperature inside the reaction vessel 72 to, for example, 500°C, and the control means (not shown) controls the operation of the high-pressure pumps 74a, 74b and the opening of the back pressure valve based on the pressure detected by the pressure sensor P provided in the outlet pipe 75, thereby controlling the pressure inside the reaction vessel 72 to, for example, 2 MPa (absolute pressure).

[0120] In this way, a control means (not shown) controls the temperature and pressure inside the reaction vessel 72 to be constant based on the temperature and pressure detected by the temperature sensor T and the pressure sensor P, thereby forming a continuous hydrothermal decomposition apparatus in which polymer oil is continuously introduced into the reaction vessel 72 and hydrothermally decomposed.

[0121] In addition, this reaction vessel 72 is provided with a safety valve, which opens when the pressure inside the reaction vessel 72 exceeds a predetermined upper limit pressure to release the pressure inside the reaction vessel 72, thereby preventing damage, etc. caused by an excessive increase in pressure inside the reaction vessel 72.

[0122] In this way, the secondary decomposition gas produced by hydrothermal decomposition in the polymer oil decomposition device 71 is then introduced into a cooling tower 77 provided in the secondary recovery means 76 and cooled, so that the oil that condenses during cooling in the cooling tower 77 can be recovered.

[0123] In the embodiment shown in Figure 7, this cooling tower has a configuration similar to that of the first coagulation tower 40 described with reference to Figure 5, and has a structure in which a spiral pipe for passing secondary decomposition gas is housed in a cooling water tank in which cooling water is stored, and is configured to introduce cooling water into the cooling water tank through a water supply port provided on the lower end side of the cooling water tank and to allow the cooling water to overflow through a drain port provided on the upper end side of the cooling water tank, thereby making it possible to maintain the temperature of the cooling water in the cooling water tank at an approximately constant temperature.

[0124] As an example, the embodiment shown in Figure 7 is configured to simultaneously condense and separate low molecular weight oils such as naphtha and high molecular weight oils such as diesel oil from the secondary cracked gas by a single cooling process.In this case, it is desirable to cool the secondary cracked gas to a temperature of 170°C or below in the cooling tower 77.

[0125] However, the coagulation of oil from secondary cracking gas by cooling can be done in a manner similar to the recovery of oil from primary cracking gas during the primary cracking process described with reference to Figure 1, by gradually lowering the cooling temperature in multiple steps to recover high molecular weight oil with a high boiling point temperature, and then sequentially recovering low molecular weight oil with a low boiling point temperature, and is not limited to the configuration shown in Figure 7.

[0126] In this way, the oil (a mixture of diesel oil and naphtha) condensed by cooling in the cooling tower 77 is introduced into a recovered oil tank 78 and stored therein, and after the oil and water remaining in the off-gas are removed via a gas-liquid separator 79, the off-gas is recovered as fuel gas, etc.

[0127] Furthermore, Figure 8 shows a modified example of the low molecular weight means 70 described with reference to Figure 7. The basic structure of the high molecular weight oil cracking device that decomposes diesel oil by hydrothermal decomposition is the same as that of the low molecular weight means described with reference to Figure 7, but it is equipped with a heat exchanger 63 that pre-cools the secondary decomposition gas derived from the high molecular weight oil cracking device 71 before introducing it into the cooling tower 77.

[0128] Furthermore, in the embodiment described with reference to Figure 7, the cooling tower 77 is a cooling tower having a configuration similar to that of the first coagulation tower 40 shown in Figure 5, that is, a spiral pipe is housed in a cooling water tank and the secondary decomposition gas is cooled by passing the secondary decomposition gas through the pipe.

[0129] In contrast, the configuration of the molecular weight reduction means 70 shown in Figure 8 uses a cooling tower 77 with a structure similar to that of the first coagulation tower 40 shown in Figure 6, and is configured so that the secondary decomposition gas can be cooled by introducing the secondary decomposition gas into the cooling chamber while circulating a refrigerant cooled by a cooler within the refrigerant flow path surrounding the outer wall of the cooling chamber.

[0130] In the embodiment described with reference to Figures 1 to 8, an example configuration has been shown in which a molecular weight reduction means 70 that performs secondary decomposition of the high molecular weight oil (diesel oil in this embodiment) obtained by the primary decomposition process to reduce the molecular weight is provided independently of the primary decomposition means 10, but instead of this configuration, a configuration in which some of the components of the molecular weight reduction means 70 are shared with the primary decomposition means 10 may also be adopted.

[0131] As an example, in the embodiment shown in FIG. 9, the plastic decomposition devices 20, 20' of the primary decomposition means 10 are configured as thermal decomposition devices, and the primary cracked gas generated in the plastic decomposition devices 20, 20' is pre-cooled by a heat exchanger 61, then introduced into the first coagulation tower 40 and cooled to a first cooling temperature (153°C as an example) to coagulate and recover high molecular weight oil (diesel oil as an example), and the primary cracked gas after the high molecular weight oil has been recovered is pre-cooled by a heat exchanger 62 and introduced into the second coagulation tower 50, where it is further cooled to a second cooling temperature (40°C as an example) to recover the coagulated low molecular weight oil (naphtha as an example), which is similar to the configuration of the plastic oil production system 1 described with reference to FIG. 1.

[0132] In this way, the polymer oil (diesel oil, as an example) that has been coagulated in the first coagulation tower 40 and stored in the polymer oil recovery tank 43 is introduced together with water by high-pressure pumps 74a and 74b into a reaction vessel provided in the polymer oil decomposition device 71, which is a hydrothermal decomposition device, and the pressure in the reaction vessel is increased to 1 MPa absolute pressure and heated to 450°C to produce subcritical water, which is used to perform secondary decomposition of the polymer oil (diesel oil) in the polymer oil decomposition device 71.

[0133] The secondary cracking gas produced by decomposing high molecular weight oil in this high molecular weight oil cracking device 71 is pre-cooled in a heat exchanger 65 and then merged with the primary cracking gas before being introduced into the first coagulation tower 40. This allows the recovery of high molecular weight oil and low molecular weight oil from the secondary cracking gas to be carried out by the first coagulation tower 40 and the second coagulation tower 50 provided in the primary cracking means 10, thereby realizing a secondary recovery means 76 that recovers oil from the secondary cracking gas using the first coagulation tower 40 and the second coagulation tower 50 provided in the primary cracking means 10.

[0134] In addition, in the embodiment shown in Figure 10, the plastic decomposition device 30 is configured as a continuous hydrothermal decomposition device that continuously decomposes plastics by hydrothermal decomposition, and the primary decomposition gas generated in the plastic decomposition device 30 is pre-cooled by a heat exchanger 61 and then introduced into the first coagulation tower 40 to cool to a first cooling temperature (153°C, for example) and coagulates and recovers high molecular weight oil (diesel oil, for example), and the primary decomposition gas after the high molecular weight oil has been recovered is pre-cooled by a heat exchanger 62 and then introduced into the second coagulation tower 50 to cool to a second cooling temperature (20°C, for example) so that the coagulated low molecular weight oil (naphtha, for example) can be recovered.

[0135] The polymer oil (diesel oil, as an example) recovered in the first coagulation tower 40 and stored in the polymer oil recovery tank 43 is introduced into a plastic decomposition device (hydrothermal decomposition device) 30 provided in the primary decomposition means by a high-pressure pump 74b, and this plastic decomposition device (hydrothermal decomposition device) 30 is configured to perform primary decomposition of plastics as well as secondary decomposition of polymer oil (diesel oil).The primary decomposition gas produced by the decomposition of plastics and the secondary decomposition gas produced by the decomposition of polymer oil (diesel oil) are both introduced into the first coagulation tower 40 and the second coagulation tower 50 to recover the oil, so that the plastic decomposition device 30 of the primary decomposition means 10 also serves as the polymer oil decomposition device 71 of the molecular weight reduction means 70, and the first coagulation tower 40 and the second coagulation tower 50 of the primary decomposition means 10 also serve as secondary recovery means 76 that recovers oil from the secondary decomposition gas in the molecular weight reduction means 70.

[0136] By configuring in this manner, simply by adding to the configuration of the primary decomposition means 10 a reflux flow path 80 that connects the polymer oil recovery tank 43 and the plastic decomposition device 30, and a high-pressure pump 74b installed in the reflux flow path 80, the main configuration of the low-molecular-weight decomposition means 70 can be used in combination with the configuration of the primary decomposition means 10, making it possible to significantly simplify the device configuration.

[0137] The method for converting plastics into oil according to the present invention described above may further include a step of recovering by-products generated during the oil conversion process, or by-products generated during dechlorination and deoxidation if dechlorination and deoxidation are performed as a pretreatment.

[0138] As for such by-products, as mentioned above, off-gas remaining after low molecular weight oil is recovered can be recovered as fuel gas, or impurities such as char and metals can be separated and recovered from the residues produced during the thermal decomposition of plastics or high molecular weight oils.

[0139] Furthermore, when a dechlorination / deoxidation process is carried out as a pretreatment, if an alkaline aqueous solution such as an aqueous NaCl solution is used during the dechlorination / deoxidation, salts such as NaCl, terephthalic acid, ethylene glycol, etc. may be precipitated and separated, and solids such as polyenes produced by the dechlorination of PVC may be separated, extracted and recovered. [Explanation of symbols]

[0140] 1. Plastic oil conversion equipment 10 Primary decomposition means 20,20' Plastic Decomposition Equipment (Thermal Decomposition Type) 21 Reaction vessel 22 Outlet pipe 23 Screw conveyor 24 Raw material input port 25 Residue outlet 30 Plastic decomposition equipment (hydrothermal decomposition type) 31 Reaction vessel 32 Outlet pipe 33 Heater 34 High-pressure pump 35 Screw Extruder 36 Raw material inlet 40 1st flocculation tower 41 Cooling water tank 42 Spiral Pipe 43 Polymer Oil Recovery Tank 44 Cooling room 45 refrigerant flow path 46 Cooler 50 Second flocculation tower 53 Low molecular weight oil recovery tank 61,62,63,64,65 Heat exchanger 70 Low-molecularization means (low-molecularization device) 71 Polymer oil decomposition equipment (oil decomposition equipment) 72 Reaction vessel 73 Heater 74a, 74b High pressure pump 75 Outlet pipe 76 Secondary Recovery Methods 77 Cooling Tower 78 Oil recovery tank 79 Gas-liquid separator 80 Reflux channel 81 Confluence

Claims

1. In a plastic oil recovery method in which plastic is chemically decomposed and recovered as oil, The oil production method includes a primary decomposition process in which plastics are decomposed and the oil is separated into high molecular weight oil and low molecular weight oil and recovered; a low molecular weight process for further decomposing the polymer oil obtained in the primary decomposition process, The primary decomposition treatment a plastic decomposition step of decomposing the plastic to produce a primary decomposition gas; a polymer oil recovery step of cooling the primary cracked gas obtained in the plastic cracking step to a first cooling temperature to condense and recover the polymer oil from the primary cracked gas; A low molecular weight oil recovery step of cooling the primary cracked gas after the high molecular weight oil has been recovered to a second cooling temperature lower than the first cooling temperature to condense and recover the low molecular weight oil from the primary cracked gas, The low molecular weight treatment is a polymer oil cracking step in which the polymer oil recovered in the polymer oil recovery step of the primary cracking treatment is further cracked to generate a secondary cracked gas; The method for converting plastics into oil comprises a secondary recovery step of cooling the secondary cracked gas obtained in the polymer oil cracking step, and condensing and recovering oil from the secondary cracked gas.

2. 2. The method for converting plastics into oil according to claim 1, wherein the decomposition of the plastics in the plastic decomposition step is carried out by thermal decomposition.

3. 2. The method for converting plastics into oil according to claim 1, wherein the decomposition of the plastics in the plastic decomposition step is carried out by hydrothermal treatment using subcritical water or supercritical water.

4. The method for converting plastics into oil according to any one of claims 1 to 3, further comprising a dechlorination / deoxidation step of dechlorinating and / or deoxidizing the plastics before the primary decomposition treatment.

5. 5. The method for converting plastics into oil according to claim 4, wherein the dechlorination and deoxidation step and the plastic decomposition step are carried out in the same reaction vessel.

6. 5. The method for converting plastics into oil according to claim 4, wherein the dechlorination and deoxidation steps are carried out under treatment conditions that do not reduce the oil yield in the primary decomposition treatment.

7. The method for converting plastics into oil according to any one of claims 1 to 3, further comprising a volume reduction step of heating the plastics at a temperature of 50°C to 200°C, which does not cause thermal decomposition, to reduce their volume, prior to the primary decomposition treatment.

8. 8. The method for converting plastics into oil according to claim 7, wherein the volume reduction step is carried out when the plastics are collected.

9. 8. The method for converting plastics into oil according to claim 7, wherein the volume reduction step is carried out during transportation and / or intermediate treatment of the plastics.

10. The high molecular weight oil recovered in the primary decomposition treatment is successively decomposed in the high molecular weight oil decomposition step in the low molecular weight treatment, The method for converting plastics into oil as described in claim 2, characterized in that the secondary decomposition gas produced in the high molecular weight oil decomposition process is merged with the primary decomposition gas prior to the high molecular weight oil recovery process, and the high molecular weight oil recovery process and the low molecular weight oil recovery process are performed on the secondary decomposition gas together with the primary decomposition gas, thereby carrying out the secondary recovery process.

11. The plastic decomposition step in the primary decomposition treatment is carried out continuously, A method for converting plastics into oil as described in claim 3, characterized in that the polymer oil produced in the primary decomposition process is sequentially decomposed together with the plastics by hydrothermal treatment in the plastic decomposition step, thereby carrying out the secondary decomposition process simultaneously with the primary decomposition process.

12. 12. The method for converting plastics into oil according to claim 3 or 11, wherein the plastics to be decomposed in the primary decomposition step of the primary decomposition treatment are plastics that have been melted in advance to a flowable state.

13. In a plastic oil-recovery device that chemically decomposes plastic and recovers it as oil, The oil-producing apparatus includes a primary decomposition means for decomposing plastics and separating the oil into high molecular weight oil and low molecular weight oil for recovery; a low molecular weight means for further decomposing the high molecular weight oil obtained by the primary decomposition means, The primary decomposition means a plastic decomposition device for decomposing the plastic to generate a primary decomposition gas; a first condensation tower that cools the primary cracked gas obtained in the plastic cracking device to a first cooling temperature to recover the condensed polymer oil from the primary cracked gas; a second coagulation tower for cooling the primary cracked gas after the high molecular weight oil has been recovered to a second cooling temperature lower than the first cooling temperature to coagulate the low molecular weight oil from the primary cracked gas; The molecular weight reduction means is a polymer oil cracking device for further cracking the polymer oil recovered in the first coagulation tower of the primary cracking means to generate a secondary cracked gas; The apparatus for producing oil from plastics further comprises a secondary recovery means for cooling the secondary cracked gas obtained in the polymer oil cracking apparatus and condensing and recovering oil from the secondary cracked gas.

14. 14. The apparatus for producing oil from plastics according to claim 13, wherein the plastic decomposition device of the primary decomposition means decomposes the plastics by thermal decomposition.

15. 14. The apparatus for producing oil from plastics according to claim 13, wherein the plastic decomposition device of the primary decomposition means decomposes the plastics by hydrothermal treatment using subcritical water or supercritical water.

16. The plastic oil production apparatus according to any one of claims 13 to 15, further comprising a dechlorination / deoxidation means for dechlorinating and / or deoxidizing the plastic before the plastic is decomposed by the plastic decomposition device of the primary decomposition means.

17. The plastic oil-making apparatus according to claim 15, characterized in that the dechlorination and deoxidation means is realized by the plastic decomposition device of the primary decomposition means performing the dechlorination and / or deoxidation.

18. 17. The apparatus for producing oil from plastics according to claim 16, further comprising a control means for controlling the treatment conditions in the dechlorination and deoxidation means so as not to reduce the yield of oil in the primary decomposition means.

19. The plastic oil-making apparatus according to any one of claims 13 to 15, further comprising a volume reduction means for reducing the volume of the plastic by heating the plastic at a temperature of 50°C to 200°C that does not cause thermal decomposition before the plastic is decomposed by the plastic decomposition device of the primary decomposition means.

20. 20. The apparatus for converting plastics into oil according to claim 19, wherein the volume reduction means reduces the volume of the plastics when the plastics are collected.

21. 20. The apparatus for converting plastics into oil according to claim 19, wherein the volume reducing means reduces the volume of the plastics during transportation and / or intermediate processing.

22. The high molecular weight oil decomposition device is configured as a continuous type that sequentially decomposes the high molecular weight oil recovered by the primary decomposition means, and a confluence flow path for confluence of the secondary cracked gas generated in the polymer oil cracking device with the primary cracked gas before being introduced into the first coagulation tower; 15. The apparatus for producing oil from plastics according to claim 14, wherein the secondary recovery means for condensing and recovering oil from the secondary cracked gas is realized by the first and second coagulation towers.

23. The plastic decomposition device in the primary decomposition means is formed as a continuous type that continuously decomposes the plastic, and The plastic oil-recovery apparatus according to claim 15, characterized in that a reflux flow path is provided for sequentially introducing the polymer oil recovered by the primary decomposition means into the plastic decomposition device, thereby realizing the polymer oil decomposition device by the plastic decomposition device, and realizing the secondary recovery means by the first flocculation tower and the second flocculation tower.

24. 24. The apparatus for converting plastics into oil according to claim 15 or 23, further comprising a plastic melt supply means for introducing plastics that have been melted to a flowable state into said plastic decomposition apparatus.

25. an oil decomposition device that decomposes the oil in the reaction vessel, the oil decomposing device comprising: a reaction vessel that is a pressure vessel; a heater that surrounds the outer periphery of the reaction vessel; a high-pressure pump that introduces oil into the reaction vessel from one end side of the reaction vessel; and an outlet pipe that communicates with the space inside the reaction vessel at the other end side of the reaction vessel; An oil decomposition apparatus characterized by comprising a secondary recovery means for cooling the cracked gas discharged through the discharge pipe of the oil cracking apparatus to condense and recover the oil.

26. a temperature detection means and a pressure detection means for detecting the temperature and pressure in the reaction vessel of the oil cracking device; The low molecular weight oil device according to claim 25, characterized in that it is provided with a control means for controlling the temperature detected by the temperature detection means and the pressure detected by the pressure detection means to be predetermined temperature and pressure within the range of 200 to 600°C and the absolute pressure within the range of 0.1 to 30 MPa.

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