Thermal decomposition oiling method and thermal decomposition oiling device for waste plastics, and FCC catalyst

Abstract

The method for converting waste plastic into thermal decomposition oil comprises: a step of heating the waste plastic and a polymerization inhibitor to vaporize the polymerization inhibitor and thermally decompose the waste plastic to produce decomposition gas, such that the polymerization inhibitor reacts with the decomposition gas in a gas phase; and a step of cooling the decomposition gas to produce decomposed oil. As a result, the decomposed oil does not convert into heavy oil when the decomposed oil is produced. Accordingly, even if the waste plastic is thermally decomposed without separating them into aliphatic and aromatic styrene types, conversion of decomposed oil to heavy oil can be prevented.

Description

Technical Field

[0001] The invention relates to a waste plastic thermal decomposition oiling method and waste plastic thermal decomposition oiling device for thermally decomposing waste plastic and regenerating it into decomposed oil, and a fluidized catalytic cracking (FCC) catalyst. Background Art

[0002] The inventor of the present application provides a waste plastic thermal decomposition oiling method disclosed in patent document 1. In this method, waste plastics mixed with resins of different compositions such as polypropylene (PP), polyethylene (PE), and polystyrene (PS) are crushed to produce crushed raw materials. The crushed raw materials are put into a decomposition evaporation tank together with a catalyst so that the crushed raw materials are thermally decomposed while reacting with the catalyst. The decomposition gas evaporated in the decomposition evaporation tank is cooled to produce a primary decomposition oil. The primary decomposition oil is distilled to produce a secondary decomposition oil. In addition, the secondary decomposition oil is heated at a constant temperature to adjust the flash point. In this way, waste plastics are regenerated into petroleum products such as kerosene.

[0003] However, the primary decomposed oil is produced in a viscous (i.e., highly viscous) slurry state and is converted into so-called heavy compounds. As a result, there is a problem of causing clogging in the pipeline path and equipment in the subsequent distillation process, the flash point adjustment process by constant temperature heating, and the pipeline until the final storage. In addition, when the stored fuel is used, there are also problems such as clogging of the burner nozzle (thereby causing poor combustion).

[0004] It is well known that the properties of polypropylene (PP), polyethylene (PE) and polystyrene (PS) when they are thermally decomposed are shown in Table 1 below, respectively.

[0005] [Table 1]

[0006]

[0007] As shown in this Table 1, polyethylene (PE) is a linear aliphatic polymer in which ethylene chains are polymerized, and polypropylene (PP) is a linear aliphatic polymer in which propylene chains are polymerized. The thermal decomposition of polyethylene (PE) and polypropylene (PP) is random.

[0008] Meanwhile, polystyrene (PS) is an aromatic polymer including a benzene ring, and has a molecular structure in which styrene including a vinyl group is polymerized. Therefore, the thermal decomposition of polystyrene (PS) is mainly of a depolymerization type and is highly reactive due to the vinyl group. As a result, when polystyrene (PS) is mixed with polyethylene (PE) and polypropylene (PP) for thermal decomposition, we face a problem in that the decomposed oil is significantly converted into heavier components in large quantities.

[0009] Therefore, the inventors of the present application have proposed a method disclosed in Patent Document 2, in which waste plastics are separated into an aliphatic type and an aromatic styrene type to be separately thermally decomposed, and a polymerization inhibitor is mixed so that the decomposed oil component from the highly reactive aromatic styrene type does not polymerize with the decomposed oil component from the aliphatic type, thereby forming a decomposed oil having high fluidity to proceed to the next distillation step.

[0010] However, in the method disclosed in Patent Document 2, waste plastics need to be separated into aliphatic type and aromatic styrene type to be separately thermally decomposed. Therefore, there are problems associated with facilities and workload for coping with this process.

[0011] Reference List

[0012] Patent Literature

[0013] Patent Document 1: JP 6631795 B

[0014] Patent Document 2: JP 2021-188023 A

[0015] Patent Document 3: WO 2007 / 086348 A1

[0016] Patent Document 4: JP 2001-89768A Summary of the invention

[0017] Technical issues

[0018] The present invention aims to effectively prevent the decomposed oil from being converted into heavier components without separating the waste plastic into aliphatic types and aromatic styrene types (especially even if the aliphatic types and aromatic styrene types are mixed and thermally decomposed).

[0019] Solution to the problem

[0020] The waste plastic thermal decomposition method according to one aspect of the present invention comprises: heating the waste plastic and a polymerization inhibitor, gasifying the polymerization inhibitor and thermally decomposing the waste plastic to generate a decomposition gas, so that the polymerization inhibitor reacts with the decomposition gas in a gas phase; and cooling the decomposition gas to generate a decomposition oil.

[0021] A waste plastic thermal decomposition device according to one aspect of the present invention includes: a decomposition evaporation tank configured to heat the waste plastic and an inhibitor, gasify the inhibitor and thermally decompose the waste plastic to generate a decomposition gas, so that the inhibitor reacts with the decomposition gas in a gas phase; and a condenser configured to be connected to the decomposition evaporation tank and cool the decomposition gas supplied from the decomposition evaporation tank to generate a decomposition oil.

[0022] The FCC catalyst according to one aspect of the present invention comprises a polymerization inhibitor.

[0023] Advantageous Effects of the Invention

[0024] According to the present invention, in the thermal decomposition treatment of waste plastics, the polymerization inhibitor is gasified and the polymerization inhibitor is caused to react with the decomposition gas of the waste plastics in the gas phase. As a result, when the decomposition gas is cooled to produce decomposition oil, the decomposition oil is not converted into heavier components. Therefore, according to the present invention, even if the thermal decomposition is performed without separating the waste plastics into aliphatic types and aromatic styrene types, the decomposition oil can be effectively prevented from being converted into heavier components. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flowchart illustrating the processing flow of Embodiment 1 of the present invention is shown.

[0026] Figure 2A A graph showing the analysis results of the primary decomposition oil in the case where hydroquinone was added is shown.

[0027] Figure 2B A graph illustrating the analysis results of the primary decomposition oil in the case where no hydroquinone was added is shown.

[0028] Figure 3 The molecular structures of hydroquinone and benzoquinone are shown.

[0029] Figure 4 The molecular structure of methylhydroquinone is shown.

[0030] Figure 5 A flowchart illustrating the processing flow of Embodiment 2 of the present invention is shown.

[0031] Figure 6 A schematic diagram illustrating the configuration of the FCC catalyst used in Embodiment 2 is shown. DETAILED DESCRIPTION

[0032] [principle]

[0033] According to one embodiment of the present invention, in the waste plastic thermal decomposition treatment, the inhibitor is gasified to react with the waste plastic decomposition gas in the gas phase. The reaction will be described using hydroquinone (molecular formula: C6H6O2) as a representative example of the inhibitor.

[0034] Assume that the waste plastic to be processed is made of a mixture of polypropylene (PP), polyethylene (PE) and polystyrene (PS). The temperature at which these substances are thermally decomposed is generally about 380°C to 420°C (as shown in Table 1). Meanwhile, the boiling point of hydroquinone is about 285°C, which is lower than the above temperature. Therefore, the gasification of hydroquinone occurs earlier than the thermal decomposition. However, hydroquinone is unlikely to be lost due to its sublimation characteristics.

[0035] Meanwhile, the decomposition components of the decomposition gas of the waste plastic become randomly distributed after dissociation. In addition, in the case of PS-derived components, PP and PE-derived components (although not too much) are more likely to randomly repolymerize through the reaction of PS-derived components (mainly styrene monomers with highly reactive vinyl groups). This is the main reason for the conversion to heavier components.

[0036] The molecular structure of hydroquinone is shown in Figure 3 Hydroquinone releases two hydrogen radicals when energy is supplied. This quenches (inhibits) random recombination and polymerization in the free radical reaction of thermal decomposition by a chain transfer reaction that extracts active hydrogen. Since the high temperature energy from the decomposition gas promotes the release of two hydrogen radicals, the quenching (inhibition) effect is high.

[0037] Meanwhile, if we focus on the reaction of hydroquinone with the PS-derived component, the presence of a large amount of styrene monomer radicals (which are PS-derived components) is prevented by the chain draw-out effect of hydrogen radicals from hydroquinone on active hydrogen. Therefore, the radicals of PP and PE-derived components cannot exist in a large amount. As a result, the excessive formation of light and heavy substances can be reduced, and the yield of medium-weight decomposed oil can be improved.

[0038] At the same time, if Figure 3 As shown, hydroquinone has a strong reducing power to return to the original hydroquinone by reacting with hydrogen radicals after releasing two hydrogen radicals and becoming benzoquinone (molecular formula: C6H4O2). Therefore, hydroquinone also has the characteristic of being easily oxidized to become p-benzoquinone. Such p-benzoquinone also has a polymerization inhibitory effect. As a result, the quenching (inhibition) effect can be sustained for a long time, and decomposition occurs while suppressing the side reaction caused by reduction.

[0039] Since the above is carried out at the stage before the decomposition gas becomes decomposition oil, the decomposition oil is not only converted into heavier components, but also unnecessary components are eliminated after becoming decomposition oil. In addition, random fracture is also suppressed, which narrows the distribution range of component carbon numbers.

[0040] As disclosed in Patent Documents 2 and 4, the purpose of using polymerization inhibitors in the present technical field is mainly to prevent clogging in pipeline paths or in devices. For this reason, the polymerization inhibitor is added only after the decomposed oil is formed (added to the liquid phase). Therefore, the hydrogen radical reaction (which is a characteristic of the polymerization inhibitor) cannot be fully utilized.

[0041] At the same time, in the waste plastic thermal decomposition treatment of this embodiment, the inhibitor is gasified and causes the inhibitor to react with the decomposition gas of the waste plastic in the gas phase. As a result, the hydrogen radical reaction (which is a characteristic of the inhibitor) can be fully utilized to eliminate the mixing of unnecessary components.

[0042] In addition, in this embodiment, the polymerization inhibitor is allowed to exist simultaneously with the FCC catalyst and heated to gasify the polymerization inhibitor, and the waste plastic is brought into contact with the FCC catalyst to perform thermal decomposition.

[0043] FCC catalysts were originally solid acid catalysts used to decompose heavy oils to convert them into lighter oils. The reaction of FCC catalysts with waste plastics (generating carbocations and decomposing waste plastics) is disclosed in Patent Document 3. However, polycyclic aromatic hydrocarbons (contained in heavy components) are highly stable, and it is generally believed that polycyclic aromatic hydrocarbons in the FCC process are unlikely to decompose.

[0044] Now, focusing on the hydrogen transfer reaction in the FCC process, it is speculated that if the hydrogen transfer reaction is promoted, the decomposition of polycyclic aromatic hydrocarbons will also be possible. Therefore, it is speculated that when an inhibitor coexists in the contact thermal decomposition treatment of waste plastics caused by an FCC catalyst, hydrogen radicals from the inhibitor will promote the hydrogen transfer reaction and promote the conversion of heavy components to lighter components by the FCC catalyst.

[0045] The inhibitor can be directly attached to the FCC catalyst. In this case, the inhibitor coexists with each particle of the FCC catalyst. Since the above-mentioned hydrogen transfer reaction promotion effect by the inhibitor occurs on each particle of the FCC catalyst, the effect of heavy components passing through the FCC catalyst to lighter compounds can be enhanced. In addition, the ratio of the inhibitor to the FCC catalyst can be adjusted in advance so that the mutual effect is optimal. In addition, there is no need to add the inhibitor from the FCC catalyst separately.

[0046] [Implementation 1]

[0047] Will refer to Figure 1Embodiment 1 of the method and apparatus for thermal decomposition of waste plastics into oil according to the present invention is described. Among the raw materials of waste plastics mixed with PP, PE, and PS, those in hard form are crushed by the first crusher 71 and sent to the raw material storage tank 74. Among the raw materials of waste plastics, those in soft or film form are crushed by the second crusher 72, and further, heated to a low temperature by warm air of, for example, 150° C. by the volume reducer 73 so that they do not undergo thermal decomposition, and then sent to the raw material storage tank 74. The raw material storage tank 74 stores and naturally cools the crushed raw material 74a sent therefrom.

[0048] The pulverized raw material 74a is air-transferred from the raw material storage tank 74 through the pipe 75, collected by the cyclone separator 42, and temporarily stored in the raw material input hopper 43. The pulverized raw material 74a is sent out from the raw material input hopper 43 at a predetermined flow rate through the rotary valve 17, mixed with the catalyst from the catalyst tank 76 in the water-cooled heat blocker 18, and input into the decomposition evaporation tank 2. Here, the FCC waste catalyst 76a (which reuses the used FCC catalyst) is used as the catalyst. The input amount of the FCC waste catalyst 76a is about 20% by weight to 30% by weight relative to the pulverized raw material 74a.

[0049] The decomposition evaporation tank 2 is in the shape of a drum. The peripheral wall and the bottom wall of the decomposition evaporation tank 2 are both sandwiched walls so as to be indirectly heated by the heating medium, and thus the heating medium circulates in the inner cavity of the peripheral wall and the bottom wall. The heating medium is heated by the heating medium heater 60 and sent to the decomposition evaporation tank 2 through a pipeline. A flow regulating valve 62 is installed on the pipeline.

[0050] It should be noted that, instead of circulating the heating medium in the inner cavity, the heating medium may be confined in the inner cavity and a warm air passage may be formed on the periphery of the inner cavity so that the warm air circulates in the warm air passage and indirectly heats the heating medium. In this way, uneven heating of the decomposition evaporation tank 2 is reduced. Alternatively, an electric heater may be wound around the periphery of the decomposition evaporation tank 2 for heating.

[0051] The stirrer 30 rotated by the motor (M) 39 is disposed in the decomposition evaporation tank 2. The pulverized raw material 74a and the FCC waste catalyst 76a are indirectly heated by the heat of the heating medium while being stirred by the stirrer 30, and are transferred to converge on the center of the bottom wall. At this time, the temperature of the heating medium from the heating medium heater 60 is detected by the temperature sensor 61, and the temperature is adjusted by controlling the flow rate of the heating medium by the flow regulating valve 62 according to the temperature. The temperature in the decomposition evaporation tank 2 is maintained in the range of 350° C. to 450° C., preferably 380° C. to 400° C. In this temperature range, the FCC waste catalyst 76a causes thermal decomposition by reacting with the pulverized raw material 74a while in contact with it. The residue 2b gathered on the center of the bottom wall of the decomposition evaporation tank 2 is discharged by the residue discharge screw 31 and collected in the residue collection tank 32.

[0052] FCC waste catalyst 76a is low in cost and beneficial in resource recycling. At the same time, compared with unused FCC catalysts, FCC waste catalyst 76a has a lower reactivity with plastics due to its reduced acid strength. As a result, thermal decomposition occurs over a wide carbon number range, and the carbon number range of the decomposed gas 2a produced by thermal decomposition in primary treatment tends to be generally wide, and unwanted components tend to remain. However, from the perspective of acid strength, FCC waste catalyst 76a is more suitable for thermal decomposition and regeneration treatment of waste plastics. If the acid strength of an unused FCC catalyst is similar to that of the FCC waste catalyst 76a, such an unused FCC catalyst can be used.

[0053] In Embodiment 1, a polymerization inhibitor feeder 3 is provided for containing hydroquinone 3a used as a polymerization inhibitor. Hydroquinone 3a is fed from the polymerization inhibitor feeder 3 into the decomposition evaporation tank 2 through a water-cooled heat blocker 18 while adjusting the amount. The amount of hydroquinone 3a fed is about 1% by weight relative to the pulverized raw material 74a.

[0054] The temperature in the decomposition evaporation tank 2 is maintained at 380° C. to 400° C. as described above. The boiling point of hydroquinone 3a is about 285° C. Meanwhile, as shown in Table 1, the thermal decomposition characteristic temperatures of PS, PP, and PE are 358° C. to 410° C., 378° C. to 425° C., and 396° C. to 441° C., respectively. Therefore, the gasification of hydroquinone 3a precedes the thermal decomposition, and when coexisting with hydroquinone 3a, the contact thermal decomposition of PS, PP, and PE by the FCC waste catalyst 76a occurs in the order of PS, PP, and PE. Hydroquinone 3a participates in the decomposition of PS, PP, and PE in the contact thermal decomposition treatment by the FCC waste catalyst 76a, and the gasified hydroquinone 3a reacts with the decomposition gas 2a of PS, PP, and PE in the gas phase.

[0055] The decomposition gas 2a reacting with the hydroquinone 3a in the decomposition evaporation tank 2 is cooled by the first condenser 46 connected to the top wall of the decomposition evaporation tank 2 via a pipe to form a primary decomposition oil 46a. For this decomposition oil 46a, the following qualitative analysis was carried out by performing a comparative experiment between the case where the hydroquinone 3a was added to the decomposition gas 2a and the case where the hydroquinone 3a was not added.

[0056] (A) The case where hydroquinone 3a is added:

[0057] About 1% by weight of hydroquinone 3a was added to the pulverized raw material 74a to form a decomposition oil 46a. A sample of the decomposition oil 46a was added to 1 ml of normal hexane and injected into a gas chromatograph mass spectrometer for analysis using an automatic sampler. As a result of the analysis, toluene, ethylbenzene, stilbenzene, methylethylbenzene, benzaldehyde, methylpyrazine, acetophenone, and a compound presumably having 2 benzene rings and one alkyl group were detected. Compared to the decomposition oil in the case of (B) in which hydroquinone 3a was not added, a large amount of low-boiling compounds were detected.

[0058] (B) The case where hydroquinone 3a is not added (no hydroquinone is added):

[0059] A sample of the decomposed oil produced without adding hydroquinone 3a was added to 1 ml of normal hexane to be injected into a gas chromatograph mass spectrometer for analysis by using an automatic sample injector. As a result of the analysis, toluene, ethylbenzene, styrene, methylethylbenzene, benzaldehyde, methylpyrazine and acetophenone were detected, as well as naphthalene, phenylnaphthalene compounds and compounds presumed to be anthracene and many unknown compounds. Here, naphthalene, phenylnaphthalene compounds and anthracene are all polycyclic aromatic hydrocarbons, which were not detected in the case of (A) where hydroquinone 3a was added. In addition, various high-boiling point compounds were detected compared to the decomposed oil 46a in the case of (A) where hydroquinone 3a was added.

[0060] Figure 2A The analysis results for the case where hydroquinone was added are shown, and Figure 2B The analysis results for the case where hydroquinone was not added are shown. Figure 2A and 2B In the figure, the horizontal axis represents the carbon number, and the vertical axis represents the component ratio (%) of a certain carbon number. Figure 2A and 2BWhen (B) is not added with hydroquinone, toluene, ethylbenzene, styrene, methylethylbenzene, benzaldehyde, methylpyrazine and acetophenone are included, as well as naphthalene, phenylnaphthalene compounds and anthracene. The above are all polycyclic aromatic hydrocarbons, and there are many kinds of unknown components with carbon numbers of 20 or more, which are considered to be unnecessary for finished oil. Meanwhile, in (A) where hydroquinone is added, there are no such components, and the carbon number is almost limited to 14 or less, and there are only a small amount of components with carbon numbers of 20 or more. The large number of unknown components that are not mixed also indicates that such components derived from the FCC waste catalyst 76a are not mixed.

[0061] Table 2 shows the carbon number distribution of the gas chromatography analysis results in the case of (A) where hydroquinone was added, in terms of area percentage.

[0062] [Table 2]

[0063] Carbon number distribution area% C7 and below 9.6 C8 25.9 C9 42.9 C10 12.3 C11 4.4 C12 2.2 C13 1.2 C14 0.6 C15 0.4 C16 0.3 C17 0.2 C18 0.1 C19 0.0 C20 0.0 C21 0.0 C22 0.0 C23 0.0 C24 0.0 C25 0.0 C26 or above 0.0 total 100.0

[0064] Based on the analysis results, it is presumed that in the catalytic thermal decomposition treatment of PS, PP and PE by the FCC waste catalyst 76a, the following situation occurs when hydroquinone 3a coexists, and the gasified hydroquinone 3a reacts with the decomposition gas 2a in the gas phase.

[0065] (1) The thermal decomposition characteristic temperature of waste plastics for thermal decomposition of PP, PE and PS is generally about 380 to 420°C, while the boiling point of hydroquinone 3a is about 285°C. Therefore, the gasification of hydroquinone 3a precedes the thermal decomposition, so that hydroquinone 3a participates in the contact thermal decomposition of PS, PP and PE by the FCC waste catalyst 76a. The vaporized hydroquinone 3a is immediately mixed with the decomposition gas 2a in the gas phase to perform a free radical reaction. Hydroquinone 3a is less likely to be lost due to its sublimation, so that the free radical reaction continues.

[0066] (2) The thermally decomposed components do not contain polycyclic aromatic hydrocarbons such as naphthalene, phenylnaphthalene compounds and anthracene. For this reason, it is presumed that during the contact thermal decomposition treatment of PS, PP and PE by the FCC waste catalyst 76a, hydroquinone 3a promotes the hydrogen transfer reaction and contributes to the decomposition of polycyclic aromatic hydrocarbons.

[0067] (3) The decomposed components of the decomposed gas 2a are separated and become randomly distributed. In addition, as mentioned above, the components derived from PP and PE are easily repolymerized randomly through the components derived from PS. This is the main reason for the conversion to heavier components. However, hydroquinone 3a has Figure 3The molecular structure shown. Hydroquinone 3a releases two hydrogen radicals when energy is given. This quenches (inhibits) random recombination and polymerization in the free radical reaction of thermal decomposition. As for the vaporized hydroquinone 3a, since the high temperature energy from the decomposition gas 2a promotes the release of two hydrogen radicals, the quenching (inhibition) effect is high.

[0068] (4) Focusing on the reaction of hydroquinone 3a with PS-derived components, the active hydrogen is pulled out from the chain of hydroquinone 3a by hydrogen radicals, which prevents the existence of a large number of styrene monomer radicals (which are PS-derived components). As a result, the free radicals of PP and PE-derived components cannot exist in large quantities. For this reason, it is estimated that the expansion of the carbon number distribution range of the decomposed components is also narrowed.

[0069] (5) At the same time, Figure 3 As shown, hydroquinone 3a has a strong reducing power to return to the original hydroquinone 3a when reacting with hydrogen radicals after releasing two hydrogen radicals and becoming benzoquinone. Therefore, hydroquinone 3a is easily oxidized to p-benzoquinone. However, due to the lack of oxygen in the thermal decomposition reaction, such a situation is unlikely to occur. As a result, the quenching (inhibition) effect lasts for a long time, and decomposition can occur while suppressing the side reaction caused by reduction.

[0070] (6) As a result of the above, decomposed components and unnecessary components causing conversion to heavier components such as polycyclic aromatic hydrocarbons are eliminated, and random fragmentation is also suppressed, thereby narrowing the distribution range of carbon numbers.

[0071] We will return to Figure 1 . The primary decomposition oil 46a having the above-mentioned properties is caused to flow into the distillation tank 48 of the distillation stabilizer 47 to be distilled and purified. The distillation tank 48 adopts an indirect heating method similar to the decomposition evaporation tank 2. The bottom wall and the peripheral wall of the distillation tank 48 have a double structure forming a cavity, in which the heating medium from the heating medium heater 60 circulates to indirectly heat the inside of the distillation tank 48. By detecting the heating medium with a temperature sensor 64 and by adjusting the flow rate of the heating medium with a flow regulating valve 65, the heating temperature herein is within a predetermined temperature range lower than the heating temperature in the decomposition evaporation tank 2. In addition, in order to distill the primary decomposition oil 46a in the distillation tank 48 while stirring it, the distillation stabilizer 47 is equipped with a stirrer 50, which is rotated by a motor (M) 49 outside the tank.

[0072] The gas fraction evaporated in the distillation tank 48 is cooled by a second condenser 51 installed above the distillation tank 48 and connected via a pipe. The condenser 51 functions as a secondary decomposition oil forming device, and the cooling here produces a secondary decomposition oil 51a having a carbon number of about C6 to C15. The low carbon number decomposition gas (exit gas) 51b having a carbon number of C1 to C5 (lower than the above carbon number) also remains unchanged here.

[0073] The distillation tank 48 is connected to the decomposition evaporation tank 2 via a return pipe 52 in which a solenoid valve is inserted. When a certain amount of compounds having a carbon number of C16 or more are accumulated in the distillation tank 48, these compounds are returned to the decomposition evaporation tank 2 as return decomposition oil 48a via the return pipe 52, and are subjected to thermal decomposition treatment again in the decomposition evaporation tank 2.

[0074] The secondary decomposed oil 51a produced in the second condenser 51 flows into a separation tank 53 installed below the second condenser 51 and connected to the second condenser 51 via a pipeline, and then separates impurities and the like by precipitation, and enters a constant temperature heating tank 55 of a flash point adjustment device.

[0075] The constant temperature heating tank 55 is heated by a heating medium similar to the decomposition evaporation tank 2 and the distillation tank 48. The heating temperature of the secondary decomposition oil 51a is substantially a constant temperature lower than the heating temperature in the distillation tank 48. Therefore, the temperature of the heating medium from the heating medium heater 60 is detected by the temperature sensor 66, and the flow rate of the heating medium is controlled by the flow control valve 67 according to the temperature. For example, when the desired flash point is 30°C, and if the temperature 126°C (which is the boiling point of carbon number C8) is used as a reference, the compounds in the range of carbon number C9 to C15 remain in the constant temperature heating tank 55, and the decomposition oil 55b of carbon number C6 to C8 (outside the above carbon number range) is separated. Since such a decomposition oil 55b of carbon number C6 to C8 is a high flash point decomposition oil having a relatively high flash point, it can be used as a liquid fuel for the heating medium heater 60.

[0076] Meanwhile, the low carbon number decomposition gas (exit gas) 51b having carbon numbers C1 to C5 (having passed through the separation tank 53 without change) is highly flammable. Therefore, if the low carbon number decomposition gas 51b is sent to the heating medium heater 60 by the vacuum pump 70 and purified by the gas purification device 69, it can be used as a gas fuel for the heating medium heater 60.

[0077] The product oil 55a with a carbon number of C9 to C15 remaining in the constant temperature heating tank 55 is sent to the product storage tank 56 by the pump (P) 68 in a timely manner and stored in the storage tank 56. The regenerated product oil 55a is kerosene, which is a petroleum product with a carbon number in the range of C9 to C15 and has a large market demand.

[0078] Similar to such temperature adjustment, it is obvious that by adjusting the heating temperature in the distillation tank 48 and the heating temperature in the constant temperature heating tank 55, other petroleum products such as light oil, heavy oil, etc. with different carbon numbers can be produced.

[0079] Since the primary decomposed oil 46a has the above-mentioned characteristics and will not be converted into heavy compounds, it can be purified by distillation and flash point adjustment in the secondary mixing treatment system while maintaining high fluidity characteristics, and there will be no blockage in the pipeline path, device or storage tank between distillation and flash point adjustment.

[0080] In Embodiment 1, an FCC catalyst is used to promote the reaction, but waste plastics can also be converted into pyrolysis oil without using an FCC catalyst. Therefore, in Embodiment 1, an FCC catalyst is not necessary.

[0081] [Implementation 2]

[0082] Embodiment 2 of the present invention will now be described. In Embodiment 1, the polymerization inhibitor (hydroquinone 3a) and the catalyst (FCC waste catalyst 76a) are added separately to the decomposition evaporation tank 2. Meanwhile, in Embodiment 2, an FCC catalyst (also FCC waste catalyst 81 in Embodiment 2) to which the polymerization inhibitor is attached is used, and such FCC catalyst is placed in the decomposition evaporation tank 2. Therefore, in Embodiment 2, instead of the catalyst tank 76 accommodating the catalyst and the polymerization inhibitor adder 3 accommodating the polymerization inhibitor, a catalyst tank 80 (such as the catalyst tank 80 accommodating the FCC waste catalyst 81 to which the polymerization inhibitor is attached is provided. Figure 5 The other configurations are the same as those of implementation scheme 1.

[0083] Figure 6 A schematic diagram of an FCC waste catalyst 81 to which a polymerization inhibitor is attached is shown. The FCC waste catalyst 81 has the same structure as a general FCC catalyst, in which zeolite 83, which is a main component of the FCC catalyst, is bonded to a mineral 84 (such as kaolin) in a matrix 82 composed of silica or the like by using a binder 85. Therefore, the matrix 82 retains the zeolite 83 and other components. The shape of the matrix 82 may have the following shapes: Figure 6 The spherical shape shown in the figure, or may have a particle shape, etc. In the FCC spent catalyst 81 used in Embodiment 2, the surface of the substrate 82 is coated with hydroquinone 86 as a polymerization inhibitor. Specifically, the surface of the substrate 82 is coated with a coating agent mixed with the hydroquinone 86. Examples of the coating agent include a glass-based coating agent containing silicon dioxide as a main component. The adhesion ratio of the hydroquinone 86 to the FCC spent catalyst 81 is adjusted so that the interaction between the two is optimal.

[0084] When such an FCC waste catalyst 81 is put into the decomposition evaporation tank 2, the process is performed as described in Embodiment 1. However, since the FCC waste catalyst 81 includes the hydroquinone 86 as a polymerization inhibitor attached thereto, the hydroquinone 86 coexists with each particle of the FCC waste catalyst 81. As a result, the above-mentioned hydrogen transfer reaction promotion effect caused by the hydroquinone 86 occurs on each particle of the FCC waste catalyst 81, and thus the effect of conversion into lighter compounds by the FCC waste catalyst 81 can be improved. In addition, the ratio of the hydroquinone 86 to the FCC waste catalyst 81 can be adjusted in advance by the attached amount of the hydroquinone 86 to optimize the mutual effect. In addition, it is not necessary to add the hydroquinone 86 separately from the FCC waste catalyst 81 as in Embodiment 1.

[0085] In the above-mentioned embodiments 1 and 2, although hydroquinone 86 is used as the polymerization inhibitor, other polymerization inhibitors having similar properties to hydroquinone 86, such as Figure 4 The molecular structure of quinone-based polymerization inhibitors such as methyl hydroquinone (molecular formula: CH3C6H3(OH)2), and phenolic polymerization inhibitors such as 4-methoxyphenol (molecular formula: CH3OC6H4OH) are shown.

[0086] In addition, embodiments 1 and 2 are described using an example of waste plastics mixed with PP, PE and PS, but any waste plastics can be used as long as it can undergo thermal decomposition and regeneration. For example, the present invention can be applied to waste plastics composed of vinyl chloride (PVC) and polyethylene terephthalate (PET).

[0087] Therefore, various combinations of waste plastic materials and inhibitors can be considered. In any combination, in order to fully utilize the hydrogen radical reaction (hydrogen transfer reaction) as a characteristic of the inhibitor, it is preferred that the boiling point of the inhibitor is lower than the thermal decomposition characteristic temperature of the waste plastic.

[0088] [Aspects of the Invention]

[0089] A first aspect of the present invention relates to a method for thermal decomposition of waste plastics into oil, comprising: heating waste plastics (74a) and an inhibitor, gasifying the inhibitor and thermally decomposing the waste plastics (74a) to produce a decomposition gas (2a), so that the inhibitor reacts with the decomposition gas (2a) in a gas phase; and cooling the decomposition gas (2a) to produce a decomposition oil (46a).

[0090] The step of heating may include the step of heating an FCC (fluid catalytic cracking) catalyst together with the waste plastic (74a) and the polymerization inhibitor to cause the waste plastic (74a) to contact the FCC catalyst to be thermally decomposed.

[0091] In this case, the thermal decomposition oilification method may also include: a step of supplying the waste plastic (74a) to the decomposition evaporation tank (2); a step of supplying the FCC catalyst (76a) from a catalyst tank (76) containing the FCC catalyst (76a) to the decomposition evaporation tank (2); and a step of supplying the inhibitor (3a) from an inhibitor adder (3) containing the inhibitor (3a) to the decomposition evaporation tank (2), wherein the heating step may include a step of heating the waste plastic (74a), the FCC catalyst (76a) and the inhibitor (3a) in the decomposition evaporation tank (2).

[0092] Alternatively, the thermal decomposition oil conversion method may further include: a step of supplying the waste plastic (74a) to the decomposition evaporation tank (2); and a step of supplying the FCC catalyst (81) to which the polymerization inhibitor (86) is attached from a catalyst tank (80) containing the FCC catalyst (81) to which the polymerization inhibitor (86) is attached to the decomposition evaporation tank (2), wherein the heating step may include a step of heating the waste plastic (74a) and the FCC catalyst (81) to which the polymerization inhibitor (86) is attached in the decomposition evaporation tank (2). The polymerization inhibitor (86) may be coated on the FCC catalyst (81).

[0093] A second aspect of the present invention relates to a waste plastic thermal decomposition oiling device, comprising: a decomposition evaporation tank (2), which is configured to heat waste plastic (74a) and an inhibitor, gasify the inhibitor and thermally decompose the waste plastic (74a) to produce a decomposition gas (2a), so that the inhibitor reacts with the decomposition gas (2a) in a gas phase; and a condenser (46), which is connected to the decomposition evaporation tank (2) and is configured to cool the decomposition gas (2a) supplied from the decomposition evaporation tank (2) to produce a decomposition oil (46a).

[0094] The thermal decomposition oiling device may also include: a raw material storage tank (74), which is connected to the decomposition evaporation tank (2) and is configured to store waste plastics (74a) and supply the waste plastics (74a) to the decomposition evaporation tank (2); and an inhibitor adder (3), which is connected to the decomposition evaporation tank (2) and is configured to contain an inhibitor (3a) and supply the inhibitor (3a) to the decomposition evaporation tank (2).

[0095] The decomposition evaporation tank (2) may be configured to heat the waste plastic (74a) and the polymerization inhibitor together with the FCC catalyst to cause the waste plastic (74a) to be thermally decomposed by contacting the FCC catalyst.

[0096] In this case, the thermal decomposition oil conversion device may further include a catalyst tank (76) connected to the decomposition evaporation tank (2) and configured to accommodate the FCC catalyst (76a) and supply the FCC catalyst (76a) to the decomposition evaporation tank (2).

[0097] Alternatively, the thermal decomposition oil conversion device may further include a catalyst tank (80) connected to the decomposition evaporation tank (2) and configured to accommodate the FCC catalyst (81) to which the polymerization inhibitor (86) is attached, and supply the FCC catalyst (81) to which the polymerization inhibitor (86) is attached to the decomposition evaporation tank (2). The FCC catalyst (81) may be coated with the polymerization inhibitor (86). In this case, there is no need to separately provide the polymerization inhibitor adder (3).

[0098] A third aspect of the present invention is an FCC catalyst (81) provided with an inhibitor (86).

[0099] The FCC catalyst (81) may further include a substrate (82) holding a main component (83) of the catalyst, wherein the surface of the substrate (82) may be coated with an inhibitor (86). The surface of the substrate (82) may be coated with a coating agent mixed with the inhibitor (86). For example, a glass-based coating agent containing silicon dioxide as a main component may be used as the coating agent.

[0100] In the first and second aspects of the present invention, the waste plastic (74a) may include aliphatic plastic and aromatic styrene plastic. The aliphatic plastic may be at least one of polypropylene and polyethylene. The aromatic styrene plastic may be polystyrene.

[0101] In the first and second aspects of the present invention, the polymerization inhibitor (3a, 86) may be a quinone-type polymerization inhibitor such as hydroquinone and methyl hydroquinone. The polymerization inhibitor (3a, 86) may be a phenol-type polymerization inhibitor such as 4-methoxyphenol. The polymerization inhibitor (3a, 86) may have a boiling point lower than the thermal decomposition characteristic temperature of the waste plastic (74a).

[0102] In the first and second aspects of the present invention, the amount of the inhibitor may be 1 wt% relative to the waste plastic (74a). The amount of the FCC catalyst may be 20 to 30 wt% relative to the waste plastic (74a). The temperature in the decomposition evaporation tank (2) may be 350 to 450°C. The temperature in the decomposition evaporation tank (2) may be 380 to 400°C.

[0103] In the first to third aspects of the present invention, the FCC catalyst (76a, 81) may be a spent FCC catalyst (76a, 81) that reuses a used FCC catalyst.

[0104] [Industrial Applicability]

[0105] The FCC catalyst according to the present invention can be used not only for the thermal decomposition treatment of waste plastics, but also for oil refining technology for converting heavy components into lighter compounds.

[0106] Reference Symbols List

[0107] 2: Decomposition evaporation tank,

[0108] 3: Inhibitor Adder,

[0109] 18: Water-cooled thermal blocker,

[0110] 43: Raw materials are put into the hopper,

[0111] 46: Condenser,

[0112] 47: Distillation stabilizer,

[0113] 48: Distillation tank,

[0114] 51: Condenser,

[0115] 53: Separation tank,

[0116] 55: Constant temperature heating tank,

[0117] 56: Product storage tank,

[0118] 74: Raw material storage tank,

[0119] 76, 80: Catalyst tank,

[0120] 81: FCC spent catalyst,

[0121] 82: matrix,

[0122] 83: Zeolite,

[0123] 84: Minerals,

[0124] 85: Adhesive,

[0125] 86: Inhibitor

Claims

1. A method for thermal decomposition of waste plastics into oil, the method comprising: A step of heating the waste plastic and the polymerization inhibitor, gasifying the polymerization inhibitor and thermally decomposing the waste plastic to generate a decomposition gas, so that the polymerization inhibitor reacts with the decomposition gas in a gas phase; as well as a step of cooling the decomposed gas to produce decomposed oil.

2. The method for thermal decomposition of waste plastics into oil according to claim 1, wherein The heating step comprises: A step of heating an FCC (fluid catalytic cracking) catalyst together with the waste plastic and the polymerization inhibitor to cause the waste plastic to contact with the FCC catalyst to be thermally decomposed.

3. The method for thermal decomposition of waste plastics into oil according to claim 2, further comprising: The step of supplying the waste plastic to a decomposition evaporation tank; The step of supplying the FCC catalyst from a catalyst tank containing the FCC catalyst to the decomposition evaporation tank; and The step of supplying the polymerization inhibitor from a polymerization inhibitor feeder containing the polymerization inhibitor to the decomposition evaporation tank, wherein The heating step includes: heating the waste plastic, the FCC catalyst and the polymerization inhibitor in the decomposition evaporation tank.

4. The method for thermal decomposition of waste plastics into oil according to claim 2, further comprising: The step of supplying the waste plastic to a decomposition evaporation tank; The step of supplying the FCC catalyst to which the polymerization inhibitor is attached from a catalyst tank containing the FCC catalyst to which the polymerization inhibitor is attached to the decomposition evaporation tank, wherein The heating step includes: heating the waste plastics and the FCC catalyst to which the polymerization inhibitor is attached in the decomposition evaporation tank.

5. The method for thermal decomposition of waste plastics into oil according to claim 2, wherein The heating step comprises: The FCC catalyst coated with the polymerization inhibitor is subjected to a heating step.

6. A waste plastic thermal decomposition oiling device, the device comprising: a decomposition evaporation tank configured to heat the waste plastic and the polymerization inhibitor, gasify the polymerization inhibitor, and thermally decompose the waste plastic to generate a decomposition gas, so that the polymerization inhibitor reacts with the decomposition gas in a gas phase; as well as A condenser is connected to the decomposition evaporation tank and is configured to cool the decomposition gas supplied from the decomposition evaporation tank to produce decomposition oil.

7. The waste plastic thermal decomposition oil conversion device according to claim 6, further comprising: a raw material storage tank connected to the decomposition evaporation tank and configured to store the waste plastic and supply the waste plastic to the decomposition evaporation tank; and A polymerization inhibitor adder is connected to the decomposition evaporation tank and is configured to contain the polymerization inhibitor and supply the polymerization inhibitor to the decomposition evaporation tank.

8. The waste plastic thermal decomposition oil conversion device according to claim 6, wherein The decomposition evaporation tank is configured to heat an FCC (fluid catalytic cracking) catalyst together with the waste plastic and the polymerization inhibitor to cause the waste plastic to contact with the FCC catalyst to be thermally decomposed.

9. The waste plastic thermal decomposition oiling device according to claim 8, further comprising a catalyst tank connected to the decomposition evaporation tank and configured to contain the FCC catalyst and supply the FCC catalyst to the decomposition evaporation tank.

10. The waste plastic thermal decomposition oil conversion device according to claim 8, further comprising: A catalyst tank is connected to the decomposition evaporation tank and is configured to accommodate the FCC catalyst to which the polymerization inhibitor is attached and supply the FCC catalyst to which the polymerization inhibitor is attached to the decomposition evaporation tank.

11. The waste plastic thermal decomposition oil conversion device according to claim 10, wherein The FCC catalyst is coated with the polymerization inhibitor.

12. An FCC catalyst comprising an inhibitor.

13. The FCC catalyst according to claim 12, further comprising A matrix holding the main components of the catalyst, wherein The surface of the substrate is coated with the polymerization inhibitor.

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