JP7499682B2 - Waste plastic processing method - Google Patents

Description

The present invention relates to a method for treating waste plastics.

The low rate of effective utilization of waste plastics and environmental pollution caused by marine plastics have become global issues.
One method for recycling waste plastics is chemical recycling, and various studies have been conducted on chemical recycling technology.

For example, Patent Document 1 discloses a method that includes melting a plastic material (1) to form a plastic melt, degassing the plastic melt, and then sending the plastic melt to a depolymerization reactor (3), and adding a fraction obtained from crude oil as a solvent (6) to the plastic melt, thereby reducing the viscosity of the plastic melt solution supplied to the depolymerization reactor (3) below the viscosity of the plastic melt.

Patent Document 2 discloses a method for cracking and treating a hydrocarbon polymer in a fluid catalytic cracking (FCC) unit, characterized in that a mixture of the hydrocarbon polymer and a hydrocarbon oil selected from FCC gasoline, light cracked gas oil, heavy cracked gas oil, cracked residual oil, atmospheric residual oil, and desulfurized residual oil is mixed with FCC feedstock oil and supplied to the FCC unit.

JP 2014-518906 A JP 2002-294251 A

Patent Document 1 describes that the viscosity of a plastic melt solution is reduced by adding a solvent to the plastic melt. However, since a plastic melt solution to which a solvent has simply been added is prone to separation, the method described in Patent Document 1 may result in a plastic melt solution in an insufficiently mixed state being supplied to a depolymerization reactor. As a result, the decomposability of the plastic material may not be sufficiently improved.
Incidentally, Patent Document 1 discloses a method for mixing plastic materials in which molten plastic is continuously discharged from a depolymerization reactor by a pump and recirculated back to the depolymerization reactor. However, since this method recirculates the molten plastic to be decomposed, it is considered difficult to improve the decomposition ability of the plastic materials relative to the molten plastic supplied to the depolymerization reactor.
Patent Document 2 discloses a method for cracking a mixture of a hydrocarbon polymer and a hydrocarbon oil using an FCC unit capable of cracking high boiling fractions in crude oil into high added value gasoline and the like by catalytic reaction, but Patent Document 2 does not pay any attention to the solubility of the hydrocarbon polymer in the hydrocarbon oil, specifically, the mixability of the hydrocarbon polymer and the hydrocarbon oil. Therefore, even in the method described in Patent Document 2, the mixture in a state of insufficient mixability may be mixed with FCC feedstock oil and supplied to the FCC unit. As a result, the decomposition ability of the hydrocarbon polymer may not be sufficiently improved.

The present invention aims to provide a method for treating waste plastics that can improve the decomposition of waste plastics.

According to one aspect of the present invention, there is provided a method for treating waste plastics using a waste plastic treatment system, comprising:
Supplying waste plastic to a melting device;
A step of preparing molten waste plastic by melting the waste plastic;
A step of preparing a molten waste plastic mixed oil by supplying raw material oil to the molten waste plastic from one or more first supply lines;
Supplying the molten waste plastic mixed oil to a mixing device;
A step of preparing a mixture for decomposition treatment by mixing the molten waste plastic mixed oil supplied to the mixer;
and supplying the prepared mixture for decomposition treatment to a decomposition treatment device.
The step of preparing the mixture for decomposition treatment includes preparing the mixture for decomposition treatment so that the mixture for decomposition treatment has a kinetic viscosity at 160° C. of 1 mm ² /s or more and 60 mm ² /s or less.
A method for treating waste plastics is provided.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the mixture for decomposition processing preferably involves preparing the mixture for decomposition processing by mixing the molten waste plastic mixed oil supplied to the mixer with the raw oil supplied to the mixer from a second supply line different from the first supply line.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the decomposition mixture preferably adjusts the kinetic viscosity of the decomposition mixture by adjusting the ratio of the total supply amount of the raw oil supplied from the melting device to the mixing device to the supply amount of the waste plastic (total supply amount of the raw oil/supply amount of the waste plastic) to a mass ratio of 10 to 200.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the decomposition mixture preferably adjusts the kinetic viscosity of the decomposition mixture by adjusting the ratio of the total supply amount of the raw oil supplied from the melting device to the mixing device to the melted amount of the molten waste plastic (total supply amount of the raw oil/molten amount of the molten waste plastic) to a mass ratio of 10 to 200.

In one embodiment of the waste plastic processing method of the present invention, it is preferable to further include an additional raw material supply step of supplying at least one additional raw material oil selected from the group consisting of the raw material oil, light hydrocarbon oil, naphtha, diesel, and heavy hydrocarbon oil different from the raw material oil.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the molten waste plastic mixed oil preferably further includes the step of supplying the additional raw material, and the molten waste plastic mixed oil is prepared by further supplying at least one of the other additional raw material oils to the molten waste plastic.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the mixture for decomposition processing preferably further includes the step of supplying additional raw materials, and the mixture for decomposition processing is prepared by further mixing the molten waste plastic mixed oil with at least one of the other additional raw material oils.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the decomposition mixture preferably adjusts the kinetic viscosity of the decomposition mixture by adjusting the ratio of the total supply amount of the raw oil supplied from the melting device to the mixing device and the additional raw oil supplied from the melting device to the mixing device to the melted amount of the waste plastic (total supply amount of the raw oil and the additional raw oil/melted amount of the waste plastic) to a mass ratio of 10 to 200.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the molten waste plastic mixed oil preferably prepares the molten waste plastic mixed oil so that the melt viscosity at 200°C is 100 mPa·s or more and 50 million mPa·s or less.

In one aspect of the present invention, the first supply line has a supply line 1A for supplying raw material oil to the melting device,
It is preferable that the process for preparing the molten waste plastic mixed oil involves supplying the raw material oil to the molten waste plastic so that the ratio of the supply amount of the raw material oil supplied from the supply line 1A to the melting device to the melted amount of the molten waste plastic (supply amount of the raw material oil/melted amount of the molten waste plastic) is at least 0.5 by mass, thereby preparing the molten waste plastic mixed oil.

In one aspect of the present invention, the first supply line has a supply line 1B for supplying raw material oil to a pipe connecting the melting device and the mixing device,
It is preferable that the process for preparing the molten waste plastic mixed oil involves supplying the raw material oil to the molten waste plastic so that the ratio of the supply amount of the raw material oil supplied to the piping from the supply line 1B to the melted amount of the molten waste plastic (supply amount of the raw material oil/melted amount of the molten waste plastic) is at least 1 by mass to prepare the molten waste plastic mixed oil.

In one embodiment of the waste plastic processing method of the present invention, the step of supplying the mixture for decomposition processing to the decomposition processing device preferably includes supplying the mixture for decomposition processing to the decomposition processing device together with the raw material oil transported from a third supply line different from the first supply line.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the mixture for decomposition processing is preferably carried out under conditions of a temperature of 160°C or higher and 260°C or lower, and a rotation speed of the stirring means of 10 rpm or higher and 20,000 rpm or lower.

In one embodiment of the waste plastic processing method according to the present invention, the melting temperature of the waste plastic in the step of preparing the molten waste plastic is 175° C. or higher and 260° C. or lower;
It is preferable that the temperature of the raw material oil in the first supply line in the step of preparing the molten waste plastic mixed oil is 80°C or higher and 240°C or lower.

In the waste plastic processing method according to one embodiment of the present invention, the feedstock oil is preferably at least one selected from the group consisting of heavy cracked gas oil, cracked residual oil, atmospheric residual oil, desulfurized residual oil, desulfurized vacuum gas oil, undesulfurized vacuum gas oil, undesulfurized atmospheric residual oil, and mineral oil.

In one embodiment of the waste plastic processing method of the present invention, the feedstock oil is preferably at least one selected from the group consisting of desulfurized vacuum gas oil, heavy cracked gas oil, and desulfurized residual oil.

In the waste plastic processing method according to one aspect of the present invention, it is preferable that the waste plastic contains at least one of polyethylene-derived waste plastic and polypropylene-derived waste plastic.

In the waste plastic processing method according to one aspect of the present invention, the step of preparing the molten waste plastic is preferably carried out using a plurality of the melting devices.

In one aspect of the waste plastic processing method of the present invention, the melting device is preferably a kneader.

In one embodiment of the waste plastic processing method of the present invention, the step of preparing the mixture for decomposition processing is preferably carried out using a plurality of the mixing devices.

In one aspect of the waste plastic processing method of the present invention, the mixing device is preferably a line mixer.

In one aspect of the waste plastic processing method of the present invention, the decomposition processing device is preferably a fluid catalytic cracking device.

According to one aspect of the present invention, a method for treating waste plastics that can improve the decomposition of waste plastics can be provided.

1 is a schematic diagram of an example of a waste plastic processing system used in a waste plastic processing method of a first embodiment. FIG. 1 is a schematic diagram of an example of a waste plastic processing system used in a waste plastic processing method of a second embodiment. FIG. FIG. 11 is a schematic diagram of an example of a waste plastic processing system used in the waste plastic processing method of the third embodiment. FIG. 13 is a schematic diagram of an example of a waste plastic processing system used in the waste plastic processing method of the fourth embodiment. 13 is a schematic diagram of an example of a waste plastic processing system used in the waste plastic processing method of the fifth embodiment. FIG. FIG. 13 is a schematic diagram of an example of a waste plastic processing system used in the waste plastic processing method of the sixth embodiment. 1 is a photograph of a mixture for decomposition treatment in which molten waste plastic and raw oil are not sufficiently mixed. This is a photograph of a mixture for decomposition treatment in which molten waste plastic and raw material oil are thoroughly mixed using a mixer.

In this specification, a numerical range expressed using "~" means a range that includes the number written before "~" as the lower limit and the number written after "~" as the upper limit.

First Embodiment
The waste plastic processing method according to this embodiment (hereinafter also simply referred to as the "processing method") is as follows:
The method includes the steps of: supplying waste plastic to a melting device; preparing molten waste plastic by melting the waste plastic; preparing molten waste plastic mixed oil by supplying raw oil to the molten waste plastic from one or more first supply lines; supplying the molten waste plastic mixed oil to a mixing device; preparing a mixture for decomposition processing by mixing the molten waste plastic mixed oil supplied to the mixing device; and supplying the prepared mixture for decomposition processing to a decomposition processing device, wherein the step of preparing the mixture for decomposition processing prepares the mixture for decomposition processing so that the kinetic viscosity at 160°C is 1 ^mm2 /s or more and 60 ^mm2 /s or less.

In the processing method of this embodiment, by having the above-mentioned steps, a mixture for decomposition processing can be obtained in which the molten waste plastics are dissolved in the raw oil in a nearly uniform state, that is, a mixture for decomposition processing in which the mixability of the molten waste plastics and the raw oil is improved.
The "decomposition treatment mixture having improved mixability" will be specifically described with reference to Figures 7A and 7B.
7A is a photograph of a mixture of molten waste plastic and raw oil in a state where the two are not sufficiently mixed. It can be seen that the molten waste plastic is dissolved in the raw oil, but is partially mottled.
7B is a photograph of a mixture for decomposition treatment prepared by mixing molten waste plastics and raw oil using a mixer. It can be seen that the molten waste plastics are uniformly dissolved in the raw oil. This mixed state of the molten waste plastics and raw oil corresponds to the mixed state of the mixture for decomposition treatment prepared in the "process of preparing a mixture for decomposition treatment" of this embodiment.
Moreover, the mixture for decomposition treatment prepared in the "step of preparing a mixture for decomposition treatment" has a kinetic viscosity at 160° C. adjusted to be within a predetermined range (1 mm ² /s or more and 60 mm ² /s or less).
According to the processing method of this embodiment, the mixability of the molten waste plastic and the raw oil is improved, and a mixture for cracking processing having a kinetic viscosity adjusted to a predetermined range can be supplied to a cracking processing device, thereby improving the decomposition ability of the waste plastic in the mixture for cracking processing.
Furthermore, according to the treatment method of this embodiment, the mixture for decomposition treatment, the kinetic viscosity of which is adjusted to a predetermined range, can be supplied to the decomposition treatment device, thereby reducing the load on transportation means such as pumps.

In the processing method of this embodiment, the step of preparing a mixture for decomposition processing is preferably a step of preparing a mixture for decomposition processing by mixing the molten waste plastic mixed oil supplied to the mixing device with raw material oil supplied to the mixing device from a second supply line different from the first supply line.
This makes it easier to adjust the kinetic viscosity of the decomposition treatment mixture at 160°C to within a predetermined range.

The treatment method of the first embodiment is an example carried out using a waste plastic treatment system (hereinafter, also simply referred to as a "treatment system") shown in FIG.
First, a processing system 100 shown in FIG. 1 will be described, and then a processing method according to the first embodiment will be described.

<Overall composition>
FIG. 1 is a schematic diagram of an example of a processing system used in the processing method of the first embodiment.
The processing system 100 shown in Fig. 1 includes a kneader 20 as a melting device, a line mixer 30 as a mixing device, and a residual oil fluid catalytic cracking unit (RFCC unit 50) (one embodiment of an FCC unit) as a cracking processing unit. The processing system 100 shown in Fig. 1 also includes a heat exchanger HE as a feed oil temperature control means.
In the following description, the ordinal expressions such as "first", "second" and "third" are intended to distinguish components and do not indicate an order.

The processing system 100 comprises a kneader 20 that prepares molten waste plastics by melting waste plastics, a line mixer 30 that prepares a mixture for decomposition processing by mixing the molten waste plastics prepared by the kneader 20 with a mixture of raw oil (molten waste plastic mixed oil), an RFCC device 50 that decomposes both the molten waste plastics and the raw oil in the mixture for decomposition processing prepared by the line mixer 30, and a second storage tank 40 provided between the line mixer 30 and the RFCC device 50.
The treatment system 100 is also provided with a first transport line 10 (an example of a third supply line) connected to the RFCC device 50 and transporting raw oil to the RFCC device 50, a piping (hereinafter also referred to as a "molten waste plastic mixed oil supply line") connecting the kneader 20 and the line mixer 30, a molten waste plastic mixed oil supply line 15 that supplies the molten waste plastic mixed oil from the kneader 20 to the line mixer 30, a supply line 12 (an example of a first supply line, an example of a supply line 1B) that connects the first transport line 10 and the molten waste plastic mixed oil supply line 15 and supplies raw oil from the first transport line 10 to the molten waste plastic mixed oil supply line 15, and a second transport line 14 that transports the decomposition treatment mixture prepared in the line mixer 30 from the line mixer 30 to the first transport line 10. In the case of FIG. 1, the decomposition treatment mixture is stored in the second storage tank 40 and then transported to the first transport line 10 via the second transport line 14 by the centrifugal pump 41.
The processing system 100 also includes a waste plastic supply control means 25 that controls the amount of waste plastic supplied to the kneader 20, a second raw oil supply control means 121 that controls the amount of raw oil supplied from the supply line 12 to the molten waste plastic mixed oil supply line 15, and a heat exchanger HE (an example of a raw oil temperature control means) that controls the temperature of the raw oil.

<Kneader 20>
The kneader 20 prepares (obtains) molten waste plastics by melting the waste plastics.
The kneader 20 is connected to a waste plastic supply control means 25 for controlling the amount of waste plastic supplied.
The waste plastic supply control means 25 has a feeder 21 as a waste plastic supply means, and a feeder controller 24 that controls the operation of the feeder 21. The waste plastic supply control means 25 controls the amount of waste plastic supplied by transmitting a control signal from the feeder controller 24 to the feeder 21 and controlling the operation of the feeder 21. The feeder controller 24 can use a microcomputer or the like.
Further, the kneader 20 is connected to a feeder 21 and a hopper 22 via a waste plastic supply line 23. The hopper 22 has a supply port (not shown) at a lower portion, and is capable of supplying waste plastic to the feeder 21 from the supply port.

The waste plastic supply control means 25 may control the amount of melted molten waste plastic by controlling the amount of waste plastic supplied from the feeder 21 to the kneader 20. The amount of melted molten waste plastic is calculated from the amount of waste plastic supplied to the kneader 20. In this case, the waste plastic supply control means 25 controls the amount of melted molten waste plastic by transmitting a control signal from the feeder controller 24 to the feeder 21 and controlling the operation of the feeder 21.

<First transportation line 10>
The first transportation line 10 is connected to the RFCC unit 50 and transports the raw oil to the RFCC unit 50. The first transportation line 10 shown in Fig. 1 has a branching point B1 at the upstream side where it branches off to a supply line 12, and a junction C1 at the downstream side where it merges with the second transportation line 14.
The raw oil in the first transport line 10 is preferably heated to, for example, 80° C. or more and 240° C. or less, and more preferably heated to 160° C. or more and 230° C. or less. The temperature of the raw oil in the first transport line 10 can be controlled, for example, by a temperature control means (e.g., a heat exchanger, a heater, etc.) installed at any position in the first transport line 10.

<Molten waste plastic mixed oil supply line 15>
The molten waste plastic mixed oil supply line 15 connects the kneader 20 and the line mixer 30. The molten waste plastic mixed oil supply line 15 merges (mixes) the molten waste plastic prepared in the kneader 20 with the raw oil transported from the supply line 12 at the junction C2 to produce molten waste plastic mixed oil (a mixture of molten waste plastic and raw oil), and supplies the molten waste plastic mixed oil to the line mixer 30.
The temperature of the molten waste plastic mixed oil supply line 15 is, for example, 160° C. or more and 260° C. or less. The temperature of the molten waste plastic mixed oil supply line 15 can be controlled, for example, by a temperature control means (for example, a heat exchanger, a heater, etc.) installed at any position of the molten waste plastic mixed oil supply line 15.

<Supply line 12>
The supply line 12 connects the first transportation line 10 to the molten waste plastic mixed oil supply line 15 , and supplies raw oil from the first transportation line 10 to the molten waste plastic mixed oil supply line 15 .
In the case of FIG. 1, the supply line 12 supplies raw material oil from a branch point B1 of the first transportation line 10 to a junction C2 with the molten waste plastic mixed oil supply line 15.
A second feedstock oil supply control means 121 is provided in the supply line 12 to control the amount of feedstock oil supplied to the junction C2.
The second feedstock oil supply control means 121 has a second adjustment valve 122 as a feedstock oil supply means, and a second controller 123 .
The second feedstock oil supply control means 121 controls the amount of feedstock oil supplied by transmitting a control signal from the second controller 123 to the second control valve 122 and controlling the operation of the second control valve 122. The second controller 123 can be a microcomputer or the like.
From the viewpoint of mixing the raw oil and the molten waste plastic well, the raw oil in the supply line 12 is preferably heated to, for example, 80° C. or more and 240° C. or less, and more preferably heated to 160° C. or more and 230° C. or less. The temperature of the raw oil in the supply line 12 can be controlled, for example, by a temperature control means (e.g., a heat exchanger, a heater, etc.) installed at any position in the supply line 12. The temperature of the raw oil is the set temperature of the temperature control means.
In the case of FIG. 1, the temperature of the feed oil in the supply line 12 is controlled by a heat exchanger HE disposed midway along the supply line 12 .
The number and installation locations of the heat exchangers HE are not particularly limited. For example, a plurality of heat exchangers HE may be provided in the first transport line 10 and the supply line 12 to heat the feed oil in stages.

<Line mixer 30>
The line mixer 30 prepares (obtains) a mixture for decomposition treatment by mixing a mixture of molten waste plastics and raw oil (molten waste plastic mixed oil).
The kinematic viscosity of the prepared mixture for decomposition treatment is adjusted to a predetermined range from the viewpoint of improving the decomposition property of the waste plastics. The predetermined range will be described later.
The line mixer 30 has a stirring means (for example, a rotor or the like).
The line mixer 30 is not particularly limited, and an in-line mixer (for example, a static mixer) can be used. The line mixer 30 may be a continuous mixer.

<Second storage tank 40>
The second storage tank 40 stores the decomposition treatment mixture prepared in the line mixer 30. A centrifugal pump 41 is connected to the second storage tank 40. The pump is preferably selected appropriately depending on the kinetic viscosity of the decomposition treatment mixture. For example, a gear pump may be used as the pump. The second storage tank 40 is preferably equipped with a pump as a means for supplying the decomposition treatment mixture, but the decomposition treatment mixture may be supplied to the second transport line 14 by its own pressure.
The second storage tank 40 preferably has a venting means for discharging gases (e.g., carbon dioxide gas, water vapor, volatile organic compounds, etc.) generated from the decomposition mixture. The venting means is not particularly limited, but may be, for example, a venting pipe.
By providing the second storage tank 40 with a gas venting means, foaming of the decomposition mixture can be prevented or reduced, and the mixture can be smoothly transferred, which is expected to improve operability. As a result, it is believed that the decomposition efficiency of waste plastics can be improved.
In addition, the second storage tank 40 may have a stirring means (e.g., a rotor or the like) from the viewpoint of further improving the mixability of the decomposition treatment mixture.
The temperature of the second storage tank 40 is preferably heated to, for example, 160° C. or more and 240° C. or less from the viewpoint of maintaining the molten state of the molten waste plastic in the decomposition treatment mixture and maintaining the kinetic viscosity of the decomposition treatment mixture within a predetermined range. The second storage tank 40 is preferably equipped with a temperature detection means (e.g., a thermometer, etc.), and the temperature of the second storage tank 40 is preferably controlled by a temperature control means (e.g., a heat exchanger, a heater, etc.).

<RFCC device 50>
The RFCC device 50 decomposes both the molten waste plastics and the raw oil in the mixture for decomposition treatment prepared in the line mixer 30 .
The RFCC unit 50 is one embodiment of a fluid catalytic cracking unit (FCC unit).
The RFCC unit 50 and the FCC unit may be units commonly used in the field of petroleum refining, and basically consist of a reaction tower, a catalyst/product oil separator, a section for removing oil from the catalyst surface, and a catalyst regeneration tower, with the catalyst circulating within this system.
The catalyst used is usually a catalyst containing synthetic zeolite, and the process may be any process developed by UOP, IFP, or the like.
The catalysts and operating conditions used in the RFCC unit 50 and the FCC unit are not particularly limited and can be set appropriately.

<Second transport line 14>
The second transport line 14 transports the decomposition treatment mixture prepared in the line mixer 30 from the line mixer 30 to the first transport line 10 using a centrifugal pump 41.
From the viewpoint of transporting the mixture for cracking treatment while maintaining the kinetic viscosity of the mixture for cracking treatment within a predetermined range, the temperature of the feed oil in the second transport line 14 is preferably heated to, for example, 160° C. or more and 240° C. or less. The temperature of the feed oil in the second transport line 14 can be controlled by a temperature control means (e.g., a heat exchanger, a heater, etc.) installed at any position in the second transport line 14.

[Treatment method of the first embodiment]
The processing method of the first embodiment is carried out through the following steps when the processing system 100 shown in FIG.
In the following description, the process of supplying waste plastic may be referred to as the "waste plastic supply process ST1", the process of preparing molten waste plastic may be referred to as the "molten waste plastic preparation process ST2", the process of preparing molten waste plastic mixed oil may be referred to as the "molten waste plastic mixed oil preparation process ST3", the process of supplying molten waste plastic mixed oil to the mixing device may be referred to as the "molten waste plastic mixed oil supply process ST4", the process of preparing a mixture for decomposition treatment may be referred to as the "mixture for decomposition treatment preparation process ST5", and the process of supplying the mixture for decomposition treatment to the decomposition treatment device may be referred to as the "mixture for decomposition treatment supply process ST6".

<Waste plastic supply process ST1>
The waste plastic supplying step ST1 is a step of supplying waste plastic to the kneader 20. In the case of Fig. 1, waste plastic is supplied to the kneader 20 from a feeder 21 serving as a waste plastic supplying means. The method of supplying waste plastic to the kneader 20 is not particularly limited.
The amount of waste plastic supplied to the kneader 20 is controlled by a waste plastic supply control means 25 .
In this specification, the supply amount of waste plastic means the amount (mass) of waste plastic supplied per unit time.

<Molten waste plastic preparation process ST2>
The molten waste plastic preparation step ST2 is a step of preparing molten waste plastic by melting waste plastic.
In this specification, molten waste plastic means solid waste plastic that has been melted and liquefied. Therefore, the only difference between molten waste plastic and solid waste plastic is the state of the material.
The waste plastic is melted in the kneader 20 to become molten waste plastic, and is discharged from the kneader 20 in a molten state, a dissolved state, or as a slurry.
The melting temperature of the waste plastic is preferably 175° C. or more and 260° C. or less, and more preferably 200° C. or more and 240° C. or less. The melting temperature of the waste plastic is the set temperature of the kneader 20.
The amount of molten waste plastic prepared in the kneader 20 is controlled by a waste plastic supply control means 25 .
In this specification, the melting amount of the molten waste plastic means the amount (mass) of the waste plastic melted per unit time. The melting amount of the molten waste plastic is calculated from the supply amount of the waste plastic.
The kneading machine 20 is not particularly limited, but examples thereof include an extruder (for example, a single-screw extruder or a multi-screw extruder), a kneader, and a mixer.

<Molten waste plastic mixed oil preparation process ST3>
The molten waste plastic mixed oil preparation process ST3 is a process for preparing molten waste plastic mixed oil by supplying raw material oil to molten waste plastic.
In the case of Figure 1, the molten waste plastic discharged from the kneader 20 is transported through the molten waste plastic mixed oil supply line 15, and at the junction C2, it is merged (mixed) with the raw oil transported from the supply line 12, and molten waste plastic mixed oil is prepared.

The amount of raw oil supplied from the supply line 12 to the molten waste plastic mixed oil supply line 15 is controlled by a second raw oil supply control means 121 .
In this specification, the feedstock oil supply amount means the amount (mass) supplied per unit time.
The number of supply lines 12 is not limited and may be one or two or more.

(Viscosity of mixed oil of molten waste plastic)
The molten waste plastic mixed oil preparation process ST3 is preferably a process of supplying raw material oil to the molten waste plastic so that the melt viscosity of the resulting molten waste plastic mixed oil at 200°C is 100 mPa·s or more and 50 million mPa·s or less.
The melt viscosity of the molten waste plastic mixed oil at 200° C. is more preferably 1,000 mPa·s or more and 25,000,000 mPa·s or less.
When the melt viscosity (200°C) of the molten waste plastic mixed oil is 100 mPa·s or more and 50 million mPa·s or less, in the decomposition treatment mixture preparation step ST5, it becomes easier to obtain a decomposition treatment mixture whose kinetic viscosity is adjusted to a predetermined range. In addition, the transportability of the molten waste plastic mixed oil is improved.
The melt viscosity at 200° C. was measured using a rheometer (MCR302 (product number) manufactured by Anton Paar) under the following conditions using a cone plate as a measuring tool.
<Conditions>
- Cone-plate measuring system: DIN EN (compliant with ISO 3219 and DIN 53019)
Angular frequency (ω): 0.1 rad/sec to 100 rad/sec Measurement temperature: 200°C
・Sample weight: 0.1g to 0.3g

<Molten waste plastic mixed oil supply process ST4>
The molten waste plastic mixed oil supplying process ST4 is a process of supplying the molten waste plastic mixed oil to the line mixer 30.
In the case of FIG. 1, the molten waste plastic mixed oil prepared at the junction C2 is supplied from the molten waste plastic mixed oil supply line 15 to the line mixer 30.

<Decomposition treatment mixture preparation step ST5>
The decomposition treatment mixture preparation step ST5 is a step of preparing a decomposition treatment mixture by mixing the molten waste plastic mixed oil supplied to the line mixer 30.
The decomposition treatment mixture preparation step ST5 is a step of preparing a decomposition treatment mixture so that the kinetic viscosity at 160° C. is 1 mm ² /s or more and 60 mm ² /s or less.
A decomposition mixture having a kinetic viscosity of 1 mm ² /s or more at 160° C. indicates that the mixture contains a high concentration of waste plastics. Therefore, when the decomposition mixture has a kinetic viscosity of 1 mm ² /s or more at 160° C., the mixture can efficiently decompose the waste plastics together with the raw material oil.
When the kinetic viscosity of the mixture for decomposition treatment at 160° C. is 60 mm ² /s or less, the feedability of the mixture for decomposition treatment to the decomposition treatment device is easily improved.
The kinematic viscosity of the mixture for decomposition treatment at 160° C. is preferably 1 mm ² /s or more and 40 mm ² /s or less, and more preferably 1 mm ² /s or more and 30 mm ² /s or less.
The kinematic viscosity at 160° C. is a value measured in accordance with JIS K 2283 (2000) “Crude oil and petroleum products--Kinematic viscosity test method and viscosity index calculation method”.

From the viewpoint of adjusting the kinetic viscosity of the decomposition mixture at 160°C to a predetermined range, in the case of FIG. 1, the decomposition mixture preparation process ST5 is preferably a process for adjusting the kinetic viscosity of the decomposition mixture by adjusting the ratio of the supply amount of raw oil supplied from the supply line 12 as the first supply line to the molten waste plastic mixed oil supply line 15 to the supply amount of waste plastic (supply amount of said raw oil/supply amount of said waste plastic) to a mass ratio of 10 or more and 200 or less (preferably 20 or more and 200 or less).

As a method for adjusting the kinetic viscosity of the decomposition mixture at 160°C to a predetermined range, it is also preferable to adjust the melting conditions of the kneader 20 (e.g., temperature, screw rotation speed and time, etc.), the mixing conditions of the line mixer 30 (e.g., temperature, stirring means rotation speed and time, etc.), the temperature of the first transport line 10, and the temperature of each supply line (in the case of Figure 1, the temperature of the supply line 12).

In the decomposition treatment mixture preparation step ST5, it is preferable to prepare the decomposition treatment mixture under conditions of a temperature of 160° C. or more and 260° C. or less and a rotation speed of the stirring means of 10 rpm or more and 20,000 rpm or less.
In the decomposition treatment mixture preparation step ST5, when the temperature and the rotation speed of the stirring means are within the above ranges, it becomes easy to adjust the kinetic viscosity of the decomposition treatment mixture at 160° C. to a predetermined range (1 mm ² /s or more and 60 mm ² /s or less).
The temperature in the decomposition treatment mixture preparation step ST5 is more preferably 170° C. or higher and 240° C. or lower. The rotation speed of the stirring means is more preferably 100 rpm or higher and 10,000 rpm or lower.

<Second storage step ST20>
The treatment method of the first embodiment includes a step of storing the decomposition treatment mixture in a second storage tank 40 (hereinafter also referred to as the "second storage step ST20").
In the case of FIG. 1 , the mixture for decomposition treatment is discharged from the line mixer 30 and then stored in the second storage tank 40 .
In the second storage step ST20, it is preferable to carry out a degassing step in which gases (e.g., carbon dioxide gas, water vapor, and volatile organic compounds) generated from the decomposition treatment mixture are discharged from the second storage tank 40 through a degassing means. The degassing means is not particularly limited, but may be, for example, a degassing pipe.
By performing a degassing process from the second storage tank 40, foaming of the mixture for decomposition treatment can be prevented or reduced, and the mixture for decomposition treatment can be smoothly transported to the decomposition treatment device, which is expected to improve operability.

<Decomposition treatment mixture supplying step ST6>
The decomposition treatment mixture supplying step ST6 is a step of supplying the prepared decomposition treatment mixture to the RFCC device 50.
In the case of Fig. 1, the mixture for cracking treatment is stored in the second storage tank 40 and then transported to the junction C1 via the second transport line 14. At the junction C1, the mixture for cracking treatment is merged (mixed) with the raw oil transported to the RFCC device 50 from the first transport line 10 (an example of a third supply line) different from the supply line 12, and is supplied to the RFCC device 50 together with the raw oil. That is, the mixture for cracking treatment supply step ST6 of the first embodiment supplies the mixture for cracking treatment to the RFCC device 50 together with the raw oil transported from the first transport line 10 (an example of a third supply line).

＜Effects＞
In the treatment method of the first embodiment, at the confluence C2, the raw oil transported from the supply line 12 is supplied to the molten waste plastic prepared in the kneader 20 (first mixing), and a molten waste plastic mixed oil is prepared (molten waste plastic mixed oil preparation step ST3). Next, the molten waste plastic mixed oil is supplied to the line mixer 30 (molten waste plastic mixed oil supply step ST4), and further mixed in the line mixer 30 (second mixing), and a mixture for cracking treatment is prepared (mixture for cracking treatment preparation step ST5).
In this way, in the treatment method of the first embodiment, the molten waste plastics and raw oil are premixed in the treatment system, and then further mixed in the line mixer 30 to prepare a mixture for decomposition treatment. Therefore, the prepared mixture for decomposition treatment is a mixture in which the molten waste plastics are dissolved in the raw oil in a nearly uniform state, and the kinetic viscosity (160°C) is adjusted to a predetermined range.
Therefore, according to the treatment method of the first embodiment, the mixability of the molten waste plastics and the raw oil is improved, and the mixture for decomposition treatment, the kinetic viscosity (160°C) of which is adjusted to a predetermined range, is supplied to the RFCC device 50, so that the decomposition ability of the waste plastics can be improved. Also, the decomposition ability of the raw oil can be improved.

Second Embodiment
The second embodiment will be described focusing on the differences from the first embodiment, and the description of similar items will be omitted or simplified by using the same reference numerals, for example.
The second embodiment is an example in which a processing method is carried out using a waste plastic processing system shown in Fig. 2. First, the processing system 200 shown in Fig. 2 will be described, and then the processing method of the second embodiment will be described.

<Overall composition>
FIG. 2 is a schematic diagram of an example of a processing system used in the processing method of the second embodiment.
The processing system 200 shown in FIG. 2 includes a kneader 20, a line mixer 30, an RFCC device 50, a first transport line 10, a molten waste plastic mixed oil supply line 15, a supply line 11 (an example of a first supply line, an example of a supply line 1A), a supply line 13 (an example of a second supply line), a second transport line 14, a first storage tank 60, and a second storage tank 40.
The processing system 200 also includes a waste plastic supply control means 25, a first raw oil supply control means 111 for controlling the amount of raw oil supplied from the supply line 11 to the kneader 20, a third raw oil supply control means 131 for controlling the amount of raw oil supplied from the supply line 13 to the line mixer 30, and a heat exchanger HE for controlling the temperature of the raw oil.
Equipped with.
2 differs from the processing system 100 described in the first embodiment in that the processing system 200 includes a supply line 11, a supply line 13, a first storage tank 60, and does not include a supply line 12. The other points are the same as those of the first embodiment.

<First storage tank 60>
The first storage tank 60 stores a mixture of the molten waste plastics prepared in the kneader 20 and the raw oil supplied from the supply line 11 to the kneader 20 (hereinafter, also referred to as "molten waste plastic mixed oil A"). A gear pump 61 is connected to the first storage tank 60. The first storage tank 60 is preferably equipped with a pump as a means for supplying the molten waste plastic mixed oil A, but the molten waste plastic mixed oil A may be supplied to the molten waste plastic mixed oil supply line 15 by its own pressure.
The first storage tank 60 preferably has a degassing means for discharging gas (e.g., carbon dioxide gas, water vapor, volatile organic compounds, etc.) generated from the molten waste plastic mixed oil A. The degassing means is not particularly limited, but may be, for example, a degassing pipe.
By providing the first storage tank 60 with a gas venting means, foaming of the molten waste plastic mixed oil A can be prevented or reduced, the molten waste plastic mixed oil can be transferred smoothly, and operability can be improved. As a result, it is believed that the efficiency of decomposing waste plastics can be improved.
In addition, the first storage tank 60 may have a stirring means (e.g., a rotor, etc.) in order to further improve the mixability of the molten waste plastic mixed oil A.
The temperature of the first storage tank 60 is preferably, for example, 160° C. or more and 260° C. or less, and more preferably 175° C. or more and 260° C. or less. The first storage tank 60 is preferably equipped with a temperature detection means (e.g., a thermometer, etc.), and the temperature of the first storage tank 60 is preferably controlled by a temperature control means (e.g., a heat exchanger, a heater, etc.).

<Supply line 11>
The supply line 11 connects the first transport line 10 to the kneader 20 and supplies the raw oil from the first transport line 10 to the kneader 20 .
In the case of FIG. 2 , the supply line 11 branches off from a branch point B 1 of the first transport line 10 , and further branches off at a branch point B 2 to supply the raw material oil to the outlet side of the kneader 20 .
A first raw material oil supply control means 111 for controlling the amount of raw material oil supplied to the kneader 20 is provided in the supply line 11 .
The first feedstock oil supply control means 111 has a first adjustment valve 112 as a feedstock oil supply means, and a first controller 113 .
The first feedstock oil supply control means 111 controls the amount of feedstock oil supplied by transmitting a control signal from the first controller 113 to the first control valve 112 and controlling the operation of the first control valve 112. The first controller 113 can be a microcomputer or the like.

<Supply line 13>
The supply line 13 serving as a second supply line connects the first transport line 10 and the line mixer 30 and supplies the raw oil from the first transport line 10 to the line mixer 30 .
In the case of FIG. 2 , the supply line 13 branches off from a branch point B 1 of the first transportation line 10 , and further branches off at a branch point B 2 to supply the raw material oil to the line mixer 30 .
A third feedstock oil supply control means 131 for controlling the amount of feedstock oil supplied is provided in the supply line 13 .
The third feedstock oil supply control means 131 has a third adjustment valve 132 as a feedstock oil supply means, and a third controller 133 .
The third feedstock oil supply control means 131 controls the amount of feedstock oil supplied by transmitting a control signal from the third controller 133 to the third adjustment valve 132 and controlling the operation of the third adjustment valve 132. The third adjustment valve 132 can use a microcomputer or the like.

[Treatment method according to the second embodiment]
The processing method of the second embodiment differs from the first embodiment mainly in the molten waste plastic preparation step ST2, the molten waste plastic mixed oil preparation step ST3, and the decomposition treatment mixture preparation step ST5.
The processing method of the second embodiment will be described focusing on the differences from the first embodiment.

<Molten waste plastic preparation process ST2 and molten waste plastic mixed oil preparation process ST3>
In the second embodiment, the molten waste plastic preparation process ST2 and the molten waste plastic mixed oil preparation process ST3 are carried out substantially simultaneously.
In the case of FIG. 2 , waste plastics supplied to the kneader 20 are melted to prepare molten waste plastics, and raw oil transported through a supply line 11 is supplied to the outlet side of the kneader 20 .
In the kneader 20, the molten waste plastics are mixed with the raw oil transported from the supply line 11 to prepare a molten waste plastic mixed oil A (a mixture of molten waste plastics and raw oil).
The melting temperature of the waste plastic is preferably in the same range as in the first embodiment.
The amount of the raw oil supplied from the supply line 11 to the kneader 20 is controlled by a first raw oil supply control means 111 .
The temperature of the raw oil in the supply line 11 is preferably 80° C. or more and 240° C. or less, more preferably 160° C. or more and 230° C. or less, from the viewpoint of mixing the molten waste plastics and the raw oil well.
The temperature of the raw oil in the supply line 11 can be controlled, for example, by a temperature control means (e.g., a heat exchanger, a heater, etc.) installed at an arbitrary position in the supply line 11. The temperature of the raw oil in the supply line 11 is the set temperature of the temperature control means. In the case of Fig. 2, the temperature of the raw oil in the supply line 11 is controlled by a heat exchanger HE arranged between the branch point B1 and the branch point B2.
The number of supply lines 11 is not limited, and may be one or two or more.

The melt viscosity at 200°C of the molten waste plastic mixed oil A prepared in the molten waste plastic mixed oil preparation process ST3 is preferably 100 mPa·s or more and 50 million mPa·s or less, and more preferably 1000 mPa·s or more and 25 million mPa·s or less.
From the viewpoint of adjusting the melt viscosity (200°C) of the molten waste plastic mixed oil within the above range, in the molten waste plastic mixed oil preparation process ST3, it is preferable that the ratio of the amount of raw material oil supplied from the supply line 11 (an example of the supply line 1A) to the melted amount of molten waste plastic (the supply amount of the raw material oil/the melted amount of the molten waste plastic) is at least 0.5 or more in mass ratio.

<First storage step ST10>
The treatment method of the second embodiment includes a process of storing molten waste plastic mixed oil A in a first storage tank 60 (hereinafter also referred to as the "first storage process ST10").
In the case of FIG. 2 , the molten waste plastic mixed oil A is discharged from the kneader 20 and stored in the first storage tank 60 .
In the first storage step ST10, it is preferable to carry out a degassing step in which gases (e.g., carbon dioxide gas, water vapor, and volatile organic compounds) generated from the molten waste plastic mixed oil A are discharged from the first storage tank 60 through a degassing means. The degassing means is not particularly limited, but may be, for example, a degassing pipe.
By performing a degassing process from the first storage tank 60, foaming of the molten waste plastic mixed oil A can be prevented or reduced, and the molten waste plastic mixed oil A can be transported smoothly, which is expected to improve operability.

<Molten waste plastic mixed oil supply process ST4>
In the case of FIG. 2 , the molten waste plastic mixed oil A is stored in a first storage tank 60 and then supplied to the line mixer 30 via the molten waste plastic mixed oil supply line 15 by a gear pump 61 .

<Decomposition treatment mixture preparation step ST5>
In the case of FIG. 2, the molten waste plastic mixed oil A supplied to the line mixer 30 is mixed with the raw material oil supplied from the supply line 13, and a mixture for cracking treatment is prepared (obtained).
The prepared mixture for decomposition treatment has a kinetic viscosity at 160° C. of 1 mm ² /s or more and 60 mm ² /s or less.
The conditions of temperature and rotation speed of the stirring means in the decomposition treatment mixture preparation step ST5 are preferably in the same range as in the first embodiment.
From the viewpoint of adjusting the kinetic viscosity (160°C) of the decomposition treatment mixture to a predetermined range,
The decomposition treatment mixture preparation process ST5 is preferably a process for adjusting the dynamic viscosity of the decomposition treatment mixture by adjusting the ratio of the total supply amount of raw oil supplied from the kneader 20 to the line mixer 30 to the supply amount of waste plastic (total supply amount of raw oil/supply amount of waste plastic) to a mass ratio of 10 or more and 200 or less (preferably 20 or more and 200 or less).
When the ratio (total supply amount of the raw material oil/supply amount of the waste plastic) is 10 or more in mass ratio, the kinetic viscosity of the decomposition treatment mixture can be adjusted to a kinetic viscosity (160°C) at which the waste plastic is easily decomposed.
When the ratio (total amount of the raw material oil supplied/amount of the waste plastic supplied) is 200 or less in mass ratio, the kinetic viscosity of the mixture for decomposition treatment can be adjusted to a kinetic viscosity (160°C) that makes it easy to supply to the decomposition treatment device.
In addition, it is also preferable that the decomposition treatment mixture preparation process ST5 is a process for adjusting the dynamic viscosity of the decomposition treatment mixture by adjusting the ratio of the total supply amount of raw material oil supplied from the kneader 20 to the line mixer 30 to the melted amount of molten waste plastic (total supply amount of raw material oil/molten amount of molten waste plastic) to a mass ratio of 10 to 200 (preferably 20 to 200).
In the case of FIG. 2 , “the total supply amount of the raw material oil supplied from the kneader 20 to the line mixer 30” is the total supply amount of the raw material oil supplied from the supply line 11 to the kneader 20 and the raw material oil supplied from the supply line 13 to the line mixer 30.
The temperature of the raw oil in the supply line 13 is preferably 80°C or higher and 240°C or lower, more preferably 160°C or higher and 230°C or lower.
The temperature of the raw oil in the supply line 13 can be controlled, for example, by a temperature control means (e.g., a heat exchanger, a heater, etc.) installed at an arbitrary position in the supply line 13. The temperature of the raw oil in the supply line 13 is the set temperature of the temperature control means. In the case of Fig. 2, the temperature of the raw oil in the supply line 13 is controlled by a heat exchanger HE arranged between the branch point B1 and the branch point B2.
The number of supply lines 13 is not limited, and may be one or two or more.

<Second storage step ST20>
As in the first embodiment, the decomposition treatment mixture discharged from the line mixer 30 is stored in the second storage tank 40.

<Decomposition treatment mixture supplying step ST6>
The mixture for cracking treatment discharged from the line mixer 30 is stored in the second storage tank 40, and then transported by a centrifugal pump 41 through the second transport line 14 to the junction C1 with the first transport line 10. At the junction C1, the mixture for cracking treatment is merged (mixed) with the raw oil transported from the first transport line 10 (an example of a third supply line) to the RFCC unit 50, and supplied to the RFCC unit 50.

＜Effects＞
In the processing method of the second embodiment, in the kneader 20, the raw oil transported from the supply line 11 is supplied to the molten waste plastic (first mixing), and the molten waste plastic mixed oil A is prepared (molten waste plastic preparation step ST2 and molten waste plastic mixed oil preparation step ST3). Next, the molten waste plastic mixed oil A is further mixed with the raw oil supplied from the supply line 13 in the line mixer 30 (second mixing), and the mixture for cracking treatment is prepared (mixture for cracking treatment preparation step ST5).
In addition, the molten waste plastic mixed oil A is also mixed in the first storage tank 60.
In this way, in the treatment method of the second embodiment, the molten waste plastics and raw oil are mixed in advance several times within the treatment system, and then further mixed in the line mixer 30 to prepare a mixture for decomposition treatment. Therefore, the prepared mixture for decomposition treatment is a mixture in which the molten waste plastics are dissolved in the raw oil in a nearly uniform state, and the kinetic viscosity (160°C) is adjusted to a predetermined range.
Therefore, according to the treatment method of the second embodiment, the mixability of the molten waste plastics and the raw oil is improved, and the mixture for decomposition treatment, the kinetic viscosity (160°C) of which is adjusted to a predetermined range, is supplied to the RFCC device 50, so that the decomposition ability of the waste plastics can be improved. Also, the decomposition ability of the raw oil can be improved.
In particular, according to the treatment method of the second embodiment, the molten waste plastic mixed oil A stored in the first storage tank 60 is supplied from the molten waste plastic mixed oil supply line 15 to the line mixer 30 by the gear pump 61. Therefore, in the decomposition treatment mixture preparation process ST5, the viscosity fluctuation range of the decomposition treatment mixture in the line mixer can be reduced, making it easier to obtain a decomposition treatment mixture with an adjusted kinetic viscosity. As a result, it is believed that the decomposition treatment mixture can be transported stably and smoothly to the RFCC device 50, and the waste plastic can be efficiently decomposed.

Third Embodiment
The third embodiment will be described with a focus on the differences from the first and second embodiments, and the same reference numerals will be used to denote similar items, and the description thereof will be omitted or simplified. The third embodiment is an example of a processing method using the waste plastic processing system shown in Fig. 3. First, the processing system 300 shown in Fig. 3 will be described, and then the processing method of the third embodiment will be described.

<Overall composition>
FIG. 3 is a schematic diagram of an example of a processing system used in the processing method of the third embodiment.
The processing system 300 shown in Fig. 3 is different from the processing system 200 described in the second embodiment in that it further includes a supply line 12 (one example of the first supply line, one example of the supply line 1B) that supplies raw material oil to a molten waste plastic mixed oil supply line 15 (a pipe that connects the kneader 20 and the line mixer 30) as a first supply line, and that it also includes gas vent lines 43 and 44. The other points are the same as those of the second embodiment.

<Supply line 12>
The supply line 12 shown in Figure 3 branches off from the branch point B1 of the first transportation line 10, and further branches off at branch points B2 and B3 to supply raw oil to the junction C3 with the molten waste plastic mixed oil supply line 15.
A second feed oil supply control means 121 having the same configuration as that of the first embodiment is provided in the supply line 12 .

[Treatment method according to the third embodiment]
The treatment method of the third embodiment is different from the second embodiment mainly in the molten waste plastic mixed oil preparation step ST3. The treatment method of the third embodiment will be described focusing on the points different from the second embodiment.

<Molten waste plastic mixed oil preparation process ST3>
In the case of Figure 3, the molten waste plastic mixed oil A (a mixture of molten waste plastic and raw oil) prepared in the kneader 20 is discharged from the kneader 20 and then mixed with the raw oil transported from the supply line 12 at the junction C3 along the molten waste plastic mixed oil supply line 15, to prepare a mixture of molten waste plastic A and raw oil (hereinafter also referred to as "molten waste plastic mixed oil B").
The temperature of the raw oil in the supply line 12 is preferably in the same range as the temperature of the raw oil in the supply line 12 described in the first embodiment. The temperatures of the raw oil in the supply lines 11 and 13 are preferably in the same range as the second embodiment.
In the molten waste plastic mixed oil preparation process ST3, it is preferable that the ratio of the amount of raw oil supplied from the supply line 11 (an example of the supply line 1A) to the melted amount of molten waste plastic (the supply amount of the raw oil/the melted amount of the molten waste plastic) is at least 0.5 or more in mass ratio.
In the molten waste plastic mixed oil preparation process ST3, it is preferable that the ratio of the amount of raw oil supplied from supply line 12 (an example of supply line 1B) to the molten waste plastic mixed oil supply line 15 to the melted amount of molten waste plastic (supply amount of raw oil/melted amount of molten waste plastic) is at least 1 or more in mass ratio.

<First storage step ST10>
The treatment method of the third embodiment includes a first storage step ST10, which is a step of storing the molten waste plastic mixed oil B in a first storage tank 60.
In the first storage step ST10 of the third embodiment, a degassing step is carried out.
The gas generated in the first storage tank 60 flows through the first gas vent line 44 to the second gas vent line 43, and is discharged to the outside from the second gas vent line 43 together with the gas generated in the second storage tank 40.
The gas venting means is not limited to the gas venting line, and gas may be discharged (vented) from each of the first storage tank 60 and the second storage tank 40 to the outside via a gas venting means.

<Decomposition treatment mixture preparation step ST5>
In the case of Fig. 3, the molten waste plastic mixed oil B supplied to the line mixer 30 is mixed with the raw material oil supplied from the supply line 13 to prepare a mixture for cracking treatment. Other than this, the mixture for cracking treatment is prepared under the same conditions as those of the mixture for cracking treatment preparation step ST5 of the second embodiment.
The prepared mixture for decomposition treatment has a kinetic viscosity at 160° C. of 1 mm ² /s or more and 60 mm ² /s or less.
The decomposition treatment mixture preparation process ST5 is preferably a process for adjusting the dynamic viscosity of the decomposition treatment mixture by adjusting the ratio of the total supply amount of raw oil supplied from the kneader 20 to the line mixer 30 to the supply amount of waste plastic (total supply amount of raw oil/supply amount of waste plastic) to a mass ratio of 10 or more and 200 or less (preferably 20 or more and 200 or less).
It is also preferable that the decomposition treatment mixture preparation process ST5 is a process for adjusting the dynamic viscosity of the decomposition treatment mixture by adjusting the ratio of the total supply amount of raw material oil supplied from the kneader 20 to the line mixer 30 to the molten amount of molten waste plastic (total supply amount of raw material oil/molten amount of waste plastic) to a mass ratio of 10 or more and 200 or less (preferably 20 or more and 200 or less).
In the case of FIG. 3 , “the total supply amount of raw material oil supplied from the kneader 20 to the line mixer 30” is the total supply amount of raw material oil supplied from the supply line 11 to the kneader 20, the supply line 12 to the kneader 20, and the supply line 13 to the line mixer 30.

<Second storage step ST20>
The treatment method of the third embodiment includes a second storage step ST20 in which the decomposition treatment mixture discharged from the line mixer 30 is stored in the second storage tank 40.
In the second storage step ST20 of the third embodiment, a degassing step is carried out.

<Decomposition treatment mixture supplying step ST6>
As in the second embodiment, the mixture for decomposition treatment is stored in the second storage tank 40 and then supplied to the RFCC device 50 .

＜Effects＞
In the processing method of the third embodiment, compared to the second embodiment, at the confluence C3 of the molten waste plastic mixed oil supply line 15, raw oil transported from the supply line 12 is supplied to the molten waste plastic mixed oil A, and a mixture of molten waste plastic mixed oil A and raw oil (molten waste plastic mixed oil B) is prepared (molten waste plastic mixed oil preparation process ST3) and stored in the first storage tank 60.
In addition, the molten waste plastic mixed oil B is also mixed in the first storage tank 60.
In this way, in the treatment method of the third embodiment, the molten waste plastics and raw oil are mixed in advance several times within the treatment system, and then further mixed in the line mixer 30 to prepare a mixture for decomposition treatment. Therefore, the prepared mixture for decomposition treatment is a mixture in which the molten waste plastics are dissolved in the raw oil in a nearly uniform state, and the kinetic viscosity (160°C) is adjusted to a predetermined range.
Therefore, according to the treatment method of the third embodiment, the decomposition property of the waste plastic can be improved, similarly to the second embodiment, and the decomposition property of the raw material oil can also be improved.
In particular, in the treatment method of the third embodiment, since raw oil is further supplied to the first storage tank 60 through the supply line 12, when the mixture (the molten waste plastic mixed oil B) stored in the first storage tank is transported from the molten waste plastic mixed oil supply line 15 to the line mixer 30 by the gear pump 61, the viscosity and the fluctuation range of the mixture can be reduced, and the mixture can be transported stably and smoothly to the line mixer 30. As a result, it becomes easier to obtain a mixture for cracking treatment with an adjusted kinetic viscosity.

Fourth Embodiment
The fourth embodiment will be described focusing on the differences from the first to third embodiments, and the description of similar matters will be omitted or simplified by using the same reference numerals, for example.
The fourth embodiment is an example in which a processing method is carried out using a waste plastic processing system shown in Fig. 4. First, the processing system 300A shown in Fig. 4 will be described, and then the processing method of the fourth embodiment will be described.

<Overall composition>
FIG. 4 is a schematic diagram of an example of a processing system used in the processing method of the fourth embodiment.
4 differs from the processing system 300 described in the third embodiment in that the processing system 300A includes two line mixers. The other points are the same as those of the third embodiment.

<Line mixers 30, 30B>
The processing system 300A of the fourth embodiment includes two line mixers 30 and 30B. The two line mixers 30 and 30B are arranged in parallel.

<Molten waste plastic mixed oil supply line 15>
The molten waste plastic mixed oil supply line 15 of the fourth embodiment connects the kneader 20, the first storage tank 60, the line mixer 30 and the line mixer 30B.
In the case of Fig. 4, the molten waste plastic mixed oil supply line 15 is branched into a first mixed oil branch line 151 and a second mixed oil branch line 152 at a branch point B5 downstream of the first storage tank 60. The first mixed oil branch line 151 is connected to the line mixer 30. The second mixed oil branch line 152 is connected to the line mixer 30B.

<Supply line 13>
The supply line 13 of the fourth embodiment connects the first transport line 10 and the line mixer 30, and the first transport line 10 and the line mixer 30B, respectively.
In the case of Fig. 4, the supply line 13 passes through branch points B2 and B3 from a branch point B1 of the first transport line 10, and then branches into a first branch line 13A and a second branch line 13B at a branch point B4. The first branch line 13A is connected to a line mixer 30. The second branch line 13B is connected to a line mixer 30B.
A third feed oil supply control means 131 similar to that in the second embodiment is provided in the first branch line 13A.
A fourth feedstock supply control means for controlling the amount of feedstock oil supplied to the line mixer 30B is also provided in the middle of the second branch line 13B, but the fourth feedstock supply control means is not shown. The fourth feedstock supply control means may have the same configuration and operating conditions as the third feedstock supply control means 131, or may have different configurations and operating conditions.

[Treatment method of the fourth embodiment]
The treatment method of the fourth embodiment is different from the third embodiment mainly in the decomposition treatment mixture preparation step ST5. The treatment method of the fourth embodiment will be described focusing on the points different from the third embodiment.

<Molten waste plastic mixed oil supply process ST4>
The molten waste plastic mixed oil B is stored in the first storage tank 60, and then transported through the molten waste plastic mixed oil supply line 15 by a gear pump 61, with a portion of it being supplied to the line mixer 30 from the branch point B5 via the first mixed oil branch line 151, and the remainder being supplied to the line mixer 30B from the branch point B5 via the second mixed oil branch line 152.

<Decomposition treatment mixture preparation step ST5>
In the decomposition treatment mixture preparation step ST5 of the fourth embodiment, a decomposition treatment mixture is prepared using two line mixers 30, 30B arranged in parallel.
In the line mixer 30, the molten waste plastic mixed oil B and the raw oil supplied from the first branch line 13A are mixed to prepare a mixture for cracking treatment (hereinafter also referred to as "mixture for cracking treatment X1"). In the line mixer 30B, the molten waste plastic mixed oil B and the raw oil supplied from the second branch line 13B are mixed to prepare a mixture for cracking treatment (hereinafter also referred to as "mixture for cracking treatment Y1").
The kinetic viscosity at 160° C. of the decomposition treatment mixture X1 and the decomposition treatment mixture Y1 is adjusted to be 1 mm ² /s or more and 60 mm ² /s or less.

<Decomposition treatment mixture supplying step ST6>
In the case of Figure 4, the decomposition treatment mixture X1 and the decomposition treatment mixture Y1 merge at the junction C4 of the second transport line 14, and then are stored in the second storage tank 40, and then supplied to the RFCC device 50 in a manner similar to the third embodiment.

＜Effects＞
In the processing method of the fourth embodiment, compared to the third embodiment, two line mixers 30, 30B are arranged in parallel, and a mixture for decomposition processing is prepared in each line mixer, so that the mixing state of the molten waste plastics and the raw oil can be further improved and the processing amount of the molten waste plastics can be increased, and a larger amount of mixture for decomposition processing to be subjected to decomposition can be prepared.
Therefore, according to the treatment method of the fourth embodiment, the decomposition ability of waste plastics can be further improved, the decomposition ability of raw oil can be improved, and the amount of decomposed waste plastics can be increased.

Fifth Embodiment
The fifth embodiment will be described focusing on the differences from the first to fourth embodiments, and the description of similar items will be omitted or simplified by using the same reference numerals, for example.
The fifth embodiment is an example in which a processing method is carried out using a waste plastic processing system shown in Fig. 5. First, the processing system 400 shown in Fig. 5 will be described, and then the processing method of the fifth embodiment will be described.

<Overall composition>
FIG. 5 is a schematic diagram of an example of a processing system used in the processing method of the fifth embodiment.
The processing system 400 shown in Fig. 5 differs from the processing system 300A described in the fourth embodiment in that the processing system 400 includes two kneaders, three line mixers, and does not include the supply line 12. The other points are the same as those of the fourth embodiment.

<Kneader 20, 20A>
The processing system 400 of the fifth embodiment includes two mixers 20 and 20A. The two mixers 20 and 20A are arranged in parallel.

<Line mixers 30, 30A, 30B>
The processing system 400 of the fifth embodiment includes three line mixers. Two line mixers 30 and 30A are arranged in series, and the remaining line mixer 30B is arranged in parallel with the two line mixers 30 and 30A.

<Molten waste plastic mixed oil supply line 15>
The molten waste plastic mixed oil supply line 15 of the fifth embodiment connects the kneader 20, the kneader 20A, the first storage tank 60, the line mixer 30 and the line mixer 30B.

[Treatment method of the fifth embodiment]
The processing method of the fifth embodiment differs from the fourth embodiment mainly in the molten waste plastic preparation step ST2, the molten waste plastic mixed oil preparation step ST3, and the decomposition treatment mixture preparation step ST5.
The processing method of the fifth embodiment will be described, focusing on the differences from the fourth embodiment.

<Waste plastic supply process ST1>
In the waste plastic supplying step ST1 of the fifth embodiment, waste plastic is supplied to two kneaders 20 and 20A in the same manner as in the first embodiment.
5, the feeder, hopper, and waste plastic supply control means connected to the kneader 20A are not shown. The configurations of the feeder, hopper, and waste plastic supply control means are not particularly limited.

<Molten waste plastic preparation process ST2>
The molten waste plastic preparation process ST2 of the fifth embodiment is carried out using two kneaders 20 and 20A.
The mixer 20A may have the same configuration and operating conditions as the mixer 20, or may have a different configuration and operating conditions.

<Molten waste plastic mixed oil supply process ST4>
In the kneader 20, the molten waste plastic obtained by melting the waste plastic is mixed with raw oil supplied to the outlet side of the kneader 20 via the supply line 11 to prepare molten waste plastic mixed oil A (a mixture of molten waste plastic and raw oil).
Although not shown in the figure, kneader 20A, like kneader 20, mixes molten waste plastic obtained by melting waste plastic with raw material oil supplied to the outlet side of kneader 20A from a supply line other than supply line 11 (e.g., an additional raw material oil supply line, etc.) to prepare molten waste plastic mixed oil A' (a mixture of molten waste plastic and raw material oil).
The amount of raw oil supplied to the kneader 20A is preferably controlled by an arbitrary raw oil supply control means. The ratio of the amount of raw oil supplied to the kneader 20A to the amount of melted molten waste plastics (the amount of raw oil supplied/the amount of melted molten waste plastics) is preferably at least 0.5 by mass ratio.
The molten waste plastic mixed oil A and the molten waste plastic mixed oil A′ are joined (mixed) at the joining point C 5 and stored in the first storage tank 60 .
The molten waste plastic mixed oil (a mixture of molten waste plastic mixed oil A and molten waste plastic mixed oil A') stored in the first storage tank 60 is transported through the molten waste plastic mixed oil supply line 15 by a gear pump 61, and a portion of it is supplied to the line mixer 30 via the first mixed oil branch line 151 from branch point B5, and the remainder is supplied to the line mixer 30B via the second mixed oil branch line 152 from branch point B5.

<Decomposition treatment mixture preparation step ST5>
The cracking process mixture preparation step ST5 of the fifth embodiment is carried out using three line mixers. In the line mixer 30, the molten waste plastic mixed oil supplied from the first mixed oil branch line 151 and the raw material oil supplied from the first branch line 13A are mixed to prepare a cracking process mixture. The cracking process mixture is then transported through the second transport line 14 connected to the outlet of the line mixer 30 and supplied to the line mixer 30A. In the line mixer 30A, the cracking process mixture is further mixed to prepare a cracking process mixture (hereinafter also referred to as "cracking process mixture X2").
Meanwhile, in the line mixer 30B, the molten waste plastic mixed oil supplied from the second mixed oil branch line 152 and the raw oil supplied from the second branch line 13B are mixed to prepare a mixture for cracking treatment (hereinafter also referred to as "mixture for cracking treatment Y2").
The kinetic viscosity at 160° C. of the decomposition treatment mixture X2 and the decomposition treatment mixture Y2 is adjusted to be 1 mm ² /s or more and 60 mm ² /s or less.
The line mixers 30A and 30B may have the same configuration and operating conditions as the line mixer 30, or may have different configurations and operating conditions from each other.

<Decomposition treatment mixture supplying step ST6>
In the case of Figure 5, the decomposition treatment mixture X2 and the decomposition treatment mixture Y2 merge at the junction C4 of the second transport line 14, are stored in the second storage tank 40, and then are supplied to the RFCC device 50 in a manner similar to the fourth embodiment.

＜Effects＞
In the fifth embodiment, the processing method is different from the fourth embodiment in that two kneaders 20 and 20A are arranged in parallel, and the molten waste plastic mixed oil A and the molten waste plastic mixed oil A' are prepared in each kneader, so that more molten waste plastic mixed oil to be decomposed can be prepared. Furthermore, the same or different operating conditions can be set in each kneader according to the type, composition, shape, and state of the waste plastic to be treated, so that the mixability of the molten waste plastic mixed oil A and the molten waste plastic mixed oil A' is improved.
In addition, in the treatment method of the fifth embodiment, the mixture for decomposition treatment prepared in the line mixer 30 is further continuously mixed in the line mixer 30A, so that a "mixture for decomposition treatment X2" with improved mixability is prepared.
Therefore, according to the treatment method of the fifth embodiment, the decomposition ability of waste plastics can be further improved, the decomposition ability of raw oil can be improved, and the amount of decomposed waste plastics can be increased.

[Fifth embodiment A]
The processing system of the fifth embodiment A differs from the processing system 400 (FIG. 5) described in the fifth embodiment in that a line mixer 30C is further provided in series downstream of the line mixer 30B. The other points are the same as those of the fifth embodiment.
That is, the processing system of the fifth embodiment A includes four line mixers. Two line mixers 30 and 30A are arranged in series, and the remaining two line mixers 30B and 30C are arranged in parallel to the two line mixers 30 and 30A.
The processing system of the fifth embodiment A is not shown in the drawings. The following description will be given by using the reference numerals in FIG.

[Treatment method of the fifth embodiment A]
The treatment method of the fifth embodiment A is different from that of the fifth embodiment in the decomposition treatment mixture preparation step ST5. The treatment method of the fifth embodiment A will be described focusing on the points different from the fifth embodiment.

<Decomposition treatment mixture preparation step ST5>
The decomposition treatment mixture preparation step ST5 of the fifth embodiment A is carried out using four line mixers.
In the line mixer 30B, a mixture for decomposition treatment Y2 is prepared. The mixture for decomposition treatment Y2 is transported through a second transport line 14 connected to the outlet of the line mixer 30B, and is supplied to the line mixer 30C. In the line mixer 30C, the mixture for decomposition treatment Y2 is further mixed to prepare a mixture for decomposition treatment (hereinafter also referred to as "mixture for decomposition treatment Y2'").
The kinetic viscosity of the decomposition treatment mixture Y2' at 160° C. is adjusted to be 1 mm ² /s or more and 60 mm ² /s or less.
The line mixer 30C may have the same configuration and operating conditions as the line mixers 30, 30A, and 30B, or may have different configurations and operating conditions.

<Decomposition treatment mixture supplying step ST6>
The decomposition treatment mixture X2 and the decomposition treatment mixture Y2' are merged at the junction C4 of the second transport line 14, then stored in the second storage tank 40, and then supplied to the RFCC device 50 in a manner similar to the fifth embodiment.

＜Effects＞
In the treatment method of the fifth embodiment A, the mixture for decomposition treatment X2 and the mixture for decomposition treatment Y2' having improved mixability are prepared.
Therefore, according to the treatment method of the fifth embodiment A, the decomposition ability of the waste plastics can be further improved, the decomposition ability of the raw oil can be improved, and the amount of decomposed waste plastics can be further increased.

Sixth Embodiment
The sixth embodiment will be described focusing on the differences from the first to fifth embodiments and the fifth embodiment A, and the description of similar matters will be omitted or simplified by using the same reference symbols, for example.
The sixth embodiment is an example in which a processing method is carried out using a waste plastic processing system shown in Fig. 6. First, the processing system 500 shown in Fig. 6 will be described, and then the processing method of the sixth embodiment will be described.

<Overall composition>
FIG. 6 is a schematic diagram of an example of a processing system used in the processing method of the sixth embodiment.
The treatment system 500 shown in Fig. 6 is different from the treatment system 100 described in the first embodiment in that it includes an additional feedstock supply line 70 for supplying another additional feedstock (hereinafter also referred to as "additional feedstock"). The other points are the same as those of the first embodiment.

<Additional Feedstock Oil Supply Line 70>
The additional feedstock oil supply line 70 shown in Fig. 6 supplies the additional feedstock oil to the outlet side of the kneader 20. An additional feedstock oil supply control means 171 for controlling the supply amount of the additional feedstock oil is provided in the additional feedstock oil supply line 70. The additional feedstock oil supply control means 171 has a fourth adjustment valve 172 as additional feedstock supply means, and a fourth controller 173.
The additional raw material supply control means 171 transmits a control signal from the fourth controller 173 to the fourth adjustment valve 172 and controls the operation of the fourth adjustment valve 172, thereby controlling the amount of additional raw material oil supplied.
The temperature of the additional feedstock oil in the additional feedstock oil supply line 70 is preferably 80°C or higher and 240°C or lower, more preferably 160°C or higher and 230°C or lower, from the viewpoint of maintaining the molten state of the molten waste plastics and mixing the molten waste plastics and the additional feedstock oil well.
The temperature of the additional feedstock oil in the additional feedstock oil supply line 70 can be controlled, for example, by a temperature control means (for example, a heat exchanger, a heater, etc.) installed at any position in the additional feedstock oil supply line 70. The temperature of the additional feedstock oil in the additional feedstock oil supply line 70 is the set temperature of the temperature control means.
The additional raw material oil supply line 70 may be connected to a storage tank for storing the additional raw material oil. In addition, the additional raw material oil supply line 70 may be, for example, the supply line 12 connected to the first transport line 10, which is used as the additional raw material oil supply line 70, so that the additional raw material oil can be supplied from the first transport line 10 to the kneader 20.
The number of additional feedstock oil supply lines 70 is not limited, and may be one or two or more.

[Treatment method according to the sixth embodiment]
The treatment method of the sixth embodiment is different from the first embodiment in that it further includes an additional feedstock supplying step (hereinafter also referred to as "additional feedstock supplying step ST7") for supplying additional feedstock oil. The other points are the same as those of the first embodiment.
The processing method of the sixth embodiment will be described, focusing on the points that differ from the first embodiment.
The additional raw material supplying step ST7 is an additional raw material supplying step for supplying at least one other additional raw material oil selected from the group consisting of the feedstock oil (at least one selected from the group consisting of heavy cracked gas oil, cracked residual oil, atmospheric residual oil, desulfurized residual oil, desulfurized vacuum gas oil, undesulfurized vacuum gas oil, undesulfurized vacuum residual oil, and mineral oil), light hydrocarbon oil, naphtha, gas oil, and heavy hydrocarbon oil different from the feedstock oil.

<Molten waste plastic preparation process ST2 and additional raw material supply process ST7>
In the sixth embodiment, the molten waste plastic preparation step ST2 and the additional raw material supply step ST7 are carried out substantially simultaneously.
In the case of Figure 6, the waste plastic supplied to the kneader 20 is melted to prepare molten waste plastic, and additional raw material oil transported from the additional raw material oil supply line 70 is supplied to the outlet side of the kneader 20.
In the kneader 20, the molten waste plastics are mixed with the additional raw material oil to prepare a molten waste plastics additional mixed oil (a mixture of molten waste plastics and the additional raw material oil).
The melting temperature of the waste plastic is preferably in the same range as in the first embodiment.

<Molten waste plastic mixed oil preparation process ST3>
It is preferable that the molten waste plastic mixed oil preparation process ST3 further has an additional raw material supply process ST7, in which at least one type of additional raw material oil is further supplied to the molten waste plastic to prepare the molten waste plastic mixed oil.
In FIG. 6, molten waste plastics and additional raw material oil are mixed in a kneader 20 to prepare molten waste plastics additional mixed oil (a mixture of molten waste plastics and additional raw material oil).
This molten waste plastic additional mixed oil is transported through the molten waste plastic mixed oil supply line 15, and at the junction C2, it is merged (mixed) with the raw oil transported from the supply line 12, to prepare molten waste plastic mixed oil (a mixture of molten waste plastic additional mixed oil and raw oil).
The melt viscosity at 200°C of the molten waste plastic mixed oil prepared in the molten waste plastic mixed oil preparation process ST3 is preferably 100 mPa·s or more and 50 million mPa·s or less, and more preferably 1000 mPa·s or more and 25 million mPa·s or less.

<Decomposition treatment mixture preparation step ST5>
In the decomposition treatment mixture preparation process ST5, it is preferable to adjust the kinetic viscosity of the decomposition treatment mixture by adjusting the ratio of the total supply amount of the raw material oil supplied from the kneader 20 to the line mixer 30 and the additional raw material oil supplied from the kneader 20 to the line mixer 30 to the melted amount of the waste plastic (total supply amount of the raw material oil and the additional raw material oil/melted amount of the waste plastic) to a mass ratio of 10 to 200 (preferably 20 to 200).
When the ratio (total supply amount of the raw oil and the additional raw oil/melted amount of the waste plastic) is 10 or more by mass, the kinetic viscosity of the decomposition treatment mixture can be adjusted to a kinetic viscosity (160°C) that allows the decomposition treatment mixture to be smoothly transported to the RFCC device 50. When the ratio is 10 or more by mass, the kinetic viscosity can be adjusted to a kinetic viscosity (160°C) that allows the waste plastic to be easily decomposed. When the ratio is 10 or more by mass, the dispersion of droplets at the feed nozzle is improved when the decomposition treatment mixture is supplied to the RFCC device 50, and the decomposition rate is improved.
When the ratio (total supply amount of the raw material oil and the additional raw material oil/melted amount of the waste plastic) is 200 or less in mass ratio, the kinetic viscosity of the mixture for decomposition treatment can be adjusted to a kinetic viscosity (160° C.) that is easy to supply to the RFCC device 50. In addition, when the ratio is 200 or less in mass ratio, more waste plastic can be decomposed.
The decomposition treatment mixture preparation process ST5 is also preferably a process for adjusting the kinetic viscosity of the decomposition treatment mixture by adjusting the ratio of the total supply amount of the raw material oil supplied from the kneader 20 to the line mixer 30 and the additional raw material oil supplied from the kneader 20 to the line mixer 30 to the supply amount of molten waste plastics (total supply amount of the raw material oil and the additional raw material oil/supply amount of the waste plastics) to a mass ratio of 10 or more and 200 or less (preferably 20 or more and 200 or less).
In the case of FIG. 6 , “the total supply amount of the raw material oil supplied from the kneader 20 to the line mixer 30 and the additional raw material oil supplied from the kneader 20 to the line mixer 30” refers to the total supply amount of the raw material oil supplied from the supply line 12 to the molten waste plastic mixed oil supply line 15 and the additional raw material oil supplied into the kneader 20.

＜Effects＞
In the processing method of the sixth embodiment, compared to the first embodiment, the molten waste plastics and the additional raw oil transported from the additional raw oil supply line 70 are mixed in the kneader 20 to prepare the molten waste plastics additional mixed oil (first mixing). Then, at the junction C2, the raw oil transported from the supply line 12 is supplied to the molten waste plastics additional mixed oil (second mixing), and the molten waste plastics mixed oil (mixture of the molten waste plastics additional mixed oil and raw oil) is prepared (molten waste plastics mixed oil preparation step ST3). Then, the molten waste plastics mixed oil is supplied to the line mixer 30 (molten waste plastics mixed oil supply step ST4), and further mixed in the line mixer 30 (third mixing), and a mixture for decomposition processing is prepared (mixture for decomposition processing preparation step ST5).
The mixture for decomposition treatment is also mixed in the second storage tank 40 .
According to the treatment method of the sixth embodiment, the molten waste plastics, the additional raw material oil, and the raw material oil are premixed in the treatment system, and then further mixed in the line mixer 30 to prepare a mixture for decomposition treatment. Therefore, the prepared mixture for decomposition treatment is a mixture in which the molten waste plastics are dissolved in the raw material oil (including the additional raw material oil) in a nearly uniform state, and the kinetic viscosity (160°C) is adjusted to a predetermined range.
Therefore, according to the treatment method of the sixth embodiment, the mixability of the molten waste plastics and the raw oil is improved, and the mixture for decomposition treatment, the kinetic viscosity (160°C) of which is adjusted to a predetermined range, is supplied to the RFCC device 50, so that the decomposition ability of the waste plastics can be improved. Also, the decomposition ability of the raw oil (including the additional raw oil) can be improved.
In particular, in the processing method of the sixth embodiment, by appropriately selecting the type of additional raw material oil, the mixability of the additional molten waste plastic mixed oil prepared in the kneader 20 can be improved, and the fluctuation range of the viscosity of the mixture for decomposition processing obtained in the line mixer 30 can be reduced. As a result, it is considered that the preparation of the mixture for decomposition processing in the line mixer 30 becomes easier, the mixture for decomposition processing becomes easier to transport to the RFCC device 50, and the waste plastic can be efficiently decomposed.

Next, we will explain the configuration common to the first to sixth embodiments. Hereinafter, the reference symbols may be omitted.

<Waste plastic>
Examples of waste plastics include non-chlorinated plastics, chlorinated plastics, and mixtures thereof.
Examples of non-chlorinated plastics include polyethylene, polypropylene, propylene ethylene copolymers, polystyrene, polybutene, ethylene oligomers, butene oligomers, styrene oligomers, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon, epoxy resins, and phenolic resins.
Examples of polyethylene include high density polyethylene, low density polyethylene, and linear low density polyethylene.
Examples of chlorinated plastics include polyvinyl chloride and polyvinylidene chloride.

The waste plastics preferably include at least any one of waste plastics derived from vinyl polymers (e.g., polyethylene, polypropylene, propylene-ethylene copolymer, polystyrene, polybutene, ethylene oligomer, butene oligomer, and styrene oligomer, etc.).
It is more preferable that the waste plastics include at least one of polyethylene-derived waste plastics and polypropylene-derived waste plastics.

It is preferable that the waste plastics not include waste plastics derived from polystyrene or ethylene vinyl acetate.

<Feedstock oil>
The feedstock oil is not particularly limited, but is preferably at least one selected from the group consisting of heavy cracked gas oil (HCO), cracked residual oil (CLO), atmospheric residual oil (RC), desulfurized residual oil (DSRC), desulfurized vacuum gas oil (VHHGO), undesulfurized vacuum gas oil (VGO), undesulfurized vacuum residual oil (VC), and mineral oil (e.g., HG500 (mineral oil of 500 neutral fraction)), and more preferably at least one selected from the group consisting of desulfurized vacuum gas oil (VHHGO), heavy cracked gas oil (HCO), desulfurized residual oil (DSRC), and mineral oil.
In addition, the first transport line 10 for transporting the raw oil may be connected to, for example, an HCO storage tank or a CLO storage tank so as to directly supply at least one of heavy cracked light oil (HCO) and cracked residual oil (CLO) recovered in the FCC unit or the RFCC unit.
In addition, the first transport line 10 may be connected, for example, to a desulfurized residual oil (DSRC) storage tank so that the desulfurized residual oil (DSRC) produced in a heavy oil direct desulfurization unit can be directly supplied.

<Decomposition treatment device>
Examples of cracking processing units include catalytic cracking units (FCC units), residual oil fluid catalytic cracking units (RFCC units) (one embodiment of an FCC unit), and hydrocracking units.
From the viewpoint of improving the decomposition property of waste plastics, the cracking treatment device is preferably a catalytic cracking device (FCC device) or a residual oil catalytic cracking device (RFCC device).

Other Embodiments
In the first to sixth embodiments, the cracking treatment mixture supplying step ST6 has been described as supplying the cracking treatment mixture to an RFCC apparatus (an example of a cracking treatment apparatus) together with the raw material oil transported from a third supply line (first transport line 10 in the cases of FIGS. 1 to 6) different from the first and second supply lines, but is not limited thereto. For example, in any of the above embodiments, the cracking treatment mixture prepared in the line mixer may be directly supplied to the RFCC apparatus from the second transport line.

In the sixth embodiment, the molten waste plastic mixed oil preparation process ST3 further includes an additional raw material supply process ST7, but the present invention is not limited to this.
For example, in any of the above embodiments, the cracking process mixture preparation step ST5 may further include an additional raw material supply step ST7. For example, the cracking process mixture preparation step ST5 may be a step of preparing a cracking process mixture by further mixing the molten waste plastic mixed oil with additional raw material oil. In this case, it is preferable that the additional raw material oil is supplied to a line mixer.
The cracking treatment mixture supplying step ST6 may further include an additional feedstock supplying step ST7. For example, the cracking treatment mixture supplying step ST6 may be a step of further mixing an additional feedstock oil with the cracking treatment mixture to prepare a mixture of the cracking treatment mixture and the additional feedstock oil, and supplying the mixture to the cracking treatment device. In this embodiment, the additional feedstock oil is preferably supplied to the second transport line 14 or the first transport line 10 in the cases of Figures 1 to 6.

In the fifth embodiment, the decomposition treatment mixture preparation process ST5 is performed using three line mixers 30, 30A, and 30B, and in the fifth embodiment A, an aspect in which the decomposition treatment mixture preparation process ST5 is performed using four line mixers 30, 30A, 30B, and 30C is described, but the number and arrangement of the line mixers are not limited to these.
For example, in any of the above-described embodiments, a plurality of line mixers may be arranged in series, in parallel, or in a combination of series and parallel to perform the decomposition treatment mixture preparation step ST5. The plurality of line mixers may be the same or different from each other.
In the fifth embodiment and the fifth embodiment A, two kneaders are arranged in parallel, and the molten waste plastic preparation step ST2 is performed by each kneader, but this is not limited thereto. For example, in any of the above embodiments, the molten waste plastic preparation step ST2 may be performed using three or more kneaders. The multiple kneaders may be the same or different from each other. The number of kneaders is not limited.

In the sixth embodiment, the additional raw oil supply line 70 is connected to the kneader 20, but this is not limited thereto. For example, in any of the above embodiments, the additional raw oil supply line may be connected to at least one of the kneader, the line mixer, the first supply line, the second supply line, the mixed oil supply line, the first transport line, and the second transport line. The number of additional raw oil supply lines is also not limited.

In any of the processing systems of the above-described embodiments, a known melting device may be used in place of the kneader 20, 20A.
In any of the processing systems according to the above embodiments, a known mixing device may be used in place of the line mixers 30, 30A, 30B, and 30C.
In any of the treatment systems of the above-described embodiments, the RFCC unit 50 may be replaced with a known cracking treatment unit used in the field of oil refining, for example.

The following describes examples of the present invention. The present invention is not limited to these examples.

[Preparation of mixture for decomposition treatment 1]
Example 1
Using compacted cylindrical polypropylene (diameter 8 mm × length 10 to 15 mm) as waste plastic, molten polypropylene (hereinafter also referred to as "molten PP") was prepared under the following conditions.
(conditions)
・Kneading machine: Shibaura Machine Co., Ltd.: Twin-screw kneading extruder (model number TEM-37SS)
Melting temperature: 200°C
Melting amount: 30 kg/hr

Next, DSRC was added as a raw material oil to molten PP (10 kg) so that the ratio of desulfurized residual oil (DSRC) to molten PP (DSRC/molten PP) was 1 by mass, thereby preparing a mixture of molten PP and DSRC (20 kg) (hereinafter also referred to as "molten PP mixed oil 1").
The melt viscosity of the molten PP mixed oil 1 was measured by the above-mentioned method. The melt viscosity of the molten PP mixed oil 1 at 200° C. was 1,000,000 mPa·s.

Next, DSRC (147 g) was further added to the molten PP mixed oil 1 (6 g) so that the ratio of desulfurized residual oil (DSRC) to molten PP (DSRC/molten PP) was 50 by mass. Thereafter, the mixture of the molten PP mixed oil 1 and the DSRC was mixed using a batch mixer under the following conditions to prepare a mixture for cracking treatment.
The kinetic viscosity of the mixture for decomposition treatment was measured by the method described above. The kinetic viscosity of the mixture for decomposition treatment at 160° C. was 10 mm ² /s.
(conditions)
・Batch mixer: Primix Corporation: Homo Mixer MKII Homo Mixer Blade ・Rotation speed: 900 rpm
Temperature: 220°C
Time: 30 seconds

Next, the mixture for cracking treatment of Example 1 was cracked under the following conditions using a small reaction evaluation apparatus (MAT apparatus) equivalent to an FCC apparatus.
(conditions)
Small reaction evaluation device: Kayser: ACE R+
Reaction temperature: 530°C
Pressure: 0.05MPaG
Time: 90 seconds (oil flow time)
Catalyst/decomposition mixture (mass ratio): 6
Catalyst: 9g
Catalyst type: FCC equilibrium catalyst
(FCC equilibrium catalyst extracted from actual equipment)

Example 2
A mixture for decomposition treatment was prepared and decomposed in the same manner as in Example 1, except that the "catalyst/mixture for decomposition treatment (mass ratio)" was changed to 5 in comparison with Example 1.

Example 3
A mixture for decomposition treatment was prepared and decomposed in the same manner as in Example 1, except that the "catalyst/mixture for decomposition treatment (mass ratio)" was changed to 3.98.

Comparative Example 1
In the same manner as in Example 1, DSRC (not including molten PP) was decomposed in a small reaction evaluation device.

Comparative Example 2
The DSRC was decomposed in the same manner as in Comparative Example 1, except that the "catalyst/DSRC (mass ratio)" was changed to 5 in Comparative Example 1.

Comparative Example 3
DSRC was decomposed in the same manner as in Comparative Example 1, except that the "catalyst/DSRC (mass ratio)" was changed to 3.98.

<Decomposition evaluation 1>
The decomposition properties of the decomposition treatment mixtures of Examples 1 to 3 and the DSRCs of Comparative Examples 1 to 3 were evaluated by the Microactivity Test (MAT), and the results are shown in Table 1.
The values in Table 1 represent the percentage of the mass of each component relative to the mass of DSRC in the product oil obtained by cracking.
The conversion rate (mass %) was calculated from the following formula (1).
Conversion rate (mass%) = 100 - (LCO + CLO) ... (1)

Explanation in Table 1: Dry Gas represents methane, ethane and ethylene.
FG stands for gasoline.
LCO stands for gas cracked oil (light gas cracked oil + heavy gas cracked oil).
CLO stands for cracked residual oil.
COKE stands for coke.
The same applies to Table 2 described later.

As a result of comparing Example 1 and Comparative Example 1, Example 1, in which a mixture for cracking treatment containing molten PP was cracked, showed improved conversion, FG yield, and yield of liquefied petroleum gases (propane, propylene, n-butane, isobutane, and butylene) compared with Comparative Example 1, in which only DSRC was cracked. In particular, the propylene yield, isobutane yield, and butylene yield were improved.
The results of comparing Example 2 with Comparative Example 2 and the results of comparing Example 3 with Comparative Example 3 were similar.
According to this example, it was confirmed that the waste plastics in the mixture for decomposition treatment can be converted into useful liquefied petroleum gases together with the raw material oil, and the decomposition property of the waste plastics can be improved.

[Preparation of mixture for decomposition treatment 2]
Example 4
Molten PP was prepared under the same conditions as in Example 1 using the same waste plastics as in Example 1. However, in Example 4, the waste plastics were melted while supplying HG500 as a raw material oil to the outlet side of the kneader so that the ratio of mineral oil (HG500) to molten PP (10 kg) (HG500/molten PP) was 1 by mass. This operation produced a mixture (20 kg) of molten PP and HG500 (hereinafter also referred to as "molten PP mixed oil 2").
The melt viscosity of the molten PP mixed oil 2 was measured by the above-mentioned method. The melt viscosity of the molten PP mixed oil 2 at 200° C. was 1,000,000 mPa·s.

Next, HG500 (96 g) was further added to the molten PP mixed oil 2 (8 g) so that the ratio of HG500 to molten PP (HG500/molten PP) was 25 by mass. Thereafter, the mixture of the molten PP mixed oil 2 and HG500 was mixed under the following conditions to prepare a mixture for cracking treatment.
The kinetic viscosity of the mixture for decomposition treatment was measured by the method described above. The kinetic viscosity of the mixture for decomposition treatment at 160° C. was 21 mm ² /s.

Next, the mixture for decomposition treatment of Example 4 was decomposed in the same manner as in Example 1 using a small reaction evaluation device (MAT device) equivalent to an FCC device.

Example 5
A mixture for decomposition treatment was prepared and decomposed in the same manner as in Example 4, except that the "catalyst/mixture for decomposition treatment (mass ratio)" was changed to 5 in comparison with Example 4.

Comparative Example 4
In the same manner as in Example 4, HG500 (not including molten PP) was decomposed in a small reaction evaluation device.

Comparative Example 5
HG500 was decomposed in the same manner as in Comparative Example 4, except that the "catalyst/HG500 (mass ratio)" was changed to 5 in Comparative Example 4.

<Decomposition evaluation 2>
The decomposition properties of the decomposition treatment mixtures of Examples 4 and 5 and HG500 of Comparative Examples 4 and 5 were evaluated by the Microactivity Test (MAT), and the results are shown in Table 2.
The values in Table 2 represent the percentage of the mass of each component relative to the mass of HG500 in the product oil obtained by cracking.
The conversion rate (mass %) was calculated from the above formula (1).

As a result of comparing Example 4 and Comparative Example 4, Example 4, in which a mixture for cracking treatment containing molten PP was cracked, showed improved conversion, FG yield, and yield of liquefied petroleum gases (propane, propylene, n-butane, isobutane, and butylene) compared with Comparative Example 4, in which only HG500 was cracked. In particular, the propylene yield, isobutane yield, and butylene yield were improved.
The results of comparing Example 5 and Comparative Example 5 were similar.
According to this example, it was confirmed that the waste plastics in the mixture for decomposition treatment can be converted into useful liquefied petroleum gases together with the raw material oil, and the decomposition property of the waste plastics can be improved.

The waste plastic processing method of the present invention can increase the effective utilization rate of waste plastic and therefore can be used industrially.

10...first transport line (third supply line), 11, 12...supply line (first supply line), 13...supply line (second supply line), 13A...first branch line, 13B...second branch line, 14...second transport line, 15...molten waste plastic mixed oil supply line, 20, 20A...kneader, 21...feeder, 22...hopper, 23...waste plastic supply line, 24...feeder controller, 25...waste plastic supply control means, 30, 30A, 30B...line mixer, 40...second storage tank, 41...centrifugal pump, 43, 44...gas venting line, 50...RFCC equipment 60: first storage tank, 61: gear pump, 70: additional feedstock supply line, 100, 200, 300, 300A, 400, 500: treatment system, 111: first feedstock supply control means, 112: first control valve, 113: first controller, 121: second feedstock supply control means, 122: second control valve, 123: second controller, 131: third feedstock supply control means, 132: third control valve, 133: third controller, 151: first mixed oil branch line, 152: second mixed oil branch line, 171: additional feedstock supply control means, 172: fourth control valve, 173: fourth controller, HG: heat exchanger.

Claims (22)

A waste plastic processing method using a waste plastic processing system,
Supplying waste plastic to a melting device;
A step of preparing molten waste plastic by melting the waste plastic;
A step of preparing a molten waste plastic mixed oil by supplying raw material oil to the molten waste plastic from one or more first supply lines;
Supplying the molten waste plastic mixed oil to a mixing device;
A step of preparing a mixture for decomposition treatment by mixing the molten waste plastic mixed oil supplied to the mixer;
and supplying the prepared mixture for decomposition treatment to a decomposition treatment device.
The step of preparing the mixture for decomposition treatment includes preparing the mixture for decomposition treatment so that the mixture for decomposition treatment has a kinetic viscosity at 160° C. of 1 mm ² /s or more and 60 mm ² /s or less.
Methods for processing waste plastic. The method for treating waste plastic according to claim 1,
The step of preparing the mixture for decomposition treatment is to prepare a mixture for decomposition treatment by mixing the molten waste plastic mixed oil supplied to the mixing device with the raw material oil supplied to the mixing device from a second supply line different from the first supply line.
Methods for processing waste plastic. In the waste plastic processing method according to claim 1 or 2,
The step of preparing the mixture for decomposition treatment includes adjusting the ratio of the total amount of the raw oil supplied from the melting device to the mixing device to the amount of the waste plastics (total amount of the raw oil supplied/amount of the waste plastics supplied) to a mass ratio of 10 to 200, thereby adjusting the kinetic viscosity of the mixture for decomposition treatment.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 3,
The process for preparing the decomposition mixture includes adjusting the ratio of the total amount of the raw oil supplied from the melting device to the mixing device to the melted amount of the molten waste plastic (the total amount of the raw oil supplied/the melted amount of the molten waste plastic) to a mass ratio of 10 to 200, thereby adjusting the kinetic viscosity of the decomposition mixture.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 4,
The method further includes a step of supplying at least one additional feedstock oil selected from the group consisting of the feedstock oil, light hydrocarbon oil, naphtha, diesel, and heavy hydrocarbon oil different from the feedstock oil;
Methods for processing waste plastic. The method for treating waste plastic according to claim 5,
The step of preparing the molten waste plastic mixed oil further includes the additional raw material supply step, and the molten waste plastic is further supplied with at least one other additional raw material oil to prepare the molten waste plastic mixed oil.
Methods for processing waste plastic. The method for treating waste plastic according to claim 5 or 6,
The step of preparing the mixture for decomposition treatment further includes the step of supplying the additional raw material, and the mixture for decomposition treatment is prepared by further mixing the molten waste plastic mixed oil with at least one other additional raw material oil.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 5 to 7,
The step of preparing the decomposition mixture includes adjusting the ratio of the total supply amount of the raw oil supplied from the melting device to the mixing device and the additional raw oil supplied from the melting device to the mixing device to the melted amount of the waste plastic (total supply amount of the raw oil and the additional raw oil/melted amount of the waste plastic) to a mass ratio of 10 to 200, thereby adjusting the kinetic viscosity of the decomposition mixture.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 8,
The step of preparing the molten waste plastic mixed oil includes preparing the molten waste plastic mixed oil so that the melt viscosity at 200 ° C. is 100 mPa · s or more and 50 million mPa · s or less.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 9,
The first supply line includes a supply line 1A for supplying raw oil to the melting device,
The step of preparing the molten waste plastic mixed oil is to supply the raw material oil to the molten waste plastic so that the ratio of the supply amount of the raw material oil supplied from the supply line 1A to the melting device to the melted amount of the molten waste plastic (the supply amount of the raw material oil / the melted amount of the molten waste plastic) is at least 0.5 by mass ratio. The molten waste plastic mixed oil is prepared by supplying the raw material oil to the molten waste plastic.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 10,
The first supply line has a supply line 1B for supplying raw material oil to a pipe connecting the melting device and the mixing device,
The step of preparing the molten waste plastic mixed oil is to prepare the molten waste plastic mixed oil by supplying the raw material oil to the molten waste plastic so that the ratio of the supply amount of the raw material oil supplied from the supply line 1B to the piping to the melted amount of the molten waste plastic (the supply amount of the raw material oil / the melted amount of the molten waste plastic) is at least 1 by mass ratio.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 11,
The step of supplying the mixture for cracking treatment to the cracking treatment unit includes supplying the mixture for cracking treatment together with the feed oil transported from a third supply line different from the first supply line to the cracking treatment unit.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 12,
The step of preparing the mixture for decomposition treatment includes preparing the mixture for decomposition treatment under conditions of a temperature of 160° C. or more and 260° C. or less and a rotation speed of a stirring means of 10 rpm or more and 20,000 rpm or less.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 13,
The melting temperature of the waste plastic in the step of preparing the molten waste plastic is 175° C. or higher and 260° C. or lower;
The temperature of the raw oil in the first supply line in the step of preparing the molten waste plastic mixed oil is 80 ° C or more and 240 ° C or less;
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 14,
The feedstock oil is at least one selected from the group consisting of heavy cracked gas oil, cracked residual oil, atmospheric residual oil, desulfurized residual oil, desulfurized vacuum gas oil, undesulfurized vacuum gas oil, undesulfurized vacuum residual oil, and mineral oil;
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 15,
The feedstock oil is at least one selected from the group consisting of desulfurized vacuum gas oil, heavy cracked gas oil, and desulfurized residual oil;
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 16,
The waste plastic includes at least one of polyethylene-derived waste plastic and polypropylene-derived waste plastic,
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 17,
The step of preparing the molten waste plastic is carried out using a plurality of the melting devices;
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 18,
The melting device is a kneader.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 19,
The step of preparing the mixture for decomposition treatment is carried out using a plurality of the mixing devices.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 20,
The mixing device is a line mixer.
Methods for processing waste plastic. In the waste plastic processing method according to any one of claims 1 to 21,
The cracking treatment device is a fluid catalytic cracking device.
Methods for processing waste plastic.

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