Thermal cracking device and method for producing hydrocarbon oil

Abstract

The present invention provides a thermal cracking apparatus that can suppress the occurrence of coking in piping even when multiple thermal cracking furnaces are used in parallel. [Solution] The thermal decomposition apparatus of the present invention comprises a plurality of thermal decomposition furnaces arranged in parallel for thermally decomposing waste plastic raw materials to obtain a hydrocarbon stream, a cooler for condensing at least a portion of the hydrocarbon stream, a separator for separating the hydrocarbon stream into hydrocarbon oil and cracked gas, a plurality of first pipes for discharging the hydrocarbon stream from each of the thermal decomposition furnaces, a junction for joining the hydrocarbon streams in each of the first pipes, a second pipe for flowing the joined hydrocarbon stream to the cooler, a third pipe for flowing the hydrocarbon stream from the cooler to the separator, a fourth pipe for discharging cracked gas from the separator, a fifth pipe for discharging hydrocarbon oil from the separator, and a sixth pipe for supplying non-condensable gas to the plurality of first pipes, each of which has a first shut-off valve, and the sixth pipe for supplying non-condensable gas to the plurality of first pipes downstream of the first shut-off valve.

Description

[Technical Field]

[0001] The present invention relates to a thermal cracking apparatus and a method for producing hydrocarbon oil. [Background technology]

[0002] In recent years, the regeneration and reuse of plastics has been attracting attention from the perspective of resource recycling. For example, processes such as reuse, material recycling, and chemical recycling are being carried out to recycle waste plastics. In particular, chemical recycling has the potential to overcome the limitations of performance degradation caused by recycling, as it can chemically decompose plastics and regenerate them into petrochemical raw materials.

[0003] As one type of chemical recycling, for example, a technology has been proposed in which waste plastics are pyrolyzed to produce oil (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-246685 Summary of the Invention [Problem to be solved by the invention]

[0005] With the advancement of chemical recycling, there is a demand for an expansion of the scale of thermal decomposition of waste plastics. However, thermal decomposition devices often have limitations on the amount of waste plastic that can be processed per device, and for example, the operation of multiple thermal decomposition furnaces arranged in parallel has been considered. By arranging multiple thermal decomposition furnaces in parallel, the amount of waste plastic that can be thermally decomposed simultaneously can be increased, and while some thermal decomposition furnaces are stopped for maintenance, the other thermal decomposition furnaces can be used to thermally decompose waste plastics.

[0006] However, when multiple pyrolysis furnaces are arranged in parallel as described above, if the operation of some of the pyrolysis furnaces is stopped, the hydrocarbon flow from the other pyrolysis furnaces may flow back into the piping of the stopped pyrolysis furnace. This backflow can cause components contained in the hydrocarbon flow to liquefy or solidify in the piping of the stopped pyrolysis furnace, and when the operation is resumed, they can be heated, decomposed, polymerized, and adhere to the inner surface of the piping (also known as coking). Therefore, in a pyrolysis system in which multiple pyrolysis furnaces are arranged in parallel, the occurrence of coking can lead to problems such as piping blockage or increased pressure loss.

[0007] Therefore, the present invention provides a thermal cracking apparatus and a method for producing hydrocarbon oil that can suppress the occurrence of coking in piping even when multiple thermal cracking furnaces are used in parallel. [Means for solving the problem]

[0008] The pyrolysis device according to the present invention comprises: a plurality of pyrolysis furnaces arranged in parallel for pyrolyzing a waste plastic feedstock containing polyolefins to obtain a hydrocarbon stream; a cooler for cooling the hydrocarbon streams obtained from the plurality of pyrolysis furnaces to condense at least a portion of the hydrocarbon streams; a separator that separates the hydrocarbon stream at least partially condensed in the cooler into hydrocarbon oil and cracked gas; a plurality of first pipes for discharging the hydrocarbon stream from each of the plurality of pyrolysis furnaces; a confluence portion that combines the hydrocarbon flows in the first pipes of the plurality of first pipes; a second pipe that causes the hydrocarbon streams joined at the joining portion to flow to the cooler; a third line for passing the hydrocarbon stream at least partially condensed in the cooler to the separator; a fourth pipe for discharging the decomposed gas from the separator; a fifth pipe for discharging the hydrocarbon oil from the separator; and a sixth pipe that supplies a non-condensable gas to the plurality of first pipes; each of the first pipes has a first shutoff valve that opens and closes a flow path of the hydrocarbon stream in each of the first pipes; The sixth pipe supplies the non-condensable gas to the plurality of first pipes downstream of the position of the first shutoff valve in each of the first pipes.

[0009] The method for producing a hydrocarbon oil according to the present invention comprises: The method includes a hydrocarbon oil production step in which the waste plastic raw material is thermally decomposed using the thermal decomposition device to obtain the hydrocarbon oil. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a thermal cracking apparatus and a method for producing hydrocarbon oil that can suppress the occurrence of coking in piping even when a plurality of thermal cracking furnaces are used in parallel. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a thermal decomposition apparatus 1 according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Pyrolysis equipment] A pyrolysis device 1 according to an embodiment of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiment.

[0013] As shown in FIG. 1, the thermal cracking apparatus 1 according to this embodiment comprises a plurality of parallelly arranged thermal cracking furnaces 2 for thermally cracking a waste plastic raw material R containing polyolefin to obtain a hydrocarbon stream; a cooler 3 for condensing at least a portion of the hydrocarbon stream obtained in the plurality of thermal cracking furnaces 2 by cooling the hydrocarbon stream; a separator 4 for separating the hydrocarbon stream at least a portion of which has been condensed in the cooler 3 into a hydrocarbon oil P and a cracked gas; and a separator 5 for discharging the hydrocarbon stream from each of the plurality of thermal cracking furnaces 2. a confluence section 6 that confluences the hydrocarbon streams in each of the first pipes 5 of the plurality of first pipes 5; a second pipe 7 that flows the hydrocarbon streams that have been combined at the confluence section 6 to the cooler 3; a third pipe 8 that flows the hydrocarbon stream that has been at least partially condensed in the cooler 3 to the separator 4; a fourth pipe 9 that discharges the cracked gas from the separator 4; a fifth pipe 10 that discharges the hydrocarbon oil P from the separator 4; and a sixth pipe 11 that supplies non-condensable gas to the plurality of first pipes 5.

[0014] (multiple pyrolysis furnaces) The pyrolysis apparatus 1 according to this embodiment includes a plurality of pyrolysis furnaces 2 arranged in parallel, which pyrolyze a waste plastic raw material R containing polyolefins to obtain a hydrocarbon stream. As shown in FIG. 1 , the plurality of pyrolysis furnaces 2 are composed of three pyrolysis furnaces 2. In the plurality of pyrolysis furnaces 2, the waste plastic raw material R containing polyolefins is pyrolyzed to produce a pyrolysate, from which a hydrocarbon stream is obtained. In the plurality of pyrolysis furnaces 2, the polymer components contained in the waste plastic raw material R are converted into low-molecular-weight hydrocarbons. That is, the hydrocarbon stream obtained in the plurality of pyrolysis furnaces 2 contains hydrocarbons. In the plurality of pyrolysis furnaces 2, pyrolysis residue may be produced from the waste plastic raw material R. The hydrocarbon stream obtained in the plurality of pyrolysis furnaces 2 is supplied to a cooler 3, which will be described later.

[0015] The waste plastic raw materials refer to plastic products that have been used for some final purpose.

[0016] The polyolefin contained in the waste plastic raw material R contains a monomer unit derived from an olefin. The polyolefin may be an olefin homopolymer or a copolymer containing a monomer unit derived from an olefin. The waste plastic raw material R may contain, as the polyolefin, at least one of an olefin homopolymer and a copolymer containing a monomer unit derived from an olefin.

[0017] Examples of the monomer derived from olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene.

[0018] The copolymer containing monomer units derived from an olefin may be a copolymer containing monomer units derived from two or more different olefins, or may be a copolymer containing monomer units derived from an olefin and monomer units derived from a monomer other than an olefin. The waste plastic raw material R may contain, as the polyolefin, one type or two or more types of copolymers containing monomer units derived from an olefin.

[0019] Examples of the monomer other than olefin include alkylene oxides such as ethylene oxide, esters such as ethylene terephthalate, etc. The monomer other than olefin may be alkylene oxide or ethylene terephthalate.

[0020] Examples of copolymers containing monomer units derived from olefins include propylene copolymers containing monomer units derived from propylene. Examples of the propylene copolymers include propylene-ethylene copolymers, propylene-1-butene copolymers, propylene-1-hexene copolymers, propylene-1-octene copolymers, propylene-ethylene-1-butene copolymers, propylene-ethylene-1-hexene copolymers, and propylene-ethylene-1-octene copolymers. The propylene copolymers may be random copolymers or heterophasic propylene polymer materials. The heterophasic propylene polymer materials are obtained by carrying out multiple polymerization steps.

[0021] The waste plastic raw material R includes polyethylene terephthalate (PET). The waste plastic raw material R may include polymer components other than the polyolefin and polyethylene terephthalate (PET). Examples of the polymer components include chlorinated polyethylene, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polybutylene terephthalate, polystyrene, nylon 66, etc.

[0022] From the viewpoint of increasing the content of polyolefins contained in the waste plastic raw material R, the waste plastic raw material R may be pre-treated before being supplied to the plurality of pyrolysis furnaces 2. Examples of the pre-treatment include a sorting treatment, a crushing treatment, a cleaning treatment, a drying treatment, a melting treatment, and a dechlorination treatment. The sorting treatment is a treatment for sorting plastics containing polyolefins from the waste plastic raw material R. The crushing treatment is a treatment for crushing the sorted plastics. The cleaning treatment is a treatment for cleaning the crushed plastics. The drying treatment is a treatment for drying the cleaned plastics. The melting treatment is a treatment for heating plastics to liquefy them. The dechlorination treatment is a treatment for removing chlorine contained in plastics.

[0023] The content of the polyolefin in the pretreated waste plastic raw material R is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, relative to 100% by mass of the waste plastic raw material R.

[0024] The hydrocarbon stream according to this embodiment comprises hydrocarbons and oxygen-containing compounds, and may also comprise nitrogen-containing compounds, sulfur-containing compounds, and chlorine-containing compounds.

[0025] The hydrocarbons may include light hydrocarbons having less than 20 carbon atoms and heavy hydrocarbons having 20 or more carbon atoms. Examples of the light hydrocarbons include alkanes such as methane, ethane, and propane; olefins such as ethylene, propylene, and butene; aromatic hydrocarbons such as benzene, toluene, and xylene; and cycloalkanes such as cyclohexane.

[0026] Examples of the oxygen-containing compound include organic compounds having an oxygen functional group such as a carboxyl group, a hydroxyl group, or an ether group, carbon dioxide, and carbon monoxide. Examples of organic compounds having an oxygen functional group include terephthalic acid, which is generated by the thermal decomposition of the above-mentioned polyethylene terephthalate (PET).

[0027] Examples of the nitrogen-containing compounds include organic compounds having a nitrogen functional group such as an amino group or an isocyanate group, nitrogen ring compounds, nitric oxide, nitrogen dioxide, etc. Examples of the sulfur-containing compounds include organic compounds having a sulfur functional group such as a thiol group, a thioether group, or a sulfonyl group, sulfur ring compounds, hydrogen sulfide, etc. Examples of the chlorine-containing compounds include chlorine-containing alkanes such as methyl chloride and chloroform, and chlorine-containing aromatic compounds, etc.

[0028] In the pyrolysis furnaces 2, the hydrocarbon stream is preferably vaporized.

[0029] The multiple pyrolysis furnaces 2 may further pyrolyze virgin plastic raw materials containing polyolefins. The virgin plastic raw materials refer to polymers produced by a process including a polymerization step, resin compositions containing the polymers, or plastic products made from the polymers or resin compositions, which have not been used for any final application. The polyolefins contained in the virgin plastic raw materials are the same as the polyolefins contained in the waste plastic raw materials.

[0030] The temperature of each of the plurality of pyrolysis furnaces 2 is preferably 350°C or higher and 800°C or lower, more preferably 370°C or higher and 600°C or lower, and even more preferably 380°C or higher and 550°C or lower.

[0031] By keeping the temperature of each pyrolysis furnace 2 within the above range, the yield of the hydrocarbon stream is improved.

[0032] The internal pressure of each of the plurality of pyrolysis furnaces 2 is preferably between atmospheric pressure -50 kPaG and atmospheric pressure +50 kPaG.

[0033] By keeping the internal pressure of each pyrolysis furnace 2 within the above range, pyrolysis is promoted.

[0034] In order to reduce the molecular weight of the hydrocarbons contained in the hydrocarbon stream, a reflux device may be provided at the outlet of each pyrolysis furnace 2. This allows high-boiling point components contained in the hydrocarbons to be liquefied in the reflux device and returned to the pyrolysis furnace 2 for re-cracking.

[0035] (cooler) The thermal cracking apparatus 1 according to this embodiment includes a cooler 3 that condenses at least a portion of the hydrocarbon stream obtained in the plurality of thermal cracking furnaces 2 by cooling the hydrocarbon stream. In the cooler 3, the hydrocarbon stream obtained in the plurality of thermal cracking furnaces 2 is cooled with a cooling medium, and at least a portion of the hydrocarbons, such as those having 5 or more carbon atoms, contained in the hydrocarbon stream is liquefied, and at least a portion of the hydrocarbons, such as those having 4 or fewer carbon atoms, contained in the hydrocarbon stream is maintained in a vaporized state, thereby forming the hydrocarbon stream into a gas-liquid mixed stream. The hydrocarbon stream at least partially condensed in the cooler 3 is supplied to a separator 4, which will be described later.

[0036] In the cooler 3, the hydrocarbon stream may be cooled by directly contacting the cooling medium with the hydrocarbon stream, or the hydrocarbon stream may be cooled via a heat exchanger cooled by the cooling medium.

[0037] Examples of the cooling medium include room temperature water, ice water, brine, mineral oil, and silicone oil.

[0038] The temperature of the cooling medium in the cooler 3 is preferably 10°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 20°C or higher and 40°C or lower.

[0039] The internal pressure of the cooler 3 is preferably −50 PaG or more and 50 PaG or less, more preferably −10 PaG or more and 10 PaG or less, and further preferably −5 PaG or more and 5 PaG or less.

[0040] (Separator) The thermal cracking apparatus 1 according to this embodiment includes a separator 4 that separates the hydrocarbon stream at least partially condensed in the cooler 3 into a hydrocarbon oil P and a cracked gas. The separator 4 separates a gas-liquid mixed stream of the hydrocarbon stream liquefied in the cooler 3 and the hydrocarbon stream maintained in a vaporized state into a hydrocarbon oil P and a cracked gas. That is, the hydrocarbon oil P is liquefied and the cracked gas is vaporized.

[0041] The hydrocarbon oil P may be supplied again to the plurality of thermal cracking furnaces 2, or may be used as a fuel or a raw material for producing olefins. The hydrocarbon oil P may be supplied directly from the separator 4 to an apparatus for catalytically cracking the hydrocarbon oil P (also referred to as a catalytic cracking apparatus), or may be supplied to an apparatus (second thermal cracking apparatus) such as a naphtha cracker for thermally cracking the hydrocarbon oil P at an even higher temperature, or may be supplied to the cracking apparatus via a refining apparatus such as a hydrotreating apparatus, or may be discharged from the separator 4 and temporarily stored before being supplied to the catalytic cracking apparatus.

[0042] The hydrocarbon oil contains hydrocarbons having 5 or more carbon atoms. Examples of hydrocarbons having 5 or more carbon atoms include alkanes having 5 or more carbon atoms such as pentane, hexane, and octane; olefins having 5 or more carbon atoms such as pentene, hexene, and octene; aromatic hydrocarbons such as benzene, toluene, and xylene; and cycloalkanes having 5 or more carbon atoms such as cyclopentane and cyclohexane.

[0043] Hydrocarbons having 4 or fewer carbon atoms are usually vaporized at room temperature and pressure, and are separated as cracked gases from the hydrocarbon oil in the separator 4. However, hydrocarbons having 4 or fewer carbon atoms can be dissolved in liquefied hydrocarbons having 5 or more carbon atoms, and therefore may be included in the hydrocarbon oil.

[0044] That is, the hydrocarbon oil may contain hydrocarbons having 4 or less carbon atoms. Examples of hydrocarbons having 4 or less carbon atoms include alkanes having 4 or less carbon atoms, such as methane, ethane, propane, and butane; and olefins having 4 or less carbon atoms, such as ethylene, propylene, and butene.

[0045] In the thermal decomposition apparatus 1 according to this embodiment, the decomposition gas is supplied to each of the first pipes 5 via a fourth pipe 9 to a sixth pipe 11, which will be described later, and is used as a non-condensable gas.

[0046] The cracked gas contains hydrocarbons having 4 or less carbon atoms. The hydrocarbons having 4 or less carbon atoms are the same as those described in the description of hydrocarbon oil.

[0047] (Multiple first pipes) The pyrolysis apparatus 1 according to this embodiment includes a plurality of first pipes 5 that discharge the hydrocarbon stream from each of the plurality of pyrolysis furnaces 2. As shown in Fig. 1 , the plurality of first pipes 5 are made up of three first pipes 5. Each of the pyrolysis furnaces 2 is connected to the plurality of first pipes 5, thereby discharging the hydrocarbon stream to the plurality of first pipes 5.

[0048] Each of the first pipes 5 in the plurality of first pipes 5 has a first shutoff valve 12 that opens and closes the flow path of the hydrocarbon flow in each of the first pipes 5 .

[0049] Since each of the first pipes 5 has a first shutoff valve 12, it is possible to close the first shutoff valve 12 to stop the operation of some of the pyrolysis furnaces 2 and perform maintenance such as cleaning of the pyrolysis furnaces 2 while continuing the operation of the other pyrolysis furnaces 2. Furthermore, productivity is improved by always having one of the pyrolysis furnaces 2 in operation.

[0050] Examples of the first shutoff valve 12 include a gate valve, a globe valve, a ball valve, a butterfly valve, and a diaphragm valve.

[0051] Each of the first pipes 5 is connected to a sixth pipe 11 (described later) downstream of the position of the first shutoff valve 12 and upstream of a junction 6 (described later).

[0052] In this specification, the term "downstream side" refers to the side that follows the flow of gas or liquid, and the term "upstream side" refers to the side that opposes the flow of gas or liquid.

[0053] By connecting each of the first pipes 5 downstream of the position of the first shut-off valve 12 and upstream of the confluence 6 to the sixth pipe 11, non-condensable gas is supplied to the multiple first pipes 5, thereby suppressing coking in the multiple first pipes 5.

[0054] The closer the position where each of the first pipes 5 and the sixth pipe 11 is to the position of the first shutoff valve 12, the more preferable it is. The distance between the first shutoff valve 12 and the position where each of the first pipes 5 and the sixth pipe 11 is connected is preferably 0.01 m or more and 0.5 m or less. Note that, if the plurality of first pipes 5 have a shape with a bent portion, which will be described later, the distance means the length along that shape. Furthermore, there may be a plurality of points where each of the first pipes 5 and the sixth pipe 11 are connected.

[0055] Examples of the non-condensable gas include nitrogen gas, argon gas, carbon dioxide gas, and cracked gas. The non-condensable gas is preferably nitrogen gas or cracked gas. The cracked gas is the same as that described in the section on separator 4.

[0056] The temperature of the non-condensable gas in the plurality of first pipes 5 is preferably 10°C or higher and 100°C or lower, more preferably 15°C or higher and 80°C or lower, and even more preferably 20°C or higher and 60°C or lower.

[0057] The temperature of the non-condensable gas in the plurality of first pipes 5 is measured by a thermocouple or a thermometer installed in the plurality of first pipes 5 .

[0058] Terephthalic acid, which is generated by thermal decomposition of polyethylene terephthalate (PET) contained in waste plastics, is easily crystallized. Therefore, when terephthalic acid is contained in the hydrocarbon stream, coking due to terephthalic acid is likely to occur in the pipes. By keeping the temperature of the non-condensable gas in the multiple first pipes 5 within the above numerical range, coking due to terephthalic acid can be easily suppressed.

[0059] Each of the first pipes 5 may have a bent portion bent in any shape. The bent portion may be bent in an L-shape, a U-shape, or a V-shape. Each of the first pipes 5 may have a plurality of bent portions.

[0060] When each of the first pipes 5 has the bent portion, when the hydrocarbon flow passes through the bent portion, the internal pressure locally increases at the bent portion, making some components contained in the hydrocarbon flow more likely to coke. Therefore, when each of the first pipes 5 has multiple bent portions, the connection position between each of the first pipes 5 and the sixth pipe 11 is preferably downstream of the position of the first shutoff valve 12 and upstream of the bent portion located most upstream of the bent portions located downstream of the first shutoff valve 12.

[0061] The cross-sectional shape of each of the first pipes 5 in a plane perpendicular to the axial direction is not particularly limited, and examples thereof include a circular shape, a polygonal shape, etc. From the viewpoint of suppressing coking, the cross-sectional shape of each of the first pipes 5 in a plane perpendicular to the axial direction is preferably a circular shape.

[0062] When the cross-sectional shape of each of the first pipes 5 in a plane perpendicular to the axial direction is circular, the inner diameter of each of the first pipes 5 is preferably determined so that the gas linear velocity of the hydrocarbon stream flowing inside each of the first pipes 5 is 5 m / s to 20 m / s.

[0063] (Confluence) The thermal cracking apparatus 1 according to this embodiment includes a confluence section 6 that joins the hydrocarbon streams in each of the plurality of first pipes 5. The confluence section 6 is formed by connecting the first pipes 5 to each other. The confluence section 6 is connected to a second pipe 7, which will be described later. In the confluence section 6, the hydrocarbon streams discharged from each of the pyrolysis furnaces 2 join together, and the joined hydrocarbon stream is supplied to the second pipe 7.

[0064] When some of the first shutoff valves 12 are closed, the non-condensable gas is supplied from the first pipes 5 whose first shutoff valves 12 are closed instead of the hydrocarbon flow, and the non-condensable gas and the hydrocarbon flow supplied from the other first pipes 5 are merged at the junction 6.

[0065] (Second piping) The thermal cracking apparatus 1 according to this embodiment includes a second pipe 7 that causes the hydrocarbon stream joined at the joining section 6 to flow to the cooler 3. The second pipe 7 is connected to the joining section 6. The second pipe 7 is connected to the cooler 3 downstream of a position where the second pipe 7 and the joining section 6 are connected. The hydrocarbon stream supplied from the joining section 6 to the second pipe 7 is supplied to the cooler 3.

[0066] (Third piping) The thermal cracking apparatus 1 according to this embodiment includes a third pipe 8 that allows the hydrocarbon stream, at least a portion of which is condensed in the cooler 3, to flow to the separator 4. The third pipe 8 is connected to the cooler 3. The third pipe 8 is connected to the separator 4 downstream of a position where the third pipe 8 and the cooler 3 are connected. The hydrocarbon stream supplied from the cooler 3 to the third pipe 8 is supplied to the separator 4.

[0067] (4th piping) The thermal decomposition apparatus 1 according to this embodiment includes a fourth pipe 9 that discharges the decomposition gas from the separator 4. The fourth pipe 9 is connected to the separator 4.

[0068] As shown in FIG. 1, in the thermal decomposition apparatus 1 according to this embodiment, the fourth pipe 9 has a blower 13 that pressurizes the decomposition gas in the fourth pipe 9 and a second shutoff valve 14 that opens and closes the flow path of the decomposition gas in the fourth pipe 9, and the fourth pipe 9 is connected to the sixth pipe 11 (described later) downstream of the second shutoff valve 14 in the fourth pipe 9, so that the decomposition gas is supplied to the plurality of first pipes 5 via the sixth pipe 11.

[0069] The blower 13 is located on the upstream side of the second shutoff valve 14 in the fourth pipe 9 .

[0070] The fourth pipe 9 has the blower 13, which makes it possible to adjust the flow rate of the cracked gas supplied to each of the first pipes 5. Furthermore, the fourth pipe 9 has the blower 13, which makes it possible to prevent the cracked gas supplied to some of the first pipes 5 from being pushed back by the hydrocarbon flow being discharged from the other first pipes 5, and to prevent the hydrocarbon flow from flowing back into some of the first pipes 5.

[0071] Since the fourth pipe 9 has the second shutoff valve 14, when the amount of the decomposition gas is insufficient to be supplied to each of the first pipes 5, the second shutoff valve 14 can be closed to stop the supply of the decomposition gas to each of the first pipes 5. In such a case, it is possible to deal with the situation by supplying a non-condensable gas other than the decomposition gas to each of the first pipes 5 through a sixth pipe 11 described later.

[0072] Examples of the second shutoff valve 14 include a gate valve, a globe valve, a ball valve, a butterfly valve, and a diaphragm valve.

[0073] By supplying the decomposition gas, which is a non-condensable gas, to the plurality of first pipes 5 through the fourth pipe 9 and the sixth pipe 11, coking in the plurality of first pipes 5 can be suppressed and the by-produced decomposition gas can be reused, thereby contributing to reducing the burden on the environment.

[0074] (5th piping) The thermal cracking unit 1 according to this embodiment includes a fifth pipe 10 that discharges the hydrocarbon oil P from the separator 4. The fifth pipe 10 is connected to the separator 4. The fifth pipe 10 may be connected to a catalytic cracking unit. The hydrocarbon oil P discharged from the separator 4 through the fifth pipe 10 may be supplied to a catalytic cracking unit, or may be supplied to a unit (second thermal cracking unit) that thermally cracks the hydrocarbon oil P at an even higher temperature, such as a naphtha cracker, or may be supplied to the cracking unit via a refining unit such as a hydrotreating unit.

[0075] (6th piping) The thermal decomposition apparatus 1 according to this embodiment includes a sixth pipe 11 that supplies a non-condensable gas to the plurality of first pipes 5. The sixth pipe 11 supplies the non-condensable gas to the plurality of first pipes 5 downstream of the position of the first shutoff valve 12 in each of the first pipes 5. The sixth pipe 11 is connected to the plurality of first pipes 5 downstream of the position of the first shutoff valve 12 in each of the first pipes 5.

[0076] The sixth pipe 11 according to this embodiment has a third shutoff valve 15 that opens and closes the flow path of the non-condensable gas in the sixth pipe 11. The third shutoff valve 15 is located upstream of the position where the fourth pipe 9 and the sixth pipe 11 are connected.

[0077] The thermal decomposition apparatus 1 according to this embodiment can select the type of gas to be supplied to the plurality of first pipes 5 by selecting whether to open or close the second shutoff valve 14 and the third shutoff valve 15. For example, when nitrogen gas flows through the sixth pipe 11 and decomposition gas flows through the fourth pipe 9, the thermal decomposition apparatus 1 can supply the nitrogen gas to the plurality of first pipes 5 by closing the second shutoff valve 14 and opening the third shutoff valve 15. The thermal decomposition apparatus 1 can supply the decomposition gas to the plurality of first pipes 5 by opening the second shutoff valve 14 and closing the third shutoff valve 15. The thermal decomposition apparatus 1 can supply a mixed gas of the nitrogen gas and the decomposition gas to the plurality of first pipes 5 by opening the second shutoff valve 14 and the third shutoff valve 15. The thermal decomposition apparatus 1 can stop the supply of non-condensable gas to the plurality of first pipes 5 by closing the second shutoff valve 14 and the third shutoff valve 15.

[0078] As shown in FIG. 1, the sixth pipe 11 is branched downstream so as to correspond to the number of the first pipes 5 and is connected to the first pipes 5 .

[0079] The thermal decomposition apparatus 1 according to this embodiment includes a plurality of parallelly arranged thermal decomposition furnaces 2 for thermally decomposing a waste plastic raw material R containing polyolefin to obtain a hydrocarbon stream; a cooler 3 for condensing at least a portion of the hydrocarbon stream obtained in the plurality of thermal decomposition furnaces 2 by cooling the hydrocarbon stream; a separator 4 for separating the hydrocarbon stream at least a portion of which has been condensed in the cooler 3 into a hydrocarbon oil P and a cracked gas; a plurality of first pipes 5 for discharging the hydrocarbon stream from each of the plurality of thermal decomposition furnaces 2; a confluence section 6 for confluence of the hydrocarbon streams in each of the plurality of first pipes 5; the hydrocarbon stream condensed in the cooler 3 to the separator 4; a fourth pipe 9 for discharging the cracked gas from the separator 4; a fifth pipe 10 for discharging the hydrocarbon oil P from the separator 4; and a sixth pipe 11 for supplying a non-condensable gas to the plurality of first pipes 5, each of the first pipes 5 having a first shut-off valve 12 for opening and closing a flow path of the hydrocarbon stream in each of the first pipes 5, and the sixth pipe 11 for supplying the non-condensable gas to the plurality of first pipes 5 downstream of the position of the first shut-off valve 12 in each of the first pipes 5.

[0080] In the thermal cracking apparatus 1 according to this embodiment, the sixth pipe 11 supplies non-condensable gas to the plurality of first pipes 5 downstream of the position of the first shutoff valve 12 in each first pipe 5, so that the non-condensable gas flows toward the junction 6 in the first pipe 5 when the first shutoff valve 12 is closed, thereby preventing the hydrocarbon flow that has reached the junction 6 from another first pipe 5 from flowing back into the first pipe 5 when the first shutoff valve 12 is closed. As a result, the thermal cracking apparatus 1 according to this embodiment can suppress the occurrence of coking in the pipes even when a plurality of thermal cracking furnaces 2 are used in parallel.

[0081] In the thermal decomposition apparatus 1 of this embodiment, the fourth pipe 9 has a blower 13 that pressurizes the decomposition gas in the fourth pipe 9 and a second shut-off valve 14 that opens and closes the flow path of the decomposition gas in the fourth pipe 9, and the fourth pipe 9 is connected to the sixth pipe 11 downstream of the second shut-off valve 14 in the fourth pipe 9, so that the decomposition gas is supplied to the multiple first pipes 5 via the sixth pipe 11.

[0082] With this configuration, the pyrolysis device 1 according to this embodiment connects the fourth pipe 9 to the sixth pipe 11 downstream of the second shutoff valve 14, and supplies the decomposition gas to the plurality of first pipes 5 via the sixth pipe 11, thereby making it possible to supply the decomposition gas as a non-condensable gas to the first pipes 5. As a result, the pyrolysis device 1 according to this embodiment can reuse the decomposition gas produced as a by-product in the thermal decomposition of waste plastics, thereby contributing to reducing the environmental load.

[0083] [Method of producing hydrocarbon oil] Hereinafter, a method for producing a hydrocarbon oil according to an embodiment of the present invention will be described, but the present invention is not limited to the following embodiment.

[0084] The method for producing a hydrocarbon oil according to this embodiment includes a hydrocarbon oil production step of obtaining the hydrocarbon oil P by thermally decomposing the waste plastic raw material R using the thermal decomposition apparatus 1 described above.

[0085] The hydrocarbon oil production method of this embodiment is highly productive because the hydrocarbon oil production process is carried out using the above-mentioned thermal cracking apparatus 1, which suppresses the occurrence of coking in the piping during the process of obtaining the hydrocarbon oil P.

[0086] In the method for producing hydrocarbon oil according to this embodiment, the hydrocarbon oil production process may include a thermal decomposition process in which the waste plastic raw material R is thermally decomposed using the plurality of thermal decomposition furnaces 2 to obtain a hydrocarbon stream, a cooling process in which the hydrocarbon stream obtained in the plurality of thermal decomposition furnaces 2 is cooled using the cooler 3 to condense at least a portion of the hydrocarbon stream, and a separation process in which the hydrocarbon stream at least a portion of which is condensed in the cooler 3 is separated into a hydrocarbon oil P and a cracked gas.

[0087] The method for producing hydrocarbon oil according to this embodiment may further include a shutoff process (also referred to as the "first shutoff process") for closing some of the first shutoff valves 12, or may further include an opening process (also referred to as the "first opening process") for opening some of the first shutoff valves 12, or may further include the first shutoff process and the first opening process.

[0088] The method for producing hydrocarbon oil according to this embodiment includes a first shut-off step, and therefore when the operation of some of the pyrolysis furnaces 2 is stopped, it is possible to prevent the contents of the pyrolysis furnaces 2 from flowing into the first piping 5, or to prevent the non-condensable gas or the hydrocarbon stream from flowing into the pyrolysis furnaces 2 from the first piping 5. The method for producing hydrocarbon oil according to this embodiment includes a first opening step, and therefore when the operation of some of the pyrolysis furnaces 2 is resumed, it is possible to discharge the hydrocarbon stream from the pyrolysis furnaces 2 into the first piping 5.

[0089] The method for producing hydrocarbon oil according to this embodiment may further include a non-condensable gas supply step of supplying the non-condensable gas through the sixth pipe 11 to the first pipe 5 with the first shut-off valve 12 closed.

[0090] In one aspect, the method for producing hydrocarbon oil according to this embodiment further includes a shut-off process for closing some of the first shut-off valves 12, and a non-condensable gas supply process for supplying the non-condensable gas through the sixth pipe 11 to the first pipe 5 having the closed first shut-off valves 12.

[0091] The method for producing hydrocarbon oil according to this embodiment may further include an opening step (also referred to as the "second opening step") of opening the second shut-off valve 14, may further include a shut-off step (also referred to as the "second shut-off step") of closing the second shut-off valve 14, or may further include the second opening step and the second shut-off step.

[0092] The method for producing a hydrocarbon oil according to this embodiment includes a second opening step, which makes it possible to supply the cracked gas into the first pipe 5. The method for producing a hydrocarbon oil according to this embodiment includes a second shutoff step, which makes it possible to stop the supply of the cracked gas into the first pipe 5.

[0093] The method for producing hydrocarbon oil according to this embodiment may further include a cracked gas supply step of supplying the cracked gas to the first pipe 5 having the first shut-off valve 12 closed through the fourth pipe 9 and the sixth pipe 11.

[0094] In another aspect, the method for producing hydrocarbon oil according to this embodiment further includes a shutoff process for closing some of the first shutoff valves 12, an opening process for opening the second shutoff valves 14, and a cracked gas supply process for supplying the cracked gas to the first pipe 5 having the closed first shutoff valves 12 through the fourth pipe 9 and the sixth pipe 11.

[0095] The method for producing a hydrocarbon oil according to this embodiment includes a hydrocarbon oil production step of obtaining the hydrocarbon oil P by thermally decomposing the waste plastic raw material R using the thermal decomposition apparatus 1 described above.

[0096] The method for producing hydrocarbon oil according to this embodiment has such a configuration and is excellent in productivity because the use of the thermal cracking apparatus 1 described above suppresses the occurrence of coking inside the piping during the process of obtaining the hydrocarbon oil P.

[0097] The method for producing hydrocarbon oil according to this embodiment may further include a shut-off process for closing some of the first shut-off valves 12, and a non-condensable gas supply process for supplying the non-condensable gas through the sixth pipe 11 to the first pipe 5 having the closed first shut-off valves 12.

[0098] Due to this configuration, the method for producing hydrocarbon oil according to this embodiment includes a non-condensable gas supply step in which non-condensable gas is supplied to the first pipe 5 having the closed first shut-off valve 12 through the sixth pipe 11, thereby further suppressing the occurrence of coking in the pipes during the process of obtaining the hydrocarbon oil P, thereby achieving even greater productivity.

[0099] The method for producing hydrocarbon oil according to this embodiment may further include a shutoff process for closing some of the first shutoff valves 12, an opening process for opening the second shutoff valves 14, and a cracked gas supply process for supplying the cracked gas to the first pipe 5 having the closed first shutoff valves 12 through the fourth pipe 9 and the sixth pipe 11.

[0100] The method for producing hydrocarbon oil according to this embodiment has such a configuration and includes a cracked gas supply step of supplying cracked gas to the first pipe 5 having the closed first shut-off valve 12 via the fourth pipe 9 and the sixth pipe 11, thereby making it possible to reuse the cracked gas produced as a by-product in the thermal decomposition of waste plastics, thereby contributing to reducing the environmental burden.

[0101] By implementing the thermal cracking apparatus 1 and the hydrocarbon oil production method of this embodiment in the above manner, it is possible to suppress the occurrence of coking in the piping even when multiple thermal cracking furnaces 2 are used in parallel.

[0102] The thermal cracking apparatus 1 and the method for producing hydrocarbon oil according to the present invention are not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. In addition, the configurations, methods, etc. of the embodiments other than those described above may be arbitrarily adopted and combined.

[0103] In the pyrolysis apparatus 1 according to the above embodiment, the plurality of pyrolysis furnaces 2 is composed of three pyrolysis furnaces 2. However, the pyrolysis apparatus according to the present invention is not limited to this, and the plurality of pyrolysis furnaces may be composed of two pyrolysis furnaces, or may be composed of four or more pyrolysis furnaces.

[0104] In the thermal decomposition apparatus 1 according to the above embodiment, the decomposition gas is supplied to each of the first pipes 5 via the fourth pipe 9 to the sixth pipe 11 and used as a non-condensable gas. However, the thermal decomposition apparatus according to the present invention is not limited to this, and the decomposition gas does not have to be supplied to each of the first pipes and used as a non-condensable gas, but may be supplied to a plurality of thermal decomposition furnaces and used as fuel.

[0105] In the thermal decomposition device 1 according to the above embodiment, the plurality of first pipes 5 is composed of three first pipes 5. However, the thermal decomposition device according to the present invention is not limited to this, and the plurality of first pipes may be composed of two first pipes, or may be composed of four or more first pipes.

[0106] In the thermal decomposition apparatus 1 according to the above embodiment, the fourth pipe 9 has a blower 13 that pressurizes the decomposition gas in the fourth pipe 9 and a second shutoff valve 14 that opens and closes the flow path of the decomposition gas in the fourth pipe 9. However, the thermal decomposition apparatus according to the present invention is not limited to this, and the fourth pipe may not have a blower, may not have a second shutoff valve, or may not have a blower or a second shutoff valve.

[0107] In the thermal decomposition apparatus 1 according to the above embodiment, the fourth pipe 9 is connected to the sixth pipe 11, which will be described later, downstream of the second shutoff valve 14 on the fourth pipe 9. However, the thermal decomposition apparatus according to the present invention is not limited to this, and the fourth pipe may be connected to the sixth pipe upstream of the second shutoff valve on the fourth pipe, or may not be connected to the sixth pipe. Alternatively, the fourth pipe may be connected to a plurality of first pipes downstream of the second shutoff valve on the fourth pipe, so that the decomposition gas can be supplied to a plurality of first pipes without passing through the sixth pipe.

[0108] In the thermal decomposition apparatus 1 according to the above embodiment, the blower 13 is located on the fourth pipe 9 upstream of the second shutoff valve 14. However, the thermal decomposition apparatus according to the present invention is not limited to this, and the blower may be located on the fourth pipe 9 downstream of the second shutoff valve.

[0109] In the pyrolysis device 1 according to the above embodiment, the sixth pipe 11 is connected to the plurality of first pipes 5 while branching downstream so as to correspond to the number of the plurality of first pipes 5. However, the pyrolysis device according to the present invention is not limited to this, and the sixth pipe may be a plurality of sixth pipes corresponding to the number of the plurality of first pipes, or each sixth pipe in the plurality of sixth pipes may be connected to each first pipe. Furthermore, when the sixth pipe is a plurality of sixth pipes and the fourth pipe is connected to the sixth pipe, the fourth pipe may be connected to the plurality of sixth pipes while branching downstream so as to correspond to the number of the plurality of sixth pipes. [Explanation of symbols]

[0110] 1 Pyrolysis equipment 2 Pyrolysis furnace 3 Cooler 4 Separator 5. First piping 6 Confluence 7 Second piping 8. Third Pipe 9. 4th Pipe 10 5th Pipe 11 No. 6 Pipe 12 First shutoff valve 13 Blower 14 Second shutoff valve 15 Third shutoff valve R Waste plastic raw materials P hydrocarbon oil

Claims

1. a plurality of pyrolysis furnaces arranged in parallel for pyrolyzing a waste plastic feedstock containing polyolefins to obtain a hydrocarbon stream; a cooler for cooling the hydrocarbon streams obtained from the plurality of pyrolysis furnaces to condense at least a portion of the hydrocarbon streams; a separator that separates the hydrocarbon stream at least partially condensed in the cooler into hydrocarbon oil and cracked gas; a plurality of first pipes for discharging the hydrocarbon stream from each of the plurality of pyrolysis furnaces; a confluence portion that combines the hydrocarbon flows in the first pipes of the plurality of first pipes; a second pipe that allows the hydrocarbon streams joined at the joining portion to flow to the cooler; a third line for passing the hydrocarbon stream at least partially condensed in the cooler to the separator; a fourth pipe for discharging the decomposed gas from the separator; a fifth pipe for discharging the hydrocarbon oil from the separator; and a sixth pipe that supplies a non-condensable gas to the plurality of first pipes; each of the first pipes has a first shutoff valve that opens and closes a flow path of the hydrocarbon stream in each of the first pipes; the sixth pipe supplies the non-condensable gas to the plurality of first pipes downstream of the positions of the first shutoff valves in the respective first pipes; Pyrolysis equipment.

2. The fourth pipe, a blower that pressurizes the decomposed gas in the fourth pipe; a second shutoff valve that opens and closes a flow path of the decomposed gas in the fourth pipe, the fourth pipe is connected to the sixth pipe at a location downstream of the second shutoff valve in the fourth pipe, thereby supplying the decomposed gas to the plurality of first pipes via the sixth pipe. The pyrolysis apparatus according to claim 1 .

3. A hydrocarbon oil production step of pyrolyzing the waste plastic raw material using the pyrolysis apparatus according to claim 1 to obtain the hydrocarbon oil. Method for producing hydrocarbon oil.

4. A hydrocarbon oil production step of pyrolyzing the waste plastic raw material using the pyrolysis apparatus according to claim 2 to obtain the hydrocarbon oil. Method for producing hydrocarbon oil.

5. a shutoff step of closing some of the first shutoff valves; a non-condensable gas supplying step of supplying the non-condensable gas through the sixth pipe to the first pipe with the first shutoff valve closed, The method for producing the hydrocarbon oil according to claim 3 .

6. a shutoff step of closing some of the first shutoff valves; an opening step of opening the second shutoff valve; a decomposition gas supplying step of supplying the decomposition gas to the first pipe with the first shutoff valve closed through the fourth pipe and the sixth pipe, The method for producing the hydrocarbon oil according to claim 4.

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